Radiative quantum efficiency of CdSe/ZnS core-shell colloidal solutions: Size-dependence

Thermo-optical parameters of CdSe/ZnS core-shell nanoparticles suspended in toluene were measured using a thermal lens (TL) technique. TL transient measurements were performed using the mode-mismatched dual-beam (excitation and probe) configuration. A He-Ne laser at λ_p = 632.8 nm was used as the probe beam and an Ar⁺ laser (at λ_e = 514.5 nm) was used as the excitation beam for studies as a function of both core size and concentration of CdSe/ZnS nanocrystals. The fraction thermal load (φ) and radiative quantum efficiencies (η) of the CdSe/ZnS were determined. Dependence on core size (∼2-5 nm) and concentration (∼0.01-0.62 mg/ml) was observed for both φ and η parameters.     

Application of an LC–ESI–QTOF–MS method for evaluating clindamycin concentrations in plasma and prostate microdialysate of rats

Clindamycin is used for infections caused by Gram-positive and Gram-negative anaerobic pathogens and Gram-positive aerobes. Propionibacterium acnes is an important opportunistic microorganism of the human skin and is related to prostatitis. An LC–electrospray ionization–quadrupole time-of-flight–MS method was validated for determining clindamycin concentrations in plasma and prostate microdialysate. Clindamycin separation was carried out on a C₁₈ column at 0.5 mL/min. The mobile phase employed gradient elution of formic acid and methanol. A mass spectrometer was operated in positive electrospray ionization mode to monitor ion 425.1784 and 253.1152 for clindamycin and cimetidine (internal standard), respectively. Linearity was obtained at 0.5–10.0 μg/mL (plasma) and 0.05–1.0 μg/mL (microdialysate) with coefficients of determination ≥0.999. The intra- and inter-day precision (coefficient of variation - CV%) values were ≤13.83% and 12.51% for plasma, respectively, and ≤10.90% and 9.35% for microdialysate, respectively. The accuracy was between 90.82% and 108.25% for plasma, and 96.97% and 106.98% for microdialysate. The present method was fully validated and applied to investigate clindamycin concentrations in both plasma and prostate by microdialysis in Wistar rats (80 mg/kg, intravenous). Because the penetration of antibiotics into the prostate may be restricted, this method allows us to investigate the prostate concentrations of clindamycin for the first time.     

Chemical immobilization of crosslinked polymeric ionic liquids on nitinol wires produces highly robust sorbent coatings for solid-phase microextraction

Super elastic nitinol (NiTi) wires were exploited as highly robust supports for three distinct crosslinked polymeric ionic liquid (PIL)-based coatings in solid-phase microextraction (SPME). The oxidation of NiTi wires in a boiling (30% w/w) H₂O₂ solution and subsequent derivatization in vinyltrimethoxysilane (VTMS) allowed for vinyl moieties to be appended to the surface of the support. UV-initiated on-fiber copolymerization of the vinyl-substituted NiTi support with monocationic ionic liquid (IL) monomers and dicationic IL crosslinkers produced a crosslinked PIL-based network that was covalently attached to the NiTi wire. This alteration alleviated receding of the coating from the support, which was observed for an analogous crosslinked PIL applied on unmodified NiTi wires. A series of demanding extraction conditions, including extreme pH, pre-exposure to pure organic solvents, and high temperatures, were applied to investigate the versatility and robustness of the fibers. Acceptable precision of the model analytes was obtained for all fibers under these conditions. Method validation by examining the relative recovery of a homologous group of phthalate esters (PAEs) was performed in drip-brewed coffee (maintained at 60 °C) by direct immersion SPME. Acceptable recoveries were obtained for most PAEs in the part-per-billion level, even in this exceedingly harsh and complex matrix.     

Collection of NMR Scalar and Residual Dipolar Couplings Using a Single Experiment

A new DMSO‐compatible aligning gel based on cross‐linked poly(2‐hydroxylethyl methacrylate) (poly‐HEMA) has been developed. Due to a significant difference in bulk magnetic susceptibility between the DMSO inside and outside the gel, it is possible to simultaneously collect isotropic and anisotropic NMR data, such as residual dipolar couplings (RDC), in the same NMR tube. RDC‐assisted structural analysis of menthol and the alkaloid retrorsine is reported as proof of concept.     

Strong optical nonlinearities of self-assembled polymorphic microstructures of phenylethynyl functionalized fluorenones

The polymorphs of a phenylethynyl functionalized fluorenone derivative, and their controlled self-assembly for microstructures with different morphologies have been studied. These polymorphic microcrystals exhibit very distinctive NLO properties, which are highly correlated to their electronic and supramolecular structures.     

Morphology and performance of CoOOH films synthesized via electrochemical oxidation: substrate effects

In the present work, CoOOH films are synthesized from the electrochemical oxidation of α-Co(OH)₂ as precursor. The substrate influences on the material electrochemical properties are studied. The samples are structural and morphologically characterized using techniques of X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy techniques are used for the electrochemical characterization. The films deposited on steel substrate grew in the vertical hexagonal platelet form. Meanwhile, films on Ti plate presented morphology in agglomerated sphere form. After electrochemical oxidation, the film initial morphology is maintained. The films deposited on steel plate have a structure which favors charge storage showing a high specific capacity value (110.92 mA h g^?1) and cyclic stability of 92% after 1000 cycles. Finally, the relaxation time constant value calculated was 5.6 s. This fact is making this material as a possible good candidate for application as electrode material or additive for other materials, in energy storage devices.