Abstract
Zinc oxide (ZnO)/laser-induced graphene (LIG) composites were prepared by mixing ZnO, grown by laser-assisted flow deposition, with LIG produced by laser irradiation of a polyimide, both in ambient conditions. Different ZnO:LIG ratios were used to infer the effect of this combination on the overall composite behavior. The optical properties, assessed by photoluminescence (PL), showed an intensity increase of the excitonic-related recombination with increasing LIG amounts, along with a reduction in the visible emission band. Charge-transfer processes between the two materials are proposed to justify these variations. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy evidenced increased electron transfer kinetics and an electrochemically active area with the amount of LIG incorporated in the composites. As the composites were designed to be used as transducer platforms in biosensing devices, their ability to detect and quantify hydrogen peroxide (H2O2) was assessed by both PL and CV analysis. The results demonstrated that both methods can be employed for sensing, displaying slightly distinct operation ranges that allow extending the detection range by combining both transduction approaches. Moreover, limits of detection as low as 0.11 mM were calculated in a tested concentration range from 0.8 to 32.7 mM, in line with the values required for their potential application in biosensors.
Highlights
Zinc oxide (ZnO) is a well-known wide bandgap material (Eg ~3.3 eV at 300 K [1]) that prevails as one of the most explored semiconductor metal oxides nowadays [2,3,4,5,6,7]
Upon scraping from the polyimide substrate to be mixed with ZnO, this foam-like appearance was completely lost, as can be observed in Figure 2b and c, where scanning electron microscopy (SEM) images of the scrapped laser-induced graphene (LIG) in powder form and after deposition on the substrate are displayed, respectively
Even though the ZnO-LIG5 composite showed an enhanced electron transfer compared with ZnO, these results indicate that the H2 O2 detection occurred due to the electrocatalytic activity of ZnO, and in this case, LIG had no significant effect on H2 O2 detection via Cyclic voltammetry (CV) using the potential at ~+0.6V vs. SCE
Summary
Zinc oxide (ZnO) is a well-known wide bandgap material (Eg ~3.3 eV at 300 K [1]) that prevails as one of the most explored semiconductor metal oxides nowadays [2,3,4,5,6,7]. ZnO properties remain extremely appealing for several technological applications, namely its piezoelectricity, high-energy radiation stability, non-toxicity, biocompatibility, improved electrical and optical responses as well as the ability to be grown by simple and low-cost techniques, enabling the production of numerous and tailored morphologies [1,2,5,8,9]. From the point of view of the optical emission properties, one major advantage is its large free-exciton binding energy (60 meV), which allows the observation of excitonicrelated emissions even above room temperature (RT). One can highlight the large surface area, mechanical properties, acceptable biocompatibility, excellent thermal and electrical conductivity (except for GO), and increased safety and ease of production in comparison to other carbon-based nanomaterials [10,11,12]. One can highlight the large surface area, mechanical properties, acceptable biocompatibility, excellent thermal and electrical conductivity (except for GO), and increased safety and ease of production in comparison to other carbon-based nanomaterials [10,11,12]. 4.0/).
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