In this work, pH dependent evolution of tungsten oxide (WO₃) nanostructures is being reported along with physical characteristics. The synthesis was carried out via an inexpensive solvothermal cum chemical reduction route, with sodium tungstate (Na₂WO₄) and cetyl trimethyl ammonium bromide (C₁₉H₄₂NBr) as main reactants. The X-ray diffraction, together with transmission electron microscopic studies have revealed formation of regular polyhedral nanocrystalline structures and fractals as one goes from higher pH (= 5.5) to lower pH (= 2) values. The average crystallite size, as calculated throughWilliamson–Hall plots, was varied within 2.8–6.8 nm for different pH samples. Fourier transform infrared spectroscopy reveals in-plane bending vibration 𝛿 (W–OH), observable at ∼1630 cm^-1 and strong stretching 𝜈 (W–O–W) located at ∼814 cm^-1. Raman spectroscopy has divulged WO₃ Raman active optical phonon modes positioned at ∼717 and 805 cm^-1. The thermochromic and photochromic properties of the nanoscale WO₃ sample prepared at pH = 5.5, are also highlighted.

An inexpensive fabrication route and growth mechanism is being reported for obtaining quality gadolinium oxide (Gd₂O₃) nanoscale rods. The elongated nanoscale systems, as produced via a hydrothermal process, were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), optical absorption spectroscopy, photoluminescence (PL) spectroscopy, Raman spectroscopy and magnetic hysteresis measurements. XRD patterns of the nanorods, as-prepared from independent precursors of different pH, depict a cubic crystal phase and an average crystallite size of 5-6.5 nm. As revealed from HRTEM micrographs, diameter of the nanorods prepared at pH = 13.3 (∼ 7nm) was much smaller than the rods prepared at pH = 10.8 (∼ 19nm). However, the aspect ratio was more than double in the former case than the latter case. PL response was found to be dominated by defect mediated emissions, whereas Raman spectrum of a given specimen (pH = 10.8) has revealed characteristic 𝐹_g + 𝐴_g modes of cubic phase of Gd₂O₃ nanorods, apart from other independent modes. Furthermore, 𝑀 ∼ 𝐻 plot of the nanorod system (pH = 10.8) exhibited slight departure from the ideal superparamagnetic behaviour, with low remanence and coercive field values. The exploitation of one-dimensional Gd₂O₃ nanorods have immense potential in the production of advanced contrast agents, smart drives and also in making novel ferrofluids of technological relevance.

Structural and optoelectronic features as well as influence of local symmetry due to inclusion of dopants are being reported for nanoscale Eu$^{3+}$: Gd$_2$O$_3$ systems with alkali metal ion (Na$^+$, K$^+$) co-doping. The origin of red emission(${\sim}$612 nm) as mediated by specific D–F transitions and nature of local symmetry are discussed. The co-doped nanosystems were synthesized following a citrate-gel route and a hydrothermal route as for nanoparticles (EuGNP) andnanorods (EuGNR), respectively. Revealing cubic crystal structure, X-ray diffractometer results also convey incorporation of the dopants into the host matrix, while the transmission electron microscopy images endorse formation of nearlyspherical nanoparticles and nanorods. Photoluminescence responses exhibit augmentation in the emissions for the co-doped phosphors with the intensity ratio between the most intense electrically driven red emission at ${\sim}$612 nm(${}^5$D$_0$ ${\to}$ ${}^7$F$_2$) to be four-fold stronger than the magnetically driven orange emission ${\sim}$590 nm (${}^5$D$_0$ ${\to}$ ${}^7$F$_1$) in the case of Na$^+$ co-doped EuGNP system. Along with comparative emission intensity and line widths, the anomalous trend inemission feature of Na$^+$ co-doped EuGNR has also been discussed.