Waters 1515 gel permeation chromatograph

Asphaltenes were separated according to ASTM D6560-2000 [40 ]. The elemental composition of the asphaltene, including carbon, hydrogen, sulfur, and nitrogen, was determined using a Vario Micro Cube Elemental Analyzer (Elementar Company, Langenselbold, Germany). The oxygen content was obtained using the subtractive difference method. X-ray photoelectron spectroscopy of the asphaltene was performed using an ESCALAB 250Xi spectrometer (Thermo Fischer Scientific, Waltham, MA, USA). The mean molecular weight and distribution of the asphaltenes were determined using tetrahydrofuran (THF) as the mobile phase on a Waters 1515 gel permeation chromatograph (WATERS, Milford, MA, USA). The ¹H NMR and ¹³C NMR spectra of the asphaltenes were obtained using an Ascend 400MHz nuclear magnetic resonance (NMR) spectrometer (BRUKER, Berlin, Germany). Deuterated chloroform (CDCl3) was used as the solvent, and tetramethylsilane (TMS) served as the internal standard. Fourier-transform infrared spectroscopy (FT-IR) analysis of the asphaltene was performed using a Nicolet 6700 Fourier transform infrared spectrometer (Thermo Fisher Scientific, Waltham, MA, USA).

Waters-1515 gel permeation chromatograph (GPC, Waters, MI, USA) was used to evaluate the molecular weight of the products. Fourier transform infrared (FT-IR) spectra were obtained using a Vertex 70v FT-IR spectrophotometer (Bruker, Karlsruhe, Germany). ¹H NMR spectra were recorded on an ASCEND 400 spectrometer (Bruker, Karlsruhe, Germany). X-ray diffraction (XRD) patterns were measured using a D8 advance X-ray diffractometer (Bruker, Karlsruhe, Germany); the relative intensity was recorded in the scattering range (2θ) of 5°–90°. X-ray photoelectron spectroscopy (XPS) spectra were obtained using PHI 5000CESCA System surface analysis equipment (PHI Co., Chanhassen, MN, USA) with Mg-K_α X-ray source (hγ = 1253.6 eV). Ultraviolet-Visible (UV-Vis) spectra were recorded in the range of 300–600 nm using UV2310II UV-Vis spectrophotometer (INESA, Shanghai, China). JEOL-2100F transmission electron microscopy (TEM, JEOL, Tokyo, Japan) was used to investigate the microstructure and size distribution of the Ag NPs. The size distribution was statistically analyzed for 300 randomly selected nanoparticles using the public software Image J. Surface morphology was observed via an SU8010 field emission scanning electron microscope (FESEM, Hitachi, Japan).