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This study introduces a one-pot, submerged photosynthesis of crystallites (SPsC) method for fabricating monohydrate tungstic acid (WO 3 ·H 2 O) nanoplates directly integrated onto a stainless steel mesh, offering a simplified production and enhanced device stability for optical functional applications. The fabricated devices demonstrate exceptional broadband light absorption across the ultraviolet (UV), visible (Vis), and near-infrared (NIR) ranges. Notably, 1% Cu doping significantly boosts the NIR absorption, yielding a high solar utilization efficiency of 81.40%. In solar water evaporation experiments, the devices exhibit a maximum temperature increase of 13 °C under 1-Sun (100 mW/cm 2 ) illumination, achieving an energy conversion efficiency of 32.5%. Moreover, electrochemical characterization reveals light-induced conductivity changes and enhanced current density, suggesting potential applications in rectifying devices. This versatile and environmentally conscious SPsC fabrication method holds promise for the sustainable development of diverse nanodevices., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Not all encapsulation techniques are universally apt for every type of phase change material (PCM), highlighting the imperative for methodological precision. This study addresses the challenges of microencapsulated PCM (MEPCM) arising from the immiscible pairing of α-Al 2 O 3 nanoparticles with Sn microparticles. The high-speed impact blending (HIB) dry synthesis technique is employed, facilitating large-volume production of Sn@α-Al 2 O 3 MEPCMs. The resulting MEPCMs not only seamlessly endure 100 cycles of melting-solidification but also, with the strategic incorporation of a glass frit, exhibit remarkable thermal durability, withstanding up to 1000 melting-solidification cycles. Even under ultrafast thermal fluctuations, the α-Al 2 O 3 shell remained resilient through 100 cycles. A marked reduction in supercooling is observed, which is attributed to the formation of SnO and SnO 2 nanoparticles within the α-Al 2 O 3 crystal lattice. The atomically resolved interface dynamics between SnO 2 and α-Al 2 O 3 play a pivotal role, lowering the energy barrier for Sn nuclei formation during solidification. This affects the accelerated Sn nucleation rate, effectively suppressing supercooling. Such insights offer a deeper understanding of the interplay between nanoscale crystal lattice imperfections and their implications for energy storage applications.

Materials imbued with uniformly dispersed, photo-responsive nanoparticles are instrumental in sustainable energy and photonic applications. Conventional methods, however, constrain their all-solar response. An innovative alternative is proposed: submerged photo-synthesis of crystallites (SPsC). It is shown that strategic doping with copper and oxygen vacancies can induce opto-critical phases from the nonstoichiometric tungstic acids (WO 3 ·H 2 O). These opto-critical phases enable a dynamic equilibrium shift in lattice defect stabilization, facilitating an unprecedented a whole solar wavelength response. This response manifests as photothermal, photo-assisted water evaporation, and photo-electrochemical characteristics. Harnessing all-solar energy, this one-pot SPsC strategy may steer the design and development of advanced oxide materials, enhancing functionality across diverse application domains., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

A synthetic protocol was developed for obtaining a single phase of polycrystalline NaAlB 14 with strongly connected intergrain boundaries. NaAlB 14 has a unique crystal structure with a tunnel-like covalent framework of B that traps monovalent Na and trivalent Al ions. Owing to the atmospheric instability and volatility of Na, the synthesis of polycrystalline NaAlB 14 and its physical properties have not been reported yet. This study employed a two-step process to achieve single-phase polycrystalline NaAlB 14 . As a first step, a mixture of Al and B with excess Al was sintered in the Na vapor atmosphere followed by HCl treatment to remove excess Al as a second step. For obtaining bulk samples with strong grain connection, vacuum or high-pressure (HP) annealing was employed. HP annealing promoted bandgap shrinkage due to the crystal strain and defect levels and suppressed intergranular resistance. As a result, the HP-annealed sample achieved superior transport properties (0.1 kΩ cm at 300 K) to the vacuum-annealed sample (260 kΩ cm). Furthermore, from the viewpoint of its crystal structure and DFT calculations, the most probable site for the defect was suggested to be the Na site.

Recently, metal oxide nanocrystallites have been synthesized through a new pathway, i.e., the submerged photosynthesis of crystallites (SPSC), and flower-like ZnO nanostructures have been successfully fabricated via this method. However, the photochemical reactions involved in the SPSC process and especially the role of light are still unclear. In the present work, we discuss the reaction mechanism for SPSC-fabricated ZnO nanostructures in detail and clarify the role of light in SPSC. The results show that both photoinduced reactions and hydrothermal reactions are involved in the SPSC process. The former produces OH radicals, which is the main source of OH - at the ZnO crystal tips, whereas the latter generates ZnO. Although ZnO nanocrystals can be obtained under both UV irradiation and dark conditions with the addition of thermal energy, light promotes ZnO growth and lowers the water pH to neutral, whereas thermal energy promotes ZnO corrosion and increases the water pH under dark conditions. The study concludes that the role of light in the submerged photosynthesis of crystallites process is to enhance ZnO apical growth at relatively lower temperature by preventing the pH of water from increasing, revealing the environmentally benign characteristics of the present process.

We report the fabrication of flower-like CuO nanostructured surfaces via submerged photo-synthesis of crystallites (SPSC), which requires only UV illumination in neutral water. In this paper, we discuss the reaction mechanism of the photochemical formation of the SPSC-fabricated CuO nanostructures in detail based on surface microstructural analyses and a radiation-chemical consideration with additional gamma-ray irradiation. Since the SPSC method for surface nanostructural fabrication can work at low temperatures at atmospheric pressure without using harmful substances, it is a potential fabrication method for green nanotechnology applications. In this vein, the antibacterial activity of the nano-flowered CuO surfaces was tested against Gram-positive (Staphylococcus aureus) bacteria and Gram-negative (Escherichia coli K12) bacteria, and the results demonstrate that the nano-flowered CuO nanostructures act as an effective antimicrobial agent.

When applied in optoelectronic devices, a ZnO semiconductor dominantly absorbs or emits ultraviolet light because of its direct electron transition through a wide energy bandgap. On the contrary, crystal defects and nanostructure morphology are the chief key factors for indirect, interband transitions of ZnO optoelectronic devices in the visible light range. By ultraviolet illumination in ultrapure water, we demonstrate here a conceptually unique approach to tune the shape of ZnO nanorods from tapered to capped-end via apical surface morphology control. We show that oxygen vacancy point defects activated by excitonic effects near the tip-edge of a nanorod serve as an optoelectrical hotspot for the light-driven formation and tunability of the optoelectrical properties. A double increase of electron energy absorption on near band edge energy of ZnO was observed near the tip-edge of the tapered nanorod. The optoelectrical hotspot explanation rivals that of conventional electrostatics, impurity control, and alkaline pH control-associated mechanisms. Thus, it highlights a new perspective to understanding light-driven nanorod formation in pure neutral water.

We report a new production pathway for a variety of metal oxide nanocrystallites via submerged illumination in water: submerged photosynthesis of crystallites (SPSC). Similar to the growth of green plants by photosynthesis, nanocrystallites shaped as nanoflowers and nanorods are hereby shown to grow at the protruded surfaces via illumination in pure, neutral water. The process is photocatalytic, accompanied with hydroxyl radical generation via water splitting; hydrogen gas is generated in some cases, which indicates potential for application in green technologies. Together with the aid of ab initio calculation, it turns out that the nanobumped surface, as well as aqueous ambience and illumination are essential for the SPSC method. Therefore, SPSC is a surfactant-free, low-temperature technique for metal oxide nanocrystallites fabrication.