Work function of the oxygen functionalized graphenic surfaces – Integral experimental and theoretical approach

Functionalization of graphenic surfaces by oxygen plasma toward enhanced wettability and cell adhesion: experiments corroborated by molecular modelling

“…This observation is directly related to an increase in the work function of the graphenic surface with oxygen surface concentration which results in a dramatic change in the ionization efficiency of the desorbing fragments. 24 In Fig. 4 (grey panel), the possible clusters detected in LDI-MS spectra are shown for the unmodified (C 54 + , C 70 + , C 87 + ) and functionalized (C 26 OH + , C 28 O + , C 32 COOH + ) graphenic surface.…”

“…In our previous works, we determined the correlation between the work function and the number of surface functional groups. 24 Following this relationship, the experimental values of water contact angle based on the surface coverage can be determined. This allows for a direct comparison between the experimental and theoretical values of WCA.…”

“…Nevertheless, the prolonged exposure to plasma (5 min) may lead to minor structural destruction as revealed by the appearance in Raman spectra of a small D band at 1350 cm À1 corresponding to a disordered carbon structure. Thus, upon higher exposure time to plasma only, the graphenic surface can be etched as discussed elsewhere in terms of DFT molecular modelling 24 and experimentally observed for several carbon materials like graphite, graphene, and CNTs when oxygen plasma was applied for their functionalization. [49][50][51] In Fig.…”

“…This observation is directly related to an increase in the work function of the graphenic surface with oxygen surface concentration which results in a dramatic change in the ionization efficiency of the desorbing fragments. 24 In Fig. 4 S1 (see the ESI †).…”

“…23 Compared to traditional wet chemical oxidation methods that require harsh chemicals like strong acids, plasma is considered to be a facile option for tuning the surface properties of carbon materials by keeping their bulk properties intact. 21,24 The plasma treatment is considered to be advantageous, as it is an environmentally friendly technique, takes a short time for functionalization, and can be precisely controlled by adjusting working parameters (type of feed gas, pressure, power of the generator, and exposure time). The plasma modification proved to be useful for the functionalization of various polymeric biomaterials such as polyethylenes, 25 polycaprolactone, 26 poly(p-xylylenes), 27 and polyurethanes 28 to mention the most often investigated in terms of biomedical applications.…”