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Azodicarbonamide (ADA) in flour can be easily decomposed to semi-carbazide and biuret, exhibiting strong genotoxicity in vitro and carcinogenicity. Glutathione (GSH) can be conjugated with some ketone-containing compounds and unsaturated aldehydes to form toxic metabolites. Here, a novel ratio fluorescence probe based on blue emitting biomass-derived carbon dots (BCDs) and yellow emitting 2,3-diaminophenazine (OxOPD) was prepared for the bifunctional determination of glutathione (GSH) and ADA. This strategy includes three processes: (1) Ag + oxidizes o-phenylenediamine (OPD) to produce OxOPD. The peak at 562 nm was enhanced, and the peak at 442 nm was reduced due to fluorescence resonance energy transfer (FRET), (2) glutathione binds Ag + and inhibits the production of OxOPD, (3) ADA oxidizes GSH to form GSSG, resulting in the release of Ag + by GSH. Therefore, the newly designed ratio fluorescence probe can be based on the intensity ratio (I 442 /I 562 ) changes and significant fluorescent color changes to detect GSH and ADA. Moreover, a smartphone WeChat applet and a yolov3-assisted deep learning classification model have been developed to quickly detect GSH and ADA on-site based on an image processing algorithm. These results indicate that smartphone ratiometric fluorescence sensing combined with machine learning has broad prospects for biomedical analysis., (Copyright © 2021 Elsevier B.V. All rights reserved.)

To provide the basis for clinical diagnosis in an emergency case, a portable smartphone device-based multi-signal sensing system for on-site determination of alkaline phosphatase (ALP) is introduced. In this system, cobalt hydroxide (CoOOH) nanoflakes can oxidize O-phenylenediamine (OPD) to produce 2,3-diaminophenazine (OxOPD), resulting in a strong fluorescence at 565 nm and an absorbance at 420 nm, respectively. The ascorbic acid 2-phosphate (AAP) can be hydrolyzed by alkaline phosphatase (ALP) to yield ascorbic acid (AA). Then, AA reduces the CoOOH nanoflakes to produce Co 2+ , and AA is oxidized to form dehydroascorbic acid (DHAA), thereby inhibiting the formation of OxOPD. The reaction product DHAA further combines with OPD to yield 3-(1,2-dihydroxyethyl)furo[3,4-b]quinoxalin-1(3H)-one (DFQ) accompanied by a strong fluorescence at 430 nm. Based on this, the fluorometric assay for ALP has a wide linear range from 0.8 to 190 U/L with a low detection limit of 0.16 U/L, and the colorimetric assay from 3 to 130 U/L with a detection limit of 1.94 U/L. Moreover, a portable smartphone sensing platform integrated with fluorescent and colorimetric signals was established for rapid determination of ALP without spectrometers. Recoveries of 97-104% for spiked samples and relative standard deviations (RSD) of less than 2% (n = 3) confirmed the feasibility of the developed platform in complicated samples, opening up new horizons for on-site evaluation in the biomedical field.

The overuse and misuse of tetracycline (TCs) antibiotics, including tetracycline (TTC), oxytetracycline (OTC), doxycycline (DC), and chlortetracycline (CTC), pose a serious threat to human health. However, current rapid sensing platforms for tetracyclines can only quantify the total amount of TCs mixture, lacking real-time identification of individual components. To address this challenge, we integrated a deep learning strategy with fluorescence and colorimetry-based multi-mode logic gates in our self-designed smartphone-integrated toolbox for the real-time identification of natural TCs. Our ratiometric fluorescent probe (CD-Au NCs@ZIF-8) encapsulated carbon dots and Au NCs in ZIF-8 to prevent false negative or positive results. Additionally, our independently developed WeChat app enabled linear quantification of the four natural TCs using the fluorescence channels. The colorimetric channels were also utilized as outputs of logic gates to achieve real-time identification of the four individual natural tetracyclines. We anticipate this strategy could provide a new perspective for effective control of antibiotics. Deep learning-assisted multi-modal logic gates to identify four tetracycline analogues using an in-house portable device. [Display omitted] • Deep learning-assisted multi-modal logic gates identify four tetracycline analogues. • High-throughput intelligent rapid on-site detection of tetracycline. • A portable detection device for smartphones based on deep learning assistance. • A new perspective for effective control of tetracycline antibiotics. [ABSTRACT FROM AUTHOR]

In this work, a colorimetric and fluorescent dual-mode probe controlled by NH 2 -MIL-88 B (Fe, Ni) nanozymes was developed to visually detect tetracycline antibiotics (TCs) residues quantitatively, as well as accurately distinguish the four most widely used tetracycline analogs (tetracycline (TC), chrycline (CTC), oxytetracycline (OTC), and doxycycline (DC)). Colorless substrate 3,3′,5,5′-tetramethylbenzidine (TMB) may be oxidized to blue oxidized TMB by the Fe Fenton reaction, which was catalyzed by the NH 2 -MIL-88 B (Fe, Ni) nanozyme with POD-like activity. The colorimetric detection system allows TCs to interact with NH 2 -MIL-88 B (Fe, Ni). This inhibits the production of ·OH, weakens the oxidation process of TMB, and ultimately lightens the blue color in the system by blocking the electron transfer between NH 2 -MIL-88 B (Fe, Ni) and H 2 O 2. Furthermore, TCs can interact with NH 2 -MIL-88 B (Fe, Ni) as a result of the internal filtering effect, which causes the fluorescence intensity to decrease as TCs concentration increases. Additionally, a portable instrument that combines a smartphone sensing platform with colorimetric and fluorescent signals was created for the quick, visual quantitative detection of TCs. The colorimetric and fluorescent dual-mode nano platform enables color change, with detection limits (LODs) of 0.182 μM and 0.0668 μM for the spectrometer and smartphone sensor, respectively, based on the inhibition of fluorescence and enzyme-like activities by TCs. Overall, the colorimetric and fluorescence dual-mode sensor has good stability, high specificity, and an efficient way to eliminate false-positive issues associated with a single detection mode. Colorimetric and fluorescence dual-mode detection of TCs based on NH 2 -MIL-88 B (Fe, Ni). [Display omitted] • Sensing of TCs by NH 2 -MIL-88 B (Fe, Ni) nanozyme with POD-like catalytic activity and fluorescence characteristics. • Oxygen vacancy induced charge transfer modulates the charge of Fe, Ni to accelerate the formation of hydroxyl radical. • A machine learning-assisted colorimetric-fluorescence dual-mode sensor was successfully prepared. • A visual and portable analysis platform based on smartphones has been established. [ABSTRACT FROM AUTHOR]

Environmental pollution caused by tetracycline antibiotics is a major concern of global public health. Here, a novel and portable molecularly imprinted electrochemiluminescence (MIECL) sensor based on smartphones for highly sensitive detection of chlortetracycline (CTC) has been successfully established. The high-performance ECL emitter of biomass carbon (BC) encapsulated CdZnTeS (CdZnTeS@BC) was successfully synthesized by hydrothermal. The enhanced ECL performance was ascribed to the introduction of the BC and increased the overall electrical conductivity of the nanoemitter, as well as increased the number of sulfur vacancies and doping on the surface of the emitter based on density functional theory calculations. An aniline-CTC molecular imprinted polymer was synthesized on the surface of the CdZnTeS@BC modified electrode by in-situ electropolymerization. The decrease in MIECL signal was attributed to the increase in impedance effect. The MIECL nanoplatform enabled a wide linear relationship in the range of 0.05–100 μmol/L with a detection limit of 0.029 μmol/L for spectrometer sensors. Interestingly, the light emitted during the MIECL reaction can be captured by a smartphone. Thus, machine learning was used to screen the photos that were taken, and color analysis was carried out on the screened photos by self-developed software, thus achieving a portable, convenient, and intelligent sensing mode. Finally, the sensor obtains satisfactory results in the detection of actual samples, with no significant differences from those of liquid chromatography. [ABSTRACT FROM AUTHOR]

[Display omitted] • Smartphone-based multicolor MIRECL sensing system was proposed. • Visual and portable optical device integrated with machine learning was designed. • App based on yolov5x algorithm with five different linearting algorithms. • A smartphone-based handheld device for on-site and rapid detection TYM. We designed a novel, portable, and visual dual-potential molecularly imprinted ratiometric electrochemiluminescence (MIRECL) sensor for tyramine (TYM) detection based on smartphone and deep learning-assisted optical devices. Molecularly imprinted polymer-Ce 2 Sn 2 O 7 (MIP-Ce 2 Sn 2 O 7) layers were fabricated by in-situ electropolymerization method as the capture and signal amplification probe. Oxygen vacancies in Ce 2 Sn 2 O 7 not only enhance the electrochemical redox capability but also accelerate the energy transfer, thereby enhancing the luminescence of cathode ECL. Under optimal conditions, the ECL signals of MIP-Ce 2 Sn 2 O 7 at the cathode and the anode response of Ru(bpy) 3 2+ was reduced, thus a wide linear range from 0.01 μM to 1000 μM with the detection limit as low as 0.005 μM. Interestingly, combined with an artificial intelligence image recognition algorithm and the principle of optical signal reading by smartphone, the developed MIRECL sensor has been applied to the portable and visual determination of TYM in aquatic samples, and its practicability has been satisfactorily verified. [ABSTRACT FROM AUTHOR]

Herein, based on the excellent redox ability of the transition metal oxide Mn 3 O 4 , the key strategy of introducing WO 3 was used to effectively modulate the electronic structure of the Mn active species and improve the catalyst nanozyme activity. The characterizations of transition electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) presented that the dropping of WO 3 accelerated the electron transfer and redistribution capacity of WO 3 /Mn 3 O 4 , thus exhibiting excellent oxidase and peroxidase activities. Density functional theory (DFT) revealed that WO 3 /Mn 3 O 4 effectively increased the adsorption capacity of O 2 molecules and drastically reduced the kinetic energy potential of the reaction-limiting step in the oxidase-like activity. An "on-off-on" colorimetric and intelligent biosensing platform for epinephrine and Ag+ was successfully constructed. It was used to visualize and monitor epinephrine levels in human serum with a linear range of 0.075–65 µM and a detection limit of 0.055 µM. The mechanism of detection was revealed using infrared spectroscopy. Moreover, WO 3 /Mn 3 O 4 took more readily to obtain the electrons of epinephrine than 3,3′,5,5′-tetramethylbenzidine. Therefore, the colorimetric sensor of epinephrine on the basis of the oxidase of WO 3 /Mn 3 O 4 had a promising future in the biomedical field. • The prepared WO 3 /Mn 3 O 4 showed excellent dual enzymatic activity. • Introduction of WO 3 could modulate the electronic structure of the active site Mn. • Establish "On-Off-On" colorimetric sensor platform for intelligent detection of epinephrine and Ag+. • This method was used for the monitoring of adrenaline in human serum. • Building an intelligent sensing platform based on deep learning [ABSTRACT FROM AUTHOR]

Deep learning-assisted smartphone optical sensing platform based on CDs@Fe-Zr-MOF smart label detects SP and HIS, and meat freshness. [Display omitted] • Two-color and dual-emitter ratio fluorescence nanoprobe for agro-food was constructed. • Portable, visual, and real-time optical device with gel label was fabricated. • Deep learning-assisted self-designed smartphone WeChat mini program for real-time sensing. • CDs coupled with Fe/Zr-MOF acts as the response units. Here, a smartphone-assisted dual-color ratiometric fluorescence smart gel label-based visual sensing platform was constructed for real-time evaluation of the freshness of agro-food based on the biogenic amines responses. Green-emission fluorescence carbon dots (CDs) coupled with blue-emission fluorescence bimetallic metal–organic framework (Fe/Zr-MOF) obtained dual-color CDs@Fe/Zr-MOF fluorescence nanoprobe acts as the response units. With the increase of SP and HIS content, the green fluorescence of CDs was enhanced, while the blue fluorescence of Fe/Zr-MOF was quenched. Therefore, this dual-color probe achieved a clear fluorescence color response to biogenic amines. The nanoprobe possessed sensitive and color-responsive with the LODs of 0.17 μM for SP and 2.95 μM for HIS in a wide range of 0–937.5 µM, respectively. Besides, these fluorescent nanoprobes were immobilized on the hydrogel carrier, and the intelligent fluorescent hydrogel tag can be obtained after freeze-drying, which realizes the real-time qualitative monitoring of SP and HIS in pork and shrimp samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • Smartphone-based tri-color ratio fluorescent sensing system is proposed. • Visual and portable optical device integrated with machine learning was designed. • A Wechat applet based on yolov3 algorithm with six different linear fitting algorithms. • A smartphone-based handheld device for on-site and rapid detection TCs. In this work, a tri-color ratiometric fluorescent optical device integrated with machine learning-assisted smartphones is designed for the visual monitoring of tetracycline antibiotics. The trichromatic sensing probe consists of blue emitting carbon dots (BCDs) at 420 nm, and red-emitting bovine serum albumin-protected copper nanoclusters (BSA-Cu NCs) at 635 nm, as well as an emission peak at 520 nm, rises in the presence of tetracycline antibiotics (TCs), therefore, a three emission system is formed. BCDs/BSA-Cu NCs present three emission responses to TCs, which are based on the internal filtering effect (IFE) and the sensitization mechanisms with BSA. The reaction mechanism was verified by density functional theory (DFT) and a series of characterizations, such as infrared spectrum, ultraviolet absorption spectrum, and fluorescence lifetime. Interestingly, the fluorescence intensity of BCDs was quenched by TCs, and due to the sensitization between BSA and TCs, a green fluorescence rose at 520 nm, while the peak of BSA-Cu NCs remained stable, resulting in a significant color shift from red to cyan. Therefore, the ratiometric fluorescence intensity of I (635+520) /I 420 can be used to determine TCs, and the colors change can be used to identify the quantitative analysis. In addition, the deep learning of the YOLO v3 algorithm assists the integrated tri-color portable optical device of smartphones, which can realize the visual detection of TCs. In general, the sensing system has many advantages, such as good stability, specificity, and rich color changes, which provide help for the visual detection of tetracycline residues. [ABSTRACT FROM AUTHOR]

Here, a novel and portable machine learning-assisted smartphone-based visual molecularly imprinted ratiometric electrochemiluminescence (MIRECL) sensing platform was constructed for highly selective sensitive detection of 2,4-Dichlorophenoxyacetic acid (2,4-D) for the first time. Te doped CdS-coated Mn 3 O 4 (Te–CdS@Mn 3 O 4) with catalase-like activity served as cathode-emitter, while luminol as anode luminophore accompanied H 2 O 2 as co-reactant, and Te–CdS@Mn 3 O 4 decorated molecularly imprinted polymers (MIPs) as recognition unit, respectively. Molecular models were constructed and MIP band and binding energies were calculated to elucidate the luminescence mechanism and select the best functional monomers. The peroxidase activity and the large specific surface area of Mn 3 O 4 and the electrochemical effect can significantly improve the ECL intensity and analytical sensitivity of Te–CdS@Mn 3 O 4. 2,4-D-MIPs were fabricated by in-situ electrochemical polymerization, and the rebinding of 2,4-D inhibits the binding of H 2 O 2 to the anode emitter, and with the increase of the cathode impedance, the ECL response of Te–CdS@Mn 3 O 4 decreases significantly. However, the blocked reaction of luminol on the anode surface also reduces the ECL response. Thus, a double-reduced MIRECL sensing system was designed and exhibited remarkable performance in sensitivity and selectivity due to the specific recognition of MIPs and the inherent ratio correction effect. Wider linear range in the range of 1 nM–100 μM with a detection limit of 0.63 nM for 2,4-D detection. Interestingly, a portable and visual smartphone-based MIRECL analysis system was established based on the capture of luminescence images by smartphones, classification and recognition by convolutional neural networks, and color analysis by self-developed software. Therefore, the developed MIRECL sensor is suitable for integration with portable devices for intelligent, convenient, and fast detection of 2,4-D in real samples. [ABSTRACT FROM AUTHOR]

A novel, portable, and smartphone-based molecularly imprinted polymer electrochemiluminescence (MIP-ECL) sensing platform was constructed for sensitive and selective determination of furosemide (FSM). In this platform, MoSe 2 nanoparticles/starch-derived biomass carbon (MoSe 2 /BC) nanocomposites as imprinted material, lucigenin (Luc) as the energy donor, CdS quantum dots (CdS QDs) were used as the luminophore (energy acceptor), and molecularly imprinted polymer (MIP) as the specificity recognition element to construct a MIP-ECL sensing system based on electroluminescence resonance energy transfer (ECL-RET) mechanism, which enhanced the sensitivity and the specificity of this system. Imprinted materials were characterized by SEM, TEM, XRD, FT-IR, etc. and the recognition performance of MIP was characterized using CV, EIS, and ECL methods. The elution and re-sorption of template molecules can be used as a switch to control ECL based on the signal that can be quenched by FSM. Interestingly, deep learning based on convolutional neural networks realizes batch processing of ECL signals. Additionally, this developed MIP-ECL method was established by using the traditional ECL analyzer detector for the assay of FSM with a detection limit of 4 nM in the range of 0.010 μM–100 μM. Besides, the consumer smartphone sensing platform based on deep learning showed an outstanding linear response between the R-value of the picture and the concentration of furosemide in the range of 1–70 μM with a detection limit of 0.25 μΜ, which is much lower than that the reported for other detection methods. More importantly, due to the transferability of deep learning, the smartphone-based MIP-ECL systems can facilitate the real-time monitoring of biochemical analytes in multiple fields. [ABSTRACT FROM AUTHOR]

A self-designed smartphone-based portable device and system for detecting Cu2+ and thiram by multi-color ratiometric fluorescence optical probe based on deep learning and density functional theory. [Display omitted] • A portable fluorescence detection device based on smartphone was designed. • Multi-color fluorescence sensing system for dual detection of Cu2+ and thiram. • Ratiometric fluorometric and colorimetric signals for on-site analysis of thiram. • Density functional theory was used to verify the detection mechanism. Dual emission ratiometric fluorescence probes have been widely used for naked visual individual detection of hazardous chemicals, but it is still limited to simultaneously detecting multiple targets in a complex system. In this work, a deep learning-assisted smartphone-integrated tricolor ratiometric fluorescence optical device has been designed for visual monitoring of Cu2+ and thiram. The tricolor sensing probes are consist of blue-emission carbon quantum dots (B-QDs), green-emission cadmium telluride quantum dots (G-QDs), and red-emission cadmium telluride quantum dots (R-QDs). The sensing system presents a three emission response to Cu2+ and thiram based on electron transfer effect, complexing effect, and inner filter effect (IFE), respectively. The reaction mechanisms were verified by density functional theory (DFT). Interestingly, the G-QDs and R-QDs' fluorescence intensity are simultaneously quenched by Cu2+, whereas the fluorescence intensity of B-QDs remained unchanged and used as the internal reference, resulting in a distinct color shift from orange-red to blue with a detection limit (LOD) of 0.05 μM. Subsequently, the addition of thiram restored the G-QDs and R-QDs' intensity while the fluorescence intensity of B-QDs was quenched accompanied by a distinguishable color transition from blue to red with LOD of 0.073 μM. Moreover, colorimetric detection of thiram is realized based on the variation of UV absorption intensity with LOD of 0.142 μM. Besides, deep learning-YOLO v3 algorithm-assisted smartphone-integrated tricolor portable optical device for in-situ monitoring of Cu2+ and thiram with ultralow LOD of 0.344 μM and 1.840 μM, respectively. In conclusion, the sensing system shows excellent stability, sensitivity, and specificity, which provides a great capacity for the convenient evaluation of Cu2+ concentration and thiram residue. [ABSTRACT FROM AUTHOR]

Pt/Co 3 O 4 nanoflowers were synthesized by precipitation and reduction methods, and they exhibited unparalleled four enzyme activities: oxidase-like, peroxidase-like, catalase-like and SOD-like activities by adjusting pH. Based on its excellent oxidase activity, a dual-functional colorimetric detection platform for pesticide residues thiram and Cu2+ had been constructed based on the turn on-off-on signal change. Combined with DFT theoretical calculations showed that Pt-Co was the active center, and in the key step of catalyzing O 2 to produce O 2 −, Pt/Co 3 O 4 needed lower energy. This study presented herein may provide an intelligent detection method to monitor environment. [Display omitted] • The pH-switchable Pt/Co 3 O 4 presented an excellent four-enzyme activity. • Establishing "on–off-on" colorimetric sensor platform to detect thiram and Cu2+ intelligently. • DFT calculation showed that the interfaces of Pt and Co 3 O 4 was the active sites. • In-depth discussion of the detection mechanism by in-situ DRIFTS. • Colorimetric detection of pesticide residues had a wide detection range and low limit of detection. Pt/Co 3 O 4 were synthesized by precipitation and reduction methods, exhibited unparalleled four enzyme activities: oxidase-like, peroxidase-like, catalase-like and superoxide dismutase activities by adjusting pH. The mechanism of enzyme activity was deeply explored, it was found that its oxidase activity originated from the oxygen vacancies of the material and O 2 −, 1O 2 , the peroxidase activity was attributed to the 1O 2 and OH formed by nanomaterials catalyzing H 2 O 2. Density functional theory calculations showed that Pt-Co with strong metal-oxide interaction interface was the active center, which needed a lower energy than others in the key step of catalyzing O 2 to produce O 2 −. Based on its excellent oxidase activity, a muti-functional colorimetric detection platform for thiram, Cu2+ and ziram had been constructed successfully. The linear ranges of thiram was 0.6–250 µM and the limit of detection was 0.065 µM. The linear ranges of Cu2+ and ziram were 10–200 µM and 5–50 µM, the limit of detection were 4.066 µM and 3.36 µM. It should be noted that the portable smart phone platforms for thiram, Cu2+ and ziram had also been established with instant and quick detection. It was worth noting that in-depth exploration of the detection mechanism combined with in situ diffuse reflectance infrared fourier transform spectroscopy revealed that hydrogen bonds can be formed between thiram and oxidation substrate. And Cu2+ would inhibit the combination. Furthermore, it also showed excellent applications in detecting pesticide and Cu2+ in environmental soil and water samples. This study presented herein may provide an intelligent detection method to monitor environment. [ABSTRACT FROM AUTHOR]

A self-designed portable smartphone electrochemiluminescence molecularly imprinted polymer (ECL-MIP) device and system for detecting NFZ based on artificial neural network (ANNs) and density functional theory (DFT). [Display omitted] • A portable smartphone device for detecting NFZ based on MIP-ECL system. • Nitrofurazone was also used as a co-reaction accelerator in the ECL system. • Density functional theory was used to find the optimal monomer for nitrofurazone. • High sensitivity MIP-ECL sensing for NFZ with a nanomolar rang of LOD value. An efficient, portable and sensitive electrochemiluminescence molecularly imprinted polymer (ECL-MIP) sensor with CsPbBr 3 perovskite nanomaterials (NMs) was developed based on a smartphone point-of-care testing (POCT) system. In this system, a rechargeable lithium-ion battery served as the power supply, and Ag+@UiO-66-NH 2 /CsPbBr 3 was regarded as an ECL emitter, while the ECL signal was read-out using a smartphone. The optimal functional monomer (pyrrole) was screened by density functional theory (DFT), and then the MIP membrane was formed by the electrochemical polymerization method with template molecule (nitrofurazone, NFZ). The luminescence images were collected by the smartphone camera and the image color was analyzed by self-designed software, and the embedded artificial neural network-assisted machine learning was used for automatic analysis. Under the optimal experimental conditions, the ECL signal responded linearly to NFZ in the range of 0.5 nM ∼ 100 μM, with the detection limit of 0.09 nM. Overall, the obtained sensor exhibited good sensitivity, desirable selectivity, and favorable stability in response to NFZ. The developed smartphone-based ECL-MIP system with the portable device provided an alternative strategy for the point-of-care monitoring of biochemical analytes. [ABSTRACT FROM AUTHOR]

[Display omitted] • A three layers FeO x @ZnMnFeO y @Fe-Mn bimetallic organogel was creatively synthesized. • The four-functional sensing platforms for H 2 O 2 , citric acid, norfloxacin and gallic acid were constructed effectively. • The smartphone detection platform for CA and NOR was established successfully. • CA and NOR were detected continuously based on the turn on-off-on signal change. • The nanozyme-like activity mechanism and the detection mechanism were analyzed systematically. In this study, the FeO x @ZnMnFeO y @Fe-Mn bimetallic organogel (FO@ZMFO@FM-MOG) with three layers structure was synthesized. It presented outstanding multi-enzyme (peroxidase, oxidase and catalase) activities. The systematical characterization results showed that Zn and Mn on the surface of FO@ZMFO@FM-MOG were nearly disappeared, and thus a large amount of Fe exposed as the active species. Accordingly, the high ratio of Fe2+/Fe3+ for FO@ZMFO@FM-MOG was conductive to the electron transfer and enzyme activity. Moreover, the multiple detection platforms were constructed based on the different nanozyme activities. As for the peroxidase-mimetic activity, citric acid (CA) and norfloxacin (NOR) were monitored continuously on the basis of the turn on–off-on signal change due to the electron transfer abilities and hydroxyl radicals (•OH) formation. The linear range of 0.415–6.21 μM was obtained with a low detection limit of 79 nM, which was rarely detecting citric acid by nanozyme. And the low detection limit of 52 nM for NOR was superior to the most published NOR assays in nanozyme field. Furthermore, an oxidase platform for gallic acid (GA) was also established due to superoxide anions (O 2 •−) generation. It should be noted that the smartphone detection platforms for CA and NOR were established successfully for on-site analysis. This study provided multifunctional detection platform for valuating CA, NOR and GA in food quality and environment monitoring. [ABSTRACT FROM AUTHOR]

CuNi/CoMoO 4 with laccase-like activity showed multifunctional applications. The total antioxidant capacity of commercial beverage was measured accurately. And epinephrine could be on-site determinate by smartphone platforms based on CuNi/CoMoO 4 laccase-like activity. Moreover, CuNi/CoMoO 4 could be applied for acid fuchsin degradation due to ·OH and SO 4 ·− formation Furthermore, the laccase-like catalytic mechanism was investigated by theoretical calculation. [Display omitted] • CuNi/CoMoO 4 with laccase-like activities had multifunctional applications. • A smartphone platform was established for visual detection of epinephrine. • The laccase-like catalytic mechanism was investigated firstly by theoretical calculation. • CuNi/CoMoO 4 had a strong ability of activation PMS to produce ·OH and SO 4 ·−. • The efficiency was up to 99.45%, which was the highest value for AF degradation. In this work, CuNi/CoMoO 4 nanozyme was synthesized the hydrothermal method, followed by calcination and impregnation techniques, which had laccase-like activity and could be used as peroxymonosulfate (PMS) activator. Thus, the total antioxidant capacity (TAC) of commercial beverage measurement and phenolic pollutants degradation were studied systematically. Besides, the portable smartphone platform integrated with an intelligence analysis APP and colorimetric signals was further established for on-site determination of epinephrine (a typical phenol). Simultaneously, as PMS activator, CuNi/CoMoO 4 could activate PMS to yield ·OH and SO 4 ·−, which was applied for organic pollutants (acid fuchsin, AF) degradation, and the degradation efficiency could reach up to 99.45% within 40 min. The results displayed that CuNi/CoMoO 4 had practical value in anti-oxidant food quality evaluation and pollution degradation. Furthermore, the theoretical calculation revealed that the activation energy of the rate-determining step over Cu/CoMoO 4 was decreased from 0.819 eV to 0.524 eV due to the enhanced interaction between Cu(I) of CuNi/CoMoO 4 and 2,4-dichlorophenol (2,4-DCP). It not only provided a multifunctional catalyst for evaluating oxidative capacity in food quality and pollutant degradation, but also provided some new evidences for further study of laccase-like mechanism. [ABSTRACT FROM AUTHOR]

Glucose oxidase catalyzes glucose to produce H 2 O 2 , and Fe2+ catalyzes H 2 O 2 , generating hydroxyl radicals to oxidize vitamin B 1 and statically quench C-dots fluorescence, accompanied by a color change from purplish-red to colorless. Furthermore, the fluorometric and colorimetric output was integrated with a smartphone to conduct on-site analysis of glucose without the need of spectrometer. • Ratiometric fluorometric and colorimetric sensing system for the H 2 O 2 and glucose was proposed. • The designed approach for glucose determination delivers a wide linear range and a low detection limit. • The synthesized C-dots have both fluorescent and colorimetric properties. • Ratiometric fluorometric and colorimetric signals were integrated with a smartphone platform for on-site analysis of glucose in real samples. In this work, a new strategy for ratiometric fluorescent and colorimetric determination of H 2 O 2 and glucose is proposed. The sensing system involves catalytic oxidation reaction of glucose oxidase (GOx) with glucose to generate H 2 O 2. Under the catalysis of Fe2+, the 580 nm emission of carbon dots (C-dots) upon 365 nm excitation is reduced by H 2 O 2 , while the fluorescence emission at 450 nm of thiochrome (oxVB 1) enhances with the oxidation reaction between H 2 O 2 /Fe2+system and VB 1 (thiamine). Simultaneously, the color of the carbon dots (C-dots) suspension changes from purplish-red to colorless. Thus, the fluorescence intensity ratio (I 450 /I 580) and the absorbance (A 557) can be used to quantitatively determine H 2 O 2 and glucose. Furthermore, we integrated fluorometric and colorimetric output with a smartphone platform to conduct on-site analysis of glucose without the need of spectrometer. A smartphone application (APP) was designed to take pictures and analyze R, G, B values of fluorometric and colorimetric signals, which delivered excellent analytical result for glucose. This ratiometric fluorescent and colorimetric sensing system on a smartphone platform ensures sensitive and convenient determination of glucose and H 2 O 2 , hence having great prospects in biomedical analysis. [ABSTRACT FROM AUTHOR]