Department of Physics

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IIT Jodhpur

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Advanced Materials

Flexible Batteries: Hierarchical Assemblies of Carbon Nanotubes for Ultraflexible Li-Ion Batteries (Adv. Mater. 31/2016)

Phytoextraction of heavy metals enhanced by using chelating agents was proposed as an effective approach to remove heavy metals from contaminated soil by use of hyper accumulator plants. The effects of application of chelating agents viz., Cyclohexane diamino tetraacetic acid (CDTA), Citric acid (CA), Diethylene triamine pentaacetic acid (DTPA), Nitrilo triacetic acid (NTA) @ 10 mmol kg-1 soil and FYM (at 3%) on the growth of Zea mays and its Pb uptake were investigated in sewage sludge un-amended and amended (at 3%) soil using the pot-culture experiments. Application of chelating agents decreased the dry matter yield of roots of Zea mays while, higher values of dry matter yield (8.86 g pot-1) was observed in case of FYM sewage sludge amended soil at 80 days after sowing. FYM addition was found beneficial as compared to control (Pb180). Dry matter yield of shoots of Zea mays increased over control due to application of CDTA and FYM. The highest dry matter yield of shoot (63.29 g pot-1) was observed in CDTA with sewage sludge amended soil at 80 days after sowing. Whereas reverse trend was observed in NTA, CA and DTPA treated soils. Addition of sewage sludge at 3% on dry weight basis was found beneficial in improving the plant growth. Chelating agents enhanced the Pb uptake by both roots and shoots. The higher values of Pb uptake by roots (2.89 mg pot-1) and shoots (13.21 mg pot-1) was observed in CDTA treated soil after 80 days of sowing in sewage sludge amended soil as compared to un-amended soil. Application of CDTA was found more effective in enhancing the Pb uptake by Zea mays roots and shoots than any other chelating agents at both the growth stages. Concentration of Pb in root was higher than that of shoots. Maximum Pb concentration was observed in NTA treated soil in both roots and shoots compare with other chelating agents. The chelating agents were found useful in enhancing phytoextractability of Pb by Zea mays. Hence, marginally Pb contaminated soil may be remediated by adding chelating agents. © 2017, Range Management Society of India. All rights reserved.

Range Management and Agroforestry

Effect of chelating agent on phytoextraction of lead from contaminated soil by Zea mays

A substantial ion flow in a normally wet protein masks any other forms of signal transmission. We use hysteresis and linear conduction (both are artifacts) as a marker to precisely wet a protein, which restricts the ionic conduction (hysteresis disappears), and at the same time, it is not denatured (quantized conductance and Raman spectra are intact). Pure electric visualization of proteins at work by eliminating the screening of ions, electrons, would change the way we study biology. Here we discuss the technical challenges resolved for imaging a protein or live cell using nonlinear dielectric response (spatial distribution of conductance, capacitance and phase, GCP trio). We electromagnetically triggered electrical, mechanical, thermal and ionic resonant vibrations in a protein. During resonant oscillations, we imaged the protein using resonant scanning tunneling microscopy of biomaterials (Brestum) and during ionic firing we imaged live what happens inside an axon core of a neuron by using our atomic scale scanning dielectric microscopy (Asadim). Both Asadim and Brestum are housed in a homebuilt scanning tunneling microscope (bio-STM) and a special micro-grid developed by us (patent JP-5187804) for fractal supercomputing. We found the trick to turn a membrane transparent and see inside without making any physical contact. We image live that a protein molecule adopts a unique configuration for each resonance frequency, - thus far unknown to biology. "Membrane alone fires" is found to be wrong after a century, micro-neuro-filaments communicate prior to firing to decide its necessity and then regulate it suitably. We introduce a series of technologies e.g., fractal grid, point contact, micro THz antenna, to discover that from atomic structure to a living cell, the biomaterials vibrate collectively. © 2016 World Scientific Publishing Europe Ltd.

Journal of Integrative Neuroscience

Inventing atomic resolution scanning dielectric microscopy to see a single protein complex operation live at resonance in a neuron without touching or adulterating the cell

Single-photon emission from the nitrogen-vacancy defect in diamond constitutes one of its many proposed applications. Owing to its doubly degenerate 3 E electronic excited state, photons from this defect can be emitted by two optical transitions with perpendicular polarization. Previous measurements have indicated that orbital-selective photoexcitation does not, however, yield photoluminescence with well-defined polarizations, thus hinting at orbital-averaging dynamics even at cryogenic temperatures. Here we employ femtosecond polarization anisotropy spectroscopy to investigate the ultrafast electronic dynamics of the 3 E state. We observe subpicosecond electronic dephasing dynamics even at cryogenic temperatures, up to five orders of magnitude faster than dephasing rates suggested by previous frequency- and time-domain measurements. Ab initio molecular dynamics simulations assign the ultrafast depolarization dynamics to nonadiabatic transitions and phonon-induced electronic dephasing between the two components of the 3 E state. Our results provide an explanation for the ultrafast orbital averaging that exists even at cryogenic temperatures.

Fulltext

Nature Communications

Jahn-Teller-induced femtosecond electronic depolarization dynamics of the nitrogen-vacancy defect in diamond

Transfer of electrons through semiconductor heterojunctions is the key process in modern electronics. We have visualized dynamics of electrons in InSe/GaAs through time and spectrallyresolved photoemission electron microscopy, which provides insight to this fundamental operating phenomenon.

Optics InfoBase Conference Papers

Visualization of electron transport in 2D semiconductor heterojunctions

Here, we expose planar and plasmonic Ag surfaces to a low-power O2/Ar plasma to form an ultrathin surface oxide layer. We study the chemical state and morphology of the plasma-treated Ag surfaces using X-ray photoelectron spectroscopy, scanning electron microscopy, and dark-field microscopy. We observe the formation of an ultrathin layer (< 10 nm) composed of both AgO x and Ag2CO3 for a plasma exposure time of 1 s by investigating shifts in the Ag3d, O1s, and C1s core level binding energies. For an exposure time of 1 s, the surface structure of the planar and plasmonic Ag surfaces remains unchanged. For exposure times of 5 - 30 s, the planar Ag surfaces become porous and exhibit increased surface roughness. We demonstrate that the plasma-treated planar and plasmonic Ag surfaces lead to improvements in the excited-state population of a polymer:fullerene coating through ultrafast pump-probe reflectometry. Copyright © Materials Research Society 2016.

MRS Advances

Oxidation of Planar and Plasmonic Ag Surfaces by Exposure to O2/Ar Plasma for Organic Optoelectronic Applications

Here, an 'in situ' co-precipitation reaction method has been reported for the preparation of CoFe2O4-RGO (CF-RGO) nanocomposites. To the best of our knowledge, this is the first time a simple synthetic method is reported for the preparation of CoFe2O4-RGO nanocomposites where a hydrothermal technique was not used. The novelty of this technique lies in its simplicity, cost-effectiveness, and the capability of large scale production of CoFe2O4-RGO nanocomposites. The synthesized CoFe2O4-RGO nanocomposites possess excellent microwave absorbing properties as well as high photocatalytic activity towards the degradation of various dyes under visible light irradiation. 85CF-15RGO (85 wt% CF and 15 wt% RGO) showed excellent microwave absorption properties with a Reflection Loss (RL) of -31.31 dB (∼99.94% absorption) at 9.05 GHz with an 8.2-10.92 GHz effective band width range. To the best of our knowledge 85CF-15RGO nanocomposite exhibited comparable and even superior microwave absorption properties in the X-band region than most of the ferrite based composites. 75CF-25RGO (75 wt% CF and 25 wt% RGO) acted as a very good magnetically separable photocatalyst for the degradation of various synthetic dyes (such as methyl orange, methylene blue, rhodamine B and a mixture of these dyes) under visible light irradiation emitted from a 100 W reading lamp. Moreover, CoFe2O4-RGO catalyst also showed easy magnetic separation with high reusability. The photocatalytic activity of 75CF-25RGO was found to be comparable and in some cases better than the various reported RGO-ferrite composites. The simple method of preparation and multifunctional character make CF-RGO nanocomposites attractive materials for application in the area of photocatalysis as well as microwave absorption. © The Royal Society of Chemistry 2016.

RSC Advances

A simple': In situ ' co-precipitation method for the preparation of multifunctional CoFe2O4-reduced graphene oxide nanocomposites: Excellent microwave absorber and highly efficient magnetically separable recyclable photocatalyst for dye degradation

The functionalization of graphene remains an important challenge for numerous applications expected by this fascinating material. To keep advantageous properties of graphene after modification or functionalization of its structure, local approaches are a promising road. A novel technique is reported here that allows precise site-selective fluorination of graphene. The basic idea of this approach consists in the local radicalization of graphene by focused ion beam (FIB) irradiation and simultaneous introduction of XeF2 gas. A systematic series of experiments were carried out to outline the relation between inserted defect creation and the fluorination process. Based on a subsequent X-ray photoelectron spectroscopy (XPS) analysis, a 6-fold increase of the fluorine concentration on graphene under simultaneous irradiation was observed when compared to fluorination under normal conditions. The fluorine atoms are predominately localized at the defects as indicated from scanning tunneling microscopy (STM). The experimental findings are confirmed by density functional theory which predicts a strong increase of the binding energy of fluorine atoms when bound to the defect sites. The developed technique allows for local fluorination of graphene without using resists and has potential to be a general enabler of site-selective functionalization of graphene using a wide range of gases. © 2016, Nature Publishing Group. All rights reserved.

Scientific reports

Site-selective local fluorination of graphene induced by focused ion beam irradiation

Mulhouse

Epitaxial Graphene Functionalization: Covalent grafting of molecules, Terbium intercalation and Defect engineering

We report the effect of Ni doping on superconductivity of PdTe. The superconducting parameters like critical temperature (T c), upper critical field (H c2) and normalized specific-heat jump (ΔC/γT c) are reported for Ni doped Pd1-xNi x Te. Samples of series Pd1-xNixTe with nominal compositions x = 0, 0.01, 0.05, 0.07, 0.1, 0.15, 0.2, 0.3 and 1.0 are synthesized via the vacuum shield solid state reaction route. All the studied samples of Pd1-xNi x Te series are crystallized in a hexagonal crystal structure as refined by the Rietveld method to space group P63/mmc. Both the electrical resistivity and magnetic measurements revealed that T c decreases with increasing Ni concentration in Pd1-xNi x Te. Magnetotransport measurements suggest that flux is better pinned for 20% Ni doped PdTe as compared to other compositions of Pd1-xNi x Te. The effect and contribution of Ni 3d electron to electronic structure and density of states near the Fermi level in Pd1-xNi x Te are also studied using first-principle calculations within the spin polarized local density approximation. The overlap of bands at the Fermi level for NiTe is larger as compared to PdTe. Also the density of states just below the Fermi level (in conduction band) drops much lower for PdTe than as for NiTe. In summary, Ni doping in Pd1-xNi x Te superconductor suppresses superconductivity moderately and also Ni is of non-magnetic character in these compounds. © 2016 IOP Publishing Ltd.