title: New Chitosan-Thiomer: An Efficient Colorimetric Sensor and Effective Sorbent for Mercury at Ultralow Concentration.
abstract: This paper describes an innovative procedure for the fabrication of a facile colorimetric sensor in one step with thiol functional group for Hg(2+) detection at trace level. The sensor was successfully synthesized via chitosan isothiouronium salt intermediate with innocuous low cost thiourea reagent under microwave irradiation. It is an innovative green approach to achieve thiol functionalization with a high degree of substitution. Thiomer was characterized by titrimetry, FTIR, (1)H NMR, elemental analysis (CHNS), and EDX for extent of modification with detail structure. The synthesized and well characterized thiomer was screened for sensor application. The sensing solution of thiomer resulted in an instantaneous sharp color change from colorless, yellow, to brown with increase in Hg(2+) concentration. Chitosan thiomer also exhibited high sensitivity and selectivity for Hg(2+) over other possible interfering ions in aqueous media. The sensing responses were visualized quantitatively with quick response, good selectivity, high sensitivity, and a low detection limit of ∼0.465 ppb by the naked eye. The same was tested with a paper strip method for technological applications. Furthermore, the as-prepared sensors also exhibited exceptional sorption potential for Hg(2+) even from ultralow concentration aqueous solution and reduced the Hg(2+) concentration from 10 ppb to the extremely low level of ∼0.04 ppb as studied by cyclic voltammetry. Thus, the proposed method is simple, promising, and rapid without any complicated modifying step and is an economical alternative to traditional Hg(2+) sensors for rapid sensor application in environmental water samples at ppb levels.
authors.affiliation: Department of Chemistry, Shoolini University , Solan 173229, India.
authors.forename: Kalpana
authors.initials: K
authors.lastname: Chauhan
authors.affiliation: Department of Chemistry, Shoolini University , Solan 173229, India.
authors.forename: Prem
authors.initials: P
authors.lastname: Singh
authors.affiliation: Analytical Chemistry Division, Bhabha Atomic Research Center , Mumbai 4000085, India.
authors.forename: Rakesh Kumar
authors.initials: RK
authors.lastname: Singhal
mesh_terms: D000327:Adsorption; D048271:Chitosan / Q000737:chemistry*; D003124:Colorimetry / Q000295:instrumentation / Q000379:methods*; D004563:Electrochemistry; D009682:Magnetic Resonance Spectroscopy; D008628:Mercury / Q000032:analysis*; D012996:Solutions; D013052:Spectrometry, X-Ray Emission; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013997:Time Factors
chemical_list: D012996:Solutions; D013438:Sulfhydryl Compounds; D048271:Chitosan; D008628:Mercury
keywords: chitosan thiomer; colorimetric sensor; paper strip method; sorption potential; ultralow concentration