InP Nanocrystals with Color-Tunable Luminescence by Microwave-Assisted Ionic-Liquid Etching

This article reports the successful synthesis of luminescent InP nanocrystals (NCs) of different sizes using microwave-assisted methods. The key to NC photoluminescence (PL) is the use of 1-butyl-4-methylpyridinium tetrafluoroborate (BMPy BF4), an ionic liquid (IL) with a fluoride-containing anion. The IL is responsible for both rapid heating of the reaction solution and efficient PL from the NCs. This is demonstrated by comparison with other ionic liquids, an analogous synthesis done using a flask and heating mantle, and a microwave-assisted synthesis in a silicon carbide (SiC) vessel. Addition of amine results in InP NC sizes ranging from ∼3.2–4.2 nm, calculated (PL from ∼545–630 nm) with quantum yields (QYs) of up to 30% and PL full-width-at-half-max (fwhm) values as small as ∼0.18 eV (∼59 at 632 nm) without optimization. By taking advantage of efficient microwave-assisted heating, this simple procedure provides a pathway to luminescent InP NCs of different diameters without changing precursors, performing sequential additions of reactants, or other postreaction processing (e.g., shell growth, HF etching).