Ionic Character Research Articles

First-principles calculations to investigate structural, elastic and thermodynamic properties of new M2ScSnC2 (M=V or Nb) quaternary compounds for 312 MAX phases

In this research, the approach of FP-LAPW (full potential linearized augmented plane wave) is employed within WIEN2K for the investigations of structural, thermodynamic, electronic, and mechanical properties of the V2ScSnC2 and Nb2ScSnC2 MAX-phases quaternary compounds. The V2ScSnC2 and Nb2ScSnC2 compounds exist in “α” and “β” polymorph structures. The formation energies (Eform) investigated insure that the α-polymorph is more stable than the β one. As it happens, Nb2ScSnC2 is more stable than V2ScSnC2. The Nb2ScSnC2 has an enhanced mechanical property compared to the V2ScSnC2 compound. The elastic constants (ECs) of interested materials fulfill all the conditions of mechanical stability and revealed a ductile nature. The predicted Cauchy's pressure and Poisson's ratio possess positive values signifying the ionic character of the V2ScSnC2 compound. The quaternary Nb2ScSnC2 compound exists as amalgamation of covalent and ionic bonds with a predominance of the ionic bonding character. The high melting temperature and high Debye temperature of V2ScSnC2 and Nb2ScSnC2 make them suitable for use in harsh environments. Furthermore, they exhibit potential as a promising material for thermal barrier coatings (TBCs). Electronic structure analysis confirm the metallic character of the two interested compounds. At high temperatures and pressures the thermodynamic properties including the Cv (Heat capacity) and ƟD(Debye temperature) are explored. We deem that this study of quaternary MAX-phase compounds will bring new insight for the experimentalists to employ for their future applications.

Structural studies of a novel tautomeric Schiff base derived from 4-(N,N’-diethylamino)salicylaldehyde and 2-amino-4-methyl phenol: An experimental and theoretical study

A novel Schiff base, LMAP synthesized from 4-(N,N’-diethylamino)salicylaldehyde and 2-amino-4-methyl phenol has been characterized by single crystal X-ray diffraction and spectroscopic methods. DFT methods is used to investigate the enol-imine (EI) ⇄ keto-amine (KA) tautomeric behavior with respect to phase and in solvent media. The synthesized Schiff base crystallizes in the keto-amine (KA) form in the orthorhombic lattice and Pna21space group with four atoms per unit cell (Z = 4). Bond length analysis indicates that the KA form possesses significant zwitter ionic character. Study of electronic absorption and emission properties was conducted in the solid state as well as in different solvents. The UV–Vis result reveals the varied structural preference of the compound depending on the solvent media: polar protic solvents stabilize the KA form, while nonpolar and polar aprotic solvents favor the EI form. Quantum mechanical computations using DFT and TD-DFT also confirm these findings. Fluorescence emission spectra show multiple emission bands which indicate both excited state intramolecular proton transfer (ESIPT) and charge transfer (CT) phenomena occur simultaneously within the molecule. DFT predicted NLO responses of KA and EI were compared and found that the NLO response of KA is superior to that of EI.

Rapid, Direct, Noninvasive Method to Determine the Amount of Immobilized Protein.

Protein immobilization is of utmost importance in many areas, where various proteins are used for selective detection of target compounds. Despite the importance given to determine the amount of immobilized protein, there is no simple method that allows direct, noninvasive detection. In this work, a method based on pH transition, occurring during change of solution ionic strength, was developed. The method utilized the ionic character of the immobilized protein while implementing biologically compatible buffers. Five different proteins, namely, glucose oxidase, horseradish peroxidase, bovine serum albumin, lysozyme, and protein A, were immobilized in different amounts on a porous polymeric matrix, and their pH transition was measured using lactate buffer of various concentrations and pH values. A linear correlation was found between the amount of immobilized protein and the amplitude of the pH transition, allowing the detection down to 2 nmol of immobilized protein. By changing the buffer concentration and pH, the sensitivity of the method could be tailored. Criteria based on the symmetry of the pH transition peak have been developed to determine if a particular measurement is within a linear range. In addition, a mathematical model was developed enabling prediction of pH transition profiles based solely on the protein amino acid sequence, the buffer pKa value(s), and the amount of immobilized protein.Hence, it can be used to design pH transition method experiments to achieve the required sensitivity for a target sample. Since the proposed method is noninvasive, it can be routinely applied during optimization of the immobilization protocol, for quality control, and also as an in-process monitoring tool.

Computational Modelling of Pyrrolic MN4 Motifs Embedded in Graphene for Catalyst Design

Carbon-based materials doped with metal and nitrogen (M-N-Cs) have promising potential in electrocatalytic applications with the advantage of material sustainability. MN4 motifs incorporated into a carbon lattice are generally known to be responsible for the activity of these materials. While many computational studies assume the tetrapyridinic MN4 motifs, recent studies have elucidated the role of tetrapyrrolic MN4 motifs in electrocatalysis. Using density functional theory, we constructed and compared various structural models to study the incorporation of tetrapyrrolic and tetrapyridinic MN4 motifs in 2D carbon materials and analyzed the type of interactions between each metal species and the N4 site. We further quantified the relative affinity of various metal species to the two types of N4 site. Upon analysis of energies, bond lengths, electronic population and charges, we found that metals that exhibit highly ionic binding characters have a greater affinity towards tetrapyrrolic MN4 motifs compared to species that participate in covalent interactions with the π-system. Furthermore, the binding strength of each species in the N4 site depend on the electronegativity as well as the availability of orbitals for accepting electrons from the π-system.

Synthesis and Electrical Properties of Nd2(WO4)3–SiO2 Composites

t—The (1 – x)Nd2(WO4)3–xSiO2 composites where the silicon oxide mole fraction is x ≤ 0.5 were manufactured by the solid-phase method. The phase compositions of the composites and their thermodynamic stability were verified by X-ray powder diffraction and thermogravimetry, respectively, in combination with differential scanning calorimetry (DSC). The morphology of the composites was studied by scanning electron microscopy (SEM) combined with energy-dispersive X-ray analysis. The electrical conductivity of the composites measured by electrochemical impedance was studied as functions of temperature, oxygen vapor pressure, and the amount of silicon oxide (the dispersed additive). The sums of ion transference numbers were studied as a function of temperature by the EMF method; the ionic character of conduction in the composites was found. The composite-conductivity effect was found to occur in the studied system: additions of 30 mol % nanosized silica to neodymium tungstate increased the ionic conductivity by more than two orders of magnitude.

Selenizing Possibilities of Cu2HgSnS4—i.e., Cu2HgSn(SexS1−x)4 Compound Semiconductor: Potential Candidate for Solar Photovoltaics and Photodetectors

Herein, the authors report the optoelectronic and mechanical properties of Cu2HgSn(SexS1−x)4 alloy (0 ≤ x ≤ 1) using density‐functional calculations. The alloy exhibits a range of bandgap 1.33–0.81 eV with small bowing 0.395, preserving direct nature at Γ point for any value of x. Hubbard parameter of ≈0.52 Ry is considered viewing the strongly correlated Cu‐3d and Hg‐4d orbitals, together with modified Becke–Johnson potential with spin–orbit coupling, to ensure accurate eigenvalues. When analyzing the charge density with a Bader charge analysis, decreasing ionic character with increasing Se concentrations is observed. The noticed elastic constant also satisfies the Born–Huang criteria and exhibits the ductile nature of Cu2HgSn(SexS1−x)4 system, making it a good candidate for flexible devices. The partial density of states highlights the dominance of Cu‐d states in the valence band edge, while the conduction band edge majorly emerges with Se states. In addition, the absorption coefficient is also found at ≈104 cm−1, and a rising degree of polarization is seen when approaching x = 1. This study provides the potential of Cu2HgSn(SexS1−x)4 alloy system for a photo‐absorber layer in graded and tandem thin‐film solar cells together with low‐bandgap Cu2HgSnSe4 as a suitable material for an infrared detector and thermoelectric applications.

Bonding, Thermodynamics, and Spectroscopy of the Metal Borides UB0/+/– and WB0/+/–

The bonding and spectroscopy of the UB0/+/- and WB0/+/- molecules were examined by performing high-level electronic structure calculation on their low-lying electronic states. The calculations were performed at the SO-CASPT2 level to obtain the low-lying excited states and at the FPD level to calculate the adiabatic electronic affinities (AEA), ionization energies (IE), and bond dissociation energies (BDE). Compared to UC and UN, UB has a much denser manifold of states below 1.7 eV. The ground state of UB is predicted to be 8I5/2, and that of WB is 6Π7/2. The calculated IEs of UB and WB are 6.241 and 7.314 eV, respectively, and the corresponding AEAs are 1.160 and 1.422 eV. The BDE of UB is predicted to be 223.1 kJ/mol, which is considerably lower than those predicted for UC and UN and ∼35 kJ/mol lower than the BDE of WB. NBO calculations show that the U and B are connected by two 1-electron π bonds and one 1-electron σ bond with substantial ionic character and a bond order of 1.5. There are three unpaired electrons in the 5f on U. WB has less ionic character than UB with a doubly occupied π bond and a singly occupied σ bond for a bond order of ∼1.5. The results show that the U in UB behaves more like an actinide and the W in WB more like a transition metal.

Application of Ionic Liquids as Mobile Phase Additives for Simultaneous Analysis of Nicotine and Its Metabolite Cotinine in Human Plasma by HPLC–DAD

Nicotine and cotinine are very polar basic molecules, which makes it difficult to analyze them by reversed-phase liquid chromatography (RPLC), especially in biological samples. Additives with an ionic character have been traditionally used in RPLC as silanol suppressors. The aim of our study was to investigate the potential of selected ionic liquids in improving chromatographic performance in comparison with common additives. The experimental design was conducted using the following ionic liquids as the mobile phase modifiers: 1-butyl-3-methylimidazolium tetrafluoroborate, BMIM[BF4] and 1-butyl-3-methylimidazolium hexafluorophosphate BMIM[PF6], with a C18 chromatographic column. The separation of these alkaloids on silica-based RPLC stationary phases was successfully conducted by the addition of BMIM[BF4] in an acetonitrile:phosphate-buffer-based mobile phase in a pH range of 2.3-5.2. The presented chromatographic method can be used as alternative for monitoring studies or pharmacokinetic application necessary for the evaluation of tobacco smoke exposure.

Acid-Base Chemistry Provides a Simple and Cost-Effective Route to New Redox-Active Ionic Liquids.

Redox-active ionic liquids (RAILs) hold great promise as high density electrochemical energy storage materials, but are hampered by high costs and low bulk conductivities. In this work, we introduce and electrochemically characterise novel redox-active protic ionic liquids (RAPILs) formed by acid-base neutralisation from cheap and plentiful starting materials. We also demonstrate a novel RAIL-in-IL solvent system for electrochemical characterisation of RAPILs, which enables efficient and cost-effective determination of redox potentials and screening for electrochemical reversibility. Of the redox-active ionic liquids tested in this work, only propylammonium 4-nitrophenylacetate demonstrates completely reversible electrochemistry and preservation of ionic character upon redox cycling under acidic or neutral conditions. Propylammonium 2,5-dihydroxyphenyl-carboxylate also demonstrates two reversible redox processes, but is unstable to oxidation at 0.27 V vs Ag (-0.14 V vs Fc), most likely forming an uncharged benzoquinone species. Using the lessons learned from this prototypical set of RAPILs, we propose design criteria to guide future experimental and computational work.

Lignin nanoparticle-decorated nanocellulose cryogels as adsorbents for pharmaceutical pollutants

Adsorption is a relatively simple wastewater treatment method that has the potential to mitigate the impacts of pharmaceutical pollution. This requires the development of reusable adsorbents that can simultaneously remove pharmaceuticals of varying chemical structure and properties. Here, the adsorption potential of nanostructured wood-based adsorbents towards different pharmaceuticals in a multi-component system was investigated. The adsorbents in the form of macroporous cryogels were prepared by anchoring lignin nanoparticles (LNPs) to the nanocellulose network via electrostatic attraction. The naturally anionic LNPs were anchored to cationic cellulose nanofibrils (cCNF) and the cationic LNPs (cLNPs) were combined with anionic TEMPO-oxidized CNF (TCNF), producing two sets of nanocellulose-based cryogels that also differed in their overall surface charge density. The cryogels, prepared by freeze-drying, showed layered cellulosic sheets randomly decorated with spherical lignin on the surface. They exhibited varying selectivity and efficiency in removing pharmaceuticals with differing aromaticity, polarity and ionic characters. Their adsorption potential was also affected by the type (unmodified or cationic), amount and morphology of the lignin nanomaterials, as well as the pH of the pharmaceutical solution.Overall, the findings revealed that LNPs or cLNPs can act as functionalizing and crosslinking agents to nanocellulose-based cryogels. Despite the decrease in the overall positive surface charge, the addition of LNPs to the cCNF-based cryogels showed enhanced adsorption, not only towards the anionic aromatic pharmaceutical diclofenac but also towards the aromatic cationic metoprolol (MPL) and tramadol (TRA) and neutral aromatic carbamazepine. The addition of cLNPs to TCNF-based cryogels improved the adsorption of MPL and TRA despite the decrease in the net negative surface charge. The improved adsorption was attributed to modes of removal other than electrostatic attraction, and they could be π-π aromatic ring or hydrophobic interactions brought by the addition of LNPs or cLNPs. However, significant improvement was only found if the ratio of LNPs or cLNPs to nanocellulose was 0.6:1 or higher and with spherical lignin nanomaterials. As crosslinking agents, the LNPs or cLNPs affected the rheological behavior of the gels, and increased the firmness and decreased the water holding capacity of the corresponding cryogels. The resistance of the cryogels towards disintegration with exposure to water also improved with crosslinking, which eventually enabled the cryogels, especially the TCNF-based one, to be regenerated and reused for five cycles of adsorption-desorption experiment for the model pharmaceutical MPL. Thus, this study opened new opportunities to utilize LNPs in providing nanocellulose-based adsorbents with additional functional groups, which were otherwise often achieved by rigorous chemical modifications, at the same time, crosslinking the nanocellulose network.

Investigation of the crystal structure, electronic and optical properties of Cr-doped BaTiO3 on the Ti site using first principles calculations

In this work, we have investigated the effect of chromium (Cr) doping on the structural, electronic and optical properties of the cubic phase of BaTiO3 using first-principles calculations. Applying the GGA + U approximation, the lattice parameters as well as the band gaps of the undoped and doped phase of BaTiO3 are in fairly good agreement with the experimental data, confirming the validity of our model. Furthermore, the chemical bonding analysis underlines the ionic character of Ba–O bonds and the covalent nature of Ti–O and Cr–O bonds. Additionally, the investigation of the optical properties using the Hubbard U-potential correction provided good agreement with the experimental data in the broad energy ranges. We have also demonstrated that the substitution of chromium on the Ti site, through the calculation of both electronic and optical properties, leads to the appearance of defects close to the Fermi level, allowing the appearance of the asymmetry of the BaTi1-xCrxO3 system. As a result, the calculated total magnetic moment is 1.6038 μB, indicating that doping with Cr renders the BaTi1-xCrxO3 system ferromagnetic. Therefore, this work demonstrates that Cr-doped BaTiO3 could reasonably constitute a new class of perovskite materials for magneto-optoelectronic applications.

Functionalization of an ionic honeycomb KF monolayer via doping.

Doping has been widely employed to functionalize two-dimensional (2D) materials because of its effectiveness and simplicity. In this work, the electronic and magnetic properties of pristine and doped KF monolayers are investigated using first-principles calculations based on density functional theory (DFT). Phonon dispersion curves and ab initio molecular dynamics (AIMD) snapshots indicate good stability of the pristine material. The band structure shows an insulating behavior of the KF monolayer, with indirect gaps of 4.80 (6.53) eV as determined using the PBE (HSE06) functional. Its ionic character is also confirmed by the valence charge distribution and Bader charge analysis, and is generated by charge transfer from the K-4s orbital to the F-2p orbital. Doping at both anion and cation sites is explored using N/O and Ca/Sr as dopants, respectively, due to their dissimilar valence electronic configuration in comparison with that of the host atoms. It is found that the KF monolayer is significantly magnetized, where total magnetic moments of 2.00 and 1.00 μB are obtained via N and O/Ca/Sr doping, respectively. Moreover, the appearance of new middle-gap energy states leads to the development of a magnetic semiconductor nature, which is regulated by N-2p, O-2p, Ca-3d, Ca-4s, Sr-4d, and Sr-5s orbitals. Further investigation of codoping indicates that a magnetic-semiconductor nature is preserved, where the synergistic effects of dopants play a key role in the electronic and magnetic properties of the codoped systems. The results presented herein introduce doping as an efficient approach to functionalize the ionic KF monolayer to obtain prospective d0 spintronic materials, a functionality that is not accounted for by the pristine monolayer.

Comparing the structures and photophysical properties of two charge transfer co-crystals.

Organic co-crystals have emerged as a promising class of semiconductors for next-generation optoelectronic devices due to their unique photophysical properties. This paper presents a joint experimental-theoretical study comparing the crystal structure, spectroscopy, and electronic structure of two charge transfer co-crystals. Reported herein is a novel co-crystal Npe:TCNQ, formed from 4-(1-naphthylvinyl)pyridine (Npe) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) via molecular self-assembly. This work also presents a revised study of the co-crystal composed of Npe and 1,2,4,5-tetracyanobenzene (TCNB) molecules, Npe:TCNB, herein reported with a higher-symmetry (monoclinic) crystal structure than previously published. Npe:TCNB and Npe:TCNQ dimer clusters are used as theoretical model systems for the co-crystals; the geometries of the dimers are compared to geometries of the extended solids, which are computed with periodic boundary conditions density functional theory. UV-Vis absorption spectra of the dimers are computed with time-dependent density functional theory and compared to experimental UV-Vis diffuse reflectance spectra. Both Npe:TCNB and Npe:TCNQ are found to exhibit neutral character in the S0 state and ionic character in the S1 state. The high degree of charge transfer in the S1 state of both Npe:TCNB and Npe:TCNQ is rationalized by analyzing the changes in orbital localization associated with the S1 transitions.

Prediction of the structures and heats of formation of MO2, MO3, and M2O5 for M = V, Nb, Ta, Pa.

Structures for the mono-, di-, and tri-bridge isomers of M2O5 as well as those for the MO2 and MO3 fragments for M = V, Nb, Ta, and Pa were optimized at the density functional theory (DFT) level. Single point CCSD(T) calculations extrapolated to the complete basis set (CBS) limit at the DFT geometries were used to predict the energetics. The lowest energy dimer isomer was the di-bridge for M = V and Nb and the tri-bridge for M = Ta and Pa. The di-bridge isomers were predicted to be composed of MO2+ and MO3- fragments, whereas the mono- and tri-bridge are two MO2+ fragments linked by an O2-. The heats of formation of M2O5 dimers, as well as MO2 and MO3 neutral and ionic species were predicted using the Feller-Peterson-Dixon (FPD) approach. The heats of formation of the MF5 species were calculated to provide additional benchmarks. Dimerization energies to form the M2O5 dimers are predicted to become more negative going down group 5 and range from -29 to -45 kcal mol-1. The ionization energies (IEs) for VO2 and TaO2 are essentially the same at 8.75 eV whereas the IEs for NbO2 and PaO2 are 8.10 and 6.25 eV, respectively. The predicted adiabatic electron affinities (AEAs) range from 3.75 eV to 4.45 eV for the MO3 species and vertical detachment energies from 4.21 to 4.59 eV for MO3-. The calculated MO bond dissociation energies increase from 143 kcal mol-1 for M = V to ∼170 kcal mol-1 for M = Nb and Ta to ∼200 kcal mol-1 for M = Pa. The M-O bond dissociation energies are all similar ranging from 97 to 107 kcal mol-1. Natural bond analysis provided insights into the types of chemical bonds in terms of their ionic character. Pa2O5 is predicted to behave like an actinyl species dominated by the interactions of approximately linear PaO2+ groups.

Doping-mediated electronic and magnetic properties of graphene-like ionic NaX (X = F and Cl) monolayers.

In this work, the stability, and electronic and magnetic properties of pristine and doped graphene-like ionic NaX (X = F and Cl) monolayers are explored using first-principles calculations. The good stability of NaF and NaCl monolayers is confirmed by phonon dispersion curves and ab initio molecular dynamics simulations. Electronic structure calculations show their insulator nature with large indirect band gaps of 5.43 (7.26) and 5.06 (6.32) eV as calculated with the PBE (HSE06) functional, respectively. In addition, their ionic character is also demonstrated. Furthermore, a doping approach is explored to functionalize NaX monolayers for spintronic applications. For such a goal, IIA- and VIA-group atoms are selected as dopants due to their dissimilar valence electronic configuration as compared with the host atoms. The results indicate the emergence of magnetic semiconductor nature with a total magnetic moment of 1μB. Herein, magnetic properties are produced mainly by the dopant atoms, which induce new middle-gap energy states around the Fermi level. Finally, the effects of codoping the NaF monolayer with Ca and O and NaCl with Ba and O are also examined. Adjacent Ca-O and Ba-O pairs preserve the non-magnetic nature. Further separating dopants leads to the emergence of magnetic semiconductor behavior, with lower magnetization than separate doping. This work introduces new ionic 2D materials for optoelectronic and spintronic applications, contributing to the research effort to find out new 2D multifunctional materials.

Dye-induced photoluminescence quenching of quantum dots: role of excited state lifetime and confinement of charge carriers.

We investigate the role of quantum confinement and photoluminescence (PL) lifetime of photoexcited charge carriers in semiconductor core/shell quantum dots (QDs) via PL quenching due to surface modification. Surface modification is controlled by varying the number of dye molecules adsorbed onto the QD shell surface forming QD-dye nanoassemblies. We selected CuInS2/ZnS (CIS) and InP/ZnS (InP) core/shell QDs exhibiting relatively weak (664 meV) and strong (1194 meV) confinement potentials for the conduction band electron. Moreover, the difference in the emission mechanism gives rise to a long and short excited state lifetime of CIS (ca. 290 ns) and InP (ca. 37 ns) QDs. Dye molecules of different ionic characters (rhodamine 575: zwitterionic and rhodamine 560: cationic) are used as quenchers. A detailed analysis of Stern-Volmer data shows that (i) quenching is generally more pronounced in CIS-dye assemblies as compared to InP-dye assemblies, (ii) dynamic quenching is dominating in all QD-dye assemblies with only a minor contribution from static quenching and (iii) the cationic dye shows a stronger interaction with the QD shell surface than the zwitterionic dye. Observations (i) and (ii) can be explained by the differences in the amplitude of the electronic component of the exciton wavefunction near the dye binding sites in both QDs, which results in the breaking up of the electron-hole pair and favors charge trapping. Observation (iii) can be attributed to the variations in electrostatic interactions between the negatively charged QD shell surface and the cationic and zwitterionic dyes, with the former exhibiting a stronger interaction. Moreover, the long lifetime of CIS QDs facilitates us to easily probe different time scales of the trapping processes and thus differentiate the origins of static and dynamic quenching components that appear in the Stern-Volmer analysis.

Structural, conductivity and dielectric studies of pure and KCL doped polymer electrolyte films

Using the solution cast method, poly (vinyl alcohol) complexed with KCl was used to make solid polymer electrolyte films. XRD was used to look at the structure of these films. The outcomes of the Powder × - ray diffraction show that the composite films had more noncrystalline phases of PVA matrix. An AC impedance spectroscopy suggested that the ionic conductivity mainly arisen from grain effect. Conductivity of pure PVA is found to be of the order of 10-8 S/cm. With the addition of 20 wt% of KCl, the conductivity is dropped to the order of 10-10 S/cm, and then increased with the addition of KCl. The increase in conductivity with dopant type is based on the ionic character of the dopant. Real part of Impedance (Z') and imaginary part of impedance (Z“) of pure PVA and various composite films with 20 wt% of KCl, additives with different weight ratios were measured as a function of frequency. Dielectric permittivity and dielectric loss of all PVA with KCl 20 wt% of Polymer films investigated as a function of frequency at a room temperature is studied.Different electrochemical applications can be developed using these kinds of solid electrolytes.

Role of Cu2O surface terminations on interface conductivity with graphene

Two-dimensional materials and their interfaces with functional oxides have increasing applications in optoelectronic devices. Cu2O is an important functional oxide and efficient charge transport across the Cu2O/contact material interface is a significant bottleneck in the development of efficient optoelectronic devices. Here, we investigate the electronic properties of graphene, a transparent contact material, interface with intrinsic (100) Cu2O thin films using first principles calculations. From the graphene-Cu2O heterojunction interface, we observe that despite the Cu2O surface termination and electronegativity order of the atoms involved, the physisorbed graphene layer is always electron depleted. The graphene heterojunction with the reconstructed Copper terminated surface shows a covalent character, a smaller tunnel barrier and blocking Schottky potential of 0.19 eV for holes. In contrast, the reconstructed oxygen terminated structure shows an ionic character, a significantly taller tunnel barrier and a transparent ohmic contact for holes. These results show that graphene is an attractive transparent contact material for Cu2O based hole transport layers in photovoltaics, chemical and photon sensing, and energy storage.

Application of anionic-nonionic mixed micellar system for solubilization of methylene blue dye

Present study highlights the interaction of methylene blue (MB), a cationic dye, with anionic surfactant, sodium dodecyl sulfate (SDS), and its mixed micelles with a nonionic surfactant Triton X-114 (TX-114). The results obtained from UV–visible spectrophotometry were used to obtain the degree of solubilization in terms of binding constant (Kb) and partition coefficient (Kx) of dye in single and mixed micellar systems (MMS). Gibb’s free energies of partitioning and binding were also calculated for both systems. Specific conductance was measured to determine the CMC of single and mixed micellar media at five different temperatures, T = (293.15 – 333.15) K. Temperature-dependent thermodynamic parameters like Gibb’s free energy of micellization (ΔGomic), enthalpy of micellization (ΔHomic), and entropy of micellization (ΔSomic) were calculated using data of specific conductance measurements. Effect of concentration of TX-114 on Kx and Kb values of the MB in MMS is also investigated. Spectroscopic and conductometric results revealed that the anionic-nonionic mixed micellar system was better and more effective for the removal and solubilization of MB from aqueous system as compared to anionic micelles only. However, it has been observed that after a critical concentration an increase of non-ionic surfactant concentration has a reverse effect on solubilizing power of ionic-nonionic mixed micellar system. This indicates that the dye-surfactant interaction became weaker due to possible decrease in ionic character of mixed micelles when the high fraction of TX-114 was used.

Ionic liquid: A green designer solvent for topical delivery of Nano system

Ionic liquids (ILs) defined as organic salts that produced from combination of organic cation with various types of organic/inorganic anions whose melting point less than 100°C. Because of their ionic character, most of ionic liquids exhibit useful properties such as no volatility, recyclability, good thermal stability, high conductivity and chemical stability. Ionic liquid cation - anion combinations permits the solvents to be prepared such as N, N-dialkylimidazolium as cation and acetate as anion. Ionic liquid was utilized as solvents or preparation components in various areas of drug delivery systems, also as novel liquid forms of APIs in various stages of design drug delivery systems. Also their incorporation with polymers has enabled the development of drug delivery systems for new therapeutic routes of administration. Recently ionic liquid can be used as solubility and permeability enhancer to deliver drugs with poor aqueous solubility and low lipophilicity by designing topical drug delivery of nano system.