Abstract
Citric acid capped CdS quantum dots (CA-CdS QDs), a new assembled fluorescent probe for copper ions (Cu2+), was synthesized successfully by a simple hydrothermal method. In this work, the fluorescence sensor for the detection of heavy and transition metal (HTM) ions has been extensively studied in aqueous solution. The results of the present study indicate that the obtained CA-CdS QDs could detect Cu2+ with high sensitivity and selectivity. It found that the existence of Cu2+ has a significant fluorescence quenching with a large red shifted (from greenish-yellow to yellowish-orange), but not in the presence of 17 other HTM ions. As a result, Cu2S, the energy level below the CdS conduction band, could be formed at the surface of the CA-CdS QDs and leads to the quenching of fluorescence of CA-CdS QDs. Under optimal conditions, the copper ions detection range using the synthesized fluorescence sensor was 1.0 × 10‒8 M to 5.0 × 10‒5 M and the limit of detection (LOD) is 9.2 × 10‒9 M. Besides, the as-synthesized CA-CdS QDs sensor exhibited good selectivity toward Cu2+ relative to other common metal ions. Thus, the CA-CdS QDs has potential applications for detecting Cu2+ in real water samples.
Highlights
Copper, a cofactor in many important enzymes, is one of the essential trace elements for the various pathological and physiological activities in the human body [1,2,3]
The Mapping and EDS were measured by filter which was soaked in CA-CdS quantum dots (QDs) solution
The results suggest that citric acid successfully decorated the surface of CdS QDs
Summary
A cofactor in many important enzymes, is one of the essential trace elements for the various pathological and physiological activities in the human body [1,2,3]. Despite the deficiency in copper in the body potentially resulting in a variety of health problems [6,7], excess copper can cause various health problems such as eczema, kidney disease, gastrointestinal diseases, and damage to serious nervous diseases [8,9,10,11,12,13,14]. The high concentration of copper ions on the water can cause great influence on aquatic organisms. What’s more, copper pollution has become a serious environmental issue due to the discharge of industrial wastewater containing copper (II) ions to surface water [15]. The U.S Environmental Protection Agency (EPA) action level for Nanomaterials 2019, 9, 32; doi:10.3390/nano9010032 www.mdpi.com/journal/nanomaterials
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
