The possibility of modifying and adjusting the properties of ZnO-based sensors in the post-fabrication stage is demonstrated by singly- and co-sputtering of ZnO thin films with zirconium and titanium nanoparticles. First, thin films of zinc oxide are created on glass substrates by sol-gel process and spin coating, and some of these films are converted to UV sensors through electrode placement on them by thermal evaporation method. Then, a number of the initial detectors are singly- and co-doped with Ti and Zr using sputtering deposition technique. Experiments show that the modification and adjustment of the parameters of the sensors through low current sputtering technique (LCST) is possible more efficiently and controllably. The transient response of all sensors are measured using I-t tests with periodic UV illumination before and after sputtering. Comparison of the results before and after doping shows that the photoresponsivity is improved on all doped sensors, and in many cases, a simultaneous improvement in this quantity and rise time is observed. In the best-case scenario, relative to undoped sensors, the photoresponsivity of the sensors doped with zirconium increases by more than 429 times, while the rise time of the sensors co-doped with titanium and zirconium decreases to less than 50%. This experience indicates that the modification and adjustment of the properties of ZnO-based sensors and actuators after electrode placement, to a large extent, is possible through LCST. It is noteworthy that this can be performed depending on the need and selectively in the shortest time, at the lowest cost. پرونده مقاله

AbstractA high efficiency band-edge cholesteric liquid crystal (CLC) laser comprising an optimal binary-dye mixture (OBD) with 62 wt% DCM and 38 wt% PM597 as the active medium is scrutinized. The measurements indicate that both the fluorescence spectrum width and the order parameter of OBD in the host of nematic liquid crystal (BL009) enhance compared with those for each individual dye. Furthermore, at the fluorescence peak, the optical efficiency of the PM597-doped CLC laser is ~ 1.5× higher than that of DCM, and the laser emission energy for OBD-doped CLC between the wavelengths 595 nm and 613 nm is even higher than that of PM597-doped CLC, so that at the maximum fluorescence of OBD, λ≈605nmdocumentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} egin{document}$$lambda approx 605;{ ext{nm}}$$end{document}, the improvement is over 20%. پرونده مقاله

AbstractAn approach for frequency stabilization of an ambience-isolated internal-mirror He–Ne laser (632.8 nm) utilizing temperature control of the laser tube with Peltier thermoelectric coolers is demonstrated. Measurements indicate that there are an optimal temperature (23 °C) and an optimal discharge current (5.5 mA) of laser tube for which the laser light power is separately maximized. To prevent the effect of fluctuation of discharge current on the laser stability, an adjustable current source is designed and fabricated so that the current is set to be optimal (5.50 ± 0.01 mA). To isolate the laser tube from the environment, the laser metallic box connected to two Peltier thermoelectric coolers is surrounded by two thermal and acoustic insulator shells. The laser has two longitudinal modes very often. Any change in the frequency of longitudinal modes at the optimal temperature is monitored by sampling the difference of longitudinal modes’ intensities. Therefore, using a feedback mechanism, the current of thermoelectric coolers is so controlled that the frequency of modes stays constant on the gain profile of the laser. The frequency stability is measured equal to 1.17 × 10−9 (∼2700×) for less than 1 min and 2.57 × 10−9 (∼1200×) for more than 1 h. پرونده مقاله

AbstractIdentification and quantification of human fingernail calcium is demonstrated by laser-induced breakdown spectroscopy (LIBS) using the modified external standardization. Since cow’s horn and hoof have structures very similar to the fingernail, either of them is individually selected as the matrix of standard samples. In total, 12 standard samples for each matrix are prepared using CaCO3 as the standard substance. In order to achieve accurate calibration curves associated with the method of modified external standard, foremost, the calcium concentration of each of matrices (horn and hoof) is determined by the method of standard additions. The results indicate that there exist 4887 µg/g (ppm) and 4156 µg/g (ppm) of calcium in the pure horn and hoof matrices, respectively. Then, the external calibration curves related to the two matrices are plotted using the information of standard samples. Finally, by the use of signals obtained from LIBS experiment for three different fingernails and inserting their amounts into the calibration curves, the calcium concentration of the fingernails under test is measured to be 10,814 µg/g (ppm), 13,106 µg/g (ppm) and 14,974 µg/g (ppm). The difference of the calcium concentrations between three specimens, as will be discussed, may be due to different physical conditions of people who have donated their fingernails. پرونده مقاله