Jin Mu

Facile assembly of silica gel/reduced graphene oxide/Ag nanoparticle composite with a core–shell structure and its excellent catalytic properties

A ternary assembly of silica gel (SG)/reduced graphene oxide (RGO)/Ag nanoparticles (Ag NPs) with a core–shell structure was prepared in aqueous solution by electrostatic self-assembly combined with a one-step reduction process. The composition and structure of the assembly (SG/RGO/Ag) were characterized by powder X-ray diffraction, transmission electron microscopy and Raman spectroscopy. The catalytic activity of the assembly was investigated for the degradation of rhodamine B (RhB) in the presence of NaBH4. The results showed that the degradation efficiency of the ternary assembly was the highest when compared with those of pure SG, SG/RGO and SG/Ag. When the loading amount of RGO and Ag NPs was 0.50% and 0.78% respectively, the degradation efficiency of the SG/RGO/Ag assembly can reach 100% within 8 min at 13 °C, and 1.2 min at 25 °C. This was about nine times the degradation efficiency of SG/RGO, and three times that of SG/Ag. The remarkably enhanced activity for the ternary assembly can be attributed to the synergy interaction between the RGO and Ag NPs. Importantly, the assembly has low a cost, convenient separability, and long-term stability for the degradation of RhB.

Facile assembly and properties of polystyrene microsphere/reduced graphene oxide/Ag composite

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.

Gold nanoparticles conjugated dopamine as sensing platform for SERS detection.

In this work, the properties of dopamine and dopamine-quinone on gold nanoparticles (Au NPs) surface were studied by the constructed Au NPs/dopamine sensing platform using surface enhanced Raman scattering (SERS) spectroscopy. Interestingly, the Au NPs/dopamine-quinone exhibited the characteristic Raman band at 1270, 1335 and 1480 cm(-1) at pH 10.0, whereas, no obvious Raman band of Au NPs/dopamine was observed at pH = 6.0. Also, dopamine-quinone could be reduced by glutathione (GSH) and dopamine could be oxidized easily by superoxide radical anion (O2(-)), thus, this sensing platform could be used to determine the concentration of GSH and O2(-) in a wide range. Importantly, the utility of Au NPs/dopamine platform was demonstrated in living HeLa and normal human liver (HL-7702) cells, and responded to the concentration changes of reactive oxygen species (ROS) in real time.

Electrochemical behavior of eugenol on TiO2 nanotubes improved with Cu2O clusters

TiO2 nanotubes incorporated with Cu2O clusters (Cu2O-TiNTs) were synthesized and employed as a probe for the rapid and sensitive voltammetric determination of eugenol. The electrochemical behavior of eugenol on the electrodes modified with Cu2O-TiNTs was explored systematically using cyclic voltammetry as a function of concentration of eugenol, scan rate, Cu2O content, and calcination temperature, respectively. Furthermore, the electrochemical response mechanism on these modified electrodes was discussed preliminarily. The results indicate that the electrodes coated with Cu2O-TiNTs possess high sensitivity to eugenol with a detectable concentration of 1.3 × 10−6 mol L−1. Here, the tubular structure of TiO2 nanotubes plays a key role in the electrochemical performance of Cu2O-TiNTs. The TiO2 nanotubes serve as an electron-transfer channel to enhance the electron transfer between eugenol molecules and electrode surface. Meanwhile, the Cu2O clusters serve as a promoter to further make the electron transfer more efficient and as a stabilizer to avoid change of the tubular structure of TiO2 nanotubes during calcination.

An efficient photocatalyst used in a continuous flow system for hydrogen evolution from water: TiO2 nanotube arrays fabricated on Ti meshes

In the present work, TiO2 nanotube arrays were fabricated on metallic Ti meshes using anodic oxidation method, and decorated with Pt via electrodeposition. Meanwhile, the application of the TiO2 nanotube arrays loaded with Pt in a continuous flow system was explored as a photocatalyst for H2 evolution from water. Furthermore, for practical purposes, the photocatalytic H2 evolution was studied as a function of content of loaded Pt, annealing temperature, anodic oxidation time, and flow velocity. The results indicate that the TiO2 nanotube arrays fabricated on metallic Ti meshes are an efficient photocatalyst which can be used in a continuous flow system for H2 evolution from water. During the first hour of irradiation, a rate of H2 evolution of approximately 4.6 L m−2 h−1 was achieved under optimal conditions. Moreover, the photocatalytic activity of the TiO2 nanotube arrays fabricated on Ti meshes is obviously higher than that of the TiO2 nanotube arrays fabricated on metallic Ti foils. The rate of H2 evolution can increase by a factor of 5 when the TiO2 nanotube arrays are fabricated on metallic Ti meshes. Finally, the photocatalytic mechanism was preliminarily discussed.

Interactions between quantum dots and dopamine coupled via a peptide bridge

Colloidal quantum dots (QDs) have a large fraction of their atoms arrayed on their surfaces and are capped with bifunctional ligands, which make their photoluminescence highly sensitive to potential charge transfer. In this report, we exploited the interactions of CdSe/ZnS QDs and dopamine (DA) coupled via a peptide bridge arginine–glycine–aspartic acid–cysteine (RGDC) and modulated the fluorescence and photoresponse of the DA–CDGR–QDs system by specific trypsin activity. Results showed that the quenching of the QDs emission was highly dependent on proper linkage which indicated that the RGDC as bridge could promote the charge transfer between the QDs and DA. Interestingly, the presence of trypsin could specifically cleave the peptide substrate, resulting in the fluorescence and photoresponse recovery of DA–CDGR–QDs system that depended on the enzyme concentration. These proximity driven interactions provide new insights for constructing the sensing assemblies to detect other enzyme activity.

Synergistic effect between eosin Y and rhodamine B on a photoelectrode coated with Pt nanoparticle-decorated graphene

In the present work, a photoelectrochemical system containing eosin Y, rhodamine B and graphene loaded with Pt nanoparticles was fabricated. The synergistic effect between eosin Y and rhodamine B was explored using photoelectrochemical techniques. The results show that there exists an obvious synergistic effect between eosin Y and rhodamine B in the as-fabricated photoelectrochemical system. Compared with the photoelectrochemical systems containing only eosin Y or rhodamine B, the photoelectrochemical system containing eosin Y and rhodamine B exhibits higher photoelectrochemical response. When graphene loaded with Pt nanoparticles is cosensitized by eosin Y and rhodamine B, the photocurrent is about 71% higher than the sum of the photocurrents of the photoelectrochemical system containing eosin Y and the photoelectrochemical system containing rhodamine B. This synergistic effect may be ascribed to the energy transfer from eosin Y to rhodamine B under irradiation. Herein, the Pt nanoparticles play an important role in the photovoltaic performance. The synergistic effect between eosin Y and rhodamine B cannot be observed if the Pt nanoparticles are absent. Moreover, the synergistic effect was investigated as a function of pH, content of Pt, molar ratio of eosin Y to rhodamine B, and total concentration of eosin Y and rhodamine B, respectively.

Facile assembly of a polystyrene microsphere/graphene oxide/porphyrin composite with core–shell structure

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.

Dramatic enhancement of the photocatalytic activity of Cd0.5Zn0.5S nanosheets via phosphorization calcination for visible-light-driven H2 evolution

In the present work, phosphorized Cd0.5Zn0.5S nanosheets were prepared through a hydrothermal process followed by phosphorization calcination at 500 °C. Meanwhile, the photocatalytic activity of the as-prepared phosphorized Cd0.5Zn0.5S nanosheets was explored for H2 evolution from water under visible light irradiation. The results indicate that the photocatalytic activity of the Cd0.5Zn0.5S nanosheets can be dramatically enhanced by phosphorization. Under optimal conditions, the H2 evolution rate over the phosphorized Cd0.5Zn0.5S nanosheets is up to 22.5 mmol h−1 g−1, and the apparent quantum efficiency is about 4.6% at 450 nm, which is 1.3 times higher than that over the pure Cd0.5Zn0.5S nanosheets. Furthermore, the photocatalytic mechanism was preliminarily discussed. It is found that the aforementioned enhancement of the photocatalytic activity may be ascribed to the introduction of Zn3P2 clusters. Here, the Zn3P2 clusters serve as charge transferring sites and/or active sites, which leads to efficient separation of the photogenerated electrons and holes, fast charge transfer and a lower hydrogen overpotential.

Visible Light Photocatalytic Hydrogen Evolution from Water Reduction Using Eosin y Containing Trace Vitamin B12 as a Light Harvesting Unit

A visible light photocatalytic system consisting of Eosin Y containing trace vitamin B12 (VB12) as a light harvesting unit, multiwalled carbon nanotubes (MWCNTs) as an electron transfer channel and CuO as a hydrogen evolution center (abbreviated to Eosin Y/VB12-MWCNTs-CuO) was prepared on the basis of the synergistic effect between Eosin Y and VB12 under visible light irradiation. The Eosin Y/VB12-MWCNTs-CuO system exhibits a higher photocatalytic activity of hydrogen evolution than the Eosin Y-MWCNTs-CuO system. The improvement of the photocatalytic activity is probably due to the effective transfer of photogenerated electrons and stabilization of VB12 to excited Eosin Y.