Morphology and photocatalytic activity of porous (In, Mg) co-doped ZnO nanoparticles

Materials & Design, 2016

Porous Mn-doped ZnO (ZnO:Mn) nanoparticles with an average diameter of ca. 21 nm were prepared by a simple and cheap solvothermal process involving no templates, post-synthetic annealing or etching. The particles produced were characterized by XRD, Raman spectroscopy, SEM, TEM, XPS, diffuse reflectance spectroscopy and BET surface area measurements and the effects of Mn 2+-doping on the structural, optical and photocatalytic properties of ZnO particles were investigated. The particles doped with 3 mol% Mn 2+ were found to exhibit the highest catalytic activity toward the photodegradation of the Orange II dye under solar light irradiation. Our results demonstrate that Mn 2+-doping shifts the optical absorption to the visible region, increases the specific surface area of the photocatalyst and reduces the recombination of electron-hole pairs. The influence of various operational parameters (amount of catalyst, concentration of dye and pH) on the photodegradation and the photocatalytic mechanism were studied. Finally, we demonstrated that the ZnO:Mn photocatalyst is stable and can be easily recycled up to ten times without any significant decrease in photocatalytic activity.

Russian Journal of Inorganic Chemistry, 2019

Mg-doped ZnO nanoparticles with different contents of Mg dopant have been synthesized by tartaric acid complex method with subsequent calcination at 600°C for 2 h. The products have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The analytical results have revealed the presence of wurtzite ZnO with hexagonal structure for undoped and Mg-doped samples with particle sizes of 100-200 nm for ZnO and 30-70 nm for 5 wt % Mg-doped ZnO. Visible light driven photocatalytic properties of ZnO and Mg-doped ZnO have been monitored through photodegradation of methylene blue (MB) identified by liquid chromatography-mass spectrometry (LC-MS). In this research, 5 wt % Mg-doped ZnO have shown the highest photocatalytic activity of 99% within 60 min.

Materials Chemistry and Physics, 2012

The location of dopant ions and the effect of doping level on the photocatalytic activity have been investigated on Co-doped ZnO nanopowders. A co-precipitation method was used to prepare ZnO nanoparticles of <50 nm in diameter doped with up to 5 at% of Co. The crystal structure of nanoparticles and local atomic arrangements around dopant ions were analysed by X-ray diffraction and extended X-ray absorption fine structure spectroscopy using synchrotron radiation. The results showed the Co ions substituted the Zn ions in ZnO crystal lattice and induced lattice shrinkage. The photocatalytic activity under simulated sunlight irradiation was characterised by the decomposition of Rhodamine B dye molecules, which revealed the successful reduction of photocatalytic activity by Co-doping.

ACS Applied Materials & …, 2012

Magnesium-doped ZnO (ZMO) nanoparticles were synthesized through an oxalate coprecipitation method. Crystallization of ZMO upon thermal decomposition of the oxalate precursors was investigated using differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. XRD studies point toward a significant c-axis compression and reduced crystallite sizes for ZMO samples in contrast to undoped ZnO, which was further confirmed by HRSEM studies. X-ray photoelectron spectroscopy (XPS), UV/vis spectroscopy and photoluminescence (PL) spectroscopy were employed to establish the electronic and optical properties of these nanoparticles. (XPS) studies confirmed the substitution of Zn 2+ by Mg 2+ , crystallization of MgO secondary phase, and increased Zn−O bond strengths in Mg-doped ZnO samples. Textural properties of these ZMO samples obtained at various calcination temperatures were superior in comparison to the undoped ZnO. In addition to this, ZMO samples exhibited a blue-shift in the near band edge photoluminescence (PL) emission, decrease of PL intensities and superior sunlight-induced photocatalytic decomposition of methylene blue in contrast to undoped ZnO. The most active photocatalyst 0.1-MgZnO obtained after calcination at 600°C showed a 2-fold increase in photocatalytic activity compared to the undoped ZnO. Band gap widening, superior textural properties and efficient electron−hole separation were identified as the factors responsible for the enhanced sunlight-driven photocatalytic activities of Mg-doped ZnO nanoparticles.

Applied Surface Science, 2017

Highlights-Na doped ZnO nanocrystals were prepared via sol-gel method.-A substitution of Zn 2+ by Na + was demonstrated.-Low Na concentration induces higher photocatalytic activity under solar irradiation.-Oxygen vacancies guided the processes of charge separation.

Cobalt doped ZnO nanodisks and nanorods were synthesized by a facile wet chemical method and well characterized by X-ray diffraction, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) with energy dispersive X-ray spectroscopy, photoluminescence spectroscopy, Raman spectroscopy and UV-visible absorption spectroscopy. The photocatalytic activities were evaluated for sunlight driven degradation of an aqueous methylene blue (MB) solution. The results showed that Co doped ZnO nanodisks and nanorods exhibit highly enhanced photocatalytic activity, as compared to pure ZnO nanodisks and nanorods. The enhanced photocatalytic activities of Co doped ZnO nanostructures were attributed to the combined effects of enhanced surface area of ZnO nanodisks and improved charge separation efficiency due to optimal Co doping which inhibit recombination of photogenerated charge carriers. The possible mechanism for the enhanced photocatalytic activity of Co doped ZnO nanostructures is tentatively proposed.

Research, Society and Development, 2022

Synthesis, characterization, and photocatalytic activity of ZnO nanostructures Síntese, caracterização e atividade fotocatalítica de nanoestruturas de ZnO Síntesis, caracterización y actividad fotocatalítica de nanoestructuras de ZnO

Thin Solid Films, 2016

Global environmental pollution and energy supply demand have been regarded as important concerns in recent years. Metal oxide semiconductor photocatalysts is a promising approach to apply environmental remediation as well as fuel generation from water splitting and carbon dioxide reduction. ZnO nanostructures have been shown promising photocatalytic activities due to their non-toxic, inexpensive, and highly efficient nature. However, its wide band gap hinders photo-excitation for practical photocatalytic applications under solar light as an abundant, clean and safe energy source. To overcome this barrier, many strategies have been developed in the last decade to apply ZnO nanostructured photocatalysts under visible light. In this review, we have classified different approaches to activate ZnO as a photocatalyst in visible-light spectrum. Utilization of various nonmetals, transition metals and rare-earth metals for doping in ZnO crystal lattice to create visible-light-responsive doped ZnO photocatalysts is discussed. Generation of localized energy levels within the gap in doped ZnO nanostructures have played an important role in effective photocatalytic reaction under visible-light irradiation. The effect of dopant type, ionic size and its concentration on the crystal structure, electronic property and morphology of doped ZnO with a narrower band gap is reviewed systematically. Finally, a comparative study is performed to evaluate two classes of metals and nonmetals as useful dopants for ZnO nanostructured photocatalysts under visible light.

Microporous and Mesoporous Materials, 2010

Highly mesoporous self-aggregated nanoclusters of pure and transition metal (Mn, Co and Ni) doped ZnO have been synthesized by refluxing their acetate precursors in diethylene glycol (DEG) medium. It was found that the porous spherical nanoclusters comprised of numerous nanocrystals are fairly stable, well-defined and discrete with hexagonal wurtzite structure. The transition metal ions, Mn, Ni and Co were successfully doped into the ZnO structure and are uniformly distributed in the samples. The presence of pronounced hysteresis loop in N 2 adsorption-desorption isotherm curves indicates the 3D intersection network of the pores (predominantly mesoporous in nature). Transmission electron microscopy (TEM) analysis indicates that the pores are irregular in shape and randomly distributed throughout the nanocluster. Furthermore, we have explored the photocatalytic activity of these mesoporus pure/doped ZnO nanoclusters using methylene blue as a model dye. It has been observed that these mesoporous ZnO could be a promising photocatalyst for degradation of organic molecules as compared to transition metal doped ZnO under UV light.

2009

ZnO nanocrystalline powders doped with up to 5 at% manganese were synthesized and their photocatalytic activity was studied. Doped ZnO powders were prepared using a sol-gel process. The crystal structure and grain size of the particles were characterized by X-ray diffractometry and optical properties were studied using UV-Vis spectroscopy. The photoactivity of undoped and doped ZnO nanocrystalline powders was evaluated by monitoring the photo-bleaching of the aqueous solutions of Rhodamine B dye in the presence of ZnO under simulated sunlight. The results showed that up to 3 at% manganese were successfully doped into the nanocrystalline ZnO and that manganese-doping reduced the photocatalytic activity of ZnO.