CO2-laser as an emerging tool to generate nanostructured optically active sensing surfaces for paper-based analytical device

Nowadays, the use of the CO2 laser to induce the formation of nanostructured films is rising, offering captivating opportunities in analytical device development, due to the possibility of directly patterning conductive graphenic and graphitic surfaces with strong sensing capabilities and on-demand geometries. However, the use of the laser to obtain optically active surfaces and paper-based colorimetric devices (cPAD) remains limited. This work aims to introduce innovative CO2-Laser approaches to obtain optical-active nanostructured sensing surfaces integrated in cPAD. The paper nano-structuration relies on the laser's ability to in situ trigger metal nanostructure synthesis with the desired/required pattern, starting from cation precursors [1]. This approach allows the formation of different metal nanostructured films on paper, named laser-induced metal nanoparticles (LIM). The LIMs are surfactant-free (naked), possess sensing and catalytic features, can be easily integrated in PAD, and, according to the need, can be formed starting from different metals, i.e., Ag, Au, Pt, Ce, Al, Ni, Cu, and Fe. Different cPADs for the determination of analytes of biological and agri-food interest, including antioxidants and contaminants, in gas and liquid phase, will be presented. The presented cPADs' sensing ability relies on the LIM optical, catalytic, nanozymatic, and fluorimetric features and their integration into PAD equipped with functional components [1, 2]. Eventually, if noteworthy, further achievements in CO2-Laser nanopatterning will be presented to demonstrate the versatility of this approach for point-of-care/-need device advancement.