Progress in supercapacitors: roles of two dimensional nanotubular materials

Overcoming the global energy crisis due to vast economic expansion with the advent of human reliance on energy-consuming labor-saving devices necessitates the demand for next-generation technologies in the form of cleaner energy storage devices. The technology accelerates with the pace of developing energy storage devices to meet the requirements wherever an unanticipated burst of power is indeed needed in a very short time. Supercapacitors are predicted to be future power vehicles because they promise faster charging times and do not rely on rare elements such as lithium. At the same time, they are key nanoscale device elements for high-frequency noise filtering with the capability of storing and releasing energy by electrostatic interactions between the ions in the electrolyte and the charge accumulated at the active electrode during the charge/discharge process. There have been several developments to increase the functionality of electrodes or finding a new electrolyte for higher energy density, but this field is still open to witness the developments in reliable materials-based energy technologies. Nanoscale materials have emerged as promising candidates for the electrode choice, especially in 2D sheet and folded tubular network forms. Due to their unique hierarchical architecture, excellent electrical and mechanical properties, and high specific surface area, nanotubular networks have been widely investigated as efficient electrode materials in supercapacitors, while maintaining their inherent characteristics of high power and long cycling life. In this review, we briefly present the evolution, classification, functionality, and application of supercapacitors from the viewpoint of nanostructured materials to apprehend the mechanism and construction of advanced supercapacitors for next-generation storage devices.

Effects of electrical conductivity on the formation and annihilation of positronium in porous materials

In this paper we show the preliminary evidence that the formation of positronium depends on the electrical conductivity of porous materials. Porous nano γ-Al₂O₃ was chosen as the base material, and it was filled with carbon of different allotropes (commercial graphite, carbon black, carbon nanotubes and home-made ordered mesoporous carbon) by a mechanical mixing method. The positron lifetime and Doppler broadening of the annihilation radiation were measured for these composites. In the pure γ-Al₂O₃ sample, there are two long positron lifetime components τ₃ (3.5 ns) and τ₄ (101.3 ns) with intensities of 1.0% and 24.6%, which indicates the formation and annihilation of positronium in small and large pores, respectively. In the carbon filled γ-Al₂O₃ samples, the longest lifetime τ₄ and its intensity I₄ both show a continuous decrease with increasing carbon content. The Doppler broadening S parameter shows a similar tendency to τ₄ and I₄. This suggests that carbon has a quenching effect on positronium and also inhibits the formation of positronium. Among these four carbon allotropes, carbon nanotubes have the strongest quenching and inhibition effect, while graphite has the weakest effect. A detailed study further reveals that the decreasing rate of τ₄ and I₄ as well as the S parameter depend on the electrical conductivity of the carbon filled γ-Al₂O₃ and also the specific surface area of the filled carbon. Our results suggest that the formation and annihilation of positronium are strongly affected by the electrical conductivity of the materials.

High temperature CO2 sensing properties and mechanism of nanocrystalline LaCrO3 with rhombohedral structure: experiments and ab initio calculations

Both experiment and calculation results show that CO₂ captures electrons from the semiconductor surface.

Effect of silica precursor transformation on diclofenac sodium release

The present paper describes the preparation of a new type of ternary composites where pure silica gel or polysilsesquioxane was deposited on a polymer carrier loaded with a high dose of diclofenac sodium.

Synthesis of aspirin-loaded polymer-silica composites and their release characteristics

This study describes a novel approach to the synthesis of polymer-drug-silica nanocomposites via encapsulation/isolation of drug molecules, introduced into the polymer matrix by the silica gel. For the first time, tetraethoxysilane (TEOS) gelation in the vapor phase of the acidic catalyst is presented as an efficient method to enter the silica gel nanoparticles into the polymer-aspirin conjugate. The conducted studies reveal that the internal structure of the polymer carrier is significantly reorganized after the embedding of aspirin molecules and the silica gel. The total porosity of the polymer-drug-silica nanocomposites and the molecular structure of the silica gel embedded in the system strongly depend on the conditions of the silica source transformation. Additionally, the release of the drug was fine-tuned by adapting the conditions of hydrolysis and condensation of the silica gel precursor. Finally, to prove the usefulness of the proposed synthesis, the controlled release of aspirin from the polymer-drug-silica nanocomposites is demonstrated.