Laser-Engineered Ag Nanoparticle on Carbon Cloth Electrodes for Enzyme-Free Electrochemical NAD⁺ Detection

Nicotinamide adenine dinucleotide ( ${\mathrm{NAD}}^{+}$ ) is a core redox cofactor, and its concentration reflects age and metabolic state, which has driven the development of ${\mathrm{NAD}}^{+}$ biochemical analytical techniques. Although electrochemical techniques can rapidly and directly detect ${\mathrm{NAD}}^{+}$ levels, the translation of laboratory sensors into deployable solutions is often limited by the complexity of electrode interface preparation and batch-to-batch variability. Especially among enzyme-assisted methods, the multi-step biochemical immobilization and activity preservation processes are required. Therefore, developing enzyme-free and scalable ${\mathrm{NAD}}^{+}$ electroanalytical manufacturing strategies remains important. Here, a rapid two-step laser-induced transfer strategy is proposed to fabricate flexible silver nanoparticle-decorated carbon cloth electrodes (AgNPs@CC) for enzyme-free ${\mathrm{NAD}}^{+}$ sensing. This strategy reduced interfacial impedance and established a robust cathodic window for enzyme-free ${\mathrm{NAD}}^{+}$ detection. The electrodes exhibit a linear operating range of 10-300  $\mu M$ , an excellent sensitivity (S = -3.16 $\mu A\mu M^{-1}{\mathrm{cm}}^{-2}$ ) at the low concentration range(10-100  $\mu M$ ), and outstanding tolerance to typical interferents (LA, UA, AA, glucose, and NADH) and robust storage stability. This method eliminates the wet-chemical nanoparticle synthesis step and simplifies the production workflow, offering potential for applications like integration into portable sensing platforms.