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Sensors 2018, 18(7), 2246; https://doi.org/10.3390/s18072246

Slight pH Fluctuations in the Gold Nanoparticle Synthesis Process Influence the Performance of the Citrate Reduction Method

1
Facultad de Ingeniería y Tecnología, Universidad San Sebastián, Lientur 1457, Concepción 4080871, Chile
2
Facultad de Ciencias de la Salud, Universidad San Sebastián, Lientur 1457, Concepción 4080871, Chile
3
Departamento de Ingeniería Eléctrica, Facultad de Ingeniería, Universidad de Concepción, Concepción 4030000, Chile
*
Author to whom correspondence should be addressed.
Received: 4 June 2018 / Revised: 4 July 2018 / Accepted: 5 July 2018 / Published: 12 July 2018
(This article belongs to the Section Biosensors)
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Abstract

Gold nanoparticles (AuNPs) are currently under intense investigation for biomedical and biotechnology applications, thanks to their ease in preparation, stability, biocompatibility, multiple surface functionalities, and size-dependent optical properties. The most commonly used method for AuNP synthesis in aqueous solution is the reduction of tetrachloroauric acid (HAuCl4) with trisodium citrate. We have observed variations in the pH and in the concentration of the gold colloidal suspension synthesized under standard conditions, verifying a reduction in the reaction yield by around 46% from pH 5.3 (2.4 nM) to pH 4.7 (1.29 nM). Citrate-capped AuNPs were characterized by UV-visible spectroscopy, TEM, EDS, and zeta-potential measurements, revealing a linear correlation between pH and the concentration of the generated AuNPs. This result can be attributed to the adverse effect of protons both on citrate oxidation and on citrate adsorption onto the gold surface, which is required to form the stabilization layer. Overall, this study provides insight into the effect of the pH over the synthesis performance of the method, which would be of particular interest from the point of view of large-scale manufacturing processes. View Full-Text
Keywords: gold nanoparticles; citrate reduction method; pH-effect; concentration gold nanoparticles; citrate reduction method; pH-effect; concentration
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Contreras-Trigo, B.; Díaz-García, V.; Guzmán-Gutierrez, E.; Sanhueza, I.; Coelho, P.; Godoy, S.E.; Torres, S.; Oyarzún, P. Slight pH Fluctuations in the Gold Nanoparticle Synthesis Process Influence the Performance of the Citrate Reduction Method. Sensors 2018, 18, 2246.

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