Anti‐Stokes Luminescence of Cadmium Telluride Nanocrystals

For the first time, the antiStokes luminescence in colloidal solutions of CdTe nanocrystals on excitation below the absorption edge has been discovered. The maximum spectral shift to the shortwave region relative to the excitation energy E _con ^max = 319 meV is obtained for meansized nanocrystals (2.5 nm). The conversion efficiency of the absorbed radiant energy is 1.3·10^–2%. The rise in the antiStokes photoluminescence intensity with increasing temperature and the linear dependence on the exciting radiation intensity have been established. It is shown that the effect observed cannot be caused by twophoton excitation or by Auger recombination. It is assumed that the basic mechanism of the luminescence observed is the radiative recombination through the energy levels of the states attributable to the disturbance of the crystal structure in the nanocrystals.     

Spectral Studies of Vanadyl-Doped Cadmium–Strontium Borosilicate Glass System

Glasses with composition CdO–(20-x) SrO–B₂O₃–SiO₂–x V₂O₅ (CdSBSi) (x = 0.5, 1, 1.5, 2, 2.5 mol%) were prepared by melt quenching technique. The amorphous nature of prepared glasses is confirmed by X-ray diffraction. Optical absorption spectra, electron paramagnetic resonance (EPR) and Fourier transform infrared (FTIR) measurements were also carried out for the prepared glass samples. The optical band gap energy (E _opt) and Urbach energy (?E) were calculated from their ultraviolet edges. The theoretical values of optical basicity (Λ _th) of glasses have been evaluated. The optical absorption spectrum exhibits two band characteristic of VO²⁺ ions in tetragonally distorted octahedral site symmetry. The two bands have been assigned to the transitions ²B₂ → ²B₁ and ²B₂ → ²E in the decreasing order of energy. The spin–Hamiltonian parameters (g and A), bonding parameters (β*² and $ \varepsilon_{\pi }^{*2} $ ), Fermi contact interaction parameter (K) have been evaluated from the EPR spectra. The VO²⁺ site symmetry is ascribed to a tetragonally (C_4v) distorted octahedron. FTIR spectra of these glasses were analyzed in order to identify the contribution of each component to the local structure. The physical properties of these glasses were also evaluated.     

Analysis of the Crystallogeometry of Tetragonal Martensite in Indium‒Cadmium Alloys by the Method of Electron Back-Scattering Diffraction

Doklady Physics - Electron back-scattering diffraction shows that a package structure consisting of colonies of tetragonal lamella plates is formed when cooled below the temperature of the...     

Novel Glutathione-Capped Cadmium Telluride Quantum Dots-Based Off–On Fluorescence Sensor for Highly Sensitive and Selective Monitoring of Histidine

A novel glutathione-capped cadmium telluride quantum dots-based fluorescence “off–on” sensor was designed and applied for highly sensitive and selective monitoring of histidine in aqueous solution. To provide a platform for histidine detection, manganese ion was first employed as an effective quencher to decrease the fluorescence of glutathione-capped cadmium telluride quantum dots because of the binding of manganese ion to glutathione on the surface of quantum dots and the electron transfer from the photoexcited glutathione-capped cadmium telluride quantum dots to manganese ion. Due to its high binding affinity with manganese ion, histidine can make the manganese ion to be dissociated from the surface of glutathione-capped cadmium telluride quantum dots to form more stable complex with histidine in solution, and set free the luminescent glutathione-capped cadmium telluride quantum dots, thereby recovering the fluorescence of glutathione-capped cadmium telluride quantum dots. Experimental results showed that the recovered fluorescence intensity was directly proportional to the concentration of histidine in the range of 0.006 to 465.0 µg mL^?1 with a correlation coefficient (R) of 0.9977, and the detection limit (3σ/K) was 1.82 ng mL^?1. Relevant experiments also revealed that the fluorescence sensor gives excellent selectivity for histidine over other common amino acids. To further investigate perfect analysis performance, this sensor was utilized to determine histidine in synthetic samples with satisfactory results.     

A Novel Pyrene Fluorescent Sensor Based on the π–π Interaction Between Pyrene and Graphene of Graphene–Cadmium Telluride Quantum Dot Nanocomposites

In this article, water-soluble graphene–cadmium telluride quantum dot nanocomposites were fabricated through the synthesis of cadmium telluride quantum dots in the presence of graphene aqueous dispersion. It was found that pyrene could remarkably quench fluorescence of graphene–cadmium telluride quantum dot nanocomposites. On this basis, a novel method for the determination of pyrene was developed. Factors affecting the pyrene detection were investigated, and the optimum conditions were determined. Under the optimum conditions, a linear relationship could be established between the quenching of fluorescence intensity of graphene–cadmium telluride quantum dot nanocomposites and the pyrene concentration in the range of 6.00 × 10^?8–2.00 × 10^?6 mol L^?1 with a correlation coefficient of 0.9959. The detection limit was 4.02 × 10^?8 mol L^?1. Furthermore, the nanocomposites were applied to practical determination of pyrene in different water samples with satisfactory results.