Ultrasensitive Copper(II) Detection Using Plasmon-Enhanced and Photo-Brightened Luminescence of CdSe Quantum Dots

Abstract

Here, we present a simple platform for the use of the enhanced emission of 16-mercaptohexadecanoic acid (16-MHA) capped CdSe quantum dots (QDs) as a probe for ultrasensitive copper(II) detection. In this study, the photoluminescence (PL) of the QDs was first enhanced by Ag nanoprisms which were self-assembled on Si surfaces and then further increased by photobrightening. Using this approach, the control and different analytes could be readily probed all on a single platform using fluorescence microscopy. The enhanced PL intensity of CdSe QDs was selectively quenched in the presence of Cu(2+), accompanied by the emergence of a new red-shifted luminescence band. The quenching mechanism was found to be due to a cation exchange mechanism as confirmed by X-ray photoelectron spectroscopy (XPS) measurements. Herein, we have demonstrated that this simple methodology can offer a rapid and reliable detection of Cu(2+) with a detection limit as low as 5 nM and a dynamic range up to 100 muM in a fixed fast reaction time of 5 min. The potential applications of this technique were tested in two ways, for mixed-ion solutions and in physiological fluids, and both experiments exhibited good selectivity toward Cu(2+).

Copper‐Doped CdSe/ZnS Quantum Dots: Controllable Photoactivated Copper(I) Cation Storage and Release Vectors for Catalysis

“…[14][15][16] The oxidation state of Cu in ZnS shells has been discussed for a long time and it has been established that Cu adopts the 1 + oxidation state in ZnS lattices, which was confirmed by our XPS measurements.…”

“…[13] Indeed, QDs have demonstrated high sensitivity towards Cu ions, where the presence of Cu dramatically quenches the QD core photoluminescence. [14][15][16] The oxidation state of Cu in ZnS shells has been discussed for a long time and it has been established that Cu adopts the 1 + oxidation state in ZnS lattices, which was confirmed by our XPS measurements. [17] Herein we show that doping small amounts of Cu into the ZnS QD shell partially quenches the QD core luminescence, but makes QDs photoactivated vectors for the release of catalytically active Cu + ions.…”

Ultrasensitive colorimetric detection of Cu2+ ion based on catalytic oxidation of l-cysteine

“…As seen from Table S1, methods such as ICP-MS (Wu and Boyle, 1997;Dai et al, 2012) and AAS (Chan and Huang, 2000;Lima et al, 2012) can detect Cu 2 þ ion with high sensitivity and selectivity, but they require large-scale instruments and highly trained operators restricting the practical on-site detection. The fluorometry methods also own good selectivity, but they are often troubled with complicated synthesis (Chan et al, 2010;Yu et al, 2011;Yuan et al, 2013;Zhang et al, 2013). The electrochemistry methods show low detection limit and broad linear range, but possibly with the disadvantages of instability and interference of organics in anodic/catholic stripping voltammetry (Liu et al, 1999;Salaun and van den, Berg, 2006;Lin et al, 2012).…”

“…Methods such as ICP-MS (Wu and Boyle, 1997;Dai et al, 2012) and AAS (Chan and Huang, 2000;Lima et al, 2012) can detect Cu 2 þ ion with high sensitivity and selectivity but with requirements of large instruments. Compared with electrochemical techniques (Liu et al, 1999;Salaun and van den Berg, 2006;Lin et al, 2012) and fluorescence methods (Chan et al, 2010;Yu et al, 2011;Yuan et al, 2013;Zhang et al, 2013) are much simpler with detection by naked eyes and UV-vis spectroscopy (Lou et al, 2011;Liu et al, 2013;Shen et al, 2013;Wang et al, 2014). However, till now, the reported colorimetric methods usually present higher detection limit and cannot easily accomplish real samples analysis.…”

Rapid Photoluminescence Quenching Based Detection of Cu2+ in Aqueous Medium by CdS Quantum Dots Surface Passivated by Thiourea

“…[29][30][31] Though various semiconductor type probes (e.g., CdSe, CdTe, CdSe/ZnS) were developed for highly sensitive detection of Cu 2+ ions but selectivity in the presence of Hg 2+ and Pb 2+ is not well documented. 31,32 It may be remarked that our surface passivated CdS QDs satisfied the required sensitivity and selectivity for Cu 2+ ion detection in the presence of almost all relevant cations and anions as interfering agents that simulate drinking water or groundwater composition. However, in our recent study we have demonstrated that the probe is highly sensitive to uranyl ion detection at sub parts per billion (ppb) concentrations (i.e., less than 1 μg/L).…”