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, along with poly(diallyldimethylammonium chloride) (PDDA) and poly(ethylene oxide) (PEO), layer-by-layer self-assembled to ultrathin S-(PDDA/GO)(10), S-PDDA/(GO/PEO)(10), and S-(PDDA/GO/PEO)(10) films (where S is the indium tin oxide- or chromium/gold-coated glass or quartz substrate and GO refers to platelets of oxidized graphite). The GO powders have been characterized by X-ray diffraction prior and by transmission electron microscopy after their dispersions. Thicknesses of each of the successively adsorbed layers were comparatively determined by absorption spectrophotometry, surface plasmon resonance spectroscopy, quartz crystal microbalance, and scanning force microscopy. Good agreements were obtained by these three different techniques.