In situ thermal synthesis of molybdenum oxide nanocrystals in thermoresponsive microgels

Abstract

In situ formation of nanocrystals within thermoresponsive microgels has become a significant technology in the fields of catalysis and biomedicine to fabricate multifunctional hybrid nanostructures. Usually, the room temperature or cooler was set to control the formation of nanocrystals using microgels as template in such process. Here, the relatively higher temperature was used to synthesize molybdenum oxide nanocrystals where the poly(N-vinyl caprolactam) microgels were found to work as both the stabilizer and the template. Specifically, ethanol was added in the solution of the microgels to raise their volume phase transition temperature (VPTT). Later, a modified hydrothermal process was performed at 70 °C with precursor molybdic acid concentrated in the microgels matrix through the hydrogen bond between molybdic acid and N-vinyl caprolactam units. 2D nanoflakes, nanorods and nanoplatelets of molybdenum oxide were successfully synthesized. Specially, the microgels with the crosslinked degree of 2% exhibited well hybrid with controlled sizes and ideal confine of the molybdenum oxide nanoplatelets within microgels, along with strong photoluminescence intensity. These results emphasized the feasibility of poly(N-vinyl caprolactam) microgels as template and stabilizer at high temperature and provided a novel synthesis strategies for hybrid microgels applicable in wide areas of nanotechnology from catalysis, sensing to therapy.