Highly efficient green-emitting ZnO:Cu2+ phosphors for NUV-pumped white-emitting diodes.

Phosphor-converted white light-emitting diodes (WLEDs) have received significant attention; however, the leaked light from their blue InGaN chips has an undesirable effect on human health. Hence, it is necessary to develop red, green, and blue-emitting phosphors, which can be excited by an NUV chip instead of a blue chip. Herein, green-emitting ZnO:Cu2+ phosphors have been successfully synthesized by a simple and facile thermal diffusion method. The obtained powder shows a broad emission band peaking at 525 nm and a strong absorption peak at 377 nm. The ZnO:5%Cu2+ phosphor annealed at 800 °C in 2 hours revealed a lifetime of 0.57 ms, an activation energy of 0.212 eV, and the highest emission intensity with (x, y) CIE colour coordinates (0.3130, 0.5253). A WLED prototype has been fabricated by coating the ZnO:5%Cu2+ phosphor on an NUV 375 nm LED chip, where this coated phosphor shows a high quantum efficiency (QE) of 56.6%. This is, so far, the highest reported QE value for ZnO-based phosphors. These results suggest that the ZnO:Cu2+ phosphor could be an excellent candidate for NUV-pumped phosphor-converted WLED applications.

Applying response surface methodology to optimize partial nitrification in sequence batch reactor treating salinity wastewater.

In this study, the operation parameters of a partial nitrification process (PN) treating saline wastewater were optimized using the Box-Behnken design via the response surface methodology (BBD-RSM). A novel strategy based on the control of the carbon/nitrogen ratio (C/N), alkalinity/ammonia ratio (K/A), and salinity in three stages was used to achieve PN in a sequence batch reactor. The results demonstrated that a high and stable PN was completed after 50 d with an ammonia removal efficiency (ARE) of 98.37 % and nitrite accumulation rate (NAR) of 85.93 %. Next, BBD-RSM was applied, where ARE and NAR were the responses. The highest responses from the confirmation experiment were 99.9 % ± 0.04 and 95.25 % ± 0.32 when the optimum C/N, K/A, and salinity were identified as 0.84, 2, and 5.5 (g/L), respectively. The results were higher than those for the nonoptimized reactor. The developed regression model adequately forecasts the PN performance under optimal conditions. Therefore, this study provides a promising strategy for controlling the PN process and shows how the BBD-RSM model can improve the PN performance.

A high quantum efficiency plant growth LED by using a deep-red-emitting α-Al2O3:Cr3+ phosphor.

Although it has been extensively studied for decades, the α-Al2O3:Cr3+ phosphor has rarely been investigated for horticultural lighting. In this work, for the first time, a prototype of a plant growth light-emitting diode (LED) has been fabricated by coating a deep-red-emitting α-Al2O3:Cr3+ phosphor onto a near-ultraviolet (NUV) chip. The α-Al2O3:Cr3+ phosphor, synthesized by a co-precipitation method and annealed at 1500 °C for 2 h, emits an outstanding narrow peak at 695 nm. The α-Al2O3:0.6%Cr3+ phosphor shows a high activation energy of 0.29 eV, a long lifetime of 3.4 ms, and a superior color purity of 100%. The chromatic coordinates and the QE value of the red LED obtained by coating an α-Al2O3:0.6%Cr3+ phosphor on a NUV chip are (x = 0.5650, y = 0.2429) and 87.1%, respectively.