Magnetic Carbon Nanofibers Prepared with Ni and Ni/Graphitic Carbon Nanoparticle Catalysts for Glycine Detection Using Surface-Enhanced Raman Spectroscopy

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 mechanism-based 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/H2O. The CVD process was performed at different temperatures with Ar/C2H2 gases, beginning with a synthesis temperature of 600 degrees 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 (similar to 6 x 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 p-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.

Automated summary

The study investigated the use of magnetic carbon nanofibers (CNFs) for surface-enhanced Raman scattering (SERS) to detect small amino acid glycine as an analyte model. The results showed that CNFs grown using Ni/C catalyst as the substrate had higher SERS enhancement compared to those grown using Ni catalyst. The increase in CVD temperature during CNF preparation led to higher Raman intensity and enhancement factor.