Okra (Abelmoschus esculentus) Plant Extract-Assisted Combustion Synthesis and Characterization Studies of Spinel ZnAl2O4 Nano-Catalysts.

Spinel ZnAl2O4 nano-catalysts were synthesized by a simple, economical and eco-friendly microwave irradiation (MIM) and conventional heating methods (CHM), using metal nitrates and Okra (Abelmoschus esculentus) plant extract, which play a dual role of both oxidizing and reducing nature. Powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, energy dispersive X-ray (EDX) and selected area electron diffraction (SAED) pattern results were confirmed that the samples have a single-phase cubic spinel structure with high crystalline nature of ZnAl2O4. Surface morphology of the samples was revealed by high resolution scanning electron microscopy (HR-SEM) and high resolution transmission electron microscopy (HR-TEM) techniques and they are confirmed particle-like structure with grain size below 50 nm. The optical band gap (Eg) was measured using Kubelka-Munk model by UV-Vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) and the Eg value is higher for MIM product than CHM, due to the smaller particle size of ZnAl2O4-MIM. The magnetic property of the samples was determined by vibrating sample magnetometer (VSM) and showed a superparamagnetic behavior. Spinel ZnAl2O4 nano-catalysts are magnetically recyclable and could be reused with no significant loss in catalytic activity. Both the samples were successfully tested as catalysts for the conversion of alcohols into respective carbonyl compounds using H2O2 (as oxidant) and acetonitrile (as a solvent) system. It was found that the ZnAl2O4-MIM nanocatalysts show best performance of conversion of alcohols into a carbonyl compounds than that of ZnAl2O4-CHM, due to the smaller particle size and higher surface area of ZnAl2O4-MIM samples.

Enhanced Catalytic Activity, Facile Synthesis and Characterization Studies of Spinel Mn-Co Aluminate Nano-Catalysts.

Undoped and Mn2+ doped CoAl2O4 (MnxCo1-xAl2O4; x = 0.0 to 1.0) spinel nanoparticles were successfully synthesized by a microwave heating method using glycine as the fuel. X-ray powder diffraction (XRD) was confirmed the cubic spinel structure. The average crystallite size of the samples was found to be in the range of 16.46 nm to 20.25 nm calculated by Scherrer's formula. The nano-sized particle-like morphology of the samples was confirmed by high resolution scanning electron microscopy (HR-SEM) and transmission electron microscopy (HR-TEM) analysis. Energy dispersive X-ray (EDX) results showed the pure form of spinel aluminate structure. The band gap energy (Eg) of pure CoAl2O4 was estimated to be 3.68 eV from UV-Visible diffuse reflectance spectroscopy (DRS), and the Eg values increased with increase of Mn2+ ions, due to the smaller grain size. The magnetic hysteresis (M-H) loop showed the superparamagnetic nature, and the magnetization and coercivity values increased with increasing Mn2+ ions, which was confirmed by vibrating sample magnetometer (VSM). All compositions of the nano-catalysts were tested as catalyst successfully for the conversion of benzyl alcohol into benzaldehyde and observed good catalytic activity.

Synthesis of Leucas Aspera Extract Loaded Gold-PLA-PEG-PLA Amphiphilic Copolymer Nanoconjugates: In Vitro Cytotoxicity and Anti-Inflammatory Activity Studies.

Gold nanoparticles (GNPs) are synthesized using the medicinal plant Leucas Aspera extract (LAE) and poly lactic acid-co-poly ethylene glycol-co-poly lactic acid (PLA-PEG-PLA) copolymer by water-in-oil (W/O) emulsion method. The proposed method of W/O emulsion technique involves synthesis of GNPs and loading of Leucas Aspera extract on to the PLA-PEG-PLA copolymer matrix simultaneously. The synthesized GNPs are characterized by Fourier transform infra-red (FTIR) spectroscopy, dynamic light scattering (DLS), X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The GNPs-LAE loaded polymer NPs are examined for the in vitro cytotoxicity on South African green monkey's kidney cells. The GNPs-LAE loaded polymer nanoconjugates exhibit maximum up to 95% of cell viability with 100 µg concentration of GNPs in the sample. The GNPs-LAE loaded polymer NPs exhibit better anti-inflammatory activity when compared to the pure LAE.

Simple Co-Precipitation Synthesis and Characterization Studies of La(1-x)NixVO3 Perovskites Nanostructures for Humidity Sensing Applications.

Ni2+ -doped LaVO3 perovskites nanostructures were successfully prepared by a simple coprecipitation method. Powder X-ray diffraction (XRD) pattern confirms that all compositions crystallize with orthorhombic LaVO3 perovskites structure. The lattice parameter decreases with increase in Ni2+ content resulting in the reduction of lattice strain in LaVO3. High resolution scanning electron microscope (HR-SEM) images revealed that the as-prepared samples are crystalline with particle size distribution in 142-250 nm range. The BET studies revealed the surface area of the required samples. The samples were subjected to humidity sensing studies by solid-state electrical conductance studies. The studies revealed that La0.4Ni0.6VO3 is a good candidate for humidity sensors with a higher sensitivity factor (Sf) of 15623.02. The higher Sf of La0.4Ni0.6VO3 is due to the larger surface area of the sample.

Aloe vera Plant Extracted Green Synthesis, Structural and Opto-Magnetic Characterizations of Spinel Co(x)Zn1₋xAl2O4Nano-Catalysts.

Spinel Co(x)Zn1₋xAl2O4 (0 ≤ x ≤ 1) nano-catalysts were synthesized by a simple Aloe vera plant extracted green synthesis route. Powder XRD patterns and Rietveld analysis confirmed the formation of single phase, cubic spinel gahnite structure without other impurities. The lattice parameter increased from 8.089 to 8.125 A with increasing CO²âº content. The average crystallite sizes were estimated using Scherrer's method, and it was found to be in the range of 15.72 nm to 26.53 nm. FT-IR spectra showed vibrational stretching frequencies corresponding to the spinel structure. HR-SEM and HR-TEM images showed the features of well particle shaped crystals with nano-sized grains. The elemental compositions of Co, Zn, Al and O were quantitatively obtained from EDX analysis. The band gap energy estimated using Kubelka-Munk method by UV-Visible DRS method, and the values are decreased with increasing the Co²âº content (4.12 eV to 3.67 eV), due to the formation of sub bands in between the energy gap. PL spectra showed emission bands in UV as well as in the visible regions for ZnAl2O4 and Co-doped ZnAl2O4, due to the defect centers acting as the trap levels. VSM measurements revealed that pure ZnAl2O4 has diamagnetic, while Co doped ZnAl2O4 samples (x = 0.2 to 0.8) have superparamagnetism, whereas the sample CoAl2O4 has ferromagnetic in nature. Catalytic oxidation of benzyl alcohol to benzaldehyde was found that the sample Co0.6Zn0.4Al2O4 showed 93.25% conversion with 99.56% selectivity, whereas for pure ZnAl2O4, the conversion was only 86.31% with 92.85% selectivity.

Sesamum indicum Plant Extracted Microwave Combustion Synthesis and Opto-Magnetic Properties of Spinel MnxCo1₋xAl2O4Nano-Catalysts.

Spine Mn(x)Co1₋xAl2O4 (x = 0, 0.3 and 0.5) nanoparticles were synthesized using Sesamum indicum (S. indicum) plant extracted microwave-assisted combustion method. S. indicum plant extract simplifies the process, provides an alternative process for a simple, economical and environment friendly synthesis. The absence of surfactant/catalysts has led to a simple, cheap and fast method of synthesis of spinel nanoparticles. The as-synthesized spinel nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, high resolution scanning electron microscopy (HR-SEM), high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), Brunauer Emmett Teller (BET) surface area analysis, UV-Visible diffuse reflectance spectroscopy (DRS), Photoluminescence (PL) spectroscopy, and vibrating sample magnetometer. The formation of spinel nanoparticles was confirmed by HR-SEM and HR-TEM and their possible formation mechanisms were also proposed. Powder XRD, FT-IR, SAED and EDX results confirmed the formation of pure and single cubic phase CoAl2O4 with well-defined crystalline. The optical property was determined by DRS and PL spectra. VSM measurements revealed that pure and Mn-doped CoAl2O4 samples have weak ferromagnetic behavior and the magnetization values increases with increasing the concentration of Mn²âº ions in the CoAl2O4 lattice. The sample Mn0.5Co0.5Al2O4 possessed higher surface area and smaller crystallite size than other samples, which led to enhance the performance toward the selective oxidation of benzyl alcohol into benzaldehyde.

Effect of Poloxamer on Zingiber Officinale Extracted Green Synthesis and Antibacterial Studies of Silver Nanoparticles.

The Zingiber officinale (Z. officinale) plant is one of the well-known medicinal plants. Poloxamer finds excellent clinical and therapeutic uses for curing of various ailments. The poloxamer 188 polymer and the plant extract of Z. officinale have been used to prepare the silver nanoparticles (AgNPs) by a green synthesis route. The Z. officinale plant extract has been used as a reducing agent, while the poloxamer 188 has been used as a stabilizing agent. The formation of face-centered cubic (fcc) structure AgNPs was confirmed by X-ray diffraction pattern. The effect of addition of poloxamer on the controlling the shape, size and morphologies of the AgNPs has been investigated by transmission electron microscopy (TEM) and dynamic light scattering techniques. The elemental composition of AgNPs was confirmed by energy dispersive X-ray (EDX) analysis. The anti-bacterial activity of AgNPs has been investigated using three human pathogens Escherichia coli, Klebsiella pneumonia and Staphylococcus aureus. The poloxamer 188 protected AgNPs inhibit the bacterial growth more effectively than the pure Z. officinale extract and the Z. officinale extract AgNPs.

Synthesis and Characterization of Fe2(MoO4)3Nano-Photocatalyst by Simple Sol-Gel Method.

Ferric molybdate (Fe2(MoO4)3) nanorods (NRs) were successfully synthesized using metal nitrates, citric acid and ethyl cellulose by a simple sol-gel method. Structural, morphological, optical and magnetic properties of the obtained powder were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, high resolution scanning electron microscope (HR-SEM), energy dispersive X-ray (EDX), UV-Visible diffuse reflectance spectra (DRS), photoluminescence (PL) spectra and vibrating sample magnetometer (VSM). XRD results indicated that the resultant powder was pure single phase crystalline with monoclinic structure. FT-IR spectra indicate the type of bonds between metals and oxygen. HR-SEM images shows that the morphology of the powder consist with well defined nanorods (NRs) structure. VSM results showed ferromagnetic behavior. The addition of TiO2 catalyst, it enhanced the photo-catalytic activity of Fe2(MoO4)3. The mixed oxide catalyst of Fe2(MoO4)3-TiO2 nano-composites (NCs) were also tested for the photocatalytic degradation (PCD) of 4-chlorophenol (4-CP). It was found that the PCD efficiency of Fe2(MoO4)3 NCs is higher than pure Fe2(MoO4)3 and TiO2 catalysts.

The Role of Mn(2+)-Doping on Structural, Morphological, Optical, Magnetic and Catalytic Properties of Spinel ZnFe2O4 Nanoparticles.

Spinel Mn(x)Zn(1-x)Fe2O4 (0.0 ≤ x ≤ 1.0) nanoparticles (NPs) were successfully synthesized by a facile one-pot microwave combustion method using urea as the fuel. The formation of single phase cubic spinel structure was confirmed by powder X-ray diffraction (XRD), Rietveld analysis and Fourier transform infrared (FT-IR) spectroscopy and the calculated average crystallite size is in the range of 37.57 nm to 25.43 nm. The high resolution scanning electron microscopy (HR-SEM) and high resolution transmission electron microscopy (HR-TEM) results indicated that the as-prepared spinel Mn(x)Zn(1-x)Fe2O4 NPs showed high crystallinity and uniform size distribution with particles-like morphologies. The energy dispersive X-ray (EDX) analysis was confirmed the elemental composition and purity of the samples. The estimated band gap energy from UV-Visible diffuse reflectance spectroscopy (UV-Vis. DRS) is about 1.88 eV to 2.35 eV. The broad visible emission band is observed in the entire photoluminescence (PL) spectroscopy for all compositions. The variation of magnetization (M(s)) value of the samples was studied by vibrating sample magnetometer (VSM) and the lower compositions (x = 0.0, 0.2 and 0.4) show a superparamagnetism and the higher composition (x = 0.6, 0.8 and 1.0) show a ferromagnetic behavior with hysteresis and that the M(s) values increased with increasing Mn2+ content to reach a maximum value of 60.99 emu/g for MnFe2O4. All composition of spinel Mn(x)Zn(1-x)Fe2O4 NPs were successfully tested as catalyst for the oxidation of benzyl alcohol into benzaldehyde, which has resulted 83.29 and 96.51% conversion efficiency of ZnFe2O4 and Mn0.6Zn0.4Fe2O4 respectively.

Comparative Studies of Spinel MnFe2O4 Nanostructures: Structural, Morphological, Optical, Magnetic and Catalytic Properties.

Spinel MnFe2O4 nanostructures with two different morphologies such as nanoflakes (NFs) and nanoparticles (NPs) were synthesized by a simple microwave-assisted combustion (MACM) and conventional combustion (CCM) methods respectively. Powder X-ray diffraction (XRD) study showed that the samples have pure cubic spinel phase and the average crystallite size is found to be 15.13 ± 2 nm and 24.38 ± 13 nm for NFs and NPs respectively. The calculated lattice parameter values of the samples NFs and NPs are 8.476 and 8.474 Å respectively. The morphology of the samples was recorded using high resolution scanning electron microscope (HR-SEM) analysis and was found that nanoflakes and nanoparticles morphologies by MACM and CCM methods respectively. Energy dispersive X-ray (EDX) results showed that the composition of the elements was relevant as expected from these combustion methods. The optical properties of the as-prepared nanostructures were also investigated by UV-Visible Diffuse Reflectance Spectroscopy (DRS) and Photoluminescence (PL) Spectroscopy. The energy band gap (E(g)) of the sample NFs is 1.78 eV, whereas the sample NPs has 1.75 eV. The magnetic properties were investigated using the Vibrating Sample Magnetometer (VSM) at room temperature and the hysteresis loops confirmed the super-paramagnetic behavior for both samples with saturation magnetization (M(s)) values in the range of 59.29 ± 11 and 66.78 ± 06 emu/g for the samples NFs and NPs respectively. The oxidation of benzyl alcohol into benzaldehyde reached a maximum of 87.65% for MnFe2O4 NFs, whereas for MnFe2O4 NPs, the conversion was only 69.43% with 100% selectivity.

A Simple Combustion Synthesis and Optical Studies of Magnetic Zn1-xNi(x)Fe2O4 Nanostructures for Photoelectrochemical Applications.

Ni-doped ZnFe2O4 (Ni(X)Zn1-x,Fe2O4; x = 0.0 to 0.5) nanoparticles were synthesized by simple microwave combustion method. The X-ray diffraction (XRD) confirms that all compositions crystallize with cubic spinel ZnFe2O4. The lattice parameter decreases with increase in Ni content resulting in the reduction of lattice strain. High resolution scanning electron microscope (HR-SEM) and transmission electron microscope (HR-TEM) images revealed that the as-prepared samples are crystalline with particle size distribution in 42-50 nm range. Optical properties were determined by UV-Visible diffuse reflectance (DRS) and photoluminescence (PL) spectroscopy respectively. The saturation magnetization (Ms) shows the superparamagnetic nature of the sample for x = 0.0-0.2, whereas for x = 0.3-0.5, it shows ferromagnetic nature. The Ms value is 1.638 emu/g for pure ZnFe2O4 sample and it increases with increase in Ni content. Photoelectrochemical (PEC) measurements showed a significant increase of photocurrent density with increase in the Ni-dopant, and 0.5% Ni-doped ZnFe2O4 sample was found to show the better photoresponse than the other doping concentrations.

Antibacterial Studies and Effect of Poloxamer on Gold Nanoparticles by Zingiber Officinale Extracted Green Synthesis.

Poloxamer finds excellent clinical and therapeutic uses for curing of various ailments. The Zin- giber officinale (Z. officinale) is one of the well-known medicinal plants. The poloxamer188 and the rhizome extract of Z. officinale have been used to synthesize the gold nanoparticles (AuNPs) by a green approach. The Z. officinale extract has been used as a reducing agent while the polox- amerl88 has been used as a stabilizing agent. The effect of addition of poloxamer on the controlling the shape and size of the AuNPs has been investigated by transmission electron microscopy (TEM) and dynamic light scattering techniques. The formation of AuNPs has also been confirmed by UV-Visible spectral, energy dispersive X-ray (EDX) and powder X-ray diffraction (XRD) analyses. The anti-bacterial activity of the green synthesized AuNPs has been investigated on the three human pathogens Staphylococcus aureus, Escherichia coli, and Klebsiella pneumonia. The poloxamer188 protected AuNPs inhibit the bacterial growth more effectively than the pure Z. officinale extract and the standard tetracycline (TA).

One-Pot Low Temperature Synthesis and Characterization Studies of Nanocrystalline α-Fe2O3 Based Dye Sensitized Solar Cells.

Dye-sensitized solar cell (DSSC) based α-Fe2O3 nanostructures with two different morphologies, such as nanorods (FeONRs) and nanoparticles (FeONPs), were synthesized by one-pot low temperature method. The crystal structure and phase purity of the as-prepared samples were characterized by X-ray powder diffraction (XRD) and further determined by Rietveld refinements XRD analysis. The average crystallite size was calculated using Debye Sherrer formula, and it shows the range of 9.43-26.56 nm. The morphologies of the products were studied by high resolution scanning electron microscopy (HR-SEM) and it was confirmed by high resolution transmission electron microscopy (HR-TEM). The formation of pure α-Fe2O3 samples was further confirmed by energy dispersive X-ray (EDX) analysis. The optical properties and the band gap energy (E(g)) were measured by UV-Visible diffuse reflectance spectra (DRS) and photoluminescence (PL) spectra. The band gap energy was measured using Kubelka-Munk method, and the values are decreased from 2.36 eV to 2.21 eV as the temperature increased from 300 to 400 degrees C with increasing the crystallite size. Magnetic hysteresis (M-H) loop revealed that the as-prepared α-Fe2O3 samples displayed ferromagnetic behavior. FeONRs sample shows higher saturation magnetization (M(s)) value (40.21 emu/g) than FeONPs sample (23.06 emu/g). The dye-sensitized solar cell based on the optimized FeONRs array reaches a conversion efficiency of 0.43%, which is higher than that obtained from FeONPs (0.29%) under the light radiation of 1000 W/m2.

Microwave Combustion Synthesis and Characterization Studies of Magnetic Zn(1-x)Cd(x)Fe2O4 (0 ≤ x ≤ 0.5) Nanoparticles.

Nano-sized pure and Cd-doped ZnFe2O4 (Zn(1-x)Cd(x)Fe2O4 with x = 0.0-0.5) samples were synthesized by a simple microwave combustion method. The X-ray diffraction (XRD) analysis confirmed the single phase cubic spinel structure. The average crystallite size was found in the range of 17.47-41.21 nm. The lattice parameter is found to increase with increase in the concentration of Cd. Pure ZnFe2O4 and all compositions of the Zn-Cd ferrites showed similar particle-like morphologies, which is confirmed by high resolution scanning electron microscopy (HR-SEM). Energy dispersive X-ray (EDX) analysis shows that the theoretical and observed percentage of the elements; Zn2+, Cd2+ and Fe3+ are in the desired stoichiometric proportion. The UV-Visible diffuse reflectance spectrum (DRS) shows the band gap value increases with increasing Cd content. All the samples showed the characteristic near-band-edge emission at around 428 nm, which is observed by photoluminescence (PL) spectra. The magnetic properties were measured by using vibrating sample magnetometer (VSM) and it was found that the saturation magnetization is increased with increase the concentration of Cd content. The results revealed that for lower Cd concentration (x = 0.0-0.2) the samples shows a superparamagnetic behavior, whereas for higher concentration (x = 0.3-0.5), it becomes ferromagnetic.

A Novel Synthesis and Characterization Studies of Magnetic Co3O4 Nanoparticles.

Cobalt oxide (Co3O4) nanoparticles were synthesized by microwave combustion method (MCM) using urea as the fuel. For the purpose of comparison, they are also prepared by conventional combustion method (CCM). The prepared samples were examined by using X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), high resolution transmission electron microscopy (HR-TEM), UV-Visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and vibrating sample magnetometer (VSM). XRD analysis indicated that the as-prepared samples have well-crystalline cubic phase. HR-TEM images showed that Co3O4 nanoparticles have sphere-like structure with an average particle size in the range of 20-25 nm (MCM) and 45-50 nm (CCM). Optical properties of Co3O4 nanoparticles revealed the presence of two band gap (1.89 and 2.54 eV (MCM), 1.68 and 2.38 eV (CCM)) values, which in turn confirmed the semi-conducting properties. VSM measurements revealed a small hysteresis loop at room temperature thus indicating a weak ferromagnetism.