Tuning the potential drop at graphene/protic ionic liquid interface by molecular structure engineering

Ionic liquids (ILs) have been extensively employed in many applications involving interfaces with carbon-based electrodes, such as energy storage devices (batteries or supercapacitors) or electrocatalytic devices, where the way each ion of the IL interacts with the electrode has a strong impact on the overall performance of the device. For instance, the amount of potential difference between the electrode and the bulk of the IL is highly sensitive to the IL composition and it is directly related to the device capacitance. The selection of the most suited pair of ions often proceeds by time-consuming and costly trial-and-error approaches. It is necessary to understand the atomistic features of the interface to determine the effect of each ion on the potential drop. By classical molecular dynamics simulations, we show that it is possible to quickly infer the interface potential arising at the carbon electrode by carefully inspecting the molecular structure of the IL. The ion orientation at the interface is, in fact, determined by the distribution of charges within the molecules. Depending on where charges are located, ions can either lie flat or perpendicular to the interface to minimize the surface energy. The interface potential is found to be mainly determined by ion-ion interactions dictating the interface energy minimization process, whereas ion-electrode interactions are found to enforce higher ordering and charge layers stacking but not to induce selective adsorption of an ion over the other

Nanoparticle Surface Functionalization: How to Improve Biocompatibility and Cellular Internalization

The use of nanoparticles (NP) in diagnosis and treatment of many human diseases, including cancer, is of increasing interest. However, cytotoxic effects of NPs on cells and the uptake efficiency significantly limit their use in clinical practice. The physico-chemical properties of NPs including surface composition, superficial charge, size and shape are considered the key factors that affect the biocompatibility and uptake efficiency of these nanoplatforms. Thanks to the possibility of modifying physico-chemical properties of NPs, it is possible to improve their biocompatibility and uptake efficiency through the functionalization of the NP surface. In this review, we summarize some of the most recent studies in which NP surface modification enhances biocompatibility and uptake. Furthermore, the most used techniques used to assess biocompatibility and uptake are also reported

GFRP hollow column to built-up beam adhesive connection:Mechanical behaviour under quasi-static, cyclic and fatigue loading

A new adhesive beam-column connection is tested which possess the highest strength and stiffness compared to any other similar adhesive or bolted connection tested in the past. A square GFRP hollow section, acting as a column, was connected to a built-up beam made of two GFRP U-profiles by means of either epoxy or steel bolts. The beam-column assembly formed an L-shaped frame which was tested by applying a point load at the beam free end while the column was fixed at its base. Five bolted and five adhesive replicate connections were subjected to quasi-static loading up to failure. Another three adhesive connections were subjected to 400, 800 or 1200 cycles of loading and unloading with the maximum load being equal to 0.50 Pu,avg, where Pu,avg is the average static strength of the replicate adhesive specimens. At the end of the cyclic loading, the latter specimens were loaded quasi-statically to failure. Finally, another two adhesive connections were subjected to fatigue type loading. They were successively subjected to at least 196 cycles of loading and unloading with the load amplitude being 0.50 Pu,avg in the first 60 cycles, 0.75 Pu,avg in the next 60 cycles, 0.85 Pu,avg in the following 60 cycles and 0.95 Pu,avg after the 180th cycle. The test results show that the proposed adhesive connection can achieve on average 82% higher strength and 380% higher rotational stiffness than the companion bolted connection. Furthermore, the above cyclic loading has negligible effect on either the strength or the stiffness of the connection. Finally, the connection can sustain the foregoing fatigue load up to almost 180 cycles without significant damage but it will not be able to withstand the full 60 cycles of the load with 0.95 Pu,avg amplitude. The current results demonstrate the superior strength and stiffness of the new adhesive connection compared to a similar bolted connection

Processing of Ti50Nb50-xHAx composites by rapid microwave sintering technique for biomedical applications

The main objective of this research is to fabricate porous mechanical-tuned (low elastic modulus and high strength) Ti-based composites with improved bioactivity for orthopaedic applications. Another objective is to demonstrate the potential of microwave sintering and temporary space alloying technique to synthesize porous Ti-based composites. In this study, porous Ti50Nb50−xHAx (x = 0, 10 and 20) composite was fabricated for orthopaedic applications using a powder metallurgical and rapid microwave sintering (PM-RMS) process. Effects of key PM-RMS parameters on the structural porosity, compressive strength, and elastic modulus of built composite were then analysed. The microstructure, pore characteristics, and mechanical properties were investigated in detail. Using high hydroxyapatite (HA) content (20%), short sintering time (5 min), and high compacting pressure (200 MPa) appears to be the best condition among those studied in terms of yielding a high degree of structural porosity (21%) and low elastic modulus (25 GPa) in the sintered composite. Since size of pores in the synthesized composite is in the range of 20–30 μm, structural porosity not only reduces elastic modulus but also enhances bio-activity of sintered composite. The combination of highly porous structure, low elastic modulus, high compressive strength, improved corrosion resistance, and enhanced bioactivity makes porous Ti-Nb-HA composites fabricated by microwave sintering process potential and promising candidates for orthopedic applications

Self-Powered Integrated Tactile Sensing System Based on Ultrastretchable, Self-Healing and 3D Printable Ionic Conductive Hydrogel

Self-healing ionic conductive hydrogels have shown significant potential in applications like wearable electronics, soft robotics, and prosthetics because of their high strain sensitivity and mechanical and electrical recovery after damage. Despite the enormous interest in these materials, conventional fabrication techniques hamper their use in advanced devices since only limited geometries can be obtained, preventing proper conformability to the complexity of human or robotic bodies. Here, a photocurable hydrogel with excellent sensitivity to mechanical deformations based on a semi-interpenetrating polymeric network is reported, which holds remarkable mechanical properties (ultimate tensile strain of 550%) and spontaneous self-healing capabilities, with complete recovery of its strain sensitivity after damages. Furthermore, the developed material can be processed by digital light processing 3D printing technology to fabricate complex-shaped strain sensors, increasing mechanical stress sensitivity with respect to simple sensor geometries, reaching an exceptional pressure detection limit below 1 Pa. Additionally, the hydrogel is used as an electrolyte in the fabrication of a laser-induced graphene-based supercapacitor, then incorporated into a 3D-printed sensor to create a self-powered, fully integrated device. These findings demonstrate that by using 3D printing, it is possible to produce multifunctional, self-powered sensors, appropriately shaped depending on the various applications, without the use of bulky batteries.A photocurable hydrogel with excellent sensitivity to mechanical deformation and spontaneous self-healing capabilities is presented. Complex-shaped wearable sensors are fabricated by 3D printing technology, increasing sensitivity with respect to simple sensor geometries. The hydrogel is also used as an electrolyte in a supercapacitor and implemented to create a self-powered, fully integrated strain sensor system.imag

Langmuir adsorption processes and ion transport under bias potential in capacitive deionisation cells

The electric response of a capacitive deionisation cell submitted to a periodic external electric field is investigated. The case in which the applied potential has a nonzero average value on one period (polarised cell) is considered. The theoretical analysis of the experimental data, relevant to nearly symmetric electrodes, is done in the framework of the Poisson-Nernst-Planck model. The current densities on the electrodes are described by kinetic equations related to the adsorption phenomenon in the presence of a bias potential. We propose a new form for the Langmuir isotherm in which the effective adsorption coefficients depend on the bias potential according to the Boltzmann statistics. This kinetic equation extends the Butler-Volmer equation for non-blocking electrodes also to the blocking ones. The equation proposed here is such that for dc external voltage the total current across the electrodes vanishes

Fast TiO2 sensitization using the semisquaric acid as anchoring group

Metal-free dye molecules for dye-sensitized solar cells application can avoid some of the typical drawbacks of common metal-based sensitizers, that are high production costs, relatively low molar extinction coefficient in the visible region, limited availability of precursors, and waste disposal issues. Recently we have proposed an innovative organic dye based on a simple hemi-squaraine molecule (CT1). In the present work, the effect of the sensitization time of the TiO2 photoelectrode in the dye solution is studied with the aim of optimizing the performance of CT1-based DSCs. Moreover, the addition of the chenodeoxycholic acid (CDCA) as coadsorbent in the dye solution at different concentrations is investigated. Both CT1-sensitized mesoporous TiO2 photoanodes and complete solar cells have been fully characterized in their electrical and absorption properties. We have found that the best photoconversion performances are obtained with 1 hour of impregnation time and a 1 mM CDCA concentration. The very fast kinetics in dye adsorption, with optimal sensitization steps almost 15 times faster than conventional Ru-based sensitizers, confirms the theoretical predictions and indicates a strong interaction of the semisquaric acid group with the anatase surface. This result suggests that this small molecule can be a promising sensitizer even in a continuous industrial process