Gold nanoparticles, prepared by the Frens method, have been electrostatically assemblied onto mica substrates treated with different concentration of MnCl\-2 solution. The assemblies have been investigated by means of atomic force microscopy(AFM). The immersing time of bare mica in Mn\+\{2+\} solution and the concentration of Mn\+\{2+\} solution both have significant effect on the assembled process of gold nanoparticulate monolayer. The coverage of gold particles shows periodical evolution on the immersing time of mica in MnCl\-2 solution. The higher is the concentration of MnCl\-2, the shorter is the time to attain maximum coverage. An ion\|exchanged and layer\|dissociated mechanism is put forth to explain the experimental results above.
We use 8 nm magnetite nanoparticles as "ink", self assembly monolayer(SAM) of bovine serum albumin(BSA) as "paper" to generate arbitrary structures at micro or nanometer scales in the DPN procedure. AFM and LFM are used to image the patterns. The height profile of pattern is about 8 nm, which is consistent with the diameter of magnetite nanoparticles. It means that the magnetic monolayer pattern has been obtained. The SAM of BSA is measured by diffuse reflection IR spectra and the data is coincided with the one of the literature. After writing the magnetite "ink", the band of magnetite appears at 570 cm -1 , which gives a further proof.
This paper covers the first application of Dip Pen Nanolithography(DPN) to directly write protein patterns with submicrometer dimensions onto Au substrate. Using Bovine Serum Albumin(BSA) as the ink in the DPN procedure, we were able to utilize lateral force microscopy(LFM) images to differentiate between Au substrate and patterned area with deposited monolayers of BSA. Then the first evidence for Au_S bonding was reported between the gold substrate and the BSA surface thiol groups given by the angle resolved XPS measurements.
