Abstract:Conventional pin-to-point continuous wave Helium Corona plasma discharge was successfully used in Soft Plasma Polymerization (SPP) processes to immobilize into water and onto glass polymerized bioactive Cerrena unicolor laccase coatings. The coatings were tested for bioactivity and durability under water wash. The coatings showed up to 59% bioactivity relative to the native laccase in water deposition, undoubtedly due to damage to and fragmentation of monomer molecules by the active, energetic species in the plasma. However, plasma deposited laccase coatings on glass delivered 7 times the laccase activity of the same non-plasma deposition process in the coating after water wash. This latter result would seem to be due to the ability of the plasma to both crosslink monomer and more strongly bond it to the glass surface by a combination of surface cleaning and the creation of active, high energy sites in both glass and laccase molecules. FTIR analysis indicated that the core copper containing moieties at the centre of the molecule largely remain undamaged by this plasma type so that bonding and cross-linking reactions are likely to mainly involve species around the outer perimeter of the molecule. The chemical composition and structure of laccase biocoatings deposited by Corona SPP are described. The combination of the coating performance parameter values for retained activity and durability under water wash indicates that a relatively simple Corona plasma process for deposition of biocoatings, which directly polymerizes the monomer with no added matrix or encapsulant material, may offer enhanced solutions for biocatalyst, sensor or lab-on-a-chip applications.

An atmospheric pressure nonthermal equilibrium corona plasma jet is described for depositing polymeric coatings with a high degree of functional chemistry retention. A long chain perfluorocarbon molecule was introduced as a vapor into a helium plasma at atmospheric pressure and coatings were deposited onto Si wafers at rates of 60-100 nm/min. XPS, FTIR and contact angle measurements indicate that a controlled polymerization reaction took place through the vinyl group of the monomer, with minimal fragmentation of the functional perfluoro chain. Electrical characterization of the corona plasma indicates that the power coupled into the jet was 6.8 W. It is proposed that low specific energy (J/cm 3 ) coupled into the plasma region is inherent to this plasma type and enables deposition of coatings with minimal fragmentation of the precursor monomer molecule. The system is inherently suitable for small-to-moderate area, high-added-value functional coating.

This work directly compares vapour and liquid aerosol states for the deposition of perfluorocarbon coatings using an atmospheric pressure, non‐thermal equilibrium plasma jet system. The objective of the study is to evaluate how the physical state of the precursor (gas or liquid), influences the fragmentation of the monomer molecules in the plasma and the subsequent coating properties. Specifically the effect of gas or liquid aerosol precursor feed on the ability to achieve a soft plasma polymerization (SPP) is assessed with a view to producing a coating that exhibits minimal fragmentation, while being well cross‐linked. The precursor (perfluoro‐1‐decene) was introduced into a helium plasma and coatings deposited at rates of up to 50 nm · min−1. The deposited coatings were examined using XPS, FTIR, contact angle and ellipsometric measurements. These indicated that a controlled polymerization reaction through the vinyl group of the monomer had taken place in the case of the gas deposited samples with only minor fragmentation of the functional perfluoro chain. Furthermore, a high level of cross‐linking was achieved and the perfluorocarbon coatings were stable to a toluene wash. In contrast, while coatings deposited using the liquid deposition technique showed good retention of monomer molecular structure, they exhibited poor stability when immersed in toluene. This is attributed to lower levels of cross‐linking of the liquid precursor in the plasma, compared with coatings deposited using the gaseous precursor technique. magnified image

Development of new techniques for deposition of biologically active coatings in the form of bio-recognition layers in biosensor construction is a current technological challenge. Biosensors are widely applied in environmental protection in determination of hazardous materials, e.g., catechol, hydrochinon or resorcinol. Application of a soft plasma polymerization (SPP) technique by lowenergy-density corona discharge has allowed significant simplification of the deposition process of bio-recognition layers. However, the mechanism of the SPP process is by no means fully understood. This paper presents insights into the mechanism of binding laccase enzyme onto graphene oxide (GO) and multiwalled carbon nanotubes (MWCNT) through analysis carried out by density functional theory (DFT) methods and Fourier transform infrared spectroscopy (FTIR). The objective was to examine the mechanism on the basis of binding energies and electrostatic interactions between laccase and carbon nanomaterials as well as enzyme structure after cold plasma deposition. The lowest binding energies have been calculated for the ON bond between the arginine amino acid of laccase and the hydroxyl group of GO and the CO bond between the serine molecule of laccase and the carboxyl groups of GO and MWCNT. FTIR and DFT studies showed that the chemical structures of the laccase enzyme and carbon nanomaterials after corona jet plasma treatment are not substantially changed. Preliminary recognition of the mechanism of biosensing layer deposition by the SPP technique opens the way to application of this innovative technique to the construction of other biosensors such as for determination of pollutants in water samples.

Development of new, faster methods of biosensor construction is a huge challenge for current science and industry. In this work, biosensor construction was carried out using a new soft plasma polymerization (SPP) method in which a bio-recognition layer of laccase enzyme was polymerized and bonded to a glassy carbon electrode (GCE) substrate under atmospheric pressure with a corona discharge jet. Laccase belongs to the oxidoreductase enzyme group with four copper atoms in its active center. Application of the corona SPP plasma method allows reduction of the time needed for biosensor construction from several hours to minutes. The presented work includes optimization of the laccase bio-recognition layer deposition time, structural studies of the deposited laccase layer, as well as study of the fabricated biosensor applicability for the determination of Rutin in real pharmaceutical samples. This method produces a biosensor with two linear ranges from 0.3 μmol/dm3 to 0.5 μmol/dm3 and from 0.8 μmol/dm3 to 16 μmol/dm3 of Rutin concentration. Results shown in this work indicate that application of the one-step, corona SPP method enables biosensor construction with comparable analytical parameters to biosensors fabricated by conventional, multi-step, wet methods.