Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys Bimetallic AuAg sharp-branch mesoflowers as catalyst for hydrogenation of acetone Vivi Fauzia a,* , Devi Irmavianti a , Liszulfah Roza b , Mas Ayu Elita Hafizah a , Cuk Imawan a , Akrajas Ali Umar c a Departemen Fisika, Fakultas MIPA, Universitas Indonesia, Depok, 16424, Indonesia b Jurusan Pendidikan Fisika, Fakultas Keguruan dan Ilmu Pendidikan, Universitas Muhammadiyah Prof. Dr. Hamka, Jakarta, Timur, Indonesia c Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia, 43600, UKM Bangi, Selangor, Malaysia HIGHLIGHTS • AuAg MFs with sharp tips have higher catalytic activity than Au MPs for hy- drogenation of acetone. • High electron density on the sharp tips of AuAg MFs donate electrons to easily generates a surface-hydrogen species. • Ag atoms on the AuAg alloy surface enhance the chemical reaction with the O atom in the C═O bond. GRAPHICAL ABSTRACT ARTICLE INFO Keywords: AuAg Bimetallic Mesoflowers Catalyst Hydrogenation ABSTRACT Colloidal metal and their alloys nanoparticles have been found to potentially offer exceptional catalytic activity. Many researchers have worked to tailor the shape, size, and atomic composition of Au-based bimetallic nano- crystals to enhance their catalytic activity. However, the study of free colloidal anisotropic Au-based particles as catalyst of hydrogenation process is still limited. Here, we evaluated the bimetallic gold-silver (AuAg) meso- flowers (MFs) with sharp tips as a catalyst for hydrogenation of acetone to isopropanol under microwave ra- diation. The shape and size of the branched MFs was adjusted by controlling the addition of AgNO 3 precursor. The resulting AuAg MFs were found to have higher catalytic activity than monometallic Au mesoparticles (Au MPs). The degradation rate of acetone without a catalyst is ± 46%, while the degradation rate of acetone in the presence of Au MPs and AuAg MFs catalysts is ± 66%, and ± 71%, respectively. These correspond to the turn over number (TON) and turn over frequency (TOF) values of approximately 1827 and 9.1 s -1 , respectively, for the AuAg MFs. This is significantly higher compared to the TON and TOF values for Au MPs, i.e. 746 and 3.7 s -1 , respectively. High electron density on their sharp tips and the presence of Ag atoms on the AuAg alloy surface may be the key points in enhancing the chemical reaction with the oxygen atom in the C═O bond and generates a surface-hydrogen species to form isopropanol molecules. https://doi.org/10.1016/j.matchemphys.2019.01.013 Received 25 October 2018; Received in revised form 31 December 2018; Accepted 4 January 2019 * Corresponding author. E-mail address: vivi@sci.ui.ac.id (V. Fauzia). Materials Chemistry and Physics 225 (2019) 443–450 Available online 07 January 2019 0254-0584/ © 2019 Elsevier B.V. All rights reserved. T