Blue luminescent InP quantum dots achieved by liquid-assisted femtosecond laser ablation

Abstract

We demonstrate a facile method to produce blue-emitting InP quantum dots (QDs) by a liquid-mediated femtosecond laser ablation in liquids (FLAL) technique. Various complementary characterizations confirmed the formation of InP nanoparticles in toluene with an average size of ∼11 nm, comparable to the Bohr exciton radius of InP (∼10 nm). An exotic high-pressure stable phase of the InP (cubic-zinc blende) is observed in the core region of the formed nanoparticles, whereas a metastable phase, such as hexagonal InP with a wurtzite structure, is observed in the edge region. The broad and intense emission observed near 400 nm is attributed to the confinement effects. Interestingly, the FLAL of InP in de-ionized water and acetone led to the formation of In2O3 and other InP-based composite nanoparticles. The important role of solvents in the production of diverse InP QDs has been discussed in detail, especially considering their polar and protic nature. The ablated surfaces have also exhibited distinct nanostructures in all three cases. These results illustrate beneficial information for the controlled production of InP-based quantum dots and to elucidate the underlying phenomenon governing the ultrafast ablation of semiconductors in liquid media.