title: Highly selective and sensitive recognition of cobalt(II) ions directly in aqueous solution using carboxyl-functionalized CdS quantum dots as a naked eye colorimetric probe: applications to environmental analysis.
abstract: Quantum dots (QDs) are usually used as fluorescent probe, and they are difficult to use in colorimetric detection. However, in this report carboxyl-functionalized CdS (COF-CdS) QDs were synthesized in aqueous solution for colorimetric detection following a classic method. On the basis of inducing the aggregation of COF-CdS QDs, a simple naked eye colorimetric method with high sensitivity and selectivity was developed for the sensing of Co(2+) ions in aqueous solutions. The Co(2+) ions induced COF-CdS QDs results in a marked enhancement of the UV-vis absorption spectra at 360 nm, and the process was accompanied by a visible color change from colorless to yellowish brown within 5 min, which proves a sensitive detection of Co(2+) ions. The sensing of Co(2+) ions can therefore be easily achieved by a UV-vis spectrophotometer or even by the naked eye. Under the optimized circumstances, this method yields excellent sensitivity (LOD = 0.23 μg mL(-1)) and selectivity toward Co(2+) ions. The calibration plot of (A - A(0)) at 360 nm against concentration of Co(2+) ions was linear over the range from 0.5 to 14 μg mL(-1) with a correlation coefficient of 0.9996. The accuracy and reliability of the method were further ascertained by recovery studies via standard addition method with percent recoveries in the range of 99.63-102.46%. The plausible mechanism for the color change reaction has also been discussed. Our attempt may provide a cost-effective, rapid, and simple solution for the inspection of Co(2+) ions in the presence of a complex matrix from environmental aqueous samples.
authors.affiliation: Fluorescence Spectroscopy Research Laboratory, Department of Chemistry, Shivaji University, Kolhapur-416 004, Maharashtra, India.
authors.forename: Anil H
authors.initials: AH
authors.lastname: Gore
authors.forename: Dattatray B
authors.initials: DB
authors.lastname: Gunjal
authors.forename: Mangesh R
authors.initials: MR
authors.lastname: Kokate
authors.forename: Vasanthakumaran
authors.initials: V
authors.lastname: Sudarsan
authors.forename: Prashant V
authors.initials: PV
authors.lastname: Anbhule
authors.forename: Shivajirao R
authors.initials: SR
authors.lastname: Patil
authors.forename: Govind B
authors.initials: GB
authors.lastname: Kolekar
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry; D003035:Cobalt / Q000032:analysis*; D003124:Colorimetry; D005456:Fluorescent Dyes / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D045663:Quantum Dots; D013056:Spectrophotometry, Ultraviolet; D013440:Sulfides / Q000737:chemistry; D013997:Time Factors; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D019187:Cadmium Compounds; D005456:Fluorescent Dyes; D007477:Ions; D013440:Sulfides; D014874:Water Pollutants, Chemical; C034939:cadmium sulfide; D014867:Water; D003035:Cobalt