Silicon (100) substrates are ubiquitous in microfabrication and, accordingly, their surface characteristics are important. Herein, we report the analysis of Si (100) via X-ray photoelectron spectroscopy (XPS) using monochromatic Al Kα radiation. Survey scans show that the material is primarily silicon and oxygen with small amounts of carbon, nitrogen, and fluorine contamination. The Si 2p region shows two peaks that correspond to elemental silicon and silicon dioxide. Using these peaks the thickness of the native oxide (SiO2) is estimated using the equation of Strohmeier. The oxygen peak is symmetric. These silicon wafers are used as the substrate for subsequent growth of templated carbon nanotubes in the preparation of microfabricated thin layer chromatography plates.

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.

We report the formation of core-shell diamond particles for solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) made by layer-by-layer (LbL) deposition. Their synthesis begins with the amine functionalization of microdiamond by its immersion in an aqueous solution of a primary amine-containing polymer (polyallylamine (PAAm)). The amine-terminated microdiamond is then immersed in an aqueous suspension of nanodiamond, which leads to adsorption of the nanodiamond. Alternating (self-limiting) immersions in the solutions of the amine-containing polymer and the suspension of nanodiamond are continued until the desired number of nanodiamond layers is formed around the microdiamond. Finally, the core-shell particles are cross-linked with 1,2,5,6-diepoxycyclooctane or reacted with 1,2-epoxyoctadecane. Layer-by-layer deposition of PAAm and nanodiamond is also studied on planar Si/SiO(2) surfaces, which were characterized by scanning electron microscopy (SEM), Rutherford backscattering spectrometry (RBS), and nuclear reaction analysis (NRA). Core-shell particles are characterized by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), environmental scanning electron microscopy (ESEM), and Brunauer-Emmett-Teller (BET) surface area and pore size measurements. Larger (ca. 50 microm) core-shell diamond particles have much higher surface areas and analyte loading capacities in SPE than nonporous solid diamond particles. Smaller (ca. 3 microm), normal and reversed-phase, core-shell diamond particles have been used for HPLC, with 36,300 plates/m for mesitylene in a separation of benzene and alkyl benzenes and 54,800 plates/m for diazinon in a similar separation of two pesticides on a C(18) adsorbent.