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

VIOLI, IANINA LUCILA; MARTINEZ, LUCIANA PAULA; GARGIULO, JULIAN; STEFANI, FERNANDO D

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

Pacific Basin Societies

Due to their low quantum yield, plasmonicnanoparticles (NPs) photoluminescence (PL) is usually a little exploitedproperty. However, as in scattering spectroscopy, the resonance frequency andwidth of their PL spectra depends on the NPs composition, shape, size, and itsenvironment.In this work, light-assisted growth ofindividual Au NPs was performed controlling their final size through real-timemeasurement of Stokes PL spectra. Au NPs having 60nm in diameter were firstdeposited onto glass through optical printing.1-4 This techniqueallows to deposit colloidal NPs in specific positions of a substrate, creatingordered arrays. In this way, the automated localization of individual NPs issimplified. Each optically printed NP was then used as seeds to obtain largerNPs by plasmon-assisted reduction of aqueous HAuCl4 using a 532 nmlaser focused on its diffraction limit (see a scheme of the process in FigureA).5 The irradiation and Stokes PL acquisition during the growth wasfully automated through a Python routine. As the nanoparticles grow, their PLmaximum redshifts in a similar way as their scattering spectrum does (seeFigure B). Therefore, by monitoring the PL maximum it is possible to stop thereaction by simply selecting their final value. This was done for several equivalentNPs in a range of 550 - 585 nm in 5 nm steps. When the set PL maximum wasreached, corresponding to a defined NP size, the reaction was automaticallystopped. As an example, the PL spectra for five different NPs is shown when theselected target is 570 nm in Figure C. PL and scattering spectra werecorrelated, shedding light also in the open question on the equivalency of theobserved signals. It is envisioned that this work can also beapplied to finely fabricate more complex systems like bimetallic NPs,monitoring the growth of different shells like Pd or Pt on optically printedNPs.