Preparation and modification of thin carbon films

Abstract

Thin carbon films, in the form of pyrolysed photoresist films (PPF), are being increasingly used for electrochemical devices. This research investigates the preparation and subsequent modification of PPF through both the electrochemical reduction of aryl diazonium salts and through the UV attachment of alkenes to the iodinated surface.

The pyrolysis of photoresist films produces PPF that is a smooth (rms < 0.5 nm), amorphous carbon film that can be used for further electrochemical studies. The pyrolysis method was investigated to see the affect of holding the pyrolysis at three different temperatures during the pyrolysis and the corresponding times for which they were held; the effect of gas flow on the PPF was also addressed. It was seen that the gas flow whilst not affecting the roughness of the surfaces, the electrochemical cleanliness towards ferricyanide was affected, whilst different temperatures during the pyrolysis and the length of time they held was also seen to have some affect on both the electrochemical performance as well.

The modification of PPF was carried out with aryl diazonium derivatives of oligo(ethylene glycols) (OEGs). The protein resistance of these modified surfaces were also investigated and compared to the equivalent gold modified surfaces, both the effect of the chain length of the OEG as well as the change in hydrophilicity of the distal end was investigated. For a comparison OEG thiol modified gold surfaces were used. A Fluorescein isothiocyanate labelled protein, bovine serum albumin, was used and two methods employed to study the protein resistance. These methods were the elution of adsorbed protein from surface and the measurement of the protein whilst on the surface using fluorescence microscopy.

The use of iodine plasma to modify the PPF produces a surface similar to that of both hydrosilysed silicon and hydrogenated diamond surfaces. The use of UV light at 514 nm to activate the surface and attach alkenes was employed. UV addition of alkenes to the surface allows patterning as was observed via the modification of the iodinated carbon film with undec-10-enyl-2,2,2-trifluoroethanethioate on areas exposed to light and the deprotection of the thiol which was then exposed to gold nano particles and surface patterning was investigated with SEM. This will allow the production of nanoarray sensors in the future.