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Abstract: A gas monitoring system based on broadband absorption spectroscopic techniques in the ultraviolet region is described and tested. The system was employed in real-time continuous concentration measurements of sulfur dioxide (SO2) and nitric oxide (NO) from a 220-tonh−1 circulating fluidized bed (CFB) boiler in Shandong province, China. The emission coefficients (per kg of coal and per kWh of electricity) and the total emission of the two pollutant gases were evaluated. The measurement results showed that the emission concentrations of SO2 and NO from the CFB boiler fluctuated in the range of 750–1300mgm−3 and 100–220mgm−3, respectively. Compared with the specified emission standards of air pollutants from thermal power plants in China, the values were generally higher for SO2 and lower for NO. The relatively high emission concentrations of SO2 were found to mainly depend on the sulfur content of the fuel and the poor desulfurization efficiency. This study indicates that the broadband UV spectroscopy system is suitable for industrial emission monitoring and pollution control. [Copyright &y& Elsevier]

Abstract: Ultraviolet (UV) and blue upconversion (UC) radiations with large and anomalous enhancement were observed in Y 2O3:Er3+ nanocrystals under laser excitation of 970 nm. Three-photon UV and blue UC radiations were enhanced by about 60 times via codoping with Li+ ions, in remarked contrast to the 45 times enhancement for two-photon green UC radiation. The integrated intensity of enhanced UV and blue UC radiations in Y 2O3:Er3+, Li+ nanocrystals can reach about half that in Y 2O3:Er3+ ceramic bulk. Such anomalous enhancement behavior for UV and blue UC radiations originates from the fact that the tailored lifetime of the state was further involved for their generation, contrasted to the green UC emission involving only the tailored lifetime of the state. Theoretical calculations based on steady state equations evidenced these conclusions. [Copyright &y& Elsevier]

Abstract: Room-temperature blue and violet upconversion (UC) emissions of Er3+ at 409nm (2H9/2 → 4I15/2) and 390nm (4G11/2 → 4I15/2) were observed in Y2O3:Yb3+–Er3+ nanocrystals by diode laser excitation of 980nm. At low Yb3+ concentration both wavelengths result from three-photon UC processes. Unexpectedly, a four-photon and a decreased three-photon UC processes were observed at high Yb3+ concentration for the violet and the blue emissions, respectively. The four-photon process supposably results from the cross relaxation 4D7/2 + 4I15/2 → 4G11/2 + 4I13/2 of Er3+ ions with the 4D7/2 state populated by the 22F5/2(Yb)+ 4F9/2(Er)→22F7/2(Yb)+ 4D7/2(Er) process, whereas the decreased photon process arises from the larger UC rate at high Yb3+ concentration. [Copyright &y& Elsevier]