p‐Nitrobenzoic Acid Adsorption on Nanostructured Gold Surfaces Investigated by Combined Experimental and Computational Approaches

Abstract

Adsorption of guest molecules on host surfaces can lead to dramatic changes in the spectral properties of the guest. One such effect is surface-enhanced infrared absorption (SEIRA), observed when the guest is adsorbed on, for example, thin films, metal surfaces, or nanotubes. p-Nitrobenzoic acid (p-NBA) exhibits a SEIRA effect when adsorbed on Ag and Au. Herein, the IR spectra of p-NBA adsorbed on a homemade rough Au surface, recorded in reflection mode with an angle of incidence of 16.5°, are reported. This SEIRA experiment reveals more bands than found by previous SEIRA studies. The intensities of both symmetric and asymmetric COO(-) and NO(2) stretching, in-plane CH, and C=C ring stretching modes are enhanced. Theoretical models constructed on the basis of density functional theory reveal the binding mode of p-NBA to gold "particles". The p-NBA anion binds to gold much more strongly than the neutral form, and interaction via the carboxylic oxygen atoms is preferred over the nitro group-gold contact. A significant charge transfer during chemisorption is found, which is considered to be crucial in leading to a high SEIRA enhancement factor.

Exploiting the Surface-Enhanced IR Absorption Effect in the Photothermally Induced Resonance AFM-IR Technique toward Nanoscale Chemical Analysis

“…In contrast, a previous FTIR-SEIRAS report indicated that the IR absorption bands for PNBA samples on an Ag island film increased very slowly (or the enhancement factor drops) after the thickness was above ca. 5 nm . This is consistent with the short-range confined electric field and the long-range confined thermal field on nanostructured metal surfaces.…”

“…5 nm. 57 This is consistent with the short-range confined electric field and the long-range confined thermal field on nanostructured metal surfaces. In the presence of the SEIRA effect, ||E loc || 2 in equation 1 is enhanced in comparison to that in the absence of the SEIRA effect and the enhancement factors vary with increasing d. As we have mentioned above, though the electric field enhancement of SEIRA occurs only within a few nanometers from the metal surface, the photothermal effect caused by SEIRA may extend to tens to hundreds of nanometers.…”

“…The absorption band centered at 1692 cm −1 corresponds to the CO stretching mode in −COOH, 1604 cm −1 to the CC ring stretching mode, 1524 cm −1 to the antisymmetric stretching vibration of −NO 2 , 1432 cm −1 to the CC ring stretching mode, 1340 cm −1 to the NO 2 symmetric stretching mode, and 1292 cm −1 to the C−O stretching mode. 57 Since the 1524 cm −1 band is the most intense and is not overlapped with other neighboring bands or artifacts, it was used for the following parameter-dependent intensity study. Therefore, unless specified, the PTIR spectra of PNBA samples were measured and presented over the 1400− 1800 cm −1 spectral region.…”

Secondary Emission From Synthetic Opal Infiltrated by Colloidal Gold and Glycine

“…The observed features in the photoluminescence spectra could be explained by the close location of the PC stop-zone and the plasmon resonance region in gold nanoparticles to the region of emission of initial opal and the fluorescence property of gold particles [8]. Thus, it was shown in [9] that gold particles have a plasmon resonance near 530 nm. Meanwhile, the gold particles or gold rough surface show the photoluminescence in the visible region [8].…”

Retracted: Adsorption Features of Flavonoids on Macroporous Adsorption Resins Functionalized with Ionic Liquids

“…Noort and co-workers suggested a five-parameter, threecompartment model that assumes a triphasic adsorption process in which the slow fraction can divide into two compartments, a slowly adsorbing one and a very slowly adsorbing one. [43][44][45][46] An advantage of this model is that it theoretically describes a continuous distribution of sorptive compartments with only two parameters. Shuler, Miller and Riddle studied a new, two-parameter model to express the kinetics of adsorption based on the statistical gamma function.…”