A new hybrid nanocomposite for wastewater treatment was developed using hemp shiv fibers coated with ZnO nanolayers. Macro hemp shives were selected for their adsorption capacity and sustainability, while ZnO provided photocatalytic activity. Low-temperature atomic layer deposition (ALD) anchored ZnO nanolayers with controlled thicknesses (30, 70, 90 nm) onto hydroxyl groups on the hemp shives' surface. The effect of the ZnO thickness on adsorption and photocatalytic performance toward water organic pollutants was systematically investigated. Characterization included spectroscopic ellipsometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM) with electron energy loss spectroscopy (EELS) and selected area electron diffraction (SAED), X-ray diffraction (XRD), thermogravimetric analysis (TGA), N2 adsorption-desorption analysis, and Fourier transform infrared spectroscopy (FTIR). Methylene blue (MB) adsorption kinetics showed ZnO coatings partially shield the intrinsic adsorption aptitude of pure porous fibers' surface, with a shielding increasing with the ZnO thickness. Photocatalytic activity under UV irradiation was evaluated using three emerging water pollutants: MB dye, sodium dodecyl sulfate (SDS), and phenol. Hemp shives coated with a 30 nm-thick ZnO layer exhibited the highest degradation efficiencies for all the tested pollutants (about 70% after 4 h of light irradiation). Recycling tests confirmed material stability, with preserved ZnO coating and crystal structure after repeated use. Scavenger experiments indicated both radicals and photo-generated holes contribute to photocatalytic mechanism. The synergistic combination of adsorption and photocatalysis makes ZnO-coated hemp shives a promising and sustainable material for advanced wastewater treatment.

Low-cost and environmentally friendly electrochemical energy storage systems are crucial to address the increasing global energy demand. Nanomaterials can play a pivotal role in catalysing charge storage and/or exchange, still the underlying mechanism often remains poorly investigated, as for ZnO/ZnS nanostructures onto Ni foam. In this work, we investigate hydrothermally grown ZnO/ZnS nanostructures decorating Ni foam for energy storage application. Morphology, structure and composition are evaluated via electron microscopy-based methodologies. The electrochemical energy storage performance is evaluated by cyclic voltammetry (CV) measurements with the aim to highlight the energy storage mechanism. When nickel foam (NF) is used as substrate, the system shows a predominant pseudocapacitive behaviour. By contrast, a modest and capacitive performance is measured on graphene paper (GP). Mott-Schottky (M-S) and open circuit potential (OCP) measurements suggests a key role of hole reservoir in ZnS decoration which boosts NF performances.

Nanostructured gallium nitride (GaN) shows strong potential in enhancing ultraviolet (UV) photodetectors through improved sensitivity and in light-emitting diodes (LEDs) via better spatial resolution. It is also promising for quantum photonics, particularly as a scalable, room-temperature single-photon emitter vital for quantum communication and sensing. A cost-effective photo-electroless etching (PEE) technique was employed to fabricate various GaN nanostructures, including vertically aligned nanowires (NWs) with a mean length of 1.75 +/- 0.21 mu m and a diameter of 39.36 +/- 11.28 nm, as well as complex nano- and microporous layers. The study evaluated how different illumination conditions, power levels, and etching durations influenced the etching efficiency and surface morphology. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses revealed the transition from porous layers to vertical NWs, which eventually detached from the substrate. Energy-dispersive X-ray spectroscopy (EDX) confirmed that the structures consist primarily of gallium and nitrogen, consistent with GaN composition, while photoluminescence (PL) and cathodoluminescence (CL) spectroscopies were employed to investigate their optical properties. The efficiency of UV photon emission relative to visible emission was quantified, revealing a strong dependence on the morphology. These results prove how PEE enhances photon extraction, positioning GaN as a versatile platform for future quantum technologies.

The need of achieving low-impact and low-cost functional materials through sustainable and efficient methodologies is one of the goals of the current research in the field of materials science and energy storage. In this study, a new facile route for obtaining battery-like electrode Bi-based films is presented. Specifically, 1.3 mu mthick (3-Bi2O3 films were prepared from oxynitrate via a simple sol-gel/elution process upon titanium foils, followed by annealing in forming gas at 350 degrees C. A multi-technique approach, involving Raman, X-ray Photoelectron Spectroscopy, X-ray Diffraction, Scanning Electron Microscopy and optical characterization, demonstrates the formation of a nanocrystalline porous bismuth oxide (20-30 nm in size) consisting of (3-Bi2O3 phase with the crucial presence of Bi0. Annealing at 350 degrees C in different environments (i.e. air and N2), do not produce crystalline phases. The reported method improves the synthesis of (3-Bi2O3 phase through a 1.3 mu m-thick film realization and a controlled phase production by reactive annealing at moderate temperatures. Cyclic Voltammetry and Galvanostatic Charge Discharge analyses reveal a double-redox behaviour for the (3-Bi2O3 /Bi0 battery electrode with a specific capacity (capacitance) of 195 mA*h/g (350 F/g) at 0.5 A/g. The data highlight the promising usage of sol-gel/elution for the realization of 1.3 mu m-thick film for energy storage applications.

Hybrid nanostructures combining semiconductor materials and noble metal clusters of atoms (nanoparticles) are of high interest in the energy sector and catalysis, with the idea of tuning the physicochemical properties of the system toward the desired performance. The design of this type of complex system requires the appropriate selection of the material combination to optimize the desired properties. However, less attention has been devoted to the effect of cluster size. In this work, we investigate the size and density effects for mass-selected monometallic Au clusters decorating ZnO-based nanostars. The Au clusters were prepared with narrow control of their size, in terms of atoms per cluster, via cluster deposition in a vacuum and mass selection with a cluster beam source. We study the coupling of ZnO nanostars with deposited Au N (N = 55, 147, and 309) clusters. We exploit transmission electron microscopy and Rutherford backscattering spectrometry for the structural characterization and for the determination of Au cluster density, obtaining 3.43 × 1012, 4.55 × 1011, and 7.98 × 1010 clusters/cm2 for samples decorated with Au clusters containing 55, 147, and 309 atoms, respectively. Moreover, we highlight the formation of a Schottky junction by performing photoluminescence investigations. We find distinctive changes in the behavior of the visible and UV emission as a function of the cluster size and density on the ZnO-based nanostars, identifying an increase of the photoluminescence efficiency with the decrease of the cluster dimension. Our findings indicate the enormous potential that a proper selection of cluster size offers in the fabrication of nanocomposite materials with precise electronic properties.

The growing demand for efficient and high-performance energy storage systems is driving the exploration of novel materials and composites. Traditional electrode materials often face limitations in terms of energy and power densities. This article demonstrates a novel spray-coated cathode electrode system composed of Ti3C2Tx MXene and zinc hydroxy fluoride/zinc oxide nanostars for energy storage applications in a neutral pH electrolyte (1M Na2SO4), thus avoiding corrosion problems related to water splitting reactions. Optimized Ti3C2Tx-nanostar electrodes exhibit superior specific capacitance, achieving 236 F g-1 at 5 mV s-1 in cyclic voltammetry and 139 F g-1 at 5 mV s-1 in galvanostatic charge-discharge measurements, which is superior to pure Ti3C2Tx (115 F g-1 at 0.5 A g-1) and pure nanostar (108 F g-1 at 0.5 F g-1) electrodes, used as reference. Additionally, an asymmetric Ti3C2Tx||Ti3C2Tx-nanostars supercapacitor device achieves a specific capacitance of 147 F g-1 at 0.5 A g-1, an energy density Ed ≈ 46 W h kg-1 at a power density Pd ≈ 875 W kg-1, and the highest Pd ≈ 16 650 W kg-1 at Ed ≈ 14 W h kg-1. These findings demonstrate that zinc oxide nanostars combined with delaminated Ti3C2Tx MXene hold a significant promise for efficient energy storage applications, leveraging the synergy between double-layer capacitance and pseudocapacitive effects.

The need of achieving low-impact and low-cost functional materials through sustainable and efficient methodologies is one of the goals of the current research in the field of materials science and energy storage. In this study, a new facile route for obtaining battery-like electrode Bi-based films is presented. Specifically, ∼1.3 μm-thick β-Bi2O3 films were prepared from oxynitrate via a simple sol-gel/elution process upon titanium foils, followed by annealing in forming gas at 350°C. A multi-technique approach, involving Raman, X-ray Photoelectron Spectroscopy, X-ray Diffraction, Scanning Electron Microscopy and optical characterization, demonstrates the formation of a nanocrystalline porous bismuth oxide (20–30 nm in size) consisting of β-Bi2O3 phase with the crucial presence of Bi0. Annealing at 350°C in different environments (i.e. air and N2), do not produce crystalline phases. The reported method improves the synthesis of β-Bi2O3 phase through a ∼1.3 μm-thick film realization and a controlled phase production by reactive annealing at moderate temperatures. Cyclic Voltammetry and Galvanostatic Charge Discharge analyses reveal a double-redox behaviour for the β-Bi2O3 /Bi0 battery electrode with a specific capacity (capacitance) of 195 mA*h/g (350 F/g) at 0.5 A/g. The data highlight the promising usage of sol-gel/elution for the realization of ∼1.3 μm-thick film for energy storage applications.

This paper highlights an affordable and straightforward method called chemical bath deposition (CBD) for generating different morphologies of ZnO-based nanostructures. In particular, a specific protocol was found to drive the growth versus a high-yield in-plane symmetric six-arm nanostructure, named a nanostar (NS). Each arm of the star consists of a cluster of parallel wires, creating a subnanostructure with a huge surface-to-volume ratio. As-grown NSs present a mixed phase of ZnOHF and ZnO, which converts to ZnO under thermal annealing at 300 degrees C. The NSs have a highly exposed surface area (13.2702 m(2)g(-1)) and exhibit an energy gap of 3.25 eV. A cradle-to-gate life cycle assessment (LCA) analysis has shown the high ecofriendly potential of this synthesis route and identified hotspots that need to be addressed to minimize the environmental impact of NS synthesis on an industrial scale.

The realization of polymeric nanocomposites is a promising strategy for large-scale applications of photocatalytic nanomaterials, limiting their dispersion into the environment. In addition, in order to obtain very efficient materials, a valid solution can be the formation of heterojunctions that, reducing the electron-hole recombination phenomena, increases the performances of the photocatalysts. For this work, we have realized promising photocatalytic polymeric nanocomposites through the simple method of sonication and solution casting, using poly (methyl methacrylate) (PMMA) as supporting matrix, ZnO nanoparticles as photoactive material, and MoS2 nanoflakes as co-catalyst for the realization of the heterojunction. Materials with several quantities of MoS2 have been synthetized and characterized by scanning electron microscopy (SEM), contact angle measurements, X-ray diffraction analysis (XRD), UV–Vis spectroscopy, transmission electron microscopy (TEM), and photoluminescence (PL). The photocatalytic performances of the obtained materials were evaluated by the photodegradation under UV light irradiation of two different common pollutants: rhodamine B (RhB) and sodium dodecyl sulfate (SDS). The mechanism of the involved photocatalytic process was studied by the investigation of the main oxidants responsible of the photodegradation, using hole or radical scavengers. The antibacterial properties were investigated using Escherichia coli as a model organism. The eventual toxic effects of the prepared materials were studied on Artemia salina.

Analytical methods for the early detection of the neurodegenerative biomarker for Parkinson’s disease (PD), α-synuclein, are time-consuming and invasive, and require skilled personnel and sophisticated and expensive equipment. Thus, a pain-free, prompt and simple α-synuclein biosensor for detection in plasma is highly demanded. In this paper, an α-synuclein electrochemical biosensor based on hierarchical polyglutamic acid/ZnO nanowires decorated by gold nanoparticles, assembled as nanostars (NSs), for the determination of α-synuclein in human plasma is proposed. ZnO NSs were prepared by chemical bath deposition (CBD) and decorated with electrodeposited Au nanoparticles (Au NPs). Then, electro-polymerized glutamic acid was grown and functionalized with anti-α-synuclein. A synergistic enhancement of electrode sensitivity was observed when Au NPs were embedded into ZnO NSs. The analytical performance of the biosensor was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), using the Fe(II)(CN)64−/Fe(III)(CN)63− probe. The charge transfer resistance after α-synuclein recognition was found to be linear, with a concentration in the range of 0.5 pg·mL−1 to 10 pg·mL−1, a limit of detection of 0.08 pg·mL−1, and good reproducibility (5% variation) and stability (90%). The biosensor was also shown to reliably discriminate between healthy plasma and PD plasma. These results suggest that the proposed biosensor provides a rapid, quantitative and high-sensitivity result of the α-synuclein content in plasma, and represents a feasible tool capable of accelerating the early and non-invasive identification of Parkinson’s disease.

The domain of wireless sensors and portable electronic devices has garnered considerable attention and expanded significantly over the years. Currently, the majority of these devices rely on chemical batteries for power. However, various environmental energy sources with diverse parameters have the potential to be transformed into electrical energy to power portable devices and wireless sensors. It is worth noting that self-generating sensors are also of interest to decrease a sensing system's overall power consumption. For these reasons, various "active" materials have been explored in the literature for converting kinetic energy, particularly emphasizing the conversion effect of thin embedded layers in integrated devices. In this context, this paper investigates the conversion effects and properties of embedded 0.5 mu m aluminum nitride films in MEMS for mechanical energy conversion. The study, conducted through a MEMS analyzer and metrological characterization, highlights the suitability of the proposed solution for use as a generating solution in micrometric scale sensing systems and autonomous nodes experiencing low-frequency distributed kinetic vibrations.

Rising plastic waste from products such as contact lenses underscores the need for innovative recycling solutions. This study presents a sustainable approach to produce reusable photocatalytic hybrid nanocomposites for water treatment through the use of waste contact lenses. TiO2 nanoparticles were uniformly integrated into postused contact lenses via a controlled spray deposition technique, resulting in nanocomposites with different spray times (10, 15, or 20 min). The innovative polymeric hybrids were comprehensively characterized from a morphological, structural, and chemical standpoint using techniques such as scanning and transmission electron microscopy, thermogravimetric analysis, X-ray diffraction analysis, Raman spectroscopy, Z-potential analysis, UV-vis spectroscopy, and Fourier transform infrared spectroscopy. The UV-photocatalytic performance of the resulting systems was successfully tested on two common pollutants: methylene blue (a cationic dye) and sodium dodecyl sulfate (an anionic surfactant). The highest efficiency was obtained through the 20 min spray-coated lenses, able to degrade similar to 100% of MB and similar to 60% of SDS within 3 h of UV-light irradiation. The difference in the photocatalytic efficiency was attributed to the electrostatic interaction between the individual pollutant and the material's surface. In addition, the antibacterial activity was assessed on Escherichia coli, a well-known indicator of water fecal contamination. This research paves the way for recycling plastic waste through an affordable and cost-effective production method that aligns with the circular economy principles.

The investigation of high-efficiency and sustainable electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media is critical for renewable energy technologies. Here, we report a low-cost and high-yield method to obtain ZnOHF-ZnO-based 2D nanostars (NSs) by means of chemical bath deposition (CBD). The obtained NSs, cast onto graphene paper substrates, were used as active materials for the development of a full water splitting cell. For the HER, NSs were decorated with an ultralow amount of Pt nanoparticles (11.2 μg cm-2), demonstrating an overpotential of 181 mV at a current density of 10 mA cm-2. The intrinsic activity of Pt was optimized, thanks to the ZnO supporting nanostructures, as outlined by the mass activity of Pt (0.9 mA mgPt-1) and its turnover frequency (0.27 s-1 for a Pt loading of 11.2 μg cm-2). For the OER, bare NSs showed a remarkable result of 355 mV at 10 mA cm-2 in alkaline media. Pt-decorated and bare NSs were used as the cathode and anode, respectively, for alkaline electrochemical water splitting, assessing a stable overpotential of 1.7 V at a current density of 10 mA cm-2. The reported data pave the way toward large-scale production of low-cost electrocatalysts for green hydrogen production.

Energy storage devices based on earth-abundant materials are key steps towards portable and sustainable technologies used in daily life. Pseudocapacitive devices, combining high power and high energy density features, are widely required, and transition metal oxides represent promising building materials owing to their excellent stability, abundance, and ease of synthesis. Here, we report an original ZnO-based nanostructure, named nanostars (NSs), obtained at high yields by chemical bath deposition (CBD) and applied as pseudocapacitors. The ZnO NSs appeared as bundles of crystalline ZnO nanostrips (30 nm thin and up to 12 µm long) with a six-point star shape, self-assembled onto a plane. X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence spectroscopy (PL) were used to confirm the crystal structure, shape, and defect-mediated radiation. The ZnO NSs, dispersed onto graphene paper, were tested for energy storage by cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) analyses, showing a clear pseudocapacitor behavior. The energy storage mechanism was analyzed and related to oxygen vacancy defects at the surface. A proper evaluation of the charge stored on the ZnO NSs and the substrate allowed us to investigate the storage efficiency, measuring a maximum specific capacitance of 94 F g−1 due to ZnO nanostars alone, with a marked diffusion-limited behavior. The obtained results demonstrate the promising efficacy of ZnO-based NSs as sustainable materials for pseudocapacitors.

Surface decoration by means of metal nanostructures is an effective way to locally modify the electronic properties of materials. The decoration of ZnO nanorods by means of Au nanoparticles was experimentally investigated and modelled in terms of energy band bending. ZnO nanorods were synthesized by chemical bath deposition. Decoration with Au nanoparticles was achieved by immersion in a colloidal solution obtained through the modified Turkevich method. The surface of ZnO nanorods was quantitatively investigated by Scanning Electron Microscopy, Transmission Electron Microscopy and Rutherford Backscattering Spectrometry. The Photoluminescence and Cathodoluminescence of bare and decorated ZnO nanorods were investigated, as well as the band bending through Mott–Schottky electrochemical analyses. Decoration with Au nanoparticles induced a 10 times reduction in free electrons below the surface of ZnO, together with a decrease in UV luminescence and an increase in visible-UV intensity ratio. The effect of decoration was modelled with a nano-Schottky junction at ZnO surface below the Au nanoparticle with a Multiphysics approach. An extensive electric field with a specific halo effect formed beneath the metal–semiconductor interface. ZnO nanorod decoration with Au nanoparticles was shown to be a versatile method to tailor the electronic properties at the semiconductor surface.

The decoration of semiconductor nanostructures with small metallic clusters usually leads to an improvement of their properties in sensing or catalysis. Bimetallic cluster decoration typically is claimed to be even more effective. Here, we report a detailed investigation of the effects of Au, Pt or AuPt nanocluster decoration of ZnO nanorods on charge transport, photoluminescence and UV sensitivity. ZnO nanorods were synthesized by chemical bath deposition while decoration with small nanoclusters (2-3 nm in size) was achieved by a laser-ablation based cluster beam deposition technology. The structural properties were investigated by scanning electron microscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry, and the optoelectronic properties by current-voltage and photoluminescence measurements. The extent of band bending at the cluster-ZnO interface was quantitatively modeled through numerical simulations. The decoration of ZnO nanorods with monometallic Au or Pt nanoclusters causes a significant depletion of free electrons below the surface, leading to a reduction of UV photoluminescence, an increase of ZnO nanorod dark resistance (up to 200 times) and, as a consequence, an improved sensitivity (up to 6 times) to UV light. These effects are strongly enhanced (up to 450 and 10 times, respectively) when ZnO nanorods are decorated with bimetallic AuPt nanoclusters that substantially augment the depletion of free carriers likely due to a more efficient absorption of the gas molecules on the surface of the bimetallic AuPt nanoclusters than on that of their monometallic counterparts. The depletion of free carriers in cluster decorated ZnO nanorods is quantitatively investigated and modelled, allowing the application of these composite materials in UV sensing and light induced catalysis.

The massive production of nanostructures with controlled features and high surface area is a challenging and timely task in view of developing effective materials for sensing and catalysis. Herein, functional ZnO nanostructures, named microflowers (MFs) have been prepared by a facile and rapid chemical bath deposition. ZnO MFs show an intriguing sheets-composed spheroidal shape, with diameters in the range 0.2–2.5 µm, whose formation is achieved by a complexing action by F in an aqueous solution of zinc nitrate hexahydrate and hexamethylenetetramine. The evolution of the physical and structural properties of the material, following post-deposition thermal annealing, has been investigated by scanning electron microscopy (SEM), energy dispersive X-ray analyses (EDX), photoluminescence (PL) and X-ray diffraction (XRD) techniques. The effectiveness of ZnO MFs in UV detection has also been tested to account for the potentiality of these nanostructures.

Zinc Oxide (ZnO) nanowalls (NWLs) are interesting nanostructures for sensing application. In order to push towards the realization of room-temperature operating sensors, a detailed investigation of the synthesis effect on the electrical and optical properties is needed. This work focuses on the low-cost synthesis of ZnO NWLs by means of chemical bath deposition (growth time of 5, 60, and 120 min) followed by annealing in inert ambient (temperature of 100, 200, and 300 °C). The as-grown NWLs show a typical intertwined network of vertical sheets whose features (thickness and height) stabilize after 60 min growth. During thermal annealing, NWLs are converted into ZnO. The electric transport across the ZnO NWL network radically changes after annealing. A higher resistivity was observed for longer deposition times and for higher annealing temperatures, at which the photoluminescence spectra resemble those obtained for ZnO material. A longer deposition time allows for a better transformation to ZnO during the annealing, thanks to the presence of ZnO seeds just after the growth. These findings can have a significant role in promoting the realization of room-temperature operating sensors based on ZnO NWLs.

Ni-based nanostructures are attractive catalytic materials for many electrochemical applications, among which are non-enzymatic sensing, charge storage, and water splitting. In this work, we clarify the synthesis kinetics of Ni(OH)2/NiOOH nanowalls grown by chemical bath deposition at room temperature and at 50 °C. We applied the results to non-enzymatic glucose sensing, reaching a highest sensitivity of 31 mA cm-2mM-1. Using scanning electron microscopy, x-ray diffraction analysis and Rutherford backscattering spectrometry we found that the growth occurs through two regimes: first, a quick random growth leading to disordered sheets of Ni oxy-hydroxide, followed by a slower growth of well-aligned sheets of Ni hydroxide. A high growth temperature (50 °C), leading mainly to well-aligned sheets, offers superior electrochemical properties in terms of charge storage, charge carrier transport and catalytic action, as confirmed by cyclic voltammetry and electrochemical impedance spectroscopy analyses. The reported results on the optimization and application of low-cost synthesis of these Ni-based nanostructures have a large potential for application in catalysis, (bio)sensing, and supercapacitors areas.