Probing Local Effects in Silica Sol−Gel Media by Fluorescence Spectroscopy of p-DASPMI

Abstract

Stillbazolium salts present remarkable potential for application in several scientific areas. Their versatile behavior is explained by invoking the "twisted intramolecular charge-transfer" (TICT) mechanism, a model that describes the multiple fluorescence of DASPMI (4-(4-(dimethylamino)styryl)- N-methylpyridiniumiodine). One feature of their behavior is the sensitivity of the fluorescence lifetime to viscosity, thus identifying them as suitable probes for microheterogeneous systems, such as cells and sol-gel derived media. Because of their optical transparency, sol-gel matrices are light addressable and therefore appropriate for performing spectroscopic studies. The sol-gel process has been successfully used to produce hosts to biomolecules like proteins, for biosensor applications; however, these systems have to be optimized. Therefore, in this study modification of the matrices was performed through the incorporation of either silanes or polymers. (Aminopropyl)triethoxysilane, trimethoxypropylsilane, or (glycidyloxypropyl)triethoxysilane were added. The modification was also extended to the incorporation of the polymers poly(ethylene glycol) (molecular weight 300 and 20000) and Gelrite. The effect of these modifiers upon the gelation and aging processes was examined via the study of the photophysics of p-DASPMI by using both steady-state and time-resolved fluorescence. It was possible to discriminate the dominant dye-host interactions in each of the main steps of the preparation of modified sol-gel matrices.

Bio-sintering processes in hexactinellid sponges: Fusion of bio-silica in giant basal spicules from Monorhaphis chuni☆

“…In turn this phase is intimately connected with aging processes of the silica network. During this terminal stage, rotation of the units is constrained through promotion of the twisted intramolecular charge transfer (TICT) state of the silica network (Rei et al, 2008). In parallel with the alteration of the TICT state the viscosity of the silica matrix is enhanced.…”

Inclusion of push–pull N-methylpyridinium salts within surfactant hydrogels: is their excited state intramolecular charge transfer mediated by twisting?

“…[1][2][3][4][5][6][7][8] Due to their push-pull character, these compounds can undergo significant photoinduced charge transfer, which makes them suitable for many applications, such as non-linear optical (NLO) materials, 9,10 biological markers 11 and fluorescence indicators for neurons, 12,13 to name but a few. [1][2][3][4][5][6][7][8] Due to their push-pull character, these compounds can undergo significant photoinduced charge transfer, which makes them suitable for many applications, such as non-linear optical (NLO) materials, 9,10 biological markers 11 and fluorescence indicators for neurons, 12,13 to name but a few.…”

Fluorescence Anisotropy of Molecular Rotors

“…[36] Styryl dyes, and in particular 4-[4-(dimethylamino)styryl]pyridine (DMASP) derivatives are also molecular rotors [37] and have also been used to probe microviscosity in cells based on ratiometric fluorescence measurements [38,39] and fluorescence lifetime measurements of sol to gel transitions. [40,41] The fluorescence lifetimes of malononitriles in non-viscous media are short and can be difficult to measure, restricting their use somewhat. More recently there has been interest in a class of molecular rotors based on the boron dipyrromethene (BODIPY) fluorophore.…”