Speaker
Description
Abstract: This work reports the fabrication and detailed characterization of a graphene-integrated alumina (Al₂O₃) platform for high-performance ionic detection. Monolayer graphene was synthesized via low-pressure chemical vapor deposition (LPCVD) at 1000 °C using methane as a carbon source and transferred onto polished Al₂O₃ substrates using a PMMA-assisted wet-transfer technique. The transferred films exhibited excellent coverage and minimal defects. Raman spectroscopy confirmed monolayer quality with a sharp 2D peak at ~2685 cm⁻¹, G/2D intensity ratio of ~0.45, and negligible D-band (ID/IG < 0.1). SEM and AFM revealed surface roughness below 2.3 nm and continuous graphene morphology across the Al₂O₃ interface. TEM imaging confirmed the lattice continuity and edge sharpness with interlayer spacing of 0.34 nm. XRD patterns showed dominant alumina crystallographic planes (2θ ≈ 25.5°, 35.1°, 43.3°), while XPS verified strong C–C (284.6 eV) and C–O (286.4 eV) signals, indicating minimal oxidation post-transfer. FTIR spectra exhibited broad O–H peaks (~3400 cm⁻¹) and surface hydroxyl groups essential for ion interaction. Electrochemical analysis demonstrated high sensitivity in Na⁺ detection (as a model ion). Cyclic voltammetry showed a well-defined redox couple at ±0.35 V (vs. Ag/AgCl). Electrochemical impedance spectroscopy (EIS) revealed a charge transfer resistance (Rct) as low as 78.5 Ω in 1 mM NaCl solution. The limit of detection (LOD) was 23.7 nM, and the sensor-maintained linearity from 100 nM to 10 mM with an R² of 0.998. Chronoamperometry yielded a response time below 2.8 seconds, and sensor repeatability was 97.2% across 30 measurement cycles. The platform retained 98% performance after 30 days of dry storage at room temperature.
