High-quality, oriented and mesostructured organosilica monolith as a potential UV sensor

Abstract

We synthesized high-quality and oriented periodic mesoporous organosilica (PMO) monoliths through a solvent evaporation process using a wide range of mole ratios of the components: 0.17–0.56 1,2-bis(triethoxysilyl)ethane (BTSE): 0.2 cetyltrimethylammonium chloride (CTACl): 0–1.8 × 10 −3 HCl: 0–80 EtOH: 5–400 H 2O. X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images indicated that the mesoporous channels within the monolith samples were oriented parallel to the flat external surface of the PMO monolith and possessed a hexagonal symmetry lattice ( p6 mm). The PMO monolith synthesized from a reactant composition of 0.35 BTSE: 0.2 CTACl: 1.8 × 10 −6 HCl: 10 EtOH: 10 H 2O had a pore diameter, pore volume, and surface area – obtained from an N 2 sorption isotherm – of 25.0 Å, 0.96 cm 3 g −1 and 1231 m 2 g −1, respectively. After calcination at 280 °C for 2 h in N 2 flow, the PMO monolith retained monolith-shape and mesostructure. Pore diameter and surface area of the calcined PMO monolith sample were 19.8 Å, 0.53 cm 3 g −1 and 1368 m 2 g −1, respectively. We performed 29Si and 13C CP MAS NMR spectroscopy experiments to confirm the presence of Si–C bonding within the framework of the PMO monoliths. We investigated the thermal stability of the PMO monoliths through thermogravimetric analysis (TGA). In addition, rare-earth ions (Eu 3+, Tb 3+ and Tm 3+) were doped into the monoliths. Optical properties of those Eu 3+, Tb 3+ and Tm 3+-doped PMO monoliths were investigated by photoluminescence (PL) spectra to evaluate their potential applicability as UV sensors.