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Bi nanoparticles embedded in a SiO2 matrix were prepared via the high energy ball milling method. The melting behavior of Bi nanoparticles was studied by means of differential scanning calorimetry (DSC) and high-temperature in situ X-ray diffraction (XRD). DSC cannot distinguish the surface melting from ‘bulk’ melting of the Bi nanoparticles. The XRD intensity of the Bi nanoparticles decreases progressively during the in situ heating process. The variation in the normalized integrated XRD intensity versus temperature is related to the average grain size of Bi nanoparticles. Considering the effects of temperature on Debye—Waller factor and Lorentz-polarization factor, we discuss the XRD results in accordance with surface melting. Our results show that the in situ XRD technique is effective to explore the surface melting of nanoparticles. [ABSTRACT FROM AUTHOR]

Copper nanoparticles (Cu-NPs) have been electrochemically synthesized onto a poly(o-phenylenediamine) (P0PD-) coated glassy carbon electrode (GCE). Electrochemical properties and surface characterizations were studied using cyclic voltammetry, atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis. Cyclic voltammetry, AFM, SEM, and XRD confirmed the presence of Cu-NPs on the electrode surface. Cu-NPs are firmly stabilized by surface attachment of the PoPD functionality that can be attached to the electrode surface, thus becoming an integral part of the polymer backbone. The Cu-NPs-polymer film-coated GCE (Cu-NPs/PoPD/GCE) showed excellent electrocatalytic activity toward the reduction of hydrogen peroxide (H2O2) and nitrite (NO2-). Amperometry was carried out to determine the concentration of H202 and NO2- at -0.3 V. The dependence of the current response on the H2O2 concentration was explored under neutral conditions, and an excellent linear concentration range from 1.0 x 106 to 1.0 x 10-3 M was found. The Cu-NPs/PoPD/GCE allows highly sensitive, low working potential, stable, and fast amperometric sensing of H2O, and NOT. This is promising for the future development of nonenzymatic sensors. The real-sample analysis of commercial H2O2 samples was performed using the proposed method, and the obtained results are satisfactory. [ABSTRACT FROM AUTHOR]

A series of new phosphors of CaAlBO4:RE3+ (RE = Ce, Tb, Eu) were synthesized by conventional solid-state reactions. The X-ray diffraction data indicate that a pure phase of CaAlBO4:RE3+ can be successfully obtained. The photoluminescence (PL) spectra, quantum efficiency, and CIE coordinates of CaAlBO4:RE3+ were investigated. The PL and PL excitation spectra indicate that the emission wavelengths of CaAlBO4:Ce3+ are 372 and 398 nm (with full width at half maximum of 33 nm) attributed to the 4f65d-4f7 transition of the Ce3+ activator, respectively. CaAlBO4:Tb3+ displays green emission at 483, 543, 584, and 620 nm, while CaAlBO4:Eu3+ shows a dominating emission peak at 621 nm, which is attributed to the Eu3+ 5D0 - 7F2 transition. The quantum efficiencies of optimized CaAlBO4:Ce3+, CaAlBO4:Tb3+, and CaAlBO4:Eu3+ were found to be 43, 21, and 19%, respectively. The phosphors may provide a new kind of luminescent material under UV excitation. [ABSTRACT FROM AUTHOR]

We have investigated the luminescence of a series of M5Eu(WO4)4-x(MoO4)x (M = Li, Na, K) phosphors and discovered that Na5Eu(WO4)4-x(MoO4)x (0 ≤ x ≤ 4.0) exhibit the most intense red emission among the three investigated. Powder X-ray diffraction investigations show that a complete solid solution can be formed in the indicated composition range. The effect of chemical compositions on the luminescence properties of Na5Eu(WO4)4-x(MoO4). has been investigated and discussed. The Commission International de l'Eclairage chromaticity coordinates were found to be (0.66,0.33) for Na5Eu(WO4)4-x(MoO4)x, which reaches the same level as that of the Y2O2S:Eu3+ commodity. The color-rendering index (Ra) of a typical white-light-light emitting diode (WL-LED) based on Na5Eu(WO4)2(MoO4)2 was found to be 82.3, higher than that (i.e., Ra ∼ 70.8) obtained for the WL-LED fabricated using the commodity of La2O2S:Eu3+ when the WL-LEDs were operated at a forward-bias current (If) of 20 mA at room temperature. Na5Eu(WO4)4-x(MoO4), is therefore suggested to be a potential red-emitting phosphor for WL-LED. [ABSTRACT FROM AUTHOR]