Uranium: occurrence,distribution across India and its potential health effects

Journal of Radioanalytical and Nuclear Chemistry - Uranium contamination in the aquatic environment is an emerging concern worldwide. With the development of the global economy, uranium...     

High yield synthesis of intrinsic, doped and composites of nano-zinc oxide using novel combinatorial method

A novel synthesis of the production of luminescent zinc oxide (ZnO), either in its intrinsic, metal, non-metal-doped or composite forms with high yield has been developed by parallel iterative techniques, within a combinatorial library prepared by the reduction of nitroarenes. The reduction of nitroarenes by aluminium/zinc dusts in alkaline medium (pH 10±2) forms azoxy compounds, whereas in acidic medium (pH 4.9±0.2) forms phenyl hydroxylamine and zinc/aluminium dust gets oxidised into respective hydroxide. Here, we demonstrate the reduction of nitroarenes at neutral pH (7.0±0.2), which forms intrinsic as well as doped ZnO at 50±5°C using zinc dust alone or mixtures of salts of several transition and non-transition metals in presence of 1:10 ratio of solvent and water. Interestingly, it is observed that the photoluminescence emission could be tuned in a wide range from 390 to 615 nm useful for many display related devices.     

Ultrasound-Assisted Microencapsulation of Soybean Oil and Vitamin D Using Bare Glycogen Nanoparticles

Ultrasonically synthesized core-shell microcapsules can be made of synthetic polymers or natural biopolymers, such as proteins and polysaccharides, and have found applications in food, drug delivery and cosmetics. This study reports on the ultrasonic synthesis of microcapsules using unmodified (natural) and biodegradable glycogen nanoparticles derived from various sources, such as rabbit and bovine liver, oyster and sweet corn, for the encapsulation of soybean oil and vitamin D. Depending on their source, glycogen nanoparticles exhibited differences in size and ‘bound’ proteins. We optimized various synthetic parameters, such as ultrasonic power, time and concentration of glycogens and the oil phase to obtain stable core-shell microcapsules. Particularly, under ultrasound-induced emulsification conditions (sonication time 45 s and sonication power 160 W), native glycogens formed microcapsules with diameter between 0.3 μm and 8 μm. It was found that the size of glycogen as well as the protein component play an important role in stabilizing the Pickering emulsion and the microcapsules shell. This study highlights that native glycogen nanoparticles without any further tedious chemical modification steps can be successfully used for the encapsulation of nutrients.     

Aligned nanogold assisted one step sensing and removal of heavy metal ions

We depict a novel strategy exploiting the chemistry of metal ion adsorption for detection and sequestration of toxic heavy metal from processed water using gold nanoparticles capped with 4-aminothiophenol. The interaction between 4-aminothiophenol capped gold nanoparticles and heavy metal ions was studied as a function of time and concentration using TEM, HRTEM, SEM, EDS, and I-V characterization. Experiments confirmed that pH is one of the crucial controlling parameters. Adsorption capacity was monitored using AAS, UV-vis spectroscopy and I-V measurement. In the absence of any alloy formation between Au and heavy metal ions, the desorption of the heavy metal ions from 4-aminothiophenol capped gold nanoparticles surface by pH modulation serves as a mean of collection of heavy metal ions. Experiments revealed that the concentration of heavy metal ions in processed water after adsorption is below the maximum permissible limit set by the WHO.     

Core–shell nanophosphor with enhanced NIR–visible upconversion as spectrum modifier for enhancement of solar cell efficiency

A distinct enhancement of upconversion luminescence from core to core/shell (C/S) structure under low flux near infrared (NIR) excitation at 976 nm has been achieved in lanthanide (Er³⁺, Yb³⁺)-doped NaYF₄ core with undoped NaYF₄ shell nanoparticles (NP). A green chemistry approach has been taken to synthesize monodisperse monophasic C/S NP with the core (~20 nm) and shell (~5 nm) crystallizing into cubic phase. Hydrophobic C/S NP have been further made hydrophilic by coating a transparent SHMP layer without affecting luminescence. C/S (NaYF₄: Er, Yb/NaYF₄) NP integrated dye-sensitized solar cell indicated 11.9% enhancement in overall conversion efficiency under AM 1.5 conditions, due to NIR–visible spectrum modification by fluorescent NPs. The results indicate great potential of such upconverting C/S nanophosphor in solar cell applications.     

Catalytically Active Copper Phosphate–Dextran Sulfate Microparticle Coatings for Bioanalyte Sensing

Engineering reactive and functional nanostructured surfaces is important for enhancing the sensitivity and versatility of biosensors and microreactors. For example, the assembly of hybrid inorganic–organic porous microparticles on surfaces may provide a catalytic microenvironment for a wide range of reactions. Herein, the synthesis of catalytically active porous dextran sulfate–copper phosphate hybrid microparticles by a facile and rapid crystallization process in aqueous solution is reported. The sulfated polysaccharide enables control over the size and hierarchical morphology of the hybrid microparticles, as well as their assembly into stable macroporous coatings. The engineered microparticle coatings display intrinsic nonenzymatic peroxidase-like catalytic activity when employed as a platform for the detection of hydrogen peroxide. Pairing of the microparticle coating with glucose oxidase affords a hybrid platform that is employed as a glucose sensor for monitoring physiological concentrations of a given analyte via a hybrid enzymatic/nonenzymatic cascade reaction. This work presents a strategy for the assembly of hybrid porous microparticles into enzyme-mimicking surfaces for copper-based catalysis and biochemical analyte sensing.     

Engineering Flexible Metal-Phenolic Networks with Guest Responsiveness via Intermolecular Interactions

Flexible metal-organic materials are of growing interest owing to their ability to undergo reversible structural transformations under external stimuli. Here, we report flexible metal-phenolic networks (MPNs) featuring stimuli-responsive behavior to diverse solute guests. The competitive coordination of metal ions to phenolic ligands of multiple coordination sites and solute guests (e.g., glucose) primarily determines the responsive behavior of the MPNs, as revealed experimentally and computationally. Glucose molecules can be embedded into the dynamic MPNs upon mixing, leading to the reconfiguration of the metal-organic networks and thus changes in their physicochemical properties for targeting applications. This study expands the library of stimuli-responsive flexible metal-organic materials and the understanding of intermolecular interactions between metal-organic materials and solute guests, which is essential for the rational design of responsive materials for various applications.     

Supramolecular Polyphenol-DNA Microparticles for In Vivo Adjuvant and Antigen Co-Delivery and Immune Stimulation

DNA-based materials have attracted interest due to the tunable structure and encoded biological functionality of nucleic acids. A simple and general approach to synthesize DNA-based materials with fine control over morphology and bioactivity is important to expand their applications. Here, we report the synthesis of DNA-based particles via the supramolecular assembly of tannic acid (TA) and DNA. Uniform particles with different morphologies are obtained using a variety of DNA building blocks. The particles enable the co-delivery of cytosine-guanine adjuvant sequences and the antigen ovalbumin in model cells. Intramuscular injection of the particles in mice induces antigen-specific antibody production and T cell responses with no apparent toxicity. Protein expression in cells is shown using capsules assembled from TA and plasmid DNA. This work highlights the potential of TA as a universal material for directing the supramolecular assembly of DNA into gene and vaccine delivery platforms.     

Application of thiolated gold nanoparticles for the enhancement of glucose oxidase activity

Glucose oxidase (GOx) has been covalently immobilized onto chemically synthesized thiolated gold nanoparticles (5-8 nm) via N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The lower value of the Michaelis-Menton constant obtained for the immobilized (3.74 mM) GOx compared with that for the free (5.85 mM) GOx suggests significant enhancement in the activity of GOx attached to thiolated gold nanoparticles. The covalently immobilized GOx thiolated nanoparticles exhibit a response time of 30 s, a shelf life of more than 6 months, and improved tolerance to both pH and temperature.     

Green chemistry-mediated synthesis of nanostructures of afterglow phosphor

Various nanostructures of SrAl₂O₄:Eu²⁺, Dy³⁺ (SAC) afterglow phosphor were prepared in a single-step reaction using a green chemistry-mediated modified combustion process. The evolution of hazardous NxOx gases during the customary combustion reaction was completely eliminated by employing an innovative complex formation route. Another fascinating feature of the process was that, a slight change in the processing conditions ensured the synthesis of either nanoparticles or nanowires. The photoluminescence spectrum of nanophosphor showed a slight blue shift in emission (∼511 nm) as compared to the bulk phosphor (∼520 nm). The afterglow (decay) profiles of SAC nanoparticles, nanowires and bulk phosphor were compared. The chemistry underlying the nanostructure synthesis and the probable afterglow mechanism were discussed.