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Among the existing two-dimensional materials, MXenes, i.e. transition metal carbides, nitrides and/or carbonitrides, stand out for their excellent electrochemical properties. Due to their high charge storage capacity, metal-like conductivity, biocompatibility as well as hydrophilicity, Ti3C2Tx MXene-based inks hold great potential for scalable production of skin conformable electronics via direct printing methods. Herein, we develop an aqueous MXene ink and inkjet-print MXene films on freestanding, flexible, and conducting polymer-based substrates. These skin-adherent MXene electrodes detect electrocardiography signals with high signal-to-noise ratio while exhibiting preserved electrical performance after 1000 cycles of bending with a 50 d long shelf life in ambient conditions. We show that printed MXene films can be further functionalized to perform as multifunctional biosensing units. When integrated with a sodium (Na+) ion selective membrane, MXene electrodes detect Na+ in artificial sweat with a sensitivity of 40 mV per decade. When the films are functionalized with antibodies, they generate an electrical signal in response to a pro-inflammatory cytokine protein (interferon gamma) with a sensitivity of 3.9 mV per decade. Our findings demonstrate how inkjet-printed MXene films simplify the fabrication of next-generation wearable electronic platforms that comprise multimodal sensors.

Starting from crystalline silicon we synthesised bright suspensions of amorphous porous silicon nanoparticles through unconventional stain etching. Upon excitation with UV light, this novel nanostructured material gives rise to an intense red photoluminescence (PL) which resembles that of some silicon nanostructures. We studied the properties of the prepared nanoparticles using a number of cutting-edge characterization techniques such as TEM, SEM and EDX. The complete crystalline-to-amorphous phase transition, confirmed by the morphological studies, seems fortuitous.