Abstract
We report a visual detection of Cr(VI) ions using silver-coated gold nanorods (AuNR@Ag) as sensing probes. Au NRs were prepared by a seed-mediated growth process and AuNR@Ag nanostructures were synthesized by growing Ag nanoshells on Au NRs. Successful coating of Ag nanoshells on the surface of Au NRs was demonstrated with TEM, EDS, and UV–vis spectrometer. By increasing the overall amount of the deposited Ag on Au NRs, the localized surface plasmon resonance (LSPR) band was significantly blue-shifted, which allowed tuning across the visible spectrum. The sensing mechanism relies on the redox reaction between Cr(VI) ions and Ag nanoshells on Au NRs. As the concentration of Cr(VI) ions increased, more significant red-shift of the longitudinal peak and intensity decrease of the transverse peak could be observed using UV–vis spectrometer. Several parameters such as concentration of CTAB, thickness of the Ag nanoshells and pH of the sample were carefully optimized to determine Cr(VI) ions. Under optimized condition, this method showed a low detection limit of 0.4 μM and high selectivity towards Cr(VI) over other metal ions, and the detection range of Cr(VI) was tuned by controlling thickness of the Ag nanoshells. From multiple evaluations in real sample, it is clear that this method is a promising Cr(VI) ion colorimetric sensor with rapid, sensitive, and selective sensing ability.
Highlights
Cr(III) and Cr(VI) are two main modes of chromium occurrence in aqueous solutions and Cr(III) is one of the essential trace elements in metabolism of glucose and lipids in human body [1]
Au and Ag nanoparticles (NPs) are being actively used in visual assays due to their unique optical response which is often called as localized surface plasmon resonance (LSPR) [29,30,31,32,33]
Due to the anisotropic morphology of the Au NRs, the dipole plasmon resonance is split into a transverse plasmon absorption at 532 nm and a longitudinal plasmon absorption at longer wavelength of 774 nm (Fig. 1a)
Summary
Cr(III) and Cr(VI) are two main modes of chromium occurrence in aqueous solutions and Cr(III) is one of the essential trace elements in metabolism of glucose and lipids in human body [1]. Chen et al developed an Au NP-based colorimetric assay for Cr(VI) ions detection using the coordinate covalent bond between meso-2,3-dimercaptosuccinic acid-Au NPs and Cr(VI) [41] This sensor is accessible for on-site application through translation of the colorimetric signal into the digital signal using a smartphone but still requires procedures for the modification of nanoparticles. Real samples were tested to confirm the practicability and the results proved that our sensor has good performance in terms of selectivity, sensitivity, linearity, and low limit of detection This is due to the high extinction coefficient of AuNR@Ag and the signal amplification effect of Ag nanoshells [44,45,46]. The longitudinal plasmon resonance of AuNR@Ag was blue-shifted as the deposited Ag nanoshells becomes thicker, which could be lead to apparent multicolor change
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
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 callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
