This study successfully demonstrated the tailoring properties of hafnium nitride (HfN) thin films via reactive gas-timing (RGT) RF magnetron sputtering for surface-enhanced Raman spectroscopy (SERS) substrate applications. The optimal RGT sputtering condition was investigated by varying the duration time of the argon and nitrogen gas sequence. The RGT technique formed thin films with a grain size of approximately 15 nm. Additionally, the atomic ratios of nitrogen and hafnium can be controlled between 0.24 and 0.28, which is greater than the conventional technique, resulting in a high absorbance in the long wavelength region. Moreover, the HfN thin film exhibited a high Raman signal intensity with an EF of 8.5 × 104 to methylene blue molecules and was capable of being reused five times. A superior performance of HfN as a SERS substrate can be attributed to its tailored grain size and chemical composition, which results in an increase in the hot spot effect. These results demonstrate that the RGT technique is a viable method for fabricating HfN thin films with controlled properties at room temperature, which makes them an attractive material for SERS and other plasmonic applications.

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A reroute process of Hummers' method was carried out to reduce some steps in the synthesis of highly exfoliated graphene oxide (HEGO). Using pure KMnO 4 and NaNO 3 in concentrated H 2 SO 4 , HEGO was successfully prepared to contain extra carbonyl functional groups that helped stabilize the GO layer exfoliation. The oxidation reached its completion by one straight temperature level at 35 °C within a short reaction time (4 h). The obtained HEGO was observed to be highly dispersible through atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscope (TEM). The X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were also used to reveal the actual structure of HEGO and its analogues, which were formed from the reaction with aliphatic amines such as L-arginine (Arg) and β-alanine (Ala) as well as one aromatic amine, aniline (Ani). The results showed an interaction based on covalent bonding. The reduction reaction with L-ascorbic acid under basic conditions at 95 °C for 24 h was also performed. These facile functionalization and reduction process indicate the possible biomolecular adsorption.