Boric acid as an efficient agent for the control of polydopamine. self-assembly and surface properties.

Transcription

1 Boric acid as an efficient agent for the control of polydopamine self-assembly and surface properties. Anne Schneider a, Joseph hemmerlé a, Manon Allais a, Jeoffrey Didierjean b, Marc Michel b, Marco d Ischia c, Vincent Ball a,d*. a: Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche 1121, 11 rue Humann, Strasbourg Cedex, France. b : Luxembourguish Institute for Science and Technology, Department of Materials Research and Technology (MRT), 41, rue du Brill, L-4422 Belvaux, Luxembourg. c: Department of Chemical Sciences, University of Naples, Federico II, Via Cintia 4, I-80126, Naples, Italy. d: Université de Strasbourg, Faculté de Chirurgie Dentaire, 8 rue Sainte Elisabeth, Strasbourg, France. Supporting Information Additional experimental details : The ellipsometry experiments were performed using a He-Ne laser, λ=632.8 nm, at a constant angle of incidence of 70. The complex refractive index of the PDA films was taken constant and equal to i as determined in our previous investigation. 34 The thickness of the thin SiO 2 layer due to spontaneous oxidation of silicon was measured before PDA deposition and taken to be constant in the following steps of the 1

2 experiment. The thickness values were obtained as the average ± one standard deviation on 5 regularly spaced points along the major axis of the rectangular shaped silicon wafers. A B 2

3 Figure SI1 : UV-vis spectra of dopamine solutions (3.5 mm) at ph 8.5 in the presence (A) of boric acid (43 mm, the ph being readjusted to 8.5) and in the absence (B) of boric acid after different exposure times to the air, as indicated in the insets. 3

4 1.2e-4 A 8.0e-5 I (A) 4.0e e E (V vs Ag/AgCl) 2e-5 B 1e-5 I (A) 0-1e-5-2e E (V vs Ag/AgCl) 4

5 Figure SI2 : A : Successive cyclo-voltamograms of dopamine at 3.5 mm in Tris buffer containing 43.0 mm boric acid with ph readjusted to 8.5. ( ) corresponds to the first oxidation-reduction cycle and ( ) corresponds to the 9 subsequent oxidation-reduction cycles. The potential scan rate was of 100 mv.s -1 in all cases. The red arrow indicates the qualitative evolution of the CV scans upon an increase in the number of performed oxidation-reduction cycles. B: Cyclo-voltamograms performed at a potential scan rate of 100 mv.s -1 in the presence of 1 mm K 4 Fe(CN) 6 in the Tris buffer on the pristine electrode ( ) and after having performed the 10 oxydation-reduction cycles in the presence of dopamine+boric acid displayed in part A ( ). 5

6 With boric acid Without boric acid Figure SI3: XPS survey spectra of PDA films deposited on silicon slides during 3 h before dilution with either Tris buffer or Tris buffer containing 430 mm boric acid. The reaction was continued during 15 h before rinse with water, drying and spectral acquisition. The two spectra are shifted for clarity. The red arrow highlights the presence of some boron in the film exposed to diluted dopamine containing boric acid. Estimation of the fraction of dopamine present on the surface of the beaker after formation of a PDA film 45 nm in thickness. The mass density of PDA is assumed to be equal to 1.4 g.cm -3 in agreement with data from the literature [1]. 6

7 The reaction vessel is a cylindrical beaker of radius r = 4 cm and is covered by a PDA film over a height h close to 5 cm. The PDA film also forms at the water /air interface and at the bottom of the reaction vessel. Hence an underestimation of the surface area of the PDA film, neglecting the surface roughness, is: S=2π.r²+2π.r.h cm² The film thickness at the end of the oxidation process in the presence of 50 mm Tris buffer at ph = 8.5 is d = 45 nm= 4.5 x 10-6 cm. Hence the film volume is about: V F = S.d=226.4 x 4.5 x cm 3 Hence the mass of the PDA film: m F =ρ.v F =1.4x 0.001= 1.4 x 10-3 g Dopamine looses 2 protons upon formation of PDA, hence the molar mass of the monomer unit is M=150 g.mol -1 and the number of dopamine molecules present in the film is then approximated by: n F =m F /M 1.4 x10-3 /150=9.3 x 10-6 mol. The number of dopamine molecules initially present in the solution, V S =100 ml at C S = 10.6 mm is: n S =C S.V S = 0.1x10.6x10-3 =1.06 x 10-3 mol. Finally the fraction of dopamine molecules present in the film is given by : n F /n S 8.8 x 10-3 hence less than 1%. 7