Intriguing Plasmonic and Fluorescence Duality in Copper Nanoparticles
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Intriguing Plasmonic and Fluorescence Duality in Copper Nanoparticles Lady V. Q. Garrido 1 & Josué M. Gonçalves 1 & Júlio C. Rocha 1 & Erick L. Bastos 1 & Henrique E. Toma 1 Vitor M. Zamarion 1
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Received: 21 November 2019 / Accepted: 17 February 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Dendrimeric copper nanoparticles (CuNPs) were prepared by the reduction of [Cu2(CH3CO2)4] with ascorbic acid at 75 °C in the presence of ranelate ions. The metallic nanoparticles exhibited a strong plasmonic band centered at 581 nm, and their average size distribution was typically in the range of 20–30 nm. By adding polyvinylpyrrolidone to the reaction mixture, the growth of the initial copper nanoparticles was hindered. Their sizes were stabilized around 1.8 nm, leading to spherical agglomerates of about 50 nm. Upon green light excitation, the agglomerates exhibited yellow-orange fluorescence emission, keeping the surface plasmon resonance band at 581 nm. This dual behavior suggested the occurrence of collective plasmonic resonance and efficient energy transfer within the agglomerated nanoparticles, in order to account for the observed fluorescence in the system. Keywords Copper nanoparticles . Ranelate CuNPs . Plasmonic-fluorescence . Nanoparticle synthesis . PVP-ranelate-CuNPs
Introduction Copper, silver, and gold nanoparticles exhibit characteristic plasmonic properties associated with the oscillating electrons in resonance with the electric field of light. This phenomenon was first described by Mie about a century ago [1] and rationalized in terms of the difference between the dielectric constants of the metallic nanoparticle and of the surrounding media. Mie’s theory has been used to explain the optical absorption and scattering features of the nanoparticles. Their remarkable colors have been extensively explored in Science and Arts. As nanotechnology evolved, plasmonic effects became quite relevant in chemistry [2–4], physics [5, 6], and medicine [7–9], providing new tools for investigating the interaction of chemical species with metallic nanomaterials, as exemplified by the surface-enhanced Raman spectroscopy or SERS [10, 11]. Considering the three elements, although copper nanoparticles have been of great interest [12], their susceptibility to oxidation can compromise the plasmonic effects, leading to the formation of Cu2O or CuO species. * Henrique E. Toma [email protected] * Vitor M. Zamarion [email protected] 1
Instituto de Química, Universidade de São Paulo, São Paulo 05508-000, Brazil
Blosi et al. [13] have produced CuNPs using alcohols as reducing agents in the presence of microwave irradiation. They have also employed ascorbic acid (AA) and polyvinylpyrrolidone (PVP) as reducing and stabilizing agents, respectively, generating face centered cubic (fcc) CuNPs of about 45–130 nm. Rufus and Philip [14] carried out a microwave-assisted synthesis of CuNPs by using aqueous copper(II) salts, hydrazine, and the extract of guava (Psidium guajava) as reducing and stabilizing
