Fabrication Of Films Research Articles

Fabrication and physicomechanical enhancement of APTES Cross-linked gelatin biopolymer films

Fabrication and physicomechanical enhancement of APTES Cross-linked gelatin biopolymer films

Air-stable and ultralong room-temperature phosphorescence from doped poly(methyl methacrylate) for visual detection of volatile organic compounds

Room-temperature phosphorescence (RTP) has attracted significant attention due to its intriguing luminescence properties and potential applications in information storage, encryption, and sensing. Herein, we reported the facile fabrication of air-stable and ultralong RTP polymer films that exhibited remarkable and multiple stimuli responses. These films were composed of poly(methyl methacrylate) (PMMA) physically crosslinked with emitter molecules, resulting in transparent and flexible RTP materials. Remarkably, these polymer films emitted a bright RTP with a lifetime of 2.93 s, which was the best performance of PMMA materials reported. This exceptional performance was attributed to the abundant and robust physical interactions between the polymer chains and emitter molecules. Intriguingly, the RTP of these polymer films could be activated through consecutive UV irradiation, and quenched via thermal annealing in a controlled manner. The UV-activated RTP remained stable in humid air at room temperature over 1 week. Notably, the RTP of these flexible polymer films was sensitive to volatile organic compound (VOC) vapor. Upon exposure to VOC vapor, the RTP intensity of the polymer films rapidly decreased due to the disruption of their physically crosslinked microstructure. This unique sensitivity enabled the visual detection of VOCs in air by utilizing RTP polymers for the first time.

Nanofiber Space-Confined Fabrication of High-Performance Perovskite Films for Flexible Conversion of Fluorescence Quantum Yields in LED Applications.

Perovskite is an advanced optoelectronic semiconductor material that has garnered significant attention in recent years. However, its drawback lies in its environmental instability, limiting its practical applications. To tackle this issue, this research delved into the idea of creating a space-confined structure and used electrospinning to produce a film of perovskite nanocomposite fibers. By effectively encapsulating perovskite nanocrystals into a polymer matrix, the perovskite could be shielded from water and oxygen in the environment, thereby reducing the likelihood of perovskite decomposition and enhancing the stability of its structure and properties. This study examined the influence of material composition and the spinning process on the nanofiber structure to create good spatial confinement. This strategy resulted in a high photoluminescence quantum yield of over 80% and a long-term environmental stability of as long as 1000 h over 90% of the original PLQY. By harnessing the flexibility of the composite fibers, this study demonstrated the potential applications and performance of this nanocomposite film in flexible quantum fluorescence conversion for LED applications.

Stress-Dependent Optical Extinction in Low-Pressure Chemical Vapor Deposition Silicon Nitride Measured by Nanomechanical Photothermal Sensing.

Understanding optical absorption in silicon nitride is crucial for cutting-edge technologies like photonic integrated circuits, nanomechanical photothermal infrared sensing and spectroscopy, and cavity optomechanics. Yet, the origin of its strong dependence on the film deposition and fabrication process is not fully understood. This Letter leverages nanomechanical photothermal sensing to investigate optical extinction κext at a 632.8 nm wavelength in low-pressure chemical vapor deposition (LPCVD) SiN strings across a wide range of deposition-related tensile stresses (200-850 MPa). Measurements reveal a reduction in κext from 103 to 101 ppm with increasing stress, correlated to variations in Si/N content ratio. Within the band-fluctuations framework, this trend indicates an increase of the energy bandgap with the stress, ultimately reducing absorption. Overall, this study showcases the power and simplicity of nanomechanical photothermal sensing for low absorption measurements, offering a sensitive, scattering-free platform for material analysis in nanophotonics and nanomechanics.

Nonconjugated Polyurethane Derivatives with Aggregation-Induced Luminochromism for Multicolor and White Photoluminescent Films.

A simple and effective strategy to obtain solid-state multicolor emitting materials is a particularly attractive topic. Nonconventional/nonconjugated polymers are receiving widespread attention because of their advantages of rich structural diversity, low cost, and good processability. However, it is difficult to control the molecular conformation or to obtain the crystal structure of amorphous molecules, which means it is a challenge to obtain nontraditional polymeric materials with multicolor emission. In this work, a polyurethane derivative (PUH) with red-shifted emission was synthesized by a simple one-pot polymerization reaction. By exploiting the aggregation-induced luminochromism of PUH, a series of plastic films with tunable emission from blue to orange, and white-light emission, was obtained by doping different amounts of PUH into poly(methyl methacrylate) (PMMA), thereby changing the aggregation degree of PUH. This work demonstrates the excellent promise of polyurethane derivatives for the simple fabrication of large-scale flexible luminescent films.

Lanthanide-Like Contraction Enables the Fabrication of High-Purity Selenium Films for Efficient Indoor Photovoltaics.

The lanthanide contraction involves a reduction in atomic radius among f-block elements below the expected level. A similar contraction is observed in group-16 elements. The atomic radius of Se (117 pm) is slightly larger than that of S (104 pm) arising from the presence of d electrons, compared to the significant increase in atomic radius from O (73 pm) to S. This lanthanide-like contraction contributes to Se's robust oxidative resistance. Here we report a selective oxidation strategy utilizing Se's strong antioxidative property to remove coexisting narrow-bandgap Te impurities from Se feedstocks. This strategy selectively oxidizes volatile Te impurities into involatile TeO2 that remains in the evaporation source, while only volatile Se deposits onto the substrate during the thermal-evaporation deposition process. This enables the fabrication of high-purity Se films possessing a wide bandgap of 1.88 eV, ideally suited to the optimal bandgap for indoor photovoltaics (IPVs). The resulting Se photovoltaics exhibit an efficiency of 20.1% under 1000-lux indoor illumination, outperforming market-dominant amorphous silicon and all types of lead-free perovskite IPVs. Unencapsulated Se devices show no efficiency degradation after 20,000 hours of storage in ambient atmosphere.

Orientation Control of Perfluorosulfonic Acid Films via Addition of 1,2,4-Triazole during Casting.

Perfluorosulfonic acid (PFSA) polymers are used as electrolyte membranes in polymer electrolyte fuel cells. To investigate the effect on proton conductivity through structural orientation control, we added 1,2,4-triazole to PFSA films during casting to impart anisotropy to the ion-cluster structure of the films. The proton conductivities of the films were found to be high in the film-surface direction and low in the film-thickness direction. Structural analysis using small-angle X-ray scattering suggested that the anisotropy in proton conductivity was due to anisotropy in the ion-cluster structure, which in turn was attributed to the formation of a phase-separated structure via strong bonding between sulfonic acid groups and 1,2,4-triazole during cast film formation and the surface segregation of fluorine. We expect the findings of this study to aid in the fabrication of PFSA films with controlled ion clusters.

Fabrication and characterization of active gelatin-based films integrated with nanocellulose-stabilized Pickering emulsion containing Oliveria Decumbens Vent. essential oil

Stabilizing essential oils (EOs) within biodegradable matrices to create homogeneous and stable films with desirable properties is challenging due to the hydrophobic nature of EOs, which hinders their uniform infusion into the matrix. In this study, we investigated the feasibility of creating active films made of gelatin, infused with nanocellulose-stabilized Pickering emulsion (PE) containing Oliveria Decumbens Vent. essential oil (OEO). The Pickering emulsion effectively stabilized the 50% v/v of OEO, which was subsequently incorporated into a gelatin film at 0, 3, 5, 7, and 9% v/v, to produce active films. FTIR data showed that the OEO-PE was physically trapped in the film matrix through hydrogen bonds, which was also verified by SEM micrographs. The addition of OEO-PE notably changed the films' mechanical properties, leading to reduced tensile strength and enhanced elongation (P < 0.05) with no significant impact on their water vapor permeability. The incorporation of OEO endowed the film matrix with high antioxidant and antibacterial activity against E. coli and S. aureus. Thermal analysis using differential scanning calorimetry showed a 36–171 °C endothermic peak in all films, due to water evaporation and melting. The gelatin film containing 9% OEO-PE exhibited superior physical properties, enhanced water resistance, and excellent antibacterial and antioxidant activity.

Controllable Crystallization of Perovskite Films during the Blade-Coating Fabrication Process for Efficient and Stable Solar Cells

The scalable production of high-quality perovskite thin films is pivotal for the industrialization of perovskite thin film solar cells. Consequently, the solvent system employed for the fabrication of large-area perovskite films via coating processes has attracted significant attention. In this study, a solvent system utilizing a volatile solvent as the primary reagent has been developed to facilitate the rapid nucleation of volatile compounds. While adding the liquid Lewis base dimethylformamide (DMF) can help to improve the microstructure of perovskite films, its slow volatilization renders the crystal growth process uncontrollable. Based on the solvent system containing DMF and ethanol (EtOH), introducing a small amount of NH4Cl increases the proportion of the intermediate phase in the precursor films. This not only results in a controllable growth process for the perovskite crystals but also contributes to the improvement of the film microstructure. Under the simulated illumination (AM1.5, 1000 W/m2), the photoelectric conversion efficiency (PCE) of the inverted solar cells has been improved to 20.12%. Furthermore, after 500 hours of continuous illumination, the photovoltaic device can retain 95.6 % of the initial, indicating that the solvent system is suitable for the scalable fabrication of high-quality FAPbI3 thin films.

Scalable Fabrication of Black Phosphorous Films for Infrared Photodetector Arrays.

Bulk black phosphorous (bP) exhibits excellent infrared (IR) optoelectronic properties, but most reported bP IR photodetectors are fabricated from single exfoliated flakes with lateral sizes of <100µm. Here, scalable thin films of bP suitable for IR photodetector arrays are realized through a tailored solution-deposition method. The properties of the bP film and their protective capping layers are optimized to fabricate bP IR photoconductors exhibiting specific detectivities up to 4.0×108cm Hz1/2 W-1 with fast 30/60 µs rise/fall times under λ = 2.2µm illumination. The scalability of the bP thin film fabrication is demonstrated by fabricating a linear array of 25 bP photodetectors and obtaining 25×25pixel IR images at ≈203ppi with good spatial fidelity. This research demonstrates a commercially viable method of fabricating scalable bP thin films for optoelectronic devices including room temperature-operable IR photodetector arrays.

Interwoven grain boundary: A general strategy for the fabrication of ultra-strong crystalline thin films

Interwoven grain boundary: A general strategy for the fabrication of ultra-strong crystalline thin films

Maize starch-PVA nanocomposite biodegradable antimicrobial packaging films for enhancement of shelf-life of Agaricus bisporus

Nanocomposite antimicrobial packaging can effectively cater to the postharvest losses of button mushrooms. This study aimed for fabrication of novel antimicrobial biodegradable packaging films using a double composite system comprised of nano-clay-essential oil (EO) composite blended with maize starch (MS) /Polyvinyl alcohol (PVA) polymers which was plasticized with glycerol. The results confirmed superior water barrier properties with the lowest film solubility (16.52 %) and water holding capacity (13.55 %) in MS+ PVA+ Nano-bentonite-basil EO blend film. The surface morphology of this blend film appeared smooth, was thermally stable with the lowest mass loss (97.92 %), and exhibited the highest tensile strength (182.15 Kg/cm2) which makes it suitable for food packaging applications. Furthermore, all the prepared films were fully degraded in the soil after 147 days except the control cling film. The addition of EOs enhanced the antimicrobial activity of starch blend films with the highest inhibition against Gram-positive microorganisms (Staphylococcus aureus and Listeria monocytogenes). Packaging of freshly harvested button mushrooms with nanocomposite blend film enhanced the shelf-life up-to 14 days of storage under refrigerated conditions (4 °C) with the lowest physiological weight loss (4.69 %) and highest firmness (1.5 Kg F). Nutritional qualities and ROS-mitigating enzymatic activity of mushroom fruiting bodies were also maintained through packaging. This innovative nanocomposite packaging films could provide a green, environment-friendly, and antimicrobial system to combat the shorter shelf life of button mushrooms.

Unified Crystal Phase Control with MACl for Inducing Single-Crystal-Like Perovskite Thin Films in High-Pressure Fusion Toward High Efficiency Perovskite Solar Cell Modules.

Perovskite solar cells, recognized for their high photovoltaic conversion efficiency (PCE), cost-effectiveness, and simple fabrication, face challenges in PCE improvement due to structural defects in polycrystalline films. This study introduces a novel fabrication method for perovskite films using methylammonium chloride (MACl) to align grain orientation uniformly, followed by a high-pressure process to merge these grains into a texture resembling single-crystal perovskite. Employing advanced visual fluorescence microscopy, charge dynamics in these films are analyzed, uncovering the significant impact of grain boundaries on photo-generated charge transport within perovskite crystals. A key discovery is that optimal charge transport efficiency and speed occur in grain centers when the grain size exceeds 10µm, challenging the traditional view that efficiency peaks when grain size surpasses film thickness to form a monolayer. Additionally, the presence of large-sized grains enhances ion activation energy, reducing ion migration under light and improving resistance to photo-induced degradation. In application, a perovskite solar cell module with large grains achieve a PCE of 22.45%, maintaining performance with no significant degradation under continuous white LED light at 100 mA cm-2 for over 1000h. This study offers a new approach to perovskite film fabrication and insights into optimizing perovskite solar cell modules.

Influence of substrate edge chamfer geometric features on the edge effect of spin-coating film

Abstract The spin-coating method is a widely employed technique for thin film fabrication. However, edge effects can adversely affect the quality and utility of the films produced. This study investigates the influence of chamfered edges on the substrate during the spin-coating process on edge effects. Both experimental and simulation results indicate that smaller chamfer angles contribute to reducing the width of edge effects. Conversely, the width of the chamfer has a relatively minor impact on the extent of edge effects.

Luminescence enhancement behavior of KSr1.96Sm0.04Nb5O15/PVDF composite thick film after electric polarization

A novel composite thick film exhibiting luminescent enhancement behavior was prepared using Sm3+ doped KSr2Nb5O15 ferroelectric microcrystals and polyvinylidene difluoride (PVDF) polymer via a tape-casting technology. After compositing with PVDF, the thick film retained the ferroelectric polarization behavior, and the PVDF phase had negligible impact on the reflectivity and optical absorption edge of ferroelectric microcrystals. The photoluminescent emission intensities of the characteristic transitions of Sm3+ exhibited significant enhancement after electric polarization, with a maximum modulation ratio exceeding 200 %. The underlying luminescence modulation mechanism is discussed. This work proposed a novel strategy for fabrication of flexible composite thick films with coupling behavior between luminescent and ferroelectric properties.

Piezoelectric Properties of As-Spun Poly(vinylidene Fluoride)/Multi-Walled Carbon Nanotube/Zinc Oxide Nanoparticle (PVDF/MWCNT/ZnO) Nanofibrous Films.

Conductive multi-walled carbon nanotubes (MWCNTs) as well as piezoelectric zinc oxide (ZnO) nanoparticles are frequently used as a single additive and dispersed in polyvinylidene fluoride (PVDF) solutions for the fabrication of piezoelectric composite films. In this study, MWCNT/ZnO binary dispersions are used as spinning liquids to fabricate composite nanofibrous films by electrospinning. Binary additives are conducive to increasing the crystallinity, piezoelectric voltage coefficient, and consequent piezoelectricity of as-spun films owing to the stretch-enhanced polarization of the electrospinning process under an applied electric field. PCZ-1.5 film (10 wt. % PVDF/0.1 wt. % MWCNTs/1.5 wt. % ZnO nanoparticles) contains the maximum β-phase content of 79.0% and the highest crystallinity of 87.9% in nanofibers. A sensor using a PCZ-1.5 film as a functional layer generates an open-circuit voltage of 10 V as it is subjected to impact loads with an amplitude of 6 mm at 10 Hz. The piezoelectric sensor reaches a power density of 0.33 μW/cm2 and a force sensitivity of 582 mV/N. In addition, the sensor is successfully applied to test irregular motions of a bending finger and stepping foot. The result indicates that electrospun PVDF/MWCNT/ZnO nanofibrous films are suitable for wearable devices.

Synthesis of hydrophobic silica without traditional aging process to construct the anti-reflective film with ultralow refractive index for improving power conversion efficiency

The fabrication of anti-reflective films to optimize sunlight utilization encounters various challenges. Herein, we have synthesized modified silica with hydrophobic properties, eliminating the conventional aging process to create an anti-reflective film with an ultralow refractive index of 1.05, marking the lowest value reported to date. This innovative methodology reduces tasks that typically require days or weeks to just a few hours, thereby significantly accelerating production. The power conversion efficiency of the photovoltaic device can increase by 6.2 % when coated with this film. This research not only advances the synthesis of silica but also develops anti-reflective films with record-low refractive indices. This breakthrough represents a substantial contribution, highlighting its significant impact on the photovoltaic field.

Solution-Processable MOF-on-MOF System Constructed via Template-Assisted Growth for Ultratrace H2S Detection.

Conductive metal-organic frameworks (c-MOFs) hold promise for highly sensitive sensing systems due to their conductivity and porosity. However, the fabrication of c-MOF thin films with controllable morphology, thickness, and preferential orientation remains a formidable yet ubiquitous challenge. Herein, we propose an innovative template-assisted strategy for constructing MOF-on-MOF (Ni3(HITP)2/NUS-8 (HITP: 2,3,6,7,10,11-hexamino-tri(p-phenylene))) systems with good electrical conductivity, porosity, and solution processability. Leveraging the 2D nature and solution processability of NUS-8, we achieve the controllable self-assembly of Ni3(HITP)2 on NUS-8 nanosheets, producing solution-processable Ni3(HITP)2/NUS-8 nanosheets with a film conductivity of 1.55 × 10-3 S·cm-1 at room temperature. Notably, the excellent solution processability facilitates the fabrication of large-area thin films and printing of intricate patterns with good uniformity, and the Ni3(HITP)2/NUS-8-based system can monitor finger bending. Gas sensors based on Ni3(HITP)2/NUS-8 exhibit high sensitivity (LOD ~ 6 ppb) and selectivity towards ultratrace H2S at room temperature, attributed to the coupling between Ni3(HITP)2 and NUS-8 and the redox reaction with H2S. This approach not only unlocks the potential of stacking different MOF layers in a sequence to generate functionalities that cannot be achieved by a single MOF, but also provides novel avenues for the scalable integration of MOFs in miniaturized devices with salient sensing performance.

Improved electrochromic device based on mesoporous TiO2 and NiO films

Fabrication of electrochromic films with micro/nanostructures is one of the most feasible ways to improve their properties for high-performance electrochromic devices (ECDs). In this work, mesoporous TiO2 and NiO electrochromic films are prepared by sol-gel technique with an auxiliary solvent of F108 (PEO[Formula: see text]PPO[Formula: see text]PEO[Formula: see text]). By adjusting the content of F108 and heat treatment temperature, the transparent and uniform mesoporous films are successfully prepared. The TiO2 and NiO films are composed of inter-connected nanoparticles with a size of about 20 nm. The thicknesses of the films are about 300 nm and the mesoporous sizes are about 13 nm. The films have a short response time during the electrochromic process. When supplied with positive/negative voltages for 50 s, the coloring/bleaching times of TiO2 and NiO mesoporous films are 15/13 and 17/12 s, respectively. The ECD fabricated with TiO2 and NiO mesoporous films shows good electrochromic properties: short response time (14/19 s, for bleaching/coloring time), wide transmittance modulation range ([Formula: see text]37.21% at 540 nm), high coloration efficiency (CE) (100.6 cm2/C at 540 nm) and outstanding cycle stability (800 cycles). These are attributed to the mesoporous channels of films, which can increase reaction activity site, shorten ions transport path, and thus improve electrochromic reaction.

Mechanically Adaptive Metal-Coordinated Electrogel Membranes.

Achieving specific mechanical properties of hydrogels, especially when used as thin films, can be crucial in diverse applications, including tissue engineering and bioelectronics. Here, a novel electrochemical approach for fabricating uniform and robust hydrogel films based on carboxymethyl cellulose cross-linked by Fe3+ ions (Fe-CMC), exhibiting tunable, dynamic properties is introduced. High modulation of the mechanical properties of the film is achieved by applying multiple electrochemical pulses of oxidative voltage during hydrogel deposition. Our study shows also a remarkable effect of the ionic strength on the properties of the electrodeposited hydrogel films. We found that switching from a salt solution to water enhanced the stiffness of the hydrogels, thereby regulating the permeability of the films. These results are supported by molecular dynamics (MD) simulations, showing that an increase in the ionic strength induces a weakening of the Fe-CMC interactions, ultimately affecting the network strength. Finally, the robustness of these electrodeposited hydrogel films enables their delamination from the electrode without any damage, thereby expanding their potential applications as freestanding smart membranes. By providing fundamental insights into the dynamics of metal-coordinated bonds and their response at the macroscopic scale, we have demonstrated the versatility of electrochemical gelation for the fabrication of robust hydrogel films with tunable mechanical properties, which could serve as smart platforms for a variety of biomedical applications.