Abstract:
This work reports a label-free, ultrasensitive, and
selective optical chemosensory system for trace level detection of
selenite (SeO3
2−), the most toxic form of selenium, in water. The
probe, i.e., carbon quantum dots (CQDs), is designed from citric acid
by means of pyrolysis and is interfaced with a newly synthesized
nitrogen-rich ligand to create a selective sensor platform (functionalized
CQDs, fCQDs) for selenite in a water matrix. Spectral (NMR,
UV−vis, photoluminescence, Raman, and Fourier transform infrared
analyses) and structural (high-resolution transmission electron
microscopy) characteristics of the designed new probe were
investigated. The developed sensor exhibits high sensitivity (limit of
detection = 0.1 ppb), a wide detection range (0.1−1000 ppb range,
relative standard deviation: 3.2%), and high selectivity even in the
presence of commonly interfering ions reported to date, including Cl−,
NO3
−, NO2
−, Br−, F−, As(V), As(III), Cu2+, Pb2+, Cd2+, Zn2+, Sr2+, Rb2+, Na+
, Ca2+, Cs+
, K+
, Mg2+, Li+
, NH4
+
, Co2+, etc. The
observed selectivity is due to designed ligand characteristics in terms of strong Se−N chemistry. Ultrafast spectroscopic analysis
of the fCQDs in the absence and presence of selenite was studied to understand the sensing mechanism. The sensor was
successfully exemplified for real water samples and exhibits comparative performance to conventional ion channel
chromatography as well as flame atomic absorption spectroscopy for selenite analysis. The promising results pave ways for
realization of a field deployable device based upon a developed probe for selenite quantification in water.
