Methotrexate-Loaded Gelatin and Polyvinyl Alcohol (Gel/PVA) Hydrogel as a pH-Sensitive Matrix.

The aim was to formulate and evaluate Gel/PVA hydrogels as a pH-sensitive matrix to deliver methotrexate (MTX) to colon. The primed Gel/PVA hydrogels were subjected to evaluation for swelling behavior, diffusion coefficient, sol-gel characteristic and porosity using an acidic (pH 1.2) and phosphate buffer (PBS) (pH 6.8 & pH 7.4) media. Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA) were performed to evaluate the chemical compatibility of the Gel/PVA hydrogel. The shape alteration and release of Gel/PVA hydrogel was conducted at pH 1.2, pH 6.8 and pH 7.4. The drug release kinetic mechanism was determined using various kinetic equations. The physicochemical evaluation tests and drug release profile results were found to be significant (p < 0.01). However, it was dependent on the polymers' concentration, the pH of the release media and the amount of the cross-linking agent. Hydrogels containing the maximum amount of gel showed a dynamic equilibrium of 10.09 ± 0.18 and drug release of 93.75 ± 0.13% at pH 1.2. The kinetic models showed the release of MTX from the Gel/PVA hydrogel was non-Fickian. The results confirmed that the newly formed Gel/PVA hydrogels are potential drug delivery systems for a controlled delivery of MTX to the colon.

Enhanced photocatalytic and electrochemical performance of TiO2-Fe2O3 nanocomposite: Its applications in dye decolorization and as supercapacitors.

This work reveals a green combustion route for the synthesis of TiO2, Fe2O3 and TiO2-Fe2O3 nanocomposites as photocatalysts for decolorization of Titan Yellow (TY) and Methyl Orange (MO) dyes at room temperature in aqueous solution concentration of 20 ppm under UV-light irradiation. We observed that the TiO2-Fe2O3 nanocomposite shows superior photocatalytic activity for TY dye compared to pure TiO2 and Fe2O3. Rate constant (k) values of TiO2, Fe2O3 and TiO2-Fe2O3 for TY and MO are 0.0194, 0.0159, 0.04396 and 0.00931, 0.00772 0.0119 kmin-1 respectively. The surface area and pore volume of TiO2-Fe2O3 nanocomposite were found to be 71.56 m2/g and 0.076 cm3/g, respectively as revealed by BET studies. From the Barrett-Joyner-Halenda (BJH) plot, the mean pore diameter of TiO2-Fe2O3 nanoparticles was found to be 2.43 nm. Further, the TiO2-Fe2O3 nanocomposite showed good electrochemical behavior as an electrode material for supercapacitors when compared to pure TiO2 and Fe2O3 nanoparticles resulted in stable electrochemical performance with nearly 100% coulombic efficiency at a scan rate of 10 mV/s for 1000 cycles. Interestingly, the novelty of this work is that the designed supercapacitors showed stable electrochemical performance even at 1000th cycle, which might be useful for rechargeable supercapacitor applications. The electrochemical properties of the nanocomposites were compared by the data obtained by cyclic voltammograms, charge-discharge tests and electrochemical impedance spectroscopic studies. These results demonstrated that the TiO2-Fe2O3 nanocomposite showed stable performance compared to TiO2 and Fe2O3 nanoparticles at current density of 5 Ag-1.

Bio-mediated route for the synthesis of shape tunable Y2O3: Tb³âº nanoparticles: Photoluminescence and antibacterial properties.

The study reports green mediated combustion route for the synthesis of Tb(3+) ion activated Y2O3 nanophosphors using Aloe Vera gel as fuel. The concentration of Tb(3+) plays a key role in controlling the morphology of Y2O3 nanostructures. The formation of different morphologies of Y2O3: Tb(3+) nanophosphors were characterized by PXRD, SEM, TEM and HRTEM. PXRD data and Rietveld analysis evident the formation of single phase Y2O3 with cubic crystal structure. The influence of Tb(3+) ion concentration on structural morphology, UV-visible absorption and PL emission were investigated systematically. The PL emission of Y2O3: Tb(3+) (1-11 mol%) nanophosphors were studied in detail under 271 and 304nm excitation wavelengths. The CIE coordinates lies well within green region and correlated color temperature values were found to be 6221 and 5562K under different excitations. Thus, the present phosphor can serve as an excellent candidate for LEDs. Further, prismatic Y2O3: Tb(3+) (3 mol%) nanophosphor showed significant antibacterial activity against Pseudomonas desmolyticum and Staphylococcus aureus. The present study successfully demonstrates Y2O3: Tb(3+) nanophosphors can be used for display applications as well as in medical applications for controlling pathogenic bacteria.

Green synthesis of Y2O3:Dy(3+) nanophosphor with enhanced photocatalytic activity.

Facile and green route was employed for the synthesis of Y2O3:Dy(3+) (1-11 mol%) nanostructures (NSs) using Aloe vera gel as fuel. The formation of different morphologies of Y2O3:Dy(3+) NSs were characterized by SEM, TEM and HRTEM. PXRD data and Rietveld analysis evident the formation of single phase Y2O3 with cubic crystal structure. The influence of Dy(3+) ion concentration on the structure morphology, UV absorption, PL emission and photocatalytic activity of NSs were investigated. NSs exhibited an intense warm white emission with CIE chromaticity coordinates (0.32, 0.33) and average CCT value ∼5525 K which corresponds to vertical day light. The control of Dy(3+) ion on Y2O3 matrix influences the photocatalytic decolorization of Metanil Yellow as a model compound was evaluated. The enhanced photocatalytic activities of core shell structured Y2O3:Dy(3+) (1 mol%) was attributed to co-operation effect of dopant concentration, crystallite size, textural properties and capability for reducing electron-hole pair recombination. Further, the recycling catalytic ability of Y2O3:Dy(3+) (1 mol%) nanostructure was also evaluated and found promising photocatalytic performance with negligible decrease in decolorization efficiency even after sixth successive cyclic runs. Considering its green, facile synthesis and recyclable feature from an aqueous solution, the present Y2O3:Dy(3+) (1 mol%) nanophosphor can be considered as one of the ideal photocatalyst for various potential applications.

Bio-inspired route for the synthesis of spherical shaped MgO:Fe(3+) nanoparticles: Structural, photoluminescence and photocatalytic investigation.

MgO:Fe(3+) (0.1-5 mol%) nanoparticles (NPs) were synthesized via eco-friendly, inexpensive and simple low temperature solution combustion route using Aloe vera gel as fuel. The final products were characterized by SEM, TEM and HRTEM. PXRD data and Rietveld analysis revealed the formation of cubic system. The influence of Fe(3+) ion concentration on the structure morphology, UV absorption, PL emission and photocatalytic activity of MgO:Fe(3+) NPs were investigated. The yellow emission with CIE chromaticity coordinates (0.44, 0.52) and average correlated color temperature value was found to be 3540 K which corresponds to warm light of NPs. The control of Fe(3+) on MgO matrix influences the photocatalytic decolorization of methylene blue (MB) under UV light. The enhanced photocatalytic activity of MgO:Fe(3+) (4 mol%) was attributed to dopant concentration, effective crystallite size, textural properties, decreased band gap and capability for reducing the electron-hole pair recombination. Further, the trends of inhibitory effect in the presence of different radical scavengers were explored. These findings open up new avenues for the exploration of Fe-doped MgO in eco-friendly water applications and in the process of display devices.

A single phase, red emissive Mg2SiO4:Sm3+ nanophosphor prepared via rapid propellant combustion route.

Mg2SiO4:Sm3+ (1-11 mol%) nanoparticles were prepared by a rapid low temperature solution combustion route. The powder X-ray diffraction (PXRD) patterns exhibit orthorhombic structure with α-phase. The average crystallite size estimated using Scherer's method, W-H plot and strain-size plots were found to be in the range 25-50 nm and the same was confirmed by Transmission Electron Microscopy (TEM). Scanning electron microscopy (SEM) pictures show porous structure and crystallites were agglomerated. The effect of Sm3+ cations on luminescence of Mg2SiO4 was well studied. Interestingly the samples could be effectively excited with 315 nm and emitted light in the red region, which was suitable for the demands of high efficiency WLEDs. The emission spectra consists of four main peaks which can be assigned to the intra 4-f orbital transitions of Sm3+ ions 4G5/2→6H5/2 (576 nm), 4G5/2→6H7/2 (611 nm), 4G5/2→6H9/2 (656 nm) and 4G5/2→6H11/2 (713 nm). The optimal luminescence intensity was obtained for 5 mol% Sm3+ ions. The CIE (Commission International de I'Eclairage) chromaticity co-ordinates were calculated from emission spectra, the values (0.588, 0.386) were close to the NTSC (National Television Standard Committee) standard value of red emission. Coordinated color temperature (CCT) was found to be 1756 K. Therefore optimized Mg2SiO4:Sm3+ (5 mol%) phosphor was quite useful for solid state lighting.

Design, synthesis and structure--activity relationship (SAR) studies of imidazo[4,5-b]pyridine derived purine isosteres and their potential as cytotoxic agents.

Drug resistance to chemotherapeutic agents paved the way to develop novel synthetic molecules which are active on MDR cancer cell lines. Regio-isomeric imidazo[4,5-b]pyridine analogues were synthesized and evaluated for their cytotoxic activity against a range of cancer cell lines. The structure-activity relationship (SAR) studies of the imidazopyridine analogues are also described. Analogue 6b displayed strong cytotoxicity and good microsomal stability.

Zn2TiO4:Eu(3+) nanophosphor: self explosive route and its near UV excited photoluminescence properties for WLEDs.

A simple and low-cost solution combustion method was used to prepare Eu(3+) (1-11mol%) doped Zn2TiO4 nanophosphors at 500°C using zinc nitrates as precursors and oxalyl di-hydrazide (ODH) as fuel. The final product was calcined at 1100°C for 3h and then characterized by powder X-ray diffraction (PXRD), fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-visible absorption (UV-Vis). The PXRD patterns of the sample calcined at 1100°C show pure cubic phase. The crystallite size was estimated using Scherrer's method and found to be in the range 20-25nm and the same was confirmed by TEM studies. Effects of Eu(3+) (1-11mol%) cations on the luminescence properties of Zn2TiO4 nanoparticles were studied. The samples exhibit intense red emission upon 395nm near ultra violet (NUV) excitation. The characteristic emission peaks recorded at ∼578, 592, 613 and 654nm may be attributed to the 4f-4f intra shell transitions ((5)D0→(7)Fj=0,1,2,3) of Eu(3+) cations. The CIE chromaticity co-ordinates and CCT were calculated from emission spectra and the values (x, y) were very close to NTSC standard values for red emission and CCT was close to Plankian locus. Therefore, the present phosphor may be highly useful for display applications.

Combustion synthesized tetragonal ZrO2: Eu(3+) nanophosphors: structural and photoluminescence studies.

Novel crystalline tetragonal ZrO2: Eu(3+) phosphors were prepared by a facile and efficient low temperature solution combustion method at 400±10 °C using oxalyl dihydrazide (ODH) as fuel. The powder X-ray diffraction patterns and Rietveld confinement of as formed ZrO2: Eu(3+) (1-11 mol%) confirmed the presence of body centered tetragonal phase. The crystallite size estimated from Scherrer's and W-H plots was found to be in the range of 7-17 nm. These results were in good agreement with transmission electron microscopy studies. The calculated microstrain in most of the planes indicated the presence of tensile stress along various planes of the particles. The observed space group (P42/nmc) revealed the presence of cations in the 2b positions (0.75, 0.25, 0.25) and the anions in the 4d positions (0.25, 0.25, 0.45). The optical band gap energies estimated from Wood and Tauc's relation was found to be in the range 4.3-4.7 eV. Photoluminescence (PL) emission was recorded under 394 and 464 nm excitation shows an intense emission peak at 605 nm along with other emission peaks at 537, 592, 605 and 713 nm. These emission peaks were attributed to the transition of (5)D0→(7)FJ (J=0, 1, 2, 3) of Eu(3+) ions. The high ratio of Intensity of ((5)D0→(7)F2) and ((5)D0→(7)F1) infers that Eu(3+) occupies sites with a low symmetry and without an inversion center. CIE color coordinates indicated the red regions which could meet the needs of illumination devices.

MgO:Eu3+ red nanophosphor: low temperature synthesis and photoluminescence properties.

Nanoparticles of Eu(3+) doped (0-9 mol%) MgO were prepared using low temperature (400°C) solution combustion technique with metal nitrate as precursor and glycine as fuel. The powder X-ray diffraction (PXRD) patterns of the as-formed products show single cubic phase and no further calcination was required. The crystallite size was obtained using Scherer's formula and was found to be 5-6 nm. The effect of Eu(3+) ions on luminescence characteristics of MgO was studied and the results were discussed in detail. These phosphors exhibit bright red emission upon 395 nm excitation. The characteristic photoluminescence (PL) emission peaks at ∼580, 596, 616, 653, 696 and 706 nm ((5)D0→(7)Fj=0, 1, 2, 3, 4) were recorded due to Eu(3+) ions. The electronic transition corresponding to (5)D0→(7)F2 of Eu(3+) ions (616 nm) was stronger than the magnetic dipole transition corresponding to (5)D0→(7)F1 of Eu(3+) ions (596 nm). The international commission on illumination (CIE) chromaticity co-ordinates were calculated from emission spectra, the values (x, y) were very close to national television system committee (NTSC) standard value of red emission. Therefore the present phosphor was highly useful for display applications.

Synthesis, structural and luminescence studies of magnesium oxide nanopowder.

Nanoparticles of magnesium oxide (MgO) have been prepared by low temperature solution combustion and hydrothermal method respectively. Powder X-ray diffraction (PXRD) patterns of MgO samples prepared by both the methods show cubic phase. The Scanning Electron Microscopy (SEM) studies reveal, the combustion derived product show highly porous, foamy and fluffy in nature than hydrothermally derived sample. The optical absorption studies of MgO show surface defects in the range 250-300 nm. The absorption peak at ∼290 nm might be due to F-centre. Photoluminescence (PL) studies were carried upon exciting at 290 nm. The sample prepared via combustion method show broad emission peak centred at ∼395 nm in the bluish-violet (3.14 eV) region. However, in hydrothermal prepared sample show the emission peaks at 395 and 475 nm. These emission peaks were due to surface defects present in the sample since nanoparticles exhibits large surface to volume ratio and quantum confinement effect.