Sigma 300 system

Multiple microscopy techniques were used to assess the surface morphology and thickness of BPNSs. Atomic force microscopy (AFM) was employed to perform a vacuum-based characterization of the surface morphology and thickness of the BPNSs at room temperature, utilizing the Dimension Icon system (Bruker, Karlsruhe, Germany). Meanwhile, scanning electron microscopy (SEM) was used to examine the surface morphology of the BPNSs by depositing them onto an aluminum foil and drying at 60 °C prior to imaging. The imaging was carried out under high vacuum with an acceleration voltage of 10 kV using the Sigma 300 system (Zeiss, Oberkochen, Germany). Lastly, transmission electron microscopy (TEM) was employed to determine the elemental compositions and morphologies of the BPNSs utilizing the FEI Tecnai F20 TEM D545 system (FEI, Hillsboro, OR, USA). The Raman spectra of the BPNSs were obtained at room temperature using Raman spectroscopy (LabRAM HR, HORIBA, Montpellier, France) with an excitation wavelength of 532 nm. The particle size distribution and polydispersity (PDI) in water were determined using a Zetasizer 3000 HS nanosizer (Malvern Instruments, Malvern, UK).

FT-IR (Fourier transform infrared) spectra were recorded on a PerkinElmer 1710 spectrometer (KBr disc) in the wavenumber range of 400–4000 cm⁻¹. XRD (X-ray diffraction) patterns were recorded on a Bruker D8 Advance system using Cu Kα radiation with 2θ = 5°–80°. XPS (X-ray photoelectron spectroscopy) analysis was conducted on a Physical Electronics Quantum 2000 Scanning ESCA Microprobe (Mono Al-Kα, hν = 1486.6 eV). The pass energy of the full-spectrum scan was 100 eV, and the pass energy of the narrow-spectrum scan was 60 eV. The XPS spectra were calibrated based on the surface contamination C 1s (284.8 eV). The residual Hf in the reaction liquid was tested by ICP-OES (inductively coupled plasma optical emission spectroscopy, Agilent 720). SEM (scanning electron microscopy) images were obtained using a ZEISS SIGMA300 system. The powder samples were bonded on conductive adhesive for the SEM measurements. HR-TEM (high-resolution transmission electron microscopy) images were obtained using an FEI TALOS F200C system, with a resolution of 0.16 nm. The TEM samples were dispersed in absolute ethanol after ultrasonic vibration and deposited on a carbon-coated copper grid.

Optical images were captured by a VMX40M microscope. SEM images were taken with a ZEISS Sigma 300 System. The crystalline structures of the thin films were identified via XRD (Malvern Panalytical Empyrean). The MCN film was ground into powder for XRD analysis to avoid interference from substrate materials. To characterize the light transmittance performance of the sensor, an MCN/SiO₂ thin film (5 mm × 5 mm) was prepared using thin film deposition technology and transferred onto a quartz substrate. The UV-Vis-IR absorption spectra of the MCN nanofilm were characterized by using a spectrophotometer (PerkinElmer Lambda 750S).
The relationship between the resistance and test temperature was measured using an automatic data acquisition system, which included a vacuum film probe system (Lake Shore) with a temperature control unit (Lake Shore Model 336) and a semiconductor parameter analyzer (Keithley 4200A-SCS). To maintain the quasi-thermal equilibrium state between the temperature sensor and the temperature control stage, every measurement was conducted for every 5 °C interval with at least 5 min of stabilization. The measurement details of the other sensor performance parameters can be found in the supplementary materials.