Characterization of primary amine capped CdSe, ZnSe, and ZnS quantum dots by FT-IR: determination of surface bonding interaction and identification of selective desorption

Surface ligands of semiconductor quantum dots (QDs) critically influence their properties and functionalities. It is of strong interest to understand the structural characteristics of surface ligands and how they interact with the QDs. Three quantum dot (QD) systems (CdSe, ZnSe, and ZnS) with primary aliphatic amine capping ligands were characterized primarily by FT-IR spectroscopy as well as NMR, UV-vis, and fluorescence spectroscopy, and by transmission electron microscopy (TEM). Representative primary amines ranging from 8 to 16 carbons were examined in the vapor phase, KBr pellet, and neat and were compared to the QD samples. The strongest hydrogen-bonding effects of the adsorbed ligands were observed in CdSe QDs with the weakest observed in ZnS QDs. There was an observed splitting of the N-H scissoring mode from 1610 cm(-1) in the neat sample to 1544 and 1635 cm(-1) when bound to CdSe QDs, which had the largest splitting of this type. The splitting is attributed to amine ligands bound to either Cd or Se surface sites, respectively. The effect of exposure of the QDs dispersed in nonpolar medium to methanol as a crashing agent was also examined. In the CdSe system, the Cd-bound scissoring mode disappeared, possibly due to methanol replacing surface cadmium sites. The opposite was observed for ZnSe QDs, in which the Se-bound scissoring mode disappeared. It was concluded that surface coverage and ligand bonding partners could be characterized by FT-IR and that selective removal of surface ligands could be achieved through introduction of competitive binding interactions at the surface.     

Comparison of urinary iodide determination in female thyroid patients by two techniques

Iodine deficiency affects a substantial portion of the world’s population, provoking severe health problems as well as important economic losses to the region in which this condition is found. In present study, evaluated the levels of urinary iodide (UI) and thyroid hormone status in female hypothyroid patients (HPs) and control subjects of same age group 16–30 years. The UI in HPs was measured by means of a Potentiometric method after microwave-assisted acid digestion, and compared the results with those obtained by the Sandell-Kolthoff method. The validity and accuracy was checked by using certified reference materials. The significantly lower concentration of iodide in the urine samples of the female goiter patients were observed as compared to control/referents subjects (p < 0.001). Serum thyroid status thyroid stimulating hormone, free triiodothyronine and free thyroxin were significantly lower in female patients as compared to control females (p < 0.003). The proposed method was relatively rapid, precise, accurate, efficient, as well as cost effective by using inexpensive equipment.     

Damage of beryllium surface under irradiation with a high-current electron beam

Radiation damage of a beryllium surface by a high-current electron beam at the GSEP-3 accelerator is considered. The degree of damage of beryllium samples has been determined. The temperature fields inside the sample and the distributions of thermal stresses have been calculated. The reasons for beryllium surface cracking formation have been found. The concentrations of point defects have been calculated. The possible reasons for an increase in microhardness of the irradiated beryllium surface layer are discussed.     

Electron spin resonance signal of Luttinger liquids and single-wall carbon nanotubes

A comprehensive theory of electron spin resonance (ESR) for a Luttinger liquid state of correlated metals is presented. The ESR measurables such as the signal intensity and the linewidth are calculated in the framework of Luttinger liquid theory with broken spin rotational symmetry as a function of magnetic field and temperature. We obtain a significant temperature dependent homogeneous line broadening which is related to the spin-symmetry breaking and the electron-electron interaction. The result crosses over smoothly to the ESR of itinerant electrons in the noninteracting limit. These findings explain the absence of the long-sought ESR signal of itinerant electrons in single-wall carbon nanotubes when considering realistic experimental conditions.     

Scintillation properties of Cs2LiGdCl6: Ce3+

In this communication, we investigated the scintillation properties of Cs₂LiGdCl₆:10% Ce³⁺ single crystal. This scintillation crystal is grown by using the vertical Bridgman technique. X-rays induced emission spectra show that, Cs₂LiGdCl₆:10% Ce³⁺ emits into the Ce³⁺ band, spanning from 365 nm to 450 nm wavelengths. Under γ-ray excitation, the sample crystal shows three main decay time components of 129 ns (51%), 573 ns (32%) and 8.9 μs (17%). It offers an energy resolution of 5.0% (FWHM) for the 662 keV full absorption peak at room temperature. We measured an absolute light yield of 20,000 photons/MeV of absorbed γ-ray energy. We found that with a little exposure to the air, the scintillation properties of the Cs₂LiGdCl₆:10% Ce³⁺ crystal deteriorate, which is attributed to the highly hygroscopic nature of this material. We believe that the Cs₂LiGdCl₆:10% Ce³⁺ crystal can be a promising material for medical imaging and radiation detection. Moreover due to the presence of Li and Gd constituents, this scintillation crystal can also be the possible candidate for thermal neutron detection.     

Ligand-Promoted [Pd]-Catalyzed α-Alkylation of Ketones through a Borrowing-Hydrogen Approach

A new class of palladium complexes bearing bidentate 2-hydroxypyridine based ligands have been prepared and fully characterized. The applications of these new complexes towards ketone alkylation reactions with alcohols through a metal-ligand cooperative borrowing-hydrogen (BH) process were demonstrated.     

Advances of responsive deep eutectic solvents and application in extraction and separation of bioactive compounds

In recent years, it has been found that changing ambient conditions (CO₂/N₂, temperature, pH) can trigger a switchable phase transition of deep eutectic solvents, and such solvents are known as responsive deep eutectic solvents. In this work, we present the development history, properties, and preparation of responsive deep eutectic solvents, followed by the application of responsive deep eutectic solvents in the extraction and separation of bioactive compounds are presented. Importantly, the mechanism of responsive deep eutectic solvents in the extraction of bioactive compounds is discussed. Finally, the challenges and prospects of responsive deep eutectic solvents in the extraction and separation of bioactive compounds are proposed. Responsive deep eutectic solvents are considered green and efficient solvents. Some methods for extraction and separation of bioactive compounds by responsive deep eutectic solvents can increase the possibility of recycling the deep eutectic solvents, and provide higher efficiency in the extraction and separation field. It is hoped that this will provide a reference for the green and sustainable extraction and separation of various bioactive compounds.