Stability enhancement of amine-rich thin films by plasma polymerized n-hexane pre-coating for biomedical applications

Amine-rich thin films have a great potential to bind biomolecules for different applications in biotechnology thus, has attracted great attention over the last decades. However, the stability of those films are still challenging which limits their usage in biotechnological applications. Here we investigate the influence of n-hexane (HEX) pre-coating on the stability of amine-rich thin film in air and liquid. Ethylenediamine (EDA) films were deposited on unmodified and n-hexane pre-coated glass and qurtz tuning fork (QTF) substrates by radio frequency generated low pressure plasma system. The influence of n-hexane prcoating on deposited EDA were studied by Fourier transform infrared spectroscopy (ATR-FTIR) for investigating functional groups, X-ray photoelectron spectroscopy for surface chemical compositions, contact angle measurement for stability in gas (air) and frequency measurement for stability in liquid phases. Plasma parameters were optimised by considering the most stable thin films in each media after characterization and stability studies. Results from aging studies indicate that HEX pre-coating those produced below and above 75 Watt was not stable in both air and liquid but pre-coating films produced at 75 Watt showed the highest stability. ATR-FTIR spectra which was collected from EDA demonstrated that below and above 75 Watt, amine groups could not be observed on substrate surfaces. Therefore, plasma parameters of the EDA were optimised to 75 Watt 5 minutes on the basis of ATR-FTIR spectra. In conclusion, a strong interaction between the substrate and plasma polymerized thin films was achieved by n-hexane pre-coating which resulted in enhanced film stability and decreased aging of amine-rich film in air and liquid thus can be adapted for various biotechnological applications.