バイオイメージング応用のためのプラズマ処理酸化亜鉛ナノ材料に関する研究

博士(工学)doctoral創造科学技術大学院静岡大学甲第814号ET

Pulsed Laser Ablation: A Facile and Low-Temperature Fabrication of Highly Oriented n-Type Zinc Oxide Thin Films

Eco-friendly and facile zinc oxide (ZnO) synthesis of zinc-oxide-based nanomaterials with specific properties is a great challenge due to its excellent industrial applications in the field of semiconductors and solar cells. In this paper, we report the production of zinc oxide thin films at relatively low deposition temperature employing a simple and non-toxic method at low substrate temperature: pulsed laser ablation, as a first step for developing a n-ZnO/p-Si heterojunction. Single-phase n-type zinc oxide thin films are confirmed by an X-ray diffraction (XRD) pattern revealed by the maximum diffraction intensity from the (002) plane. Absorbance measurements indicate an increase in the band gap energy close to the bulk ZnO. A 350 °C substrate temperature led to obtaining a highly porous film with high crystallinity and high bandgap, showing good premises for further applications

Germination and Growth Improvement of Some Micro-Greens under the Influence of Reactive Species Produced in a Non-Thermal Plasma (NTP)

Micro-greens or sprouts are commonly used in the diet of many cultures owing to their health benefits. In this work we use a non-chemical solution method to stimulate the germination and growth of seeds used for sprouting, based on non-thermal plasma discharge (NTP). Such a technology could represent an alternative not only for reducing the production costs for growing micro-greens but also as a pre-sowing method for slow germinating species or those under draught stress. To evaluate the efficiency of the treatments, Brassica oleracea and Lepidium sativum seeds were exposed to a non-thermal plasma discharge produced in atmospheric air in different conditions. The strongest modifications were recorded when the discharge was produced in a closed environment when the reactive species produced in air remained in high concentrations near the seeds. The garden cress exhibited stronger modifications, with a decreasing of the water contact angle of the seeds by up to about 14%, which means an increase of the hydrophilicity of the surface of the seeds. The stimulation of the growth was evaluated as an increase of the average stem length of (9 ± 0.4)% and of the root length of (38 ± 0.5)% as compared to sprouts grown from untreated seeds. This indicated that the reactive species were not only interacting with the surface of the seeds as proved by electron microscopy imaging but also penetrated inside the seeds, activating biological pathways that lead to the stimulation of growth in this case. A noticeable influence produced by the reactive species was also reflected in the biochemical results, where the analysis of the chlorophyll pigments indicated strong modifications, especially under the intensified action of the reactive species. The results prove an important contribution from the reactive species and show the possibility of using this technology to improve the growth of these micro-greens, reducing production time and even presenting the possibility of treating packaged seeds

Effect of Pulsing Configuration and Magnetic Balance Degree on Mechanical Properties of CrN Coatings Deposited by Bipolar-HiPIMS onto Floating Substrate

Despite its great potential for thin films deposition and technological applications, the HiPIMS technology has its own limitations including the control of ion energy and flux towards the substrate when coping with the deposition of electrical insulating films and/or the deposition onto insulating/electrically grounded substrates. The bipolar-HiPIMS has been recently developed as a strategy to accelerate the plasma ions towards a growing film maintained at ground potential. In this work, the benefits of bipolar-HiPIMS deposition onto floating or nonconductive substrates are explored. The effect of bipolar-HIPIMS pulsing configuration, magnetic balance-unbalance degree, and substrate’s condition on plasma characteristics, microstructure evolution, and mechanical properties of CrN coatings was investigated. During the deposition with a balanced magnetron configuration, a significant ion bombardment effect was detected when short negative pulses and relative long positive pulses were used. XRD analysis and AFM observations revealed significant microstructural changes by increasing the positive pulse duration, which results in an increase in hardness from 7.3 to 16.2 GPa, during deposition on grounded substrates, and from 4.9 to 9.4 GPa during the deposition on floating substrates. The discrepancies between the hardness values of the films deposited on floating substrates and those of the films deposited on grounded substrates become smaller/larger when a type I/type II unbalanced magnetron configuration is used. Their hardness ratio was found to be 0.887, in the first case, and 0.393, in the second one. Advanced application-tailored coatings can be deposited onto floating substrates by using the bipolar-HiPIMS technology if short negative pulses, relative long positive pulses together with type I unbalanced magnetron are concomitantly used

Efficient Removal of Methylene Blue and Ciprofloxacin from Aqueous Solution Using Flower-like, Nanostructured ZnO Coating under UV Irradiation

Flower-like ZnO architectures assembled with many nanorods were successfully synthesized through Thermionic Vacuum Arc, operated both in direct current (DC-TVA) and a pulsed mode (PTVA), and coupled with annealing in an oxygen atmosphere. The prepared coatings were analysed by scanning-electron microscopy with energy-dispersive X-ray-spectroscopy (SEM-EDX), X-ray-diffraction (XRD), and photoluminescence (PL) measurements. By simply modifying the TVA operation mode, the morphology and uniformity of ZnO nanorods can be tuned. The photocatalytic performance of synthesized nanostructured ZnO coatings was measured by the degradation of methylene-blue (MB) dye and ciprofloxacin (Cipro) antibiotic. The ZnO (PTVA) showed enhancing results regarding the photodegradation of target contaminants. About 96% of MB molecules were removed within 60 min of UV irradiation, with a rate constant of 0.058 min−1, which is almost nine times higher than the value of ZnO (DC-TVA). As well, ZnO (PTVA) presented superior photocatalytic activity towards the decomposition of Cipro, after 240 min of irradiation, yielding 96% degradation efficiency. Moreover, the agar-well diffusion assay performance against both Gram-positive and Gram-negative bacteria confirms the degradation of antibiotic molecules by the UV/ZnO (PTVA) approach, without the formation of secondary hazardous products during the photocatalysis process. Repeated cyclic usage of coatings revealed excellent reusability and operational stability