ABSTRACT
Eu3+-doped phosphors have been much attractive owing to their narrow-band red emission peak at 610-630 nm with high color purity; however, the weak and narrow absorption band in the NUV region limits their applications. Doping a higher amount of Eu3+ ions into a non-concentration quenching host could be key to enhancing the efficiency of the absorption value and emission intensity. Hence, the design of Eu3+-heavily doped phosphors with a suitable host lattice is key for applications. In this study, red-emitting Eu3+-doped Gd(BO2)3-Y3BO6-GdBO3 (GdYGd:Eu3+) phosphor with a high quantum efficiency of 58.4% and excellent color purity of 99.5% is reported for the first time. The phosphor is efficiently excited by NUV light at 394 nm and emits a strong red emission band in the 590-710 nm range, peaking at 612 nm. The optimal annealing temperature and Eu3+ doping content to obtain the strongest PL intensity are 1100 °C and 20 mol%, respectively. The optimized GdYGd:Eu3+ phosphor possesses a high activation energy of 0.319 eV and a lifetime of 1.14 ms. An illustration of phosphor-coated NUV LED with chromaticity coordinates (x = 0.5636,y = 0.2961) was successfully synthesized, demonstrating the great potential of GdYGd:Eu3+ phosphor for NUV-pumped WLED applications.
ABSTRACT
This work studied the application of sulfonated ZSM-5 zeolite, a bi-functional catalyst for conversion of biomass-derived glucose to HMF. Glucose hydrolysate was obtained by enzymatic hydrolysis of rice straw, that was pretreated by sodium hydroxide. Glucose hydrolysate was then subjected to a transformation reaction to achieve HMF using HSO3-ZSM-5 zeolite under the assistance of sonication. The reaction conditions including solvent, temperature, catalyst dosage and reaction time were studied. Suitable conditions, which gave the highest yield of HMF of 54.1% have been found. The HSO3-ZSM-5 zeolite presented a high catalytic efficiency for conversion of glucose to HMF, an important and useful intermediate in the chemical industry.
