Synthesis, structure, characterization and photocatalytic activity of Bi2Zr2O7 under solar radiation

Bi2Zr2O7 was synthesized via a facile solution combustion method. Two different fuels, urea and tartaric acid were used in the synthesis, which resulted in Bi2Zr2O7 crystals with different band gaps and surface areas. The structure has been determined by Rietveld refinement followed by the difference Fourier technique. The compound crystallizes in the space group Fm (3) over barm. The photocatalytic degradation of two dyes was carried out under solar radiation. Bi2Zr2O7 prepared using urea as the fuel exhibits a higher photocatalytic activity than the compound prepared using tartaric acid and comparable activity to that of commercial Evonik P-25 TiO2. It is suggested that this is due to the oxygen vacancies occurring in the two cases, the urea based compound has an occupancy of 0.216, whereas the tartaric acid based synthesis shows disorder in the oxygen position amounting to a small number of oxygen vacancies.

Purifying water containing both anionic and cationic species using a (Zn, Cu)O, ZnO, and Cobalt Ferrite based multiphase adsorbent system

For the purpose of water purification, novel and low-cost adsorbents which are promising replacements for activated carbon are being actively pursued. However, a single-phase material that adsorbs both cationic and anionic species remains elusive. Hence, a low-cost, multiphase adsorbent bed that purifies water containing both anionic and cationic pollutants is a desirable alternative. We choose anionic (Congo red, Orange G) and cationic (methylene blue, malachite green) dyes as model pollutants. These dyes are chosen since they are widely found in effluents from textile, leather, fishery, and pharmaceutical industries, and their carcinogenic, mutagenic, genotoxic, and cytotoxic impact on mammalian cells is well-established. We show that ZnO, (Zn0.24Cu0.76)O and cobalt ferrite based multiphase fixed adsorbent bed efficiently adsorbs model anionic (Congo red, Orange G) and cationic (methylene blue and malachite green) pollutants, and their complex mixtures. All adsorbent phases are synthesized using room-temperature, high-yield (similar to 96-100%), green chemical processes. The nanoadsorbents are characterized by using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, and zeta potential measurements. The constituent nanophases are deliberately chosen to be beyond 50 nm, in order to avoid the nanotoxic size regime of oxides. Adsorption characteristics of each of the phases are examined. Isotherm based analysis shows that adsorption is both spontaneous and highly favorable. zeta potential measurements indicate that electrostatic interactions are the primary driving force for the observed adsorption behavior. The isotherms obtained are best described using a composite Langmuir-Freundlich model. Pseudo-first-order, rapid kinetics is observed (with adsorption rate constants as high as 0.1-0.2 min(-1) in some cases). Film diffusion is shown to be the primary mechanism of adsorption.

Polyanhydrides of Castor Oil-Sebacic Acid for Controlled Release Applications

A family of high molecular weight castor oil (CO)-based biodegradable polyanhydrides was synthesized by a catalyst-free melt-condensation reaction between prepolymers of CO and sebacic acid (SA). The structure of the polymers was characterized by H-1 NMR and Fourier transform infrared spectroscopy, which indicated the formation of the anhydride bond along the polymer backbone. Thermal analysis and X-ray diffraction confirmed the semicrystalline nature of the polymers. Incorporation of SA enhanced the crystallinity of the polymer. The hydrophobic nature of these polymers was revealed by contact angle goniometry. Water wettability decreased with increase in SA content. Compressive tests demonstrated a sharp increase in strength and decrease in ductility with increasing SA content. In vitro hydrolytic degradation studies indicated surface-eroding behavior. The degradation rate decreased with an increase of SA content in the polymers because of increased crystallinity. The release studies of both hydrophobic and hydrophilic dyes followed zero-order kinetics. In vitro cell studies to assess the cytotoxicity of the polymer confirmed minimal toxicity of the degradation products. Thus, a family of CO-SA polyanhydrides have been synthesized and characterized for controlled release applications where the physical, mechanical, and degradation kinetics can be modulated by varying the weight fraction of the prepolymers.

Morphology controlled synthesis of wurtzite ZnS nanostructures through simple hydrothermal method and observation of white light emission from ZnO obtained by annealing the synthesized ZnS nanostructures

A controllable synthesis of phase pure wurtzite (WZ) ZnS nanostructures has been reported in this work at a low temperature of similar to 220 degrees C using ethylenediamine as the soft template and by varying the molar concentration of zinc to sulphur precursors as well as by using different precursors. A significant reduction in the formation temperature required for the synthesis of phase pure WZ ZnS has been observed. A strong correlation has been observed between the morphology of the synthesized ZnS nanostructures and the precursors used during synthesis. It has been found from Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) image analyses that the morphology of the ZnS nanocrystals changes from a block-like to a belt-like structure having an average length of similar to 450 nm when the molar ratio of zinc to sulphur source is increased from 1 : 1 to 1 : 3. An oriented attachment (OA) growth mechanism has been used to explain the observed shape evolution of the synthesized nanostructures. The synthesized nanostructures have been characterized by the X-ray diffraction technique as well as by UV-Vis absorption and photoluminescence (PL) emission spectroscopy. The as-synthesized nanobelts exhibit defect related visible PL emission. On isochronal annealing of the nanobelts in air in the temperature range of 100-600 degrees C, it has been found that white light emission with a Commission Internationale de I'Eclairage 1931 (CIE) chromaticity coordinate of (0.30, 0.34), close to that of white light (0.33, 0.33), can be obtained from the ZnO nanostructures obtained at an annealing temperature of 600 degrees C. UV light driven degradation of methylene blue (MB) dye aqueous solution has also been demonstrated using as-synthesized nanobelts and similar to 98% dye degradation has been observed within only 40 min of light irradiation. The synthesized nanobelts with visible light emission and having dye degradation activity can be used effectively in future optoelectronic devices and in water purification for cleaning of dyes.

Green colored nano-pigments derived from Y2BaCuO5: NIR reflective coatings

A green colored nano-pigment Y2BaCuO5 with impressive near infra-red (NIR) reflectance (61% at 1100 nm) was synthesized by a nano-emulsion method. The developed nano-crystalline powders were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), UV-vis-NIR diffuse reflectance spectroscopy and CIE-L*a*b* 1976 color scales. The XRD and Rietveld analyses of the designed pigment powders reveal the orthorhombic crystal structure for Y2BaCuO5, where yttrium is coordinated by seven oxygen atoms with the local symmetry of a distorted trigonal prism, barium is coordinated by eleven oxygen atoms, and the coordination polyhedron of copper is a distorted square pyramid CuO5]. The UV-vis spectrum of the nano-pigment exhibits an intense d-d transition associated with CuO5 chromophore between 2.1 and 2.5 eV in the visible domain. Therefore, a green color has been displayed by the developed nano-pigment. The potential utility of the nano-pigments as ``Cool Pigments'' was demonstrated by coating on to a building roofing material like cement slab and PVC coatings. (C) 2014 Elsevier Ltd. All rights reserved.

Metal-metal charge transfer and interfacial charge transfer mechanism for the visible light photocatalytic activity of cerium and nitrogen co-doped TiO2

Nanosized cerium and nitrogen co-doped TiO2 (Ce-TiO2-xNx) was synthesized by sol gel method and characterized by powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), FESEM, Fourier transform infrared, N-2 adsorption and desorption methods, photoluminescence and ultraviolet-visible (UV-vis) DRS techniques. PXRD analysis shows the dopant decreases the crystallite sizes and slows the crystallization of the titania matrix. XPS confirm the existence of cerium ion in +3 or +4 state, and nitrogen in -3 state in Ce-TiO2-xNx. The modified surface of TiO2 provides highly active sites for the dyes at the periphery of the Ce-O-Ti interface and also inhibits Ce particles from sintering. UV-visible DRS studies show that the metal-metal charge transfer (MMCT) of Ti/Ce assembly (Ti4+/Ce3+ -> Ti3+/Ce4+) is responsible for the visible light photocatalytic activity. Photoluminescence was used to determine the effect of cerium ion on the electron-hole pair separation between the two interfaces Ce-TiO2-xNx and Ce2O3. This separation increases with the increase of cerium and nitrogen ion concentrations of doped samples. The degradation kinetics of methylene blue and methyl violet dyes in the presence of sol gel TiO2, Ce-TiO2-xNx and commercial Degussa P25 was determined. The higher visible light activity of Ce-TiO2-xNx was due to the participation of MMCT and interfacial charge transfer mechanism.

Organic white-light emitting materials

Full-color emissive organic materials have attracted significant attention in recent years as key components in display and lighting devices based on OLEDs. An ideal white-light emitter demands simultaneous emission of red, green and blue with nearly similar distribution of intensities covering the entire region of visible spectra. However, the design of such white-light emitters is not straightforward. Mixing several emitters is seldom successful owing to the negative effects of intermolecular interactions and energy transfer processes. Nonetheless, these fundamental questions have been addressed in recent times by several research groups of vastly different expertise leading to a considerable progress in the field of organic white-light emitters. The designs cover a large area of the chemistry ranging from frustrated energy transfer to simple protonation or from designed self-assembly to simple mixing of materials. In this review, the concepts and rational approaches underlying the design of white-light emissive organic materials are described. (C) 2014 Elsevier Ltd. All rights reserved.

SUSTAINABILITY IN TRADITIONAL HANDLOOMS

The handloom sector constitutes a distinct feature of the rich cultural heritage of India and plays a vital role in the economy and cultural identity of the country. It is an ancient industry and is source of livelihood for many villages in India. Its spread varies in style, practice and scale throughout the country - in certain regions it is has a proficient industry, while in others its establishment is localized, where it is a family-based activity. While, hand-woven fabrics are well-sought after both nationally and globally, weavers currently remain marginalized and often impoverished. The well-set power loom industry has further added to their woes. Given the progressive failure of centralized production and distribution ideologies, handlooms represent a decentralized distributed means of livelihood security, environmental consonance, employment generation, skill enhancement, cultural (diversity, identity and) integrity and sustainability. The fabrics and dyes used in the handloom industry are environment-friendly and often unique to a region (based on available skill and resources). The paper comprehensively evaluates and forecasts sustainability in the context of traditional handlooms in India. Results of the study and recommendations are presented in this paper.

Effect of alkyl substituents in BODIPYs: a comparative DFT computational investigation

Random changes in the alkyl substitution patterns of fluorescent dyes, e.g. BODIPYs, are often accompanied by significant changes in their photophysical properties. To understand such alterations in properties in closely related molecular systems, a comparative DFT (density functional theory) computational investigation was performed in order to comprehend the effects of alkyl substitution in controlling the structural and electronic nature of BODIPY dyes. In this context, a systematic strategy was utilized, considering all possible outcomes of constitutionally-isomeric molecules to understand the alkyl groups' effects on the BODIPY molecules. Four different computational methods {i.e. B3LYP/631G(d); B3LYP/6-311++ G(d,p); wb97xd/6-311++ G(d,p) and mpw1pw91/6-311++ G(d,p)} were employed to rationalize the agreement of the trends associated with the molecular properties. In line with experimental observations, it was found that alkyl substituents in BODIPY dyes situated at 3/5-positions effectively participate in stabilization as well as planarization of such molecules. Screening of all the possible isomeric molecular systems was used to understand the individual properties and overall effects of the typical alkyl substituents in controlling several basic properties of such BODIPY molecules.

Heterogeneity in Dye-TiO2 Interactions Dictate Charge Transfer Efficiencies for Diketopyrrolopyrrole-Based Polymer Sensitized Solar Cells

Power conversion efficiency of a solar cell is a complex parameter which usually hides the molecular details of the charge generation process. For rationally tailoring the overall device efficiency of the dye-sensitized solar cell, detailed molecular understanding of photoinduced reactions at the dye-TiO2 interface has to be achieved. Recently, near-IR absorbing diketopyrrolopyrrole-based (DPP) low bandgap polymeric dyes with enhanced photostabilities have been used for TiO2 sensitization with moderate efficiencies. To improve the reported device performances, a critical analysis of the polymerTiO(2) interaction and electron transfer dynamics is imperative. Employing a combination of time-resolved optical measurements complemented by low temperature EPR and steady-state Raman spectroscopy on polymerTiO(2) conjugates, we provide direct evidence for photoinduced electron injection from the TDPP-BBT polymer singlet state into TiO2 through the C-O group of the DPP-core. A detailed excited state description of the electron transfer process in films reveals instrument response function (IRF) limited (<110 fs) charge injection from a minor polymer fraction followed by a picosecond recombination. The major fraction of photoexcited polymers, however, does not show injection indicating pronounced ground state heterogeneity induced due to nonspecific polymerTiO(2) interactions. Our work therefore underscores the importance of gathering molecular-level insight into the competitive pathways of ultrafast charge generation along with probing the chemical heterogeneity at the nanoscale within the polymerTiO2 films for optimizing photovoltaic device efficiencies.

Highly efficient WO3-ZnO mixed oxides for photocatalysis

Monoclinic nanocuboid WO3 enhanced the photocatalyst efficiency of quasi nanobelt zinc oxide for dye degradation in the presence of visible light radiation. Combustion synthesized ZnO resulted in a belt-like morphology through in situ cluster formation of near spherical particles but homogenously disperses and strongly adheres to nanocuboid WO3 during physical mixing. Cationic methylene blue (MB) and anionic orange G (OG) undergo degradation through a charge transfer mechanism in the presence of WO3-ZnO (1 : 9 weight percentage ratio) mixture. The photocatalytic reaction was enhanced due to the reduction in the recombination of photogenerated electron-holes. The high degree of 90% degradation of both dyes is due to the activity of the mixed oxides, which is much higher than that obtained either with WO3 or ZnO individually.

Highly efficient WO3-ZnO mixed oxides for photocatalysis

Monoclinic nanocuboid WO3 enhanced the photocatalyst efficiency of quasi nanobelt zinc oxide for dye degradation in the presence of visible light radiation. Combustion synthesized ZnO resulted in a belt-like morphology through in situ cluster formation of near spherical particles but homogenously disperses and strongly adheres to nanocuboid WO3 during physical mixing. Cationic methylene blue (MB) and anionic orange G (OG) undergo degradation through a charge transfer mechanism in the presence of WO3-ZnO (1 : 9 weight percentage ratio) mixture. The photocatalytic reaction was enhanced due to the reduction in the recombination of photogenerated electron-holes. The high degree of 90% degradation of both dyes is due to the activity of the mixed oxides, which is much higher than that obtained either with WO3 or ZnO individually.

Multispectral Bayesian reconstruction technique for real-time two color fluorescence microscopy

We have developed a real-time imaging method for two-color wide-field fluorescence microscopy using a combined approach that integrates multi-spectral imaging and Bayesian image reconstruction technique. To enable simultaneous observation of two dyes (primary and secondary), we exploit their spectral properties that allow parallel recording in both the channels. The key advantage of this technique is the use of a single wavelength of light to excite both the primary dye and the secondary dye. The primary and secondary dyes respectively give rise to fluorescence and bleed-through signal, which after normalization were merged to obtain two-color 3D images. To realize real-time imaging, we employed maximum likelihood (ML) and maximum a posteriori (MAP) techniques on a high-performance computing platform (GPU). The results show two-fold improvement in contrast while the signal-to-background ratio (SBR) is improved by a factor of 4. We report a speed boost of 52 and 350 for 2D and 3D images respectively. Using this system, we have studied the real-time protein aggregation in yeast cells and HeLa cells that exhibits dot-like protein distribution. The proposed technique has the ability to temporally resolve rapidly occurring biological events.

Copolyesters from Soybean Oil for Use as Resorbable Biomaterials

A family of soybean oil (SO) based biodegradable cross-linked copolyesters sourced from renewable resources was developed for use as resorbable biomaterials. The polyesters were prepared by a melt condensation of epoxidized soybean oil polyol and sebacic acid with citric acid (CA) as a cross-linker. D-Mannitol (M) was added as an additional reactant to improve mechanical properties. Differential scanning calorimetry revealed that the polyester synthesized using only CA as the cross-linker was semicrystalline and elastomeric at physiological temperature. The polymers were hydrophobic in nature. The water wettability, elongation at break and the degradation rate of the polyesters decreased with increase in M content or curing time. Modeling of release kinetics of dyes showed a diffusion controlled mechanism underlies the observed sustained release from these polymers. The polyesters supported attachment and proliferation of human stem cells and were thus cytocompatible. Porous scaffolds induced osteogenic differentiation of the stern cells suggesting that these polymers are well suited for bone tissue engineering. Thus, this family of polyesters offers a low cost and green alternative as biocompatible, bioresobable polymers for potential use as resorbable biomaterials for tissue engineering and controlled release.

Enhanced sunlight photocatalytic activity of Ag3PO4 decorated novel combustion synthesis derived TiO2 nanobelts for dye and bacterial degradation

This study demonstrates the synthesis of TiO2 nanobelts using solution combustion derived TiO2 with enhanced photocatalytic activity for dye degradation and bacterial inactivation. Hydrothermal treatment of combustion synthesized TiO2 resulted in unique partially etched TiO2 nanobelts and Ag3PO4 was decorated using the co-precipitation method. The catalyst particles were characterized using X-ray diffraction analysis, BET surface area analysis, diffuse reflectance and electron microscopy. The photocatalytic properties of the composites of Ag3PO4 with pristine combustion synthesized TiO2 and commercial TiO2 under sunlight were compared. Therefore the studies conducted proved that the novel Ag3PO4/unique combustion synthesis derived TiO2 nanobelt composites exhibited extended light absorption, better charge transfer mechanism and higher generation of hydroxyl and hole radicals. These properties resulted in enhanced photodegradation of dyes and bacteria when compared to the commercial TiO2 nanocomposite. These findings have important implications in designing new photocatalysts for water purification.