Generations Yi Ma,† Xiuli Wang,† Yushuai Jia,† Xiaobo Chen,‡ Hongxian Han,*,† and Can Li*,† †State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Dalian National Laboratory for Clean Energy, 457 Zhongshan Road, Dalian 116023, China ‡Department of Chemistry, College of Arts and Sciences, University of Missouri-Kansas City, 5100 Rockhill Road, Kansas City, Missouri 64110, United States

Titanium dioxide-based nanomaterials for photocatalytic fuel generations.

A surface science perspective on TiO2 photocatalysis

In this review we intend to provide a relatively comprehensive summary of the work of supramolecular hydrogelators after 2004 and to put emphasis particularly on the applications of supramolecular hydrogels/hydrogelators as molecular biomaterials. After a brief introduction of methods for generating supramolecular hydrogels, we discuss supramolecular hydrogelators on the basis of their categories, such as small organic molecules, coordination complexes, peptides, nucleobases, and saccharides. Following molecular design, we focus on various potential applications of supramolecular hydrogels as molecular biomaterials, classified by their applications in cell cultures, tissue engineering, cell behavior, imaging, and unique applications of hydrogelators. Particularly, we discuss the applications of supramolecular hydrogelators after they form supramolecular assemblies but prior to reaching the critical gelation concentration because this subject is less explored but may hold equally great promise for helping ...

Supramolecular Hydrogelators and Hydrogels: From Soft Matter to Molecular Biomaterials

In semiconductor particles of nanometer size, a gradual transition from solid-state to molecular structure occurs as the particle size decreases. Consequently, a splitting of the energy bands into discrete, quantized levels occurs. Particles that exhibit these quantization effects are often called “Q-particles” or, generally, quantized material. The optical, electronic and catalytic properties of Q-particles drastically differ from those of the corresponding macrocrystalline substance. The band gap, a substance-specific quantity in macrocrystalline materials, increases by several electron volts in Q-particles with decreasing particle size. In Q-particles there are approximately as many molecules on the surface as in the interior of the particle. Therefore, the nature of the surface as well as the particle size is also largely responsible for the physico-chemical properties of the particle. Q-particles of many materials can be prepared in the form of colloidal solutions or embedded in porous matrices and are stable over a long period of time. In sandwich colloids, in which Q-particles of different materials are coupled, as well as in porous semiconductor electrodes containing Q-particles in the pores, very efficient primary charge separation is observed. As a result, sandwich colloids have greatly enhanced photocatalytic activity relative to the individual particles, while electrodes modified with Q-particles show high photocurrents. This article deals with the size quantization effect, the synthesis and characterization of Q-particles, as well as with the spectroscopic, electrochemical, and electron-microscopic investigation of these particles.

Colloidal Semiconductor Q‐Particles: Chemistry in the Transition Region Between Solid State and Molecules

Climate change and the consumption of non-renewable resources are considered as the greatest problems facing humankind. Because of this, photocatalysis research has been rapidly expanding. TiO2 nanoparticles have been extensively investigated for photocatalytic applications including the decomposition of organic compounds and production of H2 as a fuel using solar energy. This article reviews the structure and electronic properties of TiO2, compares TiO2 with other common semiconductors used for photocatalytic applications and clarifies the advantages of using TiO2 nanoparticles. TiO2 is considered close to an ideal semiconductor for photocatalysis but possesses certain limitations such as poor absorption of visible radiation and rapid recombination of photogenerated electron/hole pairs. In this review article, various methods used to enhance the photocatalytic characteristics of TiO2 including dye sensitization, doping, coupling and capping are discussed. Environmental and energy applications of TiO2, including photocatalytic treatment of wastewater, pesticide degradation and water splitting to produce hydrogen have been summarized.

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A review of TiO 2 nanoparticles

Photochemistry and radiation chemistry of semiconductor colloids: reaction of the hydrated electron with CdS and non-linear optical effects

Kinetics of oxidation of glycine and related substrates by diperiodatoargentate (III)

Photocatalytic degradation of aniline at the interface of TiO2 suspensions containing carbonate ions.

The photophysical changes taking place by coupling of Cd(OH) 2 -coated Q-CdS with colloidal TiO 2 have been examined. The coupling of TiO 2 causes the quenching of the band gap emission of CdS and the red emission is not affected appreciably. For a typical 0.22×10 −3  mol dm −3 of TiO 2 the average emission lifetime of Cd(OH) 2 -coated CdS is reduced from 26.4 to 6.8 ns by trapping of the conduction band electron by TiO 2 . Cd(OH) 2 -coated Q-CdS does not sensitize the reaction of indole, however, the coupled CdS–TiO 2 catalyst photoinitiated this reaction efficiently. The photoactivity of the coupled semiconductor is suggested to increase due to chemical interaction between Cd(OH) 2 -coated Q-CdS and TiO 2 which removes Cd(OH) 2 layer to form possibly [CdS–TiO 2 (OH) 2 ]. The photogenerated hole in the coupled catalyst CdS(h + ) forms an emissive exciplex with indole. The exciplex is long lived and results in the decomposition of indole ( φ =0.18) to yield indigo with a quantum efficiency of 0.08.The concentration of both TiO 2 and redox couple controls the extent of charge separation in the photocatalyst. The application of coupled semiconductors as catalysts for photosynthetic work is suggested.

Photophysics and photochemistry of colloidal CdS–TiO2 coupled semiconductors — photocatalytic oxidation of indole

The present manuscript for the first time reports a novel one-step wet chemical approach to synthesize about 150–300 nm wide graphene nanoribbons (GNRs) by reduction of graphene oxide (GO) using malonic acid as a reducing agent. Optical, X-ray diffraction, high resolution transmission electron microscopy, Raman, infrared, X-ray photoelectron spectroscopy and 13C nuclear magnetic resonance (NMR) demonstrated the effective reduction of GO. The average thickness of GNRs has been estimated by atomic force microscopy at 3.3 ± 0.2 nm, which is reduced significantly to 1.1 ± 0.5 nm upon annealing at 300 °C (GNRs-300). In the process of nucleation and growth, the intermediate(s), formed between malonic acid and GO undergo twisting/folding involving supramolecular interactions to yield ∼0.15 to 1 mm long curled GNRs. 13C NMR demonstrates a significant increase in the sp2 character of the nanoribbons following the order GO < GNRs < GNRs-300, as also evidenced by the conductivity measurements. GNRs exhibited a high specific capacitance value of 301 F g−1 at 1 A g−1 with good cyclic stability for 4000 charge–discharge cycles at 15 A g−1, and high energy density/power density (16.84 W h kg−1/5944 W kg−1) in an aqueous electrolyte demonstrating their tremendous potential as electrode material for energy storage applications.

Anil Kumar

Papers

Photochemistry and radiation chemistry of semiconductor colloids: reaction of the hydrated electron with CdS and non-linear optical effects

Kinetics of oxidation of glycine and related substrates by diperiodatoargentate (III)

Photocatalytic degradation of aniline at the interface of TiO2 suspensions containing carbonate ions.

Photophysics and photochemistry of colloidal CdS–TiO2 coupled semiconductors — photocatalytic oxidation of indole

One-step chemically controlled wet synthesis of graphene nanoribbons from graphene oxide for high performance supercapacitor applications