Colorimetric Receptor Research Articles

Exploring dual-channel ion detection and theoretical insights: Chromone-based colorimetric receptor for Cu2+and its Zn(II)-complex as ultrasensitive fluorescent probe for Ag+ and Fe3+

Present article delineates the design and synthesis of a chromone-appended Schiff base (1) and its complexes with Zn(II) (2) and Cu(II) (3), which have been characterized by various spectro-analytical techniques i.e., elemental analysis, FTIR, 1H & 13C NMR, ESI-MS, UV−vis and fluorescence. Structures of 1 and 3 have also been elucidated using single crystal X-ray diffraction analysis. Compounds 2 showed significant effect in vitro cytotoxicity as compared to 1 Against MDA−MB-231 cell line. Interestingly, 1 serves as a chromogenic sensor for Cu2+ with exceptional selectivity whereas, 2 serves as an ultrasensitive fluorescent probe for Ag+ and Fe3+ in mixed aqueous−ethanol. The presence of Ag+ causes ratiometric change in the fluorescence spectral feature of 2 whereas Fe3+ induces ‘turn-off’ fluorescence in 2. Probe−analyte binding stoichiometry suggested by Job's plot analysis, ESI−MS and DFT studies, has been found to be 1:1 for 1 with Cu2+ and 2 with Ag+ whereas, 1:2 between 2 and Fe3+. Based on diverse analyses and binding constants, it is observed that 2 offers higher selectivity toward Ag+ over Fe3+. Limit of detection (LoD) of 1 for Cu2+ and 2 for Ag+ and Fe3+ have been found to be 2.33 nM, 22.4 µM and 2.05 µM, respectively. Complexes 2+Ag+ and 2+Fe3+ characterized by ESI−MS whereas DFT studies have been carried out to investigate the deeper bonding insights and provide support in our experimental investigations. Further, detection of Ag+ and Fe3+ has been practically accomplished in real water samples using probe 2.

A new colorimetric sensor based on semithiocarbazone for some anions: 2-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)-N-phenylhydrazine-1-carbothioamide

Carbazones are molecules containing important functional groups in designing anion chemosensors due to proton donor and acceptor sites in their structures. In this paper, we synthesize a novel colorimetric receptor with 1,3-dioxo-indene and thiosemicarbazone moieties by the reaction of ninhydrin and 4-phenyl-thiosemicarbazide in quantitative yield. We then identify its structure by means of FT-IR, $^{1}$H-NMR, $^{13}$C-NMR, and MS spectroscopic techniques. Moreover, we observe the reaction of the title compound with biologically important F$^¯$, OAc$^¯$, CN$^¯$, H2PO4$^¯$, and OH$^¯$ anions in the presence of other anions, such as Cl$^¯$, Br$^¯$, I$^¯$, SCN$^¯$, and OCl$^¯$ in dimethylsulfoxide solution through a color change from yellow to orange-red that can easily be distinguished even by the naked eye under ambient light. Finally, we evaluate the anion-sensing ability of the title compound via UV-vis spectroscopic studies.

Non-invasive detection of COVID-19 using a microfluidic-based colorimetric sensor array sensitive to urinary metabolites.

A colorimetric sensor array designed on a paper substrate with a microfluidic structure has been developed. This array is capable of detecting COVID-19 disease by tracking metabolites of urine samples. In order to determine minor metabolic changes, various colorimetric receptors consisting of gold and silver nanoparticles, metalloporphyrins, metal ion complexes, and pH-sensitive indicators are used in the array structure. By injecting a small volume of the urine sample, the color pattern of the sensor changes after 7 min, which can be observed visually. The color changes of the receptors (recorded by a scanner) are subsequently calculated by image analysis software and displayed as a color difference map. This study has been performed on 130 volunteers, including 60 patients infected by COVID-19, 55 healthy controls, and 15 cured individuals. The resulting array provides a fingerprint response for each category due to the differences in the metabolic profile of the urine sample. The principal component analysis-discriminant analysis confirms that the assay sensitivity to the correctly detected patient, healthy, and cured participants is equal to 73.3%, 74.5%, and 66.6%, respectively. Apart from COVID-19, other diseases such as chronic kidney disease, liver disorder, and diabetes may be detectable by the proposed sensor. However, this performance of the sensor must be tested in the studies with a larger sample size. These results show the possible feasibility of the sensor as a suitable alternative to costly and time-consuming standard methods for rapid detection and control of viral and bacterial infectious diseases and metabolic disorders.Graphical Supplementary InformationThe online version contains supplementary material available at 10.1007/s00604-022-05423-1.

Cooperative Recognition of Ni2+ Triggered by Fluoride Ions in Naturally Occurring α-Hydroxyquinone Derivatives.

Perezone is a naturally occurring hydroxyquinone that has been deeply studied from different chemical aspects, such as therapeutics, electrochemistry, physical–chemical properties, or synthetic approaches that turn it an attractive template for new semisynthetic derivatives with a wide range of purposes. Herein, we describe a facile synthetic pathway to obtain new perezone derivatives by the addition of a pyrrole moiety that can be used for ion recognition. Compounds 2–4 showed the capability to interact with several anions and M2+ cations as separate events that result in colorimetric changes. Moreover, the compounds can behave as heteroditopic receptors. Besides, a previous interaction between fluoride ions and perezone derivatives triggered a successful recognition of M2+ ions, remarking Ni2+ as the most interesting phenomenon. These results project the compounds as potential colorimetric receptors for nickel ions in complex solutions.

A novel colorimetric chemosensor for selective and highly sensitive determination of thiourea: An approach toward a molecular keypad lock

AbstractA novel simple reversible colorimetric chemosensor has been designed and developed using 4‐(2‐pridylazo) resorcinol (PAR). The colorimetric receptor PAR has been successfully applied for the determination of Hg2+ ions, and then the PAR‐Hg2+ complex has been used for thiourea (TU) measurements in aqueous‐buffer medium. This chemosensor exhibited an obvious color change from yellow to bright red in the presence of Hg2+ in aqueous solution. In addition, the resulting PAR‐Hg2+ complex sensed TU through naked‐eye, showing recovery from PAR‐Hg2+ to PAR, in aqueous solution. The detection limits reached up to 3.01 nmol/L for Hg2+ and 8.5 nmol/L for TU. The operational simplicity and cost‐effectiveness of colorimetric measurements using PAR and Hg2+ were achieved. Based on this, the designed method was well used to determine the analytes in industrial and environmental samples. The molecular switching between two chemical inputs (Hg2+, TU) consequences in the IMPLICATION molecular logic gate, which has been integrated sequentially to procedure a sequential information processing device.

Environmental effects in nitroquinoline derivatives solutions: Solvatochromism, acid-base effect and ion-sensor investigation

Since the first chemical fluorescent sensor reported in 1867, it has often been sought to find intelligent organic molecules that act as chemical sensors of high selectivity and sensitivity. In this process, the colorimetric and fluorescence methods have more advantages, as they are generally very sensitive, low cost, easily executable, versatile and of quick result. Colorimetric receptors containing several chromophores with azo-compounds have been developed since the discovery of chemosensors. Quinoline derivatives attract the interest of the scientific community in this regard. Thus, the present study using a facile synthesis aimed to help in development and behavioural study of new nitroquinolinic compounds against different solvents, pHs and organic/inorganic salts to observe potential recognition of anionic or cationic species. In four compounds a good non-linear fitting between the absorption intensity and amount of acid/base were established. The structural characterization of each of the prepared compounds was carried out with different spectroscopic and spectrometric techniques. UV–Vis and fluorescence measurements were also essential to confirm the binding/interaction process of ionic species and helped to find molecules with potential use in the identification of Co2+ and U2+ species, in addition to showing the sensitivity of species to pH and different solvents. The combination of theory and experiment is able to give a better understanding of the behavior in acidic, basic and neutral medium, DFT calculations were employed for this purpose.

Synthesis and Fluoride Detection Properties of a Coumarin Derivative

A new and simple colorimetric receptor 1 was prepared easily by one-step condensation of 3-acetyl-4-hydroxycoumarin and 8-aminoquinoline. Its absorbance at λ 296 nm significantly increased upon addition of Fe3+ with a turn-on mode. Furthermore, turn-off sensing happened when F– was added to the 1–Fe3+ complex formed in situ. The 1–Fe3+ complex showed high selectivity and low detection limit toward F– ion. Free Schiff base 1 was then given off for recognition Fe3+ again. The reversible “off-on-off” sensing occurred upon sequential addition of Fe3+ and F–.

Colorimetric Receptors for the Detection of Biologically Important Anions and Their Application in Designing Molecular Logic Gate

AbstractThree new colorimetric receptors were synthesised for the detection of biologically important anions such as fluoride and acetate in the aqueous medium. All receptors showed significant colour change for F− and AcO− ions. The synthesised receptors were characterized by spectroscopic methods such as NMR techniques for structural confirmation. The UV‐vis and 1H NMR titrations were performed to understand the binding mechanism of the receptors with F− and AcO− ions. Further, Job's plot was used to explore the stoichiometry between receptor and analyte. Besides, the visual and spectroscopic changes of receptor R1 upon the addition of F− ion was utilised to study the reversible behaviour by adding Cr3+ ions. This concept was explored to mimic the logic gates at the molecular level with “set‐reset” Boolean operations as a proof of concept.

Colorimetric molecular receptors for the sensing of acetate, fluoride and mercury based on Schiff’s bases

The real-time monitoring of biologically relevant anions and mercuric ion concentration in aqueous and physiological media and its quantitative determination across a large concentration range are of vital importance in environmental, health-care issues, industrial and scientific fields. Anion-like fluoride and acetate play an important role in a wide range of chemical and biological systems. This study reports the synthesis of a series of new molecular receptors based on Schiff’s bases by adopting a green strategy. The adopted procedures were simple and less complicated. A new simple colorimetric receptor based on salicylaldehyde Schiff’s bases sharing –OH and C=N moieties as anion binding sites have been successfully synthesized through one-step synthesis, and the sensing studies revealed that the receptors synthesized were found to be an elegant solution to the colorimetric sensing of the anions, especially acetate and fluoride.

Spectroscopic studies of colorimetric receptors for detection of biologically important inorganic F−, AcO− and H2PO4− anions in organo-aqueous medium: Real-life application

Two new 4-nitrobenzylidene based receptors 2-((E)-(((E)-4-nitrobenzylidene) hydrazono) methyl)-1H-indole (R1) and 2-((E)-(((E)-4-nitrobenzylidene)hydrazono)methyl)-1H-pyrrole (R2) have been designed and synthesized by the simple condensation reaction and characterized by using spectroscopic techniques. The receptors exhibited high sensitivity and selectivity towards biologically important anions such as F−, AcO− and H2PO4− in DMSO and sodium salts F−, AcO− and H2PO4− in aqueous medium (9:1 v/v, DMSO: H2O). The receptors R1 and R2 dispensed high sensitivity towards sodium arsenite and detection limit were found to be 0.143 ppm and 0.32 ppm in (9:1 v/v, DMSO: H2O) reflect the stable complex formation of the receptor with AsO2− ion in aqueous medium. 1H NMR titration carried out to understand the nature of interaction between receptor R1 and F− ion. Cyclic voltammetric studies performed for receptors R1 and R2 in DMSO exhibited shift in oxidation and reduction peak with addition of basic F− ion signifying strong interaction between receptors and anions. Interesting, receptor R1 exhibited high selectivity for AcO− ion in the different range of pH from (6–11). Furthermore, receptor R1 and R2 showed colorimetric sensing of F− and AcO− ion present in commercially available toothpaste and vinegar in the form of Na+F− and Na+AcO− in aqueous medium.

Recognition of Cyanide by Urea-Based Bipodal Probe

Two urea based colorimetric receptors were developed. The receptor L showed a exclusive selectivity of cyanide over the other anions in acetonitrile solution and exhibited Intramolecular charge Transfer (ICT). It was studied by UV-vis spectroscopy and their binding ability was explored by using Job’s plot and Benesi-Hildbrand routes. From that the receptor L, it recognize CNanions and it indicates 1:1 stoichiometric ratio and the receptor L 1 (monofluoro substituted) does not recognize any anions. Finally the (difluoro substituted) receptor L shows good sensitivity, selectivity towards cyanide.

Electron Deficient π-hole Assisted Colorimetric Probe for Selective Cyanide Recognition.

Here in, simple and novel electron deficient pi-Hole assisted amide based colorimetric receptor synthesized for cyanide recognition which produce yellow to brownish red color change upon the addition of cyanide in acetonitrile medium. Cyanide has selectively recognized successfully with 1:1 stoichiometric ratio and 1.5523x104 M-1 association constant. Cyanide recognition study was carried out with UV-Vis absorption and FTIR-Analysis and association constant and stoichiometric ratio were calculated by Benasi-Hildebrand plot and job’s continues variation method respectively

Dual mode detection of CN- & Cu2+ using fluorene moiety with logic gate, DFT studies and real sample analysis applications.

A simple colorimetric receptor was synthesized by the condensation of 2-amino fluorene with 2-hydroxy-5-nitrobenzaldehyde and its properties were investigated using colorimetric, fluorescence and DFT studies. The sensing mechanism was ascertained by 1H NMR titration studies. The synthesized receptor showed two-pronged chemosensing properties and exhibited remarkable colorimetric transitions from colorless to yellow in the presence of CN- and colorless to green in the presence of Cu2+ in 80:20 acetonitrile/water medium, which could be determined by naked eye observations. The detection limit of receptor to CN- and Cu2+ ion was found to be 7.9×10-7M and 4.5×10-8M respectively. Receptor was also successfully employed in the construction of molecular INHIBIT and YES logic gates. The synthesized receptor was also efficiently used for real-sample analysis in Finger Millet, also known as Ragi in Tamil. Its scientific name is Eleusine coracana.

Design and synthesis of malonohydrazide based colorimetric receptors for discrimination of maleate over fumarate and detection of F-, AcO- and AsO2- ions.

In this study, we have designed and synthesized two new organic receptors R1 and R2 based on malonohydrazide for the recognition of biologically important anions. The receptor R1 capable of colorimetric discrimination of maleate over fumarate ion, exhibit significant color change from pale yellow to wine red due to intermolecular hydrogen bond between the R1 and maleate ion, supported by 1HNMR titration, where the peak at δ12.0ppm attributed to the NH proton experiences a downfield shift upon binding with maleate ion. Receptor R1, equipped with two electron-withdrawing NO2 moieties as the chromogenic signaling unit enhance the hydrogen bonding tendency and acidity, and thus when comparing with receptor R2, R1 displayed substantial higher redshift (∆λmax) of 148nm, 143nm, and 140nm towards F-, AcO-, and maleate anion in the DMSO. In addition, the synthesized receptors R1 and R2 are able to detect F-, AcO-, and AsO2- ions as their sodium salts in an aqueous solution with visual color change. Receptor R1 exhibit electrochemical response towards F- and AcO- ions. The receptors R1 and R2 are successfully applied for quantitative detection of F- ion in the toothpaste solution in an aqueous medium. Additionally, R1 and R2 exhibit fluorescence enhancement towards F- and AcO- ions in the DMSO. As well, R1 and R2 demonstrate to be potentially useful colorimetric chemosensor for sensing maleate ion using the test strip. The theoretical calculation based on TD-DFT corroborates well with the experimental results of the receptors R1 and R2 with fluoride, acetate and maleate.

Design and synthesis new colorimetric receptors for naked-eye detection of biologically important fluoride and acetate anions in organic and arsenite in aqueous medium based on ICT mechanism: DFT study and test strip application.

Novel three colorimetric anion receptors R1, R2 and R3 have been designed and synthesized via condensation reaction and characterized using IR, MS, and NMR spectroscopic techniques. Anion sensing properties were studied using colorimetric, UV-vis titration, 1H NMR titration, and Cyclic Voltammetric Studies. Comparing the UV-visible titration data of the receptors R1 and R2, R2 showed high redshift (∆λmax) in the mixed competitive solution (DMSO: H2O, 9: 1; v/v) of about 155 nm, 157 nm, 169 nm for Na+F-, Na+AcO-, and Na+AsO2- ions with LOD of 0.23 ppm, 0.18 ppm, and 0.30 ppm, respectively. The observed spectral change of receptor R2 is due to the anion-induced deprotonation of the OH proton, which is confirmed by UV-vis titration, 1HNMR titration, and cyclic voltammetric studies. Theoretical studies via DFT calculation were carried for R1 and R2 to optimize the structure and to explain the anion-binding mechanism. The application of designed receptor R2 was successfully demonstrated for the detection of F- and AsO2- ions using a test strip. The receptors R1 and R2 proved itself to be potentially useful for real-life application by sensing F- and AcO- ions in real samples like toothpaste, mouthwash, vinegar and seawater in a complete aqueous medium.

Simple colorimetric chemosensors for detection F- ion based on phenyl urea derivatives

Abstract Colorimetric receptors 1-[2-(4-nitrobenzylideneamino)phenyl]-3-phenylurea (R1) and 1-[2-(2-hydroxy-5-nitrobenzylideneamino)phenyl]-3-phenylurea (R2) were synthesized and characterized by elemental and spectroscopic methods. Anion sensing behaviour of ssynthesized molecules were analyzed that showed a distinct color change only when treated with fluoride ions (F-) in the naked-eye experiment also supported by electronic spectral titration methods. NMR spectral titration method confirms the hydrogen bond formation between F- with OH and NH protons of R2.

A real-time tripodal colorimetric/fluorescence sensor for multiple target metal ions

In this work we report on the synthesis of a pyridyl/phenolic/benzothiazole functionalized colorimetric receptor (BPAP) that can selectively recognise Fe(III) and Fe(II) ions in aqueous medium with visible, naked eye colour changes. Moreover, BPAP behaves as a ‘turn-on’ fluorescent chemosensor, showing an excellent sensitivity towards Zn2+ and Cd2+ cations in water by exhibiting fluorometric change. BPAP exhibited a visible detection limit of 5.5 μM and 2.5 μM for Fe3+ and Fe2+, respectively, and a fluorometric selectivity towards Zn2+ and Cd2+ ions with lower detection limits of 205 nM and 642 nM. To understand the mode of binding to the sensor, both the nude sensor and the Zn-complex were isolated and characterized by X-ray crystallography. In Zn-BPAP, the ligand acts as neutral tridentate through Npyridine, Namine and Namide donor atoms. The N atom of benzothiazole group and the OH group of the phenole unit are not coordinated. Computational DFT study was performed on the free ligand BPAP and complex with Zn2+ to investigate the interaction site, to calculate the energies of the frontier molecular orbitals and to corroborate some of the experimental results.

Fading of a novel colorimetric receptor after recognizing H2PO4−

A novel selective and sensitive colorimetric receptor 1 (1, 10-phenanthroline-2, 9-dialdehyde bis-(-p-nitrophenylureasemicarbo-hydrazone)) based on urea showing distinctive color fading phenomenon towards H2PO4− ion was reported. Fancifully, the recognition process of receptor 1 to H2PO4− was not interfered by the existence of others anions. We have probed the binding mechanism of 1-H2PO4− that H2PO4− ion induced competitive hydrogen binding process via intramolecular hydrogen-bond by UV–vis, fluorescence, 1H NMR titrations and ESI-MS experiments.

A dipodal molecular probe for naked eye detection of trivalent cations (Al3+, Fe3+and Cr3+) in aqueous medium and its applications in real sample analysis and molecular logic gates.

A simple and low cost multifunctional colorimetric receptor L has been designed, synthesized and characterized by 1H-NMR, IR spectroscopy, ESI-MS spectrometry and elemental analysis. The chemosensor L can selectively detect three biologically and environmentally important trivalent metal ions (Al3+, Fe3+and Cr3+) both visually and spectrophotometrically in CH3CN–H2O (1 : 1, v/v) solution in the presence of other biologically relevant metal ions. The Job's plot analyses indicate the 2 : 2 binding stereochemistry for Al3+, Fe3+ and Cr3+ ions with L, which was further confirmed by 1H-NMR and ESI-MS studies. The binding constant values were found to be 2.9 × 104 M−1 for Al3+, 1.079 × 105 M−1 for Fe3+ and 1.366 × 105 M−1 for Cr3+ respectively. The detections limits of the sensor for Al3+ (2.8 × 10−7 M), Fe3+ (1.9 × 10−7 M) and Cr3+ (2.5 × 10−7 M) are far below than the limit set by the World Health Organization (WHO) for drinking water. Moreover, colorimetric test kits for rapid detection of Al3+, Fe3+, and Cr3+ could be successively applied for all practical purposes, indicating its potential use in environmental samples. It has also been used in building molecular logic gates.

A Naked-Eye Colorimetric Receptor for Anions Based on Nitro Group Featuring with Benzimidazole Unit

A Naked-Eye Colorimetric Receptor for Anions Based on Nitro Group Featuring with Benzimidazole Unit