Jinlin Long

Monolayered Bi2WO6 nanosheets mimicking heterojunction interface with open surfaces for photocatalysis.

Two-dimensional-layered heterojunctions have attracted extensive interest recently due to their exciting behaviours in electronic/optoelectronic devices as well as solar energy conversion systems. However, layered heterojunction materials, especially those made by stacking different monolayers together by strong chemical bonds rather than by weak van der Waal interactions, are still challenging to fabricate. Here the monolayer Bi2WO6 with a sandwich substructure of [BiO]+–[WO4]2−–[BiO]+ is reported. This material may be characterized as a layered heterojunction with different monolayer oxides held together by chemical bonds. Coordinatively unsaturated Bi atoms are present as active sites on the surface. On irradiation, holes are generated directly on the active surface layer and electrons in the middle layer, which leads to the outstanding performances of the monolayer material in solar energy conversion. Our work provides a general bottom-up route for designing and preparing novel monolayer materials with ultrafast charge separation and active surface.

Organic semiconductor for artificial photosynthesis: water splitting into hydrogen by a bioinspired C3N3S3polymer under visible light irradiation

A novel organic semiconductor photocatalyst mimicking natural light-harvesting antenna complexes in photosynthetic organisms, a disulfide (–S–S–) bridged C3N3S3polymer, was designed and developed to generate hydrogen from water under visible light irradiation. The artificial conjugated polymer shows high H2-producing activity from the half-reaction of water splitting without the aid of a sacrificial electron donor. The H2-producing efficiency and photo-stability of the catalyst could be improved greatly using Ru and single-wall carbon nanotubes as cocatalysts or by adding a sacrificial donor. The results represent a potential and prospective application of the C3N3S3polymer in solar energy conversion and offer significant guidance to develop more stable and efficient photocatalytic systems based on organic semiconductors.

Efficient Photocatalytic Degradation of Volatile Organic Compounds by Porous Indium Hydroxide Nanocrystals

Nanosized porous In(OH)(3) photocatalysts with high surface areas (as much as 110 m(2)*g(-1)) were successfully synthesized by peptization of colloidal precipitates under ultrasound radiation. The resulting catalysts were characterized by X-ray powder diffraction (XRD), thermogravimetric analysis, nitrogen adsorption, transition electron microscopy, and UV-vis diffuse reflection spectroscopy. The photocatalytic activities of the samples were evaluated by the gas-phase decomposition of several volatile organic pollutants (acetone, benzene, and toluene) under UV light illumination and were compared with that of the commercial titania (Degussa P25). Results revealed that the as-synthesized In(OH)(3) exhibited much higher photocatalytic activity and durability than both In(2)O(3) and TiO(2). One, therefore, can conclude that nanosized In(OH)(3) has potential application in environmental treatment, especially in the removal of benzene-containing exhaust emissions from shoemaking plants in China. The excellent photocatalytic performance of In(OH)(3) can be attributed to its strong oxidation capability, abundant surface hydroxyl groups, and high BET surface area as well as the porous texture.

Catalytic Role of Cu Sites of Cu/MCM-41 in Phenol Hydroxylation

Four types of copper-containing MCM-41 mesoporous silicas were synthesized by the surface organometallic chemistry (SOMC) procedure (Cu/MCM-41-S), mechanical mixing (Cu/MCM-41-M), impregnation (Cu/MCM-41-I), and the hydrothermal technique (Cu/MCM-41-H). The resultant samples were characterized in detail by X-ray diffraction (XRD), N(2) physical adsorption, transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), temperature-programmed reduction (TPR), and infrared spectroscopy (IR) of NO adsorption. Catalytic behaviors of these samples for hydroxylation of phenol with H(2)O(2) were evaluated. The results revealed that depending on the preparation methods the samples contain different copper-oxo species and thus show different catalytic behaviors. Among these samples, the one prepared by SOMC contains a predominant amount of isolated Cu(2+) and exhibits the most excellent catalytic activity and selectivity. The amount of isolated copper species decreases in the order of Cu/MCM-41-S > Cu/MCM-41-H > Cu/MCM-41-I > Cu/MCM-41-M, while the amount of copper oxide clusters increases in a reversal order. The difference in the catalytic activity and product selectivity of these four samples could be rationally explained by the distinction of chemical states of copper species. The highly dispersed isolated Cu(2+) species are identified as the active sites in the phenol hydroxylation, while the nonisolated Cu(2+) clusters or oxide are responsible for the deep oxidation of primary product HQ and the decrease of product selectivity. The mechanism of the copper-catalyzed phenol hydroxylation was proposed.

Nitrogen-doped graphene stabilized gold nanoparticles for aerobic selective oxidation of benzylic alcohols

Increasing efforts have been made to fabricate Au/graphene composites due to the fascinating properties of both graphene and gold. Some Au nanoparticles with an average size of tens of nanometers were directly deposited on reduced graphene oxide (RGO), utilizing the residual oxy-functional groups as the “hitching post” of the nanoparticles. Some functional groups, such as amino and thiol, were attached to the surface of the graphene in order to stabilize gold nanoparticles with a smaller particle size (<5 nm in general). Unfortunately, most of these strategies result in Au particles with limited exposed atoms, which is certainly a disadvantage for their application, such as catalysis. Introduction of nitrogen heteroatoms into the framework of graphene can not only modulate the electronic structure, but also change the surface properties of the graphene. In this work, naked Au nanoparticles with an average size of about 2–4 nm were fabricated on nitrogen-doped graphene nanosheets (NG) via the direct simple reduction method. The Au/NG nanocomposites were characterized by XRD, XPS, TEM, AFM and Raman. It was revealed that the nitrogen atoms doped in NG, rather than defects or oxygen moieties, play an essential role in stabilizing Au NPs. It was also found that the initial reaction rate of benzyl alcohol oxidation over the Au/NG catalyst is about ten fold higher than that over Au/graphene catalysts. Our findings may provide a clue of nitrogen incorporation to stabilize uncapped noble metal nanoparticles on graphene or other inorganic oxide supports, such as TiO2.

Urea-based hydrothermal growth, optical and photocatalytic properties of single-crystalline In(OH)3 nanocubes.

Nearly monodisperse single-crystalline In(OH)(3) nanocubes were successfully synthesized using In(NO(3))(3) x 4.5 H(2)O as indium source in the presence of urea and cetyltrimethyl ammonium bromide (CTAB) by a two-step hydrothermal process: the stock solution was heated at 70 degrees C for 24 h and then at 120 degrees C for 12 h. The structure and morphology of the resultant In(OH)(3) samples were determined by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results revealed that most of as-synthesized In(OH)(3) nanocubes were uniform in size, with the average edge length of approximately 700 nm. The influences of the reaction temperature, the reaction time, the mineralizer, and the surfactant on the morphology of the obtained products were discussed in detail. Room-temperature photoluminescence (PL) spectrum of the In(OH)(3) nanocubes showed a peculiar strong emission peak centered at 480 nm. Furthermore, the photocatalytic properties of the In(OH)(3) nanocubes were tested. It was found that In(OH)(3) exhibited not only higher activity for benzene removal, but also better H(2) evolution from water than the commercial Degussa P25 TiO(2).

In situ IR study of surface hydroxyl species of dehydrated TiO2: towards understanding pivotal surface processes of TiO2 photocatalytic oxidation of toluene

The surface species on P25-TiO(2) were characterized by FTIR after evacuation at 50-550 °C. The functions of OH groups on P25-TiO(2) catalysts have been tested by the adsorption and photooxidation of toluene in an in situ IR cell. FTIR studies show that the hydroxyl species on P25-TiO(2) are clearly temperature-dependent and P25-TiO(2) has six isolated hydroxyls with bands at 3734, 3715, 3688, 3671, 3658 and 3640 cm(-1). The OH groups on P25 play different roles in the photo-oxidation process: surface hydroxyls with bands at 3688, 3671, 3658 and 3640 cm(-1) act as adsorption sites while surface hydroxyls with bands at 3734 and 3715 cm(-1) act as sources of the ˙OH radical.

Photocatalytic and Antibacterial Properties of Medical-Grade PVC Material Coated With TiO2 Film

The TiO(2) film was coated on poly vinyl chloride (PVC) surface by dip-coating process from TiO(2)-PVC-THF suspension. The morphology and crystal structure of the as-synthesized samples were characterized by SEM and XRD. The photocatalytic properties were measured by the photodegradation reaction of RhB and the anti-adhesion and anti-bacteria for Escherichia coli. The results show that the resultant TiO(2) film is well-conglutinated on PVC surface and has the same crystal structure as the original TiO(2) powder. The TiO(2)/PVC shows excellent photocatalytic activity for the degradation of aqueous RhB and the activity increases with increasing reaction time and tends toward stable after accumulative illumination for 11.5 h. The TiO(2) film shows good bacterial anti-adhesion activity following photo-activation and sterilization property under UV irradiation. The E. coli can be killed completely after UV irradiation for 1.5 h.

Vacuum heat-treatment of carbon nitride for enhancing photocatalytic hydrogen evolution

Polymeric carbon nitride prepared by thermal condensation of cyanuric chloride with melamine was post-treated under vacuum conditions at different temperatures in order to study in depth the structure–performance relationship. The structure, composition, photoelectric and photocatalytic properties of the resulting samples were characterized in detail by physicochemical means, such as X-ray diffraction, thermogravimetry, elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, photocurrent response, electrochemical impedance spectroscopy photocatalytic hydrogen production, etc. The results revealed that the untreated polymeric carbon nitride was not a single phase but a mixture consisting of unequal-sized particles with different degrees of polymerization and chemical structures containing both s-triazine and tri-s-triazine ring building blocks. This makes it possible to modify polymeric carbon nitride through a post-treatment. Tremendous changes in the C/N ratio, IR spectra, photoresponse, morphology, and photocatalytic activity occurred mainly in two temperature ranges of 300–500 °C and 500–600 °C. Among all samples, the carbon nitride treated at 500 °C showed the highest photocatalytic activity for production of hydrogen from water, as a result of the higher content of the tri-s-triazine phase, better lamellar morphology, wider photoabsorption, and smaller electrochemical impedance. The vacuum heat-treatment at temperature above 500 °C gave rise to the broken structure, and consequently the photoactivity was reduced.

Fabrication of robust M/Ag3PO4 (M = Pt, Pd, Au) Schottky-type heterostructures for improved visible-light photocatalysis

M/Ag3PO4 (M = Pt, Pd, Au) Schottky-type heterostructures were successfully fabricated by a chemical deposition route using NaBH4 as a reduction agent. The structure and optical properties of the as-synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, and electrochemical techniques. The photocatalytic activity was evaluated by the decomposition of dyes (methyl orange, methylene blue, and rhodamine B) under visible light irradiation (λ > 420 nm). These noble metals as nanoparticles were highly dispersed on the surface of Ag3PO4 polyhedrons. The light absorption of Ag3PO4 in both the UV and visible regions was extensively increased upon noble metal deposition. The photocurrent response over M/Ag3PO4 electrodes was much higher than that of pure Ag3PO4 and followed the decreased order of Pt > Pd > Au. The metallic nanoparticles deposited on Ag3PO4 could promote the transfer of photo-generated electrons, which not only inhibited the recombination of electrons and holes effectively, but also suppressed the photocorrosion of Ag3PO4, leading to a significant increase in photocatalytic activity and stability. On the basis of radical-trapping experiments and the PL technique, h+ and ˙O2− were well-established to correspond to the quick photo-degradation of dyes and a possible mechanism was proposed.