Highly sensitive and selective detection of Cu(ii) by periodic mesoporous rhodamine derivative-based organosilicas with crystal-like pore walls

摘要

Rhodamine-6G Schiff-base bridged periodic mesoporous organosilicas (RSPMOs) were successfully synthesized by co-condensation of rhodamine Schiff-base derivative-bridged organosilanes and tetraethoxysilane (TEOS), using the ionic liquid 1-hexadecyl-3-methyiimidazolium bromide (C_(16)mimBr) as a structure-directing agent. The formation mechanism of ordered mesoporous hybrid materials with crystal-like pore walls was mediated by the self-assembly of both the long-chain ionic liquid and the new organosilane precursors. As the molar fraction of the new organosilane precursors was above 1%, hybrid materials with crystal-like pore walls were obtained, which was due to the face-to-face π-π interaction between rhodamine moieties of the new organosilane precursors within the framework. Little or no fluorescence emission of the hybrid material with rhodamine Schiff-base units was observed because of the existence of spirolactam in rhodamine moieties before chelating with metal ions. However, a dramatic enhancement in fluorescence emission was shown due to opening of the spiro structure in rhodamine moieties, which was induced by intramolecular charge transfer from metal ions to rhodamine units when the hybrid materials chelated with corresponding metal ions. RSPMOs showed high sensitivity and selectivity towards Cu~(2+) in aqueous solutions with good tolerance for other metal ions, showing great superiority in practical application.