Patterned arrays of gold nanoparticles (AuNPs) are prepared using scanning electrochemical microscopy by electrochemical reduction of a gold salt at a platinum ultramicroelectrode positioned on top of an unbiased gold surface, modified with a biphenyl dithiol self-assembled monolayer (SAM). The synthesized AuNPs are chemisorbed on the thiolated SAM, and by moving the microelectrode in a lateral direction across the surface while applying a reduction potential, particle-like lines are generated. ■ INTRODUCTION Fabrication of patterned arrays of gold nanoparticles (AuNPs) have attracted a great deal of interest for many applications including catalysts, 1,2 sensors, 3 and electronic devices develop-ment, 4,5 due to their unusual particle-size-dependent optical, electrical, magnetic, and chemical properties. 6 Particle arrays can be prepared by different techniques and procedures, mainly by lithography, 7 including photolithography, 8−10 electron beam lithography, 11−14 dip-pen nanolithography, 15−17 soft lithogra-phy such as microcontact printing, 18,19 and nanoimprinting. 20