Nanocrystal-silica composite lasers are stable in solvents

Tiny lasers made of semiconductor nanocrystals incorporated in a film would be ideal for use in microfluidic chemosensors. Such films made with titania matrices have already been shown to lase. Unfortunately, these nanocrystal-titania composites degrade in water and alcohols, so they are unsuitable for microfluidics. MIT chemistry professors Moungi G. Bawendi and Daniel G. Nocera and their coworkers have now made a solvent-stable laser with CdSe nanocrystals embedded in a silica matrix (J. Am. Chem. Soc., published online Feb. 15, dx.doi.org/10.1021/ja057980d). Earlier attempts to use silica matrices resulted in composites lacking enough nanocrystals. The researchers overcame this problem by modifying the nanocrystal surfaces with 5-amino-1-pentanol and using 3-aminopropyltrimethoxysilane as the silica precursor. Composites made with the silane had a rough surface, but replacing a small amount of the silane with (triethoxysilyl)propyl isocyanate provided smooth films. The nanocrystal-silica composites lase at room temperature even while submerged in water or alcohol solutions.