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Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Nanospiral Formation by Droplet Drying: One Molecule at a Time | Wan et al. Nanoscale Res Lett 2011 6 49 http www.nanoscalereslett.eom content 6 1 49 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Nanospiral Formation by Droplet Drying One Molecule at a Time Lei Wan Li Li Guangzhao Mao Abstract We have created nanospirals by self-assembly during droplet evaporation. The nanospirals 60-70 nm in diameter formed when solvent mixtures of methanol and m-cresol were used. In contrast spin coating using only methanol as the solvent produced epitaxial films of stripe nanopatterns and using only m-cresol disordered structure. Due to the disparity in vapor pressure between the two solvents droplets of m-cresol solution remaining on the substrate serve as templates for the self-assembly of carboxylic acid molecules which in turn allows the visualization of solution droplet evaporation one molecule at a time. Introduction Patterns formed by solvent evaporation are relevant to various coating processes as well as patterning technology. In capturing the molecular process of an evaporating droplet this work demonstrates the possibility to further modulate dewetting patterns by amphiphiles capable of self-assembly. Self-assembly as an alternative to lithography has the potential to generate reconfigurable nanostructures 1-3 . Surfactants amphiphiles are the simplest molecules to self-assemble into complex yet often predictable structures and phases. An interface perturbs and sometimes dominates the self-assembling behavior of amphiphiles. A well-known example of substrate-dominated self-assembly is the epitaxial stripe nanopatterns formed by alkanes and alkane derivatives on highly oriented pyrolytic graphite HOPG 4-10 . The 1 3-methylene group distance 0.251 nm of alltrans alkyl chains matches the distance of the next nearest neighbor of the HOPG lattice 0.246 nm along e.g. the 11 2 0 crystallographic direction. The head-to-head arrangement gives rise to the stripe nanopattern whose periodicity is 1 X or 2 X the .
