Rational Phase Control in the Synthesis of Cobalt Sulfides.

A library of substituted thioureas was used as sulfur reagents in the synthesis of cobalt sulfides. The substitution pattern of the thioureas controls the decomposition rate of precursors into sulfur monomers and thereby aids in the exploration of decomposition kinetics on cobalt sulfide-phase formation, including phase-pure jaipurite (CoS), cobalt pentlandite (CoS), linnaeite (CoS), and cattierite (CoS). We hypothesize that the available transformation pathways between phases during synthesis are dictated by the approximate ccp or hcp stacking of the sulfur lattice.

Controlling Phase in Colloidal Synthesis.

A fundamental precept of chemistry is that properties are manifestations of the elements present and their arrangement in space. Controlling the arrangement of atoms in nanocrystals is not well understood in nanocrystal synthesis, especially in the transition metal chalcogenides and pnictides, which have rich phase spaces. This Perspective will cover some of the recent advances and current challenges.

Five Hypotheses on the Origins of Temperature Dependence of Se NMR Shifts in Diselenides.

Notable thermal shifts in diselenides have been documented in Se NMR for more than 50 years, but no satisfactory explanation has been found. Here, five hypotheses are considered as possible explanations for the large temperature dependence of the Se chemical shifts of diaryl and dialkyl diselenides compared to monoselenides and selenols. Density functional theory calculations are provided to bolster hypotheses and better understand the effects of barrier height and dipole energies.

Harmonic Generation up to Fifth Order from Al/Au/CuS Nanoparticle Films.

Dual heterostructures integrating noble-metal and copper chalcogenide nanoparticles have attracted a great deal of attention in nonlinear optics, because coupling of their localized surface plasmon resonances (LSPRs) substantially enhances light-matter interactions through local-field effects. Previously, enhanced cascaded third-harmonic generation was demonstrated in Au/CuS heterostructures mediated by harmonically coupled surface plasmon resonances. This suggests a promising approach for extending nonlinear enhancement to higher harmonics by adding an additional nanoparticulate material with higher-frequency harmonic resonances to the hybrid films.

Evaluating the multiple sulfur isotope signature of Eoarchean rocks from the Isua Supracrustal Belt (Southwest-Greenland) by MC-ICP-MS: Volcanic nutrient sources for early life.

On the anoxic Archean Earth, prior to the onset of oxidative weathering, electron acceptors were relatively scarce, perhaps limiting microbial productivity. An important metabolite may have been sulfate produced during the photolysis of volcanogenic SO gas. Multiple sulfur isotope data can be used to track this sulfur source, and indeed this record indicates SO photolysis dating back to at least 3.

Celebrating the 150th anniversary of Vanderbilt University.

An introduction to the , and themed collection celebrating the 150th anniversary of Vanderbilt University, featuring work from researchers currently affiliated with Vanderbilt University, esteemed alumni, and researchers with strong connections and extensive collaborations with the university.

Qualitative Examination of the Experience of Perceived Injustice Following Disabling Occupational Injury.

Purpose: The primary objective of this study was to explore individuals' perspectives on the factors, situations or events that contributed to their perceptions of injustice following occupational injury.

Materials And Methods: The study sample consisted of 30 participants (18 women, 12 men) who had submitted a time-loss claim for a work-related musculoskeletal injury. Participants with elevated scores on a measure of perceived injustice were interviewed about the factors that contributed to their sense of injustice.

Management of chemotherapy hypersensitivity reactions and desensitization: An SGO clinical practice statement.

Objective: The goal of this practice statement is to help members and their multidisciplinary teams recognize infusion reactions and hypersensitivity reactions in the clinical setting. It will provide recommendations to help guide response to reactions and desensitization when appropriate, to promote safe use of chemotherapeutic agents among all providers in the delivery process.

Methods: A multi-disciplinary team of healthcare professionals from the Society of Gynecologic Oncology Education Committee collaborated to review peer reviewed literature and guidelines to develop a practice statement on the management of chemotherapy hypersensitivity reactions and desensitization regimens.

Phase Control in the Synthesis of Iron Sulfides.

The identity and repeating arrangement of atoms determine the properties of all solids. Even combinations of two atoms can have multiple crystal structures of varying stoichiometries and symmetries with vastly different electronic and chemical behaviors. The conditions of existing bottom-up routes for achieving one phase over another are serendipitous, and the links among precursor reactivity, decomposition mechanism, temperature, and time are elusive.

Role of carboxylates in the phase determination of metal sulfide nanoparticles.

Techniques are well established for the control of nanoparticle shape and size in colloidal synthesis, but very little is understood about precursor interactions and their effects on the resultant crystalline phase. Here we show that oleate, a surface stabilizing ligand that is ubiquitous in nanocrystal synthesis, plays a large role in the mechanism of phase selection of various metal sulfide nanoparticles when thiourea is used as the sulfur source. Gas and solid-phase FTIR, C, and H NMR studies revealed that oleate and thiourea interact to produce oleamide which promotes the isomeric shift of thiourea into ammonium thiocyanate, a less reactive sulfur reagent.

Determining the impact of gold nanoparticles on amyloid aggregation with 2D IR spectroscopy.

As nanomaterials become more prevalent in both industry and medicine, it is crucial to fully understand their health risks. One area of concern is the interaction of nanoparticles with proteins, including their ability to modulate the uncontrolled aggregation of amyloid proteins associated with diseases, such as Alzheimer's disease and type II diabetes, and potentially extend the lifetime of cytotoxic soluble oligomers. This work demonstrates that two-dimensional infrared spectroscopy and CO isotope labeling can be used to follow the aggregation of human islet amyloid polypeptide (hIAPP) in the presence of gold nanoparticles (AuNPs) with single-residue structural resolution.

Dependence of Transition-Metal Telluride Phases on Metal Precursor Reactivity and Mechanistic Implications.

Modern bottom-up synthesis to nanocrystalline solid-state materials often lacks the reasoned product control that molecular chemistry boasts from having over a century of research and development. In this study, six transition metals including iron, cobalt, nickel, ruthenium, palladium, and platinum were reacted with the mild reagent didodecyl ditelluride in their acetylacetonate, chloride, bromide, iodide, and triflate salts. This systematic analysis demonstrates how rationally matching the reactivity of metal salts to the telluride precursor is necessary for the successful production of metal tellurides.

Surface plasmon mediated harmonically resonant effects on third harmonic generation from Au and CuS nanoparticle films.

A growing class of nonlinear materials employ the localized surface plasmonic resonance (LSPR) of nanoparticles to enhance harmonic generation. Material systems containing harmonically coupled metallic and semiconductor plasmonic nanoparticles have been shown to further increase performance. Here, we explore the effect of dual plasmonic interactions in bilayer CuS and Au nanoparticle films on third harmonic generation (THG).

Molecular Decomposition Routes of Diaryl Diselenide Precursors in Relation to the Phase Determination of Copper Selenides.

H nuclear magnetic resonance (NMR), Se NMR, and powder X-ray diffraction (XRD) were used to monitor the thermal decomposition of diphenyl and dibenzyl diselenide precursors toward the synthesis of copper selenides. Copper was found to promote the decomposition of both precursors. The inorganic nanocrystals and organic byproducts were sensitive to the specific diaryl diselenides and the presence of oleylamine and copper.

Minimizing the Reorganization Energy of Cobalt Redox Mediators Maximizes Charge Transfer Rates from Quantum Dots.

Light-induced charge separation is at the very heart of many solar harvesting technologies. The reduction of energetic barriers to charge separation and transfer increases the rate of separation and the overall efficiency of these technologies. Here we report that the internal reorganization energy of the redox acceptor, the movement of the atoms with changing charge, has a profound effect on the charge transfer rates from donor quantum dots.

Alkyl selenol reactivity with common solvents and ligands: influences on phase control in nanocrystal synthesis.

This study develops mechanistic understanding of the factors which control the phase in syntheses of copper selenide nanocrystals by investigating how the chemistry of the dodecylselenol reactant is altered by the ligand and solvent environment. H NMR and Se NMR were used to study how commonly used solvents (octadecene and dioctylether) and ligands (oleylamine, oleic acid, stearylamine, stearic acid and trioctyl phosphine) change the nature of the dodecylselenol reactant at 25 °C, 155 °C and 220 °C. Unsaturations were prone to selenol additons, carboxylates underwent selenoesterification, amines caused the release of HSe gas, and the phosphine formed phosphine selenide.

Polycrystalline texture causes magnetic instability in greigite.

Magnetic stability of iron mineral phases is a key for their use as paleomagnetic information carrier and their applications in nanotechnology, and it critically depends on the size of the particles and their texture. Ferrimagnetic greigite (FeS) in nature and synthesized in the laboratory forms almost exclusively polycrystalline particles. Textural effects of inter-grown, nano-sized crystallites on the macroscopic magnetization remain unresolved because their experimental detection is challenging.

Synthesis of vulcanite (CuTe) and metastable CuTe nanocrystals using a dialkyl ditelluride precursor.

This study demonstrates that a dialkyl ditelluride reagent can produce metastable and difficult-to-achieve metal telluride phases in nanocrystal syntheses. Using didodecyl ditelluride and without the need for phosphine precursors, nanocubes of the pseudo-cubic phase (Cu1.5Te) were synthesized at the moderate temperature of 135 °C.

Tolman's Electronic Parameter of the Ligand Predicts Phase in the Cation Exchange to CuFeSNanoparticles.

The metastable and thermodynamically favored phases of CuFeS are shown to be alternatively synthesized during partial cation exchange of hexagonal CuS using various phosphorus-containing ligands. Transmission electron microscopy and energy dispersive spectroscopy mapping confirm the retention of the particle morphology and the approximate CuFeS stoichiometry. Powder X-ray diffraction patterns and refinements indicate that the resulting phase mixtures of metastable wurtzite-like CuFeS versus tetragonal chalcopyrite are correlated with the Tolman electronic parameter of the tertiary phosphorus-based ligand used during the cation exchange.

Site-Specific Protein Photochemical Covalent Attachment to Carbon Nanotube Side Walls and Its Electronic Impact on Single Molecule Function.

Functional integration of proteins with carbon-based nanomaterials such as nanotubes holds great promise in emerging electronic and optoelectronic applications. Control over protein attachment poses a major challenge for consistent and useful device fabrication, especially when utilizing single/few molecule properties. Here, we exploit genetically encoded phenyl azide photochemistry to define the direct covalent attachment of four different proteins, including the fluorescent protein GFP and a β-lactamase binding protein (BBP), to carbon nanotube side walls.

Ligand cleavage enables formation of 1,2-ethanedithiol capped colloidal quantum dot solids.

Colloidal quantum dots have garnered significant interest in optoelectronics, particularly in quantum dot solar cells (QDSCs). Here we report QDSCs fabricated using a ligand that is modified, following film formation, such that it becomes an efficient hole transport layer. The ligand, O-((9H-fluoren-9-yl)methyl) S-(2-mercaptoethyl) carbonothioate (FMT), contains the surface ligand 1,2-ethanedithiol (EDT) protected at one end using fluorenylmethyloxycarbonyl (Fmoc).

Role of Surface Morphology on Exciton Recombination in Single Quantum Dot-in-Rods Revealed by Optical and Atomic Structure Correlation.

The physical structure of colloidal quantum dot (QD) nanostructures strongly influences their optical and electronic behavior. A fundamental understanding of this interplay between structure and function is crucial to fully tailor the performance of QDs and their assemblies. Here, by directly correlating the atomic and chemical structure of single CdSe-CdS quantum dot-in-rods with time-resolved fluorescence measurements on the same structures, we identify morphological irregularities at their surfaces that moderate photoluminescence efficiencies.

Defined covalent assembly of protein molecules on graphene using a genetically encoded photochemical reaction handle.

We have created modified protein variants by introducing a non-canonical amino acid -azido-l-phenylalanine (azF) into defined positions for photochemically-induced covalent attachment to graphene. Attachment of GFP, TEM and cyt proteins was verified through a combination of atomic force and scanning tunnelling microscopy, resistance measurements, Raman data and fluorescence measurements. This method can in principle be extended to any protein which can be engineered in this way without adversely affecting its structural stability.

Site-Specific One-to-One Click Coupling of Single Proteins to Individual Carbon Nanotubes: A Single-Molecule Approach.

We report the site-specific coupling of single proteins to individual carbon nanotubes (CNTs) in solution and with single-molecule control. Using an orthogonal Click reaction, Green Fluorescent Protein (GFP) was engineered to contain a genetically encoded azide group and then bound to CNT ends in different configurations: in close proximity or at longer distances from the GFP's functional center. Atomic force microscopy and fluorescence analysis in solution and on surfaces at the single-protein level confirmed the importance of bioengineering optimal protein attachment sites to achieve direct protein-nanotube communication and bridging.

Spectroscopic Ellipsometry of Nanocrystalline Diamond Film Growth.

With the retention of many of the unrivaled properties of bulk diamond but in thin-film form, nanocrystalline diamond (NCD) has applications ranging from micro-/nano-electromechanical systems to tribological coatings. However, with Young's modulus, transparency, and thermal conductivity of films all dependent on the grain size and nondiamond content, compositional and structural analysis of the initial stages of diamond growth is required to optimize growth. Spectroscopic ellipsometry (SE) has therefore been applied to the characterization of 25-75 nm thick NCD samples atop nanodiamond-seeded silicon with a clear distinction between the nucleation and bulk growth regimes discernable.