Assembly of Doped Infrared Plasmonic Nanocrystal Cubes

Faceted metal oxide nanocrystals (NCs) are inorganic materials that may be spectrally tuned via controlled synthesis and interact in the infrared spectrum. This interaction results in Near-Field Enhancement (NFE) at the NC surface that allows for photocatalytic and molecular sensing applications. To increase the effectiveness and efficiency of these applications, this work optimizes monolayered assembly of fluorine-doped indium tin oxide (F,Sn:In₂O₃) NCs and couples the array with PbS quantum dots (QD) to enhance photoluminescence decay rate. Prior work ruled out spray coating, drop casting, and dip coating as methods of assembly, as the resulting images were not nicely dispersed arrays, but rather, had rings and clumps. The finalized assembly method, liquid-air interface assembly, proved the most effective method for producing consistent monolayers and bilayers of NCs and QDs: solutions of NCs dispersed in hexane were dropped on to viscous, immiscible ethylene glycol and drained onto a silicone substrate. This process was optimized with the creation of a Teflon well that minimized perturbation of the nanocrystal layer, producing even arrays of NCs and QDs, revealed via electron microscopy imaging. Further results with STEM-EELs imaging revealed intensified NFE in the monolayered and bilayered arrays. Ultimately, the PbS QDs were used as a probe to reveal that plasmon-exciton coupling intensifies the NC’s electromagnetic field, increasing the rate at which light emits. This work indicates the ability of NC Near-Field-Enhancement to augment the properties of neighboring materials and implies potential in innovating and enhancing energy harnessing applications. More notably, the NCs operate in the infrared spectrum, and despite infrared light’s abundancy, most solar technology operates in the visible light spectrum. Thus, the nanocrystals may prove to be a useful tool to tap into this spectrum, broadening the horizons of energy technology for future innovations.