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ctural Features and General Morphology of Copper, Zinc, Zirconium, Molybdenum, Tungsten, and Vanadium Oxide Nanostructures Synthesized by Laser Ablation Method in Water T. I. Borodinaa, G. E. Val’yanoa, V. T. Karpukhina†, M. M. Malikova,*, and M. A. Kazaryanb† a

Joint Institute for High Temperatures, Russian Academy of Sciences Moscow, 127412 Russia b Lebedev Physical Institute, Russian Academy of Sciences, Moscow, 119991 Russia * e-mail: [email protected] Received December 25, 2019; revised December 25, 2019; accepted December 25, 2019

Abstract—Nanostructures of oxides of 3d—5d transient metals: copper, zinc, zirconium, molybdenum, tungsten, and vanadium are synthesized by laser ablation of pure metals in water. Electro-optical and X-ray studies showed that the layered material composing nanostructures is mostly in an amorphous state and apparently consists of molecular clusters no larger than 1—2 nm. The structures of studied oxides are similar and are shaped as conglomerates of nanoscale solid and hollow spheroids, plates, threads, and foam formations. Keywords: transition metal oxides, laser ablation in liquid, nanostructures DOI: 10.3103/S1068335620070039

INTRODUCTION In the last few decades, interest was heightened in the use application of nanostructured transition metal oxides (TMOs) in optoelectronics in the development of integrated circuits, sensors, smart coatings, supercapacitors, elements of systems of ultrasensitive analyzers of liquid and gas mixtures, and others [1–5]. This interest is based on the applicability of unique physical and chemical TMO properties controlled by features of the electronic structure of transition metal (TM) atoms. Above all, among them is later population of d- and f-levels of electron shells in comparison with the next s-level, which means the appearance of variable valence of TM atoms. Furthermore, d-electron orbitals go far beyond atoms, which results in the strong interaction of their electrons with the coordination environment. These features appear in the existence of several oxides of one d-metal, in characteristic retention of “metal—metal” bonds in oxides, in the formation of cluster structures, in the non-stoichiometry of the composition of crystalline forms of compounds, and others [6, 7]. The transition from macrosized crystalline TMO samples to nanoscale and amorphous ones is accompanied by a noticeable change in their electrical, magnetic, optical properties, and the appearance of size quantum effects. Among them are the metal—semiconductor phase transition, the electrical switching phenomenon, electro- and the photochromic effects, high-temperature superconductivity, superparamagnetism, and others) [8–12]. Therefore, a huge number of experimental and theoretical works [13] are devoted to the study of methods for fabricating nanostructures of TM oxides, including amorphous ones, the study of their properties, and searching for application prospects. In this paper, we present the experimental data on synthesis of oxides of 3d—5d transition metals: copper, z