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.

Polyaniline and Carbon Nanotubes Based Composites Containing Whole Units and Fragments of Nanotubes

Abstract: Using surface-enhanced Raman scattering (SERS) and Fourier transform infrared (FTIR) spectroscopy, we show that composites based on polyaniline (PANI) and single-walled carbon nanotubes (SWNTs) are different when they are prepared by two different methods: (1) by adding dispersed SWNTs to the polymer solutions and (2) by chemical polymerization of aniline in the presence of SWNTs. The difference originates from the irreversible chemical transformation of SWNTs in the polymerization medium. The synthesis medium used for the preparation of PANI transforms SWNTs into fragments of shorter length like closed-shell fullerenes. This explains the similarity of SERS and FTIR spectra of the composites PANI/SWNTs and PANI/C60 chemically prepared. All compounds exhibit an absorption band at 1144 cm-1 in their FTIR spectra, increasing with the carbon nanoparticules content, as a signature of a charge transfer between the constituents. Besides, the FTIR spectrum of the compounds obtained by adding SWNTs to the polymer...

Bioactivity of a CaO−SiO2 Binary Glasses System

Abstract: Five glasses in the CaO−SiO2 binary system with different silica content (50−90% in mol) have been prepared by the sol−gel method. The referred glasses have been characterized by thermogravimetric and differential thermal analysis (TG/DTA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) showing clear differences in composition and specific surface and porosity between those glasses with low SiO2 content (50−70% in mol) and those with high SiO2 content (80−90% in mol). The in vitro bioactivity study of all glasses prepared were carried out by soaking in a simulated body fluid (SBF) at 37 °C. The FTIR, XRD, SEM, and EDS analysis of the surface of these glasses after the in vitro assays reveal the formation of a hydroxycarbonate apatite (HCA) layer. The formation process of this layer on the glass is a function of the glass composition. The rate of formation increases in those glasses with lower SiO2 (50−70...

Structure defects in g-C3N4 limit visible light driven hydrogen evolution and photovoltage

Abstract: Graphitic carbon nitride (g-C3N4) is a promising visible-light-responsive photocatalyst for hydrogen generation from water. As we show here, the photocatalytic activity of g-C3N4 is limited by structure defects generated during the calcination process. Specifically we find that the photocatalytic hydrogen production rate from aqueous methanol is inversely related to the calcination temperature (520–640 °C). The highest activity of 0.301 mmol h−1 g−1 is observed for the sample prepared at the lowest processing temperature. Surface photovoltage (SPV) spectroscopy shows that the maximum photovoltage is reduced (from 1.29 V to 0.62 V) as the processing temperature is increased, in accordance with higher defect concentrations and faster electron–hole recombination. The defects also produce additional optical absorption in the visible spectra and cause a red shifted, weakened photoluminescence (PL). Based on the sub-gap signal in the SPV and PL spectra, defect energy levels are +0.97 V and −0.38 V (vs. NHE) in the band gap of the material. According to Fourier transform infrared (FTIR) spectra, the defects are due to amino/imino groups in the g-C3N4 lattice.