Colorimetric Sensor For Selective Detection Research Articles

A coumarin based Schiff Base: An effective colorimetric sensor for selective detection of F– ion in real samples and DFT studies

Chemosensors are molecular devices which react with target and give a visible signal, which is a degree of its sensitivity. Herein, a novel coumarin based Schiff Base has been synthesized for F– ions detection. The chemosensor showed an intense color change upon the addition of F– ions (light yellow to purple). The chemosensor has fewer effects of competing anions. The limit of detection is calculated as low as 1.1 × 10–6 and the binding constant was determined as 1.61 × 104. The job’s plot confirmed 1:1 stoichiometry between chemosensor and F– ion. The reverse reaction of chemosensor with MeOH is useful to construct a combinatorial logic circuit gates. The interaction mechanism of chemosensor was deliberated by 1H NMR, FTIR, and DFT studies. Finally, the chemosensor was useful to detect F– ions in tooth-paste sample and test strip is prepared for F– ions detection.

Shape-controlled silver nanoplates colored fabric with tunable colors, photothermal antibacterial and colorimetric detection of hydrogen sulfide

Anisotropic silver nanoplates are widely anticipated in multifunctional textiles, but their large-scale promotion is limited by the shortcomings of long reaction time, uncontrollable shape and low yield in the preparation process. In this study, a microwave-assisted strategy is provided to prepare shape-controllable silver nanoplates for coloration of non-woven fabric. Anisotropic Ag nanoplates are efficiently coated on the surface of chitosan-pretreated fabric by a simple solution impregnation method, which generates the fabric with tunable color and multiple functions. The Ag nanoplates loaded fabric exhibits excellent photothermal properties at 808 nm laser irradiation due to its unique plasmonic absorption features. Colored fabric shows a strong synergistic antibacterial effect, including silver ion release and hyperthermia caused by the photothermal effect under near-infrared (NIR) light. Additionally, colored fabrics can be used as colorimetric sensors for selective detection of H2S. The colorimetric values of visible color signal of fabric-based H2S gas sensor can be real-time precisely detected using a smartphone, enlightening its high potential as a wearable toxic gas alarm device for the simple and rapid detection of hazardous gases.

Fluorenone-Based Fluorescent and Colorimetric Sensors for Selective Detection of I- Ions: Applications in HeLa Cell Imaging and Logic Gate.

Fluorenone-based fluorescent and colorimetric sensors 1 and 2 have been developed that displayed selective detection of iodide ions in the presence of interferences. Sensors displayed the fluorescence emission enhancement response toward I– with detection limits of 8.0 and 11.0 nM, respectively, which is accomplished through inhibition of intramolecular charge transfer and C=N isomerization. Excellent sensitivity and unique fluorescence enhancement response of sensors toward I– make them superior because most of the previously reported iodide sensors are based on the fluorescence quenching mechanism and are less sensitive. The sensing potential of sensors toward I– ions was investigated through 1H NMR titration, dynamic light scattering, Job’s plots, and density functional theory analysis. Further, sensors displayed reversible behavior by the alternate addition of I– and Cu2+ ions that substantiate their role as recyclable sensors for the on-site detection of I– ions. Advantageously, fluorescence enhancement response of sensors was favorably used for fluorescence imaging of I– in live HeLa cells and the design of the logic gate. These sensors were successfully applied in diversified applications such as the preparation of sensors’ coated paper strips and the determination of I– ions in blood serum, food, and real water samples.

Fluorescent and colorimetric sensors for selective detection of TNT and TNP explosives in aqueous medium through fluorescence emission enhancement mechanism

Due to rising threats of terrorism, pollution, timely and rapid detection of 2,4,6-trinitrophenol (TNP) and 2,4,6-trinitrotoluene (TNT) explosives has earned paramount significance. Herein, easily synthesized fluorenone sensor3 was found selective towards the detection of TNP with a limit of detection (LOD) value of 0.5 nM. The fluorescence detection of TNP was achieved through the electrostatic interaction between sensor and TNP. Moreover, sensors 4 and5were rationally synthesized for selective nanoscale detection of TNT (LODs; 5.0 nM (4) and 7.0 nM (5)) through fluorescence emission enhancement response. Selective detection of TNT was accomplished through blockage of ICT and ESIPT in sensors. Sensing mechanisms were supported by 1H NMR titration, Job’s plots, computational methodologies, and DLS analysis. Interestingly, sensor 3 also showed selective colorimetric response towards TNP while sensors 4 and5displayed selective colorimetric detection of TNT explosive. Explosive responsive test kits were also prepared for on-site detection of TNP by sensor 3 and TNT by sensors 4 and5. Moreover, sensors 3, 4, and5were successfully applied in the analysis of industrial effluents for the rapid detection of explosives.

Hydrazide derived colorimetric sensor for selective detection of cyanide ions

Three model hydrazide derivatives, acetohydrazide, benzohydrazide and nicotinohydrazide were synthesized and investigated for their anion sensing abilities with F-, Cl-, Br-, I-, CN–, OAc-, HCO3–, H2PO4- and ClO3-. The anion sensing properties were studied in acetonitrile by UV–Visible absorption spectroscopic and 1H NMR spectrometric techniques. The experimental results were supported with Density Functional Theory (DFT) calculations. Significant changes were observed in the absorption spectra of all hydrazides upon sensing CN–, while benzohydrazide was able to detect F- in addition to CN–. The spectral variations were accompanied by change of color that could be observed through naked eye. The proposed mechanism of sensing could be due to the deprotonation of the N-H moiety in the hydrazides. The natural bond orbital (NBO) analysis employing DFT method supports the experimental results. The efficiency of these probe molecules were successfully tested for CN– in natural sources like potato, apple seeds and cassava root. The herein reported hydrazides possess the ability to detect cyanide contamination at high levels of specificity, sensitivity and selectivity.

Stable paper-based colorimetric sensor for selective detection of phosphate ion in aqueous phase

Phosphorus is one of the vital nutrients for sustenance; however, its excess concentration can cause adverse impacts on the ecosystem. Numerous sensors have been developed and deployed to monitor phosphate ions (Pi) in the environment in the past decade. However, their high cost, non-portability, and lengthy and complex fabrication processes are detrimental to their widespread use. Accordingly, the objective of the study was to develop a low-cost, convenient paper-based colorimetric sensor with brilliant green (BG) as the probe. The use of triarylmethane dye as a colouring reagent allows naked eye-visible detection of Pi in the range of 13.6–0.27 mg L−1 with the limit of detection as 0.07 mg L−1. Moreover, the proposed sensor resolves the challenges of traditional methods like the formation of insoluble complexes, the requirement of surfactants, poor reagents storability, dependence on time and temperature. The sensitivity and selectivity of BG toward Pi was verified in the aqueous phase. Later, the paper-based sensor (W-BG) was developed via dip coating as a portable detection tool. The storability, stability, and applicability of the developed strips were tested and validated using FT-IR, UV-DRS, and XRD. Additionally, the performance of the strips was compared with a microfluid paper-based device to ensure the feasibility and versatility of the strips. The sensing mechanism is deduced as the formation of the phosphomolybdate complex, which was responsible for the delocalization of the lone pair of electrons on BG, thus rendering a distinct endpoint. The selectivity and sensitivity of the sensor were maintained in real water and wastewater samples. Overall, with affordable cost (0.08 $) and portability, W-BG can be considered as a smart and environmentally friendly water quality monitoring tool.

Highly selective, sensitive and simpler colorimetric sensor for Fe2+ detection based on biosynthesized gold nanoparticles

Herein, we describe the fabrication of green bell pepper, Capsicum annuum L. extract capped gold nanoparticles (CA-AuNPs) in aqueous medium using tetrachloroaurate (HAuCl4·3H2O) as precursor salt and sodium hydroxide (NaOH) solution as accelerator as well as pH adjuster. Formation of CA-AuNPs was verified via colour change from yellowish to ruby red with further confirmation through surface plasmon resonance (SPR) band at 519 nm using ultraviolet violet-visible (UV–Vis) spectroscopy. Other characterizations techniques include, Fourier transform infra-red (FTIR) spectroscopy, atomic force microscopy (AFM), dynamic light scattering (DLS) with Zeta-potential analysis (ZPA) and X-ray diffraction (XRD) method. The resulting AuNPs were efficaciously implemented as highly sensitive colorimetric sensor for selective detection of Fe2+ in the presence of several interfering cations including Fe3+. Importantly, the fabricated CA-AuNPs based colorimetric sensor functioned linearly in the range of 0.3–7.0 ppb Fe2+, based on increasing absorption intensity with R2 value of 0.9938 using UV–Vis spectrometry. The limit of detection (LOD) and limit of quantification (LOQ) for Fe2+ were estimated as 0.036 and 0.12 ppb, respectively. Finally, the sensor was effectively tested for determination of Fe2+ in some locally collected real water samples.

A new fluorene derived Schiff-base as a dual selective fluorescent probe for Cu2+ and CN.

A new fluorene based fluorogenic chemosensor, 2-[(9H-Fluoren-2-ylmethylene)-amino]-phenol (L), has been designed, synthesized, and characterized by CHN analyses and different spectroscopic methods. This turn-on fluorogenic chemosensor shows high selectivity and sensitivity toward Cu2+ and CN- with low detection limits of 1.54 × 10-9 M and 1.83 × 10-7 M, respectively. The stoichiometry ratio of L-Cu2+ in solution is 1:1, by the method of Job's plot and ESI-MS. The microcrystalline solid product of the chemosensor reaction with copper is characterized as CuL2. The χT value for CuL2 is temperature independent at a value of 0.403 cm3 K mol-1, which is in agreement with a mononuclear copper(II) complex with an isotropic g-value of 2.075. The fluorescence turn-on recognition process for detection of Cu2+ is attributed to the restricted imine isomerization and blocking of intramolecular charge transfer (ICT) quenching process in the analyte-bound sensor. The selectivity of L for Cu2+ is based on the chelation-enhanced fluorescence effect (CHEF) mechanism. Other interfering ions such as Na+, K+, Ca2+, Mg2+, Ag+, Fe2+, Fe3+, Co2+, Ni2+, Zn2+, Cd2+, Hg2+, Mn2+, Pb2+ and Al3+, show no change in the fluorescence intensity of L in the presence of Cu2+. Furthermore, the compound L can be used as a fluorescence and colorimetric sensor for selective detection of CN- over a number of other anions based on the nucleophilic addition to the imine CN bond, with consequent hydrogen bond formation and electrostatic interaction of the resulting product with K+. The sensing mechanism for CN- was theoretically supported by DFT calculations.

A “turn-on” fluorescent and colorimetric sensor for selective detection of Cu2+ in aqueous media and living cells

A dicyanoisophorone-based turn-on chemodosimeter 1 has been designed and synthesized to detect Cu2+ in aqueous media via selective hydrolysis reaction of the picolinate moiety accompanied with generating the fluorophore. The probe 1 exhibited remarkably selective fluorescence enhancement with a 164nm Stokes shift and highly significant color change to Cu2+ over other metal ions. The limit of detection of probe 1 was calculated as low as 0.2μM for Cu2+. The probe 1 was also successfully applied to fluorescence imaging of Cu2+ in HeLa cells.

Biological active novel 2,4-dinitro phenyl hydrazones as the colorimetric sensors for selective detection of acetate ion

Novel hydrazones such as 1-(2,4-dinitrophenyl)-2-((3-methylthiophen-2-yl)methylene)hydrazine (L1) and 1-(6-(2-(2,4-dinitrophenyl)hydrazono)ethyl)pyridine-2-yl)ethanone (L2) have been synthesized and explored as colorimetric sensors. Systematic studies of ionophores (L1 and L2) with acetate ion in DMSO revealed that they involved in H-bonding and proton transfer with acetate ion. Due to these interactions change in visible region of spectrum was observed and colour of both the ionophores changed from yellow (L1) and orange yellow (L2) to magenta. Further ligand–acetae ion interactions were studied with the help of 1H NMR titration in DMSO and found that binding is the combined function of hydrogen bonding, electrostatic interactions and structure of binding site. Antimicrobial activities of ionophores (L1 and L2) were examined and tested against fungi: Rhizoctonia solani and Bipolaris oryzae using agar well diffusion method. Both ligands L1 and L2 were found to be exhibit antifungal activity against these strains. Antibacterial activity of L1 and L2 was also studied against Gram positive bacteria: Staphylococcus aureus, Bacillus brevis and Gram negative bacteria: Escherichia coli, Pycnoclavella diminuta using disc diffusion method and it was cleared that ligands were not inhibiting the growth of these strains even at higher concentration of both the ligands.

A BODIPY-based “turn-on” fluorescent and colorimetric sensor for selective detection of Cu2+ in aqueous media and its application in cell imaging

We report a turn-on fluorescent and colorimetric sensor based on an easily prepared BODIPY derivative for selective detection of Cu2+ in aqueous media. The sensor showed effective and selective detection of Cu2+ at a low detection limit. These advantages allow for the application of sensor 1 to detect trace amounts of Cu2+ in real water samples. The sensor was successfully applied to fluorescence imaging of Cu2+ in living cells.