Template-Free Synthesis of Organically Modified Silica Mesoporous Thin Films for TNT Sensing

Abstract

In this paper, we present a facile, template-free sol-gel method to produce fluorescent and highly mesoporous organically modified silica (ORMOSIL) thin films for vapor phase sensing of TNT. An alkyltrifunctional, methyltrimethoxysilane MTMS precursor was used to impart hydrophobic behavior to gel network in order to form the spring back effect. In this way, porous films (up to 74% porosity) are obtained at ambient conditions. Fluorescent molecules are physically encapsulated in the ORMOSIL network during gelation. Fluorescence of the films was found to be stable even after 3 months, proving the successful fixing of the dye into the ORMOSIL network. The functional ORMOSIL thin films exhibited high fluorescence quenching upon exposition to TNT and DNT vapor. Fluorescence quenching responses of the films are thickness-dependent and higher fluorescence quenching efficiency was observed for the thinnest film (8.6% in 10 s). The prepared mesoporous ORMOSIL thin films have great potential in new sensor and catalysis applications.

Superhydrophobic and Omnidirectional Antireflective Surfaces from Nanostructured Ormosil Colloids

“…Also, porosities of the coatings were calculated using the relation between refractive index and porosity. 43,45 Optical transmission measurements were performed using a UV−vis−NIR spectrophotometer (Cary 5000, Varian). Static, advancing, and receding water contact angles of the coatings were measured using a contact angle meter (OCA 30, Dataphysics).…”

Template free preparation of nanoporous organically modified silica thin films on flexible substrates

“…23,27,29 In the first step, 1 ml of MTMS was dissolved in appropriate amounts of DMSO or methanol. For example, for the D7 gel a total of 7 ml DMSO was used.…”

“…An appropriate aging time is crucial for strengthening the gel network and preventing pore collapse during sonication and solvent evaporation. 28,29 Here, gels were aged during the washing steps and this was found to be sufficient to obtain highly porous colloids and thin films.…”

“…In our previous works we reported that thin films produced from such macroscopic phase separated gels have translucent appearance and for the films with thicknesses lower than 500 nm non-uniform film formation is observed due to macroporosity. 23,29 Thus, to produce uniform nanoporous thin films, the macroscopic phase separation in the MSQ gels should be prevented. Kanamori et al 24 prepared highly transparent MSQ gels (indicating no or little phase separation occurred) by using different surfactant solutions in water.…”

“…by comparing the porous film with a nonporous reference MTMS based thin film with a refractive index of 1.399. 29,31 The refractive index and porosities of the prepared films are shown with respect to MTMS concentrations (Fig. 5a).…”