Spherical assemblies with core/shell configurations are prepared through C-terminal amidated short peptide mediated self-association of platinum nanocrystals. The interactions between the peptides might drive the self-assembly of platinum nanocrystals and determine their surface properties. Thus, the nanosize assemblies collapse and spread on a hydrophilic surface, whereas maintaining their spherical shapes on a hydrophobic surface.Noble metal nanocrystals (NMNCs) possess fascinating properties, including catalytic, optical and electrical performance, and have been considered as superior building blocks for multifunctional materials. 1-4 It has been well known that many properties of the materials are dependent not only on the size, shape and composition of the building blocks, but also on their spatial conformations in the superarchitecture. 1-6 Recently, signicant progress has been made in assembling NMNCs into sophisticated superarchitectures, for example, threedimensional (3D) superspheres. 7-10 These superarchitectures have shown potential for fascinating applications in drug delivery, 11 bioimaging, 12 and catalysis. 9,13,14 In previous studies, sulfur-containing chemicals, e.g. thiols and thioethers, were mainly used as the cross-linking agents, and the assembly methodology involved organic solvents and complicated approaches, such as place-exchanging and exchanging-crosslinking. [15][16][17][18] In contrast, the self-assembly of NMNCs into well-dened functional superstructures through an easy, efficient and environment-friendly approach is still less reported, and the quest is continuously ongoing. 19 Herein, we present a type of 3D core/shell nanoassembly, easily formed by platinum nanocrystals (Pt NCs) using a short peptide as the cross-linking agent in an aqueous solution and demonstrate their selective wetting and spreading properties on a hydrophilic substrate, as shown in Scheme 1.Previously, a hepta-peptide with the sequence of NH 2 -TLHVSSY-COOH, named P7A, was found to stabilize ultra-small Pt NCs with a diameter of 1.7-3.5 nm in an aqueous solution by specically binding to their surfaces. 20-26 Our recent study revealed that the C-terminal carboxyl group of P7A is crucially important for stable dispersion of the Pt NCs in an aqueous solution, providing pH-dependent electrostatic repulsive intereactions. 27 Therefore, it will be interesting to screen such electrostatic repulsions through amidation of the carboxyl group. With an FMOC solid phase peptide synthesis (SPPS) strategy, we Scheme 1 Schematic of P7A-NH 2 mediated Pt NCs assembly into core/shell nanoassemblies with the ability of selectively wetting and spreading on the hydrophilic surface.