Plasmon-Mediated Reduction of Aqueous Platinum Ions: The Competing Roles of Field Enhancement and Hot Charge Carriers

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• 作者：Nam Hoon Kim ; Carl D. Meinhart ; Martin Moskovits
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：March 31, 2016
• 年：2016
• 卷：120
• 期：12
• 页码：6750-6755
• 全文大小：324K
• ISSN：1932-7455

文摘

Plasmonic nanosystems can enhance photochemical processes taking place in their neighborhood on account of several plasmonically mediated processes, among them: (i) the enhancement of the optical fields in the vicinity of the nanosystem and (ii) the intervention of energetic electrons and/or holes in the redox chemistry of nearby molecules pursuant to plasmon excitation and decay. We describe a series of experiments in which tetrachloroplatinate anions are reduced to zerovalent Pt at the surface of gold nanoparticles and nanoparticle assemblies. We demonstrate that the spatial pattern of deposited Pt cannot be understood in terms of enhanced fields alone but likely involves hot electrons whose momenta are initially aligned with the electric vector of the polarized light used to excite plasmons but become randomized on account of electron–electron interactions and scattering within the metallic nanoparticles before the electrons’ energy is substantially thermalized. These conclusions are supported by numerical computations of the local electromagnetic fields scattered by gold nanoparticles, using a finite element approach. SERS measurements, carried out concurrently with the photoreduction, suggest that PtO₂ is at least one of the oxidation products formed in the oxidation reaction(s) countervailing the above reduction reaction.