Tunable Photoluminescence of Ag Nanocrystals in Multiple-Sensitive Hybrid Microgels

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• 作者：Weitai Wu ; Ting Zhou ; Shuiqin Zhou
• 刊名：Chemistry of Materials
• 出版年：2009
• 出版时间：July 14, 2009
• 年：2009
• 卷：21
• 期：13
• 页码：2851-2861
• 全文大小：1130K
• 年卷期：v.21,no.13(July 14, 2009)
• ISSN：1520-5002

文摘

We report here fluorescent pH-sensitive hybrid materials based on the in situ immobilization of Ag and Ag/Au bimetallic nanoparticles (NPs) in the interior of multiple sensitive copolymer microgels of poly(N-isopropylacrylamide-co-acrylic acid-co-acrylamide) with polyacrylamide fragments serving as stabilizing ligands. Temperatures corresponding to the swollen, partially swollen, and nearly collapsed states of the template microgels were respectively applied for loading and in situ chemical reduction of Ag⁺ ions to control the size and size distribution of the Ag NPs in the microgels. Au nanoclusters were stably grown on the surface of Ag NPs through a galvanic replacement reaction between Ag and AuCl₄⁻. The pH-sensitive optical properties of hybrid microgels embedded with either Ag NPs or Ag/Au bimetallic NPs were systematically investigated. The gradual protonization of poly(acrylic acid) fragments shrank the microgels, resulting in an enhancement of photoluminescence (PL) intensity and a blue shift of the emission maximum of the Ag NPs. The surface modification of small Ag NPs with Au nanoclusters reduced the pH sensitivity of PL property changes but dramatically enhanced the PL signals in the near-infrared regime of the hybrid microgels. The method presented here opens a new door in the synthesis of materials with pH-responsive optical properties for biomedical applications.