Additive manufacturing provides a unique tool for prototyping structures toward electrochemical sensing, due to its ability to produce highly versatile, tailored-shaped devices in a low-cost and fast way with minimized waste. Here we present 3D-printed graphene electrodes for electrochemical sensing. Ring- and disc-shaped electrodes were 3D-printed with a Fused Deposition Modeling printer and characterized using cyclic voltammetry and scanning electron microscopy. Different redox probes KFe(CN):KFe(CN), FeCl, ascorbic acid, Ru(NH)Cl, and ferrocene monocarboxylic acid) were used to assess the electrochemical performance of these devices. Finally, the electrochemical detection of picric acid and ascorbic acid was carried out as proof-of-concept analytes for sensing applications. Such customizable platforms represent promising alternatives to conventional electrodes for a wide range of sensing applications.

The first models of mesoporous ZnO/Pt Janus micromotors that show fuelfree and light-powered propulsion depending on the interface roughness are shown. Two models of ZnO semiconducting particles with distinct surface morphologies and pore structures are synthesized by self-aggregation of primary nanoparticles and nanosheets into nanoscale rough and smooth microparticles, respectively. The self-assembled nanosheet model (smooth) provides a large surface for the formation of a continuous Pt layer with strong adherence, whereas the discontinuous Pt species take place inside the inter-nanoparticles pores in the self-assembled nanoparticle model (rough). The effects of the interface, surface porosity, defect, and charge transfer on the light-powered motion for both well-designed mesoporous ZnO/Pt Janus micromotors are investigated and compared to find the underlying propulsion mechanisms. The degradation of two model pollutants is demonstrated as a proof-of-concept application of these carefully engineered Janus micromotors. In this work, it is shown that by discreet material fabrication together with semiconductor/metal interface charge transport interpretation, it would be possible to develop new light-driven Janus micromotors based on other photocatalysts containing active surfaces such as TiO 2 .

Photoactivated micromachines are at the forefront of the micro-and nanomotors field, as light is the main power source of many biological systems. Currently, this rapidly developing field is based on metal-containing segments, typically TiO 2 and precious metals. Herein, we present metal-free tubular micromotors solely based on graphitic carbon nitride, as highly scalable and low-cost micromachines that can be actuated by turning on/off the light source. These micromotors are able to move by a photocatalytic-induced bubble-propelled mechanism under visible light irradiation, without any metal-containing part or biochemical molecule on their structure. Furthermore, they exhibit interesting properties, such as a translucent tubular structure that allows the optical visualization of the O 2 bubble formation and migration inside the microtubes, as well as inherent fluorescence and adsorptive capability. Such properties were exploited for the removal of a heavy metal from contaminated water with the concomitant optical monitoring of its adsorption by fluorescence quenching. This multifunctional approach contributes to the development of metal-free bubble-propelled tubular micromotors actuated under visible light irradiation for environmental applications.

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Layered transition metal dichalcogenides (TMDs) have gained attention from the scientific community because of their extended range of applications. Molybdenum diselenide (MoSe) has been proven to be an efficient catalyst for the hydrogen evolution reaction (HER), having implications in the research of new catalysts for clean energy production. One way to produce large quantities of these materials involves the use of surfactants for liquid exfoliation. Herein, we investigate the effects of cationic, anionic, and nonionic surfactants within a concentration range on the heterogeneous electron transfer rates, electrocatalytic efficiency toward the HER of MoSe, and on the stability of the dispersions. We found that surfactants can have a detrimental effect on the electrocatalytic properties of the material when used above a concentration threshold. In some cases, high surfactant levels also had a negative effect on the stability of the material. This report serves to gain an understanding on how the way TMDs are prepared, processed, and stabilized can have dramatic effects on their efficiency toward HER, one of their most popular applications, and how choosing the appropriate surfactant type and concentration is crucial to gain in stability without compromising the intrinsic properties of the material.