Carbon‐Nanotube‐Templated Microfabrication of Porous Silicon‐Carbon Materials with Application to Chemical Separations

Abstract

Carbon-nanotube-templated microfabrication (CNT-M) of porous materials is demonstrated. Partial chemical infi ltration of 3D carbon-nanotube structures with silicon results in a mechanically robust material, structured from the 10 nm scale to the 100 μ m scale. The nanoscale dimensions are determined by the diameter and spacing of the resulting silicon/carbon nanotubes, while the microscale dimensions are controlled by the lithographic patterning of the CNT growth catalyst. We demonstrate the utility of this hierarchical structuring approach by using CNT-M to fabricate thin-layer-chromatography (TLC) separations media with precise microscale channels for fl uid-fl ow control and nanoscale porosity for high analyte capacity. Chemical separations done on the CNT-M-structured media outperform commercial highperformance TLC media.

Atomic layer deposition of aluminum-free silica onto patterned carbon nanotube forests in the preparation of microfabricated thin-layer chromatography plates

“…These include monolithic silica [1], glancing angle deposition (GLAD) [2][3][4], polymer monoliths [5][6][7][8], and electrospun polymers [9,10]. Our group has also been active in this area, reporting TLC plates with high efficiencies and short run times prepared from microfabricated, patterned, and infiltrated carbon nanotube (CNT) forests [11][12][13][14]. In general, these plates are prepared as follows.…”

“…Our first attempt to microfabricate a TLC plate employed the conformal deposition of silicon onto CNTs via low-pressure chemical vapor deposition (LPCVD) of silane (SiH 4 ), where the oxidation/removal of the CNTs beneath the silicon led to their removal and the oxidation of the silicon to silica [14]. Unfortunately, the volume expansion of Si to SiO 2 that occurred in this process distorted the features of the device and led to irreproducible results.…”

High Aspect Ratio Carbon Nanotube Membranes Decorated with Pt Nanoparticle Urchins for Micro Underwater Vehicle PropulsionviaH2O2Decomposition

“…Carbon nanotube (CNT)-templated microfabrication is a new approach to constructing high aspect ratio structures that capitalizes on the very large length to diameter ratios present for carbon nanotubes. 24,25 For modest growth lengths of 1 mm and a nominal 100 nm spacing between carbon nanotubes, aspect ratios of 10À10 000 are achievable for vertically aligned growth. When combined with lithographically defined growth, almost any aspect ratio in this range can be realized.…”

Hydroxylation of the silica in microfabricated thin layer chromatography plates as probed by time-of-flight secondary ion mass spectrometry and diffuse reflectance infrared Fourier transform spectroscopy

“…[9] In this preparation, the CNT scaffolds were removed from the plates by air oxidation at 1000°C for 24 h.…”

“…[31] Our second use of surface hydroxylation was very similar to the first -the same hydroxylation conditions followed by an amino bonded phase. [11] These same hydroxylation conditions were again followed for plates made via LPCVD silicon [9] that were part of a study on the thickness of the iron catalyst used in CNT growth. [32] For this study, no bonded phase was employed, and some surface characterization by DRIFT was reported.…”