Reactions of atoms and molecules on chamber walls in contact with low temperature plasmas are important in various technological applications. Plasma-surface interactions are complex and relatively poorly understood. Experiments performed over the last decade by several groups prove that interactions of reactive species with relevant plasma-facing materials are characterized by distributions of adsorption energy and reactivity. In this paper, we develop a kinetic Monte Carlo (KMC) model that can effectively handle chemical kinetics on such heterogenous surfaces. Using this model, we analyse published adsorption-desorption kinetics of chlorine molecules and recombination of oxygen atoms on rotating substrates as a test case for the KMC model.
The modification of Pt/C catalyst by using ionic liquids to improve their catalyst activities has been reported by many researchers, but their practical behavior in operating fuel cells is still unknown. In this work, we study the ionic liquid modified Pt/C nanoparticle catalysts within cathodes for proton exchange membrane fuel cells. The influence of the ionic liquid amount, adsorption times and dispersing solvents are investigated. The experiment results show the best performance enhancement is achieved through two-time surface modification with 2 wt-% ionic liquid solution. The mechanisms are explored with the attribution to the high oxygen solubility in the ionic liquid enabling an improved oxygen diffusion in micropores and to good hydrophobicity facilitating water expelling from the active sites in fuel cell operation.
A form stable NaCl-Al2O3 (50-50 wt-%) composite material for high temperature thermal energy storage was fabricated by cold sintering process, a process recently applied to the densification of ceramics at low temperature ˂ 300°C under uniaxial pressure in the presence of small amount of transient liquid. The fabricated composite achieved as high as 98.65% of the theoretical density. The NaCl-Al2O3 composite also retained the chloride salt without leakage after 30 heating-cooling cycles between 750°C–850°C together with a holding period of 24 h at 850°C. X-ray diffraction measurements indicated congruent solubility of the alumina in chloride salt, excellent compatibility of NaCl with Al2O3, and chemical stability at high temperature. Structural analysis by scanning electron microscope also showed limited grain growth, high density, uniform NaCl distribution and clear faceted composite structure without inter-diffusion. The latent heat storage density of 252.5 J/g was obtained from simultaneous thermal analysis. Fracture strength test showed high sintered strength around 5 GPa after 50 min. The composite was found to have fair mass losses due to volatilization. Overall, cold sintering process has the potential to be an efficient, safe and cost-effective strategy for the fabrication of high temperature thermal energy storage materials.
Recently, the performance and fabrication of thin-film thermoelectric materials have been largely enhanced. Based on this enhancement, the thin-film thermoelectric cooler (TEC) is becoming a research hot topic, due to its high cooling flux and microchip level size. To fulfill a thin-film TEC, interfacial problems are unavoidable, as they may largely reduce the properties of a thin-film TEC. Moreover, the architecture of a thin-film TEC should also be properly designed. In this review, we introduced the enhancement of thermoelectric properties of (Bi,Sb)2(Te,Se)3 solid solution materials by chemical vapor deposition, physical vapor deposition and electrodeposition. Then, the interfacial problems, including contact resistance, interfacial diffusion and thermal contact resistance, were discussed. Furthermore, the design, fabrication, as well as the performance of thin-film TECs were summarized.
Prostate cancer has a high incidence in men and remains the second cause of mortality due to cancer. As the development of the disease is greatly correlated to age, the identification of novel detection methods reliable, efficient, and cost effective is a matter of significant importance in the ageing population of western societies. The detection of the prostate specific antigen (PSA) in blood samples has been the preferred method for the detection and monitoring of prostate cancer over the past decades. Despite the indications against its use in massive population screening, PSA still remains the best studied biomarker for prostate cancer and the detection of its different forms and incorporation in multiplexed designs with other biomarkers still remains a highly valuable indicator in the theranostics of prostate cancer. The latest developments in the use of nanomaterials towards the construction of PSA biosensors are reviewed hereby. The incorporation of gold nanoparticles, silica nanoparticles and graphene nanostructures to biosensing devices has represented a big leap forward in terms of sensitivity, stability and miniaturization. Both electrochemical and optical detection methods will be reviewed herein for the detection of PSA.
A facile one-step hydrothermal method has been adopted to directly synthesize the CuCo2S4 material on the surface of Ni foam. Due to the relatively large specific surface area and wide pore size distribution, the CuCo2S4 material not only effectively increases the reactive area, but also accommodates more side reaction products to avoid the difficulty of mass transfer. When evaluated as anode for Li-ion batteries, the CuCo2S4 material exhibits excellent electrochemical performance including high discharge capacity, outstanding cyclic stability and good rate performance. At the current density of 200 mA·g−1, the CuCo2S4 material shows an extremely high initial discharge capacity of 2510 mAh·g−1, and the cycle numbers of the material even reach 83 times when the discharge capacity is reduced to 500 mAh·g−1. Furthermore, the discharge capacity can reach 269 mAh·g−1 at a current of 2000 mA·g−1. More importantly, when the current density comes back to 200 mA·g−1, the discharge capacity could be recovered to 1436 mAh·g−1, suggesting an excellent capacity recovery characteristics.
Controlled growth of Bi2WO6 nanorods with exposed [0 0 1] facets and the fabrication of an Fe3O4-Bi2WO6 magnetic composite by a microwave-assisted polyol process, were achieved in this study. The adsorptivity and photocatalytic performance of the composite toward sunset yellow dye degradation were greatly enhanced by the β-cyclodextrin cavities on its surface, firmly anchored through a cetyltrimethylammonium bromide linkage. A series of examinations and characterizations were carried out to determine the influence of various factors on the morphological modulation-photocatalytic behavior of the pure Bi2WO6 prior to final functionalization. Changing the pH of the precursor solution impacted the formation of 0D, 2D, and 3D structures; however, the presence of hexamethylenetetramine surfactant induced the development of 1D nanorod structure. A reasonable crystal growth mechanism was proposed to elucidate the formation process. Conversely, the mechanism of the activity enhancement of β-cyclodextrin functionalized Fe3O4-Bi2WO6, compared to that of the non-functionalized samples, could be realized with the assistance of chemical trapping experiments on sunset yellow, and was confirmed on the colorless antibiotic (sulfamethoxazole). The high performance and durability of this composite can be attributed to the facet-dependent activity, large adsorption capacity due to inclusion interactions, enhanced visible light absorption, and efficient charge separation.
This research looks at ways of tailoring and improving the stiffness of polypyrrole hydrogels for use as flexible supercapacitor electrodes. Molecules providing additional cross-linking between polypyrrole chains are added post-polymerisation but before gelation, and are found to increase gel stiffness by up to 600%, with the degree of change dependent on reactant type and proportion. It was also found that addition of phytic acid led to an increase in pseudocapacitive behaviour of the hydrogel, and thus a maximum specific capacitance of 217.07 F·g−1 could be achieved. This is an increase of 140% compared to pristine polypyrrole hydrogels produced by this method.
The search for new fluorescent molecules for possible applications as functional p-electron systems and their conjugation with different nanomaterials is nowadays of paramount importance to broaden the availability of materials with different properties. Herein we present a diversity-oriented approach to heterocyclic luminophores based on a multicomponent Ugi reaction followed by a Pd-mediated cascade sequence. The new molecules are coupled to carbon nano-onions, and hybrid systems represent the first example of blue emitters conjugated with these carbon nanoparticles.