MoS2 QDs-Based sensor for measurement of fluazinam with triple signal output

Two three-dimensional coordination polymers as fluorescence probes for the detection of nitrobenzene, tetracycline, fluazinam and their application in green pepper

Two coordination polymers (CPs), [Zn5(L)2(phen)5](1) and [Cd2(HL)(2,2-bpy)(H2O)3](2), were synthesized by using 2',3,3',5,5'-Diphenyl ether pentacarboxylic acid (H5L), phenanthroline (phen), and 2,2'-bipyridine (2,2'-bpy) under hydrothermal conditions. The L5- ligand adopts the μ6-к2: к2: к1: к1: к1: к1 mode in 1 and the μ5-к2: к2: к2: к2: к1 mode in 2. Sensing experiments show that 1 and 2 are fluorescence probes with high sensitivity and rapid detection of nitro explosives, antibiotics, and pesticides. In order to verify the ability of 2 to detect FLU in actual samples, we performed a spiked recovery experiment in green pepper water. The spiked recoveries were 97.77-101.18 %. Interestingly, because H5L is not completely deprotonated in 2, there is abundant hydrogen bonding, which makes the fluorescence quenching rate higher and the detection limit lower. The possible fluorescence quenching mechanism of 1 and 2 can be explained by their UV-VIS absorption spectra and orbital energy levels.

Nitrogen-doped MoS2 QDs as fluorescent probes for sensitive detection of curcumin and cell imaging

BACKGROUND

Curcumin has been used in traditional medicine because of its pharmacological activity, including antioxidant, antibacterial, anticancer, and anticarcinogenic properties. Therefore, sensitive and selective monitoring of curcumin is highly demand for practical application.

RESULTS

In this study, we describe the construction of a fluorescence method for curcumin assay based on nitrogen-doped MoS2 quantum dots (N-MoS2 QDs). The N-MoS2 QDs are constructed by a solvothermal method using sodium molybdate and Cys as precursors. With the addition of curcumin, the bright blue fluorescence of N-MoS2 QDs is quenched by the inner filter effect (IFE). The QDs emitted bright blue fluorescence and could be quenched by the addition of curcumin via IFE. The dynamic range is the range of 0.1-10 μM for curcumin detection, with a detection limit of 59 nM. N-MoS2 QDs were applied for curcumin assay in real samples with good recovery. In addition, the N-MoS2 QDs exhibited relative low cytotoxicity and could be applied for fluorescence-based imaging in biological samples.

SIGNIFICANCE

Our study indicates that the sensor possesses good selectivity to monitor curcumin in water samples, human urine samples, ginger powder samples, mustard samples, and curry samples with satisfactory recoveries. The N-MoS2 QDs possess less cytotoxicity with excellent biocompatibility and were applied for in vitro cell imaging.

A dual-response ratiometric fluorescent sensor for oxytetracycline determination in milk and mutton samples

Owing to the adverse effects of oxytetracycline (OTC) residues on human health, it is of great importance to construct a rapid and effective strategy for OTC detection. Herein, we developed a dual-response fluorescence sensing platform based on molybdenum sulfide quantum dots (MoS2 QDs) and europium ions (Eu3+) for ratiometric detection of OTC. The MoS2 QDs, synthesized through an uncomplicated one-step hydrothermal approach, upon OTC integration into the MoS2 QDs/Eu3+ sensing system, exhibit a significant quenching of blue fluorescence due to the inner filter effect (IFE), simultaneously enhancing the distinct red emission of Eu3+ at 624 nm, a phenomenon attributed to the antenna effect (AE). This sensor demonstrates exceptional selectivity and sensitivity towards OTC, characterized by a linear detection range of 0.2-10 μM and a notably low detection limit of 2.21 nM. Furthermore, we achieved a visual semi-quantitative assessment of OTC through the discernible fluorescence color transition from blue to red under a 365 nm ultraviolet lamp. The practical applicability of this sensor was validated through the successful detection of OTC in milk and mutton samples, underscoring its potential as a robust tool for OTC monitoring in foodstuffs to safeguard food safety.

A sensitive sandwich-type electrochemical aptasensing platform based on Ti3C2Tx/MoS2/MWCNT@rGONR composites for simultaneous detection of kanamycin and chloramphenicol in food samples

A Ti3C2Tx/MoS2/MWCNT@rGONR nanocomposite was prepared for the first time for building a sensitive electrochemical aptasening platform to simultaneously detect kanamycin (Kana) and chloramphenicol (Cap). Owing to their accordion-like structure, rich surface groups, and high charge mobility, Ti3C2Tx/MoS2/MWCNT@rGONR composites provided a spacious covalent immobilization surface and a better electrochemical aptasensing platform. The aptamers of Kana and Cap used in sensors enhance the selectivity. Furthermore, TiP, an ion exchanger, was used for loading more different metal ions functioning as labels to form a sandwich-type sensor together with Ti3C2Tx/MoS2/MWCNT@rGONR, improving the electrochemical sensitivity and obtaining a highly distinguishable signal readout. Under the optimized conditions, the sensor has good detection limits of 0.135 nmol L-1 and 0.173 nmol L-1 for Kana and Cap, respectively, at the same linearity concentration of 0.5-2500 nmol L-1. Finally, it was successfully applied for detection in milk and fish meat, and the results were compared with the standard method HPLC, indicating its great potential for food safety monitoring.

Synthesis and Fluorescence Sensing for Nitro Explosives and Pesticides of Two Cd-Coordination Polymers

Two cadmium coordination polymers (CPs), {[Cd(zgt)(2,2'-bipy)(H2O)]·H2O}n (1) and {[Cd(zgt)(BPP)(H2O)]·H2O}n (2) (H2zgt = 5-methoxyresorcinic acid, 2,2'-bipy = 2,2'-bipyridine, and BPP = 1,3-bis(4-pyridyl)propane), were prepared by the hydrothermal method. The structures of CPs 1-2 were characterized by IR, TGA, X-ray powder diffraction, and elemental analysis. The single-crystal structure analysis shows that CP 1 is a typical 1D chain structure and CP 2 belongs to a 2D layered structure. Based on the excellent luminescence properties of CP 1 and 2, fluorescence sensing experiments were carried out for explosives and pesticides. The results of the explosion sensing experiment showed that CP 1 and 2 had an excellent fluorescence quenching effect on PNBA (p-nitrobenzoic acid) and TNP (2,4,6-trinitrophenol), respectively, and the detection limits were 3.28 and 11.4 nM, respectively. Interestingly, both CP 1 and 2 showed good fluorescence quenching against the pesticide fluridine (Flu), and CP 1 had a lower detection limit and was more sensitive. In addition, the fluorescence quenching mechanism was discussed in detail by the UV absorption spectrum and density functional theory. In order to explore its practical application, the content of Flu in water samples was detected by a labeling recovery method.

The DNA damage potential of quantum dots: Toxicity, mechanism and challenge

Quantum dots (QDs) are semiconductor nanoparticles (1-10 nm) with excellent optical and electrical properties. As QDs show great promise for applications in fields such as biomedicine, their biosafety is widely emphasized. Therefore, studies on the potential 'nanotoxicity' of QDs in genetic material are warranted. This review summarizes and discusses recent reports derived from different cell lines or animal models concerning the effects of QDs on genetic material. QDs could induce many types of genetic material damage, which subsequently triggers a series of cellular adverse outcomes, including apoptosis, cell cycle arrest and senescence. However, the individual biological and ecological significance of the genotoxicity of QDs is not yet clear. In terms of mechanisms of genotoxicity, QDs can damage DNA either through their own nanomorphology or through the released metal ions. It also includes the reactive oxygen species generation, inflammation and failure of DNA damage repair. Notably, apoptosis may lead to false positive results in genotoxicity tests. Finally, given the different uses of QDs and the interference of the physicochemical properties of QDs on the test method, genotoxicity testing of QDs should be different from traditional toxic compounds, which requires further research.

Enhancement of the Detection Performance of Paper-Based Analytical Devices by Nanomaterials

Paper-based analytical devices (PADs), including lateral flow assays (LFAs), dipstick assays and microfluidic PADs (μPADs), have a great impact on the healthcare realm and environmental monitoring. This is especially evident in developing countries because PADs-based point-of-care testing (POCT) enables to rapidly determine various (bio)chemical analytes in a miniaturized, cost-effective and user-friendly manner. Low sensitivity and poor specificity are the main bottlenecks associated with PADs, which limit the entry of PADs into the real-life applications. The application of nanomaterials in PADs is showing great improvement in their detection performance in terms of sensitivity, selectivity and accuracy since the nanomaterials have unique physicochemical properties. In this review, the research progress on the nanomaterial-based PADs is summarized by highlighting representative recent publications. We mainly focus on the detection principles, the sensing mechanisms of how they work and applications in disease diagnosis, environmental monitoring and food safety management. In addition, the limitations and challenges associated with the development of nanomaterial-based PADs are discussed, and further directions in this research field are proposed.

Nanobioengineered Sensing Technologies Based on Cellulose Matrices for Detection of Small Molecules, Macromolecules, and Cells

Recent advancement has been accomplished in the field of biosensors through the modification of cellulose as a nano-engineered matrix material. To date, various techniques have been reported to develop cellulose-based matrices for fabricating different types of biosensors. Trends of involving cellulosic materials in paper-based multiplexing devices and microfluidic analytical technologies have increased because of their disposable, portable, biodegradable properties and cost-effectiveness. Cellulose also has potential in the development of cytosensors because of its various unique properties including biocompatibility. Such cellulose-based sensing devices are also being commercialized for various biomedical diagnostics in recent years and have also been considered as a method of choice in clinical laboratories and personalized diagnosis. In this paper, we have discussed the engineering aspects of cellulose-based sensors that have been reported where such matrices have been used to develop various analytical modules for the detection of small molecules, metal ions, macromolecules, and cells present in a diverse range of samples. Additionally, the developed cellulose-based biosensors and related analytical devices have been comprehensively described in tables with details of the sensing molecule, readout system, sensor configuration, response time, real sample, and their analytical performances.

Colorimetric detection of Cr6+ ions based on surface plasma resonance using the catalytic etching of gold nano-double cone @ silver nanorods

Hexavalent chromium ion (Cr⁶⁺) is highly toxic to human health and environment. Herein, high-performance detection of Cr⁶⁺ is of great import. In this study, a rapid and sensitive multicolor colorimetric method for detection of Cr⁶⁺ in aqueous solution was established on the basis of Cr⁶⁺ etching of gold nano-double cone@silver nanorods (Au NDC@Ag NRs). Au NDC@Ag NRs was synthesized by a modified seed-mediated growth method. The catalytic etching induced by Cr⁶⁺ changed the morphology of Au NDC@Ag NRs, leading to the attenuation of surface plasma resonance (SPR) and the redshift of absorption spectra. Meanwhile, Au NDC@Ag NRs exhibits obvious color changes from orange to pink, to purple, and finally becomes colorless with the increasing concentrations of Cr⁶⁺. With such a design, naked-eye detection of Cr⁶⁺ was realized with high sensitivity. The proposed multicolor sensing method showed a good linearity between the redshift change of absorption peak (△λ) and the concentrations of Cr⁶⁺ in the range from 2.5 to 40 μM. The limit of detection (LOD) was calculated as 1.69 μM in aqueous solution. In addition, successful detection of Cr⁶⁺ in tap water and Yangtze River water, indicating the real applications of Au NDC@Ag NRs probe in monitoring Cr⁶⁺ in environment.

Recent advances in cellulose-based membranes for their sensing applications

ABSTRACT

In recent years, sensing applications have played a very important role in various fields. As a novel natural material, cellulose-based membranes with many merits can be served as all kinds of sensors. This review summarizes the recent progress of cellulose membranes as sensors, mainly focusing on their preparation processes and sensing properties. In addition, the opportunities and challenges of cellulose membrane-based sensors are also prospected. This review provides some references for the design of cellulose membrane materials for sensing applications in the future.