MXene-Derived Oxide Nanoheterostructures for Photocatalytic Sulfamethoxazole Degradation.

Herein, we report for the first time the use of ternary oxide nanoheterostructure photocatalysts derived from (Nb y , Ti1-y )2CT x MXene in the treatment of water. Three different compositions of binary MXenes, viz., (Ti0.75Nb0.25)2CT x , (Ti0.5Nb0.5)2CT x , and (Ti0.25Nb0.75)2CT x (with T x = OH, F, and Cl), were used as single-source precursor to produce TiNbO x -3:1, TiNbO x -1:1, and TiNbO x -1:3 by controlled-atmosphere thermal oxidation. Phase identification and Le Bail refinements confirmed the presence of a mixture of rutile TiO2 and monoclinic Ti2Nb10O29. Morphological investigations through scanning and transmission electron microscopies revealed the retention of layered nanostructures from the MXene precursors and the fusion of TiO2 and Ti2Nb10O29 nanoparticles in forming nanosheets. Among the three oxide nanoheterostructures, TiNbO x -3:1 exhibited the best photocatalytic performance by the removal of 83% of sulfamethoxazole (SMX) after 2 h of reaction. Such a result is explained by a complex influence of structural, morphological, and electronic properties since TiNbO x -3:1 consisted of small-sized crystallites (40-70 nm) and possessed a higher surface area. The suggested electronic band structure is a type-II heterojunction, where the recombination of electrons and holes is minimized during photocatalytic reactions. The photocatalytic degradation of SMX was promoted by the attack of •OH, as evidenced by the detection of 2.2 µM •OH, using coumarin as a probe. This study highlights the potential application of MXene-derived oxide nanoheterostructures in wastewater treatment.

One Precursor, Two Different Outcomes: SnO-Graphite Composite and Anion-Doped SnO2 with Ester Surface Functionality.

The technological importance of SnO2 and SnO has invited scientists to explore various aspects, including their synthesis in the nanosize regime, surface functionalization, and composite formation. In the present work, a binuclear Sn2-EDTA complex has been demonstrated to produce a SnO-graphite composite and C, N-codoped SnO2 nanocrystals with ester functionality in quantitative yields by thermal and solvothermal dissociation processes. The products were characterized extensively. While SnO in the SnO-graphite composite exhibited tetragonal symmetry, graphitic carbon had defects. The composite had 12 wt % of graphitic carbon. The role of the SnO-graphite composite as an anode in lithium-ion batteries (LIB) has been evaluated. Solvothermal dissociation of the Sn2-EDTA complex in a propylene glycol medium yielded nanocrystalline SnO2 with yellow color. Agglomerated crystallites had ester functionality on their surfaces. The surface functionality was thermally stable up to 200 °C, and its complete removal yielded tetragonal white-colored SnO2. Co-doping of carbon and nitrogen in yellow SnO2 reduced its optical band gap (2.9 eV). Despite the negative surface charge of the functionalized SnO2, its affinity to rapidly adsorb anionic azo dyes (Congo red and Eriochrome black T) from aqueous solutions has been validated. Following pseudo-second-order kinetics, adsorption data analysis revealed chemisorption as the primary driving force in this process.

Quasi-2D Bi0.775Ln0.225O1.5 (Ln = La, Pr, Nd, Sm, Eu): reversible iodine intercalation and their evaluation as the anode in the lithium-ion battery system.

Layered materials with a robust structure and reversible intercalation behavior are highly sought-after in applications involving energy conversion and storage systems, energy converting devices, supercapacitors, batteries, superconductors, photonic materials, and catalysis involving hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), solar cells and sensors. In the current study, quasi-2D rhombohedral Bi0.775Ln0.225O1.5 (Ln = La, Pr, Nd, Sm, and Eu) samples, synthesized by a solution combustion route, have been demonstrated to intercalate iodine reversibly. A solid-vapor reaction was employed to intercalate iodine at moderate temperatures, and deintercalation occurred on heating at higher temperatures. Expansion of the rhombohedral c-axis by ∼10 Šoccurred, and the iodine between the interlayers existed as triiodide ions (I3-) in an unsymmetrical fashion. The amount of intercalated iodide has been determined from thermogravimetric analysis. Electron microscopic analysis confirmed these systems' intercalation and subsequent lattice expansion. In the diffuse reflectance spectra, charge transfer from the triiodide ions to the host oxide was noticed, and it caused the absorption edge to fall beyond the visible region for the intercalated samples. XPS analysis of iodine intercalated Bi0.775Pr0.225O1.5 has shown the mixed valence states for Pr and the existence of I3- along with some IO3- species. The quasi-2D structure was stable during the thermal deintercalation process. The evaluation of iodine intercalated Bi0.775Ln0.225O1.5 (Ln = La, Pr, Nd, Sm, and Eu) samples as anode material in the lithium-ion battery system has given quite promising results, exhibiting fast Li+-ion diffusion, low charge transfer resistance, good reversible capacity, capacity retention (after cycling back to 10 mA g-1), and structural stability (after long cycles).

Hole and Electron Doping Outcomes in Bi2YO4Cl.

Recognizing the deficiency in the hole and electron doping outcomes in layered bismuth-based oxyhalides intergrowths, the current study was addressed to the doping of Ca2+ and Zr4+ for Y3+ in Bi2YO4Cl. The samples were rapidly synthesized by a sol-gel auto combustion method and characterized extensively. Up to 30 mol % Y could be substituted with Ca in tetragonal symmetry and without the appearance of any additional phase. The unit cell parameters varied nonlinearly with the elongation of the Y-O bond. The Raman spectra supported the local site distortion. The calcium-substituted samples displayed selected area electron diffraction characteristics similar to those of Bi2YO4Cl. A blueshift of the absorption edge was noticed with increasing calcium content yielding optical band gap values in the 2.40-2.57 eV range. The creation of 10% Bi5+ in Bi2Y0.70Ca0.30O4Cl was established with the help of XPS measurements and redox titrations. The higher reactivity of Bi5+ in an aqueous solution has been demonstrated for the oxidation of As(III) to As(V). Electron doping through Zr4+ incorporation was possible up to 30 mol % in Bi2YO4Cl. The Y-O bonds are contracted, and the Bi-O bonds are elongated with increasing Zr4+ content. Zr4+'s incorporation induced a local distortion. The color of the sample changed from bright yellow to deep yellow with Zr inclusion, resulting in a progressive decrease in optical band gap values. The introduction of electrons caused the reduction of 13.6% of Bi(III) to Bi(0). These results have established the vulnerability of Bi2O2 chains to charge carriers in Bi2YO4Cl. Density functional theory (DFT) calculations were implemented to understand the electronic and optical properties of the pristine and doped compounds. From the band structure calculations, the chosen compounds were found to be indirect band gap semiconductors. The results of the DFT calculations were in good agreement with the experiment; however, for the doped cases, virtual crystal approximation has been used considering uniform doping at the Y-site.

Zircon PrVO4: an efficient heterogeneous catalyst for tandem oxidative synthesis of 2,3-disubstituted quinoline derivatives.

The current study addresses the usage of inherent redox couplets in PrVO4 crystallizing in a zircon-type structure for tandem oxidative transformation. Monophasic PrVO4, synthesized using a solution combustion synthesis method, showed a tetragonal zircon-type structure in its PXRD pattern (S.G. I41/amd). The tetragonal symmetry of the zircon PrVO4 was also confirmed from electron microscopic and vibrational spectroscopic measurements. From XPS analysis, the existence of redox couplets Pr3+/Pr4+ and V4+/V5+ in PrVO4 was established. The catalytic utility of zircon PrVO4 for one-pot synthesis of 2,3-disubstituted quinolines through the oxidative tandem reaction of 2-aminobenzylalcohols with 1,3-dicarbonyl compounds has been demonstrated. This highly efficient method proceeds under molecular oxygen, tolerates different functional groups, and produces various substituted quinoline derivatives in good to excellent yields. The important features of the process are the easy workup, simple catalyst recovery, and reusability.

Magnetic properties of Sn- and Mn-incorporated Co2TiO4 from single-step calcination.

This report deals with the rapid synthesis of cobalt titanate spinels (Co2TiO4 (CTO), Co2Sn0.50Ti0.50O4 (CSTO), and Co2Mn0.50Ti0.50O4 (CMTO) by the single-step calcination of hydroxide precursors and their extensive characterization. The cubic unit cell expanded and contracted when Ti in CTO was partially replaced with Sn and Mn, respectively. The Raman spectra confirmed the cubic spinel structure and showed a systematic shift with the inclusion of tin and manganese. The broadening of Raman bands suggested cation disorder. The absorbance spectra of CTO and CSTO proved the existence of cobalt in the +2 and +3 states with optical bandgaps of 0.6 and 1.1 eV, respectively. X-ray photoelectron spectroscopic (XPS) analysis confirmed the presence of cobalt in both the +2 and +3 states with titanium in the +3 state in CTO. While cobalt and titanium existed in the +2 and +3 states in CMTO, mixed-valence (+3 (minor) and +4 (major amounts) states) was deduced for manganese. All these samples showed an exchange-bias effect and a long-range ferrimagnetic ordering with TN of 50 (CTO), 46 (CSTO), and 54 K (CMTO). These transitions have been independently verified from heat capacity measurements performed at zero fields and applied fields of 500 and 1000 Oe. The compensation of magnetic moments from the tetrahedral and octahedral units of the spinel structure was not observed in any of these samples, perhaps because of the asymmetric distribution of cations among the available crystallographic sites.

Anatase Nanocrystals Covalently Functionalized with EDTA-diol: Interaction with Aromatic Sulfur.

The current study addresses the generation of surface-modified nanograined anatase (5 nm) by a single-step in situ process. The EDTA-diol (ester) functionality existing on the surface of anatase nanoparticles was proved with the help of a battery of physicochemical techniques, including FTIR, XPS, and NMR spectral measurements. The sample showed excellent dispersity in ethanol. The anatase lattice showed disorder and had oxygen vacancies. From the XPS analysis, the existence of 14% of Ti3+ was established. The functionalized sample remained thermally stable up to 250 °C, beyond which it transformed into a graphite-titania nanocomposite. The interfacial ligand (ester) to metal (Ti) charge transfer (LMCT) transitions were present in the UV-visible spectrum of the sample and indicated the functionalization to be covalent. Unsaturated OH-groups on the surface yielded a ζ-potential value of -39.8 mV. The covalently functionalized nanotitania was exploited in the adsorptive desulfurization of thiophene, an aromatic sulfur model compound. The consequences of surface adsorption of thiophene were analyzed with the help of UV-visible, FTIR, and 1H and 13C NMR spectra and EDS and XPS measurements. The adsorption data, derived from the batch process, were fitted successfully to pseudo-second-order kinetics and the Temkin model. The adsorption capacity of covalently functionalized titania was compared with several other high surface area adsorbents containing thiophilic metal ions.

KLa(0.95-x)GdxF4:Eu3+ hexagonal phase nanoparticles as luminescent probes for in vitro Huh-7 cancer cell imaging.

A facile chemical route is reported for synthesizing red-emitting photoluminescent/MRI multi-functional KLa(0.95-x)GdxF4:Eu3+ (x = 0 to 0.4) bio-compatible nanomaterials for targeted in vitro tumor imaging. Hexagonal phase pure nanoparticles show a significant and systematic change in morphology with enhanced photoluminescence due to the substitution of La3+ with Gd3+ ions. Single phase ß-KLa(0.95-x)GdxF4:Eu3+ exhibits multifunctional properties, both intense red emission and strong paramagnetism for high-contrast bioimaging applications. These silica capped magnetic/luminescent nanoparticles show long-term colloidal stability, optical transparency in water, strong red emission, and low cytotoxicity. The cellular uptake of coated nanoparticles was investigated in liver cancer cell line Huh-7. Our findings suggest that these nanoparticles can serve as highly luminescent imaging probes for in vitro applications with potential for in vivo and live cell imaging applications.

Modulating the optical and magnetic properties of geometrically frustrated ZnV2O4 by the introduction of indium (nonmagnetic ions), iron, and chromium (magnetic ions).

The current study is aimed at understanding the effects of diluting the magnetic properties of a geometrically frustrated normal spinel, ZnV2O4, with the incorporation of nonmagnetic In3+ in place of V3+. Samples with the formula, ZnV2-xInxO4 (x = 0.00, 0.25, 0.50, 1.00 and 1.50), were synthesized following an epoxide mediated gel method and characterized extensively. The monophasic cubic spinel structure was retained up to 50 mol% of vanadium with indium, beyond which phase separation took place. The occupancy of indium at the octahedral site and the near-linear increment of the cubic unit cell constant were confirmed from the successful structural refinements. The optical bandgap increased from 2.80 (ZnV2O4) to 3.06, 3.19, and 3.35 eV for x values of 0.25, 0.50, and 1.00 in ZnV2-xInxO4. ZnVInO4 exhibited paramagnetic behavior down to 2 K in both the field-dependent and temperature-dependent magnetic measurements. However, the magnetization values were lower than those of ZnV2O4. A frustration index of 42 was estimated for ZnVInO4. Samples containing magnetic Cr3+ and Fe3+ ions in place of V3+ were synthesized and characterized to compare and contrast the magnetic ions' influence. For both chromium and iron substituted samples, the optical bandgap was higher than that of ZnV2O4. ZnVCrO4 showed an antiferromagnetic ordering of spins with a TN of 12.3 K. In contrast, the randomization of Zn, V, and Fe among the available crystallographic sites increased the ferrimagnetic transition temperature (TF) to 31.9 K. ZnVInO4 catalyzed the photodegradation of rhodamine-6G under UV-vis radiation to a greater extent than ZnVCrO4 and ZnVFeO4.

The emergence of bifunctional catalytic properties by the introduction of Bi3+ in defect fluorite-structured PrO1.833.

In the present study, the utility of Pr3+/Pr4+ and Bi3+/Bi(0) redox couples for oxidation and reduction reactions is demonstrated by synthesizing bismuth-substituted PrO1.833 samples following a solution combustion method. The samples retained the defect fluorite structure of PrO1.833 with the inclusion of up to 40 mol% of bismuth, beyond which the rhombohedral structure emerged. The microscopic analysis also reinforced the defect fluorite structure of these samples. The lattice expanded with the inclusion of bismuth. The samples had porous morphology, and the X-ray energy dispersive spectral analysis ensured the presence of Pr and Bi closer to the nominal molar ratio. The intense band at 565 cm-1 in the Raman spectrum shifted to higher values with a progressive increase in bismuth content due to the creation of more oxygen vacancies. In Pr0.60Bi0.40O2-δ, Pr existed in +3 and +4 oxidation states, as revealed by the X-ray photoelectron spectral analysis. The photoluminescence spectra consisted of 4f-4f transitions of Pr3+ and emission in the blue region (due to oxygen vacancies). Both Pr0.60Bi0.40O2-δ and PrO1.833 remained paramagnetic in field-dependent and temperature-dependent measurements down to 2 K. The effective magnetic moment, retentivity, and coercivity decreased on moving from PrO1.833 to Pr0.60Bi0.40O2-δ. The bismuth-substituted samples catalyzed the oxidative degradation of xylenol orange and methyl orange. The degraded products from these reactions were identified. The bismuth-substituted samples also catalyzed the reduction of nitroaromatics. These transformations followed pseudo-first-order kinetics.

Synthesis of ZnO@Ag dumbbells for highly efficient visible-light photocatalysts.

The photocatalytic activity (PCA) of ZnO@Ag nanocomposites for different concentrations of Ag is reported. Dumbbells shaped zinc oxide (ZnO) nanostructures with silver (Ag) nanoparticles were synthesized by a simple chemical colloidal method. The as synthesized nanocomposites (without any heat treatment) were used for optical and photocatalytic studies. The FESEM analysis shows that the composite catalysts are composed of ZnO dumbbells coated with spherical Ag nanoparticles. UV-visible spectrum of ZnO@Ag photocatalysts shows a strong absorption band of ZnO at 380 nm with a plasmonic peak of Ag at 440 nm. The PL emission intensity of the composites varies with Ag concentration and has a minimum for the catalyst containing 13.7% of Ag. A possible growth mechanism of ZnO nanostructures with hexagonal cross-section has been proposed. Photocatalytic property of the as synthesized ZnO and ZnO@Ag catalysts was studied by investigating the degradation of methylene blue (MB) dye on exposure to UV-visible radiation. A relatively faster degradation of the dye was observed for ZnO@Ag composites as compared to pure ZnO, showing an improved photocatalytic behavior in the visible region. We proposed a possible mechanism for the enhancement in photocatalytic activity of Ag coated ZnO photocatalysts.

Implications of including a magnetic ion (Cr3+ and Fe3+) at the vanadium site in a geometrically frustrated spinel MgV2O4: magnetic and catalytic properties.

The vanadium sublattice in a geometrically frustrated MgV2O4 is substituted partially with Cr3+ and Fe3+. With a successful Rietveld refinement of the powder X-ray diffraction patterns of MgVCrO4 and MgVFeO4, Cr and Fe occupy the octahedral sites of a spinel structure. Extensive field-dependent and temperature magnetic measurements on these samples reveal exciting results. MgV2O4 remains paramagnetic till 3 K, with a small divergence at around 20 K between ZFC and FC data. MgVCrO4 exhibits antiferromagnetic behavior with a Néel temperature of 13.6 K. MgVFeO4 shows spin-glass behavior resulting from the frustration with a glass transition temperature of 194 K. This sample shows a typical ferromagnetic behavior, with a coercivity of 194.5 Oe within an applied field of ±2 kOe. All three systems have been found to have a frustration index in the range of 1-25, and the effective magnetic moment decreases in the order MgVFeO4 > MgVCrO4 > MgV2O4. While the inclusion of chromium does not alter the bandgap of MgV2O4, iron substitution increases the bandgap. The partial replacement of V3+ with Cr3+ and Fe3+ increases the catalytic ability of the system in terms of the oxidative degradation of methylene blue dye. The catalytic efficiency follows the order MgVFeO4 > MgVCrO4 > MgV2O4, matching well with the trend noticed in the porosity, surface area, and redox ability of Fe3+, Cr3+ and V3+ in these samples. The degradation pathway has been followed by analyzing the intermediates from these experiments by mass spectrometry, and a plausible mechanism is proposed.

Color-Tunable Upconversion in Er3+/Yb3+-Codoped KLaF4 Nanophosphors by Incorporation of Tm3+ Ions for Biological Applications.

Heavily doped nanocrystals of host KLaF4 with rare earth (RE3+ = Er3+, Tm3+, and Yb3+) ions prepared by a simple one-step template-free wet-chemical route have been reported. Prepared KLaF4 nanocrystals reveal phase-pure cubic structures (lattice constant a = 5.931Å) with space group Fm3m. Precisely defined molar ratios of heavily dopant RE3+ ions allow us to achieve wide color upconversion (UC) emission tunability (blue, green to yellow-orange-red) and white light, without any morphology and structure changes. The enhanced red emission by a factor of ∼120 has been achieved in 20% Yb3+ and 5% Tm3+ ions in KLaF4:1% Er3+ nanocrystals, which is due to an efficient sensitizer-acceptor (Yb3+ to Er3+ and Tm3+ ions) energy transfer and interexchange energy process between acceptors. For the first time, the key role of sensitizer (Yb3+) for UC emission energy transfer to Er3+ and/or Tm3+ is experimentally demonstrated. The evidence of upconversion photoluminescence excitation spectra reveals a broad safe biological excitation window (690-1040 nm), which can be well demonstrated by low-cost NIR diode lasers/LEDs. The applicability of these cubic nanophosphors is demonstrated as light-emitting polymer composite coatings and blocks for LEDs and solar cell panels. These well-dispersed UC nanocrystals can also be found to have greater use in bioimaging and spectral studies.

Metastable Bi2Zr2O7 with Pyrochlore-like Structure: Stabilization, Oxygen Ion Conductivity, and Catalytic Properties.

Equimolar concentrations of Zr4+ and Bi3+ were chelated with ethylenediaminetetraacetic acid ligand with the purpose of using it as a precursor to generate pyrochlore-like Bi2Zr2O7. When the X-ray amorphous precursor was calcined at 750 °C for 3 h in air, pyrochlore-like product with superstructure reflections was identified by powder X-ray diffraction (PXRD) along with one minor reflection due to ß-Bi2O3. This phase was found to be metastable from additional experiments conducted by varying calcination conditions. Structural refinement of PXRD pattern by Le Bail method in Fd3̅ m space group yielded cubic lattice constant of 10.8421(27) Å. Flower-petal-like morphology of the sample was evident in its field-emission scanning electron microscopy image and energy-dispersive X-ray analysis performed at various locations of the specimen confirmed nearly equal concentration of zirconium and bismuth. Six bands at 260, 320, 448, 531, 597, and 828 cm-1 were observed for this sample in its Raman spectrum and supported our claim of pyrochlore-like structure. Indexation of bright spots present in selected area electron diffraction pattern and observed distances of lattice fringes in high-resolution transmission electron microscopy image were in conformity with the results from PXRD measurements. Absorbance maxima at 312, 372, and 423 nm with a broad tailing stretching up to visible region was noticed in the UV-visible spectrum of this sample. Direct band gap of 2 eV was estimated for this sample from Tauc plot. The oxygen ion conductivity of the sample in the temperature range of 333-773 K was examined, and the highest conductivity at 773 K was 3.071 × 10-6 S/cm. From activation energy estimation and dielectric loss analysis, thermally activated process related to the mobility of oxygen ion vacancy was found responsible for the observed ionic conductivity. A similar conclusion was reached after careful analysis of dielectric spectroscopy data of this sample. High surface area (125.04 m2/g) and mesoporosity (pore diameter of 3.81 nm) were possessed by this sample, which paved way for studying its catalytic role in the reduction of nitroaromatics and carcinogenic Cr6+. Cyclability experiments showed the retainment of catalytic activity up to five cycles by the sample without undergoing any structural change.

Site preference for luminescent activator ions in doped fluoroperovskite RbZnF3.

With the dual objective of investigating the site preferences of larger sized activator ions and to append luminescence property to the perovskite structured RbZnF3, doping of manganese(II), cerium(III), europium(III) and terbium(III) ions (5 mol%) was carried out. Although cubic symmetry of RbZnF3 was preserved for all the doped samples, site preference of rare-earth ions for the A-site Rb+ leading to an inverse perovskite arrangement has been noticed from careful analysis of lattice parameters from refinement of powder X-ray diffraction data. Undoped RbZnF3 exhibited rod-like morphology in the transmission electron microscopic image. In addition to an intense band around 230 nm assignable to the charge transfer from ZnF3- to Rb+, typical transitions of respective dopant ions were observed in their UV-visible spectra. The doped samples showed luminescence in blue, green and red regions and time decay experiments suggested uniform dispersion of them without any clustering effect. The lower phonon energy of RbZnF3 matrix by virtue of the presence of heavier rubidium at the A-site together with its doping with rare-earth ions resulting in an inverse perovskite like arrangement could favour their utility in various practical applications.

Catalytic Application of Oxygen Vacancies Induced by Bi3+ Incorporation in ThO2 Samples Obtained by Solution Combustion Synthesis.

Recognizing immense advantages of solution-based combustion synthesis, its applicability to determine the extent of dissolution of Bi3+ in fluorite-structured thoria has been examined to generate high-surface-area samples with massive defects. Up to 50 mol % of thorium could be substituted with bismuth retaining fluorite structure beyond which phase separation occurred. The lattice parameters from Le-Bail refinements of their powder X-ray diffraction patterns showed marginal increase with increase in bismuth content, suggesting the competing effect between the size of the cation and the oxygen vacancy concentration. Energy-dispersive X-ray spectrometry analysis and high-resolution transmission electron microscopy measurements have also confirmed the composition and structure of the limiting composition. With progressive bismuth content, the band due to the fluorite (at 460 cm-1) diffused and a defect band in the region 570-600 cm-1 emerged in the Raman spectra. From these changes, the oxygen vacancy concentrations in these samples have been determined, which increased with increase in bismuth content. Absorbance in the visible region was noticed for bismuth-containing samples, and band gap values determined from the Kubelka-Munk function were in the range 2.34-3.24 eV. In addition to the blue emission from oxygen vacancies, 3P1 → 1S0 transition of Bi3+ was noticed in the photoluminescence spectrum. From Brunauer-Emmett-Teller measurements, the surface area of Th0.50Bi0.50O2-δ obtained by solution combustion synthesis was measured to be 265.74 m2 g-1, higher than the value (39.00 m2 g-1) for the sample prepared by solid-state synthesis. All of these factors combined with oxygen vacancies as defect centers have been found to play critical control over their use as catalyst for the reductive transformation of nitroaromatics and oxidative decolorization of organic dye molecules (methyl orange and xylenol orange). A nice correlation between oxygen vacancy concentration and pseudo first-order rate constants of these catalytic conversions has been arrived. The catalyst was found to retain its efficiency up to four cycles without undergoing any structural change during these experiments.

Correlating the Influence of Two Magnetic Ions at the A-Site with the Electronic, Magnetic, and Catalytic Properties in Gd1-x Dy x CrO3.

Considering the absence of reports dealing with the perovskite-structured orthochromites containing two A-site magnetic rare-earth ions, GdCrO3 and progressively Dy3+-substituted samples of the series Gd1-x Dy x CrO3 have been synthesized employing the epoxide-mediated sol-gel procedure. The samples were characterized extensively using high-resolution powder X-ray diffraction, thermal analysis, Fourier transform infrared, Raman, and UV-visible spectroscopies, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) measurements. Monophasic samples possessing an orthorhombic perovskite structure emerged by calcining the xerogels formed by the reaction of rare-earth nitrates, chromium(III)chloride, and propylene oxide at 800 °C for 2 h. Uniform presence of wormlike morphology was observed in both the field emission SEM (FE-SEM) and TEM images of the samples. Zero-field and field-cooled magnetic measurements using a SQUID magnetometer down to 4 K showed that the Neel temperature of Gd0.5Dy0.5CrO3 was 155 K, more or less midway between the values observed for GdCrO3(169 K) and DyCrO3 (146 K). For the Gd0.5Dy0.5CrO3 sample, a spin reorientation was observed at ∼38 K when measured under an applied field. Because the optical band gap, determined by Kubelka-Munk function, of these chromites was around 3 eV, their application as a catalyst for the photodegradation of the aqueous rhodamine-6G dye solution was demonstrated, in which the percentage of the total dye that was degraded varied with the average ionic radius of A-site ions. A similar systematic trend was observed even for the catalytic oxidation of the XO dye in the presence of H2O2, with DyCrO3 influencing the reaction to a greater extent followed by Gd0.5Dy0.5CrO3 and GdCrO3. Both the photocatalytic and catalytic reactions followed pseudo-first-order kinetics.

Sol-Gel Synthesis of High-Purity Actinide Oxide ThO2 and Its Solid Solutions with Technologically Important Tin and Zinc Ions.

The applicability of epoxide-based sol-gel synthesis for actinide oxide (thoria) starting from air-stable salt, Th(NO3)4, has been examined. The homogeneous gel formed from Th(NO3)4 when calcined at 400 °C yielded nanostructured thoria, and with increasing tempeartures (600, 700, and 800 °C), the average crystallite size increased. Successful Rietveld refinement of the powder X-ray diffraction pattern of ThO2 in Fm3̅m space group was carried out with a = 5.6030(35) Å. The fingerprint vibrational mode of the fluorite structure of ThO2 was noticed as a sharp band in the Raman spectrum at 457 cm-1. In the SEM image, a near spherical morphology of thoria was noticed. Samples showed blue emission on exciting with λ = 380 nm in the photoluminescence spectrum indicative of the presence of defects. Following this approach, 50 mol % of Sn4+ could be substituted for Th4+, retaining the fluorite structure as evidenced by the PXRD, Raman spectroscopy, electron microscopy, EDAX, and XPS measurements. Randomization of the lattice was observed for the tin-substituted samples. A significant blue shift in the absorption threshold along with a persistent blue emission in the photoluminesence spectra were evident for the tin-substituted samples. The concentration of Zn2+ ion in thoria was limited to 15 mol % as revealed by PXRD and XPS measurements. The Raman peak shifted to higher values for Zn2+-substituted samples. A change in the optical absorbance characteristics was observed for the zinc-substituted thoria. A 50 mol % Sn4+-substituted thoria degraded aqueous Rhodamine 6G dye solutions in the presence of UV-vis radiation following pseudo-first-order kinetics.

An ethylene glycol intercalated monometallic layered double hydroxide based on iron as an efficient bifunctional catalyst.

Given the fact that the literature describing the intercalation of organic molecules in monometallic LDH systems is scarce, the present investigation is aimed at the generation of ethylene glycol intercalated FeII-FeIII LDH with the objective of enhancing the surface area for further catalytic applications of industrially important and environmentally harmful organics. The solvothermal reaction of FeCl3 with urea in an ethylene glycol medium yielded a brown colored powder which was characterized employing a wide range of analytical techniques including high resolution powder X-ray diffraction (PXRD), scanning electron microscopy, thermal analysis, X-ray photo electron spectroscopy (XPS), elemental (C, H, N and S) analysis, UV-visible, photoluminescence spectroscopy measurements, BET surface area and pore-size analysis. The observed reflections in the PXRD pattern were indexed in a rhombohedral symmetry with a = 3.175 and c = 31.9 Å. Combining the results from the Fe 2p core level analysis and anion contents from elemental and thermogravimetric analysis, a formula of Fe2+1.06 Fe3+0.94 (O2C2H4) (OH)4 was deduced for the sample. The intercalation of EG in the interlayer was confirmed from FTIR and Raman spectroscopy measurements. The d-d transitions of the Fe3+-ion and the charge transfer transition of the Fe(ii)-Fe(iii) lattice were evident in the UV-visible spectrum. Blue indigoid emission bands arising from the transitions present in the Fe3+-ion were noticed in the photoluminescence spectrum. The measured BET surface area and pore diameter of the sample were 144 m2 g-1 and 12.5 nm, respectively. Almost instant decolourisation of the Xylenol Orange (XO) dye occurred in the presence of H2O2 and the LDH sample as catalyst. Similar observations were encountered for Methyl Orange (MO) and Methylene Blue (MB) dyes. All these reactions followed pseudo first-order kinetics. The industrially important reductive conversion of nitro aromatics was catalyzed by the sample. The selective reduction of 2,4-dinitrophenol to 2-amino-4-nitrophenol was effected almost instantaneously by this catalyst. Both the reusability and possible mechanism of catalytic action have been discussed. The EG intercalated Fe2+-Fe3+ LDH influenced the relaxivity value of protons as determined from NMR spectroscopy experiments.

Determination of solubility limit of Sn(4+) in fluorite structured terbia with simultaneous evaluation of photocatalytic function.

Although the fluorite structure is highly common among stoichiometric and non-stoichiometric terbia compositions, high pressures are necessary to stabilize SnO2 in the fluorite structure. With this objective, the extent of solubility of Sn(4+) in terbia possessing the fluorite structure has been determined by conducting its synthesis via an epoxide mediated sol-gel method. Up to 40% of Sn(4+) can be incorporated in terbia, which retains its fluorite structure, as concluded from PXRD, FTIR, Raman spectroscopy, FESEM, HR-TEM and SAED measurements. The cubic lattice constant decreases systematically, as inferred from successful Rietveld refinements of PXRD patterns. The stretching vibration of the Tb-O bond is manifested as broad band at 734 cm(-1) for the terbia, and moves to lower wavenumber for the tin substituted samples. The broad band at 611 cm(-1) in the Raman spectrum of terbia became even broader with the maxima shifting towards higher values, which indicated the strain of the lattice and generation of oxygen vacancies with progressive tin substitution. The band gap value increased from 1.78 eV for terbia to 2.05 eV for the 40% tin substituted sample. Emission in the blue region became intense upon tin substitution, which was indicative of increased oxygen vacancies and this has been constructively utilized for environmental remediation as a catalyst to degrade aqueous Rhodamine-6G and Methylene Blue dye solutions.