Apostolos Panagiotopoulos

3D printed electrodes of 1T′/1T MoS ₂ /TiS ₂ nanosheets without conductive additives have been demonstrated to perform for durable supercapacitors.

Rechargeable Zn-ion hybrid capacitors (ZHCs) have gained considerable attention towards future energy storage applications owing to their non-flammable nature, high abundance of raw materials and remarkable energy storage performance. However, the uncontrolled growth of dendrites, interfacial corrosion of Zn anodes and limited mass loading of cathode materials, hinders their practical applicability. Herein, we demonstrate ZHCs with enhanced capacity and durability using a synergistic combination of a hybrid-ion electrolyte and a high-mass loading three-dimensionally (3D) printed graphene–carbon nanotube (Gr–C) cathode. The hybrid electrolyte composed of NaCl and ZnSO₄, features higher ionic conductivity and lower pH compared with pristine ZnSO₄, which enable uniform plating/stripping of Zn²⁺ ions on Zn anode, as demonstrated by in situ electrochemical and ex situ ToF-SIMs characterizations. Additionally, the multi-layered 3D Gr–C composite electrodes in ZHCs enable higher energy storage performance due to their porous architectures, high ion accessibility and dual-ion charge storage contributions. As a result, the 3D Gr–C//Zn cell unveiled a maximum capacity of 0.84 mA h cm⁻² at 3 mA cm⁻² with a high life cycle (78.7% at 20 mA cm⁻²) compared to the pristine electrolyte-based ZHCs (0.72 mA h cm⁻² and 14.8%). The rapid rate measurements that we propose along with benchmarked energy density (0.87 mW h cm⁻²) and power density (31.7 mW cm⁻²) of hybrid electrolyte-based 3D Gr–C//Zn, pave the way for the development of dendrite-free and highly durable 3D energy storage devices.

Graphene field-effect transistor (GFET) biosensors exhibit high sensitivity due to a large surface-to-volume ratio and the high sensitivity of the Fermi level to the presence of charged biomolecules near the surface. For most reported GFET biosensors, bulky external reference electrodes are used which prevent their full-scale chip integration and contribute to higher costs per test. In this study, GFET arrays with on-chip integrated liquid electrodes were employed for COVID-19 detection and functionalized with either antibody or aptamer to selectively bind the spike proteins of SARS-CoV-2. In the case of the aptamer-functionalized GFET (aptasensor, Apt-GFET), the limit-of-detection (LOD) achieved was about 10³ particles per mL for virus-like particles (VLPs) in clinical transport medium, outperforming the Ab-GFET biosensor counterpart. In addition, the aptasensor achieved a LOD of 160 aM for COVID-19 neutralizing antibodies in serum. The sensors were found to be highly selective, fast (sample-to-result within minutes), and stable (low device-to-device signal variation; relative standard deviations below 0.5%). A home-built portable readout electronic unit was employed for simultaneous real-time measurements of 12 GFETs per chip. Our successful demonstration of a portable GFET biosensing platform has high potential for infectious disease detection and other health-care applications.

Extrusion-based 3D printing, enables programming of device geometries not achievable with other manufacturing techniques. The fabrication of miniaturized energy storage devices is in increasing demand to enable energy autonomy in on-chip technologies. Here, we demonstrate a new fabrication route of such devices, by robocasting viscoelastic inks of atomically thin transition metal dichalcogenide sheets. We have formulated inks based on the direct exfoliation of TMD nanosheets, suspended in a hydrogel-carrier environment. By tailoring the rheological properties of the ink to aid the intrinsic shear-inducing extrusion flow, we have demonstrated 3D printed micro electrodes for symmetric supercapacitors. With the rational design of 3D electrodes, exposed 2D nanosheets unveil rapid surface non-faradaic electrostatic charges and continuous charge transfer reactions, which translates into a higher capacitance and rate capability. The highlights in this work lead to an important leap for TMDs-based 3D printed energy storage devices.

Direct Ink Writing is a promising technique for the sustainable fabrication of energy devices with arbitrary architectures.

A simple and efficient preparation method for Microperoxidase-11 modified mesoporous SnO ₂ films on ITO glass substrates for the development of a sensitive electrochemical drug sensor for the determination of artemisinin.

We present a simple and efficient method for the preparation of hemin‐modified SnO₂ films on low cost, flexible, conducting ITO‐PET substrates to enable the development of a sensitive electrochemical sensor for the determination of H₂O₂. Using a hydrothermal processing method meant that the SnO₂ films can be prepared at low temperatures, compatible with the PET substrate. The properties of the electrodes enable a high hemin loading to be achieved in a stable and functional way, allowing the direct reduction and oxidation of the immobilized hemin and maintaining its high electrocatalytic activity in the reduction of H₂O₂ on the surface. The results showed a sensitive response linearly proportional to the concentration of H₂O₂ in the range 1.5 to 90 μM.

In the present work, a nanostructured ZnO layer was synthesized onto a Metglas magnetoelastic ribbon to immobilize hemoglobin (Hb) on it and study the Hb’s electrochemical behavior towards hydrogen peroxide. Hb oxidation by H₂O₂ was monitored simultaneously by two different techniques: Cyclic Voltammetry (CV) and Magnetoelastic Resonance (MR). The Metglas/ZnO/Hb system was simultaneously used as a working electrode for the CV scans and as a magnetoelastic sensor excited by external coils, which drive it to resonance and interrogate it. The ZnO nanoparticles for the ZnO layer were grown hydrothermally and fully characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and photoluminescence (PL). Additionally, the ZnO layer’s elastic modulus was measured using a new method, which makes use of the Metglas substrate. For the detection experiments, the electrochemical cell was performed with a glass vial, where the three electrodes (working, counter and reference) were immersed into PBS (Phosphate Buffer Solution) solution and small H₂O₂ drops were added, one at a time. CV scans were taken every 30 s and 5 min after the addition of each drop and meanwhile a magnetoelastic measurement was taken by the external coils. The CV plots reveal direct electrochemical behavior of Hb and display good electrocatalytic response to the reduction of H₂O₂. The measured catalysis currents increase linearly with the H₂O₂ concentration in a wide range of 25–350 μM with a correlation coefficient 0.99. The detection limit is 25–50 μM. Moreover, the Metglas/ZnO/Hb electrode displays rapid response (30 s) to H₂O₂, and exhibits good stability and reproducibility of the measurements. On the other hand, the magnetoelastic measurements show a small linear mass increase versus the H₂O₂ concentration with a slope of 152 ng/μM, which is probably due to H₂O₂ adsorption in ZnO during the electrochemical reaction. No such effects were detected during the control experiment when only PBS solution was present for a long time.