Laser-Controlled Defect Engineering in ZnO@Au Core-Shell Nanoparticles on Porous Silicon for Enhanced CO Sensing

This study employs pulsed laser ablation in liquid (PLAL) to synthesize ZnO@Au core–shell nanoparticles with controlled size and surface properties, while avoiding contamination from stabilizers and reducing agents. A two-step synthesis was performed, with Au-target ablation at pulse energies of 800, 1000, and 1200 mJ. The ZnO@Au core–shell nanoparticles were deposited onto porous silicon substrates to improve gas-sensing performance by increasing surface area and facilitating charge transport. Structural, morphological, optical, and electrical properties were investigated using X-ray diffraction, field-emission scanning electron microscopy, UV–Vis spectroscopy, and current density–voltage measurements under dark and illuminated conditions. CO-sensing measurements assessed sensor response and response–recovery times at concentrations of 50, 100, and 150 ppm over 25–300 °C. The innovation lies in integrating laser-energy-controlled, additive-free synthesis with a porous silicon support for CO detection. The optimal sensing performance was obtained at 1000 mJ, with a reported response of approximately 85% to 150 ppm CO at 250 °C.