Multiscale Plasma-Catalytic On-Surface Assembly

Plasma-enabled superhydrophobic coatings on mild steel

This work demonstrates a new pathway to the direct on-surface fabrication of a superhydrophobic surface coating on mild steel. The coating was formed using dielectric barrier discharge (DBD) plasma to convert a liquid small-molecule precursor (1,2,4-tricholorobenzene) to a solid film via plasma-assisted on-surface polymerization. Plasma treatments were performed under a nitrogen atmosphere with a variety of power levels and durations. Samples were analysed by optical and scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), Raman spectroscopy, optical profilometry, contact angle measurement, and potentiodynamic polarisation tests. Wettability of the films varied with the plasma parameters, and through the inclusion of graphene nanoplatelets in the precursor. High-dose plasma exposures of the nanoplatelet-containing precursor created superhydrophobic films with water contact angles above 150°. Potentiodynamic polarisation tests revealed that the superhydrophobic coating provided little or no corrosion protection.

Antimicrobial adhesive films by plasma-enabled polymerisation of m-cresol

This work reveals a versatile new method to produce films with antimicrobial properties that can also bond materials together with robust tensile adhesive strength. Specifically, we demonstrate the formation of coatings by using a dielectric barrier discharge (DBD) plasma to convert a liquid small-molecule precursor, m-cresol, to a solid film via plasma-assisted on-surface polymerisation. The films are quite appealing from a sustainability perspective: they are produced using a low-energy process and from a molecule produced in abundance as a by-product of coal tar processing. This process consumes only 1.5 Wh of electricity to create a 1 cm² film, which is much lower than other methods commonly used for film deposition, such as chemical vapour deposition (CVD). Plasma treatments were performed in plain air without the need for any carrier or precursor gas, with a variety of exposure durations. By varying the plasma parameters, it is possible to modify both the adhesive property of the film, which is at a maximum at a 1 min plasma exposure, and the antimicrobial property of the film against Escherichia coli, which is at a maximum at a 30 s exposure.