N 1000

PXRD patterns were acquired using an X-ray diffractometer (MiniFlex 600; Rigaku, Tokyo, Japan), with a CuKα radiation source (λ = 1.5406 Å) at 40 kV and 15 mA. Each PXRD measurement was conducted over a 2θ range of 4–40°, with a step size of 0.02° and scan rate of 10°/min.
DSC analysis was performed using a DSC-60 calorimeter (Shimadzu, Kyoto, Japan). Each sample (2–3 mg) was placed on an alumina pan (with a blank pan used as a reference) and scanned from 30 to 250 °C at a heating rate of 10 °C/min in a nitrogen atmosphere (N₂ flow rate: 50 mL/min).
The temperature-dependent weight change was determined using a TGA instrument (N-1000; Scinco, Seoul, Korea). Specifically, 10 mg of each sample was loaded in a platinum holder and heated from 25 to 800 °C at 10 °C/min under nitrogen purging conditions.
A Spectrum Two^® attenuated total reflectance (ATR)–FTIR spectrometer (Perkin Elmer, Waltham, MA, USA) was used to acquire infrared (IR) spectra of various specimens in the solid state. Each spectrum was collected in a wavenumber range of 4000–450 cm⁻¹ with a resolution of 8 cm⁻¹.
Proton nuclear magnetic resonance (¹H NMR) spectra were recorded on a JEOL ECS 400 MHz NMR spectrometer. Each sample was dissolved in deuterated dimethyl sulfoxide (DMSO-d6) for analysis and chemical shifts for proton are reported in parts per million (ppm) downfield from tetramethylsilane.

The morphology of the samples was investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). To prepare the samples for the TEM measurement, the powdered samples were fully dispersed in ethanol in an ultrasonic bath and then dried on a copper grid. Raman spectra were recorded on a Raman spectrometer (Bruker Korea Office Co., Seongnam, Korea) with a He–Ne laser wavelength of 632.8 nm. To measure the carbon content of the Si@C NPs, thermogravimetric analysis (TGA, N-1000, Scinco Co., Seoul, Korea) was carried out from 0 to 900 °C in air with a heating rate of 10 °C min⁻¹. Fourier-transform infrared spectroscopy (FTIR) was performed to examine the chemical interaction of the samples (Spectrum Two, Perkin Elmer Korea Office Co., Daejeon, Korea).