A5072912533- Quantum Dots Synthesis And Properties
- Chalcogenide Semiconductor Thin Films
- Advanced biosensing and bioanalysis techniques
- Nanocluster Synthesis and Applications
- Spectroscopy and Quantum Chemical Studies
- Copper-based nanomaterials and applications
- Molecular Junctions and Nanostructures
- Carbon and Quantum Dots Applications
- Photochemistry and Electron Transfer Studies
- Photoreceptor and optogenetics research
- Advanced Biosensing Techniques and Applications
- Advanced Fluorescence Microscopy Techniques
- Gold and Silver Nanoparticles Synthesis and Applications
- Perovskite Materials and Applications
- Photosynthetic Processes and Mechanisms
- Receptor Mechanisms and Signaling
- Near-Field Optical Microscopy
- Circadian rhythm and melatonin
- Bipolar Disorder and Treatment
- Advanced Electron Microscopy Techniques and Applications
- Biotin and Related Studies
- Attention Deficit Hyperactivity Disorder
- Luminescence and Fluorescent Materials
- Neuroscience and Neuropharmacology Research
- nanoparticles nucleation surface interactions
Vanderbilt University
2015-2024
Oak Ridge National Laboratory
2007-2020
Center for Integrated Nanotechnologies
2020
Los Alamos National Laboratory
2020
Center for Nanoscale Science and Technology
2011-2019
Vanderbilt Health
2017
Nashville Oncology Associates
2015-2016
University of Tennessee at Knoxville
2014
Astronomy and Space
2012
School of the Art Institute of Chicago
1993-2010
Magic-sized cadmium selenide (CdSe) nanocrystals have been pyrolytically synthesized. These ultra-small exhibit broadband emission (420-710 nm) that covers most of the visible spectrum while not suffering from self absorption. This behavior is a direct result extremely narrow size distribution and unusually large Stokes shift (40-50 nm). The intrinsic properties these make them an ideal material for applications in solid state lighting also perfect platform to study molecule-to-nanocrystal...
The solvation dynamics of acetonitrile were characterized by a time resolved fluorescence shift measurement determined via the upconversion technique. response is clearly two part in character. fast initial relaxation accounts for ∼80% amplitude and well fit Gaussian 120 fs FWHM, giving decay 70 fs. slower tail exponential with ∼200 Comparison results to molecular simulations performed Maroncelli [J. Chem. Phys. 94, 2085 (1991)] reveal solvent arises from small inertial rotational motion...
InP quantum dots (QDs) have great potential as emitters for solid-state lighting, lasing, and bioimaging without the inherent toxicity concern of Cd Pb-based emitters. Indium phosphide's small bandgap high covalency make it uniquely capable color-pure fluorescence that can be tuned throughout visible lower IR spectrum. Until recently, InP-based QDs consistently underperformed when compared with CdSe-based counterparts. Recent efforts to understand indium nonclassical growth mechanisms,...
To explore the potential for use of ligand-conjugated nanocrystals to target cell surface receptors, ion channels, and transporters, we explored ability serotonin-labeled CdSe (SNACs) interact with antidepressant-sensitive, human Drosophila serotonin transporters (hSERT, dSERT) expressed in HeLa HEK-293 cells. Unlike unconjugated nanocrystals, SNACs were found dose-dependently inhibit transport radiolabeled by hSERT dSERT, an estimated half-maximal activity (EC50) 33 (dSERT) 99 μM (hSERT)....
Alloy nanocrystals provide an additional degree of freedom in selecting desirable properties for nanoscale engineering because their physical and optical depend on both size composition. We report the pyrolytic synthesis homogeneously alloyed CdSxSe1-x all proportions. The are characterized using UV−visible absorption spectroscopy, transmission electron microscopy, X-ray diffractrometry, Rutherford backscattering spectrometry to determine precisely structure, size, dependence band gap...
Nonspecific binding is a frequently encountered problem with fluorescent labeling of tissue cultures when labeled quantum dots. In these studies various cell lines were examined for nonspecific binding. Evidence suggests that related to type and may be significantly reduced by functionalizing dots poly(ethylene glycol) ligands (PEG). The length PEG required give significant reduction in as short 12−14 ethylene glycol units.
Femtosecond fluorescence upconversion has been utilized to study the band edge and deep trap emission dynamics of cadmium selenide (CdSe) nanocrystals (NC's) ranging in size from 27 72 Å diameter. Both rise time decay show a direct correlation NC size, that depends on excitation energy. Surface-oxidized non-oxidized NC's display same kinetics, but relative amplitudes short long components differ. The appears within 2 ps is attributed ultrafast relaxation surface selenium dangling bond...
The dynamics of solvation an excited chromophore in pure water and a restricted space with limited number molecules have been studied. time-dependent Stokes shift Coumarin 480 (C480) 460 (C460) were measured using femtosecond fluorescence upconversion time-correlated single-photon-counting techniques. system was inclusion complex dyes γ-cyclodextrin (γCD). results molecular simulations are compared the observed solvent response γCD cavity. relaxation times range from <100 fs to 1.2 ns....
Aberration-corrected Z-contrast scanning transmission electron microscopy of core/shell nanocrystals shows clear correlations between structure and quantum efficiency. Uniform shell coverage is obtained only for a graded CdS/ZnS material found to be critical achieving near 100% yield. The sublattice sensitivity the images confirms that preferential growth takes place on anion-terminated surfaces. This explains three-dimensional "nanobullet" shape observed in case nanorods.
The vibrational characteristics of liquid dynamics are used to describe the ultrafast relaxations observed in time-dependent fluorescence Stokes shift [J. Chem. Phys. 95, 4715 (1991)] and heterodyne detected optical Kerr effect measurements on acetonitrile, via a Brownian oscillator model. Introducing frequency distribution modes makes it possible compare two experiments. decays signals produced by destructive superposition high frequency, underdamped modes.
Individual single-wall carbon nanotubes (SWNTs) and double-wall (DWNTs) were suspended in water for optical studies using sodium-cholate other surfactants. We used time-resolved photoluminescence (PL) spectroscopy to study the influence of tube chirality diameter as well environment on nonradiative decay small tubes. The provide evidence PL from core tubes DWNTs a correlation with exciton red shift induced by interaction environment.
We report white light-emitting diodes fabricated with ultrasmall CdSe nanocrystals, which demonstrate electroluminescence from a size of nanocrystals (<2 nm) previously thought to be unattainable. These LEDs have excellent color characteristics, defined by their pure CIE coordinates (0.333, 0.333), correlated temperatures 5461−6007 K, and rendering indexes as high 96.6. The effect voltage on the trap states responsible for emission is also described.
A simple treatment method using formic acid has been found to increase the fluorescence quantum yield of ultrasmall white light-emitting CdSe nanocrystals from 8% 45%. Brighter white-light emission occurs with other carboxylic acids as well, and magnitude enhancement is shown be dependent on alkyl chain length. Additionally, nanocrystal luminescence remains enhanced relative untreated over several days. This brightened opens possibility for even further improvement potential use these in...
Nanocrystals exhibit useful properties not found in their bulk counterparts; however, a subclass of nanocrystals that consist diameters on the order 2 nm or less further unique properties. As synthetic methodologies have matured, greater emphasis has been made controlling early stages reaction to gain access these sub-2 species. This review provides an overview ultrasmall and magic-sized nanocrystals, diverse chemical means obtain them. Due small size resultant properties, distinct advantage...
We investigate near-field energy transfer between chemically synthesized quantum dots (QDs) and two-dimensional semiconductors. fabricate devices in which electrostatically gated semiconducting monolayer molybdenum disulfide (MoS2) is placed atop a homogenous self-assembled layer of core-shell CdSSe QDs. demonstrate efficient non-radiative F\"orster resonant (FRET) from QDs into MoS2 prove that modest gate-induced variation the excitonic absorption lead to large (~500%) changes FRET rate....
Quantum dots have attracted considerable interest in the fields of solid state lighting, displays, and fluorescent imaging. Their tunable optical properties by changing size solution processability lead to commercial applications. In this review, we focus on advancement white light emitting nanocrystals, their usage as emissive layer LEDs display backlights, examine increased efficiency longevity quantum based colored LEDs. addition, also explore recent discoveries biological labels, dynamic...
Novel biophotovoltaic devices were prepared by electrochemically entrapping Photosystem I in a conductive polyaniline film, grown<italic>in situ</italic>on TiO<sub>2</sub>anodes.
Thick-shell (>5 nm) InP–ZnSe colloidal quantum dots (QDs) grown by a continuous-injection shell growth process are reported. The of thick crystalline is attributed to the high temperature and relatively low lattice mismatch between InP core ZnSe shell. In addition narrow ensemble photoluminescence (PL) line-width (∼40 nm), single-particle emission dynamics measurements indicate that blinking Auger recombination reduced in these heterostructures. More specifically, single-dot ON-times (>95%)...
Spontaneous emission from reaction centers of photosynthetic bacteria has been recorded with a time resolution 50 fs. Excitation was made directly into both the special-pair band (850 nm) and Qx bacteriochlorophylls (608 nm). Rhodobacter sphaeroides R26, capsulatus wild type, four mutants Rb. were studied. In all cases fluorescence decay not single exponential well fit as sum two components. The short components are in excellent agreement component detected by measurements stimulated...
The isomerization dynamics of cis-stilbene in the first excited singlet state were studied by technique fluorescence upconversion. Lifetime measurements made with subpicosecond resolution 2-propanol, decanol, n-hexane, and tetradecane. decay curves are single exponential all solvents except for where they adequately described a double exponential. A weak viscosity dependence times is observed both alcohols alkanes. These results discussed terms Bagchi, Fleming, Oxtoby theory [J. Chem. Phys....