Plasma functionalisation

Studies from our laboratories by Pantarotto et al. (2004a, b), Wu et al. (2005) and Kostarelos et al. (2007) using covalently functionalised CNTs (1,3-dipolar cycloaddition reaction chemistry) have reproducibly described that CNTs were uptaken by cells via pathways other than endocytosis. This work has experimentally observed that CNTs were able to interact with plasma membranes and cross into the cytoplasm without the apparent need of engulfment into a cellular compartment... 

An other interesting strategy is the modification of the surface of the electrodes with multiwalled carbon nanotubes (MWNTs) or single-walled carbon nanotubes (SWNTs) [13,32]. The MWNTs are grown on the electrodes covered with a nickel catalyst film by plasma-enhanced chemical vapour deposition and encapsulated in Si02 dielectrics with only the end exposed at the surface to form an inlaid nanoelectrode array [13]. In the other case, commercial SWNTs are deposited on SPE surface by evaporation [32], The carbon nanotubes are functionalised with ssDNA probes by covalent attachment. This kind of modification shows a very efficient hybridisation and, moreover, the carbon nanotubes improve the analytical signal. 

The evolution of XPS spectra, given in Fig. 21 shows that the contribution of pristine non-functionalised C atoms remains majoritary, whatever the duration of the plasma treatment. The most noticeable change is the increase of the component (4) corresponding to covalent C—F bonds which are formed by the interaction of F radicals with the reactive sites of the material, i.e. surface defects, hydrogenated/oxygenated C atom, borders of the graphitic domains. When all these surface sites are fluorinated, the surface is saturated, what is accounted for by the value of C/F ratio of 3.2 obtained for t > 120 min [99],... 

C2 1.0 Aliphatic non-functionalised sp3 C in a non-fluorinated environment (areas modified by plasma effect ) Non-functionalised sp C in P position to one F atom... 

Plaisma polymerisation is an effective route to new surface chemistries. Plasma polymerisation is widely employed as a coating technology, whereby the value of a commodity material is substantially enhanced by the provision of a specific (new) surface property. By employing low plasma powers, highly functionalised surfaces can be fabricated. Such surfaces may be used to direct specific surface processes, e.g. cell adhesion. 

Habibovic et al., 2002 Kokubo, Kim and Kawashita, 2003 Kokubo and Yam-aguchi, 2011), formation of thin calcium phosphate films on functionalised surfaces (for example Bunker et al., 1994 Tanahashi, Yao and Kokubo, 1995 Layrolle, 2011), laser surface engineering (Kurella, 2005), plasma electrolytic oxidation (PEO, Yerokhin et al., 1999 Yerokhin, 2005 Curran and Clyne, 2005 Wang, Fu and Chen, 2012), pulsed laser deposition (PLD) (Wang et al., 1997 Koch et al., 2007 Man et al., 2009) and several other less frequently applied techniques. 

The plasma process can produce a wide range of nanomaterials om oxides, nitrides, carbides and even pure metals. The surface of the particles can be activated, and one of the main challenges will be the functionalisation of these materials by creating nanocomposites. Those new materials offer advantages in the fields of heterogeneous catalysts. 

A completely different strategy for the surface functionalisation of CNTs with nitrogen-containing groups is the treatment of CNTs under atomic nitrogen flow obtained by molecular nitrogen dissociation in an Ar -t N2 microwave plasma. X-ray photoelectron spectroscopy of the nanotube surface demonstrated the presence of amides, oximes and mainly amine and nitrile groups. ... 

Michelmore, A., Steele, D.A., Whittle, J.D., Bradley, J.W., Short, R.D., 2013a. Nanoscale deposition of chemically functionalised films via plasma polymerisation. RSC Adv. 3, 13540-13557. 

Surface functionalisation of biodegradable polylactic acid was achieved by plasma coupling reaction of chitosan. Surfaces were characterised by contact angle measurements and X-ray photoelectron spectroscopy. Two cell lines were cultured on the modified surface. Potential applications in tissue engineering are mentioned. 36 refs. CHINA SINGAPORE Accession no.906871... 

Functionalisation of VACNT. Nanotube functionalisation and exfoliation were performed in a much less powerful pulsed DC plasma reactor. The chamber walls form the anode, while the CNT samples were placed over the substrate holder cathode. The reactor chamber was first evacuated to 10 Torr by a diffusion pump to ensure low residual air. Then pure mygen (1 seem) was introduced and the ehamber pressure was controlled at 80 mTorr. The pulsed DC power supply was set at —700 V at 20 kHz and 45% duty cycle. Treatments were aeeom-plished within 2 minutes. 

The integrated intensity ratio of the D and G peaks (/d/1g) has been often used as an indication of the level of chemical functionalisation or defect density on carbon nanotube surfaces. This ratio is much larger (7d//g = 1-6) for GE-2 compared to GE-1 (7d/7g = 0-54), indicating a more defective surface for GE-2. For GE-1 the 7d/7q ratio increases from 0.54 to 0.7 upon O2 plasma etching, indicating that the defect density increases. This increase in defect density is also shown by G line broadening. For GE-2 the 7d/7g ratio reduces from 1.6 to 1.2, which gives the false idea of a... 

Paletta, J.R.J., et al., 2010. RGD-functionalisation of PLLA nanofibers by surface coupling using plasma treatment influence on stem cell differentiation. Journal of Materials Science Materials in Medicine 21 (4), 1363-1369. Available at http //link.springer.eom/10.1007/ S10856-009-3947-2. 

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