Department of Physics

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IIT Jodhpur

Chemical reaction with diazonium molecules has revealed to be a powerful method for the surface chemical modification of graphite, carbon nanotubes and recently also of graphene. Graphene electronic structure modification using diazonium molecules is strongly influenced by graphene growth and by the supporting materials. Here, carrying on a detailed study of core levels and valence band photoemission measurements, we are able to reconstruct the interface chemistry of trimethoxybenzenediazonium-based molecules electrochemically grafted on graphene on copper. The band energy alignment at the molecule-graphene interface has been traced revealing the energy position of the HOMO band with respect to the Fermi level. © 2020, The Author(s).

World University root node

Scientific reports

Interface Chemistry of Graphene/Cu Grafted By 3, 4, 5-Tri-Methoxyphenyl

RSnCl3 (R = 2-phenylazophenyl) on reaction with Na2S·9H2O in a 1:1 mixture of acetone and methanol afforded a tetranuclear monoorganotin sulfide cage [(RSnIV)4(μ-S)6]· 2CHCl3·4H2O (R = 2-phenylazophenyl) (1). Complex 1 crystallizes in the monoclinic space group P2/n. The molecular structure of 1 contains five-coordinate tin centers in distorted trigonal bipyramidal geometry. Complex 1 is monoorganotin sulfide derivative having a tetranuclear double-decker cage-like structure. In 1, four tin centers are bridged by a μ2-S unit affording a ubiquitous Sn−S−Sn motif among monoorganotin sulfide compounds. In addition, each tin also has intramolecular coordination to a nitrogen atom of a 2-phenylazophenyl substituent (N → Sn). The DFT calculation suggests that the complex 1 involves mainly ligand based transitions. The complex 1 based device was studied for its electrical behavior and was found to show stable, reproducible memristive behavior with an on−off ratio of 103, which suggests that the complex 1 is a promising material for memory device applications. © 2019 American Chemical Society

ACS Applied Electronic Materials

Molecular Memory Switching Device Based on a Tetranuclear Organotin Sulfide Cage [(RSnIV)4(μ-S)6]·2CHCl3·4H2O (R = 2-(Phenylazo)phenyl): Synthesis, structure, DFT studies, and memristive behavior

Surface-directed spinodal decomposition (SDSD) is the kinetic interplay of phase separation and wetting at a surface. This process is of great scientific and technological importance. In this paper, we report results from a numerical study of SDSD on a chemically patterned substrate. We consider simple surface patterns for our simulations, but most of the results apply for arbitrary patterns. In layers near the surface, we observe a dynamical crossover from a surface-registry regime to a phase-separation regime. We study this crossover using layerwise correlation functions and structure factors and domain length scales. © 2020 American Physical Society.

Fulltext

Physical Review E

Surface-directed spinodal decomposition on chemically patterned substrates

We study a complex mixture with bidispersity in size and polydispersity in energy using computer simulation. The energy polydispersity between the bidisperse particles is introduced by considering random pair-wise interactions. Extensive molecular dynamics simulations are performed to compute potential energy and neighborhood identity ordering (NIO) parameter as a function of temperature for different size-ratios and concentrations of the two species by quenching it from a high-temperature fluid state to a solid state. Our findings demonstrate an enhancement of the neighborhood identity ordering on the addition of particles of different sizes, which also depends on particle concentration. Moreover, a comparatively higher increase in the NIO parameter is achieved by tuning the size-ratio of the particles. We also propose that the NIO parameter is a good marker to differentiate multicomponent systems (below the liquid to solid transition temperature) with different size-ratios and concentrations. © 2020 Informa UK Limited, trading as Taylor & Francis Group.

Phase Transitions

Enhanced attraction between particles in a bidisperse mixture with random pair-wise interactions

The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers. © The Royal Society of Chemistry.

Chemical Science

Erratum: Strongly coloured thiocyanate frameworks with perovskite-analogue structures (Chem. Sci. (2019) 10 (793-801) DOI: 10.1039/C8SC04082F)

The DNA molecule, apart from carrying the genetic information, plays a crucial role in a variety of biological processes and finds applications in drug design, nanotechnology and nanoelectronics. The molecule undergoes significant structural transitions under the influence of forces due to physiological and non-physiological environments. Here, we summarize the insights gained from simulations and single-molecule experiments on the structural transitions and mechanics of DNA under force, as well as its elastic properties, in various environmental conditions, and discuss appealing future directions. © 2020 Elsevier Ltd

Current Opinion in Structural Biology

What do we know about DNA mechanics so far?

Two dimensional (2D) metal halide perovskites are being extensively studied as they can serve as promising materials for various optoelectronic devices such as light emitting diodes (LED), lasers, photodetectors etc. The optical properties of these 2D perovskite can be tuned by varying the stoichiometric compositions of metals (Pb, Sn, Ge, Bi) and halides (Cl, Br, I). Here we report, a single step synthesis process for the fabrication of mixed halide based 2D perovskite of type (C4H9NH3)2PbI4(1-y)Br4y (y=0-1). By changing of iodine with bromine in metal halide (Pb-X) network of these mixed halide 2D perovskites, we have achieved well controlled and uniform tunability of intense room temperature exciton absorption peaks from green to UV region (513nm to 405nm) of spectra. Highly crystalline and layered structure of the mixed halide 2D perovskite thin films (hereafter PTF) are confirmed by using thin film X-ray diffraction (XRD) studies whereas, Energy dispersive X-ray (EDAX) analysis confirms the uniform distribution of iodine and bromine in the thin films, thus supporting that our demonstrated synthesis route is very useful and easy in producing single phase mixed halide perovskites. © 2020 Author(s).

AIP Conference Proceedings

Exciton tunability in mixed halide hybrid layered perovskites

New and facile one-pot three component approach for the synthesis of substituted dihydropyrimidinones derivatives (4a-4h) from reaction of equimolar substituted aldehydes (1a-1h), methyl acetoacetate (2a) and urea (3a) in presence of nature derived catalyst viz. Cocos nucifera L. juice, Solanum lycopersicum L. juice and Citrus limetta juice, commonly known as coconut juice, tomato juice and musambi juice respectively, at room temperature has been carried out. All synthesized compounds were evaluated for in vitro herbicidal activity against Raphanus sativus L. (Radish seeds). The compounds (4a-4h) were also screened for their antifungal activity against Rhizoctonia solani and Colletotrichum gloeosporioides by poisoned food techniques method. Antibacterial activity was also studied against Erwinia cartovora and Xanthomonas citri by inhibition zone method. From activity data, it was found that compounds 4g and 4d were most active against Raphanus sativus L. (root) and Raphanus sativus L. (shoot) respectively. Compounds 4f and 4c was found most active against Rhizoctonia solani and Colletotrichum gloeosporioides fungus respectively at highest concentration. Compound 4g has shown maximum inhibition zone i.e. 1.00–5.50 mm against Erwinia cartovora at 2000 μg/mL concentration. Maximum Xanthomonas citrii growth was inhibited by compounds 4f showing inhibition zone 4.00–12.00 mm at highest concentration. Short reaction time, high yields, mild reaction condition and simple work-up are some merits of present methodology. Copyright: © 2020 Gulati et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

PLoS ONE

One-pot three component synthesis of substituted dihydropyrimidinones using fruit juices as biocatalyst and their biological studies

The problem of defining quantum non-Markovianity has proven elusive, with various in-equivalent criteria put forth to address it. The concept of CP-indivisibility and the hierarchy of stronger divisibility criteria going up to P-indivisibility, capture a fundamental aspect of memory in quantum non-Markovianity. In practice, however, there can be a memory-like influence associated with divisible channels in the form of weakening, if not reversing, the effects of decoherence. Arguably, such a facet of memory relates to CP-indivisibility as quantum discord relates to entanglement. We concretize this weaker notion of non-Markovianity by identifying it with deviation from “temporal self-similarity”, the property of a system dynamics whereby the propagator between two intermediate states is independent of the initial time t. We illustrate this idea through examples, and propose a geometric quantification of temporal self-similarity, and show how our approach complements the divisibility-based criterion of quantum non-Markovianity. © 2020, The Author(s).

Scientific Reports

Temporal self-similarity of quantum dynamical maps as a concept of memorylessness

The electronic and magnetic properties of the magnetoelectric solid GaFeO3 are investigated within the generalized gradient approximation including the Hubbard interaction (U) on the localized d orbitals of iron. It was found that using an onsite U=8 eV describes consistently the experimental results. The origin of ferrimagnetism was attributed to the cationic site disorders. The density of states at the iron sites, in a octahedral geometry, show that the occupied eg states are below the t2g states in contradiction with the crystal-field splitting obtained by a point-charge model. However, for the unoccupied states the ab initio data agree qualitatively with the model, showing the complexity of the electron-electron interaction in GaFeO3. The computed electric polarization of the system as a function of the temperature in the linear regime shows a monotonic decreasing trend. To determine the nature of the magnetoelectric coupling, the computed electric polarization as a function of the rotation of the magnetization axis indicates that the magnetoelectric effect observed experimentally could not have been due to a direct coupling between the electric and magnetic order parameters. Finally, the calculated x-ray absorption and x-ray magnetic circular dichroism spectra for the disordered system are shown to be in good agreement with experiment. © 2020 American Physical Society.