{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,11]],"date-time":"2026-04-11T06:24:45Z","timestamp":1775888685655,"version":"3.50.1"},"reference-count":34,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2018,7,12]],"date-time":"2018-07-12T00:00:00Z","timestamp":1531353600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>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.<\/jats:p>","DOI":"10.3390\/s18072246","type":"journal-article","created":{"date-parts":[[2018,7,12]],"date-time":"2018-07-12T06:39:59Z","timestamp":1531377599000},"page":"2246","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":43,"title":["Slight pH Fluctuations in the Gold Nanoparticle Synthesis Process Influence the Performance of the Citrate Reduction Method"],"prefix":"10.3390","volume":"18","author":[{"given":"Braulio","family":"Contreras-Trigo","sequence":"first","affiliation":[{"name":"Facultad de Ingenier\u00eda y Tecnolog\u00eda, Universidad San Sebasti\u00e1n, Lientur 1457, Concepci\u00f3n 4080871, Chile"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2343-4712","authenticated-orcid":false,"given":"V\u00edctor","family":"D\u00edaz-Garc\u00eda","sequence":"additional","affiliation":[{"name":"Facultad de Ingenier\u00eda y Tecnolog\u00eda, Universidad San Sebasti\u00e1n, Lientur 1457, Concepci\u00f3n 4080871, Chile"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6589-5667","authenticated-orcid":false,"given":"Enrique","family":"Guzm\u00e1n-Gutierrez","sequence":"additional","affiliation":[{"name":"Facultad de Ciencias de la Salud, Universidad San Sebasti\u00e1n, Lientur 1457, Concepci\u00f3n 4080871, Chile"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6419-1211","authenticated-orcid":false,"given":"Ignacio","family":"Sanhueza","sequence":"additional","affiliation":[{"name":"Departamento de Ingenier\u00eda El\u00e9ctrica, Facultad de Ingenier\u00eda, Universidad de Concepci\u00f3n, Concepci\u00f3n 4030000, Chile"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7501-7785","authenticated-orcid":false,"given":"Pablo","family":"Coelho","sequence":"additional","affiliation":[{"name":"Departamento de Ingenier\u00eda El\u00e9ctrica, Facultad de Ingenier\u00eda, Universidad de Concepci\u00f3n, Concepci\u00f3n 4030000, Chile"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8692-5749","authenticated-orcid":false,"given":"Sebasti\u00e1n E.","family":"Godoy","sequence":"additional","affiliation":[{"name":"Departamento de Ingenier\u00eda El\u00e9ctrica, Facultad de Ingenier\u00eda, Universidad de Concepci\u00f3n, Concepci\u00f3n 4030000, Chile"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6193-9949","authenticated-orcid":false,"given":"Sergio","family":"Torres","sequence":"additional","affiliation":[{"name":"Departamento de Ingenier\u00eda El\u00e9ctrica, Facultad de Ingenier\u00eda, Universidad de Concepci\u00f3n, Concepci\u00f3n 4030000, Chile"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7305-1632","authenticated-orcid":false,"given":"Patricio","family":"Oyarz\u00fan","sequence":"additional","affiliation":[{"name":"Facultad de Ingenier\u00eda y Tecnolog\u00eda, Universidad San Sebasti\u00e1n, Lientur 1457, Concepci\u00f3n 4080871, Chile"}]}],"member":"1968","published-online":{"date-parts":[[2018,7,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2739","DOI":"10.1021\/cr2001178","article-title":"Gold nanoparticles in chemical and biological sensing","volume":"112","author":"Saha","year":"2012","journal-title":"Chem. 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