Highly dispersed and uniform α-NaYF4 micron flowers with about 500nm size was synthesized by a simple wet-chemical at a low temperature, then NaYF4:Eu3+@Au hybrid structures with various amount Au nanoparticles (Au NPs) are prepared and single NaYF4:Eu3+@Au hybrid particle is taken to investigate the influence of noble metal nanoparticle on the luminescence emission and present corresponding mechanism. It is found that luminescence emissions of NaYF4:Eu3+ was quenched by introducing Au nanoparticles, and with increase of Au nanoparticles, the fluorescence quenching was more and more serous while emission intensity ratio of electric dipole to magnetic dipole transition of Eu3+ gradually become larger.
Rare-earth doped NaLaF4 nanocrystals were synthesized by solvothermal method in ethanol/oleic acid/water reaction system. The structure and porphology of samples were characterized by X-ray diffraction(XRD), scanning electron microscopy (SEM) and transmission electron microscopy(TEM). By adjusting the amount of NaOH in the precursor, we obtained NaLaF4:Er3+/Yb3+/Gd3+nanocrystals with a rich variety of morphologies, including nanoprisms, nano-dumbbells, nanorods and nanowires. A possible mechanism of formation of the NaLaF4 nanocrystals was proposed based on the time dependent experiments. The upconversion luminescence properties of rare-earth doped NaLaF4 nanocrystals with different morphology was discussed. The experimental results demonstrated that the NaLaF4:Er3+/Yb3+/Gd3+ nanocrystals with different morphologies exhibited similar up-conversion luminescence, with sharp emission peaks near 540 nm and 650 nm, and red color stronger than green light.
KEYWORDS: Visibility through fog, Visibility, LabVIEW, Data modeling, Humidity, General packet radio service, Fiber optic gyroscopes, Aerosols, Atmospheric particles, Control systems design
Visibility data have long needed to traffic meteorological monitoring and warning system, but visibility data have monitored with expensive special equipment. Visibility degradation in fog is due to the light scattering of fog droplets, which are transit from aerosols via activation. Considering strong correlation between PM2.5 (Particulate matter with diameters less than 2.5μm) mass concentration and visibility, regression models can be useful tools for retrieving visibility data from available PM2.5 data. In this study, PM2.5 is measured by low cost and commercial equipment. The results of experiment indicate that relative humidity is the key factor to impact accuracy correlation between PM2.5 and visibility, the strongest correlation locates in the RH (<60%). Results of the studies suggest that visibility decreases with increases of PM2.5 mass concentration; however, it has been found the decrease rate tapers off gradually. In order to capture the real-time visibility data, to grasp the process of low visibility events, the design of remote monitoring system is put forward. Using the GPRS network to link to cloud as a server, proposed the Arduino as the controller, design and implements a wireless serial acquisition and control system based LabVIEW and Arduino, this system can achieve the function of real-time synchronization Web publishing. The result of the test indicates that this system has typical characteristics of friendly interface, high levels of reliability and expansibility, moreover it can retrieve visibility data from available PM2.5 data that can easy to access by low-cost sensor along the highway.
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