Photocatalytic performance of oxygen vacancy rich-TiO2 combined with Bi4O5Br2 nanoparticles on degradation of several water pollutants

Despite significant advancements in the improvement of heterogeneous photocatalysis towards water treatment, these processes still have some bottlenecks. In this research paper, oxygen vacancy rich-TiO₂ was combined with Bi₄O₅Br₂ nanoparticles (denoted as TiO₂-OVs/Bi₄O₅Br₂) by eco-friendly hydrothermal approach. The outcomes demonstrated that the photoactivity strongly depends on plenteous active sites, reinforced charge segregation, as well as striking visible-light absorption ability in TiO₂-OVs/Bi₄O₅Br₂ nanocomposite with n-n heterojunction. The photoactivity was found to follow the trend: TiO₂-OVs/Bi₄O₅Br₂ (30%) > TiO₂-OVs > TiO₂. Briefly, the removal efficiencies of RhB, MB, and fuchsine were 100%, 96.2%, and 84.7% using TiO₂-OVs/Bi₄O₅Br₂ (30%) in 120 min, while they were 25.1%, 20.0%, and 15.3% over the TiO₂, respectively. Further, the boosted rate constant was observed for the photoreduction of Cr (VI) on the TiO₂-OVs/Bi₄O₅Br₂ (30%) nanocomposite, which was 19.4 and 7.8-folds more than the TiO₂ and TiO₂-OVs photocatalysts, respectively. The radical scavenging tests with different quenchers demonstrated that holes and superoxide anion radicals take part in the degradation reaction. Finally, by investigating the electrochemical properties, a mechanism was offered to describe the improved e^–/h⁺ pairs separation and migration. This research displayed that the design of n-n heterojunction using TiO₂-OVs could be suitable for severely improving photocatalytic performance of TiO₂ under visible light.     

Effect of Annealing on Virgin and Recycled Carbon Fiber Electrochemically Deposited with N-type Bismuth Telluride and Bismuth Sulfide

N-type thermoelectric bismuth telluride (Bi₂Te₃) and bismuth sulfide (Bi₂S₃) were deposited on virgin carbon fiber (VCF) and recycled carbon fiber (RCF) substrates by electrodeposition. The effects of annealing on the surface morphology and the Seebeck coefficient of the Bi₂Te₃ and Bi₂S₃ films were investigated. A nearly stoichiometric N-type Bi₂Te₃ was obtained from an electrolyte solution of 8 mM of Bi(NO₃)₃.5H₂O and 10 mM of TeO₂, which displayed the highest Seebeck coefficient of ?20.01 and ?13.0 µV/K for VCF and RCF, respectively. The deposition of Bi₂S₃ was slightly off-stoichiometry, but the improvement was still significant with a Seebeck coefficient of ?16.3 and ?12.4 µV/K for VCF and RCF, respectively. The effect of varying the annealing temperature (275°C and 350°C) and annealing time (2 and 3 hours) was studied on a nearly stoichiometric N-type Bi₂Te₃. The result shows an improvement in the Seebeck coefficient by 1.51–1.24 times at 350°C for 2 hours.     

Fission of Multielectron Bubbles in Liquid Helium Under Electric Fields

Multielectron bubbles (MEBs) are cavities in liquid helium which contain a layer of electrons trapped within few nanometres from their inner surfaces. These bubbles are promising candidates to probe a system of interacting electrons in curved geometries, but have been subjected to limited experimental investigation. Here, we report on the observation of fission of MEBs under strong electric fields, which arises due to fast rearrangement of electrons inside the bubbles, leading to their deformation and eventually instability. We measured the electrons to be distributed unequally between the daughter bubbles which could be used to control the charge density inside MEBs.     

Spectroscopic investigation confirms retaining the pristine nature of single-walled carbon nanotubes on dissolution in aniline

Carbon nanotubes in all forms are very much insoluble in both organic and inorganic solvents due to its high agglomeration and entangled morphology. General methods for dissolution of single-walled carbon nanotubes (SWNTs) are mostly associated with complexation or polymerization or addition of macromolecules which change the physical or chemical properties of SWNTs and the pristine nature of SWNTs is lost. Dissolution of SWNTs in a solvent like aniline is practiced here which is a very simple reaction method. Here aniline is capable to form a SWNT-aniline charge transfer complex without attachment of macromolecules or polymer which is also soluble in other organic solvents. Solvation of SWNTs by this method is also capable of maintaining the similarity between the structure of SWNTs before and after the dissolution, which means that the pristine nature of SWNTs is preserved. Formation of charge transfer complex in this reaction has been proven by UV-Vis/NIR absorption and photoluminescence spectroscopy. Raman spectroscopy and electron microscopy (FESEM and TEM) are the evidences for protection of the pristine nature of SWNTs even after high-temperature complexation reaction with aniline and also after solubilization in organic solvents.     

Ionic conductivity and diffusion coefficient of barium-chloride-based polymer electrolyte with poly(vinyl alcohol)–poly(4-styrenesulphonic acid) polymer complex

A composite polymer electrolyte comprising poly(vinyl alcohol)–poly(4-styrenesulphonic acid) with barium chloride dihydrate (\(\hbox {BaCl}_{2}{\cdot } 2\hbox {H}_{2}\hbox {O}\)) salt complex has been synthesized following the usual solution casting. The ionic conductivity of polymer electrolyte was analysed by impedance spectroscopy. The highest room temperature (at 30\({^{\circ }}\)C) conductivity evaluated was 9.38 \(\times \) 10\(^{-6}\) S cm\(^{-1}\) for 20 wt% loading of \(\hbox {BaCl}_{2}\) in the polymer electrolyte. This has been referred to as the optimum conducting composition. The temperature-dependent ionic conductivity of the polymer electrolyte exhibits the Arrhenius relationship, which represents the hopping of ions in polymer composites. Cation and anion diffusion coefficients are evaluated using the Trukhan model. The transference number and enhanced conductivity imply that the charge transportation is due to ions. Therefore this polymer electrolyte can be further studied for the development of electrochemical device applications.     

Machining parameters optimization for satisfying the multiple objectives in machining of MMCs

The metal matrix composites (MMCs) have gained acceptance in an extensive range of applications owing to their high strength to mass ratio. Machining of such complex MMCs is often challenging. It is essential to optimize the controllable machining parameters to simultaneously attain manifold objectives. In the current work, response surface design is created for experiments, and Genetic algorithm (GA) combined with Principal Components Analysis (PCA) coupled Grey Relational Analysis (GRA) is employed to improve the straight turning process of MMCs. The procedure is demonstrated by machining aluminum-based MMC with 25% SiC particulates. The procedure aims at identifying optimal combination of machining parameters to obtain high surface quality at lower cutting force without increasing the specific power consumption. PCA is helpful in providing the individual uncorrelated quality characteristics called as quality indices that do not have any influence on other responses. Individual quality indices have been utilized to obtain the grey relational grade through GRA. GRA has been used to alter manifold quality indices into singular column of grey relational grade as a means to change the manifold objective problem into a sole objective problem. Then, GA has been used to get the optimal parameters combination. The novelty present in this work is the avoidance of correlation existing among the quality characteristics and combining of the GRA and GA. This is an endeavor to augment the performance and accuracy of GA to solve the optimization problem associated with the turning operation.     

1D Copper Nanostructures: Progress,Challenges and Opportunities

One‐dimensional noble metal nanostructures are important components in modern nanoscience and nanotechnology due to their unique optical, electrical, mechanical, and thermal properties. However, their cost and scalability may become a major bottleneck for real‐world applications. Copper, being an earth‐abundant metallic element, is an ideal candidate for commercial applications. It is critical to develop technologies to produce 1D copper nanostructures with high monodispersity, stability and oxygen‐resistance for future low‐cost nano‐enabled materials and devices. This article covers comprehensively the current progress in 1D copper nanostructures, most predominantly nanorods and nanowires. First, various synthetic methodologies developed so far to generate 1D copper nanostructures are thoroughly described; the methodologies are in conjunction with the discussion of microscopic, spectrophotometric, crystallographic and morphological characterizations. Next, striking electrical, optical, mechanical and thermal properties of 1D copper nanostructures are highlighted. Additionally, the emerging applications of 1D copper nanostructures in flexible electronics, transparent electrodes, low cost solar cells, field emission devices are covered, amongst others. Finally, there is a brief discussion of the remaining challenges and opportunities.     

Electrical transport properties of polyvinyl alcohol–selenium nanocomposite films at and above room temperature

Here, we report the DC and AC electrical properties of polyvinyl alcohol (PVA)–selenium (Se) nanocomposite films in the temperature (T) range 298 K ≤ T ≤ 420 K and in the frequency (f) range 120 Hz ≤ f ≤ 1 MHz. The introduction of selenium nanoparticles into the PVA matrix slightly increases the values of DC conductivity whose temperature dependency obeys Vogel–Fulcher–Tammann law. The AC conductivity follows a power law with frequency in which the temperature dependence of the frequency exponent suggests that the correlated barrier hopping is the dominant charge transport mechanism for the nanocomposite films. Comparative discussions with Dyre’s random free-energy barrier model have also been made in this regard. The increase in AC conductivity with increase in nanoparticles concentration was also observed and attributed to the corresponding increase in conducting channels in the PVA matrix. The real part of the dielectric constant increases either with increase in temperature or with increase in selenium nanoparticles loading into the polymer matrix, which may be attributed to the enhancement of interfacial polarization. The frequency dispersion of the dielectric spectra has been modeled according to the modified Cole–Cole equation. Well-defined peaks were appeared in the plotting of imaginary part of electric modulus with frequency above room temperature, which was fitted with suitable equations to account for the deviations from ideal Debye-type behavior. Though the current–voltage characteristics are linear at smaller voltages, it appreciably becomes nonlinear at higher voltages. This nonlinearity has been accounted in light of Werner’s model and back to back Schottky diode model.     

Fabrication and morphological control of ion-induced zinc nanostructures

An efficient method for the fabrication of zinc (Zn) nanostructures (nanoneedles and nanofibers) of controllable density and morphology without any catalyst, hazardous chemicals or external heat supply has been investigated. By varying the ion irradiation time and the ion current density, morphological control and the density of Zn nanostructures were successfully achieved using a fast and viable ion irradiation technique. Scanning (SEM) and transmission electron microscopy (TEM) results revealed that the sputtered surface was almost entirely covered with densely distributed conical and needle-like protrusions with linear shaped (sometimes curved) nanostructures (such as nanoneedles and nanofibers) with diameters and lengths of about 20-50 nm and several hundred nanometers, respectively. Detailed analysis of selected area electron diffraction (SAED) patterns with TEM analysis indicates that the Zn nanofibers were polycrystalline in nature. A possible mechanism of the formation of Zn nanostructures is briefly discussed. These aligned arrays of Zn nanoneedles/nanofibers could be a promising material for the fabrication of zinc oxide nanostructures by subsequent oxidation of Zn nanostructures and their future application in nanodevices. Thus, it is believed that this ion irradiation technique could open up a new approach for the fabrication of many kinds of nanomaterials of controllable density.     

On I–V measurements and high field conduction of (Se80Te20)94−xGe6Bix (0 ≤ x ≤ 12) chalcogenide alloys

Journal of Materials Science: Materials in Electronics - (Se80Te20)94?xGe6Bix (0?≤?x?≤?12) chalcogenide alloys were prepared by melt quenching technique....