Plasma-Liquid Interactions for Morphology Fine-Tuning of Functional Nanoparticles

Abstract

Plasma-activated water (PAW) is a promising, sustainable alternative to conventional wet-chemical reduction methods for synthesizing functional nanoparticles without the need for hazardous chemicals. Plasma-induced liquid chemistry generates reactive species (depending on the choice of gas) that facilitate nanoparticle formation and growth and offers advantages such as shorter synthesis times, tunable particle size and shape, and functionalization with both hydrophilic and hydrophobic groups. [1,2] However, this method is still in its early stages, and little research has demonstrated control over AuNP formation in terms of size, shape, and colloidal stability. In this report, we present results that help bridge this gap by revealing an interplay between (i) the concentration of reactive species that drive water’s redox potential (controlled via the plasma jet by varying treatment time, power, and flow) and (ii) the Au precursor concentration. Using this approach, the size of well-faceted, polyhedral AuNPs can be readily tailored over the 20–120 nm range. Shorter treatment durations yield PAW with lower ROS concentrations, favoring slower reaction kinetics and the growth of larger particles. Conversely, longer plasma treatment produces PAW with higher ROS concentrations, enabling faster reaction rates and the synthesis of consistently smaller nanoparticles. This ability to control nanoparticle size and morphology via a plasma-based approach provides versatile AuNP tuning with tailored LSPR properties [3], without the need for stabilizing agents that can suppress nanoparticle performance, paving the way for applications in catalysis, biomedicine and plasmon-based sensor technology. References: 1. Patel, J., Němcová, L., Maguire, P., Graham, W. G., & Mariotti, D. (2013). Synthesis of surfactant-free electrostatically stabilized gold nanoparticles by plasma-induced liquid chemistry. Nanotechnology , 24 (24), 245604. 2. Kortshagen, U. R., Sankaran, R. M., Pereira, R. N., Girshick, S. L., Wu, J. J., & Aydil, E. S. (2016). Nonthermal plasma synthesis of nanocrystals: fundamental principles, materials, and applications. Chemical reviews , 116 (18), 11061-11127. 3. Olenik, J., Shvalya, V., Modic, M., Vengust, D., Cvelbar, U., & Walsh, J. L. (2024). Microplasma Controlled Nanogold Sensor for SERS of Aliphatic and Aromatic Explosives with PCA-KNN Recognition. ACS sensors , 10 (1), 387-397.