Making Borosilicate Nanoparticles Is Now Possible

A team of researchers at the Swiss Federal Institute of Technology, Lausanne, reports the first synthesis and characterization of borosilicate nanoparticles (Nat. Nanotechnol., DOI: 10.1038/nnano.2008.262). Borosilicate glass is inert, and as such it can withstand high temperatures and harsh chemical conditions, unlike polymers or silica used to make nanoparticles. Until now, borosilicate microparticles could be formed from a glass melt, but an unstable boron oxide precursor made the fabrication of nanoparticles impossible. Virendra K. Parashar, Martin A. M. Gijs, and colleagues got around this problem by first preparing a borosilicate gel from tetraethylorthosilicate and trimethoxyboroxine, using formic acid as a catalyst and dichloromethane and 2-propanol as solvents. Exposing a droplet of the gel to water without prior contact with air incites a dynamic reaction that immediately forms the solid nanoparticles. The researchers characterized the particles, which range from 100 to 500 nm in size, by microscopy techniques and elucidated the exothermic phase-separation mechanism that forms the nanoparticles via NMR studies. The researchers say the availability of these particles will broaden the potential of nanoparticles for chemical uses, including applications in filtration membranes, optics, and medicine.