Vol.:(0123456789) 1 3 Arabian Journal for Science and Engineering https://doi.org/10.1007/s13369-020-04760-8 RESEARCH ARTICLE-CHEMICAL ENGINEERING Biosynthesized Silver Nanoparticles for Colorimetric Detection of Fe 3+ Ions Deniz Uzunoğlu 1  · Memduha Ergüt 1  · Cemile Gamze Kodaman 1  · Ayla Özer 1 Received: 3 October 2019 / Accepted: 1 July 2020 © King Fahd University of Petroleum & Minerals 2020 Abstract In this study, the biosynthesis and characterization of silver nanoparticles (AgNPs) from orchid tree (Bauhinia variegata) leaf extract were frstly carried out, and then, the usability of AgNPs as a colorimetric sensor for detection of Fe 3+ ions in aqueous solutions was evaluated. The characterization studies showed that the synthesized particles were determined to be AgNPs in nanoscale and face-centered cubic structure. Besides, the total phenolic content of B. variegata extract was determined to be 1.826 ± 2.1 mg gallic acid equivalents/g dry leaf. Also, the biosynthesized AgNPs showed a strong surface plasmon resonance (λ SPR ) around 430 nm and λ SPR intensity decreased with the increasing in Fe 3+ concentration in aqueous solution. Based on the linear relationship between the change of λ SPR intensity and Fe 3+ ion concentration, AgNPs can be used for the sensitive and selective detection of Fe 3+ ions in aqueous solutions with a linear range of 6-100 μM and a detec- tion limit of 2.08 × 10 −6 M. Keywords Bauhinia variegata leaf extract · Biosynthesis · Colorimetric sensor · Detection of Fe 3+ ions · Silver nanoparticles 1 Introduction There is a global threat due to heavy metal pollution since the inception of the industrial revolution. Heavy metals like Zn, Fe, Cu, Pb, Ni, Cd, Hg, etc., are widely processed in many industries like paper industries, pesticides, tanner- ies, metal plating industries, mining operations, etc. The wastewater discharge from these industries causes to vari- ous environmental problems due to its toxic nature. They are also non-biodegradable and enduring components; there- fore, serious health and environmental hazards have been stemmed from the heavy metals in the receiving efuents at even low concentrations [1]. For these reasons, it is crucial to detect and monitor them in both aqueous environmental and biological samples with high sensitivity and selectiv- ity. There are various analytical techniques such as atomic absorption spectrometry [2], inductively coupled plasma mass spectrometry [3], inductively coupled plasma emission spectrometry [4], high-performance liquid chromatography [5], anodic stripping voltammetry [6], adsorptive stripping voltammetry [7], fow injection chemiluminescence mani- fold [8], and UV–visible spectrophotometer [9] for the detec- tion of metal ions. However, these methods usually require sophisticated equipments, technical expertise, and tedious sample preparation steps. Therefore, it is thought that these techniques are not economical and user-friendly. In order to overcome these disadvantages, the colorimetric sensors have been developed for the detection of metal ions in aqueous solutions. Nowadays, especially metallic nanoparticle-based sensors have been widely used for colorimetric detection of metal ions [10–13] due to their strong surface plasmon resonance (SPR), stable dispersion, bio-compatibility, and controllable physical/chemical properties. The principle of colorimetric detection with nanoparticle-based sensors is the same as the spectrophotometric method. However, the ordi- nary spectrophotometric methods required costly and time- consuming steps such as fow injection, synthesis of com- plexing reagents, and sample preparation [9, 11–17]. When these studies were examined in detail, it could be easily seen that these methods required costly and time-consuming steps such as fow injection, synthesis of complexing reagents, and sample preparation although the detection limits were low. Also, the detection time is mostly too long compared * Deniz Uzunoğlu denizuzunoglu4@gmail.com 1 Department of Chemical Engineering, Faculty of Engineering, Mersin University, Mersin 33343, Turkey