The Effects of Quantum Dot Surface Chemistry on Fluorescence and Additive Manufacturing Applications

Abstract

Quantum dots (QDs), have been extensively studied for their unique optical properties, such as their lasting photostability, size-tunable band gaps, and narrow photoluminescence. Additionally, by controlling the surface chemistry of QDs, the optical properties can be modified. With these exceptional optical properties, QDs are an ideal materiel to be used in lighting technologies and as sensors. With the discovery of ultrasmall CdSe QDs, a single-component white-light emitter, the exhibits a broad emission that spans from 420 to 710 nm was realized. For the ultrasmall CdSe to be viable for commercial lighting technologies, the quantum yield must be increased from the average 6%. This was accomplished with a post-synthesis ligand treatment with both formic acid and citric acid. The citric acid treated CdSe QDs have the highest reported quantum yield for a single-component white light emitter, with 61%, and a cool white emission. These QDs were also found to have a higher stability in solution than those of the formic acid treated QDs. With the broad white emission being determined by the surface of the CdSe QDs, these are an optimal material to be used as an in-situ material state monitor for structural health monitoring. As the surface ligands are removed from the QDs during external compressive or tensile loading the emission is observed to decrease in intensity. The unique optical properties of QDs can be utilized with the development of functional materials compatible with 3D printing applications. CdSSe QDs were embedded in a polylactic acid (PLA) host matrix to obtain nanofunctionalized, fluorescent filament compatible with stock 3D printing systems. Absorbance, photoluminescence, thermal analysis, and mechanical testing are studied to quantify how filament functionalization modulates the optical and material properties of the embedded quantum dots and PLA host matrix following printing.