Search Results (5,453)

Ultraviolet (UV) and blue-light photodetectors are vital in environmental monitoring, medical and biomedical applications, optical communications, and security and anti-counterfeiting technologies. However, conventional silicon-based devices suffer from limited sensitivity to short-wavelength light due to their narrow indirect bandgap. In this study, we investigate the influence of precursor concentration on the structural, optical, and photoresponse characteristics of nanostructured CdS thin films synthesized via chemical bath deposition. Among the CdS samples prepared at different precursor concentrations, the best photoresponsivity of 21.1 mA/W was obtained at 2 M concentration. Subsequently, a p–n heterojunction photodetector was fabricated by integrating a spin-coated CuSCN layer with the optimized CdS nanostructure. The resulting device exhibited pronounced rectifying behavior with a rectification ratio of ~750 and an ideality factor of 1.39. Under illumination and a 5 V bias, the photodetector achieved an exceptional responsivity exceeding 10⁴ A/W in the UV region—over six orders of magnitude higher than that of CdS-based metal–semiconductor–metal devices. This remarkable enhancement is attributed to the improved light absorption, efficient charge separation, and enhanced hole transport enabled by CuSCN incorporation and heterojunction formation. These findings present a cost-effective, solution-processed approach to fabricating high-responsivity nanostructured photodetectors, promising for future applications in smart healthcare, environmental surveillance, and consumer electronics. Full article

This paper investigates the performance of a spacecraft equipped with a diffractive sail in a heliocentric mission scenario that requires phasing along a prescribed elliptical orbit. The diffractive sail represents an evolution of the more traditional reflective solar sail, which converts solar radiation pressure into thrust using a large reflective surface typically coated with a thin metallic film. In contrast, the diffractive sail proposed by Swartzlander leverages the properties of an advanced metamaterial-based film to generate a net transverse thrust even when the sail is Sun-facing, i.e., in a configuration that can be passively maintained by a suitably designed spacecraft. Specifically, this study considers a sail membrane covered with a set of electro-optically controlled diffractive panels. These panels employ a (controlled) binary metamaterial arrayed grating to steer the direction of photons exiting the diffractive film. This control technique has recently been applied to achieve a circle-to-circle interplanetary transfer using a Sun-facing diffractive sail. In this work, an optimal control law is employed to execute a rapid phasing maneuver along an elliptical heliocentric orbit with specified characteristics, such as those of Earth and Mercury. The analysis also includes a limiting case involving a circular heliocentric orbit. For this latter scenario, a simplified and elegant control law is proposed based on a linearized form of the equations of motion to describe the heliocentric dynamics of the diffractive sail-based spacecraft during the phasing maneuver. Full article

Photocatalytic composite materials (TiO₂/SiO₂/BFSF) were first fabricated using the sol–gel method of loading SiO₂ and TiO₂ on blast furnace slag fibers (BFSFs) in sequence and using them as a new carrier. Then, TG-DTA, XRD, BET, SEM-EDS, and UV-Vis absorption spectra, as well as spectrophotometric measurements, were employed to analyze the physicochemical properties of TiO₂. The influence of SiO₂ coating, the number of impregnations in TiO₂ sol, the calcination temperature, and the number of repeated usages on the activity of TiO₂/SiO₂/BFSF was researched by analyzing the degradation of methylene blue (MB) aqueous solution. The results show that SiO₂ could increase the load of TiO₂, impede the growth of TiO₂ grains, and inhibit the recombination of electron–hole pairs, ultimately enhancing the photocatalytic activity of samples. The activity of TiO₂/SiO₂/BFSF first quickly increased and then slowly decreased with an increase in the loading times of TiO₂ sol and calcination temperature. After three impregnations in TiO₂ sol and calcining at 450 °C for 2.5 h, a uniform and compact anatase TiO₂ thin film was deposited on the surface of TiO₂/SiO₂/BFSF, showing the strongest activity. When this sample was used to degrade MB aqueous solution for 180 min under ultraviolet light irradiation, the degradation proportion reached a maximum of 96%. After four reuses, the degradation ratio could still reach 67%. In addition, three potential photocatalytic mechanisms were proposed. Finally, the high-value-added application of blast furnace slag for preparing photocatalytic composite materials was achieved, successfully turning solid waste into “treasure”. Full article

Transparent conductive aluminum-doped zinc oxide (AZO) films were investigated as potential recombination layers for perovskite/silicon tandem solar cells, comparing the results of atomic layer deposition (ALD) and magnetron sputtering (MS) on vertically aligned silicon nanowire (SiNW) scaffolds. Conformality and thickness control were examined by cross-sectional SEM/TEM and profilometry, revealing fully conformal ALD coatings with tunable thicknesses (40–120 nm) versus tip-capped, semi-uniform MS films (100–120 nm). Optical transmission measurements on glass substrates showed that both 120 nm ALD and MS layers exhibit interference maxima near 450–500 nm and 72–89% transmission across 800–1200 nm; the thinnest ALD films reached up to 86% near-IR transparency. Four-point probe analysis demonstrated that ALD reduces surface resistance from 1150 Ω/□ at 40 nm to 245 Ω/□ at 120 nm, while MS layers achieved 317 Ω/□ at 120 nm. These results delineate the balance between conformality, transparency, and conductivity, providing design guidelines for AZO recombination interfaces in next-generation tandem photovoltaics. Full article

Magnetron Sputter Vacuum Deposition (MSVD) has undergone significant advancements since its inception. This review explores the evolution of MSVD, encompassing its fundamental principles, various techniques (including reactive sputtering, pulsed magnetron sputtering, and high-power impulse magnetron sputtering), and its wide-ranging industrial applications. While detailing the advantages of high deposition rates, versatility in material selection, and precise control over film properties, the review also addresses inherent challenges such as low target utilization and plasma instability. A significant portion focuses on the crucial role of MSVD in the automotive industry, highlighting its use in creating durable, high-quality coatings for both aesthetic and functional purposes. The transition from traditional electroplating methods to more environmentally friendly MSVD techniques is also discussed, emphasizing the growing demand for sustainable manufacturing processes. This review concludes by summarizing the key advancements, remaining challenges, and potential future trends in magnetron sputtering technologies. Full article

Traditional forced-air cooling systems suffer from excessive energy consumption and noise pollution. This study proposes an innovative passive cooling strategy through developing aqueous radiative cooling coatings made from a combination of TiO₂-decorated carbon nanotube (TiO₂-CNT) hybrids and polyacrylic acid (PAA), designed to simultaneously enhance the heat dissipation and improve the mechanical strength of the coating films. Based on CNTs’ exceptional thermal conductivity and record-high infrared emissivity, bead-like TiO₂-CNT architectures have been prepared as the filler in PAA. The TiO₂ nanoparticles were in situ grown on CNTs, forming a rough surface that can produce asperity contacts and enhance the strength of the TiO₂-CNT/PAA composite. Moreover, this composite enhanced heat dissipation and achieved remarkable cooling efficiency at a small fraction of the filler (0.1 wt%). The optimized coating demonstrated a temperature reduction of 23.8 °C at an operation temperature of 180.7 °C, coupled with obvious mechanical reinforcement (tensile strength from 13.7 MPa of pure PAA to 17.1 MPa). This work achieves the combination of CNT and TiO₂ nanoparticles for strong radiative cooling coating, important for energy-efficient thermal management. Full article

In high energy density physics, the demand for precise detection of nanosecond-level fast physical processes is high. Ga:ZnO (GZO), GaN, and other fast scintillators are widely used in pulsed signal detection. However, many of them, especially wide-bandgap materials, still face issues of low luminous intensity and significant self-absorption. Therefore, an enhanced method was proposed to tune the wavelength of materials via coating perovskite quantum dot (QD) films. Three-layer samples based on GZO were primarily investigated and characterized. Radioluminescence (RL) spectra from each face of the samples, as well as their decay times, were obtained. Lower temperatures further enhanced the luminous intensity of the samples. Its overall luminous intensity increased by 2.7 times at 60 K compared to room temperature. The changes in the RL processes caused by perovskite QD and low temperatures were discussed using the light tuning and transporting model. In addition, an experiment under a pico-second electron beam was conducted to verify their pulse response and decay time. Accordingly, the samples were successfully applied in beam state monitoring of nanosecond pulsed proton beams, which indicates that GZO wafer coating with perovskite QD films has broad application prospects in pulsed radiation detection. Full article

Alkyd resins are among the most common coatings used for exterior wood joinery. In Romania, solvent-borne alkyd coatings are widely used to finish wood. The study aims to compare the performance after 7 years of outdoor exposure of two types of alkyd coatings, a semi-transparent brown stain with micronized pigments (Alk1) and an opaque white enamel (Alk2), applied directly on wood or wood pre-treated with three types of resins: acryl-polyurethane (R1), epoxy (R2), and alkyd-polyurethane (R3). Fir (Abies alba) wood served as the substrate. Cracking, coating adhesion, and biological degradation were periodically assessed through visual inspection and microscopy. Additionally, a cross-cut test was performed, and the loss of coating on the directly exposed upper faces was measured using ImageJ. The results indicated that resin pretreatments somewhat reduced cracking but negatively affected coating adhesion after long-term exposure. All samples pretreated with resins and coated with Alk1 lost more than 50% (up to 78%) of the original finishing film by the end of the test. In comparison, coated control samples lost less than 50%. The Alk2 coating exhibited a film loss between 2% and 12%, compared to an average loss of 9% for the coated control. Overall, samples pretreated with alkyd-polyurethane resin (R3) and coated with alkyd enamel (Alk2) demonstrated the best performance in terms of cracking, adhesion, and discoloration. Full article

Polyethylenimine (PEI) is a cationic polymer with a high density of amine groups suitable for strong electrostatic interactions with biological molecules to preserve their bioactivities during encapsulation and after delivery for biomedical applications. This review provides a comprehensive overview of PEI as a drug and gene carrier, describing its polymerization methods in both linear and branched forms while highlighting the processing methods to manufacture PEIs into drug carriers, such as nanoparticles, coatings, nanofibers, hydrogels, and films. These various PEI carriers enable applications in non-viral gene and small molecule drug deliveries. The structure–property relationships of PEI carriers are discussed with emphasis on how molecular weights, branching degrees, and surface modifications of PEI carriers impact biocompatibility, transfection efficiency, and cellular interactions. While PEI offers remarkable potential for drug and gene delivery, its clinical translation remains limited by challenges, including cytotoxicity, non-degradability, and serum instability. Our aim is to provide an understanding of PEI and the structure–property relationships of its carrier forms to inform future research directions that may enable safe and effective clinical use of PEI carriers for drug and gene delivery. Full article

TiAl alloy offers advantages including low density, high specific strength and stiffness, and excellent high-temperature creep resistance. It is widely used in the aerospace, automotive, and chemical sectors, as well as in other fields. However, at temperatures of 800 °C and above, it forms a porous oxide film predominantly composed of TiO₂, which fails to provide adequate protection. Applying high-temperature protective coatings is therefore essential. Oxides demonstrating protective efficacy at elevated temperatures include Al₂O₃, Cr₂O₃, and SiO₂. The Pilling–Bedworth Ratio (PBR)—defined as the ratio of the volume of the oxide formed to the volume of the metal consumed—serves as a critical criterion for assessing oxide film integrity. A PBR value greater than 1 but less than 2 indicates superior film integrity and enhanced oxidation resistance. Among common oxides, Al₂O₃ exhibits a PBR value within this optimal range (1−2), rendering aluminum-based compound coatings the most extensively utilized. Aluminum coatings can be applied via methods such as pack cementation, thermal spraying, and hot-dip aluminizing. Pack cementation, being the simplest to operate, is widely employed. In this study, a powder mixture with the composition Al:Al₂O₃:NH₄Cl:CeO₂ = 30:66:3:1 was used to aluminize γ-TiAl intermetallic compound specimens via pack cementation at 600 °C for 5 h. Subsequent isothermal oxidation at 900 °C for 20 h yielded an oxidation kinetic curve adhering to the parabolic rate law. This treatment significantly enhanced the high-temperature oxidation resistance of the γ-TiAl intermetallic compound, thereby broadening its potential application scenarios. Full article

To improve the postharvest preservation of cherry tomatoes and combat pathogenic, both bacterial and fungal contamination (particularly Alternaria alternata), a novel biodegradable coating was developed based on a water-in-water (W/W) Pickering emulsion system. The emulsion was stabilized by L. plantarum (Lactobacillus plantarum), with maltodextrin (MD) as the dispersed phase and hydroxypropyl methylcellulose (HPMC) as the continuous phase. Characterization of emulsions at varying concentrations revealed that the optimized W/W-PL^8 film exhibited superior stability, smooth morphology, and low water vapor permeability (WVP = 220.437 g/(m²·24 h)), making it a promising candidate for fruit and vegetable preservation. Furthermore, the coating demonstrated strong antioxidant activity, with scavenging rates of 58.99% (ABTS) and 94.23% (DPPH), along with potent antimicrobial effects, showing inhibition rates of 12.8% against Escherichia coli and 23.7% against Staphylococcus aureus. Applied to cherry tomatoes, the W/W-PL^8 coating significantly reduced respiration rates, minimized decay incidence, and maintained nutritional quality during storage. Remarkably, the coating successfully controlled Alternaria alternata contamination, enhancing the storage duration of cherry tomatoes. These findings highlight the potential of W/W-PL^8 as an eco-friendly and functional packaging material for fresh produce preservation. Full article

We investigated the protective properties of ultrathin laminated coatings, comprising three pairs of Al₂O₃ and TiO₂ sublayers with coating thicknesses < 150 nm, deposited on AISI 310 stainless steel (SS) and Si (100) substrates at 80–500 °C by atomic layer deposition. The coatings were chemically etched and subjected to corrosion, ultrasound, and thermal shock tests. The coating etching resistance efficiency (R_e) was determined by measuring via XRF the change in the coating sublayer mass thickness after etching in hot 80% H₂SO₄. The maximum R_e values of ≥98% for both alumina and titania sublayers were obtained for the laminates deposited at 250–400 °C on both substrates. In these coatings, the titania sublayers were crystalline. The lowest R_e values of 15% and 50% for the alumina and titania sublayers, respectively, were measured for laminate grown at 80 °C on silicon. The coatings deposited at 160–200 °C demonstrated a delay in the increase of R_e values, attributed to the changes in the titania sublayers before full crystallization. Coatings grown at higher temperatures were also more resistant to ultrasound and liquid nitrogen treatments. In contrast, coatings deposited at 125 °C on SS had better corrosion protection, as demonstrated via electrochemical impedance spectroscopy and a standard immersion test in FeCl₃ solution. Full article

Metal–Organic Frameworks (MOFs) have emerged as advanced porous crystalline materials due to their highly ordered structures, ultra-high surface areas, fine-tunable pore sizes, and massive chemical diversity. These features, arising from the coordination between an almost unlimited number of metal ions/clusters and organic linkers, have resulted in significant interest in MOFs for applications in gas storage, catalysis, sensing, energy, and biomedicine. Beyond their stand-alone properties and applications, recent research has increasingly explored the integration of MOFs with other substrates, particularly electrodes, polymeric thin films, and glass surfaces, to create synergistic effects that enhance material performance and broaden application potential. Coating MOFs onto these substrates can yield significant benefits, including, but not limited to, improved sensitivity and selectivity in electrochemical sensors, enhanced mechanical and separation properties in membranes, and multifunctional coatings for optical and environmental applications. This review provides a comprehensive and up-to-date summary of recent advances (primarily from the past 3–5 years) in MOF coating techniques, including layer-by-layer assembly, in situ growth, and electrochemical deposition. This is followed by a discussion of the representative applications arising from MOF-substrate coating and an outline of key challenges and future directions in this rapidly evolving field. This article aims to serve as a focused reference point for researchers interested in both fundamental strategies and applied developments in MOF surface coatings. Full article

The problem of protecting 7075 Al alloy trekking poles from corrosion in complex outdoor environments was addressed using a composite conversion coating system. This system comprised Na₂MoO₄, NaF, CoSO₄·7H₂O, ethylenediaminetetraacetic acid-2Na, and H₂(TiF₆). The influences of this system on the properties of the coating layer were systematically studied by adjusting the pH of the coating solution. The conversion temperature and pH were the pivotal parameters influencing the formation of the conversion coating. The pH substantially influenced the compactness of the coating layer, acting as a regulatory agent of the coating kinetics. When the conversion temperature and pH were set to 40 °C and 3.8, respectively, the prepared coating layer displayed optimal performance in terms of compactness and protective properties. Therefore, this parameter combination favours the synthesis of high-performance conversion coatings. Microscopy confirmed the formation of a continuous, dense composite oxide film structure under these conditions, effectively blocking erosion in corrosive media. Furthermore, the optimised process led to substantial enhancements in the environmental adaptabilities and service lives of the components of trekking poles, thus establishing a theoretical foundation and technical reference for use in the surface protection of outdoor equipment. Full article

Food waste has emerged as a critical worldwide concern, resulting in environmental deterioration and economic detriment. Bio-based natural polymer coatings and films have emerged as a sustainable solution to food preservation challenges, particularly in reducing postharvest losses and extending shelf life. Compared to their synthetic counterparts, these polymers, such as chitosan, starch, cellulose, proteins, and alginate, are derived from renewable sources that are biodegradable, safe, and functional. Within this context, this review examines the various bio-based natural polymer coatings and films as biodegradable, edible alternatives to conventional packaging solutions. It examines the different fabrication methods, like solution casting, electrospinning, and spray coating, and incorporates antimicrobial agents to enhance performance. Emphasis is placed on their mechanical, barrier, and antimicrobial properties, their application in preserving fresh produce, how they promote food safety and environmental sustainability, and accompanying limitations. This review highlights the importance of bio-based natural polymer coatings and films as a promising, eco-friendly solution to enhancing food quality, safety, and shelf life while addressing global sustainability challenges. Full article