Colorimetric Detection Based on Localized Surface Plasmon Resonance Optical Characteristics for Sensing of Mercury Using Green-Synthesized Silver Nanoparticles
Eman Alzahrani
Abstract
Development of selective colorimetric detectors that can use green-fabricated silver nanoparticles’ (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mrow><mml:mtext>AgNPs</mml:mtext></mml:mrow></mml:math>) with localized surface plasmon resonances (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mrow><mml:mtext>LSPRs</mml:mtext></mml:mrow></mml:math>) to rapidly, simply, and selectively detect <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mrow><mml:mtext>Hg</mml:mtext><mml:mfenced open="(" close=")" separators="|"><mml:mrow><mml:mtext>II</mml:mtext></mml:mrow></mml:mfenced></mml:mrow></mml:math> ions was undertaken in this study. Onion extract was used for synthesising photo-induced green crystalline silver nanoparticles (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M4"><mml:mrow><mml:mtext>NPs</mml:mtext></mml:mrow></mml:math>). The formation of nanoparticles is enhanced when ultrasound irradiation is present; bioligands could serve as stabilizing and reducing agents. Different methods of measurement, including UV-Vis, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M5"><mml:mrow><mml:mtext>TEM</mml:mtext><mml:mo>,</mml:mo><mml:mrow><mml:mrow><mml:mtext>SEM</mml:mtext></mml:mrow><mml:mo>/</mml:mo><mml:mrow><mml:mtext>EDAX</mml:mtext></mml:mrow></mml:mrow><mml:mo>,</mml:mo></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M6"><mml:mrow><mml:mtext>FT</mml:mtext><mml:mo>−</mml:mo><mml:mtext>IR</mml:mtext></mml:mrow></mml:math>, and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M7"><mml:mrow><mml:mtext>XRD</mml:mtext></mml:mrow></mml:math>, are effective for characterization of nanoparticles. The spherical nature of green-fabricated <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M8"><mml:mrow><mml:mtext>AgNPs</mml:mtext></mml:mrow></mml:math> is confirmed by TEM. High-density, spherical, and uniformly formed silver nanoparticle shapes were found in silver nanoparticle SEM images. The arrangement of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M9"><mml:mrow><mml:mtext>AgNPs</mml:mtext></mml:mrow></mml:math> in the form of face-centered cubic structures was confirmed by <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M10"><mml:mrow><mml:mtext>XRD</mml:mtext></mml:mrow></mml:math> patterns. The formation of impurity-free <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M11"><mml:mrow><mml:mtext>AgNPs</mml:mtext></mml:mrow></mml:math> was confirmed using the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M12"><mml:mrow><mml:mtext>EDAX</mml:mtext></mml:mrow></mml:math> analysis results. <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M13"><mml:mrow><mml:msup><mml:mrow><mml:mtext>Hg</mml:mtext></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> with excellent sensitivity was sensitively and selectively detected by employing green-synthesized silver nanoparticles. The reduction of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M14"><mml:mrow><mml:mtext>Ag</mml:mtext></mml:mrow></mml:math> (1) to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M15"><mml:mrow><mml:mtext>Ag</mml:mtext></mml:mrow></mml:math> (0) was confirmed by a slight increase in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M16"><mml:mrow><mml:mtext>Hg</mml:mtext></mml:mrow></mml:math> (II) concentration and progressive reduction of green-synthesized <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M17"><mml:mrow><mml:mtext>AgNPs</mml:mtext></mml:mrow></mml:math>, whose absorbance changed abruptly. The reduction of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M18"><mml:mrow><mml:mtext>LSPRs</mml:mtext></mml:mrow></mml:math> by the phosphate buffer medium enables <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M19"><mml:mrow><mml:mtext>AgNPs</mml:mtext></mml:mrow></mml:math> to sensitively and selectively detect <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M20"><mml:mrow><mml:msup><mml:mrow><mml:mtext>Hg</mml:mtext></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> ions by providing good environment. Besides, a selective, sensitive, simple, and rapid method that is proposed for detecting <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M21"><mml:mrow><mml:mtext>Hg</mml:mtext></mml:mrow></mml:math> (II) ions in samples of water is presented in the study. Harmful mercury ions in real samples of water (tap and ground water) can colorimetrically and selectively be detected using the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M22"><mml:mrow><mml:mtext> AgNPs</mml:mtext></mml:mrow></mml:math>. The results showed an RSD of below 6% and over 92% of good recovery.