Solid-state Solvatochromic Behavior of Reichardt’s Dye Crystals Hybridized with Silica Nanoparticles

Abstract

The dry bead milling of solvatochromic ET30 with silica nanoparticles gave powdery nanohybrids, which exhibited color changes depending on environmental conditions.

PyridiniumN-Phenolate Betaine Dyes

“…It was reported that dye 1 adsorbed to silica exhibits an orange-red color [λ max = 497 nm; E T (30) = 57.5 kcal mol –1 ], while a red-violet color occurs when the dye is adsorbed onto non-dried cellulose [λ max = 539 nm; E T (30) = 53.0 kcal mol –1 ] . The same dye exhibits a green color when it is adsorbed to macroporous polystyrene [λ max = 752 nm; E T (30) = 38.0 kcal mol –1 ]. , Ichimura et al used dry-bead milling of betaine dye 1 with surface-modified silica nanopowder to produce nanohybrid particles, the color of which depends notably on the external atmosphere and is green (λ max of the diffusion reflection spectra = 695 nm), blue (619 nm), and purple (566 nm) under dry, ambient, and wet conditions (Δλ = −129 nm; Δν̅ max = +3279 cm –1 ), according to the increase in surface polarity. Table shows the E T (30) and normalized E T N values determined for various inorganic and organic solid materials.…”

Solid-state photoelectron transfer in powdery nanocomposites comprised of a sensitiser, photoacid generators and silica nanoparticles

“…We have recently observed that solvatochromic Reichardt's dye E T 30 in the solid state suffers considerably from blue shift in diffusive reflection spectra when the dye is nanohybridised with m-SiO 2 to give nanopowders and exposed to water, implying the specific contact of surface molecules with water. 18 In analogy to this sort of surfacespecific behaviour of organic crystals, a portion of DPA molecules at the topmost surfaces of crystals is released from the confinement of crystal lattice to display monomeric absorption spectra.…”

Solvatochromic sensor array for the identification of common organic solvents

“…15 Historically, these color-changing dyes have been studied in liquid phase and characterized using UV-Vis absorption spectroscopy; however, some recent work has used individual solvatochromic dyes in solids (e.g., films of dyes entrapped in porous, semi-liquid, or polymer matrices). [21][22][23][24][25] Prior colorimetric sensor arrays produced from our lab have included only one or two solvatochromic sensor spots, but the response of an array of solvatochromic dyes in the solid-state has not been previously examined.We report here a colorimetric sensor array that utilizes solvatochromic dyes in semi-liquid matrices to differentiate eleven common organic solvents. Importantly, the solvatochromic dyes serve a dual function: (1) to change color with a change in local polarity and (2) to facilitate the measurement of physical changes in their matrix caused by solvent sorption.…”

“…15 Historically, these color-changing dyes have been studied in liquid phase and characterized using UV-Vis absorption spectroscopy; however, some recent work has used individual solvatochromic dyes in solids (e.g., films of dyes entrapped in porous, semi-liquid, or polymer matrices). [21][22][23][24][25] Prior colorimetric sensor arrays produced from our lab have included only one or two solvatochromic sensor spots, but the response of an array of solvatochromic dyes in the solid-state has not been previously examined.…”