Fluorescent hybrid organic–inorganic particles: influence of physical encapsulation versus covalent attachment on leaching and UV stability

Abstract

Hybrid organicinorganic materials provide the opportunity for combining organic chromophores into inorganic networks. The resulting hybrids can be used for numerous optical, biomedical and nanotechnology applications. Hybrid organicinorganic particles that absorb and fluoresce in visible or ultraviolet light are particularly useful for bio-imaging, sensors, and as a safe sunscreen. The organic component can be incorporated through physical entrapment or through covalent incorporation through siloxane linkages. By containment in the hybrid material, the performance lifetime of the chromophore can be extended significantly and environmental contamination by its leaching out can be reduced. In this study, silica particles containing 1 mol % dimethylaminonathyl-sulfonamide (dansyl) dyes were prepared by three different methods: 1) physical encapsulation inside a hollow silica particle, 2) covalent attachment of pendant chromophores through a single silyl group and 3) covalent attachment through two silyl groups. The influence of the mode of entrapment on the particles' spectroscopic properties, the propensity of the chromophores to leach from the particles, and photochemical degradation of chromophores were determined for the three classes of hybrid materials.

Dansyl-Labelled Ag@SiO2 Core-Shell Nanostructures—Synthesis, Characterization, and Metal-Enhanced Fluorescence

“…Elevation of the reaction temperature and utilization of toluene as the reaction solvent significantly increased the reaction efficiency. The yield of performed reaction is comparable to those reported in the literature and exceeds 90% [ 41 , 42 ].…”

Hybrid inorganic-organic fluorescent silica nanoparticles—influence of dye binding modes on dye leaching

“…Particles with any kind of dye label tend to be slightly larger than pure silica particles (Fig. 1), which is consistent with literature results [11].…”

“…In addition to the leaching of the dyes, which is only investigated qualitatively in most studies, this understanding should also include the localization of the dyes in or on the particle and an investigation of the binding mode. Tolbert et al showed that the extent of the dye leaching decreases as the strength of the dye's binding to the particle increases [11]. In our study, we studied leaching over a longer time period and investigated leaching-influencing factors such as the intensity of the dye-particle interaction and the position of the dye molecules in the particle.…”

“…For this synthetic approach it is necessary that the dye matches parameters such as polarity during the particle formation. The drawback of this encapsulation method is the risk of dye leakage [10,11], caused by the rather weak interaction between dye and particle as well as the porous nature of the particles. Modification of the dye molecules or the particle surface with functional groups allowing a covalent connection between dye and silica network represents a method to minimize dye leaching [12,13].…”

“…With regard to dye leaching and necessity of covalent dye incorporation, only a few detailed studies were published in the past [10][11][12]29]. Since the particles are often used in sensitive biological matrices, it is necessary to obtain a sufficient understanding of the interaction between particle and dye.…”