MXene/ZnS/chitosan-cellulose composite with Schottky heterostructure for efficient removal of anionic dyes by synergistic effect of adsorption and photocatalytic degradation.

Nowadays, dye water pollution is becoming increasingly severe. Composite of MXene, ZnS, and chitosan-cellulose material (MX/ZnS/CC) was developed to remove anionic dyes through the synergistic effect of adsorption and photocatalytic degradation. MXene was introduced as the cocatalyst to form Schottky heterostructure with ZnS for improving the separation efficiency of photocarriers and photocatalytic performance. Chitosan-cellulose material mainly served as the dye adsorbent, while also could improve material stability and assist in generation of free radicals for dye degradation. The physics and chemistry properties of MX/ZnS/CC composite were systematically inspected through various characterizations. MX/ZnS/CC composite exhibited good adsorption ability to anionic dyes with adsorption capacity up to 1.29 g/g, and excellent synergistic effects of adsorption and photodegradation with synergistic removal capacity up to 5.63 g/g. MX/ZnS/CC composite performed higher synergistic removal ability and better optical and electrical properties than pure MXene, ZnS, chitosan-cellulose material, and MXene/ZnS. After compounding, the synergistic removal percentage of dyes increased by a maximum of 309 %. MX/ZnS/CC composite mainly adsorbs anionic dyes through electrostatic interactions and catalyzes the generation of •O2-, h+, and •OH to degrade dyes, which has been successfully used to remove anionic dyes from environmental water, achieving a 100 % removal of 50 mg/L dye.

Magnetic molecular imprinted covalent organic framework composite for the magnetic solid-phase extraction of bisphenol AF.

A magnetic molecular imprinted covalent organic framework composite (MCOF-MIP) that possessed the 'dual-selectivity' of a covalent organic framework and molecular imprinted polymer (MIP) with rapid response performance was successfully prepared for the removal of bisphenol AF (BPAF) from real water and blood samples. First, the MCOF was separately synthesized using magnetic Fe3O4 as the magnetic core, 1,3,5-triaminobenzene and 2,5-dibromobenzene-1,4-diformaldehyde as precursors and a deep eutectic solvent (DES) as the solvent using a solvothermal synthesis method. The MCOF showed high crystallinity and good adsorption capacities for BPAF (107.4 mg g-1), bisphenol A (113.6 mg g-1), bisphenol S (120.0 mg g-1) and bisphenol F (82.1 mg g-1). To further improve the selectivity for BPAF, an MIP, which uses BPAF as a template, was introduced to form the MCOF-MIP. Due to the dual selectivity of MCOF and MIP, the MCOF-MIP exhibited relatively high selective adsorption capacity to BPAF (243.1 mg g-1) compared to that for the MCOF (107.4 mg g-1), while the adsorption capacities (149.7-109.4 mg g-1) for the other three compounds were not significantly improved. Furthermore, a magnetic solid-phase extraction (MSPE) method was established, and MSPE parameters such as adsorbent dosage, adsorption time, desorption solvent and desorption time were optimized. Combined with high-performance liquid chromatography with diode-array detection (HPLC-DAD) analysis, a rapid and sensitive method was developed to detect BPAF, which showed good linearity (r > 0.9969) ranging from 0.1 to 400 µg mL-1. Low limits of detection (0.04 µg mL-1, S/N = 3) and quantitation (0.1 µg mL-1, S/N = 10) and good precision with low relative SDs (<1.2 % for intra-day and <1.1 % for inter-day) were also obtained. Finally, MSPE coupled with HPLC-DAD was employed for the analysis of BPAF in water and blood samples, and the recoveries of BPAF were satisfactory (91.1-112.6 %).

Combined transcriptomic and pangenomic analyses guide metabolic amelioration to enhance tiancimycins production.

Exploration of high-yield mechanism is important for further titer improvement of valuable antibiotics, but how to achieve this goal is challenging. Tiancimycins (TNMs) are anthraquinone-fused enediynes with promising drug development potentials, but their prospective applications are limited by low titers. This work aimed to explore the intrinsic high-yield mechanism in previously obtained TNMs high-producing strain Streptomyces sp. CB03234-S for the further titer amelioration of TNMs. First, the typical ribosomal RpsL(K43N) mutation in CB03234-S was validated to be merely responsible for the streptomycin resistance but not the titer improvement of TNMs. Subsequently, the combined transcriptomic, pan-genomic and KEGG analyses revealed that the significant changes in the carbon and amino acid metabolisms could reinforce the metabolic fluxes of key CoA precursors, and thus prompted the overproduction of TNMs in CB03234-S. Moreover, fatty acid metabolism was considered to exert adverse effects on the biosynthesis of TNMs by shunting and reducing the accumulation of CoA precursors. Therefore, different combinations of relevant genes were respectively overexpressed in CB03234-S to strengthen fatty acid degradation. The resulting mutants all showed the enhanced production of TNMs. Among them, the overexpression of fadD, a key gene responsible for the first step of fatty acid degradation, achieved the highest 21.7 ± 1.1 mg/L TNMs with a 63.2% titer improvement. Our studies suggested that comprehensive bioinformatic analyses are effective to explore metabolic changes and guide rational metabolic reconstitution for further titer improvement of target products. KEY POINTS: • Comprehensive bioinformatic analyses effectively reveal primary metabolic changes. • Primary metabolic changes cause precursor enrichment to enhance TNMs production. • Strengthening of fatty acid degradation further improves the titer of TNMs.

Chitosan-alginate sponge with multiple cross-linking networks for adsorption of anionic dyes: Preparation, property evaluation, mechanism exploration, and application.

A chitosan-alginate sponge (CAS) with multiple cross-linking networks was developed using chitosan, sodium alginate, polyvinyl alcohol, and glutaraldehyde to adsorb and enrich the anionic dyes form the food samples. The multiple networks in CAS refer to the electrostatic cross-linking network, hydrogen bonding cross-linking network, and covalent cross-linking network. Compared with pure chitosan and alginate sponges, the CAS showed better three-dimensional network structure, mechanical behavior, and stability, which is benefit by multiple cross-linking networks. The physical and chemical properties of CAS were systematically studied by a series of characterizations. The adsorption performance of CAS on anionic dyes was inspected with different dye concentration, time, temperature, and pH conditions. CAS exhibited a good and stable adsorption property to amaranth, carmine, and sunset yellow with the saturation adsorption capacity of 94.34, 111.5, and 80.05 mg∙g-1, respectively. Furthermore, CAS performed outstanding selectivity to anionic dyes with the selectivity factor up to 16.99. Through electrostatic potential analysis, it is inferred that CAS mainly adsorbs anionic dyes through electrostatic interactions. CAS showed satisfactory reusability, maintaining 97 %-99 % of adsorption performance after six cycles of recycling. Finally, CAS was combined with high-performance liquid chromatography for the enrichment and detection of anionic dyes in candy and cocktail samples, achieving the enrichment factor up to 84.77.

Alcoholamine enhanced fractionation of cellulose from lignocellulosic biomass in ionic liquids.

Ionic liquid based technology is promising in the pretreatment of lignocelluloses. More efforts are still being made to intensify the separation of the main components in this biomass and to inhibit biopolymer degradation, especially in the fabrication of functional materials where excellent mechanical properties are often requisite. In this study, additives with amino and/or hydroxyl groups were proposed to improve the dissolution of lignocellulosic biomass in ionic liquids and to inhibit the degradation of cellulose. Among the tested additives (i.e., urea, L-2-aminobutyric acid, DL-aminopropanol, 3-aminopropanol and ethanolamine), 3-aminopropanol showed the best performance in enhancing wheat straw dissolution and cellulose recovery in 1-ethyl-3-methylimidazolium acetate ([EMIM]Ac). Further study revealed that this additive could also inhibit cellulose degradation in [EMIM]Ac. The interactions between the ionic liquid and additive were revealed by NMR and IR analysis. It was found that the formation of hydrogen bonds between 3-aminopropanol and [EMIM]Ac changed the interactions between ionic liquids and biomass, resulting in improved dissolution efficiency and inhibition of cellulose degradation. Optimization investigation showed that when using the 3-aminopropanol/[EMIM]Ac composite system as the solvent and pine as the raw biomass, the cellulose content in the recovered cellulose-rich material was increased from 33.3% (for the raw pine) to 66.9%. Correspondingly, the regenerated cellulose spinning in the composite system exhibited improved mechanical properties, with the elongation at break reaching 15.6% and the tensile fracture strength of 184.1 N per tex (in comparison with 9.6% for elongation at break and 99.7 N per tex for tensile fracture strength for the sample obtained in neat [EMIM]Ac).

Fluorescent covalent organic frameworks for environmental pollutant detection sensors and enrichment sorbents: a mini-review.

Covalent organic frameworks (COFs) are a class of porous crystalline materials based on organic building blocks containing light elements, such as C, H, O, N, and B, interconnected by covalent bonds. Because of their regular crystal structure, high porosity, stable mechanical structure, satisfactory specific surface area, easy functionalization, and high tunability, they have important applications in several fields. Currently, most of the established methods based on COFs can only be used for individual detection or adsorption of the target. Impressively, fluorescent COFs as a special member of the COF family are able to achieve highly selective and sensitive detection of target pollutants by fluorescence enhancement or quenching. The construction of a dual-functional platform for detection and adsorption based on fluorescent COFs can enable the simultaneous realization of visual monitoring and adsorption of target pollutants. Therefore, this paper reviews the research progress of fluorescent COFs as fluorescence sensors and adsorbents. First, the fluorescent COFs were classified according to the different bonding modes between the building blocks, and then the applications of fluorescent COF-based detection and adsorption bifunctional materials for various environmental contaminants were highlighted. Finally, the challenges and future application prospects of fluorescent COFs are discussed.

ZnS/CuFe2O4/MXene ternary heterostructure photocatalyst for efficient adsorption and photocatalytic degradation of azo dyes under visible light: Synergistic effect, mechanism, and application.

ZnS/CuFe2O4/MXene (ZSCFOM) composite with ternary heterostructures was prepared by solvothermal methods for the first time to effectively adsorb and photodegrade the azo dyes. ZSCFOM mainly adsorbed azo dyes through the hydrogen bonding and electrostatic interactions, with saturated adsorption capacities of 377 mg g-1 for direct brown M and 390 mg g-1 for direct black RN. ZSCFOM exhibited both characteristics of Schott heterostructure and p-n heterostructure, but it is not a simple superposition of the two heterostructures, but rather achieves better photocatalytic property. ZSCFOM performed a higher separation efficiency of electrons and holes than pure CuFe2O4 and pure ZnS. Under visible light, ZSCFOM was more effective in removing the azo dyes than MXene, CuFe2O4, ZnS, CuFe2O4/MXene, ZnS/MXene, and ZnS/CuFe2O4. The migration pathways of photogenerated carriers in ZSCFOM were inferred as that the electrons were concentrated in MXene and conduction band of ZnS, and holes were gathered in valence band of CuFe2O4. MXene served as a cocatalyst to accelerate the separation of electrons and holes. ZSCFOM mainly degraded DBM and DBRN by catalyzing the generation of holes, superoxide radicals, and hydroxyl radicals. The 100% of 0.05 g L-1 azo dyes were removed by ZSCFOM within 30 min from the environmental water systems.

Carbonized human hair derived carbon dots for detection of clozapine.

Clozapine (CLZ) is known as the most effective antipsychotic medication for schizophrenia. However, low dosage or over dosage of CLZ is adverse to the treatment of Schizophrenia. Thus, it is necessary to develop effective detection method for CLZ. Recently, due to the advantages such as excellent optical properties, good photobleachability and sensitivity, carbon dots (CDs)-based fluorescent sensors for the detection of target analytes have drawn a great deal of attention. In this work, blue fluorescent CDs (Named as B-CDs) with quantum yield (QY) as high as 38% were obtained by using carbonized human hair as source material through one-step dialysis method for the first time. B-CDs showed obvious graphite-like structure with an average of 1.76 nm, containing abundant functional groups such as -C=O, amino N and C-N on the surface of carbon cores. Optical analysis showed that the B-CDs exhibited excitation-dependent emission property with maximum emission wavelength of 450 nm. Moreover, B-CDs were further applied as a fluorescence sensor to the detection of CLZ. The B-CDs based sensor exhibited a good quenching response by CLZ through the inner filter effect and static quenching mechanism with a limit of detection of 67 ng/mL, which was much lower than the minimal effective concentration in blood (0.35 µg/mL). Finally, to test the practical application value of the developed fluorescence method, the determination of the content of CLZ in tablets and the concentration in blood was carried out. Compared with the results of high-performance liquid chromatography (HPLC) method, it can be found that the constructed fluorescence detection method showed high accuracy and had great application potential in the detection of CLZ. Additionally, the results of cytotoxicity experiment showed that B-CDs had low cytotoxicity, which laid the foundation for the subsequent application of B-CDs in biological systems.

Fabrication of highly crystalline covalent organic framework for solid-phase extraction of three dyes from food and water samples.

Herein, a covalent organic framework, which was fabricated at room temperature by using 1,3,5-tris(p-formylphenyl) benzene and 1,3,5-tris(4-aminophenyl)benzene as building blocks, was employed as an adsorbent for solid-phase extraction of dyes including congo red, methyl blue and direct red 80 for the first time. The prepared covalent organic framework was properly characterized by different techniques and the results revealed that it had a uniform spherical structure, high crystallinity, satisfactory surface area, and good thermal stability. Moreover, the adsorption performance of the material was explored by using static and dynamic adsorption experiments and the results indicated that the material showed good adsorption capacities for three dyes with adsorption capacities in the range of 55.25-284.10 mg/g and the adsorption equilibrium can be achieved in 15 min. Further, to achieve the best adsorption effects of the material, the influence parameters such as pH, ionic strength, type of desorption solvent, and the material dosage in the solid-phase extraction column, were optimized in turn. Finally, under optimal conditions, the solid-phase extraction coupled with HPLC was applied to the analysis of dyes in food and water samples. The recoveries of dyes in actual samples were satisfactory, revealing the unique applicability of the material in the sample pretreatment field.

Sulfuric acid induced-synthesis coupled with ethanol extraction-water precipitation purification method for orange fluorescent carbon dots with dual-emission: Application for methyl blue detection and cell imaging.

In this work, by adjusting the sulfuric acid content in reaction solvent of ethanol, orange fluorescent carbon dots (O-FCDs) with dual-emission wavelength and blue fluorescent carbon dots (B-FCDs) with single-emission wavelength were successfully prepared using 1,3-dihydroxynaphthalene as precursor. Coupling with ethanol extraction-water precipitation purification method, pure O-FCDs and B-FCDs with yields of 9.0 % and 21.3 %, quantum yields (QYs) of 43.0 % and 13.7 % were obtained, respectively. The structures and optical properties of O-FCDs and B-FCDs were investigated by TEM, AFM, Raman, FT-IR, XPS, UV-vis, fluorescence analysis etc. The results revealed that sulfuric acid promoted the carbonization and the oxidation of precursor in the reaction process. In comparison with the B-FCDs, O-FCDs showed narrower lattice spacing and band gap, demonstrating the important role of sulfur-doping in fluorescence tuning. Additionally, O-FCDs showed good sensitivity for methyl blue with a linear response range of 0.05-100 µM (LOD was 20 nM) and the satisfactory results were obtained when O-FCDs were applied to the detection of methyl blue in real fish sample. Moreover, two FCDs showed good biocompatibility and negligible cytotoxicity proved by MTT experiment, while, O-FCDs showed better cell imaging effects than that of B-FCDs. Therefore, the O-FCDs had a broad application prospect as sensing platform in detection of methyl blue and for imaging in biological field.

Hydroxyl-riched covalent organic framework for solid-phase microextraction of flavonoids aglycones or their metabolites in mice's plasma: Luteolin and quercetagetin as examples.

Herein, a hydroxyl­riched covalent organic framework (named COF-DES-1) was synthesized using 1,3,5-tris(4-aminophenyl)benzene and 2,5-dihydroxyterephthalaldehyde as building blocks and employed as a coating of solid-phase microextraction (SPME) fiber. Ascribed to the advantages (e.g. suitable pore size and rich functional group characteristics) of coating, the SPME fiber showed good adsorption capacities to flavonoids aglycones including luteolin and quercetagetin, and the maximum adsorption capacities for them were 145.31 µg and 84.75 µg, respectively. Due to the size exclusion property of COF-DES-1, SPME fiber showed good protein exclusion effects on seven selected proteins with high exclusion efficiencies (>93%). Accordingly, an attractive strategy of the combination of COF-DES-1 based SPME fiber and HPLC-MS/MS was proposed for the extraction and determination of luteolin, quercetagetin or their metabolites. The results revealed that the fiber can be effectively applied to extract luteolin and its metabolites, and quercetagetin from mice's palsma. Compared with the traditional protein precipitation methods, the extraction effects of SPME fiber based extraction method were much better, indicating the promising applicability of the fiber for the enrichment of flavonoids aglycones or their metabolites in biological samples.

A novel hydroxyl-riched covalent organic framework as an advanced adsorbent for the adsorption of anionic azo dyes.

Considering the highly carcinogenic and mutagenic of anionic azo dyes to the environment and humans, the development of high efficiency adsorbent for them are of great significance. In this study, a novel hydroxyl-riched covalent organic framework (denoted as COF-OH), which can act as an advance adsorbent for anionic azo dyes, was fabricated for the first time. The as-prepared COF-OH demonstrated good dispersion in water, remarkable adsorption performances and good selectivity for anionic azo dyes including eriochrome black T, eriochrome blue black R and congo red. The adsorption capacities of them ranged from 90.71 to 229.12 mg g-1, and the extraction efficiencies of them (>75.91%) were much higher than other dyes (e.g. Methylene blue, direct red 80, 1.46%-39.57%). By optimizing the adsorption conditions (adsorbent dosage, adsorption time, pH, and salt concentration) and desorption conditions (desorption solvent, desorption time and desorption frequency), a dispersive micro solid-phase extraction (D-µ-SPE) method was developed. Further, coupled D-µ-SPE with HPLC-PDA analysis, an effective method was fabricated for the extraction and detection of three selected dyes. The method showed good linearity in the range of 0.1-200 µg mL-1 (R2 > 0.9966), low limits of quantification (0.10 µg mL-1-2.00 µg mL-1), low limits of detection (0.03-1.50 µg mL-1) and good precision. Finally, the COF-OH based D-µ-SPE was successfully applied to extract three selected dyes from water samples (recoveries ranged from 73.90 to 104.00%) and congo red from beverages (recoveries ranged from 81.40 to 111.80%). Besides, by using computer simulation, FT-IR and UV-vis analysis, the adsorption mechanisms of COF-OH to three selected dyes were explored preliminarily.

Molecularly imprinted polymers based on magnetic metal-organic frameworks for surface-assisted laser desorption/ionization time-of-flight mass spectrometry analysis and simultaneous luteolin enrichment.

UiO-66(NH2), a metal-organic framework, exhibits excellent UV absorption and energy transfer performance and can be used as a substrate for surface-assisted laser desorption/ionization (SALDI) analysis of small molecules. Molecularly imprinted polymers (MIPs) exhibit outstanding selectivity toward certain targets. The complexes of UiO-66(NH2) and MIPs can be applied as both an adsorbent and substrate for SALDI-time-of-flight mass spectrometry (SALDI-TOF MS) analysis of small molecules. Herein, magnetic UiO-66(NH2)-molecularly imprinted polymers (MUMIPs) were prepared for the selective enrichment and detection of luteolin via SALDI-TOF MS. The amino group on UiO-66(NH2) were used as functional monomer to prepare MIPs that interact with luteolin via hydrogen bonding. The surface functional monomer can effectively control the coating thickness of the MIPs to avoid embedding template molecules and enhance adsorption performance. In addition, Fe3O4 particles were introduced for rapid magnetic separation. The physicochemical properties of the MUMIPs were characterized via scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis, vibrating sample magnetometry, Brunauer-Emmett-Teller analysis, and X-ray photoelectron spectroscopy. Adsorption experiments and selectivity studies indicated that MUMIPs exhibited good adsorption capacity, fast adsorption rates, and excellent luteolin selectivity. MUMIPs are efficient substrates for the SALDI analysis of luteolin and its structural analogs. In addition, the MUMIPs-SALDI-TOF MS method successfully detected luteolin in rat plasma and urine after administration of oral Chrysanthemum morifolium Ramat extracts. This method possessed high sensitivity with a limit of detection of 0.5 ng/mL. The traditional precipitation method combined with high-performance liquid chromatography-mass spectrometry was also used to analyze luteolin in biological samples. Compared with the traditional method, the novel MUMIP-SALDI-TOF MS method can more effectively detect the target compounds in complex samples. Ultimately, the MUMIP-SALDI-TOF MS method was applied to detect luteolin and its metabolites in rat liver after oral luteolin treatment. Three luteolin metabolites (apigenin, chrysoeriol, and diosmetin) were analyzed using the newly developed MUMIP-SALDI-TOF MS method.

Preparation of sulphuric acid-mediated N,S-codoped red emissive carbon dots: Applications in food dyes detection, solid-state luminescence and cell imaging.

As diseases such as cardiovascular disease and cancer caused by food problems are more and more frequent, food safety has received great attention. Among them, the safety problem caused by food dyes is more prominent. Thus, it is of great value to develop sensitive detection methods for food dyes. In present study, sulphuric acid-mediated N,S-codoped red emissive carbon dots (namely as R-CDs) had been manufactured by using N-phenyl-o-phenylenediamine as precursor, sulfuric acid as additive for the first time. The structural and fluorescence properties of R-CDs had been systematically studied. The results demonstrated that R-CDs showed uniform spherical morphology and had a graphite-like structure, for which the average diameters size was 5.05 nm. Due to the various functional groups such as hydroxyl, pyridinic N, pyrrolic N and -C-SO4, R-CDs emitted bright red fluorescence. Importantly, because of the interactions between the functional groups of R-CDs with the selected food dyes, three dyes including amaranth, brilliant blue FCF and methylene blue can sensitively quench the fluorescence of R-CDs through IFE and static quenching effects. The linearity ranges of them were separately detected as 0.20 µM -20 µM, 10 nM-1 µM and 60 nM-8 µM. The limits of detection (LODs) of them were 70 nM, 4 nM and 20 nM, respectively. Further, R-CDs was successfully applied to the sensitive detection of three dyes from various food samples. To maximize the fluorescence properties of R-CDs, a R-CDs/PVA composite gel was fabricated to make R-CDs fluoresce in solid state condition. The potential of R-CDs/PVA composite gel for preliminary visualization analysis of three dyes was studied. Finally, ascribed to the low toxicity and good biocompatibility, the potential of R-CDs as probe for cell imaging was explored preliminarily.

Magnetic porous cellulose surface-imprinted polymers synthetized with assistance of deep eutectic solvent for specific recognition and purification of bisphenols.

Magnetic porous cellulose molecularly imprinted polymers-based bisphenols have been developed using Fe3O4 as the magnetic material, a deep eutectic solvent as the assisted solvent, and N-isopropylacrylamide as the functional monomer. The resulting magnetic porous cellulose molecularly imprinted polymers were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometry, thermal gravimetric analysis, and Brunauer-Emmett-Teller analysis. Moreover, the adsorption properties of the magnetic porous cellulose molecularly imprinted polymers toward bisphenol A, bisphenol F, and bisphenol AF were investigated using static, dynamic, and selective adsorption experiments. The introduction of porous cellulose materials significantly improves the capabilities of the material. The adsorption capacity, mass transfer efficiency, and selectivity of the magnetic porous cellulose molecularly imprinted polymers toward bisphenol A were 5.9, 4.0, and 4.4 times those of traditional molecularly imprinted polymers. Moreover, the adsorption stability of the magnetic porous cellulose molecularly imprinted polymers was investigated under different temperature and pH conditions. The adsorption characteristics of the magnetic porous cellulose molecularly imprinted polymers toward the target molecules were investigated using adsorption isotherm, kinetic, and thermodynamic models. Hydrogen bonding is the main interaction formed between the magnetic porous cellulose molecularly imprinted polymers and the target molecules. Magnetic porous cellulose molecularly imprinted polymers have great application value with excellent stability and reusability. Finally, the combination of the magnetic porous cellulose molecularly imprinted polymers and high-performance liquid chromatography or ultra-performance liquid chromatography-mass spectrometry was successfully used for the purification and detection of bisphenols in milk (1.349 ng/mL bisphenol F and 3.014 ng/mL bisphenol AF), canned fruits (1129 ng/mL bisphenol A, 10.11 ng/mL bisphenol F, and 91.87 ng/mL bisphenol AF), and fish (11.91 ng/mL bisphenol AF) samples. Furthermore, the magnetic porous cellulose molecularly imprinted polymer method is more selective, sensitive, and accurate than the traditional precipitation method.

Sulfuric-acid-mediated synthesis strategy for multi-colour aggregation-induced emission fluorescent carbon dots: Application in anti-counterfeiting, information encryption, and rapid cytoplasmic imaging.

Aggregation-induced emission fluorescent carbon dots (AIE-CDs) have applications in the fields of multi-colour anti-counterfeiting, information encryption, and imaging. In this study, four AIE-CDs (B-AIE-CDs, G-AIE-CDs, Y-AIE-CDs, and O-AIE-CDs) with blue, green, yellow, and orange fluorescence at high concentrations were fabricated using crystal violet as a precursor, solutions with different sulfuric acid concentrations as solvents under different temperatures and reaction times for the first time. The structural properties and fluorescence behaviour of the AIE-CDs were investigated. The results revealed that the sulfuric acid concentration had a significant effect on the fluorescence colour of the AIE-CDs because sulfuric acid can affect the degree of carbonisation, the type and content of nitrogen. Moreover, the reaction temperature and time affected the surface-defect state and the degree of carbonisation of the AIE-CDs, which affected the emission wavelength and quantum yield (QY) of the AIE-CDs. Furthermore, to exploit the unique characteristics (polychromatic aggregation fluorescence and acid-sensitive properties) of the obtained-AIE-CDs, anti-counterfeiting and information encryption methodologies (i.e., acid-stimuli-response producing multi-colour fluorescence) were preliminarily developed. Finally, B-AIE-CDs with a high QY of 43.5% were successfully used for rapid cytoplasmic imaging, demonstrating their applicability in biological fields.

N,Cl-Codoped Carbon Dots from Impatiens balsamina L. Stems and a Deep Eutectic Solvent and Their Applications for Gram-Positive Bacteria Identification, Antibacterial Activity, Cell Imaging, and ClO- Sensing.

In this study, we first synthesized metal-free N,Cl-doped carbon dots (N,Cl-CDs) using Impatiens balsamina L. stems as green precursors in a deep eutectic solvent (DES). The obtained N,Cl-CDs were characterized through transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, fluorescence (FL) spectroscopy, and ultraviolet (UV) spectroscopy. In addition to the common features of carbon dots (CDs), such as high light stability, small size, low toxicity, good aqueous solubility, and favorable biocompatibility, these N,Cl-CDs exhibited excellent recognition and selectivity for Gram-positive bacteria by doping with N and Cl elements using DES. The N,Cl-CDs with positive charge cannot only differentiate Gram-positive bacteria by selective fluorescence imaging but also have antibacterial effects on Gram-positive bacteria. Through potential, ROS, and morphological analyses of bacteria before and after treatment with N,Cl-CDs, the antibacterial mechanisms of bacteriostasis, Enterococcus faecium, Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Salmonella were explored. In addition, N,Cl-CDs demonstrated low cytotoxicity and good cell imaging ability in cancer and normal cells. Moreover, they can be used as a fluorescence sensor for the detection of ClO- with a detection range from 100 nM to 40 µM and a limit of detection (LOD) of 30 nM. In summary, the prepared N,Cl-CDs could be applied as environmentally friendly Gram-positive bacterial identification and antibacterial agents. Additionally, their cell imaging and ClO- detection abilities were outstanding.

Highly Crystalline Covalent Organic Frameworks Act as a Dual-Functional Fluorescent-Sensing Platform for Myricetin and Water, and Adsorbents for Myricetin.

Selective detection of active ingredients in complex samples has always been a crucial challenge because there are many disturbing compounds, especially structural analogues that interfere with the detection. In this work, a fluorescent covalent organic framework (named COF-TD), which can be used for the selective fluorescence detection and enrichment of myricetin from complex samples, was reported for the first time. The highly crystalline COF-TD with bright blue fluorescence was formed through a solution polymerization method by the condensation reaction between 4,4',4″-(1,3,5-triazine-2,4,6-triyl)trianiline and 2,5-dihydroxy-1,4-benzenedicarboxaldehyde. Due to spatial size selectivity, multisites hydrogen bonding, and π-π interaction, myricetin can quench the fluorescence of COF-TD with an inner filter effect (IFE) and static quenching mechanisms as well as can be enriched on COF-TD. Myricetin can observably eliminate the interference of other compounds and selectively quench the fluorescence of COF-TD with a limit of detection (LOD) of 0.30 µg·mL-1. The high adsorption ability of COF-TD (Q = 124.6 mg·g-1) to myricetin was also obtained. Finally, a sensing platform based on COF-TD for myricetin was successfully developed and applied for the detection of myricetin from vine teas. In addition, COF-TD also showed good water sensing ability and could be used effectively to detect water content in organic solvent (1-18% water in acetone, 0.5-5% water in acetonitrile, 1-4.5% water in ethyl acetate, v/v). To the best of our knowledge, this is the first report where COF-TD was used to detect water in a relatively wide concentration range. In all, this work provided dual-functional fluorescent COFs with the properties of an adsorbent, opening up new methodologies for the simple, selective, and enrichment detection method for myricetin.

Striped covalent organic frameworks modified stationary phase for mixed mode chromatography.

Covalent organic frameworks (COFs) have showed expected potential in chromatographic separation due to unique structure and excellent performance. Nowadays, COF materials applied as chromatographic stationary phases is still in its infancy. Here, we modified COF materials on silica using benzene-1,4,5-tetracarboxylic dianhydride (PMDA) and 1,3,5-tris-(4-aminophenyl)triazine (TAPT) monomers by one-pot synthetic method for performing mixed-mode function, named as SiO2@COF. Five characterization methods including thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR), elemental analysis (EA) and powder X-ray diffraction (XRD) verified the morphology, structure characteristics and physicochemical properties of the materials. SiO2@COF for performing the separation of polar and nonpolar analytes on high performance liquid chromatography (HPLC) achieved the desired results. Retention mechanisms of the constructed SiO2@COF were researched via observing the effects of mobile phase with retention times. Results exhibited that the prepared stationary phase can provide various interaction modes, including hydrophobic, hydrophilic, hydrogen bonding and π-π interactions. In conclusion, the prepared SiO2@COF stationary phase can execute mixed-mode separation abilities and show potential for complex samples analysis.

Nonlinear behavior in preparative liquid chromatography: A method-development case study for hydroxytyrosol purification.

Preparative liquid chromatography has become an important purification method owing to its advantages of high separation efficiency, good reproducibility, and low solvent consumption. Because overloading in preparative liquid chromatography must be performed to increase the throughput in a cycle, nonlinear chromatographic behavior is observed. Therefore, it is crucial to carefully study nonlinear chromatography for the purification of a given product, which facilitates the efficient optimization of the purification parameters. In this work, a method for the development of a purification method using preparative liquid chromatography based on nonlinear chromatography is proposed. Hydroxytyrosol was selected as the subject for method demonstration. Using methanol and ethanol as organic modifiers, the optimum flow rate was determined on three commercial columns entitled C8 TDE, C18 ME, and C18 TDE, respectively. The curves were fitted with the van Deemter equation, with thorough analysis of the A, B, and C terms. Adsorption isotherms were subsequently studied to explore the distribution of solutes between the stationary and mobile phases at equilibrium. C18 TDE, 5 vol% ethanol-water, and 0.2 mL/min were selected as the optimal separation material, elution solvent, and flow rate, respectively. Purification of hydroxytyrosol was tentatively confirmed on a C18 TDE column with 1.6% sample loading, 90.98% recovery, and 98.01% purity.