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Nancones to protect AFM tips

Nanocones podem prolongar vida de ponta de microscópio

Publicado em Scientific Reports by Nature Inc.

Cano-Marquez, Abraham G, Schmidt, Wesller G, Ribeiro-Soares, Jenaina, Cançado, Luiz Gustavo, Rodrigues, Wagner N, Santos, Adelina P, Furtado, Clascidia A, Autreto, Pedro AS, Paupitz, Ricardo, Galv~ao, Douglas S, others (2015): Enhanced Mechanical Stability of Gold Nanotips through Carbon Nanocone Encapsulation. In: Nature Scientific reports, 5 , 2015.

Gold is a noble metal that, in comparison with silver and copper, has the advantage of corrosion resistance.

(A) SEM image of an Au@CNC tip glued into a tuning fork for AFM measurements; (B,C) Raw AFM topography images of single wall carbon nanotubes on a glass cover slip; (D) Height profile along the blue dashed line in (C), showing lateral resolution better than 14 nm.

(A) SEM image of an Au@CNC tip glued into a tuning fork for AFM measurements; (B,C) Raw AFM topography images of single wall carbon nanotubes on a glass cover slip; (D) Height profile along the blue dashed line in (C), showing lateral resolution better than 14 nm.

Despite its high conductivity, chemical stability and biocompatibility, gold exhibits high plasticity, which limits its applications in some nanodevices.

(A) One isolated MWCNC on Si substrate; (B-D) Approaching and soldering MWCNC on a gold tip; (E, F) Zoom-out views showing the Au nanotip on a larger scale; In (F) the nanocone is no longer seen.

(A) One isolated MWCNC on Si substrate; (B-D) Approaching and soldering MWCNC on a gold tip; (E, F) Zoom-out views showing the Au nanotip on a larger scale; In (F) the nanocone is no longer seen.

Here, we report an experimental and theoretical study on how to attain enhanced mechanical stability of gold nanotips. The gold tips were fabricated by chemical etching and further encapsulated with carbon nanocones via nanomanipulation. Atomic force microscopy experiments were carried out to test their mechanical stability.

Molecular dynamics simulations of pushing a bare and an encapsulated (Au@CNC) gold tips against a solid substrate.

The red (bare tip) and black (encapsulated tip) curves show the stress-strain (experienced by the gold tip) as a function of simulation time. Top and bottom insets are representative snapshots of the moments indicated in the black and red curves, respectively. The shaded area refers to the moment where the tip starts to be retracted.

Molecular dynamics simulations show that the encapsulated nanocone changes the strain release mechanisms at the nanoscale by blocking gold atomic sliding, redistributing the strain along the whole nanostructure. The carbon nanocones are conducting and can induce magnetism, thus opening new avenues on the exploitation of transport, mechanical and magnetic properties of gold covered by sp2 carbon at the nanoscale.

The authors thank the Center of Microscopy at the Universidade Federal de Minas Gerais (www.microscopia.ufmg.br) for providing the means for the microscopy work, and the Center for Computational Engineering and Sciences at Unicamp for financial support through the FAPESP/CEPID Grant #2013/08293-7. RP acknowledges FAPESP for Grants #2011/17253-3 and #2013/09536-0.