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Hydrogen peroxide (H 2 O 2 ) is extensively used in water treatment and food preservation for its pathogen-killing efficacy. Excessive H 2 O 2 intake, however, can lead to poisoning with symptoms such as abdominal pain and breathing difficulties. Additionally, small amounts of H 2 O 2 may be generated during food preservation, necessitating careful control to meet safety regulations. Real-time detection of H 2 O 2 is crucial for process safety and compliance. In this study, a Zr-MOF-based colorimetric fluorescent nanozyme sensor (NH 2 -UiO-67(Zr/Cu)) along with a smartphone-assisted portable device were developed for detecting H 2 O 2 . The sensor, NH 2 -UiO-67(Zr/Cu), combines the stable structural properties of Zr-MOF with ligand-generated fluorescence and exhibits peroxidase-like activity. The sensor demonstrated a detection range of 0-1000 μM, with limits of detection (LOD) of 0.0057 μM for the colorimetric assay and 0.0020 μM for the fluorescence assay. Additionally, we designed and developed a portable, smartphone-assisted device using 3D printing technology. This device offers a detection range of 0-750 μM, with LODs of 0.0093 μM in colorimetric mode and 0.0311 μM in fluorescence mode. The developed colorimetric fluorescent nanozyme sensor and portable device show significant potential for the rapid on-site detection of H 2 O 2 , offering a more convenient and reliable approach for quick identification of analytes in practical applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

A smartphone-assisted portable dual-mode immunoassay was constructed based on curcumin nanoparticles (CNPs) and carbon dots (CDs) for gentamicin (GEN) detection. CNPs were labeled with goat anti-mouse IgG (Ab 2 ) to create a conjugation that coupled dual signals to concentrations of GEN antigens. CNPs were introduced to pH 7.4 water and showed insignificant color and optical responses. When exposed to the high pH environment, the structure of CNPs changed and color and optical properties were restored. Because of the inner filter effect (IFE) between CNPs and CDs, the fluorescence of CNPs at 550 nm quenched the fluorescence of CDs at 450 nm. Colorimetry and ratiometric fluorescence (F 550 nm /F 450 nm ) dual-mode immunoassay linearly correlated with GEN ranged from 10 -4 to 10 0  µg/mL with a detection limit (LOD) of 8.98 × 10 -5  µg/mL and 4.66 × 10 -5  µg/mL, respectively. This work supplied a portable, sensitive, and specific platform to detect GEN., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Perfluorooctanoic acid (PFOA) poses a threat to the environment and human health due to its persistence, bioaccumulation, and reproductive toxicity. Herein, a lanthanide metal-organic framework (Ln-MOF)-based surface molecularly imprinted polymers (SMIPs) ratiometric fluorescence probe (Eu/Tb-MOF@MIPs) and a smartphone-assisted portable device were developed for the detection of PFOA with high selectivity in real water samples. The integration of Eu/Tb MOFs as carriers not only had highly stable multiple emission signals but also prevented deformation of the imprinting cavity of MIPs. Meanwhile, the MIPs layer preserved the fluorescence of Ln-MOF and provided selective cavities for improved specificity. Molecular dynamics (MD) was employed to simulate the polymerization process of MIPs, revealing that the formation of multiple recognition sites was attributed to the establishment of hydrogen bonds between functional monomers and templates. The probe showed a good linear relationship with PFOA concentration in the range of 0.02-2.8 μM, by giving the limit of detection (LOD) of 0.98 nM. Additionally, The red-green-blue (RGB) values analysis based on the smartphone-assisted portable device demonstrated a linear relationship of 0.1-2.8 μM PFOA with the LOD of 3.26 nM. The developed probe and portable device sensing platform exhibit substantial potential for on-site detecting PFOA in practical applications and provide a reliable strategy for the intelligent identification of important targets in water environmental samples., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The current work presents an on-chip electromembrane extraction (OC-EME) method using deep eutectic solvent followed by QR code-based red-green-blue (RGB) analysis for measuring salicylic acid (SA) in plasma and pharmaceutical samples. The RGB analysis was performed based on forming the SA-Fe 3+ complex in the acceptor phase giving a purple solution. The QR code readable customized app provided rapid, easy, and cost-less qualification and quantification of SA with the aid of principal component analysis (PCA). Parameters affecting OC-EME, including the supported liquid membrane (SLM), pH of the donor and acceptor phases, applied voltage, and sample flow rate, were optimized. Also, the concentration of FeCl 3 , as a chromogenic reagent, and its reaction time with SA were investigated to find the best concentration-dependent signal. Under the optimized conditions, a good relationship was observed between the green intensity and SA concentration within the range of 1.0-100.0 mg l -1 (R 2  = 0.9946) in water and 5.0-100.0 mg l -1 (R 2  = 0.9902) in plasma. Intra- and inter-day RSDs% were obtained less than 4.7% and 7.7%, respectively. Finally, the method was successfully applied for measuring SA in foot corn treatment, Aspirin medicines, and human plasma, with relative recoveries between 89.0 and 129.2%., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Urinary glucose determination using a glucose test strip is simple and convenient in daily self-monitoring of diabetes. However, diabetic patients exhibit acquired impaired color vision (ICV), which results in the inability to discriminate between hues. Even with the assistance of a color chart, it is still not easy for these patients to read the urinary glucose results with the naked eye. In this study, a smartphone camera using an image-based colorimetric detection method was successfully developed for quantitative analysis of urine glucose. A horseradish peroxidase-hydrogen peroxide-3,3'5,5'-tetramethylbenzidine (HRP-H 2 O 2 -TMB) system was optimized for a reliable and gradual color fading process via a glucose oxidase (GOD) catalyzed oxidation reaction. The color changes of the peroxidase-H 2 O 2 enzymatic reactions in the 96-well microplate were captured by a smartphone RGB camera with subsequent detection of red, green, and blue (RGB) intensities decreasing at each image pixel. The highly quantitative relationships between the glucose concentrations and the color characteristic values of the blue channel of the captured images were successfully established. The high accuracy of this method was demonstrated in urine glucose measurements with a linear response over the 0.039 mg mL -1 to 10.000 mg mL -1 glucose concentration range and a 0.009 mg mL -1 detection limit. The method has great potential as a point-of-need platform for diabetic patients with defective color vision and features high accuracy and low cost., (Copyright © 2019 Elsevier B.V. All rights reserved.)

To overcome the limitations arising from non-uniform particle size and solid-state aggregation of carbon quantum dots (CQDs), a novel dual-emissive ratiometric fluorescence probe, GCQDs@SBA-15/RCQDs@SBA-15 (G-RCQDs@SBA-15), has been successfully constructed by simplifying the synthesis process through in situ synthesis of CQDs in SBA-15 to further enhance their optical properties for highly sensitive detection of Cr(VI). The probe G-RCDs@SBA-15, based on green-emission carbon quantum dots (GCQDs) encapsulated in mesoporous molecular sieves SBA-15, provides the response signal, while red-emission carbon quantum dots (RCQDs) encapsulated in SBA-15 serve as an internal reference. The probe exhibits a satisfactory limit of detection (LOD) of 0.336 μM, which is 52 % lower than GCQDs/RCQDs. Importantly, the probe shows superior selectivity in detecting Cr(VI) compared to other metal ions. The fluorescence signal ratio of the probe decreases with increasing Cr(VI) concentration, resulting in a distinct change of fluorescence color from green to red. Based on UV–vis and fluorescence lifetime analysis, Inner filter effect (IFE) is considered the primary potential mechanism for the fluorescence color transition of G-RCDs@SBA-15 following the addition of Cr(VI). G-RCQDs@SBA-15 not only inherits the excellent optical properties of GCQDs and RCQDs but also shows high fluorescence and chemical stability. Considering the sensitive photoconversion properties of G-RCQDs@SBA-15, a smartphone-based laboratory device in combination with RGB analysis software has been used for Cr(VI) detection by directly capturing and analyzing fluorescence images. In addition, the sensing system is validated in the actual lake water samples, exhibiting recoveries from 83.3 % to 96.3 %, indicating its excellent practicality for Cr(VI) detection in real samples. [Display omitted] • CQDs synthesized through the CQDs-in-zeolite strategy require no further purification or separation. • CQDs are dispersed in SBA-15 pores, enhancing uniformity and preventing quenching from aggregation. • The CQDs-in-zeolite strategy demonstrates high versatility in the preparation of CQDs. • The synthesized ratio fluorescence probe G-RCQDs@SBA-15 exhibits high sensitivity and selectivity towards Cr(VI). • The device combines a smartphone with a custom program, offering unique advantages for Cr(VI) detection. [ABSTRACT FROM AUTHOR]

The massive use of paraquat (PQ) in agricultural practices has posed serious threats to food safety and human health. Real-time monitoring of PQ remains an obstacle. Herein, a fluorometric as well as smartphone-based very cheap sensing assay is discussed for the detection of this non-selective contact herbicide PQ based on simple off-the-shelf commercially available dyes PTSA (1) , HPTS (2) and Eosin Y (3) in pure aqueous media. Owing to their sensitivity towards PQ through electrostatic interactions, these dyes undergo a fluorescence quenching process. Dyes (2) and (3) show a rapid colorimetric change in the presence of PQ as shown by UV-Vis absorption spectral studies. 1 exhibits high sensitivity for PQ in comparison to 2 and 3 with the detection limit as low as 182 nM. All three probes exhibit high sensitivity, high selectivity for PQ over other analytes and excellent anti-interference properties. The Stern-Volmer plots and fluorescence lifetime studies confirm the static quenching process of the probes in the presence of PQ. Furthermore, sensor-coated paper-based test strips were successfully used for the ultrafast detection and quantification of PQ in spiked real water, fruit and vegetable samples. For the first time, silica-sodium alginate (SA) polymer hybrid hydrogel beads incorporated with probes 1 , 2 and 3 were used for the detection and adsorption of PQ from water samples. For assessing the reliability of the proposed sensing system for the on-site detection of PQ, an easy-to-use portable test cassette kit integrated with a smartphone was used. The signal outputs were captured and analysed via RGB color value to use the probes for the practical application by using a smartphone as a portable analytical device for the rapid point-of-care monitoring of PQ. [Display omitted] • Colorimetric and fluorescent sensor for the detection of paraquat (PQ) has been reported. • Off-the-shelf cheap dyes PTSA, HPTS and Eosin Y used for the detection of PQ. • Probes used to determine PQ in agricultural commodities such as fruits and vegetables. • Probes loaded Silica-sodium alginate composite hydrogel beads used to detect and remove PQ from water. • Practical application using a smartphone as a portable analytical device was also explored. [ABSTRACT FROM AUTHOR]

[Display omitted] • A dual-emission ratiometric fluorescent probe for carbimazole detection was prepared. • Establishment of a portable sensing platform combining test strips and smartphones. • The method is convenient and fast, which allows the on-site detection of carbimazole. • Real sample analysis results of the smartphone-assisted platform are satisfactory. The ratio-based probe improves detection precision and accuracy by minimizing the effects of various experimental conditions. Herein, we constructed a ratio fluorescent probe (Si NPs/TGA-functionalized CdTe) using silicon nanoparticles (Si NPs) as the background signal and mercaptoacetic acid-functionalized cadmium telluride quantum dots (TGA-functionalized CdTe) as the responding unit. The interaction between Carbimazole (CBZ) and sulfhydryl groups on the surface of TGA-functionalized CdTe led to a decrease in the fluorescence intensity of the probe, and the color of the solution turned red and pink turned blue. Meanwhile, a test paper-based detection method integrated with the smartphone sensing platform was established to analyze the red, green, and blue (RGB) values in the images of Si NPs/TGA-functionalized CdTe solution before and after the addition of CBZ based on the change of hue, and an analytical model was constructed based on the R/B value and CBZ concentration, realizing rapid visual detection and analysis of CBZ. In addition, the constructed smartphone sensing platform was applied to the detection of CBZ in human urine, and the limit of detection the fluorescence analysis method and the smartphone sensing platform were 40 nM and 63 nM, with the recoveries of 96.5 %-102.7 % and 90.6 %-107.2 %, and the relative standard deviations of 2.7 %-4.1 % and 3.5 %-6.8 %, respectively. This work provides a significant improvement in the proportional sensing of CBZ in human urine and broadens the use of portable quantitative sensing devices in chemical sensing applications. [ABSTRACT FROM AUTHOR]

Abstract In the present study, a microfluidic platform was exploited for electromembrane extraction. For device integration as a lab-on-a-chip system, the detection step was carried out by a colorimetric method based on fluorescence quenching of quantum dots. The model analyte was transferred under a pulsed applied electrical field across a polypropylene membrane, impregnated with 1-Octanol, into a final aqueous acceptor phase. The obtained acceptor phase was added into a solution containing CdTe quantum dots. Quenching of the quantum dots was tracked by analyzing the main three color components of red, green, and blue in different concentration levels of the analyte. All effective parameters on the extraction efficiency, fluorescence detection, and synthesis of quantum dots were optimized. Under the optimal conditions, the detection was accomplished by three different detection methods including HPLC-UV, spectrofluorometric detection, as well as colorimetry detection via a smartphone. Calibration curves were linear in the range of 2.0–500 µg L−1 for LC-UV, 30–2500 µg L−1 for fluorescence detection, and 2.5–20 µg mL−1 for image analysis. Inter- and intra-assay relative standard deviations were less than 10.1% in all detection modes. Graphical abstract fx1 Highlights • A microfluidic platform was exploited for pulsed electromembrane extraction. • Portable colorimetric detection of ciprofloxacin was done based on RGB analysis. • The efficiency of extraction system was studied with respect to the sample flow. • The system paves a new way for point-of-care colorimetric detections. [ABSTRACT FROM AUTHOR]

[Display omitted] • An on-chip electromembrane extraction was applied. • A barcode-readable Android customized app was developed for RGB analysis. • The outliers can be identified by the software using principal component analysis. • The method was used for measuring Cr(VI), Ni(ΙΙ), and Cu(ΙΙ) in water samples. • The method can provide reliable data, as the initial results, for on-site analysis. This paper presents an on-chip electromembrane extraction (OC-EME) followed by RGB analysis with a barcode-readable customized app for the determination of three heavy metal ions; Cr(VI), Ni(ΙΙ), and Cu(ΙΙ) in water samples. First, the OC-EME procedure was performed on a single transparent platform including three divided channels for extraction of analytes and subsequently complex formation with chromogenic reagents. The RGB values of colorful complexes were then analyzed by Photoshop software and green value intensities of all three colors showed the best concentration dependence signal. Effective parameters such as the composition of supported liquid membrane (SLM), the voltage of extraction, the composition of donor and acceptor solutions, sample volume, and flow rate were investigated and optimized. Also, a smartphone app was developed for RGB analysis on a barcode-readable program to detect and quantify the extracted heavy metal(s). A fast, easy, and accurate quantification analysis was offered using principal component analysis (PCA) and a trained linear regression model. Under optimized conditions, good calibration fittings were observed within the ranges of 0.05–1.5 mg l−1 for Cr(VI), 1.0–70.0 mg l−1 for Ni(II), and 0.5–30.0 mg l−1 for Cu(II) via the customized app. Intra- and inter-day RSDs% of the method were obtained less than 6.9 % and 7.8 %, respectively. Finally, the proposed procedure was successfully applied for the analysis of target ions in water samples with relative recoveries between 85.0 % and 116.4 %. [ABSTRACT FROM AUTHOR]

A simple and low-cost biosensor has been established for the detection of Cr3+ ion by using the image processing function of the smartphone. In the presence of Cr3+ ion, its dependent DNAzyme can specifically cleave the substrate strand, resulting in the release of ligation probe, which will trigger hyperbranched rolling circle amplification (HRCA) to produce hydrogen ions, causing the color change of the solution containing cresol red. A free APP named "Pixel Picker" has been further used to measure the RGB values. It can be well found that the R/G values correlate with Cr3+ ion concentrations with a linear detection range of 0.5 μM–500 μM and a lowest detection limit of 0.12 μM. In addition, the proposed biosensor has been successfully applied to determine Cr3+ ions in various milks. In a word, the constructed smartphone-assisted colorimetric biosensor has the advantages of simplicity, low cost, high specificity and anti-interference ability. [Display omitted] •A smartphone-assisted biosensor for the detection of Cr3+ ion was developed. •Cr3+ ion can mediate the formation of ligation probe, so as to trigger hyperbranched rolling circle amplification to release H+ ion. •The biosensor can sensitively detect Cr3+ ion with a lowest detection limit of 0.12 μM. •The biosensor can be applied to detect Cr3+ ion in various milks. [ABSTRACT FROM AUTHOR]