3600 plus

The SWCNTs used in this study were purified HiPco nanotubes (NanoIntegris, Lot. No. HP26-019) with a mean diameter of 0.8–1.2 nm and length of 100–1000 nm. LSZ–SWCNTs were prepared by suspending 1 mg of HiPco nanotubes and 5 mg of lysozyme from chicken egg white (Sigma Aldrich) in 1 mL of 1 mM HEPES buffer (pH 7.4) and sonicating using a cup-horn sonicator (140 mm, Qsonica, LLC) for 90 min at 1% amplitude on ice. Chitosan–SWCNTs were prepared as described in Reuel et al. [26 (link)] Briefly, 1 mg of HiPco nanotubes were suspended in 1 mL of 2.5 mg/mL Chitosan (Carl Roth) solution in 1 mM HEPES buffer with 1% acetic acid. The sample was then sonicated for 90 min at 1% amplitude on ice using cup-horn sonication.
All sonicated SWCNT suspensions were centrifuged (Eppendorf Centrifuge 5424 R) for 180 min at 16500×g to pellet SWCNT aggregates. Unbound proteins and polymers were removed through dialysis against 2 L of 1 mM HEPES buffer using a 300 kDa MWCO cellulose membrane. SWCNT concentrations were calculated from absorbance measurements at 632 nm in a UV–Vis–NIR scanning spectrophotometer (Shimadzu 3600 Plus) using an extinction coefficient of 0.036 L/(mg cm) [27 (link)].

Scanning electron microscopy (SEM, Zeiss Sigma 300, Germany) and energy dispersive X-ray analysis (EDS) were used to characterize the morphological features and element detection of the samples. The transmission electron microscope (TEM) image of the prepared sample was taken on the FEI TalosF200x (USA) electron microscope at an accelerating voltage of 200 kV. The phase of the samples was determined by X-ray diffraction (XRD, Bruker D8 Advance, Germany) measurement using Cu Ka radiation (λ = 1.5406 Å) at a scanning rate (2θ) of 2°/min in the degree range from 10° to 80°. The X-ray photoelectron spectroscopy (XPS, Thermo Scientific K-Alpha, USA) was scanned with a monochromatic Al-Kα X-ray source at a working voltage of 12 kV, and the surface chemistry of the sample was analyzed. The optical properties of the samples were characterized by ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS, Shimadzu 3600 plus, Japan).

The morphology of the products was characterized by field-emission scanning electron microscopy (FE-SEM, SU-8020, Hitachi, Tokyo, Japan) and high-resolution transmission electron microscopy (FEI, Tecnai G2 F20, USA). Their crystal structure was determined by x-ray diffraction (XRD-7000, Shimadzu, Kyoto, Japan) using CuKα radiation with 2θ set from 10 to 80°. Fourier transform infrared (FTIR) was recorded with a NICOLET iS10 FTIR spectrometer. Surface chemical composition was analyzed by x-ray photoelectron spectroscopy (XPS, Thermo Fisher Scientific, Waltham, USA) with a monochromatic Al Kα source (1486.6 eV). All binding energies were calibrated based on the C1s peak at 284.8 eV. The specific surface area was measured by nitrogen adsorption–desorption isotherms at 77 K using the Barret–Joyner–Hallender method (NOVA 3200e Sorptometer, Quantachrome, Florida, USA). The optical properties of the catalysts were analyzed by a photoluminescence fluorescent spectrometer (PL, FLS980, Livingston, Edinburgh) and an ultraviolet-visible diffuse reflectance spectrometer (UV–Vis DRS; 3600 plus, Shimadzu, Kyoto, Japan), respectively. Presence of free radicals was confirmed by electron paramagnetic resonance (EPR) (JES-FA200 JEOL, Tokyo, Japan) under visible light irradiation using 5,5-Dimethyl-1-pyrroline N-oxide (DMPO) as a trapping compound.