Institute of Materials Research and Engineering, The Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, #08-03, Innovis, 138634, Singapore.
School of Materials Science & Engineering, Nanyang Technological University, Nanyang Avenue, 639798, Singapore.
Mater Sci Eng C Mater Biol Appl. 2020 Apr;109:110525. doi: 10.1016/j.msec.2019.110525. Epub 2019 Dec 5.
Photoluminescent noble metal nanoclusters (NCs, core size <2 nm) have recently emerged as a new type of photosensitizers advantageous over conventional photosensitizers due to their high singlet oxygen (O) generation efficiency, excellent photostability and water solubility, as well as good biocompatibility for photodynamic therapy and bioimaging. However, no correlation has been established between the intrinsic O generation and photoluminescence properties of metal NCs with their size, composition, and concentration, which is important to customize the molecule-like properties of NCs for different applications. Herein, we report a systematic study to uncover the rational design of bimetallic NCs with controllable O generation efficiency by tuning their compositions through spontaneous galvanic displacement reaction. A series of ultrasmall gold/silver alloy nanoclusters (AuAgNCs) were synthesized by reacting bovine serum albumin (BSA) protein-protected AgNCs (13 Ag atoms/cluster) with varying concentrations of gold precursor at room temperature. It was found that the O generation efficiency of the resultant BSA-protected AuAgNCs were inversely correlated to their photoluminescence intensity. Interestingly, plasmonic gold nanoparticles (>10 nm) were also formed simultaneously by photobleaching of the BSA-AuAgNCs, leading to significant metal enhancement effect to the O generation rate much higher (~45 times) than that of the monometallic BSA-AgNC. This versatile two-for-one strategy to develop next generation metal-enhanced bimetallic NC photosensitizers in one pot opens up new opportunities in designing advanced hybrid nanomaterials with complementary and/or enhanced functionalities.
光致发光贵金属纳米团簇（NCs，核尺寸<2nm）作为一种新型的光敏剂，由于其具有高效的单线态氧（O）生成效率、优异的光稳定性和水溶性，以及良好的生物相容性，在光动力治疗和生物成像方面具有很大的优势，优于传统的光敏剂。然而，金属 NCs 的固有 O 生成与光致发光特性与其尺寸、组成和浓度之间尚未建立相关性，这对于定制 NCs 的分子样性质以用于不同的应用非常重要。在此，我们通过自发的电置换反应来调节其组成，报道了一项系统的研究，以揭示通过调控组成来可控地生成 O 的双金属 NCs 的合理设计。通过在室温下用不同浓度的金前驱体与牛血清白蛋白（BSA）保护的 AgNCs（13 个 Ag 原子/簇）反应，合成了一系列超小的金/银合金纳米团簇（AuAgNCs）。结果发现，所得的 BSA 保护的 AuAgNCs 的 O 生成效率与其光致发光强度呈反比。有趣的是，BSA-AuAgNCs 的光漂白同时也形成了等离子体金纳米颗粒（>10nm），导致 O 生成速率的金属增强效应显著提高（约 45 倍），高于单金属 BSA-AgNC。这种一锅法的多功能的“一石二鸟”策略，为开发新一代的金属增强型双金属 NC 光敏剂开辟了新的机遇，为设计具有互补和/或增强功能的先进混合纳米材料提供了新的机会。
