Demonstration of vacuum field emission from a self-assembling biomolecular microstructure composite

Abstract

We report the first demonstration of vacuum field emission from an electron source fabricated from self-assembling biomolecular composite microstructures. Diacetylenic lipid DC8,9PC is used to form hollow, 0.5 μm diam, ≳50 μm long, tubelike structures that are subsequently plated with metal and formed into an aligned composite in an epoxy matrix. The composite material is thin-sectioned across the axis of alignment and then etched to expose the plated tubules. The sharp edges of the exposed metal tubules produce a very large local electric field enhancement, allowing for the vacuum field emission of significant current densities at relatively low applied macroscopic fields (≤60–80 kV/cm).

Lipid Tubules: A Paradigm for Molecularly Engineered Structures

“…The generation of large electron beam currents through vacuum field emission from a large number of emission sites requires a surface with a complex microstructure. Theoretical considerations and subsequent modeling suggest that 0.5-pm hollow cylinders terminating in edges with a very small radius of curvature (5300 A) may offer significant advantages in terms of the brightness of the emission (56). Given these predictions, it SCIENCE VOL.…”

Nanotubes Self-Assembled from Amphiphilic Molecules via Helical Intermediates

“…These characteristics complement their suitability for many of the applications already mentioned, such as use in biosensors and in drug delivery. ,,− As distinct from other nanostructures with similar aspect ratios, such as carbon nanotubes, lipid nanotubes can be synthesized with a range of internal diameters, from 10 to 1000 nm, ,,− and have hydrophilic surfaces with a range of available surface functionalities. ,,,,− Further, chemical modification postassembly can provide external nanotube chemistries that are not themselves able to support self-assembly into nanotubes . This flexibility in size and chemistry provides further applications specific to lipid nanotubes including use in micro fluidic networks, , in molecular recognition devices, and as liquid-crystalline biomaterials. , Furthermore, lipid nanotubes have been shown to act as ideal templates for synthesizing useful structures from materials that otherwise do not self-assemble. ,,− The tubes can also be used in combination with other materials as nanocomposites. ,,,,− …”

Chemical Synthesis of Nanostructured Particles and Films

“…The local electric field enhancement was achieved by exploiting the large aspect ratio of the metallized tubules, the radius of curvature, and the thickness of metal coatings at the edge of the metallized tubules. [172,173] An aqueous, electroless "oxidative-soak-coating" deposition has been used to fabricate MnO 2 and CeO 2 films on glass substrates at 313 to 333 K. [174] Film deposition proceeded via oxidation of Mn 2+ and Ce 3+ ions in homogeneous solutions and then heterogeneous nucleation of MnO 2 and CeO 2 on the substrates.…”