Sensitive Colorimetric Sensor Research Articles

Development of 2D Ir-DMG nanosheets as a colorimetric sensor probe for Ni (II) sensing and a highly sensitive, reliable, and portable colorimetric sensor device for environmental analysis

The era of nanomaterials made a revolutionary change in colorimetric sensing with ultra-high sensitivity, improved reactivity, and enhanced photoactivity. The first-ever novel 2D metal–organic nanosheets were synthesized using IrCl3 and Dimethylglyoxime (DMG) by probe ultrasonication (PUS) followed by a solvothermal wet-chemical approach. This material has shown a rapid color change from yellow to crimson red with Ni (II) after the formation of complex. The UV–visible absorption spectra are the conventional methodology for colorimetric sensors and here, it was given a perfect linear relationship with an R2 of 0.99 and an LOD of 1.60 µM (0.1 ppm). The average calculated molar extinction coefficient for this system was 1889.30 M−1 cm−1. This is comparatively high absorptivity value. In addition, a novel Arduino-based colorimetric sensor device and corresponding software were developed under the name of “Chrom Metrics”. This Arduino device is unique since it can sense all wavelengths and the combined RGB delta E values. Therefore, it can provide more information/rationale for colorimetry than other devices/methods. The same Ir-DMG & Ni (II) system showed a perfect linear relationship with an R2 of 0.98 and a LOD of 0.85 µM (0.05 ppm) by the data obtained from this sensor device. Thus, this new device is easier and more accurate, highly efficient, rapid, highly selective, and sensitive.

A simple Ag-MoS2 hybrid nanozyme-based sensor array for colorimetric identification of biothiols and cancer cells.

The intracellular levels of biothiols are associated with various diseases including cancer, and biothiols are regarded as tumor biomarker. Due to the similarity of the molecular structure of biothiols, the development of simple, rapid, efficient, and sensitive colorimetric sensor arrays holds great promise for clinical cancer diagnosis. Here, we developed a simple Ag-MoS2 hybrid nanozyme-based sensor array for colorimetric identification of biothiols and cancer cells. The novel Ag-MoS2 nanoprobe was synthesized in a simple and efficient way through the in situ self-reduction reaction between MoS2 and noble metal precursor. Benefiting from to the formation of heterogeneous metal structures, the peroxidase (POD)-like catalytic activity of the synthesized Ag-MoS2 hybrid nanocomposites is significantly enhanced compared to MoS2 alone. Moreover, the catalytic activity of Ag-MoS2 nanozyme was correlated with the pH of the reaction solution and the inhibitory effects of the three biothiols on the nanozyme-triggered chromogenic system differed in the specific pH environments. Therefore, each sensing unit of this electronic tongue generated differential colorimetric fingerprints of different biothiols. After principal component analysis (PCA), the developed novel colorimetric sensor array can accurately discriminate biothiols between different types, various concentrations, and different mixture proportions. Further, the sensor array was used for the colorimetric identification of real serum and cellular samples, demonstrating its great potential in tumor diagnostic applications.

Sensitive colorimetric detection of glutathione in human serum based on peroxidase-like activity of chitosan-stabilized gold nanoparticles.

Acolorimetric sensor for the rapid and sensitive detection of GSH was developed. The hydrothermal method was utilized to synthesize chitosan-stabilized gold nanoparticles (CS-AuNPs). The synthesized CS-AuNPs were characterized by UV-vis absorption spectroscopy, transmission electron microscopy (TEM), X-ray diffractograms (XRD), and Fourier transform infrared spectroscopy (FTIR). The CS-AuNPs arewell-dispersed and possess aspherical shapewith an average particle size of 10.05 ± 2.26nm in aqueous solution. Theyshow an intrinsic peroxidase-like activity, which could efficiently catalyze the decomposition of H2O2 to produce •OH radicals. These radicals then oxidized 3, 3´, 5, 5´-tetramethylbenzidine (TMB), resulting in the formation of the blue oxidizedproduct oxTMB, observed a visible color change (from colorless to blue), and oxTMB had an obvious absorption peak at 652nm. The presence of GSH could inhibit the peroxidase-like activity of CS-AuNPs, thereby reducing the formation of oxTMB. The solution's blue hue underwent a reduction in absorption intensity. Based on this fact, a novel and sensitive colorimetric sensor for detection of GSH was constructed. Under optimal conditions, the results of detection had an excellent linear relationship between the concentration of GSH and ∆A within the range 0.5 ~ 50.0 × 10-6mol/L. The limit of detection (LOD) for GSH was 2.10 × 10-7mol/L, which was much lower than those in most previous works. Furthermore, for detection in real human serum samples, the recoveries of GSH and the relative standard deviations (RSD) in the serum were in the range 98.40 ~ 103.32% and 1.85 ~ 3.54%, respectively. Thus, this visual colorimetric method has good precision and can be used for GSH detection in practical applications, promising in the fields of bioanalysis and illness diagnostics.

Enhanced Colorimetric Detection of Volatile Organic Compounds Using a Dye-Incorporated Photonic Crystal-Based Sensor Array.

Chemoresponsive dyes offer the potential to selectively detect volatile organic compounds (VOCs) unique to certain disease states. Among different VOC sensing techniques, colorimetric sensing offers the advantage of facile recognition. However, it is often challenging to discern the color changes by the naked eye. Here, highly sensitive colorimetric VOC sensor arrays from dye-incorporated colloidal photonic crystals (dye-cPhCs) are reported. cPhCs are scalably fabricated on a 4-inch wafer by spin-coating of silica nanoparticles (NPs) dispersed in a photo-cross-linkable monomer, where the gradient shear flow along the film thickness creates densely-packed square arrays of NPs in the top layers, whereas the bulk is quasi-amorphous with larger periodicities. The broadened reflection peak allows for augmented dye absorption originating from the overlap between the photonic bandgap edge of the cPhC and the dye absorption peak, leading to a more noticeable color change upon exposure to VOCs. The sensor array generates distinct color difference maps for acetaldehyde, acetone, and acetic acid, respectively, without any data amplification. The limit of detection for acetaldehyde, acetone, and acetic acid is 1, 0.1, and 0.02ppm, respectively. Moreover, VOC can be diagonalized by visually intuitive pattern recognition, and principal component analysis at reduced dimensionality is demonstrated.

Bifunctional Pt-loaded steel slag matrix composites for the detection and degradation of tetracycline antibiotics

In this paper, a method for the simultaneous detection and degradation of tetracycline antibiotics (TCs) in water was investigated. Calcium silicate hydrate (CSH), FeO and calcium aluminate hydrate (CAH) were isolated from steel slag as carriers for Pt monomers. The produced Pt-modified modified steel slag (ALANH-Pt) possessed both peroxidase activity and photocatalytic properties. As a result, a sensitive and selective colorimetric sensor was exploited on the basis of ALANH-Pt for tetracycline (TC), oxytetracycline (OTC), and doxycycline (DOX), which exhibited a detection limit (LOD) of 1.696 μM, 0.999 μM and 3.607 μM, respectively. In addition, the degradation rate for TCs could be achieved 82 % within 60 min. The possible mechanisms of detection and degradation are discussed based on ESR spectroscopy, revealing the generation of hydroxyl radicals (OH), superoxide radicals (O2−) and holes (h+). The degradation pathway of TC was inferred by HPLC-MS. The selectivity of the colorimetric sensing platform and the application of the bifunctional ALANH-Pt to real water samples were investigated. This work provides a new idea that allows for the simultaneous detection and degradation of TCs, and offers a new approach to the utilization of steel slag.

A highly sensitive colorimetric and fluorometric sensor for the detection of cyanide

Certain anions play a vital role in metabolic reactions in our body, but the cyanide ion is highly toxic and poisonous to humans, animals, and the environment even at extremely low concentrations. To detect CN−ions, a highly sensitive electron donor-π-acceptor molecular system (IC) was designed based on the carbazole electron donor and 1,3-indanedione electron acceptor. The IC molecular probe was synthesized through simple organic transformations with good yields and characterized by all spectroscopic methods, including single-crystal X-ray diffraction. The IC probe molecule absorbs in the UV–visible region (200–550 nm), and fluorescence emission encompasses 400–750 nm with LE and CT emission bands. A systematic study suggests that the addition of cyanide ions caused both longer wavelength absorption bands and CT fluorescence emission intensity to decrease. Cyanide ion detection can be visualized with the naked eye, where the yellow color of the IC probe solution changes to colorless upon adding cyanide ion solution. Both UV–visible and fluorescence emission spectral changes with the addition of cyanide ions are attributed to the nucleophilic addition of cyanide at the vinylic carbon, which is confirmed by the 1H NMR, HRMS and fluorescence lifetime studies. The cyanide ion detection limit of the IC has been estimated to be 0.43 µM, far below the WHO permissible limit for cyanide ion concentration in potable water, thus broadening the utility of the IC probe in detecting cyanide in Tapioca. A prototype TLC testing strip has been fabricated for the qualitative determination of cyanide in THF/water medium.

A fast and sensitive colorimetric sensor for residual chlorine detection made with oxidized cellulose

Residual chlorine from widespread disinfection processes forms byproducts in water that are harmful to humans and ecosystems. Portable sensors are essential tools for the on-site monitoring of residual chlorine in environmental samples. Here, an inexpensive colorimetric sensor was developed by grafting via amidation the chromogen orthotolidine (OTO) to the surface of a TEMPO-oxidized cellulose filter paper (O-TOFP). A thorough characterization of the sensor strip demonstrated that it was highly stable and that it could be stored for a long period before usage. O-TOFP had a fast response time of 30 s, was highly selective for residual chlorine ions (ClO−) with an accuracy of at least 95 %, and exhibited an excellent limit of detection of only 0.045 mg/L when combined with smartphone image acquisition. With its many positive features, the easy-to-use and robust O-TOFP sensor described here could become a useful tool for the determination of residual chlorine in different water samples.

Simple and selective detection of trifluralin herbicide in underground waters based on modified silver nanoparticles by 4-mercaptophenylbronic acid

ABSTRACT Due to the increase in agricultural contaminants in tap water and the importance of contaminant detection analysis, we report a sensitive and accurate colorimetric sensor based on the silver nanoparticles (AgNPs) to detect Trifluralin (TFA) in tap water. Silver nanoparticles were modified with 4-mercaptophenylbronic acid (MPBA) and for obtaining better responses from MPBA-AgNPs as a colorimetric sensor, Conditions affecting the reactions were optimised. The surface morphology, chemical structure and size of the MPBA-AgNPs sensor in different conditions were examined by FE-SEM, FT-IR, DLS and TEM analyses. Finally, it was used as a sensor to detect and measure the TFA herbicide with LOD = 3.20 ppm and RSD = %3.30. The recovery was obtained in the range of %87.15–%105.45, which indicated that the presented method is very practical and highly accurate for measuring this herbicide in its real samples.

Ultrasensitive and selective colorimetric and smartphone-based detection of arsenic ions in aqueous solution using alliin-chitosan-AgNPs.

In this study, we developed a highly selective and sensitive colorimetric sensor for arsenic [As(iii)] detection using alliin-chitosan-stabilized silver nanoparticles (AC-AgNPs). The AC-AgNPs were synthesized using a complex prepared by mixing aqueous garlic extract containing alliin and chitosan extracted from shrimp. The synthesis of AC-AgNPs was confirmed by UV-vis spectroscopy, which showed a surface plasmon resonance (SPR) band at 403 nm, and TEM analysis revealing spherical nanoparticles with a mean diameter of 7.57 ± 3.52 nm. Upon the addition of As3+ ions, the brownish-coloured solution of AC-AgNPs became colourless. Moreover, the computational study revealed that among all the metal ions, only As3+ was able to form a stable complex with AC-AgNPs, with a binding energy of 8.7 kcal mol-1. The sensor exhibited a linear response to As(iii) concentrations ranging from 0.02 to 1.4 fM, with a detection limit of 0.023 fM. The highest activity was observed at pH 7 and temperature 25 °C. Interference studies demonstrated high selectivity against common metal ions. The study also demonstrated that the concentration of As3+ ions can be estimated by the decrease in red intensity and increase in green intensity in smartphone optical transduction signals. These results indicate the potential of the AC-AgNP-based sensor for reliable and efficient arsenic detection in environmental monitoring.

Fabrication of Highly Sensitive and Selective Nitrite Colorimetric Sensor Based on the Enhanced Peroxidase Mimetic Activity of Using Acetic Acid Capped Zinc Oxide Nanosheets.

Nitrite ions (NO2-), as one of the leading type-A inorganic-anion, showing significant-effects in the aquatic environment and also to humans health. Whereas, the higher uptake causes detrimental threat to human health leading to various chronic diseases, thus demanding efficient, reliable and convenient method for its monitoring. For this purpose, in the present research study we have fabricated the mimetic nonozyme like catalyst based colorimetric nitrite sensor. The acetic acid capped Zinc Oxide (ZnO) nanosheets (NSs) were introduce as per-oxidase mimetic like catalyst which shows high efficiency towards the oxidative catalysis of colorless tetramethylbenzidine (TMB) to oxidized-TMB (blue color) in the presence of Hydrogen-peroxide (H2O2). The present nitrite ions will stimulate the as formed oxidized-TMB (TMBox), and will caused diazotization reaction (diazotized-TMBox), which will not only decreases the peak intensity of UV-visible peak of TMBox at 652nm but will also produces another peak at 446nm called as diazotized-TMBox peak, proving the catalytic reaction between the nitrite ions and TMBox. Further, the prepared colorimetric sensor exhibits better sensitivity with a wider range of concentration (1 × 10-3-4.50 × 10-1 µM), lowest limit of detection (LOD) of 0.22 ± 0.05 nM and small limit of quantification (LOQ) 0.78 ± 0.05 nM having R2 value of 0.998. Further, the colorimetric sensor also manifest strong selectivity towards NO2- as compared to other interference in drinking water system. Resultantly, the prepared sensor with outstanding repeatability, stability, reproducibility, re-usability and its practicability in real water samples also exploit its diverse applications in food safety supervision and environmental monitoring.

Nanostructured transition metal dichalcogenides-based colorimetric sensors: Synthesis, characterization, and emerging applications.

Nanostructured transition metal dichalcogenides (TMDCs) have garnered significant attention as prospective materials for the development of highly sensitive and versatile colorimetric sensors. This work explores the synthesis, characterization, and emerging applications of TMDC-based sensors, focusing on their unique structural aspects and inherent properties. The synthesis methods involve tailored fabrication techniques, such as chemical vapor deposition and hydrothermal processes, aimed at producing well-defined nanostructures that enhance sensor performance. Characterization techniques, including microscopy, spectroscopy, and surface analysis, are employed to elucidate the structural and chemical features of the nanostructured TMDCs. These analyses provide insights into the correlation between the material's morphology and its sensing capabilities. The colorimetric sensing mechanism relies on the modulation of optical properties in response to specific analytes, enabling rapid and visual detection. The emerging applications of TMDC-based colorimetric sensors span diverse fields, including environmental monitoring, healthcare, and industrial processes. The sensors exhibit high sensitivity, selectivity, and real-time response, making them ideal candidates for detecting various target analytes. Furthermore, their integration with complementary technologies such as microfluidics, can facilitate the development of on-site and point-of-care applications. This work highlights the interdisciplinary significance of nanostructured TMDC-based colorimetric sensors and underscores their potential contributions to addressing contemporary challenges in sensing technology.

Copper oxide nanosheets as an effective nanozyme with haloperoxidase-like activity for the colorimetric detection of H2O2 and glucose

Copper oxide nanosheets (CuO NSs) have been successfully obtained by exploiting an effective one-step approach of sugar-blowing method followed by calcination. The nanosheets were characterized by several techniques like X-ray powder diffraction (XRD), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Impressively, CuO NSs display haloperoxidase (HPO) like catalytic activity which catalyses the oxidation of chloride ions by H2O2 giving rise to reactive chlorine species (RCS). A sensitive and selective colorimetric sensor was then demonstrated via the oxidation of chromogenic substrate 3,3′,5,5′- tetramethylbenzidine (TMB) by the novel nanoenzyme CuO NSs through the generation of RCS for H2O2 and glucose detection with limit of detection of 109 nM and 21 nM in the linear ranges of 4.6 µM to 769 µM and 0.22 µM to 19.57 µM respectively. Additionally, the methodology is validated for the analysis of glucose in real samples.

Sensitive and selective colorimetric sensor detection of Sn (II): An aqueous, paper, and gel-based method by green biomimetic silver nanoparticles

Tin contamination in waters due to mining and natural activities in high concentrations can threaten human health. This research presents the development of a sensitive and selective colorimetric sensor in aqueous, paper, and gel-based to detect Sn2+. The development of such sensors is promising, with attractive advantages such as intense color, fast naked-eye response, and simple continuous fabrication. The addition of Sn2+ ions will change the color of the medium because curcumin (Cur) interacts with Sn2+, causing a decrease in free Cur, silver nanoparticles (AgNPs) becoming less stable, and a change in particle size. Colorimetric changes in Sn2+ were achieved by visual inspection within 10 min for aqueous-based and 20 min for paper and gel-based. The good linear relationship (R2 = 0.9999) between Sn2+ and Δ absorption with a detection limit of up to 66.99 µg/L. This method is relatively scalable in determining Sn2+ and shows good recovery between 80 and 105 %. This colorimetric sensor gives good sensitivity to Sn2+ metal ions which is expected to become the basic technology for developing in-situ sensors to monitor Sn2+ levels in tin industrial waste.

Multienzyme Mimicking Cascade Mn3O4 Catalyst to Augment Reactive Oxygen Species Elimination and Colorimetric Detection: A Study of Phase Variation upon Calcination Temperature.

Over decades, nanozyme has served as a better replacement of bioenzymes and fulfills most of the shortcomings and intrinsic disadvantages of bioenzymes. Recently, manganese-based nanomaterials have been highly noticed for redox-modulated multienzyme mimicking activity and wide applications in biosensing and biomedical science. The redox-modulated multienzyme mimicking activity was highly in tune with their size, surface functionalization, and charge on the surface and phases. On the subject of calcination temperature to Mn3O4 nanoparticles (NPs), its phase has been transformed to Mn2O3 NPs and Mn5O8 NPs upon different calcination temperatures. Assigning precise structure-property connections is made easier by preparing the various manganese oxides in a single step. The present study has focused on the variation of multienzyme mimicking activity with different phases of Mn3O4 NPs, so that they can be equipped for multifunctional activity with greater potential. Herein, spherical Mn3O4 NPs have been synthesized via a one-step coprecipitation method, and other phases are obtained by direct calcination. The calcination temperature varies to 100, 200, 400, and 600 °C and the corresponding manganese oxide NPs are named M-100, M-200, M-400, and M-600, respectively. The phase transformation and crystalline structure are evaluated by powder X-ray diffraction and selected-area electron diffraction analysis. The different surface morphologies are easily navigated by Fourier transform infrared, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy analysis. Fortunately, for the mixed valence state of Mn3O4 NPs, all phases of manganese oxide NPs showed multienzyme mimicking activity including superoxide dismutase (SOD), catalase, oxidase (OD), and peroxidase; therefore, it offers a synergistic antioxidant ability to overexpose reactive oxygen species. Mn3O4 NPs exhibited good SOD-like enzyme activity, which allowed it to effectively remove the active oxygen (O2•-) from cigarette smoke. A sensitive colorimetric sensor with a low detection limit and a promising linear range has been designed to detect two isomeric phenolic pollutants, hydroquinone (H2Q) and catechol (CA), by utilizing optimized OD activity. The current probe has outstanding sensitivity and selectivity as well as the ability to visually detect two isomers with the unaided eye.

Characterization of a Food‐Safe Colorimetric Indicator Based on Black Rice Anthocyanin/PET Films for Visual Analysis of Fish Spoilage

ABSTRACTThe safety of food products is of prime importance for consumers and manufacturers. Many means can be used to validate a food product's safety before it is consumed. This study is about the preparation, characterization and evaluation of a generally recognized as safe (GRAS) sensitive colorimetric sensor that detects volatile gases (TVB‐N) resulting from fish spoilage, thus indicating the pH variation of packaged fish products. This is performed by coating a thin layer of ink sensors on the surface of the supporting matrix (corona‐treated PET). Various visual pH indicators were prepared based on black rice anthocyanin as an FDA‐approved dye. Black rice, which contains more than 80% cyanidin‐3‐glucoside, is the most prevalent anthocyanin component. Because of its low toxicity and high concentration, it can be utilized as a natural food colourant. pH indicators based on black rice can show distinct colours in various pH: from red (low pH) to violet (4–6) and deep purple/blue (6–7), blue (7–9) to yellowish/light brown (9–13) throughout the acid–base reaction by the analyte. The ink formulation was prepared by incorporating a binder system (PVOH‐PEG) for higher surface wettability, a crosslinking agent (citric acid) for higher adhesion, an antifoaming agent (natural vanillin) and acetic acid as a pH fixing agent. Corona treatments affected substrate surface chemistry in this study. The samples with thermal treatment passed the ASTM D3330 tape test, the 8000 passages for dry sponge and the 25 passages for wet sponge through the abrasion method. Anthocyanin concentration in formulated ink based on calculation by UV–vis spectra is 0.240 mg/100 g. Sensitivity tests towards TVB‐N gases were carried out at a temperature of 4°C to evaluate the performance of colorimetric films with formulated ink along with thermal treatment (temperature: 165°C, time: 5 min) using the volatile gases emitted by the fish sample inside the package.

Colorimetric sensor array for versatile detection and discrimination of model analytes with environmental relevance

In the current work, a rapid, simple, low-cost, and sensitive smartphone-based colorimetric sensor array coupled with pattern-recognition methods was proposed for the determination and differentiation of some organic and inorganic bases (i.e., OH−, CO32−, PO43−, NH3, ClO−, diethanolamine, triethanolamine) as model compounds. The sensing system has been designed based on color-sensitive dyes (Fuchsine, Giemsa, Thionine, and CoCl2) which were used as sensor elements. The color changes of a sensor array were observed by the naked eye. The color patterns were recorded using digital imaging in a three-dimensional (red, green, and blue) space and quantitatively analyzed with color calibration techniques. Distinctive colorimetric patterns for target bases via linear discriminant analysis (LDA) and hierarchical clustering analysis (HCA) were observed. The results indicated that the analytes related to each class (at the different concentration levels in the range of 0.001–1.0 mol L−1) were clustered together in the canonical discriminant plot and HCA dendrogram with high sensitivity and an overall precision of 85%. Furthermore, the first function factor of LDA correlated with the concentration of each target analyte in a correlation coefficient (R2) range of 0.864–0.996. These described procedures based on the colorimetric sensor array technique could be a promising candidate for practical applications in package technology and facile detection of pollutants.

Rapid aqueous preparation of carbon quantum dots and their application as nanozyme for the detection of hydrogen peroxide and uric acid

A green and rapid method was developed to synthesize a series of carbon quantum dots (Fe,N/CQDs, Fe,S/CQDs, S,N/CQDs and Fe,S,N/CQDs) through thermal decomposition using persimmon frost as a carbon source. All the synthesized CQDs have peroxidase-like activity, and the comparision of their steady-state kinetic parameters inferred that the peroxidase-like activity of Fe,S,N/CQDs is superior to those of Fe,S/CQDs and Fe,N/CQDs. Furthermore, Fe,S,N/CQDs exhibited good affinity towards 3,3′,5,5′-Tetramethylbenzidine (TMB) and H2O2 compared to natural horseradish peroxidase (HRP) and other nanozymes. In theory, uric acid (UA) can produce H2O2 with the catalysis by uricase. Fe,S,N/CQDs could catalyze the breakdown of H2O2 to produce reactive oxygen species (ROS), which can oxidize TMB (colorless) to oxTMB (blue). Based on the nanozyme-catalyzed oxidation of TMB, a simple and sensitive colorimetric sensor was developed for the quantitative analysis of H2O2 and UA. Low limit of detection (0.73 μM), wide linear range (1–80 μM) and good repeatability were obtained. The sensor was also demonstrated for the determination of UA in biological samples and satisfactory results were obtained.

Smartphone-assimilated colorimetric sensor for sub-nanomolar emamectin detection via KA30 capped silver nanoparticles in food, bio-fluids and water samples

In this report, we firstly synthesized nitro calix [4] resorcinarene compound (referred as KA30) and characterized it though proton (1H) nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS) and Fourier Transform Infra-red (FTIR) spectroscopy. KA30 was applied as functionalizing agent for the formation of silver nanoparticles (KA30-AgNPs). These NPs were confirmed as highly selective and extremely sensitive colorimetric sensor for ultra-low level detection of emamectin (EMA) as a novel report. Significant aspect of the sensor is its unique detection range between 0.0005 and 29.5 μM via color change from yellow to colorless with hypochromic-bathochromic shift exhibiting limit of detection (LOD) and limit of quantification (LOQ) as 0.12 nM and 0.4 nM respectively. The sensor was applied to colorimetrically and optically detect EMA in real samples of serum, urine and food. The sensor was further allied with smartphone for real-time, and on-site detection of EMA and results were validated through UPLC.

A Quick, Highly Selective and Sensitive Colorimetric and Fluorimetric Sensor for Cyanide Ion.

A newly developed diindolium moiety has been synthesized and structurally investigated by employing a number of spectroscopic methods like NMR and HRMS in order to serve as a cyanide sensor DI. The interaction between DI and the CN- ion causes a noticeable color shift from pink to colorless, making it easy to detect CN- ions with the naked eye. Besides, the sensor exhibited fluorescence color change from orange to light blue under UV lamp. Sensor DI has remarkable selectivity and sensitivity in distinguishing between CN- and a wide range of interfering anions. The sensing mechanism of sensor DI towards CN- ion involves the nucleophilic addition process of CN- to the electron deficient indolium moiety. The detection limit of cyanide ion by sensor DI is calculated to be 1.4 × 10- 7 M by UV-visible and 8.2 × 10- 8 M by fluorescence technique which are lower than the limit set by WHO. The application of sensor DI for cyanide ion is utilized by making test kit and by taking different sources of water to test the presence of cyanide ion.

MOFs@POMs-derived bimetallic oxide Fe2(MoO4)3 nanoparticles for sensitive colorimetric detection of salicylic acid in aspirin.

Acolorimetric sensing method for salicylic acid (SA) was developed by designing and fabricating bimetallic oxide nanozymes. Firstly, by calcinating MIL-100(Fe)@PMo12 (MOFs@POMs) at different temperature, Fe2(MoO4)3-Ts (T = 400℃, 500℃, 600℃, 700℃) nanoparticles (NPs) were successfully prepared. Secondly, by evaluating the peroxidase-like activities, Fe2(MoO4)3-600 NPs shows the best peroxidase-like activity attributed to the Fenton-like effect and the synergistic coupling interaction between Mo and Fe. Finally, based on the specific complexation between SA and Fe3+, a sensitive colorimetric sensor for SA was established, which exhibits superior selectivity and interference with a detection limit of 0.11μM anda linear range of 10 to 100μM, the lowest LOD for SA to date, to the best of our knowledge.