The
growth and properties of the multilayers were characterized by gold
model substrates. Although gold is chemically different from IEMs,
the bulk and surface properties of PEMs are not dependent on the type
of surface characteristics of the substrate after a sufficient number
of layers,50 (link),54 (link) making gold a suitable model
surface. Prior to LbL coating, gold substrates were sonicated for
5 min in Milli-Q water and dried in a stream of argon. Sonication
was repeated with acetone, ethanol, and dichloromethane, and the gold
substrates were subsequently cleaned from organic material by 5 min
of air-based plasma by a plasma cleaner (Diener electronic GmbH, Germany).60 (link) Afterward, the surfaces were immersed in a 10
mM MESNA solution overnight. Thiol groups of MESNA form strong dative
bonds (40–50 kcal/mol) with gold surfaces, while the sulfonate
groups (R-SO3–) of MESNA supply a negative
surface charge.61 (link) Then, the gold substrates
were coated with the PEM using the same LbL procedure as the one employed
for the CMX before drying the substrates in a vacuum oven at 30 °C.
growth and properties of the multilayers were characterized by gold
model substrates. Although gold is chemically different from IEMs,
the bulk and surface properties of PEMs are not dependent on the type
of surface characteristics of the substrate after a sufficient number
of layers,50 (link),54 (link) making gold a suitable model
surface. Prior to LbL coating, gold substrates were sonicated for
5 min in Milli-Q water and dried in a stream of argon. Sonication
was repeated with acetone, ethanol, and dichloromethane, and the gold
substrates were subsequently cleaned from organic material by 5 min
of air-based plasma by a plasma cleaner (Diener electronic GmbH, Germany).60 (link) Afterward, the surfaces were immersed in a 10
mM MESNA solution overnight. Thiol groups of MESNA form strong dative
bonds (40–50 kcal/mol) with gold surfaces, while the sulfonate
groups (R-SO3–) of MESNA supply a negative
surface charge.61 (link) Then, the gold substrates
were coated with the PEM using the same LbL procedure as the one employed
for the CMX before drying the substrates in a vacuum oven at 30 °C.
