Effect of pH on synthesis, characterization and fluorescence behavior of WO3:Eu3 nano powders

WO3:Eu3+ nanoparticles with different pH values were prepared by citric acid method. The structure and morphology of nano-powders were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The luminescence properties of the nano-powders were tested by a fluorescence spectrometer. The results showed that the average particle size of the prepared WO3:Eu3+ nano powders were the smallest and reached 32 nm at pH = 1. Under different excitation wavelengths, the main emission peak of the sample was at 615 nm, corresponding to the 5D0 →7F2 electron transition of Eu3+. The emission intensity of WO3:Eu3+ nanoparticles prepared at pH = 5 was the highest at 615 nm.

Investigation of a Separated Short-Wavelength Peak in InGaN Red Light-Emitting Diodes

We fabricated indium gallium nitride (InGaN) red light-emitting diodes (LEDs) with a peak emission wavelength of 649 nm and investigated their electroluminescence (EL) properties. An additional separated peak in the EL spectrum of the red LEDs at 20 mA was observed at 465 nm. This additional peak also exhibits a blue-shift with increasing currents as does the main emission peak. Using high-resolution microscopy, we observed many point-like emission spots in the EL emission images at the currents below 1 mA. However, these emission spots cannot be identified at currents above 5 mA because the red emission from quantum wells (QWs) is much stronger than that emitted by these spots. Finally, we demonstrate that these emission spots are related to the defects generated in red QWs. The measured In content was lower at the vicinity of the defects, which was regarded as the reason for separated short-wavelength emission in red InGaN LEDs.

Highly sensitive detection of Cr(VI), Pb(II) and Cd(II) ions by a new fluorescent sensor based on 4-amino-3-hydroxynaphthalene sulfonic acid-doped polypyrrole

A new electrosynthesized, fluorescent 4-amino-3-hydroxynaphthalene-1-sulfonic acid-doped polypyrrole (AHNSA-PPy) was used for the detection of Cr(VI), Pb(II) and Cd(II) heavy metallic ions. The optical properties of AHNSA-PPy were studied by UV-VIS absorption and fluorescence spectrometry in diluted DMSO solutions. UV-VIS spectrum showed a main band at 260 nm, a moderate band at 240 nm, and shoulders at 285, 295, 320 and 360 nm, whereas the fluorescence spectrum presented an excitation peak at 330 nm and a main emission peak at 390 nm with a shoulder at 295 nm. The effects of heavy metallic ions, including Cr(VI), Pb(II), and Cd(II), on the AHNSA-PPy UV-VIS absorption and fluorescence spectra were investigated. AHNSA-PPy fluorescence spectra were strongly quenched upon increasing the Cr(VI), Pb(II) and Cd(II) concentrations. Linear Stern-Volmer relationships were established, and polynomial equations for Pb(II) and Cd(II) were obeyed, indicating the existence of a AHNSA-PPy dynamic fluorescence quenching mechanism for Cr(VI) and a combination of dynamic and static fluorescence quenching for Pb(II) and Cd(II). The AHNSA-PPy sensor showed high sensitivity for fluorescence detection of the three heavy metallic ions, with very low limits of detection (3σ) of 1.4 nM for Cr(VI), 2.7 nM for Cd(II) and 2.6 nM for Pb(II). Therefore, this very sensitive quenching fluorimetric sensor is proposed for the detection of trace, toxic heavy metallic ions in the environment.

Enhanced Red Fluorescence Emissions of [Ru(bpy)3]Cl2 in DNA Complexes

The research on molecular devices, fluorescent labels and fluorescent probes based on the interaction between biomolecular DNA and fluorescent dyes has been paid more attention at home and abroad. In this paper, the luminescence properties of the [Ru(bpy)3]Cl2 complex itself were investigated, and the luminescence properties of the [Ru(bpy)3]Cl2 complex under the interaction of the solution and the film were observed by association of the DNA complex with the [Ru(bpy)3]Cl2 complex. The results showed that [Ru(bpy)3]Cl2 emitted red light with its main emission peak wavelength was 610nm, and its fluorescence intensity was the highest when the concentration of solution substance was 10mmol/L. When doped with DNA solution in [Ru(bpy)3]Cl2 complex, a small amount of fluorescent dye [Ru(bpy)3]Cl2 can be used to achieve a higher luminous intensity At the same time, the fluorescent dye [Ru(bpy)3]Cl2 doped with DNA solution reached a higher luminous intensity in the thin-film state. This experiment provides an important experimental basis for the application of fluorescent substance [Ru(bpy)3]Cl2 in luminescent thin films.

Ultrasensitive Optical Chemosensor for Cu(II) Detection

Herein, the main objective of this research is to design and synthesize a novel optical chemosensor, 2,6-Bis(4-dimethylaminophenyl)-4-(dicyanomethylene)-cyclohexane-1,1-dicarbo-nitrile (BDC), for detection of one of the most significant metal ions Cu(II). This novel fluorescent chemosensor exhibits unique optical properties with large Stokes shift (about 170 nm) approximately. The fluorescence and UV–vis absorption performance among the BDC probe and Cu(II) ions were examined in 1:9 (v/v) methanol–HEPES buffer (pH = 7.2) solution. Also, BDC displays high selectivity for Cu(II) concerning other cations. Moreover, this probe provides high selectivity and sensitivity based on their fluorescence properties and recognition abilities within a detection limit of the Cu(II) contents (LOD 2.3 x 10−7 M). The suggested mechanism of BDC sensor is attributed to the chelation process with Cu(II), to establish a 1:1 metal-ligand ratio complex with a binding constant (Kbind = 7.16 x 104 M−1). The detection process is accompanied by quenching the main emission peak of the BDC at 571 nm. All the experimental data were collected to investigate the effects of several important parameters such as reversibility and the concentration limits. Besides, we study the interference of various metal ions on selectivity and detection capacity of this significant Cu (II) ion. This novel chemosensor shows ultrasensitive, fast tracing of Cu(II) in the physiological pH range (pH 7.2) and therefore may propose a novel promising method for the investigation of the biological functions of Cu(II) in living cells.

Fullerene Aggregation in Thin Films of Polymer Blends for Solar Cell Applications

We report on the effects of the film morphology on the fluorescence spectra for a thin film including a quinoxaline-based co-polymer (TQ1) and a fullerene derivative ([6,6]-phenyl-C71-butyric acid methyl ester—PC70BM). The ratio between the polymer and the fullerene derivative, as well as the processing solvent, were varied. Besides the main emission peak at 700 nm in the fluorescence spectra of thin films of this phase-separated blend, a broad emission band is observed with a maximum at 520–550 nm. The intensity of this emission band decreases with an increasing degree of mixing in the film and becomes most prominent in thicker films, films with high PC70BM content, and films that were spin-coated from solvents with lower PC70BM solubility. We assign this emission band to aggregated PC70BM.

Fullerene Aggregation in Thin Films of Polymer Blends for Solar Cell Applications

We report on the effects of the film morphology on the fluorescence spectra for a thin film including a quinoxaline-based co-polymer (TQ1) and a fullerene derivative (PC70BM). The ratio between the polymer and the fullerene derivative, as well as the processing solvent were varied. Beside the main emission peak at 700 nm in the fluorescence spectra of thin films of this phase-separated blend, a broad emission band is observed with a maximum at 520 - 550 nm. The intensity of this emission band decreases with an increasing degree of mixing in the film and becomes most prominent in thicker films, films with high PC70BM content, and films that were spin-coated from solvents with lower PC70BM solubility. We assign this emission band to aggregated PC70BM.

Synthesis and Luminescent Properties of Ca2Li2BiV3O12:Eu3+ Phosphor

A red-emitting phosphor, Eu3+ activated Ca2Li2BiV3O12 was synthesized via combining combustion with solid state method and characterized by X-ray powder diffraction (XRD) and fluorescence spectrophotometer. The influence of synthesis temperature and the concentration of Eu3+ ions, on phase composition and luminescent properties of the synthesized samples was investigated systematically. The results showed that the Ca2Li2BiV3O12:Eu3+ phosphor with high phase purity and good crystallinity can be obtained by this citric acid - assisted sol combustion-solid state route at the synthesis temperature from 600°C to 700°C. The excitation spectrum of Ca2Li2BiV3O12:Eu3+ was composed of a broad band from 200 nm to 385 nm and a number of sharp small peaks extending from 390 nm to 480 nm, and the main peak was at 277 nm. The main emission peak was at 612 nm due to the electric dipole transition of 5D0 → 7F2 of Eu3+, which results in a red emitting. The sample prepared at T=680 °C, Eu3+ mol%=15 mol% has the highest emission intensity in this work.

Synthesis of Blue-Green Phosphors Sr4Si3O8Cl4:Eu2+by Gel-Combustion Method and Their Luminescent Properties

Sr4Si3O8Cl4:Eu2+blue-green phosphors were synthesized by the gel-combustion method. The as-synthesized phosphors were analyzed and characterized by X-ray diffraction and fluorescence spectrophotometer. The results indicate that orthorhombic phaseSr4Si3O8Cl4:Eu2+has been formed after the precursor calcined at 900°C reductive temperature. The excitation spectrum ofSr4Si3O8Cl4:Eu2+is a broad band in the range of 250 ~ 450 nm and the main peak at 324 nm. The emission spectrum is also a broad band with the main emission peak at about 484 nm, which is ascribed to the typical 4f5d1to 4f7transition ofEu2+. Moreover, the effects of the concentration ofEu2+, the reductive temperature, and the doping amount ofMg2+on luminescent properties were discussed.

Preparation of CsI(Tl) Scintillation Film by RF Magnetron Sputter Method and its Structural and Optical Characterization

Thallium-doped cesium iodide CsI(Tl) scintillation film has been manufactured by radio frequency (RF) magnetron sputter method onto the quartz glass substrates. The X-ray diffraction (XRD) pattern of the film shows preferable growth of the crystalline film in the (200) orientation. The optical and scintillation properties of CsI(Tl) film were investigated, including photoluminescence excitation (PLE), photoluminescence (PL), X-ray excited luminescence (XEL) spectra and decay curve. The main emission peak at about 2.28 eV is related to the radiative relaxation from the strong-off configuration of localized excitons around Tl+ ions. Under UV excitation, the 2.28 eV emission of CsI(Tl) film presents a single exponential decay with 545 ns.