Adsorption related SERS

1. Effect of the substrate charge and morphology on the SERS spectra of some benzohydroxamic acidsOrlin Blajiev, Kitty Baert, Annick Hubin Effect of the substrate charge and ..

2. Effect of the substrate charge and .. Adsorption related SERS Two diverging directions Analytical detection of organic molecules in solutions Adsorption of organic molecules on metal substrates

3. Effect of the substrate charge and .. Molecular adsorption geometry by means of SERS Parameters needed Local direction of the electric field vector Vector alignment of the scattered electric field and transition dipole moment Influence of the chemical adsorption on the directions of the transitional dipole moments

4. Effect of the substrate charge and .. Aim of the work Experimental part To decrease the influence of the SERS substrate morphology by crystallizing of round and single Ag particles. Computational part To reduce the effect of the substrate size by enlarging it as much as possible. To investigate the effect of the substrate charge on the geometry optimisation and on the vibration spectra.

5. Effect of the substrate charge and .. Experimental details • Preparation of the SERS substrate • Solution A 0.1 M AgNO3+KOH+NH4OH • Solution B 0.05 M dextrose • Copper plates were dipped for 2 seconds and immediately rinsed in water • Organic compound • Benzohydroxamic acid (BHA) • Solutions • 90 % H2O+10% MeOH+10-4 M BHA • x% H2O+(100-x)% MeOH+10-4 M BHA

6. Effect of the substrate charge and .. Morphology of the substrate SEM pictures of the SERS substrate

7. Effect of the substrate charge and .. Influence of the substrate preparation

8. Effect of the substrate charge and .. Influence of the position Intensity /arb. units Wavenumbers /cm-1

9. Effect of the substrate charge and .. Influence of the focusing Intensity /arb. units Wavenumbers /cm-1

10. Effect of the substrate charge and .. Influence of the solvent 90% water+10% MeOH+10-4 BHA 100% MeOH+10-4 BHA Intensity /arb. units 90% water+10% MeOH+10-4 BHA Wavenumbers /cm-1

11. Effect of the substrate charge and .. Previous computational models Single-atom “substrate”1 Slab substrate1,2 DFT, periodic boundary SIESTA, DZP basis set DFT, PC-Gamess 6-311G* and 3-21G (Ag)‏ 1. O. Blajiev et al. J. Raman Spectr. 34 p.295 2003, 2. O. Blajiev et al. J. Raman Spectr. 37 p.777 2006

12. Effect of the substrate charge and .. Charge topology on a slab substrate In the topmost plane of the Ag slab In the plane of the hydroxamic group

13. Effect of the substrate charge and .. Quantum-chemical approach used in this work Embedded cluster method-ONIOM Large substrate-39 Ag atoms in total, 12 of them treated explicitly Basis sets: MIDIX (BHA), LANL2DZ (Ag), UFF for the low level system Restriction of the charge flow Charges of –2, -1, 0, 1, and 2 electrons

14. Effect of the substrate charge and .. Effect of the charge on the optimization geometry Charge of -2 Charge of +2

15. Effect of the substrate charge and .. Charge distribution between the molecule and substrate

16. Effect of the substrate charge and .. Charge distribution within the hydroxamic group

17. Effect of the substrate charge and .. Effect of the charge on the quadrant stretch at 1588 cm-1

18. Effect of the substrate charge and .. Effect of the charge on the quadrant stretch at 1486 cm-1

19. Effect of the substrate charge and .. Conclusions • Yet another SERS substrate is proposed. • Stable, well resolved spectra of BHA on it were obtained. • Successful quantum-chemical calculations of BHA on charged substrates were done. • Important parameters were found to vary with the excess charge.

20. Effect of the substrate charge and .. Future work • Experimental investigation of the substrate charge influence on the adsorption parameters of some BHA derivatives • Exploration of the SERS feasibility to unravel molecular orientation in view of the variable direction of the near field