title: 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.
authors.affiliation: Dept. of Food Engineering, Trakya Univ, 22180, Edirne, Turkey.
authors.forename: Pelin Onsekizoglu
authors.initials: PO
authors.lastname: Bagci
authors.affiliation: Dept. of Biological Systems Engineering, Univ. of Wisconsin-Madison, 460 Henry Mall, Madison, WI, 53706, U.S.A.
authors.forename: Yi-Cheng
authors.initials: YC
authors.lastname: Wang
authors.affiliation: Dept. of Biological Systems Engineering, Univ. of Wisconsin-Madison, 460 Henry Mall, Madison, WI, 53706, U.S.A.
authors.forename: Sundaram
authors.initials: S
authors.lastname: Gunasekaran
mesh_terms: D019343:Citric Acid; D003116:Color; D003124:Colorimetry / Q000379:methods*; D003246:Conservation of Energy Resources; D003545:Cysteine / Q000032:analysis* / Q000737:chemistry; D000067030:Fruit and Vegetable Juices; D006046:Gold / Q000737:chemistry; D007477:Ions; D057230:Limit of Detection; D027845:Malus / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry; D019216:Metals, Heavy; D008903:Minerals; D010084:Oxidation-Reduction; D059629:Signal-To-Noise Ratio; D013696:Temperature
chemical_list: D007477:Ions; D019216:Metals, Heavy; D008903:Minerals; D019343:Citric Acid; D006046:Gold; D003545:Cysteine
keywords: amino acid; apple juice; colorimetric sensor; gold nanoparticles; green synthesis