Efficient surface functionalization with polydopamine (PDA) films can be easily achieved on virtually any object via single immersion in slightly basic dopamine solutions. In such conditions, however, poor homogeneity, low thickness, and long time of reaction are usually the major limitations. Herein, we report a rational entry to the control of PDA deposition via chemical oxidation under slightly acidic conditions (pH 5.0) ensuring inhibition of uncontrolled autoxidation processes to gain insight about the reaction mechanism and the impact of oxidation conditions on PDA structure. Comparative chemical analysis of dopamine oxidation with three different oxidants (ammonium peroxodisulfate, sodium periodate, and copper sulfate) revealed significant differences in the reaction course and allowed selection of periodate for the fast and homogeneous deposition of PDA films with thickness never before reported. Notably, PDA coatings with unprecedented superhydrophilic/superoleophobic properties were obtained under conditions of high periodate concentration due to degradation of quinone units to yield carboxyl functions. Moreover, these films still present biocompatibility and metal cation reduction properties. Overall, these results provide a novel rational methodology to tailor PDA coatings for technological applications based on periodate control over dopamine polymerization and postsynthetic functional group modification

Eumelanin is not only a ubiquitous pigment among living organisms with photoprotective and antioxidant functions, but is also the subject of intense interest in materials science due to its photoconductivity and as a possible universal coating platform, known as "polydopamine films". The structure of eumelanin remains largely elusive, relying either on a polymeric model or on a heterogeneous aggregate structure. The structure of eumelanin as well as that of the closely related "polydopamine films" can be modified by playing on the nature of the oxidant used to oxidize dopamine or related compounds. In this investigation, we show that dopamine-eumelanins produced from dopamine in the presence of either air (O2 being the oxidant) or Cu(2+) cations display drastically different optical and colloidal properties in relation with a different supramolecular assembly of the oligomers of 5,6 dihydroxyindole, the final oxidation product of dopamine. The possible origin of these differences is discussed on the basis of Cu(2+) incorporation in Cu dopamine-eumelanin.

The formation of polydopamine under mild oxidation conditions from dopamine solutions with mechanical agitation leads to the formation of films that can functionalize all kinds of materials. In the absence of stirring of the solution, we report the formation of polydopamine films at the air/water interface (PDA A/W) and suggest that it arises from an homogeneous nucleation process. These films grow two times faster than in solution and can be deposited on hydrophilic or hydrophobic substrates by the Langmuir-Schaeffer technique. Thanks to this new method, porous and hydrophobic materials like polytetrafluoroethylene (PTFE) membranes can be completely covered with a 35 nm thick PDA A/W film after only 3h of reaction. Finally the oxidation of a monomer followed by a polymerization in water is not exclusive to polydopamine since we also transferred polyaniline functional films from the air/water interface to solid substrates. These findings suggest that self-assembly from a solution containing hydrophilic monomers undergoing a chemical transformation (here oxidation and oligomerization) could be a general method to produce films at the liquid/air interface.

The metallization procedure, proposed recently for signal improvement in organic secondary ion mass spectrometry (SIMS) (Delcorte, A.; Médard, N.; Bertrand, P. Anal.Chem. 2002, 74, 4955)., has been thoroughly tested for a set of kilodalton molecules bearing various functional groups: Irganox 1010, polystyrene, polyalanine, and copper phthalocyanine. In addition to gold, we evaluate the effect of silver evaporation as a sample treatment prior to static SIMS analysis. Ion yields, damage cross sections, and emission efficiencies are compared for Ag- and Au-metallized molecular films, pristine coatings on silicon, and submonolayers of the same molecules adsorbed on silver and gold. The results are sample-dependent but as an example, the yield enhancement calculated for metallized Irganox films with respect to untreated coatings is larger than 2 orders of magnitude for the quasimolecular ion and a factor of 1-10 for characteristic fragments. Insights into the emission processes of quasimolecular ions from metallized surfaces are deduced from kinetic energy distribution measurements. The advantage of the method for imaging SIMS applications is illustrated by the study of a nonuniform coating of polystyrene oligomers on a 100-microm polypropylene film. The evaporated metal eliminates sample charging and allows us to obtain enhanced quality images of characteristic fragment ions as well as reasonably contrasted chemical mappings for cationized PS oligomers and large PP chain segments. Finally, we report on the benefit of using metal evaporation as a sample preparation procedure for laser ablation mass spectrometry. Our results show that the fingerprint spectra of Au-covered polystyrene, polypropylene, and Irganox films can be readily obtained under 337-nm irradiation, a wavelength for which the absorption of polyolefins is low. This is probably because the gold clusters embedded in the sample surface absorb and transfer the photon energy to the surrounding organic medium.

Organosilicon layers were deposited on galvanized steel to give a protective coating against corrosion. HMDSO was atomized and injected into a DBD plasma at atmospheric pressure. Plasma‐polymerized HMDSO layers were different when HMDSO nanodroplets reacted directly in the plasma area or when such droplets reacted with the plasma once deposited on the surface. Addition of a plasma curing step was also studied. Influence of the deposition method on the properties of ppHMDSO layers was also studied. Layer structure was measured by SEM and interferometry, and its chemical structure was analyzed by FTIR and XPS. Corrosion resistance, which was measured by electrochemistry, was significantly increased when a plasma curing step was performed.