Co-reporter:Mingling Li;Yiming Wu;Taishen Li;Yulin Chen;Huaiyi Ding;Yue Lin;Nan Pan
RSC Advances (2011-Present) 2017 vol. 7(Issue 77) pp:48759-48765
Publication Date(Web):2017/10/16
DOI:10.1039/C7RA09430B
In this work, we have successfully synthesized SnS flakes with different thicknesses and systematically investigated their polarization-dependent Raman properties. It is found that the different Raman mode of SnS shows distinctly anisotropic thickness dependence. For B3g mode, the polar plot of Raman intensities is insensitive to the flake thickness. However, the behavior of Ag mode is entirely different. Under parallel polarization configuration, with decreasing the flake thickness, the maximum Raman intensity of Ag mode changes from the armchair direction to the zigzag direction with 514.5 nm excitation. The results can be understood by the complex Raman tensor owing to the large absorption of SnS. Moreover, under the perpendicular polarization configuration, the Raman intensity of Ag mode along 45° direction becomes apparently different from that along 135° direction. Our finding not only deepens the understanding of anisotropic Raman properties of SnS but also provides inspiration for further studies on the other 2D IV–VI materials.
Co-reporter:Yiming Wu;Yanmeng Dai;Shenlong Jiang;Chao Ma;Yue Lin;Dongxue Du;Yukun Wu;Huaiyi Ding;Qun Zhang;Nan Pan
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 14) pp:9537-9544
Publication Date(Web):2017/04/05
DOI:10.1039/C7CP00973A
Aluminium (Al)-doped zinc oxide (ZnO) nanowires (NWs) with a unique core–shell structure and a Δ-doping profile at the interface were successfully grown using a combination of chemical vapor deposition re-growth and few-layer AlxOy atomic layer deposition. Unlike the conventional heavy doping which degrades the near-band-edge (NBE) luminescence and increases the electron–phonon coupling (EPC), it was found that there was an over 20-fold enhanced NBE emission and a notably-weakened EPC in this type of interfacially Al-doped ZnO NWs. Further experiments revealed a greatly suppressed nonradiative decay process and a much enhanced radiative recombination rate. By comparing the finite-difference time-domain simulation with the experimental results from intentionally designed different NWs, this enhanced radiative decay rate was attributed to the Purcell effect induced by the confined and intensified optical field within the interfacial layer. The ability to manipulate the confinement, transport and relaxation dynamics of ZnO excitons can be naturally guaranteed with this unique interfacial Δ-doping strategy, which is certainly desirable for the applications using ZnO-based nano-photonic and nano-optoelectronic devices.
Co-reporter:Hongwen Huang;Mei Liu;Jing Li;Laihao Luo;Jiangtao Zhao;Zhenlin Luo;Zhizhen Ye;Haiping He;Jie Zeng
Nanoscale (2009-Present) 2017 vol. 9(Issue 1) pp:104-108
Publication Date(Web):2016/12/22
DOI:10.1039/C6NR08250E
We report a room-temperature colloidal synthesis of few-unit-cell-thick CsPbBr3 QWs with lengths over a hundred nanometers. The surfactant-directed oriented attachment growth mechanism was proposed to explain the formation of such CsPbBr3 QWs. Owing to the strong quantum confinement effect, the photoluminescence (PL) emission peak of few-unit-cell-thick CsPbBr3 QWs blue-shifted to 430 nm. The ensemble PL quantum yield (PLQY) of the few-unit-cell-thick CsPbBr3 QWs increased to 21.13% through a simple heat-treatment process. The improvement of PLQY was ascribed to the reduction of the density of surface trap states and defect states induced by the heat-treatment process. Notably, the dependence of the bandgap on the diameter with different numbers of unit cells was presented for the first time in 1-D CsPbBr3 QWs on the basis of the produced few-unit-cell-thick CsPbBr3 QWs.
Co-reporter:Siwen Zhao;Yiming Wu;Kaixuan Zhang;Huaiyi Ding;Dongxue Du;Jiyin Zhao;Nan Pan
Nanoscale (2009-Present) 2017 vol. 9(Issue 44) pp:17610-17616
Publication Date(Web):2017/11/16
DOI:10.1039/C7NR05917E
We carefully prepared interfacial Al-doped (IAD) and interfacial natively-doped (IND) ZnO nanowires (NWs) by introducing atomic-layer interfacial Δ-doping between the two steps of CVD growth. Variable-temperature electron transport as well as magnetotransport behaviours of these NWs were systematically investigated. By virtue of the unique architecture and the quality-guaranteed growth technique, a series of quantum interference effects were clearly observed in the IAD ZnO NWs, including weak localization, universal conductance fluctuation and Altshuler–Aronov–Spivak oscillations. The phase-coherence length (Lφ) of electrons exceeds 100 nm in the IAD ZnO NWs, much longer than those in the IND ones and most conventionally doped ZnO NWs. This ability to efficiently manipulate a variety of quantum interference effects in ZnO NWs is very desirable for applications in nano-optoelectronics, nano- & quantum-electronics and solid-state quantum computing.
Co-reporter:Lin Quan, Yuqing Song, Yue Lin, Guanghui Zhang, Yanmeng Dai, Yukun Wu, Ke Jin, Huaiyi Ding, Nan Pan, Yi Luo and Xiaoping Wang
Journal of Materials Chemistry A 2015 vol. 3(Issue 42) pp:11129-11134
Publication Date(Web):28 Sep 2015
DOI:10.1039/C5TC02209F
Chemical enhancement is one of the important mechanisms in surface-enhanced Raman spectroscopy, however, its origin is still under debate. Recently, a two dimensional (2D) layered material has been thought to be a strong candidate to investigate the chemical mechanism of Raman enhancement because it has a flat surface, a well defined structure and is without the interference of electromagnetic enhancement. Herein we report systematic studies of the Raman enhancement effect on a gallium selenide (GaSe) flake by using a copper phthalocyanine (CuPc) molecule as a probe. It is found that the Raman signal of CuPc on the monolayer GaSe can be significantly increased by one order of magnitude compared to that on a SiO2/Si substrate. Moreover, the enhancement effect is found to decrease with increasing thickness of the GaSe flake. The origin of the Raman enhancement is attributed to the chemical mechanism resulting from the charge transfer between the GaSe flake and the detected molecules. The supposition is further verified by the investigation of the quenching photoluminescence of GaSe as well as the Raman enhancement effect of CuPc with different thicknesses on the GaSe flake. Our work will shed more light on the understanding of the chemical mechanism for Raman enhancement and expand more practical applications of GaSe.
Co-reporter:Yukun Wu, Junwen Li, Huaiyi Ding, Zhiwei Gao, Yiming Wu, Nan Pan and Xiaoping Wang
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 7) pp:5360-5365
Publication Date(Web):12 Dec 2014
DOI:10.1039/C4CP04998E
ZnO–Al2O3 core–shell nanorods (NRs) have been fabricated through the vapor phase condensation method and atomic layer deposition. It is found that the nanorod comprises a wurtzite single crystalline ZnO core with the main axes along the [0001] direction and an amorphous Al2O3 shell. The temperature-dependent photoluminescence (PL) properties of the as-grown and annealed ZnO/Al2O3 NRs are investigated systematically. The PL of the as-grown ZnO/Al2O3 NRs demonstrates a normal thermal quenching feature. However, the salient behavior of negative thermal quenching (NTQ), i.e., the increase in PL intensity with an increase in temperature, is clearly observed in the annealed ZnO/Al2O3 NRs. A multi-level model is adopted to account for this behavior and the thermal activation energy of the NTQ process is estimated to be ∼69 meV. Moreover, we suggest that the activation energy is related to the Al donor defect in ZnO resulting from the inter-diffusion between the ZnO core and the Al2O3 shell during the annealing process.
Co-reporter:Guanghui Zhang, Yukun Wu, Huaiyi Ding, Yunsong Zhu, Junwen Li, Yue Lin, Shenlong Jiang, Qun Zhang, Nan Pan, Yi Luo and Xiaoping Wang
RSC Advances 2015 vol. 5(Issue 88) pp:71883-71889
Publication Date(Web):19 Aug 2015
DOI:10.1039/C5RA14204K
All-inorganic solid-state ZnO/CdTe core–shell nanorod array solar cells (NRASCs) have been fabricated by a simple low-temperature and low-cost chemical solution method. A thin TiO2 layer with different thickness was introduced at the ZnO/CdTe interface using atomic layer deposition and its effect on the photovoltaic performance of the NRASCs was investigated. It is found that the overall power conversion efficiency of the ZnO/TiO2 (4 nm)/CdTe NRASC can reach up to 1.44% under AM 1.5G illumination (100 mW cm−2), which is about 6 times of the NRASC without TiO2 layer. By further systematic characterizations, we find that the thin TiO2 layer, serving as an efficient passivation and blocking layer at the interface of ZnO/CdTe nanorod, can remarkably suppress the charge recombination at the interface but negligibly affect the light absorption and the charge separation efficiency, thus leading to significant increases of the carrier lifetime and the open-circuit voltage of the NRASCs. This result expands the knowledge and opportunities for low-cost, high-performance NRASCs through simple interface engineering.
Co-reporter:Guanghui Zhang, Shenlong Jiang, Yue Lin, Wenzhen Ren, Hongbing Cai, Yukun Wu, Qun Zhang, Nan Pan, Yi Luo and Xiaoping Wang
Journal of Materials Chemistry A 2014 vol. 2(Issue 16) pp:5675-5681
Publication Date(Web):10 Mar 2014
DOI:10.1039/C3TA14539E
The properties of the electron donor–acceptor interface play a crucial role in the photovoltaic performance of the core–shell nanorod array solar cells (NRASCs). In this paper, all-inorganic solid-state ZnO/CdTe and ZnO/CdS/CdTe core–shell NRASCs have been fabricated by a simple low temperature and low cost solution-based process. We investigate the influence of the CdS interfacial layer with different thicknesses on the performance of the solar cells. It is found that inserting such an interfacial layer can significantly improve the short-circuit current density and the open-circuit voltage of the device. The overall power conversion efficiency of the ZnO/CdS/CdTe core–shell NRASC with a 4 nm thick CdS interfacial layer can reach 0.72% under AM 1.5G illumination (100 mW cm−2), which is three times that of the ZnO/CdTe NRASC. The improvement in the performance is attributed to the designed graded energy band alignment of ZnO/CdS/CdTe and the passivation of surface defects of the ZnO nanorod by the CdS interfacial layer, which can result in the enhanced carrier separation and collection. The result clearly demonstrates that the performance of all-inorganic core–shell photovoltaic devices can be greatly improved with uncomplicated interface engineering.
Co-reporter:Yuqing Song ; Jinyang Liu ; Lin Quan ; Nan Pan ; Hong Zhu
The Journal of Physical Chemistry C 2014 Volume 118(Issue 23) pp:12526-12531
Publication Date(Web):May 16, 2014
DOI:10.1021/jp501897a
Graphene flakes with various sizes are prepared directly on SiO2/Si substrate using a remote catalytic method. The flakes are characterized by Raman spectra, and the peak of the 2D band shows a drastic blue shift due to the in-plane compressive strain induced by the different coefficients of thermal expansion between the graphene and the substrate. More importantly, the compressive strain of the flake is found to increase with flake size. The behavior can be understood by the strain releasing through the defects and the edge of graphene flakes. Additionally, we find that the defects contribute more than 75% of strain relaxation for all graphene samples, and the width of the edge region for the strain relaxation increases from ∼50 to ∼110 nm for 2 and 5 h grown flakes. Our finding indicates that the compressive strain inevitably exists in the as-grown graphene on SiO2/Si, which may be eliminated through a new preparation method.
Co-reporter:Xinxin Yu, Ke Lin, Keqiang Qiu, Hongbing Cai, Xinjing Li, Jinyang Liu, Nan Pan, Shaojun Fu, Yi Luo, Xiaoping Wang
Carbon 2012 Volume 50(Issue 12) pp:4512-4517
Publication Date(Web):October 2012
DOI:10.1016/j.carbon.2012.05.033
Fluorinated reduced graphene oxide (F-RGO) is prepared by CF4 plasma treatment of RGO. The fluorine (F) doping is confirmed by X-ray photoelectron spectroscopy and its content is directly related to the plasma exposure time. A modest p-doping effect of the fluorination is observed from the electrical measurements. It is found that the F-RGO is an even better substrate for surface enhanced Raman spectroscopy of molecules than RGO. The relative enhancement factor can be tuned by manipulating the F content in the F-RGO. The effect is attributed to the presence of the strong local electric field induced by the local dipoles of F-containing groups on the F-RGO surface. This shows that the formation of well-designed surface dipoles could be a general way to increase the chemical enhancement of molecular Raman spectra.
Co-reporter:Yue Lin;Zhigang Geng;Hongbing Cai;Lu Ma;Jia Chen;Jie Zeng;Nan Pan
European Journal of Inorganic Chemistry 2012 Volume 2012( Issue 28) pp:4439-4444
Publication Date(Web):
DOI:10.1002/ejic.201200454
Abstract
We developed a ternary nanocomposite of graphene–TiO2–Fe3O4 (GTF) as a low-cost, recollectable, and stable photocatalyst for the degradation of organic dyes. The nanocomposite has been successfully prepared by successively growing TiO2 and Fe3O4 nanoparticles on the reduced graphene oxide (RGO). The as-synthesized GTF nanocomposite shows higher photocatalytic activity as compared with that of pure TiO2 nanoparticles and can be easily collected from water using a magnet. More importantly, benefiting from the presence of RGO, GTF can suppress the photodissolution behavior of Fe3O4 nanoparticles that usually occurrs in TiO2–Fe3O4 binary nanocomposites, rendering it a highly stable photocatalyst. Furthermore, the GTF nanocomposite works well in different pH environments and is capable of eliminating mixtures of various dyes. In addition, the GTF is also able to degrade the dyes under sunlight. These attractive features make the GTF nanocomposite a promising photocatalyst for practical use in wastewater treatment.
Co-reporter:Yiping Ye, Tao Kong, Xiaofang Yu, Yukun Wu, Kun Zhang, Xiaoping Wang
Talanta 2012 Volume 89() pp:417-421
Publication Date(Web):30 January 2012
DOI:10.1016/j.talanta.2011.12.054
A nonenzymatic hydrogen peroxide (H2O2) sensor was fabricated using the reduced graphene oxide (RGO) and ferroferric oxide (Fe3O4) nanocomposites as the sensing material. The nanocomposites were synthesized by coprecipitation method and characterized by high-resolution transmission electron microscopy and X-ray diffraction. Results showed that the RGO sheet was evenly decorated by the well-crystallized Fe3O4 nanoparticles. The nanocomposites showed enhanced catalytic ability to the reduction of hydrogen peroxide compared with the RGO, Fe3O4 nanoparticles alone and the mixture materials. The sensor has a quite wide linear range from 0.1 mM to 6 mM (R2 = 0.990) with less than 5 s response time. Moreover, its detection limit is 3.2 μM (S/N = 3). The anti-interference ability, long-term stability and potential application in real samples of the sensor is also assessed. This work expands the application of the graphene-based nanomaterials in the sensor areas.Highlights► Reduced graphene oxide/Fe3O4 nanocomposites as sensing material for H2O2 detection. ► Reduced graphene oxide prevents the Fe3O4 nanoparticles from aggregation. ► The nanocomposites show enhanced electrocatalytic performance.
Co-reporter:Jinyang Liu, Hongbing Cai, Xinxin Yu, Kun Zhang, Xinjing Li, Junwen Li, Nan Pan, Qinwei Shi, Yi Luo, and Xiaoping Wang
The Journal of Physical Chemistry C 2012 Volume 116(Issue 29) pp:15741-15746
Publication Date(Web):June 28, 2012
DOI:10.1021/jp303265d
We propose a new approach to fabricate the graphene nanomesh through the local catalytic hydrogenation of carbon by Cu nanoparticles. It allows to tune the size and density of the holes in the nanomesh as well as the total edge length of the holes through the control of the thickness of the Cu film. The upshift of both G and 2D peaks in Raman spectra of the graphene nanomeshes indicates that the nanomesh is spontaneously p-type doped. Moreover, the split of G peak reveals that the doping is localized near the edge region of the hole in the nanomesh. Importantly, the nanomesh shows improved chemical enhancement for Raman spectra of absorbed RhB molecules as compared to the graphene. The edges in the nanomesh can enhance Raman spectroscopy via increasing both the local charge transfer and the ability to absorb RhB molecules. The results show that the graphene nanomesh has a great potential for the rapid and sensitive detection for the environmental monitoring and food security.
Co-reporter:Xinxin Yu, Hongbing Cai, Wenhua Zhang, Xinjing Li, Nan Pan, Yi Luo, Xiaoping Wang, and J. G. Hou
ACS Nano 2011 Volume 5(Issue 2) pp:952
Publication Date(Web):January 6, 2011
DOI:10.1021/nn102291j
Chemical enhancement is an important mechanism in surface-enhanced Raman spectroscopy. It is found that mildly reduced graphene oxide (MR-GO) nanosheets can significantly increase the chemical enhancement of the main peaks by up to 1 order of magnitude for adsorbed Rhodamine B (RhB) molecules, in comparison with the mechanically exfoliated graphene. The observed enhancement factors can be as large as ∼103 and show clear dependence on the reduction time of graphene oxide, indicating that the chemical enhancement can be steadily controlled by specific chemical groups. With the help of X-ray photoelectron spectra, these chemical species are identified and the origin of the observed large chemical enhancement can thus be revealed. It is shown that the highly electronegative oxygen species, which can introduce a strong local electric field on the adsorbed molecules, are responsible for the large enhancement. In contrast, the local defects generated by the chemical reduction show no positive correlation with the enhancement. Most importantly, the dramatically enhanced Raman spectra of RhB molecules on MR-GO nanosheets reproduce all important spectral fingerprints of the molecule with a negligible frequency shift. Such a unique noninvasive feature, along with the other intrinsic advantages, such as low cost, light weight, easy availability, and flexibility, makes the MR-GO nanosheets very attractive to a variety of practical applications.Keywords (): chemical enhancement; mildly reduced graphene oxide; molecular fingerprint; noninvasive; oxygen-containing groups; surface-enhanced Raman spectroscopy (SERS); π-conjugation
Co-reporter:Nan Pan, Bing Wang, Xiaoping Wang and J. G. Hou
Journal of Materials Chemistry A 2010 vol. 20(Issue 27) pp:5567-5581
Publication Date(Web):26 Mar 2010
DOI:10.1039/B925007G
This feature article reviews some strategies and realizations for manipulating and tailoring the physical and chemical properties of zero dimensional (0-D) and one dimensional (1-D) nanomaterials as well as reveals the underlying mechanism. A series of high-resolution characterization techniques, such as high-resolution transmission electron microscopy (HRTEM), low temperature scanning tunneling microscopy (LT-STM), conductive atomic force microscopy (CAFM), and spatially resolved cathodoluminescence (CL), have been used in this study, which enable us to investigate the morphologies, structures and properties of individual nanomaterials experimentally. Some theoretical quantum chemistry methods such as tightbinding (TB) and density functional theory (DFT) are also applied for better understanding the experimental phenomena. Our results demonstrate that deliberate control at atomic and molecular scale, such as fabricating ordered and disordered metal nanoparticles, growing designed heterostructures, doping or grafting single molecules, and changing geometry (e.g., aspect ratio, tip sharpness, size, and surface ratio), can dramatically tailor the properties of the 0-D and 1-D nanomaterials. The results shown here can be extended to various nanomaterials and nanodevices, and therefore are useful for versatile applications in nanoscience and nanotechnology.
Co-reporter:Nan Pan;Haizhou Xue;Jinhua Huang;Guanghui Zhang;Yukun Wu;Ming Li;Jianguo Hou
European Journal of Inorganic Chemistry 2010 Volume 2010( Issue 27) pp:4344-4350
Publication Date(Web):
DOI:10.1002/ejic.201000465
Abstract
A highly oriented, well-aligned hierarchical Zn–In–O nanobelt–nanoprism array was synthesized by vapor-phase transport and condensation using GaN epilayer as the substrate. The upper nanobelts are found to be ZnO:In with an average Zn/In molar ratio of approximately 9:1, and the subjacent nanoprisms are found to be In2O3(ZnO)m (m = 2, 3, 4, and 5) structures. During self-assembly, the nanoprisms are vertically grown on GaN and well aligned along the superlattice stacking direction, upon which each nanobelt is horizontally grown along its [10–10] direction. The spatially resolved cathodoluminescence spectra collected on individual hierarchical nanostructures clearly show characteristics for the ZnO:In nanobelt and for the In2O3(ZnO)m nanoprism, which are distinctly different from the emissions of the undoped ZnO nanorod. I-V measurements on individual nanobelts reveal good conductivity over 103 S m–1 and high electron concentration of 1019–1020 cm–3. This bottom-up self-assembled, highly oriented, and well-aligned hierarchical nanoarray may find applications in newly emerging vertically integrated nanoarray circuits.
Co-reporter:Yue Lin, Kun Zhang, Wufeng Chen, Yiding Liu, Zhigang Geng, Jie Zeng, Nan Pan, Lifeng Yan, Xiaoping Wang and J. G. Hou
ACS Nano 2010 Volume 4(Issue 6) pp:3033
Publication Date(Web):May 25, 2010
DOI:10.1021/nn100134j
A linker-free connected reduced graphene oxide/CdSe nanoparticle (R-GO/CdSe NP) nanocomposite was produced by directly anchoring CdSe NPs onto R-GO. The morphological and structural characterizations evidence that the single-crystal CdSe NPs with the size of a few tens of nanometers can be efficiently decorated on the R-GO. The photoresponse of this nanocomposite is drastically enhanced compared with that of the pure CdSe NPs, the bare R-GO, and the physically mixed R-GO/CdSe NPs, while the photoluminescence of the CdSe NPs in the composite is much quenched, indicating that the photoinduced carriers generated from the CdSe NPs can be transferred to the R-GO effectively and separately. This ability makes the R-GO/CdSe NP nanocomposite a great promise for wide potential applications in optoelectronics.Keywords: charge transfer; nanocomposite; optoelectronic; photoresponse; reduced graphene oxide; semiconductor nanoparticles
Co-reporter:Tao Kong, Yang Chen, Yiping Ye, Kun Zhang, Zhenxing Wang, Xiaoping Wang
Sensors and Actuators B: Chemical 2009 Volume 138(Issue 1) pp:344-350
Publication Date(Web):24 April 2009
DOI:10.1016/j.snb.2009.01.002
A glucose biosensor is fabricated with immobilization of glucose oxidase onto ZnO nanotube arrays by cross-linking method. The ZnO nanotube arrays are synthesized by chemical etching of ZnO nanorods that are electrochemically deposited on the Au surface. Morphology and structure of ZnO nanotubes are characterized by FESEM, HRTEM and XRD. Fourier-transform infrared spectroscopy reveals that the glucose oxidase immobilized on the ZnO nanotubes retains its native conformation. The biosensor has a wide linear range for the detection of glucose from 50 μM to 12 mM (a correlation coefficient of 0.998) with 3 s response time. The sensitivity of the biosensor is found to be 21.7 μA/mM cm2. Moreover, its experimental detection limit is 1 μM (S/N = 3) and the apparent Michaelis–Menten constant is calculated to be 19 mM. The anti-interference ability and long-term stability of the biosensor are also assessed. Compared with the biosensors based on the nanorod and flat structure, the proposed biosensor shows expanded linear range and sensitivity. All these results demonstrate that ZnO nanotube can provide a promising material for the biosensor designs and other biological applications.
Co-reporter:Haizhou Xue, Nan Pan, Rongguang Zeng, Ming Li, Xia Sun, Zejun Ding, Xiaoping Wang and J. G. Hou
The Journal of Physical Chemistry C 2009 Volume 113(Issue 29) pp:12715-12718
Publication Date(Web):June 19, 2009
DOI:10.1021/jp903690g
Spatially resolved cathodoluminescence spectra are collected along the scanning positions of the electron beam across an individual hexagonally cross-sectioned ZnO nanowire to probe the surface effect on the deep-level (DL) emissions of the nanowire. A double-peak feature of DL emission intensity is observed in the intensity versus scanning position when the electron beam scans across the nanowire from one edge to the other. This spatial variation in DL intensity can be well-described by a simple core−shell model considering the strong surface effect. By further quasi-quantitative analysis and comparison with experimental results, we obtained an equivalent surface shell thickness of about 5−6 nm. The result unambiguously confirms that the surface effect plays a key role in the DL emission process of the nanowire, which should be carefully considered and cautiously modified for better performance of nanoscale functional materials and devices.
Co-reporter:Zhenxing Wang, Jinyang Liu, Kun Zhang, Hongbing Cai, Guanghui Zhang, Yukun Wu, Tao Kong, Xiaoping Wang, Jie Chen and Jianguo Hou
The Journal of Physical Chemistry C 2009 Volume 113(Issue 14) pp:5428-5433
Publication Date(Web):2017-2-22
DOI:10.1021/jp810274k
We have developed a simple, yet highly effective and reliable, poly(dimethylsiloxane) (PDMS) transfer method to fabricate highly dense and well-aligned CdS nanowires on silica substrates, following DNA templates. CdS nanoparticles are selectively deposited and confined on DNA strings aligned on a PDMS sheet to form CdS nanowires. The nanowires are then transferred to the substrate with a low occurrence of parasitic CdS nanoparticles. The mapping of elements in the nanowires by scanning Auger electron spectroscopy reveals the dense distribution of Cd and S elements along DNA scaffolds. The width and length of the nanowires can be controlled by adjusting the incubation time on the PDMS sheet. Atomic force microscopy and field emission scanning electron microscopy show that the height and width of the nanowires reach 45 and 77 nm, respectively, after 72 h of growth. The nanowire can continuously stretch over 10 μm after 96 h of incubation. The method is easily replicable, and controllable, which makes it promising for building nanophotoelectronic devices and nanosensors.
Co-reporter:Jie Zeng, Chi Liu, Jianliu Huang, Xiaoping Wang, Shuyuan Zhang, Gongpu Li and Jianguo Hou
Nano Letters 2008 Volume 8(Issue 5) pp:1318-1322
Publication Date(Web):April 5, 2008
DOI:10.1021/nl0733334
Since the discovery of WS2 nanotubes in 1992 (Nature 1992, 360, 444), there have been significant research efforts to synthesize nanotubes and fullerene-like hollow nanoparticles (HNPs) of inorganic materials (Nat. Nanotechnol. 2006, 1, 103) due to their potential applications as solid lubrications (J. Mater. Chem. 2005, 15, 1782), chemical sensing (Adv. Funct. Mater. 2006, 16, 371), drug delivering (J. Am. Chem. Soc. 2005, 127, 7316), catalysis (Adv. Mater. 2006, 18, 2561), or quantum harvesting (Acc. Chem. Res. 2006, 39, 239). Nanotubes can be produced either by rolling up directly from layer compounds (Nature 2001, 410, 168) or through other mechanisms (Adv. Mater. 2004, 16, 1497) such as template growth (Nature 2003, 422, 599) and decomposition (J. Am. Chem. Soc. 2001, 123, 4841). The Kirkendall effect, a classical phenomenon in metallurgy (Trans. AIME 1947, 171, 130), was recently exploited to fabricate hollow 0-D nanocrystals (Science 2004, 304, 711) as well as 1-D nanotubes (Nat. Mater. 2006, 5, 627). Although the dimension of resulting hollow nanostructures depends on precursors, the hollow nanomaterials can also be organized into various dimensional nanostructures spontaneously or induced by an external field. In this letter, we report, for the first time, the UV-light induced fabrication of the ends-closed 1-D CdCl2 nanotubes from 0-D CdSe solid nanocrystals through the Kirkendall effect and the head-to-end assembled process. Our results demonstrate the possibility to control the dimension (0-D to 1-D) and the configuration (solid to hollow) of nanostructures simultaneously and have implications in fabricating hollow nano-objects from zero-dimensional to multidimensional.
Co-reporter:J. Huang;J. Zeng;X. Wang;B. Wang;J. Hou;W. Lu;S. Zhang
Advanced Materials 2007 Volume 19(Issue 16) pp:2172-2176
Publication Date(Web):20 JUL 2007
DOI:10.1002/adma.200602440
Tunable fabrication of noble-metal hollow nanoparticle chains (HNPCs) is achieved by a strategy that exploits the variation of an external applied magnetic field during synthesis (see figure). The magnitude of the field has a strong effect on the nanoparticles assembly, ranging from disperse to chainlike. The length and the optical properties of the HNPCs can be tuned, and such a synthesis may provide enhanced functionality for applications such as drug delivery or catalysis.
Co-reporter:Zhenxing Wang, Tao Kong, Kun Zhang, Hailong Hu, Xiaoping Wang, Jianguo Hou, Jie Chen
Materials Letters 2007 Volume 61(Issue 1) pp:251-255
Publication Date(Web):January 2007
DOI:10.1016/j.matlet.2006.04.106
The self-assembly of various nanostructures is recently attracting a great deal of research attention. In this paper, we demonstrate that a palladium chloride aqueous solution, mixed with a proper ammonia solution, can produce Tetra-amminepalladous chloride (Pd(NH3)4Cl2·H2O) nanowires. These nanowires can spontaneously form the two-dimensional hexagon-oriented Pd(NH3)4Cl2·H2O arrays on mica surfaces. We can control the length and height of these nanowires by adjusting their deposit time on the mica substrate. This method can be potentially used in making sensors or in making templates to wire and position nanodevices.
Co-reporter:Jie Zeng, Wei Lu, Xiaoping Wang, Bing Wang, Guanzhong Wang, J.G. Hou
Journal of Colloid and Interface Science 2006 Volume 298(Issue 2) pp:685-688
Publication Date(Web):15 June 2006
DOI:10.1016/j.jcis.2006.01.015
Fine control of the photoluminescence properties of CdSe nanoparticles (NPs) dispersed in CHCl3 is achieved by simple adjustment of the NPs concentration, and the wavelength of photoluminescence emission of CdSe NPs can be tuned within the nanometer accuracy. The mechanism of the process is proposed to be relevant to the modulation of the surface states of NPs by the concentration. This solution-based approach offers an attractive and complementary process to the conventional band gap engineering of semiconductor NPs with fine tunable optical properties.The process of HDA adsorbed on and desorbed from CdSe nanoparticles (NPs) in CHCl3 can modulate the amount of the surface states of NPs by the concentration, which can be used to fine tune the photoluminescence of CdSe NPs.
Co-reporter:Xiaoping Wang, Qinwei Shi, Hailong Hu, Kun Zhang
European Polymer Journal 2004 Volume 40(Issue 9) pp:2179-2183
Publication Date(Web):September 2004
DOI:10.1016/j.eurpolymj.2004.04.010
The force distance (F–D) curves of polytert-butyl acrylate (PtBuA) films have been studied by atomic force microscopy with various probing frequencies from 20 to 70 °C. The adhesion force is found to increase as the temperature increasing, which is corresponding to the glass-to-rubber transition of the polymer film. The F–D curve shows a typical shape in the case of about 2.5 nN applied force, but a break-free tail occurs in the case of about 24 nN applied force when the probing frequency is within an appropriate ranges, in which the polymer film transfers from the glass state to the glassy–rubbery state. We attribute the break-free tail to that the segments of PtBuA chains can be resonantly adhered to and released from the tip. Our observation indicates that the polymer segments adhered to the tip can be enhanced by their relaxation during the glassy–rubbery transition, and the average activation energy of the relaxation is estimated as about 2.1 eV.
Co-reporter:Xiaoping Wang, Qinwei Shi, Hailong Hu
Thin Solid Films 2004 Volume 466(1–2) pp:183-188
Publication Date(Web):1 November 2004
DOI:10.1016/j.tsf.2004.03.029
The friction of Polytert-butylacrylate (PtBuA) film was measured at different temperatures by the friction force microscopy (FFM). The load dependence and the scanning size effect on the friction of the film were investigated. It was found that, because the Young modulus of polymer decreased drastically with the temperature, the friction showed almost linear feature with the external load at temperatures below the glass-to-rubber transition temperature (Tg) of the polymer but sub-linear feature at temperatures above Tg. The friction was also observed to increase with the scanning size from 30 to 300 nm but saturate for the larger scanning size. As a comparison, the silicon oxidation films were scanned respectively with a clean tip as well as a polymer coated tip. The results indicated that the behaviour of the scanning size effect on the friction was contributed to the stretch and the fracture of molecular chains as the tip scanning on the polymer film surface.
Co-reporter:Tao Kong, Yang Chen, Yiping Ye, Kun Zhang, Zhenxing Wang, Xiaoping Wang
Sensors and Actuators B: Chemical (24 April 2009) Volume 138(Issue 1) pp:344-350
Publication Date(Web):24 April 2009
DOI:10.1016/j.snb.2009.01.002
A glucose biosensor is fabricated with immobilization of glucose oxidase onto ZnO nanotube arrays by cross-linking method. The ZnO nanotube arrays are synthesized by chemical etching of ZnO nanorods that are electrochemically deposited on the Au surface. Morphology and structure of ZnO nanotubes are characterized by FESEM, HRTEM and XRD. Fourier-transform infrared spectroscopy reveals that the glucose oxidase immobilized on the ZnO nanotubes retains its native conformation. The biosensor has a wide linear range for the detection of glucose from 50 μM to 12 mM (a correlation coefficient of 0.998) with 3 s response time. The sensitivity of the biosensor is found to be 21.7 μA/mM cm2. Moreover, its experimental detection limit is 1 μM (S/N = 3) and the apparent Michaelis–Menten constant is calculated to be 19 mM. The anti-interference ability and long-term stability of the biosensor are also assessed. Compared with the biosensors based on the nanorod and flat structure, the proposed biosensor shows expanded linear range and sensitivity. All these results demonstrate that ZnO nanotube can provide a promising material for the biosensor designs and other biological applications.
Co-reporter:Guanghui Zhang, Shenlong Jiang, Yue Lin, Wenzhen Ren, Hongbing Cai, Yukun Wu, Qun Zhang, Nan Pan, Yi Luo and Xiaoping Wang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 16) pp:NaN5681-5681
Publication Date(Web):2014/03/10
DOI:10.1039/C3TA14539E
The properties of the electron donor–acceptor interface play a crucial role in the photovoltaic performance of the core–shell nanorod array solar cells (NRASCs). In this paper, all-inorganic solid-state ZnO/CdTe and ZnO/CdS/CdTe core–shell NRASCs have been fabricated by a simple low temperature and low cost solution-based process. We investigate the influence of the CdS interfacial layer with different thicknesses on the performance of the solar cells. It is found that inserting such an interfacial layer can significantly improve the short-circuit current density and the open-circuit voltage of the device. The overall power conversion efficiency of the ZnO/CdS/CdTe core–shell NRASC with a 4 nm thick CdS interfacial layer can reach 0.72% under AM 1.5G illumination (100 mW cm−2), which is three times that of the ZnO/CdTe NRASC. The improvement in the performance is attributed to the designed graded energy band alignment of ZnO/CdS/CdTe and the passivation of surface defects of the ZnO nanorod by the CdS interfacial layer, which can result in the enhanced carrier separation and collection. The result clearly demonstrates that the performance of all-inorganic core–shell photovoltaic devices can be greatly improved with uncomplicated interface engineering.
Co-reporter:Nan Pan, Bing Wang, Xiaoping Wang and J. G. Hou
Journal of Materials Chemistry A 2010 - vol. 20(Issue 27) pp:NaN5581-5581
Publication Date(Web):2010/03/26
DOI:10.1039/B925007G
This feature article reviews some strategies and realizations for manipulating and tailoring the physical and chemical properties of zero dimensional (0-D) and one dimensional (1-D) nanomaterials as well as reveals the underlying mechanism. A series of high-resolution characterization techniques, such as high-resolution transmission electron microscopy (HRTEM), low temperature scanning tunneling microscopy (LT-STM), conductive atomic force microscopy (CAFM), and spatially resolved cathodoluminescence (CL), have been used in this study, which enable us to investigate the morphologies, structures and properties of individual nanomaterials experimentally. Some theoretical quantum chemistry methods such as tightbinding (TB) and density functional theory (DFT) are also applied for better understanding the experimental phenomena. Our results demonstrate that deliberate control at atomic and molecular scale, such as fabricating ordered and disordered metal nanoparticles, growing designed heterostructures, doping or grafting single molecules, and changing geometry (e.g., aspect ratio, tip sharpness, size, and surface ratio), can dramatically tailor the properties of the 0-D and 1-D nanomaterials. The results shown here can be extended to various nanomaterials and nanodevices, and therefore are useful for versatile applications in nanoscience and nanotechnology.
Co-reporter:Lin Quan, Yuqing Song, Yue Lin, Guanghui Zhang, Yanmeng Dai, Yukun Wu, Ke Jin, Huaiyi Ding, Nan Pan, Yi Luo and Xiaoping Wang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 42) pp:NaN11134-11134
Publication Date(Web):2015/09/28
DOI:10.1039/C5TC02209F
Chemical enhancement is one of the important mechanisms in surface-enhanced Raman spectroscopy, however, its origin is still under debate. Recently, a two dimensional (2D) layered material has been thought to be a strong candidate to investigate the chemical mechanism of Raman enhancement because it has a flat surface, a well defined structure and is without the interference of electromagnetic enhancement. Herein we report systematic studies of the Raman enhancement effect on a gallium selenide (GaSe) flake by using a copper phthalocyanine (CuPc) molecule as a probe. It is found that the Raman signal of CuPc on the monolayer GaSe can be significantly increased by one order of magnitude compared to that on a SiO2/Si substrate. Moreover, the enhancement effect is found to decrease with increasing thickness of the GaSe flake. The origin of the Raman enhancement is attributed to the chemical mechanism resulting from the charge transfer between the GaSe flake and the detected molecules. The supposition is further verified by the investigation of the quenching photoluminescence of GaSe as well as the Raman enhancement effect of CuPc with different thicknesses on the GaSe flake. Our work will shed more light on the understanding of the chemical mechanism for Raman enhancement and expand more practical applications of GaSe.
Co-reporter:Yukun Wu, Junwen Li, Huaiyi Ding, Zhiwei Gao, Yiming Wu, Nan Pan and Xiaoping Wang
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 7) pp:NaN5365-5365
Publication Date(Web):2014/12/12
DOI:10.1039/C4CP04998E
ZnO–Al2O3 core–shell nanorods (NRs) have been fabricated through the vapor phase condensation method and atomic layer deposition. It is found that the nanorod comprises a wurtzite single crystalline ZnO core with the main axes along the [0001] direction and an amorphous Al2O3 shell. The temperature-dependent photoluminescence (PL) properties of the as-grown and annealed ZnO/Al2O3 NRs are investigated systematically. The PL of the as-grown ZnO/Al2O3 NRs demonstrates a normal thermal quenching feature. However, the salient behavior of negative thermal quenching (NTQ), i.e., the increase in PL intensity with an increase in temperature, is clearly observed in the annealed ZnO/Al2O3 NRs. A multi-level model is adopted to account for this behavior and the thermal activation energy of the NTQ process is estimated to be ∼69 meV. Moreover, we suggest that the activation energy is related to the Al donor defect in ZnO resulting from the inter-diffusion between the ZnO core and the Al2O3 shell during the annealing process.
Co-reporter:Yiming Wu, Yanmeng Dai, Shenlong Jiang, Chao Ma, Yue Lin, Dongxue Du, Yukun Wu, Huaiyi Ding, Qun Zhang, Nan Pan and Xiaoping Wang
Physical Chemistry Chemical Physics 2017 - vol. 19(Issue 14) pp:NaN9544-9544
Publication Date(Web):2017/03/13
DOI:10.1039/C7CP00973A
Aluminium (Al)-doped zinc oxide (ZnO) nanowires (NWs) with a unique core–shell structure and a Δ-doping profile at the interface were successfully grown using a combination of chemical vapor deposition re-growth and few-layer AlxOy atomic layer deposition. Unlike the conventional heavy doping which degrades the near-band-edge (NBE) luminescence and increases the electron–phonon coupling (EPC), it was found that there was an over 20-fold enhanced NBE emission and a notably-weakened EPC in this type of interfacially Al-doped ZnO NWs. Further experiments revealed a greatly suppressed nonradiative decay process and a much enhanced radiative recombination rate. By comparing the finite-difference time-domain simulation with the experimental results from intentionally designed different NWs, this enhanced radiative decay rate was attributed to the Purcell effect induced by the confined and intensified optical field within the interfacial layer. The ability to manipulate the confinement, transport and relaxation dynamics of ZnO excitons can be naturally guaranteed with this unique interfacial Δ-doping strategy, which is certainly desirable for the applications using ZnO-based nano-photonic and nano-optoelectronic devices.
