Surface-wettability and Structural Colouration Property of Certain Rosaceae Cultivars with Off-to-dark Pink Appearances

The present work reports microstructure-based wettability and reflectance responses of three varieties of Indian Rosaceae （Rosa） cultivars, viz. white rose （Rosa chinensis var spontanea）, light pink rose （Rosa ehinensis var minima） and dark pink rose （Rosa chinensis var minima）. As for wettability, static and advancing and receding Contact Angles （CA） have been measured, for each type of matured rose petals. The surface roughness factors （rφ）, which are largely dependent on the micro-papillae assembly within the rose petal, are estimated to be, 2.74, 2.27 and 2.94 in case of White （W）, Light Pink （LP） and Dark Pink （DP） petals; respectively. Moreover, the respective Contact Angle Hysteresis （CAH） values are measured as 51 °, 27° and 59°. In order to exploit structural colouration through the reflectance char- acteristics, the specimens were dipped in three different media of different Refractive Indices （R1）, viz. ethanol （RI = 1.36）, propanol （RI= 1.39） and glycerine （R/= 1.47） for about 24 h. Upon ethanol and propanol adsorption, the LP and DP rose petals showed unusually similar reflectance patterns over a wide range of wavelengths, thus indicating a common microstructural share and structural colour contribution. The wetting-dewetting and structural colouration in natural systems, to a great extent, are dictated by the surface structure and solid-liquid and liquid-air interfaces, not only offer fundamental interest but also give scope for mimicking in artificial designs of technological interest.

Effect of Annealing Temperature on the Morphology and Sensitivity of the Zinc Oxide Nanorods-Based Methane Senor

ZnO nanorods in the form of thin films were synthesized by a facile chemical route and the effect of annealing temperature on the structure and sensitivity of such ZnO-based sensors was studied in detail towards methane sensing.Morphological analyses of such films were carried out by scanning electron microscopy,whereas,the crystalline structure and phase purity of the films were analysed by X-ray diffraction technique.The films were observed to display a gradual change in their morphology from granular to dense nanorods and each of them was used to fabricate methane sensor prototype.They were also tested for temperature-dependent methane-sensing capability with varying methane concentrations.The optimized sensor exhibited highest gas response of ＊80% at 250 °C with significantly low response and recovery time.

Oriented attachment(OA) mediated characteristic growth of Gd_2O_3 nanorods from nanoparticle seeds

Herein, we demonstrated the oriented attachment (OA) driven formation and characterization of Gd2O3 nanorods. The nanorods were synthesized via a surfactant free, inexpensive hydrothermal route and considering ~30 nm nanoparticles as the seed. While maintaining a cubic phase throughout the process, complete transformation of Gd2O3nanoparticles to nanorods was found to occur at an elevated temperature (~180 oC) of the hydrothermal reaction. The elongated Gd2O3 nanostructures, as revealed from transmission electron microscopic imaging, possessed an average diameter of ~33 nm and an approximate length of 172 nm. From the kinetics of OA process, the activation energy of formation was estimated to be ~25 kJ/mole. The existence of defect mediated radia-tive emission was ascertained from the asymmetric broadening of luminescence spectra. The defect emission arising from the Gd2O3 nanorods was nearly 1.4 times stronger than that of nanoparticles. The morphological evolution and growth kinetics were discussed along with the luminescence and electron paramagnetic resonance features.