ZnAl2O4 Nanoparticles Research Articles

Optical properties of Cr doped ZnAl2O4 nanoparticles with Spinel structure synthesized by hydrothermal method

Zn1−xCrxAl2O4 (x = 0, 0.01, 0.03, 0.05 and 0.07) nanoparticles were synthesized by hydrothermal method and heat treatment technology, and the effects of Chromium doping ratios on the microstructure, morphology, element distribution, binding energy and optical property of the samples were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), x-ray energy dispersive spectroscopy (XEDS), x-ray photoemission spectroscopy (XPS), ultraviolet-visible (UV–vis) spectroscopy, photoluminescence spectra (PL) and fourier transform infrared spectroscopy (FT-IR). The experimental results show that Zn1−xCrxAl2O4 nanoparticles possess cubic spinel structure without other impurity phases. The average crystallite size decrease and the lattice parameter increase with the increase of Cr doping concentration. The morphology of the samples exhibits irregular spherical or ellipsoid particles with uniform particle size. XEDS spectra display Cr3+ successfully used as doping agent replaced Zn2+ and entered ZnAl2O4 matrix. XPS spectra demonstrate that the doped Cr ions mainly occupy the tetrahedral sites in Zn0.95Cr0.05Al2O4 sample. UV–vis spectra indicate the band gap of the doped sample decrease and exhibit red shift with the increase of Cr ion concentration. The intensity of FT-IR spectra for Zn1−xCrxAl2O4 samples decreases slowly and occurs red shift. PL spectra show the intensity decrease and occur luminescence quenching phenomenon for Cr doped sample.

Green Synthesis of Zinc based Nanoparticles for Thermal Industry based Applications

Spinel ZnAl2O4 nanoparticles were prepared effectively by simplistic, economical microwave heating method using Hibiscus rosa-sinensis extract as reducing agent. The samples were successfully characterized by XRD pattern, EDX spectra, FT-IR analysis, HR-SEM analysis, and VSM instrumentation techniques. XRD, EDX and FT-IR results demonstrated that the products contain a pure single-phase spinel structure lacking of other secondary phase impurities. SEM results confirmed the spherical shaped nanoparticle morphology of the sample. Magnetic characterization property was confirmed by VSM analysis. VSM hysteresis loop established the superparamegnetism of the sample and the magnetization (Ms) value of ZnAl2O4 is 0.023 emu/g.

Zinc aluminate nanoparticles: Preparation, characterization and application as efficient and economic catalyst in transformation of waste cooking oil into biodiesel

In this study, an efficient and economic transesterification process for waste cooking oil (WCO) using methanol was contemplated. The process was preceded using zinc aluminate nanoparticles as heterogeneous catalyst. High purity porous ZnAl2O4 nanoparticles with polycrystalline nature were effectively prepared using co-precipitation technique at two annealing temperatures of 700 and 800 °C. The prepared ZnAl2O4 nanoparticles were described using FTIR, XRD, EDX, and SEM spectroscopy. The structure, morphological and chemical properties of the ZnAl2O4 catalyst annealed at 800 °C showed high reactivity compared to that annealed at 700 °C. The transesterification process parameters were studied, including catalyst dose, conversion temperature, time of the process, and the ratio of oil to methyl alcohol. The optimized process conditions were produced a maximum biodiesel yield of 94.88% after 3 h at 100 °C using 5 wt% catalyst and 1:18 oil/methanol ratio. The physicochemical properties of the obtained biodiesel were in accordance with the biodiesel standards D-6571 (ASTM) and the Egyptian standards EN 14214.

Effect of pH on material properties of ZnAl2O4:Cr3+ nano particles prepared by sol–gel method

ZnAl2O4 nanoparticles (NPs) doped with Cr3+ (1.0 mol%) were prepared by citric acid assisted sol–gel method at pH values of 3, 5, 7, 9, 11 and 13 with the use of ammonia as pH controller. Analysis of x-ray diffraction (XRD) spectra show that the synthesized ZnAl2O4 NPs are cubic structured and the pH did not affect the structure significantly. The average crystallite size increases with an increase in pH. The photoluminescence (PL) intensity was found to be minimum and maximum for the sample synthesized at pH 3 and pH 13, respectively. The PL emission intensity was found to depend on the synthesis pH conditions. The scanning electron microscope (SEM) revealed that the morphology of ZnAl2O4:Cr3+ NPs changed with the pH values of the solution. Ultraviolet–visible (UV–Vis) measurements show that reflectance is maximum in UV and visible region for sample synthesized under acidic pH of 5. The energy band gap energy was tuned from 3.10 to 3.88 eV with increase in pH value from 3 to 13. It was observed that a strong alkaline nature of the solution enhances the structural and optical properties of ZnAl2O4:Cr3+ nanostructures.

High surface area ZnAl2O4/reduced graphene oxide nanocomposites with enhanced photocatalytic performance

AbstractIn this study, the fabrication of ZnAl2O4/reduced graphene oxide nanocomposites is reported for the initial time. Two nanocomposites, ZnAl2O4/reduced graphene oxide‐50 and ZnAl2O4/reduced graphene oxide‐100, with different reduced graphene oxide contents (50 mg/ml and 100 mg/ml initial graphene oxide concentration respectively) were synthesized via a hydrothermal route; and characterized with the aid of suitable characterization and analytical techniques. For comparative purposes, two pure ZnAl2O4 samples were fabricated by citrate sol‐gel and urea combustion methods. The photocatalytic activity of the synthesized pure nanospinels and nanocomposites was studied for the degradation of rhodamine B dye under ultraviolet–A light irradiation. Compared to pure ZnAl2O4 nanoparticles, ZnAl2O4/reduced graphene oxide nanocomposites exhibited superior photocatalytic activity. The highest efficiency was observed for ZnAl2O4/reduced graphene oxide‐100 composite, where; full degradation of rhodamine B occurred after 45 min. The enhancements of the photocatalytic performance of ZnAl2O4/reduced graphene oxide composites were mainly attributed to unique electronic and surface properties of reduced graphene oxide.

Synchrotron X-ray absorption spectroscopy and cation distribution studies of NiAl2O4, CuAl2O4, and ZnAl2O4 nanoparticles synthesized by sol-gel auto combustion method

An array of modern approaches to X-ray including X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) were employed to examine the local atomic structure, cation distribution, and degree of inversion of nanocrystalline metal aluminate MAl2O4 (M = Ni, Cu, Zn) powders produced using the sol-gel auto combustion technique. All samples were revealed to display single-phase cubic spinel structure with Fd-3m space group, as established by the XRD results. The cation distribution within these aluminate spinel structures were completely unique as suggested by the divergent disparity in comparative intensity between (220), (400), (422), and (440) diffraction plans for each XRD pattern. Rietveld refinement examination of the XRD data validates the ZnAl2O4 samples as having normal spinel structure, while CuAl2O4 and NiAl2O4 samples comprise partially-inverse spinel structures with low and high degree of inversion, respectively. The investigative findings gained from experimental Ni, Cu, Zn, and Al K-edge XANES spectra accommodated with the hypothetical computation of absorption spectra using the FEFF9.7 code reinforce this. Four-fold synchronization with oxygen atoms was demonstrated by all Zn ions discovered in the ZnAl2O4 samples. Conversely, the Ni and Cu ions located in the NiAl2O4 and CuAl2O4 samples tend to be synchronized in both tetrahedral and octahedral fashion by four or six oxygen atoms, respectively. Additionally, M2+ altering from Zn2+ ions to be Cu2+ and Ni2+ ions caused a substantial translocation of divalent metal (M2+) ions from the tetrahedral (A) sites to octahedral (B) sites, as clearly demonstrated by the EXAFS spectra. Specifically, the degree of inversion in these metal aluminates is completely dissimilar and identified as 0.83 for NiAl2O4, 0.42 for CuAl2O4 and 0 for ZnAl2O4, as indicated by the curve-fitting analysis of Ni, Cu, and Zn K-edge EXAFS spectra. These values comprise vital data for comprehension of numerous pertinent properties.

Long-lasting green, yellow, and red phosphorescence of carbon dots embedded on ZnAl2O4 nanoparticles synthesized by a combustion method

This work presents the luminescent, structural and morphological properties of carbon dots (CDs) synthesized on ZnAl2O4 (ZAO) by a simple combustion method. The samples were annealed at different temperatures (600 °C, 700 °C, 800 °C, and 900 °C) in order to change the concentration and size of the CDs on ZAO. The XRD patterns indicated that the annealed samples present a cubic phase (spinel structure). According to the TEM analysis, the CDs on ZAO (CZAO) have a particle size in the range of 2.0–4.0 nm. The annealing treatment, allowed to tune their luminescence emission from green (517 nm) to red (650 nm) under excitation with blue light (455 nm). Yellow, orange, and red phosphorescence were observed for the first time from CDs. The green/yellow and orange/red phosphorescence lasted 5 min and 15 min, respectively, which are the longest phosphorescence times reported for CDs. It is proposed that CDs’ luminescence originates from the deep levels formed after the annealing treatment. Due to the color tunability presented by the CDs in fluorescence and phosphorescence, the CZAO samples can be useful for applications in biolabeling, bioimaging, lighting, and signaling for buildings and roads.

Optical properties and versatile photocatalytic degradation ability of MAl2O4 (M = Ni, Cu, Zn) aluminate spinel nanoparticles

Nanocrystalline NiAl2O4, CuAl2O4 and ZnAl2O4 aluminate spinels were successfully synthesized by the sol–gel auto combustion method using diethanolamine as a novel fuel. The structures, morphologies, particle sizes, and optical properties of these aluminate particles were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and UV–Visible diffuse reflectance spectroscopy (UV-DRS). All characterization results confirmed that a single-phase spinel structure was obtained for all calcined aluminate powders with various crystallite sizes (40–60 nm) and distinct band gap energies, E g (3.0–5.5 eV). The photocatalytic activity of NiAl2O4, CuAl2O4 and ZnAl2O4 nanoparticles were evaluated by the decomposition of four types of pollutants: phenol rhodamine B, heteropolyaromatic methylene blue, azoic methyl orange, and methyl red under ultraviolet irradiation. The photocatalytic degradation efficiencies of all organic dyes by aluminate spinels reach 80–95% within 100 min. These results suggested that NiAl2O4, CuAl2O4 and ZnAl2O4 can serve as photocatalysts for the degradation of a wide range of organic pollutants in environment.

Novel green synthesis of ZnAl2O4 and ZnAl2O4/graphene nanocomposite and comparison of electrochemical hydrogen storage and Coulombic efficiency

Abstract In this experimental work, a green biosynthesize method was used to synthesis of ZnAl2O4 nanoparticles. To synthesis of the ZnAl2O4 spinel, beside the Zn2+ and Al3+ sources, olive leaf and green tea extracts were used as reagents. The Electrochemical hydrogen storage performance of ZnAl2O4 synthesized via olive leaf and green tea extracts were compared via chronopotentiometry method in aqueous KOH electrolyte, for first time. The hydrogen storage capacity of ZnAl2O4 spinel enhanced by synthesize nanocomposite of ZnAl2O4 with graphene nanosheet. Also, different analysis were served to study the products structure, composition and morphologies. The porous structure of samples was investigated by BET analysis. X-ray diffraction (XRD) patterns were used to investigate the phase and purity of the synthesized nanostructures. Energy dispersive X-ray spectroscopy (EDS) was used to obtaine the chemical compositions of the nanostructures and also to approve the XRD results. To further study the chemical composition of the products, Fourier transform infrared (FT-IR) analysis was served. The products size and morphology was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. The results showed that the reagents specially olive leaf and green tea extracts had significant role in product size and morphology.

Influence of pH tuning at the precursor-preparation process on the structural characteristics and catalytic performance of hydrothermally synthesized ZnAl2O4 nanoparticles

ABSTRACTThe relationship between the structural characteristics of hydrothermally synthesized ZnAl2O4 nanoparticles and the pH of the source solution used during the precursor preparation process was investigated. A pH of approximately 9 was the turning point between large and small crystallite-sized regimes, and between stoichiometric and nonstoichiometric compositions. This difference can likely be attributed to the formation process of ZnAl2O4, because the stabilities of the Zn2+ and Al3+ hydroxides in the source solution change at pH 9. Additionally, we compared the catalytic performance with regards to the decomposition of methylene blue for the nanoparticles made from source solution with pH 7 (NP7) and 10.5 (NP10.5). The smaller-sized NP7 did not show any catalytic performance; whereas, the larger NP10.5 accelerated the decomposition of methylene blue. The critical difference between NP7 and NP10.5 is the Zn2+ deficiency, rather than the particle size. This result is important for future investigations in order to improve the catalytic properties of ZnAl2O4 nanoparticles.

Effects of Cobalt Doping on the Microstructure and Optical Properties of ZnAl2O4 Nanoparticles

Co-doped ZnAl2O4 nanoparticles were prepared by hydrothermal method. The samples were characterized by XRD, HRTEM, EDX, FT-IR, XPS, PL, and UV–Vis, and the effects of cobalt doping on the microstructure and optical property of the samples were studied. The experimental results showed that Co-doped ZnAl2O4 nanoparticles synthesized by this method are single phase with cubic crystal structure, no other impurity phases were observed. Furthermore, with increasing the Co2+ concentration, the average crystallite size of the Co-doped samples became smaller. The absorption bands in FT-IR spectra are broadened in the low frequency region, the PL spectra had the red-shift and the UV–Vis peaks intensity gradually enhanced.

Facile synthesis of phase pure ZnAl2O4 nanoparticles for effective photocatalytic degradation of organic dyes

The present work focuses on the surfactant mediated synthesis of ZnAl2O4 nanoparticles (1−3) using sol–gel method. 1 has been synthesized without any surfactant and during the synthesis of 2 and 3 cationic (cetyltrimethylammonium bromide) and anionic (sodium lauryl sulfate) surfactant, respectively, have been added. 1–3 have been characterized by P-XRD, FT-IR, SEM, SAED, TEM and BET techniques which suggest that surfactant reduces the particle size of ZnAl2O4 nanoparticles to half (12 nm in 1, 6 nm in 2 and 3). Zeta (ζ) potential measurements have been performed to determine the surface charges of all the samples. Moreover, the photocatalytic activities of these ZnAl2O4 nanoparticles have also been investigated. 2 exhibits better adsorption (28–41%) and degradation (97–99%) efficiency for anionic dyes due to high surface area (129.62 m2 g−1) and positively charged surface (ζ potential 30.06 mV). Radical trapping experiments suggest O2− and OH to be the major reactive species for the degradation of dyes.

Cr‐doped ZnAl2O4: Microwave solution route for ceramic nanoparticles from metalorganic complexes in minutes

AbstractA combination of microwave irradiation and metalorganic precursors in solution was used for the synthesis of Cr:ZnAl2O4nanoparticles with high yields (~92%). Though the spinel phase is formed after ~40 minutes, 60 minutes of microwave irradiation was required for the complete transformation of precursors into the spinel. The as‐prepared material is nanocrystalline and phase‐pure and was subjected to annealing in air at different temperatures. Annealing improved the crystallinity, and the material turned pink at 1200°C. The structural and optical properties were investigated by XRD, HR‐TEM, FE‐SEM, FT‐IR, diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The two bands in the excitation spectra (400 and 540 nm) became more intense as the annealing temperature was raised. The 400 nm band was asymmetric and consisted of two peaks, suggesting a trigonal distortion. The emission spectra consisted of a zero phonon line (ZPL), along with its associated multi‐phonon side bands. The high Dq/B (3.21) suggested the presence of Cr3+in a strong crystal field. With annealing, the emission lifetimes increased from ~7 to ~34 ms. This work demonstrates rapid, low‐temperature synthesis of a red‐emitting phosphor, with potential applications in bio‐imaging, sensors, and lighting.

Rapid annealing: A novel processing technique for Cr:ZnAl2O4 nanoparticles

Nanocrystalline Cr:ZnAl2O4 was synthesized for the first time by rapid thermal annealing the corresponding hydroxide precipitate in just 10 min. The XRD patterns showed that synthesis between 500 °C and 700 °C had smaller crystallites (∼2.4 – 4 nm), while at 800 °C and 900 °C, had ∼10 nm crystallites. HRTEM images of the 900 °C sample showed the well-developed lattice fringes confirming the high crystallinity. The particles were polyhedral having an average size of ∼16 nm. The diffuse reflectance spectra showed characteristic 4A2g → 4T1g and 4A2g → 4T2g transitions, while the photoluminescence emission spectrum comprised of the zero phonon line (R-line) along with other multi-phonon side bands that are characteristic of the spin – parity forbidden transitions of the Cr3+ ion. The emission spectra and photoluminescence lifetimes are comparable with reports on sensing and imaging applications. Our work demonstrates the suitability of this technique to quickly synthesise phosphors for a variety of applications.

Structural, optical and electrical properties of ZnO/ZnAl2O4 nanocomposites prepared via thermal reduction approach

ZnO/ZnAl2O4 nanocomposites (Z r A-MMO) with homogeneously distributed ZnAl2O4 nanoparticles in the interpenetrating network of ZnO were successfully prepared via two-step solution process, namely co-precipitation of Zn/Al–NO3 layered double hydroxide (Z r A-LDH) precursor and thermal treatment methods. The effect of cation molar ratio (r) between Zn2+ and Al3+ on the morphological, structural, thermal, optical as well as electrical properties of ZnO-based MMOs was investigated in detail. A mechanism study related to the surface modification, optical band edge alteration as well as improvement of electrical conductivity after phase transformation from LDH to MMO was also elucidated. The optimum Z5A-MMO sample presents the highest electrical conductivity of 8.23 × 10−3 S/cm as compared to 7.26 × 10−7 S/cm for the standard ZnO nanocrystal. It is believed that the bathochromic shift in optical band gap of Z5A-MMO plays a pivotal role in facilitating the photoemission process and leads to the increase in number of carrier concentration in the sample. This method could provide alternative pathways for fabricating a high electrical conductivity MMO-based material and benefit in future optoelectronic devices.

Multifunctional magnetic-fluorescent Ni-doped ZnAl2O4 nanoparticles with second biological NIR window fluorescence

Nanocrystals with combined properties of magnetic and fluorescence are considered as “multifunctional materials” or “smart materials” which have promising biological applications including dual-modal imaging, biological research, targeted drug delivery, clinical diagnostics and therapeutics. Utilizing a green hydrothermal method, magnetic nanocrystals Ni-doped ZnAl2O4 with broadband emission at ∼1200nm have been developed as a new type of multifunctional material. The obtained ultrasmall nanocrystals in sub-10nm range are more easily for body clearance and less toxicity in theory. Ni ions are demonstrated distribute homogeneously in +2 valance state, which provides ferromagnetism in the diamagnetic matrix of ZnAl2O4. Under the excitation of 670nm, the whole broad emission band centered at 1200nm fully covers the second near-infrared window (1.1–1.4μm). These ultrasmall Ni-doped ZnAl2O4 nanocrystals with magnetic-fluorescent multifunctionality open a door to more efficient and safer biological probes.

Synthesis and characterization of spinel metal aluminate by a simple microwave assisted green synthesis

In the current research report we present a simple, eco-friendly, cost and time saving biosynthesis of ZnAl2O4 spinel nano and micro particles using Pomegranate peel extract, that act as the reducing as well as stabilizing agent. Thus synthesized products are then consistently characterized under powder X-ray diffraction (PXRD), scanning electron microscopy (SEM). The powder XRD analysis has confirmed their chemical composition. Optical properties including diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and fourier transform infrared spectroscopy (FTIR) are also investigated. The ZnAl2O4 nanoparticles formation is been confirmed by PXRD, FT-IR and SEM. From XRD the calculated crystalline size of the ZnAl2O4 nanoparticles is in the range of 11.2 nm.

Microwave solution route to ceramic ZnAl2O4 nanoparticles in 10 minutes: inversion and photophysical changes with thermal history

Within 10 minutes microwave synthesis using metal complexes can form crystalline ZnAl2O4 nanoparticles with significant inversion.

Investigation of catalytic activity of ZnAl2O4 and ZnMn2O4 nanoparticles in the thermal decomposition of ammonium perchlorate

ZnAl2O4 and ZnMn2O4 nanoparticles were synthesized by a modified co-precipitation method and characterized by means of Fourier transform infrared spectroscopy, X-ray diffraction, energy-dispersion X-ray spectrometer, and their morphology investigated by means of scanning electron microscopy. The effects of these nanoparticles on the thermal decomposition of ammonium perchlorate (AP) were examined by differential scanning calorimetery and thermogravimetery analyses. The results revealed that ZnAl2O4 nanoparticles have little catalytic effect on this process, but ZnMn2O4 nanoparticles have good catalytic effect on decreasing the decomposition temperature of AP and increasing the released heat. ZnAl2O4 and ZnMn2O4 nanoparticles increased the released heat of AP decomposition from 400 to about 736 and 1130 Jg−1, respectively, and AP decomposition temperature decreased from 420 to 400 and 358 °C in the same order. The higher catalytic activity of ZnMn2O4 can be due to its p-type semiconductivity and the presence of some positive hole and defects. Also, the kinetic parameters such as pre-exponential factor and activation energy were calculated using Kissinger method.

ZnAl2O4 Nanoparticles as Efficient and Reusable Heterogeneous Catalyst for the Synthesis of 12-phenyl-8,12-dihydro-8,10-dimethyl-9H-naphtho[1′,2′:5,6] pyrano[2,3-d] pyrimidine-9,11-(10H)-diones Under Microwave Irradiation

ABSTRACTA simple and one-pot synthesis of naphthopyranopyrimidines is reported by the three-component condensation reaction of aldehydes, β-naphthol, and 1,3-dimethylbarbituric acid using ZnAl2O4 nanoparticles under microwave irradiation. This flexible and nano-catalytic procedure showed good recyclability and provides a clean condensation reaction in a short reaction time.