Enhanced electrical and magnetic functionality of Ni-Zn-co-doped CoFe2O4 rGO nanocomposites.

Enhancement in electrical and magnetic functionalities of rGO CoFe2O4 and Co0.7Zn0.3Fe1.7Ni0.3O4 nanocomposites was identified compared to their spinel-type metal oxides. Moreover, changes in morphology that occurred during the formation of the composites were fabricated via a simple in situ hydrothermal route. Electron microscopic investigations confirmed that the microspheres of the metal oxides were constructed by porous nanolamellae comprising nanoparticles interconnected to form highly stable porous microspheres. Conversely, in rGO-CoFe2O4 and rGO-Co0.7Zn0.3Fe1.7Ni0.3O4 composites, distorted spinel-type metal oxide spheres on rGO sheets were observed. Frequency-dependent conductivity increased with an increase in temperature, obeying Jonscher's power law and Koop's phenomenological theory. The resistance of ferrites decreased from ∼1.4 MΩ to 30 KΩ for their respective rGO-based nanocomposites. The hysteresis curves of all the compounds showed them to be isotropic, soft ferrimagnetic in nature. Furthermore, a 30-50% enhancement in the values of magnetic parameters of the ferrites occurred when they were interfaced with rGO sheets. This enhancement was probably due to the interfacial interaction of rGO with ferrites. Such enhancement may afford an advancement in the potential applications of these nanocomposites.

Organoamine Templated Multifunctional Hybrid Metal Phosphonate Frameworks: Promising Candidates for Tailoring Electrochemical Behaviors and Size-Selective Efficient Heterogeneous Lewis Acid Catalysis.

The successful discovery of novel multifunctional metal phosphonate framework materials that incorporate newer organoamines and their utilization as a potential electroactive material for energy storage applications (supercapacitors) and as efficient heterogeneous catalysts are the most enduring challenges at present. From this perspective, herein, four new inorganic-organic hybrid zinc organodiphosphonate materials, namely, [C5H14N2]2[Zn6(hedp)4] (I), [C5H14N2]0.5[Zn3(Hhedp) (hedp)]·2H2O (II), [C6H16N2][Zn3(hedp)2] (III), and [C10H24N4][Zn6(Hhedp)2(hedp)2] (IV) (H4hedp = 1-hydroxyethane 1,1-diphosphonic acid), have been synthesized through the introduction of different organoamines and then structurally analyzed using various techniques. The compounds (I-IV) possess a three-dimensional network through alternate connectivity of zinc ions and diphosphonate ligands, as confirmed using single-crystal X-ray diffraction. The investigations of electrochemical charge storage behaviors of the present compounds indicate that compound III exhibits a high specific capacitance of 190 F g-1 (76 C g-1) at 1 A g-1, while compound II shows an excellent cycling stability of 90.11% even after 5000 cycles at 5 A g-1 in the 6 M KOH solution. Further, the present materials have also been utilized as active heterogeneous Lewis acid catalysts in the ketalization reaction. The screening of various substrate scopes during the catalytic process confirms the size-selective heterogeneous catalytic nature of the framework compounds. To our utmost knowledge, such a size-selective heterogeneous Lewis acid catalytic behavior has been observed for the first time in the amine templated inorganic-organic hybrid framework family. Moreover, the excellent size-selective catalytic efficiencies with the d10 metal system and recyclability performances make the compounds (I-IV) more efficient and promising Lewis acid heterogeneous catalysts.

An extensive study of depth dose distribution and projectile fragmentation cross-section for shielding materials using Geant4.

Geant4 Monte Carlo simulation was executed for 16O beam in various elemental and hydrogenous materials for assessment of ion characteristics and shielding efficacy. In the energy-dependent comparison, at energies 200-594 MeV/n, the peak to entrance ratio decrement up to 78.6% in water target validates the substantial increase in fragmentation factor. Further, hydrogenous materials and low Z elements (C, Al) demonstrate a low peak-to-entrance ratio (0.92-1.66) compared to heavy element (Cu, Sn, Pb) ratio (2.73-3.54), at 594 MeV/n, indicating the high fragmentation properties of hydrogenous and low Z elements. Accordingly, the depth dose reduction percentage was found to be significantly higher for hydrogenous materials (0.92-1.72%) having 4.20-14.37 H wt.% than non-hydrogenous targets (0.09-0.82%). LiH was found to exhibit the lowest peak-to-entrance ratio and highest depth dose reduction. The high shielding effectiveness of LiH (12.59%) irrespective of having a low H fraction compared to polyethylene (14.37%) which is widely used shielding material, suggests the contribution of low Z element Li (87.41 wt%) over the C (85.63 wt%) element in the material. Also, simulated results of fragmentation for high Z materials were compared with the experimental data for the reliability of Geant4. Finally, the comparison of these properties recommends the use of hydrogenous materials with low Z elements for effective space radiation shielding.

L-cysteine functionalized graphene quantum dots for sub-ppb detection of As (III).

Here, we report functionalized graphene quantum dots (GQDs) for the optical detection of arsenic at room temperature. GQDs with the fluorescence of three fundamental colors (red, green, and blue) were synthesized and functionally capped with L-cysteine (L-cys) to impart selectively towards As (III) by exploiting the affinity of L-cys towards arsenite. The optical characterization of GQDs was carried out using UV-vis absorption spectroscopy, Fourier transform infrared spectroscopy, and fluorescence spectrometry, and the structural characterizations were performed using transmission electron microscopy. The fluorescence results showed instantaneous quenching in intensity when the GQDs came in contact with As (III) for all test concentrations over a range from 0.025 to 25 ppb, which covers the permissible limit of arsenic in drinking water. The experimental results suggested excellent sensitivity and selectivity towards As (III).

MoS2 nanoparticle/activated carbon composite as a dual-band material for absorbing microwaves.

In the search for novel high-performance microwave (MW) absorbers, MoS2 has shown promise as a MW-absorbing material, but its poor impedance matching limits its applications. Herein, a facile hydrothermal method was used to produce a composite consisting of activated carbon (AC) derived from waste biomass and in situ-grown MoS2 nanoparticles. Its microwave absorption properties were examined in the 2-18 GHz frequency range, and FESEM and HRTEM images confirmed the formation of MoS2 nanoparticles on the AC. The maximum reflection loss (RLmax) for the MoS2/AC composite was -31.8 dB (@16.72 GHz) at 20 wt% filler loading. At 50 wt% filler loading, the MoS2/AC (MAC50) composite exhibited unique dual-band absorption characteristics in the C and Ku bands. An effective absorption bandwidth (RL < -10 dB) of 10.4 GHz (3-5.2 GHz, 9.8-18 GHz) was achieved at various thicknesses that covered the entire Ku band. Therefore, a sole dielectric absorber can easily be tuned to absorb MWs at multiple frequency ranges. The large surface area and conduction losses of AC combined with the superior dielectric loss properties of MoS2 resulted in improved impedance matching and attenuation ability of the MoS2/AC composite. Thus, MoS2/AC is a promising low-cost dielectric absorber for MW absorption applications.

Photocatalytic degradation of methylene blue with Fe doped ZnS nanoparticles.

Fe doped ZnS nanoparticles (Zn1-xFexS; where x=0.00, 0.03, 0.05 and 0.10) were synthesized by a chemical precipitation method. The synthesized products were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, UV-Vis and photoluminescence spectrometer. The X-ray diffraction and transmission electron microscope studies show that the size of crystallites is in the range of 2-5 nm. Photocatalytic activities of ZnS and 3, 5 and 10 mol% Fe doped ZnS were evaluated by decolorization of methylene blue in aqueous solution under ultraviolet and visible light irradiation. It was found that the Fe doped ZnS bleaches methylene blue much faster than the undoped ZnS upon its exposure to the visible light as compared to ultraviolet light. The optimal Fe/Zn ratio was observed to be 3 mol% for photocatalytic applications.

Structural and photocatalytic studies of Mn doped TiO2 nanoparticles.

Mn-doped TiO(2) nanoparticles (Ti(1-)(x)Mn(x)O(2); where x=0.00-0.10) were synthesized by sol-gel method. The synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and UV-Vis spectrometer. The SEM and TEM micrographs revealed the agglomerated spherical-like morphology and measurements show that the size of crystallites is in the range of 10-20 nm. Optical measurements indicated a red shift in the absorption band edge after Mn doping. Direct allowed band gap of undoped and Mn-doped TiO(2) nanoparticles measured by UV-Vis spectrometer were 3.00 and 2.95 eV at 300 °C, respectively. Photocatalytic activities of TiO(2) and Mn doped TiO(2) were evaluated by irradiating the sample solution of methylene blue (MB) dye under ultraviolet and visible light exposure. It was found that Mn-doped TiO(2) bleaches MB much faster than undoped TiO(2) upon its exposure to the visible light as comparison to ultraviolet light. The experiment demonstrated that the photodegradation efficiency of Mn-doped TiO(2) was significantly higher than that of undoped TiO(2) upon its exposure to visible light.

Flexible ZnO-cellulose nanocomposite for multisource energy conversion.

Materials with the ability to harness multiple sources of energy from the ambient environment could lead to new types of energy-harvesting systems. It is demonstrated that nanocomposite films consisting of zinc oxide nanostructures embedded in a common paper matrix can be directly used as energy-conversion devices to transform mechanical and thermal energies to electric power. These mechanically robust and flexible devices can be fabricated over large areas and are capable of producing an output voltage and power up to 80 mV and 50 nW cm(-2) , respectively. Furthermore, it is shown that by integrating a certain number of devices (in series and parallel) the output voltage and the concomitant output power can be significantly increased. Also, the output voltage and power can be enhanced by scaling the size of the device. This multisource energy-harvesting system based on ZnO nanostructures embedded in a flexible paper matrix provides a simplified and cost-effective platform for capturing trace amounts of energy for practical applications.

Direct synthesis of lithium-intercalated graphene for electrochemical energy storage application.

A novel approach for bulk synthesis of lithium-intercalated graphene sheets through the reduction of exfoliated graphene oxide in liquid ammonia and lithium metal is reported. It is demonstrated here that as-synthesized lithiated graphite oxide sheets (Li-RGO) can be directly used as an electrode material in lithium batteries. The electrochemical studies on Li-RGO electrodes show a significant enhancement in the specific capacity of the lithium battery over commercially available graphite electrodes. Partial intercalation of lithium ions in between graphene layers makes this material a good candidate for electrochemical energy storage applications.

Thermal decomposition properties of NaClO4 functionalized CNT arrays.

Aligned CNT mats were prepared by thermal chemical vapor deposition (CVD) method by exposing a mixture of ferrocene and xylene vapor to the SiO2/Si substrates. Aligned CNT mats functionalized with reactive chemicals without disturbing CNT alignment were characterized by SEM, XRD, FT-IR, FT-Raman and XPS. The thermal stability of the CNT, CNT-OH and CNT-NaCIO4 are investigated using TG-DSC analysis. Oxidation and combustion temperatures of CNT mats were found to be decreased by functionalizing the CNT mats with NaClO4.

Flexible piezoelectric ZnO-paper nanocomposite strain sensor.

The fabrication of a mechanically flexible, piezoelectric nanocomposite material for strain sensing applications is reported. Nanocomposite material consisting of zinc oxide (ZnO) nanostructures embedded in a stable matrix of paper (cellulose fibers) is prepared by a solvothermal method. The applicability of this material as a strain sensor is demonstrated by studying its real-time current response under both static and dynamic mechanical loading. The material presented highlights a novel approach to introduce flexibility into strain sensors by embedding crystalline piezoelectric material in a flexible cellulose-based secondary matrix.

Metal salt induced synthesis of hybrid metal core-siloxane shell nanoparticles and siloxane nanowires.

We demonstrate a one-step method for synthesizing hybrid siloxane nanowires and metal (gold, silver) core-siloxane shell nanoparticles at room temperature by mixing a metal salt with an octadecylsilane solution. This method avoids the use of pre-synthesized nanoparticles and allows us to tailor the shape of the nanostructures.

Gold and silver nanoparticles conjugated with heparin derivative possess anti-angiogenesis properties.

Silver and gold nanoparticles display unique physical and biological properties that have been extensively studied for biological and medical applications. Typically, gold and silver nanoparticles are prepared by chemical reductants that utilize excess toxic reactants, which need to be removed for biological purposes. We utilized a clean method involving a single synthetic step to prepare metal nanoparticles for evaluating potential effects on angiogenesis modulation. These nanoparticles were prepared by reducing silver nitrate and gold chloride with diaminopyridinyl (DAP)-derivatized heparin (HP) polysaccharides. Both gold and silver nanoparticles reduced with DAPHP exhibited effective inhibition of basic fibroblast growth factor (FGF-2)-induced angiogenesis, with an enhanced anti-angiogenesis efficacy with the conjugation to DAPHP (P<0.01) as compared to glucose conjugation. These results suggest that DAPHP-reduced silver nanoparticles and gold nanoparticles have potential in pathological angiogenesis accelerated disorders such as cancer and inflammatory diseases.

Hyaluronan- and heparin-reduced silver nanoparticles with antimicrobial properties.

AIMS: Silver nanoparticles exhibit unique antibacterial properties that make these ideal candidates for biological and medical applications. We utilized a clean method involving a single synthetic step to prepare silver nanoparticles that exhibit antimicrobial activity. MATERIALS & METHODS: These nanoparticles were prepared by reducing silver nitrate with diaminopyridinylated heparin (DAPHP) and hyaluronan (HA) polysaccharides and tested for their efficacy in inhibiting microbial growth. RESULTS & DISCUSSION: The resulting silver nanoparticles exhibit potent antimicrobial activity against Staphylococcus aureus and modest activity against Escherichia coli. Silver-HA showed greater antimicrobial activity than silver-DAPHP, while silver-glucose nanoparticles exhibited very weak antimicrobial activity. Neither HA nor DAPHP showed activity against S. aureus or E. coli. CONCLUSION: These results suggest that DAPHP and HA silver nanoparticles have potential in antimicrobial therapeutic applications.

Synthesis of gold and silver nanoparticles stabilized with glycosaminoglycans having distinctive biological activities.

Metal nanoparticles have been studied for their anticoagulant and anti-inflammatory efficacy in various models. Specifically, gold and silver nanoparticles exhibit properties that make these ideal candidates for biological applications. The typical synthesis of gold and silver nanoparticles incorporates contaminants that could pose further problems. Here we demonstrate a clean method of synthesizing gold and silver nanoparticles that exhibit biological functions. These nanoparticles were prepared by reducing AuCl(4) and AgNO(3) using heparin and hyaluronan as both reducing and stabilizing agents. The particles show stability under physiological conditions and narrow size distributions for heparin particles and wider distribution for hyaluronan particles. Studies show that the heparin nanoparticles exhibit anticoagulant properties. Additionally, either gold- or silver-heparin nanoparticles exhibit local anti-inflammatory properties without any significant effect on systemic hemostasis upon administration in carrageenan-induced paw edema models. In conclusion, gold and silver nanoparticles complexed with heparin demonstrated effective anticoagulant and anti-inflammatory efficacy, having potential in various local applications.

In situ Synthesis of Metal Nanoparticle Embedded Free Standing Multifunctional PDMS Films.

We demonstrate a simple one-step method for synthesizing noble metal nanoparticle embedded free standing polydimethylsiloxane (PDMS) composite films. The process involves preparing a homogenous mixture of metal salt (silver, gold and platinum), silicone elastomer and the curing agent (hardener) followed by curing. During the curing process, the hardener crosslinks the elastomer and simultaneously reduces the metal salt to form nanoparticles. This in situ method avoids the use of any external reducing agent/stabilizing agent and leads to a uniform distribution of nanoparticles in the PDMS matrix. The films were characterized using UV-Vis spectroscopy, transmission electron microscopy and X-ray photoemission spectroscopy. The nanoparticle-PDMS films have a higher Young's modulus than pure PDMS films and also show enhanced antibacterial properties. The metal nanoparticle-PDMS films could be used for a number of applications such as for catalysis, optical and biomedical devices and gas separation membranes.

Silver-nanoparticle-embedded antimicrobial paints based on vegetable oil.

Developing bactericidal coatings using simple green chemical methods could be a promising route to potential environmentally friendly applications. Here, we describe an environmentally friendly chemistry approach to synthesize metal-nanoparticle (MNP)-embedded paint, in a single step, from common household paint. The naturally occurring oxidative drying process in oils, involving free-radical exchange, was used as the fundamental mechanism for reducing metal salts and dispersing MNPs in the oil media, without the use of any external reducing or stabilizing agents. These well-dispersed MNP-in-oil dispersions can be used directly, akin to commercially available paints, on nearly all kinds of surface such as wood, glass, steel and different polymers. The surfaces coated with silver-nanoparticle paint showed excellent antimicrobial properties by killing both Gram-positive human pathogens (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli). The process we have developed here is quite general and can be applied in the synthesis of a variety of MNP-in-oil systems.

Flexible energy storage devices based on nanocomposite paper.

There is strong recent interest in ultrathin, flexible, safe energy storage devices to meet the various design and power needs of modern gadgets. To build such fully flexible and robust electrochemical devices, multiple components with specific electrochemical and interfacial properties need to be integrated into single units. Here we show that these basic components, the electrode, separator, and electrolyte, can all be integrated into single contiguous nanocomposite units that can serve as building blocks for a variety of thin mechanically flexible energy storage devices. Nanoporous cellulose paper embedded with aligned carbon nanotube electrode and electrolyte constitutes the basic unit. The units are used to build various flexible supercapacitor, battery, hybrid, and dual-storage battery-in-supercapacitor devices. The thin freestanding nanocomposite paper devices offer complete mechanical flexibility during operation. The supercapacitors operate with electrolytes including aqueous solvents, room temperature ionic liquids, and bioelectrolytes and over record temperature ranges. These easy-to-assemble integrated nanocomposite energy-storage systems could provide unprecedented design ingenuity for a variety of devices operating over a wide range of temperature and environmental conditions.