Co-reporter:Yanping Miao, Ping Yang, Katarzyna Matras-Postolek
Journal of Luminescence 2017 Volume 181() pp:63-70
Publication Date(Web):January 2017
DOI:10.1016/j.jlumin.2016.08.064
Large flexible silica films encapsulating hydrophilic CdTe quantum dots (QDs) were fabricated via controlling the hydrolysis of 3-aminopropyltrimethoxysilane (APS). Hydrophilic CdTe quantum dots with green to red emitting were encapsulated in the films through a sol–gel incorporation process for retaining high photoluminescence (PL) efficiency and stability. Fluorescence microscopy and a scanning electron microscopy were employed to examine dispersion of CdTe QDs in the emitting films, which illustrated that structure of silica films was uniform. The PL stability of these flexible silica films was investigated in argon condition, the PL properties of the films encapsulated green-, yellow-, and red-emitting CdTe QDs were very stable. Furthermore, the silica-CdTe QDs emitting films revealed high PL stability under ultraviolet (UV) light irradiation, proper concentration of QDs in silica films can make the films more stable. In addition, different emission flexible silica-CdTe QDs films with large area were obtained. The dual-emitting silica-CdTe QDs films exhibited coordinates (0.384, 0.350) in the Commission Internationale de I׳Eclairage (CIE) chromaticity diagram under blue light as excitation source. Due to flexibility, adjustable colors, high stability, large area, easy to operate, silica-CdTe QDs emitting films show potential application in lighting devices and flat panel displays.
Co-reporter:Yunshi Liu, Ping Yang, Jia Li, Katarzyna Matras-Postolek, Yunlong Yue
Materials Chemistry and Physics 2017 Volume 186() pp:312-316
Publication Date(Web):15 January 2017
DOI:10.1016/j.matchemphys.2016.11.001
•Metal oxides with verious morphologies were fabricated via controlling calcination process.•Heating rate plays important role for the morphologies.•Hollow fibers were created via a two-step calcination which controlling matter diffusion.One dimensional metal oxide materials with verious morphologies were successfully fabricated via a single nozzle electrospinning method and subsequent calcination process. The matter diffusion in calcination process plays an important role for the morphology. With low heating rate of 1 or 5 °C/min, SnO2 samples tended to form solid nanofibers consisted of small nanoparticles with uniform size. Using same conditions, CeO2 samples preferred to form belt morphology while Co3O4 tended to form a chain. This is ascribed to the difference of diffusion of these metal oxides during calcination. To fabricate hollow fibers, a two-step calcination route was used. A heating rate of 1 °C/min was used at less than 300 °C to create dense solid fiber. Low heating rate at low temperature could be beneficial to enhancing Kirkendall effect remarkably. A heating rate of 15 °C/min was used during temperature rising from 300 to 550 °C, in which the quick decomposition of poly(vinylpyrrolidone) occurred. Such quick decomposition resulted in the fast diffusion of metal oxides to the surface layer of fibers. SnO2, CeO2, and SnO2/CeO2 hollow fibers were successfully fabricated through the two-step calcination. In addition, SnO2 and Co3O4 tended to form on SnO2/CeO2 and Co3O4/CeO2 composite structure during calcination process.
Co-reporter:Meng Li, Xiao Zhang, Yingying Du, Ping Yang
Journal of Luminescence 2017 Volume 190(Volume 190) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.jlumin.2017.05.080
Halide perovskites have attracted enormous attention as a novel optoelectronic material showing bright emission recently. In this paper, we chose CsPbX3 nanocrystals (NCs) as an example to study the structural, morphological and optical properties. We have synthesized monodispersed colloidal inorganic cesium lead halide perovskites (CsPbX3, X = Cl, Br and I, or mixed lead halide CsPb(Cl/Br)3 and CsPb(Br/I)3) NCs with various morphologies and brightly luminescent properties. The emission wavelength of resulting CsPbX3 NCs can be tuned from 440 nm to 696 nm by varying the amount of different PbX2 (X = Cl, Br and I), while maintaining high quantum yields up to 95% and narrow emission spectra. The average lifetime of the NCs is several ns to hundred with changing the composition. The blinking of the NCs in terms of a binary (on/off) process is different from II-VI quantum dots. Interestingly, we find that CsPbBr3 NCs to Cs4PbBr6 NCs or a mixture of CsPbBr3 NCs and Cs4PbBr6 NCs were obtained by adjusting the amount of oleic acid (OA)-Cs precursor. The optical properties of these NCs have been controlled by varying their composition. Moreover, the injection speed of Cs-OA precursor enables the control of CsPbI3 NCs with different morphology, which can be tuned from litter nanoparticles to uniform nanorods. This finding can serve as an ideal platform for the investigation of fundamental properties.CsPbX3 (X = Cl, Br and I) and mixed CsPb(Cl/Br)3, CsPb(Br/I)3 with adjusting morphologies and phase composition, tunable photoluminescence wavelength, as well as high luminescent efficiency were synthesized through changing preparation parameters.Download high-res image (229KB)Download full-size image
Co-reporter:Yan Zheng;Xiao Zhang
CrystEngComm (1999-Present) 2017 vol. 19(Issue 1) pp:171-178
Publication Date(Web):2016/12/21
DOI:10.1039/C6CE02383E
Anatase hexagonal prism TiO2 with high thermal stability was prepared through the decomposition of precursors (HTiOF3). HTiOF3 was firstly synthesized, using a solvothermal method, from n-octanol, tetrabutyl titanate and hydrofluoric acid. The obtained precipitates were then calcined at different temperatures (200–900 °C) for 2 h. The formation process of the hexagonal prism HTiOF3 precursors included three steps: nuclei growth, dissolution–recrystallization and further growth. The morphologies of the precursors depended strongly on the reaction temperature and the amount of solvent. The precursors were transformed into TiO2 after calcination and the effect of the calcination temperature on the morphology and phase composition of the hexagonal prism TiO2 was investigated. The results indicated that the anatase hexagonal prism TiO2 exhibited a rather high thermal stability, maintaining both the anatase structure and precursor shape up to 800 °C. The sample that was calcined at 550 °C exhibited a superior photocatalytic performance.
Co-reporter:Xiao Zhang;Changchao Jia;Yuehua Xue
RSC Advances (2011-Present) 2017 vol. 7(Issue 69) pp:43888-43893
Publication Date(Web):2017/09/07
DOI:10.1039/C7RA07706H
Herein, g-C3N4 nanosheets (NSs) were grown on reduced graphene oxide (rGO) using cross linking molecules by an electrostatic assembly process from carboxyl and amine groups via π–π stacking interaction to fabricate heterostructures. Detailed characterizations such as Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electronmicroscopy, photoelectrochemical measurements, X-ray photoelectron spectroscopy, and photoluminescence (PL) spectroscopy demonstrated step-by-step immobilization of 1-pyrene carboxylic acid, polyaniline (PANI), and g-C3N4 on rGO. The π–π stacking plays an important role for the formation of rGO/g-C3N4 composites. The surface of rGO was homogeneously decorated with monodispersed g-C3N4 NSs. The resulting rGO/g-C3N4 composites obtained endowed the heterostructures with novel functions. Both the rGO–COOH/g-C3N4 and rGO–PANI/g-C3N4 composites revealed enhanced conduction properties. Absorption and PL spectra of the composite samples confirmed the attachment of g-C3N4 on rGO. Due to the presence of carboxyl groups on 1-pyrene carboxylic acid, rGO–COOH/g-C3N4 composites demonstrated enhanced photocatalysis properties.
Co-reporter:Ying Chen, Hui Li, Qian Ma, Zhanming Zhang, Junpeng Wang, Gang Wang, Quande Che, Ping Yang
Materials Letters 2017 Volume 202(Volume 202) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.matlet.2017.05.086
•Carambola-like SnO2/C composites are fabricated by novel electrospun approach.•Various SnO2/C microstructures are obtained by tuning calcination temperature.•Monodispersed SnO2 nanocrystals are homogeneously embedded into carbon matrix.•SnO2/C samples show superior photocatalytic properties for the degradation of RhB.•Different morphologies of other inorganic oxides can be obtained by this method.The highly-dispersed carambola-like SnO2/C composite microparticles have been fabricated through a novel electrospun approach using tetrobutylammonium bromide and paraffin liquid as functional additives in the precursor solution. The presence of carbon matrix can availably contribute for the reduced agglomeration, decreased migration, and controllable sizes of SnO2 nanocrystals. The influence of calcination temperature on the microstructures and photocatalytic properties of SnO2/C products and the relevant photocatalytic mechanism were investigated. The carambola-like SnO2/C photocatalysts showed the superior photocatalytic performance for the degradation of rhodamine B (RhB) with the high efficiency of 94.6% as the irradiation time increasing to 210 min as well as the good photocatalytic cycle stability. The preparation technology can be potentially applied for adjusting microstructures of other inorganic oxide photocatalysts in the field of water treatment.Download high-res image (161KB)Download full-size image
Co-reporter:Yue Zhao, Simin Lu, Katarzyna Matras-Postolek, Ping Yang
Chemical Engineering and Processing: Process Intensification 2017 Volume 122(Volume 122) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.cep.2017.02.009
•SiO2 monomer-triggered self-assembly makes hybrid CdTe QDs into various nanostructures.•The assemblies retained high photoluminescence.•The hybrid QDs retained high stability and assembled in PBS solutions.The self-assembly activity of quantum dots (QDs) including thioglycolic acid (TGA)-capped CdTe and hybrid SiO2-coated CdTe QDs into one- to three-dimensional (3D) nanostructures was reported using a slow growth process. SiO2 monomers from a sol-gel process and TGA play vital roles for the self-assembly. The hybrid SiO2-coated QDs were assembled into 1D nanotube, 2D nanosheets, and 3D nanoflowers by adjusting QD concentrations. It is found that the assemblies actually are CdTe@Cd-TGA-SiO2 complex hybrid nanostructures in which many well-separated CdTe QDs are uniformly distributed. Such assembly also occurred in an initial CdTe QD solution or in PBS and NaCl solutions. The assembly in the initial CdTe QD solution is accompanied by a hybrid SiO2 layer which resulted in red-shifted photoluminescence (PL) from green to yellow. Because of the domain growth of NaCl to form fractal structures through tip splitting and side branching dynamics, the hybrid SiO2-coated QDs were assembled into leaf morphology. As a result, the CdTe QDs with their in effective protection by hybrid Cd-TGA-SiO2 complex, these nanostructures show visually bright PL and retain the size-quantized properties of the QDs. These QD-based assemblies may be suitable for subsequent processing into quantum-confined materials and devices.Download high-res image (113KB)Download full-size image
Co-reporter:Ping Yang, Yunshi Liu
Journal of Industrial and Engineering Chemistry 2017 Volume 53(Volume 53) pp:
Publication Date(Web):25 September 2017
DOI:10.1016/j.jiec.2017.05.002
•Belt-like Co3O4/CeO2 heterostructures with fine structure was created.•Formation of heterojunction can improve their catalysis performance.•Au NPs loading resulted in superior catalytic performance at relevant low temperature.Co3O4 nanochain and Co3O4/CeO2 heterostructures were prepared via an electrospinning process and subsequent calcination. The formation and shape evolution from Co3O4 nanochains to Co3O4/CeO2 composite nanobelts were investigated, suggesting that both components and preparation parameters play important roles in resulted morphology and properties. Homogeneous Co3O4/CeO2 junctions in belt samples were formed towards enhanced catalysis performance. Well-dispersed Au nanoparticles were deposited on Co3O4/CeO2 composite nanostructures or doped inside through reduction and direct calcination route method, respectively. The loading of Au nanoparticles significantly enhanced catalytic performance with onset CO conversion at 100 °C and resulted in CO conversion over at 127 °C.Belt-like Co3O4/CeO2 heterostructures with fine microstructure was created for improving the properties. Au NPs loading resulted in superior catalytic performance with onset CO conversion at 100 °C and complete CO conversion at 127 °C.Download high-res image (137KB)Download full-size image
Co-reporter:Xueling Song, Yumeng Liu, Yan Zheng, Kun Ding, Shijie Nie and Ping Yang
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 6) pp:4577-4584
Publication Date(Web):12 Jan 2016
DOI:10.1039/C5CP07187A
Zinc oxide (ZnO) nanostructures with diverse morphologies were successfully fabricated via a simple one-step hydrothermal synthesis and subsequent calcination. The formation of butterfly-like ZnO was mainly ascribed to a typical nucleation–growth–assembly process as a result of electrostatic interactions between the nanoparticles and the reconstructed sheets. Au nanoparticles (NPs) created from Au3+ ions were deposited on the butterfly-like ZnO without the use of any reducing agents by simply stirring the solution at room temperature. Tartaric acid was present in the ZnO calcined at a low temperature (300 °C), which resulted in the self-reducing ability of ZnO toward the Au3+ ions. The Au NPs were closely connected with the ZnO matrix. This close connection resulted in hierarchical ZnO–Au composites with efficient photocatalytic activity for use in environmental remediation. Compared with the pure ZnO sample calcined at 300 °C, the hierarchical ZnO–Au composites showed an enhanced photocatalytic performance toward rhodamine B. The results of photodegradation indicated that the incorporation of the Au NPs drastically increased the photocatalytic efficiency by promoting the separation of the electron–hole pairs created by the absorption of photons.
Co-reporter:Xueling Song, Dehua Dong and Ping Yang
RSC Advances 2016 vol. 6(Issue 57) pp:51544-51551
Publication Date(Web):20 May 2016
DOI:10.1039/C6RA07874E
Clew-like ZnO mesocrystals comprised of ZnO nanoplates were created through a hydrothermal procedure in an aqueous solution using tartaric acid as the structure-directing additive. A detailed formation process of the nanoplate-based clew-like ZnO mesocrystal was investigated by varying reaction conditions especially the concentration of hexamethylenetetramine (HMT) and reaction time. It was found that the concentration of HMT played a significant role in the size distribution of ZnO products and the pileup degree of the nanoplates. Combined with the results obtained from the systematic time-dependent experiments, the formation of the nanoplate-based ZnO mesocrystal was mainly ascribed to the synergistic effect of the dipole moment generated among nanoplates and the electric field derived from a pre-formed inner core. The photocatalytic activity of samples synthesized using different HMT concentrations was also investigated. The results demonstrated that the adsorption percentage in the dark and degradation efficiency under UV-light irradiation were gradually improved with increasing the concentration of HMT. This was mainly ascribed to the increased specific surface area which promoted the migration of photon-generated carriers between the photocatalysts and rhodamine B (RhB) molecules.
Co-reporter:Yumeng Liu, Junpeng Wang and Ping Yang
RSC Advances 2016 vol. 6(Issue 41) pp:34334-34341
Publication Date(Web):30 Mar 2016
DOI:10.1039/C6RA04430A
Highly efficient visible-light-driven Ag2O/g-C3N4, Ag/g-C3N4, and BiOBr/g-C3N4 heterostructured photocatalysts were prepared by solution synthesis methods at room temperature. Compared with Ag/g-C3N4 (1:30 mass ratio) and Ag2O/g-C3N4 (2:1 mass ratio) photocatalysts, the BiOBr/g-C3N4 composite (1:3) displayed enhanced photocatalytic activities for Rhodamine B (RhB) degradation under visible-light irradiation. The reaction kinetics of phenol RhB dye photodegradation of Ag2O/g-C3N4 (1:1, 2:1, 4:1 mass ratios) and BiOBr/g-C3N4 were fitted with the pseudo-first-order model, ln(C0/C) = kt, while the data of Ag/g-C3N4 and pure g-C3N4, Ag2O/g-C3N4 (1:20 mass ratio) were fitted with the zero-order model. The former has enhanced photocatalytic activity, and BiOBr/g-C3N4 composites exhibit the highest degrading rate for RhB. The enhanced photocatalytic activity of two dimensional BiOBr/g-C3N4 photocatalysts was mainly attributed to the formation of type II p–n heterojunctions, as well as the well-matched band gap and the synergetic effects between two components, which accelerate the separation efficiency of photogenerated electrons–holes at the interface. Finally, possible photocatalytic and charge separation mechanisms of Ag2O/g-C3N4 and BiOBr/g-C3N4 composites were proposed via active species capture experiments.
Co-reporter:Simin Lu, Ling Chen, Ping Yang and Katarzyna Matras-Postolek
RSC Advances 2016 vol. 6(Issue 23) pp:19620-19625
Publication Date(Web):12 Feb 2016
DOI:10.1039/C6RA01889K
The detection of catalase associated with various diseases is very important due to the fact that it is frequently downregulated in human cancer tissues. Noble metal nanomaterial-assisted sensors have achieved rapid development for wide applications but few for detecting catalase. Thus, a novel colourimetric strategy has been developed for the selective and rapid visual detection of catalase by using the decelerating etching of gold nanorods (NRs). In the presence of hexadecyltrimethylammonium bromide and SCN−, which can reduce the redox potential of Au(I)/Au (0), Au NRs would be etched by H2O2 along the longitudinal direction. As a consequence, the colour of solutions changed from bluish green to pink accompanied by the localized surface plasmon resonance (LSPR) extinction peak being shifted to short wavelength. In contrast, the etching process would be prohibited in the presence of catalase, and the colour and LSPR extinction peak of Au NRs would remain unchanged. Furthermore, this Au NR based sensor is applied to test paper that could be used in the detection of catalase in real samples. The discussion of the mechanism indicates that such a sensing method has an ideal performance in terms of sensitivity, selectivity, and linearity.
Co-reporter:Yunshi Liu, Ping Yang, Jia Li, Katarzyna Matras-Postolek, Yunlong Yue and Baibiao Huang
RSC Advances 2016 vol. 6(Issue 16) pp:13371-13376
Publication Date(Web):27 Jan 2016
DOI:10.1039/C5RA25878B
SiO2@SnO2 core–shell nanofibers (NFs) were successfully prepared by single-spinneret electrospinning and subsequent calcination process. The precursor solutions were prepared from poly(vinylpyrrolidone), SnO2 precursors, and tetraethylorthosilicate (TEOS) with prehydrolysis. The prehydrolysis of TEOS plays an important role for the formation of core–shell structure. After calcining, the resulting fiber sample had an amorphous SiO2 core and a shell consisted of SnO2 particles. The fibers with various morphologies were obtained through adjusting the molar ratio of Sn and Si and the possible formation mechanism of core–shell NFs was proposed. Both Kirkendall effect and grain growth played important roles for the formation of core–shell structure. Furthermore, SiO2 was used as support material to fix the SnO2 particles and avoid the collapse of the SnO2 structure. The amount of SnO2 precursors directly determined the compactness of the shell, resulting in the different gas sensing properties. The SiO2@SnO2 core–shell NF network sensor responds to ethanol, ammonia, benzene, toluene, chloroform, and hexane gases, but it exhibited enhanced gas response to ethanol with a short response time. Those SnO2 particles formed on the exterior of the fibers provided lots of contact area with the target gas to reduce resistance. In addition, the connectivity between particles also had certain influence on the electrical conductivity of the sample. The results demonstrate that single-spinneret electrospinning can also be used to prepare core–shell fibers with various applications.
Co-reporter:Xiaobin Dong, Ping Yang, Yunshi Liu, Changchao Jia, Dan Wang, Junpeng Wang, Ling Chen, Quande Che
Ceramics International 2016 Volume 42(Issue 1) pp:518-526
Publication Date(Web):January 2016
DOI:10.1016/j.ceramint.2015.08.140
One-dimensional ZnO nanostructures with various morphologies including nanotubes, nanobelts, solid fibers, nanochains, and porous nanotubes were created through adjusting the parameters in single-spinneret electrospinning and calcination processes. The evolution of morphology depended strongly on the viscosity of precursor solutions and calcination process. Namely, the nanotube was fabricated via a two-step calcination process while the nanochain and solid fiber were created using a one-step calcination process. The nanotubes consisted of small ZnO nanoparticles. Furthermore, the nanobelt was fabricated when much more zinc precursor was added to increase the viscosity of the precursor solution. A possible mechanism based on Kirkendall effect and the decomposition of polyvinyl pyrrolidone was proposed to explain the formation of ZnO nanotubes and other one-dimensional structures. The photocatalytic activity of these ZnO samples for the degradation of Rhodamine B under ultraviolet light was investigated, and nanobelts showed the best degradation efficiency. Besides, the deposition of Au nanoparticle on ZnO nanobelts can further enhance the photocatalytic performance due to the formation of ohmic contact.
Co-reporter:Haiyan He, Yanping Miao, Yingying Du, Jie Zhao, Yunshi Liu, Ping Yang
Ceramics International 2016 Volume 42(Issue 1) pp:97-102
Publication Date(Web):January 2016
DOI:10.1016/j.ceramint.2015.07.143
TiO2 nanobelts with uniform morphology were prepared via a hydrothermal method, and subsequent sulfuric acid treatment procedure was needed for the coarse surface. A nanocomposite of highly dispersed Ag2O nanoparticles on TiO2 nanobelts was designed with a wet-chemical deposition precipitation method. As-prepared samples were systematically characterized by field emission scanning electron microscope, transmission electron microscope, X-ray diffraction and photoluminescence spectra. The photocatalytic performance was investigated under UV light toward degradation of methyl orange (MO) dye aqueous solution. Compared with the pure TiO2 nanobelts, the Ag2O/TiO2 nanobelts represented a quick degradation rate for MO dye, and the best photocatalytic activity was obtained when the molar ratio value of Ag2O and TiO2 was 0.17. The enhanced photocatalytic activity could give the credit to the formation of heterostructure between Ag2O nanoparticles and TiO2 nanobelts, in which the Ag2O nanoparticles acted as electron capture agent to promote the separation of photoinduced electrons and holes.
Co-reporter:Yan Zhang, Ruixia Shi, Ping Yang, Xueling Song, Yuanna Zhu, Qian Ma
Ceramics International 2016 Volume 42(Issue 12) pp:14028-14035
Publication Date(Web):September 2016
DOI:10.1016/j.ceramint.2016.06.009
Abstract
The porous CeO2 nanofibers with diameter of 100–140 nm were successfully synthesized by single-capillary electrospinning of a Ce(NO3)3·6H2O/PVP precursor solution, followed by calcination. The preparation parameters, including solution parameters and process parameters, affecting the spinnability and the morphology of nanofibers were investigated and discussed systematically. And the effects of different calcination temperatures on the microstructure CeO2 nanofibers were also studied. A plausible mechanism was proposed to explain the formation process of the CeO2 nanofibers. The N2 adsorption-desorption isotherm analysis showed that the specific surface area and average pore size of the nanofibers were 195.75 g/m2 and 2.4 nm, respectively. Moreover, as absorbent, the porous CeO2 nanofibers adsorbed the MO effectively. The adsorption experiment indicated that the adsorption process can be divided into two stages, including quick adsorption and gradual adsorption. And the adsorption capacities were not only determined by the specific surface area, but closely related to the pore size. Finally, the adsorption data were modeled by the pseudo-first-order and pseudo-second-order kinetics equations. The results showed that the pseudo-second order kinetics could best describe the adsorption of MO onto the porous CeO2 nanofibers.
Co-reporter:Zhixiang Jiang, Katarzyna Matras-Postolek and Ping Yang
RSC Advances 2016 vol. 6(Issue 31) pp:25656-25661
Publication Date(Web):26 Feb 2016
DOI:10.1039/C6RA03408J
Several kinds of hydrophobic quantum dots (QDs) including CdSe, CdTe, CdSe/CdxZn1−xS, and CdTe/CdSe/ZnSe were fabricated via organic synthesis to observe morphology variation during shell coating. CdSe QDs prepared at a relatively high temperature revealed a hexagonal structure and rod morphology. On being coated with a CdxZn1−xS shell, tetrahedron and rod morphologies were observed. It was found that the reaction temperature and injection rate play important roles. The photoluminescence properties of the core/shell QDs depended strongly on their preparation conditions such as temperature and ligands. For CdSe cores created at a relatively low temperature, CdxZn1−xS shell coating resulted in the formation of cubic CdSe/CdxZn1−xS core/shell QDs. This is ascribed to the role of a CdS interlayer. In contrast, multishell CdTe/CdSe/ZnSe QDs revealed a spherical morphology. Furthermore, the self-assembly of QDs with hexagonal structures occurs while regular assembled structures were not observed for QDs with a cubic morphology according to their transmission electron microscopy images. This is ascribed to a dipole force between QDs. This phenomenon is just related to the morphology and crystal structures rather than their composition.
Co-reporter:Yan Zheng, Zhixiang Jiang and Ping Yang
RSC Advances 2016 vol. 6(Issue 19) pp:15485-15491
Publication Date(Web):29 Jan 2016
DOI:10.1039/C5RA27740J
Carambola-like TiO2 consisting of nanosheets with exposed {001} facets was synthesized via a one-step solvothermal method for the first time. The carambola-like TiO2 was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller nitrogen adsorption isotherm experiments. The formation mechanism of the carambola-like TiO2 is discussed by investigating the effect of reaction time, temperature and the volume of hydrofluoric acid. The results from different growth stages demonstrated that the formation of carambola-like TiO2 included alcoholysis of precursor to nucleation, nuclei growth, dissolution–recrystallization growth and further growth. Reaction temperatures affected the morphologies and surface areas of carambola-like TiO2 samples. The photocatalytic performances of samples prepared at different temperatures were tested. The carambola-like TiO2 sample prepared at 160 °C exhibited the best photocatalytic activity. Such enhanced photocatalytic performance is ascribed to the large surface area and the exposed {001} facets with high activity.
Co-reporter:Yingying Du;Katarzyna Matras-Postolek
Journal of Nanoparticle Research 2016 Volume 18( Issue 2) pp:
Publication Date(Web):2016 February
DOI:10.1007/s11051-016-3347-8
A silanization process was employed to transfer hydrophobic quantum dots (QDs) prepared via an organic route at high temperature into water phase. The QDs were further coated with a thin organic SiO2 shell to form QDs@SiO2 composite nanoparticles by ligand exchange or remaining initial organic ligands on the surface. In this study, QDs with different ligands, either trioctylphosphine oxide (TOPO) or oleic acid (OA), were employed to investigate the effects of ligands on the reverse micelles in preparing QDs@SiO2 nanoparticles. In the preparing process, hydrophobic QDs were silanized by partially hydrolyzed tetraethyl orthosilicate (TEOS). For TOPO-capped CdSe QDs, surface TOPO ligands were completely replaced by partially hydrolyzed TEOS. As for OA-capped CdSe/CdxZn1−xS QDs, surface OA ligands were partially replaced. It was found that the ligand exchange drastically reduced the photoluminescence (PL) efficiency of CdSe QDs. Furthermore, the cytotoxicity studies of QDs@SiO2 have been carried out in detail. The results indicate that CdSe/CdxZn1−xS QDs@SiO2 composite nanoparticles exhibit lower cytotoxicity compared with CdSe QDs@SiO2, because the SiO2 shell and remained OA ligand layer can effectively prevent the leakage of toxic Cd2+ ions. Meanwhile, it was found that these CdSe/CdxZn1−xS QDs@SiO2 nanocomposites could keep excellent PL properties even for 24 h incubating with Siha cells, which indicating that our prepared composite nanoparticles are potentially applicable for cell imaging in biological systems.
Co-reporter:Dr. Changchao Jia; Ping Yang; Jia Li; Baibiao Huang; Katarzyna Matras-Postolek
ChemCatChem 2016 Volume 8( Issue 4) pp:839-847
Publication Date(Web):
DOI:10.1002/cctc.201501045
Abstract
Ag nanowire@TiO2 (Ag NW@TiO2) heterostructures with core–shell, necklace-like, and particle-decorated morphologies were fabricated to investigate the evolution of the photocatalytic properties. The deposition of the TiO2 phase on the surface of the Ag NWs was achieved through a solvothermal method. Thioglycolic acid (TGA) not only solves the tricky issue of substantial lattice mismatch between the Ag NW core and TiO2 shell, but also plays an important role in precisely controlling how the TiO2 is coated on the Ag NW surface. H2O molecules affect the deposition of the TiO2 phase on the Ag NWs. The photocatalytic activity of the Ag NW@TiO2 heterostructures with different morphologies was evaluated by degradation of methyl orange. The molar ratio of TiO2 to Ag is crucial for the photocatalytic activity, and the Ag NW@TiO2 sample with core–shell structure exhibits an excellent performance compared with the others, owing to the TiO2 phase being densely attached to the Ag NW surface, which forms a well-developed combined interface.
Co-reporter:Jie Zhao, Ping Yang, Hsueh-Shih Chen, Jia Li, Quande Che, Yuanna Zhu and Ruixia Shi
Journal of Materials Chemistry A 2015 vol. 3(Issue 11) pp:2539-2547
Publication Date(Web):21 Jan 2015
DOI:10.1039/C4TC02752C
We investigated the marked morphological changes of α-Fe2O3 nanocrystals from nanoplates to nanospindles via an environmentally friendly hydrothermal route. An aqueous Fe salt was used as the precursor and the volume ratio of ammonia to ethylene glycol was varied. The product was uniform and obtained at a high yield. By simply increasing the ratio of the aqueous phase, the morphology could be continuously tuned from nanoplates to nanospindles with the (001) facets gradually disappearing. A fundamental understanding of the shape evolution was obtained via a series of characterizations including X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. The NO3− ions and NH3 molecules played vital parts at increased temperatures, not only in the phase structure of the iron oxide, but also in the formation of different hematite morphologies with different properties. The decrease in the photocatalytic efficiency in the visible region with the change from nanoplates to nanospindles under the same conditions indicated that the increase in the number of exposed (001) facets promoted the photocatalytic performance. The magnetic and electrochemical properties of typical morphologies were investigated and showed the potential applications of the nanostructures in various fields.
Co-reporter:Sha Zhang, Hsueh-Shih Chen, Katarzyna Matras-Postolek and Ping Yang
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 45) pp:30300-30306
Publication Date(Web):14 Oct 2015
DOI:10.1039/C5CP04860E
In this paper, ZnO nanoflowers (NFs) were fabricated by thermal decomposition in an organic solvent and their application in gas sensors and photocatalysis was investigated. These single crystal ZnO NFs, which were observed for the first time, with an average size of ∼60 nm and were grown along the {100} facet. It was suggested that oleylamine used in the synthesis inhibited the growth and agglomeration of ZnO through the coordination of the oleylamine N atoms. The NFs exhibited excellent selectivity to acetone with a concentration of 25 ppm at 300 °C because they had a high specific surface area that provided more active sites and the surface adsorbed oxygen species for interaction with acetone. In addition, the ZnO NFs showed enhanced gas sensing response which was also ascribed to abundant oxygen vacancies at the junctions between petals of the NFs. Furthermore, ZnO–reduced graphene oxide (RGO) composites were fabricated by loading the ZnO NFs on the surface of the stratiform RGO sheet. In the photodegradation of rhodamine B tests, the composite revealed an enhanced photocatalytic performance compared with ZnO NFs under UV light irradiation.
Co-reporter:Changchao Jia, Ping Yang, Hsueh-Shih Chen and Junpeng Wang
CrystEngComm 2015 vol. 17(Issue 15) pp:2940-2948
Publication Date(Web):03 Feb 2015
DOI:10.1039/C4CE02358G
Monodispersed mesoporous anatase titania (TiO2) hollow microspheres with controllable morphology and size are prepared via thioglycolic acid (TGA) chemically induced self-assembly for the first time. The formation process of TiO2 hollow spheres consists of three steps: hydrolysis of titanium butoxide (TBT) forming Ti-oxo clusters followed by connecting TGA via hydrogen bonding, assembly of the Ti-oxo clusters to solid spheres, and transformation of the TiO2 solid spheres into hollow spheres through the synergistic effect of thermodynamic (Ostwald ripening process) and kinetic (gas release) factors. TGA molecules firstly provide acidic conditions slowing down the hydrolysis rate of TBT, then control the formation of solid spheres, and finally create hollow structures. The prepared TiO2 hollow sphere with mesoporous structure has a large specific surface area (292.20 m2 g−1). Photocatalytic degradation of methyl orange (MO) by the TiO2 hollow spheres after reflux treatment improves significantly, owing to removal of TGA molecules from the TiO2 hollow spheres. Moreover, photocatalytic water splitting of highly crystalline TiO2 hollow spheres decorated with Pt nanoparticles exhibits an impressive performance for producing H2 (0.477 mmol h−1).
Co-reporter:Jie Zhao, Hsueh-Shih Chen, Katarzyna Matras-Postolek and Ping Yang
CrystEngComm 2015 vol. 17(Issue 37) pp:7175-7181
Publication Date(Web):04 Aug 2015
DOI:10.1039/C5CE01251A
Hematite (α-Fe2O3) crystals with different morphologies were successfully fabricated via an environmental friendly hydrothermal route by applying alkaline earth metal ions along the row from Mg2+ to Ba2+ ions as structure-directing agents without employing any surfactants or templates. It was found that the ionic radii mismatch degree between the alkaline earth metal ions and Fe3+ ions played a vital role in determining the crystalline phase and morphology of the iron oxide. Pure α-Fe2O3 crystals were created with Mg2+, Ca2+ and Sr2+ ions (30.9%, 81.8% and 114.5% ionic radii mismatch degree with that of Fe3+) as additives while goethite iron oxide nanoparticles were obtained with Ba2+ ions (145.5% ionic radius mismatch degree with that of Fe3+) as additives. Mg2+ ion-induced α-Fe2O3 crystals had a quasi-cube structure with a rough surface while Ca2+-induced α-Fe2O3 crystals had a quasi-cube structure with a very smooth surface, and the edge length of which is much smaller than that of the Mg2+ ion-controlled α-Fe2O3 crystals. However, when Sr2+ ions were introduced into the reaction system, the product tended to have plate-like structures. The effects of alkaline earth metal ions on the crystal growth rate and final morphology through anisotropic incorporation were proposed in this paper. Moreover, the effects of incorporation of alkaline earth metal ions on the magnetic properties of α-Fe2O3 crystals were investigated.
Co-reporter:Changchao Jia, Hsueh-Shih Chen and Ping Yang
CrystEngComm 2015 vol. 17(Issue 26) pp:4895-4902
Publication Date(Web):21 May 2015
DOI:10.1039/C5CE00705D
In this paper, TiO2 beads were deposited on Ag nanowires to create necklace-like Ag nanowire@TiO2 (Ag NW@TiO2) heterostructures for the first time. They were fabricated via a two-step synthetic method, including the preparation of uniform Ag NWs and the deposition of TiO2 on the Ag surface. Thioglycolic acid (TGA) molecules were used as binding agents to solve the tricky issue of substantial lattice mismatch between the Ag NW core and the TiO2 shell. The amount of water and the permittivity of the solvents are found to be important factors for the formation of the necklace-like heterostructures. Moreover, by varying the amount of titanium butoxide (TBT), the diameter of the TiO2 beads can be feasibly changed. The photocatalytic performance of necklace-like Ag NW@TiO2 was evaluated via degradation of methyl orange (MO) under ultraviolet (UV) light. The results reveal that the molar ratio of TiO2 to Ag contributes to the synergistic effect on the photocatalytic activity, and the best Ti/Ag ratio is found to be 2.8 for the highest photocatalytic performance of the Ag NW@TiO2 heterostructures.
Co-reporter:Ping Yang, Changchao Jia, Haiyan He, Ling Chen and Katarzyna Matras-Postolek
RSC Advances 2015 vol. 5(Issue 22) pp:17210-17215
Publication Date(Web):03 Feb 2015
DOI:10.1039/C4RA16325G
Ag/AgCl nano heterostructures with different degrees of molecular homogeneity and high photocatalytic activity have been created through a two-step synthesis in ethanol via an in situ oxidation route at room temperature. The result offers an alternative method for synthesizing molecular homogeneous metal/semiconductor nanocomposites. The heterostructures with AgCl ratios of 50% and 80% revealed excellent performance for the photocatalytic degradation of methyl orange molecules. This technique had the advantages of convenient operation, low cost, and mass production and built up a great molecularly homogeneous composite structure of Ag/AgCl which exhibited high photocatalytic activity and stability towards the decomposition of organic methyl orange.
Co-reporter:Yumeng Liu, Junpeng Wang, Ping Yang and Katarzyna Matras-Postolek
RSC Advances 2015 vol. 5(Issue 76) pp:61657-61663
Publication Date(Web):13 Jul 2015
DOI:10.1039/C5RA07079A
One-dimensional (1D) titanium dioxide (TiO2) nanowires and nanobelts have been fabricated via a hydrothermal synthesis and subsequent calcination process in different atmospheres. Ti2O3 was used as a raw material to directly provide Ti3+ in the resulting TiO2 nanomaterials. The Ti3+ concentration in TiO2 could be adjusted by annealing TiO2 precursors in different atmospheres. The photocatalysis activity of samples calcinated in air or nitrogen with different Ti3+ concentrations was investigated. By means of analyzing photocatalytic degradation curves, 1D TiO2 nanowires calcinated in nitrogen revealed enhanced photocatalysis activity compared with that one calcinated in air while the TiO2 nanobelts exhibited an opposite result. The enhanced photocatalytic activity is ascribed to the enhanced light absorption from the narrowing band gap. The proper concentrations of Ti3+ and oxygen vacancies result in the efficient separation of photo-generated charge carriers in these nanomaterials.
Co-reporter:Yunshi Liu, Ping Yang, Jia Li, Katarzyna Matras-Postolek, Yunlong Yue and Baibiao Huang
RSC Advances 2015 vol. 5(Issue 119) pp:98500-98507
Publication Date(Web):13 Nov 2015
DOI:10.1039/C5RA23446H
SnO2 and SnO2/CeO2 one dimensional (1D) nanostructures with various morphologies including solid nanofibers (NFs), nanobelts (NBs), nanotubes (NTs), and wire-in-tubes (WTs) were successfully prepared via a single-spinneret electrospinning process and a subsequent heat-treatment by adjusting the heating rate and the amount of CeO2. The interesting morphology evolution of samples from NTs to NBs was reported with increasing amounts of CeO2. In addition, SnO2 particles existed on the surface of the CeO2 matrix to form diverse structures in the 1D nanofibers. The band gap of the composite oxides decreased with the addition of CeO2. Compared with other nanostructures, SnO2/CeO2 NTs exhibited superior gas sensing properties, such as the highest response to ethanol. Due to the existence of Ce3+ and oxygen vacancies and the hollow structure, SnO2/CeO2 NTs revealed great CO oxidation performance, indicating the enhanced interactions between the catalyst and the target gas. These excellent properties were attributed to the prominent 1D hollow morphology, the good dispersion of SnO2 nanoparticles on the surface of the CeO2 matrix, the ideal crystallinity, and the composite interactions between the two oxides. In addition, the current method could be utilizable to fabricate other metal oxides with various morphologies for property controlling and important applications.
Co-reporter:Yunshi Liu, Hsueh-Shih Chen, Jia Li and Ping Yang
RSC Advances 2015 vol. 5(Issue 47) pp:37585-37591
Publication Date(Web):17 Apr 2015
DOI:10.1039/C5RA02392K
One dimensional (1D) CeO2 nanostructures have been successfully fabricated via a single nozzle electrospinning method and subsequent two-step calcination route by adjusting heating rates. The formation process of CeO2 nanotubes (NTs) and nanobelts (NBs) was investigated by observing the morphology evolution of fibers during calcination. Control of the heat-treatment procedure including solvent evaporation, the Kirkendall effect, polymer softening, and thermal decomposition of poly(vinylpyrrolidone) plays an important role in the morphologies of the samples. Well-dispersed and small Au nanoparticles (NPs) were deposited on 1D CeO2 nanostructures through a direct wet-chemical reaction or adding Au precursors during electrospinning. The results of the catalytic performance for CO oxidation suggest that CeO2 NTs display enhanced catalytic activities compared with CeO2 NBs. The loading of Au NPs significantly enhanced the catalytic properties of 1D CeO2 nanostructures. Because of the large surface areas, good crystallinity and the strong interfacial interactions between Au NPs and the CeO2 matrix, the 1% Au/CeO2 NTs exhibit superior catalytic activity with onset CO conversion at 65 °C and complete CO conversion at 142 °C.
Co-reporter:Xueling Song, Ping Yang, Changchao Jia, Ling Chen and Katarzyna Matras-Postolek
RSC Advances 2015 vol. 5(Issue 42) pp:33155-33162
Publication Date(Web):01 Apr 2015
DOI:10.1039/C5RA01255D
Urchin-like AlOOH microspheres with large specific surface area were successfully synthesized by a one-pot chemical induced solvothermal method. Thioglycolic acid (TGA) was used as inductive agent to fabricate AlOOH with various morphologies. Al(OH)3–TGA clusters played an important role in the formation of AlOOH with unique spherical morphology. The preparation parameters such as reaction time, reaction temperature, and the volume ratio of deionized water to ethanol influenced the formation of AlOOH microspheres. Urchin-like AlOOH microspheres with uniform morphology were created through reaction for 20 h at either 150 or 220 °C. The specific surface area and pore-size distribution of urchin-like AlOOH were determined by N2 absorption–desorption measurement, indicating that the AlOOH microspheres exhibited porous properties and a large specific surface area of 319.15 m2 g−1. A possible formation mechanism for the urchin-like AlOOH microspheres was proposed. Urchin-like AlOOH spheres prepared at 220 °C for 20 h revealed high efficiency for the removal of Congo red pollutant from waste water compared with other samples.
Co-reporter:Ruixia Shi, Xueling Song, Jia Li, Ping Yang
Materials Chemistry and Physics 2015 Volume 156() pp:61-68
Publication Date(Web):15 April 2015
DOI:10.1016/j.matchemphys.2015.02.020
•Hierarchical ZnO constructed by twinned structures have been synthesized.•The formation mechanisms of ZnO with twinned structure were discussed.•Football-like microspheres were obtained due to the slower nucleation and growth.•Hamburger-like ZnO was formed due to the amount of initial nuclei and growth units.•Pore sizes have important effects on the photocatalytic activity of sample.Various hierarchical ZnO architectures constructed by twinned structures have been synthesized via a trisodium citrate assisted hydrothermal method on a large scale. The probable formation mechanisms of hierarchical ZnO structures with twinned structure were proposed and discussed. The hierarchical ZnO with twinned structures are composed of two hemispheres with a center concave junction to join them together at their waists. The ZnO microspheres with rough surfaces were obtained when the concentration of trisodium citrate is 0.1 M. However, the football-like microspheres consisted of hexagonal nanosheets were formed when adding glycerol into the water, which should be attributed to the slower nucleation and growth rate of nanocrystals. The hamburger-like ZnO with different aspect ratio and nonuniform ZnO microspheres were generated due to the different quantity of initial nuclei and growth units when simply modulating the concentration of trisodium citrate. The surface area of football-like ZnO is about 3.51 times of microspheres composed of irregular particles. However their photocatalytic performances are similar under UV light irradiation, which indicates that pore sizes of the sample have more important influences on the photocatalytic activity.
Co-reporter:Yongqiang Cao, Ning Liu, Ping Yang, Ruixia Shi, Qian Ma, Aiyu Zhang, Yuanna Zhu, Junpeng Wang, Jianrong Wang
Materials Chemistry and Physics 2015 s 149–150() pp: 51-58
Publication Date(Web):
DOI:10.1016/j.matchemphys.2014.09.030
Co-reporter:Ping Yang, Dan Wang, Jie Zhao, Ruixia Shi
Materials Research Bulletin 2015 65() pp: 36-41
Publication Date(Web):
DOI:10.1016/j.materresbull.2015.01.002
Co-reporter:Xiaoyu Li;Xiao Zhang;Dr. Changchao Jia;Katarzyna Matras-Postolek; Ping Yang
ChemPlusChem 2015 Volume 80( Issue 5) pp:865-870
Publication Date(Web):
DOI:10.1002/cplu.201500032
Abstract
A two-step synthesis was developed to fabricate Ag/AgBr necklace-like nano-heterostructures at room temperature. Multiple crystalline Ag nanowires were used as templates following an oxidation route in situ from CuBr2 to create Ag/AgBr heterostructures. Polyvinylpyrrolidone can govern the formation of one-dimensional Ag/AgBr necklace-like nano-heterostructures. The composition of the heterostructures was adjusted by changing the amount of CuBr2. Experimental conditions were optimized. In particular, the concentration and injection rate of copper bromide solution play an important role in controlling the oxidation of the Ag nanowires for the purpose of adjusting the morphology of the Ag/AgBr heterostructures. As a result, the heterostructures with 40 mol % AgBr displayed a regular necklace-like morphology. Under visible-light irradiation, Ag/AgBr necklace-like heterostructures with AgBr molar ratios of 10 to 50 % exhibited enhanced plasmonic photocatalytic performance for the degradation of organic pollutants (methyl orange, methylene blue, and rhodamine B).
Co-reporter:Yingying Du, Ping Yang, Hsueh-Shih Chen, Quande Che, Yunshi Liu, Haiyan He, Yanping Miao and Jie Zhao
RSC Advances 2014 vol. 4(Issue 104) pp:59733-59739
Publication Date(Web):04 Nov 2014
DOI:10.1039/C4RA08770D
Highly luminescent hydrophobic CdSe and CdSe/CdxZn1−xS quantum dots (QDs) were synthesized via an organic route. The phase transfer of the QDs was carried out through a ligand exchange from 3-aminopropyltrimethoxysilane (APS) instead of an organic capping agent to get aqueous QDs. A functional sol–gel SiO2 sol with a high QD concentration was obtained from the aqueous QD colloidal solution with APS through the hydrolysis and condensation which subsequently occurred. Flexible inorganic SiO2 films with QDs were fabricated via various methods. The photodegradation experiments of the resulting films were completed. It is surprising that the QDs in films were revealed to be highly stable. Especially, the PL intensity of the films increased dramatically after irradiation by 365 nm UV light. By integrating a thin CdSe QD–silica film on a solar cell, the enhanced current demonstrated that a thin film can facilitate the continuous development of solar cells. Because of their high PL brightness, multicolor emission, flexibility and stability, these films will have great potential applications.
Co-reporter:Ping Yang, Hsueh-Shih Chen, Sha Zhang, Jie Zhao, Yingying Du, Yanping Miao, Haiyan He and Yunshi Liu
RSC Advances 2014 vol. 4(Issue 82) pp:43800-43805
Publication Date(Web):02 Sep 2014
DOI:10.1039/C4RA07399A
CdSe/Cd0.5Zn0.5S core/shell quantum dots (QDs) with high photoluminescence (PL) efficiency up to 85% were fabricated in organic solutions at high temperature via an anisotropic shell growth on CdSe nanorods. The core/shell QDs with PL peak wavelengths from green to red were obtained by controlling the size of the cores and the thickness of the array Cd0.5Zn0.5S shells. Both the cores and the core/shell QDs revealed narrow size distributions which resulted in narrow PL spectra. Green-emitting CdSe cores with a Se-rich surface revealed a long average lifetime of ∼44 ns. After being coated with Cd0.5Zn0.5S shells, the average lifetime of QDs decreased drastically up to ∼23 ns. The average decay time of the core/shell QDs depended on their shell thickness. The temperature-dependent PL in a temperature range of 293 to 393 K was investigated for CdSe cores and highly luminescent CdSe/Cd0.5Zn0.5S core/shell QDs. Luminescent quenching occurred with increasing temperature for the cores even though the cores exhibited high crystallinity. In contrast, with increasing temperature, the emission PL peak wavelength of the core/shell QDs shifts towards lower energies, the PL bandwidth increases a little and the PL efficiencies decrease slightly. The red-shifted degree of the PL spectra with temperature is small (less than 10 nm).
Co-reporter:Ping Yang, Hsueh-Shin Chen, Junpeng Wang, Quande Che, Qian Ma, Yongqiang Cao and Yuanna Zhu
RSC Advances 2014 vol. 4(Issue 39) pp:20358-20363
Publication Date(Web):14 Apr 2014
DOI:10.1039/C4RA01739K
A sol–gel SiO2 film prepared from 3-aminopropyltrimethoxysilane (APS) has been developed as an excellent medium to encapsulate both hydrophobic and hydrophilic quantum dots (QDs). The film was fabricated by spin and dip coating on flat substrates as well as by a spraying approach on various substrates with a 3-dimensional (3D) surface. Pre-heat-treatment of the substrate plays an important role for creating homogeneous films on a 3D surface. In the case of aqueous CdTe and ZnSe0.9Te0.1 QDs, APS did not decrease the photoluminescence (PL) efficiency of the QDs. For hydrophobic QDs, a phase transfer from oil to water phase was first performed through the ligand exchange process between APS and the capping agent. By mixing QDs with different emitting colors, silica gel with white-light emission was obtained. Based on hydrophobic and hydrophilic QDs, white-light-emitting diodes with adjustable chromaticity coordinates were fabricated using a UV-emitting InGaN chip as excitation source. Because of the facile preparation procedure, high stability, and high PL efficiency, the magic film shows great potential for use in white-lighting-emission applications.
Co-reporter:Xiaobin Dong, Ping Yang, Ruixia Shi
Materials Letters 2014 Volume 135() pp:96-98
Publication Date(Web):15 November 2014
DOI:10.1016/j.matlet.2014.07.102
•Electrospinning technique is used to prepare a ZnO seed layer for the first time.•Electrospinning coating time plays an important role in controlling morphology.•Bundle-like and well-oriented ZnO nanorod arrays can be obtained by our strategy.ZnO nanorod arrays have been fabricated on glass substrates via an electrospinning assisted hydrothermal method at relatively low temperature. This is the first time using electrospinning technique to create a ZnO seed layer. Because of the seeds unique dispersed in the substrate, well-defined ZnO nanorods with a diameter range of 100–130 nm, which possess the typical hexagonal wurtzite structure, were developed into several bundles after a hydrothermal growth. The plausible formation mechanism of ZnO bundles was discussed. With prolonging coating time, the density of ZnO bundles increased. Finally, eventually densely well-oriented ZnO nanorod arrays are obtained. Such an electrospinning assisted method makes a possible for the large-scale fabrication of ZnO nanorod arrays. This method will be useful for the growth of other nanomaterials on substrates.
Co-reporter:Changchao Jia, Ping Yang, Aiyu Zhang
Materials Chemistry and Physics 2014 Volume 143(Issue 2) pp:794-800
Publication Date(Web):15 January 2014
DOI:10.1016/j.matchemphys.2013.10.015
•Multiple crystalline uniform silver nanowires created by a facile one-pot polyol-thermal method.•The silver nanowires were fabricated using glycerol together with ethylene glycol.•The yield of the silver nanowires dependent on the volume ratio of ethylene glycol and glycerol.•V-shaped silver nanostructure was obtained through adjusting parameters.The large scale synthesis of multiple crystalline silver nanowires (NWs) with uniform diameter were carried out by using glycerol and ethylene glycol (EG) as co-mediated solvents in the presence of poly(vinyl pyrrolidine) (PVP). Experimental results and structural characterizations reveal that Ag NWs are evolved from the multiple crystalline seeds initially generated by the reduction of AgNO3 with EG and glycerol. Owing to the different reduction ability and viscosity of EG and glycerol, which play an important role for controlling the nucleation at the beginning of reaction, glycerol with high viscosity slows down the migration velocity of Ag0 in favor of forming the uniform Ag NWs with small diameter (40 nm) in the presence of PVP molecules selectively adsorbed on the surface of Ag seeds. The yield of the Ag NWs is dependent on the volume ratio of EG and glycerol. In the absence of EG, large amount of Ag nanoparticles (NPs) and few Ag NWs were created. In contrast, Ag nanorods and polyhedral particles are prepared in the case of no glycol added. This paper provides a new approach for the large scale synthesis of Ag NWs with uniform diameter by simply adjusting the solvent components. Furthermore, V-shaped Ag nanostructure was obtained and the possible growth mechanism was discussed.Large scale synthesis of multiple crystalline silver nanowires with uniform diameter were carried out using glycerol and ethylene glycol solvents in the presence of poly(vinyl pyrrolidine) as a polymer surfactant.
Co-reporter:Dan Wang, Ping Yang, Yuanna Zhu
Materials Research Bulletin 2014 49() pp: 514-520
Publication Date(Web):
DOI:10.1016/j.materresbull.2013.09.019
Co-reporter:Qian Ma;Mengkai Lu;Aiyu Zhang;Yongqiang Cao
Luminescence 2014 Volume 29( Issue 4) pp:386-392
Publication Date(Web):
DOI:10.1002/bio.2557
ABSTRACT
In this study, a series of LaNbTiO6:RE3+ (RE = Tb, Dy, Ho) down-converting phosphors were synthesized using a modified sol–gel combustion method, and their photoluminescence (PL) properties were investigated as a function of activator concentration and annealing temperature. The resultant particles were characterized using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, UV/Vis diffuse reflectance spectroscopy and PL spectra. The highly crystalline LaNbTiO6:RE3+ (RE = Tb, Dy, Ho) phosphors with an average size of 200–300 nm obtained at 1100°C have an orthorhombic aeschynite-type structure and exhibit the highest luminescent intensity in our study range. The emission spectra of LaNbTiO6:RE3+ (RE = Tb, Dy, Ho) phosphors under excitations at UV/blue sources are mainly composed of characteristic peaks arising from the f–f transitions of RE3+, including 489 nm (5D4 7F6) and 545 nm (5D4 7F5) for Tb3+, 476 and 482 nm (4F9/2 6H15/2) and 571 nm (4F9/2 6H13/2) for Dy3+, and 545 nm (5F4 + 5S2 5I8) for Ho3+, respectively. The luminescent mechanisms were further investigated. It can be expected that these phosphors are of intense interest and potential importance for many optical applications. Copyright © 2013 John Wiley & Sons, Ltd.
Co-reporter:Ning Liu
Luminescence 2014 Volume 29( Issue 6) pp:566-572
Publication Date(Web):
DOI:10.1002/bio.2581
ABSTRACT
Hybrid SiO2-coated CdTe/CdSe quantum dots (QDs) were prepared using CdTe/CdSe QDs prepared by hydrothermal synthesis. A CdSe interlayer made CdTe/CdSe cores with unique type II heterostructures. The hybrid SiO2-coated CdTe/CdSe QDs revealed excellent photoluminescence (PL) properties compared with hybrid SiO2-coated CdTe QDs. Because of the existence of spatial separations of carriers in the type II CdTe/CdSe core/shell QDs, the hybrid QDs had a relatively extended PL lifetime and high stability in phosphate-buffered saline buffer solutions. This is ascribed to the unique components and stable surface state of hybrid SiO2-coated CdTe/CdSe QDs. During the stabilization test in phosphate-buffered saline buffer solutions, both static and dynamic quenching occurred. The quenching mechanism of the hybrid QDs was not suited with the Stern–Volmer equation. However, the relative stable surface of CdTe/CdSe QDs resulted in lower degradation and relative high PL quantum yields compared with hybrid SiO2-coated CdTe QDs. As a result, hybrid SiO2-coated CdTe/CdSe QDs can be used in bioapplications. Copyright © 2013 John Wiley & Sons, Ltd.
Co-reporter:Ping Yang;Yongqiang Cao;Xiaoyu Li;Ruili Zhang;Ning Liu ;Yulan Zhang
Luminescence 2014 Volume 29( Issue 5) pp:407-411
Publication Date(Web):
DOI:10.1002/bio.2560
ABSTRACT
Alloy CdTe1-xSex quantum dots (QDs) have been fabricated by an organic route using Cd, Te and Se precursors in a mixture of trioctylamine and octadecylphosphonic acid at 280 °C. The variation of photoluminescence (PL) peak wavelength of the CdTe1-xSex QDs compared with CdTe QDs confirmed the formation of an alloy structure. The Se component drastically affected the stability of CdTe1-xSex QDs. A Cd0.5Zn0.5S shell coating on CdTe1-xSex cores was carried out using oleic acid as a capping agent. CdTe1-xSex/Cd0.5Zn0.5S core/shell QDs revealed dark red PL while a yellow PL peak was observed for the CdTe1-xSex cores. The PL efficiency of the core/shell QDs was drastically increased (less than 1% for the cores and up to 65% for the core/shell QDs). The stability of QDs in various buffer solutions was investigated. Core/shell QDs can be used for biological applications because of their high stability, tunable PL and high PL efficiency. Copyright © 2013 John Wiley & Sons, Ltd.
Co-reporter:Xiaobin Dong; Ping Yang;Junpeng Wang; Baibiao Huang
ChemPlusChem 2014 Volume 79( Issue 12) pp:1681-1690
Publication Date(Web):
DOI:10.1002/cplu.201402182
Abstract
ZnO rhombic sheets consisting of small particles with a size range of 150–250 nm have been prepared successfully using zinc glycerolate as a template through calcining at 600 °C. The crystallinity of the small particle plays an important role toward highly efficient photocatalysis. The sheet consisting of regular ZnO particles with fewer surface defects revealed enhanced photocatalysis compared with that constructed from small ZnO nanoparticles. Monodisperse Ag2O nanoparticles were deposited on the rhombic sheet. Highly efficient photocatalysis was observed after Ag2O nanoparticle decoration under ultraviolet and visible-light irradiation for degradation of methyl orange (MO) and 2,4-dichlorophenol (2,4-DCP). The results of photocatalysis investigations demonstrated that the ZnO rhombic sheets with Ag2O/ZnO molar ratio of 1:6 had great activity for decomposing MO and 2,4-DCP. Ag2O/ZnO rhombic sheets are favorable for the separation of the photocatalyst, which is important for applications.
Co-reporter:Changchao Jia; Ping Yang; Baibiao Huang
ChemCatChem 2014 Volume 6( Issue 2) pp:611-617
Publication Date(Web):
DOI:10.1002/cctc.201300804
Abstract
Ag/AgCl necklace-like nano-heterostructures with an average diameter of 55 nm were prepared by a facile in situ oxidation process. As a result of the presence of multiple crystalline Ag nanowires with lots of grain boundaries, uniform Ag/AgCl necklace-like heterostructures can be successfully obtained in the presence of polyvinylpyrrolidone (PVP). Ag and AgCl are evenly distributed in the necklace-like structures, which were divided into a number of tiny units that consisted of Ag and AgCl and enabled easy electron transfer. In contrast, a loose Ag/AgCl structure with large particles was prepared without the addition of PVP. A formation mechanism of the Ag/AgCl nano-heterostructures was proposed. Furthermore, the molar ratio of Ag and AgCl plays an important role in the photocatalytic activity of the nano-heterostructures, which can be tuned simply. The results of photocatalytic investigations demonstrate that the Ag/AgCl heterostructures with an 85 % AgCl component have an excellent activity for the decomposition of organic pollutants and water splitting to produce oxygen.
Co-reporter:Ruixia Shi, Ping Yang, Xiaobin Dong, Changchao Jia, Jia Li
Materials Science and Engineering: B 2014 Volume 186() pp:68-72
Publication Date(Web):August 2014
DOI:10.1016/j.mseb.2014.03.011
•Upright-standing ZnO sheet microcrystals were hydrothermally fabricated.•The ZnO sheets were prepared with sodium oxalate at 70 °C without any surfactant.•The preferable adsorption of oxalate anions causes the formation of ZnO sheet.•The continuous growth in six directions leads to the formation of hexagonal sheets.Large-scale upright-standing ZnO sheet microcrystals were fabricated on Zn substrate using sodium oxalate as structure-directing agent by a hydrothermal method at low temperature (70 °C) without any surfactant. The sheets are about 3–5 μm in dimension and 100–300 nm in thickness. The strong and narrow diffraction peaks of ZnO indicate that the sample has a good crystallinity and size. The morphology of sheet-like ZnO varied with the concentrations of sodium oxalate and reaction time. The sheet-like ZnO would transform into rod-like ones when sodium oxalate was substituted by equivalent sodium acetate. The formation of sheet-like ZnO is attributed to the preferable adsorption of oxalate anions on (0 0 0 1) face of ZnO, which inhibits the intrinsic growth of ZnO. Additionally, the continuous growth in six (0 1 −1 0) directions that have the lowest surface energy leads to the formation of hexagonal sheets.
Co-reporter:Xiaobin Dong; Ping Yang;Junpeng Wang; Baibiao Huang
ChemPlusChem 2014 Volume 79( Issue 12) pp:
Publication Date(Web):
DOI:10.1002/cplu.201402305
Abstract
Invited for this month’s cover is the group of Prof. Ping Yang from the University of Jinan, China. This cover picture symbolizes the beauty of a clean environment, while the inset outlines the photocatalysis mechanism of ZnO rhombic sheets decorated with Ag2O nanoparticles useful for degradation of pollutants. Read the full text of the article at 10.1002/cplu.201402182
Co-reporter:Xiaobin Dong; Ping Yang;Junpeng Wang; Baibiao Huang
ChemPlusChem 2014 Volume 79( Issue 12) pp:
Publication Date(Web):
DOI:10.1002/cplu.201402306
Co-reporter:Dan Wang, Ping Yang, Qian Ma, Yongqiang Cao, Aiyu Zhang and Baibiao Huang
CrystEngComm 2013 vol. 15(Issue 44) pp:8959-8965
Publication Date(Web):17 Sep 2013
DOI:10.1039/C3CE41085D
Micro- and nano-structures of iron oxide with tunable morphologies were fabricated through a solvothermal process by adjusting experimental parameters. In this route, the ethylene glycol (EG) solution of ferric chloride hexahydrate (FeCl3·6H2O), sodium bicarbonate (NaHCO3), and ethylenediamine (EDA) was heat-treated to create the micro- and nano-structures of Fe3O4, where EG acted as both solvent and reducing agent. NaHCO3 and EDA were crucial for the morphology and size of these micro- and nano-structures. Fe3O4 micro- and nano-structures revealed solid, porous and hollow morphologies by changing the reaction time, the type of solvent, and the amount of EDA and NaHCO3. Fe3O4 nanoparticles were created by controlling experimental parameters. As the reaction progressed, nanoparticles aggregated together to form solid Fe3O4 spheres, and then inner nanoparticles dissolved and recrystallized onto the outer shell of Fe3O4 spheres having been obtained through agglomerating together and then gradually developing into hollow micro- and nano-spheres due to an Ostwald ripening mechanism. Hematite (α-Fe2O3) was synthesized using ethyl alcohol instead of EG. These magnetic micro- and nano-structures revealed excellent magnetic properties.
Co-reporter:Sha Zhang, Ping Yang, Aiyu Zhang, Ruixia Shi and Yuanna Zhu
CrystEngComm 2013 vol. 15(Issue 44) pp:9090-9096
Publication Date(Web):24 Sep 2013
DOI:10.1039/C3CE41218K
Hollow hamburger-like and other coupled-layered ZnO microstructures have been fabricated by a facile solvothermal process using the mixture of water and alcohol as solvents. The volume ratios of water/glycerol play an important role for the morphologies of the microstructures. In the case of a volume ratio of 1/2, the hamburger-like ZnO microstructures are created by employing zinc glycerolate (C3H6O3Zn) as a sacrificial template. A possible formation process from precursor C3H6O3Zn to ZnO is proposed by arresting a series of intermediate phases and the formation mechanism of the microstructures is proposed accordingly. The volume ratios of water/glycerol, such as 1/10, 1/6, 1/4, 1/2 and 1/1, were adjusted to create microstructures with various morphologies. The results indicated that the morphologies of the resulting samples changed from quasi-rhombic C3H6O3Zn plates to various coupled-layered ZnO microstructures, suggesting that water is responsible for the formation of coupled-layered structures. In addition, investigations into the formation of ZnO microstructures in mixtures of water and various alcohols, including water/ethanol, water/isopropyl alcohol, water/n-butyl alcohol, water/ethylene glycol and water/glycerol, reveal that alcohols are crucial for control of the morphologies of the microstructures. The multi-hydroxyl alcohols, e.g. ethylene glycol and glycerol, favour the formation of hollow structures compared with the case of single-hydroxyl alcohols.
Co-reporter:Ping Yang, Aiyu Zhang, Xiaoyu Li, Ning Liu, Yulan Zhang, Ruili Zhang
Materials Chemistry and Physics 2013 Volume 141(Issue 1) pp:530-534
Publication Date(Web):15 August 2013
DOI:10.1016/j.matchemphys.2013.05.056
•CdTe0.5Se0.5/Cd0.5Zn0.5S quantum dots created via organic synthesis.•Chemicals affected the properties of the quantum dots.•The quantum dots revealed high photoluminescence efficiency and stability.•The quantum dots with tunable photoluminescence in a range from yellow to dark red.•The QDs are utilizable for various applications such as biological labeling.CdTe0.5Se0.5/Cd0.5Zn0.5S core/shell quantum dots (QDs) with a tunable photoluminescence (PL) range from yellow to dark red (up to a PL peak wavelength of 683 nm) were fabricated using various reaction systems. The core/shell QDs created in the reaction solution of trioctylamine (TOA) and oleic acid (OA) at 300 °C exhibited narrow PL spectra and a related low PL efficiency (38%). In contrast, the core/shell QDs prepared in the solution of 1-octadecene (ODE) and hexadecylamine (HDA) at 200 °C revealed a high PL efficiency (70%) and broad PL spectra. This phenomenon is ascribed that the precursor of Cd, reaction temperature, solvents, and ligands affected the formation process of the shell. The slow growth rate of the shell in the solution of ODE and HDA made QDs with a high PL efficiency. Metal acetate salts without reaction with HDA led to the core/shell QDs with a broad size distribution.CdTe0.5Se0.5/Cd0.5Zn0.5S quantum dots (QDs) with tunable photoluminescence, high PL efficiency, and high stability through organic synthesis, in which chemicals affected the properties of the QDs.
Co-reporter:Ruili Zhang, Ping Yang
Journal of Physics and Chemistry of Solids 2013 Volume 74(Issue 5) pp:759-764
Publication Date(Web):May 2013
DOI:10.1016/j.jpcs.2013.01.019
High-quality colloidal Zn1−xCdxSe nanocrystals (NCs) with tunable photoluminescence (PL) from blue to orange were synthesized using oleic acid as a capping agent. The Zn1−xCdxSe NCs were prepared through two approaches: using CdSe or ZnSe seeds. In the case of CdSe NCs as seeds, Zn1−xCdxSe NCs were fabricated by the reaction of Zn, Cd, and Se precursors in the coordinating solvent system at high temperature. The Zn1−xCdxSe NCs revealed orange emitting. A significant blue-shift of absorption and PL spectra were observed with time, indicating the formation of ternary NCs. In contrast, Zn1−xCdxSe NCs revealed blue to green PL for ZnSe NCs as seeds. This is ascribed to an embryonic nuclei-induced alloying process. With increasing time, the Zn1−xCdxSe NCs exhibited a red-shift both in their absorption and PL spectra. This is attributed to the engineering in band gap energy via the control of NC composition. The PL properties of as-prepared alloyed NCs are comparable or even better than those for the parent binary systems. The PL peak wavelength of the Zn1−xCdxSe NCs depended strongly on reaction time and the molar ratio of Cd/Zn. The Zn1−xCdxSe NCs revealed a spherical morphology and exhibited a wurtzite structure according to transmission electron microscopy observation and an X-ray diffraction analysis.Highlights► High-quality Zn1−xCdxSe nanocrystals (NCs) were fabricated through a step synthesis. ► The alloy structure of the NCs depended strongly on preparation procedures. ► CdSe or ZnSe cores created in the NCs due to different growth kinetics. ► The CdSe and ZnSe cores in the NCs affected photoluminescence properties of theNCs.
Co-reporter:Yulan Zhang, Ping Yang, Lipeng Zhang
Materials Chemistry and Physics 2013 Volume 138(2–3) pp:767-772
Publication Date(Web):15 March 2013
DOI:10.1016/j.matchemphys.2012.12.055
We developed a facile method (a polyol synthesis) to prepare uniform silver nanostructures with various morphologies using ethylene glycol (EG) reduction of silver nitrate at 120 °C in the presence of poly(vinyl pyrrolidone) (PVP) and NaCl. Ag rods were fabricated by simply aging the freshly prepared AgNO3 solution with PVP, EG, and NaCl under ambient atmosphere without changing other parameters. The formation and degradation of the rods were systematically investigated. The result indicates that twinned-crystal seeds play an important role for the growth of anisotropic Ag rods. The NaCl concentration in solutions affected the formation of the rod. The rod was degraded subsequently via an etching process of O2/Cl¯ (NaCl), resulting in the formation of Ag nanostructures with various shapes. Twinned Ag seeds in solutions were etched by increasing the concentration of NaCl, yielding uniform Ag cubes. Regular Ag cubes were fabricated under optimal preparation conditions. Ag cubes with various sizes (150–600 nm) were created by adjusting PVP concentrations in solutions.Graphical abstractSilver nanostructures with various morphologies were fabricated using a polyol synthesis, where the degradation of Ag rods resulted in the creation of various silver nanostructures.Highlights► A polyol synthesis created uniform silver nanostructures with various shapes. ► Twinned seeds play an important role for fabricating Ag rods. ► The rods degraded via the etching process of O2/Cl−. ► Uniform Ag cubes could be created by adjusting NaCl concentrations. ► The size of the cubes depended on PVP concentrations during preparation.
Co-reporter:Fanghong Yang
Journal of Cluster Science 2013 Volume 24( Issue 3) pp:643-656
Publication Date(Web):2013 September
DOI:10.1007/s10876-013-0552-9
Highly luminescent thioglycolic acid-capped CdTe-based core/shell quantum dots (QDs) were synthesized through encapsulating CdTe QDs in various inorganic shells including CdS, ZnS and CdZnS. CdTe/CdS core/shell QDs exhibited a significant redshift of emission peaks (a maximum emission peak of 652 nm for the core/shell QDs and 575 nm for CdTe cores) with increasing shell thickness. In contrast, the redshift of photoluminescence (PL) peak wavelength of CdTe/ZnS QDs was less than 15 nm. The PL peak wavelengths of the core/shell QDs depended strongly on core size and shell thickness. The PL quantum yields (QYs) of the CdTe/CdS core/shell QDs are up to 67 % while that of CdTe/ZnS core/shell QDs is 45 %. A composite CdZnS shell made CdTe cores a high PL QY up to 51 % and broadly adjusted PL spectra (a maximum PL peak wavelength of 664 nm). The epitaxial growth of the shell was confirmed by X-ray powder diffraction analysis and luminescence decay experiments. Because of high PL QYs, tunable PL spectra, and low toxicity from a ZnS surface layer, CdTe/CdZnS core/shell QDs will be great potential for bioapplications.
Co-reporter:Fanghong Yang;Yongqiang Cao
Journal of Fluorescence 2013 Volume 23( Issue 6) pp:1247-1254
Publication Date(Web):2013 November
DOI:10.1007/s10895-013-1256-0
Alloyed semiconductor quantum dots (QDs) enriched the synthetic routes for engineering materials with unique structural and optical properties. High-quality thiol-stabilized CdTexSe1-x alloyed QDs were synthesized through a facile and economic hydrothermal method at 120 °C, a relatively low temperature. These water-soluble QDs were prepared using different capping agents including 3-mercaptopropionic acid (MPA) and L-cysteine (L-Cys). The photoluminescence (PL) intensity and stability of L-Cys-capped CdTexSe1-x QDs were found to be higher than that of MPA-stabilized ones. The molar ratios of Se-to-Te upon preparation were adjusted for investigating the effect of composition on the properties of the resulting QDs. We also investigated the effect of the pH value of the reaction solution on the growth kinetics of the alloyed CdTexSe1-x QDs. The resulting CdTexSe1-x QDs were characterized by UV–vis absorbance and PL spectroscopy, powder X-ray diffraction, and transmission electron microscopy. Being coated with a CdS inorganic shell, the PL intensity and stability of the CdTexSe1-x/CdS core-shell QDs were drastically enhanced, accompanied by the red-shift of the PL peak wavelength. Owing to the unique optical properties, the QDs hold great potential for application and have to be further exploited.
Co-reporter:Aiyu Zhang;Ning Liu;Yongqiang Cao;Ruixia Shi
Journal of Cluster Science 2013 Volume 24( Issue 2) pp:427-437
Publication Date(Web):2013 June
DOI:10.1007/s10876-013-0566-3
Mercaptoacetic acid-capped CdTe quantum dots (QDs) are potential luminescent markers for biological analysis. The photoluminescence (PL) stability of the QDs in buffer solutions determines their practicability as markers in electrophoresis. The stability of the QDs was thus investigated in electrophoresis buffers including tris–borate–ethylenediaminetetraacetic acid (TBE) and tris–acetate–ethylenediaminetetraacetic acid (TAE). The QDs were completely unstable in high-concentrated buffers (≥0.1×). In the case of low concentrations (≤0.07× for TAE, ≤0.035× for TBE), the PL intensity of the QDs in two kinds of buffers decreased with increasing buffer concentrations. A red-shifted PL peak wavelength and PL intensity fluctuation were observed after dispersing the QDs in diluted TAE buffer solutions with concentrations of ≤0.07× for long time. According to the Stern–Volmer plots of PL degradation, the factors leading to the degradation were complicated, which was attributed to the actions of the components including tris, borate or acetic acid, and ethylenediaminetetraacetic acid as well as their mutual effects.
Co-reporter:Ping Yang;Jianrong Wang;Lipeng Zhang
Journal of Cluster Science 2013 Volume 24( Issue 2) pp:399-426
Publication Date(Web):2013 June
DOI:10.1007/s10876-013-0561-8
In this paper, we review the preparation and properties of CdS-like clusters as well as their important applications in several nanostructures. The clusters created by the reaction of S2− ions generated by the decomposition of thioglycolic acid (TGA) and Cd2+ ions play important roles for the construction of novel nanocrystals (NCs), the assembly of the NCs, and the formation of nanostructures including 1D solid and tubal fibers, 2D dendritic morphology, and 3D crystals. The formation and property of the clusters depended strongly on the molar ratio of TGA and Cd2+ ions in solutions. When aqueous CdTe NCs coated with a hybrid SiO2 shell containing the clusters, they revealed a drastic increase in photoluminescence (PL) efficiency (from 28 to 80 %) and temperature-dependent PL. These excellent PL properties were ascribed to the clusters very closed to CdTe cores. This is confirmed through the observation of a lengthening of the Auger recombination lifetime by a factor of ~3.5 in the presence of the clusters. The size of the clusters determined the PL properties of the hybrid SiO2-coated NCs and those fibers. Because of their high PL, these biofunctional materials could provide a platform for various applications.
Co-reporter:Yongqiang Cao;Aiyu Zhang;Qian Ma;Ning Liu
Luminescence 2013 Volume 28( Issue 3) pp:287-293
Publication Date(Web):
DOI:10.1002/bio.2379
ABSTRACT
A new ion sensor based on hybrid SiO2-coated CdTe nanocrystals (NCs) was prepared and applied for sensitive sensing of Cu2+ and Ag+ for the selective quenching of photoluminescence (PL) of NCs in the presence of ions. As shown by ion detection experiments conducted in pure water rather than buffer solution, PL responses of NCs were linearly proportional to concentrations of Cu2+ and Ag+ ions < 3 and 7 uM, respectively. Much lower detection limits of 42.37 nM for Cu2+ and 39.40 nM for Ag+ were also observed. In addition, the NC quenching mechanism was discussed in terms of the characterization of static and transient optical spectra. The transfer and trapping of photoinduced charges in NCs by surface energy levels of CuS and Ag2S clusters as well as surface defects generated by the exchange of Cu2+ and Ag+ ions with Cd2+ ion in NCs, resulted in PL quenching and other optical spectra changes, including steady-state absorption and transient PL spectra. It is our hope that these results will be helpful in the future preparation of new ion sensors. Copyright © 2012 John Wiley & Sons, Ltd.
Co-reporter:Fanghong Yang;Lipeng Zhang
Luminescence 2013 Volume 28( Issue 6) pp:836-841
Publication Date(Web):
DOI:10.1002/bio.2442
ABSTRACT
We exploited the synthesis of near-infrared (NIR) emitting ternary-alloyed CdTeSe and quaternary-alloyed CdZnTeSe quantum dots (QDs) with rod and tetrapod morphologies, which have tunable emission in the NIR electromagnetic spectrum. The morphologies of the QDs depended strongly on their growth kinetics, probably due to the coordinating ligands used in the preparation. Using oleic acid, stearic acid and hexadecylamine as ligands and keeping the same reaction parameters, QDs with tetrapod and rod morphologies were created. Not only had the capping ligands influenced the morphologies of QDs, but also they influenced the optical properties of QDs. The molar ratios of Cd/Zn and Te/Se upon preparation were adjusted for investigating the effect of composition on the properties of resulting QDs. By varying the composition of QDs, the photoluminescence (PL) wavelength of QDs was tuned from 650 nm to 800 nm. To enhance PL efficiency and stability, QDs were coated with a CdZnS shell. As NIR PL has numerous advantages in biological imaging detection, these QDs hold great potential for application. Copyright © 2012 John Wiley & Sons, Ltd.
Co-reporter:Zhimin Yuan;Jianrong Wang
Luminescence 2013 Volume 28( Issue 2) pp:169-175
Publication Date(Web):
DOI:10.1002/bio.2358
ABSTRACT
To create core/shell/shell quantum dots (QDs) with high stability against a harmful chemical environment, CdTe/CdS QDs were coated with a ZnO shell in an aqueous solution. An interfaced CdS layer sandwiched between a CdTe core and ZnO shell provided relaxation of the strain at the core/shell interface since lattice parameters of CdS are intermediate between those of CdTe and ZnO. The photoluminescence (PL) peak wavelength of the core/shell/shell QDs was shifted from 569 to 615 nm by adjusting the size of CdTe cores and thickness of CdS and ZnO shells, along with the highest PL quantum yield of the core/shell/shell QDs reaching 80%, which implies promising applications in the field of biomedical labeling. Due to the decrease of surface defects, it was observed that PL lifetimes significantly increased at room temperature as follows: 29.6 34.2, and 47.5 ns for CdTe (537 nm), CdTe/CdS (555 nm) and CdTe/CdS/ZnO (581 nm) QDs, respectively. Copyright © 2012 John Wiley & Sons, Ltd.
Co-reporter:Ning Liu
Luminescence 2013 Volume 28( Issue 4) pp:542-550
Publication Date(Web):
DOI:10.1002/bio.2491
ABSTRACT
Novel hybrid SiO2-coated CdTe quantum dots (QDs) were created using CdTe QDs coated with a hybrid SiO2 shell containing Cd2+ ions and a sulfur source via a sol–gel process in aqueous solution. Aqueous CdTe QDs with tunable emitting color created through a reaction between cadmium chloride and sodium hydrogen telluride was used as cores for the preparation of hybrid SiO2-coated CdTe QDs. In our experiments we found that the surface state of the cores and preparation conditions that affect the formation of the hybrid SiO2 shell also greatly affect photoluminescence of the hybrid SiO2-coated CdTe QDs. The generation of CdS-like clusters in the vicinity of the CdTe QDs, caused the quantum size effect of the QDs to be greatly reduced, which changes photoluminescence properties of the hybrid QDs fundamentally. Namely, the novel hybrid SiO2 shell played an important role in generating a series of specific optical properties. In addition, the novel hybrid SiO2 shell can be created if no CdTe QD is added. In order to gain an insight into the inter structure of the hybrid shell, we characterized the hybrid SiO2-coated CdTe QDs using X-ray diffraction analysis and discuss the formation mechanism of such a hybrid structure. This work is significant because the novel hybrid SiO2-coated CdTe QDs with its excellent properties can be used in many applications, such as biolabeling and optoelectronic devices. Copyright © 2013 John Wiley & Sons, Ltd.
Co-reporter:Yulan Zhang, Jianrong Wang, Ping Yang
Materials Research Bulletin 2013 48(2) pp: 461-468
Publication Date(Web):
DOI:10.1016/j.materresbull.2012.11.011
Co-reporter:Ping Yang, Yulan Zhang, Baibiao Huang
Materials Research Bulletin 2013 48(10) pp: 3756-3760
Publication Date(Web):
DOI:10.1016/j.materresbull.2013.05.106
Co-reporter:Zhimin Yuan, Ping Yang
Materials Research Bulletin 2013 48(7) pp: 2640-2647
Publication Date(Web):
DOI:10.1016/j.materresbull.2013.03.038
Co-reporter:Qian Ma, Mengkai Lu, Ping Yang, Aiyu Zhang, Yongqiang Cao
Materials Research Bulletin 2013 48(10) pp: 3677-3686
Publication Date(Web):
DOI:10.1016/j.materresbull.2013.05.070
Co-reporter:Ruixia Shi, Ping Yang, Jianrong Wang, Aiyu Zhang, Yuanna Zhu, Yongqiang Cao and Qian Ma
CrystEngComm 2012 vol. 14(Issue 18) pp:5996-6003
Publication Date(Web):08 Jun 2012
DOI:10.1039/C2CE25606A
Without any surfactant, rod-like and three kinds of flower-like ZnO microstructures were synthesized on indium-doped tin oxide (ITO) glass substrates through a simple and environmentally-benign hydrothermal process at 70 °C. The result indicated that rod-like ZnO would be transformed into flower-like ZnO microstructures with decreasing the concentration of sodium hydroxide. The ends, numbers and diameters of the petals of flower-like ZnO varied greatly by modulating the concentration of sodium hydroxide. The secondary nucleation and growth phenomena of ZnO were observed. Time-dependent experiments results indicate that the flower-like ZnO formed in a short period of time. The evolution of morphology and size of ZnO microstructures depended on the reaction time. The amounts and diameters of the petals of flower-like ZnO changed with increasing reaction time. On the basis of our observations and the mechanism proposed previously, the possible growth mechanism for flower-like ZnO was proposed.
Co-reporter:Jie Yang, Qian Ma, Ping Yang
Materials Chemistry and Physics 2012 Volume 135(2–3) pp:486-492
Publication Date(Web):15 August 2012
DOI:10.1016/j.matchemphys.2012.05.012
Spherical CdSe cores with tunable photoluminescence (PL) between green and red were fabricated through a novel organic synthesis. The CdSe cores were coated with ZnS or Cd1−xZnxS shells through an environmentally friendly approach using oleic acid as a capping agent. These shells resulted in those core/shell quantum dots (QDs) with different morphologies and PL properties. Namely, CdSe/ZnS core/shell QDs revealed a spherical morphology while CdSe/Cd1−xZnxS core/shell QDs exhibited an irregular tetrahedron shape. This phenomenon indicated that the growth kinetic of these core/shell QDs depended strongly on the shell composition. Two kinds of core/shell QDs exhibited narrow size distributions and tunable PL spectra. Under optimal preparation conditions, the PL quantum yields of CdSe/ZnS and CdSe/Cd1−xZnxS core/shell QDs were up to 48% and 55%, respectively. The absorption and PL spectra have a significant red shift after coating with ZnS and Cd1−xZnxS on CdSe cores. The red shift degree depended on the thickness and composition of those shells. Especially, two kinds of QDs revealed red emission (PL peak wavelength of 648 nm for CdSe/ZnS and 653 nm for CdSe/Cd1−xZnxS) when large CdSe cores with a PL peak wavelength of 624 nm were used. These core/shell QDs will have an important application as biomarkers.Graphical abstractAn environmentally friendly approach has been developed for spherical CdSe cores coated with ZnS and Cd1−xZnxS shells, where spherical and tetrahedron core/shell quantum dots created by controlling shell growth kinetics.Highlights► Spherical CdSe cores with tunable photoluminescence fabricated via a novel synthesis. ► The cores coated with ZnS and Cd1−xZnxS shells using oleic acid as a capping agent. ► These shells resulted in quantum dots (QDs) with spherical and tetrahedron shapes. ► Significantly red shifted absorption and PL spectra were observed after a shell coating. ► Red emitting peak of 648 nm for CdSe/ZnS and 653 nm for CdSe/Cd1−xZnxS were observed.
Co-reporter:Ping Yang, Lipeng Zhang, Xiaoyu Li, Yulan Zhang, Ning Liu, Ruili Zhang
Journal of Non-Crystalline Solids 2012 Volume 358(Issue 23) pp:3069-3073
Publication Date(Web):1 December 2012
DOI:10.1016/j.jnoncrysol.2012.08.031
Multi hydrophobic CdSe/ZnS or CdSe/CdxZn1 − xS quantum dots were encapsulated into SiO2 beads through a three-step sol–gel procedure. First, the quantum dots were transferred from toluene to water phase via silanization using tetraethyl orthosilicate. The control of ligand exchange (partially hydrolyzed tetraethyl orthosilicate instead of organic amine) resulted in the quantum dots retaining their initial photoluminescence efficiencies after the phase transfer. Second, the assembly of the quantum dots occurs by the hydrolysis and condensation of tetraethyl orthosilicate to form seeds. The amount of 3-mercaptopropyltrimethoxysilane during incorporation plays an important role in controlling the quantum dot number per seed. Third, the seeds are coated with a SiO2 shell by a subsequent Stöber process. The resulting SiO2 beads with a controlled number of hydrophobic quantum dots revealed high photoluminescence efficiency. The SiO2 beads were functionalized with amine, carboxyl, and thiol-terminated biolinkers for surface modification. To confirm the surface modification by carboxyl groups, the SiO2 beads were conjugated with amino functional polystyrene beads. The silica beads introduced here represent a new platform for nanoparticulate multimodality bioanalysis.Highlights► CdSe/ZnS and CdSe/CdxZn1 − xS quantum dots (QDs) were encapsulated into SiO2 beads. ► CdSe/ZnS QDs retained their initial photoluminescence (PL) efficiency in the beads. ► The PL efficiency of CdSe/CdxZn1 − xS QDs in the SiO2 beads decreased. ► After being surface modified, the SiO2 beads conjugated with the polystyrene beads.
Co-reporter:Zhimin Yuan;Aiyu Zhang;Yongqiang Cao;Jie Yang;Yuanna Zhu
Journal of Fluorescence 2012 Volume 22( Issue 1) pp:121-127
Publication Date(Web):2012 January
DOI:10.1007/s10895-011-0937-9
CdTe quantum dots (QDs) were prepared in an aqueous solution using various mercaptocarboxylic acids, such as 3-mercaptopropionic acid (MPA) and thioglycolic acid (TGA), as stabilizing agents. The experimental result indicated that these stabilizing agents played an important role for the properties of the QDs. Although both TGA and MPA-capped CdTe QDs exhibited the tunable photoluminescence (PL) from green to red color, the TGA-capped QDs revealed a higher PL quantum yield (QY) up to 60% than that of MPA-capped QDs (up to 50%) by using the optimum preparation conditions, such as a pH value of ~11.2 and a TGA/Cd molar ratio of 1.5. PL lifetime measurements indicate that the TGA-capped QDs exhibited a short average lifetime while the MPA-capped QDs revealed a long one. Furthermore, the average lifetime of the TGA-capped QDs increased with the increase of the QDs size, while a decreased lifetime for the MPA-capped QDs was obtained. This means that the PL lifetime depended strongly on the surface state of the CdTe QDs. These results should be utilized for the preparation and applications of QDs.
Co-reporter:Qian Ma, Mengkai Lu, Zhimin Yuan, Yuanna Zhu, Ping Yang
Materials Research Bulletin 2012 47(12) pp: 4126-4130
Publication Date(Web):
DOI:10.1016/j.materresbull.2012.08.055
Co-reporter:Ping Yang, Norio Murase, Qian Ma, Yongqiang Cao, Aiyu Zhang, Ruixia Shi, Yuanna Zhu and Jianrong Wang
CrystEngComm 2011 vol. 13(Issue 24) pp:7276-7283
Publication Date(Web):07 Oct 2011
DOI:10.1039/C1CE05905J
We have demonstrated a two-step synthesis for preparing morphology- and luminescence-tunable fibers that uses green-emitting CdTe nanocrystals (NCs), Cd2+, thioglycolic acid (TGA), and tetraethyl orthosilicate (TEOS). Hybrid CdTe NCs consisted of a CdTe core and CdS-like clusters in the fibers were created during the synthesis. The CdTe NCs were first coated with a very thin SiO2 shell containing Cd2+ and TGA molecules in an alkaline condition. The SiO2-coated CdTe NCs were assembled together with Cd–TGA clusters for the formation of the fibers. A subsequent reflux process enabled the creation of fibers and caused the formation of CdS-like clusters in the vicinity of CdTe NCs in the fibers. Because of these clusters closed to the CdTe NCs, their effective size increases to reduce the quantum size effect. This special core-shell structure was found to have extraordinary properties: a narrowed photoluminescence (PL) spectrum, a red-shifted PL peak, and a high PL efficiency. The morphology of the fibers (tubal and solid) depends on the concentrations of TGA, Cd2+ ions, and TEOS in the precursor solution together with the concentration of CdTe NCs in a subsequent reflux. These fibers, especially for nanotubes, exhibited not only a tunable morphology and emitting color but also a functional surface, making them well suited for a variety of applications, such as bio-probing and drug delivery. The nanotubes were conjugated with immunoglobulin G (IgG) by using a zero-length cross linker because of carboxyl groups on their surface. The SiO2 component in the nanotubes enables bio-conjugation with IgG through other functional groups, making these nanotubes amenable for bioapplications.
Co-reporter:Ping Yang, Zhimin Yuan, Jie Yang, Aiyu Zhang, Yongqiang Cao, Qinghui Jiang, Ruixia Shi, Futian Liu and Xin Cheng
CrystEngComm 2011 vol. 13(Issue 6) pp:1814-1820
Publication Date(Web):28 Oct 2010
DOI:10.1039/C0CE00350F
Hybrid SiO2-coated CdTe nanocrystals (NCs) show a drastic increase in fluorescence quantum yield with a significant red-shifted photoluminescence (PL) peak because of the hybrid shell containing CdS-like clusters which are very close to the CdTe core. With their hybrid SiO2 shell, CdTe NCs reveal self-assembly activity which creates one-dimensional nanostructured materials (fibers) with bright PL. Additionally, we experimentally observed the self-assembly of the hybrid SiO2-coated CdTe NCs into two-dimensional dendritic morphology and three-dimensional crystals through a droplet dewetting technique on a hydrophilic glass surface by using NaCl molecules as scaffolds. This phenomenon is ascribed to the domain growth of NaCl to form fractal structures through tip splitting and side branching dynamics. This is also due to a hydrodynamic mechanism through outward capiliary flow. The evaporation speed of solvent during droplet dewetting plays an important role in controlling the self-assembly of the hybrid SiO2-coated CdTe NCs. The experimental parameters such as the amount of sample on the hydrophilic glass surface and dewetting time are key for getting assemblies with tunable morphologies. The present strategy provides a new approach to study the self-assembly of a variety of NCs. This has a potential application for pattern manufacture in a natural way.
Co-reporter:Ping Yang;Jinghua Yu
Journal of Fluorescence 2011 Volume 21( Issue 5) pp:1913-1919
Publication Date(Web):2011 September
DOI:10.1007/s10895-011-0889-0
The photo-degradation of green-, yellow-, orange- and red-emitting CdTe nanocrystals (NCs) in sol–gel SiO2 films was investigated quantitatively by measuring the PL efficiency as a function of the irradiation intensity. The degradation behaviors of the NCs depended strongly on the particle size and the surface state. Green- and yellow-emitting CdTe NCs exhibited a red-shifted PL peak wavelength and decreased PL efficiency after irradiation. In contrast, the PL peak wavelength of red-emitting CdTe NCs remained unchange and their PL efficiency increased. Furthermore, the degraded degree of green-emitting NCs depended linearly on the irradiation intensity \( \left( {{\text{rate}}\,{\text{constant}}\,{k_{{1}}} = \left( {{1}.{1}0\pm 0.0{4}} \right) \times {1}{0^{{ - {6}}}}\,{\text{photon}}} \right) \), whereas hat of red-emitting NCs showed a quadratic dependence \( \left( {{\text{rate}}\,{\text{constant}}\,{k_{{2}}} = \left( {{2}.{26}\pm 0.{1}} \right) \times {1}{0^{{ - {26}}}}\left( {{\text{c}}{{\text{m}}^{{2}}}\,{\text{s}}} \right)/{\text{photon}}} \right) \) at room temperature. This is ascribed to the different surface state of green- and red-emitting CdTe NCs.
Co-reporter:Ping Yang, Guangjun Zhou
Materials Research Bulletin 2011 46(12) pp: 2367-2372
Publication Date(Web):
DOI:10.1016/j.materresbull.2011.08.041
Co-reporter:Ping Yang, Hongsheng Sun, Aiyu Zhang, Yongqiang Cao, Qinghui Jiang, Ruixia Shi, Futian Liu, Guangjun Zhou
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2011 Volume 377(1–3) pp:336-341
Publication Date(Web):5 March 2011
DOI:10.1016/j.colsurfa.2011.01.008
CdTe nanocrystals (NCs) were coated with a hybrid SiO2 shell containing CdS-like clusters by a facile reflux. These hybrid SiO2-coated CdTe NCs exhibited tunable photoluminescence (PL) and high fluorescence quantum yields (QYs) up to 70% (the QY of initial CdTe NCs is 24%) due to the CdS-like cluster in the SiO2 shell nearby the CdTe core. The average fluorescence lifetime of the hybrid SiO2-coated NCs and the CdTe NCs are 36 and 25 ns, respectively. Because increased fluorescence QYs and slightly blue-shifted PL peak wavelength for these hybrid NCs were observed after the removing of TGA and Cd2+, the hybrid SiO2 shell can sufficiently passivate PL, improve chemical stability, and prevent the surface deterioration of the CdTe NCs. This is crucial for applications in biolabeling and optoelectronic devices.Graphical abstractCdTe nanocrystals (NCs) were coated with a hybrid SiO2 shell containing CdS-like clusters, where the clusters resulted in the hybrid NCs with tunable photoluminescence and increased fluorescence quantum yields.Research highlights► Hybrid SiO2-coated CdTe NCs were prepared by a two-step synthesis. ► The hybrid SiO2 shell contained CdS-like clusters. ► The CdS-like clusters closed the CdTe core resulted in high fluorescence QYs and red-shifted PL peak wavelength. ► The QYs of the hybrid NCs increased after the movement of TGA from solution.
Co-reporter:Ping Yang, Norio Murase, Jinghua Yu
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2011 Volume 385(1–3) pp:159-165
Publication Date(Web):20 July 2011
DOI:10.1016/j.colsurfa.2011.06.001
SiO2 beads with quantum dots (QDs) including hydrophilic CdTe or hydrophobic CdSe/ZnS were prepared through sol–gel procedures. These beads contained single or multiple QDs by controlling the ligand exchange and the QD assembly during incorporation. Namely, SiO2 beads with CdTe QDs retained high photoluminescence (PL) efficiencies up to 40% when thioglycolic acid was partially replaced by 3-mercaptopropyltrimethoxysilane. Multiple CdSe/ZnS QDs were assembled into a SiO2 bead (∼7 QDs in each bead) through surface silanization using tetraethyl orthosilicate instead of organic ammine. The stability of CdTe QDs and luminescent SiO2 beads was investigated by measuring the degradation of PL intensity against the concentration of phosphate-buffered saline (PBS) buffer solutions. The Stern–Volmer quenching constant Ksv of QDs depended strongly on the properties of the QDs and the thickness and porous type of SiO2 shell. Red- and green-emitting CdTe QDs exhibited Ksv of 2.02 × 10−2 and 8.93 × 10−2 mM−1, respectively. The II-type pores (cylindrical pores) in the SiO2 shell resulted in quick degradation while the IV-type pores (ink-bottle-shaped pores) led the QDs a high stability. Because both two kinds of QDs in SiO2 beads revealed high PL efficiency and stability in buffer solution, these luminescent beads should be utilizable for bioapplications.Graphical abstractThe Stern–Volmer quenching constant Ksv of quantum dots (QDs) in SiO2 beads depended strongly on the QD properties and the thickness and porous type of SiO2 shell.Highlights► SiO2 beads with hydrophilic CdTe or hydrophobic CdSe/ZnS quantum dots (QDs) were prepared. ► The SiO2 beads with CdTe QDs retained high photoluminescence efficiencies up to 40%. ► Multiple CdSe/ZnS QDs were assembled into SiO2 beads through surface silanization. ► The Stern–Volmer quenching constant of QDs depended the thickness and porous type of SiO2 shell.
Co-reporter:Ping Yang, Aiyu Zhang, Hongsheng Sun, Futian Liu, Qinghui Jiang, Xin Cheng
Journal of Colloid and Interface Science 2010 Volume 345(Issue 2) pp:222-227
Publication Date(Web):15 May 2010
DOI:10.1016/j.jcis.2010.01.072
A sol–gel approach including partially removing capping agents, depositing SiO2 monomers, and growing a SiO2 shell was developed to generate a bio-compatible functionalization on CdTe quantum dots (QDs). The QDs retained their high photoluminescence (PL) efficiency after coating with a SiO2 shell (22.5%) by controlling the surface state of the QDs to decrease PL degradation during a sol–gel preparation. Furthermore, the CdTe QDs with a SiO2 shell were conjugated with IgG using 3-sulfo-N-hydroxysuccinimide or streptavidin–maleimide as linkers. The biotin–streptavidin linker resulted in a high PL efficiency retained (only ∼23% lower than the initial value of the QDs), which is crucial for bio-applications.A sol–gel approach was developed to prepare highly luminescent SiO2-coated CdTe quantum dots where they further conjugated with IgG using 3-sulfo-N-hydroxysuccinimide or streptavidin–maleimide as linkers.
Co-reporter:Ping Yang, Aiyu Zhang, Xin Cheng, Guangjun Zhou, Mengkai Lü
Journal of Colloid and Interface Science 2010 Volume 351(Issue 1) pp:77-82
Publication Date(Web):1 November 2010
DOI:10.1016/j.jcis.2010.07.041
A facile method has been developed to encapsulate Fe3O4 nanocrystals (NCs) in morphology-tunable fibers (belt-like, solid, and tubal) by using a sonochemistry driven synthesis and a subsequent reflux procedure. By adapting the use of tetraethyl orthosilicate, ammonia, Cd2+, and thiolglycolic acid (TGA) to an ultrasound-driven synthesis, the Fe3O4 NCs were coated with a thin composite shell. Supersonic treatment plays an important role to prevent the agglomeration of the Fe3O4 NCs in an alkaline condition. The composite shell became thicker due to the deposition of SiO2 monomers, Cd–TGA clusters, Cd2+, and free TGA molecules during reflux. In addition, these composite shell-coated Fe3O4 NCs were assembled in composite fibers which were created by the growth of Cd–TGA clusters and the deposition of SiO2 monomers. The Fe3O4 NCs mono-dispersed in fibers revealed superparamagnetic behavior. The magnetic saturation value of tubal fibers is lower than those of belt-like and solid fibers. These fibers with Fe3O4 NCs would be utilizable for further application. The strategy described here should give a useful enlightenment for the design and fabrication of morphology-tunable fibers with functional NCs.Graphical abstractMorphology-tunable (tubal, solid, and belt-like) composite fibers with Fe3O4 nanocrystals (NCs) were fabricated through the assembly of the NCs, SiO2 monomers, and the clusters of Cd2+ and thioglycolic acid.Research highlights► Cd–TGA clusters were formed at room temperature. ► Fe3O4 NCs were coated with a thin composite shell by a sonochemistry driven synthesis. ► Composited shell-coated Fe3O4 NCs were assembled in composite fibers. ► The fibers exhibited three kinds of morphologies.
Co-reporter:Tao Dong, Gang Wang, Ping Yang
Diamond and Related Materials (March 2017) Volume 73() pp:
Publication Date(Web):March 2017
DOI:10.1016/j.diamond.2016.09.024
•NiFe2O4@C fibers were fabricated by electrospinning and followed calcination process.•NiFe2O4 nanoparticles were embedded in carbon fibers with large surface area and mesoporous structure.•Carbon matrix can prevent growth and aggregation of NiFe2O4 crystal during calcination.•Carbon matrix can improve the electrical conductivity and prevent particles pulverization/agglomeration during cycling.NiFe2O4 nanoparticles (about 18 nm) homogeneously encapsulated in porous carbon fibers (denoted as NFO@C) were successfully fabricated using single-nozzle electrospinning technique with subsequent two-step calcination process. The formation of inverse spinel-type NiFe2O4 was determined by X-ray diffraction patterns. Stable fibrous NFO@C with average diameter of 400 nm exhibited large surface area and porous structure. Moreover, as anode materials for lithium-ion batteries (LIBs), NFO@C fibers electrode exhibited excellent cycling performance (497 mAh g− 1 after 100 cycles at 100 mA g− 1) and excellent rate performance compared with NFO fibers electrode. This is owing to the special structure of small NiFe2O4 nanoparticles embedded in porous carbon fibers, which effectively improve the electrical conductivity of the electrodes, decrease the diffusion path of Li+ ions, as well as prevent the particle pulverization/agglomeration during cycling. Thus, this work paves a potential pathway for designing efficient transition metal oxides-based LIBs anode materials by the combination of carbon matrix.NiFe2O4 nanoparticles were homogeneously encapsulated in carbon fibers with large surface area and mesoporous structure. As anode materials for lithium-ion batteries, it exhibited excellent lithium storage performance with stable structure.
Co-reporter:Sha Zhang, Hsueh-Shih Chen, Katarzyna Matras-Postolek and Ping Yang
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 45) pp:NaN30306-30306
Publication Date(Web):2015/10/14
DOI:10.1039/C5CP04860E
In this paper, ZnO nanoflowers (NFs) were fabricated by thermal decomposition in an organic solvent and their application in gas sensors and photocatalysis was investigated. These single crystal ZnO NFs, which were observed for the first time, with an average size of ∼60 nm and were grown along the {100} facet. It was suggested that oleylamine used in the synthesis inhibited the growth and agglomeration of ZnO through the coordination of the oleylamine N atoms. The NFs exhibited excellent selectivity to acetone with a concentration of 25 ppm at 300 °C because they had a high specific surface area that provided more active sites and the surface adsorbed oxygen species for interaction with acetone. In addition, the ZnO NFs showed enhanced gas sensing response which was also ascribed to abundant oxygen vacancies at the junctions between petals of the NFs. Furthermore, ZnO–reduced graphene oxide (RGO) composites were fabricated by loading the ZnO NFs on the surface of the stratiform RGO sheet. In the photodegradation of rhodamine B tests, the composite revealed an enhanced photocatalytic performance compared with ZnO NFs under UV light irradiation.
Co-reporter:Yumeng Liu, Xiao Zhang, Junpeng Wang and Ping Yang
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 46) pp:NaN31520-31520
Publication Date(Web):2016/10/19
DOI:10.1039/C6CP06371C
In this study, the nano-heterostructures of Zn1−xCdxS (0 < x < 1) nanoparticles and small g-C3N4 nanosheets (Zn1−xCdxS/CN) were prepared via in situ growth. Bulk g-C3N4 was first delaminated into thin layers by an acid and alkali assisted ultrasound method. Zn1−xCdxS nanoparticles were deposited on the surface of small g-C3N4 nanosheets in situ to fabricate Zn1−xCdxS/CN photocatalysts. The absorption band edges of the as-prepared Zn1−xCdxS/CN composites shifted to a longer wavelength region compared to g-C3N4. The Zn1−xCdxS/CN heterojunctions revealed super-enhanced visible-light photocatalytic activities compared to pure g-C3N4 and Zn1−xCdxS nanoparticles. To investigate the composition dependence, the mass ratios of Zn1−xCdxS and g-C3N4 were adjusted. Zn0.8Cd0.2S nanoparticles (5 wt%) grown in situ on g-C3N4 nanosheets as sample 5-Zn0.8Cd0.2S/CN revealed a very high photocatalytic activity compared to other Zn0.8Cd0.2S/CN and CdS/CN samples where the degradation of RhB was up to 99% within 15 min under visible light irradiation. This was ascribed to the well-matched band gap structure, large specific surface area and intimately contacted interfaces. The controllable band gap of the Zn1−xCdxS/CN composites was a key factor for their enhanced photocatalytic performance. In addition, O2− was the leading reactive oxidative species in this photocatalytic process in the 5-Zn0.8Cd0.2S/CN composite system.
Co-reporter:Jie Zhao, Ping Yang, Hsueh-Shih Chen, Jia Li, Quande Che, Yuanna Zhu and Ruixia Shi
Journal of Materials Chemistry A 2015 - vol. 3(Issue 11) pp:NaN2547-2547
Publication Date(Web):2015/01/21
DOI:10.1039/C4TC02752C
We investigated the marked morphological changes of α-Fe2O3 nanocrystals from nanoplates to nanospindles via an environmentally friendly hydrothermal route. An aqueous Fe salt was used as the precursor and the volume ratio of ammonia to ethylene glycol was varied. The product was uniform and obtained at a high yield. By simply increasing the ratio of the aqueous phase, the morphology could be continuously tuned from nanoplates to nanospindles with the (001) facets gradually disappearing. A fundamental understanding of the shape evolution was obtained via a series of characterizations including X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. The NO3− ions and NH3 molecules played vital parts at increased temperatures, not only in the phase structure of the iron oxide, but also in the formation of different hematite morphologies with different properties. The decrease in the photocatalytic efficiency in the visible region with the change from nanoplates to nanospindles under the same conditions indicated that the increase in the number of exposed (001) facets promoted the photocatalytic performance. The magnetic and electrochemical properties of typical morphologies were investigated and showed the potential applications of the nanostructures in various fields.
Co-reporter:Xueling Song, Yumeng Liu, Yan Zheng, Kun Ding, Shijie Nie and Ping Yang
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 6) pp:NaN4584-4584
Publication Date(Web):2016/01/12
DOI:10.1039/C5CP07187A
Zinc oxide (ZnO) nanostructures with diverse morphologies were successfully fabricated via a simple one-step hydrothermal synthesis and subsequent calcination. The formation of butterfly-like ZnO was mainly ascribed to a typical nucleation–growth–assembly process as a result of electrostatic interactions between the nanoparticles and the reconstructed sheets. Au nanoparticles (NPs) created from Au3+ ions were deposited on the butterfly-like ZnO without the use of any reducing agents by simply stirring the solution at room temperature. Tartaric acid was present in the ZnO calcined at a low temperature (300 °C), which resulted in the self-reducing ability of ZnO toward the Au3+ ions. The Au NPs were closely connected with the ZnO matrix. This close connection resulted in hierarchical ZnO–Au composites with efficient photocatalytic activity for use in environmental remediation. Compared with the pure ZnO sample calcined at 300 °C, the hierarchical ZnO–Au composites showed an enhanced photocatalytic performance toward rhodamine B. The results of photodegradation indicated that the incorporation of the Au NPs drastically increased the photocatalytic efficiency by promoting the separation of the electron–hole pairs created by the absorption of photons.
