Silylated Coumarin Dyes in Sol−Gel Hosts. 1. Structure and Environmental Factors on Fluorescent Properties

Abstract

Several silylated coumarin dyes with different linkages and degrees of functionality have been synthesized and incorporated in both SiO 2 xerogels and various solvent hosts. The absorption and fluorescence spectra were examined to explore selected structural and environmental effects on the optical properties of these dyes. Silylated dyes (also referred to as grafted or functionalized dyes) are dye molecules that have been chemically altered to provide alkoxysilane functionality allowing the active molecule to be covalently bonded to the host. Silylation of dye molecules had little effect on the absorption and fluorescence spectra in neutral solvent environments. The optical spectra of silylated dyes compared to those of their conventional counterpart were less influenced by the local chemical environment (e.g., pH) and thus allow for greater control and stability of the fluorescent properties of the dyes in different host environments. Spectroscopy during the drying/gelling of a derCoum xerogel film containing a silylated coumarin dye illustrate changes in the chemical forms of the dye molecules associated with changes in the local chemical environment of the dye.

Photostability of silylated coumarin dyes in polyceram hosts

“…and then decayed linearly over long times. The shapes of these curves are very similar to those of the same dyes in xerogel hosts [8]. The initial decay was found to be partially reversible in the Polyceram monoliths and xerogels.…”

“…3. The coumarin dyes in Polycerams have absorption maxima near 320 nm, similar to the same dyes in solvent and xerogel hosts [9]. The only exception was the derCoum Polyceram which had an absorption spectrum that was slightly blue shifted.…”

“…We have recently reported the use of silylated or grafted laser dyes [7][8][9]. These are laser dyes which are chemically attached to an alkoxysilane group.…”

“…Numerous coumarin silylated dyes have been synthesized and incorporated within xerogels at high concentrations. The use of a silylated laser dye resulted in (1) improved solubility of the silylated dye with respect to its unsilylated counterpart, allowing for higher concentration of active molecules within a sol-gel matrix [7]; (2) higher fluorescence efficiency, attributed to the greater rigidity and isolation of the silylated dye within its host [7]; (3) improved chemical stability, associated with the lack of leachability of the dye from the host [7]; (4) control of dye/matrix interactions affecting optical spectra [9]; and (5) improved photostability [8].…”

Photoactive Europium Hybrids of β‐Diketone‐Modified Polysilsesquioxane Bridge Linking Si–O–B(Ti)–O Xerogels

“…[6] Similarly, luminescent lanthanide hybrid materials obtained by grafting lanthanide complexes onto some matrices, such as silica-based materials, [7] polymers, [8] or liquid crystals, [9] can exhibit excellent optical properties and good thermal and compressive stabilities [10] relative to the pure lanthanide complexes. According to the different force acting between the two phases, organic-inorganic hybrid materials are divided into two major classes.…”