Catalytic Scanning Probe Nanolithography (cSPL): Control of the AFM Parameters in Order to Achieve Sub-100-nm Spatially Resolved Epoxidation of Alkenes Grafted onto a Surface

Abstract

Scanning probe lithography (SPL) appears to be a reliable alternative to the use of masks in traditional lithography techniques as it offers the possibility of directly producing specific chemical functionalities with nanoscale spatial control. We have recently extend the range of applications of catalytic SPL (cSPL) by introducing a homogeneous catalyst immobilized on the apex of a scanning probe. Here we investigate the importance of atomic force microscopy (AFM) physical parameters (applied force, writing speed, and interline distance) on the resultant chemical activity in this cSPL methodology through the direct topographic observation of nanostructured surfaces. Indeed, an alkene-terminated self-assembled monolayer (alkene-SAM) on a silicon wafer was locally epoxidized using a scanning probe tip with a covalently grafted manganese complex bearing the 1,4,7-triazacyclononane macrocycle as the ligand. In a post-transformation process, N-octylpiperazine was covalently grafted to the surface via a selective nucleophilic ring-opening reaction. With this procedure, we could write various patterns on the surface with high spatial control. The catalytic AFM probe thus appears to be very robust because a total area close to 500 μm(2) was patterned without any noticeable loss of catalytic activity. Finally, this methodology allowed us to reach a lower lateral line resolution down to 40 nm, thus being competitive and complementary to the other nanolithographical techniques for the nanostructuration of surfaces.

Controlling a Chemical Coupling Reaction on a Surface: Tools and Strategies for On-Surface Synthesis

“…Copyright 2017 Royal Society of Chemistry. (b) Adapted with permission from ref (294). Copyright 2016 American Chemical Society.…”

“…297−304 The technique could be extended to the use of a homogeneous catalyst immobilized onto the tip upon modification with an appropriate ligand (see Figure 26b). 294,305−307 The use of a homogeneous catalyst in principle opens the way to a large variety of chemical reactions. It was shown that the catalytic activity of the tip-supported catalyst was barely affected during the reaction process, and large areas could be covalently modified without significant loss of the reactivity.…”

Spatially resolved acyl transfer on surface by organo-catalytic scanning probe nanolithography (o-cSPL)

“…The high forces required are consistent with results obtained with related organometallic cSPL methodologies described previously. 33 …”

“…A second step of derivatization with piperazine or amine-based moieties was required to reveal the formation of nanostructures. 33 Despite its intrinsic robustness, this catalytic system still suffers from some inherent drawbacks such as: (i) multi-step synthesis of the catalyst supported on the tip, (ii) the necessity of a post-functionalization step to “reveal” the topography of the new nanostructures, and finally, (iii) the impossibility to selectively graft more than one type of molecular objects during the “writing” process (catalysis and post-functionalization).…”

Parallelized biocatalytic scanning probe lithography for the additive fabrication of conjugated polymer structures

“…Such an approach would combine the precision of SPL with the chemical selectivity of catalysis, thereby greatly increasing the chemical scope and complexity that can be achieved by SPL. 1,12 This type of direct synthesis is of particular relevance to the lithography of materials that are otherwise difficult to process by other approaches, such as conducting polymers. For example, polyaniline is a conjugated polymer that exhibits high electrical conductivity and electrochemical stability, and is therefore of interest in the development of organic electronic devices.…”