Fourier transform infrared spectroscopy

About: Fourier transform infrared spectroscopy is a research topic. Over the lifetime, 48250 publications have been published within this topic receiving 1134369 citations.

Preparation of activated carbon from peanut shell by conventional pyrolysis and microwave irradiation-pyrolysis to remove organic dyes from aqueous solutions

Abstract: Activated carbon samples were prepared from peanut shell by conventional pyrolysis (P sample) and microwave irradiation followed by pyrolysis (MW-P sample). These samples as well as peanut shell were characterized by N2 adsorption/desorption isotherms (BET), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), being applied to remove Direct Black 38 (DB38) and Reactive Red 141 (RR141) dyes from aqueous solutions. In order to evaluate the performance of adsorption process, pH effect, kinetic, equilibrium and desorption studies were carried out in this work. It was found that the MW-P sample exhibited superior characteristics such as texture, surface area, pore volume and pore size than the peanut shell and P sample. In addition, MW-P presented higher values of adsorption capacity, mainly at pH 2.5. The pseudo-second order kinetic model was suitable to represent the adsorption of DB38 and RR141 dyes on the MW-P sample. The Sips isotherm model was adequate to represent the adsorption of DB38 and RR141 on the MW-P sample, being the maximum adsorption capacities of 110.6 and 284.5 mg g−1, respectively. The dyes were desorbed from MW-P sample using an alkaline solution. The results demonstrated that the microwave irradiation followed by pyrolysis is an alternative way to prepare an activated carbon with interesting characteristics and high adsorption capacities for organic dyes.

Adsorption and solar light decomposition of acetone on anatase TiO2 and niobium doped TiO2 thin films.

Abstract: Adsorption and solar light decomposition of acetone was studied on nanostructured anatase TiO2 and Nb-doped TiO2 films made by sol-gel methods (10 and 20 mol % NbO2.5). A detailed characterization of the film materials show that films contain only nanoparticles with the anatase modification with pentavalent Nb oxide dissolved into the anatase structure, which is interpreted as formation of substituted Nb=O clusters in the anatase lattice. The Nb-doped films displayed a slight yellow color and an enhanced the visible light absorption with a red-shift of the optical absorption edge from 394 nm for the pure TiO2 film to 411 nm for 20 mol % NbO2.5. In-situ Fourier transform infrared (FTIR) transmission spectroscopy shows that acetone adsorbs associatively with eta1-coordination to the surface cations on all films. On Nb-doped TiO2 films, the carbonyl bonding to the surface is stabilized, which is evidenced by a lowering of the nu(C=O) frequency by about 20 cm(-1) to 1672 cm(-1). Upon solar light illumination acetone is readily decomposed on TiO2, and stable surface coordinated intermediates are formed. The decomposition rate is an order of magnitude smaller on the Nb-doped films despite an enhanced visible light absorption in these materials. The quantum yield is determined to be 0.053, 0.004 and 0.002 for the pure, 10% Nb:TiO2, and 20%Nb:TiO2, respectively. Using an interplay between FTIR and DFT calculations we show that the key surface intermediates are bidentate bridged formate and carbonate, and H-bonded bicarbonate, respectively, whose concentration on the surface can be correlated with their heats of formation and bond strength to coordinatively unsaturated surface Ti and Nb atoms at the surface. The oxidation rate of these intermediates is substantially slower than the initial acetone decomposition rate, and limits the total oxidation rate at t>7 min on TiO2, while no decrease of the rate is observed on the Nb-doped films. The rate of degradation of key surface intermediates is different on pure TiO2 and Nb-doped TiO2, but cannot explain the overall lower total oxidation rate for the Nb-doped films. Instead the inferior photocatalytic activity in Nb-doped TiO2 is attributed to an enhanced electron-hole pair recombination rate due to Nb=O cluster and cation vacancy formation.

Fabrication of Hydroxyapatite Hierarchical Hollow Microspheres and Potential Application in Water Treatment

Abstract: Many efforts have been made in fabricating three-dimensional (3D) ordered hydroxyapatite (Ca10(PO4)6(OH)2, HAp) nanostructures due to their growing applications as a bone cement, drug deliverer, tooth paste additive, dental implant, gas sensor, ion exchange, catalyst, etc. Here, we developed a new synthetic route to 3D HAp-based hollow microspheres through a water-soluble biopolymer (polyaspartic acid) assisted assembly from HAp nanorods. The as-obtained products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and Brunauer–Emmett–Teller (BET) gas sorptometry. SEM and TEM results showed that 3D HAp hollow microspheres are constructed by a number of one-dimensional (1D) nanorods as primary building units. The influences of the additive polyaspartic acid and reaction time on final morphology and assembled structure of the products were system...

Infrared spectroscopy study of low-dielectric-constant fluorine-incorporated and carbon-incorporated silicon oxide films

Abstract: Bonding characteristics of low-dielectric-constant (low-k) fluorine-incorporated silicon oxide (SiOF) and carbon-incorporated silicon oxide (SiOC) films prepared by plasma enhanced chemical vapor deposition were investigated by Fourier transform infrared spectroscopy (FTIR). The frequency of Si–O stretching vibration mode in SiOF film shifted to higher wave number (blueshift) with the increase of fluorine incorporation, while that in SiOC film shifted to lower wave number (redshift) as the carbon content increased. In N2-annealed SiOC film, the Si–O stretching frequency slightly shifted to lower wave number. To elucidate these phenomena, we have developed the “bonding structure model” based on the electronegativity of an atom. The frequency shifts observed in the FTIR spectra of SiOF and SiOC films were well explained by this model.