Nanosynthesis

Colloidal Synthesis of Noble Metal Nanocrystals

We utilize seed-mediated synthesis of noble metals (gold and silver) nanocrystals of different shapes (triangular nanoprisms (TNPs), nanorods (NRs), and nanobipyramids (NBiPs). The final NC structure is controlled by three factors: 1) crystal phase and shape of the initial seeds, 2) dynamic and selective binding affinity of passivating ligands to specific crystal facets, and 3) chemical potential of the inorganic precursors Dm, which is the difference between chemical potential of the solute and solid crystal. The seed-mediated synthesis allows precise control over NC dimension, and thus the LSPR properties. Standard equipment, including temperature-controlled hot-plate/stirrer, centrifuge, ultra-cleaned glassware, is commonly used to conduct the synthesis.

Plasmonic Metal-Oxide Nanocrystal Synthesis Using Hot-Injection Methods

Colloidal, passivated NC formation is considered a three-stage process following the LaMer Model: supersaturation, nucleation, and growth. Critical is inorganic “seed” formation which bridge nuclei and NCs yielding anisotropic NCs. Utilizing defined, ultrasmall nanoclusters (“magic-sized”) as seeds, anisotropic metal chalcogenide NCs were prepared. Seeds are small (<2.0 nm diameter), ligand-passivated NCs with known crystal phases have been successfully synthesized and isolated.

Very recently, we synthesized anisotropic Sn-doped In₂O₃ NCs using isolated, ultrasmall nanocluster seeds. Our long-term research objectives are to: (1) synthesize well-defined seeds with known crystal structure and surface passivation, (2) develop a reliable crystal terminating agent for facet-directed growth of metal-oxide NCs, and (3) manipulate kinetically controlled directional growth through ligand binding affinities and monomer concentration (Δµ). The future research plans are to find answers to the following key chemical questions in order to synthesize uniquely-shaped, LSPR-active metal-oxide (e.g., WO_3-x, Al₂O₃, etc.) NCs and determine structure-property relationships:

• Can organohalide compounds act as crystal terminating agents to dictate facet-directed growth?
• What ligand choice is appropriate for causing faceted growth of transition metal-oxide NCs?
• How does seed crystal morphology dictate the final NC shape?
• How does monomer concentration (Dm) impact facet specific growth anisotropy?

Representative Publications

• Davis, G. A.; Prusty, G.; Hati, S.; Lee, J. T.; Langlais, S. R.; Zhan, X.; Sardar, R. Design of Anisotropically-Shaped Plasmonic Nanocrystals from Ultrasmall Sn-Decorated In2O3 Nanoclusters Used as Seed Materials. J. Phys. Chem. C 2022, 126, 21438-21452.
• Prusty, G.; Lee, J. T.; Seifert, S.; Muhoberac, B. B.; Sardar, R. Ultrathin plasmonic tungsten oxide quantum wells with controllable free carrier densities. J. Am. Chem. Soc.  2020, 142, 1526-1536.
• Teunis, M. B.; Johnson, M. A.; Muhoberac, B. B.; Sardar, R. Programmable colloidal approach to hierarchiral structures of methylammonium lead bromide perovskite nanocrystals with bright photoluminescent properties. Chem. Mater. 2017, 29, 3562-3537.
• Teunis, M. B.; Jana, A.; Dutta, P.; Johnson, M. A.; Mandal, M.; Muhoberac, B. B; Sardar, R. Mesoscale growth and assembly of bright luminescent organolead halide perovskite quantum wires. Chem. Mater. 2016, 28, 5043-5054.
• Dolai, S.; Nimmala, P. R.; Mandal, M.; Muhoberac, B. B.; Dria, K.; Dass, A.; Sardar, R. Isolation of bright blue light-emitting CdSe nanocrystals with 6.5 kDa core in gram scale: High photoluminescence efficiency controlled by surface ligand chemistry. Chem. Mater. 2014, 26, 1278-1285.
• Dennis, N. W.; Muhoberac, B. B.; Newton, J. C.; Kumbhar, A. Sardar, R. Correlated optical spectroscopy and electron microscopy studies of the slow Ostwald-ripening growth of silver nanoparticles under controlled reducing conditions. Plasmonics 2014, 9, 111-120.
• Newton, J. C.; Ramasamy, K.; Mandal, M.; Joshi, G. K.; Kumbhar, A.; Sardar, R. Low temperature synthesis of magic-sized CdSe nanoclusters: Influence of ligands on photophysical properties. J. Phys. Chem. C 2012, 116, 4380-4389.