Adsorption characteristics of 4-dimethylaminobenzoic acid on silver and titania: diffuse reflectance infrared Fourier transform spectroscopy study

Abstract We have investigated the adsorption behavior of 4-dimethylaminobenzoic acid (4-DMABA) on Ag and TiO2 by virtue of diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. 4-DMABA was found to chemisorb on silver as carboxylate, after deprotonation, with its two oxygen atoms bound symmetrically to the metal substrate. 4-DMABA was also very favorably adsorbed on TiO2 but with two different adsorption schemes. Most of the adsorbate was present as 4-DMABA− with its carboxylate group being held via a bidentate coordination to Ti4+ cations. The remaining adsorbate appeared to form a H-bond between the carbonyl group of 4-DMABA and the surface hydroxyl group of TiO2. Temperature dependent DRIFT spectra dictated that 4-DMABA molecules were surprisingly more strongly bonded to TiO2 than to Ag. This could be evidenced from the fact that the vibrational peaks of the adsorbed species were seen up to 600 K on TiO2, while they became substantially weakened around 450 K on Ag. From a cyclic thermal treatment, certain structural change appeared to occur around 400 and 500 K on Ag and TiO2, respectively.

[1]  J. E. Tackett.  FT-IR Characterization of Metal Acetates in Aqueous Solution , 1989 .

[2]  M. Primet,et al.  Infrared study of the surface of titanium dioxides. I. Hydroxyl groups , 1971 .

[3]  S. McEvoy,et al.  A comparison of 254 nm and 350 nm excitation of TiO2 in simple photocatalytic reactors , 1992 .

[4]  Paul A. Connor,et al.  Infrared Spectroscopy of the TiO2/Aqueous Solution Interface , 1999 .

[5]  Kwan Kim,et al.  Diffuse reflectance infrared spectra of stearic acid self-assembled on fine silver particles , 1998 .

[6]  H. S. Han,et al.  Diffuse Reflectance Infrared Spectra of 4-Nitrobenzoic Acid and 4-Cyanobenzoic Acid Self-Assembled on Fine Silver Particles , 1998 .

[7]  G. López,et al.  Chemical Sensors Based on Surface-Modified Sol-Gel-Coated Infrared Waveguides , 1998 .

[8]  S. Joo,et al.  Adsorption of 1,4-phenylene diisocyanide on silver investigated by infrared and Raman spectroscopy , 1999 .

[9]  D. Ollis,et al.  Is photocatalysis catalytic , 1980 .

[10]  S. Ahn,et al.  Vibrational Spectroscopic Investigation of Benzoic Acid Adsorbed on Silver , 1994 .

[11]  T. Kawai,et al.  Photocatalytic decomposition of gaseous water over TiO2 and TiO2—RuO2 surfaces , 1980 .

[12]  D. Ollis,et al.  Heterogeneous photocatalysis: Degradation of dilute solutions of dichloromethane (CH2Cl2), chloroform (CHCl3), and carbon tetrachloride (CCl4) with illuminated TiO2 photocatalyst , 1983 .

[13]  H. S. Han,et al.  Infrared and Raman spectra of 4-cyanobenzoic acid on powdered silver , 1999 .

[14]  H. Knözinger,et al.  Carbon monoxide — A low temperature infrared probe for the characterization of hydroxyl group properties on metal oxide surfaces , 1987 .

[15]  R. Greenler.  Infrared Study of Adsorbed Molecules on Metal Surfaces by Reflection Techniques , 1966 .

[16]  M. Yoon,et al.  Photoinduced intramolecular charge-transfer state of p-dimethylaminobenzoic acid in CdS and TiO2 colloid solutions , 2000 .

[17]  A. Ghosh,et al.  Photocatalytic decomposition of water at semiconductor electrodes , 1978 .

[18]  David F. Ollis,et al.  Photoassisted heterogeneous catalysis: the degradation of trichloroethylene in water , 1983 .

[19]  H. S. Han,et al.  Adsorption and Reaction of 4-Nitrobenzoic Acid on ω-Functionalized Alkanethiol Monolayers on Powdered Silver: Infrared and Raman Spectroscopy Study , 2000 .

[20]  G. D. Parfitt,et al.  Infra-red study of the surface properties of rutile. Water and surface hydroxyl species , 1971 .

[21]  V. Farmer.  The Infrared spectra of minerals , 1974 .

[22]  T. Kawai,et al.  Conversion of carbohydrate into hydrogen fuel by a photocatalytic process , 1980, Nature.

[23]  A. Gericke,et al.  The effect of cations on the order of saturated fatty acid monolayers at the air-water interface as determined by infrared reflection-absorption spectrometry , 1994 .