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Multicolor immunoassay is a powerful tool for rapid analysis without the use of bulky instruments owing to various color conversions, which is suitable for on-site visual analysis for pesticides. Herein, this study developed a multicolor immunoassay for the rapid detection of isocarbophos. After competitive immunoassay, the secondary antibody (GAM-ALP) catalyzed ascorbyl-2-phosphate (AAP) into ascorbic acid (AA). The AA can reduce K3[Fe(CN)6] into K4[Fe(CN)6]. The latter can react with Fe3+ to form Prussian blue; otherwise, the orange AAP-Fe3+ complex was generated. Therefore, the multicolor immunoassay achieved a color conversion of orange–green–blue in response to isocarbophos, allowing for rapid semiquantitative analysis by the naked eye. After parameter optimization, the multicolor immunoassay was developed depending on the ratiometric absorbance between the Prussian blue and AAP-Fe3+ complex. Moreover, a smartphone was used to measure the RGB value of the color conversion for the development of portable visual, quantitative analysis. Both the absorbance-based and RGB-based multicolor immunoassays showed good accuracy and practicability in the recovery test. This study provided a common approach for the development of dual-readout multicolor immunoassay, which can be used for on-site rapid screening by quantitative or visual semiquantitative analysis. [ABSTRACT FROM AUTHOR]

One of the factors that influence shrimp cultivation is the presence of algae. Precise knowing algae content in the pond is essential for effective management. Most research in the field of algae species carried out by researchers were observing Chlorella Sp. more than the other algae species, with a particular emphasis on substance concentrations. This study proposed non-invasive techniques for quantifying algae abundance, utilizing optical density (OD) and image processing (IP) methods. Three different algae species are frequently found in Indonesia i.e., Chlorella Sp., Thalassiosira Sp., and Skeletonema Sp. are used as sample. Those samples are cultured and prepared in a certain volume with a certain quantity. For experimental and observation purposes, those samples are then diluted into water based on percentage value. The experimental results provided RGB values, which were then used to establish polynomial equations. To verify these equations, two approaches were employed: synthetic image analysis and evaluation using additional data. The mean average error (MAE) was found to be 3.467 for IP method and 3.513 for OD method. It shows that IP method give better result compared to OD method in this study. However, it is very possible that the two methods will complement each other. [ABSTRACT FROM AUTHOR]

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 (Ab2) 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 (F550 nm/F450 nm) dual-mode immunoassay linearly correlated with GEN ranged from 10−4 to 100 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. [ABSTRACT FROM AUTHOR]

Multicolor immunoassay is a powerful tool for rapid analysis without the use of bulky instruments owing to various color conversions, which is suitable for on-site visual analysis for pesticides. Herein, this study developed a multicolor immunoassay for the rapid detection of isocarbophos. After competitive immunoassay, the secondary antibody (GAM-ALP) catalyzed ascorbyl-2-phosphate (AAP) into ascorbic acid (AA). The AA can reduce K3[Fe(CN)6] into K4[Fe(CN)6]. The latter can react with Fe3+ to form Prussian blue; otherwise, the orange AAP-Fe3+ complex was generated. Therefore, the multicolor immunoassay achieved a color conversion of orange–green–blue in response to isocarbophos, allowing for rapid semiquantitative analysis by the naked eye. After parameter optimization, the multicolor immunoassay was developed depending on the ratiometric absorbance between the Prussian blue and AAP-Fe3+ complex. Moreover, a smartphone was used to measure the RGB value of the color conversion for the development of portable visual, quantitative analysis. Both the absorbance-based and RGB-based multicolor immunoassays showed good accuracy and practicability in the recovery test. This study provided a common approach for the development of dual-readout multicolor immunoassay, which can be used for on-site rapid screening by quantitative or visual semiquantitative analysis.

A novel portable smartphone-assisted colorimetric method was reported for the determination of Hg2+ with good analytical performance. A Zr(IV)-based metal–organic framework functionalized with amino groups (NH2-UiO-66) has been adopted as a supporting platform to anchor gold nanoparticles (AuNPs), avoiding the migration and aggregation of AuNPs. With the addition of Hg2+, the formation of gold amalgam proved possible to enhance peroxidase-like activity of the composite (AuNPs/NH2-UiO-66), accelerating the oxidization of zymolyte 3,3′,5,5′-tetramethylbenzidine (TMB). In the meantime, the color of the reaction solution turned a vivid blue, and the red, green, and blue (RGB) values of the solution color changed accordingly. On account of this strategy, the quantitative detection of Hg2+ could be achieved. After the optimization of the experiment conditions, the average color intensity (Ic) resulting from RGB values was linear related to the concentration of Hg2+ from 10 to 100 nM, accompanied with a detection limit (LOD) down to 5.4 nM calculated by 3σ/S. The successful application of the designed method has been promoted to detect Hg2+ in some water samples, displaying a great potential in practical application. Furthermore, the use of a smartphone made our proposed method simple and accurate, and thus puts forward a possible way for in situ and real-time monitoring. A portable smartphone-assisted RGB colorimetric method for Hg2+ detection based on Hg2+-enhanced peroxidase-like activity of AuNPs modified on NH2-UiO-66. [ABSTRACT FROM AUTHOR]

17–4 PH Stainless Steel Foam (SSF) is widely used in biomedical implants due to its low cost, high mechanical properties, good corrosion resistance, and biocompatibility. In order to expand its applicability in the near future, it is necessary to improve the surface properties of the porous structure. This study primarily focuses on the surface modification of SSF with silver nanoparticles (Ag NPs) synthesized from various plant extracts and their superficial characterization. The Ag NPs were synthesized with extracts from some plants such as locust bean gum, matcha tea, and maca root by a sonochemical method, and their morphology, crystal structure, and chemical functional groups were characterized. The different matrix-based Ag NPs were then coated on 17–4 PH SSF, which has irregularly shaped pores and a porosity of approximately 70%, using the drop-casting method. To understand the effects of different matrix-based Ag NPs coatings on the surface characteristics of the porous structure, versatile investigations were carried out using traditional and digital image-based methods. While the structural and surface properties of the SSFs changed after nanocoating, they showed similar properties when the different matrix-based Ag NPs were used. The RGB analysis results and opacity values showed differences depending on the coating solution obtained from different plant extracts. Overall, the results illustrate the importance of surface nanomodification of the different matrix-based Ag NPs-coated 17–4 PH SSF to achieve favorable surface performance to obtain promising multifunctional nanoplatforms for biomedical applications. [ABSTRACT FROM AUTHOR]

A smartphone-assisted determination of copper ions is introduced by using a down-scaled microfluidic mixer. The system was coupled with a micro-column packed with a periodic mesoporous organosilica (PMO) material for preconcentration of copper ions. Copper ions were reduced to Cu(I) on-chip to selectively form an orange-colored complex with neocuproine. A novel Android-based software was made to determine the color change of the adsorbent by analyzing red-green-blue (RGB) components of images from the packed PMO material. Four porous framework materials with high porosity and chemical stability were synthesized and compared for the extraction of the Cu-neocuproine complex. The main parameters influencing the complex extraction efficiency were optimized. The analytical performance of the method showed limit of detection and quantification of 0.2 μg L−1 and 0.5 μg L−1, respectively. The accuracy and precision of the method were determined as recovery > 92% and relative standard deviations < 5.2% at medium concentration level (n = 5). Due to accumulation of the retained analyte in a single point and elimination of the stripping step, the RGB-based method showed sensitivity and precision higher than inductively coupled plasma-atomic emission spectrometry (ICP-AES) for determination of copper ions. To investigate the applicability of the method, six different water samples were analyzed. The t-test on the data showed that the method has no significant difference when compared with ICP-AES determination. [ABSTRACT FROM AUTHOR]

In this research, two one-minute wastewater treatment approaches were developed using polyacrylonitrile (PAN) and polyvinyl chloride (PVC) powders. The former process led to higher than 90% and the latter higher than 95% removal efficiencies of methylene blue from the aqueous solutions. The rapidity of the treatment process and the exhaustive removal of the pollutant are the highlights of the developed methods. The adsorbents were thoroughly characterized using scanning electron microscopy, Fourier transform infrared spectrophotometry, energy-dispersive X-ray, and Brunauer–Emmett–Teller analyses before being applied. PAN showed tiny particles piled up on each other ranging from 60 to 84 nm. The composing elements were 70.27% carbon and 29.73% nitrogen. Also, the surface area was determined to be 12.585 m2 g−1. On the other hand, PVC showed spherical morphology ranging from 132 to 543 nm. The elemental composition of 97.19% carbon and 2.81% chlorine was recorded for PVC. Also, the surface area of PVC was documented to be 13.302 m2 g−1. To conduct the procedures, the determined weights of each adsorbent were separately added into the dye-contaminated solutions and stirred on magnetic stirrers. In different time intervals, samples were taken, centrifuged to separate the adsorbent particles, and underwent colorimetric analysis. This approach dramatically reduced the analysis costs and location limitations, besides the need for no expert users. Evaluation of the isotherm models of the adsorption also revealed the preference of Freundlich and Langmuir models for PAN- and PVC-based remediation methods, respectively. [ABSTRACT FROM AUTHOR]

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]

[Display omitted] • NH 2 -UiO-67(Zr/Cu) nanozyme synthesized using a classic solvothermal method. • Developed a dual-mode colorimetric/fluorescent sensor for sensitive H 2 O 2 detection. • Designed a smartphone-assisted portable device for on-site H 2 O 2 detection. • The sensor exhibits high selectivity and interference resistance in complex matrices. • Portable device enables rapid, reliable, and user-friendly H 2 O 2 monitoring. 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. [ABSTRACT FROM AUTHOR]

Contamination by hexavalent chromium [Cr (VI)] poses a threat to groundwater quality and its detection at point source is essential to provide early mitigating solutions. In this work, we report the fabrication of paper-based sensing system embedded with a novel nanochromogenic complex having spherical gold nanoparticles modified with 1,5-diphenylcarbazide dye. This Au-DPC Functionalized paper strip develops pink color in <2 sec upon interaction with Cr (VI). With the developed optical fiber device a limit of detection of 0.02 ppm was achieved within a linear range of 0.01-0.4 ppm. RGB color analysis and data driven predictive modelling (KNN-model) demonstrated highest balanced accuracy score of 0.833 and cross validation accuracy of 0.714. Further, the portable optical fiber-based device offers advantages such as real-time monitoring, remote sensing capabilities, and the ability to integrate with existing optical systems for enhanced detection and analysis. [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]

The continuous spread of invasive alien species, as zebra mussel (Dreissena polymorpha), is a major global concern and it is urgent to stop it. Early stages of an invasion are crucial and challenging; however, detection tools based on environmental DNA analysis are promising alternatives. We present an alternative DNA target amplification strategy for signal enhancement followed by dual-mode colorimetric naked eye and optical smartphone analysis for the early detection of zebra mussel environmental DNA. Target amplification was designed based on the nicking endonuclease probe cleavage upon probe and complementary target hybridization. The cleaved/intact probe interacts with DNA-modified nanoparticles for colorimetric detection. We have demonstrated that enzyme amplification strategy enhanced 12-fold the sensitivity by naked eye detection, achieving a detection limit of ~8 nM (4.48×1010 copies) in controlled conditions, whereas target in complex environmental samples allowed the detection of 22.5 nM (1.26×1011 copies). Competitive assays also showed that the system can discriminate specific zebra mussel DNA sequences from other DNA sequences. Additionally, smartphone analysis for DNA quantification further improved the sensitivity of its detection by 130-fold, more than 2 orders of magnitude, when applied to environmental samples. The limit of detection to 0.17 nM (9.52×108 copies) is based on RGB coordinates, which is especially relevant to monitor early aggregation stages, being more accurate and reducing naked eye detection subjectivity. DNA extracted from zebra mussel meat, zebra mussel contaminated river water, and non-contaminated river water samples were successfully tested. Dual-mode colorimetric detection is useful in field analysis without the need for expensive laboratory equipment. [ABSTRACT FROM AUTHOR]

The construction professionals attempt to enhance construction site visualization and modeling using unmanned aerial vehicle (UAV) technology. However, there is no research covering best flying and environmental variables for this purpose. This research aimed to determine the optimized flying and environmental variables for 2D dronography and 3D modeling for the construction progress monitoring. The research focused on building façade facing east and conducted an experimental study in the Eco-Home building at the University of Technology Malaysia. For 2D visualization, 900 photos were captured based on the three setpoints (20 m, 30 m, and 40 m) perpendicular to the building façade. Flying operation features of the employed drone (i.e., DJI Phantom4) enforced to set the first setpoint at 20 m perpendicular to the façade to get the whole façade in the required 80% of the photos. The 30 m and 40 m setpoints were defined based on the horizontal circles making the angle of 12° from the drone's z-ax to x-ax perpendicular to the façade. The images were analyzed using image color summarizer (ICS) software. The research found that the best distance is 30 m, and noontime is the best time for dronography. The proper temperature, humidity, lux, and wind speed to quality 2D image are; 38.1°, 55.5% Rh, 38,107 lx, and 0.1 m/s. The ICS software results were validated by applying the Image Processing Toolbox of MATLAB, particularly the thresholding-based image RGB pixel analyzing technique. The regression analysis showed 93% accuracy and completeness of the results. A trajectory optimization study has also been conducted, which determined that the drone could considerably control trajectories at the target positions and referenced velocity. The findings can significantly help the construction professionals to calibrate their drone's flying variables for quality 3D modeling the construction progress monitoring. [ABSTRACT FROM AUTHOR]

Naked-eye semi-quantitative (NEQ) assays should exhibit vivid color variations and one-to-one correspondence between the analyte concentrations and the color display. Herein, we report a bisubstrate multi-colorimetric system, constituted by 3,3′,5,5′-tetramethylbenzidine (TMB) and dopamine (DA), which carries out a controllable NEQ assay based on the complementary colorharmonic principle. This bisubstrate system is a universal threshold NEQ assay with tunable sensitivity and detection window depending on the H2O2 concentration. The peroxidase-like activity of PEG@Fe3O4 NPs was used to catalyze the oxidations of TMB and DA by H2O2 to the colored products. On the basis of UV–vis spectra data, it was speculated that the oxidation product of TMB (TMB·+) could oxidize DA in this system. The concentration of DA controls the consumption of oxidant (H2O2) and the oxidation of TMB. By controlling the molar ratio of TMB to DA, the bisubstrate system precisely showed multicolor displays (e.g., three-color display: orange, gray, and blue) at submillimolar and millimolar concentrations of H2O2. The detection limit and sensitivity for H2O2 were 0.4 mM and 0.1 mM, respectively. Next, the system was applied to the threshold detection of hypoglycemia (orange), normal (gray), and hyperglycemia (blue) in spiked samples on both gel- and paper-based test strips. Digitalized colorimetric results using the red–green–blue (RGB) analysis with smartphone application were achieved. This work provides a new strategy of multi-colorimetric assay that takes advantages of controllability, threshold detection, vivid color variations, and reproducibility (CVs were 1.1–2.1%), which could be potentially useful for in-field and point-of-care applications. [ABSTRACT FROM AUTHOR]

Mechanochromic materials, when exposed to mechanical deformation, undergo a modification of optical properties. This behaviour can stem from either conformational rearrangements, disruptions of intermolecular interactions, or molecular structure changes affecting absorption, emission, or reflection abilities. Here reversible colour change of Disperse Red 1/polyvinylpyrrolidone films resulting from humidity annealing and subsequent stretching is reported. Due to the humidity-induced blue shift of the absorbance peak related to exciton coupling of the chromophores, the tone of films abruptly changes from red to orange. Upon stretching, the gradual disaggregation of the chromophores takes place and therefore the colour switches back to red in a stepless manner. Using either red–green–blue analysis of time lapse photography or UV–Visible measurements, this transformation, which is also well visible by the naked eye, can be followed with high accuracy. This work offers the opportunity to apply the strain sensor in humid environments to prevent the mechanical failures by showing a colour change in areas subjected to undesired stress. Moreover, dip-coating yarns with mechanochromic coating allows fabrication of functional yarns that change their colour based on their stretching state – thus enabling preparation of colour-changing stretchable textiles was demonstrated.

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. [ABSTRACT FROM AUTHOR]

[Display omitted] • A host–guest synergistic strategy was employed to prepare the Cr(VI)-responsive composite material Si,N-CQDs@SBA-15. • Si,N-CQDs@SBA-15 exhibited excellent sensitivity towards Cr(VI), with a detection limit of 0.213 μM. • The selectivity and anti-interference ability of Si,N-CQDs@SBA-15 towards Cr(VI) were evaluated. • The fluorescence quenching mechanism of Si,N-CQDs@SBA-15 was discussed. • A RGB analysis app based on Si,N-CQDs@SBA-15 was developed, with a detection limit of 0.201 μM. Carbon quantum dots (CQDs) are highly efficient fluorescent probes for metal ion detection; however, they are limited by non-uniform particle size, aggregation, and the inability to facilitate quantitative analysis. Herein, a smart host–guest strategy is utilized, wherein CQDs are immobilized in mesoporous molecular sieves, proving to be an effective method to minimize these drawbacks. Si,N-CQDs@SBA-15 is successfully synthesized by the one-step hydrothermal route using Si,N-CQDs precursor materials as guests and the mesoporous molecular sieve SBA-15 as the host. A good linear relationship between the concentration of Cr(VI) ions and fluorescent intensity is observed from 0 μM to 100 μM (R 2 = 0.9986). The limit of detection (LOD) is 0.213 μM, approximately three times lower than that of pristine Si,N-CQDs (0.677 μM). Additionally, Si,N-CQDs@SBA-15 exhibit good detection selectivity for Cr(VI) detection over other metal ions. Moreover, a smartphone-based laboratory device and RGB analysis app are employed to capture and analyze fluorescence images, revealing a LOD for Cr(VI) of 0.201 μM. Förster Resonance Energy Transfer (FRET) is identified as the possible mechanism for the fluorescence quenching of Si,N-CQDs@SBA-15 by Cr(VI) through UV–vis and fluorescence experiments. The practicability of the synthesized fluorescent probes is further validated in river water, yielding satisfactory spiked recoveries ranging from 99.24 % to 106.21 %. [ABSTRACT FROM AUTHOR]

Activated sludge process is the most common method for biological treatment of industrial and municipal wastewater. One of the most important parameters in performance of activated sludge systems is quantitative monitoring of biomass to keep the cell concentration in an optimum range. In this study, a novel method for activated sludge quantification based on image processing and RGB analysis is proposed. According to the results, the intensity of blue color in the macroscopic image of activated sludge culture can be a very accurate index for cell concentration measurement and R2 coefficient, Root Mean Square Error (RMSE), Mean Absolute Error (MAE), and Mean Absolute Percentage Error (MAPE) which are 0.990, 2.000, 0.323, and 13.848, respectively, prove this claim. Besides, in order to avoid the difficulties of working in the three-parameter space of RGB, converting to grayscale space has been applied which can estimate cell concentration with R2 = 0.99. Ultimately, an exponential correlation between RGB values and cell concentrations in lower amounts of biomass has been proposed based on Beer-Lambert law which can estimate activated sludge biomass concentration with R2 = 0.97 based on B index.

Activated sludge process is the most common method for biological treatment of industrial and municipal wastewater. One of the most important parameters in performance of activated sludge systems is quantitative monitoring of biomass to keep the cell concentration in an optimum range. In this study, a novel method for activated sludge quantification based on image processing and RGB analysis is proposed. According to the results, the intensity of blue color in the macroscopic image of activated sludge culture can be a very accurate index for cell concentration measurement and R2 coefficient, Root Mean Square Error (RMSE), Mean Absolute Error (MAE), and Mean Absolute Percentage Error (MAPE) which are 0.990, 2.000, 0.323, and 13.848, respectively, prove this claim. Besides, in order to avoid the difficulties of working in the three-parameter space of RGB, converting to grayscale space has been applied which can estimate cell concentration with R 2 = 0.99. Ultimately, an exponential correlation between RGB values and cell concentrations in lower amounts of biomass has been proposed based on Beer-Lambert law which can estimate activated sludge biomass concentration with R 2 = 0.97 based on B index. [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]

The present work reports the development of a biologically inspired analytical system known as Electronic Eye (EE), capable of qualitatively discriminating different tequila categories. The reported system is a low-cost and portable instrumentation based on a Raspberry Pi single-board computer and an 8 Megapixel CMOS image sensor, which allow the collection of images of Silver, Aged, and Extra-aged tequila samples. Image processing is performed mimicking the trichromatic theory of color vision using an analysis of Red, Green, and Blue components (RGB) for each image’s pixel. Consequently, RGB absorbances of images were evaluated and preprocessed, employing Principal Component Analysis (PCA) to visualize data clustering. The resulting PCA scores were modeled with a Linear Discriminant Analysis (LDA) that accomplished the qualitative classification of tequilas. A Leave-One-Out Cross-Validation (LOOCV) procedure was performed to evaluate classifiers’ performance. The proposed system allowed the identification of real tequila samples achieving an overall classification rate of 90.02%, average sensitivity, and specificity of 0.90 and 0.96, respectively, while Cohen’s kappa coefficient was 0.87. In this case, the EE has demonstrated a favorable capability to correctly discriminated and classified the different tequila samples according to their categories.

[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]

Fluorescent metal-organic frameworks (MOFs) are promising sensing materials with tunable and robust structural properties and remarkable luminescent capabilities. In this study, a novel dual-emission fluorescent metal-organic framework (EY@MOF-5) composite is synthesized by a one-pot bottle-around-ship approach. Eosin Y (EY) is encapsulated in MOF-5 to enhance its fluorescence properties and selectivity, effectively addressing typical MOF-5 limitations. EY@MOF-5 serves as a versatile dual-functional fluorescent sensor for two different analytes, daclatasvir (DCT) and nitenpyram (NTP), showing an impressive linear range of 10-200 nM and 0.1-300 μM, with detection limits of 233 pM and 65 nM, respectively. The established method is ultrafast, highly sensitive, and extremely selective for DCT and NTP detection in complex biological and food samples. Fluorescence results are compared and validated with the recommended UPLC method. Then, a smartphone-integrated sensing system is introduced for on-site, real-time, and quantitative analysis of DCT and NTP. The smartphone-assisted intelligent sensing method manifests promising results for DCT and NTP monitoring in biological and food samples, demonstrating its promising potential for the on-site detection of biologically and environmentally significant analytes.

Abstract Background The time taken for epinephrine to achieve its optimal effect during local anesthesia has recently become the subject of debate. The time from injection to commencement of surgery is traditionally quoted to be 7 to 10 min, while recent reports claim that it may take 30 min to achieve maximum hypoperfusion, which would prolong the time required for surgical procedures. The discrepancy may be related to difficulties associated with the techniques used to measure blood perfusion. The aim of this study was to test two methods of determining the time to maximum hypoperfusion. Methods Laser speckle contrast imaging (LSCI) and red, green, blue (RGB) analysis of images obtained with a commercial digital camera, were used to monitor the effect of infiltration with commonly used local anesthetic preparations: lidocaine (20 mg/ml) + epinephrine (12.5 μg/ml), lidocaine (10 mg/ml) + epinephrine (5 μg/ml), and lidocaine (20 mg/ml) alone, in healthy subjects. Results LSCI showed a paradoxical increase in signal after the injection of local anesthetics containing epinephrine, probably due to a change in the laser penetration depth resulting from blanching of the skin. However, RGB analysis of digital photographs gave more reliable results, showing skin blanching that corresponded to the expected effect of epinephrine in local anesthetics. The time to maximum effect was found to be 7 (range 5–10) minutes for 12.5 μg/ml epinephrine, and 9 (range 7–13) minutes for 5 μg/ml epinephrine in lidocaine. Conclusions RGB analysis of digital images proved to be a valid technique for monitoring the effect of local anesthetics with epinephrine in human skin. The technique requires only a commercial digital camera and constitutes a cheap, simple method. The optimal delay between epinephrine injection and incision, to minimize bleeding, was found to be 7 to 9 min, which is in good agreement with common surgical practice. Highlights • Red, green and blue (RGB) analysis of digital photographs proved to be a reliable technique for measuring hypoperfusion in human skin. • The maximum hypoperfusion after epinephrine injection is reached in 7 to 9 minutes. • Laser speckle contrast imaging (LSCI) is not a valid method for monitoring hypoperfusion, after epinephrine injection in human forearm skin. [ABSTRACT FROM AUTHOR]

The colours of the hermatypic corals Porites sp. and Acropora cytherea at Sesoko Island, Okinawa, Japan, were photographed continuously, from 19 July to 6 September 2016, by an underwater camera equipped with a lens wiper. The average seawater temperature during the study period was 29.9 °C. The daily average seawater temperature (DAST) was >30.0 °C until 23 August 2016, and a maximum value of 31.2 °C was recorded on 2 August 2016. Red, green, and blue (RGB) values of these corals were analysed based on photographs taken at 14:00. The RGB values of Porites sp. were stable throughout the observation period, while those of A. cytherea gradually increased (i.e. moved toward the “white” end of the spectrum) until the beginning of September. The present study demonstrated the usefulness of RGB analysis of photographs taken by an underwater camera equipped with a lens wiper for monitoring coral beaching. [ABSTRACT FROM AUTHOR]

• A portable on-chip electromembrane extraction was used for salicylic acid analysis. • Coumarin/thymol deep eutectic solvent was used as the selective liquid membrane. • The Trinder reaction and a smartphone was used for the quantitative color analysis. • The method effectively eliminated the main interferences for salicylic acid analysis. • The HPLC-UV results confirmed the reliability of the proposed method. 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-Fe3+ 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 (R2 = 0.9946) in water and 5.0–100.0 mg l−1 (R2 = 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%. [ABSTRACT FROM AUTHOR]

A novel green fabrication approach is being proposed based on radiation assisted modification of Whatman filter paper 1 (WFP) for development of Acid Free-Paper based Analytical Devices (A f -PADs). A f -PADs exude immense potential as handy tools for on-site detection of toxic pollutants such as, Cr(VI), boron, etc., which have established detection protocols involving acid mediated colorimetric reactions that necessitate external acid addition. The proposed A f -PAD fabrication protocol asserts its novelty through elimination of external acid addition step, making the detection process safer and simpler. To achieve this, poly(acrylic acid) (PAA) was grafted onto WFP via a single step, room temperature process of gamma radiation induced simultaneous irradiation grafting, introducing acidic -COOH groups in the paper thereon. Grafting parameters namely, absorbed dose and concentrations of monomer, homopolymer inhibitor and acid were optimized. The -COOH groups incorporated in PAA-grafted-WFP (PAA- g -WFP) provide localized acidic conditions for colorimetric reactions between pollutants and their sensing agents, anchored on the PAA- g -WFP. A f -PADs loaded with 1,5-diphenylcarbazide (DPC) have been ably demonstrated for visual detection and quantitative estimation of Cr(VI) in water samples using RGB image analysis, with LOD value of 1.2 mg.L−1 and a measurement range comparable to that of commercially available PADs based Cr(VI) visual detection kits. [Display omitted] [ABSTRACT FROM AUTHOR]

Paper-based analytical devices are an emerging class of lightweight and simple-to-use analytical platform. However, challenges such as instrumental requirements and chemical reagents durability, represent a barrier for less-developed countries andmarkets. Herein, we report an advanced laminated device using red emitting copper nanocluster and RGB digital analysis for signal improvement. Upon RGB system assistance, the device signal-to-background ratio and the calibration sensitivity are highly enhanced under a filter-free setup. In addition, the calibration sensitivity, limit of detection, and coefficient of determination are on par with those determined by instrumental fluorescence analysis. Moreover, the limitation of using oxidation-susceptible fluorescent nanomaterials is overcome by the introduction of protecting tape barriers, antioxidative sheets, and lamination enclosing. The robustness of device is highly advanced, and the durability is prolonged to more than tenfold. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new dual-functional probe L was synthesized via solid phase peptide synthesis (SPPS) technology. • L has strong specificity to Cu2+ based fluorescent and colorimetric methods, the LOD was 7.1 nM. • The in situ generated L -Cu2+ ensemble was used for detection of l -His with a low detection limit (15.3 nM). • L was successfully used to sequential detection of Cu2+ and l -His in living cells based on low cytotoxicity. • Test strips and smartphone were designed for quick and easy visual inspection of Cu2+ and l -His with " naked eye". A new fluorometric and colorimetric dual-modalitye probe L for detection of Cu2+ and l -His was constructed based on peptide skeleton via solid phase peptide synthesis (SPPS) technology. L exhibited highly selective recognition towards Cu2+ through formation of L -Cu2+ ensemble with a 2:1 binding stoichiometry, and the limit of detection (LOD) for Cu2+ was determined to be 7.1 nM. Correspondingly, L -Cu2+ ensemble was investigated by fluorescence technique which clearly established the high selectivity towards l -His based on fluorescence "off–on" response, and the limit of detection (LOD) for l -His was calculated to be approximately 15.3 nM. The selective sensing of Cu2+ was efficiently reversible with l -His, which was no loss of fluorescence intensity in 10 cycles. Notably, the sensing behavior of L towards Cu2+ and l -His detections was shown to be available within the wider pH interval (7.0–12.0). Cells imaging studies have shown that L was easily applied to the continuous imaging of Cu2+ and l -His in living cells. Furthermore, the test strips were also prepared for rapid and sensitive identification of Cu2+ and l -His. Combining smartphones and color changes, the semi-quantitative relationship between the R/B and the concentration of Cu2+ was established, and the limit of detection (LOD) reached up to 0.29 µM. [ABSTRACT FROM AUTHOR]

Preparation and application of ratiometric fluorescent sensing platform for dual-mode TC-PBQ sensing. [Display omitted] • Fluorescent test paper coated with dual emission ratiometric fluorescent sensor. • The system exhibited a wide range of color changes in the presence of TC-PBQ. • Introduces a reliable portable smartphone-assisted RGB-dependent sensing model. • Realization of rapid and visual on-site detection of TC-PBQ in river water. Tetrachloro-p-benzoquinone (TC-PBQ) can be harmful to the environment as a pesticide residue, but its analytical detection has been largely neglected. In this work, a smartphone-assisted RGB-dependent TC-PBQ ratiometric sensing platform for rapid recognition is introduced. Here, the red-emitting mercaptopropionic acid-capped CdTe quantum dots (MPA-capped CdTe) as the reaction unit can be quenched by TC-PBQ, while the blue-emitting carbon dots (CDs) as the reference signal remain unchanged. The limit of detection (LOD) of the sensing platform can reach 59 nM in aqueous solution. By constructing an analysis model with the system RBG value, the smartphone-assisted sensor-coated fluorescent test paper can complete the qualitative and quantitative visual detection of TC-PBQ (LOD is 93 nM). The applicability of smartphone-dependent RGB analysis significantly simplifies and speeds up the operation process, which provides a new analytical method for real-time analysis of TC-PBQ in real samples. [ABSTRACT FROM AUTHOR]

An unbalanced diet and lifestyle nowadays are very concerning as it lacks desired nutrition's which in the long term ultimately led to high cholesterol and other health problems. The present work reports the development of a HgAu alloy stabilized 4H -chromene organic nanoparticles (G4) following a simple condensation technique and characterized via HRTEM, SEM, AFM, DLS, EDAX, and STEM. Furthermore, G4 exhibits increased stability in comparison to bare Hg-Au alloy and ultrahigh selectivity and sensitivity towards cholesterol by changing its color from yellow to pink and blue on report of high and low levels of cholesterol respectively. The color change was quantified using RGB analysis and compared with the UV-Visible absorption data. Further for the rapid on-site detection of cholesterol, pristine paper based lateral flow device has been developed and tested for the human serum, where it gives significantly good results with a recovery percentage of 101.7% with 0.011 nM limit of detection (LOD), linearity of 99.3%, and reproducibility of ± 4% (relative standard deviation). To the best of our knowledge, the present work represents the first report on: (a) preparation of HgAu alloy@ 4H -chromene , and (b) detection of hypocholesteraemia. [Display omitted] • First report on fabrication of Hg-Au amalgam coated ONPs. • First report on detection of hypocholestremia as well as hypercholestremia. • Cholesterol detection with low LOD, using toxic mercury. • Lateral flow device for instant cholesterol detection: Anywhere, Anytime, Anyplace. [ABSTRACT FROM AUTHOR]

[Display omitted] • A ratiometric nanoprobe was designed by combining copper and silver nanoclusters (Cu@Ag NCs). • For the first time, two nanoclusters were used as nanocomposite ratiometric fluorescent platform for the detection of biothiols. • The stability of silver nanoclusters was improved by the use of uracil as a capping agent. • The quantitative detection methods for biothiols were established using a smartphone-based visual detection. Ratiometric-based probes improve detection precision and accuracy by minimizing the influence of various experimental conditions. Here, we present a unique dual-emission fluorescence probe constructed by a dual-nanocluster. This sensing platform is composed of copper nanoclusters (CuNCs) as a reference signal and silver nanoclusters (AgNCs) as a response signal. Uracil was used as a capping agent to improve the stability of AgNCs by forming a complex with silver metal. Ratiometrically, the composite of copper/silver bimetallic nanoclusters (Cu@Ag NCs) was used to measure the amount of cysteine as a typical biothiol. The Cu@Ag NCs showed a reddish fluorescence that originated from AgNCs and CuNCs when excited by a UV lamp. Under UV illumination, the addition of cysteine caused a noticeable fluorescence color shift from red to blue. Due to the color tonality, a smartphone and the Color Grab app were used to analyze red, green, and blue (RGB) values from the images of the dual-nanocluster solutions before and after the addition of cysteine. A satisfactory linear correlation between the ratio of red to blue values as a function of cysteine concentration was established for the quantitative measurement of cysteine from 20 to 180 μM with a limit of detection of 7.0 μM. The proposed probe was applied to assay cysteine in human serum with satisfactory accuracy and precision. [ABSTRACT FROM AUTHOR]

[Display omitted] • GSHCQD-Au Np nanoprobe can detect the AA in a normal aqueous solution. • GSHCQD-Au Np pair disintegrates in the presenceof AA. • The limit of detection for sensing acryl amide in water is 0.12 pM. • Detection of AA can be done through RGB app using a smart phone. Selective, sensitive, and accurate detection of acrylamide (AA) in thermally processed food is a great challenge for food safety. This paper describes a "turn-on" fluorescence strategy to detect AA in real samples. Herein, the fluorescence intensity of glutathione-modified carbon quantum dots (GSHCQDs) was quenched initially upon the addition of gold nanoparticles (Au NPs) via fluorescence resonance electron transfer (FRET) to form a quenched GSHCQD-Au nanoprobe. When AA was introduced to the quenched GSHCQD-Au nanoprobe, the strong thiol-ene Michael addition (M−A) reaction among the -SH group of GSHCQD and AA occurred which releases GSHCQD to the medium and FL intensity at 520 nm is regained. The GSHCQD-Au nanoprobe can detect the AA in a normal aqueous solution (pH 7) selectively over a short response time of 5 min. Under the optimized conditions, the detection limit of AA was obtained to be 0.12 pM, over a wide linear range of 0–200 nM. Especially, this FRET-based sensing method was utilized successfully for the sensitive detection of AA using an RGB app installed on a smartphone, opening a new approach for the smart sensing of food contaminants. [ABSTRACT FROM AUTHOR]

The ability to detect glucose concentrations in human urine offers a non-invasive approach to monitor changes in blood glucose, kidney health and vascular complications associated with diabetes. We show the potential of employing catalytically active nanoparticles directly grown on textiles to produce a dose-dependent colorimetric sensor for glucose. We use a galvanic replacement (GR) reaction for the synthesis of bimetallic nanoparticles. Here, Cu nanoparticles act as a sacrificial template that undergoes a spontaneous electroless GR reaction when exposed to metal ions of gold, silver, platinum, and palladium to form bimetallic Cu-M nanoparticles (M = Au, Ag, Pt, or Pd). The evaluation of their intrinsic peroxidase-mimicking catalytic activity ("nanozyme") in comparison to that of the Cu nanozyme revealed that the bimetallic systems show a higher catalytic rate with the Cu–Pt nanozyme showing the highest catalytic efficiency. This property of the Cu–Pt nanozyme was then utilized to detect glucose in human urine using the glucose oxidase enzyme as a molecular recognition element. A key outcome of our study is the ability to detect urine glucose without requiring sample dilution which is an advantage over the gold standard GOx-POx method and significantly more reliable performance over commercial urine glucose dipsticks. The difference in the intensity of the colorimetric response between different glucose concentrations further allowed this sensor system to be combined with digital imaging tools for multivariate analysis. [ABSTRACT FROM AUTHOR]

Inductively coupled plasma mass spectrometry and laser-induced breakdown spectroscopy are the most popular techniques for monitoring toxic gases in the environments. Apart from sensitivity and resolution of the techniques, they suffer from several issues including portability and high cost. For design and realization of a low cost, spark spectrometry based portable instrument for monitoring toxic gases in our environments is the main motive of the present work. We have introduced several toxic smokes into a gas chamber containing our developed instrument. We have also investigated the capability of the instrument for online analysis of suspended particulate matter as well as various gaseous elements in the smokes. We have also developed software for the practical interface. The apparatus has been successfully tested to monitor several toxic fumes including cigarette smoke and NO. It has also been demonstrated that the instrument is equally efficient to monitor air quality in the open environment, for example, presence of nitrogen, oxygen, and water vapor in the ambient condition. In the present work, we have demonstrated some important spectroscopic studies including role of water vapor (solvation) in the ionization of potassium, which is an active ingredient of toxic smokes, in the ionization which leading to the generation of atomic emission under the spark spectrometer can also be achieved with our instrument. The sensitivity of the instrument is found to be sub ppm (0.27 ± 0.13 ppm) in the case of cigarette smoke in ambient condition. The simplicity and extremely cost-effective design can provide an alternative method of detection of fumes in air and can serve as a cheap alternative for costly/bulky bench-top instruments. [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]

As per the WHO reports, it has been estimated that almost 25% of food crops contain mycotoxins as the major contaminant. In this work, we developed a paper-based colorimetric lateral flow device (CLFD) impregnated with an organic cation receptor (OCR) for sensitive and selective detection of zearalenone (ZEN). Various techniques such as ultraviolet (UV)-visible absorption, cyclic voltammetry, and fluorescence spectroscopy were used for the detection of mycotoxins, and it was observed that OCR shows sensitivity and selectivity toward zearalenone (ZEN) only, irrespective of any other analytes. Furthermore, the colorimetric test revealed that the developed OCR shows a change in color with the addition of ZEN from greenish-gray to blue that is visible to the naked eye. The quantification of ZEN was also achieved using RGB analysis and compared with UV-visible spectroscopy data. Further, for the on-site detection of ZEN, a paper-based CLFD was also developed and used to evaluate the spiked corn sample containing ZEN, and it provided significant results with a limit of detection (LOD) of 0.31 nM (3σ method), good linearity ( R 2 = 0.9702), good reproducibility (SD = ±6%, triplicate), and good recovery of ZEN of 95-102% with a variation coefficient (VC) varying from 1.56 to 4.62%. Therefore, the device has the potential to check the mycotoxin toxicity in food products and is helpful in remote and developing areas.

[Display omitted] • A portable sensing hydrogel loaded with Au@MnO 2 core-shell nanocomposites is prepared. • The colorimetric detection of total volatile basic nitrogen (TVB-N) is achieved based on the sensing hydrogel. • A smartphone combined with RGB analysis is applied to quantify the variation of TVB-N. • The hydrogel sensing platform is further used to non-invasive and portable monitoring fish freshness successfully. Total volatile basic nitrogen (TVB-N) content is the most widely used index for the assessment of fish freshness. Herein, a smartphone-integrated colorimetric sensor of TVB-N is developed based on a functional hydrogel loaded with Au@MnO 2 core-shell nanocomposites and β- d -glucose pentaacetate (β- d -GP). In the sensing hydrogel, Au@MnO 2 serves as a colorimetric substance and β- d -GP is a precursor of reducing agent. TVB-N can permeate the sensing hydrogel, causing an alkaline environment in which β- d -GP is hydrolyzed to produce β- d -glucose. A redox reaction between MnO 2 and β- d -glucose can occur and thus the TVB-N can induce the etching of MnO 2 layer of the Au@MnO 2. Owing to the change of localized surface plasma resonance (LSPR) effect, the color of AuNPs changing from purple to red is easily distinguished by the naked eye. To quantify the variation conveniently, the color information is digitized by a smartphone combined with RGB analysis. The hydrogel sensing platform is further used for real-time monitoring of fish spoilage successfully. The introduction of smartphone avoids the usage of expensive instrument and opens a practical way for cost-effective, non-invasive, and portable monitoring of foodstuff freshness. [ABSTRACT FROM AUTHOR]

The present work reports the development of a biologically inspired analytical system known as Electronic Eye (EE), capable of qualitatively discriminating different tequila categories. The reported system is a low-cost and portable instrumentation based on a Raspberry Pi single-board computer and an 8 Megapixel CMOS image sensor, which allow the collection of images of Silver, Aged, and Extra-aged tequila samples. Image processing is performed mimicking the trichromatic theory of color vision using an analysis of Red, Green, and Blue components (RGB) for each image's pixel. Consequently, RGB absorbances of images were evaluated and preprocessed, employing Principal Component Analysis (PCA) to visualize data clustering. The resulting PCA scores were modeled with a Linear Discriminant Analysis (LDA) that accomplished the qualitative classification of tequilas. A Leave-One-Out Cross-Validation (LOOCV) procedure was performed to evaluate classifiers' performance. The proposed system allowed the identification of real tequila samples achieving an overall classification rate of 90.02%, average sensitivity, and specificity of 0.90 and 0.96, respectively, while Cohen's kappa coefficient was 0.87. In this case, the EE has demonstrated a favorable capability to correctly discriminated and classified the different tequila samples according to their categories. [ABSTRACT FROM AUTHOR]