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1.
Adv Sci (Weinh) ; : e2401783, 2024 May 13.
Artículo en Inglés | MEDLINE | ID: mdl-38741280

RESUMEN

Reliable fabrication of large-area perovskite films with antisolvent-free printing techniques requires high-volatility solvents, such as 2-methoxyethanol (2ME), to formulate precursor inks. However, the fabrication of high-quality cesium-formamidinium (Cs-FA) perovskites has been hampered using volatile solvents due to their poor coordination with the perovskite precursors. Here, this issue is resolved by re-formulating a 2ME-based Cs0.05FA0.95PbI3 ink using pre-synthesized single crystals as the precursor instead of the conventional mixture of raw powders. The key to obtaining high-quality Cs-FA films lies in the removal of colloidal particles from the ink and hence the suppression of colloid-induced heterogeneous nucleation, which kinetically facilitates the growth of as-formed crystals toward larger grains and improved film crystallinity. Employing the precursor-engineered volatile ink in the vacuum-free, fully printing processing of solar cells (with carbon electrode), a power conversion efficiency (PCE) of 19.3%, a T80 (80% of initial PCE) of 1000 h in ISOS-L-2I (85 °C/1 Sun) aging test and a substantially reduced bill of materials are obtained. The reliable coating methodology ultimately enables the fabrication of carbon-electrode mini solar modules with a stabilized PCE of 16.2% (average 15.6%) representing the record value among the fully printed counterparts and a key milestone toward meeting the objectives for a scalable photovoltaic technology.

2.
Heliyon ; 10(5): e26530, 2024 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-38434320

RESUMEN

Agricultural soils naturally enriched with Arsenic (As) represent a significant global human health risk. In the present investigation, a series of pot experiments were conducted to study the efficacy of three levels of Yellow Gypsum (YG) application on bioavailability of As to kharif groundnut followed by boro-rice grown under 17 different levels of soil As contamination for two consecutive years. The results revealed that application of YG @ 60 kg ha-1 effectuated the lowest soil As content and the highest percent decline in soil extractable As at pegging (9.42 mg kg-1 and 9.81%) and harvesting (8.81 mg kg-1 and 11.85%) in groundnut, maximum tillering (7.52 mg kg-1 and 16.95%) and harvesting (6.77 mg kg-1 and 19.85%) in boro-rice respectively. It was also observed that irrespective of its level, the extractable As content of soil decreased significantly (P < 0.05) with increasing dosage of YG. Increase in YG dose effectuated a significant (P < 0.05) increasing trend and increase in As content in soil indicated a decreasing trend of Ca:As, Fe:As and S:As ratios which pointed out the potentiality of YG for reducing As bio-availability in contaminated soils and thus could be a good option for mitigating the risk of As contamination in food chain.

3.
Sci Rep ; 14(1): 4029, 2024 02 18.
Artículo en Inglés | MEDLINE | ID: mdl-38369546

RESUMEN

Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) has significantly affected maize crop yields, production efficiency, and farmers' incomes in the Indian Eastern Gangetic Plains region since it was first observed in India in 2018. A lack of awareness by maize growers of the appropriate selection, method, and timing of insecticide application not only creates a barrier to sustainable FAW control but also contributes to increased environmental pollution, reduced human health and increased production costs. We demonstrated that FAW inflicted the most damage in early whorl growth stage of maize, regardless of whether chemical insecticides were applied. FAW egg masses and larvae collected from maize fields in which no insecticides had been sprayed showed high parasitism rates by parasitoid wasps; in contrast fields that had been sprayed had much lower rates of parasitism on FAW. Ten hymenopteran parasitoids were observed in maize fields across the study region, suggesting a diversity of natural methods to suppress FAW in maize at different growth stages. These included two FAW egg parasitoids and eight FAW larval parasitoids. Microplitis manilae Ashmead was the most abundant FAW larval parasitoid species, and Telenomus cf. remus was the dominant FAW egg parasitoid species. Endemic FAW parasitoids such as those observed in this study have great potential as part of a sustainable, cost-effective agroecological management strategy, which can be integrated with other methods to achieve effective control of FAW.


Asunto(s)
Insecticidas , Avispas , Animales , Humanos , Spodoptera , Insecticidas/farmacología , Larva , Zea mays
4.
Nat Commun ; 15(1): 1428, 2024 Feb 16.
Artículo en Inglés | MEDLINE | ID: mdl-38365898

RESUMEN

Lead-free, silicon compatible materials showing large electromechanical responses comparable to, or better than conventional relaxor ferroelectrics, are desirable for various nanoelectromechanical devices and applications. Defect-engineered electrostriction has recently been gaining popularity to obtain enhanced electromechanical responses at sub 100 Hz frequencies. Here, we report record values of electrostrictive strain coefficients (M31) at frequencies as large as 5 kHz (1.04×10-14 m2/V2 at 1 kHz, and 3.87×10-15 m2/V2 at 5 kHz) using A-site and oxygen-deficient barium titanate thin-films, epitaxially integrated onto Si. The effect is robust and retained upon cycling upto 6 million times. Our perovskite films are non-ferroelectric, exhibit a different symmetry compared to stoichiometric BaTiO3 and are characterized by twin boundaries and nano polar-like regions. We show that the dielectric relaxation arising from the defect-induced features correlates well with the observed giant electrostriction-like response. These films show large coefficient of thermal expansion (2.36 × 10-5/K), which along with the giant M31 implies a considerable increase in the lattice anharmonicity induced by the defects. Our work provides a crucial step forward towards formulating guidelines to engineer large electromechanical responses even at higher frequencies in lead-free thin films.

5.
J Phys Condens Matter ; 36(3)2023 Oct 19.
Artículo en Inglés | MEDLINE | ID: mdl-37813102

RESUMEN

A popular signature of Majorana bound states in topological superconductors is the quantized zero-energy conductance peak. However, a similar zero energy conductance peak can also arise due to non-topological reasons. Here we show that these trivial and topological zero energy conductance peaks can be distinguished via the zero energy local density of states (LDOSs) and local magnetization density of states (LMDOSs). We find that the zero-energy LDOSs and the LMDOSs exhibit periodic oscillations for a trivial zero-bias conductance peak (ZBCP). In contrast, these oscillations disappear for the topological ZBCP because of perfect Andreev reflection at zero energy in topological superconductor junctions. Our results suggest that the zero-energy LDOSs and the LMDOSs can be used as an experimental probe to distinguish a trivial zero-energy conductance peak from a topological zero-energy conductance peak.

6.
Science ; 381(6665): 1433-1440, 2023 Sep 29.
Artículo en Inglés | MEDLINE | ID: mdl-37769088

RESUMEN

Functional polyethylenes possess valuable bulk and surface properties, but the limits of current synthetic methods narrow the range of accessible materials and prevent many envisioned applications. Instead, these materials are often used in composite films that are challenging to recycle. We report a Cu-catalyzed amination of polyethylenes to form mono- and bifunctional materials containing a series of polar groups and substituents. Designed catalysts with hydrophobic moieties enable the amination of linear and branched polyethylenes without chain scission or cross-linking, leading to polyethylenes with otherwise inaccessible combinations of functional groups and architectures. The resulting materials possess tunable bulk and surface properties, including toughness, adhesion to metal, paintability, and water solubility, which could unlock applications for functional polyethylenes and reduce the need for complex composites.

7.
J Am Chem Soc ; 145(39): 21527-21537, 2023 Oct 04.
Artículo en Inglés | MEDLINE | ID: mdl-37733607

RESUMEN

Polyethylene is a commodity material that is widely used because of its low cost and valuable properties. However, the lack of functional groups in polyethylene limits its use in applications that include adhesives, gas barriers, and plastic blends. The inertness of polyethylene makes it difficult to install groups that would enhance its properties and enable programmed chemical decomposition. To overcome these deficiencies, the installation of pendent functional groups that imbue polyethylene with enhanced properties is an attractive strategy to overcome its inherent limitations. Here, we describe strategies to derivatize oxidized polyethylene that contains both ketones and alcohols to monofunctional variants with bulk properties superior to those of unmodified polyethylene. Iridium-catalyzed transfer dehydrogenation with acetone furnished polyethylenes with only ketones, and ruthenium-catalyzed hydrogenation with hydrogen furnished polyethylenes with only alcohols. We demonstrate that the ratio of these functional groups can be controlled by reduction with stoichiometric hydride-containing reagents. The ketones and alcohols serve as sites to introduce esters and oximes onto the polymer, thereby improving surface and bulk properties over those of polyethylene. These esters and oximes were removed by hydrolysis to regenerate the original oxygenated polyethylenes, showing how functionalization can lead to materials with circularity. Waste polyethylenes were equally amenable to oxidative functionalization and derivatization of the oxidized material, showing that this low- or negative-value feedstock can be used to prepare materials of higher value. Finally, the derivatized polymers with distinct solubilities were separated from mechanically mixed plastic blends by selective dissolution, demonstrating that functionalization can lead to novel approaches for distinguishing and separating polymers from a mixture.

8.
Insects ; 14(7)2023 Jul 13.
Artículo en Inglés | MEDLINE | ID: mdl-37504637

RESUMEN

The brown planthopper [Nilaparvata lugens (Stål.)] is one of the most destructive insect pests in all the rice-growing regions of the world. The pest is complicated to manage through the blanket application of chemical pesticides. The development of stable, durable N. lugens-resistant rice varieties is the most economical and efficient strategy to manage the pest. Landraces of red rice genotypes possess numerous nutritional and stress-resistant properties, though an exclusive study on the same is yet to be carried out. In the present study, we evaluated 28 red rice genotypes, along with two resistance checks and one susceptibility check, for their resistance to N. lugens. These promising lines revealed differential responses in the defense mechanism against the pest. The resistant accessions showed a greater accumulation of phenols, peroxidase, polyphenol oxidase, catalase, and superoxide dismutase under N. lugens-stressed conditions. However, the concentration of soluble proteins was substantially decreased in all the test genotypes. The concentration of crude silica was at maximum in highly resistant genotypes. Six red rice genotypes, namely Mata Meher, Manipuri Black, Hermonona, Sonahanan, Bavdi, and Bacharya Khuta fall under the highly resistant category, and can be utilized as valuable sources of resistance in breeding programs.

9.
Macromol Rapid Commun ; 44(18): e2300218, 2023 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-37435988

RESUMEN

A new heterocyclic monomer is developed via simple Diels-Alder reaction which is reluctant to polymerize in dichloromethane (DCM) whereas undergoes facile polymerization in tetrahydrofuran with excellent control over molecular weight (Mn ) and dispersities (D) using Grubbs' third generation catalyst (G3). The deprotection of the tert-butoxycarbonyl group from the polymeric backbone yielded a water-soluble ring opening metathesis polymerization (ROMP) polymer easily. Moreover, in DCM this new monomer copolymerizes with 2,3-dihydrofuran under catalytic living ROMP conditions to give backbone degradable polymers. All the synthesized polymers are characterized by size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy. It is believed that this new route to water soluble ROMP homopolymers as well as the cost-effective and environmentally friendly route to degradable copolymers and block-copolymers could find applications in biomedicine in the near future.


Asunto(s)
Polímeros , Agua , Polimerizacion , Solventes , Polímeros/química , Catálisis
10.
J Biol Chem ; 299(6): 104837, 2023 06.
Artículo en Inglés | MEDLINE | ID: mdl-37209824

RESUMEN

Group I metabotropic glutamate receptors (mGluRs) play important roles in many neuronal processes and are believed to be involved in synaptic plasticity underlying the encoding of experience, including classic paradigms of learning and memory. These receptors have also been implicated in various neurodevelopmental disorders, such as Fragile X syndrome and autism. Internalization and recycling of these receptors in the neuron are important mechanisms to regulate the activity of the receptor and control the precise spatiotemporal localization of these receptors. Applying a "molecular replacement" approach in hippocampal neurons derived from mice, we demonstrate a critical role for protein interacting with C kinase 1 (PICK1) in regulating the agonist-induced internalization of mGluR1. We show that PICK1 specifically regulates the internalization of mGluR1, but it does not play any role in the internalization of the other member of group I mGluR family, mGluR5. Various regions of PICK1 viz., the N-terminal acidic motif, PDZ domain, and BAR domain play important roles in the agonist-mediated internalization of mGluR1. Finally, we demonstrate that PICK1-mediated internalization of mGluR1 is critical for the resensitization of the receptor. Upon knockdown of endogenous PICK1, mGluR1s stayed on the cell membrane as inactive receptors, incapable of triggering the MAP kinase signaling. They also could not induce AMPAR endocytosis, a cellular correlate for mGluR-dependent synaptic plasticity. Thus, this study unravels a novel role for PICK1 in the agonist-mediated internalization of mGluR1 and mGluR1-mediated AMPAR endocytosis that might contribute to the function of mGluR1 in neuropsychiatric disorders.


Asunto(s)
Proteínas Portadoras , Receptores AMPA , Animales , Ratones , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Endocitosis/fisiología , Plasticidad Neuronal , Transporte de Proteínas/fisiología , Receptores AMPA/metabolismo
11.
ACS Polym Au ; 3(1): 132-140, 2023 Feb 08.
Artículo en Inglés | MEDLINE | ID: mdl-36785838

RESUMEN

The assembly of ligand-functionalized (macro)monomers with suitable metal ions affords metallosupramolecular polymers (MSPs). On account of the reversible and dynamic nature of the metal-ligand complexes, these materials can be temporarily (dis-)assembled upon exposure to a suitable stimulus, and this effect can be exploited to heal damaged samples, to facilitate processing and recycling, or to enable reversible adhesion. We here report on the plasticization of a semicrystalline, stimuli-responsive MSP network that was assembled by combining a low-molecular-weight building block carrying three 2,6-bis(1'-methylbenzimidazolyl) pyridine (Mebip) ligands and zinc bis(trifluoromethylsulfonyl)imide (Zn(NTf2)2). The pristine material exhibits high melting (T m = 230 °C) and glass transition (T g ≈ 157 °C) temperatures and offers robust mechanical properties between these temperatures. We show that this regime can be substantially extended through plasticization. To achieve this, the MSP network was blended with diisodecyl phthalate. The weight fraction of this plasticizer was systematically varied, and the thermal and mechanical properties of the resulting materials were investigated. We show that the T g can be lowered by more than 60 °C and the toughness above the T g is considerably increased.

12.
Artículo en Inglés | MEDLINE | ID: mdl-36622595

RESUMEN

Groundwater is an essential source of drinking as well as irrigation water. It has recently become a significant challenge to maintain good and safe drinking water for all living beings. The continuous supply of arsenic detected in groundwater poses a severe health problem and has adverse effects on humans and the ecosystem. Researchers also identified arsenic contamination globally across various regions. However, a few studies also identified that the groundwater of Patna, Saran, and Vaishali districts of Bihar is intoxicated by arsenic. To assess the toxic level of arsenic in groundwater, samples from various GPS-based pointed locations were collected from the study area using a GARMIN GPS device. The total concentration of arsenic in drinking water (mostly traces of arsenic, level of µg L-1 or less) can be detected only by sophisticated analytical techniques such as ICP-MS, GF-AAS, and HG-AAS. The standard procedures were followed to determine quality attributes in groundwater. Arsenic contamination persists in most areas and exceeds the permissible limits prescribed by the World Health Organization (WHO), negatively impacting the health of more than 10 million people in the state. The 90.47% and 85.71% groundwater samples of the study area exceeded the permissible limit of the WHO (0.01 mg L-1) and Bureau of Indian Standards (BIS (0.05 mg L-1), respectively. The analyzed data was obtained, and variability was noticed in total arsenic concentrations ranging from 0.002 to 7.801 mg L-1, with a mean value of 0.87 mg L-1. Similarly, the water quality attribute like total dissolved solids were identified in 14.28% of samples, which crossed 201 to 1026 mg L-1, with a mean value of 375.33 mg L-1.

13.
ACS Macro Lett ; 11(7): 847-853, 2022 07 19.
Artículo en Inglés | MEDLINE | ID: mdl-35736023

RESUMEN

Terminal alkynes display high reactivity toward Ru-carbene metathesis catalysts. However, the formation of a less reactive bulky carbene hinders their homopolymerization. Simultaneously, the higher reactivity of alkynes does not allow efficient cross propagation with sterically less-hindered cycloalkene monomers, resulting in inefficient copolymerization. Nonetheless, terminal alkynes undergo rapid cross-metathesis with vinyl ethers. Therefore, an efficient cross propagation can be achieved with terminal alkynes and cyclic enol ether monomers. Here, we show that terminal alkyne derivatives can be copolymerized in an alternating fashion with 2,3-dihydrofuran using Grubbs' third generation catalyst (G3). A linear relationship of the number-average molecular weight versus monomer to initiator ratio and block copolymer synthesis confirmed a controlled copolymerization. The SEC and NMR analyses of the synthesized copolymers confirmed the excellent control over molecular weight and exclusive alternating nature of the copolymer. The regioselective chain transfer of G3 to vinyl ether and the high reactivity of the Fischer-type Ru carbene toward terminal alkynes was also exploited for polymer conjugation. Finally, the presence of an acid labile backbone functionality in the synthesized alternating copolymers allowed complete degradation of the copolymer within a short time interval which was confirmed by SEC analyses.


Asunto(s)
Alquinos , Polímeros , Alquinos/química , Catálisis , Polimerizacion , Polímeros/química
14.
J Phys Condens Matter ; 34(30)2022 Jun 03.
Artículo en Inglés | MEDLINE | ID: mdl-35551119

RESUMEN

A 1D Josephson junction (JJ) loop, doped with a spin-flipper and attached to two thermal reservoirs is shown to operate as a heat engine, or a refrigerator, or a Joule pump or even as a cold pump. When operating as a quantum heat engine, the efficiency of this device exceeds that of some recent Josephson heat engine proposals. Further, as a quantum refrigerator, the coefficient of performance of this device is much higher than previously proposed JJ based refrigerators. In addition, this device can be tuned from engine mode to refrigerator mode or to any other mode, i.e., Joule pump or cold pump by either tuning the temperature of reservoirs, or via the flux enclosed in the JJ loop. In presence of spin flip scattering we can tune our device from engine mode to other operating modes by only changing the enclosed flux in JJ loop without changing the temperatures of the reservoirs. This is potentially an advantage with respect to other proposals. This makes the proposed device much more versatile as regards possible applications.

15.
Sci Rep ; 12(1): 6390, 2022 Apr 16.
Artículo en Inglés | MEDLINE | ID: mdl-35430579

RESUMEN

The enhanced electrocaloric (EC) effect in solid-state-based lead-free ferroelectric Ba0.875(Bi0.5Li0.5)0.125TiO3 system is investigated under light as an external stimulus. The sample exhibits an analogous value of maximum change in entropy at Curie temperature, extracted from the two different measurements process. Notably, the sample depicts maximum value of adiabatic change in temperature (ΔT) as 1.27 K and isothermal entropy change (ΔS) as 2.05 J/K kg along with the EC coefficient value of 0.426 K mm/kV, under dark conditions. In addition, the sample exhibits > 0.5 K adiabatic temperature change over a broad temperature range (~ 35 K). Remarkably, the EC parameters display ~ 27% enhancement upon 405 nm light illumination. The demonstrated photoelectrocaloric effect is found to be in accordance with theoretical formalism. The present work elucidates the light as an additional degree of freedom to widen the potential of solid-state-based technologies for advanced environment-friendly cooling devices.

16.
J Neurosci ; 42(5): 731-748, 2022 02 02.
Artículo en Inglés | MEDLINE | ID: mdl-34907024

RESUMEN

Group I mGluRs have diverse functions in some fundamental neuronal processes, including modulation of synaptic plasticity; and dysregulation of these receptors could lead to various neuropsychiatric disorders. Trafficking of Group I mGluRs plays critical roles in controlling the precise spatiotemporal localization and activity of these receptors, both of which contribute to proper downstream signaling. Using "molecular replacement" approach in hippocampal neurons derived from mice of both sexes, we demonstrate a critical role for the postsynaptic density protein Norbin in regulating the ligand-induced internalization of Group I mGluRs. We show that Norbin associates with protein kinase A (PKA) through its N-terminus and anchors mGluR5 through its C-terminus, both of which are necessary for the ligand-mediated endocytosis of mGluR5, a member of the Group I mGluR family. A point mutation (A687G) at the C-terminus of Norbin inhibits the binding of Norbin to mGluR5 and blocks mGluR5 endocytosis. Finally, we demonstrate an important mechanism by which Norbin regulates mGluR-mediated AMPAR endocytosis in hippocampal neurons, a cellular correlate for mGluR-dependent synaptic plasticity. Norbin, through its PKA-binding regions, recruits PKA to AMPARs on activation of mGluRs; and deletion of the PKA-binding regions of Norbin inhibits mGluR-triggered AMPAR endocytosis. We further report that Norbin is important specifically for the mGluR-mediated AMPAR endocytosis, but not for NMDAR-dependent AMPAR endocytosis. Thus, this study unravels a novel role for Norbin in the internalization of mGluRs and mGluR-mediated AMPAR endocytosis that can have clinical relevance to the function of Group I mGluRs in pathologic processes.SIGNIFICANCE STATEMENT The postsynaptic protein Norbin interacts with mGluR5, and both of them have been implicated in disorders, such as schizophrenia. However, the mechanistic basis underlying the regulation of mGluRs by Norbin remains elusive. We have identified Norbin as an essential mediator of ligand-mediated endocytosis of Group I mGluRs. Mechanistically, Norbin N-terminus associates with protein kinase-A (PKA) and C-terminus binds to mGluR5 to coordinate receptor internalization. A point mutation NorA687G inhibits endocytosis by disrupting this interaction. Additionally, Norbin is critical for the recruitment of PKA to AMPARs on activation of Group I mGluRs that assists in mGluR-mediated AMPAR endocytosis. Thus, Norbin has a dual function in the hippocampus: regulation of mGluR internalization and PKA-dependent modulation of mGluR-mediated AMPAR endocytosis, a prerequisite for mGluR-mediated synaptic plasticity.


Asunto(s)
Endocitosis/fisiología , Proteínas del Tejido Nervioso/metabolismo , Plasticidad Neuronal/fisiología , Receptor del Glutamato Metabotropico 5/metabolismo , Receptores AMPA/metabolismo , Sinapsis/metabolismo , Animales , Animales Recién Nacidos , Células Cultivadas , Femenino , Células HEK293 , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Proteínas del Tejido Nervioso/genética , Receptor del Glutamato Metabotropico 5/genética , Receptores AMPA/genética , Receptores de N-Metil-D-Aspartato/genética , Receptores de N-Metil-D-Aspartato/metabolismo , Sinapsis/genética
17.
Nat Chem ; 13(7): 705-713, 2021 07.
Artículo en Inglés | MEDLINE | ID: mdl-34103692

RESUMEN

Polycondensation polymers typically follow step-growth kinetics assuming all functional groups are equally likely to react with one another. If the reaction rates with the chain end can be selectively accelerated, living polymers can be obtained. Here we report on two chlorophosphonium iodide reagents that have been synthesized from triphenylphosphine and tri(o-methoxyphenyl)phosphine. The former activates aromatic carboxylic acids as acid chlorides in the presence of secondary aromatic amines and the latter even in the presence of primary aromatic amines. These reagents allow p-aminobenzoic acid derivatives to form solution-stable activated monomers that polymerize in a living fashion in the presence of amine initiators. Other aryl amino acids and even dimers of aryl amino acids can be polymerized in a living fashion when slowly added to the phosphonium salt in the presence of an amine initiator. Diblock copolymers and triblock terpolymers of aryl amino acids can be prepared even in the presence of electrophilic functional groups.

18.
Chem Sci ; 12(19): 6705-6711, 2021 Apr 07.
Artículo en Inglés | MEDLINE | ID: mdl-34040745

RESUMEN

Higher ring-opening metathesis propagation rates of exo-norbornene derivatives over endo derivatives are well established in the literature. Here, we report for the first time that endo-isomers of oxanorbornene derivatives show higher reactivity towards ring-opening metathesis with Grubbs' 3rd generation catalyst (G3) than the corresponding exo-isomers. A very high selectivity for the reaction of G3 with endo over the exo-isomers could be shown. Furthermore, single molecular addition of the endo-isomers with G3 was observed. On the other hand, pure exo-monomers could successfully be homopolymerized. Mixtures of exo- and endo- monomers, however, prevented the homopolymerization of the exo-monomer. Such mixtures could successfully be copolymerized with cycloalkenes, resulting in alternating copolymers. An oxanorbornadiene derivative could be shown to undergo single addition reactions, exploited in the preparation of mono-end functional ROMP polymers. These could be selectively derivatized via endgroup selective thiol-ene click reactions. A thiol and alcohol end functional ROMP polymer was synthesized, and the efficient end functionalization was confirmed by 1H NMR spectroscopy and MALDI-ToF spectrometry.

19.
Artículo en Inglés | MEDLINE | ID: mdl-32750682

RESUMEN

Ferroelectric systems with multi-phase co-existence are found to exhibit anomalous photovoltaic response. In this work, detailed photovoltaic studies are carried out under 405 nm light illumination on Ba1-x(Bi0.5Li0.5)xTiO3ferroelectric oxides having the coexistence of tetragonal and orthorhombic phases. The linear and sinusoidal photocurrent-dependence as a function of light intensity and polarization-direction, respectively elucidate the experimental evidence for linear bulk-photovoltaic effect. Importantly, the temperature-dependent photovoltaic studies display 2-fold enhancement in photovoltage near the ferroelectric transition temperature (TC). The observed features in photovoltage follow inverse temperature-dependence of the photoconductivity. The linear relationship between the calculated bulk-photovoltaic tensor component and the photocurrent established from the proposed phenomenological model is verified through their composition-dependent studies. These studies provide the desired design parameters to engineer the ferroelectric system for better photovoltaic characteristics suitable for device applications.

20.
J Phys Condens Matter ; 32(36): 365401, 2020 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-32357355

RESUMEN

The compositionally induced ferroelectric to relaxor transformation via diffuse phase transition and structural disorder by external stimuli is explored in lead-free Ba1-x (Bi0.5Li0.5) x TiO3 (x = 0, 0.05, 0.1, 0.15, and 0.20) ferroelectric system. X-ray diffraction studies reveal the coexistence of the monoclinic phase along with the orthorhombic and tetragonal phases in BaTiO3, which could be the reason for its superior dielectric properties. The dielectric studies reveal that the x = 0.15 sample shows intrinsic dielectric relaxation due to the quenched-in random field caused by the atomic displacement. The ferroelectric to relaxor phase transformation is analysed by modified Curie-Weiss law. Furthermore, the driving forces for the relaxor behaviour in the system are attributed to the compositionally induced charge disorder, quenched-in random field, and oxygen vacancy related defects in the BBLT system. The detailed structural analysis on the relaxor ferroelectric samples displays direct evidence for the electric field and mechanical stress driven structural inhomogeneity. Notably, mechanically stressed and electrically poled x = 0.15 sample exhibits a remarkable 50% and 37% increase in orthorhombic phase fraction, respectively. Overall, the comprehensive studies on the lead-free modified BaTiO3 samples give further insight into understanding the relaxor system.

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