•A novel Cu2O/porphyrin hybrid with special structure was facilely prepared.•Mechanisms of assembly and electron transfer for the hybrid were studied in detail.•There exists strong synergetic interaction between the porphyrin and Cu2O.•The hybrid showed more excellent photocatalytic performance for hydrogen production.A novel composite with special structure and excellent performance, 5,10,15,20-tetrakis(4-hydroxyphenyl) porphyrin (THPP) coated Cu2O nanoparticle (Cu2O/THPP), was facilely prepared by a simple method. UV–vis spectra, FTIR and fluorescence spectra were used to explore the interaction mechanism between THPP molecule and Cu2O nanoparticle. The results demonstrated that the center of the THPP macrocycle could coordinate with Cu2O, besides hydrogen bond and/or electrostatic interaction between peripheries of THPP macrocycle and Cu2O. Furthermore, photocatalytic hydrogen evolution performance of the composite was investigated. The composite displayed more excellent performance for hydrogen evolution than that of pure THPP, pure Cu2O or 5,10,15,20-tetraphenylporphyrin (TPP) coated Cu2O nanoparticle (Cu2O/TPP). By means of fluorescence spectra, electrochemical impedance spectra and photoelectronic performance measurement, the mechanism of electron transfer in the composite was explored. The results showed that the strong synergetic interaction caused by the special combination mode between THPP and Cu2O can quicken the transfer of photo-generated electrons, and was very favorable to improve the performance of the Cu2O/THPP composite.A novel Cu2O/tetrakis(4-hydroxyphenyl) porphyrin nanocomposite (Cu2O/THPP) with special structure showed higher photocatalytic activity for hydrogen evolution. The mechanisms of assembly, electron transfer and hydrogen evolution were explored in detail. It was demonstrated that the synergistic effect and strong interaction between THPP and Cu2O were the important factors to photocatalytic activity. The composite of Cu2O and THPP is an efficient approach for preparing cheap metal oxides/porphyrin based photocatalyst with higher photocatalytic activity.Download high-res image (229KB)Download full-size image

Graphene nanohybrids loaded with CuxNiy bimetallic nanoalloys (CuxNiy/G) were obtained via a facile co-reduction process. The composition and structure of the CuxNiy/G were characterized by X-ray diffraction, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The results showed that, besides composition, the size and morphology of CuxNiy particles on the graphene were different from those of Cu particles or Ni particles on graphene by the same preparation process. Furthermore, with eosin Y and rose bengal (ER) as co-sensitizers, and the CuxNiy bimetallic nanoalloy as the co-catalyst, the photocatalytic activity of hydrogen evolution over the CuxNiy/G increased and reached 5.05 mmol g−1 h−1 when the molar ratio of Cu2+ to Ni2+ was 1 : 3. Compared with that of pure graphene (G), its activity was enhanced by up to 8.2 times. It was also higher than those of Cu or Ni loaded G, and even comparable to that of Pt loaded graphene under the same conditions. The higher activity of the CuxNiy/G could be attributed to the small size effect and special morphology of the CuxNiy alloy, fast interfacial electron transfer and synergic interaction in the CuxNiy/G system. Therefore, the CuxNiy bimetallic nanoalloy could act as a cheap and highly efficient noble metal-free cocatalyst for enhancing photocatalytic activity for hydrogen production over graphene-based photocatalysts.

A new class of cytochrome c (Cyt c) detection fluorescence sensor (GQDs-GO) based on graphene quantum dots (GQDs) supported by graphene oxide (GO) has been developed through simply mixing a certain amount of GQDs and GO. It is found that fluorescence “turn on” or “turn off” can be adjusted easily according to the concentration of Cyt c. When the concentration of Cyt c is lower than 1.9 μmol L−1, the fluorescence is “turn on”, whereas it is “turn off” beyond 1.9 μmol L−1. The process is fast and can be completed within 10 s. By means of UV-vis absorption spectra, it is demonstrated that the changed fluorescence comes from the different interactions among GQDs, GO and Cyt c. Additionally, the GQDs-GO shows a high selectivity for Cyt c detection, and further exhibits favorable intracellular imaging in A549 cells. This study opens a new direction for developing a low-cost, highly efficient, GQDs-based fluorescence sensor for Cyt c detection, which make it very attractive for biological imaging applications.

•RGO intercalated potassium niobate nanoscrolls were prepared by a facile approach.•The nanoscrolls were with high and stable photocatalytic activity for H2 evolution.•The quick separation of carriers were vital to the improved activity.A new type of potassium niobate/reduced graphene oxide (RGO) composite nanoscrolls was prepared by the intercalation of RGO in the process of curling of the potassium niobate nanosheets. The as-prepared potassium niobate/RGO composite nanoscrolls were characterized with powder X-ray diffraction, transmission electron microscopy, Raman spectroscopy, solid diffuse reflectance UV–visible spectroscopy and fluorescence spectroscopy. The photocatalytic activity of the composite nanoscrolls was evaluated by hydrogen evolution from aqueous methanol under UV irradiation. It was found that the photocatalytic activity was enhanced as 3.1 times after introducing 2% RGO, compared with the pure potassium niobate nanoscrolls. It was ascribed to the enhanced separation efficiency of electron/hole pairs as testified by electrochemical impedance spectrum and fluorescence spectrum. Moreover, the composite photocatalyst was stable and easy to be recycled.

A novel silanized metalloporphyrin cobalt monomer (SMPCM) was prepared by using 5,10,15,20-tetra(4-hydroxyphenyl)porphyrin cobalt (CoTHPP) and γ-isocyanatopropyltriethoxysilane (ICPTES) as the reactants. Followed by the hydrolysis–polymerization of the organosilanes in the axial direction and peripheries of the SMPCM, the ordered porphyrin thin films with uniform morphology were facilely prepared on various substrates by the self-directed assembly of the SMPCM. The thin films formed was characterized by UV-vis spectra, electron microscopies, X-ray diffraction spectra, Fourier transform infrared spectra, fluorescence spectra and X-ray photoelectron spectra. The results demonstrated that the axial assembly between the Co3+ ion in the center of porphyrin macrocycle and ICPTES can prevent porphyrin lamellar from curling in horizontal direction, and then enhanced the order and stability of the films. Especially, the thin films possessed high, sensitive and stable photoelectronic response.

By a layer-by-layer self-assembly method, reduced graphene oxide (RGO)-based composite films with high photoelectronic activity were assembled with 5,10,15,20-tetrakis(p-N,N,N-trimethylanilinium)porphyrin tetraiodide (TAPPI) and copper sulfophthalocyanine (CuTsPc) as the co-sensitizers. The π–π interaction and electrostatic interaction were the main driving forces of the assembly. The linear dependence of the absorption on the layer numbers of the films demonstrated the formation of the ordered films. In the composite film, an efficient photoinduced electron transfer can take place as evidenced by fluorescence spectra. Furthermore, the photoelectronic response for the RGO/TAPPI/CuTsPc film was higher than that of the RGO/TAPPI film, the RGO/CuTsPc film or the TAPPI/CuTsPc film. The complementary absorption spectra of TAPPI and CuTsPc and the quick transfer of photoproduced electrons could be the main reasons for the enhanced photoelectronic response in the RGO/TAPPI/CuTsPc film.

•Three kinds of graphene oxide–porphyrin composites were facilely assembled.•The influence of functional groups on the binding mode of the composite is studied.•Properties of the composites can be adjusted by modifying the combination mode.Three kinds of graphene oxide (GO)–porphyrin composites were facilely assembled by means of non-covalent interaction. It was found that the functional groups linked on the peripheries of the porphyrins had an important influence on the combination mode of porphyrin and GO, and also the properties of GO–porphyrin composites. 5, 10, 15, 20-Tetrakis(4-hydroxyphenyl)porphyrin (THPP) was easy to react with GO and flat on the GO due to the strong hydrogen bond and π–π interaction between THPP and GO. It was reasonable to conclude that the distance between THPP and GO was reduced owing to the flattening of THPP on the surface of GO, which further strengthened the interactions. Therefore, the photoelectronic activity of the GO–THPP composite was higher than those of the other two porphyrins–GO composite. These results provided some hints for how to adjust the properties of the GO–porphyrin composites by modifying the combination mode between porphyrins and GO.

A novel and facile approach for preparing highly oriented porphyrin metal–organic framework films on various substrates is explored by employing self-directed assembly of silanized porphyrin cobalt monomers (SPCMs). The three-dimensional ordered porphyrin films display excellent photo-electronic performance.

5,10,15,20-Tetrakis(4-trimethylaminophenyl)porphyrin iodide (TAPPI) was easily assembled on the surface of graphene oxide (GO) coated polystyrene (PS) microspheres by electrostatic interactions combined with π–π interactions. In the monodisperse ternary composite with core–shell structure (PS microspheres/GO/TAPPI), effective electron transfer from excited TAPPI to GO can be achieved as evidenced by fluorescence spectra. Under continuous UV illumination, TAPPI molecules in the ternary composite displayed high UV stability compared with that of pure TAPPI. Furthermore, enhanced thermal stability could also be obtained for the ternary composite. It was possible to enhance the stability of the TAPPI molecules through conjugation of the delocalized π-electron systems between the PS microsphere supported GO and TAPPI.

•Cu2O loaded reduced graphene oxide (Cu2O/RGO) was prepared by a facile approach.•The Cu2O/RGO showed an enhanced photocatalytic activity for H2 evolution.•The composite photocatalyst was cheap and highly efficient.•The less recombination of electron-holes were conducive to the improved activity.Cu2O loaded reduced graphene oxide (Cu2O/RGO) was prepared via a one-step in-situ reduction method. Composition and structure of the Cu2O/RGO were characterized by X-ray diffraction, high resolution transmission electron microscope and X-ray photoelectron spectroscopy. With eosin Y (EY) and rose bengal (RB) as co-sensitizers, the activity of hydrogen evolution over the Cu2O/RGO dramatically increased and achieved a maximum when the loading amount of Cu on the RGO was about 3 wt.%. It exceeded that of RGO and Cu2O by a factor of 7.3 and 4.2 at the same conditions, respectively. It could be even comparable to that of the Pt/RGO under the same reaction conditions. This work showed a possibility of utilizing Cu2O as an alternative for noble metals (such as Pt) due to its low cost and high performance in photocatalytic hydrogen production.

•RGO loaded potassium niobate microspheres were prepared by a facile approach.•The microspheres showed an enhanced photocatalytic activity for H2 evolution.•The composite photocatalyst was cheap and stable.•The less recombination of electron–holes was conducive to the improved activity.A facile approach to synthesize reduced graphene oxide (RGO) loaded potassium niobate microspheres was reported. The composition, microstructure and electron-transfer properties of the obtained product were characterized. Compared to pure potassium niobate microspheres and commercial P25 TiO2, the as-prepared potassium niobate microspheres/RGO composite showed much higher photocatalytic activity for generating hydrogen under UV irradiation. It was ascribed to the enhanced separation efficiency of electron/hole pairs as testified by electrochemical impedance spectrum and fluorescence spectrum. Importantly, the composite photocatalyst was stable and easy to recycle, and the amount of hydrogen evolution did not decrease after six recycles. The results are potentially applicable to a range of semiconductors useful in water reduction as well as other areas of heterogeneous photocatalysis.

•RGO and Ag were evenly assembled on the surface of PS sphere using a facile method.•The composite assembly showed high stability and dispersion performance in water.•The excellent SERS activity indicated its potential application in sensor.A ternary assembly consisting of reduced graphene oxide (RGO), Ag nanoparticles, and polystyrene (PS) microsphere was prepared in aqueous solution by an electrostatic assembly combined with one-step reduction process. The composition and structure of the assembly (PS microsphere/RGO/Ag) were characterized by powder X-ray diffraction, transmission electron microscope, scanning electron microscope, X-ray photoelectron spectroscopy, and Raman spectroscopy. The interactions among RGO, Ag nanoparticles, and PS microsphere were investigated by surface enhanced Raman scattering spectroscopy. The results showed that there existed strong interactions among RGO, Ag nanoparticles, and PS microsphere. Importantly, the assembly showed high heat stability and good dispersion in water.

•The AuNPs/glycine derivatives (Gn)/GQDs composites with tunable bi-functionalities were fabricated.•The fluorescence and SERS response could be tuned effectively by changing the chain length of Gn.•This composite could be used in a wide pH range and exhibited good stability.•This composite displayed low cytotoxicity in A549 cells.Controllable assembly of the hybrids composed of various types of nanoscale objects provides new opportunities for material fabrication. Herein, the tunable bi-functionalities of fluorescence and surface enhanced Raman scattering (SERS) signals were collected by the assembled composites of gold nanoparticles (AuNPs)/glycine derivatives (Gn, n = 0, 3, 4, 5, 6 and 9)/graphene quantum dots (GQDs). The composition and structure of the AuNPs/Gn/GQDs composites were characterized by Fourier-transform infrared (FT-IR) spectroscopy and high resolution transmission electron microscope (HRTEM). Results indicated that the fluorescence and SERS response could be tuned effectively by changing the chain length of Gn. Also, the AuNPs/Gn/GQDs composites could be used in a wide pH range and exhibited good stability at room and physiological temperatures. Moreover, the AuNPs/Gn/GQDs composites displayed low cytotoxicity in A549 cells, and the cell viability was found to be above 90% at concentrations ranging from 6.42 to 200 μg/mL, which made AuNPs/Gn/GQDs composites very attractive for biological imaging applications in vivo.The biofunctional-composites of gold nanoparticles (AuNPs)/glycine derivatives (Gn, n = 0, 3, 4, 5, 6 and 9)/graphene quantum dots (GQDs) were assembled. The fluorescence and SERS response could be tuned effectively by changing the chain length of Gn. Also, the AuNPs/Gn/GQDs composites displayed low cytotoxicity in living cells, which made AuNPs/Gn/GQDs composites very attractive for biological imaging applications in vivo.Download high-res image (163KB)Download full-size image

A novel and facile approach for preparing highly oriented porphyrin metal–organic framework films on various substrates is explored by employing self-directed assembly of silanized porphyrin cobalt monomers (SPCMs). The three-dimensional ordered porphyrin films display excellent photo-electronic performance.