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.
Encapsulation of curcumin-loaded oil droplets with chitosan-based cryogels, made from a ternary system of colloidal chitosan, κ-carrageenan, and carboxymethylcellulose (CMC) sodium salt, was carried out and the effects of the freezing condition (unidirectional freezing rate with and without post-freezing incubation) and the initial concentration ratio of carrageenan to CMC on the properties of the cryogel nanocapsules were experimentally investigated. Both the freezing condition and initial concentration ratio had significant effects on the gel fraction yield, swelling extent, particle size and zeta potential, as well as the curcumin release pattern. Specimen I-S1-02, which was made of polymer set 1 (carrageenan:CMC = 4:6) at a rapid freezing rate of −2℃/min with 10-hr incubation at −10℃, showed the slowest release rate (first-order type) of curcumin. In comparison, it was found that microcapsules obtained by spray-drying a similar O/W curcumin emulsion with dextran as stabilizer exhibited the fastest rate of curcumin release, similar to a burst release.
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