Search

As a kind of organic basic compound containing nitrogen, biogenic amine is released from food spoilage and considered as an indicator for monitoring food freshness. Herein, an excellent dual-emission ratiometric fluorescent sensor for eight kinds of biogenic amines was established via the facile mixing of pH-responsive carbon dots and Rhodamine B. The developed sensor shows a rapid response (10 s), low limit of detection (0.733–3.943 μM) and a wide linear range (0–150 μM). More importantly, a portable fluorescent filter paper was prepared by simple dispersing the filter paper in a solution mixture of carbon dots and Rhodamine B. The obtained fluorescent filter paper based sensor showed an obvious color change in the presence of biogenic amine vapor derived from shrimp and mushroom. The results revealed that this sensor could realize the on-site and visual detection of biogenic amines in real food samples, making it suitable for potential application in food safety monitoring. [ABSTRACT FROM AUTHOR]

Nowadays, kidney dysfunction is a common health issue due to the modernized lifestyle. Even though medications are commercially available to treat kidney diseases, early diagnosis is crucial and challenging. Clinically, measuring urine creatinine and pH has gained significant interest as a way to diagnose kidney diseases early. In the present work, we attempted to develop a low-cost, robust, accurate and naked-eye colorimetric method to determine both creatinine levels and pH variations in artificial urine samples using a simple 3D-printed hybrid microfluidic device. Creatinine was detected by the incorporation of the traditional Jaffe test onto the hybrid paper–PMMA microfluidic device and pH (4–8) was measured by a simple anthocyanin test. Notably, the tests were established without employing any sophisticated or costly instrument clusters. The developed 3D-printed microfluidic probe showed a limit of detection (LOD) of 0.04 mM for creatinine over a concentration range of 1–10 mM, with a regression coefficient (R2) of 0.995 in laboratory conditions. Interestingly, the experimental data obtained with artificial urine exhibited a wide linear range from 0.1 mM to 5 mM under different pH values ranging from 4 to 8 in the presence of matrices commonly found in urine samples other than proteins, indicating the potential use of this method in pre-clinical analysis. Since the wide linear range of urine creatinine in artificial urine samples falls well below the clinically relevant concentrations in humans (0.07–0.27 mM), the developed lab-on-chip device is further suitable for clinical evaluation with proper ethical clearance. This 3D-printed hybrid microfluidic colorimetry-based creatinine detection and pH indicator platform can be beneficial in the healthcare sector due to the on-site testing capability, cost-effectiveness, ease of use, robustness, and instrument-free approach. [ABSTRACT FROM AUTHOR]

We reported a colorimetric paper-based device by integrating the modified acid RNA-cleaving DNAzymes (MaRCD-EC1) for highly sensitive (detection limit = 102 CFU mL−1), and rapid (within 30 min) detection of E. coli without amplification. This device exhibited a clinical sensitivity of 100% and a specificity of 100% in identifying E. coli-associated urinary tract infections (UTIs) using the clinical urine samples. [ABSTRACT FROM AUTHOR]

Gossypol, a phytotoxicant in cotton-seed oil, has been found to sensitize Tb(III)-luminescence in a supramolecular hydrogel. Based on this observation, a paper-based sensor has been developed to detect gossypol with a limit of detection (LOD) of 2.9 nM. This is the first report of water-based detection with the highest sensitivity involving turn-on time-gated luminescence. This method was also able to sense gossypol in commercial crude cotton-seed oil. [ABSTRACT FROM AUTHOR]

A simple, rapid chemical coating and patterning method was developed and optimized for paper-based substrates for use in paper spray mass spectrometry (PS-MS). A variety of chlorosilanes were explored for coating paper substrates, and their effectiveness in forming hydrophobic surfaces was characterized via contact angle goniometry, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Trichloromethylsilane was selected as the primary coating agent because of the short time required to produce a hydrophobic surface (contact angle > 130°), as well as the ease of patterning. Patterning was performed using 3D-printed masks and an oxygen/plasma cleaner. Optimal mask thickness and oxygen/plasma cleaning parameters were determined to produce channels varying from 0.5 to 2.5 mm in width. The effectiveness of the patterned substrates for PS-MS was determined via analysis of four antiretrovirals: emtricitabine, lamivudine, efavirenz, and dolutegravir. Calibration curves were made for each antiretroviral at varying channel widths, and the limits of detection and limits of quantification for each drug were determined. These results show that this patterning method results in an average 7.2-fold improvement in sensitivity and an average 190-fold improvement in limits of detection over uncoated paper substrates in a neat matrix. In a proof-of-concept experiment, calibration curves were generated for each antiretroviral in urine. A patterned paper substrate with a 2-mm channel resulted in an average 7.4-fold improvement in sensitivity and an average 18-fold improvement in limits of detection over uncoated paper substrates. [ABSTRACT FROM AUTHOR]

This communication describes the development of polyvinyl chloride electrochemical system in which a paper layer loaded with reagents is inserted into the device, demonstrating a new concept of a paper card-like pad for a reagent-free and easy measurement of the target analyte in solution. This device detects glucose in artificial tears in the range of 0.2–2 mM with a detection limit of 50 μM by simply adding the artificial tears to the paper card-like pad. The novel configuration goes beyond the state of the art, widening the application range of paper in the design of smart analytical devices. [ABSTRACT FROM AUTHOR]

Based on surface biomolecular imprinting technology, a rotary microfluidic electrochemical paper-based chip (MIP-ePADs) was proposed for sensitive and selective detection of human interleukin 6 (IL-6) and procalcitonin (PCT). Compared with the traditional method, the sample can be added directly on the MIP-ePAD by rotating the working electrode, which avoids the loss of the liquid to be tested and greatly simplifies the process of electropolymerization imprinting and template elution. Our experimental results show that linear concentration ranges of IL-6 and PCT in the electrochemical molecularly imprinted microfluidic paper-based chip ranged from 0.01 to 5 ng mL−1, with their detection limits being 3.5 and 2.1 pg mL−1, respectively. For the detection of actual serum samples, there was no significant difference between the results of MIP-ePADs and the traditional electrochemiluminescence method used in hospitals, indicating that the paper-based chip can be used for stable and accurate analysis and detection. The chip greatly reduces the cost of clinical trials due to its advantages of easy preparation and low cost. The chip can be used for the analysis of non-antibody inflammation markers and can be widely used in home and hospital treatment detection. This method will not only play an important role in rapid detection, but also provide new ideas for the improvement of rapid detection technology. [ABSTRACT FROM AUTHOR]

We created novel Pd/CB-Ni@rGO nanomaterials for glucose detection. The as-synthesized nanomaterials were dropped on the electrode surface using the drop casting technique. The prepared electrode was then attached to a paper-based device containing the sample zone and the reaction zone, enabling plasma isolation and an enzymatic reaction for glucose detection in whole blood. The nanomaterials and surfaces of electrodes were characterized by FTIR, TEM, and SEM. The proposed approach is a disposable glucose detection method that is unaffected by protein fouling on the electrode, and it requires only one drop of human blood. Therefore, there is no need for extensive sample preparation, and there is less sample consumption. Under optimal conditions, Pd/CB-Ni@rGO can accurately measure blood glucose levels with a linear range of 7 to 7140 μM (R2 = 0.9986) and a low detection limit of 0.82 μM. Besides, the developed sensor shows excellent anti-interference capacity, stability, and satisfactory reproducibility and repeatability. Importantly, Pd/CB-Ni@rGO was successfully applied for glucose in whole blood from 4 volunteers, with results that correlated well with those obtained using an Accucheck glucometer at a 95% confidence level. Given its low cost, high accuracy, and ease of use, the blood glucose sensor holds significant potential for clinical use and broadens the area of future noninvasive sensor development. [ABSTRACT FROM AUTHOR]

Pesticide residues are a serious problem towards agriculture, environment and food safety, so it is highly desirable to develop a swift, efficient and portable pesticide detection method. A fluorescence visual sensing method for glyphosine based on a nitrogen-doped biomass carbon quantum dot (N-CQD) paper-based sensor was developed. The fluorescence signal was quenched by Fe3+ in a static quenching process, and then the fluorescence of N-CQDs was recovered after adding glyphosine. Under the optimal experimental conditions and when tested with a fluorescence spectrofluorometer, the detection of glyphosine showed a two-stage linear pattern in the range of 0.1–0.6 μM and 0.6–1.6 μM with a detection limit of 0.075 μM. Then, the RGB values of different concentrations of glyphosine on the filter paper chip were detected by the software of the smartphone-color identifier. The logarithm of the glyphosine concentration was linearly related to the G value of RGB in the range of 0.25–10.00 mM and with a detection limit of 0.15 mM. The method was applied to measuring glyphosine-spiked juice and flour samples, and the recovery rates were 87.60–112.69% and 93.27–105.83%, respectively. The proposed N-CQDs/Fe3+ system had wide applications, and it was expected to be fast and effective at detecting pesticide residues. [ABSTRACT FROM AUTHOR]

Sodium thiocyanate (NaSCN) is a naturally antibacterial component in milk, but excessive consumption of thiocyanate may cause potential risks to human health. Currently available methods for the detection of thiocyanate have some disadvantages such as poor sensitivity and high price. Here, we report a robust and cost-effective method to detect NaSCN based on paper substrates deposited with in situ reduced Ag nanoparticles by surface-enhanced Raman spectroscopy (SERS). Densely packed multilayer AgNPs provide uniform narrow nanogaps, which exponentially enhance the Raman signals. Moreover, these homogeneous narrow hotspots ensure that this method has high sensitivity (the limit of detection is 10−12 mol L−1), a wide linear range (from 10−9 mol L−1 to 10−4 mol L−1), and remarkable reproducibility (the coefficient of variation within a SERS sensor is 6.5%). Spiked milk samples were detected and the recovery rates of NaSCN were in the range of 95.1%–108.0%. This paper-based SERS sensor offers great potential for sensitive NaSCN detection and milk analysis. [ABSTRACT FROM AUTHOR]

Herein, a unique electrochemiluminescence (ECL) sensor combined with a paper electrode was proposed for the detection of phenylalanine (L -Phe) in blood samples. The L -Phe detection was performed by converting L -Phe into ammonia using phenylalanine ammonia-lyase (PAL) enzyme and the ECL signal of Ru(bpy)32+ was produced in combination with ammonia as a co-reactant. In this report, we used AuNP decorated paper electrodes to obtain the ECL signal of Ru-(bpy)32+ in the presence of NH3. The produced ammonia molecules were carried to the working electrode and their contact with the sample was cut off. Since there was no contact between the sample matrix and the electrode, the developed method achieved excellent selectivity. According to experimental data, a linear increase of the ECL signals with the logarithms of varying L -Phe concentrations between 1.5 × 10−2 and 1.211 mM was observed with a correlation coefficient (R2) of 0.9898 and a limit of detection (LOD) of 8.4 × 10−3 mM. The proposed method was efficiently applied for L -Phe detection in reference blood samples and the average recovery was calculated as 96.8%. Furthermore, the HPLC-UV method as a comparison verified that the recovery values provided by the proposed method were acceptable with a similarity of 95.1% for L -Phe detection in a reference blood sample. The results showed that the developed ECL sensor combined with the paper electrode can be considered as a promising unique and powerful technique for a point-of-care diagnosis of PKU. [ABSTRACT FROM AUTHOR]

Paper-based microfluidic solution sampling is a viable option for potentiometric sensors to be used for the determination of analytes in samples with high solid-to-liquid ratios. Unfortunately, heavy metal sensitive electrodes cannot be easily integrated with paper-based solution sampling as heavy metals have strong physicochemical adsorption affinity towards paper substrates. In this work, paper substrates were modified with an ion-selective membrane (ISM) cocktail (used for the preparation of Pb2+-ion-selective electrodes (ISEs)) and coupled with model heavy metal Pb2+-ISEs. It was found that the super-Nernstian response of Pb2+-ISEs was eliminated when 10 to 50 mg ml−1 of the ISM cocktail was used for the modification of paper substrates. The modification of the paper substrates by Pb2+-ISM allowed the elimination of adsorption sites. In addition, it resulted in an improvement of sensor performance in terms of their detection limits to be similar to those for conditioned electrodes in standard beaker-based measurements. It is believed that the elimination of super-Nernstian response of the electrodes and improving the potentiometric responses and detection limits of ISEs were attributed to the compatibility improvement of the paper substrates and Pb2+-ISEs to the same type of ISM. [ABSTRACT FROM AUTHOR]

As a part of our ongoing research, we have synthesized a new fluorescence probe, p-C4A, based on a calix[4]arene substituted with 4-aminoquinoline moieties with amide linkages. p-C4A can selectively recognize Li+ and PO43− ions and has been characterized via an emission study, an absorption study, ESI-MS spectroscopy, a 1H NMR study and cyclic voltammetry. The fluorescence sensor p-C4A can operate over a concentration range of 5–170 nM for Li+ sensing and 5–80 nM for PO43− sensing. The R2 values obtained for the sensing of Li+ and PO43− ions are 0.9962 and 0.9911, respectively. p-C4A demonstrates a minimum detection limit of 6.15 nM for Li+ and 9.0 nM for PO43−. The quantum yields of p-C4A as its Li+ and PO43− ion complexes were found to be 0.014 and 0.27, respectively. Herein, we report an easy-to-use, low-cost, disposable, paper-based, fluorescent, wax-printed device for the rapid chemical screening of Li+ and PO43−. This device can be used as a quick, portable, multiple-test panel that is simple, lightweight, and disposable. Moreover, in order to assess its analytical applicability, the prepared sensor was successfully used for the determination of Li+ and PO43− from wastewater samples, validating the proposed ion recovery method with 96–99% recovery rates. [ABSTRACT FROM AUTHOR]

Exosomes are vesicles released by healthy and cancer cells into the extracellular matrix and bodily fluid. Cancer cell-derived exosomes have attracted much attention in early-stage detection and prognostication of treatment response. Thus, detecting exosomes is of great interest to biology and medicine. However, many conventional detection methods require high-cost equipment and centralized laboratory facilities, making diagnostics inaccessible in limited-resource settings. This study reports a proof-of-concept low-cost electrochemical paper-based analytical device to quantify both the total bulk and cancer cell-derived exosomes in cell culture media. The device employs a sandwich immune assay design, where exosomes are initially captured using the electrode-bound generic antibodies (i.e. CD9) and subsequently detected via ovarian cancer-specific CA125 antibodies. Our proposed device quantifies the total bulk exosome concentration with a detection limit of 9.3 × 107 exosomes per mL and ovarian cancer cell-derived exosomes with a detection limit of 7.1 × 108 exosomes per mL, with a relative standard deviation of <10% (n = 3). We suggest that this low-cost and simple electrochemical paper-based device could be an alternative tool for detecting disease-specific exosomes in biological samples with the potential to be further developed for point-of-care diagnosis. [ABSTRACT FROM AUTHOR]

A direct mass spectrometry method utilizing reactive paper spray ionization was developed for sensitive cannabinoid quantitation in biofluid matrices. The ca. 2-minute sample measurements used on-paper derivatization to significantly increase paper spray mass spectrometry (PS-MS) positive ion mode sensitivity while minimizing sample preparation steps. Calibrations demonstrate high linearity, with R2 > 0.99 for (−)-trans-Δ9-tetrahydrocannabinol (THC) in oral fluid and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) in urine. The limit of detection and lower limit of quantitation were 0.78 and 10 ng mL−1 for THC in oral fluid and 1.3 and 10 ng mL−1 for THC-COOH in urine, respectively. THC-COOH levels measured by reactive PS-MS in seven spiked human urine samples showed bias of −9.4 to 5.9%, and percent difference values of −16.8 to 9.8% in comparison with a reference LC-MS method. Based upon the method simplicity, validation experiments, sensitivity, and rapidity, we conclude that reactive PS-MS has potential applications for rapid cannabinoid drug testing in urine and oral fluid. [ABSTRACT FROM AUTHOR]

tert-Butylhydroquinone (TBHQ) residues in foods pose a threat to human health. Therefore, it is necessary to develop a rapid method for TBHQ detection. In this study, a sensitive monoclonal antibody 5C3 (IgG2a subclass) against TBHQ was produced. It possessed a half maximal inhibitory concentration of 7.43 ng mL−1. A gold nanoparticle-based immunochromatographic assay (ICA) was established for the rapid and sensitive screening of TBHQ in soybean oil. Qualitative analysis results were obtained within 10 min and observed with the naked eye. The visual limit of detection (LOD) was 50 ng g−1 and the cut-off value was 1000 ng g−1. A hand-held strip reader was used for quantitative analysis, in which the calculated LOD was defined as 18.68 ng g−1. The average recoveries of TBHQ ranged from 89.55% ± 2.70% to 100.66% ± 3.02% for soybean oil, with a coefficient of variation of 2.89%–7.05%. Therefore, our developed ICA is a useful tool for the rapid and on-site detection of TBHQ in real food samples. [ABSTRACT FROM AUTHOR]

A luminescent trimethylamine (TMA) sensor, PTMA-Ir, has been designed and synthesized through immobilizing a phosphorescent iridium(III) complex on a TMA-imprinted polymer. Detailed study shows that the quenching of phosphorescence of PTMA-Ir can serve as a reporter for the binding of TMA on the imprinting sites, thus providing a sensitive, selective, and rapid detection of TMA in both aqueous solutions and gaseous states. Loading PTMA-Ir on filter paper produced a deposition T-Ir, the phosphorescence of which is quenched within 5 s upon exposure to TMA vapor with detection limits of 9.0 ± 0.1 ppm under argon and 15.0 ± 0.1 ppm in an air atmosphere. This work provided an effective method for establishing an imprinting polymer-immobilized luminescent amine sensor. [ABSTRACT FROM AUTHOR]

In this paper, Tesla coil discharge (TCD) was combined with laser-induced breakdown spectroscopy (LIBS). The TCD successfully enhanced the emission of Al atomic lines and AlO molecular bands in Al LIBS, and improved the sensitivity of quantitative analysis of Cr and Pb elements detected by LIBS in water. Firstly, the paper explored the effect of the distance from the TCD tip to the sample surface on the emission of Al atomic lines and AlO molecular bands, finding that 5 mm was the optimal distance. Secondly, the paper investigated the effect of laser energy on the emission of Al atomic lines and AlO molecular bands, finding that 25.1 mJ was the optimal laser energy. Finally, the paper constructed the calibration curves of Cr and Pb elements in water and calculated the limit of detection (LoD), finding that compared with surface enhanced LIBS (SELIBS), TCD–SELIBS reduced the LoDs of Cr and Pb elements from 16.7 ng mL−1 and 12.2 ng mL−1 to 7.3 ng mL−1 and 5.5 ng mL−1, respectively. It indicated that the combination of TCD and SELIBS can achieve high-sensitivity detection of Cr and Pb elements in the water. The combination of TCD and LIBS is a simple, low-cost, easy-to-operate, industrialized and commercialized technology, and has a promising application prospect in the high-sensitivity analysis of heavy metals in water. [ABSTRACT FROM AUTHOR]

Reported herein is an ultra-sensitive turn-off fluorescence sensor for hydrogen peroxide based on its reaction with bimane 1. This reaction is highly efficient, resulting in a detection limit of 7.9 pM. It also maintains sensor efficacy when adsorbed on paper and enables both solution-state and vapor-phase detection. [ABSTRACT FROM AUTHOR]

Herein, the serendipitous discovery of two water-recyclable and reusable fluorescent sensors IMPC (cyan–blue–cyan) and IMPC-OH (green–blue–green) is reported for sensing nerve agent simulants diethylcyanophosphonate and diethylchlorophosphate, respectively, with high sensitivity, short response time, and low detection limits. The unique features of these probes are their regeneration with the addition of a green and cheap solvent, namely water in CHCl3, and ease of fabrication into a portable paper-strip system that can also be regenerated. Various spectroscopic studies were employed to understand the mechanism of sensing and regeneration of both probes; the results reveal that water plays a critical role in the hydrolysis of the adduct formed with DCNP and DCP, which enables the retrieval of the probe with its original fluorescence. [ABSTRACT FROM AUTHOR]

Electrochemical detection methods hold many advantages over their optical counterparts, such as operation in complex sample matrices, low-cost and high volume manufacture and possible equipment miniaturisation. Despite these advantages, the use of electrochemical detection is currently limited in the clinical setting. There is a wide range of potential electrode materials, selected for optimal signal-to-noise ratios and reproducibility when detecting target analytes. The use of carbon paste electrodes (CPEs) for electrochemical detection can be limited by their analytical performance, however they remain very attractive due to their low cost and biocompatibility. This paper presents the fabrication of an easy-to-make and use graphite powder/paraffin wax paste combined with a substrate produced via additive manufacturing and confirms its functionality for both direct and indirect electrochemical measurements. The produced CPEs enable the direct voltammetric detection of hexaammineruthenium(III) chloride and dopamine at an experimental limit of detection (ELoD) of 62.5 μM. The key inflammatory biomarker Interleukin-6 through an enzyme-linked immunosorbant assay (ELISA) was also quantified, yielding a clinically-relevant ELoD of 150 pg ml−1 in 10% human serum. The performance of low-cost and easy-to-use CPEs obtained in 0.5 hours is showcased in this study, demonstrating the platform's potential uses for point-of-need electroanalytical applications. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have unique potential in the field of gas sensing due to their ultra-high specific surface area and abundant mesoporous structure. In this paper, a mesoporous Co3O4 hollow polyhedron structure with high specific surface area (141.6 m2 g−1) was synthesized by annealing at the optimum temperature. The gas response of the mesoporous Co3O4 hollow polyhedron structure to volatile organic compounds such as xylene, ethanol, methanol and acetone was systematically tested. The experimental results show that the mesoporous Co3O4 hollow polyhedron structure has the highest sensitivity (21.33) and excellent stability for xylene gas, and the detection limit is low (1 ppm). The excellent sensing performance benefits from large surface area, high oxygen defect concentration and mesoporous structure. [ABSTRACT FROM AUTHOR]

In this paper, we report on the development of an 'off–on' fluorescent probe for the detection of hydrogen peroxide (H2O2) and mercury ions (Hg2+) using an in situ synthesized carbon quantum dot and gum Arabic silver nanoparticle composite (CQDs@GA-Ag NPs). Electron microscopy measurement clearly shows that CQDs are attached to the surface of the GA-Ag NPs. The fluorescence intensity of the CQDs was dramatically quenched in the synthesized nanocomposite via the inner filter effect (IFE) mechanism. After adding H2O2 to the nanocomposite system, the Ag NPs got oxidized leading to the formation of Ag+ ions, and the CQDs regained their photoluminescence (PL) property. This facilitates the detection of H2O2 with an extremely low detection limit of 1.02 μM. Furthermore, the as-developed nanocomposite was also tested for the detection of Hg2+ ions, obtaining a remarkably low detection limit of 1.82 μM. The developed probe was extremely selective over a wide range of interfering ions and substances. [ABSTRACT FROM AUTHOR]

A volumetric bar-chart chip (V-chip) is a microfluidic device based on distance-based quantitative measurement that visualizes analyte concentration without the need for apparatus or data processing. This typically utilizes special receptors and catalysis parts that generate oxygen, so ink can be moved inside the channels, and enables instant visual quantitation of the analyte. However, the low stability of some macromolecules, the use of expensive catalysts, and difficulty in controlling the process cause inaccurate readings, and therefore, limit further development and the use of these systems. In this article, we introduced a novel approach that eliminates the use of catalysts in V-chips and provides an efficient and simple path in the design of biosensors. The product of the enzymatic reaction of urease with urea is bicarbonate, which turns into CO2 gas in an acidic environment. Therefore, the amount of gas produced is proportional to the amount of urea in the sample, and it can be quantitatively measured by visual detection from the amount of ink movement caused by CO2 gas pressure. This biosensor has a linear response range of 0 to 1000 µg ml-1 and a detection limit of 3.6 µg ml-1 in raw milk. The recovery of urea in raw milk at 100 and 400 µg ml-1 concentrations was 96.5% and 98.9%, respectively. This volumetric chip shows potential for determining urea levels in real samples without requiring additional equipment. The combination of the sensitivity and specificity of enzymatic reactions, inherent gas-generating reactions, and the processability of microchips discussed in this paper can be the basis for the comprehensive development of volumetric chips, which can create a new path for the development of efficient and cheap biosensors. [ABSTRACT FROM AUTHOR]

A europium-functionalized, dual-emissive, metal–organic framework-based fluorescence sensor (EuUCNDA) was constructed via post-synthetic modification of an UiO-66-type precursor through coordination interactions. EuUCNDA exhibited extremely high selectivity and sensitivity for malachite green (MG) with a low detection limit of 13.01 nM, a wide linear concentration range (0.05–50 μM), excellent anti-interference properties, a rapid response (<1 min), and the possibility of recycling. The good sensing performance of EuUCNDA enables the practical detection of MG in fish pond water and grass carp with good recoveries. Moreover, EuUCNDA can be reused for sensing MG and over 90% of fluorescence intensity can be restored after 7 cycles. Furthermore, EuUCNDA-embedded paper-based sensors combined with smartphone imaging afford portable and visual monitoring of MG in real samples. Notably, besides good sensing performance, EuUCNDA could efficiently remove MG from water. Hence, this work provides a recyclable and sensitive fluorescence sensor for portable, visual, rapid detection and efficient removal of MG. [ABSTRACT FROM AUTHOR]

Sensitive detection of glucose is important for public health, but non-enzymatic glucose biosensors still face significant challenges. In this paper, a novel and sensitive non-enzymatic glucose sensor was developed by in situ preparation of CuO nanorod-supported NiCo LDH nanosheet arrays on copper foam (CuO@NiCo LDH NSAs/CF). Because the hierarchical core–shell nanostructure provides more active sites and increases the exposed surface area of the catalyst, the catalytic activity of the electrode was significantly increased. As a working electrode, the CuO@NiCo LDH NSAs/CF catalyst showed good glucose sensing performance in a linear range of 0.6 μM–3 mM and a detection limit of 0.16 μM (S/N = 3). The sensor also showed repeatable responses over a month with negligible interference, and satisfactory recoveries with real human serum samples. [ABSTRACT FROM AUTHOR]

Hypochlorite (ClO−) is closely involved in human health and environmental safety. Therefore, it is of vital importance to realize the detection and separation of ClO−. Herein, a nanoprobe with analysis and removal capabilities of ClO− was synthesized via immobilizing coumarin-based functional molecules on halloysite nanotubes. The probe can easily detect ClO− in aqueous solution without the need for organic solvents, showing a fast detection time (10 s), a wide pH range (4–11), a low detection limit (8.4 nM), and a credible recovery rate range of 93.6–105.1%. The probe was further prepared into convenient test papers to realize the visual detection of ClO−. More importantly, it also enabled the removal of ClO−, and the removal rate was as high as 99.6%. [ABSTRACT FROM AUTHOR]

Environmental water pollution caused by hexavalent chromium (Cr(VI)) is a threat to living beings due to its carcinogenic nature. Herein, we report the synthesis of a highly fluorescent water-soluble conjugated polyelectrolyte PPMI and its application as a fluorescence sensor to monitor traces of carcinogenic Cr(VI) ions in water. PPMI was synthesized via the oxidative polymerization method followed by post-polymer functionalization. Fluorescent PPMI exhibited a photoluminescence quantum yield of 23.87 and displayed a rapid, very selective, and sensitive turn-off fluorescence signal in response to Cr(VI), with a significantly high quenching constant of 1.32 × 106 M−1. The mechanism of sensing was found to be static quenching. The limit of detection of this highly accessible analytical method was found to be in nanomolar ranges, i.e. 0.85 nM. Additionally, sensing on solid platforms such as economical paper strips was successfully achieved, which is very challenging and highly recommended for any reliable, portable, and economical analytical method. [ABSTRACT FROM AUTHOR]

The development of sensors with high sensitivity, selectivity, long-term stability and other excellent performances is still the focus of current research on gas sensors. In this paper, biomorphic zinc oxide composite reduced graphene oxide nanomaterials (C–Z–ZnO–rGO) based on a metal–organic framework are synthesized by an impregnation calcination method using cotton as a biological template. The microscopic morphologies and structural composition of the composites are characterized. The response value of C–Z–ZnO–rGO to acetic acid gas is much higher than that of other gas sensors. At an operating temperature of 350 °C, the C–Z–ZnO–rGO gas-sensitive sensors have a response value of 410 for 100 ppm acetic acid, a response time of 43 s, and a recovery time of 18 s, and have good repeatability and long-term stability. The response value of 2.614 for 1 ppm of acetic acid gas further indicates that the C–Z–ZnO–rGO sensor has a low detection limit. The hollow structure of the C–Z–ZnO–rGO composites has the advantages of high specific surface area, multiple pores, diverse structures and abundant active sites, which improves the adsorption performance on acetic acid gas. [ABSTRACT FROM AUTHOR]

Development of an effective and convenient sensor for sensitive detection of nitrites is of great concern since excessive amounts of nitrites can be harmful to both human health and the environment. In this work, Cu-MOF modified exfoliated graphite paper (EGP) was employed as a signal reporter to enable the visual and electrochemical dual-mode sensing of nitrites. Cu-MOFs were in situ synthesized on EGP, which exhibited an excellent oxidase enzyme-like activity to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) into its oxidation product (oxTMB). The multi-layer structure and the superior electrical conductivity of EGP not only facilitated the loading of the Cu-MOF nanozyme for colorimetric sensing but also enabled its use as an underlying backbone to support electroanalysis. Based on the recognition of nitrite through a highly specific diazo reaction between nitrite and oxTMB, the addition of nitrite caused the colorimetric sensing solution to change color from blue to green, which allowed for the colorimetric sensing of nitrite with a limit of detection (LOD) of 8.5 × 10−6 mol L−1. Meanwhile, the Cu-MOF/EGP electrochemical platform was employed for ratiometric detection of nitrite based on the electrochemical oxidation of nitrite and TMB. Compared with the colorimetric mode, the electrochemical mode possessed higher sensitivity with a LOD of 5.4 × 10−7 mol L−1, indicating the high sensitivity and accuracy of the proposed dual-mode sensing strategy. Furthermore, the determination of nitrite in different pickled food samples is demonstrated. [ABSTRACT FROM AUTHOR]

The development of a rapid and selective method for the identification of dipicolinic acid (DPA), a specific biomarker in Bacillus anthracis spores, is of great importance for the avoidance of anthrax infection. Herein, a chain-based EuIII metal–organic framework with the formula {[Eu3(BTDB)3(μ3-OH)3(H2O)]·solvents}n (JXUST-38, H2BTDB = (benzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoic acid) was obtained using 2-fluorobenzoic acid as the pH regulator. JXUST-38 exhibits good chemical and thermal stability and can specifically recognize DPA in N,N-dimethylformamide solution through luminescence enhancement and blue-shift effects with a detection limit of 0.05 μM. Furthermore, the significant luminescence enhancement and blue shift under UV lamps are obviously observable by the naked eye. The luminescence sensing mechanism is attributed to absorbance-induced enhancement between JXUST-38 and DPA. Test paper and mixed-matrix membrane based on JXUST-38 are designed for DPA detection. In addition, the feasibility of using JXUST-38 in biosensing is discussed in detail. [ABSTRACT FROM AUTHOR]

This paper introduces an enclosed microfluidic chip that integrates sample preparation and the chamber-based digital polymerase chain reaction (cdPCR). The sample preparation of the chip includes nucleic acid extraction and purification based on magnetic beads, which adsorb nucleic acids by moving around the reaction chambers to complete the reactions including lysis, washing, and elution. The cdPCR area of the chip consists of tens of thousands of regularly arranged microchambers. After the sample preparation processes are completed, the purified nucleic acid can be directly introduced into the microchambers for amplification and detection on the chip. The nucleic acid extraction performance and digital quantification performance of the system were examined using synthetic SARS-CoV-2 plasmid templates at concentrations ranging from 101–105 copies per μL. Further on, a simulated clinical sample was used to test the system, and the integrated chip was able to accurately detect SARS-CoV-2 virus particle samples doped with interference (saliva) with a detection limit of 10 copies per μL. This integrated system could provide a promising tool for point-of-care testing of pathogenic infections. [ABSTRACT FROM AUTHOR]

In this work, a simple and sensitive colorimetric fluorescence sensing probe was designed for the detection of uric acid (UA). UA can quench the fluorescence emission of CsPbBr3via hydrogen-bonding interactions. The probe can directly detect UA with an ultralow detection limit of 62.7 ppb and a fast response time of 30 s in a linear range of 0.0031–1.33 μM. The designed sensor displays a gradual color change from green to blue upon conjugation with UA. The applicability of the proposed sensor was also investigated as a paper sensor probe for detecting UA. Further, the method was successfully applied for the detection of UA in human blood serum. This work proposes CsPbBr3 as a novel platform for detecting UA well in clinical diagnosis. [ABSTRACT FROM AUTHOR]

A novel three-dimensional Eu3+-based metal–organic framework with the formula {[(CH3)2NH2][Eu(BTDI)]·H2O·DMF}n (JXUST-25) was prepared by solvothermal method based on Eu3+ and 5,5′-(benzothiadiazole-4,7-diyl)diisophthalic acid (H4BTDI) with benzothiadiazole (BTD) luminescent groups. Due to the presence of Eu3+ and organic fluorescence ligand, JXUST-25 displays turn-on and blue-shift fluorescence toward Cr3+, Al3+ and Ga3+ with limits of detection (LOD) of 0.073, 0.006 and 0.030 ppm, respectively. Interestingly, the alkaline environment can change the fluorescence of JXUST-25 toward Cr3+/Al3+/Ga3+ and the addition of HCl solution realizes the reversible change of the fluorescence of JXUST-25 toward Cr3+/Al3+/Ga3+. It is noteworthy that the fluorescent test paper and light-emitting diode lamp based on JXUST-25 can effectively detect Cr3+, Al3+ and Ga3+ by the visual changes. In addition, the turn-on and blue-shift fluorescence between JXUST-25 and M3+ ions may be caused by the host–guest interaction and the absorbance caused enhancement mechanism. [ABSTRACT FROM AUTHOR]

In this paper, a novel fluorescent probe, TPA-PAT, with continuous recognition based on triphenylamine was designed, synthesized, and characterized by NMR, IR, and fluorescence spectrophotometry techniques. The research results showed that the probe could specifically recognize Cu2+ in DMSO/H2O (99:1, v/v) with a detection limit as low as 0.40 mM and a coordination ratio of 1: 2. On this basis, it was found that its complex TPA-PAT-Cu2+ could achieve a continuous progressive recognition of the anion S2- and amino acids GSH, L-His, and L-Gly, while simultaneously showing high sensitivity for them with low detection limits of 25.7, 18.9, 21.7, and 45.9 nM, respectively. The probe had good reversibility and could be recycled. In addition, the probe TPA-PAT could simultaneously recognize Cu2+ and Hg2+ in acetone/H2O (99:1, v/v) with detection limits of 0.16 and 0.20 mM, respectively, while their coordination ratios were 1: 2. Similarly, its complex TPA-PAT-Hg2+ was able to continuously recognize the amino acids Cys and GSH with detection limits of 0.34 and 0.29 mM, respectively. It was also found that the probe and its complexes were able to be prepared for convenient dipstick applications, which could achieve a rapid fluorescence response to anions and amino acids and suggested its very good application prospects. [ABSTRACT FROM AUTHOR]

A xanthene fluorophore-based probe, Xanth-NO2, has been reported for the detection of thiophenol. Xanth-NO2 exhibited quenched fluorescence in an aqueous buffer due to its aggregate state, which allows a fluorescence turn-on response via the PhSH-induced transetherification process. In an aqueous buffer, the half-time for the reaction of Xanth-NO2 with thiophenol is 15 min. There is a linear overlap between the Xanth-NO2 fluorescence and thiophenol concentrations (0–10 μM), with a 130 nM detection limit. Xanth-NO2 reacted differently with hydrogen sulfide and thiophenol, allowing us to distinguish between these two analytes. Additionally, the ability of Xanth-NO2 to detect thiophenol in the presence of competing molecules or ions was demonstrated. Real-water samples and paper strip-based vapour phase detection of thiophenol were used to show the potential use of the reported probe. [ABSTRACT FROM AUTHOR]

Antibiotic abuse is considered a serious problem affecting human health, necessitating that great attention be paid to explore robust, simple and sensitive methods for rapid evaluation. In this paper, we developed a fluorescent aptasensor for visual and real-time kanamycin detection by taking advantage of the label-free strategy based on H-aggregate disassembly of a chiral cyanine dye induced by a G-quadruplex aptamer. The good sensitivity and selectivity enabled this aptasensor to have a detection limit as low as 43 nM and have high specificity for kanamycin recognition. Furthermore, this assay was successfully applied for the detection of kanamycin in lake water and urine with excellent recoveries. [ABSTRACT FROM AUTHOR]

A novel water-stable CdII-based metal–organic framework, namely {[Cd(BIBT)(TDC)]·2H2O}n (JXUST-28, BIBT = 4,7-bi(1H-imidazol-1-yl)benzo-[2,1,3]thiadiazole and H2TDC = 2,5-thiophenedicarboxylic acid), was synthesized using a mixed-ligand strategy. Structural analysis demonstrates that JXUST-28 exhibits a two-dimensional layer structure with 4-connected sql topology. Intriguingly, JXUST-28 presents good stability in boiling water (at least 5 days), common organic solvents and aqueous solutions with different pH values of 2–12 (more than 24 hours). Furthermore, fluorescence experiments revealed that JXUST-28 could sense Hg2+ ions in aqueous solution via a quenching effect with a detection limit of 0.097 μM. Meanwhile, JXUST-28 can also be regenerated at least 5 times to detect Hg2+ ions. In addition, light-emitting diode lamps, luminescent films, and test papers of JXUST-28 have been successfully developed for practical applications. [ABSTRACT FROM AUTHOR]

In this article, a novel triphenylamine-modified salicylaldehyde Schiff base 2-(((4-(diphenylamino)phenyl)imino)methyl)-4-(pyridine-4-yl)phenol (HL) was synthesized and structurally characterized. HL possessed D–π-A structure and exhibited typical AIE property in THF/H2O. It was applied to selectively recognize Cu2+ through an on–off mode in THF/H2O (1/9, v/v), and the fluorescence attenuation was attributed to a paramagnetic quenching effect of Cu2+ together with the abatement of HL aggregates. Hence, the detection limit achieved was as low as 1.32 × 10−7 M. The spectroscopic and ESI-HRMS results revealed a 1 : 2 complexation ratio of Cu2+ with HL. The mechanism for sensing Cu2+ was further confirmed by performing DFT calculations. Owing to the large affinity between Cu2+ and His, the resultant CuL2 system was further used to detect His via the off–on method based on the displacement of ligands. The detection limit for His reached 5.14 × 10−8 M. Furthermore, HL was available to prepare handy indicator papers for the on-site recognition of Cu2+ and His. Confocal fluorescent imaging demonstrated that HL could sequentially respond to intracellular Cu2+ and His. [ABSTRACT FROM AUTHOR]

In this paper we describe the synthesis, characterization, and use of a glucose-assisted magnetic aluminum oxyhydroxide@carbon (γ-AlOOH/Fe3O4@C) nanocomposite as a novel sorbent for the extraction and pre-concentration of deferasirox (DFX) present in plasma and urine samples using the ultrasonic-assisted dispersive solid-phase microextraction (UA-DSPME) method prior to HPLC-UV measurement. The sorption process was systemically optimized by experimental design and statistical analysis to maximize the extraction efficiency of DFX. The proposed method could be successfully employed for DFX determination in double-distilled water, plasma, and urine samples (real and spiked samples), with recovery range of 96.1–105%. Also, a good linear range from 10 to 3500 ng mL−1 was found with a correlation value of 0.9938, and relative recoveries between 2.09 and 5.22% were achieved adequately. Furthermore, the limit of quantification (LOQ) and the limit of detection (LOD) were found to be 5.421 and 0.163 ng mL−1 (based on a signal-to-noise ratio of 3) which were acceptable values compared to those of other reports. [ABSTRACT FROM AUTHOR]

In this study, we synthesized two unsymmetrical and dipodal Schiff–Mannich combo ligands, namely benzoic acid (3-benzoimidazol-1-ylmethyl-2-hydroxy-5-methyl-benzylidene)-hydrazide (H2BBH) and the hydroxyl analogue 2-hydroxy-benzoic acid (3-benzoimidazol-1-ylmethyl-2-hydroxy-5-methyl-benzylidene)-hydrazide (H3BSH), for the selective detection of Zn2+ in semi-aqueous media. Both the probes selectively depict a turn-on response to Zn2+ as a result of the combined effect of chelation-induced enhanced fluorescence (CHEF) and photo-induced electron transfer (PET). Detailed experimental studies reveal that H2BBH and H3BSH can detect Zn2+ in solutions with limit of detections of 27 nM and 46 nM, respectively. The structures of probe-Zn2+ ensembles were proposed as [(HBBH)2Zn] and [(H2BSH)2Zn] by ESI-MS, FT-IR spectroscopy, 1H NMR titration and DFT/TD-DFT methods. Moreover, both the probes were successfully employed in the detection of Zn2+ in HuH-7 cells, seedlings of chickpea and mung beans, and paper strips. [ABSTRACT FROM AUTHOR]

In this paper, NiCo-X (X = OH, S, P, Se) nanodiscs (NDs) were synthesized. Firstly, nickel-cobalt hydroxide (NiCo-OH) precursors with a nanodisc-like structure were prepared by a hydrothermal method. In the next step, nickel-cobalt sulfide nanodiscs (NiCo-S NDs), nickel-cobalt selenide nanodiscs (NiCo-Se NDs), and nickel-cobalt phosphide nanodiscs (NiCo-P NDs) were obtained from the synthesized NiCo-OH NDs in the previous step. The NiCo-Se NDs and NiCo-P NDs were prepared by selenization and phosphidation processes of the NiCo-OH NDs in a tube furnace containing a N2 atmosphere. The electrocatalytic performance of the mentioned nanodiscs is compared in the electrochemical determination of isoprenaline (IP) as a template. The results showed that the NiCo-Se NDs show better electrocatalytic activity compared to the other nanodiscs studied. The NiCo-Se ND-modified glassy carbon electrode (NiCo-Se NDs/GCE) showed a low detection limit (0.16 μM) and wide linear range (0.5−750 μM) of IP. The proposed substrate was successfully used for measuring IP in human blood serum samples. This study provides insights into the development of polymetallic nanodiscs in the field of electrochemical applications. In addition, our results are promising for usage in other electrochemical applications. [ABSTRACT FROM AUTHOR]

The highly luminescent complex [CdQ2(H2O)2] (1) shows ultra-selectivity and high sensitivity to the explosive organo-toxin trinitrophenol (TNP). This detection is extremely fast with a high quenching constant (5.3 × 104 M−1) and a very low limit of detection (LOD) of 137 nM/59 ppb. This motivated us to detect the lethal carcinogenic arsenical drug roxarsone (ROX), which is reported here for the first time. The quenching constant and LOD for ROX using 1 were found to be 4.9 × 104 M−1 and 86 nM (or 37 ppb), respectively. Moreover, the probe also recognizes three lethal toxic oxo-anions (MnO4−, Cr2O72− and CrO42−) with outstanding quenching constant (2.2 × 104 M−1, 1.4 × 104 M−1 and 1.1 × 104 M−1) and very low LODs (141 nM/61 ppb, 178 nM/78 ppb and 219 nM/95 ppb). Compared to the previously reported homogeneous sensing nature of the discrete complexes, our complex showed the detection of toxic pollutants in a heterogeneous manner, which results in high recyclability and hence multi-cycle sensing capability. Interestingly, 1 shows the possibility for real-time monitoring through naked eye detection by visible colorimetric changes in solid, solution and strip paper methods, i.e., triphasic detection ability. In addition, the sensor also exhibited the cross-sensing ability for these pollutants. The experimental sensing mechanism is strongly supported by the exhaustive theoretical investigation. Based on the fluorescence signal shown by each analyte, an integrated AND-OR logic gate is constructed. Furthermore, the sensing ability of 1 remains intact towards the detection of versatile real field samples including lethal carcinogenic arsenical drug roxarsone in the real food sample. [ABSTRACT FROM AUTHOR]

The current luminescent metal-organic framework (MOF) based fluorescence detection mostly focuses on achiral molecules. The stereospecific recognition and determination of MOF-based detection remain challenging. A novel luminescent terbium-based MOF (Tb-MOF) based biosensing system with excellent performance for stereoselective detection of D-amino acids (D-AAs) was introduced in this paper. D-Amino acid oxidase catalyzes stereospecific oxidative deamination of D-AAs, producing H2O2. The generated H2O2 effectively quenches the fluorescence of Tb-MOF. Under optimum conditions, the D-AAs were detected with excellent efficiency. The linear working range was 0.5-100 mM for D-Alanine (D-Ala) and 0. 5-5 mM for D-Proline (D-Pro), respectively. The limit of detection (Ksv detection) for D-Ala and D-Pro was 0.09 mM and 0.14 mM, respectively. The detection can be performed within 30 min with high selectivity and long-term stability. The fluorescent sensing platform required simple fabrication and operation and was free from complicated reaction processes and expensive reagents. The present sensing system was successfully applied in D-AA detection in human serum with good recovery, indicating its potential application in detection in biological samples. [ABSTRACT FROM AUTHOR]

A novel oxime-based fluorescent chemosensor (E)-2-(4′-(7,8,13,14-tetrahydrodibenzo[a,i]phenanthridin-5-yl)-[1,1′-biphenyl]-4-yl)ethen-1-ol (PBO) has been developed for the fluorimetric detection of hypochlorite ion (OCl−). On account of the optical behavior of the sensor PBO, distinctive spectral alterations in the presence of OCl− were detected. Furthermore, an obvious fluorescent color change from cyan to blue was also observed. An explicit linear relationship was found between the fluorimetric ratio of PBO and the concentration of OCl−. The detection limit (LOD) of PBO was evaluated to be 8 nM. The optical response was caused by the nucleophilic attack of OCl− on the imine group of the PBO probe, which stimulates intramolecular charge transfer. NMR titration investigation verified the detection mechanism. The PBO probe causes a quick spectral response towards OCl−, within 10 seconds. Furthermore, the practical utility of PBO was investigated through test paper analysis. The detection of OCl− in various water samples was also explored. The fluorescence bio-imaging experiment indicates the potential ability of the sensor PBO to detect OCl− in live E. coli cells. [ABSTRACT FROM AUTHOR]

According to the nucleophilicity of sulfur dioxide derivatives, a reactive fluorescent probe was designed and synthesized by linking triphenylamine with benzoindole. When the probe reacts with sulfur dioxide derivatives, the two fluorophores of the probe are disconnected to release strong blue fluorescence, and the fluorescence signal at 475 nm is significantly enhanced. The probe can rapidly identify sulfur dioxide derivatives (within 300 s), and has the advantages of strong selectivity and low detection limit (2.75 × 10−6 M). The probe with low toxicity can be used to detect sulfur dioxide derivatives in HepG-2 cells. In addition, detection test paper and silica functional materials prepared based on the probe also achieved excellent results in the detection of sulfur dioxide derivatives, which provides a potential direction for the further commercialization of the probe. [ABSTRACT FROM AUTHOR]

Considering the scarcity of palladium ion probes with subcellular organelle targeting, especially probes with near-infrared (NIR) emission wavelength fluorophores, our group has been working to overcome this problem and looking forward to providing potential practical tools for exploring the toxicity of palladium ions at the subcellular level. In this paper, a novel colorimetric and NIR fluorescent probe, BHCy-Pd, for the specific detection of palladium ions (Pd2+) in lysosomes via an internal charge-transfer (ICT) mechanism was designed and synthesized. As expected, BHCy-Pd exhibited a rapid, selective, and sensitive response for palladium with an ultralow limit of detection at 5.9 nM, accompanied by a distinct color change from purple to blue. Furthermore, BHCy-Pd can be made into a simple test strip for rapid and easy detection of Pd2+ in practical applications. Importantly, BHCy-Pd is capable of specific distribution in lysosomes, and thus can detect Pd2+ in real-time, thereby providing a potential tool for studying the cytotoxicity of Pd2+ ions at the subcellular level. [ABSTRACT FROM AUTHOR]

A new water-stable three-dimensional (3D) Eu(III) metal–organic framework with the formula of {[Eu3(BTDC)4(HCOO)(H2O)2]·solvents}n (JXUST-9) was successfully obtained by the solvothermal reaction of 2,1,3-benzothiadiazole-4,7-dicarboxylic acid (H2BTDC) and Eu(NO3)3·6H2O. The PXRD patterns indicate that JXUST-9 exhibits good stability when soaked in boiling water for at least 24 h. The fluorescence experiments indicate that JXUST-9 could be considered as a good multi-responsive sensing material for detecting Fe3+, MnO4− and Cr2O72− in aqueous solutions via the turn-off effect, and the detection limits are 0.94 μM, 1.23 μM and 1.23 μM, respectively. JXUST-9 can also be regenerated at least five times for sensing Fe3+, MnO4− and Cr2O72−. Moreover, a rapid detection test paper incorporated with JXUST-9 has been produced, which is helpful for carrying out visual detection of Fe3+, MnO4− and Cr2O72− in daily applications. [ABSTRACT FROM AUTHOR]

Scientists are still working on developing a "turn-on" fluorescence sensor for Co2+, especially in acidic solutions. A novel "on–off–on" fluorescence sensor based on g-C3N4 nanosheets was designed and prepared in this paper. It was able to detect (2-(5-bromo-2-pyridylazo)-5(diethylamino)phenol (abbreviated to 5-Br-PADAP) and Co2+ quantitatively by quenching and restoring the fluorescence of the g-C3N4 nanosheet system, respectively. Also discussed are the effects of solvent, pH, order of addition, and interaction time of 5-Br-PADAP and Co2+, as well as the concentration range of the object on measurement. Furthermore, in acidic conditions, the sensor demonstrated good selectivity and sensitivity. In the solvent system EtOH : H2O (v/v = 1 : 9, pH = 3), the fluorescence intensity had a good linear relationship with 5-Br-PADAP and Co2+ concentrations in the ranges of 0–15 μM and 0–10 μM, with low detection limits of 64 nM and 44 nM, respectively. Experiments and theoretical calculations were used to describe the interaction characteristics and sensing mechanism. It was eventually successful in detecting Co2+ in environmental samples. [ABSTRACT FROM AUTHOR]

As a stable donor for releasing controlled amounts of CO, carbon monoxide releasing molecule-2 (CORM-2) is a new type of therapeutic drug that contributes to exploring the pathophysiological effects of CO. The accurate detection of CORM-2 in biological systems is of great significance for controlling its dosage as a therapeutic drug and elucidating the reaction mechanisms of CO, but currently there is a lack of metal-free near-infrared fluorescent probes. Herein, a new metal-free near-infrared fluorescent probe based on nitrofuran which could selectively identify CORM-2 was designed and it has been successfully applied in living cells, zebrafish and mice. After reacting with CORM-2, both the color and fluorescence signal of the solution are restored, which is ascribed to the reduction of the nitro group. The spectroscopic probe DXPN shows high sensitivity to CORM-2 with a low detection limit of 87 nM and near-infrared fluorescence emission of 712 nm. Notably, this is the first time that paper chips are being used as a carrier to detect CORM-2 through fluorescence signals instead of the traditional liquid phase detection mode of fluorescent probes. These superior properties of the probe make it a promising and reliable tool for exploring the role played by CORM-2 in biological systems. [ABSTRACT FROM AUTHOR]