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Influence of pH-control in phosphoric acid treatment of zinc oxide
摘要： Zinc oxide is often used as a white pigment for cosmetics; however, it shows photocatalytic activity that causes decomposition of sebum on the skin when exposed to the ultraviolet radiation in sunlight. In this work, zinc oxide was reacted with phosphoric acid at various pH values to synthesize a novel white pigment for cosmetics. The chemical composition, powder properties, photocatalytic activities, colors, and smoothness of these pigments were studied. The obtained materials exhibited X-ray diffraction peaks relating to zinc oxide and phosphate after phosphoric acid treatment. The ratio of zinc phosphate to zinc oxide was estimated from inductively coupled plasma - atomic emission spectroscopy results. Samples treated at pH 4-7 yielded small particles with sub-micrometer sizes. The photocatalytic activity of zinc oxide became lower after phosphoric acid treatment. Samples treated at pH 4-7 showed the same reflectance as zinc oxide in both the ultraviolet and visible ranges. Adjustment of the pH was found to be important in the phosphoric acid treatment of zinc oxide.
关键词： zinc oxide,photocatalytic activity,particle size,phosphoric acid treatment
更新于2025-09-04 15:30:14
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A revisit to atomic layer deposition of zinc oxide using diethylzinc and water as precursors
摘要： Nanophase zinc oxide (ZnO) has been widely studied as an important multi-functional material in many applications. Atomic layer deposition (ALD) is a unique thin-film synthesis technique, featuring its extreme uniformity, unrivaled conformal coverage, low deposition temperature, and precise controllability. Using diethylzinc (DEZ) and water as precursors, ALD has been reported previously for growing nanophase ZnO thin films. However, the growth characteristics and the resultant ZnO crystallinity have not been well characterized and understood. To this end, we revisited the ALD process of ZnO using DEZ and water. Through employing a suite of advanced characterization techniques, we systematically addressed the growth characteristics, morphological changes, and the crystallinity evolution of ZnO along with growth temperature in the range of 30–250 °C. The growth characteristics of the ALD ZnO films were investigated using in situ quartz crystal microbalance (QCM), scanning electron microscopy, atomic force microscopy, and synchrotron-based X-ray reflectivity. The crystallinity of the ALD ZnO films was determined using synchrotron-based X-ray diffraction and high-resolution transmission electron microscopy. In addition, through further analyzing QCM data, we proposed the adsorption-limited surface reaction for ALD ZnO growth with the temperature-dependent number of –OH surface group reacting with one DEZ molecule. Thus, this study contributes to offer new and deep insights on the fundamental ALD process of ZnO.
关键词： Atomic layer deposition,Water,Diethylzinc,Crystallinity,Zinc oxide,Growth characteristics
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Saint Petersburg, Russia (2018.10.22-2018.10.23)] 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Study of Gas-Sensitive Properties of Zinc Oxide Nanorod Array at Room Temperature
摘要： In this paper, we present a technique for the synthesis of zinc oxide nanorods and the study of their sensitivity to organic solvent vapors. Zinc oxide nanorods were synthesized by hydrothermal method. Investigation of gas-sensitive properties was carried out by the method of impedance spectroscopy. Studies of gas-sensitive properties of zinc oxide showed a significant response of the system to the vapor of reducing gases at room temperature. It is shown that the thickness of the seed layer and, correspondingly, the density of the structure on the basis of ZnO nanorods, strongly affect the sensitivity of the sensor.
关键词： impedance spectroscopy,nanorods,hydrothermal synthesis,zinc oxide,gas sensors
更新于2025-09-04 15:30:14
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Low-Cost Integrated Zinc Oxide Nanorods Based Humidity Sensors for Arduino Platform
摘要： Realization of a simple integrated and low-cost intensity modulation/direct detection (IM/DD) based humidity and vapor detection system utilizing zinc oxide (ZnO) nanorods as the active material is demonstrated. The sensing device comprises of ZnO nanorods optimally grown on a glass substrate and mounted on 3D printed platform for the alignment with a green light-emitting diode (LED) set-up for edge excitation. An Arduino platform was used for signal processing of the detection of the transmitted light. Both forward and backward scattering are affected due to light leakage while propagating through the glass substrate that are further attenuated in the presence of humidity. In this work, backward scattering was found to be dominant and thus with increasing humidity a reduction in the transmitted light was monitored. When the sensor was tested in a humidity controlled environment, it was found that the output voltage drops by approximately 750 mV upon changing the relative humidity (RH) level from 35% to 90% in a non-linear fashion. The average sensitivity of the sensor was observed to be -12 mV/% throughout the tested RH levels. Sensitivity was found to be higher at -24.6 mV/% for RH’s beyond 70%. An average response time of 3.8 s was obtained for RH levels of 85% with respect to the standard ambient humidity conditions (RH 50%), which showed a quicker recovery time of 2.2 s. The proposed sensor device provides numerous advantages including low cost production, simplicity in design, ease of use and stability during handling.
关键词： light scattering,humidity sensor,nanorods,fast sensing,zinc oxide,arduino
更新于2025-09-04 15:30:14