From Bare Metal Powders to Colloidally Stable TCO Dispersions and Transparent Nanoporous Conducting Metal Oxide Thin Films

06 Transparent conductive oxides (TCOs) are a technologically important class of materials. [ 1 ] Herein we describe a facile, universal, and green ‘one-pot’ approach to produce stable dispersions comprising TCO nanoparticles (NPs) such as SnO 2 , In 2 O 3 , ATO ( ≡ SnO 2 :Sb), ITO ( ≡ In 2 O 3 :Sn), and ZTO ( ≡ SnO 2 :Zn). The synthesis begins by etching the bare metal powder precursors (Sn, In, Sb, and Zn) with HCl and is completed by adding aqueous hydrogen peroxide below room temperature. No complex work-up or time-consuming purifi cation is required, only simple fi ltration. Moreover, this approach avoids organic surfactants, capping ligands and/ or organic solvents, metal halides like SnCl 4 or SbCl 3 , coordination compounds and sol–gel precursors like Sn(O t Bu) 4 , which are commonly used in all reported syntheses of TCOs NPs and which often contaminate and therefore complicate their subsequent utilization and purifi cation. [ 2 , 3 ] It is noteworthy that TCO nanoparticles have been synthesized in different reaction media including ionic liquids, [ 4 ] polyols, [ 5 ] and water. [ 6 ] The herein reported TCO NPs possess diameters of 3–6 nm, are colloidally stable, can be produced on a multigram scale and are well-suited for spin-coating nanoporous, transparent, and conductive TCO thin fi lms [ 7 ] (see Scheme 1 ) with potential utility in lithium ion batteries, solar and photoelectrochemical cells, electrochromics and sensors, fl at-panel displays, transparent thin-fi lm transistors, optoelectronic devices, and photonic crystal architectures. [ 8–12 ] Additionally,