Self-Charging Power System Empowered by Bismuth Halide Perovskite-Based Hybrid Nanogenerator and Lithium-ion Battery.

Halide perovskite, renowned for its multifunctional properties, shows considerable promise for realizing self-charging power systems. In this study, a lead-free methylammonium bismuth iodide (MA3Bi2I9) perovskite is used to create a self-charging power unit (SPU). This involves constructing a hybrid piezoelectric-triboelectric nanogenerator (Hybrid-TENG) and utilizing MA3Bi2I9 for energy storage as an anode in a lithium-ion battery (LIB). Initially, MA3Bi2I9 nanorods are synthesized and composited with a polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene polymer. The dielectric and mechanical properties of composite films having perovskite loading content are investigated. The optimized Hybrid-TENG exhibits superior performance, generating a voltage of 537 V, current density of 13.2 µA cm- 2, and maximum power density of 3.04 mW cm-2, which can be attributed to the high piezoelectric coefficient of MA3Bi2I9 nanorods (≈20.6 pm V-1). A MA3Bi2I9 thin film, serving as an electrode in LIB, demonstrates a high specific capacity of 2378.9 mAh cm-3 (578.8 mAh g-1) with a capacity retention of ≈87.5% over 100 cycles, underscoring its stable performance. Furthermore, a Hybrid-TENG is employed to charge the MA3Bi2I9-based LIB, thus realizing an SPU for driving portable electronics. This study highlights the promising potential of perovskites for developing efficient nanogenerators and LIBs, paving the way for sustainable energy solutions in small-scale electronics.

An Overview of Polymer Composite Films for Antibacterial Display Coatings and Sensor Applications.

The escalating presence of pathogenic microbes has spurred a heightened interest in antimicrobial polymer composites tailored for hygiene applications. These innovative composites ingeniously incorporate potent antimicrobial agents such as metals, metal oxides, and carbon derivatives. This integration equips them with the unique ability to offer robust and persistent protection against a diverse array of pathogens. By effectively countering the challenges posed by microbial contamination, these pioneering composites hold the potential to create safer environments and contribute to the advancement of public health on a substantial scale. This review discusses the recent progress of antibacterial polymer composite films with the inclusion of metals, metal oxides, and carbon derivatives, highlighting their antimicrobial activity against various pathogenic microorganisms. Furthermore, the review summarizes the recent developments in antibacterial polymer composites for display coatings, sensors, and multifunctional applications. Through a comprehensive examination of various research studies, this review aims to provide valuable insights into the design, performance, and real-time applications of these smart antimicrobial coatings for interactive devices, thus enhancing their overall user experience and safety. It concludes with an outlook on the future perspectives and challenges of antimicrobial polymer composites and their potential applications across diverse fields.

Adjusted Bulk and Interfacial Properties in Highly Stable Semitransparent Perovskite Solar Cells Fabricated by Thermocompression Bonding between Perovskite Layers.

In order to shield perovskite solar cells (PSCs) from extrinsic degradation factors and ensure long-term stability, effective encapsulation technology is indispensable. Here, a facile process is developed to create a glass-glass encapsulated semitransparent PSC using thermocompression bonding. From quantifying the interfacial adhesion energy and considering the power conversion efficiency of devices, it is confirmed that bonding between perovskite layers formed on a hole transport layer (HTL)/indium-doped tin oxide (ITO) glass and an electron transport layer (ETL)/ITO glass can offer an excellent lamination method. The PSCs fabricated through this process have only buried interfaces between the perovskite layer and both charge transport layers as the perovskite surface is transformed into bulk. The thermocompression process leads the perovskite to have larger grains and smoother, denser interfaces, thereby not only reducing defect and trap density but also suppressing ion migration and phase segregation under illumination. In addition, the laminated perovskite demonstrates enhanced stability against water. The self-encapsulated semitransparent PSCs with a wide-band-gap perovskite (Eg ∼ 1.67 eV) demonstrate a power conversion efficiency of 17.24% and maintain long-term stability with PCE > ∼90% in the 85 °C shelf test for over 3000 h and with PCE > ∼95% under AM 1.5 G, 1-sun illumination in an ambient atmosphere for over 600 h.

Eco-friendly silk fibroin/tannic acid coacervates for humid and underwater wood adhesives.

Bioadhesives derived from biomass are steadily gaining spotlight as substitutes for formaldehyde-based resins in the adhesive industry. However, there is a need to develop novel water-resistant bioadhesives with high adhesive and cohesive strengths because the currently available biomaterial-based adhesives have low mechanical strength. In this study, a complex coacervate was prepared easily by mixing silk fibroin and tannic acid to produce a bioadhesive with high adhesive and cohesive strengths as well as water resistance. The silk fibroin-tannic acid coacervate adhered well to various substrates, and its adhesive strength according to the type of substrate and water contact angle were evaluated comparatively. In particular, the adhesive strength of this adhesive on a wood substrate was systematically analyzed by varying different experimental parameters (relative humidity, surface roughness of the substrate, water stability, and pH). This cost-effective coacervate is applicable as an eco-friendly wood adhesive.

High-Performance Flexible Ultraviolet Photodetectors Based on Facilely Synthesized Ecofriendly ZnAl:LDH Nanosheets.

Recent studies have focused on the development of efficient, flexible, and highly sensitive ultraviolet photodetectors (UV PDs) with various wide band-gap materials. In the present study, the application of environmentally friendly zinc-aluminum layered double hydroxide (ZnAl-CO3:LDH) is demonstrated for a high-performance, flexible UV PD. The vertically oriented ZnAl:LDH nanosheets (ZnAl:LDH Ns) are facilely synthesized by dipping the sputtered 10 wt % aluminum-doped zinc oxide thin films in deionized water at room temperature. Without passivation, the UV PDs exhibit an exceptional light-to-dark current ratio of 104 and a responsivity of ∼34.7 mA/W at a bias of 1 V. Moreover, the spectral responsivity and detectivity are enhanced to ∼148.3 mA/W and 2.5 × 1012 Jones, respectively, by passivating the ZnAl:LDH Ns with polydimethylsiloxane (PDMS), thus making the device suitable for application in UV detectors. In addition, the ambient atmosphere effect on PD performance, which elucidates the clear understanding of the PD working mechanism, is also investigated. The passivation of the Ns by PDMS also helps to enhance the mechanical robustness and long-term stability of the PD. The methodology demonstrated herein highlights the potential of the ZnAl:LDH material in realizing the next generation of flexible UV PDs.

Direct Growth of Highly Conductive Large-Area Stretchable Graphene.

The direct synthesis of inherently defect-free, large-area graphene on flexible substrates is a key technology for soft electronic devices. In the present work, in situ plasma-assisted thermal chemical vapor deposition is implemented in order to synthesize 4 in. diameter high-quality graphene directly on 10 nm thick Ti-buffered substrates at 100 °C. The in situ synthesized monolayer graphene displays outstanding stretching properties coupled with low sheet resistance. Further improved mechanical and electronic performances are achieved by the in situ multi-stacking of graphene. The four-layered graphene multi-stack is shown to display an ultralow resistance of ≈6 Ω sq-1, which is consistently maintained during the harsh repeat stretching tests and is assisted by self-p-doping under ambient conditions. Graphene-field effect transistors fabricated on polydimethylsiloxane substrates reveal an unprecedented hole mobility of ≈21 000 cm2 V-1 s-1 at a gate voltage of -4 V, irrespective of the channel length, which is consistently maintained during the repeat stretching test of 5000 cycles at 140% parallel strain.

Ensemble Design of Electrode-Electrolyte Interfaces: Toward High-Performance Thin-Film All-Solid-State Li-Metal Batteries.

In accordance with the fourth industrial revolution (4IR), thin-film all-solid-state batteries (TF-ASSBs) are being revived as the most promising energy source to power small electronic devices. However, current TF-ASSBs still suffer from the perpetual necessity of high-performance battery components. While every component, a series of a TF solid electrolyte (i.e., lithium phosphorus oxynitride (LiPON)) and electrodes (cathode and Li metal anode), has been considered vital, the lack of understanding of and ability to ameliorate the cathode (or anode)-electrolyte interface (CEI) (or AEI) has impeded the development of TF-ASSBs. In this work, we suggest an ensemble design of TF-ASSBs using LiPON (500 nm), an amorphous TF-V2O5-x cathode with oxygen vacancies (Ovacancy), a thin evaporated Li anode (evp-Li) with a thickness of 1 µm, and an artificial ultrathin Al2O3 layer between evp-Li and LiPON. Well-defined Ovacancy sites, such as O(II)vacancy and O(III)vacancy, in amorphous TF-V2O5-x not only allow isotropic Li+ diffusion at the CEI but also enhance both the ionic and electronic conductivities. For the AEI, we employed protective Al2O3, which was specially sputtered using the facing target sputtering (FTS) method to form a homogeneous layer without damage from plasma. In regard to the contact with evp-Li, interfacial stability, electrochemical impedance, and battery performance, the nanometric Al2O3 layers (1 nm) were optimized at different temperatures (40, 60, and 80 °C). The TF-ASSB cell containing Al2O3 (1 nm) delivers a high specific capacity of 474.01 mAh cm-3 under 60 °C at 2 C for the 400th cycle, and it achieves a long lifespan as well as ultrafast rate capability levels, even at 100 C; these results were comparable to those of TF Li-ion battery cells using a liquid electrolyte. We demonstrated the reaction mechanism at the AEI utilizing time-of-flight secondary ion mass spectrometry (TOF-SIMS) and molecular dynamics (MD) simulations for a better understanding. Our design provides a signpost for future research on the rational structure of TF-LIBs.

Light-Driven Piezo- and Triboelectricity in Organic-Inorganic Metal Trihalide Perovskite toward Mechanical Energy Harvesting and Self-powered Sensor Application.

A single-structured multifunctional device capable of energy harvesting and sensing multiple physical signals has significant potential for a wide range of applications in the Internet of Things (IoT). In this study, the fabricated single-structured device based on methylammonium lead iodide-polyvinylidene fluoride (MAPbI3-PVDF) composite can harvest mechanical energy and simultaneously operate as a self-powered light and pressure sensor because of the combined photoelectric and piezoelectric/triboelectric properties of the MAPbI3-PVDF composite. Light-dependent dielectric and piezoelectric properties of composite films are thoroughly investigated. Light and contact electrification effect on device performance in both piezoelectric and triboelectric modes is also systematically investigated. When the device is operated as a harvester in both piezoelectric and triboelectric modes, remarkable light-driven outputs were observed under illumination; the outputs decreased in the piezoelectric mode, while they increased in the triboelectric mode. Such light-controlled properties enabled the device to operate as a self-powered photodetector with outstanding responsivity (∼129.2 V/mW), rapid response time (∼50 ms), and satisfactory detectivity (∼1.4 × 1010 Jones) in the piezoelectric mode. The same device could also operate as a pressure sensor that exhibited excellent pressure sensitivity values of 0.107 and 0.194 V/kPa in the piezoelectric and triboelectric modes, respectively. In addition, the device exhibits a fast response time with long-term on-off switching properties, excellent mechanical durability, and long-term stability.

Structural, Optical and Electrical Properties of HfO2 Thin Films Deposited at Low-Temperature Using Plasma-Enhanced Atomic Layer Deposition.

HfO2 was deposited at 80-250 °C by plasma-enhanced atomic layer deposition (PEALD), and properties were compared with those obtained by using thermal atomic layer deposition (thermal ALD). The ALD window, i.e., the region where the growth per cycle (GPC) is constant, shifted from high temperatures (150-200 °C) to lower temperatures (80-150 °C) in PEALD. HfO2 deposited at 80 °C by PEALD showed higher density (8.1 g/cm3) than those deposited by thermal ALD (5.3 g/cm3) and a smooth surface (RMS Roughness: 0.2 nm). HfO2 deposited at a low temperature by PEALD showed decreased contaminants compared to thermal ALD deposited HfO2. Values of refractive indices and optical band gap of HfO2 deposited at 80 °C by PEALD (1.9, 5.6 eV) were higher than those obtained by using thermal ALD (1.7, 5.1 eV). Transparency of HfO2 deposited at 80 °C by PEALD on polyethylene terephthalate (PET) was high (> 84%). PET deposited above 80 °C was unable to withstand heat and showed deformation. HfO2 deposited at 80 °C by PEALD showed decreased leakage current from 1.4 × 10-2 to 2.5 × 10-5 A/cm2 and increased capacitance of approximately 21% compared to HfO2 using thermal ALD. Consequently, HfO2 deposited at a low temperature by PEALD showed improved properties compared to HfO2 deposited by thermal ALD.

Unveiling Predominant Air-Stable Organotin Bromide Perovskite toward Mechanical Energy Harvesting.

Organotin halide perovskites are developed as an appropriate substitute to replace highly toxic lead-based hybrid perovskites, which are a major concern for the environment as well as for human health. However, instability of the lead-free Sn-based perovskites under ambient conditions has hindered their wider utility in device applications. In this study, we report a predominantly stable lead-free methylammonium tin bromide (MASnBr3) perovskite that has air stability over 120 days without passivation under ambient conditions. Further, the feasibility of this predominant air-stable MASnBr3 perovskite for use in the harvesting of mechanical energy is described with the fabrication of an ecofriendly, flexible, and cost-effective piezoelectric generator (PEG) using MASnBr3-polydimethylsiloxane composite films. The fabricated PEG exhibits high performance along with good mechanical durability and long-term stability. This flexible device reveals a high piezoelectric output voltage of ∼18.8 V, current density of ∼13.76 µA/cm2, and power density of ∼74.52 µW/cm2 under a periodic applied pressure of 0.5 MPa. Further, the ability of PEG to scavenge energy from various easily accessible biomechanical movements is demonstrated. The energy generated from PEG by finger tapping is stored in a capacitor and is used to power both a stopwatch and a commercial light-emitting diode. These findings offer a new insight to achieve long-term air-stable Sn-based hybrid perovskites, demonstrating the feasibility of using organotin halide perovskites to realize highly efficient, ecofriendly, mechanical energy harvesters with a wide range of utility that includes wearable and portable electronics as well as biomedical devices.

Reduction of magnetic resonance image artifacts of NiTi implant by carbon coating.

A paramagnetic NiTi substrate was coated with diamagnetic carbon materials, i.e., graphene, graphene oxide (GO), and carbon nanotubes (CNTs), in order to reduce magnetic resonance (MR) image artifacts of NiTi implants. The present study focused on the effect of magnetic susceptibility variations in NiTi caused by the carbon coating on MR image artifacts. In the case of the graphene and GO coatings, the reduction of the magnetic susceptibility was greater along the perpendicular direction than the parallel direction. In contrast, the CNT coating exhibited a larger reduction along the parallel direction. The reduction of magnetic susceptibility measured in CNT-coated NiTi (CNT/NiTi) was smaller than the theoretical prediction especially when measured along the parallel direction, because CNTs on the NiTi surface were randomly arranged, rather than in a single direction. MR image artifacts were substantially reduced in all carbon-coated NiTi specimens, which is due to the reduction of magnetic susceptibility in NiTi by the carbon coating. This method can also be applied to other paramagnetic bio-metallic materials such as Co-Cr.

Ultra Small, mono dispersed green synthesized silver nanoparticles using aqueous extract of Sida cordifolia plant and investigation of antibacterial activity.

The present study is focused on the synthesis of silver nano particles (Ag NPs) using an aqueous extract of the whole plant of Sida cordifolia as a potential bio-reducing agent and assessment of their antibacterial activity. UV-Vis spectroscopy of composed silver colloidal solution displayed surface Plasmon resonance peak at 420 nm. XRD and TEM analysis revealed the morphology as ultra-small, monodispersed spherical nanoparticles with face-centered cubic structure and mean particle size of 3-6 nm. This ultra-small nano size might owe to the slow reaction time and phytochemicals existing in the S. cordifolia extract. The Ag NPs are trailed for antibacterial activity against 5 fish (Aeromonas hydrophila, Pseudomonas fluorescence, Flavobacterium branchiophilum, Edwardsiella tarda and Yersinia rukeri) and 4 human (Escherichia coli, Klebsiella pneumonia, Bacillus subtilis and Staphyloccocus aureus) bacterial pathogens. In all the cases, Ag NPs from Sida cordifolia plant extract manifested noteworthy antibacterial effects on par with positive control i.e.; Gentamicin.

Precise Determination of the Temperature Gradients in Laser-irradiated Ultrathin Magnetic Layers for the Analysis of Thermal Spin Current.

We investigated the temperature distribution induced by laser irradiation of ultrathin magnetic films by applying a finite element method (FEM) to the finite difference time domain (FDTD) representation for the analysis of thermal induced spin currents. The dependency of the thermal gradient (∇T) of ultrathin magnetic films on material parameters, including the reflectivity and absorption coefficient were evaluated by examining optical effects, which indicates that reflectance (R) and the apparent absorption coefficient (α*) play important roles in the calculation of ∇T for ultrathin layers. The experimental and calculated values of R and α* for the ultrathin magnetic layers irradiated by laser-driven heat sources estimated using the combined FDTD and FEM method are in good agreement for the amorphous CoFeB and crystalline Co layers of thicknesses ranging from 3~20 nm. Our results demonstrate that the optical parameters are crucial for the estimation of the temperature gradient induced by laser illumination for the study of thermally generated spin currents and related phenomena.

Defect-Free Graphene Synthesized Directly at 150 °C via Chemical Vapor Deposition with No Transfer.

Direct graphene synthesis on substrates via chemical vapor deposition (CVD) is an attractive approach for manufacturing flexible electronic devices. The temperature for graphene synthesis must be below ∼200 °C to prevent substrate deformation while fabricating flexible devices on plastic substrates. Herein, we report a process whereby defect-free graphene is directly synthesized on a variety of substrates via the introduction of an ultrathin Ti catalytic layer, due to the strong affinity of Ti to carbon. Ti with a thickness of 10 nm was naturally oxidized by exposure to air before and after the graphene synthesis, and the various functions of neither the substrates nor the graphene were influenced. This report offers experimental evidence of high-quality graphene synthesis on Ti-coated substrates at 150 °C via CVD. The proposed methodology was applied to the fabrication of flexible and transparent thin-film capacitors with top electrodes of high-quality graphene.

Surface engineering for improved stability of CH3NH3PbBr3 perovskite nanocrystals.

Organohalide perovskite nanocrystals (NCs) with a variety of nano-scale structures and morphologies have shown promising potential owing to their size- and composition-dependent optoelectronic properties. Despite extensive studies on their size-dependent optical properties, a lack of understanding on their morphological transformation and the relevant stability issues limits a wide range of applications. Herein, we hypothesize a mechanism for the morphological transformation of perovskite NCs, which leads to dissolving NCs and forming microscale rectangular grains, resulting in a reduction of photoluminescence. We found that the morphological transformation from nanocrystal solids to microscale rectangular solids occurs via Ostwald ripening. A surface treatment with a surfactant suppresses the transformation, resulting in nearly monodisperse NCs with a square shape (∼20 nm edge size), and thus improves the stability of NC solution, as well as their photoluminescence performance and quantum yield (PLQY = 82%). Furthermore, we employed similar amine derivatives to investigate the effect of a molecular architecture (i.e. steric hindrance) on perovskite NC stability, which exhibited much enhanced PLQY (93%). These experimental results provide new insights into the fundamental relationship between the physical properties and the structure of perovskite nanocrystals required to understand their diverse optoelectronic properties.

Green synthesis, characterization and antimicrobial activity of silver nanoparticles using methanolic root extracts of Diospyros sylvatica.

The current research study focuses to formulate the biosynthesized silver nanoparticles for the first time from silver acetate using methanolic root extracts of Diospyros sylvatica, a member of family Ebenaceae. TEM analysis revealed the average diameter of Ag NPs around 8nm which is in good agreement with the average crystallite size (10nm) calculated from X-ray Diffraction (XRD) analysis. Further the study has been extended to the antimicrobial activity against test pathogenic Gram (+) ve, Gram (-) ve bacterial and fungal strains. The bioinspired Ag-NP showed promising activity against all the tested bacterial strains and the activity was enhanced with increased dosage levels.

Wrinkle-free graphene electrodes in zinc tin oxide thin-film transistors for large area applications.

Wrinkle-free graphene was used to form the source-drain electrodes in thin film transistors based on a zinc tin oxide (ZTO) semiconductor. A 10 nm thick titanium adhesion layer was applied prior to transferring a conductive graphene film on top of it by chemical detachment. The formation of an interlayer oxide between titanium and graphene allows the achievement of uniform surface roughness over the entire substrate area. The resulting devices were thermally treated in ambient air, and a substantial decrease in field effect mobility is observed with increasing annealing temperature. The increase in electrical resistivity of the graphene film at higher annealing temperatures may have some influence, however the growth of the oxide interlayer at the ZTO/Ti boundary is suggested to be most influential, thereby inducing relatively high contact resistance.

A graphene meta-interface for enhancing the stretchability of brittle oxide layers.

Oxide materials have recently attracted much research attention for applications in flexible and stretchable electronics due to their excellent electrical properties and their compatibility with established silicon semiconductor processes. Their widespread uptake has been hindered, however, by the intrinsic brittleness and low stretchability. Here we investigate the use of a graphene meta-interface to enhance the electromechanical stretchability of fragile oxide layers. Electromechanical tensile tests of indium tin oxide (ITO) layers on polymer substrates were carried out with in situ observations using an optical microscope. It was found that the graphene meta-interface reduced the strain transfer between the ITO layer and the substrate, and this behavior was well described using a shear lag model. The graphene meta-interface provides a novel pathway for realizing flexible and stretchable electronic applications based on oxide layers.

Achieving Antifingerprinting and Antibacterial Effects in Smart-Phone Panel Applications Using ZnO Thin Films without a Protective Layer.

When crystalline ZnO films with a thickness of 30 nm and hydrophilic properties were deposited at room temperature onto a glass substrate via radio frequency sputtering, they exhibited antifingerprinting qualities following annealing treatment that was simple and accomplished at low temperature (100 °C). Hydrophobic properties were achieved using as-deposited ZnO films with hydrophilic properties via annealing treatment without the deposition of a protective layer with hydrophobic properties. The annealed 30 nm ZnO films showed a high transmittance (∼91.3%) comparable to that of a glass substrate at a wavelength of 550 nm. The annealed films showed strong antibacterial activity against E. coli and S. aureus bacteria. The ZnO films with a thickness of 30 nm showed predominant mechanical durability with strong antibacterial activity for smart-phone panel applications.