In-situ monitoring of gold nanoparticles plasmon-assisted growth using their photoluminescence emission

IANINA L. VIOLI; MARTINEZ, LUCIANA PAULA; GARGIULO, JULIAN; FERNANDO STEFANI

Pacifichem

Congreso; 2021 International Chemical Congress of Pacific Basin Societies; 2021

Pacifichem

Due to their low quantum yield, plasmonic nanoparticles (NPs) photoluminescence (PL) is usually a little exploited property. However, as in scattering spectroscopy, the resonance frequency and width of their PL spectra depends on the NPs composition, shape, size, and its environment.In this work, light-assisted growth of individual Au NPs was performed controlling their final size through real-time measurement of Stokes PL spectra. Au NPs having 60nm in diameter were first deposited onto glass through optical printing.1-4 This technique allows to deposit colloidal NPs in specific positions of a substrate, creating ordered arrays. In this way, the automated localization of individual NPs is simplified. Each optically printed NP was then used as seeds to obtain larger NPs by plasmon-assisted reduction of aqueous HAuCl4 using a 532 nm laser focused on its diffraction limit (see a scheme of the process in Figure A).5 The irradiation and Stokes PL acquisition during the growth was fully automated through a Python routine. As the nanoparticles grow, their PL maximum redshifts in a similar way as their scattering spectrum does (see Figure B). Therefore, by monitoring the PL maximum it is possible to stop the reaction by simply selecting their final value. This was done for several equivalent NPs in a range of 550 - 585 nm in 5 nm steps. When the set PL maximum was reached, corresponding to a defined NP size, the reaction was automatically stopped. As an example, the PL spectra for five different NPs is shown when the selected target is 570 nm in Figure C. PL and scattering spectra were correlated, shedding light also in the open question on the equivalency of the observed signals. It is envisioned that this work can also be applied to finely fabricate more complex systems like bimetallic NPs, monitoring the growth of different shells like Pd or Pt on optically printed NPs.