Interfacial negative magnetization in Ni encapsulated layer-tunable nested MoS2 nanostructure with robust memory applications.

Combining interfacial interactions and layer-number tunability, the evolution of magnetism in low-dimensional diamagnetic systems like MoS2 is indeed an interesting area of research. To explore this, Ni nanophases with an average size of 12 nm were encapsulated in MoS2 and the magnetization dynamics were studied over the temperature range of 2-300 K. Surprisingly, the newly formed hybrid nanostructure was found to have a negative magnetization state with giant exchange bias that showed a reversible temperature-induced increase in both spin magnetic moment and coercivity. Density functional theory calculations proved an interfacial charge transfer interaction with a spin-polarized density of states. The magnetization state, along with giant exchange correlation among the magnetic clusters, suggested the possibility of robust thermomagnetic memory. The dc magnetization and relaxation, investigated with different measurement protocols, unveiled robust thermoremanent magnetization as a memory effect. The time-dependent magnetization study indicated that contributions from the negative magnetization state along with charge transfer induced spin states are responsible for the memory effect, which can be controlled by both temperature and external field.

Melting of hybrid organic-inorganic perovskites.

Several organic-inorganic hybrid materials from the metal-organic framework (MOF) family have been shown to form stable liquids at high temperatures. Quenching then results in the formation of melt-quenched MOF glasses that retain the three-dimensional coordination bonding of the crystalline phase. These hybrid glasses have intriguing properties and could find practical applications, yet the melt-quench phenomenon has so far remained limited to a few MOF structures. Here we turn to hybrid organic-inorganic perovskites-which occupy a prominent position within materials chemistry owing to their functional properties such as ion transport, photoconductivity, ferroelectricity and multiferroicity-and show that a series of dicyanamide-based hybrid organic-inorganic perovskites undergo melting. Our combined experimental-computational approach demonstrates that, on quenching, they form glasses that largely retain their solid-state inorganic-organic connectivity. The resulting materials show very low thermal conductivities (~0.2 W m-1 K-1), moderate electrical conductivities (10-3-10-5 S m-1) and polymer-like thermomechanical properties.

Photoluminescence and photo-induced conductivity in 2D siloxene nanosheet for optoelectronic applications.

Semiconducting 2D siloxene nanosheets of thickness 1.7 nm and band gap of 2.54 eV are synthesized using simple chemical route. Strong photoluminescence is observed in the as-synthesized nanosheets due to presence of oxygen atoms. The photoluminescence behaviour of siloxene nanosheets is investigated by controlling temperature, excitation and pH of the solution to understand the optical response and stability of the material. The as-synthesized sample heated with temperature 200 °C shows a blue shift of 90 nm compared to the sample synthesized at room temperature. The low temperature luminescence measurements of as-synthesized samples dried at different temperatures viz. 27, 100 and 200 °C. It is seen that the luminescence intensity is increasing with decreasing temperature for the sample dried at room temperature. However, after heating the sample at 100 °C, the luminescence intensity is not only increased but also red-shifted up to 52 nm. The photocurrent has been measured for the device structure of ITO/PEDOT: PSS/Siloxene/Al with different film thicknesses to optimize the photocurrent and the maximum percentage change in photo power gain. The maximum photopower gain of 2693% is observed for the film thickness of 600 nm.

White light emitting lanthanide based carbon quantum dots as toxic Cr (VI) and pH sensor.

Although, great attention is paid to synthesize fluorescent carbon quantum dots (CQDs) for versatile applications, the field remains still attractive to achieve white light using these nano materials. In the present work, CQDs are synthesized from citric acid and lanthanide ions viz. Europium (Eu) and Terbium (Tb) are doped in CQD moiety to explore superior optical response for multifunctional applications. By proper tuning of excitation wavelength, perfect white light with Commission Internationale de l'Elcairage (CIE) index (0.345, 0.344) is obtained using these Europium Terbium co-doped CQDs (Eu-Tb-CQD). The observed photoluminescence of white light emitting lanthanide based CQD is pH dependent and will be used as a visual pH sensor. These luminescent Eu and Tb co-doped CQDs are also very useful to detect toxic Cr (VI) with excellent selectivity and sensitivity as compared to pure CQDs. It shows high quenching efficiency (∼95%) in presence of only 160 µM Cr(VI). The selectivity and lower detection limit are also obtained as ∼80% and 0.175 µM respectively.

A green luminescent MoS2-CdTe hybrid nanostructure synthesized through surface charge interaction.

During the last few years, intensive research has been carried out on the synthesis of different hybrid nanostructures mostly using hydrothermal and solvothermal techniques. But the fabrication of the hybrid nanostructure through surface charge interaction of the individual components is comparatively less explored. Here in this work, a hybrid nanostructure based on MoS2 and CdTe quantum dots is synthesized through a simple surface charge interaction process using the negative surface charge of the excess sulfide ions (S2-) present at the edge of the MoS2 QDs and positively charged CdTe QDs where the positive surface charge was induced in CdTe by using a cysteamine ligand in acidic medium. In the photoluminescence (PL) emission spectrum, a new peak is observed which is different from those of both of the individual components. Interestingly, with increasing the concentration of CdTe QDs during the preparation of the hybrid nano-structure, the peak of hybrid QDs is gradually blue shifted towards the emission of MoS2 QDs. The maximum blue shift occurs up to 1 : 1 (v/v) ratio of MoS2 : CdTe as in this concentration ratio all S2- ions are neutralized by -NH3 +. This new emission occurs from a newly generated hybrid energy level. The energy level positions of the two different QDs along with the hybrid ones are estimated via cyclic voltammetry and absorption experiments.

Nickel-Doped Silver Sulfide: An Efficient Air-Stable Electrocatalyst for Hydrogen Evolution from Neutral Water.

A low-cost, platinum-free electrocatalyst for hydrogen (H2) generation via the water splitting reaction holds great promise to meet the demand of clean and sustainable energy sources. Recent studies are mainly concerned with semiconducting materials like sulfides, selenides, and phosphides of different transition metals as electrocatalysts. Doping of the transition metals within the host matrix is a good strategy to improve the electrocatalytic activity of the host material. However, this activity largely depends on the nature of the dopant metal and its host matrix as well. To exploit this idea, here, in the present work, we have synthesized semiconducting Ag2S nanoparticles and successfully doped them with different transition metals like Mn, Fe, Co, and Ni to study their electrocatalytic activity for the hydrogen evolution reaction from neutral water (pH = 7). Among the systems doped with these transition metals, the Ni-doped Ag2S (Ni-Ag2S) system shows a very low overpotential (50 mV) with high catalytic current in neutral water. The trend in electrocatalytic activity of different transition metals has also been explained. The Ni-Ag2S system also shows very good stability in ambient atmosphere over a long period of time and suffers no catalytic degradation in the presence of oxygen. Structural characterizations are carried out using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy to establish the phase purity and morphology of the materials.

Dual-Emissive Carbon Quantum Dot-Tb Nanocomposite as a Fluorescent Indicator for a Highly Selective Visual Detection of Hg(II) in Water.

We report very fast, green, and large-scale synthesis of amino-functionalized carbon quantum dots (CQDs) using a domestic microwave to investigate CQD-Tb-based dual emission for visual detection of toxic Hg2+. Citric acid and p-phenylenediamine are used as precursor materials to synthesize the CQD, which shows excitation-independent blue luminescence. To achieve the dual emission, Tb-containing CQD is synthesized in a very easy and cost-effective way. These dual-emissive fluorescent materials have been successfully used as a fluorescent indicator for visual detection of toxic Hg2+ metal ions. An instant color change from blue to green in the presence of a very low amount of Hg2+ under a UV lamp (λ365nm) is observed. The material is highly sensitive and selective toward detection of mercury ions in the presence of other metal ions. The photoluminescence quenching mechanism (photoinduced electron transfer process) has been explained using an electronic band diagram supported by zeta-potential and time-correlated single photon counting measurements.

1-Aza-15-Crown-5 Functionalized Graphene Oxide for 2D Graphene-Based Li⁺-ion Conductor.

Attachment of Li(+) ion on graphene surface to realize Li(+)-ion conductor is a real challenge because of the weak interaction between the ions and the functional groups of graphene oxide; although, a large number of theoretical results are already available in the literature. To overcome this problem, graphene oxide is functionalized by 1-aza-15-crown-5, the cage-like structure containing four oxygens that can bind Li(+) ion through electrostatic interaction. Li(+) migration on graphene surface has been investigated using ac relaxation mechanism. Perfect Debye-type relaxation behavior with ß (relaxation exponent) value ≈1 resulting from single ion is observed. The activation energy of Li(+) migration arising due to cation-π interaction is found to be 0.37 eV, which agrees well with recently reported theoretical value. It is believed that this study will help to design isolated ion conductors for Li(+)-ion battery.

Emerging photoluminescence in azo-pyridine intercalated graphene oxide layers.

Inspite of being a potential material for electronic applications graphene possesses very poor optical properties, which need to be modified to make it suitable for optoelectronic devices. To achieve superior optical properties, graphene oxide (GO) sheets are functionalized with azo-pyridine to form a new intercalated structure with an interlayer separation of 0.9 nm. These azo-pyridine intercalated GO sheets show superior optical properties with bright blue emission via excited state intra-molecular proton transfer (ESIPT) which have potential applications in graphene based optoelectronic devices.

A graphite-like zero gap semiconductor with an interlayer separation of 2.8 Å.

The synthesis of a highly crystalline graphite-like new material with an interlayer separation of 2.8 Å is demonstrated by re-stacking GO sheets in the form of a thin film. The optical absorption spectra and electrical data indicate that the new crystal phase is an indirect zero gap semiconductor.

Ni/graphene/Ni nanostructures for spintronic applications.

Here, we demonstrate chemical synthesis of graphene based nano-spin valve like structures using nickel layers as ferromagnetic contacts grown on both sides of graphene sheets. Magnetic measurements indicate that the spins on two opposite nickel layers are coupled through antiferromagnetic interaction up to room temperature. However, they switch into parallel configuration when a magnetic field of about 2000 Oe is applied resulting in a change in magnetoresistance of ~19%.

Epitaxial growth of crystalline polyaniline on reduced graphene oxide.

Due to its unique electronic properties, graphene has already been identified as a promising material for future carbon based electronics. To develop graphene technology, the fabrication of a high quality P-N junction is a great challenge. Here, we describe a general technique to grow single crystalline polyaniline (PANI) films on graphene sheets using in situ polymerization via the oxidation-reduction of aniline monomer and graphene oxide, respectively, to fabricate a high quality P-N junction, which shows diode-like behavior with a remarkably low turn-on voltage (60 mV) and high rectification ratio (1880:1) up to a voltage of 0.2 V. The origin of these superior electronic properties is the preferential growth of a highly crystalline PANI film as well as lattice matching between the d-values [∼2.48 Å] of graphene and {120} planes of PANI.

Antidiarrheal effects of L-histidine-supplemented rice-based oral rehydration solution in the treatment of male adults with severe cholera in Bangladesh: a double-blind, randomized trial.

BACKGROUND: Because of the antisecretory potential of L-histidine in the intestinal tract, its antidiarrheal effects were determined in cholera. METHODS: In a double-blind trial of 126 adult male patients with cholera, L-histidine (2.5 g/L) was mixed with a rice-based oral rehydration solution (ORS) and administered to 62 patients; 64 patients received the same ORS without L-histidine. All patients received ciprofloxacin at a dosage of 500 mg every 12 h for 72 h. Fluid output (of stool, urine, and vomit) and intake (of ORS, water, and intravenous fluid) were determined every 8 h for 72 h. RESULTS: Administration of ORS with L-histidine significantly (P<.05) reduced the frequency of stool output during 32-64 h after initiation of ORS treatment, compared with that in patients given ORS without L-histidine ([all data are means+/-SD] 32-48 h, 11.5+/-6.9 mL/kg vs. 18.8+/-16.0 mL/kg; 40-48 h, 6.7+/-4.4 mL/kg vs. 11.5+/-9.7 mL/kg; and 56-64 h, 6.3+/-5.8 mL/kg vs. 7.8+/-4.1 mL/kg). An overall reduction of 22% in the volume of stool was observed in patients given ORS without L-histidine. The amount of required unscheduled intravenous fluid was lower in patients given ORS with L-histidine, compared with that in patients given ORS without L-histidine (0-24 h, 82.5+/-44.4 mL/kg vs. 158.6+/-72.2 mL/kg [P<.01]; and 24-48 h, 41.6+/-40.4 mL/kg vs. 52.5+/-22.1 mL/kg [P>.05]). Administration of ORS with L-histidine also significantly reduced (P<.05) the intake of ORS and the duration of illness. No adverse effects were observed in these patients. CONCLUSIONS: L-histidine reduces the weight of stool and the frequency of stool output in cholera and could be a useful and safe adjunct treatment that will increase the success rate of ORS and antibiotic therapy in cholera.