RESEARCH PAPER Development of a new colorimetric assay for detection of bisphenol-A in aqueous media using green synthesized silver chloride nanoparticles: experimental and theoretical study Shiva Khalililaghab 1 & Safieh Momeni 2 & Maryam Farrokhnia 2 & Iraj Nabipour 2 & Sadegh Karimi 1 Received: 1 November 2016 /Revised: 13 January 2017 /Accepted: 26 January 2017 /Published online: 8 February 2017 # Springer-Verlag Berlin Heidelberg 2017 Abstract In the present study, a cost-effective, green and sim- ple synthesis method was applied for preparation of stable silver chloride nanoparticles (AgCl-NPs). The method was done by forming AgCl-NPs from Ag + ions using aqueous extract of brown algae (Sargassum boveanum) obtained from the Persian Gulf Sea. This extract served as capping agent during the formation of AgCl-NPs. Creation of AgCl-NPs was confirmed by UV–visible spectroscopy, powder X-ray diffraction, energy-dispersive X-ray spectroscopy, and high- resolution transmission electron microscopy, while the mor- phology and size analyses were characterized using high- resolution transmission electron microscopy and dynamic light scattering. After optimization of some experimental con- ditions, particularly pH, a simple and facile system was devel- oped for the naked-eye detection of bisphenol-A. Moreover, a theoretical study of AgCl interaction with bisphenol-A was performed at the density functional level of theory in both gas and solvent phases. Theoretical results showed that elec- trostatic and van der Waal interactions play important roles in complexation of bisphenol-A with AgCl-NPs, which can lead to aggregation of the as-prepared AgCl-NPs and results in color change from specific yellow to dark purple, where a new aggregation band induced at 542 nm appears. The absor- bance at 542 nm was found to be linearly dependent on the bisphenol-A concentration in the range of 1 × 10 −6 –1× 10 −4 M, with limit of detection of 45 nM. In conclusion, ob- tained results from the present study can open up an innova- tive application of the green synthesis of AgCl-NPs using brown algae extract as colorimetric sensors. Keywords Silver chloride nanoparticle . Green synthesis . Bisphenol-A . Colorimetric detection . Brown algae . Density functional theory Introduction Metal nanoparticles (NPs) have attracted much attention due to their unique optical properties which originate from charge density oscillations [1, 2]. These optical properties which are referred to as localized surface plasmon resonance (LSPR) have wide applications in bio-sensing [3], catalysis [4], cel- lular imaging [5], cancer clinical diagnosis [6], and cell targeting and therapy [7]. Hence, several strategies have been reported in the literature for preparation of nanoparticles com- prising wet chemical approach [8], mechanical preparation [9], photochemical synthesis [10], and electrochemical methods [11]. However, the most commonly used procedure among the aforementioned ones is the wet chemical method, in which chemical reducing reagents are employed such as citrate [12, 13], hydroxylamine hydrochloride [14], and NaBH 4 [15]. These conventional methods of nanoparticle synthesis have their own weakness and drawbacks. First of all, most of them are expensive and often produce unstable nanoparticles; hence, surfactants should be used [ 16]. Moreover, Murphy and Wyatt [17] indicate that using surfac- tant might introduce certain unfavorable cytotoxic effects. Electronic supplementary material The online version of this article (doi:10.1007/s00216-017-0230-0) contains supplementary material, which is available to authorized users. * Sadegh Karimi karimi.sadegh@gmail.com; sakarimi@pgu.ac.ir 1 Department of Chemistry, College of Science, Persian Gulf University, Bushehr, Iran 2 The Persian Gulf Marine Biotechnology Research Center, The Persian Gulf Biomedical Sciences Research Institute, Bushehr University of Medical Sciences, Bushehr 7514763448, Iran Anal Bioanal Chem (2017) 409:2847–2858 DOI 10.1007/s00216-017-0230-0