Diffractometer

The IR spectra of the produced materials were captured using a Bruker Tensor II FTIR spectrometer, ranging from 400 to 4000 cm⁻¹, to identify the functional groups within the f-HNTs. To ascertain the crystallinity and phase of both pure and f-HNTs, X-ray diffraction patterns were carefully analyzed using a Rigaku diffractometer, which operated with an incident wavelength of Cu Kα (λ = 1.542 Å). To assess the morphology and microstructures of both unmodified and f-HNTs, scanning electron microscopy (SEM, MIRA3 TESCAN) was employed at an operating voltage of 10 kV. In addition, energy-dispersive X-ray spectroscopy (EDX), integrated with SEM, was utilized for the elemental analysis of the nanomaterials. Furthermore, a Shimadzu AA 670 flame atomic absorption spectrophotometer was used specifically to measure the chromium(vi) ions.

The crystal structures of the samples were analyzed by a Rigaku diffractometer using Cu Kα radiations, and the X-ray tube was operated at 40 kV and 40 mA. The Fourier Transform-IR (FT-IR) spectroscopy measurements were performed on a Nicolet 6700 spectrometer using the KBr pellet support. The scanning electron microscope (SEM) image was obtained on a JSM-6610 system. The transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), and the selected area electron diffraction (SAED) images were taken at a JEM2100 electron microscope. X-ray photoelectron spectroscopy (XPS) and valence band X-ray photoelectron spectroscopy (VBXPS) were performed using a PHI 5000 Versa Probe X-ray photoelectron spectrometer with monochromatized Al Kα X-ray radiation. The binding energies of all elements were calibrated by the C 1s peak at 284.6 eV. UV-vis diffuse reflection spectroscopy (DRS) was carried out on a Shimadzu UV-2600 spectrometer, and BaSO₄ was used as the reference at room temperature. The photoluminescence (PL) spectra of the samples were collected by an Agilent MY15170004 spectrometer with an excitation wavelength of 350 nm. Electron spin resonance (ESR) spectra were obtained from a Bruker model EMXplus spectrometer.

The physical and chemical nature of AgNPs were elucidated by XRD (X‐ray diffraction) analysis using the Rigaku diffractometer. The samples were analysed by powder diffraction using finely ground powder of AgNPs.