Abstract
Water pollution caused by hexavalent chromium (Cr(VI)) ions represents a serious hazard for human health due to the high systemic toxicity and carcinogenic nature of this metal species. The optical sensing of Cr(VI) through specifically engineered nanomaterials has recently emerged as a versatile strategy for the application to easy-to-use and cheap monitoring devices. In this study, a one-pot oxidative method was developed for the cage opening of C60 fullerene and the synthesis of stable suspensions of N-doped carbon dots in water–THF solutions (N-CDs-W-THF). The N-CDs-W-THF selectively showed variations of optical absorbance in the presence of Cr(VI) ions in water through the arising of a distinct absorption band peaking at 550 nm, i.e., in the transparency region of pristine material. Absorbance increased linearly, with the ion concentration in the range 1–100 µM, thus enabling visual and ratiometric determination with a limit of detection (LOD) of 300 nM. Selectivity and possible interference effects were tested over the 11 other most common heavy metal ions. The sensing process occurred without the need for any other reactant or treatment at neutral pH and within 1 min after the addition of chromium ions, both in deionized and in real water samples.
Highlights
The pollution of drinking water due to heavy metals (HMs) represents a serious hazard for human health since increasing industrialization, illegal or poor waste dumping practices and, for some metal species, natural occurrence have become worldwide issues
The samples were characterized by FT-IR spectroscopy to determine the type of functional groups present during synthesis and the ensuing post-synthesis addition of THF
The resulting N-CDs-water–THF mixture (W-THF) have a smaller hydrodynamic range compared to N-CDs-W, which is likely due to the strong hydrogen bonding, as determined by IR
Summary
The pollution of drinking water due to heavy metals (HMs) represents a serious hazard for human health since increasing industrialization, illegal or poor waste dumping practices and, for some metal species, natural occurrence have become worldwide issues. Hexavalent chromium (Cr(VI)) is one of the most common water contaminants since it comes from a variety of industrial processes, such as chrome-plating, leather tanning, printing, and pigment production. It is considered very harmful since it can cause damage to multiple organs, even at low concentrations, and it has been classified as a human carcinogen [2]. For this reason, the Guidelines for Drinking-Water Quality by the World Health Organization (WHO) [3] have set the Cr(VI)
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