Nanoscope 4 multimode

Surface analysis of multifunctional DNA 4WJ on carboxyl-MoS₂ was performed by tapping-mode AFM using Nanoscope IV/Multimode (Digital Instruments, New York, NY, USA). The bare Au substrate, carboxyl-MoS₂-modified substrate, and multifunctional DNA 4WJ-modified substrate were investigated for comparison. The n-type doped Si phosphorous (RTESP, Bruker, Billerica, MA, USA) tip was introduced with resonance peaks. The resonance peak of the frequency response was approximately 230–305 kHz, and the spring constant of the cantilever was 20–80 N/m. In addition, the surface morphology of carboxyl-MoS₂ immobilized on the electrode was also analyzed using FE-SEM (Auriga, Carl Zeiss, Berlin, Germany).

To confirm the immobilization of the Hb/GNP hybrid layer, the surface topography of the Hb/GNP heterolayer was investigated through AFM. The tapping-mode AFM was operated with a Nanoscope IV/Multimode from Digital Instruments. The tips used for the AFM measurement were phosphorous (n-type doped Si), and the resonance peaks in the frequency response of the cantilever were selected at around of 230–305 kHz. Spring constants of 20–80 N/m were used. Before scanning the sample, the set point was adjusted to optimize the force between the tip and the biomolecule.
For SERS measurement, indium tin oxide (ITO)-coated glass (G-mek, Seoul, Korea) was prepared by sonication for 30 min in 1% Triton X-100, DIW, and ethanol, sequentially. The preparation of SERS substrate was followed by our previous study. Then, the hemoglobin was immobilized via 6-MHA linker, and the gold nanoparticle was dropped onto the hemoglobin-modified substrate for SERS measurement [34 (link)].