K alpha

The surface roughness of the control and NTAPP-treated groups was measured using an optical profilometer (Contour GT, Bruker, Tuscon, AZ, USA). The average of surface roughness (Ra and Sa values, μm) was confirmed using Vision64 software (Bruker, Tuscon, AZ, USA). Surface chemical composition of the control and NTAPP-treated groups was confirmed using X-ray photoelectron spectra (XPS; K-alpha, Thermo VG Scientific, Waltham, MA, USA). A monochromatic Al Kα source was operated as the X-ray source (Al Kα line: 1486.6 Ev). The binding energy was referenced and calibrated to the C1s peak at 284.8 Ev. Detailed scans were taken for the C1s, O1s, N1s, and Ti2p regions. The contact angle and surface tension of the control and experimental groups were assessed using electro optics (Phoenix-300, SEO, Seoul, Korea). Specifically, 10 μL distilled polar (water) and non-polar (ethylene glycol, Sigma-Aldrich. St. Louis, MO, USA) liquid was dropped on the center of titanium specimens and left at room temperature. After 10 s, an image of the contact angle was measured and surface energy was calculated using Image XP (ver.5.9, SEO, Suwon, Korea) according to the Owens-Wendt method.

Fully dried films were measured for XPS (K-alpha, Thermo VG Scientific) with a monochromic Al K-alpha source under a high vacuum condition of 10⁻⁹ Torr.

The electrical measurements of CNT-FETs were performed with HP 4145B (Agilent HP, US) semiconductor parameter analyser. For Cys sensing, the CCD1 modified CNT-FETs were placed in a pH 7.4 PBS solution, and the source-drain currents were measured under a 100 mV source-drain bias after adding Cys at different concentrations. Fluorescence and UV/vis absorption spectra were recorded with Shimadzu RF-5301PC and Shinco S-3100 spectrophotometers, respectively. Fourier transform infrared (FT-IR) spectra were performed with a NICOLETiS10 (Thermo scientific Korea Ltd.). Energy dispersive spectroscopy (EDS) data were taken on a JSM-6701F (JEOL, Ltd., Japan). X-ray photoelectron spectroscopy (XPS) spectra were recorded with a K-alpha (Thermo VG Scientific, USA).

The morphological characteristics of CFO and CFO-Ni were examined by field emission scanning electron microscopy (FE-SEM, SU5000, Hitachi). To analyze the elemental composition, energy-dispersive X-ray (EDX) spectroscopy was conducted using FE-SEM (XL 30 S FEG, Philips, Netherlands) with a beam voltage of 10 kV. Both morphological and crystal properties of CFO and CFO-Ni were examined by high resolution transmission electron microscopy (HRTEM, Tecnai F20) operating at 200 kV. The crystal structures of CFO and CFO-Ni were confirmed by X-ray diffractometer (XRD, D/MX-200, Rigaku). The chemical states of both CuFeO₂ and NiFe₂O₄ were analyzed by X-ray photoelectron spectroscopy (XPS, K-alpha, Thermo VG Scientific). To analyze the redox reactions with Li, cyclic voltammetry (CV) analysis was conducted in the scan rate of 0.1 mV s⁻¹ using the battery testing device (Maccor Series 4000, KOREA THERMO-TECH). To further investigate the internal cell resistances, impedance tests were carried out using 1-channel potentiostat (ZIVE SP1, Wonatech).

TEM images were acquired using a Titan G2 Cube 60-300 operation at 80 kV. XPS data were collected using K-alpha (Thermo VG Scientific) XPS. ¹³C NMR spectra were obtained with an Avance Neo (Prodigy, Bruker Biospin) 600-MHz spectrometer. Pristine GQDs, BA₁-GQDs, and BA₂-GQDs were dispersed in deuterium oxide, and TPE₂-GQDs were dispersed in d₆-DMSO to conduct NMR measurements. FTIR spectra were collected using a Nicolet iS50 (Thermo Fisher Scientific Instrument) FTIR spectrometer. SAXS measurements of GQD powders were performed using Nanopix SAXS instrument (Rigaku) with Cu-target x-ray. Ultraviolet-visible (UV-vis) absorption was measured using a SolidSpec-3700 UV-vis/near-infrared spectrophotometer. PL and PLE analyses were performed using an F-7000 (Hitachi) fluorospectrophotometer. Afterglow spectra were obtained with an F-7000 using a 40-Hz chopper with a gate delay time of 1 ms. TRES were also obtained using the same equipment by varying the gate delay time from 1 to 8000 μs. PF, RTP, and TADF decay lifetimes were collected via TCSPC using Fluorolog3 (Horiba). The absolute PL PLQYs were measured using Quantaurus-QY C13534-11 (Hamamatsu). The space charge–limited current behavior of GQDs was assessed with current-voltage characteristics using a Keithley 2635A source meter unit.