Xiangqing Li

Promoting visible light-driven hydrogen evolution over CdS nanorods using earth-abundant CoP as a cocatalyst

Exploiting earth-abundant cocatalysts for photocatalytic hydrogen evolution is of great interest. Herein, earth-abundant CoP was used as a cocatalyst to fabricate a CdS nanorod based photocatalytic system. Meanwhile, visible light-driven H2 evolution over the CoP decorated CdS nanorods was investigated. Moreover, the electrochemical behavior and photoelectrochemical behavior of the CdS/CoP photocatalytic system were explored to deeply demonstrate the essential role that CoP played in the photocatalytic process. Lastly, the photocatalytic mechanism was preliminarily discussed. The results indicated that the photocatalytic activity of the CdS nanorods could be remarkably enhanced due to the introduction of CoP. Under optimal conditions, a rate of H2 evolution of approximately 2.12 mmol h−1 was achieved and the apparent quantum yield was up to 27.1% at 435 nm, which was about 20 times higher than that over the CdS nanorods and 1.5 times higher than that over the Pt loaded CdS nanorods, respectively. This dramatic photocatalytic activity of the CoP modified CdS nanorods may be ascribed to the low H+ reduction overpotential on the CoP particles and the efficient electron transfer between CdS and CoP. The present work demonstrates that CoP is a promising alternative to Pt as an efficient cocatalyst for CdS.

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.

Visible Light Photocatalytic Activity of Porphyrin Tin(IV) Sensitized TiO2 Nanoparticles for the Degradation of 4-Nitrophenol and Methyl Orange

A stable metalloporphyrin sensitized TiO2 (Degussa P25) photocatalyst was prepared by using trans-dihydroxo[5,10,15,20-tetraphenylporphyrin]tin(IV) (SnP) as a sensitizer in a simple impregnation process. The solid diffuse reflectance ultraviolet-visible (UV-vis) spectrum of the SnP sensitized TiO2 photocatalyst (SnP-TiO2) indicated that there existed interaction between SnP and TiO2. It was found that SnP-TiO2 exhibited an enhanced visible light photocatalytic activity as compared with that over P25 for the degradation of 4-nitrophenol (4-NP) and methyl orange (MO) in aqueous solutions. The mechanism exploration showed that the degradation of MO and 4-NP experienced two different ways, that is, MO was photodegraded by reactive oxygen species and 4-NP was directly photodegraded by the excited state of SnP. Furthermore, it was found that the loading content of SnP had an important influence on the photocatalytic activity of TiO2. The maximum photocatalytic efficiency was achieved when the contents of SnP were 25 mg and 30 mg per gram TiO2 for MO and 4-NP, respectively. Importantly, SnP-TiO2 was particularly stable and the photocatalytic activity was hardly decreased after being recycled seven times in the presence of oxygen, which could be attributed to the easy reductive regeneration of SnP.

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.

Fabrication and Properties of Porphyrin Nano- and Micro- particles with Novel Morphology

New types of porphyrin nano- and micro-particles composed of J- and H-heteroaggregates were prepared by electrostatic self-assembly of two oppositely charged porphyrins, tetrakis(4-trimethylammoniophenyl)porphyrin (H2TAPP4+) and tetrakis(4-sulfonatophenyl)porphyrin cobalt(II) (CoTPPS4−), in aqueous solutions. Transmission electron microscopy (TEM) images showed novel morphology and size distribution of porphyrin particles fabricated under different experimental conditions. The assembly process of the nano- and micro-particles was monitored by UV–Vis spectra. Fluorescence spectra and UV–Vis spectra provided optical information on the formation of the nano- and micro-particles. Cyclic voltammograms of the porphyrin particles indicated that the electron gain and loss of the H2TAPP4+ion were restrained, and the electron transfer of the CoTPPS4−ion was promoted in the J- and H-type porphyrin heteroaggregates within the particles. The stability and constitution of the nano- and micro-particles were confirmed by UV-light irradiation, heat-treatment, and pH and ionic strength changes. Photoelectrochemical measurements showed that the photoelectron transfer of TiO2modified with the particles was more efficient than that of TiO2sensitized by either monomers. The photoelectronic and photocatalytic properties of the products indicated that the pyramidal or spherical configuration of the nano- and micro-particles was favorable for the absorption and transfer of the energy. It can be found that TiO2sensitized by the porphyrin nano- and micro-particles exhibits significant improvement in energy conversion and photocatalytic activity with reference to pure TiO2.

Photoluminescence Properties of Silica Xerogels Co‐doped with Eu3+ Ions and CdS Nanoparticles

Silica xerogels doped with Eu3+ ions and co‐doped with Eu3+ ions and CdS nanoparticles were prepared using a two‐step hydrolysis process. The effect of temperature on photoluminescence properties of Eu3+‐doped silica xerogel was investigated. The results showed that the photoluminescence of Eu3+‐doped silica xerogel was significantly dependent on the temperature of heat treatment. The study of the photoluminescence of co‐doped xerogels showed that the defect emission of silica was weakened due to competition among defects, CdS nanoparticles, and Eu3+ ions.

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.

Synergetic effect of Cu–Pt bimetallic cocatalyst on SrTiO3 for efficient photocatalytic hydrogen production from water

Herein, a series of novel SrTiO3 (STO) based photocatalysts loaded with Cu–Pt bimetallic co-catalysts have been synthesized through a simple photodeposition process. This photocatalyst of STO/Cu–Pt displayed enhanced photocatalytic activity for hydrogen generation from water in the presence of methanol as a sacrificial reagent. Moreover, the hydrogen generation efficiency over the STO/Cu95–Pt5 photocatalyst was about 2.79 and 1.76 times of STO/Cu100–Pt0 and STO/Cu0–Pt100, respectively. Thus, this Cu–Pt synergetic cocatalyst presents an inexpensive and high efficiency cocatalyst to achieve efficient hydrogen evolution from water.