Turn on fluorescence strip based sensor for recognition of Sr2+ and CN- via lowerrim substituted calix[4]arene and its computational investigation

Construction of coumarin-appended calix[4]arene-based fluorescence sensor for the detection of carbofuran in cabbage

This study presents a novel approach for the detection of carbofuran (CBF) insecticide by systematically exploring a calix[4]arene-derived fluorescence probe, CouC4S, functionalized with two coumarin-labelled cystamine linkages at the narrow edge of the calix[4]arene platform. The proposed method showed a fluorescence "signal - off" effect when CBF binds with CouC4S by quenching the fluorescence intensity of CouC4S. Its limit of detection was as low as 5.55 μM according to the emission study. The working concentration range for this ligand was observed to be up to 5-65 μM. This method could be applied for the on-spot detection of CBF in real samples such as cabbage by spiking CBFvia in situ experiments, which exhibited a limit of detection of 8.823 ppm. For the further confirmation of CouC4S:CBF binding, cyclic voltammetry, differential pulse voltammetry, powder X-ray diffraction, FT-IR spectroscopy, 1H NMR titration, MALDI-TOF and computational investigations were carried out.

Pyrene functionalized oxacalix[4]arene architecture as dual readout sensor for expeditious recognition of cyanide anion

A pyrene functionalized oxacalix[4]arene architecture (DPOC) was utilized as a fluorescence probe for selective recognition of cyanide ions. The receptor DPOC shows excellent selectivity towards cyanide ion with a red shift of 108 nm in absorption band along with a significant change in colour from light yellow to pink. The fluorescence titration experiments further confirm the lower limit of detection as 1.7µM with no significant influences of competing anions. ¹ H-NMR titration experiments support the deprotonation phenomena, as the -NH proton disappears upon successive addition of cyanide ions. The DFT calculation also indicates a certain increment of -NH bond length upon interaction with cyanide ions. The spectral properties as well as colour of DPOC-CN^- system may be reversed upon the addition of Ag⁺/ Cu²⁺ ions up to 5 consecutive cycles. Moreover, DPOC coated "test strips" were prepared for visual detection of cyanide ions.

A versatile enrichment of functionalized calixarene as a facile sensor for amino acids

Amino acids have become the most important part of the human biological system due to their roles in the living processes. Role of amino acids stretches beyond their traditional role as a building block for proteins, deficiency of the same could lead to decreased immunity, digestive problems, depression, fertility issues, lower mental alertness, slowed growth in children, and many other health issues. The acute detection of amino acids is necessary to determine the human health domain. Here in this review, we summarize and study the calixarenes as a complex detailed being of an immeasurable value and its utilization for the amino acids' detection. The key factors responsible such as noncovalent forces, LOD and supramolecular chemistry of calixarenes with amino acids are described well. This study presents the most recent efforts made for the development of potential and highly efficient calixarene based sensors for the detection of amino acids.

Disposable paper-based PET fluorescence probe linked with calix[4]arene for lithium and phosphate ion detection

As a part of our ongoing research, we have synthesized a new fluorescence probe, p-C4A, based on a calix[4]arene substituted with 4-aminoquinoline moieties with amide linkages for lithium and phosphate ions.

A New Benzothiazin-functionalized Calix[4]arene-based Fluorescent Chemosensor for the Selective Detection of Co2+ Ion

Calixarenes, which have a great place in supramolecular chemistry, have become the most prominent macrocyclic compounds in synthetic organic chemistry due to their easy synthesis and functionalization. In this study, p-tert-butyl calix[4]arene dihydrazide derivative was synthesized and then reacted with 3-oxo-3,4-dihydro-2 H-benzo[b][1,4] thiazin-2-ylideneacetyl chloride to prepare new calixarene based chromophore compound 4. The structure of the synthesized compound was elucidated by spectroscopic methods such as ¹H NMR ¹³C NMR and FT-IR spectroscopy. Chromogenic and fluorescence properties of compound 4 were evaluated. It was observed from both studies that compound 4 was Co²⁺ selective and shows fluorescence Switched-off behavior. Stoichiometry, binding constant and the detection limit were calculated. The stoichiometry between compound 4 and Co²⁺ was found to be 1:1. The binding constant value (K) was calculated as 666.67 M^- 1 using Benesi-Hildebrand equation, while the detection limit for Co²⁺ ion was calculated as 0.0465 µM.

A Multi-response Aluminum Metal-organic Frameworks for Fluorescence Sensing of Fe3+, Sr2+, SiO32-and Toluene

A new Aluminum metal-organic frameworks(Al-MOF) based on tricarboxylate ligands(L){L = 2,2',2'-([1,3,5]-triazine-2,4,6-triimino)tribenzoic acid)} has been designed and synthesized. It can be served as a platform of multi-responsive fluorescence sensor for Fe³⁺, Sr²⁺and SiO₃^2-in water, which is mainly due to the significant enhancement effect of these ions on the fluorescence intensity of Al-MOF. Especially, Fe³⁺ions are rarely able to induce MOFs fluorescence enhancement. The limit of detection for three kinds of ions is 6.62* 10^-6M, 5.37* 10^-6M, 6.85* 10^-10M respectively. Meanwhile, It can also be used as a multi-response fluorescence probe to detect toluene in DMF solution, limit of detection is 9.16* 10^-3M respectively. The structure of Al-MOF was characterized by FTIR,¹H NMR, SEM, TAG, PXRD and element analysis. The PXRD showed that the structure of Al-MOF remained the high water stability and pH stability. The application of water samples and vegetables showed that Al-MOF had high sensitive detection for Fe³⁺ions.

A highly sensitive and selective fluorescent turn-on chemosensor bearing a 7-diethylaminocoumarin moiety for the detection of cyanide in organic and aqueous solutions

Novel 7-diethylaminocoumarin based dyes showed high sensitivity and selectivity to cyanide anions in both organic and aqueous solutions, which was observed by a drastic increment in the emission intensity.