Showing papers on "Layer by layer published in 2022"

Achieving 15.81% and 15.29% efficiency of all-polymer solar cells based on layer-by-layer or bulk heterojunction structure

Abstract: Wide bandgap polymer donor PM6 and narrow bandgap polymer acceptor PY-IT were selected to construct all-polymer solar cells (all-PSCs) with layer-by-layer (LbL) or bulk heterojunction (BHJ) structure. The additive 1-chloronaphthalene...

There is still plenty of room for layer-by-layer assembly for constructing nanoarchitectonics-based materials and devices

Abstract: Nanoarchitectonics approaches can produce functional materials from tiny units through combination of various processes including atom/molecular manipulation, chemical conversion, self-assembly/self-organization, microfabrication, and bio-inspired procedures. Existing fabrication approaches can be regarded as fitting into the same concept. In particular, the so-called layer-by-layer (LbL) assembly method has huge potential for preparing applicable materials with a great variety of assembling mechanisms. LbL assembly is a multistep process where different components can be organized in planned sequences while simple alignment options provide access to superstructures, for example helical structures, and anisotropies which are important aspects of nanoarchitectonics. In this article, newly-featured examples are extracted from the literature on LbL assembly discussing trends for composite functional materials according to (i) principles and techniques, (ii) composite materials, and (iii) applications. We present our opinion on the present trends, and the prospects of LbL assembly. While this method has already reached a certain maturity, there is still plenty of room for expanding its usefulness for the fabrication of nanoarchitectonics-based materials and devices.

Efficient Semitransparent Layer‐by‐Layer Organic Photovoltaics via Optimizing Wide Bandgap and Narrow Absorption Polymer Layer Thickness

Abstract: Layer‐by‐layer organic photovoltaics (LbL‐OPVs) are fabricated using wide bandgap polymer D18 with narrow photon harvesting range in visible light region and narrow bandgap small molecular N3 with strong near‐infrared photon harvesting; the only difference is D18 layer thickness adjusted by spin coating speed. A 15.75% power conversion efficiency (PCE) is obtained from the LbL‐OPVs with D18 layer prepared under 7000 round per minute of spin coating condition; the corresponding D18/N3 layers have a 52.06% of average visible transmittance (AVT) in the spectral range from 370 to 740 nm. Based on the optimized D18/N3 layers, semitransparent LbL‐OPVs are built with 1 nm Au/(10, 15, 20 nm) Ag as the top electrode. The PCE and AVT of semitransparent LbL‐OPVs can be simultaneously adjusted by altering Ag layer thickness due to its variable reflectance and conductivity of top electrode dependence on Ag layer thickness. The PCE/AVT of 12.58%/22.81%, 13.80%/15.09%, and 14.85%/9.48% can be individually achieved from the semitransparent LbL‐OPVs with 10, 15, or 20 nm‐thick Ag layer, which should be among the highest values of semitransparent OPVs based on bulk heterojunction or LbL structures. Adjusting donor layer thickness may be an effective method to construct efficient semitransparent LbL‐OPVs.

Molecular-Scale Manipulation of Layer Sequence in Heteroassembled Nanosheet Films toward Oxygen Evolution Electrocatalysts.

Abstract: Flocculation or restacking of different kinds of two-dimensional (2D) nanosheets into heterostructure nanocomposites is of interest for the development of high-performance electrode materials and catalysts. However, lacking a molecular-scale control on the layer sequence hinders enhancement of electrochemical activity. Herein, we conducted electrostatic layer-by-layer (LbL) assembly, employing oxide nanosheets (e.g., MnO2, RuO2.1, reduced graphene oxide (rGO)) and layered double hydroxide (LDH) nanosheets (e.g., NiFe-based LDH) to explore a series of mono- and bilayer films with various combinations of nanosheets and sequences toward oxygen evolution reaction (OER). The highest OER activity was attained in bilayer films of electrically conductive RuO2.1 nanosheets underlying catalytically active NiFe LDH nanosheets with mixed octahedral/tetrahedral coordination (NiFe LDHTd/Oh). At an overpotential of 300 mV, the RuO2.1/NiFe LDHTd/Oh film exhibited an electrochemical surface area (ECSA) normalized current density of 2.51 mA cm-2ECSA and a mass activity of 3610 A g-1, which was, respectively, 2 and 5 times higher than that of flocculated RuO2.1/NiFe LDHTd/Oh aggregates with a random appearance of a surface layer. First-principles density functional theory calculations and COMSOL Multiphysics simulations further revealed that the improved catalytic performance was ascribed to a substantial electronic coupling effect in the heterostructure, in which electrons are transferred from exposed NiFe LDHTd/Oh nanosheets to underneath RuO2.1. The study provides insight into the rational control and manipulation of redox-active surface layers and conductive underlying layers in heteroassembled nanosheet films at molecular-scale precision for efficient electrocatalysis.

Layer-by-Layer Deposition: A Promising Environmentally Benign Flame-Retardant Treatment for Cotton, Polyester, Polyamide and Blended Textiles

Abstract: A detailed review of recent developments of layer-by-layer (LbL) deposition as a promising approach to reduce flammability of the most widely used fibers (cotton, polyester, polyamide and their blends) is presented. LbL deposition is an emerging green technology, showing numerous advantages over current commercially available finishing processes due to the use of water as a solvent for a variety of active substances. For flame-retardant (FR) purposes, different ingredients are able to build oppositely charged layers at very low concentrations in water (e.g., small organic molecules and macromolecules from renewable sources, inorganic compounds, metallic or oxide colloids, etc.). Since the layers on a textile substrate are bonded with pH and ion-sensitive electrostatic forces, the greatest technological drawback of LbL deposition for FR finishing is its non-resistance to washing cycles. Several possibilities of laundering durability improvements by different pre-treatments, as well as post-treatments to form covalent bonds between the layers, are presented in this review.

Polyelectrolyte Multilayered Capsules as Biomedical Tools

Abstract: Polyelectrolyte multilayered capsules (PEMUCs) obtained using the Layer-by-Layer (LbL) method have become powerful tools for different biomedical applications, which include drug delivery, theranosis or biosensing. However, the exploitation of PEMUCs in the biomedical field requires a deep understanding of the most fundamental bases underlying their assembly processes, and the control of their properties to fabricate novel materials with optimized ability for specific targeting and therapeutic capacity. This review presents an updated perspective on the multiple avenues opened for the application of PEMUCs to the biomedical field, aiming to highlight some of the most important advantages offered by the LbL method for the fabrication of platforms for their use in the detection and treatment of different diseases.

Advancing bone tissue engineering one layer at a time: a layer-by-layer assembly approach to 3D bone scaffold materials.

Abstract: The layer-by-layer (LbL) assembly technique has shown excellent potential in tissue engineering applications. The technique is mainly based on electrostatic attraction and involves the sequential adsorption of oppositely charged electrolyte complexes onto a substrate, resulting in uniform single layers that can be rapidly deposited to form nanolayer films. LbL has attracted significant attention as a coating technique due to it being a convenient and affordable fabrication method capable of achieving a wide range of biomaterial coatings while keeping the main biofunctionality of the substrate materials. One promising application is the use of nanolayer films fabricated by LbL assembly in the development of 3-dimensional (3D) bone scaffolds for bone repair and regeneration. Due to their versatility, nanoscale films offer an exciting opportunity for tailoring surface and bulk property modification of implants for osseous defect therapies. This review article discusses the state of the art of the LbL assembly technique, and the properties and functions of LbL-assembled films for engineered bone scaffold application, combination of multilayers for multifunctional coatings and recent advancements in the application of LbL assembly in bone tissue engineering. The recent decade has seen tremendous advances in the promising developments of LbL film systems and their impact on cell interaction and tissue repair. A deep understanding of the cell behaviour and biomaterial interaction for the further development of new generations of LbL films for tissue engineering are the most important targets for biomaterial research in the field. While there is still much to learn about the biological and physicochemical interactions at the interface of nano-surface coated scaffolds and biological systems, we provide a conceptual review to further progress in the LbL approach to 3D bone scaffold materials and inform the future of LbL development in bone tissue engineering.

Layer-by-layer assembly methods and their biomedical applications.

Abstract: Layer-by-layer (LbL) assembly has attracted much interest because of its ability to provide nanoscale control over film characteristics and because of a wide choice of available materials. The methods of LbL not only determine the process properties, but also directly affect film properties. In this review, we will discuss LbL methodologies that have been used in biomedical fields. Special attention is devoted to different properties arising from methods that allow for diverse biomedical applications, ranging from surface modification to tissue engineering. We conclude with a discussion of the current challenges and future perspectives.

Highly Efficient Layer-by-Layer Large-Scale Manufacturing Polymer Solar Cells with Minimized Device-to-Device Variations by Employing Benzothiadiazole-Based Solid Additives

Abstract: Layer-by-layer (LBL) processing approach is recently under intensive investigation to fabricate efficient polymer solar cells (PSCs) reconsidering its many positive aspects over bulk-heterojunction configuration. Moreover, with recently reported successful solid...

Atomic layer deposition and other thin film deposition techniques: From principles to film properties

Abstract: Thin film is a modern technology aimed at improving the structural, electrical, magnetic, optical, and mechanical properties of bulk materials. This technology has so far found applications in integrated circuits, semiconductor devices, transistors, light-emitting diodes, light crystal displays and photoconductors, rectifiers, solar cells, sensors, and micro-electromechanical systems (MEMS). Methods of thin film deposition such as physical and chemical vapor deposition (PVD and CVD), sputtering, spin and dip coatings, and spray pyrolysis have been utilized for several years. But in recent times, the atomic layer deposition (ALD) technique has attracted the attention of researchers. In this current review, we have explored the most used techniques in the depositions of thin film materials with a focus on the properties of film produced, and the advantages and disadvantages of each technique. Generally, it was observed that the quality of films produced by these techniques depends greatly on the choice of substrate, deposition temperature, temperature window, and precursor used. It concluded by identifying ALD as an optimum technique in depositing ultra-thin film materials due to its simplicity, reproducibility, control over film composition and thickness, and high conformal deposited films at the atomic level. This study has established the opportunity for upcoming researchers to have an insight of selecting the most suitable technique for their study in various fields of research. Finally, the challenges and future perspectives of deposition techniques were highlighted.

The Growth Mechanism of a Conductive MOF Thin Film in Spray‐based Layer‐by‐layer Liquid Phase Epitaxy

Abstract: The layer-by-layer liquid-phase epitaxy (LBL-LPE) method is widely used in preparing metal-organic framework (MOF) thin films with the merits of controlling thickness and out-of-plane orientation for superior performances in applications. The LBL-LPE growth mechanism related to the grain boundary, structure defect, and orientation is critical but very challenging to study. In this work, a novel "in-plane self-limiting and self-repairing" thin-film growth mechanism is demonstrated by the combination study of the grain boundary, structure defect, and orientation of Cu3 (HHTP)2 -xC thin film via microscopic analysis techniques and electrical measurements. This mechanism results a desired high-quality MOF thin film with preferred in-plane orientations at its bottom for the first time and is very helpful for optimizing the LBL-LPE method, understanding the growth cycle-dependent properties of MOF thin film, and inspiring the investigations of the biomimetic self-repairing materials.

High-Efficiency and Durable Flame Retardant Cotton Fabric with Good Physical and Mechanical Properties by Layer-by-Layer Assembly Polyethylenimine/Phytic Acid Coating

Abstract: ABSTRACT In this study, intumescent flame retardant coating of polyethylenimine/phytic acid (PEI/PA) with gradient structure was constructed on cotton fabric through a facile layer-by-layer (LBL) assembly method. The LOI value of coated cotton fabric reached over 40%, indicating excellent flame retardancy. Reasonable controlling the LBL assembly process of PEI/PA coating brought less influence to the physical properties of cotton fabrics. And the coated cotton fabric revealed good flame retardant washing durability. Thermogravimetric analysis results of coated cotton fabrics showed that PEI/PA flame retardant coating changed the thermal decomposition process and promoted char formation revealing the obviously condensed phase flame retardant action. SEM images of char residues revealed that PEI/PA flame retardant coating promoted to form the intumescent flame retardant (IFR) char layer showing obvious IFR action. This research provides novel strategy for the development of high-efficiency flame retardant cotton fabric with good durability and physical properties using a simple LBL assembly method.

Graphene Oxide-Cytochrome c Multilayered Structures for Biocatalytic Applications: Decrypting the Role of Surfactant in Langmuir-Schaefer Layer Deposition.

Abstract: Graphene, a two-dimensional single-layer carbon allotrope, has attracted tremendous scientific interest due to its outstanding physicochemical properties. Its monatomic thickness, high specific surface area, and chemical stability render it an ideal building block for the development of well-ordered layered nanostructures with tailored properties. Herein, biohybrid graphene-based layer-by-layer structures are prepared by means of conventional and surfactant-assisted Langmuir-Schaefer layer deposition techniques, whereby cytochrome c molecules are accommodated within ordered layers of graphene oxide. The biocatalytic activity of the as-developed nanobio-architectures toward the enzymatic oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt and decolorization of pinacyanol chloride is tested. The results show that the multilayer structures exhibit high biocatalytic activity and stability in the absence of surfactant molecules during the deposition of the monolayers.

Electrochemical Studies of LbL Films With Dawson Type Heteropolyanion Glassy Carbon Electrode Sensor Modified for Methyl Parathion Detection

Abstract: Rapid methyl parathion detection was measured using a fabricated glassy carbon electrode (GCE) sensor designed using the layer-by-layer (LBL) method. Multilayer assemblies were developed on the glassy carbon electrode by alternating depositions of anions and cations in which a Dawson Type Polyoxometalate β-K6[(P2W18O62·H2O)]·14H2O (∼P2W18 POM) and polyethyleneimine (PEI) stabilized silver nanoparticles (∼PEI-AgNPs) acted as anions and cations, respectively. The redox behavior of P2W18 POM within LBL assembly was carried out via cyclic voltammetry. This LBL assembly was thoroughly characterized by UV-Visible, FT-IR, XRD, AFM, and SEM techniques. The fabricate GCE sensor was investigated for the electrocatalytic activity to detect methyl parathion. The results clearly showed that the fabricated GCE sensor was successfully synthesized. More interestingly, the current response for detecting methyl parathion was found to be less than 1 ppm, proving that this fabricated GCE sensor may exhibit potential applications in the detection of targeted pesticide. Graphical Abstract

Transition-metal hydroxide nanosheets with peculiar double-layer structures as efficient electrocatalysts

Abstract: Single- or few-layer nanosheets with a molecular-level thickness may provide an ideal model for the fundamental investigation of layer-number-dependent properties. Herein, we report a new strategy for a selective synthesis of transition-metal-containing Co-Fe and Co-Ni-Fe hydroxide nanosheets with peculiar double-layer structures. A unique second-stage phase was obtained from topochemical oxidative intercalation of brucite-type metal hydroxides, e.g., Co5/6Fe1/6(OH)2 and Co2/3Ni1/6Fe1/6(OH)2, with a molar ratio of Fe fixed at 1/6. After anion exchange, the second-stage phase was exfoliated into double-layer hydroxide nanosheets with an average thickness of ∼1.9 nm, which was approximately twice that of their single-layer counterparts (∼1.0 nm). Electrocatalytic measurements combined with theoretic calculations revealed that the double-layer hydroxide nanosheets exhibited excellent oxygen evolution reaction (OER) catalytic activity and kinetics, outperforming their single-layer counterparts, which validates the great potential of transition-metal hydroxide nanosheets with both tunable composition and layer numbers for efficient electrocatalysis.