Supporting Information for: Surface effects on. catechol/semiconductor interfaces

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1 Supporting Information for: Surface effects on catechol/semiconductor interfaces Arrigo Calzolari,, Alice Ruini, and Alessandra Catellani CNR-NANO, Istituto Nanoscienze, Centro S3 I Modena, Italy, Istituto Nanoscienze, Centro S3 I Modena, Italy, Dipartimento di Fisica, Università di Modena e Reggio Emilia, I Modena, Italy, and CNR-IMEM, Parco Area delle Scienze, 37A, I Parma, Italy and CNR-NANO, Istituto Nanoscienze, Centro S3 I Modena, Italy arrigo.calzolari@nano.cnr.it To whom correspondence should be addressed CNR-NANO, Istituto Nanoscienze, Centro S3 I Modena, Italy Istituto Nanoscienze, Centro S3 I Modena, Italy Dipartimento di Fisica, Università di Modena e Reggio Emilia, I Modena, Italy CNR-IMEM, Parco Area delle Scienze, 37A, I Parma, Italy and CNR-NANO, Istituto Nanoscienze, Centro S3 I Modena, Italy S1

2 S1. Structural and electronic properties of clean surfaces The results reported below correspond to fully relaxed clean (10 10) surfaces of the semiconductor substrates under investigation. Structural and electronic properties are in very good agreement with previous experimental and theoretical studies. See for instance References S1-S5. Table S1: Structural parameters for clean (10 10) surfaces. Lattice parameters a 0 and c and distances d X are expressed in Å. Subscript labels refer to atoms as in Figure 1 (main text). a 0 c d AC d d z SiC GaN ZnO a InN CdS CdSe a From Ref. S6. S2

3 Figure S1. Surface bandstructures of relaxed (10 10)-(1 1) surfaces of hexagonal SiC, GaN, InN, CdS and CdSe substrates. Zero energy is fixed to the top of the valence band of each system. Labels of high symmetry directions refer to the scheme on the left of the 2D Brillouin Zone (BZ). Fully occupied and empty surface states lying in the gap area are marked with SS v and SS c respectively. S3

4 S2. Effect of surface strain on molecular deprototonation Figure S2. Adsorption configurations of isolated catechol molecules on strained SiC(10 10) surface. Linear strain is applied separately along x and y directions as percentage of the undistorted lattice parameters a 0 and c. S4

5 Figure S3. Adsorption configurations of isolated catechol molecules on strained CdSe(10 10) surface. Linear strain is applied separately along x and y directions as percentage of the undistorted lattice parameters a 0 and c. S5

6 S3. Adsorption of catechol on hydroxylated SiC Fig. S4 summarizes the structural and electronic properties of catechol/water/sic interface, described in the main text. For sake of completeness we compared these results with the case of ZnO substrate, that has been previously investigated in Ref. S6. In catechol/water/zno interface the presence of water has a less dramatic effect, since it saturates a bounce of surface states that intrinsically lays at the top of the valence band [S7], instead of the center of the gap, as in SiC. The most evident difference in the two cases is related to the energy position of the HOMO-derived state. In ZnO case, the inclusion of solvent pushed the H m state towards the CBM, the opposite happens in the case of SiC where the catechol HOMO displaces into the valence band. This different behavior may be ascribed to the different electrostatic polarization (i.e. surface acidity) of the two substrates. Figure S4. (a) Adsorption configurations of isolated catechol molecules on hydroxylated OH:SiC(10 10) surface. Dashed lines identify H-bonds. (b) Total and projected DOS for catechol on OH:SiC(10 10) surface. Zero energy is referred to Fermi level. Labels refers to Figure 3 (main text). Inset: HOMO- LUMO (blu lines) energy alignment of catechol with respect to the OH:SiC band gap (red shaded area). All energies are aligned to vacuum level. S6

7 SI References [S1] Magnusson, K. O.; Flodstrom, S. A. Phys. Rev. B 1988, 38, [S2] Northup J. E.; Neugebauer, J. Phys. Rev. B 1996, 53, R10477 R [S3] Pollmann, J.; Kruger, P.; Sabisch, M. Phys. Stat. Sol. B, 1997, 202, 421. [S4]Ivanov, I.; Pollmann, J. Phys. Rev. B 1988, 24, 7275Ű [S5] Terentjevs, A.; Catellani, A.; Prendergast, D.; Cicero, G Phys. Rev. B 2010, 82, [S6] Calzolari, A.; Ruini, A.; Catellani, A. J. Am. Chem. Soc. 2011, 133, [S7] Calzolari, A.; Catellani, A. J. Phys. Chem. C 2009, 113, 2896Ű2902. S7