Humidity-Dependent Reversible Aggregation of Rhodamine 6G Dye Immobilized within Layered Niobate K₄Nb₆O₁₇

Abstract

The spectroscopic behavior of rhodamine 6G (R6G) dye intercalated in layered hexaniobate K4Nb6O17 was investigated. R6G cations were intercalated into the niobate through displacement of preintercalated alkylammonium ions. Powder X-ray diffraction and elemental analysis indicated that the dye molecules were densely accommodated in the interlayer spaces of niobate. The spectroscopic behavior of intercalated R6G was characterized by humidity-dependent aggregation at room temperature. The dye molecules were present dominantly as monomers under humid conditions (93% relative humidity (RH)), while they formed dimers under relatively dry conditions (20% RH). The aggregation-deaggregation of dye occurred reversibly depending on the humidity. The reversible aggregation was not accompanied by a large alteration of the interlayer structure of the sample, because only a small amount of water was adsorbed/desorbed with a small change in the basal spacing of the intercalation compound during the humidity change.

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

“…However, we may observe photochemical communications in the R6G-niobate intercalation compound under appropriate conditions, because photoinduced electronic/energetic interactions should be allowed between the niobate layers and the R6G molecules if we consider previous studies of niobate-dye systems. 17), 18) Since the R6G molecules exhibit peculiar aggregative behavior in the interlayer spaces of niobate, 35) the photochemical host-guest interactions may be related to the aggregated state of the intercalated dye species.…”

“…32), 35) The R6G-niobate intercalation compound was synthesized with stepwise intercalation of propylammonium (C3N) and R6G cations into potassium hexaniobate K4Nb6O17. 35) K4Nb6O17 prepared by a solid-state reaction 36) was allowed to react with an excess amount of a 1 mol dm -3 aqueous C3N solution at room temperature for 90 min. Then, the C3N-intercalated niobate was allowed to react with an excess amount of a 0.03 mol dm -3 aqueous R6G solution at 353 K for 3 weeks.…”

Preparation of porous solids composed of layered niobate walls from colloidal mixtures of niobate nanosheets and polystyrene spheres

“…Thus, the macroporous solids whose walls are composed of the propylammonium/K 4 Nb 6 O 17 intercalation compound were obtained in this case. The interlayer space in the walls of the macroporous solid should be further modifiable by ion-exchange of the interlayer propylammonium ions with other cationic guest species, as reported for powders of propylammonium/K 4 Nb 6 O 17 intercalation compounds [28]. By calcination at 500 • C for 6 h, the peaks due to the layered structure were displaced by the new peaks at 2θ = 14.5, 29.3, and 44.5 • (d = 0.61, 0.31, and 0.20 nm), indicating that the layered structure is converted to crystalline K 8 Nb 18 O 49 phase [29].…”

“…Before calcination (Fig. 4a), the peaks are observed at 2θ = 4.7, 9.5, and 14.0 • , which corresponds to d = 1.86, 0.93, and 0.63 nm, and they are ascribed to the first-, second-, and third-order peaks due to the layered structure of propylammonium/K 4 Nb 6 O 17 intercalation compound [28]. This result indicates that the nanosheets were restacked as a propylammonium/K 4 Nb 6 O 17 intercalation compound by evaporating the solvent.…”

Photoinduced electron accumulation in colloidally dispersed wide band-gap semiconductor nanosheets

“…The XRD pattern of the niobate colloid in the absence of the additives shows the basal reflection at d = 2.2 nm (2h = 4.0°) with the second-and third-order reflections (Fig. 2a), the pattern which is assigned to that of hexaniobate intercalated with propylammonium ions [35]. This pattern indicates that the negatively charged niobate nanosheets are surrounded by propylammonium cations in the colloidal state, and restacked with the counter cations to the intercalation compound.…”