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.