Bacterial Prostatitis Secondary to Salmonella enterica serovar Enteritidis in an Immunocompetent Dog.

Salmonella is a rod-shaped gram-negative bacterium of the family Enterobacteriaceae, commonly present in the gastrointestinal tract in humans and animals. Salmonella-associated bacteriuria and prostatitis are rare but have been reported in humans, predominantly older patients with underlying diseases, including urinary tract obstructions, diabetes mellitus, and compromised immunity. In dogs, Salmonella bacteriuria and prostatitis have only been described in patients on immunosuppressive medications.

Colossal Core/Shell CdSe/CdS Quantum Dot Emitters.

Single-photon sources are essential for advancing quantum technologies with scalable integration being a crucial requirement. To date, deterministic positioning of single-photon sources in large-scale photonic structures remains a challenge. In this context, colloidal quantum dots (QDs), particularly core/shell configurations, are attractive due to their solution processability.

Ligand Desorption and Fragmentation in Oleate-Capped CdSe Nanocrystals under High-Intensity Photoexcitation.

Semiconductor nanocrystals (NCs) offer prospective use as active optical elements in photovoltaics, light-emitting diodes, lasers, and photocatalysts due to their tunable optical absorption and emission properties, high stability, and scalable solution processing, as well as compatibility with additive manufacturing routes. Over the course of experiments, during device fabrication, or while in use commercially, these materials are often subjected to intense or prolonged electronic excitation and high carrier densities. The influence of such conditions on ligand integrity and binding remains underexplored.

Enhanced Charge Transfer from Coinage Metal Doped InP Quantum Dots.

This paper describes coinage-metal-doped InP quantum dots (QDs) as a platform for enhanced electron transfer to molecular acceptors relative to undoped QDs. A synthetic strategy is developed to prepare doped InP/ZnSe QDs. First-principles DFT calculations show that Ag and Cu dopants localize photoexcited holes while leaving electrons delocalized.

Effect of a redox-mediating ligand shell on photocatalysis by CdS quantum dots.

Semiconductor quantum dots (QDs) are efficient organic photoredox catalysts due to their high extinction coefficients and easily tunable band edge potentials. Despite the majority of the surface being covered by ligands, our understanding of the effect of the ligand shell on organic photocatalysis is limited to steric effects. We hypothesize that we can increase the activity of QD photocatalysts by designing a ligand shell with targeted electronic properties, namely, redox-mediating ligands.

Differentiating Thermal Conductances at Semiconductor Nanocrystal/Ligand and Ligand/Solvent Interfaces in Colloidal Suspensions.

Infrared-pump, electronic-probe (IPEP) spectroscopy is used to measure heat flow into and out of CdSe nanocrystals suspended in an organic solvent, where the surface ligands are initially excited with an infrared pump pulse. Subsequently, the heat is transferred from the excited ligands to the nanocrystals and in parallel to the solvent. Parallel heat transfer in opposite directions uniquely enables us to differentiate the thermal conductances at the nanocrystal/ligand and ligand/solvent interfaces.

Light-Induced Transient Lattice Dynamics and Metastable Phase Transition in CHNHPbI Nanocrystals.

Methylammonium lead iodide (MAPbI) perovskite nanocrystals (NCs) offer desirable optoelectronic properties with prospective utility in photovoltaics, lasers, and light-emitting diodes (LEDs). Structural rearrangements of MAPbI in response to photoexcitation, such as lattice distortions and phase transitions, are of particular interest, as these engender long carrier lifetime and bolster carrier diffusion. Here, we use variable temperature X-ray diffraction (XRD) and synchrotron-based transient X-ray diffraction (TRXRD) to investigate lattice response following ultrafast optical excitation.

Synthetic Ligand Selection Affects Stoichiometry, Carrier Dynamics, and Trapping in CuInSe Nanocrystals.

CuInSe nanocrystals exhibit tunable near-infrared bandgaps that bolster utility in photovoltaic applications as well as offer potential as substitutes for more toxic Cd- and Pb-based semiconductor compositions. However, they can present a variety of defect states and unusual photophysics. Here, we examine the effects of ligand composition (oleylamine, diphenylphosphine, and tributylphosphine) on carrier dynamics in these materials.

Photogenerated Spin-Correlated Radical Pairs: From Photosynthetic Energy Transduction to Quantum Information Science.

More than a half century ago, the NMR spectra of diamagnetic products resulting from radical pair reactions were observed to have strongly enhanced absorptive and emissive resonances. At the same time, photogenerated radical pairs were discovered to exhibit unusual electron paramagnetic resonance spectra that also had such resonances. These non-Boltzmann, spin-polarized spectra were observed in both chemical systems as well as in photosynthetic reaction center proteins following photodriven charge separation.

Photothermal behaviour of titanium nitride nanoparticles evaluated by transient X-ray diffraction.

The photothermal properties of metal nitrides have recently received significant attention owing to diverse applications in solar energy conversion, photothermal therapies, photoreactions, and thermochromic windows. Here, the photothermal response of titanium nitride nanoparticles is examined using transient X-ray diffraction, in which optical excitation is synchronized with X-ray pulses to characterize dynamic changes in the TiN lattice. Photoinduced diffraction data is quantitatively analyzed to determine increases in the TiN lattice spacing, which are furthermore calibrated against static, temperature-dependent diffraction patterns of the same samples.

Anisotropic Transient Disordering of Colloidal, Two-Dimensional CdSe Nanoplatelets upon Optical Excitation.

Nanoplatelets (NPLs)-colloidally synthesized, spatially anisotropic, two-dimensional semiconductor quantum wells-are of intense interest owing to exceptionally narrow transition line widths, coupled with solution processability and bandgap tunability. However, given large surface areas and undercoordinated bonding at facet corners and edges, excitation under sufficient intensities may induce anisotropic structural instabilities that impact desired properties. We employ time-resolved X-ray diffraction to study the crystal structure of CdSe NPLs in response to optical excitation.

Charge Transfer and Spin Dynamics in a Zinc Porphyrin Donor Covalently Linked to One or Two Naphthalenediimide Acceptors.

Quantum coherence effects on charge transfer and spin dynamics in a system having two degenerate electron acceptors are studied using a zinc 5,10,15-tri(-pentyl)-20-phenylporphyrin (ZnP) electron donor covalently linked to either one or two naphthalene-1,8:4,5-bis(dicarboximide) (NDI) electron acceptors using an anthracene (An) spacer, ZnP-An-NDI () and ZnP-An-NDI (), respectively. Following photoexcitation of and in toluene at 295 K, femtosecond transient absorption spectroscopy shows that the electron transfer (ET) rate constant for is about three times larger than that of , which can be accounted for by the statistical nature of incoherent ET as well as the electron couplings for the charge separation reactions. In contrast, the rate constant for charge recombination (CR) of is about 25% faster than that of .

Singlet fission in core-linked terrylenediimide dimers.

We have studied two regioisomeric terrylenediimide (TDI) dimers in which the 1-positions of two TDIs are linked via 1,3- or 1,4-phenylene spacers, mTDI and pTDI, respectively. The nature and the dynamics of the multiexciton state are tuned by altering the through-bond electronic couplings in the ground and excited states and by changing the solvent environment. Our results show that controlling the electronic coupling between the two chromophores by an appropriate choice of linker can result in independent triplet state formation, even though the initial correlated triplet pair state is confined to a dimer.

Transient Lattice Response upon Photoexcitation in CuInSe Nanocrystals with Organic or Inorganic Surface Passivation.

CuInSe nanocrystals offer promise for optoelectronics including thin-film photovoltaics and printed electronics. Additive manufacturing methods such as photonic curing controllably sinter particles into quasi-continuous films and offer improved device performance. To gain understanding of nanocrystal response under such processing conditions, we investigate impacts of photoexcitation on colloidal nanocrystal lattices via time-resolved X-ray diffraction.

Using Photoexcited Core/Shell Quantum Dots To Spin Polarize Appended Radical Qubits.

The synthetic tunability, flexibility, and rich spin physics of semiconductor quantum dots (QDs) make them promising candidates for quantum information science applications. However, the rapid spin relaxation observed in colloidal quantum dots limits their functionality. In the current work, we demonstrate a method to harness photoexcited spin states in QDs to produce long-lived spin polarization on an appended organic ligand molecule.

Determination of the In-Plane Exciton Radius in 2D CdSe Nanoplatelets Magneto-optical Spectroscopy.

Colloidal, two-dimensional semiconductor nanoplatelets (NPLs) exhibit quantum confinement in only one dimension, which results in an electronic structure that is significantly altered compared to that of other quantum-confined nanomaterials. Whereas it is often assumed that the lack of quantum confinement in the lateral plane yields a spatially extended exciton, reduced dielectric screening potentially challenges this picture. Here, we implement absorption spectroscopy in pulsed magnetic fields up to 60 T for three different CdSe NPL thicknesses and lateral areas.

Quintet-triplet mixing determines the fate of the multiexciton state produced by singlet fission in a terrylenediimide dimer at room temperature.

Singlet fission (SF) is a photophysical process in which one of two adjacent organic molecules absorbs a single photon, resulting in rapid formation of a correlated triplet pair (TT) state whose spin dynamics influence the successful generation of uncorrelated triplets (T). Femtosecond transient visible and near-infrared absorption spectroscopy of a linear terrylene-3,4:11,12-bis(dicarboximide) dimer (TDI), in which the two TDI molecules are directly linked at one of their imide positions, reveals ultrafast formation of the (TT) state. The spin dynamics of the (TT) state and the processes leading to uncoupled triplets (T) were studied at room temperature for TDI aligned in 4-cyano-4'-pentylbiphenyl (5CB), a nematic liquid crystal.

Photoinduced, reversible phase transitions in all-inorganic perovskite nanocrystals.

Significant interest exists in lead trihalides that present the perovskite structure owing to their demonstrated potential in photovoltaic, lasing, and display applications. These materials are also notable for their unusual phase behavior often displaying easily accessible phase transitions. In this work, time-resolved X-ray diffraction, performed on perovskite cesium lead bromide nanocrystals, maps the lattice response to controlled excitation fluence.

Semiconductor Nanoplatelet Excimers.

Excimers, a portmanteau of "excited dimer", are transient species that are formed from the electronic interaction of a fluorophore in the excited state with a neighbor in the ground state, which have found extensive use as laser gain media. Although common in molecular fluorophores, this work presents evidence for the formation of excimers in a new class of materials: atomically precise two-dimensional semiconductor nanoplatelets. Colloidal nanoplatelets of CdSe display two-color photoluminescence resolved at low temperatures with one band attributed to band-edge fluorescence and a second, red band attributed to excimer fluorescence.

Auger Heating and Thermal Dissipation in Zero-Dimensional CdSe Nanocrystals Examined Using Femtosecond Stimulated Raman Spectroscopy.

We report femtosecond stimulated Raman spectroscopy (FSRS) measurements on dispersions of CdSe semiconductor nanocrystals (NCs) as a function of particle size and pump fluence. Upon photoexcitation, we observe depletion of stimulated Raman gain corresponding to generation of longitudinal optical (LO) phonons followed by recovery on picosecond timescales. At higher fluences, production of multiple excitons slows recovery of FSRS signals, which we attribute to sustained increases of LO phonon populations due to multiexcitonic Auger heating.

Material Dimensionality Effects on Electron Transfer Rates Between CsPbBr and CdSe Nanoparticles.

Films containing mixtures of zero- or two-dimensional nanostructures (quantum dots or nanoplatelets) were prepared in order to investigate the impacts of dimensionality on electronic interactions. Electron transfer from CsPbBr to CdSe was observed in all of the mixtures, regardless of particle dimensionality, and characterized via both static and transient absorption and photoluminescence spectroscopies. We find that mixtures containing nanoplatelets as the electron acceptor (CdSe) undergo charge transfer more rapidly than those containing quantum dots.

Understanding the Seed-Mediated Growth of Gold Nanorods through a Fractional Factorial Design of Experiments.

Since the development of simple, aqueous protocols for the synthesis of anisotropic metal nanoparticles, research into many promising, valuable applications of gold nanorods has grown considerably, but a number of challenges remain, including gold-particle yield, robustness to minor impurities, and precise control of gold nanorod surface chemistry. Herein we present the results of a composite fractional factorial series of experiments designed to screen seven additional potential avenues of control and to understand the seed-mediated silver-assisted synthesis of gold nanorods. These synthesis variables are the amount of sodium borohydride used and the rate of stirring when producing seed nanoparticles, the age of and the amount of seeds added, the reaction temperature, the amounts of silver nitrate and ascorbic acid added, and the age of the reduced growth solution before seed nanoparticles are added to initiate rod formation.

Engineering high refractive index sensitivity through the internal and external composition of bimetallic nanocrystals.

High refractive index sensitivity (RIS) of branched Au-Pd nanocrystals (NCs) is engineered through lowering the dielectric dispersion at the NC resonant wavelength with internal or external atomic % Pd. To our knowledge, these NCs display the highest ensemble RIS measurement for colloids with LSPR maximum band positions ≤900 nm, and these results are corroborated with FDTD computations.