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Chemical Routes to Colloidal Chalcogenide Nanosheets
This project began with an emphasis on developing new low-temperature synthetic routes to intermetallic alloys in order to advance the synthesis and processing science of superconducting materials, as well as to potentially discover new materials that would be inaccessible using more traditional higher-temperature methods. Our initial target materials, chosen as model systems for developing new low-temperature solution-based synthetic platforms, were based on well known superconducting alloys, including Nb 3 M (M = Ga, Ge, Sn), Bi-M (M = In, Cu), and MgCNi 3 . Several key, fundamental synthetic challenges that underpinned the formation of these materials using solution chemistry routes were identified and investigated.
Understanding the reactivity of molecular precursors to colloidal nanocrystals
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What can we learn from previous tracer tests to optimize a colloid-facilitated transport test?
No abstract provided.
Evaluation of the Need to Consider Colloid-Facilitated Plutonium Transport in Contaminant Boundary Calculations for Pahute Mesa at the Nevada Nuclear Security Site
The testing of nuclear weapons at the Nevada National Security Site (NNSS), formerly the Nevada Test Site, has led to the deposition of substantial quantities of plutonium (Pu) into the environment. While tritium ( 3 H) is the most abundant anthropogenic radionuclide deposited in the NNSS subsurface from an activity standpoint (4.7×10 6 TBq decay corrected to September 23, 1992), Pu is the most abundant anthropogenic element by mass. Between 1951 and 1992, 828 underground nuclear tests were performed and approximately 2.8 metric tons (3.1×10 4 TBq) of Pu remains in the NNSS subsurface (Smith et al., 2003). The vast majority of this Pu is sequestered in nuclear melt glass that pools at the bottom of cavities formed by nuclear explosions.
Manipulation of Colloidal Aggregation Behavior and Optical PropertiesUsing Applied Electric Fields
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Colloidal Semiconductor Nanocrystals: Surface Chemistry, Photonics, and Electronics [Slides]
Abstract not provided.
Colloidal Semiconductor Nanocrystals: Surface Chemistry, Photonics, and Electronics [Slides]
Abstract not provided.
Functional, Hierarchical Colloidal Liquid Crystal Gels and Liquid Crystal Elastomers Nanocomposites. Final Report
Biological systems rely on a hierarchy of dynamic, complex and reconfigurable compartments to carry out functions essential for life. This hierarchical organization serves as an amplifier that allows highly localized, molecular events to propagate into the mesoscale, resulting in dynamic functional properties of biological systems that have not yet been fully realized in synthetic material designs. We pursued a program of research in which we recreated such principles using synthetic liquid crystals (LC) as a versatile platform. We elucidated new hierarchical design strategies that heavily leverage surface anchoring, coexisting phases and interfacial tension gradient to realize equilibrium and non-equilibrium, dynamic mesoscale phenomena in the context of micrometer-sized LC droplets containing multiple compartments. Specifically, we unmasked how equilibrium and dynamical phenomena emerged from hierarchical organizations in reconfigurable, thermotropic liquid crystalline assemblies. The long-term impact of the project is to advance new hierarchical designs of complex soft matter systems in which biomimetic principles, including the propagation of events or information over multiple temporal and spatial scales, are enacted in a facile manner.
2024 Colloidal, Macromolecular and Polyelectrolyte Solutions Gordon Research Conference and Seminar
Final Conference Program & Meeting Summary
Low Temperature Colloidal Synthesis of Iron Nitride Nanoparticles for the Oxygen Evolution Reaction
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Engineered Colloidal Hetero-nanocrystals for Photocatalytic Hydrogen Production
This research is focused on the development of novel semiconductor hetero-structured nanocrystals which can convert solar energy into hydrogen using photocatalytic water splitting reactions. The newly developed nanomaterials could produce cost-effective chemical fuel by employing less-energy intensive technology.
Computationally designed coiled coil ‘bundlemers’ as model colloidal nanoparticles for solution assembly and materials design (Final Report)
As a collaborative team at the University of Delaware and the University of Pennsylvania, Kloxin, Pochan and Saven designed new biomimetic nanomaterials de novo, leveraging a variety of complementary areas of expertise: computational design of biopolymers (Saven at the University of Pennsylvania), and synthesis and characterization (Kloxin and Pochan at the University of Delaware). Overall activities included: sequence-specific peptide synthesis; covalent crosslinking; noncovalent assembly; site-specific functionalization; and nanostructural characterization using electron microscopy and solution-phase (x-ray and neutron) scattering. Using natural and non-natural amino acids, the team created modular, functional peptide building blocks for elaboration of new nanostructured materials. Ultimately, the development of robust peptide-based, building blocks provides tools for researchers to readily produce complex nanomaterial structures in a wide range of applications. The project had three, interconnecting goals in an effort to provide the broader scientific community with a new peptide-based paradigm for materials design and characterization. First, we further developed the coiled-coil bundle-based toolbox (otherwise known as the ‘bundlemer’ toolbox) via computational design with experimental bundle assembly verification. Second, we developed new uses of covalent interactions, in addition to desired physical (noncovalent) interactions, to assemble bundlemers into 1-D polymer chains with targeted chain rigidity, length, and dispersity. Thirds, we used the above designs to experimentally realize (physical or covalent) polymers to target the creation of liquid crystals or to realize interparticle assembly into nanoporous lattices. The close integration of the three groups was instrumental in success of the biomolecular materials design, formation, and understanding for future designs.
Reconfigurable Optical Response of Colloidal Discoid Liquid Crystals
Presentation at APS annual meeting
Effect of Janus Balance and Shape Anisotropy on the Propulsion Dynamics of Active Colloidal Particles
Conference presentation at the annual meeting of the American Institute of Chemical Engineers
Deformation of Nano‐Metallic Glasses Made using Colloidal Synthesis
Final report
Facile Synthesis of a Broad Range of Colloidal Nanocrystals by Membrane-Mediated pH Gradient under Ambient Conditions
We report a simple synthesis process for a wide variety of ultrasmall nanocrystals. Simply immersing a dialysis bag containing an aqueous solution of a metal salt mixed with citric acid in a NaOH solution reservoir for 10 min, nanocrystals measuring only a few nanometers in size are formed inside the dialysis bag. We demonstrated the synthesis of ultrasmall nanocrystals of Co, Ni, Cu, Ag, Au, Pd, Cu 2 O, FeO, and CeO 2 , and found that the gradual change in pH caused by the diffusion of OH – ions through the dialysis membrane played an essential role in the formation of these nanocrystals. This method can be readily adapted for almost all transition metal elements, providing researchers in the fields of catalysis and nanomedicine an easy access to a wide range of ultrasmall metal and oxide nanocrystals.
Intrinsic and Extrinsic Exciton Recombination Pathways in AgInS 2 Colloidal Nanocrystals
Ternary I-III-VI 2 nanocrystals (NCs), such as AgInS 2 and CuInS 2 , are garnering interest as heavy-metal-free materials for photovoltaics, luminescent solar concentrators, LEDs, and bioimaging. The origin of the emission and absorption properties in this class of NCs is still a subject of debate. Recent theoretical and experimental studies revealed that the characteristic Stokes-shifted and long-lived luminescence of stoichiometric CuInS 2 NCs arises from the detailed structure of the valence band featuring two sublevels with different parity. The same valence band substructure is predicted to occur in AgInS 2 NCs, yet no experimental confirmation is available to date. Here, we use complementary spectroscopic, spectro-electrochemical, and magneto-optical investigations as a function of temperature to investigate the band structure and the excitonic recombination mechanisms in stoichiometric AgInS 2 NCs. Transient transmission measurements reveal the signatures of two subbands with opposite parity, and photoluminescence studies at cryogenic temperatures evidence a dark state emission due to enhanced exchange interaction, consistent with the behavior of stoichiometric CuInS 2 NCs. Lowering the temperature as well as applying reducing electrochemical potentials further suppress electron trapping, which represents the main nonradiative channel for exciton decay, leading to nearly 100% emission efficiency.