mater.scichina.com link.springer.com .................... Published online 25 January 2018 | https://doi.org/10.1007/s40843-018-9213-4 Sci China Mater 2018, 61(8): 1129–1131 Amine facilitates the synthesis of silica-supported ultrasmall bimetallic nanoparticles Nanfeng Zheng * and Pengxin Liu Supported catalysts based on metal nanoparticles are a class of widely used heterogeneous catalysts in industry. The catalytic performances of supported metal catalysts are highly determined by many parameters of metal na- noparticles such as their particle size, composition, sur- face structure and also interfacial interaction with supports [1]. Supported metal catalysts are commonly prepared by depositing metal precursors on high-surface area supports through various methods such as impreg- nation (IMP), co-precipitation (CP), and deposition- precipitation (DP), followed by thermal or chemical re- duction of the metal precursors deposited thereon to form supported metal nanoparticles. The difficulty for conventional methods to prepare high-quality supported metal nanoparticles with uniform particle size and composition mainly lies in the following two aspects: 1) The interaction between metal precursors and supports is not strong enough to prevent their sin- tering during the post thermal or chemical reduction processes; 2) The deposition of metal precursors is not homogenous so that the phase separation often occurs after the reducing treatment. By addressing these two issues, the DP method has been outstanding among other conventional methods in preparing supported small metal nanoparticles [2]. However, the DP method has met great difficulties in preparing high-quality metal nanoparticles catalysts on many acidic supports (such as silica, WO x , zeolites) due to their relatively low point of zero charge (PZC) [3]. During the past decade, there has thus been an emergence of research efforts directed toward the use of pre-made uniform nanoparticles as precursors to prepare well-controlled metal nanocatalysts for investigating complicated interfacial catalytic mechanism [4–6]. In these colloidal methods, the influence of organic capping agents is often concerned. As compared to supported monometallic nanoparticles, the preparation of high-quality supported alloyed nano- particles is even more challenging. Alloying has been well-documented as an effective strategy to tailor the catalytic performance of supported metal catalysts. On one hand, alloying provides an avenue to reduce the usage of expensive scare metal without compromising the overall catalytic activity. On the other hand, the electronic density and/or dispersion of catalytically active metal can be manipulated by the introduction of another metal species, thus tailoring the reaction pathway and often optimizing the overall catalytic properties. In order to obtain high-quality supported alloyed catalysts with uni- form ultrasmall size and uniform composition, it is es- sential to have the metal precursors uniformly deposited onto the surface of supports before being converted into alloyed nanoparticles. Recently, Regalbuto and colleagues have developed a general and simple method to prepare ultrasmall alloyed metal nanoparticles based on both noble (i.e., Pt, Pd) and base metals (i.e., Ni, Co, Cu) [7]. The homogeneously alloyed metal nanoparticles have a narrow size distribu- tion around 1 nm. In the developed method, positively charged metal-amine complex precursors were deposited onto negatively charged surface of silica support through strong electrostatic adsorption (SEA) [8,9], and then re- duced by H 2 at an elevated temperature to give supported uniform ultrasmall alloyed nanoparticles (Fig. 1a). The key of this work is to use positively charged metal-amine complexes as metal precursors. Since the surface point of zero charge of silica (Aerosil 300 silica) is around 3.6, the surface charge of silica in water is negative in a wide range of pH value (4–13) before silica is dissolved. The strong electrostatic interaction can thus promote the homo- genous deposition, making the method outstanding conventional preparation methods for the production of ultrasmall alloyed nanoparticles with different combina- Collaborative Innovation Center of Chemistry for Energy Materials, State Key Laboratory for Physical Chemistry of Solid Surfaces, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China * Email: nfzheng@xmu.edu.cn SCIENCE CHINA Materials ............................. HIGHLIGHTS August 2018 | Vol. 61 No.8 .................................................................................... 1129 © Science China Press and Springer-Verlag GmbH Germany 2018