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Zinc oxide is a promising multifunctional material. The practical use of nano- and polycrystalline ZnO devices faces a serious problem of instability of electrical and luminescent characteristics, due to the adsorption of oxygen by the surface during aging. In this paper, the aging effect in ZnO films and nanorod arrays was studied. It was found that ZnO samples demonstrate different behavior of the degradation process, which corresponds to at least two different types of adsorbing surface sites for O2, where O2 adsorption is of a different nature. The first type of surface sites is rapidly depassivated after hydrogen passivation and the aging effect takes place due to these centers. The second type of surface sites has a stable structure after hydrogen passivation and corresponds to HO–ZnO sites. The XPS components of these sites include the Zn2p3/2 peak at 1022.2 ± 0.2 eV and Zn2p1/2 peak at 1045.2 ± 0.2 eV, with a part of the XPS O1s peak at 531.5 ± 0.3 eV. The annealing transforms the first type of site into the second one, and the subsequent short-term plasma treatment in hydrogen results in steady passivation, where the degradation of characteristics is practically reduced to zero.

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Currently, significant progress is being made in the prevention, treatment and prognosis of many types of cancer, using biological markers to assess current physiological processes in the body, including risk assessment, differential diagnosis, screening, treatment determination and monitoring of disease progression. The interaction of protein coding gene CD44 with the corresponding ligands promotes the processes of invasion and migration in metastases. The study of new and rapid methods for the quantitative determination of the CD44 protein is essential for timely diagnosis and therapy. Current methods for detecting this protein use labeled assay reagents and are time consuming. In this paper, a fiber-optic biosensor with a spherical tip coated with a thin layer of zinc oxide (ZnO) with a thickness of 100 nm, deposited using a low-cost sol–gel method, is developed to measure the CD44 protein in the range from 100 aM to 100 nM. This sensor is easy to manufacture, has a good response to the protein change with detection limit of 0.8 fM, and has high sensitivity to the changes in the refractive index (RI) of the environment. In addition, this work demonstrates the possibility of achieving sensor regeneration without damage to the functionalized surface. The sensitivity of the obtained sensor was tested in relation to the concentration of the control protein, as well as without antibodies—CD44.

Photoluminescence (PL) and electrical properties of boron doped zinc oxide (ZnO) thin films, deposited by metalorganic chemical vapour deposition on a glass substrate, were investigated. The effects of annealing in air, as well as the influence of the radiofrequency—plasma treatment in hydrogen atmosphere, on the PL and electrical conductivity of the ZnO films were studied. A correlation between photoluminescence and electrical properties during annealing was observed. Hydrogen plasma treatment causes an increase in the carrier mobility and concentration and results in a very intensive near band edge emission (NBE). It was found that defects responsible for the dramatic increase in the intensity of NBE band in the hydrogen-treated ZnO films are hydrogen-related complexes formed near or at the surface of the samples. The intensity of NBE in hydrogen-treated samples decreases after aging in the dark, and, conversely, the NBE intensity increases under UV light illumination. This effect is fully reversible and depends on the gas atmosphere during the UV exposure and subsequent aging. It was proposed that the NBE band in the ZnO films annealed in the air and treated in hydrogen plasma emerges due to O-H complexes forming at zinc vacancy sites, n(O-H)-VZn.