Ag nanocubes (AgNCs) are predominantly synthesized by the polyol method, where the solvent (ethylene glycol) is considered the reducing agent and poly(N-vinylpyrrolidone) (PVP) the shape-directing agent. An experimental phase diagram for the formation of Ag nanocubes as a function of PVP monomer concentration (Cm) and molecular weight (Mw) demonstrated end groups of PVP impact the final Ag product. Measured rates of the initial Ag+ reduction at different PVP Cm and Mw confirmed the reducing effect originates from end-groups. PVP with well-defined aldehyde and hydroxyl end groups lead to the formation of Ag nanocubes and nanowires respectively, indicating the faster reducing agent formed kinetically preferred nanowires. We demonstrate PVP end-groups induce initial reduction of Ag+ to form seeds followed by autocatalytic reduction of Ag+ by ethylene glycol (and not solvent oxidation products) to form Ag nanostructures. The current study enabled a quantitative description of the role of PVP in nanoparticle shape-control and demonstrates a unique opportunity to design nanostructures by combining nanoparticle synthesis with polymer design to introduce specific physicochemical properties.

中文翻译：

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聚（N-乙烯基吡咯烷酮）端基的化学特性影响银纳米结构合成过程中的形状演变

银纳米立方体（AgNCs）主要通过多元醇法合成，其中溶剂（乙二醇）被认为是还原剂，聚（N-乙烯基吡咯烷酮）（PVP）被认为是形状导向剂。作为 PVP 单体浓度 (Cm) 和分子量 (Mw) 的函数的 Ag 纳米立方体形成的实验相图表明 PVP 的端基会影响最终的 Ag 产品。在不同 PVP Cm 和 Mw 下测量的初始 Ag+ 还原率证实了还原效果源自端基。具有明确定义的醛基和羟基端基的 PVP 分别导致形成 Ag 纳米立方体和纳米线，表明形成动力学优选纳米线的还原剂更快。我们证明 PVP 端基诱导 Ag+ 的初始还原形成种子，然后通过乙二醇（而不是溶剂氧化产物）自催化还原 Ag+ 以形成 Ag 纳米结构。目前的研究能够定量描述 PVP 在纳米颗粒形状控制中的作用，并展示了通过将纳米颗粒合成与聚合物设计相结合来引入特定物理化学特性来设计纳米结构的独特机会。