Selective colorimetric and fluorescence ‘turn-on’ sensor for Ag + and in-situ sensing of CN − (off–on-off) via displacement approach

A fluorescence sensor for thiram detection based on DNA-templated silver nanoclusters without metal ion-mediator

In this work, we firstly found a strong competitive interaction between thiram and silver atoms of DNA-templated silver nanoclusters (DNA-AgNCs), leading to fluorescence quenching of DNA-AgNCs without additional metal ion-mediator. Furthermore, this thiram-induced fluorescence quenching phenomenon was used to develop a sensor for thiram detection. This fluorescence sensor exhibited good linearity with thiram concentration from 0.20 to 2.0 μM and 0.012-0.20 μM under optimized conditions, with a low detection limit of 0.2 μM and 0.01 μM, respectively. Moreover, this sensor showed superior selectivity towards thiram, and its practicability was verified in apples and soil. This study provides a convenient and rapid "mix and detect" approach for thiram detection within 10 min, suggesting its potential for rapid on-site evaluation of thiram in real samples.

Single Organic Ligands Act as a Bifunctional Sensor for Subsequent Detection of Metal and Cyanide Ions, a Statistical Approach toward Coordination and Sensitivity

The detection of key ions in environmental samples has garnered significant attention in recent years in the pursuit of a cleaner environment for living organisms. Bifunctional and multifunctional sensors, as opposed to single-species sensors, have emerged as a rapidly developing field. Many reports in the literature have documented the use of bifunctional sensors for the subsequent detection of metal and cyanide ions. These sensors, consisting of simple organic ligands, form coordination compounds with transition metal ions, resulting in clear visible or fluorescent changes that facilitate detection. In some cases, a single polymeric material can act as a ligand and coordinate with metal ions, forming a complex that serves as a sensor for cyanide ion detection in biological and environmental samples through various mechanisms. Nitrogen is the most dominant coordinating site in these bifunctional sensors, with the sensitivity of the sensors being directly proportional to the denticities of ligands for metal ions, while for cyanide ions the sensitivity was found independent of the denticity of the ligands. This review covers the progress made in the field over the past fifteen years (2007-2022), with most ligands detecting copper (II) and cyanide ions, but with the capability to detect other metals such as iron, mercury, and cobalt as well.

Medicinal importance and chemosensing applications of Schiff base derivatives for the detection of metal ions: A review

Schiff bases, named after Hugo Schiff, are formed when primary amine reacts with carbonyl compounds (aldehyde or ketone) under specific conditions. Schiff bases are economical, simple synthetic routes, and easily accessible in laboratories. They have medicinal and biological applications such as antiviral, antioxidant, antifungal, anticancer, anthelmintic, antibacterial, antimalarial, anti-inflammatory, antiglycation, anti-ulcerogenic, and analgesic potentials. A number of Schiff bases are reported for the detection of various metal ions. They are also used as catalysts, polymer stabilizers, intermediates in organic synthesis, and corrosion inhibitors. In this review, we have highlighted the recent advancements in the development of bioactive Schiff base derivatives and their sensing applications for detecting metal cations. Additionally, various spectroscopic techniques for structural characterization, such as X-ray diffraction analysis (XRD), FT-IR, UV-vis, and NMR spectroscopy were also discussed.

A Review on Organic Fluorimetric and Colorimetric Chemosensors for the Detection of Ag(I) Ions

Organic compounds display several electronic and structural features which enable their application in various fields, ranging from biological to non-biological. These compounds contain heteroatoms like sulfur, nitrogen and oxygen, which provide coordination sites to act as ligands in the field of coordination chemistry and are used as chemosensors to detect various metal ions. This review article covers different organic compounds including thiourea, Schiff base, pyridine, thiophene, coumarin, triazolyl pyrenes, imidazole, fluorescein, thiazole, tricarbocyanine, rhodanine, porphyrin, hydrazone, benzidine and other functional groups based chemosensors, that contain heteroatoms like sulfur, nitrogen and, oxygen for fluorimetric and colorimetric detection of Ag+ in different environmental, agricultural, and biological samples. Further, the sensing mechanism and performances of these chemosensors have been discussed, which could help the readers for the future design of highly efficient, selective, and sensitive chemosensors for the detection and determination of Ag+ ions.

Silver ions involved fluorescence "on-off" responses of gold nanoclusters system for determination of carbendazim residues in fruit samples

Herein, a fluorescence "on-off" system was developed for monitoring carbendazim (CBZ) residues in fruit samples, based on glutathione-gold nanoclusters (GSH-Au NCs) and silver ions (Ag⁺). First, the fluorescence intensity of GSH-Au NCs was greatly enhanced (turn on) with aggregation-induced emission enhancement (AIEE) effect in the presence of Ag⁺, then fluorescence quenching occurred (turn off) with adding CBZ by the chelation between CBZ and Ag⁺. The quenching degree was well linearly dependent on CBZ concentration covering from 0.5 to 20 μM. Moreover, the GSH-Au NCs-Ag⁺ system exhibited superior selectivity towards CBZ and was sensitive for the determination of CBZ in apple and orange juices with a low detection limit of 0.12 μM. The recoveries of CBZ spiked in fruit samples ranged from 81.0 % to 111.4% with the relative standard deviations less than 6.6%, demonstrating its great potential for monitoring CBZ residues in fruit samples.

Recent Development in Coordination Compounds as a Sensor for Cyanide Ions in Biological and Environmental Segments

Rapid detection of toxic ions has taken great attention in the last few decades due to its importance in maintaining a greener environment for human beings. The extreme toxicity of cyanide (CN-) ions is a great environmental concern as its continued industrial use generates interest in facile and sensitive methods for CN- ions detection. Since CN- ions act as a ligand in coordination chemistry which rapidly coordinates with suitable metals and forms complexes, this ability was mainly explored in its detection. It also attacks the central metal in coordination compounds and gives a fluorimetric response. Coordination compounds behave as a sensor for the detection of important ions like CN- ions and have gained great attention due to their facile synthesis, multianalyte detection, clear detection and low detection limit. Recently, considerable efforts have been devoted to the detection and quantification of hazardous multianalyte using a single probe. Cu2+ complexes are the main complexes used for CN- ions detection; however, the complexes of many other metals are also used as sensors. Four basic types of interaction have been discussed in coordination compound sensors for CN- detection. The performances of different sensors are compared with one another and the sensors which have the lowest detection limit are highlighted. This review comprises the progress made by coordination compounds as sensors for the detection of CN- ions in the last six years (2015-2021). To the best of our knowledge, there is no review on coordination compounds as a sensor for CN- ions during this period. [Figure: see text].

Bifunctional single-labelled oligonucleotide probe for detection of trace Ag(I) and Pb(II) based on cytosine-Ag(I)-cytosine mismatches and G-quadruplex

A novel bifunctional oligonucleotide (OND) probe with single fluorescent group HEX labelled at 5'-end was designed for detecting trace Ag(I) and Pb(II) in real samples. In the presence of Ag(I), the hairpin structure originating from Ag(I) induced cytosine-Ag(I)-cytosine mismatches causes the proximity of the HEX to the consecutive guanine bases (G)₄ at 3'-terminal, resulting in the fluorescence quenching of the HEX. While in the presence of Pb(II), the G-quadruplex structure originating from two G-quartet planes by the intramolecular hydrogen bond with Pb(II) also causes the HEX approaching the (G)₄ terminal and consequently the fluorescence quenching. The results showed the quantitative detection of trace Ag(I) and Pb(II) both in the linear response ranges of 1.0-20.0 × 10^-9 mol L^-1 with no visible interferences of other 11 metal ions observed. And the detection limits were 82 × 10^-12 mol L^-1 for Ag(I), 92 × 10^-12 mol L^-1 for Pb(II), respectively. The fluorescence quenching mechanism of the (G)₄ to HEX was verified to be the photoinduced electron transfer in the aspect of thermodynamics. This method provided a feasible application for sensitive and selective detection of Pb(II) and Ag(I) in water and Chinese traditional herbs with convenient operation.

A new chromogenic and fluorescent chemosensor based on a naphthol-bisthiazolopyridine hybrid: a fast response and selective detection of multiple targets, silver, cyanide, sulfide, and hydrogen sulfide ions and gaseous H2S

A novel chemosensor 1 based on a naphthol-bisthiazolopyridine hybrid was synthesized and characterized. Among the various screened cations and anions, chemosensor 1 selectively recognized Ag+ and CN- ions by relying on the color change and distinct absorption and emission changes. Moreover, the probe 1·Ag+ was well operable for the selective monitoring of S2-, HS- and H2S as evidenced by the different color and optical changes. The selective detection of all the anions was simply based on the breakage of the intramolecular hydrogen bonding of 1, followed by the protonation or deprotonation mechanism. In general, chemosensor 1 is a promising indicator in terms of its ease-of-use, selectivity, sensitivity, and rapid response (<1 s). Moreover, the visual detection and concentration determination of these analytes by solution or solid kits are the advantages for the practical applications of this sensor.

A Water-Soluble Fluorescent Probe for the Selective Sensing of Ag+ and its Application in Imaging of Living Cells and Nematodes

In this study, an imidazole-coumarin based fluorescent probe was developed for the selective and sensitive detection of Ag⁺ in aqueous solution. Using a combination of Job plot, NMR titrations, and DFT calculations, the binding properties between Ag⁺ and the probe were deeply investigated, and the results revealed a 1:1 binding stoichiometry between the probe and Ag⁺ with a binding constant of 1.02 × 10⁶ M^-1. The detection limit was found to be 150 nM, which satisfies the requirement for the quantitative detection of Ag⁺ in real water samples. Moreover, the new probe, Ic, was successfully applied to sense Ag⁺ in HeLa and HepG2 cells as well as in C. elegans, indicating that it could be a useful tool for the environmental monitoring of Ag⁺ pollution. These results demonstrated that Ic could serve as a high-efficiency and low-cost fluorescent probe for tracking Ag⁺ in an aquatic environment and biological organisms.

Copper Complex-Embedded Vesicular Receptor for Selective Detection of Cyanide Ion and Colorimetric Monitoring of Enzymatic Reaction

Detection of environmentally important ion cyanide (CN^-) has been done by a new method involving displacement of both metal and indicator, metal indicator displacement approach (MIDA) on the vesicular interface. Terpyridine unit was selected as the binding site for metal (Cu²⁺), whereas Eosin-Y (EY) was preferred as an indicator. About 150 nm sized nanoscale vesicular ensemble (Lip-1.Cu) has shown good selectivity and sensitivity for CN^- without any interference from other biologically and environmentally important anions. Otherwise, copper complexes are known for the interferences of binding with phosphates and amino acids. The Lip-1.Cu nanoreceptor also has the possibility to be used for real-time colorimetric scanning for the released HCN via enzymatic reactions. Lip-1.Cu has several superiorities over the other reported sensor systems. It has worked in 100% aqueous environment, fast response time with colorimetric monitoring of enzymatic reaction, and low detection limit.

A phenanthro[9,10-d]imidazole-based AIE active fluorescence probe for sequential detection of Ag+/AgNPs and SCN- in water and saliva samples and its application in living cells

Ag⁺ and SCN^- play extremely important roles in the fields of the physiology and environment. In this work, on the basis of phenanthro[9,10-d]imidazole derivative (DIPIP) which can exhibit the aggregation-induced emission (AIE) properties in aqueous solution, we achieved a sequential on-off-on switch for Ag⁺ and SCN^- with high selectivity and sensitivity. A remarkable fluorescence quenching effect of Ag⁺ on the probe DIPIP was observed with 1:2 stoichiometry, Subsequently, the fluorescence intensity of in situ generated DIPIP-Ag⁺ ensemble was easily switched on after the interaction between Ag⁺ and SCN^-, which was attributed to the stronger affinity of SCN^- to capture Ag⁺. In particular, the extreme limits of detection (LOD) for Ag⁺ and SCN^- in standard solutions were as low as to be 74.5 nM and 7.8 nM, respectively. Furthermore, the probe DIPIP and the DIPIP-Ag⁺ ensemble could be used to detect Ag⁺ in the real water and SCN^- in smoker saliva samples, respectively. In addition, the sequential "on-off-on" fluorescence mode of DIPIP to Ag⁺ and SCN^- were also successfully applied in living HeLa cells.