Can Severe Plastic Deformation Tune Nanocrystallization in Fe-Based Metallic Glasses?

The effects of severe plastic deformation (SPD) by means of high-pressure torsion (HPT) on the structural properties of the two iron-based metallic glasses Fe73.9Cu1Nb3Si15.5B6.6 and Fe81.2Co4Si0.5B9.5P4Cu0.8 have been investigated and compared. While for Fe73.9Cu1Nb3Si15.5B6.6, HPT processing allows us to extend the known consolidation and deformation ranges, HPT processing of Fe81.2Co4Si0.5B9.5P4Cu0.8 for the first time ever achieves consolidation and deformation with a minimum number of cracks. Using numerous analyses such as X-ray diffraction, dynamic mechanical analyses, and differential scanning calorimetry, as well as optical and transmission electron microscopy, clearly reveals that Fe81.2Co4Si0.5B9.5P4Cu0.8 exhibits HPT-induced crystallization phenomena, while Fe73.9Cu1Nb3Si15.5B6.6 does not crystallize even at the highest HPT-deformation degrees applied. The reasons for these findings are discussed in terms of differences in the deformation energies expended, and the number and composition of the individual crystalline phases formed. The results appear promising for obtaining improved magnetic properties of glassy alloys without additional thermal treatment.

Whole genome sequencing and comparative genomics of Mycobacterium orygis isolated from different animal hosts to identify specific diagnostic markers.

Introduction: Mycobacterium orygis, a member of MTBC has been identified in higher numbers in the recent years from animals of South Asia. Comparative genomics of this important zoonotic pathogen is not available which can provide data on the molecular difference between other MTBC members. Hence, the present study was carried out to isolate, whole genome sequence M. orygis from different animal species (cattle, buffalo and deer) and to identify molecular marker for the differentiation of M. orygis from other MTBC members. Methods: Isolation and whole genome sequencing of M. orygis was carried out for 9 samples (4 cattle, 4 deer and 1 buffalo) died due to tuberculosis. Comparative genomics employing 53 genomes (44 from database and 9 newly sequenced) was performed to identify SNPs, spoligotype, pangenome structure, and region of difference. Results: M. orygis was isolated from water buffalo and sambar deer which is the first of its kind report worldwide. Comparative pangenomics of all M. orygis strains worldwide (n= 53) showed a closed pangenome structure which is also reported for the first time. Pairwise SNP between TANUVAS_2, TANUVAS_4, TANUVAS_5, TANUVAS_7 and NIRTAH144 was less than 15 indicating that the same M. orygis strain may be the cause for infection. Region of difference prediction showed absence of RD7, RD8, RD9, RD10, RD12, RD301, RD315 in all the M. orygis analyzed. SNPs in virulence gene, PE35 was found to be unique to M. orygis which can be used as marker for identification. Conclusion: The present study is yet another supportive evidence that M. orygis is more prevalent among animals in South Asia and the zoonotic potential of this organism needs to be evaluated.

Biosafety Concerns During the Collection, Transportation, and Processing of COVID-19 Samples for Diagnosis.

The coronavirus disease 2019 (COVID-19) pandemic, which started in China, has created a panic among the general public and health care/laboratory workers. Thus far, there is no medication or vaccine to prevent and control the spread of COVID-19. As the virus is airborne and transmitted through droplets, there has been significant demand for face masks and other personal protective equipment to prevent the spread of infection. Health care and laboratory workers who come in close contact with infected people or material are at a high risk of infection. Therefore, robust biosafety measures are required at hospitals and laboratories to prevent the spread of COVID-19. Various diagnostic platforms including of serological, molecular and other advanced tools and techniques have been designed and developed for rapid detection of SARS-CoV-2 and each has its own merits and demerits. Molecular assays such as real-time reverse transcriptase polymerase chain reaction (rRT-PCR) has been used worldwide for diagnosis of COVID-19. Samples such as nasal swabs or oropharyngeal swabs are used for rRT-PCR. Laboratory acquired infection has been a significant problem worldwide, which has gained importance during the current pandemic as the samples for rRT-PCR may contain intact virus with serious threat. COVID-19 can spread to workers during the sampling, transportation, processing, and disposal of tested samples. Here, we present an overview on advances in diagnosis of COVID-19 and details the issues associated with biosafety procedures and potential safety precautions to be followed during collection, transportation, and processing of COVID-19 samples for laboratory diagnosis so as to avoid virus infection.

Soft Ferromagnetic Bulk Metallic Glass with Potential Self-Healing Ability.

A new concept of soft ferromagnetic bulk metallic glass (BMG) with self-healing ability is proposed. The specific [Fe36Co36B19.2Si4.8Nb4]100-x(Ga)x (x = 0, 0.5, 1 and1.5) BMGs prepared by copper mold casting were investigated as a function of Ga content. The Ga-containing BMGs still hold soft magnetic properties and exhibit large plastic strain of 1.53% in compression. Local melting during shearing produces molten droplets of several µm size throughout the fracture surface. This concept of local melting during shearing can be utilized to produce BMGs with self-healing ability. The molten regions play a vital role in deflecting shear transformation zones, thereby enhancing the mechanical properties.

High-Performance Hybrid InP QDs/Black Phosphorus Photodetector.

Zero-dimensional-two-dimensional (0D-2D) hybrid optoelectronic devices have demonstrated high sensitivity and high performance due to the high absorption coefficient of 0D materials with a tunable detection range and a high carrier transport property of 2D materials. However, the reported 0D-2D hybrid devices employ toxic nanomaterials as sensitizing layers, which can limit the practical applications. In this study, we first fabricated the 0D-2D hybrid photodetector using nontoxic InP quantum dots (QDs) as a light-absorbing layer and black phosphorus (BP) as a transport layer. The surface treatment using 1,2-ethanedithiol and thermal treatment were carried out to remove the surface long ligands of colloidal QDs, which can accelerate the charge injection of the photogenerated carriers through the interfaces between InP QDs and BP. The InP QDs/BP hybrid photodetector demonstrates a high responsivity of 1 × 109 A/W and detectivity of 4.5 × 1016 Jones at 0.05 µW cm-2 under 405 nm illumination. The results show that 0D-2D hybrid photodetectors based on III-V semiconducting QD materials can be optimized for high-performance photodetectors.

Polymorphic Transformation and Magnetic Properties of Rapidly Solidified Fe26.7Co26.7Ni26.7Si8.9B11.0 High-Entropy Alloys.

In this work, the microstructural evolution and magnetic performance of the melt-spun amorphous and amorphous-crystalline Fe26.7Co26.7Ni26.7Si8.9B11.0 high-entropy alloys (HEAs) during crystallization were investigated, respectively. Upon heating fully amorphous ribbons, a metastable BCC supersaturated solid solution together with a little Ni31Si12 crystals first precipitated and then the (Fe,Co)2B crystals formed until the full crystallization was achieved. With further increasing temperature after full crystallization, a polymorphic transformation from a metastable BCC phase to two types of FCC solid solutions occurred. For the amorphous-crystalline HEAs, the dominant crystallization products were the metastable FCC but not BCC crystals. During crystallization, the primary metastable FCC crystals first transform into the metastable BCC crystals and then the newly-generated BCC phase transforms into two types of FCC phases with further increasing temperature. This temperature dependence of the gradual polymorphic transformation results in the change of magnetic properties of the present high-entropy amorphous alloys.

Solution-phase synthesis of rubidium lead iodide orthorhombic perovskite nanowires.

Recently, metal halide perovskite nanocrystals have demonstrated outstanding properties in various optoelectronic applications. Cesium lead halides (CsPbX3) are the most studied perovskites in nanoscale dimensions. However, halide perovskite nanocrystals with other cations have rarely been reported. It is important to develop new perovskite compositions to further expand their application in various fields. In this paper, we first report the synthesis of colloidal rubidium lead iodide (RbPbI3) nanowires (NWs). RbPbI3 NWs have an orthorhombic crystal structure and are single-crystalline in nature. The diameter of the NWs is around 32 nm with lengths up to several tens of micrometers. RbPbI3 NWs absorb strongly below 450 nm. RbPbI3 devices exhibited good photoresponsive behavior, suggesting a potential use in optoelectronics.

Hybrid metal-Cu2S nanostructures as efficient co-catalysts for photocatalytic hydrogen generation.

In this communication, we present a new synthesis method for the fabrication of hybrid metal-Cu2S (M = Pt, FePt) nanocrystals (HNs). The metal-Cu2S HNs were investigated in photocatalytic hydrogen generation as effective co-catalysts on TiO2. The Pt-Cu2S/TiO2 catalyst showed a higher hydrogen generation rate compared with a pure TiO2 catalyst. This enhancement is attributed to the synergistic effects between Cu2S and Pt, which significantly improve the light absorption ability and the charge separation activity.

High pressure die casting of Fe-based metallic glass.

Soft ferromagnetic Fe-based bulk metallic glass key-shaped specimens with a maximum and minimum width of 25.4 and 5 mm, respectively, were successfully produced using a high pressure die casting (HPDC) method, The influence of die material, alloy temperature and flow rate on the microstructure, thermal stability and soft ferromagnetic properties has been studied. The results suggest that a steel die in which the molten metal flows at low rate and high temperature can be used to produce completely glassy samples. This can be attributed to the laminar filling of the mold and to a lower heat transfer coefficient, which avoids the skin effect in the steel mold. In addition, magnetic measurements reveal that the amorphous structure of the material is maintained throughout the key-shaped samples. Although it is difficult to control the flow and cooling rate of the molten metal in the corners of the key due to different cross sections, this can be overcome by proper tool geometry. The present results confirm that HPDC is a suitable method for the casting of Fe-based bulk glassy alloys even with complex geometries for a broad range of applications.

Beneficial effects of water in the colloidal synthesis of InP/ZnS core-shell quantum dots for optoelectronic applications.

We demonstrate that the presence of a small amount of water as an impurity during the hot-injection synthesis can significantly decrease the emission lines full width at half-maximum (FWHM) and improve the quantum yield (QY) of InP/ZnS quantum dots (QDs). By utilizing the water present in the indium precursor and solvent, we obtained InP/ZnS QDs emitting around 530 nm with a FWHM as narrow as 46 nm and a QY up to 45%. Without water, the synthesized QDs have emission around 625 nm with a FWHM of 66 nm and a QY of about 33%. Absorption spectra, XRD and XPS analyses revealed that when water is present, an amorphous phosphate layer is formed over the InP QDs and inhibits the QD growth. This amorphous layer favors the formation of a very thick ZnS shell by decreasing the lattice mismatch between the InP core and the ZnS shell. We further show the possibility to tune the emission wavelengths of InP/ZnS QDs by simply adjusting the amount of water present in the system while keeping all the other reaction parameters (i.e., precursor concentration, reaction temperature and time) constant. As an example of their application in light-emitting diodes (LEDs), the green and red InP/ZnS QDs are combined with a blue LED chip to produce white light.

Bandgap tunable colloidal Cu-based ternary and quaternary chalcogenide nanosheets via partial cation exchange.

Copper based ternary and quaternary semiconductor nanostructures are of great interest for the fabrication of low cost photovoltaics. Although well-developed syntheses are available for zero dimensional (0D) nanoparticles, colloidal synthesis of two dimensional (2D) nanosheets remains a big challenge. Here we report, for the first time, a simple and reproducible cation exchange approach for 2D colloidal Cu2GeSe3, Cu2ZnGeSe4 and their alloyed Cu2GeS(x)Se(3-x), Cu2ZnGeS(x)Se(4-x) nanosheets using pre-synthesized Cu(2x)Se nanosheets as a template. A mechanism for the formation of Cu(2-x)Se nanosheets has been studied in detail. In situ oxidation of Cu(+) ions to form a CuSe secondary phase facilitates the formation of Cu(2-x)Se NSs. The obtained ternary and quaternary nanosheets have average lateral size in micrometers and thickness less than 5 nm. This method is general and can be extended to produce other important ternary semiconductor nanosheets such as CuIn(1-x)Ga(x)Se2. The optical band gap of these nanosheets is tuned from 1 to 1.48 eV, depending on their composition.

All-inorganic cesium lead halide perovskite nanocrystals for photodetector applications.

Herein, we describe simple, fast and reproducible halide ion exchange reactions in CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) at room temperature. Through the simple adjustment of the halide ion concentration, the photoluminescence of these NCs can be tuned over the entire visible region (425-655 nm). Photodetector devices based on entirely inorganic CsPbI3 NCs are demonstrated for the first time. The photodetectors exhibited a good on/off photocurrent ratio of 10(5).

Wurtzite Cu2GeS3 Nanocrystals: Phase- and Shape-Controlled Colloidal Synthesis.

The first colloidal synthesis of Cu2 GeS3 (CGS) nanocrystals with a thermodynamically metastable wurtzite crystal phase is reported. As a benefit of the sulfur precursors used in the synthesis, the shape of the as-synthesized wurtzite CGS nanocrystals can be controlled in the form of spherical nanoparticles, nanorectangles, and hollow nanorectangles. A detailed investigation into the effects of reaction conditions necessary to obtain phase-pure wurtzite CGS nanocrystals is presented. The choice of sulfur precursor and precursor injection temperature play a significant role in determining the crystal phase of the CGS nanocrystals. The band gap of the new wurtzite phase CGS was measured to be 1.76 eV and the CGS nanocrystals exhibited a good electrochemical photoresponse, which was indicative of their potential application as an active layer in the field of solar cells.

Use of urchin-like Ni(x)Co(3-x)O4 hierarchical nanostructures based on non-precious metals as bifunctional electrocatalysts for anion-exchange membrane alkaline alcohol fuel cells.

Bifunctional electrocatalysts based on non-precious metals were developed for the dioxygen reduction and methanol oxidation reactions. These electrocatalysts can be considered as candidate cathode and anode materials for anion-exchange membrane (AEM) alkaline alcohol fuel cells. A series of Ni-doped cobalt oxide (NixCo3-xO4) hierarchical nanostructures composed of one-dimensional nanorods was prepared by an inexpensive hydrothermal method. X-ray diffraction patterns showed that the NixCo3-xO4 crystallized in a cubic spinel phase. The electrochemical performance of the catalysts was investigated using a conventional cyclic voltammetry technique. The electrocatalytic behaviour of the NixCo3-xO4 hierarchical nanostructures was compared with the behaviour of Co3O4 and Co0.33Ni0.67O. The synergistic behaviour of the Ni in the NixCo3-xO4 nanostructures was established with respect to the Ni content. NixCo3-xO4 hierarchical nanostructures show a better catalytic behaviour than Co3O4 and Co0.33Ni0.67O. Although the NixCo3-xO4 compositions all showed good catalytic behaviour, Ni1Co2O4 was identified as a superior bifunctional electrocatalyst for the oxygen reduction and methanol oxidation reactions in alkaline media. The effect of the Ni content on the electrocatalytic properties of the NixCo3-xO4 hierarchical nanostructures was clearly shown. The use of these electrocatalysts based on non-precious metals could have a commercial impact on the development of non-platinum electrocatalysts for application in AEM alkaline alcohol fuel cells.

Facile hot-injection synthesis of stoichiometric Cu2ZnSnSe4 nanocrystals using bis(triethylsilyl) selenide.

Cu2ZnSnSe4 is a prospective material as an absorber in thin film solar cells due to its many advantages including direct band gap, high absorption coefficient, low toxicity, and relative abundance (indium-free) of its elements. In this report, CZTSe nanoparticles have been synthesized by the hot-injection method using bis-(triethylsilyl)selenide [(Et3Si)2Se] as the selenium source for the first time. Energy dispersive X-ray spectroscopy (EDS) confirmed the stoichiometry of CZTSe nanoparticles. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies showed that the nanocrystals were single phase polycrystalline with their size within the range of 25-30 nm. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy measurements ruled out the existence of secondary phases such as Cu2SnSe3 and ZnSe. The effect of reaction time and precursor injection order on the formation of stoichiometric CZTSe nanoparticles has been studied by Raman spectroscopy. UV-vis-NIR data indicate that the CZTSe nanocrystals have an optical band gap of 1.59 eV, which is optimal for photovoltaic applications.

Combined plasmonic and upconversion rear reflectors for efficient dye-sensitized solar cells.

A novel rear reflector structure that combines NIR light harvesting ß-NaGdF4:Yb, Er, Fe upconversion nanoparticles (UCNPs) and light reflecting silver particles has been successfully used to improve the performance of dye-sensitized solar cells (DSSCs). The power conversion efficiency of DSSCs with a rear reflector was 7.04%, which is an increase of 21.3% compared to the cell without a rear reflector (5.8%).

Enhanced upconversion luminescence in NaGdF4:Yb,Er nanocrystals by Fe3+ doping and their application in bioimaging.

The visible green and red upconversion emissions in Er(3+)/Yb(3+) doped ß-NaGdF4 nanoparticles were enhanced by tridoping with Fe(3+) ions (0-40 mol%). XRD, XPS, ICP-AES and EDS data demonstrated successful incorporation of Fe(3+) ions in NaGdF4:Yb(3+)/Er(3+) nanoparticles. The effect of Fe(3+) tridoping on the upconversion luminescence in NaGdF4:Yb(3+)/Er(3+) NPs was investigated in detail. The green and red emission intensities were enhanced by 34 and 30 times, respectively. The maximum emission was observed in a sample containing 30 mol% Fe(3+) ions. A possible mechanism for the enhanced upconversion emission is proposed. In addition, a layer of silica was coated onto the surface of UCNPs to improve the biocompatibility. Folic acid was covalently linked to the silica coated UCNPs to form UCNP@SiO2-FA nanoprobes, which have been successfully applied to the fluorescent imaging HeLa cells.

Complete Genome Sequence of a Peste des Petits Ruminants Virus Recovered from an Alpine Goat during an Outbreak in Morocco in 2008.

Here, we announce the first complete genome sequence of a field isolate of a peste des petits ruminants virus (PPRV) from northern Africa. This isolate is derived from an Alpine goat that suffered from severe clinical disease during the 2008 outbreak in Morocco. The full genome sequence of this isolate clusters phylogenetically with the lineage IV isolates of PPRV, sharing high levels of sequence identity with other lineage IV isolates.