Photoelectrochemical behavior of a rhodamine dye intercalated in a photocatalytically active layered niobate and photochemically inert clay

Abstract

We investigated photoelectrochemical behavior of rhodamine 6G (R6G) dye intercalated in layered oxides of semiconducting hexaniobate and photochemically inert saponite clay. The R6G-clay intercalation compound generated comparable cathodic and anodic photocurrents. Photocurrent action spectra indicated that both the photocurrents were ascribed to photoexcitation of R6G monomers and dimers present in the interlayer spaces. On the other hand, the R6G-niobate intercalation compound exhibited a relatively large cathodic and small anodic photocurrents. Action spectra of the R6G-niobate system indicated that the photocurrents were generated by photoexcitation of only the R6G monomers while that the coexisting dimeric species were apparently silent. This result was explained by that the photocurrents were generated through photosensitization of the photocatalytically active semiconducting niobate layers with electron transfer from the photoexcited R6G monomers, whereas that the dimers were deactivated through dye-dye interactions.

Visible-light-induced electron transfer in intercalation-type composites organized on photocatalytically active layered niobate

“…The PF + molecules photoexcited by the visible light transfer electrons to the niobate layers, which have been suggested to be interacting with the dye molecules because of the hypsochromic shift of the absorption band in the visible spectra. The electrons migrate on the semiconducting oxide layers, as has been reported in previous studies, 20),22), 28) and meet the MV 2+ cations to generate the MV +• species. This mechanism can be rationalized by previous studies in an aqueous solution where photoexcited PF + reduces MV 2+ .…”

“…3) Another type of photochemical events has been reported for intercalation compounds of the layered niobates and titanates with dyes, where the photoprocesses can be initiated by photoexcitation of the intercalated dye molecules with visible light. Photoinduced electron/energy transfer from the intercalated dye species to the oxide layers has been achieved in the intercalation compounds or structurally compatible layer-bylayer assemblies of the semiconducting oxides with a ruthenium complex, 14) 16) porphyrin, 17),18) cyanine 19) and rhodamine dyes, 20) and polyaniline. 21) These studies provide important basis of photosensitizing the semiconducting layers required for effective utilization of solar energy, and thus, one can construct multicomponent systems for visible-light-induced electron transfer, which is a key process of artificial photosynthesis, by combining an electron acceptor and photosensitizer with the layered niobates and titanates.…”

Spectral properties of rhodamine 6G in smectite dispersions: Effect of the monovalent cations

“…Photophysical properties of organic dye molecules incorporated in porous compounds, such as aluminum and silicon oxides, have been studied last two decades [7,8]. Another group of the hybrid materials with intercalated organic dyes are based on layered inorganic matrices, such as layered phosphates [9], niobates [10], silicates (e.g. smectites) [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27], etc.…”