The detection of ultraviolet (UV) radiation and greenhouse gases such as carbon dioxide (CO₂) has attracted increasing research interest in recent years due to climate change and industrial development. The increasing concentration of CO₂ in the atmosphere is a major driver of global climate change and may indirectly contribute to increased exposure of the Earth's surface to harmful UV radiation. In this context, this study proposes a novel approach to sensor development based on hydrothermally synthesized titanium dioxide (TiO₂) nanoparticles. A high-performance UV photodetector and a UV-assisted CO₂ gas sensor were fabricated using a cost-effective spin-coating method on Au/Cr interdigitated ceramic electrodes. Functionalization of TiO₂ with gold nanoparticles (AuNPs) significantly enhances UV sensitivity, responsivity, and detectivity, while reducing response and recovery times. The UV-assisted CO₂ sensing results further confirm the beneficial role of AuNPs. Moreover, this study highlights both the advantages and challenges associated with designing TiO₂/Au junction-based materials, contributing to a better understanding of sensing mechanisms and opening new perspectives in sensor development.

Adsorption and corrosion caused by Cl- are the main reasons for the low performance of Pt-based catalysts for the hydrogen evolution reaction (HER) in seawater. Although the introduction of hydroxyl species is an ideal approach to enhance HER kinetics and resist harmful Cl-, achieving this goal in Pt-based catalysts is challenging. In this study, we developed a high-temperature reduction process to generate PtNi alloy particles that contain Ni vacancies (Lewis acid sites) that participate in transforming lattice hydroxyls to dissociative hydroxyls on Ni layered double hydroxides (Ni-LDH). The hydroxyls in Ni-LDH bind with Lewis acid active sites to form hydroxyl rich species, a process which enhances the hydrophilicity of PtNi/Ni-LDH to promote water adsorption and enhance resistance to Cl- absorption. Owing to these properties, PtNi/Ni-LDH exhibits superior performance as an electrocatalyst for the HER in alkaline natural seawater as reflected by a low overpotential of 19 mV to drive a current density of 10 mA cm(-2), a low Tafel slope of 31 mV dec(-1), and an only slightly elevated overpotential after 100 h of operation. This study throws light on the development of new strategies for the design of high-performance catalysts for hydrogen production by electrolytic seawater splitting.

Highly porous, ultra-lightweight materials are widely used in various applications. Aerogels based on both organic and inorganic components have been known for a long period of time as an important class of functional materials. However, a new subclass of ultra-porous inorganic materials prepared by using technologies different from those derived from a gel is nowadays emerging, thereby contributing to a significant expansion of their areas of application. In this review paper, highly porous semiconductor materials prepared on the basis of ZnO sacrificial templates consisting of 3D architectures built up from interconnected microrods, tetrapods or multipods, so called aero-semiconductors, are reviewed from the point of view of technologies applied for their preparation, properties and applications. For the purpose of comparison, other materials prepared on the basis of similar templates are discussed, such as aerographites and other highly porous inorganic nanomaterials and composites containing a semiconductor component. A special focus is put on their applications in sensors, electromagnetic shielding, light emission, microfluidics, microrobotics, biomedicine, photocatalysis and electrochemical applications.

Efficient detection of toxic and flammable vapors remains a major technological challenge, especially for environmental and industrial applications. This paper reports on the fabrication technology and gas-sensing properties of nanostructured Ga2O3/GaS0.98Se0.02. The β-Ga2O3 nanowires/nanoribbons with inclusions of Ga2S3 and Ga2Se3 microcrystallites were obtained by thermal treatment of GaS0.98Se0.02 slabs in air enriched with water vapors. The microstructure, crystalline quality, and elemental composition of the obtained samples were investigated using electron microscopy, X-ray diffraction, and Raman spectroscopy. The obtained structures show promising results as active elements in gas sensor applications. Vapors of methanol (CH3OH), ethanol (C2H5OH), and acetone (CH3-CO-CH3) were successfully detected using the nanostructured samples. The electrical signal for gas detection was enhanced under UV light irradiation. The saturation time of the sensor depends on the intensity of the UV radiation beam.

In this work, we report on a comparative study of the topology, luminescence, and wettability properties of ZnMgO films prepared by a cost-effective spray pyrolysis technology on GaAs substrates with (100), (001), and (111) crystallographic orientations, as well as on Si(100) substrates. Deposition on nanostructured GaAs substrates was also considered. It was found that film growth is not epitaxial or conformal, but rather, it is granular, depending on the nucleating sites for the crystallite growth. The distribution of nucleation sites ensured the preparation of nanostructured films with good uniformity of their topology. The observed difference in columnar growth on Si substrates and pyramidal growth on GaAs ones was explained in terms of the impact of chemical bonding in substrates. The films grown on GaAs substrates with a (001) orientation were found to be made of larger crystallites compared to those deposited on substrates with a (111) orientation. These effects resulted in a difference in roughness of a factor of 1.5, which correlates with the wetting properties of films, with the most hydrophobic surface being found on films deposited on GaAs substrates with a (111) orientation. The prospects for photocatalytic and gas sensor applications of films produced on flat substrates, as well as for plasmonic and other applications of films deposited on nanostructured substrates, are discussed, taking into account the results of the analysis of their photoluminescence properties.

The escalating global problem of antibiotic contamination in wastewater demands innovative and sustainable remediation technologies. This paper presents a highly efficient photocatalytic material for water purification: a three-dimensional ultra-porous structure of interconnected GaN hollow microtetrapods (aero-GaN), its performance being further enhanced by noble metal nanodot functionalization. This novel aero-nanomaterial achieves more than 90 % of tetracycline degradation within 120 min under UV and solar irradiation, demonstrating its effectiveness in both static and dynamic flow conditions, with the potential for reuse and recyclability. The higher surface area and chemical stability of the 3D aero-GaN architecture, compared to analogous ZnO structures, establish its significant potential for advanced water treatment applications and filter technologies.

One of the biggest issues of wide bandgap semiconductor use in photocatalytic wastewater treatment is the reusability of the material and avoiding the contamination of water with the material itself. In this paper, we report on a novel TiO2 aeromaterial (aero-TiO2) consisting of hollow microtetrapods with Zn2Ti3O8 inclusions. Atomic layer deposition has been used to obtain particles of unique shape allowing them to interlock thereby protecting the photocatalyst from erosion and damage when incorporated in active filters. The performance of the aero-TiO2 material was investigated regarding photocatalytic degradation of tetracycline under UV and visible light irradiation. Upon irradiation with a 3.4 mW/cm(2) UV source, the tetracycline concentration decreases by about 90% during 150 min, while upon irradiation with a Solar Simulator (87.5 mW/cm(2)) the concentration of antibiotic decreases by about 75% during 180 min. The experiments conducted under liquid flow conditions over a photocatalyst fixed in a testing cell have demonstrated the proper reusability of the material.

Aeromaterials represent a class of increasingly attractive materials for various applications. Among them, aero-ZnS has been produced by hydride vapor phase epitaxy on sacrificial ZnO templates consisting of networks of microtetrapods and has been proposed for microfluidic applications. In this paper, a cost-effective technological approach is proposed for the fabrication of aero-ZnS by using physical vapor transport with Sn2S3 crystals and networks of ZnO microtetrapods as precursors. The morphology of the produced material is investigated by scanning electron microscopy (SEM), while its crystalline and optical qualities are assessed by X-ray diffraction (XRD) analysis and photoluminescence (PL) spectroscopy, respectively. We demonstrate possibilities for controlling the composition and the crystallographic phase content of the prepared aerogels by the duration of the technological procedure. A scheme of deep energy levels and electronic transitions in the ZnS skeleton of the aeromaterial was deduced from the PL analysis, suggesting that the produced aerogel is a potential candidate for photocatalytic and sensor applications.

The material design of functional "aero"-networks offers a facile approach to optical, catalytical, or and electrochemical applications based on multiscale morphologies, high large reactive area, and prominent material diversity. Here in this paper, the synthesis and structural characterization of a hybrid β-Ga2 O3 /ZnGa2 O4 nanocomposite aero-network are presented. The nanocomposite networks are studied on multiscale with respect to their micro- and nanostructure by X-ray diffraction (XRD) and transmission electron microscopy (TEM) and are characterized for their photoluminescent response to UV light excitation and their electrochemical performance with Li-ion conversion reaction. The structural investigations reveal the simultaneous transformation of the precursor aero-GaN(ZnO) network into hollow architectures composed of β-Ga2 O3 and ZnGa2 O4 nanocrystals with a phase ratio of ≈1:2. The photoluminescence of hybrid aero-β-Ga2 O3 /ZnGa2 O4 nanocomposite networks demonstrates narrow band (λem  = 504 nm) green light emission of ZnGa2 O4 under UV light excitation (λex  = 300 nm). The evaluation of the metal-oxide network performance for electrochemical application for Li-ion batteries shows high initial capacities of ≈714 mAh g-1 at 100 mA g-1 paired with exceptional rate performance even at high current densities of 4 A g-1 with 347 mAh g-1 . This study provides is an exciting showcase example of novel networked materials and demonstrates the opportunities of tailored micro-/nanostructures for diverse applications a diversity of possible applications.

Planar and core-shell structures prepared on the basis of semiconductor nanowires with various semiconductor films constitute a basis for a wide variety of devices for multiple applications. Planar structures have been prepared in this study by atomic layer deposition (ALD) of ZnO and TiO2 thin layers on semiconductor substrates, and their morphologies and the luminescence properties have been compared with those of coaxial core-shell structures obtained by coating of GaAs nanowires with ZnO and TiO2 shells. The prepared structures have been characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analysis, and photoluminescence (PL) spectroscopy. Polarization characteristics of PL bands related to different recombination channels have been investigated in core-shell structures, and the results were analyzed in terms of the either contrast in dielectric constants, or selection rules associated with crystal structure symmetry, or local strain related to specific microscopic structure of recombination centers involved in electronic transitions responsible for specific PL bands.

In this paper, three types of microstructures are argued as substrates for electrochemical deposition of Au nanodots. They include: (a) aero-GaN consisting of hollow GaN microtetrapods, (b) microdomains of pores with a controlled design produced by anodization of InP wafers, and (c) patterned microdomains composed of strips with alternating electrical conductivity in GaN crystals grown by hydride vapor phase epitaxy. Uniform deposition of Au nanodots with controlled density is demonstrated by using pulsed electroplating, the voltage pulse width and amplitude as well as the pause between pulses and the conductivity of the substrate serving as adjustable parameters. The morphology of the produced hybrid microarchitectures was investigated by scanning electron microscopy. The explored microstructures are proposed as platforms for the development of complex 3D hybrid micro-nano-architectures via the vapor–liquid–solid deposition of various semiconductor nanowires with Au nanodots as catalysts.

The self-catalyzed growth of InP nanowires on an aerographite substrate is demonstrated in this study by using high growth rate hydride vapor-phase epitaxy technology. Nanowires with aspect ratios higher than 200 and diameters of 0.2–2 μm were analyzed by scanning electron microscopy, transmission electron microscopy, energy-dispersive x-ray analysis, Raman spectroscopy, and photoelectrical characterization. The nanowires were found to be of constant diameter over their length, except for a well-faceted hexagonal tapered end. The novel growth process results in formation of self-catalyzed nanowires compatible with integrated circuit technology. Single-wire InP photodetectors with predominant sensitivity in the infrared spectral range have been prepared and characterized. Semiconductor nanowires gain wider application in light and gas sensors, memory and memristive devices. In this article, we describe a fast and rather simple approach of fabricating catalyst-free InP nanowires with aspect ratio of 200. Important benefits of this method are stoichiometric chemical composition and freestanding arrangement of wires on the aerographite substrate. We demonstrate the development of a robust IR single-nanowire sensor stable at 20–300 K both in the air and vacuum atmosphere, with Iph/Idark ratio in the range 4–1.7.

In this paper, we show in a series of experiments on 10 nm thick SnS thin film-based back-gate transistors that in the absence of the gate voltage, the drain current versus drain voltage ( I D – V D ) dependence is characterized by a weak drain current and by an ambipolar transport mechanism. When we apply a gate voltage as low as 1 μ V, the current increases by several orders of magnitude and the I D – V D dependence changes drastically, with the SnS behaving as a p -type semiconductor. This happens because the current flows from the source (S) to the drain (D) electrode through a discontinuous superficial region of the SnS film when no gate voltage is applied. On the contrary, when minute gate voltages are applied, the vertical electric field applied to the multilayer SnS induces a change in the flow path of the charge carriers, involving the inner and continuous SnS layer in the electrical conduction. Moreover, we show that high gate voltages can tune significantly the SnS bandgap.

Network Materials In article number 2207492, Niklas Wolff, Ion Tiginyanu, Lorenz Kienle, and co-workers report on the synthesis and structural characterization of a hybrid wide-band-gap semiconductor nanocomposite network of interconnected hollow microtubes composed of β-Ga2O3/ZnGa2O4 phases using X-ray powder diffraction and transmission electron microscopy. The aero-network morphology shows ZnGa2O4-dominated narrow band green light emission under UV light excitation and high initial electrochemical capacity versus Li-ion loading.

Over the last decades, controlling 3D micro-nano-architectures of semiconductor materials has been used to bring to light new characteristics and even new phenomena. This approach is especially promising when applied to the design of hybrid micro-nano-architectures. The aim of this paper is to review the research efforts undertaken last years to develop novel hybrid three-dimensional micro-nano-architectures based on wide-band-gap binary compounds for multifunctional applications. Special attention will be paid to 3D micro-nano-architectures based on GaN, but results of investigation of architectures based on Ga2O3, ZnS, ZnO will be presented as well. Self-interaction of aero-tetrapods of GaN on water surface leads to the formation of elastic membranes that exhibit high degree of porosity with impressive cargo capabilities. Wrapping liquid droplets into aero-GaN we demonstrate the formation of liquid marbles, that show unique characteristics like self-propulsion on water surface at record velocities, pulsed rotations and pendulum-like oscillations of liquid marbles. Higher photocatalytic response was achieved by functionalizing aero-nanomaterials with noble metal nanoparticles. Besides microfluidic applications, aero-GaN proves to be highly efficient in shielding electromagnetic fields in the GHz and THz region, while aero-Ga2O3 is completely transparent in the same spectral region.

We report on possibilities to convert, by means of thermal treatment, the wettability properties of networks consisting of ZnO microtetrapods from hydrophobic to super-hydrophilic. The ZnO microtetrapods were produced by flame transport synthesis. The ZnO powder containing the ZnO tetrapods were pressed in pellets with the density of 1 g cm−3 using a compression mold. The comparative study was performed on two sets of samples, and namely: the as-grown ZnO tetrapods pressed in pellets and the annealed pellets. The wettability conversion proved to be an irreversible process for a long period. As a result, the thermal treatment process not only increase the mechanical stability of the ZnO pellets but also essentially increase the hydrophilic behavior of ZnO tetrapods, which is a very important issue for further chemical or electrochemical functionalization. Apart from wettability characteristics investigated by Water Contact Angle (WCA) measurements, the structural and optical properties were investigated by X-ray diffraction (XRD) and photoluminescence (PL) techniques, respectively. The XRD patterns revealed the hexagonal wurtzite structure and a high structural quality of both as-grown samples and annealed networks of microtetrapods at 950 ℃. Their high quality was also confirmed by the presence of PL bands related to exciton recombination in the emission spectrum. The possible nature of other PL bands, especially green emission band attributed to specific recombination channels and their evolution with thermal treatment are discussed.

Porous semiconductor compounds represent a class of materials which is under an intense research focus over the last years. Herein, morphologies and topologies produced by anodization in binary semiconductor compounds having various bandgaps and crystallographic orientations are demonstrated with a focus on technological procedures applied for generating arrays of pores with a controlled design. The mechanism of pores growth under the photoresist masks is discussed and the connection between the design of the mask and the architecture of the produced porous structure is disclosed. The evolution of physical characteristics of the materials such as luminescence, optical, photonic, vibrational, hydrophilic, and hydrophobic properties as a result of anodization is investigated. Investigations are performed by means of scanning electron microscopy, photoluminescence and cathodoluminescence spectroscopy, and contact angle measurements. Some possible practical applications of the proposed technological approaches and the produced porous structures are briefly discussed.

The effect of pressure on the structural, vibrational, and optical properties of lead thiogallate, PbGa 2 S 4 , crystallizing under room conditions in the orthorhombic EuGa 2 S 4 -type structure (space group Fddd ), is investigated.

We propose to use hybrid networks of ZnO microtetrapods produced by flame transport synthesis and Au nanodots deposited by pulsed electroplating, for the preparation of more complex 3D micro-nano-structures via Au catalyst-assisted vapor-liquid-solid growth of semiconductor nanowires on the surface of ZnO microtetrapod arms. The pulsed electrochemical deposition of Au nanodots with optimized pulse parameters was realized in pressed pellets containing the ZnO tetrapods with the density 1 g cm−3. The mechanical stability was increased by means of thermal treatment of pressed hybrid networks of ZnO microtetrapods at 950 ℃ for 1 h. The morphology of the ZnO microtetrapod networks and the density of the deposited Au nanodots were investigated by scanning electron microscopy. The deposition of Au nanodots with various densities and of monolayers of self-assembled nanodots was demonstrated on ZnO microtetrapods possessing different conductivities. The optical quality of the ZnO microtetrapods was investigated by photoluminescence (PL) spectroscopy in the temperature interval from 10 to 300 K. PL bands related to neutral donor bound excitons D0X and donor–acceptor pairs (DAP) recombination were observed at low temperature. We assume that the presence in the spectrum of PL bands related to excitonic radiation is indicative of a high enough quality of the investigated ZnO microtetrapods for various optoelectronic and photonic applications.

In this paper nanostructured thin films with thickness of 150 nm have been prepared by aerosol deposition method on p-Si in the system (MgO)x(In2O3)(1−x) with the composition range x = 0.2, 0.4 and 0.6, using indium chloride and magnesium chloride as precursors. The produced films were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) to determine the morphology and roughness, energy dispersive X-ray (EDX) analysis for the chemical composition estimation, and X-ray diffraction (XRD) for establishing the structural and crystallographic phases. It was found that the nano-crystallites sizes grow with increasing the Mg content, therefore influencing the roughness of the films. The film surface roughness calculated from topographic AFM images is in the RMS range from 5.7 to 7.5 nm with increasing Mg concentration, but the value of the Coefficient of Kurtosis parameter is from 0.18 to 0.64. The evolution of the crystalline phases content with increasing the x value from 0.2 to 0.6 was established. The electrical and photoelectrical properties were studied by I-V characterization under the illumination with the light with the wavelength of 365 nm. It was shown that the films are sensitive to this radiation with the ratio of the photocurrent to the dark current from 5 to 7 at the excitation density of 2.4 mW/cm−2.