Iron ions (Fe3+) is one of the most hazardous metals found in the water supply. The contamination of that metal originated from the corrosion process of pipes and cracks from waste disposal sites. High levels of iron would affect a bad impact to the environment. The current study aimed to synthesize silver nanoparticles (AgNPs) for heavy metals detection using a method which depends on colorimetric and optical changes. The approach to synthesize AgNPs adapted from polyol reduction method, i.e. by mixing polyvinyl alcohol (PVA), sodium chloride (NaCl) and silver nitrate (AgNO3). The colorimetric response of AgNPs to Fe3+ ions was observed visually and measured quantitatively by a spectroscopic method using a UV-Vis spectrophotometer. This work shows that the colloidal AgNPs were sensitive to identify Fe3+ ions.
The detection of chemical pollution in an ecosystem requires rapid and accurate analysis in the field. The method presented here can help minimize preparation time and simple detection of the metal ions. Silver nanoparticles are known for their surface plasmon resonance characteristics that visibly display distinctive colors; this makes it possible to develop as colorimetric indicators. In this study, silver nanoparticles were synthesized on paper using velvet apple (Diospyros discolor Willd.) leaf extract as the Ag+ reducing agent. The paper was immersed in the water extract for 1 hour and for 24 hours. The formation of silver nanoparticles was indicated by the change in the paper’s color from white to light brown and dark brown. Furthermore, the paper was tested using several types of metal ions, namely, Cu2+, Mn2+, Pb2+, Zn2+, Mg2+, Ni2+ and Co2+. For all types of metal ions, the paper’s color changed selectively while detecting Cu2+ ions. The paper-based silver nanoparticles were sensitive enough to detect Cu2+ ions starting at concentrations of 100 mg/L. The Transmission Electron Microscope (TEM) revealed that the silver nanoparticles tended to aggregate after the addition of Cu2+ ions, which caused changes in the size and LSPR of the nanoparticles. This potential method needs further refinement and development to enhance the sensitivity of the paper-based colorimetric indicator, so that it can detect Cu2+ at lower concentrations.
Detection of the heavy metal presence in an environment requires a rapid and facile method. Silver nanoparticles (AgNPs) can be develop as colorimetric indicator related to their unique characteristics of its LPSR properties. In this research, biosynthetically AgNPs using Diospyros discolor leaf extract used as a colorimetric indicator for detecting Hg2+ ions. The solution color changes that occur when detecting the analyte was observed. The characterization was performed using a UV-Vis spectrophotometer to study changes in the LSPR spectrum of silver nanoparticles when detecting the presence of Hg2+ ions. In addition, the image analysis from Transmission Electron Microscope (TEM) was carried out to determine the shape and size of the AgNPs. The results obtained indicate that there was a tendency for the solution color change from brown to light-brown when AgNPs interact with Hg2+ ions at 500-1000 mg. L−1. This result showed that without modification the biosynthesized AgNPs tend to be selective and sensitive to the presence of Hg2+ ions.
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