Homogeneous Co-precipitation Method Research Articles

Photocatalytic Degradation of Organic Pollutants-Nile Blue, Methylene Blue, and Bentazon Herbicide-Using NiO-ZnO Nanocomposite.

Water pollution poses a significant threat to both human health and ecosystem integrity. Chemical pollutants such as dyes and pesticides affect the water quality and endanger aquatic life. Among the methods for water purification from organic pollutants, photodegradation is certainly a valid technique to decrease such contaminants. In this work, pristine NiO, ZnO, and NiO-ZnO photocatalysts were synthesized by the homogeneous co-precipitation method. X-ray diffraction confirms the formation of a photocatalyst consisting of ZnO (Hexagonal) and NiO (Cubic) structures. The crystalline size was calculated by the Scherrer formula, which is 19 nm for the NiO-ZnO photocatalyst. The band gap measurements of the prepared samples were obtained using the Tauc Plot, equation which is 2.93 eV, 3.35 eV and 2.63 eV for NiO, ZnO, and NiO-ZnO photocatalysts, respectively. The photocatalytic performance of NiO-ZnO nanocomposite was evaluated through the degradation of Methylene Blue and Nile Blue dyes under sunlight, and Bentazon herbicide under a UV light. Photocatalyst degradation efficiency was 95% and 97% for Methylene Blue and Nile Blue in 220 min under sunlight while a degradation of 70% for Bentazon after 100 min under UV light source was found.

Mechanistic study of nitrogen-modified titanium dioxide nanoparticles for enhancing the degradation of organic dyes and antibacterial properties under visible-light irradiation

Titanium oxide sulfate, the raw material for one of the industrial preparation methods of titanium dioxide (TiO2), and urea as the nitrogen source were used to synthesize N-modified TiO2 materials (N-TiO2) with different chemical bonding of N elements by a relatively simple homogeneous co-precipitation method, providing a theoretical basis and experimental foundation for the industrial preparation of N-TiO2 photocatalytic materials. According to the analysis of its microscopic morphology, structural composition, and optoelectronic properties, the material consisted of porous spherical clusters formed by the aggregation of spherical nanoparticles. Nitrogen atoms were uniformly distributed on the surface of the material, causing a red shift in its optical response range and a reduction in the electron-hole recombination rate, which contributed to the photocatalytic performance of the material. The conducted photocatalytic degradation experiments of methyl orange and rhodamine B revealed that both dyes can be effectively degraded under visible-light conditions. Methyl orange interacted with the oxygen vacancies and Brønsted acid sites on the surface of the material, converting from an azo structure to a more degradable quinoid structure. In antibacterial experiments, N-TiO2 demonstrated excellent antibacterial properties, which led to a preliminary discussion of its antibacterial mechanism. According to electron paramagnetic resonance investigations and reactive oxygen species (ROS) scavenging experiments, the material can generate multiple ROS at the same time, among which·OH is the key active substance.

Multi-element imaging of urinary stones by LA-ICP-MS with a homogeneous co-precipitation CaC2O4-matrix calibration standard.

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) studies on trace element concentration and their spatial distribution in CaC2O4-matrix urinary stones are important but powerfully rely on matrix-matched external calibration. In this work, CaC2O4 precipitate CaOx-1 which was doped with Mg, Cr, Mn, Fe, Co, Cu, Zn, and Sr was prepared by the homogeneous co-precipitation method. It had a homogeneous distribution of major (RSD of 0.46%) and trace elements (RSD of 1.83-6.92%) due to thenegligible concentration difference compared with that prepared by the heterogeneous co-precipitation method. Based on this, an analytical method for quantitative determination of elemental concentration in CaC2O4-matrix samples was established using CaOx-1 as a calibration standard, and the accuracy of this method was assessed by calibrating theelemental concentration in another synthetic CaC2O4 precipitate CaOx-2 with relative deviation (Dr) from - 11.43% (Mn) to 9.76% (Mg). Finally, a methodology for quantitative imaging of Mg, Cr, Mn, Fe, Co, Cu, Zn, and Sr in urinary stones via LA-ICP-MS was developed. From the elemental distributional maps, an annular texture can be found for Mg, Cu, Zn, and Sr, which corresponds to the annular white and brown texture in the real urinary stone. A homogeneous distribution of Fe and low concentrations of Cr and Co were found throughout the stone, while Mn was highly concentrated in the margin of the stone. All these results demonstrate that quantitative distribution patterns of Mg, Cr, Mn, Fe, Co, Cu, Zn, and Sr can be obtained by LA-ICP-MS using CaOx-1 as a calibration standard, which can provide potential evidence for urological and other medical studies.

Ultrasound assisted synthesis of Fe‐TiO2 and Ce‐TiO2 catalysts and subsequent application for photocatalytic, sonocatalytic, and sonophotocatalytic decolorization of basic Victoria blue dye

AbstractSynthesis of Fe‐TiO2 and Ce‐TiO2 catalysts using conventional, and ultrasound assisted (US) homogeneous coprecipitation method has been investigated. Effects of ultrasonic irradiation time and ultrasonic power on catalyst synthesis were studied and it was elucidated that best conditions were 140 W and 60 min, respectively. Characterization using FE‐SEM revealed spherical particles with the size range from 36.4 to 49.4 nm whereas XRD analysis affirmed a mixture of anatase, rutile, and brookite TiO2 phase with crystallite size ranging from 4.18 to 12.99 nm. BET analysis revealed highest specific surface area (211.59 m2/g) for the sonochemically synthesized Ce‐TiO2. The process intensification benefits demonstrated in catalyst synthesis were better crystallinity, lower particle size, and higher surface area. The application of catalyst efficacy was tested for photocatalytic, sonocatalytic, and sonophotocatalytic oxidation where maximum decolorization as 71.97% was obtained for sonochemically synthesized Ce‐TiO2 applied in the sonophotocatalytic approach. Studies related to regeneration, stability, and leaching of Ce and Ti ion from the sonochemically synthesized Ce‐TiO2 catalyst were also performed. It was observed that the catalyst can be regenerated easily and there were no structural changes in the catalyst after regeneration with negligible leaching of the ions from the catalyst into the solution. Overall, an improved process for catalyst synthesis with intensified decolorization application was demonstrated based on the use of ultrasound.

Synthesis and Characterization of Nd2O3 Nanoparticles Using Urea As Precipitation Agent

Nanoparticles (NPs) of neodymium oxide were prepared by homogeneous co-precipitation method using neodymium nitrate and urea as precursors. X-ray diffraction (XRD) patterns have been refined by the Rietveld method and the Fourier-transform infrared spectroscopy (FT-IR) showed that the sample had a bandgap of about 4.59 eV. On the other hand, the photoluminescence (PL) spectrum indicated that the sample had a low concentration of singly ionized oxygen vacancies. The paramagnetic property of the NPs has been also tested by vibrating-sample magnetometer (VSM) measurements.

Synthesis and characterization of Yb3+ activated Lu2O3 nanoparticles doped optical fiber preform for high power laser application

Yb3+-activated Lu2O3 is known to exhibit excellent thermal conductance, which can be a potential candidate to develop high-power laser fiber. Here we report the synthesis of Yb3+-activated Lu2O3 nanoparticles following the homogeneous coprecipitation method along with their material and optical characterization. Five different samples were synthesized using different concentrations of Cetyl Trimethyl Ammonium Bromide (CTAB) as a cationic surfactant, Yb–Lu ratio in the presence/absence of aluminium (Al) as an additional dopant, followed by calcination at different temperatures. Differential thermal analysis (DTA) and thermogravimetry (TG) analysis were performed to optimize the thermal annealing condition while the X-ray diffraction (XRD) analysis shows the formation of a pure bixbyite structure with an average particle size of ∼ 15 nm at 800°C that reaches up to ∼ 120 nm with increasing calcination temperature to 1400°C. The field emission scanning electron microscope (FESEM) analysis shows nearly cubic morphology while high-resolution Transmission Electron Microscope (HRTEM) analysis confirms the crystalline nature and the average particle size corroborates with the XRD analysis result. The developed nanoparticle was found to exhibit characteristics of Yb-absorption and emission peaks showing no interference with Lu2O3. The emission intensity and fluorescence lifetime of the Yb3+-activated Lu2O3 nanoparticles were found to depend on the Yb concentration, average particle size, and presence of aluminium as a co-dopant. To evaluate the practical application of the developed nanoparticles, an optical preform is developed using synthesized nanoparticles as Yb-source through modified chemical vapor deposition (MCVD) coupled with solution doping (SD) technique and the initial performance of the preform is also reported.

Effects of Mg2+ on enhancing luminescence efficiency for a red long persistent phosphor γ-Zn3(PO4)2: Mn2+

A red long persistent phosphor of γ-Zn3(PO4)2: Mn2+, Mg2+ was prepared through a homogeneous co-precipitation and conventional solid-state calcining method. The crystalline structures and properties of samples were confirmed utilizing X-ray diffractions, scanning electron microscopes, X-ray photoelectron spectroscopies, photoluminescence spectra, decay curves and thermoluminescence spectra. The XRD results reveal that the dopant of Mg2+ will be responsible for the phase transition of Zn3(PO4)2: Mn2+ from α to γ as well as the improvement of the crystallinity of phosphors. The photoluminescence emission spectrum of the red γ-Zn3(PO4)2: Mn2+, Mg2+ phosphor exhibits a prominent peak at 620 nm attributed to the 4T1g-6A1g transition of Mn2+ ion. The luminescence properties of γ-Zn3(PO4)2: Mn2+ can be effectively enhanced by the dopant of Mg2+. The TL curves are employed for the discussion of intrinsic defects. The working mechanism of the persistent luminescence is proposed.

Efficient ammonia synthesis over Ru/CeO2-PrOx catalysts with controlled Ru dispersion by Ru-Pr interaction

Ru/CeO2-PrOx catalysts for NH3 synthesis were prepared using the urea-based homogeneous co-precipitation method, and the effect of Pr-doped CeO2 support on the catalytic activity was investigated. An optimal range of Pr content (25–75 %) improved NH3 synthesis activity. CO pulse adsorption and operando X-ray absorption fine structure (XAFS) measurements revealed that the increase in NH3 synthesis activity was due to the improvement in Ru dispersion by the interaction between PrOx and Ru, rather than the generally discussed Ce3+/Ce4+ ratio. However, excess Pr doping prevented the Ru reduction and formation of active sites. In this Ru/CeO2-PrOx catalyst system, the activity is governed by the number of active sites that can be controlled by the Pr content. In the high-pressure evaluation (5 MPaG), the NH3 synthesis rate of the Ru/CeO2-PrOx catalyst (Ce/Pr = 1) was 9.0 mmol g-1h−1, which is 1.4 times higher than that of the Ru/CeO2 catalyst.

Potential of Fluoride-Containing Zinc Oxide and Copper Oxide Nanocomposites on Dentin Bonding Ability.

Despite recent advances in bonding restorations, which are the basis of restorative dentistry, secondary caries are still able to form. Previously, a novel fluoride-containing zinc and copper (ZCF) nanocomposite was introduced to prevent the formation of caries due to its antibacterial activity. In this study, we studied the impact of ZCF nanoparticles on the adhesive strength of bonding restorations through micro-tensile bond strength (µTBS) testing. The impact of antibacterial and matrix metalloproteinase (MMP) inhibitors on the nanoparticles was also examined. The nanocomposites were prepared using a simple one-step homogeneous co-precipitation method at a low temperature. A self-etch adhesive was applied to 10 extracted caries-free human molars with (test group) and without (control group) the ZCF nanoparticles. This was followed by composite resin build-up and µTBS testing, MMP activity assays, and evaluation of the antibacterial effects. The results showed no significant differences in the µTBS between the ZCF and the control groups. However, the ZCF exhibited a significant inhibitory effect against MMP-2, MMP-8, and MMP-9, in addition to an antibacterial effect on Streptococcus mutans. Therefore, the present study demonstrated that the addition of ZCF nanoparticles to adhesive systems can result in MMP inhibition and antibacterial action while maintaining the mechanical properties of the bonding restorations.

Morphology controllable synthesis of GdOF nanocrystals and application in theranostic purpose

In this present paper, GdOF nanostructures have been synthesized by the urea based homogeneous coprecipitation method combining with high temperature (500 °C) calcination in presence of N2. The nanostructures were structurally characterized by X-ray diffraction in conjunction with Rietveld refinements. The effects of pH of the reaction medium on the shape, size and morphology were explored and discussed in detail. The formation of GdOF nanostructures were represented with proper reaction mechanism elaborately. Vibrational energies of different bonds and defects states in our desired crystal structures were investigated using FTIR and Raman spectroscopy respectively. Under ultraviolet excitation, the GdOF nanomaterials show violet, blue and green emissions and get information about band edge energies. Based on its photoluminescence property, generation of reactive oxygen species (ROS) was investigated in detail.

Effect of Ti-promoting on propane dehydrogenation over porous Zn-based catalysts: A strategy to enhance activity and selectivity

In this work, low-cost and environmentally friendly catalysts Ti-doped ZnAl2O4 spinel were prepared by a homogeneous co-precipitation method and employed to catalyze propane dehydrogenation. In situ FTIR revealed that Ti accelerated the conversion of zinc propyl species (intermediate species) to propene, which is rate-determining step for propane dehydrogenation over active site coordinatively unsaturated Zn (Zncus). Characterizations, such as H2-TPR, temperature programmed surface reaction (TPSR) and C3H6-TPD illustrated that Ti improved oxygen mobility resulting in the improved catalytic activity, and promoted desorption of propene leading to significant enhancements in propene selectivity and the stability of catalyst. Zn1.5Ti1Al2 exhibited an excellent catalytic performance due to the existence of more Zncus, at 43% C3H8 conversion, a 84% of C3H6 selectivity was obtained at 500 ° C. The deactivation of Ti-doped ZnAl2O4 spinel is due to the formation of coke rather than the reduction of Zn species. This work provided an effective strategy to improve the catalytic activity of Zn-based catalysts for propane dehydrogenation.

Synthesis and characterization of Tm2O3-doped Lu2O3 nanoparticle suitable for fabrication of thulium-doped laser fiber

Synthesis of Tm2O3-doped Lu2O3 nanoparticle using homogeneous co-precipitation method along with its material/optical characterization is reported. Four different compositions with variation of Tm: Lu ratios are synthesized followed by calcination at different temperatures (800, 1000 and 1200 °C) was performed to optimize the synthesis process as well as composition. The XRD analysis indicates steady growth of particle size with increasing calcination temperature and an average particle size of 100 nm was achieved at 1200 °C. Pure bixbyite structure was observed for every sample independent of Tm: Lu ratio. The FESEM and HRTEM analysis associated with EDX indicates formation of pure crystalline particles and results are in good agreement with XRD analysis. The photoluminescence spectra observed under 808 nm excitation exhibit characteristic Tm emission peak that extended beyond 2 micron region the intensity of which is strongly depends on Lu: Tm ratio as well as calcination temperature. The overall result reveals that the synthesized material which indicates good thermal stability is a potential doping material for the development of Thulium-doped fiber suitable for eye-safe laser application.

Re-utilization of spent Cu2+-immobilized MgMn-layered double hydroxide for efficient sulfamethoxazole degradation: Performance and metals synergy

Abstract MgMn-layered double hydroxide (MgMn-LDH) was fabricated by a homogeneous co-precipitation method. MgMn-LDH exhibited excellent Cu2+ immobilization with the maximum removal capacities of 668 mg·g−1. Based on the outstanding fixation ability, the feasibility of re-utilization of spent Cu-MgMn-LDH as catalyst for drug degradation was investigated. Calcination in muffle furnace at 300 °C strengthen the stability of spent Cu-MgMn-LDH and obtained CuO-MgMn-LDO-300. As-obtained CuO-MgMn-LDO-300 consisted of CuO, Mg2MnO4 and MgO. CuO-MgMn-LDO-300 exhibited superior catalytic performance, almost 97% of sulfamethoxazole (SMX) was removed within 30 min. The TOC removal for CuO-MgMn-LDO-300 reached to 76%, while that of MgMn-LDO-300 was only 5%. These were profit from convenient electronics transfer due to oxygen vacancy and synergism between Cu and Mn. Therefore, CuO-MgMn-LDO-300 could effective activate persulfate (PS) to generate 1O2 and SO4– for SMX degradation. The performance showed good adaptability in a wide pH (from 3 to 9), low dissolution of Cu and Mn verified the security of re-utilization. Moreover, more than 95% of ciprofloxacin (CIP), tetracycline (TC) and sulfadiazine (SD) could also be degraded by the obtained materials. The catalysis system of CuO-MgMn-LDO-300 was also effective applied in lake and river water contaminated by SMX. Hence, the re-utilization strategy of spent Cu-MgMn-LDH was feasible and obtained an excellent catalytic material for antibiotics degradation.

Efficient Color Tuning of Upconversion Luminescence from Core-Shell Oxysulfide Nanoparticles

The Y2O2S:Er3+@Y2O2S:Yb3+,Ho3+ core-shell up-conversion (UC) nanoparticles were successfully synthesized by the homogeneous co-precipitation method. The Y2O2S:Er3+@Y2O2S:Yb3+,Ho3+ core-shell nanoparticles exhibit bright green emissions under 980 nm excitation, while the triple-ion doped Y2O2S:Er3+,Yb3+,Ho3+ sample presents mainly red emissions. The intensity ratio of green-to-red emission of the core-shell and conventional triple-ion doped samples are 2.8 and 0.3, respectively. Investigations on the UC mechanisms show that emissions from Er3+ and Ho3+ ions are achieved simultaneously in the core-shell nanoparticles. This is due to the efficient energy transfers of Yb3+→Ho3+ within the shell layer and Yb3+→Er3+ between the shell and the core. While the triple-ion doped Y2O2S: Er3+,Yb3+,Ho3+ sample exhibits mainly the emissions of Er3+ along with weak luminescence of Ho3+ ion. Since the cross relaxation between Er3+ and Ho3+ ions in the Y2O2S:Er3+,Yb3+,Ho3+ nanoparticles can effectively suppress the emissions of Ho3+ ions. Yet, in the core-shell structure, this cross relaxation can be successfully restrained in the core-shell structure where Er3+ is in the core and Ho3+ is in the shell. Therefore, the construction of core-shell structure can improve the luminescence efficiency and provide a route for adjustment of emission color.

Multi metal oxide NiO-CdO-ZnO nanocomposite–synthesis, structural, optical, electrical properties and enhanced sunlight driven photocatalytic activity

In this article, ternary oxide NiO-CdO-ZnO nanocomposite along with pure NiO, CdO and ZnO were prepared by the homogeneous co-precipitation method. The XRD pattern confirmed the formation of nanocomposite with NiO (cubic)–CdO (cubic)–ZnO (hexagonal). The volume fractions were 38% NiO, 6% CdO and 56% ZnO phase in nanocomposite determined by direct comparison method. Crystallite size and lattice strain were calculated using Scherrer plot, Williamson-Hall and Size-Strain plot methods. The UV–vis was used to study optical properties such as bandgap (Eg), refractive index (n), extinction coefficient (k), optical conductivity (σopt) and dielectric constants (εr, εi). FTIR and Raman analyses have confirmed the successful formation of NiO-CdO-ZnO nanocomposite. The current-voltage measurements revealed that nanocomposite has high electrical response. SEM images shown that nanocomposite has roughly spherical morphology and EDX described that Zn has higher concentration than Ni and Cd. PL spectra of nanocomposite demonstrated the emission bands associated with new energy levels induced by defects. The photocatalytic activity of grown nanocomposite against rhodamine B (RhB) and methylene blue (MB) dyes under sunlight revealed high degradation efficiency 99% for RhB and 98% for MB in 60 and 90 min illumination respectively, indicated that grown nanocomposite is a propitious sunlight-driven photocatalyst to eliminate organic toxins.

Synthesis, Characterization and Anti-Microbial Activity of Oxalate-Assisted CO3O4 Nanoparticles Derived from Homogeneous Co-Precipitation Method

Nano-sized cobalt oxide particles exhibit unique and fascinating physical, chemical and anti-microbial activity owing to their large surface to volume ratio. The study of metal oxide nanoparticles interaction with pathogenic microorganisms is great importance for various biomedical applications. The main purpose of this work is to study the anti-bacterial and anti-fungal behavior of cobalt oxide (CO3O4) nanoparticles against gram-positive and gram-negative bacterial strains and different fungi. The structure and morphology of CO3O4 nanoparticles were characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and UV-Visible Spectroscopy, respectively. The CO3O4 nanoparticles showed a significant anti-bacterial activity against two gram-positive bacteria, Staphylococcusaureus (G[Formula: see text]), Streptococcus mutans (G[Formula: see text]), and two gram-negative bacteria, Klebsilla pneumonia (G[Formula: see text]), E. coli (G[Formula: see text]), and it shows a good anti-fungal activity against the two different fungal i.e., Aspergillus flavus (F) and Aspergillus niger (F), at different solvents. It was noted that synthesized CO3O4 nanoparticles exhibited the solvent-dependent anti-bacterial activity against all tested bacterial strains. CO3O4 NPs could be employed effectively for anti-microbial applications.

Antibacterial effect of a fluoride-containing ZnO/CuO nanocomposite

Dental materials that are antimicrobial and acid-resistant can inhibit bacterial colonization and demineralization, thereby preventing caries. Zinc and copper are well-known for their antibacterial effect, as is nanostructured ZnO–CuO composite. Minerals such as fluorine and calcium, can remineralize and demineralize teeth. Therefore, we developed novel fluoride-containing ZnO–CuO (ZCF) nanocomposites; to the best of our knowledge, these are the first nanocomposites of this kind. The fluoride concentrations and antibacterial effects of the ZCF nanocomposites were evaluated.Nanocomposites comprising zinc and copper (ZC), and zinc, copper, and fluorine (ZCF), were prepared by a simple one-step homogeneous coprecipitation method at a low temperature (80 °C), without the use of organic solvent or surfactant.The structure and composition of the ZC and ZCF nanocomposites were examined by scanning electron microscopy–energy-dispersive spectroscopy (SEM-EDS). Quantitative analysis of the mass concentration was performed by using ZAF correction methods. The fluorine content in nanocomposites was evaluated by using proton-induced gamma emission (PIGE) at the Takasaki Advanced Radiation Research Institute in Japan. By using 96-well microtiter plates, we analyzed the antibiotic susceptibility of ZC, ZCF, and the control buffer (phosphate-buffered saline) with Streptococcus mutans (ATCC 25175).The SEM images showed that ZC and ZCF nanocomposites were composed of 3D flower-like microstructures with diameters of approximately 1 μm. Environmental SEM-EDS analysis revealed that ZC contained 43.2% Cu, 55.1% Zn, 2.2% F, and 0.1% Cl, whereas ZCF contained 47.5% Cu, 40.5% Zn, 6.7% F, and 5.9% Cl.Analysis by PIGE showed that ZCF nanocomposite contained 2553.6 ± 199.2 ppm fluorine, whereas no fluoride was detected in ZC. The control buffer enabled bacterial growth to 4 × 107 ± 9 × 106 CFU/mL, whereas ZC allowed growth of 12 ± 8 CFU/mL, and ZCF showed no bacterial growth.Thus, we developed novel fluoride-containing ZnO–CuO nanocomposites, which exhibited antibacterial effects and have the potential for remineralization, thereby demonstrating their potential as multifunctional dental materials.

One-Pot Synthesis of Ru-Doped ZnO Oxides for Photodegradation of 4-Chlorophenol

The photocatalytic degradation of 4-chlorophenol in water using Ru-doped ZnO mixed oxides (0, 0.5, 1, and 3 wt% RuO2) synthesized by the one-pot homogeneous coprecipitation method is reported. ZnO with wurtzite structure was present in the mixed oxide as corroborated by Raman spectroscopy and X-ray diffraction analysis. All the samples showed nanorod morphological features. The presence of Ru6+/Ru4+ couples on ZnO modified the band gap of the mixed oxides and led to a shift of the band gap energy from 3.20 eV to 3.07 eV. Ru addition increased the surface area and significantly promoted the formation of active surface oxygen species such as hydroradicals evidenced by the fluorescence spectroscopy measurement. In the photodegradation of 4-chlorophenol solution under UV irradiation, a notable increase in photoactivity was obtained as the amount of RuO2 in the mixed oxides increased to 3 wt%. The charge transfer between Ru6+/Ru4+ couples and ZnO nanoparticles together with the formation of free radical oxidant species effectively inhibits electron-hole recombination rate, thus favoring the photodegradation of 4-chlorophenol.

Photoluminescence properties of (Y1−xCex)3Al5O12 (x = 0.005–0.03) nanophosphors and transparent ceramic by a homogeneous co-precipitation method

Fine and dispersed (Y1−xCex)3Al5O12 (x = 0.005–0.03) nanophosphors were co-precipitated uniformly using a homogeneous co-precipitation process. With an excitation wavelength λex of 455 nm, the YAG:Ce phosphors showed strong luminescence with maxima at 550 nm in the range of 475–650 nm. The emission intensity becomes stronger due to the improved crystallinity and decreased surface defects of the resultant phosphors with increasing calcination temperatures. The quenching concentration of Ce3+ was 1.5 at% and the quenching mechanism was Ce–Ce interactions and lattice defects. The fluorescence lifetime of the phosphors decreased with increasing Ce concentrations and temperatures. The mechanism is influenced by defects both in surface and body. The resultant YAG:Ce powders showed an excellent sintering activity and can be sintered into transparent ceramic under vacuum technique. Compared with the phosphors, the transparent ceramic exhibits stronger luminescence properties and shorter fluorescence lifetime.

ZnO and carbon nanocomposites for enhanced photoelectrochemical sensing activity: influence of the carbon content

In this work, carbon and zinc oxide (ZnO:C) nanocomposites were obtained by a hydrothermal reaction process. ZnO nanoparticles were first prepared by a homogeneous coprecipitation method. Nanocomposites with atomic concentrations of carbon ranging from 39.4 to 69.7 wt.% were then attained. The microstructure and morphology of each prepared nanocomposite was investigated by X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). The ZnO:C nanocomposites were found to present a wurtzite-type hexagonal crystalline structure that shifted towards an amorphous state with increasing C content. Results showed that incorporating the covalent carbon at O sites in the ZnO lattice causes lattice compression. Due to their low band-gap energies, the photoresponses of the ZnO:C nanocomposites extended into the visible region. The sensing characteristics of ZnO:C nanocomposite films were also investigated, and a major improvement in the photoelectrochemical (PEC) efficiency was obtained when the C content was 39 wt.%.