Morphological and spectroscopic studies on enlargement of Pd nanoparticle in l-cysteine aqueous solution by AFM and XPS

We have revealed the enlargement mechanism of Pd nanoparticles (NPs) on SiO2/Si by the AFM observation and the XPS measurement, when the Pd NPs react with the l-cysteine under water environment. Furthermore, the adsorbates on the Pd NPs/SiO2/Si have been confirmed by the XPS measurement. The Pd NPs with clean surface are fabricated and deposited on the SiO2/Si substrate by the gas evaporation method. In that aspect, the Pd NPs possess an interaction with the SiO2/Si surface. When the Pd NPs/SiO2/Si is reacted into the l-cysteine aqueous solution, the adsorbates originated from the l-cysteine exist on the Pd NPs surface. On the contrary, the l-cysteine hardly adsorb on the SiO2/Si. The enlargement of the Pd NPs is stimulated by the contributions of the H2O and/or the l-cysteine molecules because the Pd NPs can be more easily migrated on the SiO2/Si surface due to those contributions.