Schiff Base Reaction Research Articles

Construction of MOF@COF Z-scheme heterojunction for efficient photocatalytic degradation of tetracycline in water: synthesis, mechanism, degradation pathway, and DFT calculation

As emerging pollutants, antibiotics in water environment posed a significant threat to human health and ecosystem. A lot of attention has been focused on tetracycline (TC). Photocatalysis, a green and efficient water treatment technology, has shown broad application prospects. Currently, the construction of photocatalytic heterojunctions is often limited to matching suitable energy band structures. However, simple surface doping largely restricted the carriers transport efficiency and stability. In this study, a series of composite photocatalysts (designated as NMSN-x) were prepared by functionalized metal organic framework Ti-MOF and covalent organic framework SNW-1 for TC removal. The schiff-based reaction was employed to achieve covalent linkage between the monomer catalysts, which greatly enhanced the carrier transport efficiency of the composite photocatalysts. Under UV light, the NMSN-1.5 demonstrated impressive removal capability to TC, which removed 93.10 ± 2.86% of TC in 60minutes and achieved 61.37 ± 2.18% under visible light, with up to 76.51 ± 3.37% removal in a natural water background. Carrier separation and transfer was greatly enhanced by the covalent connection between the monomers forming the heterojunction. Combined with density functional theory, the electron transfer mechanism was identified as Z-scheme heterojunction. In addition, the photodegradation intermediates of NMSN-1.5 were assessed to be significantly less environmentally toxic than TC itself. This study introduced a novel strategy for constructing photocatalytic heterojunctions for removal of TC, serving as a valuable reference in the field.Keywords

Rhodamine 6G-conjugated β-cyclodextrin as a novel fluorescence sensor for meat spoilage detection

Meats are abundant in proteins and a variety of lipids that are essential for the human body. Nevertheless, they are susceptible to enzymatic reactions and bacterial microorganisms during various processes, which can result in food deterioration. This study endeavors to create an ammonia-sensitive sensor for the detection of meat decomposition by rhodamine 6G fluorophore and β-cyclodextrin which are joined together via a Schiff-base reaction, in recognition of the significance of appropriate food monitoring. The rhodamine 6G and β-cyclodextrin-based sensor (R6GBCD) was characterized using proton nuclear magnetic resonance (1H NMR), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). The R6GBCD sensor showed a pH-dependent fluorescent properties and also selective responsivity to ammonia. The sensor demonstrated its capability to detect ammonia and generate yellow fluorescence, enabling it to identify rotting meat. As a result, it shows great promise as a mean of verifying the safety of food.

A composite film of oxidized levan crosslinked with gelatin: strong hydrophobic and mechanical properties and effective preservation of fresh Mozzarella cheese.

The fructosan levan was synthesized in vitro using a recombinant levansucrase. The levan was oxidized with sodium periodate to prepare oxidized levan (OLevan) with three oxidation degrees. OLevan, gelatin (Gel), and gallic acid (GA) were used to prepare the composite films by the method of plate pouring. The analytical results of FT-IR and XPS indicated that OLevan and gelatin were covalently crosslinked through a Schiff base reaction. The crosslinked films had better properties compared to the non-crosslinked films, especially the Gel/GA/50%OLevan film. The film had the lowest swelling degree (44.4 %), while that of Gel/GA/Levan film was 352.6 %. Gel/GA/50%OLevan film also had the highest tensile strength (25.48 MPa), while that of Gel/GA film was 9.48 MPa. Also, Gel/GA/50%OLevan film was used as a packaging material of Mozzarella cheese. The film effectively slowed down changes in the texture and color of the cheese. On the first day, the coliform in the control and PE groups had already exceeded the maximum acceptable limit of cheese (2.0 Log CFU/g). However, that of Gel/GA/50%OLevan group reached the limit on the fifth day. The results show that the new film prepared by crosslinking and composite of natural edible materials has good potential as a safe food packaging material.

Sustainable production of BioAIE materials from biomass

The research of aggregation‐induced emission (AIE) materials has aroused extensive interests during the past 20 years. Until recently, biomass‐inspired AIE (BioAIE) materials have become highly attractive owing to the advantages of natural structural diversity, renewability, biocompatibility, and biodegradability of the biomass. In this concept, we focus on the sustainable production of BioAIE materials from biomass resources (biomacromolecules and small natural products) through extraction, chemical conversion, and physical conversion. Chemical conversion is especially stated, including catalytic conversion, Schiff base reaction, “in water” reaction, and other chemical modifications. The luminescence mechanism of AIE behaviors along with their structure‐property relationships is emphasized, and the applications are addressed as well. An outlook is provided to highlight the challenges and opportunities associated with the future development trend in this field.

An Immunoregulatory and Metabolism-Improving Injectable Hydrogel for Cardiac Repair After Myocardial Infarction

Abstract The hypoxia microenvironment post myocardial infarction (MI) critically disturbs cellular metabolism and inflammation response, leading to scarce bioenergy supplying, prolonged inflammatory phase and high risk of cardiac fibrosis during cardiac restoration. Herein, an injectable hydrogel is prepared by Schiff-base reaction between fructose-1,6-bisphosphate (FBP)-grafted carboxymethyl chitosan (CF) and oxidized dextran (OD), following by loading fucoidan-coated baicalin (BA)-encapsulated zein nanoparticles (BFZ NPs), in which immunoregulatory and metabolism improving functions are integrally included. The grafted FBP serves to enhance glycolysis and provide more bioenergy for cardiomyocytes survival under hypoxia microenvironment, and elevating cellular antioxidant capacity via pentose phosphate pathway. OD with intrinsic anti-inflammatory effect can induce M2 polarization of macrophages to accelerate inflammatory elimination. While facing the possibility of endothelial-to-mesenchymal transition (EndoMT) caused by excessive expressed TGF-β1 secreted from M2 macrophages, BFZ NPs can target endothelia cells and intracellularly release BA to regulate the level of fatty acid oxidation, resulting in retained endothelial features and decreased risk of cardiac fibrosis. After being injecting the hydrogel into rats’ infarcted cardiac, the 28 day-post surgical outcomes demonstrate its benign effects on restoring cardiac functions and attenuating adverse left ventricular remodeling. This study shows a promising measure for MI treatment with immunoregulating and metabolism regulation comprehensively.

In Situ SERS Monitoring of Schiff Base Reactions via Nanoparticles on a Mirror Platform

Schiff base reactions are widely used in pharmacy, catalysis, and volatile aldehyde detection. However, common biomarker sensing methods struggle to monitor this reaction process precisely due to their sensitivity, their time-consuming nature, and complex substrates. Here, we introduce the Nanoparticle-on-Mirror structure for in situ monitoring this reaction process through the application of a Au nanoparticle-p-Aminothiophenol-Au thin-film platform by surface-enhanced Raman scattering (SERS). Owing to the exposure of -NH2 groups and the local ultra-strong electromagnetic field in the nanocavity, the Schiff base reactions process can be rapidly monitored within two minutes. Meanwhile, the monitoring platform can detect benzaldehyde molecules as low as 10−6 M, showing excellent SERS performance. Notably, the Au-nanoparticle-p-Aminothiophenol-Au thin-film platform exhibited anti-interference and specificity, being able to identify BA in the presence of interference. The use of the Au-nanoparticle-p-Aminothiophenol-Au thin-film platform provides a sensing method for Schiff base reactions with accuracy and simplicity of operation, achieving a balanced approach for low-cost and high-performance real-time monitoring, which is expected to be applied in various catalytic reaction process monitoring and catalyst design processes.

Engineering Robust Silver-Decorated calcium peroxide Nano-Antibacterial Platforms for chemodynamic enhanced sterilization

Calcium peroxide (CaO2) is commonly used as a hydrogen peroxide (H2O2) donor to eliminate bacterial infections. However, the rapid dissociation of CaO2 and the explosive release of H2O2 have limited the development of CaO2 in the antibacterial field. Therefore, a series of silver nanoparticles (AgNPs) functionalized bacteria-triggered smart hydrogels (CSA-H) that integrate sustained release of nanoparticles and localized chemodynamic sterilization were constructed. The pH-responsive hydrogel formed through the Schiff base reaction enables the responsive release of CaO2 nanoparticles while simultaneously regulating the concentration of H2O2 within the bacterial infection microenvironment. AgNPs are capable of reacting with H2O2 under mildly acidic conditions to produce hydroxyl radicals with enhanced antimicrobial activity. The antimicrobial results demonstrated that AgNPs functionalized silicon dioxide-coated calcium peroxide (CaO2@SiO2/AgNPs) nanoparticles exhibited enhanced bactericidal activity compared to AgNPs or CaO2 alone. Furthermore, CSA-H hydrogels exhibited significant antibacterial activity against S. aureus and E. coli under the dual effect of AgNPs and pH-driven Fenton-like reactions. This chemodynamic antibacterial platform is environmentally responsive and provides a promising strategy for creating multifunctional hydrogels loaded with nano-enzymes, thus advancing the development of AgNPs in chemodynamic-antibacterial related applications.

High performance loose-structured membrane enabled by rapid co-deposition of dopamine and polyamide-amine for dye separation

Textile wastewater poses a significant environmental challenge that demands effective treatment. Membrane separation offers a promising solution, with high-flux tight ultrafiltration membranes recognized as an effective technology for dye separation. Polyamide amine (PAMAM), a dendritic macromolecule renowned for its regular structure, high monodispersity, excellent solubility, and tunable molecular weight, has emerged as a promising material for membrane fabrication. This study introduces a novel, eco-friendly, and time-efficient method for preparing polymer composite membranes through one-step co-deposition of dopamine (DA) and PAMAM, predominantly utilizing Michael addition and Schiff base reactions. The incorporation of ammine-rich PAMAM imparts ultra-high hydrophilicity to the membranes (contact angle of 38°), facilitating strong adhesion of water molecules to the membrane surface. The effects of co-deposition time and concentrations of DA and PAMAM on the separation performance of the resulting membranes were systematically investigated. Notably, the optimal membrane demonstrated a high water flux (126.1 L m-2h−1 bar−1), primarily due to the incorporation of PAMAM, which resulted in a looser selective separation layer. Furthermore, the membrane demonstrated excellent rejection of methyl blue (MB) at 98.9 % and low rejection os methyl orange (MO) at 13.2 %, making it well-suited for the selective separation of mixed dyes. Our approach offers a sustainable and technologically advanced solution for addressing resource recovery from textile wastewater.

Multifunctional composite paper fabricated by graphene oxide/tannin decorated carbon fiber with excellent electromagnetic interference shielding, antibacterial and sound absorption properties

Considering the distinctive oxidative coupling characteristic of tannin acid, it was used as an interfacial interlayer to build a nano-coating structure on the surface of carbon fiber (CF)using amino-modified graphene oxide (GON) via Schiff base reaction. Furthermore, a kind of multifunctional composite paper (PTCF/GON) with excellent electromagnetic interference shielding, antibacterial and sound absorption properties was fabricated using surface modified CF (TCF/GON) and plant fibers. The increased active groups on the surface of TCF/GON improved its hydrophilicity and enhanced its dispersibility in water, which facilitated to form an effective interconnected conductive network of composite paper via traditional wet forming process. Composite paper fabricated by 30 wt% surface decorated CF (PTCF1.5/GON1.2) achieved an electromagnetic interference shielding effectiveness as high as 43.4 dB in X-band, shielding 99.9 % of incident electromagnetic energy. Meanwhile, PTCF1.5/GON1.2 exhibits good sound absorption performance in specific frequency bands, with a sound absorption coefficient of 0.98 around 1180 Hz. Besides, PTCF1.5/GON1.2 also exhibited excellent antibacterial properties. This strategy provides an economical and practical method for manufacturing multifunctional electromagnetic shielding materials with superior performance.

Tailoring ion-accessible pores of robust nitrogen heteroatomic carbon nanoparticles for high-capacity and long-life Zn-ion storage

Designing highly endogenous zincophilic sites and ion-accessible pore architectures is crucial but remains a formidable challenge for carbon cathodes in zinc-ion hybrid capacitors (ZHCs) with superior capacity activity and ultralong cycling life. Herein, nitrogen heteroatomic carbon nanoparticles with hierarchical porous architectures were tailor-made by a well-established and efficient Schiff base reaction. The nucleophilic addition of amine modules and reactive carbonyl groups forms ordered organic nanoparticles with the specific internal ring pore size (1.27 nm) and high-level N heteroatomic doping. The tailored internal ring pore size, the robust macroporous networks formed by aggregated and interwoven nanoparticles and controlled carbonization/activation processes collaborate to obtain hierarchical porous architectures, robust carbon skeletons and high specific surface area (SSA) (2504 m2 g−1). Most notably, the pore architectures of NHPCs-700 (∼1.2 nm) can perfectly match the solvated ion diameter of Zn2+ (0.86 nm) and CF3SO3− (1.16 nm), realizing highly accessibility of zincophilic sites and fast diffusion behaviors. Additionally, ex-situ characterization and DFT calculation reveal the following energy storage mechanism: the ultrahigh zinc-ion capturing ability of pyridine N motifs, and fast diffusion behaviors alternately physical uptake of Zn2+/CF3SO3− charge carriers. The highly endogenous zincophilic sites, ion-accessible pore architectures and dual ion storage mechanism ensure exceptional specific capacity (253 mAh g−1 at 0.2 A g−1), outstanding energy density (157.8 Wh kg−1 at 125.3 W kg−1), and ultralong cycling life (200, 000 cycles at 10 A g−1). This work provides a strategic fabrication method for the advanced carbon cathodes with highly endogenous zincophilic site.

A multifunctional soybean protein isolates crosslinked gelatins composite mulch film: Fabrication, characterization, and application

The development of sustainable agriculture has boosted an increase in demand for biodegradable and multifunctional biomass-based mulch films. Herein, a sort of eco-friendly and multifunctional soybean protein isolates crosslinked gelatins (SPI-c-Gel) composite mulch films were elaborately designed through the Schiff base reaction. The formation of physical entanglement and chemical cross-linking between the molecular chains of SPI and Gel could effectively dissipate the loading energy and thereby strengthen the resistance of the composite mulch films to water penetration. Specifically, the maximum tensile strain and tensile stress were observed to increase from 4.05 MPa at 73.3 % for pure SPI film to 14.7 MPa at 151 % for optimized SPI-c-Gel0.3 mulch film. The swelling rate in water declined from 280 % for pure SPI film to 141 % for SPI-c-Gel0.3 composite film. Furthermore, the fabricated composite mulch film exhibited satisfied water retention, urea slow-release properties, and biodegradability. The application experiments of SPI-c-Gel0.3 composite mulch have shown that the seeds grew faster when cabbage seeds were covered by such mulch film during seed germination. Our findings provide a novel strategy for regulating the physical and chemical properties of biopolymer-based multifunctional mulch films, which may be employed to promote the development of sustainable agriculture.

An injectable carboxymethyl chitosan-based hydrogel with controlled release of BMP-2 for efficient treatment of bone defects

Although biological scaffolds containing bone morphogenetic protein-2 (BMP-2) have been widely used for osteogenic therapy, achieving stable and controlled release of BMP-2 remains a challenge. Herein, a novel BMP-2 sustained-release system composed of carboxymethyl chitosan (CMCS)/polyethylene glycol (PEG)/heparin sulfate (HS) (CMCS/PEG/HS) was constructed with a Schiff base reaction, yielding an injectable hydrogel for the release of BMP-2 in a controlled manner. For the CMCS/PEG/HS/BMP-2 hydrogel, the HS component had a negatively charged structure, which can bind to positively charged growth factors and prevent early hydrolytic metabolism of growth factors, thus achieving sustainable release of BMP-2. Notably, the release of BMP-2 in hydrogels was dependent mainly on degradation of the hydrogel matrix rather than simple diffusion. Generally, the CMCS/PEG/HS/BMP-2 hydrogel scaffold demonstrated excellent recoverability, good injectability, excellent biocompatibility and high adaptability, as well as efficient self-healing features to occupy irregularly shaped bone marrow cavities. The in vitro results revealed that the CMCS/PEG/HS/BMP-2 hydrogel promoted the osteogenic differentiation of MC3T3-E1 cells. Furthermore, the in vivo results suggest that the hydrogel has promising osteogenic effects that promote bone regeneration in a skull bone defect model. The injectable hydrogel scaffold shows great promise for bone treatment in the future.

Design of Self-Standing Chiral Covalent-Organic Framework Nanochannel Membrane for Enantioselective Sensing.

Nanochannel membranes are promising materials for enantioselective sensing. However, it is difficult to make a compromise between the selectivity and permeability in traditional nanochannel membranes. Therefore, new types of nanochannel membranes with high enantioselectivity and excellent permeability should be explored for chiral analysis. Here, asymmetric catalysis strategy is reported for interfacial polymerization synthesis of chiral covalent-organic framework (cCOF) nanochannel membrane for enantioselective sensing. Chiral phenylethylamine (S/R-PEA) and 2,4,6-triformylphloroglucinol (TP) are used to prepare chiral TP monomer. 4,4',4″-triaminotriphenylamine (TAPA) is then condensed with chiral TP to obtain cCOF nanochannel membrane via a C═N Schiff-base reaction. The molar ratio of TP to S/R-PEA is adjusted so that S/R-PEA is bound to the aldehyde only or both the aldehyde and hydroxyl groups on TP to obtain chiral-induced COF (cCOF-1) or both chiral-induced and modified COF (cCOF-2) nanochannel membrane, respectively. The prepared cCOF-2 nanochannel membrane showed two times more selectivity for limonene enantiomers than cCOF-1 nanochannel membrane. Furthermore, cCOF-2 nanochannel platform exhibited excellent sensing performance for other chiral molecules such as limonene, propanediol, methylbutyric acid, ibuprofen, and naproxen (limits of detection of 19-42ngL-1, enantiomer excess of 63.6-86.3%). This work provides a promising way to develop cCOF-based nanochannel enantioselective sensor.

Hyperbranched polylysine/oxidized carboxymethyl cellolose integrated gelatin composite for wound treatment

Herein, we report the preparation and evaluation of a new composite consisting of gelatin matrix, oxidized carboxymethyl cellulose (OCMC), and hyperbranched polylysine (PL) components for full-thickness wound treatment. To enhance the antimicrobial activity of the gelatin matrix, OCMC/PL was successfully combined with this matrix via the Schiff base reaction. Moreover, allantoin (Alla) as a drug model was loaded by this composite and the optimal formulation for wound healing (PLOCG-Alla) was obtained. The structural properties, thermal stability, crystallinity and interactions between materials were investigated using SEM, TGA, XRD and FTIR techniques. Cytotoxicity and antibacterial capacity were evaluated by MTT assay and colony counting methods, respectively. The release behavior was investigated at two different pH values. Blood coagulation and wound healing potential were also evaluated in vivo. PLOCG-Alla exhibited high antibacterial capacity, pH-dependent release behavior, biocompatibility and high blood clotting ability. It also accelerated wound healing in vivo.

Multi-functional Gleditsia sinensis galactomannan-based hydrogel with highly stretchable, adhesive, and antibacterial properties as wound dressing for accelerating wound healing

Design and development of a multifunctional wound dressing with self-healing, adhesive, and antibacterial properties to attain optimal wound closure efficiency are highly desirable in clinical applications. Nevertheless, conventional hydrogels face significant barriers in their mechanical strength, adhesive performance, and antibacterial properties. Herein, a tough hydrogel based on aldehyde-grafted galactomannan was synthesized through radical copolymerization and Schiff base reaction, incorporating hyaluronic acid, acrylamide, and the zwitterionic monomer to create a multi-crosslinked structure. The multiple crosslink structure pattern consisting of multiple hydrogen bonding, ionic interactions, reversible Schiff bases bonds, and molecular chain entanglement endowed this hydrogel with multiple functionalities, including high tensile strength (25 kPa), tensile strain (2200 %), toughness (391.59 kJ/m3), and Young's modulus (9.77 kPa). The presence of catechol groups and zwitterionic groups endow hydrogels with outstanding adhesion strength (42.21 kPa), which satisfied the adhesive demand for the ample motion of specific areas. The zwitterionic monomer provided long-lasting antibacterial properties and promoted migration and growth of negatively charged cells, capable of establishing efficient antibacterial barriers and serving as wound dressing. The in vivo and vitro experiments manifested that the optimized hydrogel demonstrated an inconspicuous inflammatory response, facilitating rapid healing of full-thickness skin wound in rat models. Therefore, this work provides a promising strategy and an ideal candidate for wound healing dressings in treating infected skin wounds.

Boosting lithium/magnesium separation performance of selective electrodialysis membranes regulated by enamine reaction

Monovalent cation exchange membranes (MCEMs) have progressively played an important role in the field of ion separation. However, according to transition state theory (TST), synchronously tuning the enthalpy barrier (△H) and entropy barrier (△S) for cation transport to improve ion separation performance is challenging. Here, the enamine reaction between the -NH- and -CHO groups is applied to regulate the subsequent Schiff-base reaction between the -CHO and -NH2 groups, which reduces the positive charges of the selective layer but increases the steric hindrance. The increased -T△S (△S term) for cation transport plays an important role in improving Li+/Mg2+ separation performance. The optimal positively-charged glutaraldehyde@piperazine/polyethyleneimine assembled membrane (M-Glu@PIP/PEI) has a perm-selectivity (Li+/Mg2+) of 31.83 with a Li+ flux of 1.87 mol·m-2·h-1, surpassing the Li+/Mg2+ separation performance of state-of-the-art monovalent ion selective membranes (MISMs). Most importantly, the selective electrodialysis (S-ED) process with M-Glu@PIP/PEI can be directly applied to treat simulated salt-lake brines (SLBs), and its superior Li+/Mg2+ separation performance and operational stability enables 74.44 % of the lithium resources with a Li+ purity of 34.02 % to be recovered. This study presents new insights into the design of high-performance MCEMs for energy-efficient resource recovery.

Schiff base approach to introduce chitosan-phytic acid complex for flame-retardant cotton fabrics

In this study, chitosan was integrated onto cotton fabric fibers through a Schiff base reaction, followed by the in-situ generation of Chitosan-Phytic acid (CH-PA) complex to achieve green flame retardancy. The process began with oxidizing the fabric using sodium periodate (NaIO4) to create numerous aldehyde groups on the fiber surface. Subsequently, CH was grafted onto the fabric via a Schiff base reaction. The fabric was then immersed in a PA solution to form a CH-PA complex, resulting in a novel and highly efficient flame-retardant (FR) fabric. The structure of the treated fabric was analyzed by using Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS), confirming the successful formation of the desired structure. The thermal stability and flame retardancy of the fabric were systematically evaluated using thermogravimetric analysis (TGA), cone calorimetry (CONE), vertical combustion tests, and limiting oxygen index (LOI) measurements. The LOI increased from 17.6 % to 30.6 %, and vertical combustion tests demonstrated self-extinguishing capabilities when the fabric was treated by the NaIO4 solution at concentrations of 0.02 g/mL or higher. In the CONE test, the modified fabric showed significant improvements, with peak heat release rate (pHRR) and total heat release (THR) decreasing by approximately 80 % and 60 %, respectively. Comprehensive analysis indicated that the FR mechanism involved both gas phase and condensed phase actions. Further characterization of the material included tensile testing and wash resistance assessments. By comparing these findings with recent research on similar topics, the advantages and disadvantages of the materials were thoroughly evaluated. Notably, this work provides a robust experimental foundation and conceptual expansion for the green flame retardancy of cotton fabrics.

Pyrene‐Functionalized Silicon Hybrid Porous Polymer for an Efficient Adsorption of Dyes

AbstractPyrene‐functionalized silicon hybrid porous polymer (TAPPy‐HPP). The hybrid polymer was successfully prepared via a Schiff base reaction using tetra(4‐aminophenyl)pyrene (TAPPy) and tetra(4‐formylphenyl)silane (TFS) as the building blocks.. This hybrid polymer was characterized using IR, solid‐state 13C and 29Si NMR, and elemental analysis. Its morphology was analyzed by PXRD and SEM. Thermal analysis using Thermal analysis using TGA shows that the synthetic polymer has greater thermal stability than its monomers at a temperature of 5 % weight loss (Td5 %) of 392 °C. Although TAPPy‐HPP has a Brunauer‐Emmet‐Teller surface area of 45.4 m2 g−1, it adsorbed dyes with high efficiency, particularly the anionic dye Congo Red (CR), with an adsorption capacity of up to 358 m2 g−1. Moreover, TAPPy‐HPP showed excellent recycling and regenerative properties. This polymer is a promising candidate for a fluorescent chemical sensor for the absorption of dyes due to its exceptional physiochemical stability and intense luminescence.

Enhancing cementitious materials with polymer dots: Size effects on strength and chloride resistance

Polymer dots (PDs), as emerging carbon-based nanomaterials, show promise for improving cement material properties due to their small size, excellent dispersity, and affordability. However, the relevant research remains uncovered. Especially, the impact of PDs particle size on mechanical performance and chloride binding capacity is still blank. In light of this, this work offers a comprehensive insight into the size effects of PDs on the mechanical properties and chloride binding capacity of cement pastes, along with the corresponding influencing factors. Specifically, PDs with three particle sizes of ca. 13.69, 5.81, and 2.55 nm (namely, LPDs, MPDs, and SPDs) are efficiently synthesized by altering the reaction temperature based on the Schiff base reaction. In comparison with the blank group, the mechanical properties of paste specimens containing LPDs, MPDs, and SPDs are improved by 3.8 %, 12.9 %, and 16.5 % separately, and their chloride binding capacity are significantly enhanced by 53 %, 117 %, and 129 % respectively. More significantly, the relevant influence mechanism is that smaller-sized PDs can more effectively exert their nucleating effect to further facilitate the formation of C–S–H, further resulting in a denser pore structure and enhanced chloride physical adsorption in cement matrices. Meanwhile, the smaller-sized PDs are conducive to promoting Friedel's salt generation, dramatically improving the chloride chemical binding. This research would provide comprehensive guidance on synthesizing PDs suitable for cementitious materials to enhance their strength and anti-chloride-corrosion properties more efficiently, thereby fostering the development of high-performance cement composites.

A smartphone-assisted chromogenic and fluorogenic dual-channel sensor for specific determination of toxic Pb2+ ions with multifaceted applications

Heavy metal pollutants, such as Pb2+ ions, pose a substantial hazard to human health and ecosystems, and it was of great significance to develop cost-effective and portable techniques for online and visual detection of Pb2+. Herein, we fabricated a novel chromogenic and fluorogenic dual-channel sensor NQA through a Schiff base reaction involving a dicyanoisophorone derivative and isoniazid, enabling effective detection of Pb2+ ions. Upon complexation with Pb2+ ions at a 1:1 M ratio, the fluorescence intensity of NQA exhibited a remarkable enhancement. The naked-eye colorimetric detection utilizing NQA demonstrated a distinct color change to specific Pb2+ ions concentration from yellow to light pink. Based on this principle, a smartphone-assisted sensing platform was developed for visual and high-quality identification of Pb2+ in real samples. The UV binding constant for Pb2+ ions was determined to be 1.84 × 105 M−1, with a detection limit of 0.38 μM. Furthermore, the versatility of NQA extended to applications in naked-eye test paper experiments, the detection of Pb2+ ions in real water samples and living cells, showcasing its potential for environmental and biological monitoring.