Quantachrome instrument

Brunauer–Emmett–Teller analysis was performed by absorption-desorption isotherms using Quantachrome Instruments (Version 5.0, Anton Paar, FL, USA). Approximately 0.2 to 0.4 g of AgNPs were placed in a sample tube and degassed for 2 h using nitrogen to remove moisture and adsorbed gas. The static absorption-desorption isotherms curves plotted by adsorbed gas volume against pressure, in addition to its pore size distribution curve was also plotted by cumulative pore volume vs. average pore radius [26 (link)].

N₂ adsorption-desorption isotherms were measured at −196 °C using a Quantachrome Instruments (A brand of Anton Paar, Boynton Beach, Florida, USA) Autosorb 1C surface area analyzer. Prior to the analysis, samples were degassed at 150 °C for 5 h under high vacuum. Pore size was analyzed with a density functional theory (DFT) model using N₂ at 77 K on carbon cylindrical pores. The thermal stability of the samples was measured by thermogravimetry analysis (TGA) using a NETZSCH STA 449F3 analyser (NETZSCH, Selb, Germany) within the temperature range 25–1000 °C at a heating rate of 10 °C/min in air. X-ray photoelectron spectroscopy (XPS) was recorded by VG ESCALAB MK2 (ThermoFisher Scientific, Waltham, MA, USA) using AlKα (hλ = 1486.6 eV) as the excitation source. Fourier transform infrared spectra (FT-IR) were documented on a Nicolet Nexus 470 IR spectrometer (ThermoFisher Scientific, Waltham, MA, USA). Field-emission scanning electron microscopy (JEOL JEM 6700F FE SEM, JEOL, Tokyo, Japan) was used to examine the morphology of powder samples. Transmission electron microscopy (TEM) experiments were executed using HITACHI HT7700 (HITACHI, Tokyo, Japan) at an acceleration voltage of 100 kV. Carbon, hydrogen and nitrogen contents were determined using a Perkin Elmer 2400 Series II CHN analyzer (Perkin Elmer, Waltham, MA, USA).