Quanta 200f

X-ray diffraction (XRD) analyses were recorded on a Rigaku D/max 2500 diffractometer with Cu K_α radiation (λ = 0.15418 nm). Fourier transform infrared (FTIR) pattern was measured using a Nicolet 60-SXB FT-IR spectrometer. The morphologies and microstructures of samples were examined with a field-emission scanning electron microscope (FE-SEM, FEI Quanta 200 F), and a transmission electron microscope (TEM, JEOL JEM 2100). Thermogravimetry and differential thermal analysis (TG-DSC) was performed in a temperature ramping rate of 10 °C min⁻¹ from 25 to 850 °C in N₂ atmosphere (SDT Q600 V20.9 Build 20). X-ray photoelectron spectra (XPS) were performed using a K-Alpha spectrometer (Thermofisher Scienticfic Company). A drop of ethanol containing the magnetite nanorings was placed on a Si substrate, and then naturally dried in air prior to characterization by atomic force microscopy (AFM, Bruker Dimension ICON-PT).

Surface morphology images were taken on a high-resolution field emission scanning electron microscope (SEM, FEI Quanta 200F) with an accelerating voltage of 15 kV, also equipped with Energy Dispersive Spectrometer (EDS) and cathodoluminescence (CL). Optical absorption was measured on a UV-VIS-NIR spectrophotometer (Shimadzu UV3600 Plus). PL lifetime was measured on a lifetime and steady state spectrometer (FLS980, Edinburgh, UK). X-ray diffraction (XRD) patterns were measured using X-ray diffraction platform (Model PANalytical X'Pert Pro) with a Cu-Kα radiation source (λ = 0.1541874 nm) at 40 kV and 40 mA. The angle accuracy was within ±0.0025°. PL was excited at 355 nm by a pulsed Nd:YAG laser (pulse width 8.0 ns, repetition rate 1.0 kHz).

UV-vis absorption spectrum is obtained using a Perkin Lambda UV-vis-NIR spectrophotometer. The transparency and reflectance are recorded using a UV-via NIR spectrometer with an integrating sphere unit. X-ray diffraction (XRD) is recorded using a Shimadzu XRD-7000 with Cu-Kradiation. The morphology and characterizations of the obtained samples is assessed on a field emission scanning electron microscope (FESEM, FEI Quanta 200 F) and with transmission electron microscopy (TEM, FEI Tecnai G2 S-Twin) with an operating voltage of 300 kV. Electrical conductivity is measured by multimeter. Optical microscope image is recorded on Leica DM500. All optical measurements are performed at room temperature.
The external adjustable power 808 nm NIR laser with a spot size of 0.6 cm² is used to measure the photothermal conversion performance of nanofilm. The output power is independently calibrated using a handy optical power meter. The in-situ temperature is recorded by an infrared thermometer with accuracy of ±0.1 °C tilted 45°relative to the path of the laser.

The internal structure of the straw and composites was observed by a scanning electron microscope (SEM, Quanta 200F field emission scanning electron microscope, FEI Company, Waltham, MA, USA). The specimen was frozen in liquid nitrogen and then broken. The cross-section of the specimen was sprayed with gold, and then observed and photographed in the SEM at an accelerating voltage of 12.5 kV.