Shape-Controlled Synthesis of Gold Nanoprism and Nanoperiwinkles with Pronounced Electrocatalytic Activity Bikash Kumar Jena and C. Retna Raj* Department of Chemistry, Indian Institute of Technology, Kharagpur 721 302, India ReceiVed: March 26, 2007; In Final Form: August 6, 2007 We report the one-pot shape-controlled aqueous synthesis of triangular gold nanoprisms (GNPMs) and nanoperiwinkles (GNPWs) and their electrocatalytic activity toward reduction of oxygen and oxidation of methanol. The GNPMs and GNPWs were synthesized using 5-hydroxytryptamine (HT) as a reducing/stabilizing agent at room temperature. The UV-visible absorption spectrum of the nanostructured colloidal particles exhibits transverse and longitudinal surface plasmon bands at 535 and 900 nm, respectively. The transmission electron microscopy measurement shows that the nanostructured particles have prism and periwinkle-like morphology. The concentration of HT controls the shape and morphology of the nanostructured particles. The GNPMs have the size of 70-110 nm whereas GNPWs have the size of 150-230 nm. The X-ray diffraction profiles of GNPMs and GNPWs reveal that the nanoparticles are composed of mainly a Au(111) lattice plane. The GNPMs and GNPWs were self-assembled on a three-dimensional silicate network derived from (3-mercaptopropyl)trimethoxysilane, and their spectral and electrochemical properties have been investigated. The UV-visible diffuse reflectance spectral measurement shows that both GNPM and GNPW retain their morphology on the silicate network. The nanoparticles on the silicate network show excellent electrocatalytic activity toward oxidation of methanol and reduction of oxygen. The electrocatalytic activity of GNPMs and GNPWs is higher than the spherical gold nanoparticles. Introduction Nanosized metal and semiconductor particles play an impor- tant role in many different areas due to their unique properties. The electronic, optical, optoelectronic, magnetic, and catalytic properties of these nanostructured particles can be conveniently tuned by controlling the size and shape. 1 Because the catalytic properties depend on size, shape, and morphology, various approaches have been employed to obtain metallic nanostruc- tures. 2 Synthesis of anisotropic nanoparticle-like triangular gold nanoprism (GNPM) is of great interest because of its unique properties. The field enhancement effect near the triangle tips of metal nanoprism makes it useful in atomic force microscopy (AFM) and scanning tunneling microscopy (STM); 3 they are also very promising for medicinal applications. 4 The methodolo- gies available for the synthesis of these nanostructured particles are difficult and time-consuming, and they often require structure-regulating reagents or techniques. 5,6 The control of crystal morphology by proteins has been observed in a biological system. 7 Recently, proteins, biological extracts, and small biomolecules have been used for the synthesis of metal nanoparticles. 5e,8 Dong and co-workers synthesized the hex- agonal and truncated triangular shaped single-crystalline Au nanoparticles by using L-amino acids without any templates. 9 Sastry and co-workers recently reported the biological synthesis of triangular nanoprism using the lemongrass extract. 5e However, in these approaches, the desired nanostructure was obtained after a very long time (6-12 h). 5e,9 Although the optical properties of these anisotropic nanoparticles are well studied, the electro- chemical and electrocatalytic properties have not been inves- tigated. The deliberate tailoring of electrochemical interfaces with nanostructured metal and semiconductor particles have gained enormous interest in the development of electrochemical nanos- cale devices. 10,11 Particularly the gold (Au) nanoparticle has attracted much attention in many different areas such as catalysis, biosensing, etc. Although bulk Au is a poor catalyst, recently it has been demonstrated that nanosized Au particles have excellent catalytic activity. 12 The high catalytic activity of these nanosized particles are attributed to the large surface- to-volume ratios and the existence of special binding sites on the surface of the particles. The electrocatalytic property of Au nanoparticles has been investigated by different groups. 13-19 Zhong et al. explored the possible utilization of monolayer- protected nanosized Au particles for the oxidation of methanol in alkaline solution. 15 Ohsaka and co-workers have extensively studied the electrocatalytic behavior of electrochemically de- posited Au nanoparticles on different conducting support toward reduction of oxygen. 16 It is generally observed that the catalytic property of the nanostructured metal particles largely depends on the size and shape. 20 Li and Shi have demonstrated that the electrocatalytic behavior of electrochemically grown Au particles depend on their shape. The electrochemically deposited flower- like Au nano structure showed higher electrocatalytic activity than that of the pine cone and sheet structures. 21 Very recently, Ogumi and co-workers have shown the electrocatalytic applica- tion of Au nanoparticles in the development of direct methanol fuel cell. 22 Significant enhancement in the electrocatalytic activity of Pt-Ru/C was noticed in the presence of nanosized Au particles. The promotional effect of Au nanoparticles in the electrooxidation of methanol has also been observed recently. 23 Our group is interested in exploring the electrocatalytic and electroanalytical application of nanostructured metal particles. * Corresponding author. E-mail: crraj@chem.iitkgp.ernet.in. 15146 J. Phys. Chem. C 2007, 111, 15146-15153 10.1021/jp072363s CCC: $37.00 © 2007 American Chemical Society Published on Web 10/03/2007