Hexagonal Crystalline Phase Research Articles

Synthesis of ZnO semiconductor nanoparticles using extracts of Capsicum annuum L. for photocatalytic activity in degradation of polluting dyes

In this work, ZnO semiconductor nanoparticles were green-synthesized using Capsicum annuum L. var. Caribe pepper extracts at 1%, 2%, and 4% w/v (weight/volume) as stabilizing agents. The nanoparticles were applied in photocatalytic processes for the degradation of Methylene Blue (MB), Methyl Orange (MO), and Rhodamine B (RhB) in aqueous media. Characterization involved Fourier Transform Infrared Spectroscopy (FTIR), identifying the Zn-O bond at 421 cm-1. X-Ray Diffraction (XRD) analysis revealed a hexagonal Wurtzite-type crystalline phase with crystallite sizes ranging from 13 to 23 nm. Scanning Electron Microscopy (SEM) showed hemispherical clusters smaller than 5 micrometers. UV–Visible spectrophotometry determined band gap values between 3.05 and 3.13 eV. These materials exhibited significant photocatalytic degradation efficiency for the tested dyes.

The process of evaporation of a colloidal solution of stabilized Boron nitride nanoparticles

Purpose. Characterization of the chemical structure of boron nitride nanoparticles by IR spectroscopy during the evaporation of their colloidal system and their sizes by small-angle X-ray scattering.Methods. The solvent evaporation process from the colloidal system was studied using a Nicolet iS 50 FT-IR spectrometer in the mid-IR range (400 – 4000 cm-1), with an attenuated total reflectance accessory with a diamond crystal (incident angle of 45°) and a liquid cell (200 μL). The sizes of the colloidal particles were determined using an smallangle X-ray scattering diffractometer in linear collimation mode (resolution 0.03 nm-1, copper anode X-ray tube 2.2 kW, λ = 0.154 nm, exposure time 30 s).Results. The IR spectrum of boron nitride nanoparticles powder was measured, containing lines characteristic of cubic (952 cm-1) ) – c-BN and hexagonal crystalline phases (758, 1301, and 1372 cm-1) – h-BN. The average size of boron nitride nanoparticles in the colloidal system, according to small-angle X-ray scattering data, was 46 and 84 nm. The size of stearic acid, which acts as a stabilizing shell, was 0.8, 1.3, and 2.5 nm. Analysis of the IR spectra showed complete evaporation of the solvents (hexane and chloroform) from a drop of colloidal solution 1.2 mm thick within 30 minutes.Conclusion. In this work, the average sizes of boron nitride nanoparticles stabilized with stearic acid in a colloidal system were determined and the process of its evaporation was studied.

ZnO nanostructures with controlled morphological and optical properties for applications as efficient photocatalyst for malachite green degradation

This study aims to comparatively investigate the morphological and optical characteristics of zinc oxide nanoparticles as a function of the preparation conditions. A series of ZnO nanoparticles were synthesized by facile precipitation method at constant temperature, by varying the zinc sources (zinc acetate, zinc nitrate and zinc chloride) or the precipitant nature (hexamethylenetetramine, urea). The structural, morphological and optical attributes of the prepared ZnO samples were assessed by SEM, XRD, FTIR, UV–Vis and photoluminescence analyses. The morphology of the achieved samples varies from spiky sticks to hexagons or foils with irregular shapes, observing that urea favour the development of two- or three-dimensional ZnO nanostructures, while hexamethylenetetramine predominantly triggered the formation of highly organized one-dimensional structures. The XRD patterns of all ZnO samples matches zincite crystalline hexagonal phase and the evaluation of crystallite size revealed higher values for the samples prepared in the presence of hexamethylenetetramine (HMTA). The optical band gap of ZnO NPs, as estimated from the UV–Vis absorption spectra, varied slightly from 3.13 to 3.21 eV, while fluorescence investigation proves that samples prepared with urea precipitant have a lower rate of charge recombination. Tests on the photocatalytic degradation of malachite green dye under UV light irradiation demonstrated that the dynamics of photogenerated charge carriers play a significant role in the photocatalytic performance of ZnO samples.

Synthesis of Wrinkled MoS2 Thin Films Using a Two-Step Method Consisting of Magnetron Sputtering and Sulfurization in a Confined Space

Considering the increasing need for sustainable and economical energy storage solutions, the integration of layered materials such as MoS2 into these systems represents an important step toward enhancing energy sustainability and efficiency. Exploring environmentally responsible fabrication techniques, this study assesses wrinkled MoS2 thin films synthesized from distinct Mo and MoS2 targets, followed by sulfurization conducted in a graphite box. We utilized magnetron sputtering to deposit precursor Mo and MoS2 films on Si substrates, achieving thicknesses below 20 nm. This novel approach decreases sulfur by up to tenfold during sulfurization due to the confined space technique, contributing also to avoiding the formation of toxic gases such as SO2 or the necessity of using H2S, aligning with sustainable materials development. Thinner MoS2 layers were obtained post-sulfurization from the MoS2 precursors, as shown by X-ray reflectometry. Raman spectroscopy and grazing X-ray diffraction analyses confirmed the amorphous nature of the as-deposited films. Post-sulfurization, both types of films exhibited crystalline hexagonal MoS2 phases, with the sulfurized Mo showing a polycrystalline nature with a (100) orientation and sulfurized MoS2 displaying a (00L) preferred orientation. The X-ray photoelectron spectroscopy results supported a Mo:S ratio of 1:2 on the surface of the films obtained using the MoS2 precursor films, confirming the stoichiometry obtained by means of energy dispersive X-ray spectroscopy. Scanning electron microscopy and atomic force microscopy images revealed micrometer-sized clusters potentially formed during rapid cooling post-sulfurization, with an increased average roughness. These results open the way for the further exploration of wrinkled MoS2 thin films in advanced energy storage technologies.

Photocatalytic degradation of methylene blue by TiO2/Nd2O3 composite thin films

To improve the photocatalytic property of TiO2 thin films, the composite thin films of TiO2/Nd2O3 structure were fabricated by electron-beam physical vapor deposition method, and the photocatalytic property of the fabricated films was experimentally studied in the present work. The XRD and Raman analyses show that the TiO2/Nd2O3 films are mainly hexagonal crystalline phase of Nd2O3. The XPS analysis for the chemical state changes of Ti, O and Nd of the basic elements in the films is confirming the electron flow in the internal electric field which generated in the TiO2/Nd2O3 films. The surface morphology shows the lattice distortion which affects the changes in the energy band structure. Moreover, the formation of n-n homojunctions improved the separation efficiency of electrons and holes, and enhanced the catalytic activity. The photocatalytic performance for the methylene blue target dye shows that the sample with TiO2 thickness of 20–25 nm has better performance, high degradation efficiency and high reaction rate.

Novel Indium nanocomposites for Photonic applications

In the present communication, MgO:In2O3- 1:1 (MIO), SrO/MgO/In2O3 (1:1:1) (SMIO), SrO/Al2O3/In2O3 (1:1:1) (SAIO) and CeO2/ZnO/In2O3 (1:1:1) (CZIO) NCs are synthesized by Punicagranatum juice extract as a reducing agent followed by calcination at 600 °C for 3 h. The Bragg reflections confirm that Magnesium indate, SrO, Al2O3, ZnO crystallizes in orthorhombic, trigonal, rhombohedral and hexagonal crystalline phases whereas CeO2, In2O3 and MgO crystallizes in cubic phase. Surface morphology consists large number of irregularly sized and shaped nanoparticles along with few pores and hallows. The direct energy band gap was determined using Wood and Tauc’s plot. The direct energy band gap was found to be 3.12, 3.15, 3.18 and 3.05 eV. The optical nonlinearity of the specimens was investigated using the open aperture Z-scan technique. With the exception of SAIO, the synthesized samples exhibited reverse saturable absorption attributed to a two-photon absorption (2PA) process. The nonlinear absorption coefficient follows the order CZIO > MIO > SMIO. However, the optical limiting threshold follows the order SMIO > MIO > CZIO NCs. These findings distinctly highlight the superior potential of CZIO binary NCs for optical limiting applications. This characteristic is advantageous for shielding sensors and the human eye, providing protection against the detrimental effects of intense green laser radiation. Unexpectedly, the SAIO NCs displayed Q-switching behavior. This behavior holds potential applications in optical discriminators, spatial light filters, optical isolation, and other photonic mode-locking devices.

Chemical bath deposited CdTe thin film: Optical, electrical, and photoresponse aspects

Owning a narrow bandgap, remarkable optical and electrical properties with notable stability has made cadmium telluride (CdTe) an immensely vital semiconductor to develop cutting-edge optoelectronics. Taking these properties in to account, CdTe thin film is deposited employing the chemical bath deposition (CBD) technique. The X-ray diffraction analysis of the as-deposited thin film unveiled the composite crystalline structure, incorporating cubic, hexagonal, and tetragonal phases. The energy dispersive X-ray analysis and X-ray photoelectron spectroscopy ascertained the chemical composition of CdTe thin film. Distinctive Raman peaks are detected at 141 and 167 cm−1, signifying the presence of Cd-Te bond in the deposited thin film. The comprehensive evaluation of scanning electron micrographs emphasized the firm adhesion of the film to the substrate and displayed a uniform overlay of microstructures resembling rods. The observations from atomic force microscopy unveiled uniform grain structure with topographical features of hills and valleys. The UV-Visible spectroscopic examination elucidated that the as-deposited thin films exhibits a direct optical bandgap value of 1⋅59 eV. Temperature-dependent analysis of d.c. electrical resistivity exhibited a descending pattern, substantiating thin film's semiconducting attributes. The investigation into the photoresponse attributes of the thin film is accomplished by subjecting it to a polychromatic light, green and red monochromatic light source with an intensity of 50 mW/cm² employing three different biasing voltages. The thin film demonstrated maximum photocurrent for red light source than polychromatic and green light with maximum responsivity of 59⋅4 μA/W and detectivity of 17⋅7 × 106 Jones. These findings provide valuable insights on the photoresponse behavior of CBD deposited CdTe thin film in its as-deposited form.

Green synthesis of hybrids of zinc oxide, titanium oxide, and calcium oxide nanoparticles from Foeniculum vulgare: an assessment of biological activity

The increased prominence in the use of nanoparticles has made it important to employ synergy between nanoparticles while harnessing individual metallic and biological properties to improve and modify the surface, the versatility, and efficiency of nanoparticle hybrid. This study aims to conduct a bio-assessment assay of nanoparticle hybrid systems within an in-vitro set-up and improve the surface modifications of these systems. The hybrid surfaces are characterized using a scanning electron microscope, dynamic light scattering (DLS), X-ray diffraction analysis (XRD), and Fourier-transform infrared spectroscopy (FTIR). FTIR reveals the presence of functional groups like phenols, carboxylic acids, and esters. The XRD confirms the hexagonal crystalline phase of Fe-NZnO, the cubic lattice of Fe-NCaO, and the rutile phase of TiO2. The hydrodynamic diameter of Fe-NZnO-NCaO, Fe-NTiO2-NCaO, and Fe-NTiO2-NZnO are shown to be 163.2, 164.6, and 219.4 nm, respectively, using DLS analysis. Turbidity analysis indicates that Fe-NZnO-NCaO is the least aggregated particle following a 14-day observation period, meaning that it is the most stable over that period. Anti-hemolytic erythrocyte assay demonstrates the relative biocompatibility and ability of the hybrids to enhance cell protein protection. Fe-NZnO-NCaO and Fe-NTiO2-NCaO exhibit higher post-treatment cytotoxicity across the concentrations than Fe-NTiO2-NZnO.

Study on the pathway of performance improvement and mechanism of Gd2O2S:Tb3+ green phosphor

To improve the luminescence performance of Gd2O2S:Tb3+, Gd2O2S:Tb3+, Tm3+, Gd2O2S:Tb3+, Dy3+, Tm3+ and Gd2O2S:Tb3+, Dy3+, Tm3+@SiO2 phosphors have been prepared by molten salt method. The samples are characterized using XRD, SEM, TEM, FT-IR, UV-Vis absorption spectroscopy, photoluminescence, cathodoluminescence and thermal stabilization tests. XRD tests and refinement results show that the crystal structure of the phosphor is still the hexagonal Gd2O2S crystalline phase and the lattice parameter decrease due to Dy3+/Tm3+ occupying the Gd3+ sites. SEM images and mapping of each element show that the particle grain and all expected elements distribute uniformly. TEM results illustrate that SiO2 coating is in an amorphous form on the surface of the powder grains. FT-IR tests indicate that SiO2 is present on the powder surface through Si-O-Gd bonding. The results of photoluminescence and cathodoluminescence show that the luminescence intensity increase 50% while adding Tm3+ into Gd2O2S:Tb3+, Gd2O2S:Tb3+, Dy3+ phosphors caused mainly by the energy transfer from Dy3+/Tm3+ to Tb3+. The core-shell structure of Gd2O2S:Tb3+, Dy3+, Tm3+@SiO2 has better photoluminescence and cathodoluminescence and the fluorescence lifetime remains unchanged while SiO2 coats phosphor. And it has good thermal stability. Its luminescence intensity at 425 K reaches 71.4% of that at room temperature, which is better than the corresponding value (46.4%) for the uncoated sample.

Liquid crystalline inverted lipid phases encapsulating siRNA enhance lipid nanoparticle mediated transfection

Efficient cytosolic delivery of RNA molecules remains a formidable barrier for RNA therapeutic strategies. Lipid nanoparticles (LNPs) serve as state-of-the-art carriers that can deliver RNA molecules intracellularly, as exemplified by the recent implementation of several vaccines against SARS-CoV-2. Using a bottom-up rational design approach, we assemble LNPs that contain programmable lipid phases encapsulating small interfering RNA (siRNA). A combination of cryogenic transmission electron microscopy, cryogenic electron tomography and small-angle X-ray scattering reveals that we can form inverse hexagonal structures, which are present in a liquid crystalline nature within the LNP core. Comparison with lamellar LNPs reveals that the presence of inverse hexagonal phases enhances the intracellular silencing efficiency over lamellar structures. We then demonstrate that lamellar LNPs exhibit an in situ transition from a lamellar to inverse hexagonal phase upon interaction with anionic membranes, whereas LNPs containing pre-programmed liquid crystalline hexagonal phases bypass this transition for a more efficient one-step delivery mechanism, explaining the increased silencing effect. This rational design of LNPs with defined lipid structures aids in the understanding of the nano-bio interface and adds substantial value for LNP design, optimization and use.

Magnetic and magnetocaloric properties of the multi-component Mn0.5Fe0.5Ni0.95Cr0.05Si0.95Al0.05 intermetallic compound

The first-order phase transition and associated magnetocaloric properties of Mn0.5Fe0.5Ni0.95Cr0.05Si0.95Al0.05 have been studied by x-ray diffraction and dc magnetization measurements. The diffraction data for the sample showed that both the orthorhombic and hexagonal crystalline phases coexisted at room temperature. The temperature dependence of magnetization was measured at a constant field of 0.2 T. The first-order phase transition was observed at 325 K during heating and at 306 K during cooling, showing a thermomagnetic hysteresis of 19 K. For magnetic field change of 5 T, the entropy changes evaluated from the isothermal magnetization data peaked at 322 K during warming and at 313 K during cooling, showing a thermomagnetic hysteresis of 9 K. This difference in the magnitude of the thermomagnetic hysteresis was attributed to the virgin effect due to stress and crack formation during the first cooling from hexagonal to orthorhombic phase. Peak entropy changes of −16 J kg−1 K−1 and −42 J kg−1 K−1 were observed on heating for field changes of 2 and 5 T, respectively. The related refrigeration capacities were 74 J/kg (2 T) and 194 J/kg (5 T).

Growth and Structural Characterization of h-LuMnO3 Thin Films Deposited by Direct MOCVD.

In this work, we investigated the MOCVD conditions to synthesize thin films with the hexagonal P63cm h-LuMnO3 phase as a potential low-band gap ferroelectric material. The main parameters investigated were the ratio of organometallic starting materials, substrate temperature, and annealing effect. Two different substrates were used in the study: fused silica (SiO2) glass and platinized silicon (Pt\Ti\SiO2\Si(100)). In order to investigate the thermodynamic stability and quality of the developed phases, a detailed analysis of the crystal structure, microstructure, morphology, and roughness of the films was performed by X-ray diffractometer, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), Raman spectroscopy, and piezoelectric force microscopy (PFM). Molar compositions in the film within 0.93 < |Lu|/|Mn| < 1.33 were found to be suitable for obtaining a single-phase h-LuMnO3. The best films were obtained by depositions at 700 °C, followed by thermal treatments at 800 °C for long periods of up to 12 h. These films exhibited a highly crystalline hexagonal single phase with a relatively narrow direct band gap, around 1.5 eV, which is within the expected values for the h-LuMnO3 system.

Interface-engineering in MOF-derived In2O3 for highly sensitive and dual-functional gas sensor towards NO2 and triethylamine

Nitrogen dioxide (NO2) and triethylamine (TEA) vapor are two typical reactive nitrogen species harmful to personal health and the environment. Thus, multi-functional and reliable sensors were momentous. Herein, the interface engineering of MOF-derived In2O3 with various contents of oxygen vacancy (OV) and different crystalline phases was achieved via pyrolysis of NH2-MIL-68(In) at different temperatures. High-proportional mixed hexagonal and cubic crystalline phases were presented in the MOF-derived In2O3 obtained by pyrolysis of NH2-MIL-68(In) at 400 °C (MOF-In2O3-400). Benefiting from the larger surface and interface area, MOF-In2O3-400 exhibited abundant OV and improved gas-sensing performance compared with the samples obtained at 500 °C and 600 °C. Interestingly, the MOF-derived In2O3 sensors exhibited dual-selective and ppb-level detection of NO2 and TEA vapor at distinct optimum operating temperatures. MOF-In2O3-400 exhibited ultra-high response of 1210 to 200 ppb NO2, and can detect as low as 1 ppb NO2 at 30 °C and TEA vapor as low as 500 ppb at 200 °C. It was also assessed for excellent long-term stability up to 120 days. As a practical demonstration, a prototype device was fabricated on an integrated circuit platform to issue a warning when NO2 or TEA concentrations exceeded the safety thresholds. The results indicate that the MOF-In2O3-400 is an excellent candidate in temperature-dependent dual-functional gas sensors towards NO2 and TEA vapor.

Morphology and luminescent properties of NaYF4 microcrystalline upconversion materials doped with ytterbium(III) and holmium(III) ions

Microcrystalline upconversion materials NaY0.8- x Yb0.2Ho x F4 ( x = 0-0.1) were synthesized by hydrothermal synthesis for the first time. All the synthesized compounds have hexagonal β-NaYF4 crystalline phase. Holmium(III) ions isomorphically replace yttrium ions. The maximum upconversion emission intensity is observed for NaY0.78Yb0.2Ho0.02F4 in the visible region of the spectrum upon excitation at a wavelength of 973 nm.

Morphology and luminescent properties of nanocrystalline NaGdF4 phosphors doped with neodymium(III) ions

Nanocrystalline phosphors NaGd1- x Nd x F4 ( x = 0-1) were synthesized by hydrothermal synthesis for the first time. All the synthesized compounds have hexagonal β-NaYF4 crystalline phase. Neodymium(III) ions isomorphically replace gadolinium ions. NaGd0.96Nd0.04F4 compound has the largest photoemission intensity in NIR range upon 808 nm excitation; further doping with Nd3+ results in concentration quenching.

Improved Supercapacitor Performance with Enhanced Interlayer Spacing of Nanoflower MoS2 in Long Discharge Time in LED‐Glowing Application

The 2D materials have seen recent significant development in terms of material features with superior electrochemical capability. This urges for extensive research as potential aspirants for energystorage applications. Herein, the synthesis of MoS2 nanostructures with molar ratio 1:30 (nanosheets) and 1:15 (nanoflower) of ammonium molybdate tetrahydrate and thiourea single‐steps hydrothermal methods through different reaction times and observed enhanced interlayer spacing is reported. Field emission scanning electron microscopy analysis reveals that synthesized MoS2 nanostructure has 3D flower‐like and ultrathin 2D sheet‐like morphologies. The enhanced interlayer spacing in nanoflower over nanosheet is confirmed through high‐resolution transmission electron microscopy. The X‐ray diffraction and Raman studies reveal the hexagonal crystalline phase of MoS2 (2H‐MoS2). Surface functional groups present are studied by Fourier transform infrared. Through X‐ray photoelectron spectroscopy, the chemical composition with its binding energy of prepared MoS2 is observed. Specific surface area and pore‐size distribution of both 2H‐MoS2 nanosheets and nanoflower are examined by Brunauer–Emmett–Teller and Barrett–Joyner–Halenda analysis. Owing to these excellent physicochemical properties, nanoflower also exhibits energy‐storage device capability. MoS2 nanoflower demonstrates high specific capacitance and cyclic stability in three‐electrode systems. A practical approach is investigated to test the practical application of enhanced interlayer spacing by studying the time of charge and discharge of light‐emitting diode.

Strain induced structural changes and magnetic ordering in thin MoS2 flakes as a consequence of 1.5 MeV proton ion irradiation

We report the effects of 1.5 MeV proton ion irradiation on thin MoS2 (Molybdenum disulfide) flakes. The XRD (X-ray diffraction) analysis of both the unirradiated and irradiated samples revealed a known hexagonal crystalline phase, with the peaks of the irradiated samples slightly shifting towards lower diffraction angle. The change in the peak position can be attributed to the defects created by the proton ion beam indicating strain in the relevant phases. All the irradiated MoS2 samples showed distinct and increasing room temperature ferromagnetism, as compared to the unirradiated MoS2 sample. The presence of any kind of impurities and transition metal element in the irradiated and unirradiated samples, has been ruled out by X-ray photoelectron spectroscopy analysis and it further confirms sulfur vacancies in the sample post irradiation. Raman spectroscopy analysis of the samples revealed a red shift in the fundamental vibrational modes of MoS2 indicating presence of tensile strain in the samples after irradiation. The observed ferromagnetic ordering has been attributed to locally aligned magnetic dipole moments induced by sulfur vacancies and defects produced by tensile strain as a consequence of proton beam irradiation.

Synthesis, structural and optical properties of Cu doped ZnO and CuO–ZnO composite nanoparticles

Hydrothermal synthesis was used to obtain pure, doped and composite semiconductor oxide materials. We synthesized ZnO, CuO, Cu doped ZnO with 1, 2 and 3 wt %, and for Cu additions at 6, 8, 10, 15, 30 and 50 wt% this resulted in ZnO–CuO composites with different morphologies. X-ray diffraction (XRD) showed hexagonal and monoclinic crystalline phases for pure ZnO and CuO, respectively. Electron microscope images showed two-dimensional (2D) shaped particles. The Cu element could dope ZnO up to 3 wt%, whilst above this value, composites of ZnO–CuO were generated, with two segregated phases having flake-like shaped elongated particles. The visible-light absorption increases for the doped samples, being directly proportional to the Cu content for the dopant and the composite particles, showing a broad absorption range between 200 and 800 nm. Two bandgap energy values of 3.22 and 1.45 eV were determined for the ZnO–CuO samples. The samples were studied by X-ray photoelectron spectroscopy (XPS) in order to understand the doping process and composite formation.

Novel Sol-Gel Route to Prepare Eu3+-Doped 80SiO2-20NaGdF4 Oxyfluoride Glass-Ceramic for Photonic Device Applications.

Oxyfluoride glass-ceramics (OxGCs) with the molar composition 80SiO2-20(1.5Eu3+: NaGdF4) were prepared with sol-gel following the "pre-crystallised nanoparticles route" with promising optical results. The preparation of 1.5 mol % Eu3+-doped NaGdF4 nanoparticles, named 1.5Eu3+: NaGdF4, was optimised and characterised using XRD, FTIR and HRTEM. The structural characterisation of 80SiO2-20(1.5Eu3+: NaGdF4) OxGCs prepared from these nanoparticles' suspension was performed by XRD and FTIR revealing the presence of hexagonal and orthorhombic NaGdF4 crystalline phases. The optical properties of both nanoparticles' phases and the related OxGCs were studied by measuring the emission and excitation spectra together with the lifetimes of the 5D0 state. The emission spectra obtained by exciting the Eu3+-O2- charge transfer band showed similar features in both cases corresponding the higher emission intensity to the 5D0→7F2 transition that indicates a non-centrosymmetric site for Eu3+ ions. Moreover, time-resolved fluorescence line-narrowed emission spectra were performed at a low temperature in OxGCs to obtain information about the site symmetry of Eu3+ in this matrix. The results show that this processing method is promising for preparing transparent OxGCs coatings for photonic applications.

Effect of phenol concentration on the photocatalytic performance of ZnO nanoparticles

AbstractBACKGROUNDPhenol and its derivatives are considered toxic compounds, even at low concentrations. Their accumulation in water effluents has become a serious problem that could be resolved by using zinc oxide (ZnO)‐based photocatalysts.RESULTSZnO nanoparticles were synthesized through the precipitation method, using zinc nitrate and sodium carbonate as reagents. The as‐synthesized powder was calcined for 4 h at 500 °C (2° C min−1). X‐Ray diffraction analysis confirmed a hexagonal crystalline phase (wurtzite) with an average crystallite size of 38 nm. The Kubelka‐Munk method was used to determine a band gap of 3.27 eV through UV–Vis diffuse reflectance spectrum and a Brunauer‐Emmett‐Teller (BET) specific area of 12 m2 g−1 was obtained from N2 adsorption analysis. The photocatalytic activity of ZnO was evaluated under visible light (300 W) lamp, with 1 mg mL−1 of photocatalyst and using phenol solutions at different concentrations of 5, 10, 25, and 50 ppm; the obtained degradation percentages were 98%, 97%, 94%, and 71%, respectively. Three cycles were performed with the ZnO used in the reactions with phenol at 5 and 50 ppm, decreasing the degraded percentages to 87% and 65%, respectively. The generation of hydroxyl radicals was estimated for the ZnO and ZnO samples after three cycles by means of fluorescence spectroscopy analysis. It was observed that the first‐used ZnO material generated a significant amount of hydroxyl radicals.CONCLUSIONWhen compared to ZnO after three cycles of reaction, the amount of generated hydroxyl radicals decreased. It was observed that the higher the amount of phenol, the lower the generation of hydroxyl radicals after reuse; this was probably due to the presence of some adsorbed by‐products of the photocatalytic reaction on the surface of ZnO, as the FTIR spectrum of the post‐reaction sample showed. © 2023 Society of Chemical Industry (SCI).