Flexible CO₂ Sensor Architecture with Selective Nitrogen Functionalities by One-Step Laser-Induced Conversion of Versatile Organic Ink

Nitrogen-containing carbons (NC) are a class of sustainable materials for selective CO₂ adsorption. A versatile concept is introduced to fabricate flexible NC-based sensor architectures for room-temperature sensing of CO₂ in a one-step laser conversion of primary films cast from abundant precursors. By the unidirectional energy impact in conjunction with depth-dependent attenuation of the laser beam, a layered sensor heterostructure with a porous transducer and active sensor layer is formed. Comprehensive microscopic and spectroscopic cross-sectional analyses confirm the preservation of the high content of imidazolic nitrogen in the sensor. The performance is optimized in terms of material morphology, chemical composition, and surface chemistry to achieve a linear relative resistive response of up to ΔR/R₀ = −14.3% (10% of CO₂). Thermodynamic analysis yields Δ_adsH values of −35.6 and 34.1 kJ·mol⁻¹ for H₂O and CO₂, respectively. The sensor is operable even in humid environments (e.g., ∆R/R_0,RH = 80% = 0.53%) and shows good performance upon strong mechanical deformation.