Work

Study of pH Role in the Green Synthesis of Gold Nanoparticles: From Reduction to Size and Shape Control

Year: 2026

Type: article

Abstract: This study investigates the influence of pH and extract concentration on the green synthesis of gold nanoparticles (AuNPs) using Camellia sinensis extract as a reducing and stabilizing agent. Synthesis was performed at pH 1–12 using undiluted and diluted extracts (2:5 and 1:5). The colloids were characterized by UV–Vis spectroscopy, TEM, SAED, and elemental mapping. Both parameters significantly affected nanoparticle formation, morphology, and optical properties. At extreme pH values and low extract concentrations, AuNP formation was suppressed. The pH range of 3–6 produced diverse morphologies: spherical (~18 nm), triangular (~21 nm), rod-shaped (~25 nm), and anisotropic flower-like structures (~53 nm). At higher pH values, smaller, more uniform spherical nanoparticles formed, including red (~18 nm) and yellow colloids (~6 nm). These changes were reflected in distinct UV–Vis spectra and color variations. Toxicity tests using Chlorella kessleri revealed no inhibition of algal growth. In contrast, selected AuNPs colloids reduced germination and root growth of Sinapis alba, with germination falling below 50% for spherical AuNPs smaller than 18 nm and root length decreasing by more than 60% compared to the positive control. Under the tested conditions, controlled adjustment of pH and extract concentration allows tuning of AuNP properties through a simple green synthesis approach.

Source: Materials

DOI: 10.3390/ma19132780

Authors: Oksana Velgosova, Maksym Lisnichuk, Jesús Hernández-Saz

Institutions: Technical University of Košice, University of Pavol Jozef Šafárik, Institute of Materials Research of the Slovak Academy of Sciences, Universidad de Sevilla

Language: English

Topic: Nanoparticles: synthesis and applications

Subfield: Materials Chemistry

Field: Materials Science

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,137

Funders: Agentúra na Podporu Výskumu a Vývoja, Vedecká Grantová Agentúra MŠVVaŠ SR a SAV