Menglian Gong

Effects of the structure of ligands and their Ln3+ complexes on the luminescence of the central Ln3+ ions

According to the literature and our experimental results, it was found that (1) the suitability of the energy gap between the excited triplet energy level of the ligands and the lowest excited energy level of Ln3+ is a critical factor for sensitized luminescence of the central Ln3+; (2) the high intensity of the sensitized luminescence of Ln3+ should be caused by a rigid planar molecular structure of the complex; (3) the existence of both a suitable conjugated system and ideal coordinating groups should be considered for ligand-design.

A novel approach for preparation of Y2O3:Eu3+ nanoparticles by microemulsion–microwave heating

A novel approach for preparation of europium (III)-doped yttrium oxide (Y2O3:Eu3+) nanoparticles by microemulsion–microwave heating was reported in this paper. Y2O3:Eu3+ nanoparticles were successfully obtained by microwave-heating the as-prepared particles of yttrium hydroxide and europium hydroxide, formed in a reaction between Y(NO3)3–Eu(NO3)3 and NH3·H2O in the reverse microemulsion composed of Triton X-100, n-hexanol, cyclohexane and water. Field-emission scanning electron microscopy (FE-SEM) and powder X-ray diffraction (XRD) results indicated that the resultant nanoparticles showed a narrow size distribution, small size (20–30 nm) and spherical shape. The ratios of Eu to Y in the products, determined by energy dispersive spectroscopy (EDS), were in good agreement with those of the feed. The nanoparticles emitted much strong red light at 611 nm under UV excitation, especially around 255 nm. Furthermore, this novel method required a very short heating-time and the energy consumption was much smaller compared with conventional heating ways.

Hydrothermal growth of ZnO nanoscrewdrivers and their gas sensing properties

Single crystalline ZnO nanoscrewdrivers have been prepared by hydrothermal growth on a modified ITO glass substrate. The as-prepared samples were characterized by x-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). Gas sensors were fabricated using the as-prepared sample. Gas sensing measurements reveal that sensors based on ZnO nanoscrewdrivers show high sensitivity to dilute H2S gas. The detection limit of the sensors achieved several ppb. The response mechanism of the sensors to H2S is discussed according to the response transients of the gas sensors.

Encapsulation of fluorescein into MCM-41 mesoporous molecular sieve by a sol-gel method

Abstract MCM-41-hosted fluorescein mesophase was prepared by addition of the dye into the sol–gel mixture for the synthesis of MCM-41 mesoporous molecular sieve under microwave radiation. The as-synthesized organo-silica-surfactant material possessed hexagonal mesostructure with short-range symmetry and a uniform nanosize of about 30 nm. Furthermore, fluorescence spectrum, increase in lifetime and lack of aggregation at high concentration were discussed in terms of the effect of the host–guest interaction on these properties.

Synthesis, photoluminescence and Judd–Ofelt analysis of red LiGd5P2O13 : Eu3+ phosphors for white LEDs

A series of LiGd5P2O13u2006:u2006Eu3+ phosphors with a red-emitting band centered at 622 nm were synthesized by a high temperature solid-state reaction method. Structure-luminescence correlation, concentration quenching and thermal stability of the LiGd5P2O13u2006:u2006Eu3+ phosphors were studied combined with XRD, PL/PLE spectra as well as temperature-dependent PL and decay curves. The optimum concentration of Eu3+ doped in the LiGd5P2O13 is 20 mol%, and the corresponding concentration quenching mechanism is found to be via dipole/quadrupole–quadrupole interactions. Intensity parameters (Ω2 and Ω4) and various radiative properties such as transition rates (A), branching ratios (β) and stimulated emission cross-section (δe) were calculated using the Judd–Ofelt theory. LiGd5P2O13u2006:u2006Eu3+ exhibited good thermal stability and its emission intensity decreased slightly at temperature above 150 °C. The CIE coordinates of LiGd5P2O13u2006:u20060.20Eu3+ (0.644, 0.339) are very close to s-RGB standard red (0.640, 0.330), and the corresponding quantum efficiency is 46.5%. The results show that LGPOu2006:u2006Eu3+ may be considered as a potential red emitting phosphor for NUV/blue pumped WLEDs.

Single-crystalline LaFeO3 nanotubes with rough tube walls: synthesis and gas-sensing properties

Single-crystalline LaFeO3 nanotubes with rough tube walls have been prepared by a new two-step method: co-precipitation followed by molten-salt synthesis. The as-prepared samples were characterized by x-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution TEM, selected area electron diffraction (SAED) and energy dispersive x-ray spectroscopy (EDS). Gas sensors were fabricated using the as-prepared sample. It was found that the sensors based on the LaFeO3 nanotubes showed good sensing properties to Cl2 at room temperature. The detection limit of the sensors reached 1 ppm Cl2 at room temperature and the sensors showed good selectivity and stability.

Synthesis and luminescence of a novel conjugated europium complex with 6-parachloroaniline carbonyl 2-pyridine carboxylic acid

A novel organic ligand, 6-aniline carbonyl 2-pyridine carboxylic acid (HAP), and the corresponding europium complex, tris(6-aniline carbonyl 2-pyridine carboxylato) europium (III) (Eu-AP) have been designed and synthesized. The results showed that Eu-AP was a conjugated complex, emitting strong red luminescence. The lifetimes of 5D0 of Eu3+ in the complex were examined using time-resolved spectroscopic analysis, and the lifetime value was 0.55 ± 0.01 ms for solid Eu(AP)3. Thermogravimetric analysis showed that the europium complex had good thermal stability.

Thermal quenching of luminescence of LiSr4(BO3)3:Eu2+ orange‐emitting phosphor

An orange-emitting phosphor, Eu(2+)-activated LiSr4(BO3)3, was synthesized using the conventional solid-state reaction. The photoluminescence excitation and emission spectra, and temperature dependence of the luminescence intensity of the phosphor were investigated. The results showed that LiSr4(BO3)3:Eu(2+) could be efficiently excited by incident light of 250-450u2009nm, and emits a strong orange light. With increasing temperature, the emission bands of LiSr4(BO3)3:Eu(2+) show an abnormal blue-shift with broadening bandwidth and decreasing emission intensity.

Synthesis and luminescence of a novel conjugated europium complex with 6-paramethylaniline carbonyl 2-pyridine carboxylate

Abstract A novel organic ligand, 6-paramethylaniline carbonyl 2-pyridine carboxylic acid (Hp-MAP), and the corresponding europium complex, tris(6-paramethylaniline carbonyl 2-pyridine carboxylato) europium(III) (Eu-p-MAP) have been designed and synthesized. The results showed that Eu-p-MAP was a conjugated complex, emitting remarkably strong red luminescence. The lifetimes of 5 D 0 of Eu 3+ in the complex were examined using time-resolved spectroscopic analysis; the lifetime values were 0.72±0.01 ms for 1.0×10 −5 molxa0l −1 Eu(p-MAP) 3 ethanol solution and 1.16±0.01 ms for solid of Eu(p-MAP) 3 , respectively. Thermogravimetric analysis showed the europium complex had good thermal stability.

Luminescence and thermal stability of sodium tris(pyridine dicarboxylate) terbate(III) complex incorporated in silica matrix by sol-gel method

Abstract A terbium(III) complex, Na 3 Tb(DPA) 3 ·9H 2 O, where H 2 DPA is 2,6-dicarboxy pyridine acid, has been synthesized and incorporated into silica gel by sol-gel method to obtain a composite material, SiO 2 :Na 3 Tb(DPA) 3 . Photoluminescent properties of SiO 2 :Na 3 Tb(DPA) 3 composite were studied after heat treatments between room temperature and 600°C. The strong green emission of the composite material was intensified by heat-treatment under appropriate conditions. The effects of the dopant concentration and heat-treatment on the luminescence for the composite material have been examined. The results indicate that SiO 2 :Na 3 Tb(DPA) 3 composite material possesses high thermal stability with intense green fluorescence, and may be applied as a potential luminescent material.