Phonon mode of TiO2 coupled with the electron transfer from N3 dye

Low frequency vibrational spectra of submonolayer N3 dye (Ru(4,4(')-dicarboxy-2,2(')-bipyridine)2(NCS)2) adsorbed on TiO2 (110) were reported by using fourth-order coherent Raman spectroscopy, which is interface-sensitive vibrational spectroscopy. Most of the peaks observed in the experiment were at the same frequency as that of Raman and infrared spectra of the dye and TiO2. Two interfacial modes at 640 and 100 cm(-1) and one resonantly enhanced phonon at 146 cm(-1) appeared in addition to the pure TiO2 and N3 spectra. Adsorption of N3 dye on TiO2 contributed to the enhancement of 100 and 146 cm(-1) mode. The results not only reported interfacial low-frequency vibrations of TiO2 (110) with N3 dye adsorption but also suggested the coupling between the surface vibrations of TiO2 and charge transfer between N3 dye and TiO2 on the surface.

Fourth-order coherent Raman spectroscopy of liquid-solid interfaces: near-surface phonons of TiO2 (110) in liquids

The fourth-order coherent Raman response of a TiO2 (110) surface covered by HCl aqueous solution, neat octanol, acetic acid, or carbon tetrachloride layers is acquired. Four fourth-order optical responses were identified at 837-826, 452-448, 371-362, and 184-183 cm(-1) and assigned to near-surface phonons of TiO2. A third-order response produced in the bulk liquid layer was superimposed on the fourth-order response, when coherent vibrations are efficiently excited in the layer.

Scanning tunneling microscopy study of black dye and deoxycholic acid adsorbed on a rutile TiO2(110)

Trithiocyanato(4,4',4''-tricarboxy-2,2':6',2''-terpyridine)ruthenium(II), "black dye", was adsorbed on a rutile TiO(2)(110) surface and imaged by an ultrahigh vacuum scanning tunneling microscope. The TiO(2)(110)-(1 x 1) surface was prepared in a vacuum, covered with pivalate monolayer, and immersed in acetonitrile containing black dye. Black dyes exchanging preadsorbed pivalates were observed on the surface as protrusions with lateral dimensions from 2 to 10 nm. Protrusions with a minimum lateral dimension of 2 nm were assigned to single, isolated black dyes, and larger protrusions were attributed to aggregated dyes. When deoxycholic acid was added to the dye solution, the number ratio of the single dyes to the aggregated dyes increased, while adsorbed deoxycholic acid was not observed.

Surface vibrational modes of alpha-quartz(0001) probed by sum-frequency spectroscopy

Infrared-visible sum-frequency spectroscopy was used to probe surface vibrations of alpha-quartz(0001) under ambient conditions. Two modes at 880 and 980 cm(-1) were observed and identified as arising from Si-O-Si and Si-OH structures of the surface. Heat treatment and hydroxylation could convert Si-OH to Si-O-Si and vice versa. The technique is generally applicable to studies of surface phonons of other oxides, semiconductors, and insulators.