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.
Thiol-capping of CdTe nanocrystals were prepared in aqueous solution. The emission wavelengths of CdTe nanocrystals could be tuned by the refluxing time. Bioinorganic conjugates between CdTe nanocrystals and BSA were formed via electrostatic/coordinate self-assembly. The photoluminescence intensity of the bioinorganic conjugates was improved obviously. BSA could stabilize the CdTe nanocrystals, and the bioinorganic conjugates at room temperature were stable for a long time. We also demonstrated that CdTe nanocrystals could be blocked with BSA and avoid the nonspecific adsorption.
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.
