Synthesis and optical properties of covalently bound Nile Red in mesoporous silica hybrids – comparison of dye distribution of materials prepared by facile grafting and by co-condensation routes

Abstract

The fluorescence dye Nile Red (NR) can be covalently ligated to hexagonally ordered, mesoporous silica materials (MCM-41) via co-condensation and post grafting routes in order to investigate possible differences in the dye distributions. The obtained hybrid materials display emission properties similar to free NR but in contrast to free dye molecules even aqueous gels are luminescent, rendering these materials particularly interesting for biolabeling applications. All materials were structurally characterized by nitrogen sorption measurements, small angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). Their optical properties were characterized by UV/Vis and fluorescence spectroscopy.

Multimodality Imaging of Silica and Silicon Materials In Vivo

“…The physical adsorption of dye onto the surface of ready‐made silica particles is another option, but this poses the risk of leakage and migration of the dye during application, unless the pores are further capped, e.g., by a surface coating. In the literature, different dye doping strategies into silica matrices have been compared to evaluate the homogeneity and the optical properties of particles after doping . In an extensive study, Börgardts et al have investigated the effects of in situ cocondensation and postsynthesis grafting strategies on the homogeneity of incorporated Nile Red (NR) dye in the silica matrices, and the consequential optical properties of the resulting silica hybrid material.…”

Energy down converting organic fluorophore functionalized mesoporous silica hybrids for monolith-coated light emitting diodes

“…Commencing from a 2-hydroxy-substituted Nile red 1 or 3-hydroxymethylperylene ( 2 ) the alkyne-substituted fluorophore derivatives 4 and 5 were accessible by Williamson ether synthesis [ 24 ]. The alkyne-functionalized green benzofurazane derivate 6 was obtained by nucleophilic aromatic substitution of 4-chloro-7-nitrobenzo[ c ][1,2,5]oxadiazole ( 3 ) with propargylamine.…”

“…Therefore, the respective dye precursors 9 , 10 , and 8 at variable concentrations were reacted with free silanol groups displayed on the surface of MCM-41 furnishing hybrid materials with different dye loadings in a μmol·g −1 range. The amount of dye incorporated into the hybrid material was estimated by UV–vis spectroscopic analysis according to our previous report [ 24 ].…”

“…If dye loadings of the hybrids are correlated with the surface area of the silica material, typically 700 m 2 ·g −1 , self-quenching effects should occur at loadings higher than 10 μmol·g −1 as illustrated in Fig. 3 [ 24 ]. Although aggregation-induced self-quenching can be prevented by covalently ligating dye molecules to the silica matrix, intermolecular energy transfer causing losses in quantum yield can be expected at higher dye loadings.…”

“…As benzofurazane and Nile red dyes exhibit solvatochomism, their spectral properties are clearly affected by incorporation into the polar silica environment. A detailed study of the spectral properties and solvatochromism of the Nile red hybrid materials in comparison to the precursor molecule 8 was previously reported and extensively discussed [ 24 ].…”