The modification of structural and optical properties of nano- and submicron ZnO powders by variation of solvothermal syntheses conditions

Abstract

Nano-(30-60 nm) and submicron (100-350 nm) ZnO particles were synthesized using solvothermal method at 200°C from an ethanolic solution of zinc acetate dihydrate, applying different reaction conditions, i.e., pH value of precursor and time of the reaction. The X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance (DR), Raman spectroscopy, and photoluminescence (PL) spectroscopy have been employed for characterization of synthesized ZnO powders. It was shown that the structural, morphological, and optical properties are largely determined by reaction conditions during solvothermal synthesis. The particle crystallinity improves with the decrease of pH value and/or the increase of time of the reaction. The Raman and PL spectra analyses indicate that the oxygen interstitials are dominant intrinsic defects in solvothermally synthesized ZnO powders. It was observed that concentration of defects in wurtzite ZnO crystal lattices slightly changes with the variation of pH value of the precursor and time of the solvothermal reaction. The correlation between structural ordering and defect structure of particles and corresponding growth processes was discussed.

Effect of zinc oxide quantum dots on the photovoltaic properties of natural dye‐sensitized solar cells

“…The results showed that the average particle size distribution is about 3 nm, which is lower than the Bohr radius of ZnO (~5 nm) and confirms the preparation of quantum dots. In fact, it can be concluded that the results obtained from TEM and DLS are consistent with the results obtained from the XRD test and show the quantum dimensions and quantum confinement effects of the synthesized points 59,60,62 …”

“…The average crystallite size was equal to 3 nm. 54,[59][60][61] TEM was used to study the size of quantum dots synthesized using 0.5 g of PVP40 (Qd-B), and the TEM images are shown in Figure 5A. The size of the quantum dots was between 3 and 5 nm, which is close to the crystallite size obtained by XRD.…”

“…The size of ZnO‐QDs was investigated using the X'Pert software. The average crystallite size was equal to 3 nm 54,59‐61 …”

“…In fact, it can be concluded that the results obtained from TEM and DLS are consistent with the results obtained from the XRD test and show the quantum dimensions and quantum confinement effects of the synthesized points. 59,60,62 3.4 | Absorption, emission, and charge transfer mechanism of the QD, dyesensitized SCs…”

Review on grain size effects on thermal conductivity in ZnO thermoelectric materials

“…Luković Golić et al 86 demonstrated controlled morphology of micro- and nano-sized ZnO powders using variable pH levels of lithium hydroxide (LiOH) solution to examine the effects of the solvent's pH on ZnO grain size. Firstly, the Zn particles were dissolved in ethanol/zinc acetate dihydrate solution using the sol–gel method.…”