Understanding the NaxMnO2 System: A Thermodynamics and XPS Approach.

The NaxMnO2 system is an important class of materials with potential applications in rechargeable batteries, supercapacitors, catalysts, and gas sensors. This work reports the synthesis of NaxMnO2 (x = 0.39, 0.44, 0.48, 0.66, and 0.70) compounds and their characterization by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and impedance spectroscopy (IS) techniques. The compounds in this series exhibit a significant variation in their structures with the extent of Na-content. The change in the nature of bonding with increasing Na content was investigated, and its effect on material stability as well as electrotransport properties was investigated. A detailed thermodynamic evaluation of these materials was carried out employing calorimetric techniques, and the data were correlated with changes in the chemical environment around the Na ion. This analysis is crucial for predicting the thermodynamic stability of NaxMnO2 compounds under different environments for their applications in Na-ion batteries.

An insight into the sodium-ion and lithium-ion storage properties of CuS/graphitic carbon nitride nanocomposite.

Metal sulfides are gaining prominence as conversion anode materials for lithium/sodium ion batteries due to their higher specific capacities but suffers from low stability and reversibility issues. In this work, the electrochemical properties of CuS anode material has been successfully enhanced by its composite formation using graphitic carbon nitride (g-C3N4). The CuS nanoparticles are distributed evenly in the exfoliated g-C3N4 matrix rendering higher electronic conductivity and space for volume alterations during the repeated discharge/charge cycles. The 0.8CuS:0.2g-C3N4 composite when used as an anode for lithium ion coin cell exhibits a reversible capacity of 478.4 mA h g-1 at a current rate of 2.0 A g-1 after a run of 1000 cycles which is better than that reported for CuS composites with any other carbon-based matrix. The performance is equally impressive when 0.8CuS:0.2g-C3N4 composite is used as an anode in a sodium ion coin cell and a reversible capacity of 408 mA h g-1 is obtained at a current rate of 2.0 A g-1 after a run of 800 cycles. A sodium ion full cell with NVP cathode and 0.8CuS:0.2g-C3N4 composite anode has been fabricated and cycled for 100 runs at a current rate of 0.1 A g-1. It can be inferred that the g-C3N4 matrix improves the ion transfer properties, alleviates the volume alteration happening in the anode during the discharge/charge process and also helps in preventing the leaching of polysulfides generated during the electrochemical process.

Efficient Selective Sorption of Cationic Organic Pollutant from Water and Its Photocatalytic Degradation by AlVO4/g-C3N4 Nanocomposite.

This study reports the synthesis, characterization and water remediation application of novel AlVO4/g-C3N4 nanocomposites. The nanocomposite has been synthesized by a low temperature solid-state reaction using graphitic carbon nitride (g-C3N4) obtained via calcination of melamine and AlVO4 prepared via assisted sonochemical technique. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier Transform Infrared spectroscopy (FTIR), ultraviolet-visible diffuse reflection spectroscopy (UV-vis DRS), and the N2 gas adsorption Brunauer-Emmett-Teller (BET) method has been used to characterize the pristine and composite samples. AlVO4 and g-C3N4 interact with each other forming a hybrid composite, which shows excellent ability for selective sorption of cationic MB (methylene blue) dye from wastewater. The initial dye concentration, pH and amount of sorbent has been varied and their effect on the adsorption process has been analysed. The photocatalytic efficiency of the MB dye adsorbed pristine g-C3N4, AlVO4:g-C3N4 (1:3) and AlVO4:g-C3N4 (1:1) composite has been tested under visible light. With increased proportion of AlVO4 in the samples, the photocatalytic efficiency improved and the best photodegradation has been observed for the AlVO4:g-C3N4 (1:1) sample. Photoluminescence (PL) studies, photocurrent response measurements and electrochemical impedance spectroscopy (EIS) indicates enhanced separation of the photogenerated electron/hole pairs leading to effective degradation of the MB dye solution in case of the AlVO4:g-C3N4 (1:1) composite sample. The photocatalytic mechanism has been elucidated and it could be inferred that photogenerated holes and superoxide anion radicals play a major role in the photocatalysis process.

Phase evolution in sonochemically synthesized Fe(3+) doped BaTiO3 nanocrystallites: structural, magnetic and ferroelectric characterisation.

The properties of nanomaterials are highly dependent on their size, morphology, crystal phase, etc., which in turn depend on the method of synthesis. We report here the electrical and magnetic characterisation of sonochemically synthesized Fe(3+) doped nano BaTiO3 samples. The dopant ion concentration has been optimized and the coexistence of ferromagnetism and ferroelectricity has been observed in the sample. With increase in Fe(3+) doping from 0 to 20 mol%, a gradual phase change from tetragonal to hexagonal occurred in these sonochemically synthesized BaTiO3 nanomaterials. Below 15 mol% Fe concentration the material displays ferroelectric behaviour with the absence of any magnetic ordering, while at an Fe concentration of ∼15 mol% the material exhibits both room temperature ferromagnetism and ferroelectricity. Ferromagnetism as well as relaxor type behaviour has been observed in the BaTiO3:Fe(3+)(20%) sample. We have studied the ferromagnetic and ferroelectric ordering in these sonochemically synthesized Fe(3+) doped BaTiO3 nanomaterials and have tried to correlate the results with their crystal structure and morphology. The origin of ferromagnetism in these materials has been attributed to both intrinsic as well as extrinsic factors.

Enhanced magneto-dielectric coupling in multiferroic Fe and Gd codoped PbTiO3 nanorods synthesized via microwave assisted technique.

The quest for new multiferroic materials is on the rise due to their potential application in spintronics and futuristic multiple state memory devices. Here we report the microwave synthesis of iron/gadolinium co-doped PbTiO3 nanorods, which display multiferroic behavior. Both the undoped and doped PbTiO3 samples have been characterized using powder X-ray diffraction, energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) techniques. The morphology of the samples has been studied using transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM), which confirmed the formation of nanorods. The substitution of Fe ions for Ti and Gd ions for Pb enhances the ferromagnetic and ferroelectric properties of this system. The reasons for this observation have been explored in detail. The ferroelectric, magnetic and magneto-capacitive measurements at room temperature substantiate the multiferroic nature of the codoped samples with significant magnetoelectric coupling observed in case of nano PbTiO3:Gd(3+)(0.5%):Fe(3+)(5%).

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.

Multifunctionality of rare earth doped nano ZnSb2O6, CdSb2O6 and BaSb2O6: photocatalytic properties and white light emission.

Undoped MSb2O6 (where M = Zn, Cd, Ba) and single and double doped MSb2O6:RE (where RE = Tb(3+) and Eu(3+)) nanophosphors were synthesized through a simple sonochemical process and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), diffuse reflectance (DRS) and photoluminescence (PL) spectrophotometry. The TEM micrographs show that the resulting nanoparticles have mostly a spherical shape. Energy transfer was observed from the host to the dopant ions and characteristic green emissions from Tb(3+) ions and red emissions from Eu(3+) ions were observed. The chromaticity diagrams of the ZnSb2O6:Tb(3+)(1.2%):Eu(3+)(0.8%), CdSb2O6:Eu(3+)(0.5%):Tb(3+)(1.5%) and BaSb2O6:Eu(3+)(1%):Tb(3+)(1%) nanophosphors yielded CIE and CCT (correlated color temperature) values in the white light region. The photocatalytic activities of the undoped and double doped antimonates were evaluated for the degradation of rhodamine B (RhB) under UV light. Undoped MSb2O6 (where M = Zn, Cd, Ba) as well as ZnSb2O6:Tb(3+)(1.2%):Eu(3+)(0.8%), CdSb2O6:Eu(3+)(0.5%):Tb(3+)(1.5%) and BaSb2O6:Eu(3+)(1%):Tb(3+)(1%) samples exhibited good photodegradation capacity for RhB. Thus double doped ZnSb2O6:Tb(3+)(1.2%):Eu(3+)(0.8%), CdSb2O6:Eu(3+)(0.5%):Tb(3+)(1.5%) and BaSb2O6:Eu(3+)(1%):Tb(3+)(1%) can be termed a bifunctional material exhibiting both photocatalytic properties and white light emission.

Dual function of rare earth doped nano Bi2O3: white light emission and photocatalytic properties.

Undoped Bi(2)O(3) and single and double doped Bi(2)O(3) : M (where M = Tb(3+) and Eu(3+)) nanophosphors were synthesized through a simple sonochemical process and characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), EDS, diffuse reflectance (DRS) and photoluminescence (PL) spectrophotometry. The TEM micrographs show that resultant nanoparticles have a rod-like shape. Energy transfer was observed from host to the dopant ions. Characteristic green emissions from Tb(3+) ions and red emissions from Eu(3+) ions were observed. Interestingly, the Commission International de l'Eclairage (CIE) coordinates of the double doped Bi(2)O(3) : Eu(3+)(0.8%) : Tb(3+)(1.2%) nanorods lie in the white light region of the chromaticity diagram and it has a quantum efficiency of 51%. The undoped Bi(2)O(3) showed a band gap of 3.98 eV which is red shifted to 3.81eV in the case of double doped Bi(2)O(3) : Eu(3+)(0.8%) : Tb(3+)(1.2%) nanorods. The photocatalytic activities of undoped nano Bi(2)O(3) and double doped nano Bi(2)O(3) : Eu(3+)(0.8%) : Tb(3+)(1.2%) were evaluated for the degradation of Rhodamine B under UV irradiation of 310 nm. The results showed that Bi(2)O(3) : Eu(3+)(0.8%) : Tb(3+)(1.2%) had better photocatalytic activity compared to undoped nano Bi(2)O(3). The evolution of CO(2) was realized and these results indicated the continuous mineralization of rhodamine B during the photocatalytic process. Thus double doped Bi(2)O(3) : Eu(3+)(0.8%) : Tb(3+)(1.2%) nanorods can be termed as a bifunctional material exhibiting both photocatalytic properties and white light emission.

Sonochemical synthesis of doped CeF3 nanoparticles exhibiting room temperature ferromagnetism and white light emission.

In this study we demonstrate the remarkable bi-functionalities of doped CeF3 nanoparticles. The sonochemically synthesized triple doped CeF3:Mn2+:Dy3+:Tb3+ nanoparticles exhibited room temperature ferromagnetism and also serves as a good white light emitting phosphor material. The particles were found to be mostly spherical in shape and the average size was in the range of approximately 75 nm. Room temperature ferromagnetism was observed for this triple doped sample and the saturation magnetization was found to be 4.56 x 10(-3) microB/Mn atom. First-principles spin-polarized plane wave based supercell calculations, using the projector augmented wave potentials, on Mn-doped CeF3 confirmed its ferromagnetic properties. The simultaneous observation of both room temperature ferromagnetism and white light emission from doped fluoride nanoparticles reveals the complexity and uniqueness of these results.

White light emission from spin coated Gd2O3:Dy nano phosphors synthesized using polyol technique.

Water dispersible Gd2O3:Dy3+ (2%) nanophosphors were synthesized through a facile polyol process and characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), Dynamic Light Scattering (DLS) and photoluminescence (PL) spectrophotometry. The results of XRD, TEM and DLS show that resultant nanoparticles are single phasic and have spherical shape with 17 to 22% dispersibility. An efficient energy transfer was observed from host to the dopant ions. Characteristic blue and yellow emissions from Dy3+ ions were observed. The CIE coordinates of the nanophosphor lie in the white light region of the chromaticity diagram. Spin coating of the nanophosphor was done on quartz substrate. Bright white luminescence of this film was observed under ultraviolet light with lamda exc = 310 nm.

Effect of doping on the morphology and multiferroic properties of BiFeO3 nanorods.

In this study we report the synthesis of BiFeO(3) nanorods using a sonochemical technique. The nanorods had a diameter of 20-50 nm, a length of 100-500 nm and exhibit aspect ratios in the range of 5-10. However, after doping, the TEM images of Bi(0.9)Ba(0.1)Fe(0.9)Mn(0.1)O(3) and Bi(0.9)Ca(0.1)Fe(0.9)Cr(0.1)O(3) samples show that the aspect ratios of both the double doped samples have reduced considerably, while retaining the crystallinity of the particles. BiFeO(3) nanorods show a weak ferromagnetic order at room temperature, which is quite different from the linear M-H relationship reported for bulk BiFeO(3). The saturation magnetization of these BiFeO(3) nanostructures has been found to increase on doping with various metal ions (Ba(2+), Ca(2+), Mn(2+), Cr(3+)), reaching a maximum value of 1.35 emu g(-1) for the Bi(0.9)Ba(0.1)Fe(0.9)Mn(0.1)O(3) nanostructures. However, saturation of electric polarization was observed only in case of the Bi(0.9)Ca(0.1)Fe(0.9)Cr(0.1)O(3) nanostructures.

Sonochemical synthesis of lanthanide ions doped CeF3 nanoparticles: potential materials for solid state lighting devices.

Nanocrystalline CeF3 and CeF3 doped with Dy3+, Tb3+ and Eu3+ ions have been successfully synthesized via a mild ultrasound assisted route from an aqueous solution of cerium nitrate and potassium borofluoride. The nanoparticles obtained were characterized extensively by techniques like powder X-ray diffraction, transmission electron microscopy and selected area electron diffraction. Their luminescence properties have also been studied. The nanoparticles showed characteristic emission of respective dopants (Dy3+ and Tb3+) when excited at the 4f --> 5d transition of Ce3+. The chromaticity coordinates for these samples were calculated and it was observed that the CeF3 co doped with Dy3+ and Tb3+ gave an emission very close to white light.

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.

Room temperature ferromagnetism in CoO nanoparticles obtained from sonochemically synthesized precursors.

In this paper we report the magnetic properties of nanosized CoO particles, prepared from sonochemically synthesized precursors and characterized using x-ray diffraction (XRD), conventional transmission electron microscopy (TEM) and scanning tunneling electron microscopy combined with energy dispersive x-ray analysis (STEM-EDX) techniques. The nanoparticles were faceted and the sizes varied between 30 and 60 nm depending on the time of annealing. They were stable even in the absence of any organic coating on them. Magnetic measurements reveal the presence of ferromagnetic interactions at low temperatures in the CoO nanoparticles synthesized after 2 and 4 h of annealing of the sonochemically synthesized precursor under nitrogen. However, after 6 h of annealing, the nanoparticles show hysteresis not only at low temperatures (1.5 K) but also at higher temperatures (100 K and room temperature), indicating the presence of room temperature ferromagnetism.

A facile synthesis of CuInS2 nanoparticles from molecular single source precursors.

CuInS2 nanoparticles have been synthesized via solvent thermolysis of novel bimetallic complexes of the general formula [(Ph3P)2CuIn(S2COR)4] (where R = CH3; C2H5; C(CH3)2); and [(Ph3P)2CuIn(SCH2CH2S)2]. These complexes have been prepared by the reactions of Na/KS2COR and NaSCH2CH2SNa with InCl3 and [(Ph3P)2CuNO3] in methanol, respectively. Solvent thermolyses of these complexes were carried out in ethylene glycol at 196 degrees C for different time periods. The nanoparticles obtained were characterized extensively by techniques like powder X-ray diffraction, transmission electron microscopy, selected area electron diffraction, and X-ray photoelectron spectroscopy. The optical band gap of the nanoparticles was determined by diffuse reflectance spectroscopy (DRS).

Synthesis and characterization of indium xanthates and their use for the preparation of beta-In2S3 nanoparticles.

Synthesis and characterization of various classical indium xanthate complexes of the type [InCl(3-n)(S2COR)n] (n = 1, 2, or 3; R = Me, Et, Pr(i), and Bu(s)) have been discussed. Crystalline beta-ln2S3 nanoparticles were obtained by the solvent thermolysis of indium tris-alkylxanthates in ethylene glycol at 196 degrees C, and were characterized by elemental analysis, IR, powder XRD, and XPS techniques. TEM results showed that the size of beta-In2S3 nanoparticles depended on the nature of the precursor used. The optical properties of beta-In2S3 nanocrystals have shown quantum confinement of the excitonic transition.