Chemical synthesis semiconductor catalysis

Semiconductor Catalysis for Chemical Synthesis. In recent years, the use of semiconductor photocatalysts have been investigated in a variety of applications. Anatase phase titania has applicability as a photocatalyst for several problems of environmental interest (/5,19), including use as catalyst for sulfur removal (20), for toxic... 

Tin oxide is an -1ype semiconductor with ca. 3.8 eV energy gap. It is the basic material commonly used in gas sensing, oxidative catalysis, photocatalysis, dye-sensitized solar cell and conductive glass. In order to enhance the performance of SnOa-based device, many studies have been focused on the synthesis of nanostructure Sn02-based materials with controllable microstructure, particle size and physico-chemical properties [1-6]. The sol-gel method was reported to be a simple and reproducible route for one-step synthesis of nanostructured... 

Novolac resins are produced commercially from cresol mixtures that contain amounts of m-cresol and p-cresol isomers in varying proportions, depending on the specific application. The reaction proceeds with both metal cation and acid catalysis (Scheme 1.1) Because of strict guidelines for metallic contaminants in semiconductor grade process materials and chemicals, acid catalysis is employed in the synthesis of novolacs used in photoresist applications. In a typical commercial production process, a mixture of m- and p-cresol isomers, formaldehyde (most often in the form of formalin, a 35-40% aqueous solution of formaldehyde) and an oxalic acid catalyst are reacted, following the description of Pampalone ... 

In recent years, W/O microemulsions have found numerous applications as microreactors for specific reactions (for comprehensive reviews, see Refs. 94 and 95). Thus, it has been shown that hydrophilic enzymes can be solubilized without loss of enzymatic activity and used to catalyze various chemical and photochemical reactions [96,97]. Other interesting applications involve the polymerization of solubilizates in microemulsions [98] and the preparation of micro-porous polymeric materials by polymerization of single-phase microemulsions [99]. Furthermore, microemulsions have been used as microreactors for the synthesis of nanosized particles for various applications [93,95] such as metal clusters (Pt, Pd, Rh, Au) for catalysis [100,101], semiconductor clusters [102-104] (ZnS, CdS, etc.), silver halides [105], calcium carbonates, and calcium fiuoride [106]. Recently it was shown [107,108] that it is possible to use W/O microemulsions for the control of polymorphism of water-soluble organic compounds. In most of these appUcations, one or more reactants are solubilized within a microemulsion and then a reaction is initiated. Depending on its molecular structure. 

Cadmium sulphide (CdS) is an II-VI semiconductor material with a direct band gap of 2.42 eV at room temperature with many outstanding physical and chemical properties, which has promising applications in photochemical catalysis, gas sensors, detectors for laser and infrared, solar cells, nonlinear optical materials, luminescence devices and optoelectronic devices [36-39]. CdS also exhibited excellent visible light detecting properties [40]. In the last decades, many techniques have been reported on synthesis of CdS nanoparticles [41-43]. 

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