Sol-gel Synthesis Method Research Articles

Assembly of Two-Dimensional δ-V2O5-Ti3C2Tx Heterostructure Electrodes for Li-Ion Batteries

The bilayered phase of vanadium oxide (δ-V2O5∙nH2O or BVO) synthesized via sol-gel synthesis method is an attractive candidate to be used as a cathode material for Li-ion batteries (LIBs) due to its expanded interlayer spacing, and high theoretical capacity. However, poor electrical conductivity and rapid capacity fade present challenges for achieving high-rate performance and good cycle life during cycling in LIBs. A viable solution to mitigating these drawbacks is to fabricate two-dimensional (2D) heterostructures comprised of vanadium oxide and an additional selected 2D material. Titanium carbide (Ti3C2Tx) MXenes are particularly of interest for their high electronic conductivity (103 S cm-1) and well developed delamination protocols. Herein, we present a wet-based approach for assembling BVO and MXene nanoflakes into 2D heterostructures in suspension.In this study, we first demonstrate a simple liquid phase exfoliation technique utilizing probe ultrasonication to exfoliate bulk -LixV2O5·nH2O (LVO). Previous experiments from our group showed the exfoliation technique in n-methyl-2-pyrrolidone, an organic solvent that is toxic, flammable, and resulted in low yield during exfoliation. Here, for the first time, we have successfully performed exfoliation of LVO in aqueous media and obtained few layered nanoflakes with high yield after centrifugation. Despite the partial solubility of vanadium oxide in water, these nanoflakes suspended in aqueous media maintained chemical stability and readily assembled into a free-standing film using vacuum filtration. The LVO nanoflake films have a two-dimensional (2D) layered morphology as confirmed by SEM and maintain the bilayered structure as confirmed by XRD.Due to the hydrated nature of LVO, we also highlight the importance of controlling interlayer water content with vacuum drying for achieving better cycling stability. The comparison of a 105°C and 200°C vacuum drying temperature and corresponding interlayer water content was carried out using XRD, TGA, and Raman spectroscopy characterization methods. The 200°C vacuum dried LVO nanoflake cathode achieved an initial ion storage capacity of 212 mAh g-1 which was 32.5% higher than the sample dried at 105°C. In addition, galvanostatic cycling experiments conducted for the 200°C vacuum dried LVO nanoflake cathode show there were significant improvements in capacity retention by ~35%, compared to the 105°C dried sample, after 100 cycles at a current density of 20 mA g-1.Subsequently, dispersions of LVO and Ti3C2Tx flakes in water were combined in different weight ratios of 9:1, 4:1, and 1:1 LVO to Ti3C2Tx. The heterostructure electrostatic assembly was facilitated by the introduction of a cationic species into the mixed suspensions. Resistivity measurements showed that heterostructure films achieved electronic conductivities as high as ~105 higher than pristine LVO. Through electrochemical testing, the 9:1 heterostructure cathodes delivered the highest ion storage capacity of 167 mAh g-1. At the cost of lower capacity (125.3 mAh g-1), the 4:1 heterostructures maintain a superior capacity retention of ~96% after 10 cycles. Furthermore, rate capability experiments for the 9:1 heterostructure cathodes demonstrate that the addition of 10 wt % Ti3C2Tx to LVO enables greater tolerance to high current densities with a capacity retention of ~90% after cycling through increasing current densities. In this work we also show that increased capacities can be acquired upon the extension of the potential window below 2V covering where Ti3C2Tx exhibits redox activity.These results demonstrate an environmentally friendly and safe approach to obtaining 2D LVO nanoflakes and offers pathways to constructing novel vanadium oxide based 2D heterostructures for improving electrochemical performance in energy storage devices.

Cobalt and Nickel Free Disorder Rock Salt Cathodes – Recent Developments

Disordered Li-excess rock salt (DRX) cathodes are a promising class of high capacity (and voltage) cathodes for next-generation Li-ion batteries. Compared to conventional Li-ion cathodes which are generally restricted to Co/Ni-based compositions with specific cation ordering, DRX materials have a wide compositional design space based on earth abundant metals such as Mn, Ti, Mo, Al, Zr, V, and Nb. Furthermore, Li-rich oxyfluoride DRX cathodes have demonstrated specific energies up to 1,000 Wh/kg which exceeds that of state-of-the-art layered LiNixMnyCo1-x-yO2 (NMC) cathodes (~700 Wh/kg). Despite such scientific advancements, widespread adoption of DRX cathodes has been hindered by several technical challenges. First, most of the high fluorine content DRX compositions are synthesized using mechano-chemical synthesis that has inherent limitation in scalability and maintaining a uniform particle-size and morphology. Further, DRX compositions have about 3-4 order lower electronic conductivity compared to layered cathodes requiring a high carbon loading in the electrode (up to 25%) compromising energy density. The focus of this talk will be on developing alternate synthesis method for Li-Mn rich DRX compositions. Specifically solid-state and sol-gel synthesis methods to produce DRX cathodes with the nominal composition Li1.2Mn0.4+xTi0.4-xO2-xFx (x = 0-0.3). Detailed advanced characterization (i.e., neutron total scattering and electron microscopy) and modelling efforts (i.e., Reverse Monte Carlo simulations) to understand how SRO impacts cathode performance will be presented. Different choice of precursors based on thermodynamic and kinetic consideration that minimizes formation of LiF impurity phases will be proposed.AcknowledgmentThis work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Vehicle Technologies Office, under the Applied Battery Materials Program, of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725

High Throughput Studies of Li-La-Zr-O Garnet Solid Electrolytes

Development of next-generation Li-ion batteries has increasingly focused on all-solid batteries employing either ceramic, polymer, or glass electrolytes in order to address shortcomings in currently commercialized liquid electrolyte Li-ion batteries including safety, limited lifetime, and lower energy densities resulting from instability with respect to Li metal anodes.[1] Lithium lanthanum zirconium oxide (LLZO) is a leading candidate for solid Li-batteries due to its high Li-ion conductivity, stability in air and against Li metal, and compatibility with high-voltage cathodes.[2],[3] Despite significant progress being made, our understanding of LLZO is limited by the relatively small number of compositions which have been studied; especially considering the leading contender is a pseudo-quaternary oxide (Ga-doped LLZO) and many studies are now utilizing multiple dopants.[4] Herein, we have applied a high-throughput methodology for synthesizing, characterizing, and testing sets of 64 LLZO electrolytes at the mg-scale. We employ a citrate sol-gel synthesis method whereby reagent solutions are dispensed across a well-plate to give a composition gradient. After drying the samples and burning off the citrates, the resulting powders are pressed into pellets using a custom-made 64-pellet die and the pellets are sintered at the desired temperature. The high-throughput characterization techniques utilized include powder X-ray diffraction, electrochemical impedance spectrometry and electrochemical cycling in order to test electrolyte stability; with each method performed on up to 64 samples simultaneously.Using our methodology, we have studied over 700 samples to produce a full phase stability diagram for the Li-La-Zr-O pseudoternary system. We find that within the Li-La-Zr-O system, there is significant solubility of Li into the La2Zr2O7 pyrochlore structure commonly found as an impurity in LLZO synthesis due to lithium loss. We also find that LLZO appears as both tetragonal and cubic forms throughout the system, with the cubic LLZO appearing in an extremely restricted region that is difficult to access as pure phase due to lithium loss, while excess lithium leads to the tetragonal LLZO. Li conductivity measurements show that both cubic and tetragonal undoped LLZO have similar bulk conductivities, but there is only a limited region near the formal Li7La3Zr2O12 composition where grain boundary conductivity is high. Our methodology is also applied to a comprehensive doping study where over 40 different dopants are evaluated and promising dopants are tested in co-doped compositions. [1] D. Aurbach et al., Electrochimica Acta 2004, 50, 247-254. [2] Q. Liu, et al., J. Power Sources 2018, 389, 120-134. [3] T. Thompson, et al., ACS Energy Letters 2017, 2, 462-468. [4] F. Zheng, et al., J. Power Sources 2018, 389, 198-213.

Application of Box–Behnken design to optimize a sol-gel synthesis method for Ag and Zn doped CuO nanoparticles with antibacterial and photocatalytic activity

Application of Box–Behnken design to optimize a sol-gel synthesis method for Ag and Zn doped CuO nanoparticles with antibacterial and photocatalytic activity

Tetrahedrally modified MnMe0.1Co1.9O4 (Me = Zn, Mg, Li) spinels for non-enzymatic glucose sensing

• Tetrahedrally modified MnMe 0.1 Co 1.9 O 4 (Me = Zn, Mg, Li) spinels were prepared via the sol–gel synthesis. • The influence of partial substitution of cobalt in MnCo 2 O 4 spinel on physicochemical properties is shown. • MnLi 0.1 Co 1.9 O 4 exhibits the highest glucose-sensing ability among studied samples. In this work, tetrahedrally modified MnMe 0.1 Co 1.9 O 4 (Me = Zn, Mg, Li) spinels were prepared via the sol–gel synthesis method with subsequent ball-milling fragmentation. The prepared samples were evaluated as glucose–sensing catalyst. The reference MnCo 2 O 4 spinel exhibited a sensitivity of 49 µA mM −1 cm −2 and a nonlinearity error of 5.2% in the response range from 0.02 to 1 mM. The partial substitution of cobalt in the reference spinel enhanced the glucose–sensing abilities, and the sample with Li was found to be the most active catalyst, exhibiting a sensitivity of 73.1 µA mM −1 cm −2 . Finally, the proposed material was tested for selectivity in the presence of interfering sucrose.

Metal-doped TiO2 photocatalyst as antibacterial - A Review

Photocatalyst nanomaterials are developing as new materials for many applications. Titanium dioxide (TiO2) is a photocatalyst nanomaterial widely applied to solar cells, chemical sensors, health products and paint pigmentation. In this review article, we aim to provide a comprehensive overview of the development of the metal as a TiO2 doping material and its application as an antibacterial. TiO2 as an antimicrobial photocatalyst has been widely reported. Sol-gel synthesis method on semiconductors can make nanoparticle size, not agglomerate, homogeneous, pure and control mass distribution. Metal-doped TiO2 can activate the performance of TiO2 to work on visible light, thereby increasing the performance of TiO2 in its application as an antibacterial. Nickel (Ni), copper (Cu), manganese (Mn) and sulfur (S) have been shown to affect increasing the performance of TiO2 to inhibit bacteria in visible light. TiO2/Ni has antibacterial activity against Staphylococcus aureus (S. aureus) bacteria. TiO2/Cu has antibacterial activity against Escherichia coli (E.coli), S. aureus, Klebsiella pneumonia (K. Pneumonia) and Saccharomyces sp.. TiO2/Mn/S has antibacterial activity against Bacillus coagulans (B. Coagulans) and (K. Pneumonia). This review can add to the knowledge and the latest developments of metaldoped TiO2 photocatalysts based on antibacterial properties to be applied to water-purifying membranes, skin health and self-cleaning paints.

The Role of the Sol-Gel Synthesis Process in the Biomedical Field and Its Use to Enhance the Performance of Bioabsorbable Magnesium Implants

In the present day, the increment in life expectancy has led to the necessity of developing new biomaterials for the restoration or substitution of damaged organs that have lost their functionalities. Among all the research about biomaterials, this review paper aimed to expose the main possibilities that the sol-gel synthesis method can provide for the fabrication of materials with interest in the biomedical field, more specifically, when this synthesis method is used to improve the biological properties of different magnesium alloys used as biomaterials. The sol-gel method has been widely studied and used to generate ceramic materials for a wide range of purposes during the last fifty years. Focused on biomedical research, the sol-gel synthesis method allows the generation of different kinds of biomaterials with diverse morphologies and a high potential for the biocompatibility improvement of a wide range of materials commonly used in the biomedical field such as metallic implants, as well as for the generation of drug delivery systems or interesting biomaterials for new tissue engineering therapies.

The Effect of Zinc Doped Bismuth Ferrite on Changes in Structural and Microwave Absorption Properties through the Sol-gel Synthesis Method

The zinc (Zn) doped bismuth ferrite (BiFeO3) have been successfully synthesized through the sol-gel autocombustion method as a microwave absorbent material through a composite process with silicone rubber. The characterizations of zinc doped bismuth ferrite nanoparticles was done using the X-ray diffraction (XRD), the Fourier transform infrared (FTIR), the vibration sample magnetometer (VSM), and the vector network analyzer (VNA). Through the XRD test, the nanoparticle BiFe1-xZnxO3 (x = 0, 0.06, and 0.12) have a crystal structure of rhombohedral R3c. Through the FTIR test, it was observed that the area of wave number 491–569 cm-1 were used as an absorber for BiFeO3, while the one in zinc doped BiFeO3 were observed to be 489–636 cm-1. The VSM test shows that the BiFe1-xZnxO3 nanoparticles (x = 0, 0.06, and 0.12) have ferromagnetic properties and potentially change to paramagnetic properties with the addition of zinc doping. The VNA test were obtained, bismuth ferrite without doping has a reflection loss (RL) of –25.79 dB with a narrower frequency range and bismuth ferrite with zinc doping (%wt x = 0.12) has a RL of –30.02 dB with a wider frequency range so that zinc doped BiFeO3 potentially to be a good absorbent material.

Spin reorientation behavior and enhanced multiferroic properties of co-doped YFeO3 towards a monophasic multiferroic ceramic Co0.05Y0.95Fe0.95Ti0.05O3

Monophasic nanocrystalline lead-free relaxor ferroelectric samples of YFeO3 and Co0.05Y0.95Fe0.95Ti0.05O3 were prepared via the standard sol-gel synthesis method. The influence of Co and Ti co-doping on the structural, dielectric, ferroelectric, and magnetic properties were investigated using X-ray, Neutron Diffraction, Electric Polarisation, and magnetization measurement techniques. The structural analysis by the Rietveld method revealed an orthorhombic (Pnma) distorted perovskite structure. The analysis of the neutron diffraction data showed a spin reorientation from IR Γ4 to Γ2 in the doped sample. The universal dielectric response (UDR) phenomenon was used to explain the dielectric behavior. The temperature-dependent dielectric constant measurement shows a shift in the ferroelectric to paraelectric phase in Co0.05Y0.95Fe0.95Ti0.05O3. The observed P-E loops indicate lossy ferroelectric nature for YFO and CYFTO. Enhancement in the value of saturation magnetization at room temperature was observed on co-doping. Furthermore, the presence of magnetodielectric coupling was established for the co-doped sample. Co-doping with Co and Ti in YFeO3 enhanced the multiferroic properties of the pristine sample which may be helpful for future device applicability.

Sol-gel auto-combustion synthesis and luminescence properties of GdCaAl3O7: RE3+ (RE=Eu, Tb, Eu@Tb) phosphors for near-ultraviolet light-triggered indoor illumination

The color-tunable GdCaAl3O7: RE3+ (RE = Eu, Tb, Eu@Tb) phosphors were synthesized via an ultrafast sol-gel auto-combustion synthesis method. The X-ray diffraction patterns confirmed the forming of GdCaAl3O7 tetragonal phase, and the scanning electron microscopy images indicated that the obtained products presented honeycomb-like structure due to the gas releasing during the auto-combustion process. The luminescent properties, concentration quenching mechanism, energy transfer mechanism, luminescent dynamics, thermal stability and product practicability of GdCaAl3O7: RE3+ (RE = Tb, Eu, Eu@Tb) phosphors were investigated systematically. All the GdCaAl3O7: RE3+ products presented the characteristic emission of doped RE3+. Using GdCaAl3O7: 50% Tb3+@3.0% Eu3+ as yellow-emitting phosphors in combination with commercial BAM: Eu2+ blue-emitting phosphors and a NUV chip can successfully package a warm white LED device with high color rendering index (CRI, 86.3) and low correlated color temperature (CCT, 3348 K) that was very suitable for near-ultraviolet light-triggered indoor illumination.

Photocatalytic degradation of paracetamol by semiconductor oxides under UV and sunlight illumination.

In this study, photocatalytic degradation of paracetamol (acetaminophen), an analgesic and antipyretic drug, was investigated in using semiconductors under UV-B and sunlight irradiation. Semiconductor materials, Bi2O3, ZnO, TiO2, and ZrO2, were prepared using simple sol-gel, coprecipitation, and microwave synthesis methods. These photocatalyts were characterized by various spectroscopic and other techniques. As a result of the reactions, 25 ppm paracetamol with Bi2O3 and ZnO photocatalyst, total degradation was achieved with UV-B irradiation in 90 min. The results of photocatalytic activities showed that the highest degradation rate was obtained with the Bi2O3 photocatalyst. In the light of all findings, the nanorod-shaped Bi2O3 semiconductor which has a low band gap energy and high quantum efficiency exhibited significant effect on the activity despite of its low surface area.

Magnetic and dielectric properties of BaFe1/2Sn1/2O3-δ ceramics

Ceramic samples of barium ferrostannate BaFe1/2Sn1/2O3-δ have been prepared by the sol-gel and hydrothermal synthesis methods. To reduce the number of oxygen vacancies, annealing in oxygen has been performed. The heat capacity, magnetization, Mössbauer and dielectric spectroscopy data point to the appearance of antiferromagnetic ordering below ∼55 K followed by further spin glass magnetic ordering below 15 K. The giant dielectric response seems to be due to the relaxation of electrons trapped by oxygen vacancies. Comparison of the Fe K-edge X-ray absorption spectra of BaFe1/2Sn1/2O3-δ confirmed substantial difference from those of the similar stoichiometric BaFe1/2Nb1/2O3 perovskite.

Amalgamation of g-C3N4 with KNbO3 for enhanced removal of Bisphenol A under sunlight irradiation

Bisphenol A (BPA) is a pollutant exits in an enormous amount in wastewater effluent resulted from the rapid industrialization. Advanced oxidation technology (AOP) based on solar photocatalysis can be employed to solve this issue. This study will focus on adopting photocatalyst graphitic carbon nitride (g-C3N4) with potassium niobate (KNbO3) via a simple sol-gel synthesis method. The different weight percentages 0.5, 1.0 and 1.5 wt% g-C3N4, were adopted to formed KNbO3/g-C3N4composites. The physicochemical properties of the created KNbO3/g-C3N4composites were characterized with advanced analysis methods to unveil this composite’s ability to enhance the photodegradation of BPA under sunlight irradiation. It was found that 1.0 wt% KNbO3/g-C3N4composites exhibited the highest photocatalytic degradation of 69.39% in 5 h. This superior photodegradation of BPA was achieved resulted from the presence of g-C3N4that enhances light-harvesting, especially in the visible light spectrum. The increase of light-harvesting enables the composite to excite more electrons and holes leading to the massive formation of active radicals. These massive active radicals will then enhance the redox reaction and further improve the efficacy of the photodegradation of BPA. Hence, the outcome of this study path an alternative solution for eliminating complex organic pollutants in wastewater treatment.

Hydrothermal assisted conventional sol-gel method for synthesis of bioactive glass 70S30Cы

Bioactive glasses (Bioglasses) are widely synthesized by the conventional sol-gel method consisting of two main steps for sol and gel formation. However, the conversion from sol to gel requires a long time (5–7 days). In this study, the hydrothermal system was used to quickly synthesize the bioactive glass by reducing the conversion time from sol to gel. The hydrothermal assisted conventional sol-gel method was applied for synthesis of the bioactive glass 70SiO2–30CaO (mol%) (noted as 70S30C). The synthetic glass was investigated by the physical-chemical techniques. The ‘‘in vitro’’ experiments in SBF (Simulated Body Fluid) solution was also performed to evaluate the bioactivity of synthetic material. The obtained results show that the bioactive glass 70S30C was successfully elaborated by using the hydrothermal assisted conventional sol-gelmethod. The consuming time was reduced compared to the conventional method. The physical-chemical characterization confirmed that the synthetic glass is amorphous material with mesoporous structure consisting of interconnected particles.The specific surface area, pore volume and average pore diameter of synthetic glass were 142.8 m2/g, 0.52 cm3/g, and 19.1 nm, respectively. Furthermore, synthetic bioactive glass exhibited interesting bioactivity when immersed in simulated body fluid (SBF) solution for 1 days and good biocompatibility when cultured in cellular media.

SrSnO3-Assembled MWCNT Heterojunctions for Superior Hydrogen Production under Visible Light.

A one-step sol–gel method for SrSnO3 nanoparticle synthesis and the incorporation of multi-walled carbon nanotubes (MWCNTs) to produce a SrSnO3@MWCNT photocatalyst is presented. The incorporation of MWCNTs results in enhancement of structural, optical, and optoelectrical properties of SrSnO3. The optimized 3.0% addition of MWCNTs results in light absorption enhancement and a reduction of the band gap from 3.68 to 2.85 eV. Upon application of the photocatalyst in the photocatalytic hydrogen production reaction, SrSnO3@MWCNT-3.0% yields 4200 μmol g–1 of H2 in just 9 h with the use of 1.6 g L–1 of the photocatalyst. SrSnO3@MWCNT exhibits remarkable chemical and photocatalytic stability upon regeneration. Enhanced photocatalytic ability is attributed to improved surface properties and charge-carrier recombination suppression induced by the MWCNT addition. This study highlights the remarkable improvements in chemical and physical properties of semiconductors with MWCNT incorporation.

6, 13-pentacenequinone/zinc oxide nanocomposites for organic dye degradation

The organic semiconductor photocatalyst 6, 13-Pentacenequinone (PQ) and inorganic photocatalyst ZnO were synthesised independently. PQ was synthesised by previously reported solution method and nanostructured ZnO by sol–gel synthesis method. Keeping in mind the previous photocatalyst composite systems of PQ, PQ/ZnO nanocomposite system prepared with different weight ratios by simple wet impregnation method. The as synthesised organo-inorganic nanocomposite catalyst system was characterized with various spectroscopic methods. XRD confirms the monoclinic and hexagonal wurtzite phase of PQ and ZnO, respectively. FE-SEM showed the sheet/plate like morphology of PQ, whereas the composite material depicts the formation of homogeneous layer of ZnO on PQ surface in all three compositions. Photocatalytic activity of these semiconductor nanosystems was studied and compared with PQ/TiO2 composite systems for degradation of methylene blue (MB) dye under sunlight. As compared to individual, the coupled organo-inorganic catalyst showed higher photocatalytic MB degradation. The PQ/ZnO nanocomposite having 0.5 wt% PQ showed highest MB degradation.

Investigation of structural, morphological, and optoelectronic properties of Ga-doped TiO2 nanoparticles for electron transport layer in solar cell applications: An experimental and theoretical study

In the current work, the sol-gel synthesis method was used to synthesize both undoped and gallium (1%-Ga) doped TiO2 nanoparticles. The as-deposited materials were calcined at 400–500 °C with a temperature variation rate of 5 °C per minute. The crystallographic properties of the semiconductor materials were determined from X-ray diffraction (XRD) which showed the formation of anatase TiO2. The average crystallite sizes, determined from the widths of the XRD reflections, were 11 and 4 nm for undoped and Ga-doped TiO2, respectively. The materials were further studied by density functional theory with meta-generalized gradient approximation exchange–correlation functional. Supercell systems consisting of 24 and 48 atoms were created to form 12.5% and 6.25% Ga dopant substitution, respectively. These structures were optimized to obtain the ground state properties. Transmission electron microscopy showed polycrystalline, spherical powders, with grain sizes comparable to those found using XRD. The surface morphology of the doped TiO2 obtained from scanning electron microscopy showed an improved surface structure compared to pristine TiO2. Moreover, the electronic states of the materials were investigated using X-ray photoelectron spectroscopy. Energy dispersive X-ray spectroscopy verified the elemental composition of titanium, oxygen, and Ga present in the nanoparticles. The surface chemical bonds were analyzed by Fourier-transform infrared spectroscopy. Ultraviolet diffused reflectance spectra analysis was used to examine their optical properties. The experimentally obtained bandgaps of pristine and 1% Ga-doped TiO2 nanoparticles were 2.9 and 3.09 eV, respectively. The optical properties were further analyzed by computing the band structures and density of states using density functional theory. Similar to the experimental results, these electronic structures showed an increase in bandgap after 6.25% Ga incorporation. However, with 12.5% doping, there was a decrement in the bandgap. The analysis showed that, with an appropriate amount of substitution, Ga-doped TiO2 semiconductor material can be used in the electron transport layer and many other fields of photoelectric cells.

Unveiling Semiconductor Nanostructured Based Holmium-Doped ZnO: Structural, Luminescent and Room Temperature Ferromagnetic Properties.

This research work describes the synthesis of ZnO nanostructures doped with Ho3+ ions using a conventional sol–gel synthesis method. The nanostructured produced exhibited a wurtzite hexagonal structure in both ZnO and ZnO:Ho3+ (0.25, 0.5, 0.75 mol%) samples. The change in morphology with addition of Ho3+ dopants was observed, which was assigned to Ostwald ripening effect occurring during the nanoparticles’ growth. The photoluminescence emission properties of the doped samples revealed that Ho3+ was emitting through its electronic transitions. Moreover, reduced surface defects were observed in the Holmium doped samples whose analysis was undertaken using an X-ray Photoelectron Spectroscopy (XPS) technique. Finally, enhanced room temperature ferromagnetism (RT-FM) for Ho3+-doped ZnO (0.5 mol%) samples with a peak-to-peak line width of 452 G was detected and found to be highly correlated to the UV–VIS transmittance results.

Analysis of sol aging effects on self-cleaning properties of TiO2 thin film

This study investigated the effect of aging TiO2 Sol on the final thin film performance using the heat-assisted sol-gel synthesis method. The sol was aged 24 h, 48 h, and 72 h respectively before being spin-coated on glass substrates. The annealing of the coated thin films occurred at 600 °C. The scanning electron microscope, x-ray diffraction (XRD), and UV–vis spectrophotometer characterized the thin films to ascertain morphological, structural, and optical properties. Also, methylene blue degradation characterized the thin films to confirm the self-cleaning properties. The result revealed that aging time influences the ability of the electrons to gather or transit. The light absorption experienced an increasing shift in value. Also, light absorption optimized with absorption bands with peak intensities becoming strong as aging time increased. Aging the TiO2 Sol caused micro and macro-structural transformations. The structural analysis showed anatase with possible transitioning to rutile as aging time increased. Crystallite size from the most prominent peak range from 3.61 nm to 21.77 nm as aging time increased from 24 h to 72 h and 19.31 nm for rutile at 72 h. The optical bandgap dropped from 3.51 eV to 3.26 eV as aging time increased from 24 h to 72 h. The morphology showed increasingly uniformly distributed shapes of TiO2 particles scattered over the surface of the substrate as aging time increased. The self-cleaning test showed the thin film has a high degradation efficiency of methylene blue dye in the range of 72.50 to 92.90% confirming substantial, self-cleaning property.

Influence of Aloe vera and PEG on the evaluation of photocatalytic degradation of MG dye under UV light and visible light irradiation of ZnO nanomaterials

Photocatalytic degradation is an effective method to prevent the environmental pollution caused by organic pollutants. The effect of different combinations on the properties of zinc oxide was studied by preparing polyethylene glycol (PEG) capped ZnO, Aloe vera mediated ZnO, and PEG/Aloe vera combined ZnO via the sol-gel synthesis method. The size and structure of the synthesized samples were confirmed by XRD and SEM analysis. The decrease in bandgap energy value of ZnO/Aloe/PEG than ZnO/Aloe, and ZnO/PEG indicates the easy excitation of electrons in the latter. Here, the photocatalytic degradation of three different ZnO combinations was tested against Malachite Green (MG) dye with twenty minutes of UV light and visible light irradiation time. Furthermore, the photocatalytic degradation efficiency of textile dye wastewater was also evaluated by ZnO/Aloe/PEG combination under both UV light and visible light irradiation. These findings proved the overwhelming photocatalytic degradation of plant extract and surfactant based ZnO, which has been used as effective remediation to treat textile dye effluent.