RESUMEN
A series of x%Ho3+, 5 %Tm3+, y%Yb3+:Bi2WO6 (x = 0, 0.5, 1, 3, 5; y = 0.5, 1, 3) luminescent materials was prepared using a high-temperature solid-phase method. The microstructure, up-conversion luminescence, and temperature sensing properties of the synthesized powders were analyzed. X-ray diffraction patterns revealed that doping with Ho3+, Tm3+, and Yb3+ ions at certain concentrations did not affect the orthorhombic crystal structure of the Bi2WO6 host. Scanning electron microscopy revealed that the morphology of the sample consisted of lumpy particles with a particle size range of 1-5 µm and agglomeration. SEM mapping and energy-dispersive X-ray spectroscopy analyses revealed that each element was relatively uniformly distributed on the particle surface. Under 980 nm excitation (380 mW), the strongest luminescence of the sample was obtained when both Ho3+ and Yb3+ doping concentrations were 1 %. Compared with the luminescence of the 5 %Tm3+ and 1 %Yb3+:Bi2WO6 sample, with increasing Ho3+ concentrations, the luminescence intensity of Tm3+ was first enhanced and subsequently weakened, whereas the luminescence of Ho3+ was significantly weakened, which indicates the positive energy transfer from Ho3+ â Tm3+. At 980 nm (80-380 mW), for the 1 %Ho3+, 5 %Tm3+, and 1 %Yb3+:Bi2WO6 sample, the 538 nm, 545 nm, 660 nm, and 804 nm emission peaks originated from the two-photon absorption. FIR660 nm/804 nm, FIR545 nm/804 nm, and FIR538 nm/804 nm were used to characterize the temperature and corresponded to temperature sensitivities Sr of 0.0046 K-1, 0.022 K-1 and 0.024 K-1 at 573 K, respectively. At 498 K, the minimum temperature resolution δT values were 0.03384 K, 0.03203 K and 0.04373 K. When the temperature increased from 298 K to 573 K, the powder sample luminescence gradually shifted from the yellow-green region to the red region. The results of environmental discoloration and thermochromic performance tests indicate that this sample has potential application in optical anti-counterfeiting. FIR804 nm /660 nm and FIR804 nm /538 nm were obtained for the 40 NTU turbidity suspension under identical excitation conditions. At 298 K, for the 40 NTU turbidity sample, the maximum Sr values were 0.0197 K-1 and 0.0405 K-1; at 340 K, the minimum temperature resolutions δT values were 0.54037 K and 0.66237 K. When the temperature decreased from 340 K to 298 K, the luminescence of the 40 NTU suspension samples gradually shifted from the yellow region to the green region.
RESUMEN
Ho3+ and Yb3+-codoped Bi2WO6 upconversion luminescent materials at different concentrations were prepared via a high-temperature solid-phase method. The X-ray diffraction patterns showed that Ho3+ and Yb3+ doping basically did not affect the orthorhombic crystal system structure of the Bi2WO6 matrix material. Scanning electron microscopy images showed that 3%Ho3+,10%Yb3+:Bi2WO6 consisted of irregular bulk particles with sizes in the range of 0.5-2 µm and some powder agglomeration. SEM mapping and EDS measurements of the powder showed that the elements were relatively uniformly distributed. Under 980 nm excitation, the emission intensity of Ho3+ was the largest for the 3%Ho3+- and 10%Yb3+-doped sample. With an excitation power ranging from 45 mW to 283 mW for the 3%Ho3+,10%Yb3+:Bi2WO6 sample, the relationship between the luminescence intensity and pump power was determined; the results indicated that the Ho3+ (538 nm, 546 nm, 660 nm, 756 nm) emission peaks originated from two-photon absorption. In the temperature range of 298 K-573 K, under 980 nm laser excitation, the maximum absolute temperature sensitivity Sa was 0.029% K-1 (373 K), the maximum relative temperature sensitivity Sr was 0.034% K-1 (348 K) for the Ho3+ thermally coupled energy levels 5F4/5S2, and the minimum temperature resolution δT was 1.2857 K (298 K). Under the same conditions, the maximum Sa was 51.02% K-1 (573 K), the maximum Sr was 1.85% K-1 (523 K) for the Ho3+ nonthermally coupled energy levels 5F5/5F4, and the minimum δT is 0.2477 K (448 K). The colour coordinates showed that the luminescence of the 3%Ho3+,10%Yb3+:Bi2WO6 sample gradually shifted from the green region to the red region with increasing temperature.
RESUMEN
OBJECTIVE: To study the effect of heating time on the chemical composition of bamboo juice. METHODS: GC-MS was used to analyze the chemical components of bamboo juice collected from the bamboo heating for 10 min and 50 min. RESULTS: 153 peaks were detected from the bamboo juice of 10 min. Among of them, 36 peaks were identified. As for the bamboo juice of 50 min, 80 peaks were detected and 29 identified. CONCLUSION: Heating time has effect on the chemical composition of bamboo juice, the substances detected in short time are more than that in long time.