Computational evaluation of transport parameters and logic circuit designing of L-Lysine amino acid stringed to Au, Ag, Cu, Pt, and Pd electrodes.

The integrants of proteins, i.e., amino acids, have grossed exceptional recognition for their applications towards designing imminent switching devices. Among 20 amino acids, L-Lysine (i.e., positively charged) has the highest number of CH2 chains, and such chains affect the rectification ratio in several biomolecules. Towards molecular rectification, we investigate the transport parameters of L-Lysine in conjunction with five different coinage metal electrodes, i.e., Au, Ag, Cu, Pt and Pd to form five distinct devices. We deputize the NEGF-DFT formulism for computing conductance, frontier molecular orbitals, current-voltage, and molecular projected self-Hamiltonian calculations using a self-consistent function. We focus on the most widely used electron exchange correlation combination, i.e., the PBE version of GGA with DZDP basis set. The molecular devices under inquisition exhibit phenomenal rectification ratios (RR) in conjunction with negative differential resistance (NDR) regimes. The nominated molecular device offers a substantial rectification ratio of 45.6 with platinum electrodes and a prominent peak to valley current ratio of 1.78 with copper electrodes. We deduce from these findings that L-Lysine based molecular devices would implicit in future bio-nanoelectronic devices. The OR and AND logic gates are also proposed hinged on highest rectification ratio of L-Lysine-based devices.

Is #SDG13 Trending Online? Insights from Climate Change Discussions on Twitter.

Anthropogenic activities over the past few decades have led to increased vulnerability of environmental and ecological stability on this planet. Accelerated climate change is one such subset of the environmental problems that threatens the very existence of humankind in twenty first century. Governments, United Nations (UN) and other humanitarian agencies across the globe have developed and devised strategies for climate action that requires grater public awareness and actions. Social media has played a vital role in information dissemination and raising public awareness of climate change in the digital era. To this aid, an upsurge has been documented in recent times regarding discussions over climate change with #SDG13 (Sustainable Development Goals) at its epicenter. Following the principles of Actor Network Theory (ANT) we analyzed a large volume of Twitter data to understand general citizens' perception and attitude towards climate change. Our findings unveil people's opinion on causes and concerns related to barriers of adopting a more sustainable consumption and lifestyle practice. There is also a growing apathy towards sluggish government actions that makes little difference. People were also found to exchange innovative concepts and measures towards mitigating the effects of climate change.

Molecular electronics behaviour of L-aspartic acid using symmetrical metal electrodes.

Protein-based electronics is one of the growing areas of bio-nanoelectronics, where novel electronic devices possessing distinctive properties are being fabricated using specific proteins. Furthermore, if the bio-molecule is analysed amidst different electrodes, intriguing properties are elucidated. This research article investigates the electron transport properties of L-aspartic acid (i.e. L-amino acid) bound to symmetrical electrodes of gold, silver, copper, platinum and palladium employing NEGF-DFT approach using self-consistent function. The theoretical work function of different electrodes is calculated using local density approximation and generalized gradient approximation approach. The calculated work function correlates well with the hole tunneling barrier and conductance of the molecular device, which further authenticate the coupling strength between molecule and electrode. Molecule under consideration also exhibits negative differential resistance region and rectification ratio with all the different electrodes, due to its asymmetrical structure. The molecular device using platinum electrodes exhibits the highest peak to valley ratio of 1.38 and rectification ratio of 3.20, at finite bias. The switching characteristics of different molecular device are justified with detailed transmission spectra and MPSH. These results indicate that L-aspartic acid and similar biomolecule can be vital to the growth of Proteotronics.

Adenine based molecular junction as biosensor for detection of toxic phosgene gas.

The possibility of adsorption of toxic phosgene gas (COCl2) molecule on one of the nucleobase of DNA-adenine-has been analyzed using the first principle calculations based on density function theory. In accordance with the geometry of the nucleobase, two possible positions have been considered for effective adsorption of gas molecule. The calculations performed on adsorption energies suggest that the gas molecule is able to physisorb at both the considered positions with negligibly small values of charge transfer. The in-depth analysis of electron charge densities depicts that there is no orbital overlapping between the gas molecule and adenine. We observe a significant variation of transport properties of adenine-based molecular junction on adsorption of phosgene molecule while calculation the transport parameters at both the equilibrium as well as non-equilibrium. Also, the variation of HOMO-LUMO gap of adenine molecule on adsorption of phosgene leads to alteration of current and voltage, thus implying that adenine-based sensor can be effectively utilized to sense the presence of phosgene gas in a given environment. Small adsorption energies and recovery time suggest that the rate of desorption of phosgene is very high; thus, the proposed adenine sensor can be effectively used as a highly stable and selective reusable sensor.

First principle approach to elucidate transport properties through L-glutamic acid-based molecular devices using symmetrical electrodes.

Protein-based electronics is one of the emerging technology in which inventive electronic devices are being adduced and developed based on the selective actions of specific proteins. The explicit actions can be predicted if the building blocks of proteins (i.e., amino acids) are studied decorously. We emphasize our work on electronic transport properties of L-glutamic acid (i.e., L-amino acid) stringed to gold, silver, and copper electrodes, respectively, to form three distinct devices. For our calculations, we employ NEGF-DFT approach using self-consistent function. Electronic coupling and tunneling barriers between the molecule and the electrodes have been emphasized with an inception of delocalization of molecular orbitals within the device. We observe strong correlation between tunneling barrier and Mulliken charge transfer between molecule and electrodes. The asymmetrical carbon chain (-CH2) within the molecule exhibits negative differential resistance (NDR) and rectification ratio. The device using molecule with copper electrodes exhibits the highest peak to valley current ratio of 1.84. The rectification ratio of the device with gold, silver, and copper electrodes is 2.35, 2.25, and 15.62, respectively, at finite bias. These results yield fresh insight on the potential of L-glutamic acid like bio-molecule in the emerging field of proteotronics.

A pursuit to design highly sensitive fullerene-based sensors: adsorption and dissociation phenomenon of toxic sulfur gases on B40 fullerene.

The adsorption phenomenon of toxic sulfur gases namely H2S and SO2 on B40 fullerene is scrutinized utilizing density functional theory-non-equilibrium Green's function (DFT-NEGF) regime. Adsorption of gas molecules is considered at both the hexagonal and heptagonal rings of the fullerene and adsorption energies, charge transfer, electron charge densities, density of states, transmission spectra, molecular energy spectra; Eigen states, HOMO-LUMO gap, current voltage curve, and differential conductance are premeditated. It is inferred that H2S molecule is physisorbed on the heptagonal ring of the fullerene while it is dissociative-chemisorbed on the hexagonal ring. SO2 dissociates into SO and O species on adsorption on both the hexagonal and heptagonal rings. From the transmission spectra and DOS analysis, LUMO dominant transmission is noticed in all the devices except the one formed with heptagonal ring adsorption of H2S which favors HOMO-dominated transmission. From the I-V curve and differential conductance investigation, different conductance values are noticed for all the junctions, thus proving that B40 is an efficient material to be engaged in sensing toxic sulfur gases.

Comparative evaluation of NANO transport properties for DNA nucleobase based molecular junction devices.

The feasibility of electron transport conduction through a guanine base of DNA was investigated and then compared with another component of DNA, i.e., cytosine. A mathematical approach based on the jellium model using non-equilibrium Green's function combined with semi empirical extended Huckel theory was applied using the Atomistik Tool Kit. This was further used to measure significant transport parameters such as current, conductance, transmission spectra and the HOMO-LUMO gap of the suggested molecular system. An important revelation from our research work is that the cytosine-based molecular device exhibits metallic behavior with current ranging up to 70 µA, and hence establishes itself as a good conductor. On the other hand, the guanine-based device is comparatively less conductive, exhibiting current in the order of 3 µA. Another interesting observation about the guanine-based device is the visibility of a prominent negative differential resistance effect during the positive bias and a tunneling effect during negative bias. The uniform charge transfer through the cytosine device confirms its application as a molecular wire. The observations on the guanine-based device give better insights into its application as a memory device for nano-scale devices.

Ab initio scrutiny of endohedral C20 fullerenes implanted in between gold electrodes.

Using the smallest non-classical fullerene, we investigate the impact of endohedral fullerene molecules on the quantum transport through molecular junctions, and then compared this with the pure C20-based molecular junction. By employing the density functional theory combined with the non-equilibrium Green's function, we contemplated different electronic parameters, namely, density of states, transmission coefficient, energy levels, molecular orbitals, conduction gaps, electron density and their charge transfer. A knowledge of these physical parameters is necessary in order to calculate current and conductance computed using Landauer-Büttiker formalism. The molecule-electrode coupling influenced by endohedral molecules affects junction devices in a unique manner. We observe that the highest quantum transport is possible in an Au-N@C20-Au and Au-O@C20-Au junction device, and is even higher than that of the intrinsic C20 fullerene junction. Another notable observation is that the F@C20 molecule exhibits the least conducting nature, being even lower than that of the endohedral molecule formed by inserting the noble element, neon. Graphical abstract Electrical characteristics of Endohedral fullerene junctions.

The DFT-NEGF scrutiny of doped fullerene junctions.

Using the smallest non-classical fullerene, we investigate the impact of doping at the molecule-electrode interface on the electron transport of molecular junctions. This is accomplished by employing the density functional theory combined with the non-equilibrium Green's function. We contemplate different electronic parameters, namely, density of states, transmission coefficient, energy levels, molecular orbitals, conduction gaps, electron density, and their charge transfer. The relevance of these physical parameters is obtained to calculate their electrical parameters, current, and conductance, computed from Landauer-Büttiker formalism. The molecule-electrode coupling is influenced by the nature of doping atoms and affects the junction devices in a unique course. A particular aftermath is noticed in Au-C18O2-Au device with highest ballistic transport despite the electro-negative nature of oxygen atoms. Moreover, an interesting feature is observed in Au-C18Be2-Au device with double-barrier transmission resonance and corresponding oscillating conductance. Graphical abstract The doped C20 fullerene in molecular and device mode.

Electrical characterization of C28 fullerene junctions formed with group 1B metal electrodes.

We present an atomistic theory of electronic transport through single molecular junctions based on smallest stable fullerene molecule, C28. The electronic properties of single molecular junctions critically depend on the nature of electrode material. The two probe device is modeled by constraining C28 between two semi-infinite metal electrodes, from group 1B of periodic table, copper, silver and gold. We have highlighted the correlated phenomena of resonant conduction and current driven dynamics in molecular junctions using extendend Huckel theory in combination with non equilibrium Green's function framework. We conclude strong dependence of conductance on transmissions, which leads to oscillating conductance spectrum. An interesting interplay between conducting channels and different degrees of spatial localization and delocalization of molecular orbitals is evinced. The physical origin of current and conductance of so-formed C28 molecular junctions is discussed in detail by analysing their density of states, transmission spectra, molecular orbital analysis, rectification ratio and molecular projected self consistent Hamiltonian eigen states at different operating voltages ranging from -2V to +2V.

First principle electron transport modeling of Be-doped organic molecular junctions.

The transport properties of beryllium doped anthracene molecular junction are investigated using density functional non-equillibrium Green's function method. The equilibrium conductance of anthracene Metal-molecule-Metal (MmM) junction increases by approximately 77% by adding beryllium impurity to it. The electronic transport characteristics under both zero bias as well as finite bias are explored of such molecular junction. We observe novel attributes such as molecular rectification and NDR behavior for the molecular junction under consideration. It is found that the doping effect of Be- atom significantly changes the transport properties of aromatic molecular junction. Our findings shed light on the electron transport metrics that affect the conductance of MmM junctions within appreciable transmission limits. We firmly believe that the results deduced in this paper can be generalized for other aromatic molecular junctions as well.

Proliferating miller indices of C20 fullerene device under DFT-NEGF regime.

We present ab-initio scrutiny of electron transport through C20 fullerene cleaved with gold electrodes having unique set of miller orientations. The three families of miller indices {100}, {110} and {111} are considered with four exclusive device models for elucidating electronic transport under applied potential of - 2 to +2V. Thereafter, the quantum calculations employing DFT-NEGF are performed for envisaging density of states, transmission function, energy levels, molecular orbitals, charge transfer. These electronic transfer parameters lead to the study of its two electrical parameters: current and conductance. We conclude that in molecular-devices of constituted miller family {110}, HOMO-LUMO gap are inversely proportional to extent of charge carriers. While for miller devices {100} and {111}, the situation is fully contrasting with HOMO-LUMO gap being directly proportional to its charge carriers. Another important conclusion is that the gold electrodes having miller family {100} and {111} are providing equal opportunity to fullerene molecule to imply its behavior while electrodes of miller family {110} are over shadowing the performance of fullerene molecule.