Optical Absorption Measurements Research Articles

Transport properties of polymer blends and composite membranes for selective permeation of hydrogen

Graphene Oxide (GO) dispersed in a polymer blend of Polystyrene (PS)/Poly (methyl methacrylate) (PMMA) nanocomposite membranes have been prepared by the solution cast method for hydrogen gas permeation application. This paper reports a study of blends of PMMA and PS that were prepared in different ratios of weight percentage for PMMA: PS (80:20, 50:50 and 60:40) composite with 1 wt% of GO and 2 wt% of GO. The structural and morphological properties of these prepared composite membranes have been characterized using gas permeation, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). UV Spectroscopy and FT-IR have carried out the optical absorbance measurement of the composite membranes. The permeability measurements indicate that the GO nanofillers in blends of PS/PMMA have shown higher permeability for hydrogen gas than that of pure polymers. The gases used for the permeation measurements were H2, CO2, N2 and CH4. Selectivity has been calculated for H2/CO2, H2/N2 and H2/CH4 gas pairs and plotted to show Robeson's 2008 upper bound and compared with reported data. The transport properties of these gases have been compared with that of a neat membrane. The permeability of all gases has increased to that of the unmodified polymer membrane. The selectivity measurements show that GO composite with PS/PMMA blend membranes is highly selective for hydrogen gas from different gas pairs, therefore, these composite membranes can be used for hydrogen purification. There is a trade-off between permeability and selectivity parameters; GO nanofillers keep selectivity constant as permeability increases, which the nanogap theory could explain.

Deconvolution of photoluminescence spectra and electronic transition in carbon dots nanoparticles from microcrystalline cellulose

Carbon dots (CDs) are nanomaterials with promising applications in several areas such as optoelectronics and biomedicine due to their low toxicity and strong luminescence intensity. Understanding the emission and bandwidth of the fluorescence spectrum is still a challenge in the scientific community due to the dependence of emission on the excitation wavelength. In this work, the photoluminescence properties of carbon dots obtained from microcrystalline cellulose (MCC) were studied. The optical properties were studied through measurements of photoluminescence (PL), photoluminescence excitation (PLE), and absorption. Systematic adjustments were made through Gaussian deconvolution of the PL spectrums and the coupling between electronic states was analyzed through PLE and optical absorption measurements. From the Gaussian adjustments, bandwidth values of ∼25 nm and ∼100 nm were found for the emission associated with the core and the surface states respectively, these values are consistent with the bandwidth of the PLE spectra with tuned detection in these states. As evidenced by the results, there are contributions from the core and surface functional groups in the luminescence emission of CDs. Furthermore, with recent analyzes that attribute the radiative emission of CDs only to the surface trap states, we observed that the core present emission and absorption of light for samples with specific pH and reaction times. These results should contribute to the understanding of the electronic transitions of CDs for applications related to the luminescent optical properties of these nanomaterials.

Surface reconstruction via Eu3+-coating and recrystallization to improve photochemical properties of BiLa2O4.5 particles

Eu3+ can act as electron acceptor to capture electrons and thus delay the recombination of photo-created h+/e− pairs. In this work, Eu3+-surface coated BiLa2O4.5 was prepared via the surface ion exchange and subsequent calcination consolidation. The prepared particles were characterized using XRD, FT-Raman, SEM, UPS, XPS, and optical absorption measurements. The luminescence and photocatalysis of the samples were evaluated. Surface coating of Eu3+ induces recrystallization on the surface of the particles. Significant improvement of Eu3+ surface coated BiLa2O4.5 on photocatalysis was realized compared to the Eu3+ uniformly doped samples. The microstructure, electrical impedance, and photocurrent properties were analyzed. The surface coated Eu3+ can act as traps to delay the recombination of photo-created h+/e− pairs. The experimental results show that the surface modification of rare earth is effective to improve the surface light absorption and photochemical properties of semiconductor materials.

Pressure-induced phase transition and band-gap decrease in semiconducting Na3Bi(IO3)6

We report a combined experimental/theoretical high-pressure study of Na3Bi(IO3)6 under compression to 11.2 GPa at ambient temperature. Through a combination of single-crystal and powder synchrotron X-ray diffraction, optical absorption measurements and ab initio density functional theory calculations we unambiguously show a first-order pressure-induced phase transition at around 9.5 GPa from the ambient pressure phase, referred to here as α-Na3Bi(IO3)6, to a new crystalline structure referred to here as β-Na3Bi(IO3)6. The triclinic (P-1) to triclinic (P1) phase transition is characterised by a doubling of the primitive cell volume, whereby the crystallographic b-axis doubles in length, and by a decrease in the volume per formula unit of approximately 3 %. The phase transition is also characterised by an indirect → indirect electronic bandgap decrease of approximately 0.1 eV as measured by absorption spectroscopy (3.44(1) → 3.32(1) eV) and calculated via density functional calculations (2.48 → 2.33 eV). We also report the pressure evolution of the crystal lattice parameters and isothermal compressibility tensor of the ambient pressure phase α-Na3Bi(IO3)6, which reveals highly anisotropic compressibility and a bulk modulus of 30.4(7) GPa.

Comparative analysis of the electronic energy structure of nanocrystalline polymorphs of Y2O3 thin Layers: Theory and experiments

The results of fabrication and characterization of atomic structure of nanocrystalline thin layers of Y2O3 in cubic and monoclinic phases is reported. Experimental data demonstrate crystalline ordering in nanocrystalline films with average grain size of ∼ 10–14 nm both for cubic and monoclinic studied structures. Density Functional Theory (DFT) based simulations demonstrate insignificant differences of electronic structure of these phases in the bulk and on the surfaces. Theoretical modeling also pointed out the significant broadening of valence and conductive bands caused by means of energy levels splitting in agreement with experimental data (X-ray photoelectron and photoluminescence spectra). The presence of various intrinsic and extrinsic defects (including surface adsorption of carbon mono- and dioxide) does not promote visible changes in electronic structure of Y2O3 surface for both studied phases. Optical absorption and luminescence measurements indicate insignificant bandgap reduction of Y2O3 nanocrystalline layers and the very little contribution from defect states. Simulation of extrinsic compression and expanding demonstrate stability of the electronic structure of nanocrystalline Y2O3 even under significant strain. Results of comprehensive studies demonstrate that yttrium oxide based nanocrystalline layers are prospective for various optical applications as a stable material.

The Electronic Disorder Landscape of Mixed Halide Perovskites.

Band gap tunability of lead mixed halide perovskites makes them promising candidates for various applications in optoelectronics. Here we use the localization landscape theory to reveal that the static disorder due to iodide:bromide compositional alloying contributes at most 3 meV to the Urbach energy. Our modeling reveals that the reason for this small contribution is due to the small effective masses in perovskites, resulting in a natural length scale of around 20 nm for the "effective confining potential" for electrons and holes, with short-range potential fluctuations smoothed out. The increase in Urbach energy across the compositional range agrees well with our optical absorption measurements. We model systems of sizes up to 80 nm in three dimensions, allowing us to accurately reproduce the experimentally observed absorption spectra of perovskites with halide segregation. Our results suggest that we should look beyond static contribution and focus on the dynamic temperature dependent contribution to the Urbach energy.

Intercomparison of airborne and surface-based measurements during the CLARIFY, ORACLES and LASIC field experiments

Abstract. Data are presented from intercomparisons between two research aircraft, the FAAM BAe-146 and the NASA Lockheed P3, and between the BAe-146 and the surface-based DOE (Department of Energy) ARM (Atmospheric Radiation Measurement) Mobile Facility at Ascension Island (8∘ S, 14.5∘ W; a remote island in the mid-Atlantic). These took place from 17 August to 5 September 2017, during the African biomass burning (BB) season. The primary motivation was to give confidence in the use of data from multiple platforms with which to evaluate numerical climate models. The three platforms were involved in the CLouds–Aerosol–Radiation Interaction and Forcing for Year 2017 (CLARIFY-2017), ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES), and Layered Atlantic Smoke and Interactions with Clouds (LASIC) field experiments. Comparisons from flight segments on 6 d where the BAe-146 flew alongside the ARM facility on Ascension Island are presented, along with comparisons from the wing-tip-to-wing-tip flight of the P3 and BAe-146 on 18 August 2017. The intercomparison flight sampled a relatively clean atmosphere overlying a moderately polluted boundary layer, while the six fly-bys of the ARM site sampled both clean and polluted conditions 2–4 km upwind. We compare and validate characterisations of aerosol physical, chemical and optical properties as well as atmospheric radiation and cloud microphysics between platforms. We assess the performance of measurement instrumentation in the field, under conditions where sampling conditions are not as tightly controlled as in laboratory measurements where calibrations are performed. Solar radiation measurements compared well enough to permit radiative closure studies. Optical absorption coefficient measurements from all three platforms were within uncertainty limits, although absolute magnitudes were too low (<10 Mm−1) to fully support a comparison of the absorption Ångström exponents. Aerosol optical absorption measurements from airborne platforms were more comparable than aircraft-to-ground observations. Scattering coefficient observations compared adequately between airborne platforms, but agreement with ground-based measurements was worse, potentially caused by small differences in sampling conditions or actual aerosol population differences over land. Chemical composition measurements followed a similar pattern, with better comparisons between the airborne platforms. Thermodynamics, aerosol and cloud microphysical properties generally agreed given uncertainties.

Cobalt as a promising dopant for producing semi-insulating β-Ga2O3 crystals: Charge state transition levels from experiment and theory

Optical absorption and photoconductivity measurements of Co-doped β-Ga2O3 crystals reveal the photon energies of optically excited charge transfer between the Co related deep levels and the conduction or valence band. The corresponding photoionization cross sections are fitted by a phenomenological model considering electron–phonon coupling. The obtained fitting parameters: thermal ionization (zero-phonon transition) energy, Franck–Condon shift, and effective phonon energy are compared with corresponding values predicted by first principle calculations based on density functional theory. A (+/0) donor level ∼0.85 eV above the valence band maximum and a (0/−) acceptor level ∼2.1 eV below the conduction band minimum are consistently derived. Temperature-dependent electrical resistivity measurement at elevated temperatures (up to 1000 K) yields a thermal activation energy of 2.1 ± 0.1 eV, consistent with the position of the Co acceptor level. Furthermore, the results show that Co doping is promising for producing semi-insulating β-Ga2O3 crystals.

Downstream Electric Field Effects during Film Deposition with a Radio Frequency Plasma and Observations of Carbon Reduction

Strong electric fields are generated by radio frequency (RF) plasma sources, and though the RF portion is too high a frequency for ions to react, the direct current (DC) portion of these fields has been shown to cause the atomic migration of metals, which can influence film morphology even downstream of the plasma where ionized plasma species are absent. In particular, we have observed the growth of nanopillars due to metal atoms migrating toward the positive field of the remote plasma. A biased grid placed between the plasma and the substrate can shield the substrate from these fields so that, when grounded, smooth films can be grown to a root mean square roughness of less than 1 nm. Positively biasing the grid returns the growth of nanocolumns. Interestingly, negatively biasing the grid significantly reduced the carbon and hydrocarbon content of gallium nitride films grown at a low temperature (~660 °C) using a nitrogen plasma, as observed using secondary ion mass spectroscopy (SIMS) and optical absorption measurements. The films also showed a notable improvement in conductivity and visible appearance.

Investigation of structural, optical and electrical properties of PCBM/ZnOEP thin films

In the present work, the spin coating technique was used to prepare the (6, 6)-Phenyl C61 butyric acid methyl ester (PCBM)/Zinc (II) octaethylporphyrin (ZnOEP) thin films by adjusting their relative ratio in blend solutions. X-ray powder diffraction (XRD) patterns assumed growth in the amorphous nature of the films with increasing PCBM concentration. Scanning electron microscopy (SEM) images clearly were showed homogeneous agglomeration. The simultaneous presence of ZnOEP and PCBM Raman modes in the Raman spectrum proved composite production. Values of the indirect-energy band gap were calculated using optical absorption measurements. The disorder in the films affected optical constants, dispersion parameters, and dielectric parameters such as dispersion energy, Ed oscillator energy Eo, plasma frequency ωp, lattice dielectric constant εL, and the carrier concentration to effective mass ratio (N/m*). The change in the charge transfer (CT) of the composite might be due to the presence of PCBM improving the nonlinear optical parameters of PCBM/ZnOEP thin films. Lastly, the dark J-V showed how changing the amount of PCBM could make the current density better. Overall, the findings for PCBM/ZnOEP thin films showed that they offer a new range of potential optoelectronic device applications.

Investigation on nonlinear optical and optical limiting properties of Cd0.7Zn0.3Te quantum dots

Ternary alloyed Cd0.7Zn0.3Te colloidal quantum dots were synthesized under open atmosphere conditions. The Cd0.7Zn0.3Te quantum dots were characterized under XRD studies, DLS technique and optical absorption measurements. Using tauc and urbach relation the optical energy bandgap and urbach energy were obtained. The intensity depended nonlinear optical parameters of Cd0.7Zn0.3Te quantum dots were determined with Z-scan experimental setup using a green laser source working on continuous wave mode. The nonlinear absorption coefficient β, along with optical limiting capacity of Cd0.7Zn0.3Te quantum dot is investigated through the open aperture set up. The transmittance of Cd0.7Zn0.3Te quantum dot showed a sharp dip at the maximum intensity point of the laser which indicates reverse saturable absorption. The optical limiting threshold value for Cd0.7Zn0.3Te quantum dot was obtained around 4.6 KJ/cm2. The nonlinear refractive index of Cd0.7Zn0.3Te quantum dot is find out using closed aperture set up. The nonlinear refractive index with a negative sign was obtained for the Cd0.7Zn0.3Te quantum dot which is attributed to the self-defocusing phenomena. The nonlinear studies indicate that the sample exhibits good nonlinear properties and find applications in optical limiting materials.

Low frequency photoacoustic optical absorption measurement of aerosols

Atmospheric optical absorption, including the contribution from aerosols, is important in modeling optical propagation and for climate research. An open-celled photoacoustic aerosol sensing system was developed to operate at 150 Hz for measurement of absorption aerosols up to 3 microns in diameter with the design goal to achieve a sensitivity adequate to measure an absorption corresponding to a 1/e optical absorption length of 1 Mm. The advantage of a photoacoustic system is that it measures optical absorption only and is not sensitive to optical extinction due to scattering at low absorption levels. The system was calibrated against an existing black carbon absorption measurement unit made by Droplet Measurement Technologies, which operates at a shorter optical wavelength and higher acoustic frequency. With previous work focusing on measuring optical absorption by black carbon aerosols [J.A. Case and R.W. Smith,182nd meeting of the Acoustical Society of America in Denver, CO (5aPA)], this work covers measuring absorption by wet salt solutions of similar salt concentration to that oceanic aerosols. Experiments with the current system showed an anomalous photoacoustic signal appearing in the absence of any aerosols. Several solutions to eliminating the unwanted signal from the desired measurement are proposed and tested.

ШИРИНА ЗАБОРОНЕНОЇ ЗОНИ ТА ПОКАЗНИК ЗАЛОМЛЕННЯ ПОЛІАНІЛІНУ

e-mail: yuliia.stetsiv@lnu.edu.ua Polyaniline (PAn) films, doped with citric acid, were synthesized on a polyethylene substrate by chemical oxidative polymerization using ammonium peroxydisulfate as an oxidant. The influence of monomer concentration on the optical properties of PAn films was investigated. Optical band gap, absorption coefficient, extinction coefficient, refractive index were calculated as a function of wavelength. Different methods for determining the energy of the energy gap (Tauc method and absorption spectrum fitting) were considered. It was found that the optical band gap for all thin PAn films is due to the direct allowed optical transitions. It was found that the band gap of PAn films decreases with increasing thickness of deposited PAn films. It is established that the optical energies of the band gap of PAn films of different thickness, estimated by the results of optical absorption measurements using Tauc methods and absorption spectrum fitting, are practically commensurate and are in the range of 3.13–2.36 eV for film thicknesses equal to 18.7–137.4 nm, respectively. Based on the correlations between the optical energy of the band gap and the refractive index of semiconductors using Moss, Ravindra, Ravindra-Gupta, Reddy-Ahammed, Gerve-Vandamme, Kumar-Singh, Annani and Duffy-Reddy ratios, the value of the refractive index of PAn films was calculated and these results were compared with the values obtained from the experimental results. From the obtained results it is seen that the refractive index of PAn films increases with increasing polyaniline film thickness on a polyethylene substrate. The values obtained from the Ravindra and Ravindra-Gupta relations are the closest to the experimental ones. Therefore, the synthesized PE/PAn films can be an available material for the production of optoelectronic devices, for example, for organic field transistors and LEDs.

Is the Bandgap of Bulk PdSe 2 Located Truly in the Far‐Infrared Region? Determination by Fourier‐Transform Photocurrent Spectroscopy

Is the Bandgap of Bulk PdSe ₂ Located Truly in the Far‐Infrared Region? Determination by Fourier‐Transform Photocurrent Spectroscopy

Dimethyl fumarate molecule, crystal, and plane: Optical absorption measurement and structural/optoelectronic properties by density functional theory calculations

Dimethyl fumarate (DMF) is the main fumaric acid ester of the Fumaderm advanced medicament for the treatment of psoriasis and multiple sclerosis. Many properties of the DMF molecule and its crystal are still unknown. Here, the structural, electronic, and optical properties of DMF in molecular form and in the form of triclinic van der Waals crystals are addressed within the framework of density functional theory (DFT) formalism. The computations were performed using local density and generalized gradient exchange-correlation functionals, LDA and GGA, respectively, including one dispersion correction scheme for the former and two for the latter. Besides, the Δ-sol correction method was applied to improve the band-gap energy estimated from the DFT computations. The UV/Vis spectra of the DMF molecule solvated in ethanol and in the crystal were measured and compared with theoretical data obtained from time-dependent DFT (molecule) and DFT (crystal) calculations. One of the dispersion-corrected GGA functionals achieved very accurate descriptions of the lattice parameters, while analysis of the Kohn–Sham band structure indicated that the DMF crystal has a direct band-gap energy of 3.12 eV, differing from the experimental band-gap (4.00 eV) by 0.88 eV. By applying the Δ-sol correction method, the band-gap energy increased to 3.95 eV, only 0.05 eV below the experimental value. Lastly, simulations were also carried out for a single DMF monolayer, for which a band-gap of 3.26 eV was predicted. Hence, intermolecular interactions tend to decrease the electronic energy gap according to the sequence Gapcrystal < Gapmonolayer < Gapmolecule.

Alexandrite: investigation of a natural material for radiation dosimetry

In this work we performed experimental analyses of the dose-response curves of natural alexandrite, using thermoluminescence (TL) and optically stimulated luminescence (OSL). The natural alexandrite crystals from Bahia, Brazil, were pulverized and the optical absorption measurements were carried out in the range of 200 to 800 nm, comparing a non-irradiated sample with a 10 Gy beta irradiated one. OSL and TL measurements were performed using the Risø equipment (model DA-20) with irradiation doses from 1 to 5 Gy. Glow curve analysis was done using GlowFit software for TL, and R Studio software for OSL measurements. The irradiated sample (10 Gy) shows an absorption spectrum similar to the non-irradiated one, containing the same bands. The samples of natural alexandrite showed a linear dose-response for both OSL and TL measurements. From the TL and OSL analyses, it was possible to infer a correlation between the slow OSL component with the most intense TL peaks of alexandrite.

Structure and electronic properties of amorphous strontium titanate

Understanding the short-range structure of an amorphous material is the first step in predicting its macroscopic properties. Amorphous strontium titanate (a-STO) presents a unique challenge due to contradictory experimental findings regarding the local oxygen environment of titanium, concluded to be either tetrahedral or octahedral. To elucidate the discrepancy, 72 models of a-STO with density ranging from the crystalline value 5.12 to $3.07\phantom{\rule{4pt}{0ex}}\mathrm{g}/{\mathrm{cm}}^{3}$ were prepared using ab initio molecular dynamics liquid-quench simulations and characterized by extended x-ray absorption fine structure (EXAFS) for both Ti and Sr K edge. An excellent agreement between the calculated and two independent experimental EXAFS measurements demonstrates that the discrepancy in the Ti coordination stems from differences in the material's density. Next, density-dependent structural characteristics, including Ti-O and Sr-O coordination, distances, angles, polyhedral sharing, and vibrational density of states in a-STO are thoroughly analyzed and correlated with disorder-induced changes in the electronic properties that are calculated using a hybrid density functional. The obtained increase in the band gap and broadening of Ti-$d\phantom{\rule{4pt}{0ex}}{e}_{g}$-orbital contributions in the conduction band are in excellent agreement with our x-ray absorption spectroscopy for Ti L-edge spectra and optical absorption measurements for crystalline and amorphous STO grown by pulsed laser deposition. The derived microscopic understanding of the structure-property relationship in amorphous ``perovskite'' serves as a foundation for further investigations of a-STO and related materials.

Room-temperature cost-effective in-situ grown MAPbBr3 crystals and their characterization towards optoelectronic devices

We report the in-situ, room-temperature synthesis of methylammonium lead bromide CH3NH3PbBr3 crystals using N-methyl formamide as a source of methylammonium (MA+) ions during the crystallization process to explore the structural, dielectric, and electronic properties of CH3NH3PbBr3 crystals for optoelectronic applications. Optical absorption and radio-luminescence measurements affirm the direct bandgap nature of the crystals. Impedance spectroscopy measurements with various applied AC voltages within the 20 Hz–10 MHz frequency range depict the influence of ionic motions on electrical transport across crystal planes. We have extracted electrical transport parameters in CH3NH3PbBr3 crystals from the Nyquist plots, which we found to be distinctly varied wherein two different AC voltage amplitude regimes, broadly for 10–50 mV and 100–500 mV AC voltage range.

(Invited, Digital Presentation) Optoelectronic Processes in Single-Chirality Carbon Nanotube Thin Films

Much understanding exists regarding chirality-dependent properties of single-wall carbon nanotubes (SWCNTs), primarily obtained through single-tube studies. However, macroscopic manifestations of chirality dependence have been limited, especially in electronic transport. Here, recent progress in our optical and electronic transport studies of single-chirality SWCNT thin films will be reviewed. We observed pronounced chirality-dependent electronic localization in temperature and magnetic field dependent conductivity measurements on macroscopic films of single-chirality SWCNTs [1]. We also performed optical absorption measurements in aligned single-chirality (6,5) SWCNT films, and through comparison with detailed theoretical calculations based on the Boltzmann scattering equation, we demonstrated that the background absorption is due to phonon-assisted transitions from the semiconductor vacuum to finite-momentum continuum states of excitons [2]. Furthermore, we conducted terahertz emission and photocurrent studies on films of aligned single-chirality semiconducting SWCNTs and found that excitons autoionize, i.e., spontaneously dissociate into electrons and holes [3]. Some of these studies were enabled by our recent improvement of the controlled vacuum filtration technique [4,5], which allows us to fabricate wafer-scale aligned SWCNTs with extremely anisotropic optical properties [6-9]. W. Gao et al., “Band Structure Dependent Electronic Localization in Macroscopic Films of Single-Chirality Single-Wall Carbon Nanotubes,” Carbon 183, 774 (2021).S. Dal Forno et al., “Origin of the Background Absorption in Carbon Nanotubes: Phonon-Assisted Excitonic Continuum,” Carbon 186, 465 (2021).F. R. G. Bagsican et al., “Terahertz Excitonics in Carbon Nanotubes: Exciton Autoionization and Multiplication,” Nano Letters 20, 3098 (2020).X. He et al., “Wafer-Scale Monodomain Films of Spontaneously Aligned Single-Walled Carbon Nanotubes,” Nature Nanotechnology 11, 633 (2016).W. Gao and J. Kono, “Science and Applications of Wafer-Scale Crystalline Carbon Nanotube Films Prepared through Controlled Vacuum Filtration,” Royal Society Open Science 6, 181605 (2019).F. Katsutani et al., “Direct Observation of Cross-Polarized Excitons in Aligned Single-Chirality Single-Wall Carbon Nanotubes,” Physical Review B 99, 035426 (2019).W. Gao et al., “Macroscopically Aligned Carbon Nanotubes as a Refractory Platform for Hyperbolic Thermal Emitters,” ACS Photonics 6, 1602 (2019).N. Komatsu et al., “Groove-Assisted Global Spontaneous Alignment of Carbon Nanotubes in Vacuum Filtration,” Nano Letters 20, 2332 (2020).A. Baydin et al., “Giant Terahertz Polarization Rotation in Ultrathin Films of Aligned Carbon Nanotubes,” Optica 8, 760 (2021).

Gradual growth of ZnO nanoparticles from globules-like to nanorods-like shapes: Effect of annealing temperature

We report the microstructure, optical properties and high photocatalytic performance, with correlations between them, of coprecipitated and post-annealed ZnO nanoparticles. The obtained ZnO single phase after post annealing at different temperatures (200–600 °C) was identified by X-ray diffraction (XRD) and its morphology was investigated by transmission electron microscopy (TEM). The TEM results indicate a gradual growth of the spherical-like nanoparticles to nanorod-like shapes by post annealing with common nanorods shape by annealing at 600 °C. XRD Rietveld refinements indicated that the global structure parameters such as lattice constants, bond lengths, and oxygen position are slightly affected by the post annealing. While the crystallite size and number of unit cells per a particle gradually increase, the dislocation density, micro-strain and residual stress gradually decrease by the post annealing with a further change at annealing temperature of 500 °C, indicating correlations to the particles shape. Based on optical absorbance measurements, it was found that the optical energy gap gradually decreases from 3.22 to 2.89 eV by increasing the annealing temperature up to 600 °C. After a period up to 90 min of irradiation, photo-catalytic efficiency of up to 95 % was observed in the photo-degradation of methylene blue. In addition, the nanoparticles annealed at low temperature showed better performance in the photo-degradation of methylene blue. The observed high photocatalytic performance is discussed in correlation to the microstructure and optical properties of the investigated samples.