Photon upconversion is the conversion of two lower energy photons into one higher energy photon, which can be used in applications such as photovoltaics, optogenetics, and bioimaging. Currently, cadmium and lead-based nanoparticles are used for upconversion systems because of their relatively high upconversion quantum yields. However, their high toxicity precludes their use in biomedical applications. Indium phosphide nanoparticles (InP) are a non-toxic alternative that possess the desired characteristics of the highly toxic, heavy metal-based nanoparticles: size tunability, higher upconversion quantum yields, and facile surface modification. Larger InP nanoparticles can absorb wavelengths in the near-infrared (NIR) region, which is ideal for biomedical applications. The NIR region is considered the biological window because these wavelengths can penetrate the skin and are used for in-vivo imaging. In order to be able to apply this non-toxic upconversion system in biomedical applications, hydrophobic InP nanoparticles need to be placed in the human body and therefore need to be water-soluble. The goal here is to create a system in which we can encapsulate these non-toxic InP upconversion systems in water-soluble micelles in hopes of being able to use them for biomedical applications like bioimaging. We will use DSPE-mPEG, a pegylated phospholipid polymer as the amphiphilic polymer that will form the micelle around the hydrophobic InP upconversion system. The InP upconversion system is made up of three main components the InP nanocrystal which are the light absorbers, 9,10-diphenylanthracene (DPA) which is the light emitter and the organic solvent in which upconversion takes place. The size of the particles will be measured through dynamic light scattering. Photon upconversion quantum yields in solution will be presented.

InP QD based oil-in-water micelles for photon upconversion in biology

ACS Spring 2022

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