FULL PAPER © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com (1 of 11) 1604685 separation, the mixing of electronic states, and how synergistic properties of metals and the semiconductors occur in the same particle. [1b,2] The great advantage of ultra- fast electron transfer and charge carrier (electron–hole) separation at the metal– semiconductor interface has motivated researchers to discuss applications in, e.g., photocatalytic water splitting, [3] pollutant degradation, [4] field effect tran- sistors, [5] CO 2 reduction reactions, [6] etc. The metal-decorated nanostructures are also employed for self-assembling in solu- tions or on substrates to measure their electrical transport properties. [7] Various synthetic approaches (such as reduction, thermal annealing, photoinduced reac- tions, nanowelding, and many others) have enabled scientists to produce nano- heteroparticles with many possible com- binations of metals (e.g., Au, Pt, Pd, Ni, or Co) and different shapes of metal-chal- cogenide semiconductors, starting from spherical dots, [2a,3b,4c,8] nanorods, [1b,2b,9] nanowires, [9a] tetrapods, [1b,10] and pyramids, [11] to cubes [4b,12] and many more. [9g,13] In some cases, selective deposition of the metal domains (Au, Pt, Ag, Ni, Co, or Cu) at one end or both ends of the nanorods, at the tips of tetrapods, or only at the sides of rod-shaped semiconductor domains are shown in literature. [2a,9b,14] Synthesis of Ternary and Quaternary Au and Pt Decorated CdSe/CdS Heteronanoplatelets with Controllable Morphology Suraj Naskar, Franziska Lübkemann, Saher Hamid, Axel Freytag, Andreas Wolf, Julian Koch, Irina Ivanova, Herbert Pfnür, Dirk Dorfs, Detlef W. Bahnemann, and Nadja C. Bigall* A variety of new ternary and quaternary metal–semiconductor inorganic nanostructures with unprecedented structural morphologies is achieved by the decoration of five monolayer-thick CdSe/CdS core/crown nanoplatelets with Au and Pt domains. Significant differences in metal growth behavior are observed by varying the CdSe core and the CdS crown dimensions. Depending on the core size, Au growth can be directed only to the CdS edges, or both at the edges and at the center of the nanoplatelets. In contrast, the nucleation of Pt domains always happens at the CdS edges independently of the core and crown dimensions. Furthermore, quaternary structures are obtained by additional Au growth on Pt-decorated CdSe/CdS nanoplatelets, where the effect of steric hindrance of the existing Pt domains results in the Au nucleation to occur only at the CdSe core. Instead, a change in the order of growth of the two noble metals results in Pt-Au alloys present only at the surrounding edges of the nanoplatelets. Additionally, the metal-decorated nanoplatelets are found to be efficient catalysts for H 2 fuel generation under white light irradiation. The highest apparent quantum efficiency measured is 19.3% ± 1.4% with a turnover frequency of ≈10 5 molecules of H 2 per hour per nanoplatelet. DOI: 10.1002/adfm.201604685 S. Naskar, F. Lübkemann, A. Freytag, A. Wolf, Dr. D. Dorfs, Dr. N. C. Bigall Institute of Physical Chemistry and Electrochemistry Leibniz Universität Hannover Callinstraße 3A, D-30167 Hannover, Germany E-mail: nadja.bigall@pci.uni-hannover.de S. Naskar, F. Lübkemann, S. Hamid, A. Freytag, A. Wolf, J. Koch, Dr. I. Ivanova, Prof. H. Pfnür, Dr. D. Dorfs, Prof. D. W. Bahnemann, Dr. N. C. Bigall Laboratory for Nano and Quantum Engineering Leibniz Universität Hannover Schneiderberg 39, 30167 Hannover, Germany S. Hamid, Dr. I. Ivanova, Prof. D. W. Bahnemann Institute for Technical Chemistry Leibniz Universität Hannover Callinstraße 3, D-30167 Hannover, Germany Prof. D. W. Bahnemann Laboratory for Nanocomposite Materials Department of Photonics Faculty of Physics Saint-Petersburg State University Ulianovskaia street 3, Peterhof, Saint Petersburg 198504, Russia J. Koch, Prof. H. Pfnür Institut für Festkörperphysik Leibniz Universität Hannover Appelstraße 2, 30167 Hannover, Germany 1. Introduction Metal–semiconductor nanoheterostructures are known to be materials with fascinating electronic and electrochemical prop- erties. [1] The nanostructures are currently being researched by investigating the following topics; the extent of charge carrier www.afm-journal.de Adv. Funct. Mater. 2017, 1604685 www.advancedsciencenews.com