Thin Layer Of Material Research Articles

Two-dimensional Ruddlesden-Popper perovskite solar cells with an efficiency exceeding 19 % by inserting a self-assembled monolayer

Two-dimensional Ruddlesden-Popper (2DRP) phase perovskites have excellent long-term environmental and structure stability. However, the efficiency of 2DRP perovskite solar cells (PSCs) still lags seriously behind 3D counterparts due to the large exciton binding energy between the large-volume organic spacer and the inorganic plate compared to their 3D analogs. Here, a thin layer of self-assembled monolayer material (2-(3,6-dibromo-9H-carbazol-9-yl)ethyl)phosphonic acid (2PACz-Br) is employed between poly (3,4-ethylene dioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) and β-guanidinopropanoic acid (β-GUA)-based perovskite film (β-GUA)2(FA)4Pb5I16 for efficient and stable 2DRP-based PSCs. The 2PACz-Br-based 2DRP perovskite films show superior crystallinity and quality compared with the control perovskite films. The defect density in 2PACz-Br-based perovskite films is reduced, and the non-radiative recombination is further suppressed. The experimental results show that introducing 2PACz-Br can effectively promote the matched energy levels between the perovskite thin film and the charge-carrier transport layer. Benefiting from the conducive collection and transmission of charge carriers, (β-GUA)2(FA)4Pb5I16 (n = 5)-based PSCs can realize an outstanding power conversion efficiency of 19.13 %, much higher than that of devices without 2PACz-Br modification (17.70 %). Moreover, 2PACz-Br-based 2DRP PSCs show better stability than the control devices. Our work paves the way to efficient and stable 2DRP-based PSCs by inserting a multifunctional self-assembled monolayer.

Electrochemical grafting of diazonium salts on silica-terminated versus H-terminated silicon

Diazonium salts are one of the most widely used molecules for functionalising electrode surfaces, due to their high reactivity toward a range of different electrodes but have mostly been studied on carbon and gold. Recent work has demonstrated that diazonium salts can be reduced on silica-terminated silicon (Si/SiOx) despite silica (SiOx) being an electrically insulating material, but this interesting phenomenon was only demonstrated on one specific crystal orientation, Si(111) using specific diazonium salts molecules – a more complete understanding of the electrochemical properties of these silica-terminated silicon electrodes remains unclear. In this work, we develop a thorough understanding of the reduction of diazonium compounds on silica-terminated silicon using silicon with different crystal orientation and using nano-structured silicon surfaces that are chemically etched to simultaneously expose different crystal orientations. A comparison between the reduction process on oxide free silicon (Si–H) and silica-terminated Si is then made to reveal the effect of the crystal orientation (amorphous vs crystalline) and the insulating nature of the distal surface (Si‒H vs SiOx) on the reduction process. Results show that diazonium salts form, well-packed thin films on silica-terminated silicon regardless of the crystal orientation of the silicon. The rate of diazonium reduction was found to be sensitive to the crystal orientation of Si only when the diazonium salts are in direct contact with the crystal plane (i.e. in contact with Si–H) as opposed to when there is a thin layer of native amorphous oxide material in between. The reduction rate is sufficiently slow on silica-terminated silicon that at slow scan rates, the system reaches a steady state current and become diffusion controlled. This is not observed on oxide-free silicon electrodes which are observed to be governed by a kinetically driven mechanism. These findings deepen our understanding of the electrochemical activity of silica-terminated silicon surfaces which are widely used in solar cells, electronics, chemical and biosensors.

Protective potential of high-contrast mineral-bonded layers on reinforced concrete slabs subjected to uniform shock waves

This study compares the blast performance of reinforced concrete (RC) slabs with and without strengthening on the impact-facing side. The strengthening strategy employed the application of two thin layers of materials with a high mutual stiffness offset, i.e., high-contrast layers. The first is a low-strength, low-modulus damping layer made of infra-lightweight concrete, followed by a second layer of high-ductility fiber-reinforced concrete. The plain RC slabs under investigation vary in thickness of either 40mm or 100mm. The layered specimens consist of a 40mm thick RC slab strengthened with a 40mm damping layer and a 20mm cover SHLC3 layer. This configuration enables a comparison of its behavior with the unstrengthened specimen (a plain 40mm thick RC slab) and a specimen with a similar eigenfrequency (the plain 100mm thick RC slab). The employed shock tube subjects the specimens to two rapidly rising areal pressures: a low-pressure wave reaching approximately 0.4MPa and a high-pressure wave peaking at around 1.2MPa. The study assesses the specimens’ response in terms of accelerations, velocities, and deformations. Additionally, it evaluates damage by analyzing crack patterns, Ultrasonic Pulse Velocity (UPV) measurements, and damping analysis. Overall, the layered specimens exhibited performance nearly equivalent to the 100mm thick specimens, displaying similar deformations and velocities despite having lower mass and bending stiffness. The high-pressure shock wave hardly damaged the layered specimens, unlike the 40mm thick slabs.

Slicing on the Tessellated Model for the 3D Printing Process based on the Variable Thickness Layers

Additive Manufacturing (AM) is a modern technology that enhances manufacturing by building thin layers of material from digitized (3D) designs, entirely constructed using advanced CAD software. This method facilitates the creation of new types of objects with unique material properties. However, while AM is often hailed as the next industrial revolution, significant challenges remain for its successful commercialization. This project focuses on the microstructural aspects and the dimensional accuracy of the product. Additionally, the paper discusses the slicing algorithm and the material extrusion process in detail.

Characterization of a conductive hydrogel@Carbon fibers electrode as a novel intraneural interface

Peripheral neural interfaces facilitate bidirectional communication between the nervous system and external devices, enabling precise control for prosthetic limbs, sensory feedback systems, and therapeutic interventions in the field of Bioelectronic Medicine. Intraneural interfaces hold great promise since they ensure high selectivity in communicating only with the desired nerve fascicles. Despite significant advancements, challenges such as chronic immune response, signal degradation over time, and lack of long-term biocompatibility remain critical considerations in the development of such devices. Here we report on the development and benchtop characterization of a novel design of an intraneural interface based on carbon fiber bundles. Carbon fibers possess low impedance, enabling enhanced signal detection and stimulation efficacy compared to traditional metal electrodes. We provided a 3D-stabilizing structure for the carbon fiber bundles made of PEDOT:PSS hydrogel, to enhance the biocompatibility between the carbon fibers and the nervous tissue. We further coated the overall bundles with a thin layer of elastomeric material to provide electrical insulation. Taken together, our results demonstrated that our electrode possesses adequate structural and electrochemical properties to ensure proper stimulation and recording of peripheral nerve fibers and a biocompatible interface with the nervous tissue.

Effects of silver diammine fluoride with/without potassium iodide on enamel and dentin carious lesions in primary teeth.

To assess the effects of SDF and SDF+KI treatment on enamel and dentin carious lesions in primary teeth using x-ray Microtomography (XMT) and back scattered scanning electron microscopy (BSE-SEM). Artificial enamel caries of 3 caries free primary teeth were created by immersion of the samples in 50 ml demineralization solution for 72 h. Three other teeth with natural dentin caries were selected. Both groups were divided into 3 subgroups: EC-Enamel Control; ES-Enamel with SDF application; ESK-Enamel with SDF followed by KI application; DC-Dentin Control; DS-Dentin with SDF application; DSK-Dentin with SDF followed by KI application. Each tooth was imaged using XMT at 3 time points: (1) Pretreatment; (2) after immersion in remineralization solution for 120 h, with or without SDF or SDF+KI; (3) after subsequent immersion in demineralization solution for 72 h. The change of radiopacities of the lesions in these time points were assessed from the XMT images. After the XMT scans, all teeth were investigated microscopically using BSE-SEM. In EC, no change in linear attenuation coefficient (LAC) was observed after remineralization, but LAC reduction was observed after subsequent demineralization. For ES, thin layer of high LAC material was deposited on the enamel surface after remineralization, and further reduction of LAC was observed after demineralization. In ESK, the surface layer was lost after SDF+KI, and small reduction of LAC was observed after demineralization. In DC, no LAC change was observed after remineralization, but reduction of LAC was detected after demineralization. In DS, high LAC material was formed on the carious dentin surface and randomly inside the lesion. No further LAC change was found after demineralization. In DSK, thick layer of high LAC material was deposited on the carious surface and inside the dentinal tubules. No further LAC reduction was found after subsequent demineralization. SDF and SDF+KI did not protect artificial enamel under acid attack even though Ag products were deposited in the porous enamel. However, SDF and SDF+KI shows protective properties against acid challenges and Ag products are deposited in carious dentin lesion without tubular structure randomly; and within dentinal tubules when these structures are retained.

Simulation and analysis of solar cells based on InN/p-Si: influence on thickness, doping concentration, and temperature dependence

ABSTRACT The current research project intends to enhance solar cells' power and conversion efficiency based on InN/p-Si utilizing the PC1D simulator. A broad direct bandgap of Indium nitride (0.65 eV) makes it suitable for various applications. The InN-based solar cells show an excellent candidate for generating a higher efficiency device, incorporating well-established silicon substrate technology. The open-source PC1D is well-known software for simulating future solar devices without the need to fabricate real devices. The simulated area was adjusted to 10 cm2. The Si substrate and InN layer thicknesses were designed to be 350 μm and 1×10-3 μm, respectively. The n- and p-regions have doping concentrations of 1×1021 cm-3 and 1×1017 cm-3, respectively. This work analyses the influence of geometrical and technological aspects such as both n-p regions thickness, doping concentrations, and temperature dependency to enhance the conversion efficiency of these structures under the AM1.5G solar spectrum with intensity 0.1 W/cm2. It has been demonstrated that the growth of high-quality InN layers and p-type doping persists to be problematic. It appears challenging to find the most suitable material substrate for InN solar. To produce compatible solar cells with simple structures and cost-effective, however, extremely thin layers of n-layer material are required due to the high absorption coefficient of type III-nitrides. The results illustrate that by adjusting the optimized parameter at room temperature to the lowest temperature (200 K), the solar efficiency may increase up from 19.18% to 27.67%.

Novel Approach for the Preparation of a Highly Hydrophobic Coating Material Exhibiting Self-Healing Properties.

A concept to prepare a highly hydrophobic composite with self-healing properties has been designed and verified. The new material is based on a composite of a crystalline hydrophobic fluoro wax, synthesized from montan waxes and perfluoroethylene alcohols, combined with spherical silica nanoparticles equipped with a hydrophobic shell. Highly repellent layers were prepared using this combination of a hydrophobic crystalline wax and silica nanoparticles. The novel aspect of our concept was to prepare a ladder-like structure of the hydrophobic shell allowing the inclusion of a certain share of wax molecules. Wax molecules trapped in the hydrophobic structure during mixing are hindered from crystallizing; therefore, these molecules maintain a higher mobility compared to crystallized molecules. When a thin layer of the composite material is mechanically damaged, the mobile wax molecules can migrate and heal the defects to a certain extent. The general preparation of the composite is described and XRD analysis demonstrated that a certain share of wax molecules in the composite are hindered to crystallize. Furthermore, we show that the resulting material can recovery its repellent properties after surface damage.

Direct synthesis of controllable ultrathin heteroatoms-intercalated 2D layered materials

Two-dimensional (2D) layered materials have been studied in depth during the past two decades due to their unique structure and properties. Transition metal (TM) intercalation of layered materials have been proven as an effective way to introduce new physical properties, such as tunable 2D magnetism, but the direct growth of atomically thin heteroatoms-intercalated layered materials remains untapped. Herein, we directly synthesize various ultrathin heteroatoms-intercalated 2D layered materials (UHI-2DMs) through flux-assisted growth (FAG) approach. Eight UHI-2DMs (V1/3NbS2, Cr1/3NbS2, Mn1/3NbS2, Fe1/3NbS2, Co1/3NbS2, Co1/3NbSe2, Fe1/3TaS2, Fe1/4TaS2) were successfully synthesized. Their thickness can be reduced to the thinnest limit (bilayer 2D material with monolayer intercalated TM), and magnetic ordering can be induced in the synthesized structures. Interestingly, due to the possible anisotropy-stabilized long-range ferromagnetism in Fe1/3TaS2 with weak interlayer coupling, the layer-independent magnetic ordering temperature of Fe1/3TaS2 was revealed by magneto-transport properties. This work establishes a general method for direct synthesis of heteroatom-intercalated ultrathin 2D materials with tunable chemical and physical properties.

Evaluation of lignin and dip coating for elemental analysis by thin film microextraction followed by laser-induced breakdown spectroscopy

Separation and preconcentration procedures are often necessary to eliminate interferents, enhance sensitivity, and improve detection limits. Conventional solid-phase extraction (batch) finds extensive applications in the determination of various analytes, particularly in low concentrations and complex matrices such as environmental, food, and biological samples. However, drawbacks include high reagent consumption, time-consuming sample processing and low analytical throughput. To address these issues and promote Green Analytical Chemistry (GAC), novel methods have emerged, with solid-phase and liquid-phase microextraction being notable examples. Thin Film Microextraction (TFME) represents an innovative approach involving a solid support coated with a thin layer of adsorbent material, attached to a rod and immersed in the sample solution. Extracted analytes can be quantified either after desorption (elution) or directly on the thin film. This article aims to explore TFME's potential when combined with Laser-Induced Breakdown Spectroscopy (LIBS) for Cd, Cr and Ni determination using lignin as adsorbent material deposited on a solid substrate by dip coating. Under optimized conditions, limits of detection obtained were 1.76 μg kg−1 (Cd), 5.72 μg kg−1 (Cr), and 3.27 μg kg−1 (Ni). The accuracy of the proposed method was evaluated through the analysis of a certified reference material (ERM® CA713), drinking and tap water.

Seismic vulnerability distribution of the earthquake prone area in Central Aceh

Abstract Central Aceh is known as an earthquake-prone area due to the presence of the Sumatra Fault and secondary fault crossing the area resulting the M 6.1 earthquake in 2013. The objective of the research is to investigate seismic vulnerability of Central Aceh. Microtremor observations were conducted at 25 locations in Central Aceh analysed using the Horizontal to Vertical Spectral Ratio (HVSR). Seismic amplification is represented by the maximum values of H/V. The dominant frequency f0 representing the sediment thickness was obtained when the H/V curve is maximum. The frequency values ranged from 14.9 to 25.9 Hz, and the seismic vulnerability values varied from 0.02 to 3.1. The top soil consists of thin layers of sedimentary material dominated by tertiary rocks. The rocks are classified as Type IV and Class I based on the dominant frequency values. This result is consistent with the geology, consisting of sedimentary and volcanic rocks. Areas with a seismic vulnerability value > 1.0 is considered to have a high risk of earthquake damage because they are likely to experience earthquake amplification. Areas with seismic vulnerability value > 1.0 are found in West Aceh and the Geureudong volcano area.

Fabrication of pbs films for air mass filter of solar simulator

The production of solar panels is continuously increasing due to increasing demands at industrial and residential levels. This also leads to an increasing demand for solar simulator testing tools. A solar simulator is a tool to assess a solar panel's performance in lab and industry scales. One of the main components of the solar simulator is the Air Mass Filter (AMF). The primary function of AMF is to remove unwanted wave bands from the solar simulator light source (e.g., Xe arc lamp) so that the filtered spectrum is commensurate to that of solar irradiation. An AMF can be produced by fabricating a thin material layer on a transparent substrate like glass. The film would absorb certain wave bands in different ways. This paper reports the fabrication of the chalcogenide PbS thin films for applying AMF. The thermal evaporation technique is used for the film fabrication. PbS is known for its versatility for applications in different optical devices due to its tailorable optical properties. Different amounts (in grams) of PbS source powders are used to deposit the PbS thin films. The optical properties of the films are then examined using UV-Vis spectroscopy. The distributions of the transmittance intensity of the Xe-arc-lamp light with and without the use of the films as an optical filter are then examined using a solar simulator. From the experiments, the film deposited using a 0.012 g PbS powder source is regarded as the optimum one regarding the transmittance intensity distribution.

Efficient modeling of heat conduction in multiply bonded composites covered with thermal barrier coating

In engineering practice, 3D (three-dimensional) composites consisting of multiply thin layers of anisotropic materials have been extensively applied. For enhancing their thermal endurance, the composites are often coated with a very thin layer of medium with low conductivity, usually referred to as the thermal barrier coating (TBC). This paper presents an efficient algorithm for the boundary element method (BEM) to accurately compute the nearly singular integrals in modeling 3D anisotropic heat conduction in TBC-coated composites, consisting of several thin anisotropic media. This algorithm is especially efficient because no analytical transformation of the integrands is involved as proposed in the past. When the TBC is prescribed with Dirichlet condition, a new equivalent convective condition is proposed to replace the TBC modeling. Moreover, thin films of adhesives on interfaces are considered by introducing interfacial conductance. In the end, several examples are presented.

The Effect of Applying UV LED-Cured Varnish to Metalized Printing Elements during Cold Foil Lamination

The coating process involves applying a thin material layer to a surface to engender it with specific desirable properties or enhance its performance. In the production of print media (labels, packaging, printed textiles, and promotional materials), the standard functions of the coating process include visual decoration, which involves the addition of appealing colors, textures, and patterns. A pertinent issue in the printing industry is that at present, the predominant coating process uses printing and coating technologies (gravure, flexo, letterset, letterpress, screen printing, inkjet, and electrophotography) and lamination (i.e., attaching decorative layers of materials, such as films or fabrics). In this paper, we present a new method for testing the efficiency with which different-sized metalized printing elements (using gold foil) may be applied to paper substrates; to do so, we gradually vary the amount UV-cured inkjet varnish (or adhesive) that is applied. To test the effectiveness of this method in producing metallic visual effects, we utilize seven different thicknesses of UV-cured varnish with the aid of modular piezo inkjet heads (KM1024 iLHE-30) and three different printing speeds. Our research shows that to achieve optimal production of cold metalized foil, a 21 µm layer should be deposited, and the substrate should move at a speed of 0.30 m/s.

Indentation of a thin incompressible layer with finite friction

If a thin layer of an incompressible elastic material is pressed between two plane surfaces, the effective stiffness is very sensitive to the presence of frictional slip. This effect is investigated using a low-order polynomial representation of the through-thickness displacement profile. Results show good agreement with finite element studies and also show that the stiffness is significantly affected by that part of the layer [if any] outside the loaded region. The same result is then used in convolution to approximate the load–displacement response for a convex indenter.

Polarization-independent Spatial Kramers-Kronig medium for omnidirectional reflectionless absorption of unpolarized light

Spatial Kramers-Kronig (KK) media offer a possible route to obtain omnidirectional light absorption within a thin layer of material. However, the experimental realizations are typically limited to a specific polarization, i.e., either transverse electric (TE) or transverse magnetic (TM), hence lacking specific implementations for the absorption of unpolarized light. In this work, we propose theoretically and demonstrate experimentally a polarization-independent KK medium which performs omnidirectional reflectionless absorption for both TE and TM polarized waves. Our design makes use of a special matryoshka metamaterial, whose electric and magnetic responses can be independently controlled with minimized crosstalk. To extend the absorption spectrum, the inner truncation boundary of the KK medium is set at a position far away from the spatial Lorentz resonance, where the constitutive parameter of the metamaterial remains unitary over a broad frequency band. A mini anechoic chamber, 6.83-wavelength in diameter, is constructed using the designed annulus-shaped KK medium. The measured fields for both TE and TM polarizations confirm the polarization-independent omnidirectional and nearly reflectionless absorption in a broadband frequency range.

Graphene-integrated microring cavity for electronically controlled molecular fingerprinting

Microring cavities supporting whispering-gallery modes (WGMs) have an exceptionally high quality factor (Q) and a small mode volume, greatly improving the interaction between light and matter, which has attracted great attention in various microscale/nanoscale photonic devices and potential applications. Recently, two-dimensional van der Waals (vdW) materials such as graphene have emerged as a potential platform for next-generation biosensing by enabling the confinement of light fields at the nanoscale. Here, we propose what we believe to be a novel approach to achieve molecular fingerprint retrieval by integrating graphene into a microring cavity and conducting numerical simulations using the finite-difference time-domain (FDTD) method. The hybrid cavity exhibits high-quality WGMs with a high Q factor of up to 800. Moreover, the resonant wavelength can be electronically controlled through modulation of graphene’s Fermi level, enabling coverage of the entire free spectral range at infrared frequencies. By depositing a thin layer of biomolecular material (e.g., CBP) onto the surface of our hybrid cavity, we are able to accurately read out the absorption spectrum at multiple spectral points, thereby achieving broadband fingerprint retrieval for the targeted biomolecule. Our results pave the way for highly sensitive, chip-integrated, miniaturized, and electrically modulated infrared spectroscopy biosensing.

Physical Mechanism of Nanocrystalline Composite Deformation Responsible for Fracture Plastic Nature at Cryogenic Temperatures.

In this work, we consider the physical basis of deformation and fracture in layered composite nanocrystalline/amorphous material-low-melting crystalline alloy in a wide temperature range. Deformation and fracture at the crack tip on the boundary of such materials as nanocrystalline alloy of the trademark 5BDSR, amorphous alloy of the trademark 82K3XSR and low-melting crystalline alloy were experimentally investigated. The crack was initiated by uniaxial stretching in a temperature range of 77-293 K. A theoretical description of the processes of deformation and fracture at the crack tip is proposed, with the assumption that these processes lead to local heating and ensure the plastic character of crack growth at liquid nitrogen temperatures. The obtained results improve the theoretical understanding of the physics of fracture at the boundary of nanocrystalline and crystalline alloys in a wide temperature range. The possibility of preserving the plastic nature of fracture in a thin boundary layer of crystalline-nanocrystalline material at cryogenic temperatures has been experimentally shown.

A high-precision wound healing assay based on photosensitized culture substrates.

Quantitative assessment of cell migration in vitro is often required in fundamental and applied research from different biomedical areas including wound repair, tumor metastasis or developmental biology. A collection of assays has been established throughout the years like the most widely used scratch assay or the so-called barrier assay. It is the principle of these assays to introduce a lesion into an otherwise confluent monolayer in order to study the migration of cells from the periphery into this artificial wound and determine the migration rate from the time necessary for wound closure. A novel assay makes use of photosensitizers doped into a polystyrene matrix. A thin layer of this composite material is coated on the bottom of regular cell culture ware showing perfect biocompatibility. When adherent cells are grown on this coating, resonant excitation of the photosensitizer induces a very local generation of 1O2, which kills the cells residing at the site of illumination. Cells outside the site of illumination are not harmed. When excitation of the photosensitizer is conducted by microscopic illumination, high-precision wounding in any size and geometry is available even in microfluidic channels. Besides proof-of-concept experiments, this study gives further insight into the mechanism of photosensitizer-mediated cell wounding.

Composite Coatings Applied to Fresh and Blanched Chayote (Sechium edule) and Modeling of the Drying Kinetics and Sorption Isotherms.

Sustainable methods such as convective drying have regained interest in reducing the loss and waste of food produce. Combined with techniques like blanching and edible coatings, they could serve as useful tools in food processing development. Composite coatings comprising pectin, soy protein isolate, and xanthan gum were optimized using response surface methodology with the Box-Behnken design. This optimization aimed to investigate their effects on the moisture content, water activity, total color, and rehydration ratio of fresh and blanched chayote slices. Additionally, the study explored the modeling of the drying kinetics and sorption isotherms of chayote (Sechium edule) slices. Soy protein and xanthan gum were found to primarily influence the moisture content (ranging from 5.44% to 9.93%), and pectin influenced water activity (033 to 0.53) of the fresh-coated chayote, while pectin affected the aw (2.13-8.28) and rehydration of the blanch-coated chayote. The optimized formulations for both fresh and blanched chayote were utilized to assess the drying kinetics behavior and sorption isotherms. The best fit (R2: 0.996 to 0.999) was achieved with the parabolic model for thin-layer materials. Furthermore, the sorption isotherms of chayote displayed a Type IV behavior, with the BET model being the most suitable for describing the sorption behavior of materials with low water activity. The predicted values offer valuable data for optimizing processing conditions to enhance the quality and stability of dried chayote.