In the present article, an effective, one-step, and environmentally benign protocol for the synthesis of gold nanoparticles has been discussed. The black cardamom extract is used as a reducing agent ...for HAuCl
4
.3H
2
O. In order to synthesize gold nanoparticles, an aqueous solution of HAuCl
4
.3H
2
O was mixed with an optimized concentration of black cardamom extract where 1,8-cineole is the dominant component. Choosing black cardamom extract as a reducing agent can be justified under the light of the fact that it has a very fast reducing ability. Gold nanoparticles with different shapes and sizes were synthesized by varying the ratio of AuCl
4
ions to black cardamom extract. Kinetics of reactions has been evaluated through monitoring of surface plasmon behavior of gold nanoparticles as a function of time. Based on Fourier transform infrared spectroscopy (FTIR) studies, a tentative mechanism of reduction of Au nanoparticles has also been proposed which includes oxidation of 1,8-cineole to 2-oxo-1,8-cineole. Further, a comprehensive study to investigate the effect of pH on the synthesis of Au nanoparticles has been carried out.
In this article, we proposed a facile one-step synthesis of Fe
3
O
4
nanoparticles of different shapes and sizes by co-precipitation of FeCl
2
with piperidine. A careful investigation of TEM ...micrographs shows that the shape and size of nanoparticles can be tuned by varying the molarity of piperidine. XRD patterns match the standard phase of the spinal structure of Fe
3
O
4
which confirms the formation of Fe
3
O
4
nanoparticles. Transmission electron microscopy reveals that molar concentration of FeCl
2
solution plays a significant role in determining the shape and size of Fe
3
O
4
nanoparticles. Changes in the shape and sizes of Fe
3
O
4
nanoparticles which are influenced by the molar concentration of FeCl
2
can easily be explained with the help of surface free energy minimization principle. Further, to study the magnetic behavior of synthesized Fe
3
O
4
nanoparticles, magnetization vs. magnetic field (M-H) and magnetization vs. temperature (M-T) measurements were carried out by using Physical Property Measurement System (PPMS). These results show systematic changes in various magnetic parameters like remanent magnetization (Mr), saturation magnetization (Ms), coercivity (Hc), and blocking temperature (
T
B
) with shapes and sizes of Fe
3
O
4
. These variations of magnetic properties of different shaped Fe
3
O
4
nanoparticles can be explained with surface effect and finite size effect.
In search of affordable, flexible, lightweight, efficient and stable supercapacitors, metal oxides have been shown to provide high charge storage capacity but with poor cyclic stability due to ...structural damage occurring during the redox process. Here, we develop an efficient flexible supercapacitor obtained by carbonizing abundantly available and recyclable jute. The active material was synthesized from jute by a facile hydrothermal method and its electrochemical performance was further enhanced by chemical activation. Specific capacitance of 408 F/g at 1 mV/s using CV and 185 F/g at 500 mA/g using charge-discharge measurements with excellent flexibility (~100% retention in charge storage capacity on bending) were observed. The cyclic stability test confirmed no loss in the charge storage capacity of the electrode even after 5,000 charge-discharge measurements. In addition, a supercapacitor device fabricated using this carbonized jute showed promising specific capacitance of about 51 F/g, and improvement of over 60% in the charge storage capacity on increasing temperature from 5 to 75 °C. Based on these results, we propose that recycled jute should be considered for fabrication of high-performance flexible energy storage devices at extremely low cost.
•Genetic gain for rice grain yield for International Rice Research Institute drought breeding program was estimated.•Positive trend of 0.68 %, 0.87 %, 1.9 % under irrigated control, moderate and ...severe drought achieved.•Superiority of new rice varieties over currently grown demonstrated on farmers’ fields.•International Rice Research Institute developed rice varieties can protect farmers from crop losses under drought conditions.
The complexity of genotype × environment interactions under drought reduces heritability, which determines the effectiveness of selection for drought tolerance and development of drought tolerant varieties. Genetic progress measured through changes in yield performance over time is important in determining the efficiency of breeding programmes in which test cultivars are replaced each year on the assumption that the new cultivars will surpass the older cultivars. The goal of our study was to determine the annual rate of genetic gain for rice grain yield in a drought-prone rainfed system in a series of multi-environment trials conducted from 2005 to 2014 under the Drought Breeding Network of Indian sites in collaboration with the International Rice Research Institute (IRRI). Our results show a positive trend in grain yield with an annual genetic yield increase of about 0.68 % under irrigated control, 0.87 % under moderate reproductive stage drought stress and 1.9 % under severe reproductive stage drought stress due to breeding efforts. The study also demonstrates the effectiveness of direct selection for grain yield under both irrigated control as well as managed drought stress screening to improve yield in typical rainfed systems. IRRI's drought breeding programme has exhibited a significant positive trend in genetic gain for grain yield over the years under both drought stress as well as favorable irrigated control conditions. Several drought tolerant varieties released from the programme have outperformed the currently grown varieties under varied conditions in the rainfed environments on farmers’ fields.
Background
Climate extremes such as drought and flood have become major constraints to the sustainable rice crop productivity in rainfed environments. Availability of suitable climate-resilient ...varieties could help farmers to reduce the grain yield losses resulting from the climatic extremities. The present study was undertaken with an aim to develop high-yielding drought and submergence tolerant rice varieties using marker assisted introgression of
qDTY
1.1
,
qDTY
2.1
,
qDTY
3.1
and
Sub1.
Performance of near isogenic lines (NILs) developed in the background of Swarna was evaluated across 60 multi-locations trials (MLTs). The selected promising lines from MLTs were nominated and evaluated in national trials across 18 locations in India and 6 locations in Nepal.
Results
Grain yield advantage of the NILs with
qDTY
1.1
+ qDTY
2.1
+
qDTY
3.1
+
Sub1
and
qDTY
2.1
+
qDTY
3.1
+
Sub1
ranged from 76 to 2479 kg ha
− 1
and 396 to 2376 kg ha
− 1
under non-stress (NS) respectively and 292 to 1118 kg ha
− 1
and 284 to 2086 kg ha
− 1
under reproductive drought stress (RS), respectively. The NIL, IR96322–34-223-B-1-1-1-1 having
qDTY
1.1
+ qDTY
2.1
+
qDTY
3.1
+
Sub1
has been released as variety CR dhan 801 in India. IR 96321–1447-651-B-1-1-2 having
qDTY
1.1
+
qDTY
3.1
+
Sub 1
and IR 94391–131–358-19-B-1-1-1 having
qDTY
3.1
+
Sub1
have been released as varieties Bahuguni dhan-1′ and ‘Bahuguni dhan-2’ respectively in Nepal. Background recovery of 94%, 93% and 98% was observed for IR 96322–34-223-B-1-1-1-1, IR 96321–1447-651-B-1-1-2 and IR 94391–131–358-19-B-1-1-1 respectively on 6 K SNP Infinium chip.
Conclusion
The drought and submergence tolerant rice varieties with pyramided multiple QTLs can ensure 0.2 to 1.7 t ha
− 1
under reproductive stage drought stress and 0.1 to 1.0 t ha
− 1
under submergence conditions with no yield penalty under non-stress to farmers irrespective of occurrence of drought and/or flood in the same or different seasons.
Low field magnetotransport in manganites Siwach, P K; Singh, H K; Srivastava, O N
Journal of physics. Condensed matter,
07/2008, Letnik:
20, Številka:
27
Journal Article
Recenzirano
Odprti dostop
The perovskite manganites with generic formula RE(1-x)AE(x)MnO(3) (RE = rare earth, AE = Ca, Sr, Ba and Pb) have drawn considerable attention, especially following the discovery of colossal ...magnetoresistance (CMR). The most fundamental property of these materials is strong correlation between structure, transport and magnetic properties. They exhibit extraordinary large magnetoresistance named CMR in the vicinity of the insulator-metal/paramagnetic-ferromagnetic transition at relatively large applied magnetic fields. However, for applied aspects, occurrence of significant CMR at low applied magnetic fields would be required. This review consists of two sections: in the first section we have extensively reviewed the salient features, e.g. structure, phase diagram, double-exchange mechanism, Jahn-Teller effect, different types of ordering and phase separation of CMR manganites. The second is devoted to an overview of experimental results on CMR and related magnetotransport characteristics at low magnetic fields for various doped manganites having natural grain boundaries such as polycrystalline, nanocrystalline bulk and films, manganite-based composites and intrinsically layered manganites, and artificial grain boundaries such as bicrystal, step-edge and laser-patterned junctions. Some other potential magnetoresistive materials, e.g. pyrochlores, chalcogenides, ruthenates, diluted magnetic semiconductors, magnetic tunnel junctions, nanocontacts etc, are also briefly dealt with. The review concludes with an overview of grain-boundary-induced low field magnetotransport behavior and prospects for possible applications.
High performance carbonized bamboo fibers were synthesized for a wide range of temperature dependent energy storage applications. The structural and electrochemical properties of the carbonized ...bamboo fibers were studied for flexible supercapacitor applications. The galvanostatic charge-discharge studies on carbonized fibers exhibited specific capacity of ~510F/g at 0.4 A/g with energy density of 54 Wh/kg. Interestingly, the carbonized bamboo fibers displayed excellent charge storage stability without any appreciable degradation in charge storage capacity over 5,000 charge-discharge cycles. The symmetrical supercapacitor device fabricated using these carbonized bamboo fibers exhibited an areal capacitance of ~1.55 F/cm(2) at room temperature. In addition to high charge storage capacity and cyclic stability, the device showed excellent flexibility without any degradation to charge storage capacity on bending the electrode. The performance of the supercapacitor device exhibited ~65% improvement at 70 °C compare to that at 10 °C. Our studies suggest that carbonized bamboo fibers are promising candidates for stable, high performance and flexible supercapacitor devices.
We report a simple and cost effective way for synthesis of metallic nanoparticles (Au and Ag) using natural precursor clove. Au and Ag nanoparticles have been synthesized by reducing the aqueous ...solution of AuCl
4
and AgNO
3
with clove extract. One interesting aspect here is that reduction time is quite small (few minutes instead of hours as compared to other natural precursors). We synthesized gold and silver nanoparticles of different shape and size by varying the ratio of AuCl
4
and AgNO
3
with respect to clove extract, where the dominant component is eugenol. The evolution of Au and Ag nanoparticles from the reduction of different ratios of AuCl
4
and AgNO
3
with optimised concentration of the clove extract has been evaluated through monitoring of surface plasmon behaviour as a function of time. The reduction of AuCl
4
and AgNO
3
by eugenol is because of the inductive effect of methoxy and allyl groups which are present at ortho and para positions of proton releasing –OH group as two electrons are released from one molecule of eugenol. This is followed by the formation of resonating structure of the anionic form of eugenol. The presence of methoxy and allyl groups has been confirmed by FTIR. To the best of our knowledge, use of clove as reducing agent, the consequent very short time (minutes instead of hours and without any scavenger) and the elucidation of mechanism of reduction based on FTIR analysis has not been attempted earlier.
This paper reports the catalytic effects of mischmetal (Mm) and mischmetal oxide (Mm-oxide) on improving the dehydrogenation and rehydrogenation behaviour of magnesium hydride (MgH2). It has been ...found that 5 wt.% is the optimum catalyst (Mm/Mm-oxide) concentration for MgH2. The Mm and Mm-oxide catalyzed MgH2 exhibits hydrogen desorption at significantly lower temperature and also fast rehydrogenation kinetics compared to ball-milled MgH2 under identical conditions of temperature and pressure. The onset desorption temperature for MgH2 catalyzed with Mm and Mm-oxide are 323 °C and 305 °C, respectively. Whereas the onset desorption temperature for the ball-milled MgH2 is 381 °C. Thus, there is a lowering of onset desorption temperature by 58 °C for Mm and by 76 °C for Mm-oxide. The dehydrogenation activation energy of Mm-oxide catalyzed MgH2 is 66 kJ/mol. It is 35 kJ/mol lower than ball-milled MgH2. Additionally, the Mm-oxide catalyzed dehydrogenated Mg exhibits faster rehydrogenation kinetics. It has been noticed that in the first 10 min, the Mm-oxide catalyzed Mg (dehydrogenated MgH2) has absorbed up to 4.75 wt.% H2 at 315 °C under 15 atmosphere hydrogen pressure. The activation energy determined for the rehydrogenation of Mm-oxide catalyzed Mg is ∼62 kJ/mol, whereas that for the ball-milled Mg alone is ∼91 kJ/mol. Thus, there is a decrease in absorption activation energy by ∼29 kJ/mol for the Mm-oxide catalyzed Mg. In addition, Mm-oxide is the native mixture of CeO2 and La2O3 which makes the duo a better catalyst than CeO2, which is known to be an effective catalyst for MgH2. This takes place due to the synergistic effect of CeO2 and La2O3. It can thus be said that Mm-oxide is an effective catalyst for improving the hydrogen sorption behaviour of MgH2.
•Mischmetal oxide nanoparticles were found to be a very effective catalyst for MgH2.•Mm-oxide is found to be a better catalyst than the corresponding metals: La and Ce.•The unique catalytic activity of mischmetal oxide is due to the synergistic effect.•Improved rehydrogenation behaviour as compared to other oxides catalyzed MgH2.
In present investigation, the selective removal of Al from the quasi-lattice sites of quasicrystalline alloy surface was examined in order to produce the nano-particles of metal/metal oxides within ...the micro-porous network. Al was selectively etched from both the as-cast as well as annealed Al63Cu25Fe12 quasicrystalline alloys through the treatment with 10 mol NaOH solution at different time interval. In the as-cast sample, higher density of porosity was observed compared to that of annealed alloy. However, dealloying specifically for 4 and 8 h yielded nano-size particles on quasicrystalline surface (of both the alloys) in which very fine particles were detected at 8 h. The increase in density and decrease in size of the nano-particles was found with dealloying duration. X-ray diffraction analysis was performed to characterize the samples. Scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray analysis were carried out to investigate the surface microstructure, internal morphology and chemical composition. The chemical dealloying treatments yielded nano-particles of Cu and Fe along with their oxides on the quasicrystalline surface. Furthermore, the catalytic activity of leached quasicrystalline materials was evaluated towards degradation of non-biodegradable and hazardous methylene blue (organic dye).
•The Evolution of porous structure on poly-grain Al63Cu25Fe12 quasicrystalline alloy surface.•The chemical dealloying yielded nano-particles of Cu and Fe on the quasicrystalline surface.•Excellent catalytic activity of leached quasicrystals on the degradation of methylene blue.
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