Self-assembled Layer Research Articles

A Multifunctional Dye Molecule as the Interfacial Layer for Perovskite Solar Cells.

In perovskite solar cells (PSCs), defects in the interface and mismatched energy levels can damage the device performance. Improving the interface quality is an effective way to achieve efficient and stable PSCs. In this work, a multifunctional dye molecule, named ThPCyAc, was designed and synthesized to be introduced in the perovskite/HTM interface. On one hand, various functional groups on the acceptor unit can act as Lewis base to reduce defect density and suppress nonradiative combinations. On the other hand, the stepwise energy-level alignment caused by ThPCyAc decreases the accumulation of interface carriers for facilitating charge extraction and transmission. Therefore, based on the ThPCyAc molecule, the devices exhibit elevated open-circuit voltage and fill factor, resulting in the best power conversion efficiency (PCE) of 23.16%, outperforming the control sample lacking the interface layer (PCE = 21.49%). Excitingly, when attempting to apply it as a self-assembled layer in inverted devices, ThPCyAc still exhibits attractive behavior. It is worth noting that these results indicate that dye molecules have great potential in developing multifunctional interface materials to obtain higher-performance PSCs.

Triblock PolyA-Mediated Protein Biosensor Based on a Size-Matching Proximity Hybridization Analysis.

The antibodies in the natural biological world utilize bivalency/multivalency to achieve a higher affinity for antigen capture. However, mimicking this mechanism on the electrochemical sensing interface and enhancing biological affinity through precise spatial arrangement of bivalent aptamer probes still pose a challenge. In this study, we have developed a novel self-assembly layer (SAM) incorporating triblock polyA DNA to enable accurate organization of the aptamer probes on the interface, constructing a "lock-and-key-like" proximity hybridization assay (PHA) biosensor. The polyA fragment acts as an anchoring block with a strong affinity for the gold surface. Importantly, it connects the two DNA probes, facilitating one-to-one spatial proximity and enabling a controllable surface arrangement. By precisely adjusting the length of the polyA fragment, we can tailor the distance between the probes to match the molecular dimensions of the target protein. This design effectively enhances the affinity of the aptamers. Notably, our biosensor demonstrates exceptional specificity and sensitivity in detecting PDGF-BB, as confirmed through successful validation using human serum samples. Overall, our biosensor presents a novel and versatile interface for proximity assays, offering a significantly improved surface arrangement and detection performance.

Flexible 3D Plasmonic Web Enables Remote Surface Enhanced Raman Spectroscopy.

Nanoplasmonic materials concentrate light in specific regions of dramatic electromagnetic enhancement: hot spots. Such regions can be employed to perform single molecule detection via surface-enhanced Raman spectroscopy. However, this phenomenon is challenging since hot spots are expected to be highly intense/abundant and positioning of molecules within such hot spots is crucial to manage with ultrasensitive SERS. Herein, it is discovered that a 3D plasmonic web embedded within a biohybrid (3D-POWER) exhibits plasmonic transmission, spontaneously absorbs the analyte, and meets these so much needed criteria in ultrasensitive SERS. 3D-POWER is built with nanopaper and self-assembled layers of graphene oxide and gold nanorods. According to in silico experiments, 3D-POWER captures light in a small region and performs plasmonic field transmission in a surrounding volume, thereby activating a plasmonic web throughout the simulated volume. The study also provides experimental evidence supporting the plasmonic field transport ability of 3D power, which operates as a SERS signal carrier (even beyond the apparatus field of view), and the ultrasensitive behavior of this ecofriendly and flexible material facilitating yoctomolar limit of detection. Besides, 3D-POWER is proven useful in food and biofluids analysis. It is foreseen that 3D-POWER can be employed as a valuable platform in (bio)analytical applications.

Application of a Self-Assembly Sensing Layer to Grating Sensor Cabinets for Biomedical Sensing of Rheumatoid Arthritis Antigen–Antibodies

Application of a Self-Assembly Sensing Layer to Grating Sensor Cabinets for Biomedical Sensing of Rheumatoid Arthritis Antigen–Antibodies

A superhydrophilic and robust fabric, featuring self-assembled layers of chitosan and carbon nanotubes, facilitates high-throughput oil–water separation

Petroleum pollution and industrial emissions of organic pollutants have become significant issues affecting both ecological and human living environments. High-performance oil–water separation membranes, due to their advantages such as low cost, environmental friendliness, and ease of operation, hold vast application prospects. Therefore, the development of efficient oil–water separation membranes is crucial. We propose a clever approach involving the synergistic self-assembly of chitosan (CS) and hydroxylated multi-walled carbon nanotubes (MWCNTs) on cotton fabric to construct a rough structure. Combined with hydrophilic modification using polyvinyl alcohol (PVA), not only does this enhance wettability, but it also addresses challenges related to mechanical strength and dispersibility of cotton fabric. The resulting CMF-PVA fabric performs well under challenging conditions, exhibiting excellent separation efficiency and permeance. Particularly noteworthy is that CMF-PVA achieves separation efficiencies exceeding 99.33 % for various organic substances, with a water flux reaching 35,476.52 L m−2 h−1 and a surfactant-stabilized emulsion permeance of 1199.0 L m−2 h−1·bar−1. Furthermore, CMF-PVA demonstrates outstanding mechanical durability under harsh conditions and excellent acid-base resistance. This method harnesses the inherent properties of CS and MWCNT self-assembly while enhancing the material's applicability on cotton fabric through hydrophilic modification. CMF-PVA fabric is poised to enhance selectivity, efficiency, anti-pollution properties, and accessibility in oil–water separation technology.

Theoretical and experimental research of polyelectrolyte multilayer membrane prepared by layer by layer self-assembly

Layer-by-layer self-assembly of polyelectrolytes is one of the most promising methods for preparing nanofiltration membranes. Here poly (sodium 4-styrenesulfonate) (PSS) and poly (diallyldim-ethylammonium chloride) (PDADMAC) were chosen to prepare polyelectrolyte multilayer (PEM) membrane. The effects of background salt concentration, PSS concentration, background salt types, the number of layers and the outermost functional groups on the separation performance of the PEM were investigated systematically. Molecular dynamic simulation was employed to simulate the influence of background salt on the diffusion of PDADMAC. The simulation results agree well with the experimental results. The optimized (PSS/PDADMAC)4.5 membrane with Na2SO4 as background salt shows permeance of 15.9 LMH/bar, Na2SO4 rejection of 98.2 %, and an excellent stability. Our study provides both theoretical and experimental supports for the preparation of PEM membranes using LBL method.

Chemical Instability-Induced Wettability Patterns on Superhydrophobic Surfaces.

Chemical instability of liquid-repellent surfaces is one of the nontrivial hurdles that hinders their real-world applications. Although much effort has been made to prepare chemically durable liquid-repellent surfaces, little attention has been paid to exploit the instability for versatile use. Herein, we propose to create hydrophilic patterns on a superhydrophobic surface by taking advantage of its chemical instability induced by acid solution treatment. A superhydrophobic Cu(OH)2 nanoneedle-covered Cu plate that shows poor stability towards HCl solution (1.0 M) is taken as an example. The results show that 2.5 min of HCl solution exposure leads to the etching of Cu(OH)2 nanoneedles and the partial removal of the self-assembled fluoroalkyl silane molecular layer, resulting in the wettability transition from superhydrophobocity to hydrophilicity, and the water contact angle decreases from ~160° to ~30°. Hydrophilic dimples with different diameters are then created on the superhydrophobic surfaces by depositing HCl droplets with different volumes. Afterwards, the hydrophilic dimple-patterned superhydrophobic surfaces are used for water droplet manipulations, including controlled transfer, merging, and nanoliter droplet deposition. The results thereby verify the feasibility of creating wettability patterns on superhydrophobic surfaces by using their chemical instability towards corrosive solutions, which broadens the fabrication methods and applications of functional liquid-repellent surfaces.

Efficient self-powered cathodic corrosion protection system based on multi-layer grid synergistic triboelectric nanogenerator and power management circuits

The last few years have seen a boom in the use of triboelectric nanogenerators (TENGs) for capturing wave energy in the ocean. This work reports a multi-layer grid synergistic triboelectric nanogenerator (MLGS-TENG). In this work, the independent layer triboelectric nanogenerator in the grid format is skillfully employed, and the design of the multi-layer parallel structure can effectively increase the capture rate of blue energy in the ocean. The shell of the triboelectric nanogenerator adopts a gyroscopic structure, which, when combined with its internal architecture, operates effectively on the surface of ocean waves. Moreover, it can be very effective in harvesting low-frequency wave energy in the ocean and converting it into mechanical energy, and then converting it into electrical energy through the friction of the internal self-assembly layer. In low-frequency mechanical tests, when the frequency is about 1 Hz and the load impedance is 400 MΩ, the peak power output of the generator in a single layer can reach 77 mW/m2. Given the excellent energy harvesting performance of MLGS-TENG, it is applied to build a high-efficiency cathodic corrosion protection system in conjunction with a buck rectifier circuit. This work is of great significance for the wide application of triboelectric nanogenerators in the marine environment and provides a feasible way to ensure the long-term stability of offshore platforms.

Engineering a robust, multifunctional superhydrophobic/oleophobic microporous aluminum surface via a two-step chemical etching process

Surfaces with unique wettability properties are gaining attention for their widespread applications. Particularly, superhydrophobic surfaces, known for their remarkable water-repellent properties and low adhesion, have gained substantial interest in recent years owing to their versatile applications. Despite their versatile applications, the durability of such surfaces faces challenges like mechanical abrasion, chemical deterioration, and environmental factors, limiting their effectiveness in real-world scenarios. In this study, we successfully fabricated a mechanically robust, cost-effective, and easy-to-process superhydrophobic surface on an aluminum substrate using a two-step chemical etching process. Initially, the hierarchical microporous (HMP) structure was created through chemical etching, followed by the deposition of a self-assembled layer of PFOTS onto the fabricated aluminum substrate, attaining superhydrophobic and oleophobic properties. The surface exhibits remarkable superhydrophobicity with a water contact angle of 162°, while coupled with oleophobic characteristics against a wide spectrum of oils with surface tensions ranging from 21.5–63.3 mN m − 1. We conducted comprehensive characterizations of surface morphology and chemical composition, while also investigating the impact of surface morphology on wettability, physicochemical stability, and antibacterial properties. Mechanical testing revealed that the surface maintained its superhydrophobicity even after undergoing linear abrasion for a distance of 120 cm under an applied pressure of 12.25 kPa. Furthermore, the surface displayed self-cleaning, and anti-fouling, along with significant antibacterial properties against Staphylococcus aureus bacteria, creating a 23 mm zone of inhibition. We believe the proposed method will inspire the fabrication of large-scale superhydrophobic metallic surfaces endowed with multifunctional properties, making them highly suitable for a wide range of industrial applications.

Rapid Fabrication of High-Resolution Flexible Electronics via Nanoparticle Self-Assembly and Transfer Printing.

Printed electronic technology serves as a key component in flexible electronics and wearable devices, yet achieving compatibility with both high resolution and high efficiency remains a significant challenge. Here, we propose a rapid fabrication method of high-resolution nanoparticle microelectronics via self-assembly and transfer printing. The tension gradient-electrostatic attraction composite-induced nanoparticle self-assembly strategy is constructed, which can significantly enhance the self-assembly efficiency, stability, and coverage by leveraging the meniscus Marangoni effect and the electric double-layer effect. The close-packed nanoparticle self-assembly layer can be rapidly formed on microstructure surfaces over a large area. Inspired by ink printing, a transfer printing strategy is further proposed to transform the self-assembly layer into conformal micropatterns. Large-area, high-resolution (2 μm), and ultrathin (1 μm) nanoparticle microelectronics can be stably fabricated, yielding a significant improvement over fluid printing methods. The unique deformability, recoverability, and scalability of nanoparticle microelectronics are revealed, providing promising opportunities for various academic and real applications.

Evaluation of Interfacial Structure of Self-Assembled Nanoparticle Layers: Use of Standard Deviation between Calculated and Experimental Drop Profiles as a Novel Method.

The self-assembly of nanoparticles (NPs) at interfaces is currently a topic of increasing interest due to numerous applications in food technology, pharmaceuticals, cosmetology, and oil recovery. It is possible to create tunable interfacial structures with desired characteristics using tailored nanoparticles that can be precisely controlled with respect to shape, size, and surface chemistry. To address these functionalities, it is essential to develop techniques to study the properties of the underlying structure. In this work, we propose an experimental approach utilizing the standard deviation of drop profiles calculated by the Laplace equation from experimental drop profiles (STD), as an alternative to the Langmuir trough or precise microscopic methods, to detect the initiation of closely packed conditions and the collapse of the adsorbed layers of CTAB-nanosilica complexes. The experiments consist of dynamic surface/interfacial tension measurements using drop profile analysis tensiometry (PAT) and large-amplitude drop surface area compression/expansion cycles. The results demonstrate significant changes in STD values at the onset of the closely packed state of nanoparticle-surfactant complexes and the monolayer collapse. The STD trend was explained in detail and shown to be a powerful tool for analyzing the adsorption and interfacial structuring of nanoparticles. Different collapse mechanisms were reported for NP monolayers at the liquid/liquid and air/liquid interfaces. We show that the interfacial tension (IFT) is solely dependent on the extent of interfacial coverage by nanoparticles, while the surfactants regulate only the hydrophobicity of the self-assembled complexes. Also, the irreversible adsorption of nanoparticles and the increasing number of adsorbed complexes after the collapse were observed by performing consecutive drop surface compression/expansion cycles. In addition to a qualitative characterization of adsorption layers, the potential of a quantitative calculation of the parameter STD such as the number of adsorbed nanoparticles at the interface and the distance between them at different states of the interfacial layer was discussed.

Sustainable 3D-printed β-galactosidase immobilization coupled with continuous-flow reactor for efficient lactose-free milk production

The production of low-lactose and lactose-free milk remains a critical challenge. Novel enzyme immobilization integrated with the flow reactor that could be applied to hydrolyze milk with cost-effectiveness, facilitation, and safety is highly expected. Here, we present a novel continuous-flow bioreactor loaded with β-galactosidase (β-Gal) covalently immobilized 3D-printed scaffolds for the production of lactose-free milk. 3D-printed polylactic acid (PLA) scaffolds modified by self-assembly of polyethyleneimine and sodium hyaluronate layers are rapidly branched with functional groups, followed by covalent immobilization of β-Gal using genipin as the cross-linker. The use of genipin allows efficient and stable immobilization of the enzyme (92.87 % immobilization efficiency), and the immobilized enzyme retains 90.53 % activity after 6th repeated use. Moreover, the 3D-printed scaffolds integrated into the flow reactor perturbed the fluids in the different reactors through directional channels, which improved the internal mass transfer to achieve high catalytic activity (94.20 % lactose hydrolysis efficiency). The lactose residues of milk reacted in the β-Gal flow reactor for 6 and 12 h were 1.87 g dL-1 and 0.38 g dL-1, which fully met the requirements of the national food safety standards for low-lactose and lactose-free milk. Due to the high efficiency of enzyme immobilization and the stable catalytic activity of the reactor, it has a broad application prospect for the production of low-lactose and lactose-free milk and other biocatalytic fields.

Self-Assembled Layer of Organic Phosphonic Acid Enables Highly Stable MnO2 Cathode for Aqueous Znic Batteries.

Manganese dioxide (MnO2) is an attractive cathode material for aqueous zinc batteries (AZBs) owing to its environmental benignity, low cost, high operating voltage, and high theoretical capacity. However, the severe dissolution of Mn2+ leads to rapid capacity decay. Herein, a self-assembled layer of amino-propyl phosphonic acid (AEPA) on the MnO2 surface, which significantly improves its cycle performance is successfully modified. Specifically, AEPA can be firmly attached to MnO2 through a strong chemical bond, forming a hydrophobic, and uniform organic coating layer with a few nanometers thickness. This coating layer can significantly inhibit the dissolution of Mn2+ by avoiding the direct contact between the electrolyte and cathode, thus enhancing thestructural integrity and redox reversibility of MnO2. As a result, the MnO2@AEPA cathode achieves a high reversible capacity of 223mAhg-1 at 0.5Ag-1 and a high capacity retention of 97% after 1700cycles at 1Ag-1. This work provides new insights in developing stable Mn-based cathodes for aqueous batteries.

A reversible self-assembled molecular layer for lithium metal batteries with high energy/power densities at ultra-low temperatures

We have demonstrated a molecular interface engineering strategy to address the design dilemma of low-temperature electrolytes for lithium metal batteries.

On-surface polymerization reactions of dibrominated hexaphenylbenzene influenced by densely packed self-assembly.

Controlled bottom-up fabrication of molecular nanostructures through on-surface reactions of tailor-made precursors is of scientific and technological interest. Recently, on-surface polymerization reactions influenced by precursor self-assembly have been reported. Thus, a fundamental understanding of the reaction process is a prerequisite for controlled formation. Herein, we report on the influence of molecular self-assembly of dibrominated hexaphenylbenzene (Br2-HPB) on the on-surface polymerization reactions on a Au(111) substrate. By using low-temperature scanning tunnelling microscopy (STM), we find that the polymerization of Br2-HPB proceeds while maintaining the long-range ordered self-assembly, despite a decrease in HPB-HPB distance due to debromination and successive covalent bonding of Br2-HPB. From the STM investigations of the polymerization process, we conclude that the polymerization of Br2-HPB is accompanied by molecular rotations to maintain the periodic array of the self-assembled structure, contrary to the conventional understanding of the polymerization of the self-assembled precursor layer.

Integrating the amino-functionalized MOF-5 film with the silver nanoparticle substrate for a high SERS enhancement effect and long-term stability

SERS effective region of the plasmonic electric field is strongly enhanced by the self-assembled layer of MOF-5-NH2.

Influence of the 2,5-bis(pentadecyloxy)terephthalic acid self-assembly layer on the structure and charge transfer properties of poly(p-phenylene vinylene) for application in organic solar cells

Representative procedure for the synthesis of the composite PPV/PDTPA and its potential application in organic solar cells.

LAYER-BY-LAYER SELF-ASSEMBLY APPROACH IN THE UV PROTECTIVE MODIFICATION OF ARAMID-BASED MATERIALS

This paper presents the Layer by Layer self-assembly (LbL) approach for developing the UV resistance of aramid yarns. Initially, a pretreatment was achieved by polyethyleneimine to obtain cationic surface charges on aramid yarns. Then zinc oxide and titanium dioxide nanoparticles were self-assembled on these yarns by the LbL process. The findings revealed that the LbL nano coatings significantly improved the UV resistance and tensile properties of the aramid yarns. This study highlights the unique opportunities offered by the LbL methodology to both modify aramid-based materials in mild conditions and provide an effective UV protection.

Spontaneously homogeneous alignment of liquid crystals on self-assembly organic rubrene

A novel spontaneously homogeneous liquid crystal (LC) alignment with self-assembled organic rubrene layer on the substrate surface has been reported. The spontaneous alignment technique without surface pre-treatment results in low cost, short processing time, and the room-temperature processing extends application to plastic device. The rubrene-nematic LC mixture is used to fabricate the LC cell. During the capillary filling, the LC molecules align in the flow direction. Meanwhile, the flow-induced LC alignment enforces the tetracene of the rubrene dopants along the flow direction because of the van der Waals and π–π interactions between the rubrene and LC molecules. Afterwards, the rubrene dopants spontaneously migrate onto substrate surface and self-assemble as the triclinic crystalline rubrene (TCR) with ribbon morphology. The LC alignment on TCR has a low pretilt angle, thereby providing a homogeneous LC alignment spontaneously. LC alignment on TCR shows a higher thermal stability compared to conventional polyimide due to the strong interactions of the rubrene and LC molecules. Moreover, the rubrene molecules remain in the bulk suppress the free-ions, decrease the rotational viscosity of LCs and hence shortening the response time of cell. The suppressed free-ions also decrease the screening effect on the substrate surfaces and hence the operation voltage of cell. The TCR structure on the substrate surface and the residual rubrene molecules dispersed in the bulk simultaneously contribute to the enhancement in electro-optical performance of the LC cell.

High-Stable Lead-Free Solar Cells Achieved by Surface Reconstruction of Quasi-2D Tin-Based Perovskites.

Tin halide perovskites are an appealingalternative to lead perovskites. However, owing to the lower redox potential of Sn(II)/Sn(IV), particularly under the presence of oxygen and water, the accumulation of Sn(IV) at the surface layer will negatively impact the device's performance and stability. To this end, this work has introduced a novel multifunctional molecule, 1,4-phenyldimethylammonium dibromide diamine (phDMADBr), to form a protective layer on the surface of Sn-based perovskite films. Strong interactions between phDMADBr and the perovskite surface improve electron transfer, passivating uncoordinated Sn(II), and fortify against water and oxygen. In situ grazing incidence wide-angle X-ray scattering (GIWAXS) analysis confirms the enhanced thermal stability of the quasi-2D phase, and hence the overall enhanced stability of the perovskite. Long-term stability in devices is achieved, retaining over 90% of the original efficiency for more than 200 hours in a 10% RH moisture N2 environment. These findings propose a new approach to enhance the operational stability of Sn-based perovskite devices, offering a strategy in advancing lead-free optoelectronic applications.