A controlled and up-scalable biosynthetic route to nanocrystalline silver particles with well-defined morphology using cell-free aqueous filtrate of a non-pathogenic and commercially viable biocontrol agent Trichoderma asperellum is being reported for the first time. A transparent solution of the cell-free filtrate of Trichoderma asperellum containing 1 mM AgNO(3) turns progressively dark brown within 5 d of incubation at 25 °C. The kinetics of the reaction was studied using UV-vis spectroscopy. An intense surface plasmon resonance band at ∼410 nm in the UV-vis spectrum clearly reveals the formation of silver nanoparticles. The size of the silver particles using TEM and XRD studies is found to be in the range 13-18 nm. These nanoparticles are found to be highly stable and even after prolonged storage for over 6 months they do not show significant aggregation. A plausible mechanism behind the formation of silver nanoparticles and their stabilization via capping has been investigated using FTIR and surface-enhanced resonance Raman spectroscopy.

We report the synthesis of undoped and Sc3+-doped BiFeO3 nanoparticles using the sonochemical technique. X-ray diffraction reveals that all samples are single phase with no impurities detected. EDX analysis was done to confirm the extent of Sc3+ doping in the samples. The size and morphology of the nanoparticles have been analyzed using transmission electron microscopy (TEM). XPS studies were done to check the presence of Fe2+ ions in the samples. The BiFeO3 nanoparticles show a weak ferromagnetic behavior at room temperature, which is quite different from the linear M–H relationship reported for bulk BiFeO3. The substitution of Sc ions for Bi enhances the ferromagnetic as well as ferroelectric properties of this system, which is mainly attributed to the antiferromagnetic core and ferromagnetic surface of the nanoparticles, together with the mild structural distortion. Temperature and field dependence of magnetization curves reveal the frustrated magnetic behavior of this system. The leakage current is considerably reduced, and electric polarization increases significantly in the case of BiFe0.95Sc0.05O3 nanoparticles. Magnetoelectric coupling was observed in the BiFe0.95Sc0.05O3 sample. Thus, it can be inferred that Sc3+-doped BiFeO3 nanoparticles show promise as good multiferroic materials.

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Powder X‐ray diffraction (XRD) and Raman spectroscopic studies on Ce1−xYbxO2−x/2 and Ce1−xTmxO2−x/2 (0.0≤x≤1.0) are being reported in this manuscript. It has been observed that ceria when heavily doped with ytterbia and thulia get transformed from single‐phasic F type to single‐phasic C type through the formation of a biphasic mixture. The critical concentrations at which the phase transition takes place have also been ascertained from XRD measurements and verified using Raman spectroscopy. From XRD studies, it has been found that in the case of Ce1−xYbxO2−x/2, pure F‐type lattice continues until x=0.4 and then the biphasic region comprising F‐type and C‐type solid solutions starts, which is followed by single‐phasic pure C‐type region above x=0.9. For Ce1−xTmxO2−x/2, XRD studies reveal that the biphasic region comprising C‐type and F‐type lattice is formed from x=0.5 onward. However, it has been confirmed from Raman spectroscopic studies that the C‐type lattice is formed even in the sample at x=0.4. The discrepancy is believed to have originated because of the small domain size (smaller than the coherence length of X‐rays) of the C‐type lattice that are inhomogeneously distributed within the F‐type solid solution in the composition Ce1−xTmxO2−x/2 (x=0.4), which could not be directly detected from XRD measurements.