Publications

Controlling microscopic morphology of energetic materials is of significant interest for the improvement of their performance and production consistency. As an important insensitive high explosive material, triaminotrinitrobenzene (TATB) has attracted tremendous research effort for military grade explosives and propellants. In this study, a new, rapid and inexpensive synthesis method for monodispersed TATB microparticles based on micelle-confined precipitation was developed. Surfactant with proper hydrophilic-lipophilic balance value was found to be critical to the success of this synthesis. The morphology of the TATB microparticles can be tuned between quasi-spherical and faceted by controlling the speed of recrystallization.

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The performance of energetic materials (EM) varies significantly across production lots due to the inability of current production methods to yield consistent morphology and size. Lot - to - lot variations and the inability to remake the needed characteristics that meet specification is costly, increases uncertainty, and creates additional risk in programs using these materials. There is thus a pressing need to more reliably formulate EMs with greater control of mor pholog y . The goal of this project is to use the surfactant - assisted self - assembly to generate EM particles with well - defined size and external morphologies using triaminotrinitrobenzene (TATB) and hexanitrohexaazaisowurtzitane (CL - 20) as these EMs are both prevalent in the stockpile and present interesting/urgent reprocessing challenges. W e intend to understand fundamental science on how molecular packing influences EM morphology. We develop scale up fabrication of EM particle s with controlled morphology, p romising to eliminate inconsistent performance by providing a trusted and reproducible method to improve EM s for NW applications.

Low dimensional lead halide perovskite particles are of tremendous interest due to their size-tunable band gaps, low exciton binding energy, high absorption coefficients, outstanding quantum and photovoltaic efficiencies. In this paper, we report a new solution-based synthesis of stabilized Cs₄PbBr₆ perovskite particles with high luminescence. This method requires only mild conditions and produces colloidal particles that are ideal for highly efficient solution-based device fabrications. The synthesized microstructures not only display outstanding luminescence quantum yield but also long term stability in atmospheric conditions. Partial halide substitutions were also demonstrated to extend photoluminescence spectra of the perovskite particles. Finally, this convenient synthesis and optical tunability of Cs₄PbBr₆ perovskite particles will be advantageous for future applications of optoelectronic advices.

In an effort to utilize their unique photoactive properties, porphyrin monomers were assembled into tetragonal microparticles by a surfactant-assisted neutralization method through the cooperative interactions between the porphyrin building blocks including π-π stacking, J-aggregation and metal-ligand coordination. Electron microscopy characterization in combination with X-ray diffraction confirmed the three-dimensional ordered tetragonal microstructures with stable crystalline frameworks and well defined external surface morphology. Optical absorption and fluorescence spectroscopy revealed enhanced absorbance properties as compared with the raw porphyrin material, favourable for chromophore excitation and energy transport. With active and responsive optical properties, these new porphyrin microparticles look to serve as promising components for a wide range of applications including sensing, diagnostics, solar cells, and optoelectronic devices.

A new quantum dot synthesis method based on metallic-block copolymer precursors was developed. The synthesis produced CdS QDs assembled into chains. This method provides a new model for the study of 1D QD chains to determine its effect on charge transport and optoelectronic coupling. This synthesis method was readily extended to other semiconductor materials including PbS and perovskites producing QDs of various shapes. It evidenced further promise of this synthesis method to assist in the assembly, shape and size control of various nanomaterials.

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