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Laser‐induced graphene (LIG) produced by irradiation of paper (paper‐LIG)holds substantial promise for flexible devices. This article presents paper‐LIG humidity and temperature sensors fabricated by single‐step irradiation of common filter paper with a pulsed UV laser (355 nm). The influence of the process parameters on the conversion of cellulose fibers into LIG is discussed based on the resulting morphology, structure, conductivity, and chemical composition, revealing a distinct barrier to transformation and a propagation behavior not seen under CO2 laser irradiation. The obtained material is constituted by a porous, electrically conductive network of fibers. The paper‐LIG relative humidity (RH) and temperature sensors with sensitivities of up to 1.3 × 10−3%RH−1 and ‐ 2.8 × 10−3 °C−1, respectively, are examined in terms of their linearity, reproducibility, and response time. A detailed discussion on the response mechanism is presented in the context of literature, pointing towards the absorption of water molecules in the interlayer spacing of graphene as the main reason for the increase in resistance with RH. Additionally, a contribution from variable range hopping along the ab plane of graphene at high RH is suggested. These results demonstrate the potential of paper‐LIG for low‐cost, sustainable, and environmentally friendly sensing. [ABSTRACT FROM AUTHOR]

Laser‐induced graphene (LIG) is inexpensive, fast, and easy to produce when compared to many other forms of graphene. Within the biosensing field, LIG electrodes are most often produced via infrared (IR) laser irradiation of polyimide sheets. Nevertheless, the usage of ultraviolet (UV) laser to produce LIG provides advantages in terms of sensor miniaturization because of its inherently higher scribing resolution. Yet, studies on the electrochemical performance of UV LIG, its relation with morphological and structural aspects as well as its comparison with IR LIG are still lacking. This work shows that both LIGs present swift electron transfer kinetics constituting excellent electrodes for electroanalysis. Extreme sensitivities of 93 and 58 µA µm−1 cm−2 at physiologically relevant dopamine (DA) concentrations are found for IR and UV LIG, respectively. Such sensitivities and good selectivity are achieved in the presence of physiologically relevant concentrations of ascorbic and uric acids, contrasting to the related literature employing IR LIG where such interferents are below the physiological range. Despite providing lower sensitivity, UV LIG is still an excellent material for DA biosensors, with the above‐mentioned advantages in terms of miniaturization. To our knowledge, these are among the highest sensitivities reported for voltammetric measurement of DA using carbon‐based materials. [ABSTRACT FROM AUTHOR]

Monitorization of gait‐related parameters is of the utmost importance to prevent complications in several diseases, ensuring affordable healthcare for the growing amount of chronic, lifestyle‐related diseases and also for improving motion performance. Sensorized insoles allow to both pressure data and gait timings to be extracted non‐intrusively in a point of care paradigm. Laser‐induced graphene (LIG) offers a path to the integration of sensors in different kinds of materials, including cork, a common insole material. In this work, piezoresistive sensors are developed by providing conductivity to natural cork and agglomerate cork through the direct synthesis of LIG by UV irradiation. Highly isotropic conductive LIG regions with less than 100 Ω sq−1 are patterned and their piezoresistive response for up to 1132 kPa is assessed with sensitivities up to 0.02 kPa−1. A low‐cost prototype insole is devised and tested, proving the potential of this kind of functional cork as a green alternative for gait analysis platforms. [ABSTRACT FROM AUTHOR]

A promising concept of consumable anode materials for high-temperature pyroelectrolysis process, which is expected to overcome the environmental and economical impacts of classical extractive metallurgy, relies on substituted magnetite-based ferrospinels, presenting high electrical conductivity, appropriate refractoriness, and redox stability. The present work aims assessment of the processing effects on structural, redox, and electrical properties of Fe2.3Al0.2Mg0.5O4 spinel, prepared by conventional solid-state route ( SSR) and laser floating zone ( LFZ) method. The observed trends for high-temperature electrical conductivity behavior indicated that the electronic transport is only slightly affected by the preparation method, suggesting the minor effects from the grain boundaries. For scaled-up ferrospinel-based consumable anodes the impact of oxidation during thermal cycling on electrical properties and electrode integrity can be minimized even in air, by using relatively fast cooling/heating rates. [ABSTRACT FROM AUTHOR]

Laser‐induced graphene (LIG) can be obtained by irradiation of a polymer by a laser source. The present work demonstrates that it is possible to obtain this kind of material using an ultraviolet laser instead of the typical infrared source. Using this approach, a fourfold decrease in the penetration depth (5 µm) is achieved, while the spatial resolution is doubled. Electromechanical strain LIG sensors are patterned in polyimide substrates with different thicknesses and their performance to strain, bending, and force inputs is measured. A low‐cost arterial pulse wave monitor is built, exploring the high force sensitivity of the sensors produced on the thinner substrates. Laser‐induced graphene is obtained by irradiation of polyimide by an ultraviolet laser instead of the typical infrared source, with a fourfold decrease in the penetration depth and doubled spatial resolution. Electromechanical strain sensors are patterned in substrates with different thicknesses and their performance is measured. A low‐cost arterial pulse wave monitor is built, exploring the higher sensitivity of thinner substrates. [ABSTRACT FROM AUTHOR]

With a bandgap energy of ≈3.3 eV at room temperature, zinc oxide (ZnO) exhibits physical properties that make it a potential candidate for several technological applications. Sustainable development requires, among other actions, removal of organic pollutants by employing non‐toxic structures, which can be achieved considering the photocatalytic properties of ZnO. In this work, high optical and structural quality ZnO crystals with distinct morphologies (nanotetrapods and microrods) are produced by laser‐processing. By adding silver to the growth precursors it is possible to produce ZnO/Ag composites in a single and short step, boosting a synergetic conjugation of the properties of both materials. The ZnO structures produced with and without silver are fully characterized by electronic microscopy and optical spectroscopy. Moreover, their photocatalytic activity is analyzed using methylene blue as a model‐test contaminant, revealing that the nanotetrapods exhibit a better performance than the microrods. This effect is further enhanced by the presence of silver on the ZnO surface, hindering the photoinduced carriers' recombination, as corroborated by the photoluminescence results. ZnO micro and nanocrystals with different morphologies (nanotetrapods and microrods) are produced by laser‐assisted flow deposition method and their photocatalytic activity is tested, reveling a better performance for the nanotetrapods. By adding silver to the precursor rods, ZnO/Ag composites are formed in a single and short step. Nanotetrapods grown in the presence of silver evidence the best performance in the degradation of the dye when compared to the remained crystals. [ABSTRACT FROM AUTHOR]