Electrostatic Self-assembly Method Research Articles

Synthesis of Co3O4@C/Ti3C2Tx MXene composites for enhanced electromagnetic wave absorption

Due to the harmful effects of electromagnetic pollution on human bodies and electronic devices, efficient microwave absorbing materials have garnered significant attention. In this paper, highly efficient microwave-absorbing Co3O4@C/Ti3C2Tx composites were synthesized by a combination of hydrothermal and electrostatic self-assembly methods. Benefiting from the synergistic effects of the multiple reflections in the Co3O4@C core-shell structure and the high conductivity coupled with the large surface area of Ti3C2Tx, the composite material, with a mass ratio of 1: 2, exhibits remarkable wave absorption capabilities, achieving a minimum reflection loss (RL) of −35.2 dB at a thickness of 4.5 mm and an effective absorption bandwidth (EAB) of 7.4 GHz within the 2–18 GHz frequency range. It is noteworthy that the smaller the RL value, the higher the material's absorption performance, and the wider the frequency range covered by the EAB, the better the overall absorption effect. Specifically, an RL value below −10 dB corresponds to an absorption rate of 90 %, which further enhances to 99 % for RL values below −20 dB. The outstanding electromagnetic wave absorption performance of the Co3O4@C/Ti3C2Tx composites can be primarily attributed to the synergy between the multiple reflective absorptions offered by the core-shell structure and the exceptional conductivity and high specific surface area inherent in the MXene material. These findings underscore the promising potential of Co3O4@C/Ti3C2Tx composites for electromagnetic absorption applications and offer a novel perspective for the design of MXene-based magnetic absorption materials.

Preparation of curcumin-loaded chitosan/lecithin nanoparticles with increased anti-oxidant activity and in vivo bioavailability

As a natural polyphenol, curcumin (Cur) has exhibited a range of bioactive properties, including anti-inflammatory, anti-oxidant, and anti-infection properties. However, the chemical instability and low water solubility of Cur hinder its wide application. Herein, Cur-loaded chitosan/lecithin nanoparticles (CCL NPs) were prepared by the electrostatic self-assembly method. The prepared CCL NPs showed a small particle size (122.86 ± 1.53 nm) with homogeneous distribution (PDI = 0.17 ± 0.01). The high EE (79.34 ± 2.93 %) and LC (9.33 ± 0.34 %) indicated that most of Cur was encapsulated in CCL NPs. Meanwhile, the Cur was released from CCL NPs in a quick and sustained way after being exposed to simulated gastrointestinal fluids. The CCL NPs displayed superior anti-oxidant activity than that of free Cur. Moreover, the in vivo pharmacokinetic studies showed that the CCL NPs could lead to a ~ 2.64-fold increase in oral bioavailability compared with that of free Cur. All these findings indicated that the formation of CCL NPs would be a promising platform to deliver Cur in the food industry.

Facile synthesis and electrochemical properties of sheet-rod-sheet structured NiCo2S4/EG/Ti3C2Tx nanocomposites

Electrode materials with outstanding stability and electrochemical activity are ideal for high-performance supercapacitors. Herein, we developed a simple two-step method for fabricating NiCo2S4/EG/Ti3C2Tx nanocomposites with a sheet(2D)-rod(1D)-sheet(2D) structure. The NiCo2S4 rods were embedded into the expanded graphite (EG) sheets via an in-situ hydrothermal method, then the Ti3C2Tx sheets were assembled with NiCo2S4/EG by an electrostatic self-assembly method. The obtained NiCo2S4/EG/Ti3C2Tx nanocomposites exhibited a synergistic effect among the components. The addition of EG inhibited the volumetric effect of NiCo2S4 during charging and discharging processes, while the high conductivity of Ti3C2Tx promoted charges transfer. The rod-like structure of NiCo2S4 effectively inhibited the self-stacking of Ti3C2Tx sheets. Consequently, the optimized composite exhibited an excellent specific capacitance of 1837.9 F·g−1 at a current density of 1 A·g−1. Additionally, the composite electrode exhibited a capacitance retention of 73.5 % during 10,000 charging-discharging cycles at a current density of 20 A·g−1.

Charge separation by switching heterojunction system from Type-II to S-scheme for enhanced photocatalytic activity: Environmental detoxification and H2 production

The development of highly efficient photocatalysts is essential for harnessing solar energy for pollutant degradation and hydrogen (H2) production. This study provides a novel ternary S-scheme photocatalyst (Fe2O3/Bi2O3/g-C3N4), prepared from optimized binary 20-Bi-C via a simple electrostatic self-assembly method for the first time. Using various methods including UV–vis DRS, PL, ESR, photocurrent, Mott-Schottky, XPS, XRD, FTIR, SEM, TEM, and BET, the optical, structural, and morphological characteristics of the produced materials were fully studied. The photocatalytic performance of as-manufactured materials was evaluated through the degradation of the Ciprofloxacin (CIP) and H2 production. Under optimized conditions determined by the RSM method, a maximum CIP degradation of 97.20 % was achieved at a rate of 0.053 min−1, with the catalyst dosage: 0.44 g/l, CIP concentration: 26.07 mg/l, pH: 6.29 and Time: 63.01. The optimized heterojunction exhibited an exceptional photocatalytic H2 generation rate of 2428 μmol·g−1·h−1 within 2 h, surpassing the binary 20-Bi-C photocatalyst by 1.3 times. Furthermore, after five continuous cycles, the 5-Fe2O3/Bi-C photocatalyst showed good chemical stability and reusability, sustaining a degradation rate of over 96 % and a TOC removal of 80 %. Experiments on the identification of free radicals have demonstrated the important roles that O2−, h+, and OH species play in the photocatalytic process. The enhancement mechanism of 5-Fe2O3/Bi-C involves the successful synthesis of Fe2O3/Bi-C photocatalyst with well-aligned positions of band gap edges, enabling the facile charge transfer through S-Scheme mechanism. Furthermore, the study investigates the impact of environmental factors, including solution pH, water matrices, and the efficiency of the synthesized photocatalyst on other organic pollutants. The photocatalytic degradation behavior of CIP is predicted using LC-MS analysis. This work provides a new method for building S-scheme heterojunctions by creatively converting the type-II heterojunction system to an S-scheme by metal oxide doping.

Constructing piperazine pyrophosphate@LDH@rGO with hierarchical core-shell structure for improving thermal conductivity, flame retardancy and smoke suppression of epoxy resin thermosets

The integration and miniaturization development of electronic devices placed the great demand for epoxy resin (EP) thermosets with excellent thermal management, flame retardancy and electrical insulation. Herein, a multifunctional additive piperazine pyrophosphate@layered double hydroxide@reduced graphene oxide (PPAP@LDH@rGO) with hierarchical core-shell structure was constructed by solvothermal and electrostatic self-assembly methods to meet the above requirements. Profiting from the distinct structure of PPAP@LDH@rGO, the thermal conductivity of EP/PPAP@LDH@rGO reached 0.951 W m−1 K−1 at 7 wt% addition (3 wt% rGO containing), which is 320.8 % increment compared to pristine EP. Meanwhile, when 4 wt% PPAP@LDH@rGO was added, the EP thermoset reached UL-94 V-0 rating during vertical burning tests with the limiting oxygen index of 29.8 % due to the synergistic effect of PPAP, LDH and rGO. The release of hazard products including smoke and carbon monoxide for EP/PPAP@LDH@rGO visibly declined during combustion. Besides, the EP thermosets also well-maintained the electrical insulation and mechanical properties. This work provided an alternative approach for preparing high performance EP thermosets which was suitable to be applied in electronics and electrical fields.

Preparation and characterization of a konjac glucomannan-based bio-nanocomposite film and its application in cherry tomato preservation

Strategies to overcome the limitations of konjac glucomannan (KGM) films, including their poor mechanical properties, low water resistance, and limited bioactivity, are being developed. In this study, fucoidan-chitosan nanoparticles encapsulating tea polyphenols (TP-FCNPs) were prepared using an electrostatic self-assembly method. Subsequently, a novel bio-nanocomposite film was prepared by incorporating TP-FCNPs as fillers into a KGM-based membrane. The microstructural, physical, and biological properties of the nanocomposite films were evaluated. Scanning electron microscopy (SEM) observations showed that in the KGM/TP-FCNPs containing 1–7% TP-FCNPs, the TP-FCNPs were uniformly distributed throughout the KGM film matrix. The highest tensile strength of KGM/TP-FCNPs films was 33.05 ± 1.57 MPa, which was 404.53% that of pure KGM film. Incorporating TP-FCNPs also significantly enhanced the UV absorption ability and antimicrobial and antioxidant activities of the bio-nanocomposite films, while reducing their transmittance. In addition, KGM/TP-FCNPs used as packaging effectively reduced fruit mass loss and firmness loss, inhibited microbial growth, and significantly prolonged fruit shelf-life on day 21 of the cherry tomato (Lycopersicon esculentum var. cerasiforme A. Gray) packaging trial. In conclusion, the KGM/TP-FCNPs bio-nanocomposite films exhibit satisfactory properties, and thus, show potential for applications in fruit preservation.

Photocarrier relay modulating solar CO2-to-Syngas conversion

Solar-driven syngas generation by CO2 reduction provides a sustainable strategy to produce renewable fossil fuels. Nevertheless, this promising approach often suffers from tough CO2 activation, sluggish reaction kinetics and complex selectivity. Herein, we exquisitely constructed spatially directional charge transport channel over two-dimensional transition metal chalcogenide (TMC)-based heterostructure via a facile and universal electrostatic self-assembly method. Tailor-made positively charged non-conjugated insulating polymer of poly(diallyl-dimethyl-ammonium chloride) (PDDA) and negatively charged graphene oxide (GO) precursor as building blocks are controllably anchored on the TMC substrate, by which ultrathin PDDA layer is intercalated at the interface of GO and TMC. We ascertain that, in this customized sandwiched heterostructures, PDDA interim layer functions as an electron-relaying mediator, whilst graphene (GR) obtained from in-situ GO reduction during the photocatalytic reaction serves as a terminal electron-trapping reservoir, synergistically facilitating the spatially vectorial charge separation/migration over TMC, thus endowing the TMC/PDDA/GR heterostructures with conspicuously enhanced visible-light-driven photoactivity toward CO2-to-syngas conversion. Our work would inspire judicious ideas for finely modulating charge transfer over polymer-mediated photosystems and benefit our fundamental understanding of solar CO2 conversion.

Enhanced photocatalytic degradation of organic dyes by dual heterojunction of ZnO/NiWO4/V2C MXene

Multiphase composite catalysts can be designed for efficient photocatalytic treatment of organic pollutants in wastewater. Herein, the multiphase ZnO/NiWO4/V2C composite catalysts with dual heterojunction and hierarchically assembled nanoflower structures were constructed via a facile two-step hydrothermal and electrostatic self-assembly method. Utilizing NiWO4 and V2C as co-catalysts, these catalysts effectively degraded cationic dyes, methylene blue (MB) and rhodamine B (RhB) under visible light irradiation. The ZnO/NiWO4/V2C catalyst exhibited higher photocatalytic activity than ZnO in the degradation of MB and RhB, with rate constants of 0.0194 min−1 (a 7.43-fold enhancement) and 0.0176 min−1 (a 3.13-fold enhancement). The higher activity can be attributed to the construction of the double heterojunction using NiWO4 and V2C, which can facilitate efficient electron transport, improve charge separation efficiency, and provide more active sites. After four cycles, the ZnO/NiWO4/V2C catalyst still maintained good stability. Consequently, this work can offer a promising approach for environmental pollution treatment.

Efficient degradation of tetracycline by cobalt ferrite modified alkaline solution nanofibrous Ti3C2Tx MXene activated peroxymonosulfate system: Mechanism analysis and pathway

Magnetic CoFe2O4 nanoparticles have received considerable attention as an activator for peroxymonosulfate (PMS) in the degradation of tetracycline. However, it is still challenging to construct CoFe2O4 composites with good dispersion and highly exposed reactive sites. Herein, the KOH fiber-functionalized MXene matrix decorated by cobalt ferrite nanoparticles (denoted as CoFe2O4@Alk-MXene) was developed by electrostatic self-assembly method. The layered fibrotic structure effectively disperses and fixes cobalt ferrite nanoparticles, increasing the exposure of reactive sites. The as-prepared CoFe2O4@Alk-MXene material exhibited rapid removal of 100% tetracycline hydrochloride (TC-HCl) within 10 minutes by activating PMS, leveraging the excellent conductivity of alkalized MXene and the efficient activation of transition metal atoms. The experimental and theoretical analysis revealed that the electron transfer process of Ti2+/Ti4+, Co2+/Co3+ and Fe3+/Fe2+, as well as the free radical and non-free radical attack behaviors produced by the adsorption of PMS by the composite, are the primary mechanisms for achieving rapid removal of pollutants. A comprehensive degradation mechanism and potential pathways were proposed based on these findings. Overall, CoFe2O4@Alk-MXene/PMS emerges as a promising catalytic system for TC removal.

Enhanced Gas Barrier and Mechanical Properties of Styrene-Butadiene Rubber Composites by Incorporating Electrostatic Self-Assembled Graphene Oxide @ Layered Double Hydroxide Hybrids.

Rubber composites with a high gas barrier and mechanical properties have received considerable attention due to their potential applications. Constructing complex filler networks in a rubber matrix is an effective strategy to simultaneously enhance the gas barrier and mechanical properties. In this work, graphene oxide layered double hydroxide (GO@LDHs) hybrids were obtained by the electrostatic self-assembly method. A unique interspersed and isolated structure was formed in GO@LDHs hybrids due to the chemical interactions between the functional groups on GO sheets and the metal cations on LDH layers. Subsequently, the GO@LDHs hybrids were incorporated into a styrene-butadiene rubber (SBR) matrix using a green latex compounding method. The results showed that the GO@LDHs hybrids were uniformly embedded in the SBR matrix, constructing an overlapped filler network and forming physical bonding points that reduced the free volume of the composites. The electrostatic interactions between GO@LDHs hybrids facilitated energy dissipation during stretching, thereby improving the mechanical performance of the rubber composites. More importantly, the N2 gas permeability and fracture toughness of GO@LDHs/SBR composites decreased by 52.2% and increased by 845%, respectively, compared to those of a pure SBR matrix. The construction of GO@LDHs hybrids offers new insights for designing rubber composites with a high gas barrier and mechanical properties.

Ultrathin 2D[sbnd]2D WO3-x-C3N4 heterostructure-based high-efficiency photocatalyst for selective oxidation of toluene

Photocatalytic oxidation of toluene for the organic synthesis of value-added benzaldehyde has attracted great attention in recent years. However, activation of CH bonds and selective production of benzaldehyde under mild green conditions remains a great challenge. Herein, a series of two-dimensional (2D) ultrathin heterostructure-based components (WO3-x-C3N4 nanosheets), fabricated by coupling oxygen-deficient WO3-x with amorphous C3N4 via a simple electrostatic self-assembly method, was demonstrated as high-efficiency photocatalysts to produce benzaldehyde in the presence O2 as oxidant at room temperature. Under optimal conditions, the prepared 10WCN sample (10 wt% WO3-x-C3N4) exhibited improved photocatalytic oxidation ability with a good benzaldehyde selectivity (96 %) and high benzaldehyde yield (2738.6 μmol g−1 h−1) within 6 h, which is 6.6 and 3.3 times than that of pure WO3-x (412.5 μmol g−1 h−1) and C3N4 (835.7 μmol g−1 h−1). The enhanced photocatalytic performance was due to the constructed 2D type II heterojunction and abundant oxygen vacancies (OVs), contributing to the photoinduced carriers' separation and migration efficiently. This work indicates the synergistic effect of defect metal oxides and 2D ultrathin sheet-to-sheet heterojunctions in photocatalytic hydrocarbon conversion.

Kirkendall Effect-Induced Ternary Heterointerfaces Engineering for High Polarization Loss MOF-LDH-MXene Absorbers.

Heterogeneous interfacial engineering has garnered widespread attention for optimizing polarization loss and enhancing the performance of electromagnetic wave absorption. A novel Kirkendall effect-assisted electrostatic self-assembly method is employed to construct a metal-organic framework (MOF, MIL-88A) decorated with Ni-Fe layered double hydroxide (LDH), forming a multilayer nano-cage coated with Ti3C2Tx. By modulating the surface adsorption of Ti3C2Tx on LDH, the heterointerfaces in MOF-LDH-MXene ternary composites exhibit excellent interfacial polarization loss. Additionally, the Ni-Fe LDH@Ti3C2Tx nano-cage exhibits a large specific surface area, abundant defects, and a large number of heterojunction structures, resulting in excellent electromagnetic wave absorption performance. The MIL-88A@Ni-Fe LDH@Ti3C2Tx-1.0 nano-cage achieves a reflection loss value of -46.7 dB at a thickness of 1.4mm and an effective absorption bandwidth of 5.12 GHz at a thickness of 1.8mm. The heterojunction interface composed of Ni-Fe LDH and Ti3C2Tx helps to enhance polarization loss. Additionally, Ti3C2Tx forms a conductive network on the surface, while the cavity between the MIL-88A core and the Ni-Fe LDH shell facilitates multiple attenuations by increasing the transmission path of internal incident waves. This work may reveal a new structural design of multi-component composites by heterointerfaces engineering for electromagnetic wave absorption.

The effect of lambda-cyhalothrin nanocapsules on the gut microbial communities and immune response of the bee elucidates the potential environmental impact of emerging nanopesticides

Emerging nanopesticides are gradually gaining widespread application in agriculture due to their excellent properties, but their potential risks to pollinating insects are not fully understood. In this study, lambda-cyhalothrin nanocapsules (LC-NCs) were constructed by electrostatic self-assembly method with iron mineralization optimization, and their effects on bee gut microbial communities and host immune-related factors were investigated. Microbiome sequencing revealed that LC-NCs increase the diversity of gut microbial communities and reduce the complexity of network features, disrupting the overall structure of the microbial communities. In addition, LC-NCs also had systemic effects on the immune response of bees, including increased activity of SOD and CAT enzymes and expression of their genes, as well as downregulation of Defensin1. Furthermore, we noticed that the immune system of the host was activated simultaneously with a rise in the abundance of beneficial bacteria in the gut. Our research emphasizes the importance of both the host and gut microbiota of holobiont in revealing the potential risks of LC-NCs to environmental indicators of honey bees, and provides references for exploring the interactions between host-microbiota systems under exogenous stress. At the same time, we hope that more research can focus on the potential impacts of nanopesticides on the ecological environment.

Highly active Ni atomic clusters loaded with coal gasification slag derivatives effectively remove tetracycline by activating persulfate to enhance electron transfer ability

In this study, low-cost coal gasification slag derivative (CGD) was used as a carrier, and highly active Ni atom clusters were successfully loaded on the carrier using the electrostatic self-assembly method to prepare a Ni-CGD composite catalyst. It was used to activate persulfate (PDS) and monopersulfate (PMS) to efficiently remove tetracycline (TC) from aqueous solutions. Experimental results show that Ni-CGD/PDS and Ni-CGD/PMS system exhibits nearly 100 % degradation efficiency for TC between pH 4 and 11. PDS and PMS molecules can be adsorbed on the surface of Ni-CGD materials effectively, and a reaction center with high redox potential can be formed on the catalyst surface through the interaction between molecules. This phenomenon enhances the transfer of electrons from the relatively high-potential functional groups on the TC molecules to the catalyst surface. In addition, the strong interaction between Ni-CGD and the activator promotes the formation of more surface active sites, which can receive electrons from TC molecules, leading to the oxidative degradation of TC. Quenching experiments and EPR tests indicate that direct electron transfer is the main reaction pathway for TC degradation.

Fabrication of RuO2-graphene/graphene thick-and-dense micro-hole array material by femtosecond laser for high volumetric rate performance

Nanostructured materials have a great application prospect in the next generation of electrochemical energy storage devices. However, there is a great obstacle for thick and dense electrodes with large tortuosity to simultaneously attain high areal and rate performance at the same time to meet the practical requirements. Herein, a simple electrostatic self-assembly method is adopted to anchor RuO2 onto graphene nanoflakes, the thick and dense film of RuO2-Graphene/Graphene(RuO2-G G-1) are prepared by filtration and mechanical compression, and then the micro-hole array structure was fabricated by femtosecond laser drilling, which shortened the diffusion path of hydrogen ion (H+). After etching, the pore diameter is 7 μm; the pore spacing is 40 μm and the array was regular. The mass loss of the electrode caused by etching was only 3 %, and the relative density of the electrode reached 79 %. Under the same thickness of the electrode, the pore electrode obviously reduces the ion resistance. The micro-hole array not only improves the areal and volumetric capacity of the RuO2-G G-1 electrode, but also improves the rate performance of the electrode., the rate capability increased from 65.6 % to 87.7 % at 20 A g-1. The study provides a powerful technique for the fabrication of dense and thick electrode in energy storage system.

Quantitative detection of tapered fiber SERS probes prepared in batches by electrostatic adsorption self-assembly method

The tapered fiber Surface-enhanced Raman scattering (SERS) probe is a highly sensitive SERS substrate for on-site detection. However, fiber probes prepared by the current technology lack interchangeability and are difficult to meet the practical quantitative detection demands. In this paper, we develop a batch preparation technology of tapered fiber SERS probes, with good interchangeability between each of the 20 tapered fiber SERS probes prepared in batches. Furthermore, we propose and demonstrate a spectral data assimilation method, through which the differences in interchangeability between different batches can be eliminated. Using 10 batches of spectral data assimilated with this method, we obtain a high-precision calibrated quantitative relationship curve with a fitting degree of 0.99464, with recovery rates of the two thiram spiked samples 106.88% and 95.75%, respectively. The batch preparation technology and the spectral data processing method provide a new option for practical quantitative detection.

Heteropoly blue-modified ultrathin bismuth oxychloride nanosheets with oxygen vacancies for efficient photocatalytic nitrogen fixation in pure water

Photocatalytic nitrogen reduction is a promising green technology for ammonia synthesis under mild conditions. However, the poor charge transfer efficiency and weak N2 adsorption/activation capability severely hamper the ammonia production efficiency. In this work, heteropoly blue (r-PW12) nanoparticles are loaded on the surface of ultrathin bismuth oxychloride nanosheets with oxygen vacancies (BiOCl-OVs) by electrostatic self-assembly method, and a series of xr-PW12/BiOCl-OVs heterojunction composites have been prepared. Acting as a robust support, ultrathin two-dimensional (2D) structure of BiOCl-OVs inhibits the aggregation of r-PW12 nanoparticles, enhancing the interfacial contact between r-PW12 and BiOCl. More importantly, the existence of oxygen vacancies (OVs) provides abundant active sites for efficient N2 adsorption and activation. In combination of the enhanced light absorption and promoted photogenerated carriers separation of xr-PW12/BiOCl-OVs heterojunction, under simulated solar light, the optimal 7r-PW12/BiOCl-OVs exhibits an excellent photocatalytic N2 fixation rate of 33.53 µmol g-1h−1 in pure water, without the need of sacrificial agents and co-catalysts. The reaction dynamics is also monitored by in situ FT-IR spectroscopy, and an associative distal pathway is identified. Our study demonstrates that construction of heteropoly blues-based heterojunction is a promising strategy for developing high-performance N2 reduction photocatalysts. It is anticipated that combining of different defects with heteropoly blues of different structures might provide more possibilities for designing highly efficient photocatalysis systems.

Constructing Heterostructured MWCNT-BN Hybrid Fillers in Electrospun TPU Films to Achieve Superior Thermal Conductivity and Electrical Insulation Properties.

The development of thermally conductive polymer/boron nitride (BN) composites with excellent electrically insulating properties is urgently demanded for electronic devices. However, the method of constructing an efficient thermally conductive network is still challenging. In the present work, heterostructured multi-walled carbon nanotube-boron nitride (MWCNT-BN) hybrids were easily prepared using an electrostatic self-assembly method. The thermally conductive network of the MWCNT-BN in the thermoplastic polyurethane (TPU) matrix was achieved by the electrospinning and stack-molding process. As a result, the in-plane thermal conductivity of TPU composite films reached 7.28 W m-1 K-1, an increase of 959.4% compared to pure TPU films. In addition, the Foygel model showed that the MWCNT-BN hybrid filler could largely decrease thermal resistance compared to that of BN filler and further reduce phonon scattering. Finally, the excellent electrically insulating properties (about 1012 Ω·cm) and superior flexibility of composite film make it a promising material in electronic equipment. This work offers a new idea for designing BN-based hybrids, which have broad prospects in preparing thermally conductive composites for further practical thermal management fields.

π-π conjugated PDI supramolecular regulating the photoluminescence of imine-COFs for sensitive smartphone visual detection of levofloxacin

As the contamination and enrichment in food chain of levofloxacin (LV) antibiotics have caused a significant threat to life safety, the instant detection of LV has become an urgent need. Here, a PDI-functionalized imine-based covalent organic framework (PDI-COF300) was prepared by the electrostatic self-assembly method as fluorescent probe for smartphone visual detection of LV, which exhibited excellent fluorescence quantum yield (82.68%), greater stability, high sensitivity with detection limit of 0.303 μM. Based on the results of molecular docking and Stern-Volmer equation, the LV detection by PDI-COF300 was mainly a static quenching process through π-π stacked hydrophobic interactions and fluorescence resonance energy transfer. Besides, PDI-COF300 was applied to LV detection in environmental medium and milk samples with recoveries from 85.56% to 108.34% and relative standard deviations <2.70%. This work also provided a new general strategy for using PDI-COF in smartphone devices and fluorescent papers for LV fluorescence detection and microanalysis.

Electrostatic Self-Assembly of CdS Quantum Dots with Co9S8 Hollow Nanotubes for Enhanced Visible Light Photocatalytic H2 Production.

CdS quantum dots (CdS QDs) are regarded as a promising photocatalyst due to their remarkable response to visible light and suitable placement of conduction bands and valence bands. However, the problem of photocorrosion severely restricts their application. Herein, the CdS QDs-Co9S8 hollow nanotube composite photocatalyst has been successfully prepared by loading Co9S8 nanotubes onto CdS QDs through an electrostatic self-assembly method. The experimental results show that the introduction of Co9S8 cocatalyst can form a stable structure with CdS QDs, and can effectively avoid the photocorrosion of CdS QDs. Compared with blank CdS QDs, the CdS QDs-Co9S8 composite exhibits obviously better photocatalytic hydrogen evolution performance. In particular, CdS QDs loaded with 30% Co9S8 (CdS QDs-30%Co9S8) demonstrate the best photocatalytic performance, and the H2 production rate reaches 9642.7 μmol·g-1·h-1, which is 60.3 times that of the blank CdS QDs. A series of characterizations confirm that the growth of CdS QDs on Co9S8 nanotubes effectively facilitates the separation and migration of photogenerated carriers, thereby improving the photocatalytic hydrogen production properties of the composite. We expect that this work will facilitate the rational design of CdS-based photocatalysts, thereby enabling the development of more low-cost, high-efficiency and high-stability composites for photocatalysis.