Agilent cary 300 uv vis spectrophotometer

Scanning electron microscopy (SEM) experiments were performed on a SHIMADZU SSX-550 microscope (Shimadzu, Kyoto, Japan). Fourier transform infrared (FT-IR) patterns were obtained using a Bruker IFS 66V/S spectrometer (Bruker, Hamburg, Germany) with the KBr tablet method at a resolution of 1 cm⁻¹ between 400 and 6000 cm⁻¹. XRD pattern was measured using a Bruker D8 (Bruker, Hamburg, Germany) diffractometer with Cu-Kα X-ray source. The specific surface area calculated on the basis of the Brunauer–Emmett–Teller (BET) theory and the pore size distribution analyzed with the non-local density functional theory (NLDFT) were measured using N₂ adsorption–desorption measurements (ASAP 2020, Micromeritics, Norcross, GA, USA). The samples were degassed at 180 °C for 12 h under vacuum before the measurement, and the data were recorded at liquid nitrogen temperature. The surface chemistry was analyzed by X-ray photoelectron spectroscopy (XPS, Escalab 250, Thermo Fisher, Waltham, MA, USA) equipped with Mg-Kα X-ray source. Raman study of the carbon material was carried out using an inVia Raman spectrometer (Renishaw, Gloucestershire, UK) with the laser wavelength of 488 nm. The concentrations of the dye solutions were determined using an Agilent Cary 300 UV-Vis spectrophotometer (Agilent, Palo Alto, CA, USA).