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This paper describes a sensitive and selective method for the simultaneous determination of bispinacolato diboron (B

Understanding the electronic structure of doped semiconductors is essential to realize advancements in electronics and in the rational design of nanoscale devices. Reported here are the results of time-resolved X-ray absorption studies on copper-doped cadmium sulfide nanoparticles that provide an explicit description of the electronic dynamics of the dopants. The interaction of a dopant ion and an excess charge carrier is unambiguously observed via monitoring the oxidation state. The experimental data combined with DFT calculations demonstrate that dopant bonding to the host matrix is modulated by its interaction with charge carriers. Furthermore, the transient photoluminescence and the kinetics of dopant oxidation reveal the presence of two types of surface-bound ions that create midgap states.

Silver dimetal chalcogenides (Ag–V–VI2) are ternary semiconductors that have potential alternative energy applications due to their optimal band gaps and large extinction coefficients. The synthesis of these materials is challenging due to the lack of effective pnictide precursors. We report the use of tris[N,N-bis(trimethylsilyl)amido]antimony (Sb[N(SiMe3)2]3) and tris[N,N-bis(trimethylsilyl)amido]bismuth (Bi[(N(SiMe3)2]3) to synthesize nanocrystalline AgSbSe2 and AgBiSe2 quantum dots. The use of these reagents results in the creation of high quality nanomaterials with good crystallinity and narrow size distributions. Furthermore, electrical measurements on monolithic pellets of processed AgSbSe2 and AgBiSe2 nanomaterials demonstrate linear current–voltage behavior at room temperature, which indicates potential for use in electrical applications.

Molecular oxygen is known to be an efficient quencher of the excited states of organic molecules. This fact has been exploited to develop fluorescent O2 sensors, which is topical for cancer screening and many other applications. In this regard, our group and others have reported the development of robust, ratiometrically reporting chemosensors by conjugating O2-sensitive organic chromophores to inorganic quantum dots. Recently, an attempt was made to prepare a multifunctional sensor system by attaching the emissive poly(aromatic) hydrocarbons pyrene and perylene to magnetic nanomaterials, specifically CdSe/CdMnZnS and ZnSe/ZnMnS/ZnS quantum dots. However, the fluorescence of both dyes became invariant to oxygen levels even if the solutions were fully saturated. We ruled out any material dependency beyond the presence of Mn2+ ions by studying control samples, while molecular dynamics simulations negated any possibility of spatial sequestration of O2 by the magnetic fields. In the case of pyrene, the proxim...

This paper describes a sensitive and selective method for the simultaneous determination of bispinacolato diboron (B2Pin2) and tetrahydroxy diboron (B2(OH)4) in a small molecule Active Pharmaceutical Ingredient (API) by gas chromatography - mass spectrometry (GC-MS). These reagents are commonly used in the Suzuki-Miyaura coupling reaction and analytical methods are typically required to monitor these reagents at the Threshold of Toxicological Concern (TTC) level since they are Class II impurities based on ICH M7 guideline. In this study, hexylene glycol was added to derivatize B2(OH)4 before direct injection to the GC-MS, and B2Pin2 is analyzed in the same analysis without derivatization. Under the optimal conditions, the limit of detection (LOD) and the limit of quantitation (LOQ) were 65 ng/mL and 130 ng/mL respectively. Average recoveries of the analytes spiked in the drug substance at the 13 ppm (LOQ) and 104 ppm (TTC) levels were in the range of 77.9 %-85.3 % with relative standard deviations (RSDs) of 2.8 %-6.8 %. The linearity for both analytes was established in the range of 0.130-2.080 μg/mL with a correlation coefficient (r) of 0.9998 and the derivatization reaction is very rapid and complete within 15 minutes.

A quantum-dot based ratiometric fluorescent oxygen probe for the detection of hypoxia in live cells is reported. The system is comprised of a water-soluble near-infrared emissive quantum dot conjugated to perylene dye. The response to the oxygen concentration is investigated using enzymatic oxygen scavenging in water, while in vitro studies were performed with HeLa cells incubated under varying O2 levels. In both cases a significant enhancement in dye/QD emission intensity ratio was observed in the deoxygenated environment, demonstrating the possible use of this probe for cancer research.

The synthesis of metal arsenide semiconductor nanocrystals is challenging compared to other conventional materials (e.g., II–VI family CdSe) due to a high degree of covalency in crystal lattice and a lack of a variety of effective pnictide precursors. We reported here the use of [(Me3Si)2N]2AsCl (“arsenic silylamide”) to synthesize a variety of binary and tertiary quantum confined species such as InAs (III–V), Cd3As2 (II–V), and Cu3AsS4 (enargite, I3–V–VI4) nanocrystals. The physical properties of this reagent resolve many issues, especially concerning safety, with other precursors such as pyrophoric (TMS)3As and highly toxic AsH3 gas. Furthermore, usage of this reagent has allowed for the realization of enargite quantum rods for the first time. The role of arsenic silylamide in the reaction mechanism to form InAs has been elucidated with a combination of NMR spectroscopy as well as quantum chemical modeling. Cd3As2 and Cu3AsS4 nanostructures form via a diffusion mechanism.

We report a platform for the ratiometric fluorescent sensing of the endogenously generated gaseous transmitter H2S in its aqueous form (bisulfide, or hydrogen sulfide anion) based on the alteration of Förster resonance energy transfer from an emissive semiconductor quantum dot (QD) donor to a dithiol-linked organic dye acceptor. The disulfide bridge between the two chromophores is cleaved upon exposure to bisulfide, resulting in termination of FRET as the dye diffuses away from the QD. This results in enhanced QD emission and dye quenching. The resulting ratiometric response can be correlated quantitatively to the concentration of bisulfide, and was found to have a detection limit as low as 1.36 ± 0.03 μM. The potential for use in biological applications was demonstrated by measuring the response of the QD-based FRET sensor microinjected into live HeLa cells upon extracellular exposure to bisulfide. The methodology used here is built upon a highly multifunctional platform that offers numerous advantages such as low detection limit, enhanced photochemical stability, and sensing ability within a biological milieu.

A one-step method to produce ≈12 nm hydrodynamic diameter water-soluble CdSe/ZnS quantum dots (QDs), as well as CdS/ZnS, ZnSe/ZnMnS/ZnS, AgInS2 /ZnS, and CuInS2 /ZnS QDs, by ligand exchange with a near-monolayer of organosilane caps is reported. The method cross-links the surface-bound silane ligands such that the samples are stable on the order of months under ambient conditions. Furthermore, the samples may retain a high quantum yield (60%) over this time. Several methods to functionalize aqueous QD dispersions with proteins and fluorescent dyes have been developed with reaction yields as high as 97%.

Nano-structured pure Co2SnO4 powders have been synthesized using the co-precipitation method in the presence of oleic acid (OA) as a capping agent. The Taguchi L4 statistical design was used to investigate the effect of the main parameters (i.e., OA concentration, calcination time, and calcination temperature) on Co2SnO4 formation, crystallite size, and morphology. Co2SnO4 particles were characterized by powder x-ray diffraction (XRD), energy-dispersive x-ray spectroscopy, scanning electron microscopy (SEM), Fourier transform of infrared spectroscopy (FT-IR), dynamic light scattering (DLS), and Brunauer-Emmett-Teller (BET) surface area measurements. The formation of small and well-crystalline particles, on the order of 41.12-90.60 nm in crystal size, has been determined from XRD patterns and confirmed by SEM and DLS. The specific surface area was measured by a BET method to be 25.43 m2/g. The particle size of the product was observed by DLS to be in the range of 40-105 nm. The results indicated that calcination temperature has the most significant effect on the produced cobalt stannate crystal size.

In the present work nano crystalline copper aluminate (CuAl2O4) has been synthesized by the Pechini method using aqueous solutions containing corresponding metal nitrates. A Taguchi L4 statistical design was employed for investigating the most effective factors on the synthesis conditions and their interactions and production optimization. Nano crystalline CuAl2O4 particles with crystal size between 17 and 26 nm were obtained. The product characterized by XRD, FT-IR, DLS and TGA. The morphological properties have investigated using SEM. The photocatalytic degradation was investigated using methyl orange under the irradiation of visible light.

Presented are a set of procedures to produce water-soluble AgInS(2)/ZnS near-infrared emitting quantum dots for use as biological imaging agents. The known difficulty of producing near-infrared core/shell materials is resolved by overcoating the AgInS(2) cores at a low temperature using highly reactive precursors. Several methods are explored to impart water solubility of the hydrophobic as-prepared materials. Insofar as achieving aqueous dispersion of quantum dots has only limited biological utility, several methods to further functionalize them are examined. In vivo studies are conducted using these quantum dots to demonstrate the ability to model delivery of nanoparticles to the tumour microenvironment.