Studies on constricted hollow anode plasma source for negative ion production

Electronegative plasmas have a wide ranging applications following its primary role in the production of energetic neutral beams of hydrogen used for plasma heating in fusion devices. In technological plasma applications electronegative gases are used for plasma etching which readily form stable negative ions. Significant population of negative ions in a discharge can greatly influence the discharge properties by reducing electron density while modifying the sheath structures adjacent to the substrates. Formation of negative ions is a complex process. They are primarily formed in the bulk phase by the dissociative attachment of low energy electron to an excited molecule. However intermediate excitation of the neutral molecules requires the presence of energetic electrons in the discharge. An efficient mechanism of negative ion production is via interaction with a low work function material such as Caesium coated surface as used in the negative ion source for neutral beam extraction. However, caesium migration between the acceleration grids can be a major concern for the failure of ion source during long pulse operation. Therefore suitably tailoring the plasma properties of the source can help in improving the efficiency of negative ion production in the bulk phase rather than surface production. The thesis deals with the study of oxygen negative ion formation in the anodic glow plasma. The anodic glow is characterized by a double layer having a steep gradient in Te and electron density. This region provides a natural favourable condition for the production of negative ions. The anodic glow is created via D.C discharge between a hollow tubular-anode in conjunction with parallel plate cathodes. The results show significant fraction of negative oxygen ions near the anodic glow. Theoretical estimates of negative ions at each spatial location are obtained by providing electron density and temperature measured using plasma diagnostic probes. The results show reasonable agreement with the experimental data suggesting that anodic glow can provide a suitable breeding ground for the production of negative ions. A qualitative model is presented for observing the oscillation in the discharge current due to ionization instability at the anode sheath

State-of-Art Functional Biomaterials for Tissue Engineering

Nanobiotechnology-enabled tissue engineering strategies have emerged as an innovative and promising technique in the field of regenerative medical science. The design and development of multifunctional smart biomaterials compatible to human physiology is crucial to achieve the required biological function with a reduced negative biological response. Several medical bioimplants have been tested to boost life expectancy and better-quality life. The concept of biocompatibility focuses on body acceptance and no harmful effects after implantation, which require shaping the properties of materials synthesis, surface functionalization, and biofunctionality. Such developed bioactive and biodegradable materials have been utilized to achieve the required function at a specific period and sustainability to withstand the surrounding tissues for treating severe injuries and diseases. Thus, exploring new approaches to design multifunctional biocompatible advanced nanostructures to develop next-generation therapies for tissue engineering, this mini-review is an attempt to summarize the advancements in biofunctional smart materials. The review focuses on bio-mimic materials, biomaterials, self-assembly biomaterials, bioprinting functional hydrogels, new polymeric architectures, and hybrid synthetic–natural hydrogels in the field of tissue engineering and regenerative medicine (TERM). This mini-review will serve as a guideline to design future research where the selection of a smart multifunctional biomaterial is crucial to obtain best TERM performance

Atmospheric Plasma Treatment Enhances the Biosensing Properties of Graphene Oxide-Silver Nanoparticle Composite

This work presents an approach to tailor the properties of the graphene oxide- silver nanoparticle (GO-AgNPs) composite using room temperature atmospheric plasma treatment. In particular, the aerosolized deposition of graphene oxide-silver nanoparticle composite (GO-AgNPs), the rapid reduction of GO at room temperature, and AgNPs surface excitation are investigated in this work. The plasma treatment of aerosolized GO leads to the reduced graphene oxide (rGO) formation which is observed from the increase in D to G band ratio from 0.65 for GO to 1.2 for rGO in the Raman spectra. Scanning Electron Microscopy, Transmission Electron Microscopy, and Selected Area Electron Diffraction patterns show that the plasma treatment leads to the morphological changes and the Electrochemical Impedance spectroscopy results show the improvement in the conductivity of the rGO-AgNP composite. To demonstrate the efficacy of the technique, plasma treated GO and silver nanoparticles (AgNPs) composite is used for the electrode surface modification of the commercial screen-printed electrodes for the cortisol detection. The cyclic voltammetry scans to detect cortisol shows that the sensitivity of the surface modified electrodes is increased after plasma treatment. This room temperature atmospheric plasma annealing technique is of specific interest for rapid processing of nanoparticles on flexible surfaces without subjecting them to elevated temperatures

Erratum: Tiwari, S., et al. Biosensors for Epilepsy Management: State-of-Art and Future Aspects. Sensors 2019, 19, 1525.

The authors wish to make the following correction to the above-mentioned published paper [...]

Magnesium-Palm Kernel Shell Biochar Composite for Effective Methylene Blue Removal: Optimization via Response Surface Methodology

This study investigates the properties and potential application of Mg-PKS biochar composite for methylene blue solution (MB) adsorption. The Mg-PKS biochar composite was developed from palm kernel shell biochar via steam activation followed by MgSO4 treatment and carbonization. The effect of process parameters such as solution pH (4-10), contact time (30-90 min) and adsorbent dosage (0.1-0.5 g) were investigated via central composite design, response surface methodology. Results revealed that the Mg-PKS biochar composite has irregular shapes pore structure from SEM analysis, a surface area of 674 m2g-1 and average pore diameters of 7.2195 μm based on BET analysis. RSM results showed that the optimum adsorption of MB onto Mg-biochar composite was at pH 10, 30 min contact time and 0.5 g/100 mL dosage with a removal efficiency of 98.50%. In conclusion, Mg treatment is a potential alternative to other expensive chemical treatment methods for biochar upgrading to the adsorbent

Carbon-based Nanomaterials for Energy Storage and Sensing Applications

This chapter reviews carbon-based nanomaterials and their potential applications in energy storage and sensing. Several methods of synthesizing carbon nanomaterials have been developed over the years. They include exfoliation, thermal decomposition, chemical vapor deposition, chemical-based techniques (including Hummer’s method), laser abrasion, and arc-discharge method. There are several synthesis methods developed over the years for carbon nanomaterials. There are mainly three different approaches to the chemical vapor deposition (CVD) technique, namely, atmospheric pressure CVD, low pressure CVD, and plasma enhanced CVD (e.g., microwave plasma enhanced CVD). Chemical-based techniques are the chemical extraction of graphene films from graphite, unlike the liquid phase exfoliation technique. Laser ablation relies on the laser exfoliation or ablation of amorphous graphite, and is sometimes called pulsed laser deposition. In the field of materials science, electrochemical energy storage has become a big challenge due to the rising need for portable electronic devices and systems

Microwave Hydrothermal Carbonization of Rice Straw: Optimization of Process Parameters and Upgrading of Chemical, Fuel, Structural and Thermal Properties.

The process parameters of microwave-induced hydrothermal carbonization (MIHTC) play an important role on the hydrothermal chars (hydrochar) yield. The effect of reaction temperature, reaction time, particle size and biomass to water ratio was optimized for hydrochar yield by modeling using the central composite design (CCD). Further, the rice straw and hydrochar at optimum conditions have been characterized for energy, chemical, structural and thermal properties. The optimum condition for hydrochar synthesis was found to be at a 180 °C reaction temperature, a 20 min reaction time, a 1:15 weight per volume (w/v) biomass to water ratio and a 3 mm particle size, yielding 57.9% of hydrochar. The higher heating value (HHV), carbon content and fixed carbon values increased from 12.3 MJ/kg, 37.19% and 14.37% for rice straw to 17.6 MJ/kg, 48.8% and 35.4% for hydrochar. The porosity, crystallinity and thermal stability of the hydrochar were improved remarkably compared to rice straw after MIHTC. Two characteristic peaks from XRD were observed at 2? of 15° and 26°, whereas DTG peaks were observed at 50?150 °C and 300?350 °C for both the materials. Based on the results, it can be suggested that the hydrochar could be potentially used for adsorption, carbon sequestration, energy and agriculture applications

Magnetically modified sugarcane bagasse biochar as cadmium removal agent in water

Heavy metals are hazardous to health at certain levels. Currently, heavy metals are removed by physicochemical treatments, such as adsorption, flotation, and electrochemical deposition, and also biological treatments, such as algal biofilm reactor and anaerobic ammonium oxidation. In this study, magnetic biochar was produced to enhance the effectiveness and performance of the adsorbent for heavy metal removal. This study aimed to synthesise high-performance magnetic biochar, to determine the optimum parameters and conditions for high yield of magnetic biochar and high removal of cadmium (Cd2+) from aqueous solution, and to determine the adsorption kinetics and isotherms for Cd2+ removal. Nickel oxide (NiO)-impregnated sugarcane bagasse was subjected to slow pyrolysis to produce magnetic biochar. The impregnated metal, pyrolysis temperature, and pyrolysis time were varied to determine the optimum parameters and conditions to produce high-performance magnetic biochar. The removal of Cd2+ from aqueous solution and batch adsorption study were conducted. The synthesised magnetic biochar was characterised using field-emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, Fourier transform infrared (FTIR), and vibrating sample magnetometer (VSM). The adsorption data agreed well with the pseudo-second-order model and followed the Langmuir isotherm model. This study achieved 88.47% removal efficiency of Cd2+ from aqueous solution. Thus, the removal of this heavy metal as a human carcinogen reduces the hazardous effects on human health and reduces the toxicity in the environment

Structural Changes and Electrochemical Stability of Ionogel Incorporating Tetraethyl Orthosilicate and PVDF-HFP

Ionogels are emerging hybrid materials and are widely studied due to the combination of thermophysical properties from ionic liquid and mechanical integrity from the polymer matrix. Ionic liquid has received wide attention due to its promising properties, high ionic conductivity, and thermal stability. The liquid nature of ionic liquid has restricted its application. Thus, the confinement of ionic liquid within a polymer matrix has allowed ionogel to be applied in strain sensors and lithium-ion batteries. Nevertheless, the compatibility between the polymer matrix and ionic liquid is crucial for ionogel. Incompatibility between polymer host and ionic liquid results in low ionic conductivity, poor mechanical strength, and undesired for practical application. The interaction between polymer matrix and ionic liquid is studied in this study through optical microscopy. The addition of ionic liquid resulted in the disappearance of the polymer matrix’s highly porous nature, as evidenced by the optical microscopy images. This disappearance of the porous nature suggests the compatibility of the polymer matrix with ionogel. Furthermore, the electrochemical stability of the ionogel is also examined through linear sweep voltammetry technique and achieved 2.3V