Suppression of Hydrophobic Recovery by Plasma Polymer Films with Vertical Chemical Gradients

Abstract

Vertical chemical gradients extending over a few nanometers were explored. The gradients are based on plasma-polymerized oxygen-containing ethylene (ppOEt) films. Using plasma conditions with low CO2/C2H4 ratio and high energy input, cross-linked films were deposited as base layer, while increasing CO2 and lowering energy input resulted in less cross-linked yet highly functional films as applied as top layer. Aging studies indicate that, in particular, for very thin gradient structures, the cross-linked subsurface zone effectively hinders reorientation of the surface functional groups, thus restricting hydrophobic recovery and oxidation effects.

Enhancing Surface Plasmon Resonance Detection Using Nanostructured Au Chips

“…Therefore, it is intriguing to use a functional ultrathin film, e.g., a plasma polymer film, both for adjusting the working range and the interaction with biomolecules. Such films, however, needs to be highly stable in the used environment in order to maintain the working range, which is currently under investigation [24–26]. …”

Enhancing sensitivity of SPR sensors by using nanostructured Au chips coated with functional plasma polymer nanofilms

“…To ensure deposition of stable plasma polymer films a gaseous mixture of CO 2 and C 2 H 4 was selected at gas flow rates of 8 and 4 sccm, respectively (gas ratio 2:1), the operation gas pressure of 10 Pa, and a power input of 70 W. Functional plasma polymer nanofilms with the thickness of nominally 5 and 10 nm were deposited onto the Au SPR chips. These coatings were already characterized in a previous study [17], where a deposition rate of 6 nm⋅min −1 , a film density of 1.5 g⋅cm −3 and a [O]/[C] ratio of 21% were determined. To increase the surface reactivity, the terminal O-rich layer was deposited by increasing the CO 2 /C 2 H 4 ratio towards the end of the plasma process without weakening the film structure [24].…”

“…One of the most suitable candidates to substitute SAMs for biosensors surface modification is plasma deposition of ultrathin functional polymer films (thickness of 5…20 nm) [17,18]. On the one hand, such thin layers should not disturb the SPR formation, and on the other hand, they should provide a substantial number of -COOH, -NH 2 , anhydride or other reactive groups.…”

Stable, nanometer‐thick oxygen‐containing plasma polymer films suited for enhanced biosensing

“…Plasma functionalization of surfaces, that is, stable incorporation of various functional groups or moieties, has recently made considerable progress with respect to oxygen‐, nitrogen‐, sulfur‐, and chlorine‐containing plasma polymer films (PPFs) . Various strategies to minimize aging and film loss in aqueous environments have been examined – also considering vertical chemical gradient structures . Therefore, plasma chemistry (gas phase and film growth processes) as well as post‐plasma chemistry (aging effects) need to be considered due to the pronounced chemical non‐equilibrium environment of a plasma.…”

“…This work investigates the characteristics of stable oxygen‐containing PPFs, which have previously been optimized based on a vertical chemical gradient structure, as surface functionalization on Au‐coated biosensor chips with flat and nanostructured surfaces. Such coatings were deposited from CO 2 /C 2 H 4 plasma allowing high control of oxygen incorporation, cross‐linking and etching conditions during film growth .…”