A thiophene-linked terpyridine based phenanthridine chemoreceptor for Cd and Cr selective ratiometric fluorescence detection in environmental water and rice samples.

Background: The studied materials, Cadmium (Cd) and Chromium (Cr) are highly toxic, and it focuses on investigating various environmental sources, such as industrial processes and waste water. When quantities of Cr and Cd 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 Cr and Cd ions.

Results: We created a newly designed luminous TPTP sensor based on intramolecular charge transfer (ICT). TPTP sensor probe specifically determined Cr and Cd ions with an immediate colour shift from cyan to green and orange in CHCN: HO (6:4) solvent solution. The permissible level set by the Environmental Protection Agency (EPA) of the United States for the presence of Cr and Cd 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 Cr and Cd ions in an environmental system using a ratiometric methodology. In addition, TPTP was used to determine the concentration of Cr and Cd ions in natural water and food samples. Fluorescent bio-imaging studies revealed that the present sensor TPTP could identify Cr and Cd 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.