Dip-pen nanolithography(DPN) has been developed to pattern monolayer film of various molecules in submicrometer dimensions through the controlled movement of ink-coated atomic force microscopy(AFM) tip on a desired substrate, which makes DPN a potentially powerful tool for making the functional nanoscale devices. In this letter, using direct-write dip-pen nanolithography to generate nanoscale patterns of poly-L-lysine on mica was described. Poly-L-lysine molecules can anchor themselves to the mica surface through electrostatic interaction force, so stable poly-L-lysine patterns, such as square, line, circle and cross, could be obtained on freshly cleaved mica surface. From AFM image of the patterned poly-L-lysine nanostructures on mica, we know that poly-L-lysine was flatly bound to the mica surface. These oriented patterns of poly-L-lysine on mica can provide the prospect of building functional nanodevices and offer new options for this technique in a variety of other significant biomolecules.
In this paper, the fixing and stretching effect of Ni(phen) 2+ 3 with different concentrations on DNA had been studied by Tapping mode AFM. Under an ambient condition, the high resolution DNA images were obtained, the average height, width and length of well spread DNA molecules were measured. The results showed that because of the variations of ionic concentration, the density and topography of DNA molecules on substrate had a great difference. The AFM and gel electrophoresis results also showed that, under our experimental condition, DNA molecules kept intact, Ni(phen) 2+ 3 did not catalyze the cleavage activity of EcoRI, therefore, Ni(phen) 2+ 3 would be used to make high resolution physical mapping of DNA by AFM.
