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Special data handling techniques for Fourier-transform infrared photoacoustic spectra : estimation and characterization of the N contents on ammoniated trichlorosilylated silica-gel, using partial least-squares regression and curve fitting on the Si-H stretching vibration
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| Abstract |
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| The reaction of silica gel with trichlorosilane (HSiCl3) and subsequently with gaseous NH3, resulting in a surface covered with =Si-O-Si(H)(NH2), and NH4Cl species, has been studied. The Si-H stretching vibration (2270 cm-1) of the trichlorosilylated silica perturbs, upon ammonia adsorption, into three overlapping bands. It is shown that partial least-squares regression (PLSR) is able to predict the concentration of the different surface species, using the Si-H stretching vibration region as the only spectral dataset. It is noticeable that this vibration has a constant intensity, since the Si-H species are generated during the trichlorosilylation step, and not during the ammoniation. The mechanisms, causing this perturbation are investigated in more detail, using curve fitting and Si-29 cross-polarisation magic-angle-spinning (CP MAS) NMR. The occurrence of an ammoniated secondary species [(=Si-O),-Si(H)(NH2)] on the silica surface is proposed and its infrared (IR) absorbing frequency is determined. An introduction to PLS for the spectroscopist is included. | | |
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English
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Journal of the Chemical Society: Faraday transactions: physical chemistry and chemical physics / Chemical Society [Londen] - London | |
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London : 1993
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0956-5000
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89:1(1993), p. 63-68
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A1993KH27700011
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