Scanning Probe Block Co-Polymer Lithography (SPBCL)
Elemental analysis of a seven-element library of multi-phase heterostructured nanoparticles with complex interfacial chemistry that can be prepared using SPBCL. Taken from Science, 2016, 352, 1565 and Science, 2019, 363, 959.
In 2010, scanning probe block copolymer lithography (SPBCL), a method that could be utilized to prepare polymeric nanoreactors for complex structurally and chemically diverse nanoparticles, was invented by the Mirkin group. SPBCL utilizes dip-pen nanolithography (DPN) and polymer pen lithography (PPL) to create arrays of block co-polymer features (atto-liter volumes) on hydrophobic substrates. The block co-polymer (e.g., poly(ethyleneoxide)-b-poly(2-vinylpyridine) (PEO-b-P2VP)) concentrates nanomaterial precursors through metal ion association (gold precursor ions were used in the initial demonstration) and forms hemi-spherical domes a the hydrophobic substrate. Post-plasma or thermal treatment under a reducing environment results in the formation of individual inorganic particles in each reactor. This work led to the later introduction of the concept of nanocombinatorial chemistry via MegaLibraries and, since this initial demonstration, particle libraries with as many as seven elements and four phases with complex interfacial chemistries have been prepared. MegaLibraries allow for the high-throughput synthesis of massive libraries of gradients of complex nanomaterials that can be analyzed and screened on a large scale to discover new physical and chemical properties and redefine the materials genome. Case in point, the Mirkin group has identified novel catalysts for the hydrogen evolution reaction (HER) to produce the alternative fuel, H2, and single-walled carbon nanotube growth. SPBCL can be performed with commercial tools available through TERA-print, a company founded by Mirkin.
Left: Scheme showing a typical scanning probe block co-polymer lithography (SPBCL) experiment to prepare bimetallic nanoparticles. Taken from J. Am. Chem. Soc. 2015, 137, 9167.