Electrostatic Assembly Research Articles

Regulated electron migration in sandwich-like m-Ti3C2/Fe3O4 composites derived from electrostatic assembly boosted electromagnetic wave absorption

Sandwich-like m-Ti3C2/Fe3O4 composites derived from electrostatic assembly exhibit highly effective electromagnetic (EM) wave absorption capacity. We demonstrate the influence of regulating electron hopping behaviors on EM characteristics and absorption performance.

Boosting photocatalytic H2O2 production in pure water over a plasmonic photocatalyst with polyethylenimine modification

A novel TiO2/PEI/AgNP plasmonic photocatalyst fabricated via electrostatic assembly and in situ polyethylenimine reduction for boosted H2O2 production is reported.

A universal approach to 'host' carbon nanotubes on a charge triggered 'guest' interpenetrating polymer network for excellent 'green' electromagnetic interference shielding.

The widespread use of miniaturized electronic gadgets today faces stiff reliability obstacles from factors like stray electromagnetic signals. The challenge is to design lightweight shielding materials that combine small volume and high-frequency operations to reliably reduce/eliminate electromagnetic interference. Herein, in the first of its kind, a sequential interpenetrating polymeric network (IPN) membrane was used to host a CNT construct through a stimuli-responsive trigger. The proposed construct besides being robust, sustainable, and scalable is a universal approach to fabricate a CNT construct where conventional strategies are not amenable. This approach of self-assembling counter-charged CNTs also maximizes the number of CNTs in the final construct, thereby greatly enhancing the shielding performance dominated by 90% absorption in a wide frequency band of 8.2-26.5 GHz. The IPN-CNT construct achieves specific shielding effectiveness in the range of ca. 1607-5715 dB cm2 g-1 by tuning the thickness of the CNT construct with an endearing green index (gs ≈ 1.8). The performance of such an ultra-thin, light-weight IPN-CNT construct remained unchanged when subjected to 10 000 bending cycles and on exposure to different chemical environments, indicating outstanding mechanical/chemical stability.

Construction of an antibacterial low-defect hybrid layer by facile PEI electrostatic assembly promotes dentin bonding.

Dentin bonding is the most common form of human tissue repair among tissue-biomaterial adhesions, concerning billions of people's oral health worldwide. However, insufficient adhesive infiltration in the demineralized dentin matrix (DDM) always produces numerous defects in the bonding interface termed the hybrid layer, which causes high levels of bacteria-related secondary dental diseases, and less than 50% of the bonding lasts more than 5 years. Therefore, it is urgent and vital to construct an antibacterial low-defect hybrid layer to solve the durability-related problems. A DDM with a hydrogel-like surface formed by the hydration of highly-anionic non-collagenous proteins (NCPs) is firstly used as a template to electrostatically assemble polyethyleneimine (PEI). The formation of a stable antibacterial polyelectrolyte complex of PEI/NCPs rapidly eliminates NCP hydration capacity and significantly improves the infiltration of various adhesives. Simultaneously, both the PEI during the assembly and the PEI-assembled DDM can directly destroy a biofilm of S. Mutans on the DDM. Consequently, a long-term antibacterial and low-defect hybrid layer is successfully created, which greatly improves the bonding effectiveness. This helps to improve the clinical treatment of bacteria-based dental diseases and the tooth-restoration repair effect and prevent secondary dental diseases, having significance in clinical dentistry and providing insights for other tissue-biomaterial adhesions.

Polyoxometalate-immobilized carbon nanotube constructs triggered by host-guest assembly result in excellent electromagnetic interference shielding.

In the era of fifth-generation networks and the Internet of Things, new classes of lightweight, ultrathin, and multifunctional electromagnetic interference (EMI) shielding materials have become inevitable prerequisites for the protection of electronics from stray electromagnetic signals. In the present study, for the first time, we have designed a unique nanohybrid composed of a copper-based polyoxometalate (Cu-POM)-immobilized carbon nanotube construct, having a micron (∼100 μm)-level thickness, through a facile vacuum-assisted filtration technique. In this course of study, a total of four Cu-POMs, two from each category of Keggin and Anderson bearing opposite charges, i.e., positive and negative, have been rationally selected to investigate the effects of the host-guest electrostatic interaction between CNT and POMs in the EMI shielding performance. This approach of the host-guest electrostatic assembly between Cu-based polyanionic oxo clusters and counter-charged CNTs in the construct synergistically enhances the EMI shielding performance compared to the individual components dominated by 90% absorption in the X-band (8.2-12.4 GHz) frequency regime. Further, mutable EMI SE can be achieved by tuning the concentration of POMs and CNTs with different weight ratios. Such Cu-POM-immobilized CNT constructs demonstrating excellent shielding (∼45 dB) are not amenable via any other conventional routes, including flakes and dispersion.

Self-assembled A-D-A type indacenodithiophene-based small conjugated molecule/TiO2 for enhancing the photocatalytic activity.

Herein, A-D-A type indacenodithiophene-based small conjugated molecule IDT-COOH and IDT-COOH/TiO2 photocatalysts with stable non-covalent bonding have been successfully synthesized via in situ electrostatic assembly. The self-assembled three-dimensional π-conjugation structure IDT-COOH with high crystallinity not only broadens the visible absorption to produce more photogenerated carriers but also provides directional charge-transfer channels to accelerate the charge mobility. Thus, 7 log inactivation of S. aureus in 2 h and 92.5% decomposition of TC in 4 h under visible light exposure are achieved for optimized 30% IDT-COOH/TiO2. The dynamic constants (k) of S. aureus disinfection and TC degradation for 30% IDT-COOH/TiO2 are 3.69 and 2.45 times compared to those of self-assembled IDT-COOH, respectively. The notable inactivation performance is among the best reported for conjugated semiconductor/TiO2 photocatalysts for photocatalytic sterilization. ˙O2-, e- and ˙OH are the primary reactive species in the photocatalytic process. The strong interfacial interaction between TiO2 and IDT-COOH is in favour of rapid charge transfer, which leads to enhanced photocatalytic performance. This work offers a feasible method to fabricate TiO2-based photocatalytic agents with a wide visible light response and improved exciton dissociation.

Molecular metal oxide cluster-soldered interpenetrating polymer network “hosts” carbon nanotube “guest” for green millimeter wave absorption

Copper-based Keggin-type polyoxometalate-soldered IPN-CNT construct has been designed through host–guest electrostatic assembly between counter-charged CNTs and Cu-POM-soldered charge-triggered IPN for enhanced millimeter wave absorption in X-band.

Electrostatic assembly of gold nanoparticle and metal-organic framework nanoparticles attenuates amyloid β aggregate-mediated neurotoxicity.

The deposition of amyloid β (Aβ) is a conventional pathological hallmark of Alzheimer's disease (AD). Consequently, the inhibition of Aβ aggregation combined with the disaggregation of Aβ fibrils is an important therapeutic method for AD treatment. In this study, a gold nanoparticle-decorated porous metal organic framework MIL-101(Fe) (AuNPs@PEG@MIL-101) was created as an Aβ inhibitor. The high positively charged MIL-101 induced a high number of Aβ40 to be absorbed or aggregated on the surface of nanoparticles. In addition, AuNPs improved the surface property of MIL-101, causing it to uniformly bind Aβ monomers and Aβ fibrils. Thus, this framework can efficiently suppress extracellular Aβ monomer fibrillation and disrupt the preformed Aβ fibers. AuNPs@PEG@MIL-101 also decreases intracellular Aβ40 aggregation and the amount of Aβ40 immobilized on the cell membrane, thus protecting PC12 cells from Aβ40-induced microtubular defects and cell membrane damage. In summary, AuNPs@PEG@MIL-101 shows great potential for application in AD therapy.

Electrostatic assemblies of molecularly imprinted polymers on the surface of electrospun nanofiber membranes for the point-of-care detection of thiodiglycol, a sulfur mustard poisoning metabolic marker.

In this study, molecularly imprinted polymers (MIPs) were assembled on the surface of ethylene imine polymer (PEI)/poly(vinyl alcohol) (PVA) electrospun nanofiber membranes for the point-of-care testing (POCT) of thiodiglycol (TDG), a sulfur mustard poisoning metabolic marker, using concentrated gold nanoparticles (AuNPs) as the signal reporting units. The MIPs/PEI/PVA nanofiber membranes could capture TDG specifically through the recognition interaction between MIPs and TDG. Then, AuNPs were adsorbed onto the MIPs/PEI/PVA nanofiber membranes through the Au-S interaction between TDG and AuNPs to produce a visible red color. In order to improve the sensitivity, the silver-enhanced solutions were used to deepen the color of the nanofiber membranes and the software Image J was used to read the gray value as the signal response for subsequent analysis. There was a good linear relationship between the color change of the MIPs/PEI/PVA nanofiber membranes and the TDG concentration from 0.1 ng mL-1 to 1.0 μg mL-1, and the limit of detection was 38 pg mL-1. This method was applied for the selective detection of TDG in urine, showing great potential for the clinical diagnosis of mustard gas poisoning.

Exploring the supramolecular chemistry of cyclopropeniums: halogen-bonding-induced electrostatic assembly of polymers.

Exploring new noncovalent synthons for supramolecular assembly is essential for material innovation. Accordingly, we herein report a unique type of cyclopropenium-based supramolecular motif and demonstrate its applications to polymer self-assembly. Because of the "ion pair strain" effect, trisaminocyclopropenium iodides complex strongly with fluoroiodobenzene derivatives, forming stable adducts. Crystal structure analysis reveals that halogen-bonding between the iodide anion and the iodo substituent of the fluoroiodobenzene is the driving force for the formation of these electrostatically complexed adducts. Such halogen-bonding-induced electrostatic interactions were further successfully applied to drive the assembly of polymers in solution, on surfaces, and in bulk, demonstrating their potential for constructing supramolecular polymeric materials.

Silicon Nanospheres Supported on Conductive MXene Nanosheets as Anodes for Lithium-Ion Batteries

Silicon (Si) anodes are expected to be employed in future for lithium-ion batteries (LIBs), due to their high capacity. However, the main challenge is to assemble Si with conductive materials to increase the conductivity and stability of Si anodes. In this work, we optimized a method to prepare Si nanoparticles (NP)/MXene anode materials for LIBs via electrostatic assembly of positively charged Si nanospheres, coated with poly-diallyl dimethyl ammonium chloride, and negatively charged MXene nanosheets, which increase the number of active sites for strong Si NP attachment and minimize both restacking of MXene nanosheets and Si NP aggregation. The Si NP/MXene anodes have a capacity of 1917.9 mA h g–1 after 300 charge/discharge cycles at 0.5 A g–1. The electrochemical characterization of Si NP/MXene nanocomposite shows high energy storage, cycle stability, and rate performance. Optimization of Si/MXene composites can improve their performance as anode materials for high energy density LIBs.

Conductance-stable and integrated helical fiber electrodes toward stretchy energy storage and self-powered sensing utilization

Highly conductive and stretchable fibers are of great significance for wearable applications. Practical applications usually require high robustness and repeatability for these electronics under various mechanical deformations, which is a contradiction for most of existing strain-sensitive fibers conductors. In this work, core–shell hydrogel fiber with adjustable three-dimensional (3D) helical structure was fabricated, in which Ti3C2Tx (MXene)/poly(3,4-ethylenedioxythiophene) (PEDOT) were modified onto the surface of helical sodium alginate/polyacrylic acid (SA/PAA) hydrogel fibers via the combination of in situ polymerization and electrostatic assembly. The hybrid fiber possess a insensitive conductance (<5% resistance change) under various deformation, including stretching (0–800 %), bending (0-180°), pressuring and twisting, attributed to both the double tortuous conductive network and pre-strain release from helical structure. Moreover, conductance-stable helical fibers could be appropriately assembled into coaxial energy fibers and integrated into fabric, both acting as strain-insensitive energy storage device and self-powered wearable sensor.

A FRET assembly of fluorescent gold nanoclusters for ratiometric monitoring peroxynitrite in living cells and zebrafish

Developing reliable probes for accurate monitoring peroxynitrite (ONOO–) in living systems with high sensitivity and selectivity is imperative for both elucidating its functions in many life-threatening diseases and improving therapeutic interventions. Herein, a novel nano-assembly structure (d-AuGP) was developed by electrostatic interaction-induced assembly between dichromatic gold nanoclusters (Au NCs). The assembly further induced fluorescence resonance energy transfer (FRET) and endowed d-AuGP with a well single-excitation, dual-emission fluorescence characteristic. The prepared nanostructure showed a quantitative ratiometric fluorescence response toward ONOO– with a remarkable decrease of emission peak at 685 nm and a stable peak at 470 nm. A good linear relationship between the ratio of emission intensities at 685 and 470 nm (I685/I470) with ONOO– concentration in the range of 0–100 μM was achieved and the limit of detection (LOD) was 0.39 μM. The possible fluorescence response mechanism was ascribed to the combined effects of dissociation-disturbed FRET and surface structure reconstruction. The Au NCs-based probe was demonstrated to possess high stability, low cytotoxicity, good cell and tissue permeability and high biocompatibility. It was effectively employed for biological imaging and monitoring exogenous and endogenous ONOO– levels in living cells and zebrafish with high contrast.

Comparative Study of Physicochemical Properties of Alginate Composite Hydrogels Prepared by the Physical Blending and Electrostatic Assembly Methods.

Alginate hydrogel commonly suffers from defects, such as weak mechanical properties, the shortage of long-term stability in physiological medium and the lack of mammalian cell adhesivity due to its strong hydrophilicity in biomedical application. For this reason, the homogeneous alginate hydrogels (Alg Gel) were successfully prepared by the D-glucono-δ-lactone/hydroxyapatite (HAP/GDL) cross-linking system, and then, the physical blending and alternating electrostatic assembly technology were proposed to fabricate alginate composite hydrogels (Alg-GT, Alg-CS-GT and ALG/GT-CS). The feasibility of the design methods was verified through the comparative analysis of their physicochemical properties and biological activity. In particular, the effects of physical blending and alternating electrostatic assembly technology on the pore structure, mechanical properties, swelling, degradation, cell adhesion and proliferation of composite hydrogels were also investigated. Experimental results showed that the formation of polyelectrolyte complexes by electrostatic assembly between biological macromolecules and the covalent cross-linking of EDC/NHS to GT improved the vulnerability of ion cross-linking, enhanced the mechanical properties and swelling stability of the composite hydrogels, and regulated their pore structure and in vitro biodegradability properties. Furthermore, MC3T3-E1 cells could exhibit good cell adhesion, cell viability and cell proliferation on the alginate composite hydrogels. Among them, Alg-CS-GT showed the best cell proliferation ability and differentiation effect due to its good cell adhesion. In view of the excellent physicochemical properties and biological activity of Alg-CS-GT, it exhibited great potential in biomedical application for tissue engineering.

Topographic Manipulation of Graphene Oxide by Polyaniline Nanocone Arrays Enables High‐Performance Solar‐Driven Water Evaporation

AbstractTuning the surface topography of solar evaporators is of significance for boosting light absorption and enhancing solar‐to‐vapor efficiency. Herein, a novel strategy to manipulate the surface topography of graphene oxide (GO) via electrostatic assembly coupled with in situ polymerizations of aniline is reported. The GO surface is fully hybridized with the polyaniline (PANI) nanocone arrays, manifesting periodic structures with highly foldable configurations. Additionally, the PANI arrays tune the surface chemistry of GO and retard the redispersion of GO into water, thus enabling corresponding composite (PG) robust structural durability. Featuring these intriguing attributes, when applied as an evaporator in pure water, the PG delivers an improved evaporation performance of 1.42 kg m−2h−1and a high evaporation efficiency of 96.6% under one sun illumination. Further investigations reveal that the periodically conical structures of PANI over GO surface strengthen light absorption via multiple reflections and facilitate heat localization. Desalination test substantiates the reliability of PG for practical freshwater production. The numerical simulations and optical microscopy observation exhibit the surface topography‐strengthened vapor generation effect. This study sheds new light on the rational manipulation of surface topography of photothermal materials for high‐efficiency solar evaporation.

MXene-PANI/PES composite ultrafiltration membranes with conductive properties for anti-fouling and dye removal

The appearance of the composite membrane provides a new research direction for reducing membrane fouling. In this study, polyaniline (PANI) and Ti3C2Tx (MXene) were combined by the electrostatic assembly method where PANI was used to adjust the distance between MXene layers and construct the conductive network. The conducting mixed ultrafiltration membranes were prepared by the non-solvent induced phase separation method, in which MXene and PANI were mixed into a polyethersulfone (PES) matrix. The permeation flux of pure water of the MXene-PANI/PES membrane was increased by 200.9%, the retention rate of bovine serum albumin (BSA) was kept above 99%, and the retention rate of Congo Red and Methyl blue dyes was 99.1% and 98.4%, respectively, this goes well beyond the PES membrane. In addition, through a series of conductivity tests, it has been proved that the conductive properties of composite membranes were greatly improved, and the conductivity of the MXene-PANI/PES composite membrane can reach 0.5 S m−1. After applying a negative voltage to the membrane, the negative charge around the surface of the membrane repels the negatively charged contaminant under the action of an electrostatic repulsion force, thereby the enrichment of pollutants on the membrane surface can be effectively reduced, and the FRR reached 93.7%. On the basis of ensuring membrane conductivity, we improved the permeability, selective separation, and anti-fouling ability of the membrane. This research shows great potential for the efficient development of an anti-fouling conductive separation membrane based on MXene.

Growing CoNi nanoalloy@N-doped carbon nanotubes on MXene sheets for excellent microwave absorption

• 0D CoNi nanoalloy-encapsulated 1D NCNT were grown on 2D Ti 3 C 2 T x sheets. • High surface areas and excellent thermal oxidation stabilities were achieved for the composite. • The minimum RL reached −55.3 dB at 2.1 mm. • The EAB of 4.3 GHz at 1.5 mm could be attained. Recently, two-dimensional MXene materials have attracted numerous attention in electromagnetic wave shielding/absorption. Hybridizing magnetic materials and constructing multi-dimensional structures in MXene is highly beneficial to improve electromagnetic wave absorption properties. Herein, we demonstrate a strategy for in situ growing 0D CoNi nanoalloy-encapsulated 1D N-doped carbon nanotubes on a 2D Ti 3 C 2 T x MXene sheet through an electrostatic assembly process followed by a high-temperature pyrolysis process. The resultant 201-structured MXene-CoNi@N-doped carbon nanotube (MXene-CoNi@NCNT) composites displayed high surface areas (55.6–103.7 m 2 /g), moderate magnetism (19.8–24.6 emu/g), and excellent thermal oxidation stabilities (≥ 307 °C). In addition, the unique 2D/0D/1D architectures entrusted the composites with abundant interfaces, various defects, and numerous nitrogen dopants. Taking advantage of the special 201 structure and the existence of both magnetic and dielectric loss, the MXene-CoNi@NCNT composite showed great impedance matching and strong attenuation performance. A strong reflection loss of –55.3 dB was achieved when the coating thickness was 2.1 mm, and a wide effective absorption bandwidth of 4.3 GHz was achieved at a thickness of 1.5 mm, much superior to that of similar absorbers. This work demonstrates a novel strategy for designing electromagnetic wave absorbers with magnetic and dielectric losses accompanied by multiple dimensional structures.

Silica decorated with Ti3C2Tx nanosheets for reinforcing epoxy resin dielectric properties and energy density

Advances in electronic technology and power devices have placed increased demands on the performance of polymer dielectrics. The preparation of dielectric polymer composites with high dielectric constant and breakdown strength remains a critical challenge. Herein, SiO 2 @Ti 3 C 2 T x hybrids were prepared by decorating few-layer Ti 3 C 2 T x nanosheets on the surface of modified silica nanospheres by electrostatic self-assembly method. A series of EP/SiO 2 @Ti 3 C 2 T x composites were prepared by using the heterohybrids as fillers, and the composites demonstrated the enhanced dielectric constant and breakdown strength. After filling with 7 wt% of SiO 2 @Ti 3 C 2 T x , the dielectric constant of the composite was 4.25. At this point, the breakdown strength of the composite is 41.6 kV/mm, and the dielectric loss at 1 kHz is 0.005. The improved performance of epoxy resin-based composites can be attributed to the fact that Ti 3 C 2 T x nanosheets contain surface hydroxyl groups capable of improving the dispersion of fillers in epoxy resin, while the addition of Ti 3 C 2 T x nanosheets improves the interfacial polarization behavior. The reasonably designed nano-hybrid filler has broadened the application of polymer dielectric in energy storage, power equipment and other engineering fields. • Hybrid with core-shell structure was synthesized by electrostatic assembly strategy. • The effect of dielectric parameter control on the energy storage property is exposed. • The relationship between filler content and resin intrinsic properties is studied. • The maximum U dis of the composite is 6.45×10 -2 J/cm 3 when the filling is 7 wt%.

Bionic Assembly of Layered Double Hydroxides Nanosheets and Positively Charged Micelles by Counterions Balance and Their Selective Detection of Mannose.

The selective detection of mannose is significant for tumor early diagnosis. However, current methods for detecting mannose are expensive and time-consuming, limiting their application. In this paper, we have obtained a 25-layer positively charged micellar/LDHs nanocomposite film system by electrostatic layer-by-layer assembly with reference to the unique properties of homogeneous charge ion attraction and charge overcompensation in biomolecules: hexadecyl trimethylammonium bromide (CTAB) was used to coat neutral molecules of fluorescein (FLU) to form (FLU@CTAB) cationic micelles, which were electrostatically assembled with laminate positively charged layered double hydroxides (LDHs) nanosheets to form (FLU@CTAB/LDHs)n ultrathin films (UTFs) by the layer-by-layer electrostatic assembly, where the mediating role of the Br- counteranion had a profound effect on the success of the assembly. Moreover, compared to pure FLU solution, the fluorescence intensity and the lifetime of (FLU@CTAB/LDHs)20 UTFs were enhanced by 1.6 and 2 times, respectively. (FLU@CTAB/LDHs)20 UTFs exhibited selective detection for d-mannose with a detection limit of 0.05 mg·mL-1. Therefore, the (FLU@CTAB/LDHs)n UTFs can be a novel biosensor. Compared to conventional powder sensors, (FLU@CTAB/LDHs)n thin-film fluorescent sensors are more promising for device implementation. Moreover, the design strategy of positively charged micellar/LDHs nanocomposite systems breaks the current limitation that LDHs can only be assembled with anions or neutral molecules and extends the scope of counterion-mediated host-guest to the nanosheet-micellar system.

Core-satellite nanostructures and their biomedical applications.

Plasmonic core-satellite nanostructures assembled from simple building blocks have attracted extensive attention since they were reported by the way of DNA-directed assembly in 1998, because of their unique enhanced and synergistic optical properties and widespread potential applications in biosensing, imaging, drug delivery, and diagnostics. In this review, we introduce the synthetic methods of core-satellite nanostructures, emphazisingthe bottom-up synthesis method, including DNA, molecular, protein, peptide, amino acids, metal ion-assisted assembly, electrostatic adsorption assembly, clicked-to-assembly, and in situ deposition. Than we review and discuss their morphology classification, and summarize influencing factors of morphology. This is followed by overviews on optical properties, including localized surface plasmon resonance, surface-enhanced Raman scattering, surface-enhanced fluorescence and quenching, and applications in thebiomedical field. Finally,the challenges and prospects of these kinds of nanostructures are discussed.