A dual-functional chemical sensor for the detection of Cu2+ and Cd2+ based on the photochromic diarylethene

A thiophene-linked terpyridine based phenanthridine chemoreceptor for Cd2+ and Cr3+ selective ratiometric fluorescence detection in environmental water and rice samples

BACKGROUND

The studied materials, Cadmium (Cd2+) and Chromium (Cr3+) are highly toxic, and it focuses on investigating various environmental sources, such as industrial processes and waste water. When quantities of Cr3+ and Cd2+ exceed the allowable limit, biological toxicity and hazardous environmental pollution are unavoidable. In order to address this problem, we introduce 5-(5-(4-([2,2':6',2″-terpyridin]-4'-yl) phenyl) thiophen-2-yl)-7,8,13,14-tetrahydrodibenzo [a,i] phenanthridine (TPTP), a dual-emission response chemosensor that employs a colorimetric and fluorescence turn-on approach for the rapid, sensitive, and discriminate detection of Cr3+ and Cd2+ ions.

RESULTS

We created a newly designed luminous TPTP sensor based on intramolecular charge transfer (ICT). TPTP sensor probe specifically determined Cr3+ and Cd2+ ions with an immediate colour shift from cyan to green and orange in CH3CN: H2O (6:4) solvent solution. The permissible level set by the Environmental Protection Agency (EPA) of the United States for the presence of Cr3+ and Cd2+ ions in drinking water was higher than the detection level of 3.5 and 9.7 nM, by this sensor respectively. NMR titrations, HRMS, and theoretical calculation methods were employed to examine the accurate sensing processes of TPTP and complexes.

SIGNIFICANCE

This is an effective method of detecting Cr3+ and Cd2+ ions in an environmental system using a ratiometric methodology. In addition, TPTP was used to determine the concentration of Cr3+ and Cd2+ ions in natural water and food samples. Fluorescent bio-imaging studies revealed that the present sensor TPTP could identify Cr3+ and Cd2+ ions inside living HeLa cells. A paper kit analysis has been done on TPTP, which has a time-to-result of less than 1 s and offers a cost-effective assay. As a result, the platform offers portability.

Configuration of super-fast Cu2+-responsive chemosensor by attaching diaminomaleonitrile to BODIPY scaffold for high-contrast fluorescence imaging of living cells

A highly fluorescent Cu2+-responsive sensor, 2-amino-3-(BODIPYmethyleneamino)maleonitrile (BD) was constructed by attaching diaminomaleonitrile to a BODIPY scaffold. Cu2+ can be selectively recognized on a 2-s time-scale by way of fluorescence emission. When Cu2+ and BD coexist in solution, typical BODIPY emission was observed and the emission intensity could be increased to 334 times that of the blank dye solution. The mechanism of fluorescence increase is based on the generation of highly fluorescent species by Cu2+-triggered oxidative cyclization of the attached diaminomaleonitrile. The absolute fluorescence quantum yield (AFQY) of the cyclization product is 98% determined by integrating sphere. The highly emissive character can be attributed to the imidazole ring and dicarbonitrile on the BODIPY scaffold. It surpasses the meso-phenyl substituted analogue in AFQY and detection limits (DL). The specific Cu2+ recognition behavior was also validated in Hela cells with high-contrast fluorescence images.

A biphenyl thiosemicarbazide based fluorogenic chemosensor for selective recognition of Cd2+: application in cell bioimaging

A diversified biphenyl thiosemicarbazide based chemosensor (HBMC) has been fabricated and reported for the specific detection of Cd2+ in a MeOH : H2O (4 : 1) solution. We observed a chromogenic change from colorless to light yellow colour, and it showed a "turn-on" fluorogenic change from non fluorescent to blooming cyan colour. In fluorometric titration a sharp "turn-on" emission for Cd2+ was observed with a ∼16 fold increase in fluorescence intensity value at 496 nm by incremental addition of Cd2+ ions in the MeOH : H2O (4 : 1) solution. The reversibility of the chemosensor (HBMC) was confirmed by a sequential addition of the EDTA solution. Again the binding stoichiometry of HBMC with Cd2+ was found to be 2 : 1, as confirmed by Job's plot analysis and HRMS spectra of the HBMC-Cd2+ complex. The mechanism for Cd2+ sensing in MeOH : H2O (4 : 1) is based upon the inhibition of CN isomerization and ESIPT process and simultaneously turning on the CHEF (chelation enhanced fluorescence) process. The limit of detection for Cd2+ was found to be in the order of 10-8 (M), which implies that HBMC is an efficient probe to detect Cd2+ at the microscopic level. A reusability study was performed and on-sight detection of cadmium ions by the chemosensor (HBMC) was established by dip-stick experiment. In vitro detection of Cd2+ in human breast cancer cells (MDA-MB-231) by HBMC discloses its cell permeability and biocompatible nature. Computational studies (DFT and TDDFT) with the probe HBMC and HBMC-Cd2+ complex were also performed.

A novel phenanthridine and terpyridine based D-π-A fluorescent probe for the ratiometric detection of Cd2+ in environmental water samples and living cells

A "turn-on" Donor-π-Acceptor (D-π-A) containing phenanthridine-functionalized extended π-conjugate terpyridine, 5-(4'-([2,2':6',2''-terpyridin]-4'-yl)-[1,1'-biphenyl]4-yl)7,8,13,14-tetrahydrodibenzo [a, i] phenanthridine (TBTP) was synthesised. It shows strong selectivity for the detection of toxic Cd²⁺ without interference from other metal ions. In the presence of Cd²⁺, the absorption of the TBTP changes dramatically along with the fluorescent emission with the large Stokes shift of 6300 cm^-1. When the compound TBTP is exposed to UV light, its colour changes from blue to orange over the addition of Cd²⁺. Adding other transition metal ions has no effect. This is based on the mechanism of intramolecular charge transfer. The detection limit for Cd²⁺ was found to be around 1.181 × 10^-8 M. An investigation of the sensing mechanism includes job plot, NMR titration, DFT calculation, and HRMS analyses. Excitingly, the recognition of Cd²⁺ in CH₃CN: H₂O (8:2, v/v) medium is quantitative without interference from Zn^2+, which is a common interferent for Cd²⁺. Furthermore, the probe was used for detecting Cd²⁺ in real water samples and cell imaging in living cells was also performed.