Carbon dots capped cerium oxide nanoparticles for highly efficient removal and sensitive detection of fluoride

Magnetic recyclable metal-organic framework sheets grafted with curcumin for highly efficient adsorption and sensitive detection of fluoride

The contents of fluoride in drinking water should be limited to a safe range. Hence, design and development of a simple and efficient technology for adsorption and detection of fluoride is urgently required. We presented a curcumin in situ grafted MOF magnetic material (Fe3O4/MOF-Cur) for dual-functionalized applications of fluoride detection and adsorption. Owing to the electrostatic interaction, ligand exchange at the metal sites and boron-fluorine complexation, the adsorption capacity of Fe3O4/MOF-Cur for fluoride is 99.92 mg/g, and the detection limit is 1.17 μM. The fluoride adsorption behavior on different active units was further visualized by theoretical calculations. Favorable stability (79.52 mg/g after 5 adsorption-desorption cycles and insignificant change of fluorescence intensity within 30 days), mild reaction conditions (pH = 3-5) and excellent anti-interference ability promote the application of Fe3O4/MOF-Cur in real samples. Finally, the paramagnetic properties (29 emu/g) allow for easy recovery from water. These findings deepen the understanding on the design and development of dual-functionalized MOF materials, and prove the application potential of Fe3O4/MOF-Cur for the remediation of fluoride-related environmental pollution.

Biomass-based carbon dot-modified cerium oxide nanoparticles (BCDs@CeO2) efficiently promote Myriophyllum aquaticum to remove NH4+-N and TP in eutrophic water

Aquatic plants are widely used for eutrophication remediation. However, strong abiotic plant stress often limits their remediation efficiency. This study proposed biomass-based carbon dot-modified cerium oxide nanoparticles (BCDs@CeO2) with good biocompatibility to mitigate abiotic plant stress. The BCDs@CeO2 pretreated Myriophyllum aquaticum exhibited enhanced removal rates of NH4+-N and TP, with the 10 mg/L BCDs@CeO2 treatment showing increases of 39.23 % and 29.11 %, respectively, compared to the pure water-precultured plant system (p < 0.05). Plant physiological changes and transcriptomic analysis revealed that BCDs@CeO2 treatment upregulated glycolysis/gluconeogenesis and α-linolenic acid metabolism pathways in rhizomes, inducing increased ATP synthase and antioxidant enzyme (Peroxidase, Catalase, and Superoxide Dismutase) activities, and enhancing amino acid metabolism, which further boosted Glutamine Synthetase activity and promoted NH4+-N and TP absorption and utilization. ICP-MS and microscopic analysis confirmed the uptake and migration of BCDs@CeO2 in plants. In summary, this study provides an effective strategy to enhance eutrophication phytoremediation.

Polymer-enhanced peroxidase activity of ceria nanozyme for highly sensitive detection of alkaline phosphatase

Nanoceria have demonstrated a wide array of catalytic activity similar to natural enzymes, holding considerable significance in the colorimetric detection of alkaline phosphatase (ALP), which is a biomarker of various biological disorders. However, the issues of physiological stability and formation of protein corona, which are strongly related to their surface chemistry, limit their practical application. In this work, CeO2 nanoparticles characterized by enhanced dimensional uniformity and specific surface area were synthesized, followed by encapsulation with various polymers to further increase catalytic activity and physiological stability. Notably, the CeO2 nanoparticles encapsulated within each polymer exhibited improved catalytic characteristics, with PAA-capped CeO2 exhibiting the highest performance. We further demonstrated that the PAA-CeO2 obtained with enhanced catalytic activity was attributed to an increase in surface negative charge. PAA-CeO2 enabled the quantitative assessment of AA activity within a wide concentration range of 10 to 60 μM, with a detection limit of 0.111 μM. Similarly, it allowed for the evaluation of alkaline phosphatase activity throughout a broad range of 10 to 80 U/L, with a detection limit of 0.12 U/L. These detection limits provided adequate sensitivity for the practical detection of ALP in human serum.

The application of a novel biomimetic enzyme p-BEs cascade catalytic platform for the rapid detection of glucose

The blood glucose concentration in aquatic organisms, a crucial indicator reflecting their health status, holds significant importance for detecting glucose levels in serum in terms of processing and quality monitoring. In this study, a novel POD biomimetic enzyme (p-BEs) with horseradish peroxidase catalytic properties was designed, optimized, and its mechanism was discussed in detail. Based on this, a portable system has been developed capable of determining glucose levels in three ways: quantitatively analyzed through UV-Vis/MD, quantitatively analyzed on-site using a mobile phone RGB, and semi-quantitatively analyzed through a drip plate. Meanwhile, compared with other catalytic methods for detecting glucose, we achieved a lower limit of detection (0.03 μM) and shorter detection time (12 min), with high catalytic activity. This study provides new insights into the design of efficient and reliable cascade catalytic systems responsive to glucose, offering a low-cost, simplicity of operation method for glucose detection.

Facile preparation, characterization and application of novel sugarcane bagasse-derived nanoceria-biochar for defluoridation of drinking water: kinetics, thermodynamics, reusability and mechanism

Although expensive, rare-earth oxides are well known for being powerful defluoridation agents. Being costlier, cerium is used as a hybrid adsorbent in conjunction with a prudent and environmentally benign substance like biochar. The novel CeO2/BC (surface area 260.05 m2/g) composite was shaped using the facile chemical precipitation technique without any cross-linkers. Surface properties of synthesised CeO2/BC were investigated using powder XRD, FTIR, BET, pH point of zero charge and SEM. According to XRD analysis, immobilized Ce is primarily in form of CeO2, while pristine biochar is in an amorphous state. Batch mode adsorption tests were carried out with different solution pH, F- initial concentration, adsorbent dosage and contact time and counter anions. CeO2/BC can be used in a varied pH range (2-10) but shows maximum removal at pH 4. The Langmuir adsorption isotherm and a pseudo-second-order kinetic model are best fitted to support the adsorption process with a maximum Langmuir adsorption capacity of 16.14 mg/g (F- concentration 5 to 40 mg/L). The removal phenomenon is non-spontaneous in nature. The plausible mechanism of fluoride uptake was explained using XPS and pHPZC, and it was demonstrated that the fluoride was mainly removed by ion exchange and electrostatic attraction. The adsorbent could be successfully used up to fourth cycle after regenerating.

The function of doping nitrogen on removing fluoride with decomposing La-MOF-NH2: Density functional theory calculation and experiments

Fluoride is an important pollutant in wastewater, and adsorption is an effective way to remove fluoride. Because nitrogen plays an important role in adsorbent materials, computational models were developed to understand the changes in work function resulting from nitrogen doping. La-N-C-800°C, was prepared by pyrolyzing La-MOF-NH2 to verify the influence on the performance of removing fluoride by electrosorption. Material and electrochemical performance tests were performed to characterize La-N-C-800°C. Adsorption kinetics, adsorption thermodynamics, initial concentrations, pH, and ions competition were investigated using La-N-C-800°C for fluoride removal. In addition, density functional theory was applied to evaluate the function of nitrogen. When nitrogen atoms were added, the density of states, partial density of states, populations, and different orbits of charge were calculated to discover deep changes. Nitrogen strengthened the carbon structure and La2O3 structure to remove fluoride. In addition, nitrogen can also act as an adsorption site in the carbon structure. These results provide design ideas for improving the performance of adsorbent materials by doping elements.

Artificial intelligence-integrated smartphone-based handheld detection of fluoride ion by Al3+-triggered aggregation-induced red-emssion enhanced carbon dots

Artificial intelligence (AI)-integrated smartphone-based handheld determination platform, based on 3D printed accessory, Al3+-triggered aggregation-induced red-emssion enhanced carbon dots (CDs) test strip, and smartphone with self-developed YOLO v3 AI algorithm-based application, proves the feasibility for intelligent real-time on-site quantitation of F- through tracking a consecutive fluorescence (FL) colour change. CDs, manifesting dual emission of moderate green emission at 512 nm and weak red one at 620 nm under 365 nm excitation, were synthesized hydrothermally from alizarin carmine and citric acid. CDs@Al3+, with distinct aggregation-induced red-emssion enhancement and green-emssion quenchment, were prepared by adding Al3+ to the CDs solution. Inspiringly, due to intrinsic ratiometric FL variation (I620/I512), CDs@Al3+ engender a successive FL colour variation from red to green in response to different concentrations of F- with low limit of detection of 7.998 μM and wide linear range of 150-1200 µM based on excellent linearity correlation between R/G value and F- concentration. Furthermore, F- content in tap water, toothpaste and milk could be intelligently, speedily, and straightforwardly analyzed through the AI-integrated smartphone-based handheld detection platform. It is fervently desired that our study will motivate a brand-new perspective for the promotion of efficacious detection strategy and the extension of practical application promise.

Fluoride-activated photothermal system for promoting bacteria-infected wound healing

Although photothermal therapy (PTT) employing nanozymes has shown excellent antibacterial potential, excessive heating generally harms host cells and hinders recovery. Herein, we report an innovative technique for acquiring the programmed temperature by managing the catalytic activity of nanozymes. The photothermal system of CeO2 + F- + TMB can obtain precise photothermal temperature by adjusting the concentration of fluoride ions under near-infrared irradiation. At the optimized photothermal temperature, the photothermal system affords fine photothermal antibacterial treatment with high-efficiency antibacterial effects against Staphylococcus aureus and Escherichia coli in vitro. In vivo wound healing experiments confirm that the system can effectively promote fibroblast proliferation, angiogenesis and collagen deposition with remarkable wound healing efficiency. This strategy offers a novel design concept for creating a new generation of PTT and opens the way for the creation of alternative antibiotics.

Highly luminescent nitrogen and sulfur co-doped carbon dots for Sn2+ and S2- sensing and dual-mode anti-counterfeiting

The preparation of nitrogen and sulfur co-doped carbon dots (N, S-CDs) with highly bright orange-red fluorescence is reported through a facile solvothermal approach with naphthalenetetracarboxylic dianhydride as starting material. The N, S-CDs exhibited superior properties, including intense long-wavelength emission with a narrow full width at half maxima (FWHM) of 33 nm, high fluorescence quantum yield (QY) of 60.5% in aqueous solution, excitation-independent emission behavior, and excellent water dispersibility. In addition, sulfide ions (S^2-) could selectively recover the fluorescence of N, S-CDs quenched by Sn²⁺. The selective experiment suggested that the N, S-CDs/Sn²⁺ complex could be used as a fluorescence-enhancement sensor for sulfide ions (S^2-), with the linear range of 5-50 μM and the LOD of 0.35 μM. The practicality and feasibility of this sensor for the determination of sulfide ions in tap and lake water were verified with good recoveries. Furthermore, because of their highly bright fluorescence and strong water solubility, the N, S-CDs could be easily fabricated into fluorescent ink and transparent films, demonstrating the promising application in anti-counterfeiting. Therefore, the designed N, S-CDs exhibited the advantages of facile preparation, intense fluorescence, high stability, easy processing, and selective fluorescence change for specific analytes, which showed high potential in fluorescence detection and anti-counterfeiting.

Tunable Fluorine-Functionalized Scholl-Coupled Microporous Polymer for the Selective Adsorption and Ultrasensitive Analysis of Environmental Liquid-Crystal Monomers

Liquid-crystal monomers (LCMs), especially fluorinated biphenyls and analogues (FBAs), are identified to be an emerging generation of persistent organic pollutants. However, there is a dearth of information about their occurrence and distribution in environmental water and lacustrine soil samples. Herein, a series of fluorine-functionalized Scholl-coupled microporous polymers (FSMP-X, X = 1-3) were designed and synthesized for the highly efficient and selective enrichment of FABs. Their hydrophobicity, porosity, chemical stability, and adsorption performance (capacity, rate, and selectivity) were regulated preciously. The best-performing material (FSMP-2) was employed as the on-line fluorous solid-phase extraction (on-line FSPE) adsorbent owing to its high adsorption capacity (313.68 mg g^-1), fast adsorption rate (1.05 g h^-1), and specific selectivity for FBAs. Notably, an enrichment factor of up to 590.2 was obtained for FSMP-2, outperforming commercial C₁₈ (12.6-fold). Also, the underlying adsorption mechanism was uncovered by density functional theory calculations and experiments. Based on this, a novel and automated on-line FSPE-high-performance liquid chromatography method was developed for ultrasensitive (detection limits: 0.0004-0.0150 ng mL^-1) and low matrix effect (73.79-113.3%) determination of LCMs in lake water and lacustrine soils. This study offers new insight into the highly selective quantification of LCMs and the first evidence for their occurrence and distribution in these environmental samples.

Portable Smartphone Platform Based on Aggregation-Induced Enhanced Emission Carbon Dots for Ratiometric Quantitative Sensing of Fluoride Ions

The development of an instrument-free, on-site, real-time, sensitive, and visualized fluoride-ion (F^-) content rapid detection strategy is crucial to ensuring the health of the population. Smart microdevices that are portable, directly read, and easy to operate have recently attracted much attention. Herein, a ratiometric fluorescent probe (AA-CDs@[Ru(bpy)₃]²⁺)-based smartphone sensing platform was developed for the detection of F^-. The red fluorescent ruthenium bipyridine [Ru(bpy)₃]²⁺ molecule was chosen as the reference signal, and the carbon dots (AA-CDs) with Al³⁺ aggregation-induced enhanced emission (AIE) were designed as the response signal. The ratiometric probe fluorescence changed continuously from red to cyan in response to different concentrations of F^-, and the red-green-blue (RGB) channel values of the fluorescence image were extracted through the smartphone color recognition application (APP). There was a linear relationship between the blue-red (B/R) ratio and the F^- concentration, with a limit of detection (LOD) of 1.53 μM, far below the allowable content of F^- in drinking water prescribed by the World Health Organization. The F^- content was rapidly detected on-site with satisfactory repeatability and relative standard deviation using several water and toothpaste samples as the real sample. The platform features low cost, portability, easy operation, and good stability, selectivity, and repeatability, which provides a powerful tool for the visual quantitative detection of smartphone-based microsensing platforms possibly in the fields of environmental protection, diagnosis, and food safety assessment.

Luminescent carbon dots with excellent peroxidase mimicking property for fluorometric and colorimetric detection of glucose

The luminescent carbon dots with peroxidase mimicking property had attracted considerable attention in biomedical field. In this work, iron-doped carbon dots (Fe-CDs) were prepared by one-pot hydrothermal method with 5, 10, 15, 20-tetra (4-borate phenyl)-21H, 23H-porphyrin Fe (II) (Fe-TBPP) as precursor. The obtained Fe-CDs emitted intense blue luminescence under ultraviolet light irradiation. Moreover, the Fe-CDs exhibited remarkable peroxidase mimicking property, which can efficiently catalyze the oxidation of 3, 3', 5, 5'-tetramethylbenzidine (TMB) into blue ox-TMB in the presence of hydrogen peroxide (H₂O₂). More importantly, the emission of Fe-CDs could be gradually quenched with the addition of H₂O₂. Based on these phenomena, a new optical dual-mode (colorimetric and fluorometric) method for the detection of H₂O₂ and glucose was successfully established. The detection limits of glucose were calculated to be 3.86 and 7.27 μM (S/N = 3) respectively based on the colorimetric and fluorometric methods. Furthermore, we combined this dual-mode detection method with smartphone imaging. The colorimetric and fluorescent images were collected by recognition software of smartphone, which were then transformed into the corresponding HSL values for quantitative determination of glucose. Finally, the dual-mode approach based on Fe-CDs was used for the detection of glucose content in human serum, demonstrating the potential application of carbon dots in the biological area.

Construction of a ratiometric fluorescent probe for visual detection of urea in human urine based on carbon dots prepared from Toona sinensis leaves and 5-carboxyfluorescein

In this work, pH-sensitive blue fluorescent carbon dots (CDs) with high fluorescence quantum yield (17.24%) were synthesized by hydrothermal method using Toona sinensis leaves and ethylenediamine (EDA) as raw materials. The CDs can detect urea with a limit of detection (LOD) of 6.700 mmol L^-1. For more sensitive detection of urea, we constructed a ratiometric fluorescent probe (CDs@5-FAM) using CDs and 5-carboxyfluorescein (5-FAM). The CDs@5-FAM probe can rapidly and sensitively detect urea according to the changes of I₅₁₄/I₄₀₅, with LOD as low as 0.014 mmol L^-1. Furthermore, with the help of a smartphone and RGB analysis software, urea's visual intelligent detection was realized using a CDs@5-FAM probe. The method proposed in this paper is consistent with the standard method, which indicates that the pH-sensitive ratiometric fluorescent probe CDs@5-FAM is accurate and reliable for practical application. It provides a new way for rapid and visual detection of urea.