Enhanced UV emission from ZnO nanoflowers synthesized by the hydrothermal process

Abstract

ZnO nanoflowers were synthesized by the hydrothermal process at an optimized growth temperature of 200 • C and a growth/reaction time of 3 h. As-prepared ZnO nanoflowers were characterized by x-ray diffraction, scanning electron microscopy, UV-visible and Raman spectroscopy. X-ray diffraction and Raman studies reveal that the as-synthesized flower-like ZnO nanostructures are highly crystalline with a hexagonal wurtzite phase preferentially oriented along the (1 0 1 1) plane. The average length (234-347 nm) and diameter (77-106 nm) of the nanorods constituting the flower-like structure are estimated using scanning electron microscopy studies. The band gap of ZnO nanoflowers is estimated as 3.23 eV, the lowering of band gap is attributed to the flower-like surface morphology and microstructure of ZnO. Room temperature photoluminescence spectrum shows a strong UV emission peak at 392 nm, with a suppressed visible emission related to the defect states, indicating the defect free formation of ZnO nanoflowers that can be potentially used for UV light-emitting devices. The suppressed Raman bands at 541 and 583 cm −1 related to defect states in ZnO confirms that the ZnO nanoflowers here obtained have a reduced presence of defects.

Synthesis and characterization of ZnO nanoflowers using Chlamydomonas reinhardtii: A green approach

“…Figures 1B-1E shows the HR-SEM images of zinc oxide nanoparticles that have formed nanoflower and nanorod like structures. Similar structures were observed using hydrothermal methods at elevated temperatures (2008C) over 3 h [5]. Till date there have been no reports of zinc oxide nanoflowers synthesized using algae.…”

“…Bulk zinc oxide absorbs around 373 nm due to its wide band gap whereas a red shift of 13 nm was observed in our sample. This has been previously observed in ZnO nanoflowers and was ascribed to the oriented attachment of the nanorods [5,17]. ZnO nanoparticles were also synthesized at a pH of 7 and the spectrum was found to be blue-shifted compared to the bulk; at more alkaline conditions no nanoparticles were formed (data not shown).…”

Mn2+‐induced room‐temperature ferromagnetism and spin‐glass behavior in hydrothermally grown Mn‐doped ZnO nanorods

“…The initial reactants were dissolved in distilled water and maintained at a pH of about 8–10. The reactants were placed in a sealed Teflon‐lined stainless steel autoclave and maintained at a temperature of 200 °C for 3 h under autogenous pressure . After the heating process, the autoclave was allowed to cool naturally to reach room temperature.…”

Influence of Parametric Variations on Hydrothermal Growth of ZnO Nanostructures for Hybrid Polymer/ZnO Based Photodetector

“…A sharp band edge emission in near UV region at 390 nm and a wide broad band extending laterally between 450 nm and up to 700 nm with peaks centered around 580 nm were clearly observed in the emission spectra. 31 The edge emission for ZnO nanodumbbells shows significant presence of defects. It is extensively reported that broad DLE band is a defect-related emission.…”