Synthesis of stabilizer-free, homogeneous gold nanoparticles by cold atmospheric-pressure plasma jet and their optical sensing property

Recently, cold atmospheric-pressure plasma has been studied extensively as an efficient and green method to synthesize gold nanoparticles (AuNPs). Although the characteristics of the AuNPs, especially their homogeneousness, depend very much on the plasma synthesis parameters, there is a lack of a study involving these parameters systematically. Moreover, most of AuNPs-cold-plasma synthesis reports so far either required organic capping agents or resulted in highly non-uniform AuNPs. In this work, we systematically study the effect of most important synthesis parameters– including distance from the plasma jet to the solution, gas flow rate, plasma rate, volume and concentration of the precursor, plasma interaction time as well as the effect of the synthesis environment (humidity and temperature) – on the uniformity of the AuNPs. Through various characterization measurements, we show that homogeneous and highly stable intrinsic AuNPs with an average size of 45 nm can be obtained with optimized synthesis parameters and in the absence of a stabilizer. The synthesized AuNPs yield advanced optical sensing properties in comparison with commercial AuNPs and can be further applied in developing versatile and high-sensitivity biosensors.

One-Step Synthesis of SnO2/Carbon Nanotube Nanonests Composites by Direct Current Arc-Discharge Plasma and Its Application in Lithium-Ion Batteries

Tin dioxide (SnO2)-based materials, as anode materials for lithium-ion batteries (LIBs), have been attracting growing research attention due to the high theoretical specific capacity. However, the complex synthesis process of chemical methods and the pollution of chemical reagents limit its commercialization. The new material synthesis method is of great significance for expanding the application of SnO2-based materials. In this study, the SnO2/carbon nanotube nanonests (SnO2/CNT NNs) composites are synthesized in one step by direct current (DC) arc-discharge plasma; compared with conventional methods, the plasma synthesis achieves a uniform load of SnO2 nanoparticles on the surfaces of CNTs while constructing the CNTs conductive network. The SnO2/CNT NNs composites are applied in LIBs, it can be found that the nanonest-like CNT conductive structure provides adequate room for the volume expansion and also helps to transfer the electrons. Electrochemical measurements suggests that the SnO2/CNT NNscomposites achieve high capacity, and still have high electrochemical stability and coulombic efficiency under high current density, which proves the reliability of the synthesis method. This method is expected to be industrialized and also provides new ideas for the preparation of other nanocomposites.

Concurrent Synthesis and Immobilization of Ag Nanoparticles over TiO2 via Plasma Reduction for Photocatalytic Treatment of Methyl Blue in Water

Pure TiO2 nanoparticles (TiO2NPs) were produced via the sol–gel method and then coated with silver nanoparticles (AgNPs) to reduce their optical band gap. The concurrent synthesis and immobilization of AgNPs over TiO2NPs was achieved through the interaction of an open-air argon plasma jet with a solution of silver nitrate/stabilizer/TiO2NPs. The one-pot plasma synthesis and coating of AgNPs over TiO2NPs is a more straightforward and environmentally friendly method than others. The plasma-produced Ag/TiO2 nanocomposites were characterized and tested for their photocatalytic potential by degrading different concentrations of methyl blue (MB) in water. The dye concentration, oxidant dose, catalyst dose, and reaction time were also optimized for MB degradation. XRD results revealed the formation of pure AgNPs, pure TiO2NPs, and Ag/TiO2 nanocomposites with an average grain size of 12.36 nm, 18.09 nm, and 15.66 nm, respectively. The immobilization of AgNPs over TiO2NPs was also checked by producing SEM and TEM images. The band gap of AgNPs, TiO2NPs, and Ag/TiO2 nanoparticles was measured about 2.58 eV, 3.36 eV, and 2.86 eV, respectively. The ultraviolet (UV) results of the nanocomposites were supportive of the degradation of synthetic dyes in the visible light spectrum. The AgNPs in the composite not only lowered the band gap but also obstructed the electron–hole recombinations. The Ag/TiO2 composite catalyst showed 90.9% degradation efficiency with a 5 ppm dye concentration after 120 min of light exposure.

Application of plasma polymerized pyrrole nanoparticles to prevent or reduce de-differentiation of adult rat ventricular cardiomyocytes

Cardiovascular diseases are the leading cause of death in the world, cell therapies have been shown to recover cardiac function in animal models. Biomaterials used as scaffolds can solve some of the problems that cell therapies currently have, plasma polymerized pyrrole (PPPy) is a biomaterial that has been shown to promote cell adhesion and survival. The present research aimed to study PPPy nanoparticles (PPPyN) interaction with adult rat ventricular cardiomyocytes (ARVC), to explore whether PPPyN could be employed as a nanoscaffold and develop cardiac microtissues. PPPyN with a mean diameter of 330 nm were obtained, the infrared spectrum showed that some pyrrole rings are fragmented and that some fragments of the ring can be dehydrogenated during plasma synthesis, it also showed the presence of amino groups in the structure of PPPyN. PPPyN had a significant impact on the ARVC´s shape, delaying dedifferentiation, necrosis, and apoptosis processes, moreover, the cardiomyocytes formed cell aggregates up to 1.12 mm2 with some aligned cardiomyocytes and generated fibers on its surface similar to cardiac extracellular matrix. PPPyN served as a scaffold for adult ARVC. Our results indicate that PPPyN-scaffold is a biomaterial that could have potential application in cardiac cell therapy (CCT).

Spark Plasma Synthesis and Tribological Behaviour of Ti-Ni-TiCN Nanocomposite

The conventional method of producing titanium components introduces defects into the matrix of the materials, thus resulting in poor microstructure, tribological properties and performance of the materials in service. To overcome these challenges, a Ti-Ni-TiCN nanocomposite was developed using the novel spark plasma sintering (SPS) technique. The morphology and the phases present in the initial powders and the sintered specimen were investigated using the scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The dry sliding wear behaviour of the sintered samples was studied at ambient temperature by ball-on-disc tests, under an applied normal load of 25 N. The presence of unreacted TiCN, in-situ formed TiN and Ti2Ni intermetallic phases were revealed by the SEM/EDS analysis and confirmed by the XRD results. The developed titanium matrix nanocomposite displayed a much lower coefficient of friction and wear resistance than the CP-Ti. The strong interface between the matrix and the reinforcements prevents the reinforcements from pulling out of the matrix. Ti-Ni-TiCN nanocomposite showed the predominance of abrasive wear while mixed wear mode was observed, in the CP-Ti. The developed material has the capacity to replace CP-Ti and perform admirably in a tribo-system.