Fluorescence response mechanism of green synthetic carboxymethyl chitosan-Eu3+ aerogel to acidic gases

Visual detection of ciprofloxacin using a multi-emission ratiometric fluorescence sensor based on the molecularly imprinted polymers doped with terbium(III) ions

Ciprofloxacin (CIP) is a commonly used antibiotic, but its abuse may cause bacterial resistance, posing a high risk to the environment and human health. Herein, based on the molecular imprinting technology, this study proposed a ratiometric fluorescence sensor employing the "post-doping" strategy, which aims to be rapid, selective, and visually easy-to-use for CIP detection to address antibiotic residues and environmental risks. Specifically, by exploiting the "antenna effect" of lanthanide metal ions (Ln3+), terbium (III) (Tb3+) chosen as a fluorescence-assisted functional monomer as well as the red emitting CdTe quantum dots (QDs) as the internal reference signal were introduced into multi-emission Tb3+-CdTe@SiO2@MIPs (TbMIPs). With the increase of CIP concentration, the variations among the fluorescence peaks within a multi-emission ratiometric fluorescence sensor not only induce a broader range of color changes, but also produce a more sensitive and stable effect through self-internal standard correction. The sensor showed a good trend in a wide concentration range within 0.08-50 μM and provided a satisfactory detection limit of 0.018 μM, which had lower detection limit for CIP than most of methods. It had demonstrated exceptional selectivity and had been successfully used to efficiently detect CIP in real samples including seawater, river water, milk and urine. Furthermore, when integrated with smartphone-based data processing capabilities, this sensor enabled highly sensitive visual detection under the 365 nm UV lamp device. Through innovative development, the wide color transition observed with the sensor makes it highly suitable for practical applications, enhancing its usability for further real-time monitoring.

Preparation of carboxymethyl chitosan-Tb3+ (CMCh-Tb3+) fluorescent probe: For high-sensitivity Cu2+ detection and mechanism study

Carboxymethyl chitosan (CMCh) is a natural polysaccharide derivative with biodegradability, rich in active amino and carboxyl groups. It can act as a ligand to coordinate with rare earth ions, transferring absorbed energy to the central ion to sensitize its luminescence. In this paper, CMCh-Tb3+ was prepared as a solid fluorescent probe by mixing CMCh solution with Tb3+. The morphology, structure and properties of CMCh-Tb3+ were characterized and analyzed by SEM, IR and XPS, and then the chemical structure of CMCh-Tb3+ was determined. CMCh-Tb3+, as a highly sensitive fluorescent sensor for detecting Cu2+, has a detection limit (LOD) of 27.14 nmol/L. Through characterization using fluorescence spectroscopy, ultraviolet absorption spectroscopy, and fluorescence lifetime, we further explored the mechanism of Cu2+ fluorescence quenching, finding that this process is primarily achieved through dynamic quenching. Additionally, we discovered that glutathione (GSH) can form a strong coordination with Cu2+, thereby inhibiting the quenching effect of Cu2+ on the emission intensity of CMCh-Tb3+ and restoring its luminescence characteristics. This finding indicates that CMCh-Tb3+ can not only serve as a fluorescence sensor for detecting Cu2+ but also as a reversible fluorescence sensor, significantly enhancing its performance in practical applications.

Investigation of silicon doped carbon dots/Carboxymethyl cellulose gel platform with tunable afterglow and dynamic multistage anticounterfeiting

The remarkable optical properties of carbon dots, particularly their tunable room-temperature phosphorescence, have garnered significant interest. However, challenges such as aggregation propensity and complex phosphorescence control via energy level manipulation during synthesis persist. Addressing these issues, we present a facile gel platform for tunable afterglow materials. This involves chemically cross-linking biomass-derived silicon-doped carbon dots with carboxymethylcellulose and incorporating non-precious metal salts (BaCl2, CaCl2, MgCl2, ZnCl2, ZnBr2, ZnSO4) to enhance phosphorescence. Metal salts boost intersystem crossing via spin-orbit coupling, elevating triplet state transitions and activating phosphorescence. Chemical bonding and salt-induced coordination/electrostatic interactions establish confinement effects, suppressing non-radiative transitions. Diverse salt-gel interactions yield gels with tunable phosphorescence lifetimes (9.48 ms to 32.13-492.39 ms), corresponding to afterglow durations ranging from 3.20 to 11.86 s. With its broad tunability and high recognition, this gel material exhibits promising potential for dynamic multilevel anti-counterfeiting applications.

Impact of the COVID-19 Pandemic on Cockroach Allergy: A 4-Year Retrospective Study

INTRODUCTION

Sensitivity to indoor allergens increases the risks of asthma and the emergence of allergic diseases. Indoor allergens include house dust mite (HDM), pet dander, cockroach (CR), and molds. We investigated how CR sensitivity was affected during the pandemic period.

METHODS

This study included patients aged ≥18 years who visited the allergy unit of our clinic between March 2018 and March 2022 and who underwent skin prick tests (SPTs) for aeroallergens. Patients were divided into two groups: those of the prepandemic and pandemic periods, depending on the visit dates.

RESULTS

In all, 7,687 patients were recruited; 5,074 individuals with negative SPT results were excluded. Among the 2,613 atopic patients, CR sensitivity was detected in 278 (10.6%). The prevalence of CR sensitivity was significantly higher in the pandemic group than in the prepandemic group (12% vs. 8.6%; p < 0.05). The frequency of asthma was higher in patients with CR sensitivity than in others (33.1% vs. 26%, p = 0.011). In addition, individuals with CR sensitivity were older than others (p = 0.001). CR sensitivity was more common in males than in females (44.2% vs. 37.7%, p = 0.034). Moreover, dog and HDM sensitivities were more common in individuals with CR sensitivity than in others (p = 0.004, p < 0.001, respectively).

CONCLUSION

This study reveals an increased sensitivity to CR during the pandemic and establishes an association between such sensitivity and the frequency of asthma. Variability in terms of CR sensitivity across different countries is emphasized. In addition, HDM and dog sensitivities were more common in individuals with CR sensitivity.

Silicon-Doped Carbon Dots Crosslinked Carboxymethyl Cellulose Gel: Detection and Adsorption of Fe3

The excessive emission of iron will pollute the environment and harm human health, so the fluorescence detection and adsorption of Fe3+ are of great significance. In the field of water treatment, cellulose-based gels have attracted wide attention due to their excellent properties and environmental friendliness. If carbon dots are used as a crosslinking agent to form a gel with cellulose, it can not only improve mechanical properties but also show good biocompatibility, reactivity, and fluorescence properties. In this study, silicon-doped carbon dots/carboxymethyl cellulose gel (DCG) was successfully prepared by chemically crosslinking biomass-derived silicon-doped carbon dots with carboxymethyl cellulose. The abundant crosslinking points endow the gel with excellent mechanical properties, with a compressive strength reaching 294 kPa. In the experiment on adsorbing Fe3+, the theoretical adsorption capacity reached 125.30 mg/g. The introduction of silicon-doped carbon dots confers the gel with excellent fluorescence properties and a good selective response to Fe3+. It exhibits a good linear relationship within the concentration range of 0-100 mg/L, with a detection limit of 0.6595 mg/L. DCG appears to be a good application prospect in the adsorption and detection of Fe3+.

Polyhedral Oligomeric Sesquioxane Cross-Linked Chitosan-Based Multi-Effective Aerogel Preparation and Its Water-Driven Recovery Mechanism

The use of environmentally friendly and non-toxic biomass-based interfacial solar water evaporators has been widely reported as a method for water purification in recent years. However, the poor stability of the water transport layer made from biomass materials and its susceptibility to deformation when exposed to harsh environments limit its practical application. To address this issue, water-driven recovery aerogel (PCS) was prepared by cross-linking epoxy-based polyhedral oligomeric silsesquioxane (EP-POSS) epoxy groups with chitosan (CS) amino groups. The results demonstrate that PCS exhibits excellent water-driven recovery performance, regaining its original volume within a very short time (1.9 s) after strong compression (ε > 80%). Moreover, PCS has a water absorption rate of 2.67 mm s-1 and exhibits an excellent water absorption capacity of 22.09 g g-1 even after ten cycles of absorption-removal. Furthermore, a photothermal evaporator (PCH) was prepared by loading the top layer with hydrothermally reacted tannins (HAs) and Zn2+ complexes. The results indicate that PCH achieves an impressive evaporation rate of 1.89 kg m-2 h-1 under one sun illumination. Additionally, due to the antimicrobial properties of Zn2+, PCH shows inhibitory effects against Staphylococcus aureus and Escherichia coli, thereby extending the application of solar water evaporators to include antimicrobial purification in natural waters.

Recent studies on proteins and polysaccharides-based pH-responsive fluorescent materials

Polymer-based pH-responsive fluorescent materials have the characteristics of fast response, real-time monitoring, visualisation, and easy forming. Consequently, they have attracted widespread attention in wound healing, sweat monitoring, security and anti-counterfeiting, freshness detection of aquatic products, metal-ion sensing and bioimaging. This paper analyses the preparation principles and characteristics of pH-responsive fluorescent materials based on cellulose, chitosan and proteins. It then outlines the fluorescence properties, environmental response mechanisms and applications of various luminescent materials. Next, the research indicates that amines, N-heterocyclic rings, carboxyl groups and amino plasmonic groups on the fluorescent molecule structure and polymer skeleton appear to change the degree of ionisation under acid or alkali stimulation, which affects the light absorption ability of chromophore electrons, thus producing fluorescence changes in fluorescent materials under different pH stimuli. On this basis, the challenges and growth encountered in the development of proteins and polysaccharides-based pH-responsive fluorescent materials were prospected to provide theoretical references and technical support for constructing pH-responsive fluorescent materials with high stability, high sensitivity, long-lasting pH-response and wide detection range.

Preparation and p-phenylenediamine detection mechanism of a dialdehyde cellulose and a 7-amino-4-methylcoumarin-based fluorescent probe

A novel fluorescent probe, fluorescent dialdehyde cellulose (FDAC), was prepared to detect p-phenylenediamine (PPD) in water samples conveniently and quickly. This was achieved by grafting 7-amino-4-methylcoumarin (AMC) onto dialdehyde cellulose (DAC) via an aldol-amine condensation reaction. This method is greener, more economical, and simpler than existing methods for preparing fluorescent probes. The probe was found to be more effective for PPD detection in polar solvents, with less interference from pH and other compounds present in the sample matrix. The photoluminescence of FDAC at λex/λem = 340/430 nm was statically quenched by PPD, allowing for accurate detection within the range of 10-100 μmol/L under optimal conditions, with a detection limit of 3.2 μmol/L (3 σ/s). Meanwhile, the Schiff base (-C=N- group) generated by the condensation of DAC and AMC increased the reaction activity of the fluorescent moiety and changed the AMC conjugated structure, making FDAC more susceptible to aminolysis with PPD than AMC. This study presents a promising solution for fluorescence detection of aniline compounds, with significant potential for application in fields such as environmental analysis.

Smart Stimulation Response of a Pyrene-Based Lanthanide(III) MOF: Fluorescence Enhancement to HX (F and Cl) or R-COOH and Artificial Applicable Film on HCl Vapor Sensing

Toxic acids produced by industries are major hazards to the environment and human health, and luminescent pyrene-based crystalline metal-organic frameworks (MOFs) demonstrate promising performance in the detection of toxic acids. Herein, two novel isostructural 3D porous lanthanide MOFs, H3O·[Ln3(TBAPy)2(μ2-H2O)2(OH)2]·2DMA·2Diox·6.5H2O (Ln = Pr (1) and Ce (2); H4TBAPy (1,3,6,8-tetrakis(p-benzoic acid)pyrene); and DMA: N,N-dimethylacetamide) were synthesized, which showed alb topology. Based on the protonation and hydrogen bond mechanism, complex 1 could be used as a fluorescence recognition sensor for HX (X = F, Cl, Br, and I) acid solutions with different luminescence behaviors. It is worth noting that complex 1 exhibited high sensitivity in the fluorescence enhancement sensing of hydrofluoric acid, oxalic acid, and trichloroacetic acid. In particular, complex 1 had a low limit of detection (LOD) for OA (0.1 μM) and was applied to real monitoring of orange fruit samples. In addition, the PVA@1 film could selectively, sensitively, and quantitatively respond to hydrochloric acid (HCl) vapor through fluorescent quenching; due to its protonation and adsorption capacity, the LOD was 0.18 ppm. Therefore, the portable optical device, the PVA@1 film, can detect HCl gas in trace amounts, achieving the ultimate goal of real-time and rapid detection, which has potential application value for industrial production safety.

Energy transfer mechanism of carboxymethyl chitosan-Eu3+/Tb3+ complex materials and application in multicolor LED

Biological macromolecules had been studied as ligands in recent years, which not only give the complexes excellent polymer properties, but also have many advantages such as biodegradability. Carboxymethyl chitosan (CMCh) is excellent biological macromolecular ligand because of its abundant active amino and carboxyl groups, and it can smoothly transfer energy to Ln³⁺ after coordinating. To further study the energy transfer mechanism of CMCh-Ln³⁺ complexes, CMCh-Eu³⁺/Tb³⁺ complexes with different Eu³⁺/Tb³⁺ ratios were prepared by using CMCh as a ligand. The morphology, structure, and properties of CMCh-Eu³⁺/Tb³⁺ were characterized and analyzed by infrared spectroscopy, XPS, TG and Judd-Ofelt theory, thus the chemical structure of CMCh-Eu³⁺/Tb³⁺ was determined. The mechanism of energy transfer was explained in detail, also the Förster resonance transfer model is confirmed, and the hypothesis of energy transfer back was verified by the characterization and calculation methods of fluorescence spectra, UV spectra, phosphorescence spectra and fluorescence lifetime. Finally, CMCh-Eu³⁺/Tb³⁺ with different molar ratios were used to prepare a series of multicolor LED lamps, and it extends the application range of biological macromolecules as ligands.

Preparation and characterization of carboxymethyl chitosan/pullulan composite film incorporated with eugenol and its application in the preservation of chilled meat

To solve the problem of easy spoilage of chilled meat during storage, we fabricated a novel composite film using carboxymethyl chitosan (CMCS)/pullulan (Pul)/eugenol (E) by casting method. The results showed that the mechanical properties of the films were better when the CMCS/Pul ratio was 2.5/2.5. The Fourier transform infrared spectroscopy (FTIR) results showed that intermolecular hydrogen bonds were formed among E, CMCS, and Pul, which was consistent with the rheological test results. Scanning electron microscopic (SEM) images showed that eugenol was well dispersed in the CMCS/Pul matrix. The addition of eugenol significantly increased the antibacterial properties and antioxidant properties. Moreover, when 5% eugenol was added, the water vapor permeability (WVP) of the film reduced to 2.41 × 10^-11 g/m·s·Pa. Finally, the freshness of the chilled meat wrapped with the eugenol-containing composite film was prolonged, thereby offering a potential alternative to synthetic materials.