Nanohybrids of BCN-Fe1-x S for Sodium and Lithium Hybrid Ion Capacitors.

Hybrid ion capacitors (HIC) are receiving a lot of attention due to their potential to achieve high energy and power densities, but they remain insufficient. It is imperative to explore outstanding and environmentally benign electrode materials to achieve high-performing HIC systems. Here, a unique boron carbon nitride (BCN)-based HIC system that comprises a microporous BCN structure and Fe1-x S nanoparticle incorporated BCN nanosheets (BNF) as cathode and anode, respectively is reported. The BNF is prepared through a facile one-pot calcination process using dithiooxamide (DTO), boric acid, and iron source. In situ, crystal growth of Fe1-x S facilitates the formation of BCN structure through the creation of holes/defects in the polymeric structure. The first principle density functional (DFT) theory simulations demonstrate the structural and electronic properties of the hybrid of BCN and Fe1-x S as compelling anode materials for HIC applications. The DFT calculations reveal that both BCN and BNF structures have excellent metallic characters with Li+ storage capacities of 128.4 and 1021.38 mAh g-1  respectively. These findings are confirmed experimentally where the BCN-based HIC system delivers exceptional energy and power densities of 267.5 Wh kg-1 /749.5 W kg-1 toward Li+ storage, which outweighs previous HIC performances and demonstrates favorable performance for Li+ and Na+ storages.

Evaluation of Therapeutic Efficiency of Stylicin against Vibrio parahaemolyticus Infection in Shrimp Penaeus vannamei through Comparative Proteomic Approach.

The shrimp immune system defends and protects against infection by its naturally expressing antimicrobial peptides. Stylicin is a proline-rich anionic antimicrobial peptide (AMP) that exhibits potent antimicrobial activity. In this study, stylicin gene was isolated from Penaeus vannamei, cloned into vector pET-28a ( +), and overexpressed in Escherichia coli SHuffle T7 cells. The protein was purified and tested for its antibiofilm activity against shrimp pathogen Vibrio parahaemolyticus. It was resulted that the recombinant stylicin significantly reduced the biofilm formation of V. parahaemolyticus at a minimum inhibitory concentration (MIC) of 200 µg. Cell aggregation was observed by using scanning electron microscopy and confocal laser scanning microscopy, and it was resulted that stylicin administration significantly affects the cell structure and biofilm density of V. parahaemolyticus. In addition, real-time PCR confirmed the downregulation (p < 0.05) of genes responsible for growth and colonization. The efficacy of stylicin was tested by injecting it into shrimp challenged with V. parahaemolyticus and 7 days after infection, stylicin-treated animals recovered and survived better in both treatments (T2-100 µg stylicin, - 68.8%; T1-50 µg stylicin, 60%) than in control (7%) (p < 0.01). Comparative proteomic and mass spectrometry analysis of shrimp hemolymph resulted that the expressed proteins were involved in cell cycle, signal transduction, immune pathways, and stress-related proteins representing infection and recovery, and were significantly different in the stylicin-treated groups. The result of this study suggests that the stylicin can naturally boost immunity and can be used as a choice for treating V. parahaemolyticus infections in shrimp.

Smart apparel using nano graphitic carbon nitride/PVA in a cotton cloth for military application.

An eco-friendly, low-cost smart attire was made of metal-free graphitic carbon nitride (GCN) as a semiconductor material in a biodegradable synthetic polymer (polyvinyl alcohol) and cotton material. Various concentrations such as 0.04, 0.08, 0.12, 0.16, and 0.2 weight percentage of GCN is entrenched in PVA. UV absorption spectra displayed two peaks, one matching PVA (317 nm) and the other excitonic peak of GCN (390 nm).0.2% GCN in PVA showed a low bandgap (2.84 eV) harnessing maximum solar light. Due to the charge transfer mechanism, enhanced blue emission at 450 nm was observed for the higher concentration of graphitic carbon nitride. Due to more defect centers of higher weight percentage of GCN, higher electrical conductivity (7.6462 × 10-3 S/cm) and optical conductivity (0.113 S) were noticed. Due to the higher conductivity of 5GCN, it was embedded with cotton fabric. The fabricated smart apparel can be used to manufacture flexible, lightweight, eco-friendly optoelectronic devices. Further, according to literature, GCN possesses high antibacterial activity, hence it can serve as clothing for the military and medical community.

Tailoring the Pore Size, Basicity, and Binding Energy of Mesoporous C3 N5 for CO2 Capture and Conversion.

We investigated the CO2 adsorption and electrochemical conversion behavior of triazole-based C3 N5 nanorods as a single matrix for consecutive CO2 capture and conversion. The pore size, basicity, and binding energy were tailored to identify critical factors for consecutive CO2 capture and conversion over carbon nitrides. Temperature-programmed desorption (TPD) analysis of CO2 demonstrates that triazole-based C3 N5 shows higher basicity and stronger CO2 binding energy than g-C3 N4 . Triazole-based C3 N5 nanorods with 6.1 nm mesopore channels exhibit better CO2 adsorption than nanorods with 3.5 and 5.4 nm mesopore channels. C3 N5 nanorods with wider mesopore channels are effective in increasing the current density as an electrocatalyst during the CO2 reduction reaction. Triazole-based C3 N5 nanorods with tailored pore sizes exhibit CO2 adsorption abilities of 5.6-9.1 mmol/g at 0 °C and 30 bar. Their Faraday efficiencies for reducing CO2 to CO are 14-38% at a potential of -0.8 V vs. RHE.

Capacity enhancement of polylithiated functionalized boron nitride nanotubes: an efficient hydrogen storage medium.

By using first principles density functional theory simulations, we report detailed geometries, electronic structures and hydrogen (H2) storage properties of boron nitride nanotubes (BNNTs) doped with selective polylithiated molecules (CLi2). We find that unsaturated bonding of Li-1s states with BNNT significantly enhances the system stability and hinders the Li-Li clustering effect, which can be detrimental for reversible H2 storage. The H2 adsorption mechanism is explained on the basis of polarization caused by the cationic Li+ of CLi2 molecules bonded with BNNT. The incident H2 molecules are adsorbed with BNNT-nCLi2 through electrostatic and van der Waals interactions. We find that with a maximum of 5.0% of CLi2 coverage on BNNT, an H2 gravimetric density of up to 4.41 wt% can be achieved with adsorption energies in the range of -0.33 eV per H2, which is suitable for ambient condition H2 storage applications.

Elemental Substitution of Two-Dimensional Transition Metal Dichalcogenides (MoSe2 and MoTe2): Implications for Enhanced Gas Sensing.

The quest for a suitable material with the potential of capturing toxic nitrogen-containing gases (NH3, NO, and NO2) has motivated us to explore the structural, electronic, and gas-sensing properties of transition metal dichalcogenides (TMDs); MoSe2 and MoTe2. Spin-polarized density functional theory (DFT) calculations demonstrate weak binding of nitrogen-containing gases (NCGs) with the pristine TMDs, which limits the use of the latter as efficient sensing materials. However, suitable elemental substitutions improve the binding mechanism enormously. Our dispersion-corrected DFT calculations revealed that Se (Te) substitution with Ge (Sb) in MoSe2 (MoTe2) not only enhances the binding energies but also causes a significant variation in the electronic properties and work functions. A charge-transfer mechanism based on Bader analysis indicates that transfer of charges from MoSe2-Ge (MoTe2-Sb) to the NCGs is responsible for the improvement in the binding characteristics. Based on our findings, it is evident that 2.08% of elemental substitutional makes both MoSe2 and MoTe2 promising materials for NH3, NO, and NO2 gas sensing.

Efficient Adsorption Characteristics of Pristine and Silver-Doped Graphene Oxide Towards Contaminants: A Potential Membrane Material for Water Purification?

In this work, we have investigated the potential of pristine and silver (Ag)-functionalized graphene oxide monolayers GO (GO-Ag) as efficient membranes for water filtration. Our first principles calculations based on density functional theory (DFT) reveal the hydrophilic nature of GO surfaces. The phonon frequency calculations within density functional perturbation theory (DFPT) confirmed the stability of GO sheets in aqueous media. Van der Waals-corrected binding energies of GO sheet towards heavy metals suggest that even pristine GO sheets are completely impermeable to various heavy metals like arsenic (As) and lead (Pb). However, compared to GO, the GO-Ag sheets have a much higher affinity towards the three amino acids histidine, phenyl-alanine and tyrosine, which are the main component of a bacteria cell wall. The GO-Ag sheet is found to be extremely efficient for bacteria inactivation.

Assessing the electrochemical properties of polypyridine and polythiophene for prospective applications in sustainable organic batteries.

Conducting polymers are being considered promising candidates for sustainable organic batteries mainly due to their fast electron transport properties and high recyclability. In this work, the key properties of polythiophene and polypyridine have been assessed through a combined theoretical and experimental study focusing on such applications. A theoretical protocol has been developed to calculate redox potentials in solution within the framework of the density functional theory and using continuous solvation models. Here, the evolution of the electrochemical properties of solvated oligomers as a function of the length of the chain is analyzed and then the polymer properties are estimated via linear regressions using ordinary least square. The predicted values were verified against our electrochemical experiments. This protocol can now be employed to screen a large database of compounds in order to identify organic electrodes with superior properties.

A new, layered monoclinic phase of Co3O4 at high pressure.

We present the crystal structures and electronic properties of a Co3O4 spinel under high pressure. Co3O4 undergoes a first-order transition from a cubic (CB) Fd3̄m to a lower-symmetry monoclinic (MC) P21/c phase at 35 GPa, occurring after the local high-spin to low-spin phase transition. The high-pressure phase exhibits the octahedral coordination of Co(II) and Co(III), whereas the CB phase contains the fourfold coordination of Co(II) and the sixfold coordination of Co(III). The CB-to-MC transition is attributed to the charge-transfer between the di- and trivalent cations via the enhanced 3d-3d interactions.

Pressure control of magnetic clusters in strongly inhomogeneous ferromagnetic chalcopyrites.

Room-temperature ferromagnetism in Mn-doped chalcopyrites is a desire aspect when applying those materials to spin electronics. However, dominance of high Curie-temperatures due to cluster formation or inhomogeneities limited their consideration. Here we report how an external perturbation such as applied hydrostatic pressure in CdGeP2:Mn induces a two serial magnetic transitions from ferromagnet to non-magnet state at room temperature. This effect is related to the unconventional properties of created MnP magnetic clusters within the host material. Such behavior is also discussed in connection with ab initio density functional calculations, where the structural properties of MnP indicate magnetic transitions as function of pressure as observed experimentally. Our results point out new ways to obtain controlled response of embedded magnetic clusters.

Sensing propensity of a defected graphane sheet towards CO, H2O and NO2.

We have used density functional theory to investigate the sensing property of a hydrogenated graphene sheet (graphane) towards CO, H2O and NO2 gas molecules. Though the pristine graphane sheet is found not to have sufficient affinity towards the mentioned gas molecules, the defected sheet (removing few surface H atoms) has a strong affinity towards the gas molecules. While CO and H2O are found to be weakly physisorbed, the NO2 molecules are found to be strongly chemi-sorbed to the defected graphane sheet. With NO2, the N(p) and O(p) states are found to have strong hybridization with the most active C(p) states which lie at the defected site of the graphane sheet. While increasing the coverage effect of the mentioned gas molecules toward the defected sheet, the adsorption energies do not change significantly. At the same time, the work function of the defected graphane sheet shows an increasing trend while adsorbed with CO, H2O and NO2 gas molecules, opening up the possibilities for a future gas sensor.

Hole induced Jahn Teller distortion ensuing ferromagnetism in Mn-MgO: bulk, surface and one dimensional structures.

Using density functional theory, we investigate the magnetic properties of Mn doped MgO in its bulk (3D), surface (2D) and one dimensional (1D) structures. At a low dilute limit (1.5 %), the Mn impurity behaves indifferent to its position in 3D but energetically prefers to be on one of the surfaces of 2D and 1D structures. At a higher dilute limit (3.1 %), the Mn impurities stabilizing at MN(d)((3+)) ionic states prefer to be in a close configuration (4.2 Å compared to 5.95 Å) and the antiferromagnetic ordering (AFM) between them is preferred over the ferromagnetic ordering. The n-type extrinsic defects (O vacancy), when introduced to Mn doped MgO structures, also result in similar AFM exchanges as between the Mn impurities. However, the p-type defects (Mg vacancy) in the Mn doped MgO structures result in a reduced magnetic moment for the Mn atoms and bring a significant Jahn Teller (JT)-type of distortion to the eg and t2g degenerate states of MN(d)((3+)) ions. The strong hybridization between distorted Mnd states and O2p states results in a FM exchange coupling between the Mn ions, in all the three mentioned Mn doped MgO structures. As we move from 3D to 2D, to 1D structures, the influence of JT distortion decreases, reflecting a decreasing trend for the strength of the FM exchange coupling between the Mn atoms.

Enriching physisorption of H2S and NH3 gases on a graphane sheet by doping with Li adatoms.

We have used density functional theory to investigate the adsorption efficiency of a hydrogenated graphene (graphane) sheet for H2S and NH3 gases. We find that neither the pristine graphane sheet nor the sheet defected by removing a few surface H atoms have sufficient affinity for either H2S or NH3 gas molecules. However, a graphane sheet doped with Li adatoms shows a strong sensing affinity for both the mentioned gas molecules. We have calculated the absorption energies with one [referred to as half coverage] molecule and two molecules [referred to as full coverage] for both gases with the Li-doped graphane sheet. We find that for both the gases, the calculated absorption energies are adequate enough to decide that the Li-doped graphane sheet is suitable for sensing H2S and NH3 gases. The Li-doped sheet shows a higher affinity for the NH3 gas compared to the H2S gas molecules due to a stronger Li(s)-N(p) hybridization compared to that of Li(s)-S(p). However, while going from the half coverage effect to the full coverage effect, the calculated binding energies show a decreasing trend for both the gases. The calculated work function of the Li-doped graphane sheet decreases while bringing the gas molecules within its vicinity, which explains the affinity of the sheet towards both the gas molecules.

Tweaking the magnetism of MoS2 nanoribbon with hydrogen and carbon passivation.

Using density functional theory (DFT), we report the modulated electronic and magnetic properties of MoS2 nanoribbon by passivating the ribbon edges with H and C separately. For the modeled symmetric MoS2 nanoribbon with a zig-zag type edge, one side is terminated at Mo and the other side is terminated at S. For the zig-zag type, we have studied two ribbons of width ~3 Å and 6 Å respectively. Both of these pristine zig-zag type nanoribbons are found to be metallic and also ferromagnetic. However, the increase in the ribbon width results in a decrease in the net magnetic moment of the nanoribbon. Thereafter, we study the modulated electronic and magnetic properties of the nanoribbon of ~3 Å width by saturating the ribbon edges with H and C. In one case, by passivating the zig-zag type ribbon with H at the S terminated edge, we find a net increase in magnetic moment of the ribbon when compared with the pristine one. Furthermore, when the ribbon is passivated with H at both of the edges, the net magnetic moment shows a decreasing trend. In another case, the zig-zag nanoribbon is passivated with C in a similar fashion to H and we find with one edge passivation the net magnetic moment of the ribbon decreases, whereas with both edges C passivated the ribbon magnetism increases significantly. However, the nanoribbon modeled with the armchair type of edge and terminated with Mo at both sides is found to be non-magnetic and semiconducting. Passivating the armchair type nanoribbon with H and C, we find the band gap shows an increasing trend when going from one side to both sides passivation. In all cases, the armchair type nanoribbons show non-magnetic behavior.

Crafting ferromagnetism in Mn-doped MgO surfaces with p-type defects.

We have employed first-principles calculations based on density functional theory (DFT) to investigate the underlying physics of unusual magnetism in Mn-doped MgO surface. We have studied two distinct scenarios. In the first one, two Mn atoms are substitutionally added to the surface, occupying the Mg sites. Both are stabilized in the Mn[Formula: see text] valence state carrying a local moment of 4.3 [Formula: see text] having a high-spin configuration. The magnetic interaction between the local moments display a very short-ranged characteristic, decaying very quickly with distance, and having antiferromagnetic ordering lower in energy. The energetics analysis also indicates that the Mn ions prefer to stay close to each other with an oxygen atom bridging the local interaction. In the second scenario, we started exploring the effect of native defects on the magnetism by crafting both Mg and O vacancies, which are p- and n-type defects, respectively. It is found that the electrons and holes affect the magnetic interaction between Mn ions in a totally different manner. The n-type defect leads to very similar magnetism, with the AFM configuration being energetically preferred. However, in the presence of Mg vacancy, the situation is quite different. The Mn atoms are further oxidized, giving rise to mixed Mn(d) ionic states. As a consequence, the Mn atoms couple ferromagnetically, when placed in the close configuration, and the obtained electronic structure is coherent with the double-exchange type of magnetic interaction. To guarantee the robustness of our results, we have benchmarked our calculations with three distinct theory levels, namely DFT-GGA, DFT-GGA+U and DFT-hybrid functionals. On the surface, the Mg vacancy displays lower formation energy occurring at higher concentrations. Therefore, our model systems can be the basis to explain a number of controversial results regarding transition metal doped oxides.