Jem 2100 transmission electron microscopy

The morphologies of the PPY hydrogels were observed by a SU-70 scanning electron microscopy (Hitachi, Japan) at an accelerating voltage of 20 kV equipped with an energy dispersive X-ray analyzer. The morphology of V₂O₅ nanowires was observed on JEM-2100 transmission electron microscopy (JEOL, Japan) at 200 kV. Rheology measurements were carried out by using a MCR 302 Rhometer (Anton Paar, Austria). Raman spectra were recorded at room temperature with a MicroRaman System RM3000 spectrometer and an argon ion laser operating at a wavelength of 532 nm as the excitation laser. Thermogravimetric analysis (TGA) was carried out on a STA 449 F3 Jupiter simultaneous thermal analyzer with a heating rate 20 °C min⁻¹ in the air condition. Zeta potential was determined by electrophoretic light scattering (ELS) with Zetaplus (Brookhaven Instruments Corporation, Holtsville, NY, USA). BET surface area was measured by TriStar 3000 specific surface area analyzer.

Step 1: PVP (0.58 g, molecular weight 58,000) was dissolved in 5 mL ethylene glycol under magnetic stirring. Step 2: DTAB or TTAB or DeTAB (0.02 g) were dissolved in 1 mL pure water, which was then combined with 10 mg individual ferric tetroxide (Fe₃O₄) nanoparticles in chloroform solution. Step 3: after 3 min vigorous vortex, the mixture in step 2 was transferred into a three-necked flask that was incubated at 40 °C in a water bath, while chloroform was removed in a nitrogen flow (this process takes about 3 min). Step 4: The ethylene glycol solution from step 1 was added into the mixture from step 3 (with a pipette gun, within 15 s) and mechanically stirred for 10 min at a rotation speed of 350 rad·min⁻¹. Then, the resulting mixture was then heated to 80 °C and maintained at that temperature for 6 h. After cooling down to room temperature, the as-formed clusters were divided into two 10 mL centrifuge tubes, washed once with ethanol and centrifuged at 5000 rpm for 15 min to collect the final products that were dispersed in ethanol at a concentration of 20 mg/mL. The morphology of the as-synthesized nanoparticle clusters was characterized with a JEOL JEM-2100 transmission electron microscopy (TEM).