Chemical binding

About: Chemical binding is a research topic. Over the lifetime, 1822 publications have been published within this topic receiving 52516 citations.

Preparation and application of poly(dimethylsiloxane)/β-cyclodextrin solid-phase microextraction fibers

Abstract: A novel poly(dimethylsiloxane)/beta-cyclodextrin (PDMS/beta-CD) coating was prepared for solid-phase microextraction (SPME). The PDMS/beta-CD coating proved to have a porous structure, providing high surface areas and allowing for high extraction efficiency. The coating had a high thermal stability (340 degrees C) and a long lifetime due to its chemical binding to the fiber surface. Polar phenols and amines were used to evaluate the character of the coating fiber by headspace (HS) extraction and thermal desorption, followed by GC-FID analysis. Parameters that affected the extraction process were investigated; these include extraction time and temperature, desorption time, pH, and ionic strength of the solution. For phenols, the range of linearity of the method was 4-500 microg/L and the LOD was 1.3-2.1 microg/L. For amines, the range of linearity was 1-1000 microg/L and the LOD was 1.2-2.8 microg/L. The presence of beta-CD not only increases the thermal stability of the fiber coating, but also enhances its selectivity. Compared with commercially available SPME fibers, the new phases show better selectivity and sensitivity towards polar compounds.

The Physics of Semiconductor Materials

Abstract: Publisher Summary This chapter presents the physics of semiconductors. It discusses chemical binding and energy band structures of semiconductors, lifetime of electron-hole pairs, and impurity and lattice defect center. Sufficient information is now available about the semiconductor properties of a wide variety of materials to understand qualitatively the relations between the semiconductor properties and chemical binding and to indicate trends in the fundamental properties of semiconductor materials. In discussing these relations and trends, however, the chapter is restricted to homologous series of semiconductors with simple structures. These include (1) the group IV-B elements with diamond structures, (2) the M III- B - N V-B , M II-B - N VI-B , and M I-B - N VII-B compounds having the zinc blende or wurtzite structures, (3) the M IV-B - N VI-B , M III-B - N VI-B and the M I-B - N VII-B compounds having the sodium chloride or cesium chloride structures, and (4) the M 2 II-A - N IV-B compounds having the fluorite structure. The chapter discusses forbidden energy gaps and mobilities of materials in the various homologous series of semiconductors with other pertinent physical properties.

Intrinsic surface reaction equilibrium constants of structurally charged amphoteric hydrotalcite-like compounds

Abstract: The relative equations among intrinsic surface reaction equilibrium constants (K in 1-pK model, Ka1int and Ka2int in 2-pK model, and ∗ K Na int and ∗ K Cl int in inert electrolyte chemical binding model), points of zero charge (PZC), and structural charge density (σst) for amphoteric solids with structural charge were established to investigate the effects of σst on intrinsic equilibrium constants and PZC. The intrinsic equilibrium constants of HTlc with general formulas [(Zn,Mg)1−xAlx(OH)2](Cl,OH)x and [Mg1−x(Fe,Al)x(OH)2](Cl,OH)x were evaluated. The following main conclusions were obtained. For amphoteric solids with structural charge, a point of zero net charge (PZNC) independent of electrolyte concentration (c) exists. A common intersection point (CIP) should appear among the acid–base titration curves at different c, and the pH at the CIP is pHPZNC. The pK, pKa1int, and pKa2int may be expressed as a function of pHPZNC and σst, and these intrinsic equilibrium constants can be directly calculated from pHPZNC and σst. The inert electrolyte chemical binding does not exist for amphoteric surfaces with structural charge. PZNC is not equal to the point of zero net proton charge (PZNPC) when σst≠0. pHPZNC > pHPZNPC when σst>0; pHPZNC

Growth mechanism of thin oxide films under low‐energy oxygen‐ion bombardment

Abstract: Bombardment of silicon surfaces by low‐energy oxygen ions has been investigated as a possible process for growing films of SiO2 at room temperature. Broad ion beams of energy 40–200 eV and variable oxygen content have been used to grow ultrathin oxides of extremely uniform thickness. The ion beam oxides are similar to thin thermal oxides in many respects—composition, chemical binding, optical, and electrical properties. The dependence of the thickness and quality of the oxide films on ion dose, ion energy, and substrate temperature have been investigated. The obtained thickness is observed to vary only slightly with increasing substrate temperature up to 650 °C which indicates nonthermal process kinetics. The ion‐beam oxides reach a limiting thickness of 40–60 A which is largely independent of ion dose and is also found to be insensitive to ion energy. The observed oxidation is explained on the basis of surface implantation and radiation‐enhanced diffusion and reaction processes. Limited thicknesses are o...

Superhydrophobic treatment for textiles via engineering nanotextured silica/polysiloxane hybrid material onto fibres

Abstract: A rapid, cost effective and easy to implement method for treating wool and wool blend textiles to superhydrophobic with controllable interference on other properties such as handle is demonstrated. The process is based on in situ chemical binding of inexpensive silica and polysiloxane hybrid material onto fibres. Superhydrophobicity is achieved upon architecting nanoroughness on textile surfaces using silica nanoparticles. Modified textiles exhibit extremely high water repellency with contact angle reaching 166° and sliding angle ≤6°. Superhydrophobicity was maintained after three times of accelerated washing (equally 15 times of standard laundry wash). Topographical studies using AFM indicate that nanoscale roughness has been engineered on fibres with original size ~22 μm. The rough structure at two length scales plays a key role in enhancing surface hydrophobicity. Simplicity of processing such coatings onto textiles makes it possible for potentially large scale production.