Dimple P. Dutta

Rare-earth doped gadolinia based phosphors for potential multicolor and white light emitting deep UV LEDs

Gadolinium oxide host and europium/dysprosium/terbium doped gadolinium oxide nanoparticles were synthesized using the sonochemical technique. Gadolinium oxide nanocrystals were also co-doped with total 2 mol% of Eu(3+)/Dy(3+),Eu(3+)/Tb(3+),Dy(3+)/Tb(3+), and also Eu(3+)/Dy(3+)/Tb(3+) ions, by the same method. The nanoparticles obtained were characterized using powder x-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) techniques. The size of the particles ranged from 15 to 30 nm. The triple doped samples showed multicolor emission on single wavelength excitation. The photoluminescence results were correlated with the lifetime data to get an insight into the luminescence and energy transfer processes taking place in the system. On excitation at 247 nm, the novel nanocrystalline Gd(2)O(3):RE (RE = Dy, Tb) phosphor resulted in having very impressive CIE chromaticity coordinates of x = 0.315 and y = 0.316, and a correlated color temperature of 6508 K, which is very close to standard daylight.

Ag incorporated nano BiPO4: sonochemical synthesis, characterization and improved visible light photocatalytic properties

We report an efficient route for the sonochemical synthesis of undoped BiPO4, Ag3PO4 and silver doped BiPO4:Ag(x%) (x = 2, 5, 10 and 20) nanostructures using bismuth/silver nitrate and ammonium dihydrogen phosphate as precursors. The products obtained have been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS) and X-ray photoelectron spectroscopy (XPS). The size and morphology of BiPO4 exhibited drastic changes on Ag doping. The surface areas of the samples have been estimated using the Brunauer–Emmett–Teller (BET) method. The catalytic activities of all the samples for the rhodamine-B degradation were investigated systematically under UV and visible-light irradiation. Undoped BiPO4 exhibited excellent photocatalytic activity under UV light but the degradation of RhB was only ∼60% under visible light, while Ag doped BiPO4 samples showed almost complete degradation of the dye under visible light. Amongst all of them, BiPO4:Ag(10%) exhibited the best photocatalytic activity. Furthermore, after photocatalysis, the nanoparticles could be readily separated from the reaction system by low-speed centrifugation and reused. Stability of the photocatalysts was ascertained using FT-IR and Raman spectroscopy. After five recycles, the nanoparticles did not exhibit any apparent loss in activity, confirming its stability despite recycling. By tuning the band gap and measuring the surface area of the nanoparticles using BET tests, we found that the combined effect of these two factors resulted in good performance of the BiPO4:Ag(10%) photocatalyst under visible light irradiation.

Magnetic properties of sonochemically synthesized CoCr2O4 nanoparticles

Cobalt chromite (CoCr2O4) is a potential multiferroic material. In order to understand the temperature dependent magnetic transitions on particle morphology, here we prepared CoCr2O4 nanoparticles by sonochemical technique. We used powder x-ray diffraction, transmission electron microscopy, selected area electron diffraction, superconducting quantum interference device magnetometer, and ac susceptibility measurement techniques for characterization. The low-temperature magnetic behavior of CoCr2O4 nanoparticles have been investigated in more detail. While the bulk CoCr2O4 exhibits two magnetic transitions viz., Tc≈98 K and Ts≈26 K, the nanoparticles here showed a Tc≈84 K and Ts≈25 K. We tentatively attribute this shift in Tc to finite size effects.

Improved magnetic and ferroelectric properties of Sc and Ti codoped multiferroic nano BiFeO3 prepared via sonochemical synthesis

The room temperature multiferroic properties of bulk BiFeO3 are not exciting enough for its application in devices. Here, we report the sonochemical synthesis of scandium and titanium codoped BiFeO3 nanoparticles which exhibit improved magnetic and ferroelectric properties at room temperature. The nanoparticles have been checked for phase purity and composition using powder X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The size and morphology of the nanoparticles have been confirmed using scanning electron microscopy (SEM), and both low and high resolution transmission electron microscopy (TEM/HRTEM). The breaking of the spin cycloid due to the smaller size and slight structural distortion caused by the doping has been found to be instrumental for the enhancement of multiferroic properties. The electrical polarization increases significantly in the case of BiFe(0.925)Sc(0.05)Ti(0.025)O3 nanoparticles. A marked reduction in the leakage current was seen compared to undoped BiFeO3. Magnetoelectric coupling was also observed in the BiFe(0.925)Sc(0.05)Ti(0.025)O3 sample. Our results demonstrate that codoping with Sc and Ti ions is an effective way to rectify and enhance the multiferroic nature of BiFeO3.

Dithiocarbamates of gallium(III) and indium(III): syntheses, spectroscopy, and structures

Abstract Several complexes of the type, [M{S2CNR}3] (1) (M=Ga or In; R=CH2CH2OCH2CH2, CH2CH2N(Me)CH2CH2), [MCl2{S2CN(CH2CH2)2O}] (2) (M=Ga or In), [MCl{S2CN(CH2CH2)2O}2] (3) (M=Ga or In), [Ga{S2CN(CH2CH2)2O}{S2P(OR)2}2] (4) (R=Et, Pri) and [M{S2CNR}{(SCH2CH2)2O}] (5) (M=Ga or In; R=CH2CH2OCH2CH2, CH2CH2N(Me)CH2CH2) have been prepared. All the complexes were characterized by elemental analysis, IR and NMR (1H, 13C{1H}) spectroscopy. 71Ga NMR chemical shifts and half line widths are influenced by the coordination number of gallium and the substituents on the ligand moiety. Single crystal X-ray structures of two complexes [M{S2CN(CH2CH2)2O}3] (M=Ga, In) have been determined.

Inorganic Phosphor Materials for Solid State White Light Generation

Solid-state lighting (SSL) is emerging as a highly competent field and a possible alternative to existing lighting technologies. Development of a suitable phosphor is an important aspect of SSL. The aim of this review is to summarize status of Inorganic Phosphors towards SSL applications. Various examples have been taken from oxide, fluoride, nitride, sulfide and phosphate based host lattices. The important concepts like CIE coordinates and Color Correlated Temperature (CCT) will also be discussed. The sections encompasses of red, blue and green light emitting phosphors. The white light emitting phosphors will also be discussed in details.

Serendipitous discovery of super adsorbent properties of sonochemically synthesized nano BaWO4

The superior adsorbent properties of BaWO4 nanostructures have been reported for the first time. Flower shaped aggregates (∼250 nm) of BaWO4 nanoparticles, having an average size of ∼10–15 nm with a high surface area of ∼148.0 ± 0.2 m2 g−1, have been synthesized sonochemically and used for the adsorption of various cationic dyes from aqueous solutions. The sonochemically synthesized BaWO4 have been characterized by scanning electron microscopy (SEM), selected area electron diffraction (SAED), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectra (FTIR). The adsorbent capacity of this tungstate is much higher than that reported for other nanomaterials like Fe2O3, MnO2, WO3, etc. Complete removal of dyes like rhodamine B and methylene blue was possible within a short time span of 10–15 minutes. The adsorption process was followed using UV-Visible spectroscopy, while the material before and after adsorption has been characterized using physicochemical and spectroscopic techniques. Various isotherms have been used to fit the data, and kinetic parameters were evaluated. Moreover, the adsorbed dyes could be desorbed completely from nanoparticle surfaces by annealing at moderate temperature and were found to be efficient for multicyclic use. Thus this sonochemically synthesized nano BaWO4 has great significance in treatment of dye industry effluents as a promising adsorbent for cationic dyes from aqueous solution.

Selective sorption and subsequent photocatalytic degradation of cationic dyes by sonochemically synthesized nano CuWO4 and Cu3Mo2O9

Sorption of harmful organic pollutants from industrial effluents and their concomitant photodegradation by the sorbent under visible light can be an effective method for wastewater remediation. In this work, we report the facile synthesis of CuWO4 and Cu3Mo2O9 nanoparticles via a simple sonochemical approach. The materials exhibit superior selective sorption of cationic dyes. The uptake of cationic dyes like rhodamine B (RhB), methylene blue (MB) and malachite green (MG) have been studied along with their adsorption kinetics. The sorption plots have been fitted to various isotherms and the results have been discussed in detail. Removal of the dye from the sorbent has been carried out via mechanical agitation as well as via photocatalysis. The dye sorbed nanosorbents have been subjected to photocatalytic degradation under visible light and they show promising results. The sorbents can be completely removed from the system by simple centrifuging. The reusability of the sorbents has also been tested and they have been found to retain their efficiency after several consecutive runs. Thus, these materials show promise as effective remediators for industrial dye effluents.

Sorption of dyes and Cu(II) ions from wastewater by sonochemically synthesized MnWO4 and MnMoO4 nanostructures

MnWO4 and MnMoO4 nanoparticles have been synthesized using a facile sonochemical technique. The nanostructures were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and nitrogen adsorption–desorption measurements. The as-prepared spherical MnWO4 and MnMoO4 nanostructures have a high specific surface area and their excellent adsorbent properties to remove organic pollutants have been demonstrated for the first time. Complete removal of dyes like Rhodamine B and Methylene blue was possible within 2–10 minutes. The influences including initial pH, dosage of adsorbent and contact time have been researched in order to find the optimum adsorption conditions. The experimental data were analyzed by the Langmuir and Freundlich adsorption models. MnWO4 also proved to be a good sorbent for Cu(II) ions. The kinetic modeling for Cu(II) sorption has been discussed. These studies showed that there is a possible application for the complete and fast removal of the organic dyes in the presence of inorganic cations using MnWO4/MnMoO4 sorbents. The thermal regeneration of the sorbents is possible and they show similar adsorption efficiency up to ten consecutive cycles. The sonochemically synthesized MnWO4 and MnMoO4 nanomaterials could serve as promising adsorbents for the removal of organic dyes, especially, cationic dye, and Cu(II) ions from polluted water.

Immobilization of Uranyl Schiff Base in Mesoporous MCM-41

A uranyl Schiff base complex [UO2{ OC6H4N = C(H)C6H4O} ⋅H2O] has been immobilized inside the periodic mesopore channels of MCM-41 by the impregnation route. The samples have been characterized by XRD, N2 adsorption/desorption, TG-DTA, DR UV-vis, 29Si MAS NMR and FTIR techniques. While the host is found to retain its structural integrity, the surface area and the pore volume decrease considerably as a result of the intrapore confinement of complex molecules. The spectroscopy results indicate that the complex molecules are anchored with the silanol groups of MCM-41 via hydrogen bonding.