Jem 2100f microscopy

X-ray diffraction (XRD) measurement was carried out using the Rigaku RAD-3C diffractometer instrument (Cu Kα, λ = 1.5405 Å, 35 kV, 20 mA, 2-Theta angles: 10°–70°). The morphology and structure were investigated by scanning electron microscopy (SEM, JEOL S-4800) under the condition of 3.0 kV operating voltage. Transmission electron microscopy (TEM, JEOL JEM-2100F microscopy) with an energy dispersive X-ray spectroscope (EDS) was also carried out to investigate the element distributions of porous NiMn₂O₄ NSs@NF under the condition of 200 kV accelerating voltage. X-ray photoelectron spectroscopy (XPS, ESCALB-MKII250) was performed to analyze the elemental compositions and its valence of porous NiMn₂O₄ NSs@NF under a monochromatic 150 W Al Kα source radiation. Nitrogen adsorption/desorption measurement was performed to analyze the specific surface area of porous NiMn₂O₄ NSs@NF on a Micromeritics ASAP 2010 analyzer at 77 K.

Measurements of nanoparticle sizes and zeta potential values were performed using NanoBrook 90Plus instruments (Brookhaven Co., New York, USA). To measure zeta potentials, a BI-ZEL electrode assembly for aqueous systems was used. For measurement, each formulation sample before and after freeze-drying was diluted to the appropriate concentration with water. The results of the size and zeta potential were expressed as mean ± standard deviation of the three measurements. In addition, transmission electron microscopic imaging (TEM) was performed to observe the morphologies of the drug particles using JEM 2100F microscopy (JEOL Ltd., Tokyo, Japan) at 160 kV. The appropriately diluted specimen was loaded on cooper TEM grids (300-mesh carbon-coated), allowed to dry, and followed by staining with osmium tetroxide.