A Simple and Green Route for Room‐Temperature Synthesis of Gold Nanoparticles and Selective Colorimetric Detection of Cysteine

Abstract

Gold nanoparticles (AuNPs) were synthesized at room temperature following a simple, rapid, and green route using fresh-squeezed apple juice as a reducing reagent. The optimal AuNPs, based on the particle color, stability, and color change suitable for colorimetric detection of cysteine (Cys), are synthesized using 5 mL of 10% apple juice, 1 mL of 10 mM gold precursor solution, and 1 mL of 0.1 M NaOH. Under this set of parameters, the AuNPs are synthesized within 30 min at room temperature. The average size (11.1 ± 3.2 nm) and ζ potential (-36.5 mV) of the AuNPs synthesized were similar to those of AuNPs prepared via the conventional citrate-reduction method. In the presence of Cys, unlike with any other amino acid, the AuNPs aggregated, possibly due to the gold-sulfur covalent interaction, yielding red-to-purple color change of the sample solution. The red-shift of the localized surface plasmon resonance peak of the AuNPs responsible for the color change was recorded by UV-vis spectrometer. The effect of other potential interferents such as glucose, ascorbic acid, K(+) , Na(+) , Ca(2+) , Zn(2+) , Ag(+) , Ni(2+) , Cu(2+) , Co(2+) , and Hg(2+) were also examined. The results show that AuNPs can be used to selectively detect and measure Cys with a linear dependency in the range of 2 to 100 μM and a limit of detection (signal-to-noise ratio > 3) of 50 nM. The results suggest that the green-synthesized AuNPs are useful for simple, rapid, and sensitive colorimetric detection of Cys, which is an essential amino acid in food and biological systems.

Biopolymer/gold nanoparticles composite plasmonic thermal history indicator to monitor quality and safety of perishable bioproducts

“…Alginate is a non-toxic, biocompatible, and inexpensive polysaccharide; it is widely used in pharmaceutical and biomedical applications (Boland et al 2007;Xu et al 2010). The AuNPs are highly biocompatible and possess distinct surface plasmon properties (Bagci et al 2015;Ghosh et al 2008;Guan et al 2015;Lu et al 2016;Wang et al 2015b;Wei et al 2015;Zhang et al 2015). Furthermore, our results indicate, contrary to Einstein-Batchelor viscosity law, that in situ synthesis of AuNPs in alginate solution lowers its viscosity, as had been reported for some other polymeric solutions with nanoparticles addition (Jain et al 2008;Mangal et al 2015).…”

Chitosan-capped gold nanoparticles for indicating temperature abuse in frozen stored products

“…Biological methods for nanoparticle synthesis using microorganisms, enzymes, vitamins, sugar, and biodegradable polymers of plant or animal origin have been suggested as possible ecofriendly alternatives to chemical and physical methods. 2,3…”

Facile Synthesis of Gold Nanoparticles with Alginate and Its Catalytic Activity for Reduction of 4-Nitrophenol and H2O2 Detection

“…Studies have reported that many natural compounds, such as those derived from fungi, algae, bacteria, and plants, were used in green synthesis of AuNPs [7,8,9,10]. These natural compounds-mediated procedures for synthesis of AuNPs represent advantages over conventional chemical and physical methods, as they are simply, low-cost, energy-efficient, and nontoxic green routes [11,12,13,14]. In this regard, we focused our attention on natural polysaccharide extracted from seaweed, which is a proven source of bioactive compounds [15].…”