RESUMO
We demonstrate the efficiency of meniscus-mask lithography (MML) for fabrication of precisely positioned nanowires in a variety of materials. Si, SiO2, Au, Cr, W, Ti, TiO2, and Al nanowires are fabricated and characterized. The average widths, depending on the materials, range from 6 to 16 nm. A broad range of materials and etching processes are used and the generality of approach suggests the applicability of MML to a majority of materials used in modern planar technology. High reproducibility of the MML method is shown and some fabrication issues specific to MML are addressed. Crossbar structures produced by MML demonstrate that junctions of nanowires could be fabricated as well, providing the building blocks required for fabrication of nanowire structures of varied planar geometry.
RESUMO
Described here is a planar top-down method for the fabrication of precisely positioned very narrow (sub-10 nm), high aspect ratio (>2000) graphene nanoribbons (GNRs) from graphene sheets, which we call meniscus-mask lithography (MML). The method does not require demanding high-resolution lithography tools. The mechanism involves masking by atmospheric water adsorbed at the edge of the lithography pattern written on top of the target material. The GNR electronic properties depend on the graphene etching method, with argon reactive ion etching yielding remarkably consistent results. The influence of the most common substrates (Si/SiO2 and boron nitride) on the electronic properties of GNRs is demonstrated. The technique is also shown to be applicable for fabrication of narrow metallic wires, underscoring the generality of MML for narrow features on diverse materials.
RESUMO
Here we show the efficacy of graphene oxide (GO) for rapid removal of some of the most toxic and radioactive long-lived human-made radionuclides from contaminated water, even from acidic solutions (pH < 2). The interaction of GO with actinides including Am(III), Th(IV), Pu(IV), Np(V), U(VI) and typical fission products Sr(II), Eu(III) and Tc(VII) were studied, along with their sorption kinetics. Cation/GO coagulation occurs with the formation of nanoparticle aggregates of GO sheets, facilitating their removal. GO is far more effective in removal of transuranium elements from simulated nuclear waste solutions than other routinely used sorbents such as bentonite clays and activated carbon. These results point toward a simple methodology to mollify the severity of nuclear waste contamination, thereby leading to effective measures for environmental remediation.