Christopher L. Reeves

Derivatized Porous Silicon Mirrors: Implantable Optical Components with Slow Resorbability

The stability of derivatized mesoporous silicon mirrors in simulated human blood plasma has been assessed. The rate at which they are dissolved in-vivo is predicted to be tunable by surface chemistry over timescales of weeks to years, and high reflectivity can be maintained until the bottom of the multilayer stack starts to corrode. Such biodegradable optical components could be utilized to direct and define optical path lengths for therapeutic treatments and minimally-invasive diagnostics.

Tuning the Pore Size and Surface Chemistry of Porous Silicon for Immunoassays

To use porous silicon as an optical interferometric biosensor, the pores must be sufficiently large to allow easy ingress of reagents and the layer must also display Fabry-Perot optical cavity modes. Here the detection antibody is rabbit IgG and the analyte is α-rabbit IgG conjugated to horseradish peroxidase (HRP). For this model system, the pores should be >50 nm in diameter. Such diameters have been obtained in 0.05 Ω cm n-type silicon using anodisation followed by chemical etching in ethanolic KOH and also by anodising 0.005 Ω cm p-type material. The latter also displays optical cavity modes. The silicon surface is oxidised in ozone, silanised using aminopropylmethoxysilanes with one, two or three methoxy groups, and cross linked to IgG using glutaraldehyde. High specific binding is found for mono-, di- and tri-methoxy silanes, but the lowest non-specific binding is found for silanisation with the tri-methoxy silane.

Liquid injection metal organic chemical vapour deposition of nickel zinc ferrite thin films

Abstract Liquid injection metal organic chemical vapour deposition has been used to grow thin films of the single metal oxides of nickel, zinc and iron, the binary ferrites of nickel ferrite and zinc ferrite and the ternary nickel zinc ferrite. The precursor chemicals used for the deposition of the metal oxide layers were solutions of the metal thd compounds (thd=2,2,6,6-tetramethyl-3,5-heptanedionato) dissolved in tetrahydrofuran. The growth rates of the single metal oxide layers have been systematically determined as a function of substrate temperature in the temperature range 300–650°C and the ferrite layers were deposited at a substrate temperature of 500°C. The ferrite layers were polycrystalline with well-defined spinel crystal structures.

Autoclaving of Porous Silicon within a Hospital Environment: Potential Benefits and Problems

The microstructure and chemical composition of silicon surfaces subjected to standard sterilization protocols in hospital autoclaves has been examined. Both metallic contamination and structural changes can accompany porous Si hydrolysis. The in-vitro incubation of bulk and porous Si discs with human lymphocytes reveals potential sources of cytoxicity such as silane emission, and the supersaturation of media with eluted Si.