Sari Suvanto

Controlled deposition of Co2(CO)8 on silica in a fluidized bed reactor: IR, chemisorption and decomposition studies

Abstract Dicobalt octacarbonyl, Co 2 (CO) 8 , was deposited on silica support pretreated at 300°C, 500°C and 600°C, by vapour-phase adsorption at low temperature in a fluidized bed reactor. Adsorption of cobalt carbonyl on the silica surface and decarbonylation during heat treatment were followed by diffuse reflectance IR spectroscopy. The Co 2 (CO) 8 rearranged to Co 4 (CO) 12 and the surface was completely decarbonylated via subcarbonyl species. The decarbonylation of cobalt carbonyl on silica was also studied by temperature programmed reduction. Energy dispersive X-ray fluorescence was used to determine the cobalt content on the silica surface. Pretreatment temperature did not affect the saturation level of the cobalt carbonyl but influenced the hydrogen uptake of the non-decarbonylated samples in hydrogen chemisorption studies. Therefore, in gas phase preparation method the pretreatment temperature of the silica support could prove to be useful in the preparation of catalyst systems. A higher amount of cobalt on the support could be achieved through repetition of the deposition–decarbonylation sequence.

Scalable fabrication of the graphitic substrates for graphene-enhanced Raman spectroscopy

We propose direct synthesis of ultra-thin graphitic films on a dielectric substrate using sacrificial Ni catalyst layer, which significantly increases the crystallinity of the photoresist pyrolyzed at the temperature of 800 °C and above. A considerable amount of multilayer graphene in the photoresist film pyrolyzed in the presence of the Ni catalyst gives rise to an enhancement of the Raman signal of dye Sudan III molecules deposited on the substrate. We demonstrate comparable enhancement of the Raman signal from Sudan III molecules deposited on the fabricated graphitic substrate and those deposited on graphene, which was conventionally transferred to the silica substrate.