Preparation and characterization of ultrathin films layer-by-layer self-assembled from graphite oxide nanoplatelets and polymers

Graphite, oxidized by HNO3 and NaClO3 to 25% (GO-25), 42% (GO-42), and 33% (GO-33), has been dispersed to partially exfoliated nanoplatelets and, alon g with poly(diallyldimethylammonium chloride) (PDDA) and poly(ethylene oxid e) (PEO), layer-by-layer self-assembled to ultrathin S-(PDDA/GO)(10), S-PDD A/(GO/PEO)(10), and S-(PDDA/GO/PEO)(10) films (where S is the indium tin ox ide- or chromium/gold-coated glass or quartz substrate and GO refers to pla telets of oxidized graphite). The GO powders have been characterized by X-r ay diffraction prior and by transmission electron microscopy after their di spersions. Thicknesses of each of the successively adsorbed layers were com paratively determined by absorption spectrophotometry, surface plasmon reso nance spectroscopy, quartz crystal microbalance, and scanning force microsc opy. Good agreements were obtained by these three different techniques.