Abstract
The chemical interaction between biogenic gold nanoparticles (AuNPs) and several metal (II) ions can be regarded as a practical, twofold, colorimetric, and plasmon resonance sensing method for the recognition of some divalent metal ions in aqueous solutions. The green synthesized AuNPs, using Camellia sinensis as a reducing agent, were characterized by a surface plasmon resonance (SPR) using UV-Vis spectroscopy, infrared spectroscopy, and transmission electron microscopy. The AuNP colloidal solutions obtained have a pink-reddish color with SPRs centered between 529 and 536 nm. AuNPs with spherical, triangular, and hexagonal shapes were found by TEM analyses. Despite their divergent morphologies, these AuNPs can be employed as colorimetric and plasmon resonance sensors for detection of Ca2+, Sr2+, Cu2+, and Zn2+, primarily, in aqueous solutions. Sensibility studies based on molar concentrations were also performed for these metal ions. Furthermore, solid biogenic AuNPs/cellulosic biocomposites were prepared with the aim of developing portable, fast, and dependable colorimetric sensors; nevertheless, these biocomposites resulted to be good adsorbent materials of metal ions.
Highlights
Divalent metal ions are responsible for the accomplishment of a great number of biological reactions in live organisms
The addition of Camellia sinensis extract (0.4 mL) to a 10-3 M HAuCl4 solution led to the appearance of a dark pink color in the solution after 0.5 h of reaction, indicating the formation of AuNPs and the excitation of SP vibration in the NPs (Figure 1(b))
The colloidal solution resulting from the previous experiment was examined by the UV-Vis spectroscopy
Summary
Divalent metal ions are responsible for the accomplishment of a great number of biological reactions in live organisms. Among the noble metal nanoparticles, gold and silver nanoparticles are perhaps the most studied, due to the relatively easy synthesis methods and to their inherent chemical and optical properties [5, 6] These particles can be used in applications such as fabrication of optical devices, surface-enhanced Raman scattering, bioimaging, colorimetric sensors, localized surface plasmon sensing, and fluorescence-enhanced sensors [7]. Biogenic AuNPs were synthesized using a simple one-pot methodology with Camellia sinensis (green tea) extract, as a reducing and capping agent These AuNP colloidal solutions were used as colorimetric and plasmon resonance sensors of different divalent metal ions in aqueous solution: Mg2+, Ca2+, Sr2+, Cu2+,Zn2+, Hg2+, and Pb2+. AuNPs/cellulosic material composites were prepared and tested as potential portable-metal ion sensor
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