Dependence of photoluminescence of CdSe/ZnS on excitation wavelength

We have found that the photoluminescence (PL) intensity of CdSe/ZnS nanocrystals placed on a thin film of insulator (GaAsOx/GaAs) depends on excitation wavelength through the interference effects of the excitation light. By employing the multi-reflection/interference calculation, the insulator thickness of the underlying non-uniform patterns can be evaluated by the simple observation of CdSe/ZnS PL with a couple of excitation wavelengths. Moreover, the differences observed for the temporal evolution of CdSe/ZnS PL (blue shifts and degradation) among the excitation wavelengths suggest that the photo-induced changes of chemical composition and surface ligands are responsible for blue shifts and degradation, respectively.     

Synthesis of nano-size BaMgAl10O17:Eu blue phosphor by a rapid exothermic reaction

Ultrafine particles of BaMgAl₁₀O₁₇:Eu²⁺ (BAM) phosphor were synthesized by a solid-state combustion reaction in a powder bed of 0.9BaCO₃+MgO+5Al₂O₃+0.05Eu₂O₃+k(KClO₃+1.5C) composition. A large exothermic reaction of the mixture (KClO₃+1.5C) leads to a self-sustaining combustion mode. Under optimized combustion conditions, the product consisted of BAM powder and KCl was obtained. BAM ultrafine particles resulting from the combustion process were easily obtained by simply washing the salt by-product with water. Combustion-processed BAM phosphor shows a homogeneous grain size of 100-500 nm, good dispersity, regular morphology, and improved luminescence properties.     

Direct Blue 71 staining as a destaining‐free alternative loading control method for Western blotting

In Western blotting, a suitable loading control is indispensable for correcting errors in the total amount of loaded protein. Immunodetection of housekeeping proteins and total protein staining have traditionally been used as loading control methods. Direct Blue 71 (DB71) staining—a novel, sensitive, dye‐binding staining method compatible with immunodetection—may offer advantages over these traditional loading control methods. Three common neuroscientific samples (human plasma, human oligodendrocytes, and rat brain) were employed to assess DB71 staining as a loading control method for Western blotting. DB71, CBB, one traditional housekeeping protein, and one protein of interest were comparatively assessed for reliability and repeatability and linear dynamic range over 2.5–40 μg of protein loaded. DB71's effect on the reliability and repeatability and linear dynamic range of immunoreaction were also assessed. Across all three sample types, DB71 was either equivalent or superior to CBB and housekeeping protein‐based methods in terms of reliability and repeatability and linear dynamic range. Across all three sample types, DB71 staining did not impair the reliability and repeatability or linear dynamic range of immunoreaction. Our results demonstrate that the DB71 staining can be used as a destaining‐free alternative loading control method for Western blotting.     

Luminescence Study of ZnS Quantum Dots Prepared by Chemical Method

We report synthesis of ZnS quantum dots by chemical method at room temperature. In this technique, ZnS quantum dots are produced by simple chemical reactions where zeolite, acts as matrix, plays the key role in controlling particle growth during synthesis. Quantum dots exhibit luminescence properties such as Zn²⁺ related emission, efficient low voltage electroluminescence, and super linear voltage-brightness EL characteristics. This study demonstrates the technological importance of semiconductor nanosystems prepared by low cost chemical route.     

Synthesis and property of diazocine derivatives substituted with imidazole in various positions

ABSTRACT

TIACA-I, TIACA-II were synthesized by changing the substitution position of the imidazole group in the diazocine core. TIACA-I, TIACA-II in the film state showed absorption in the range of 354 to 392 nm and exhibited blue photoluminescence (PL) emissions at 448 and 462 nm, respectively. The PL wavelength of TIACA-II is red-shifted by 14 nm than that of TIACA-I due to the electron-donating intensity depending on the position of the imidazole group. The use of TIACA-II in a non-doped OLED device resulted in blue emission with current efficiency of 2.84 cd/A and CIE of (0.15, 0.18).     

Electroluminescence of colloidal ZnSe quantum dots

The article reports a green chemical synthesis of colloidal ZnSe quantum dots at a moderate temperature. The prepared colloid sample is characterised by UV-vis absorption spectroscopy and transmission electron microscopy. UV-vis spectroscopy reveals as-expected blue-shift with strong absorption edge at 400 nm and micrographs show a non-uniform size distribution of ZnSe quantum dots in the range 1-4 nm. Further, photoluminescence and electroluminescence spectroscopies are carried out to study optical emission. Each of the spectroscopies reveals two emission peaks, indicating band-to-band transition and defect related transition. From the luminescence studies, it can be inferred that the recombination of electrons and holes resulting from interband transition causes violet emission and the recombination of a photon generated hole with a charged state of Zn-vacancy gives blue emission. Meanwhile electroluminescence study suggests the application of ZnSe quantum dots as an efficient light emitting device with the advantage of colour tuning (violet-blue-violet).     

Green synthesis of activated carbon doped tungsten trioxide photocatalysts using leaf of basil (Ocimum basilicum) for photocatalytic degradation of methylene blue under sunlight

Tungsten oxide (WO₃) nanoparticles were prepared hydrothermally by basil leaves extract, and Activated Carbon (AC) was prepared by the carbonization of date pits. Moreover, 1, 2 and 3% of AC doped WO₃ nanoparticles have been fabricated under hydrothermal conditions. The obtained samples have been characterized by using different techniques such as x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), simultaneous thermogravimetric analysis (TG-DTGA), fourier transform infrared (FT-IR), BET surface area, and Ultra-Violet spectroscopy (UV–Vis). It was observed that band-gap energy of the fabricated materials decreases by increasing AC amount. Similarly, BET surface area and porosity results showed increasing the content of AC, surface area, pore size and pore volume were decreased. The functional groups, determined by FT-IR, played a significant role in the photocatalytic performance. The photocatalytic performance of fabricated samples was used for the degradation of methylene blue (MB) at neutral pH under visible light radiations, and it is observed that WO₃/3%AC photocatalyst showed the highest degradation of MB. Both, capped phytochemicals of basil extract and the nanocomposites, were improved the photocatalytic performance, about 94% photodegradation was observed within 25 min under the reaction conditions. The photocatalyst was stable and about 85% and 81% photodegradation of MB were found under the two times of reusability tests.     

Electrochemical properties of Meldola's Blue immobilized on silica-titania phosphate prepared by the sol-gel method

The mixed oxide phosphate (≡SiO)₂Ti(O₃POH)₂ having a specific surface area of S_BET= 595 m² g⁻¹ and an average pore volume of 0.43 mL g⁻¹ was prepared by the sol-gel processing method. The material showed the following characteristics: Ti=11.6 wt% and P=10.5 wt%; ion exchange capacity of 0.60 mmol g⁻¹. Meldola's Blue (MLB) dye was adsorbed, by an ion exchange reaction, from an aqueous solution in a quantity of 0.62 mmol g⁻¹. The dye was strongly retained and was not easily leached from the matrix even in presence of 0.5 M electrolyte solution. Changing the solution pH between 2.5 and 7.0, the midpoint potential of the dye-adsorbed (≡SiO)₂ Ti(O₃POMLB)₂ matrix carbon paste electrode remained practically constant, i.e. about 20 mV vs. SCE. This is not the usual behaviour of MLB since its midpoint potential changes considerably in solution phase as the pH is changed. The modified electrode has proved to be stable and electrocatalytically active for hydrazine oxidation at pH 6. Received: 22 June 1999 / Accepted: 7 September 1999     

碘—淀粉络合物褪色光度法测定微量氰化物

研究了在 p H 7.0的混合磷酸盐缓冲溶液条件下 ,氰根使碘与淀粉形成的蓝色络合物褪色 ,络合物吸光度的降低值 ΔA与加入的氰根量成正比。 λmax=570 nm,氰根在 0～ 2 0 μg/2 5ml范围内呈良好的线性关系 ,检出限为 0 .52μg/2 5ml,其表观摩尔吸光系数为 2 .6× 1 0 4 ,方法成功地用于含氰废水中氰化物的测定。     

Electroanalytical applications of Prussian Blue and its analogs

The applications of transition metal hexacyanoferrates in electroanalysis are surveyed. Prussian Blue (ferric hexacyanoferrate) is recognized as the most promising low-potential transducer for hydrogen peroxide reduction among all known systems. The advantages of Prussian Blue over platinum or peroxidase electrodes for hydrogen peroxide detection are discussed. Various types of biosensors based on transition metal hexacyanoferrates and oxidase enzymes are considered. Amperometric biosensors based on Prussian Blue-modified electrodes allow the detection of glucose and glutamate down to 10^–7 mol L^–1 in the flow-injection mode. The future prospects of Prussian Blue-modified electrodes in analytical chemistry for the monitoring of chemical toxic agents, in clinical diagnostics, and in food control are outlined.