Contents lists available at ScienceDirect Colloids and Surfaces A journal homepage: www.elsevier.com/locate/colsurfa Rapid colorimetric detection of mercury using biosynthesized gold nanoparticles Nafisa Zohora a,1 , Dipesh Kumar a,1 , Mahdieh Yazdani b , Vincent M. Rotello b , Rajesh Ramanathan a, ⁎ , Vipul Bansal a, ⁎ a Ian Potter NanoBioSensing Facility, NanoBiotechnology Research Laboratory (NBRL), School of Science, RMIT University, GPO Box 2476, Melbourne, VIC 3000, Australia b Department of Chemistry, University of Massachusetts Amherst, 710 North Pleasant Street, Amherst, MA 01003, United States GRAPHICAL ABSTRACT ARTICLE INFO Keywords: Biosynthesis Gold nanoparticles Plant Hg 2+ ion Sensing SPR ABSTRACT There is an increasing focus on expanding the applicability of biologically synthesized nanomaterials. Herein, we show the use of Cinnamomum tamala (cinnamon) leaf extract for the synthesis of gold nanoparticles with con- trollable optical properties. This ability to synthesize optically tunable AuNPs was exploited for the detection of mercuric ions (Hg 2+ ) by capitalizing upon the amalgamation tendency of mercury with gold. The changes in both the longitudinal and transverse plasmon absorption bands of gold nanoparticles (AuNPs) suggest the po- tential of using both of these SPR features either independently using traditional analyses or in combination using discriminant analysis for the detection of mercury in aqueous media. Minimal cross-reactivity with other environmentally relevant metal ions confirms that the change in the optical property is exclusively due to the strong amalgamation of mercury and gold. Natural plant-based esters were found to act as capping agents during biological synthesis of AuNPs, and the involvement of these esters during Hg 2+ ions sensing revealed underlying mechanistic processes. http://dx.doi.org/10.1016/j.colsurfa.2017.04.036 Received 1 March 2017; Received in revised form 18 April 2017; Accepted 18 April 2017 ⁎ Corresponding authors. 1 These authors contributed equally. E-mail addresses: rajesh.ramanathan@rmit.edu.au (R. Ramanathan), vipul.bansal@rmit.edu.au (V. Bansal). Colloids and Surfaces A 532 (2017) 451–457 Available online 21 April 2017 0927-7757/ © 2017 Elsevier B.V. All rights reserved. MARK