The chemical vapor deposition (CVD) synthesis of magnetic carbon nanotubes (mCNT) using carbon dioxide/carbon catalyst has been successfully carried out in various pressures. The temperatures were set at 800° C for 10 minutes reaction time. Nitrogen (N2) gas in 20 Torr was flown in followed by ethanol vapor until the final pressure reached 80 and 100 Torr without added air, and 180 Torr with added air. The formation of mCNT was confirmed by shifted X-ray diffraction (XRD) peak of graphite from 26.53° to 25.53° which were highly considered to the other carbon allotropes with sp2 hybridized carbon atom hybridization structures. The higher pressure with added atmospheric air led to the excessive oxidation which influenced the growth of mCNT. Transmission electron microscopy (TEM) analysis observed mCNT filled by catalyst particles which suggested as magnetic phase induced the magnetic property of mCNT. The best electrical conductivity performance (lower electrical resistance) was owned by mCNT produced in the lower pressure condition with no air added.

The combination of a noble metal with a carbon nanomaterial for surface-enhanced Raman scattering (SERS) has been commonly explored using metal-outside surface decoration to achieve a dominant electromagnetic enhancement mechanism. The use of a non-noble metal encapsulated inside carbon nanofibers (CNFs) for SERS is an interesting field of research because its heterogeneous structure possibly amplifies charge transfer, which induces the chemical enhancement mechanismbased SERS phenomena. This study investigated the use of magnetic CNFs in SERS for detecting small amino acid glycine as an analyte model. The magnetic CNFs were successfully synthesized via chemical vapor deposition (CVD) using Ni and carbon-wrapped Ni nanoparticles (Ni/C) as catalysts. The Ni/C catalyst was prepared via submerged arc discharge in a medium of ethanol/H 2 O. The CVD process was performed at different temperatures with Ar/C 2 H 2 gases, beginning with a synthesis temperature of 600 °C. The morphological analysis of the CVD product showed that the products had a typical structure of CNF-encapsulated Ni nanoparticles. However, Ni and Ni/C catalysts grew CNFs in different features. Ni/C-CNFs had a homogeneous diameter size and more crystalline graphitic carbon layers than Ni-CNFs. All produced CNFs possessed magnetic properties that correlated well with the Ni amount and its crystallization. The Raman intensity of glycine with the SERS substrate of dispersed CNFs grown using both catalysts was significantly higher than the normal Raman signal. The enhancement factor (EF) using the Ni/C-CNF substrate was higher (∼6 × 10 3 ) than that of the Ni-CNF substrate. The increase in the CVD temperature during CNF preparation led to increased Raman intensity and EF value. The crystalline graphitic structure in CNFs consisting of π-bonds and intra-and inter-layer overlapping p-orbital possessed accumulated electron transfer, which remarkably yielded SERS enhancement. The present work opens potential future research avenues to use these magnetic CNFs as SERS substrate with a considerable EF in biosensor applications.

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Abstract. The carbon nanotube has widely taken great attractive in carbon nanomaterial research and application. One of its preparation methods is catalytic chemical vapor deposition (CCVD) using catalyst i.e. iron, nickel, etc. Generally, except the catalyst, carbon source gasses as the precursor are still required. Here, we report the use of the bifunctional material of Fe3O4/C which has an incorporated core/shell structures of carbon-encapsulated iron compound nanoparticles. The bifunctional catalyst was prepared by submerged arc discharge that simply performed using carbon and carbon/iron oxide electrodes in ethanol 50%. The prepared material was then used as a catalyst in thermal chemical vapor deposition at 800 o C flown with ethanol vapor as the primer carbon source in a low-pressure condition. This catalyst might play a dual role as a catalyst and secondary carbon source for growing carbon nanotubes at the time. The synthesized products were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. The successful formation of carbon nanotubes was assigned by the shifted X-ray diffracted peak of carbon C(002), the iron oxides of Fe3O4 and -Fe2O3, and the other peaks which were highly considered to the other carbon allotropes with sp 2 hybridization structures. The other assignment was studied by electron microscopy which successfully observed the presence of single-wall carbon nanotubes. In addition, the as-prepared carbon nanotubes have a magnetic property which was induced by the remaining of metal catalyst inside the CNT.