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In this study, based on aggregation-induced emission (AIE) effect and antenna effect, a novel portable fluorescent responsive membrane was constructed with red carbon dots (R-CDs) as reference signal and terbium coordination polymer (Tb-AMP CPs) as response signal for visual, instrument-free, and sensitive detection of fluoroquinolones (FQs). Specifically, the fluorescent responsive membrane (R-T membrane) was prepared by physically depositing R-CDs with AIE property and Tb-AMP CPs on the surface of polyvinylidene fluoride filter membranes at ambient temperature. In the presence of FQs, Tb3+ in the Tb-AMP CPs of the prepared membrane coordinated with the β-diketone structure of FQs, which turned on the yellow-green fluorescence through the "antenna effect". As the concentration of FQs increased, the R-T membrane achieved a fluorescent color transition from bright pink to yellow-green. Its visual detection sensitivity for three FQs, including ciprofloxacin, difloxacin, and enrofloxacin, was 0.01 μM, and the detection limits were 7.4 nM, 7.8 nM, and 9.2 nM, respectively, by analyzing the color parameter green. In the residue analysis of FQs in real samples, the constructed membrane also exhibited remarkable anti-interference and reliability, which is of great significance for ensuring the safety of animal-derived food. [ABSTRACT FROM AUTHOR]

Herein, a novel bimodal ratiometric probe for sensitive and selective detection of biothiols (including glutathione (GSH), cysteine (Cys) and homocysteine (Hcys)) was constructed, which was based on the redox reaction between manganese dioxide nanoflakes (MnO 2 NFs) and rhodamine (RhB) and biothiols. When MnO 2 NFs was added into RhB solution, RhB was oxidized to a series of derivatives, accompanying with the colorimetric color changing from purple to light pink and fluorescence changing from red to green. In the presence of GSH, Cys or Hcys, they could reduce MnO 2 NFs to Mn2+, thereby preventing the following oxidization of RhB and the corresponding color and fluorescence changes. The absorption intensity ratio and fluorescence intensity ratio showed good linear relationships with the concentrations of biothiols. The colorimetric detection limits for GSH, Cys and Hcys were 0.057 μM, 0.140 μM and 0.087 μM, respectively. And the fluorescence detection limits were 0.177 μM, 0.282 μM and 0.161 μM. More importantly, this probe was successfully applied to monitor the concentration of GSH/Cys/Hcys in human serum samples, with satisfactory recovery. Thus, this MnO 2 NFs-RhB platform can potentially be a candidate for the detection of biothiols. Image 1 • A bimodal ratiometric probe based on RhB and MnO 2 nanoflakes was fabricated. • This probe utilized the redox reactions between MnO 2 nanoflakes and RhB and biothiols. • It had a high sensitivity and a low detection limit. • It was applied in detecting biothiols in serum sample with satisfactory recoveries. • It can be used for detection biothiols with naked eyes under daylight and UV lamp. [ABSTRACT FROM AUTHOR]

Novel 3D porous Ni/Cu(OH) 2 nanospheres (Ni/Cu(OH) 2 NS) were directly grown on a Ni foam (NF) via a facile one-step potentiostatic deposition synthesis route. The resultant Ni/Cu(OH) 2 NS possessed an abundance of catalytic which gave them excellent catalytic properties for the electrochemical detection of glucose in alkaline conditions. Using these NS in a promising and integrated non-enzymatic glucose sensor, a high sensitivity of 8722 μA mM−1 cm−2, a low detection limit of 1.27 μM, and a linear detection range from 10 to 1490 μM were obtained at the Ni/Cu(OH) 2 NS/NF anode. Additionally, the proposed sensor exhibited excellent anti-interference capability, good reproducibility, and long duration stability. It was successfully applied to glucose detection in human blood serum, showing excellent effectiveness. • Porous Ni/Cu(OH) 2 nanospheres supported on the Ni foam was fabricated by a facile one-step potentiostatic deposition strategy. • As-prepared Ni/Cu(OH) 2 /NF anode shows excellent catalytic activity to glucose. • The porous Ni/Cu(OH) 2 nanospheres could offer more abundant active sites and easier access to electrolyte. [ABSTRACT FROM AUTHOR]

In this study, based on the oxidase activity and photothermal effect of manganese dioxide nanosheets (MnO 2 NSs), with thiamine (TH) as the fluorescence response signal and tris (2,2'-bipyridyl) ruthenium (II) hexahydrate as the reference signal, an enzyme-regulated ratiometric fluorescence and photothermal dual-mode probe was constructed for the quantitative detection of organophosphorus pesticide (OPs) residues. OPs reduced the production of the reductive product thiocholine by inhibiting the activity of acetylcholinesterase, thereby regulating the residual amount of MnO 2 NSs. With the increase of OPs concentration, the color of the probe solution gradually transitioned from red to blue, and the temperature gradually increased. Using dichlorvos and chlorpyrifos as pesticide models, the developed probes exhibited sensitive responses to OPs in a wide linear range of 0.1–8000 ng/mL. The detection limits of dichlorvos and chlorpyrifos in fluorescence mode were 1.13 × 10−3 ng/mL and 0.86 ng/mL, respectively. The corresponding detection limits in photothermal mode were 1.01 ng/mL and 1.02 ng/mL, respectively. The proposed probe displayed excellent anti-interference and reliability in the analysis of OPs residues in real samples. The dual-mode probe with self-verification function is expected to provide more accurate and robust detection results than the single-mode probe, and has a wider application prospect. [ABSTRACT FROM AUTHOR]

• Metal-polydopamine framework (MPF) based lateral flow assay (LFA) was developed. • MPF displayed excellent affinity with antibodies to detect tetracycline. • Assay performance of this LFA was 66-fold higher than that of traditional AuNP-LFA. • This work expands the application of MOFs as a novel label in immunoassays. Gold nanoparticles (AuNPs)-based lateral flow assay (LFA) enables a rapid detection of tetracycline (TET) in food samples but suffers from low sensitivity. Herein, metal-polydopamine framework (MPF), as a label, was employed to load monoclonal antibodies (mAbs) directly as the probe in LFA for highly sensitive sensing of TET. Combining zeolitic imidazolate framework (ZIF-67) and polydopamine (PDA), a stable MPF with large size, well water-dispersible, excellent affinity and optical properties was prepared through a versatile layer-by-layer assembly (LLA) strategy. Under optimized conditions, the biosensor (MPF-LFA) exhibited a great linear relationship in the range of 0.09–6 ng/mL and a detection limit of 0.045 ng/mL for TET detection, which was over 66-fold more sensitive than traditional AuNPs based LFA. Furthermore, the MPF-LFA was successfully applied to the screening of TET in fish, chicken, milk and shrimp samples with satisfied recoveries from 91% to 114%. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have attracted tremendous interest due to their promising applications, including electrocatalysis originating from their unique structural features. However, it remains a challenge to prepare COFs for p-nitrophenol (PNP) and o-nitrophenol (ONP) electrocatalysis because it is quite difficult to manipulate their dimension, composition, and morphology with abundant active sites. Here, a facile ambient temperature synthesis of unique Fe 3 O 4 -based magnetic COFs nanosphere (Fe 3 O 4 @AT-COFs) with different surface morphologic structure is reported, which exhibits higher surface area, good water dispersity, long-term stability, excellent electrical conductivity and pre-concentration effect. The prepared Fe 3 O 4 @AT-COF-based electrochemical sensor is then directly employed for the simultaneous detection of PNP and ONP with a wide linear detection range of 10–3000 μM and low detection limits (LOD) of 0.2361 μM and 0.6568 μM, respectively. Meanwhile, the Fe 3 O 4 @AT-COF can be also well-applied in lake and tap water for monitoring PNP and ONP with outstanding sensitivity and reliability, which is expect to be a high-efficient electrocatalyst with great promise for signal amplification of electrochemical sensing. Image 1 • Facile synthesis of Fe 3 O 4 -based magnetic COFs with different surface morphologic structure. • COFs as the enrichment carriers of Fe 3 O 4 were employed for amplifying electrochemical sensing signals. • Fe 3 O 4 plays a dual role in magnetic attraction with the electrode and synergistic catalysis effect with COFs. • A sensitive and reliable simultaneously detection of PNP and ONP were achieved with a low limit of detection. [ABSTRACT FROM AUTHOR]

• Ferrous selenide nanorods on carbon cloth was prepared via in situ synthesis. • The self-supported nitrite sensor displays high sensitivity and low detection limit. • The proposed sensor detected nitrite in real samples with acceptable results. In this paper, a self-supported electrode for nitrite detection was obtained by loading ferrous selenide nanorods on carbon cloth (FeSe NR/CC) via in situ synthesis. The morphology and chemical composition of the FeSe NR/CC were characterized using scanning electron microscope (SEM), X-ray diffractogram (XRD), and X-ray photoelectron spectroscopy (XPS). Owing to the synergistic effect between FeSe nanorods and carbon cloth, the rich redox active sites, and the lower transferring resistance, the binder-free and self-supported sensor based on FeSe NR/CC exhibits a wide linear relationship from 0.625 μM to 6775.5 μM, a fast-current response of 3 s, and a high sensitivity of 1107.7 μA mM−1 cm−2. The detection limit of the FeSe NR/CC was evaluated as 0.07 μM and the developed sensor displays excellent selectivity, stability, and reproducibility. Additionally, the as-prepared sensor has been successfully applied to detect nitrite in pickled vegetable samples, proving its feasibility for practical applications. Therefore, the self-supported and binder-free electrode proposed in this study could be used as a highly efficient and cost-effective electrochemical nitrite sensing device to achieve rapid quantitative detection of nitrite in food samples. [ABSTRACT FROM AUTHOR]

• A sensitive biosensor that introduced MoS 2 as extraordinary probes was constructed to detect tetracycline. • Exfoliated nanosheets with large, middle, and small sizes and all exhibited excellent water-dispersibility and stability. • The versatile MoS 2 can label antibodies without the need for surfactant modification. • A very low limit of detection of 0.023 ng/mL was obtained for tetracycline detection. In this study, we report a simple approach for synthesizing three kinds of molybdenum disulfide (MoS 2) nanosheets with different sizes of large, middle, and small (which are defined as L -MoS 2 , M -MoS 2 and S -MoS 2) by an aqueous-phase exfoliation and differential-zone centrifugation (AE-DC) strategy, and for the first time explored the MoS 2 labeled antibodies (Abs) as probes for sensitive detection of tetracycline (TET) on lateral flow assays (LFAs). The hierarchical MoS 2 had uniform sizes (Average size: 366 ± 65.70 nm, 131 ± 24.39 nm and 55 ± 8.56 nm for L -MoS 2 , M -MoS 2 , and S -MoS 2 , respectively; thickness: 3 nm, 1 nm for and 0.5 nm for L -MoS 2 , M -MoS 2 and S -MoS 2 , respectively), and all exhibited excellent water-dispersibility and stability. Compared with M -MoS 2 and S -MoS 2 based LFAs, L -MoS 2 based LFA particularly displayed highly sensitive detection of TET due to the larger surface area and stronger color intensity. Under optimized experimental conditions, the developed L -MoS 2 -based immunosensor showed a great linear relationship over the range of 0.012–0.75 ng/mL in 15 min and a signal sensitivity up to 0.023 ng/mL for TET detection, which was at least 17-fold lower than traditional gold nanoparticles based LFA. The assay resulted in excellent specificity and reproducibility, and can be well-applied in milk, honey, and beef samples for monitoring TET. [ABSTRACT FROM AUTHOR]

• A novel, sensitive, and stable fluorescent sensor was developed for TET detection. • The synthesized MoS 2 NPs possessed superior solubility and strong blue fluorescence. • A low detection limit of 0.032 μM with good linear relationship was achieved. • This prominent technique could be applied in milk and bovine muscle samples. The wide use of tetracyclines (TCs) for prevention and therapy of animal diseases may result in excessive residues in animal products, which could pose serious risks to human health. A novel molybdenum disulfide nanoplates (MoS 2 NPs)-based fluorescent sensor for tetracycline (TET) is reported. The MoS 2 NPs, synthesized via a facile bottom-up hydrothermal route, showed blue fluorescence at 430 nm in aqueous solution. Interestingly, its fluorescence was quenched significantly upon addition of TET, which is mainly due to a combination of the inner filter effect and electron transfer. Thus, the MoS 2 NPs based fluorescence sensor was delineated for the detection of TET. The methodology here presented showed a low detection limit of 0.032 μM and satisfied recoveries from 88.46% to 108.62% in spiked milk, milk powder and bovine muscle samples. [ABSTRACT FROM AUTHOR]