Search Results (145)

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

Titanium thin films with thicknesses of up to 105 nm were deposited on borosilicate glass implementing low-power continuous (25 W) and pulsed (85 W, with an ultra-low duty cycle) DC magnetron sputtering. The characteristics of the resulting films were studied via atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), VIS spectroscopy, and four-point-probe measurements. Both deposition modes yield films with low surface roughness, and AFM analysis showed no topographical features indicative of columnar-and-void structures. The films exhibited high optical reflectivity and stable transmittance and reflectance across the visible spectrum. The electric resistivity could be measured even at single nanometer thickness, emphasizing the metallic character of the films and approaching the bulk titanium value at higher film thicknesses. The low power regime of magnetron sputter deposition not only offers the possibility of studying the development of physical characteristics during the growth of ultra-thin films but also provides the advantage of extremely low heat development and no evident mechanical stress on the substrate during the coating process. These results outline a path for low-power DC sputtering as a reliable approach for studying the evolution of functional properties in ultra-thin films and for the gentle fabrication of coatings where thermal stress must be avoided, making the method compatible with temperature-sensitive applications. Full article

The development of bioactive coatings for metallic implants is essential to enhance osseointegration and improve implant longevity. In this study, composite thin films based on bioactive glass and melittin were synthesized using the matrix-assisted pulsed laser evaporation technique and deposited onto titanium substrates. The coatings were characterized using physicochemical analysis methods, including scanning electron microscopy, atomic force microscopy, contact angle measurements, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and electrochemical impedance spectroscopy. Simulated body fluid immersion tests were also conducted to assess bioactivity over time. Scanning electron microscopy and atomic force microscopy revealed dense, irregular surface textures with nanoscale features and an average roughness of ~120 nm, favorable for cell adhesion. Contact angle measurements showed a significant shift from hydrophobic (~95° for bare titanium) to moderately hydrophilic (~62° for the bioglass and melittin coating) surfaces, indicating improved biocompatibility. Electrochemical impedance spectroscopy demonstrated enhanced corrosion resistance in simulated body fluid, with the coating exhibiting a ~45% decrease in impedance magnitude after 12 h of immersion, compared to only 4% for bare titanium. Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy analyses confirmed the progressive formation of a carbonated apatite layer after 7 days of simulated body fluid exposure, suggesting high bioactivity and osteoconductive potential. The combined effects of bioactive glass and melittin in the thin film structure offer promising applications in orthopedic and dental implants, enhancing both biological performance and structural integrity. Full article

Pixel circuits are key components of flat panel displays, including liquid crystal displays (LCDs), organic light-emitting diode displays (OLEDs), and micro light-emitting diode displays (micro-LEDs). Depending on the active layer material of the thin film transistor (TFT), pixel circuits are categorised into amorphous silicon (a-Si) technology, low-temperature polycrystalline silicon (LTPS) technology, metal oxide (MO) technology, and low-temperature polycrystalline silicon and oxide (LTPO) technology. In this review, we outline the fundamental display principles and four major TFT technologies, covering conventional single-gated TFTs to novel two-gated TFTs. We focus on novel pixel circuits for three glass-based display technologies with additional mention of pixel circuits for silicon-based OLED and silicon-based micro-LED. Full article

Three-dimensional flexible solar fabrics based on hydrogenated amorphous silicon (a-Si:H) thin film solar cells were prepared and characterized. A glass fiber fabric with a polytetrafluoroethylene (PTFE) coating proved to be a suitable textile substrate. Interwoven metal wires enable an integrated electrical interconnection. An array of solar cells consisting of an a-Si:H layer stack with a highly p-type/intrinsic/highly n-type doping profile was deposited onto it. Silver was used as the back contact with indium tin oxide (ITO) as the front contact. The best solar cells show an efficiency of 3.9% with an open-circuit voltage of 876 mV and a short-circuit current density of 11.4 mA/cm². The high series resistance limits the fill factor to 39%. The potential of the textile solar cells is shown by the achieved pseudo fill factor of 79% when neglecting the series resistance, resulting in a pseudo efficiency of 7.6%. With four textile solar cells connected in a series, an open-circuit voltage of about 3 V is achieved. Full article

Solar photovoltaic (PV) systems in buildings must comply with both electrotechnical standards for module safety and local building codes, which typically do not address their electrical nature. This regulatory gap creates challenges in assessing the fire performance of PV systems. This paper presents a procedure to adapt a common test method used in some building codes to assess external fire conditions for roofs, while maintaining operative PV modules. Two configurations were tested: an organic PV thin film on a metallic sandwich panel and a glass–glass-encapsulated organic PV module. The tests were conducted under high voltage and current conditions to simulate the systems’ behavior within a larger PV array. Significant electric arcs were observed during testing of the metallic sandwich panel configuration without glass protection when subjected to high voltages or currents. In these cases, total heat release increased by at least 30% compared to non-electrically loaded scenarios or glass-insulated PV modules, likely due to a greater damaged surface area. Electric arcs created new ignition sources, damaging whole PV modules, whereas in the case with no electrical load, propagation flames advanced toward both the upper edge and the corners of the sample, ultimately damaging the entire triangular area above the fire source. The results indicate that the electrical characteristics of PV systems can significantly impact external fire spread behavior. The study identifies challenges in maintaining system activity during testing and simulating real scenarios and proposes for future research directions. Full article

We investigated patterns formed during the polymerization process of bifunctional monomers in a liquid crystal for both large polymer concentrations (polymer-dispersed liquid crystals, PDLC) and small concentrations (polymer-stabilized liquid crystals, PSLC). The resulting experimental patterns are reminiscent of Voronoi diagrams, so a reverse Voronoi algorithm was developed that provides the seed locations of cells, thus allowing a computational reproduction of the experimental patterns. Several metrics were developed to quantify the commonality between the faithful experimental patterns and the idealized and generated ones. This led to descriptions of the experimental patterns with accuracies better than 90% and showed that the curvature or concavity of the cell edges was below 2%. Possible reasons for the discrepancies between the original and generated Voronoi diagrams are discussed. The introduced algorithm and quantification of the patterns could be transferred to many other experimental problems, for example, melting of thin polymer films, ultra-thin metal films, or bio-membranes. The discrepancies between the experimental and ideal Voronoi diagrams are quantified, which may be useful in the quality control of privacy windows, reflective displays, or smart glass. Full article

Zinc–tin oxide (ZTO) thin films (ZnO)_x(SnO₂)_1−x with different material composition x (0 < x < 1) are deposited by spin coating on glass substrates at room temperature. The Differential Scanning Calorimetry (DSC) data of the precursor compounds show gradual phase transitions up to 480 °C. These data are used for an appropriate regime for thermal annealing of the layers. X-ray photoelectron spectroscopy (XPS) data show mixed oxide compound formation in states Zn²⁺, Sn⁴⁺ and O²⁻ of the constituents. Optical investigation manifests high transmittance above 80% in the visible spectral range and an optical band gap of 3.3–3.7 eV. The work functions vary between 4.1 eV and 5 eV, depending on the annealing, with deviations less than 1% for surface 1 mm² scans. Stack devices ITO/ZTO/metal with different metal contacts are formed. The I–V (current–voltage) measurements of the fabricated stacks exhibit Ohmic or nonlinear behavior, depending on the material composition and the work function levels. Full article

Transition metal nitrides have extensive applications, including magnetic storage devices, hardware resistance coatings, and low-temperature fuel cells. This study investigated the structural, electrical, and mechanical properties of thin zirconium nitride (ZrN) films by examining the effects of laser irradiation times. Thin ZrN films were deposited on glass substrates using pulsed DC magnetron sputtering and irradiated with a diode laser for 6 and 10 min. Characterization was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), nanoindentation, and four-point probe techniques. Extended laser irradiation times resulted in increased numbers of peaks on XRD analysis, indicating enhanced crystalline behavior of thin ZrN film. SEM analysis revealed surface voids, while HRTEM showed nanostructured ZrN with uniform plane orientation. The electrical properties of the thin ZrN film improved with extended laser irradiation, as demonstrated by a reduction in sheet resistance from 0.43 × 10⁹ Ω to 0.04 × 10⁹ Ω. Additionally, nanoindentation tests revealed an increase in hardness, rising from 8.91 GPa to 9.36 GPa. Full article

Thin films (TFs) of TiO₂ and ZrO₂ were prepared and characterized to evaluate their structural and optical (SO) properties and, later, to test their efficiency for the photocatalytic degradation (PD) of methylene blue (MB) in aqueous solution. The X-ray diffraction patterns showed that the TiO₂ TFs had an anatase crystalline structure, unlike the ZrO₂ TFs, which showed a tetragonal crystalline structure that was verified by Raman spectroscopy. The band gap (BG) energies, as calculated from UV-Vis spectroscopy and diffuse reflectance spectroscopy, corresponded to 3.2 and 3.7 eV for the TiO₂ and ZrO₂ TFs, respectively. SEM examination of the obtained materials was also carried out to assess the surface morphology and topography. The comparative study of the FTIR spectra of the TiO₂ and ZrO₂ TFs successfully confirmed the composition of the two-metal oxide TFs. The electrical properties of the films were studied by conductivity measurements. The two films also showed a similar thickness of about 200 nm and a substantially different photocatalytic performance for the discoloration of MB in aqueous solution. The corresponding rate constants, as obtained from a pseudo-first-order kinetic model, revealed that TiO₂ films promote color removal of the model dye solution almost 20 times faster than the rate observed for ZrO₂ modified glass substrates. We suggest that this difference may be related to the hydrophilic character of the two films under study, which may affect the charge carrier injection process and, therefore, the overall photocatalytic performance. Full article

This study aimed to investigate the degradation of dry biopotential electrodes using the anodic stripping voltammetry (ASV) technique. The electrodes were based on Ti-Cu thin films deposited on different polymeric substrates (polyurethane, polylactic acid, and cellulose) by Direct Current (DC) magnetron sputtering. TiCu_0.34 thin films (chemical composition of 25.4 at.% Cu and 74.6 at.% Ti) were prepared by sputtering a composite Ti target. For comparison purposes, a Cu-pure thin film was prepared under the same conditions and used as a reference. Both films exhibited dense microstructures with differences in surface topography and crystalline structure. The degradation process involved immersing TiCu_0.34 and Cu-pure thin films in artificial sweat (prepared following the ISO standard 3160-2) for different durations (1 h, 4 h, 24 h, 168 h, and 240 h). ASV was the technique selected to quantify the amount of Cu(II) released by the electrodes immersed in the sweat solution. The optimal analysis conditions were set for 120 s and −1.0 V for time deposition and potential deposition, respectively, with a quantification limit of 0.050 ppm and a detection limit of 0.016 ppm. The results showed that TiCu_0.34 electrodes on polyurethane substrates were significantly more reliable over time compared to Cu-pure electrodes. After 240 h of immersion, the TiCu_0.34 electrodes released a maximum of 0.06 ppm Cu, while Cu-pure electrodes released 16 ppm. The results showed the significant impact of the substrate on the electrode’s longevity, with cellulose bases performing poorly. TiCu_0.34 thin films on cellulose released 1.15 µg/cm² of copper after 240 h, compared to 1.12 mg/cm² from Cu-pure films deposited on the same substrate. Optical microscopy revealed that electrodes based on polylactic acid substrates were more prone to corrosion over time, whereas TiCu thin-film metallic glass-like structures on PU substrates showed extended lifespan. This study underscored the importance of assessing the degradation of dry biopotential electrodes for e-health applications, contributing to developing more durable and reliable sensing devices. While the study simulated real-world conditions using artificial sweat, it did not involve in vivo measurements. Full article

Thin films are the backbone of the electronics industry, and their widespread application in heat sensors, solar cells, and thin-film transistors has attracted the attention of researchers. The current study involves the deposition of a hetero-structured (ZnO/Zn/ZnO) thin film on a well-cleaned glass substrate using the DC magnetron sputtering technique. The samples were then annealed at 100, 200, 300, 400, and 500 °C. The structural, morphological, and electrical characteristics of the annealed samples as well as one as-deposited sample were then examined using atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and a Hall effect measuring apparatus. XRD analysis showed a hexagonal ZnO crystal structure for the samples annealed at 300 and 400 °C, whereas the samples annealed at 100 and 200 °C showed metallic zinc and hexagonal ZnO, and the crystallinity decreased for the sample annealed at 500 °C with pure hexagonal crystal symmetry. According to the AFM study, as the annealing temperature increases, the average roughness (R_a) decreases. Temperature has an inverse relationship with particle size. The optimal annealing temperature was determined to be 400 °C. Over this temperature range, the average roughness and particle size increased. Similarly, when R_a decreased, the conductivity increased and the resistance decreased. A fundamental difficulty is that the heating of the heterostructure to 400 °C melts the Zn-based intermediate layer, which alters the Zn phase and disrupts the sample homogeneity. Full article

Conformal thin film sensing represents a cutting-edge technology capable of precisely measuring complex surface temperature fields under extreme conditions. However, fabricating high-temperature-resistant conformal thin film thermocouple arrays remains challenging. This study reports a method for manufacturing conformal thin film thermocouple arrays on metal spherical surfaces using a printable paste composed of silicates and Ag. Specifically, the use of silicate glass phases enhances the high-temperature performance of the silver printable paste, enabling the silver ink coatings to withstand temperatures up to 947 °C and survive over 25 h at 900 °C. The thermocouples, connected to Pt thin films, exhibited a Seebeck coefficient of approximately 17 μV/°C. As a proof of concept, an array of six Ag/Pt thin film thermocouples was successfully fabricated on a metal spherical surface. Compared to traditional wire-type thermocouples, the conformal thin film thermocouple arrays more accurately reflect temperature variations at different points on a spherical surface. The Ag/Pt conformal thin film thermocouple arrays hold promise for monitoring temperature fields in harsh environments, such as aerospace and nuclear energy applications. Full article

Direct ink writing (DIW) of high-temperature thin-film sensors holds significant potential for monitoring extreme environments. However, existing high-temperature inks face a trade-off between cost and performance. This study proposes a SiCN/RuO₂/TiB₂ composite ceramic ink. The added TiB₂, after annealing in a high-temperature atmospheric environment, forms B₂O₃ glass, which synergizes with the SiO₂ glass phase formed from the SiCN precursor to effectively encapsulate RuO₂ particles. This enhances the film’s density and adhesion to the substrate, preventing RuO₂ volatilization at high temperatures. Additionally, the high conductivity of TiB₂ improves the film’s overall conductivity. Test results indicate that the SiCN/RuO₂/TiB₂ film exhibits high linearity from room temperature to 900 °C, high stability (resistance drift rate of 0.1%/h at 800 °C), and high conductivity (4410 S/m). As a proof of concept, temperature sensors and a heat flux sensor were successfully fabricated on a metallic hemispherical surface. Performance tests in extreme environments using high-power lasers and flame guns verified that the conformal thin-film sensor can accurately measure spherical temperature and heat flux, with a heat flux sensor response time of 53 ms. In conclusion, the SiCN/RuO₂/TiB₂ composite ceramic ink developed in this study offers a high-performance and cost-effective solution for high-temperature conformal thin-film sensors in extreme environments. Full article

Ni₆₀Nb₄₀ amorphous particles (APs) and amorphous thin films (ATFs) with various sizes were investigated by molecular dynamic simulations. It is revealed that sample size has effects on both Ni₆₀Nb₄₀ APs and ATFs composed of shell or surface and core components. Ni₆₀Nb₄₀ APs have an average bond length of 2.57 Å with major fivefold-symmetry atomic packing and low bond-orientation orders of Q₆ and Q₄ in both core and shell components. Ni atoms in Ni₆₀Nb₄₀ APs and ATFs prefer to segregate to the shell and surface regions, respectively. Atomic packing structure differences between various-sized Ni₆₀Nb₄₀ APs and ATFs affect their glass transition temperatures T_g, i.e., T_g decreases as the particle size or the film thickness decreases in Ni₆₀Nb₄₀ APs and ATFs, respectively. Our obtained results for Ni₆₀Nb₄₀ APs and ATFs clearly reveal a size effect on atomic packing and glass transition temperature in low-dimensional metallic glass systems. Full article