Applied Surface Science, Vol.480, 235-242, 2019
Covalent immobilization of 4-pyridinepropanol monolayers on Si(111) surfaces: Axially ligation F16CoPc on pyridine moieties
Mild photochemical and thermal methods were employed for grafting 4-pyridinepropanol (4PP) directly on the surface of Si(111). Equipped with high powered LEDs, the home-made photochemical cell (lambda=470 nm) was designed and modified to handle the physical/chemical properties of 4PP, e.g. very basic, extremely hygroscopic and self-degradable under UV radiation, toward hydrosilylation. Atomic force microscopy (AFM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and static contact angel measurement (SCA) were used to examine the presence as well as the quality of the 4PP monolayers attached to the surface of silicon, 4PP-Si(111). AFM images of 4PP-Si(111) were either created by mild photochemical or thermal approaches, and displayed well defined atomic steps and terraces. In addition, it was demonstrated that the lone pair in pyridine moieties of the 4PP-Si(111) surfaces are available to axially ligate F16CoPc macrocycle forming F16CoPc-4PP-Si(111). The surface of F16CoPc-4PP-Si(111) was characterized by means of AFM, ATR-FTIR, SCA and cyclic voltammetry (CV). These investigations confirmed that the atomic steps of Si(111) were preserved and monolayers of F16CoPc-4PP-Si(111) were formed with a packing densities similar to 4.6x10(-11).
Keywords:Si(111);Silicon (111) atomic steps;Phthalocyanine;Hydrosilylation;Attenuated total reflectance;Fourier transform infrared spectroscopy;Cyclic voltammetry;Monolayers surface functionalization