Development of the Gel -Assisted Transfer Technique

点击翻译按钮获取中文摘要

We have studied two-dimensional organization of water-solubie nanoparticles by the use of hydrogel surface as substrate, and provide the first experimental report on gel-assisted transfer (GAT) of nanoparticles onto solid substrates.Colloidal dispersions of silica nano-particles (diameter, 100 nm) were spread on agarose gel surface. The spreading solution on the gel disappeared either by penetration or by evaporation after ca. 12 hrs. Solid substrates (HOPG, mica) were subsequently pressed against the gel surface. In scanning electron microscopy, densely packed silica nanoparticles are found due to their transfer from the gel surface on the solid substrates. In these examples, nanoparticles are transferred as monolayers and multilayers, without formation of uniform array.These silica particles transferred on HOPG and mica surfaces were easily removed upon dipping in water (5 ml), as demonstrated by SEM observation. The resultant surface was further investigated by atomic force microscopy (AFM). After rinsing off the transferred nanoparticles, fragmentary network of agarose with heights of ca. 25 nm and widths of 50-70 nm are abundantly observed. Undoubtedly, ultrathin network of agarose is transferred together with nanoparticles, suggesting that the surface layer of gel is comprised of ultrathin networks of agarose fibers that are distinguished from three dimensionally cross linked structures as generally considered. The surface network of agarose must assist the transfer by supporting silica particles together and making them adherent to anionic mica surface as "molecular glue".