Conformation-mediated Förster resonance energy transfer (FRET) in blue-emitting polyvinylpyrrolidone (PVP)-passivated zinc oxide (ZnO) nanoparticles

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• 作者：Hasan Kurt^a ; Ece Alpaslan^a ; ¹ ; Burç ; in Yildiz^a ; Alpay Taralp^a ; Cleva W. Ow-Yang^a ; ^b ; ^{cleva@sabanciuniv.edu}
• 关键词：PVP ; polyvinylpyrrolidone ; FRET ; Fö ; rster resonance energy transfer ; NMR ; nuclear magnetic resonance ; DLS ; dynamic light scattering ; PL/PLE ; photoluminescence emission and excitation
• 刊名：Journal of Colloid and Interface Science
• 出版年：2017
• 出版时间：15 February 2017
• 年：2017
• 卷：488
• 期：Complete
• 页码：348-355
• 全文大小：4384 K
• 卷排序：488

文摘

Homopolymers, such as polyvinylpyrrolidone (PVP), are commonly used to passivate the surface of blue-light emitting ZnO nanoparticles during colloid nucleation and growth. However, although PVP is known to auto-fluoresce at 400 nm, which is near the absorption edge of ZnO, the impact of PVP adsorption characteristics on the surface of ZnO and the surface-related photophysics of PVP-capped ZnO nanoparticles is not well understood. To investigate, we have synthesized ZnO nanoparticles in solvents containing PVP of 3 concentrations—0.5, 0.7, and 0.11 g mL−1. Using time-domain NMR, we show that the adsorbed polymer conformation differs with polymer concentration—head-to-tail under low concentration (e.g., 0.05 g mL−1) and looping, then train-like, with increasing concentration (e.g., 0.07 g mL−1 and 0.11 g mL−1, respectively). When the surface-adsorbed PVP is entrained, the surface states of ZnO are passivated and radiative emission from surface trap states is suppressed, allowing emission to be dominated by exciton transitions in the UV (ca. 310 nm). Moreover, the reduced proximity between the PVP molecule and the ZnO gives rise to increased efficiency of energy transfer between the exciton emission of ZnO and the HOMO-LUMO absorption of PVP (ca. 400 nm). As a result, light emission in the blue is enhanced in the PVP-capped ZnO nanoparticles. We thus show that the emission properties of ZnO can be tuned by controlling the adsorbed PVP conformation on the ZnO surface via the PVP concentration in the ZnO precipitation medium.