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Photocatalysis is an advanced oxidation process where light exposure triggers a semiconducting nanomaterial (nano-photocatalyst) to generate electron-hole (e−/h+) pairs and free radicals. This phenomenon is widely used for the photocatalysis-assisted removal of organic and other contaminants using wide range of nano-photocatalysts, offering an efficient approach to environmental remediation. However, the introduction of powdered nano-photocatalysts into water systems often leads to unintended secondary pollution in the form of residual nano-photocatalysts, ion leaching, free radicals, toxic by-products etc. Such practices potentially introduce emerging secondary contaminants into aquatic environments, posing risks to both aquatic life and human health. The resulting chemical by-products and intermediates can effectively induce chronic toxicity, neurological and developmental disorders, cardiovascular defects, and intestinal ailments in humans and aquatic species. Despite having a range of health and environmental consequences, this dark side of nano-photocatalysts has been comparatively less explored and discussed in the literature. In this review, the pros and cons of powder nano-photocatalysts are discussed in view of their advantages as well as disadvantages in wastewater treatment. The discussion encompasses their classification based on composition, dimensions, structure, and activity, as well as recent advancements in improving their photocatalytic efficiency. The article also explores the recent advances on their applications in photocatalytic removal of various water pollutants/contaminants of emerging concern (i.e., organic pollutants, micro/nano plastics, heavy ions, disinfections, etc.) Furthermore, an emphasis on the role of such nano-photocatalysts as emerging (secondary) contaminants in water system, along with a thorough discussion of latest studies related to the health and environmental issues, has been discussed. Additionally, it addresses critical issues in applying powder nano-photocatalysts for wastewater detoxification and explores potential solutions to these challenges followed by future prospects.

The rhombohedral phase of gallium oxide (α-Ga2O3) is of interest because of its highest bandgap among the rest of the Ga2O3 polymorphs, making it particularly attractive in applications. However, even though the ion beam processing is routinely used in device technology, the understanding of radiation phenomena in α-Ga2O3 is not mature. Here, we study non-linear effects for radiation disorder formation in α-Ga2O3 by varying both the defect generation rate and the density of collision cascades, enabled by comparing monoatomic and cluster ion implants, also applying systematic variations of ion fluxes. In particular, we show that the collision cascade density governs the surface amorphization rates, also affected by the ion flux variations. These trends are explained in terms of the non-linear in-cascade and inter-cascade defect interactions occurring during ballistic and dynamic defect annealing stages. As such, these data reveal new physics of the radiation phenomena in α-Ga2O3 and may be applicable for more predictive ion beam processing of α-Ga2O3-based devices.

Recently discovered double gamma/beta (γ/β) polymorph Ga2O3 structures constitute a class of novel materials providing an option to modulate functional properties across interfaces without changing the chemical compositions of materials, in contrast to that in conventional heterostructures. In this work, for the first time, we investigate thermal transport in such homo-interface structures as an example of their physical properties. In particular, the cross-plane thermal conductivity (k) was measured by femtosecond laser-based time-domain thermoreflectance with MHz modulation rates, effectively obtaining depth profiles of the thermal conductivity across the γ-/β-Ga2O3 structures. In this way, the thermal conductivity of γ-Ga2O3 ranging from 1.84 to 2.11 W m−1 K−1 was found to be independent of the initial β-substrates orientations, in accordance with the cubic spinel structure of the γ-phase and consistently with the molecular dynamics simulation data. In turn, the thermal conductivity of monoclinic β-Ga2O3 showed a distinct anisotropy, with values ranging from 10 W m−1 K−1 for [−201] to 20 Wm−1 K−1 for [010] orientations. Thus, for double γ-/β-Ga2O3 polymorph structures formed on [010] β-substrates, there is an order of magnitude difference in thermal conductivity across the γ/β interface, which can potentially be exploited in thermal energy conversion applications.

Abstract Recently, the optoelectronic memory is capturing growing attention due to its integrated function of sense and memory as well as multilevel storage ability. Although tens of states have been reported in literature, there are still three obvious deficiencies in most of the optoelectronic memories: large programming voltage (>20 V), high optical power density (>1 mW cm−2), and poor compatibility originating from the over-reliance on channel materials. Here, we firstly propose an optoelectronic memory based on a new photosensitive dielectric (PSD) architecture. Data writing and erasing are realized by using an optical pulse to switch on the PSD. The unique design enables the memory to work with a programming voltage and optical power density as low as 4 V and 160 µW cm−2, respectively. Meanwhile, this device may be extended to different kinds of transistors for specific applications. Our discovery offers a brand-new direction for non-volatile optoelectronic memories with low energy consumption.

Abstract Radiation tolerance is determined as the ability of crystalline materials to withstand the accumulation of the radiation induced disorder. Nevertheless, for sufficiently high fluences, in all by far known semiconductors it ends up with either very high disorder levels or amorphization. Here we show that gamma/beta (γ/β) double polymorph Ga2O3 structures exhibit remarkably high radiation tolerance. Specifically, for room temperature experiments, they tolerate a disorder equivalent to hundreds of displacements per atom, without severe degradations of crystallinity; in comparison with, e.g., Si amorphizable already with the lattice atoms displaced just once. We explain this behavior by an interesting combination of the Ga- and O- sublattice properties in γ-Ga2O3. In particular, O-sublattice exhibits a strong recrystallization trend to recover the face-centered-cubic stacking despite the stronger displacement of O atoms compared to Ga during the active periods of cascades. Notably, we also explained the origin of the β-to-γ Ga2O3 transformation, as a function of the increased disorder in β-Ga2O3 and studied the phenomena as a function of the chemical nature of the implanted atoms. As a result, we conclude that γ/β double polymorph Ga2O3 structures, in terms of their radiation tolerance properties, benchmark a class of universal radiation tolerant semiconductors.

Abstract Ion irradiation is a powerful tool to tune properties of semiconductors and, in particular, of gallium oxide (Ga2O3) which is a promising ultra-wide bandgap semiconductor exhibiting phase instability for high enough strain/disorder levels. In the present paper we observed an interesting interplay between the disorder and strain in monoclinic β-Ga2O3 single crystals by comparing atomic and cluster ion irradiations as well as atomic ions co-implants. The results obtained by a combination of the channeling technique, X-ray diffraction and theoretical calculations show that the disorder accumulation in β-Ga2O3 exhibits superlinear behavior as a function of the collision cascade density. Moreover, the level of strain in the implanted region can be engineered by changing the disorder conditions in the near surface layer. The results can be used for better understanding of the radiation effects in β-Ga2O3 and imply that disorder/strain interplay provides an additional degree of freedom to maintain desirable strain in Ga2O3, potentially applicable to modify the rate of the polymorphic transitions in this material.

In this study, the results of hydrogen plasma treatments of β-Ga2O3, α-Ga2O3, κ-Ga2O3 and γ-Ga2O3 polymorphs are analyzed. For all polymorphs, the results strongly suggest an interplay between donor-like hydrogen configurations and acceptor complexes formed by hydrogen with gallium vacancies. A strong anisotropy of hydrogen plasma effects in the most thermodynamically stable β-Ga2O3 are explained by its low-symmetry monoclinic crystal structure. For the metastable, α-, κ- and γ-polymorphs, it is shown that the net result of hydrogenation is often a strong increase in the density of centers supplying electrons in the near-surface regions. These centers are responsible for prominent, persistent photocapacitance and photocurrent effects.

The purpose of the article is to describe the innovative theoretical communicator-centered triune model of an integrative approach towards organizing learning activities of first-year students of International Education department as one of the many possible productive models for vocationally oriented higher education training. The development of a theoretical model took into account the organizational, pedagogical, linguistic, linguodidactic and methodological aspects of its implementation. The key theoretical approach to solving the complex of objectives is based on modern understanding of the nature of professional pedagogical communication as distinguished by such traits as controllability, flexibility, interactivity, representativeness and interpretability, reflected in the adopted international 21st Century Skills Concept. The results of the study include the theoretical model, disclosed as a set of essential characteristics, the outline of the program of forming of a professionally-oriented linguistic personality, description of means of methodological support. The pilot experiment confirmed the productivity of the innovative teaching model. The practical significance of the research results is determined by the productivity of the proposed integrative three-dimensional approach to the organization of the educational process in the context of international education in English.

Zn interstitial (Zni) is one of the fundamental intrinsic defects in ZnO and prominently affects the physical properties of the material. Here, the energetics and migration properties of Zni have been studied in ion implanted ZnO using a new approach based on the Li marker diffusion. Specifically, ZnO single crystals were implanted with 3.2 keV/amu B and BF2 ions and the release of Zni from the implanted regions during annealing was correlated with the advance of the characteristic Li depleted region into the bulk of the samples. Using this methodology, we calculate the activation energy of 1.45 eV to govern the process for B implants. Assuming that the migration energy of Zni to be of ~0.6 eV, as discussed previously in literature, a barrier for releasing Zni from the implanted region may be estimated as ~0.8–0.9 eV. Meanwhile, in the BF2 implanted samples, the migration of Zni is less efficient, as interpreted from the Li redistribution features in these samples; in particular, it is argued that Zni may be trapped by defect complexes related to the presence of F. [ABSTRACT FROM AUTHOR]