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Nickel foam (NF) was evaluated as a medium for the capture of polyethylene (PE) particles in water. NF is a hydrophobic and porous material with a large surface area, making it a promising candidate for attracting PE particles. However, the particle-capturing efficiency using bare NF was only 69.5%. To increase capturing efficiency, a circular polydimethylsiloxane (PDMS)-coated NF (PDMS@NF, diameter: 6 mm) was employed to enhance the hydrophobicity. The capturing efficiency using the PDMS@NF was substantially increased to 97.6 % owing to the increase in hydrophobicity. To quantify the captured PE particles on/in the PDMS@NF using Raman spectroscopy, a wide area illumination (WAI) scheme providing 6 mm-diameter laser illumination was adopted to fully cover the PDMS@NF for representative spectroscopic sampling and accurate quantification. The intensity ratios of PE to PDMS peaks in the collected spectra clearly increased with the quantity of dispersed PE particles (0.1 ∼ 4.0 mg range, R²: 0.992) in the water samples, and the limit of detection was 0.08 mg. Moreover, the capturing efficiencies for polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) particles (1 mg of each) using the PDMS@NF were also superior, ranging from 96.4 to 98.2 %. Therefore, the proposed scheme incorporating the PDMS@NF as a particle-capturing and Raman measurement platform has potential as a method for on-line detection of microplastics in water.

A highly sensitive detection system for α-amylase was developed via host-guest complexation between γ-cyclodextrin and dansyl-modified diphenylalanine (FF-Dns). The host-guest inclusion of FF-Dns into the cavity of γ-CD in a HEPES buffer solution (10 mM, pH 7.4) significantly enhanced the fluorescence intensity, and the emission wavelength gradually shifted from 558 to 535 nm. The hydrolysis of γ-CD by the addition of α-amylase released FF-Dns, leading to the recovery of the fluorescence emission characteristics. Therefore, the FF-Dns/γ-CD host-guest complexation system can serve as a platform for the sensitive detection of α-amylase with good selectivity against potential interference. The limit of detection (LOD) of the system was 0.004 U/mL, with a linear working range of 0-6 U/mL. The detection assay was successfully applied in 0.1 % serum, achieving an LOD of 0.017 U/mL and a linear working range of 0-10 U/mL.

In view of the significant role of reactive sulfur species (RSS) and reactive oxygen species (ROS) in maintaining the redox homeostasis of organisms, we proposed a colorimetric fluorescent probe (HTN) for reversible detection of HSO₃^-/H₂O₂ and effective discrimination of HSO₃^-/ClO^-. C = C is the active site for the Michael addition of HSO₃^- and the oxidation of ClO^-. When HTN interacts with HSO₃^- and ClO^-, it exhibits fluorescence quenching. The addition of oxidizing H₂O₂ to the system can restore the conjugate structure of the addition product of HSO₃^- (HTN-HSO₃^-) and the fluorescence recovery, but it cannot restore the structure of the oxidation product of ClO^- (HTN-ClO^-). By studying the change of the reversibility/non-reversibility of the probe structure with the addition of H₂O₂, the purpose of reversible detection of HSO₃^-/H₂O₂ and distinguishing HSO₃^-/ClO^- is achieved. In addition, HTN can not only be used as a fluorescent ink to detect HSO₃^- on the test paper, but also has excellent detection effect on HSO₃^- and ClO^- in real food samples and water samples. Meantime, HTN has good biocompatibility and can target mitochondria to achieve reversible detection of HSO₃^-/H₂O₂ and effective discrimination of HSO₃^-/ClO^- in living cells. Therefore, HTN has great potential as a molecular tool for studying redox homeostasis in the interaction network of complex living systems.

Sulfur ion (S^2-) plays a significant and considerable role in many living organisms and ecosystems, while its abnormal content can pose a serious hazard to human health and ecological environment. Hence, it is extremely meaningful to construct a highly sensitive and selective analytical platform for S^2- detection in complex microenvironment, particularly in biological systems. In this study, phosphomolybdic acid and L-Arg were utilized to prepare a new molybdenum doped carbon-dots nanozyme (Mo-CDs) with great peroxidase-like activity by one-step hydrothermal approach. In the presence of H₂O₂, Mo-CDs converted 3,3',5,5'-tetramethyl benzidine (TMB) into blue oxTMB, but S^2- strongly reduced the blue solution to colorless and then brown, which established significant selectivity toward S^2-. Mo-CDs illustrated a wide linear range (2.5 μM-900 μM) and low detection limit (LOD = 76 nM) by ultraviolet and smartphone-assisted visualized colorimetric analysis. Especially, the smartphone-assisted analysis platform successfully realized quick, portable, sensitive and visible identification of S^2- with high recovery (95.7-106.7 %) and excellent specificity in water samples. More importantly, Mo-CDs was developed to antibacterial applications based on good peroxidase-like activity. This research not only constructed a new and efficient carbon-dots nanozyme and a low-cost, portable, visual analysis platform for real-time detection of S^2-, but also proposed a novel design strategy and methodology for exploiting multifunctional nanozyme detection tool with great practical application.

Hollow polymer microspheres (HPMs) were synthesized, which were then hydrolyzed in aqueous ammonia to produce carboxyl (-COOH) groups on their surface. L-phenylalanine (L-Phe) was grafted to the hydrolyzed HPMs (H-HPMs) through amidation reactions, endowing the H-HPMs with chirality. The resultant chiral HPMs (C-HPMs) were used for the chiral discrimination of tryptophan (Trp) isomers. Due to the same rotatorydirection of L-Phe and L-Trp, the C-HPMs showed greatly higher selectivity toward L-Trp than its isomer. After being adsorbed by the C-HPMs, the absorbance of the residual L-Trp is significantly lower than that of the residual D-Trp, and thus spectroscopic chiral discrimination of the Trp isomers was successfully achieved. The Trp isomers were also discriminated by the chiral solid polymer microspheres (C-SPMs), while the difference in the absorbance of the residual L-Trp and D-Trp is remarkably smaller than that obtained by the C-HPMs. The outstanding discrimination capability of the C-HPMs might be ascribed to their high surface permeability resulted from their unique hollow structure.

Carbon dots were synthesized from fenugreek seeds through a single step hydrothermal method. The method is simple, fast, pleasant to the environment and cheaper. The CDs were characterized by Fourier Transform Infrared (FTIR), UV-visible spectrophotometer, X-ray diffraction (XRD), High Resolution Transmission electron microscopy (HR-TEM), and fluorescence. The CDs obtained were extremely fluorescent. The fluorescent carbon dots exhibited excitation-dependent behavior with the maximum excitation at 372 nm. The interaction of CDs was studied with different selected cations Al³⁺, Ca²⁺, Cd²⁺, Cr³⁺, Co²⁺, Cu²⁺, Cu⁺, Fe²⁺, Fe³⁺, K⁺, Sn⁴⁺, Na⁺, Ni²⁺, Pb²⁺, Mn²⁺, Zn²⁺, Sr²⁺, (NH₄)₆Mo₇O_24, 4H₂O, Cr⁶⁺, Sb³⁺, Ba²⁺, Li⁺, and Mg²⁺. None of the ions studied showed any effect on its fluorescence intensity except Pb²⁺ which decreased its intensity. A direct relationship was found between Pb²⁺ concentrations and quenching of CDs intensity. Detection limit (DL) and quantification limits (QL) were determined as three and ten times of the standard deviation of the blank for ten number of measurements. DL and QL were found in the order 9.345 μM and 31.15 μM respectively. This linear behavior between quenching and Pb²⁺ concentration is useful for analytical purpose.

With the development of global industry, carbon dioxide emissions surged. The conversion of carbon dioxide from the air results in some CO₃^2-, which can exacerbate environmental disasters like ocean acidification. Therefore, the content of CO₃^2- in seawater is an important indicator of the degree of ocean acidification. In this study, natural fluorescent protein phycocyanin (PC) was used as a fluorescent probe, and a fluorescence detection method was established for quantitative monitoring of CO₃^2- with quick response time (within 50 s), high sensitivity, and selectivity. The fluorescence quenching phenomenon between PC and CO₃^2- was mainly attributed to static quenching. The limit of detection (LOD) was 0.42 μM and the method was successfully applied to monitor CO₃^2- in tap water and seawater, acquiring satisfactory recovery between 99.28 % and 106.40 %. More importantly, paper-based test strips were easily fabricated using PC, enabling the rapid, visual, and on-site detection of CO₃^2- with the aid of a smartphone. The visual detection integrated with the smartphone was converted to data information (RGB value) through a Color Picker APP and successfully used for quantitative identification of CO₃^2-. By capturing fluorescent images and analyzing the corresponding RGB value via a smartphone, the linear calibration ranged from 0.5 μM to 500.0 μM with LOD of 0.11 μM was obtained. Satisfactory recoveries were acquired in tap water (98.00 %-107.50 %) and seawater (97.30 %-101.74 %), respectively. Therefore, integrating the PC fluorescent paper with a smartphone realizes the rapid, visual, and on-site detection of CO₃^2- in the water environment, which is expected to broaden application prospects of monitoring ocean acidification degree.

Hazelnut market prices fluctuate significantly based on cultivar and provenance, making them susceptible to counterfeiting. To develop an accurate authentication method, we compared the performances of three spectroscopic methods: near infrared (NIR), handheld near infrared (hNIR), and medium infrared (MIR), on over 300 samples from various origins, cultivars, and harvest years. Spectroscopic fingerprints were used to develop and externally validate PLS-DA classification models. Both cultivar and origin models showed high accuracy in external validation. The hNIR model effectively distinguished cultivars but struggled with geographic distinctions due to lower sensitivity. NIR and MIR models showed over 93 % accuracy, with NIR slightly outperforming MIR for geographic origin. NIR proved to be a fast and suitable tool for hazelnut authentication. This study is the first to systematically compare spectroscopic tools for authenticating hazelnut cultivar and origin using the same dataset, offering valuable insights for future food authentication applications.

As a cutting-edge technique, fluorescence imaging in the second near-infrared window (NIR-II) is vital for both biomedical research and clinical applications. However, its intravital imaging capacity has been restricted by the extremely limited brightness of NIR-II fluorophores. To address this challenge, we elucidated the inner mechanism of constructing high-performance NIR-II chromophores based on molecular isomer engineering from detailed computational investigations. Herein, three pairs of cis-trans isomers (cis-1, 2, 3 and trans-1, 2, 3) are designed by attaching amino, methoxyl and nitro moieties to different positions on the donor-acceptor-donor molecular skeleton with benzobisthiadiazole as the acceptor and triphenylamine as the donor. All the compounds feature efficient NIR-II emission ranging in 1000-1164 nm, and the photophysical characterizations are regulated by molecular isomer manipulation. Interestingly, fluorescence quantum yields of cis-isomers are higher than those of their trans-counterparts. These enhancements can be attributed to the significant reduction in non-radiative transition, as evidenced by the non-adiabatic excitation energy, non-adiabatic electron coupling and electron-vibration coupling. Meanwhile, fluorophores with nitro terminal group exhibit superior performance facilitated by the prominently intramolecular charge transfer. As a result, cis-3 achieves an optimal brightness maxima of 196.36 M^-1 cm^-1 at 632 nm. Notably, the energy gap and the hole-electron related H index are respectively identified as strongly relevant to the emission wavelength and brightness, making them capable of evaluating the feasibility of fluorophores as effective NIR-II candidates. These findings highlight the correlations between molecular geometry and luminescent properties, which will inspire more insights into the development of highly efficient NIR-II fluorophores through rational isomer engineering for biomedical applications.

A simple, low-cost hydrothermal method was employed to synthesize highly fluorescent nitrogen-, fluorine-, and sulfur-co-doped carbon dots (NFS-CDs) using flufenamic acid and L-cysteine as precursors. The synthesized NFS-CDs exhibited dual emission peaks at 490 and 580 nm with a quantum yield of 24.7 %. They exhibit excellent stability, excitation-dependent fluorescent, and particle sizes ranging from 2 to 8 nm. The fluorescent chemosensor probe, NFS-CDs, showed strong selectivity and sensitivity for Hg²⁺ over other metal ions investigated in aqueous solutions (pH ∼ 7.4). Strong fluorescent enhancement at 490 nm and considerable quenching at 580 nm was observed in the presence of Hg²⁺ ions. The stoichiometric ratio of the NFS-CDs/Hg²⁺ complex was optimized to 1:1 according to the Benesi-Hildebrand and Stern-Volmer plot methods. The NFS-CDs exhibited a linear dynamic detection range from 0 to 10 × 10^-6 M for Hg²⁺ ions with a lower detection limit of 18.0 and 67.5 × 10^-9 M, respectively, at 490 and 580 nm. Practical applications of NFS-CDs in detecting Hg²⁺ ions in natural water samples showed high recovery rates (98.9-104.6 %) and low relative standard deviation (RSD ≤ 2.47 %). The NFS-CDs/Hg²⁺ achieved 78.7 ± 2.6 % and 83.4 ± 2.3 % antibacterial activity against E. coli and S. aureus as NFS-CDs/Hg²⁺ could damage the bacterial walls when they entered the bacteria. Furthermore, the NFS-CDs were used to detect Hg²⁺ ions intracellularly in HCT116 cells with low toxicity using live cell imaging.