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.

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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.

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