Atmospheric-pressure plasma deposited epoxy-rich
thin films as platforms for biomolecule immobilization
– application for anti-biofouling and xenobioticdegrading
surfaces
G. Camporeale, M- Moreno-Couranjou, S. Bonot, R. Mauchauffé, N.
D. Boscher, C. Bebrone, C Van de weerdt, H.-M. Cauchie, P. Favia
and P. Choquet
Plasma Process. Polym., 2015, 12, 1208-1219
Introduction
 LP plasma processes have been used for deposition of thin films funcionalized with
groups such as amino, carboxylic, or epoxy for covalent bonding of peptides/proteins
with biological activity
 APDBD used for fast deposition of epoxy-rich layers
 study of influence of plasma process parameters on the chemical and morphological
properties of layer
 two enzymes with different activities (dispersin, laccase) have been used in order to
explore the possibilities of the epoxy-containing layer as a platform for biomolecule
immobilization
Experiment
 two kinds of substrates
• mirror-polished stainless steel disks
• two face-polished silicon (111) wafers
 Ar + GMA (flow 10,5 ml/min)
 plasma was generating using corona source
• CW and PW discharge mode
• P = 50W
• in PW mode - ton fixed at 10 ms, toff varied
from 10 ms to 80 ms
Obr 1: GMA structure and plasma source.
Used characterization methods
 Scanning electron microscopy (SEM)
• thickness of ppGMA
• film deposition rate
 Atomic force microcopy (AFM)
 Fourier-transform infrared spectroscopy (FTIR)
 X-ray photoelectron spectroscopy (XPS)
Scanning electron microscopy
 SEM is based on imaging of sample by scanning it with focused electron beam
 types of signal
 secondary electrons (SE)
• SE are emitted from very close to the sample surface (~ 100 nm)
• SE used for topography imaging (emitted mostly from sharp edges)
 backscattered electrons (BSE)
• BSE emerge from deeper locations ((~ 1 um)
• intensity of BSE signal is related to atomic number
• BSE provide information about the distirbution of different elements in the sample
 characteristic x-rays
• used to identify the composition and measure the abundance of elements in the sample
Scanning electron microscopy
Obr 2: Principle od SEM.
Atomic force microcopy
 AFM is suitable technique for study of the surface of thin solid films
 the cantilever with a sharp tip scans the surface of the analyzed sample
 lateral scanning ensures piezoelectric crystal which moves the probe over the sample
 three possible modes
• contact
• non-contact
• tapping
Obr 3: Principle of AFM.
Atomic force microcopy
Obr 4: Principle of AFM.
SEM and AFM results
 PW mode leads to higher film rates FR
• FR (CW) = 1,2 nm/s
• FR (PW, 10:80) = 1,8 nm/s
 pinhole free coating
 PW mode leads to smoother surface without aggregates
SEM and AFM results
Fourier-transform infrared spectroscopy
 IR spectroscopy is based on absorption of IR radiation which influence vibrational and
rotational states of chemical compound
 FTIR use Michelson interferometer includes beamsplitter
 interference signal measured by the detector as a function of the optical pathlength
difference is called the interferogram
 IR spectrum is computed from the interferogram by performing a Fourier transform
 quantitative analysis – Lambert-Beer law
where I0 is the intensity of incident light, I is intensity of the light transmitted by sample, a is absorption coefficient, b is thickness of
the sample and C is the sample concentration.
)exp(0 abCII 
Fourier-transform infrared spectroscopy
Obr 7: Principle of FTIR.
Fourier-transform infrared spectroscopy
 four characteristic epoxide peaks
• 3060 cm-1 C-H epoxide ring stretching
• 1258 cm-1 epoxide ring breathing
• 910 cm-1 epoxide ring asymmetric deformation
• 852 cm-1 epoxide ring symmetric deformation
 in CW mode, all peaks barely detectable
 increasing toff leads to increasing
the epoxide bands intensity
 in PW mode film with high monomer
structure retention due to chemical
reactions occurring during the toff between
intact monomer molecules and surface radical
centers generated during the ton period
X-ray photoelectron spectroscopy
 XPS is based on irradiation of a material with a beam of Xrays that cause emission
of the inner shell electron
 measurement of the kinetic energy Ek of the emitted electron and determination of
elemental composition and chemical and electronic states of the elements
where EB is the binding energy,
hf is energy of photon and
ϕ is spectrometer work function.
 kB EhfE
Obr 8: Principle of XPS.
X-ray photoelectron spectroscopy
 PW mode allows a higher retention of the initial ester and epoxy groups
 increasing the toff leads to an increase of the epoxy surface content
What I like
 information about uncertainty related to the XPS measurement (2 at%)
 thickness measurements were carried out on at least three samples for each condition
What I miss
 no information about layer thickness
 FTIR results could be discussed in more details
• more details about manipulation with background – which method was used?
• area evolution of other epoxide peaks – is there the same trend?
Thank you for attention!
Šárka Trochtová