UV Diffuse Reflectance Spectra Research Articles

Using novel open-framework copper borovanadate as an effective catalyst in the conversion of cyclohexanol to cyclohexanone

A new open-framework copper borovanadate containing two oxidation states of V4+ and V5+ cations {[Cu5(1,2-dap)10][VV2VIV10B18O54(OH)6(H2O)]}·2H3BO3·9H2O (1,2-dap: 1, 2-propylene diamine) (1) using 1,2-dap as template agent has been successfully prepared. It is composed of five coordination cations [Cu(1,2-dap)2]2+and one borovanadate anion [VV2VIV10B18O54(OH)6(H2O)]10- constructed by one {B18O30(OH)6} and two {V6O18} subunits, as well as two isolated H3BO3 molecules and nine H2O molecules. The compound exhibits for the first time penta-coordinated copper cations, uncoordinated H3BO3 molecules and 1, 2-dap ligands in the series of open-framework borovanadates. Its UV diffuse-reflectance spectrum, Mott-Schottky curve, fluorescent emission, chromaticity and second-order lifetime were investigated in detail. The stable pH range (5.8–2.3) of the borovanadate anion in DMF solution was explored by means of fluorescence and UV spectra. In particular, it showed effective catalytic activity in the conversion of cyclohexanol to cyclohexanone (conversion: 86.8 %, selectivity: 97.4 %). The possible catalytic mechanism for the catalytic reaction had been also established. The studies revealed that the borovanadate could be used as a potential stable catalyst for the selective oxidation of cyclohexanol.

Green and Abrasion-Resistant Superhydrophobic Coatings Constructed with Tung Oil/Carnauba Wax/Silica for Wood Surface.

As a renewable, environmentally friendly, natural, and organic material, wood has been receiving extensive attention from various industries. However, the hydrophilicity of wood significantly impacts the stability and durability of its products, which can be effectively addressed by constructing superhydrophobic coatings on the surface of wood. In this study, tung oil, carnauba wax, and silica nanoparticles were used to construct superhydrophobic coatings on hydrophilic wood surfaces by a facile two-step dip-coating method. The surface wettability and morphology of the coatings were analyzed by a contact angle meter and scanning electron microscope, respectively. The results suggest that the coating has a micron-nanosized two-tiered structure, and the contact angle of the coating is higher than 150° and the roll-off angle is lower than 10°. Sandpaper abrasion tests and UV diffuse reflectance spectra indicate that the coatings have excellent abrasion resistance and good transparency. In addition, the coated wood shows excellent self-cleaning and water resistance, which have great potential for applications in industry and furniture manufacturing.

Distinguishable photocatalytic activity of nano polyaniline with quantum dots metal oxide as photocatalysts for photodegradation of Dianix blue dye and different industrial pollutants

Nanopolyaniline (PAN) polymers have recently been under active investigation as promising photocatalysts. In this work, a simple modified sol–gel method is used to make nano PAN polymers, and a chemical polymerization method is used to make nano polyaniline titanium dioxide quantum dots (PAN-TiQD) polymers as an active photocatalyst during the photodegradation of Dianix blue dye as an organic pollutant under xenon light. The traditional colloidal sol–gel method and the microwave-assisted hydrothermal method were used to make TiQD, which was then mixed with nanoPAN to make PAN-5 % TiQD (W/W) nanocomposites. Characterizations like XRD, FTIR, UV and visible diffuse reflectance spectra, TGA, surface area, EDX, and TEM were used to characterize the nanoPAN and PAN-TiQD that were made. Also, the photocatalytic activity of all synthesized polymers was investigated by the photodegradation process of Dianix blue dye as an organic hazardous pollutant in aqueous medium using a xenon photoreactor with an initial power of 75 W/Cm2. The effects of irradiation time and photocatalyst type on the photodegradation process efficiency of Dianix blue dye were examined. After 3 h of photodegradation processes, the photodegradation efficiency of PAN-TiQD reached 69 % compared to 36 % of nanoPAN due to the fact that it contains 5 % TiQD as a highly active catalyst, which reached 91 %. As an added value for this study, a significant contribution is the examination of eight hazardous industrial wastewater samples, which were assessed under direct sunlight and were in accordance with the KSA environmental permissible limit of 1000 ppm.Finally, the recycling processes in the presence of all synthesized catalysts were investigated and evaluated six times. The photodegradation rate of the recycling processes of Dianix blue dye was highly decreased in the presence of nano PAN than PAN-TiQD, while it had a low decreasing percentage in the case of TiQD. The recycling process using sunlight for industrial pollution samples was investigated at one of the KSA textile plants by using six synthetic catalysts and assessing COD and TOC values.

Sol-gel combined mechano-thermal synthesis of Y2O3, CeO2, and PdO partially coated ZnO for sulfamethazine and basic yellow 28 photodegradation under UV and visible light

The presence of organic pollutants in marine systems has made wastewater treatment extremely complicated, due to the release of a series of harmful contaminants into the ocean and causing direct damage to humans and the aquatic ecosystem. The present research aims to examine the impact of ZnO partial coating with different nonmetric layers based on CeO2, Y2O3, or PdO for water-charged organic contaminants treatment, using a photocatalysis process. In this vision, the photodegradation of two organic pollutants, sulfamethazine (SMZ) and basic yellow 28 (BY28), using ZnO and ZnO partially coated with cerium, yttrium or palladium oxides was studied. These materials have been successfully synthesized by the combination of both sol-gel and mechano-thermal methods. The prepared catalysts were characterized using X-ray diffraction, scanning electron microscopy SEM-EDX, UV diffuse reflectance spectra (DRS), and X-ray photoelectron spectroscopy analysis (XPS). The XRD measurements discovered that all the synthesized photocatalysts have the hexagonal crystal system of ZnO, and the crystallite size value is calculated to be 36 nm. EDX results affirmed the existence of yttrium, cerium and palladium elements in the prepared ZnO/Y2O3, ZnO/CeO2, and ZnO/PdO materials, respectively, with good dispersion and homogeneity. The XPS spectra of ZnO/Y2O3, ZnO/CeO2, and ZnO/PdO, confirmed the presence of Zn, O, Y, Ce, and Pd elements, where they are, excited as Zn2+, Y3+, Ce4+, and Pd2+ oxidation state, respectively. The photoactivity tests demonstrate that the partial coating increases the degradation efficiency of ZnO, with a total photodegradation of BY28 and SMZ under UV irradiation. Moreover, ZnO/PdO under visible light degrades 94% of BY28 in 120 min and 60% of SMZ in 180 min due to the effective separation of photo-induced charge carriers between PdO and ZnO.

A facile method for synthesis rGO/Ag nanocomposite and its uses for enhancing photocatalytic degradation of Congo red dye

The enhancing breakdown of dyes using facile, novel and eco-friendly photocatalyst without remaining any hazards secondary intermediates from the dye species regarded one of the most challenges to the healthy world. A novel facile method was used to synthesize reduced graphene oxide (rGO) with various doping ratios of silver nanoparticles (Ag NPs) and applied as photocatalyst to enhancing removal of Congo red (CR) dye using UV light irradiation from aqueous solution. Some characterization features such as UV-diffuse reflectance spectra, TEM, SEM, FTIR, X-ray diffraction, and EDX were measured to demonstrate the energy gap, morphology, size distribution, crystalline nature, phase structure, and elemental compositions of as-synthesized nanoparticles. The effect of some important factors such as pH of solution, initial CR concertation (Co), amount of rGO@Ag (g) and contact time (t) were studied to detect the optimum adsorption condition. The results indicated that, the maximum CR dye photodegradation is obtained at pH 7, 120 min, 50 mg/L initial CR concentration and 0.4 g/L photocatalyst dosage. The photodegradation data declared that, the higher the Ag doping ratio, the higher the degrading efficiency. Isotherm and kinetic studies showed that Langmuir and Freundlich models and the pseudo-second-order model are well fitting the adsorption process with maximum CR adsorption values ranging between 86.95 and 98.04 mg/L with corresponding R2 > 0.99.

Construction of g-C3N4/Au/NH2-UiO-66 Z-scheme heterojunction for label-free photoelectrochemical recognition of D-penicillamine

The wide clinical application of d-penicillamine (D-PA) makes it inevitably accumulates in the environment, seriously threatening human health and the ecological environment. To better supervisory control D-PA, a highly sensitive and reliable photoelectrochemical (PEC) sensor based on gold nanoparticles (Au NPs) loaded on graphitic carbon nitride sheet and hexagonal NH2-UiO-66 composite (g-C3N4/Au/NH2-UiO-66) was synthesized. Tactfully using the strong bonding between D-PA and Au NPs and the effective carrier separation of Z-scheme heterojunction, the designed g-C3N4/Au/NH2-UiO-66 PEC sensor without an extra recognition unit exhibited a selective and sensitive photocurrent to D-PA. With the aid of UV diffuse reflectance spectra (UV-DRs), electron paramagnetic resonance (EPR) characterization, and free radical capture experiments, the electron transfer path of the PEC sensing system was deduced. The proposed g-C3N4/Au/NH2-UiO-66 PEC-based sensor achieved a low detection limit of 0.0046 μM (S/N = 3) with a wide linear response ranging from 10 nM to 400 μM. In addition, its good stability and selectivity also laid a good foundation for practical applications.

Ceria-doped SnO2 nanocubes for solar light-driven photocatalytic hydrogen production.

The photocatalytic generation of hydrogen via solar energy using metal oxide semiconductor catalysts is a clean and renewable process which has the potential of solving the current energy nexus. SnO2 is one such well-studied and established photocatalyst currently in practice but is only ultraviolet-light active which accounts for only 4% of the total incoming solar energy. The current study focuses on bringing this SnO2 into the visible range using ceria as a dopant. Sol-gel and combustion methods were employed for synthesis and the as-synthesized catalysts were characterized using XRD, BET, UV diffuse reflectance spectra, PL spectra, and SEM micrographs. A unique cuboid type morphology was observed in 6% ceria-doped SnO2 which provided more active sites for light absorption and thus reported a remarkable hydrogen production rate of 1.978mmol/h under sunlight which was almost 346 times that of pure SnO2 (5.71µmol/h). Photoluminescence spectra of ceria-doped SnO2 showed lower peak positions as compared to the pure SnO2 indicating a reduction in charge recombination and an increase in the life time of the active species which explains the enhanced hydrogen production rates. The recyclability study of the catalysts showed that the hydrogen amount produced in the fifth recycle was nearly 80% as the first cycle showing that the catalyst can be used very effectively for more than five cycles without compromising on the yield.

Hantzsch synthesis of 1,4-dihydropyridine derivatives over ZnO/ZrO2 catalyst under solvent free condition

Hantzsch synthesis of 1,4-dihydropyridine derivatives is accomplished using novel and efficient ZnO/ZrO2 catalyst. The catalysts prepared by facile precipitation and wet impregnation method have been characterized by using techniques like XRD, SEM, EDS, UV-diffuse reflectance spectra, FTIR, XPS, BET surface area. Ex situ Pyridine absorption FTIR spectroscopy is used to determine the Bronsted and Lewis acidic sites. Enhanced activity of the zirconia supported zinc catalyst is attributed to tetragonal phase, more acidic sites and high surface area of the catalyst. The products attained in good to excellent yields in short duration under solvent free condition, minimizing the disposal problem and energy dissipation. The catalyst can be reused umpteen times without significant loss in activity.

Intermolecular interactions, photocatalysis and THz-TDS interrelationships for lanthanide phosphine oxide complexes based on {PW12}

A series of rare earth complexes containing (α-PW12O40)3- and PO ligand are synthesized by water bath in 70 °C, [Ln(OPPh3)4(H2O)3](PW12O40)·4CH3CN (Ln = La, Pr, Nd, Sm, Gd, Tb, Ho 1–7) (OPPh3 = Triphenylphosphine oxide, {PW12} = phosphotungstic acid). The precise structures are confirmed by X-ray single crystal diffraction and the result shows all complexes are isostructural. Complexes 1–7 are fully characterized by PXRD, FT-IR, TGA, UV diffuse reflectance spectra and terahertz time-domain spectroscopy (THz-TDS). Complex 3 exhibits the highest photocatalytic degradation efficiency for methylene blue (MB) in this series of complexes. The experimental results showed that the photodegradation efficiency can remain constant at the level of 95% after five consecutive cycles. The photocatalytic reaction kinetics and mechanism of complexes were investigated. Additionally, complexes also exhibit photocatalytic hydrogen evolution activity. THz-TDS was used to characterize the complexes and its raw materials, the characteristic peaks of OPPh3 (broad peak at 1.20 THz) and phosphotungstic acid (sharp peaks at 0.23, 0.32 THz) were obtained.

Hollow Nanorods and Amorphous Co9S8 Quantum Dots Construct S-Scheme Heterojunction for Efficient Hydrogen Evolution

The hollow materials have stronger absorption capacity for visible light than other materials due to their special internal cavity structure. In this paper, NiTiO3 hollow nanorods and Co9S8 QDs were used to prepare composite materials with strong light absorption capacity and photocatalytic hydrogen production activity using an in situ growth method. The results of UV diffuse reflectance spectra prove that the existence of NiTiO3 hollow nanorod effectively improves the visible light absorption capacity of the composite material. Additionally, the existence of hollow nanorods can evenly disperse Co9S8 QDs on the surface and increase the number of active sites. X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and electrochemical measurements further attest that the S-scheme heterojunction constructed between the two semiconductors not only provides a special transmission path for carrier transfer but also retains more useful electrons and holes that participate in the hydrogen evolution reaction. Therefore, the maximum hydrogen production of NiTiO3@Co9S8 QDs can reach 5.38 times that of pure Co9S8 QDs. The consequences show that the S-scheme heterojunction constructed by NiTiO3 has certain development potential in the field of photocatalysis.

Examining dye degradation and antibacterial properties of organically induced α-MoO3 nanoparticles, their uptake and phytotoxicity in rice seedlings

A thermodynamically stable, organically induced α-MoO3 nanoparticles (NPs) consisting of orthorhombic units were synthesized and investigated for its photocatalytic activity in presence of visible light and for antibacterial properties. The XRD studies confirmed the formation of crystalline α-MoO3-NPs. HRTEM revealed its sheet morphology with 21.34 nm of crystallite size. The α-MoO3-NPs had dual optical band gap of 1.67 eV and 2.22 eV in UV Diffuse Reflectance Spectra (UV-DRS). In presence of LED light (12 W) and absence of an oxidizing agent the exhibits strong photocatalytic degradation of both cationic (Methylene Blue) and anionic (Eosin Yellow) dyes with 99 % and 94 % removal efficiency, respectively. The α-MoO3-NPs exhibit antibacterial activity towards microorganisms of health importance viz. Gram positive (B. cereus) and Gram negative (E. coli) at low concentration of 100 mg/l. Uptake, translocation and bioaccumulation of α-MoO3-NPs when studied in rice seedling cv HUR3022 at 15 days of growth revealed the uptake of Mo be 7.3 ppm in roots and 4.5 ppm in shoots under 100 mg/l α-MoO3-NPs treatment. More translocation of Mo from root to shoot upon application of organically induced α-MoO3-NPs were noted however, the translocation factor was 0.6, almost similar to that in controls. The translocation and bioaccumulation factor both were below 1.0 suggesting novel α-MoO3-NPs to be non-phytotoxic and environmentally safe. The synthesized α-MoO3-NPs via simple steps and their remarkable photocatalytic properties, reusability, antibacterial activity and safe for environment makes them a promising nanomaterial for varied applications including membrane technology, water treatment, control of bacterial infections and in agriculture.

Comprehensive analysis of crystal structure, optical and luminescent behavior of Fe doped MgO nanophosphors

The structural and optical properties of iron doped magnesium oxide nanophosphors (NPs) with composition Mg1-xO: Fex where x = 0, 0.1, 0.2, 0.3 and 0.4 mol% were synthesized via solution combustion method. Rietveld refinement of obtained XRD data confirms the cubic structure of synthesized samples. FTIR spectra show the presence of absorption bands associated with stretching vibrations of MgO along with Fe-O-Mg deformation vibrations. UV diffuse reflectance spectra of the pristine and gamma irradiated nanophosphors reveals that Fe as dopant reduces the band gap ‘Eg’ of nanophosphors. Photoluminescence emission spectra under excitation at 270 nm wavelength show broad emission centered at ∼ 398 nm and ∼ 485 nm which is attributed to surface defects mainly oxygen vacancies i.e. F2+, F and F+-centers and surface states of the host material. The optimum dopant concentration of Fe ion is found to be 0.2 mol % and CIE color coordinates (0.140, 0.062) located in the blue region advocates its applications in White LEDs. TL glow curves show that TL intensity of gamma exposed Nanophosphors decreases tremendously with increase in Fe doping. The kinetic parameters are estimated using peak shape method and obtained values reveals peaks exhibit 2nd order kinetics having trap depth ranging from 0.5845 to 3.0577 eV.

A novel photochromism material based on both pyrimidinium and polyoxometalate: (C4N2H4–C4N2H3) [Mn(H2O)6]0.5{SiW12O40}0.5ˑ5H2O

We used the traditional hydro-thermal synthesis method to generate the first photochromic pyrimidinium/polyoxometalate (POM) salt material (C4N2H4–C4N2H3) [Mn(H2O)6]0.5{SiW12O40}0.5ˑ5H2O in situ by using silicotungstic acid and pyrimidine as raw materials. The solid UV diffuse reflectance spectrum of compound 1 was shifted before and after illumination. There was a new broad absorption peak appeared near 370 nm and 624 nm after illumination. With the increase of irradiation time, the peak at 624 nm will shift to 588 nm at which the sample reached light saturation. The color of the sample changed from yellow to grayish green. By studying a series of test: EPR, XPS, UV–Vis, X-ray single crystal diffraction, and density of states (PDOS) calculation, we conclude that the charge transfer mechanism of photochromism may be due to: the generation of pyrimidinium free radicals by light-induced, photochemical reduction of polyoxometalates and the interaction of two aspects. This work enriches the family of photochromism and its theory.

Methylammonium iodo bismuthate perovskite (CH3NH3)3Bi2I9 as new effective visible light-responsive photocatalyst for degradation of environment pollutants

In this work, the photocatalytic activity of a new visible light-responsive (CH3NH3)3Bi2I9 hybrid organic-inorganic perovskite (HOIP) was addressed for the very first time in the treatment of aqueous solutions of model organic dyes. The photocatalyst was successfully prepared by a low temperature solvo-termal method, easily reproducible. The catalyst was characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction spectrometer (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDS), X-ray photoelectron spectroscopy (XPS) techniques and UV diffuse reflectance spectrum. The efficiency of photocatalyst was tested for the removal of different type of dyes: fluorone dye (rhodamine B), thiazine dye (methylene blue) and azo dye (reactive Blue 4). Moreover, a multi-contaminated solution, with methylene blue and crystal violet (triarylmethane dye), was used to simulate a real industrial wastewater effluent. The results highlighted an increase of the photocatalytic activity respect the pristine precursor, bismuth iodide. The experiments showed that the values of removal was higher for rhodamine B respect the other dyes, with a removal of 98% after three hours under visible light irradiation. The efficiency of the photocatalyst was also confirmed under optimal conditions with high pressure liquid chromatography (HPLC). The gradual disappearance of rhodamine B peak accompanied by the appearance of by-products peaks was investigated. The stability of the photocatalyst was tested for three consecutive re-cycles. Analysis on different visible light sources was performed: halogen provided higher efficiency respect LED lamp. The outcomes of the present work aim to open the possibility of considering HOIP as a new potential photocatalyst for contaminants treatment.

Neodymium doped on the manganese‒copper nanoferrites: analysis of structural, optical, dielectric and magnetic properties

Mixed manganese‒neodymium‒copper (Mn–Nd–Cu) nanoferrites were synthesized using the sonochemical method. The X-ray diffraction (XRD) pattern showed a cubic spinel structure and lattice parameters were determined from the XRD spectra. Fourier transform infrared spectra were used to characterize the chemical bond of tetrahedral and octahedral sites in the spinel ferrites. The surface morphology and elemental composition were analyzed by scanning electron microscopes coupled with energy-dispersive X-ray spectroscopy, which showed spherical elongated agglomeration with desired elemental peak. The optical bandgap energies increased with the inclusion of Nd3+, which was investigated using the UV-diffuse reflectance spectrum. The dielectric parameter decreased with an increase in frequency. The relatively low AC conductivity values were obtained for the Mn–Nd–Cu nanoferrites. The magnetic hysteresis curve showed that low coercivity indicates that the prepared nanoferrites had a soft magnetic material with ferromagnetic nature. The enhanced optical bandgap, decreased dielectric loss, and low coercivity of NMC4 indicated that the prepared nanoferrites could be used in electronic devices at a super high frequency.

Study of oxidation states of Fe- and Co-doped TiO2 photocatalytic energy materials and their visible-light-driven photocatalytic behavior

In this work we propose a study to determine the structure of Fe and Co doped TiO2 by using the Fe K-edge, Co K-edge and Ti K- edge X-ray absorption near edge spectroscopy. The detailed analysis of Fe and Co-doped TiO2 before and after Methylene blue (MB) treatment was examined under the irradiation of 35 W xenon arc lamp for 3 h. The materials treated with MB were studied by X-ray absorption spectroscopy, EPR and FT-IR which revealed that the oxidation state of Co2+ was photo-oxidized to Co3+ and Fe3+ was photo-reduced to Fe2+ or less. Thermodynamic, kinetic properties were studied at different reaction temperature and the activation energy (Ea), enthalpy (ΔH), entropy (ΔS) and free energy (ΔG) of activation were calculated for the reaction. The activation energy has been found for TiO2, FeTiO2 and CoTiO2 as 24.771, 11.413 and 15.801 kJ mol−1 respectively. The structure, morphology and optical properties were studied by XRD, UV-diffuse reflectance spectra, FESEM, TEM and PL. Moreover, electrochemical studies were carried out to demonstrate the oxygen evolution reaction (OER) activity on TiO2, FeTiO2 and CoTiO2 in 1 M of H2SO4 electrolyte, with a scan rate of 50 mV s−1 and the as-prepared photocatalysts could act as the promising electrode materials for water splitting.

Visible light removal of reactive dyes using CeO2 synthesized by precipitation

Ceria (CeO2) nanoparticles were synthesized by the precipitation method without use of any organometallic precursors. Photocatalytic degradation of reactive dyes such as Reactive Green 19 (RG19), Reactive Orange 84 (RO84), Reactive violet 1 (RV1) and Reactive Yellow 81 (RY 81) were investigated in a batch reactor catalysed by CeO2. XRD characterization confirmed cubic phase of CeO2 with 19 nm crystallite size, which was supported by SEM and TEM analyses. The band gap of synthesized CeO2 was found to about 3.05 eV from the Kubelka-Munk function analysis of UV-diffuse reflectance spectra. Synthesized CeO2 showed the effective catalytic activity towards the photocatalytic removal of reactive dyes under visible light. Photocatalytic activity was studied to identify the effect of reaction parameters such as catalyst loading, initial dye concentration and pH of dye solutions for the removal of reactive dyes. >95% removal of reactive dyes, reactive green-19, reactive orange-84 and reactive yellow-81, was found under solar irradiation, while in case of reactive violet-1 > 99.9% removal was obtained. Highest activity was found at neutral pH and at 1.5 g/L loading. The photogenerated holes were the most active species responsible for the degradation of reactive dyes. Thus, CeO2 photocatalyst shows great potential for passive solar degradation of reactive dye effluents.

Spectral investigations and DFT studies of 3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione (caffeine) interaction and recognition by single amino acid derived self-assembled nanostructures

Recognition of xanthine alkaloid caffeine with 3,5-bis(trifluoromethyl)benzylamine derived peptide nanotubes (BTTPNTs) through chemical interaction have been achieved through the host-guest like interaction. DFT simulation is carried out for caffeine interacted with BTTPNTs system and also experimentally characterized by ultraviolet–visible (UV–vis) absorbance, confocal Raman spectra (CRS) with microscopic imaging (CRM), FT-Raman, surface enhanced Raman scattering (SERS), UV-diffuse reflectance spectra (UV-DRS), high resolution transmission electron microscopy (HR-TEM) and cyclic voltammetry (CV) studies. The results are used to examine the morphologies, size of the nanostructure and study of its interaction with the caffeine molecule. The results show that BTTPNTs is having potential for sensing the caffeine molecules through the binding occurred from the NH2 of tyrosine moiety of the BTTPNTs. This intermolecular association through face-to-face stacking of BTTPNTs is explained by detailed DFT calculations.

Hazard free green synthesis of ZnO nano-photo-catalyst using Artocarpus Heterophyllus leaf extract for the degradation of Congo red dye in water treatment applications

The present study describes the use Artocarpus Heterophyllus leaves extract for the synthesis of Zinc oxide nanoparticles (ZnO NPs). The particles were calcined at 400, 600 and 800°C for 1h. Powder X-Ray Diffraction (PXRD) results showed the ZnO NPs calcined at different temperature to be crystalline with hexagonal wurtzite phase. The morphology was studied using scanning electron microscopy (SEM) and elemental composition investigated using energy dispersive spectroscopy (EDS) showed peaks for Zn and O only. The exact size of ZnO particles and its crystalline nature were investigated from transmission electron microscopy (TEM),High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). The TEM showed the size range of the ZnO NPs to be ∼ 10–15nm at 400°C, ∼ 15–25nm at 600°C and ∼ 25–30 at 800°C which are in good agreement with the SEM observation. The band gap energy was calculated from UV diffuse reflectance spectra and found to be 3.42, 3.38 and 3.35eV for 400, 600 and 800°C respectively. The fourier transform infra-red spectroscopy (FTIR) spectra of leaf extract confirmed the presence of phyto constituents such as amines, amides, quinines and ketones in the leaf extract. The ZnO NPs calcined at 400°C having higher band gap energy and smaller size was used for photocatalytic degradation. The studies showed the efficiency greater than 90% towards degradation of 20ppm Congo red dye solution at 0.24g/L ZnO NPs in 1h at pH 9.

Luminescence properties, local symmetry and Judd–Ofelt analysis of a Sr2CaWO6:Eu3+, Na+ red phosphor

A series of red phosphors Sr2CaWO6:Eu3+ and Sr2CaWO6:Eu3+, M+ (M=Li, Na, K) were synthesized by conventional solid-state reactions. The optical band gap was calculated through the UV-diffuse reflectance spectrum and strong CT band absorption was observed in compounds in the near ultraviolet region. The optimum doped concentration of Eu3+ was determined to be 20mol%, and the concentration quenching mechanism was found to be electric dipole–dipole interaction. After the introduction of charge compensators Na+, the intensity of the red emission band at 615nm was almost three times than before and shows the strongest emission. Finally, the Ωλ (λ=2 and 4) intensity parameters was calculated according to Judd–Ofelt theory. The CIE colour co-ordinates of the Sr2CaWO6:Eu3+, Na+ was calculated (x=0.661, y=0.339), which are close to NTSC standard values of primary red.