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Flexible electronics is a new paradigm with strong implications from healthcare to energy applications. In this context, electrically conductive polymers are the critical components. Here, we report the design, formation mechanism, and applications of a polymer nanocomposite obtained by single-step laser integration of functionalized graphene into a polymer matrix. Laser processing manipulates the physical-chemical properties of this nanocomposite in a controlled and straightforward way, tuning the electrical resistance from a dielectric (MΩ sq−1) to a highly conductive material (Ω sq−1). We combine experimental and computational approaches to elucidate graphene nanocomposite's nature and formation mechanism, evidencing different processes from photothermal polymer melting to shock wave mixing in a liquid phase within a millisecond time scale. We exploit these fundamental insights on the graphene/polymer nanocomposite in the design and fabrication of electrochemical sensing and antenna devices, showing the potential for healthcare and the Internet of Things.

Highly-oriented pyrolytic graphite (HOPG), i.e., the 3D stack of sp2-hybridized carbon sheets, is an attractive material thanks to its high electrical conductivity, chemical inertness, thermal stability, atomic-scale flatness, and ease of exfoliation. Despite an apparently ideal and uniform material, freshly cleaved HOPG shows domains in Kelvin probe force microscopy (KPFM) with surface potential contrast over 30 mV. We systematically investigated these domains using an integrated approach, including time-dependent KPFM and hyperspectral Raman imaging. The observed time-evolving domains are attributed to locally different hydrocarbon adsorption from the environment, driven by structural defects likely related to rotational mismatch, i.e., twisted layers. These defects affect the interlayer coupling between topmost graphene and the underlying layers. Our hypothesis was supported by Raman spectroscopy results, showing domains with G peak shifts and 2D line shape compatible with bilayer graphene. We attribute the selective sensitivity of our Raman spectroscopy results to the top graphene layers as resonances due to van Hove singularities. Our results show that the chemical and electrical properties of HOPG are far more complex than what is generally believed due to the broken symmetry at the top surface, giving rise to graphene bilayer-like behavior.