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Fe3S4, commonly known as greigite, is a transition metal chalcogenide and has attracted enormous attention in the field of energy storage and environmental remediation.

Synthetically benign and facile, highly sensitive nZVI@Biochar sensor derived from lotus stem for sensing of glyphosate in aqueous solution.

Efficient storage of hydrogen is one serious impediment in using H2 as an alternate clean fuel, at a larger scale, in the context of alarming levels of global warming and fast depleting fossil fuel resources. Metal nitrides such as Li2N4, Na2N4 and K2N4 using density functional theory with PBE1PBE and B3LYP functional and 6-31G (d,p), 6–31 ++ G (d,p) and 6–311 ++ G (d,p) as basis sets. This has revealed that doping of alkali metal atoms on the nitride systems increases their hydrogen adsorption ability, due to the electron transfer that occurs from the metal atom to the nitrogen surface. The charged surface created around the metal atom is found to enhance the hydrogen adsorption capacity of the complex from 9 to 16.79wt% with an average binding energy from 0.06 to 0.30 eV/H2. Various conceptual reactivity descriptors, bond parameters, Gibbs free energy change (ΔG) and energy gap values support the idea that the stability of the complex increases on hydrogen uptake. Efficient storage of hydrogen is one serious impediment in using H2 as an alternate clean fuel, at large scale, in the context of alarming levels of global warming and fast depleting fossil fuel resources. Herein, we report theoretical studies on some novel metal nitrides in order to probe its hydrogen storage potential. M2N4 systems (where M = Li, Na, K) can store hydrogen around 5–12 H2 molecules with an gravimetric density of 9–16.79 wt% and an average binding energy in the range of 0.06–0.30 eV/H2. It was found that among all the three metal nitrides Li2N4 is found to possess highest binding energy and energy gap, whereas K2N4 adsorbs maximum number of H2 molecules.

As a fascinating two-dimensional (2D) layered inorganic ion exchange material, zirconium phosphate (hereafter ZrP) has drawn interdisciplinary attention as an ion exchange material and a competent ...

Fluorescent carbon dot sensing probes have attracted much attention in recent times due to their amazing properties regarding chemical inertness, solubility, non-toxicity, optoelectronic behavior, and charge transport functionality. Herein, we report the green synthesis of lotus stem-derived carbon dots (LS-CQDs) from the naturally available lotus stem by a simple and economical hydrothermal method without the use of an oxidizing agent. HR-TEM and DLS measurements confirm the quasi-spherical shaped LS-CQDs, with a 2.5 nm average diameter. The LS-CQDs possess better aqueous dispersibility and stability due to the presence of hydrophilic hydroxyl, carboxyl, and amine surface functional groups, as manifested by FT-IR analysis. The LS-CQDs demonstrate excellent fluorescence properties that are sensitive to conditions of pH, time, and temperature. Furthermore, the prepared LS-CQDs display an interesting fluorescence “ON–OFF–ON” property. The LS-CQDs depict a selective and sensitive fluorescence quenching response in the presence of ferric ions. Moreover, the prepared LS-CQDs exhibit a quantum yield of about 0.44%. The LS-CQDs show an excellent sensing response with the limit of detection (LOD) equal to 0.212 ppm. The promising sensitivity and selectivity of LS-CQDs were utilized for the detection of ferric ions in the water samples collected from three polluted sources viz. lake water (Dal lake), underground water (tube well), and stream water. For all the collected water samples the results were reasonably good with the achievement of recovery factor above 1. Therefore, we strongly believe that the present study will serve as a good guiding star for the selective and sensitive detection of ferric ions from various polluted water bodies.

In aqueous systems, heavy metal ions, when present in excess than permissible limits, are dangerous for human beings and aquatic life. Heavy metals cannot be degraded. Rather, they accumulate in living organisms either directly or through the food chain. Inside the body, metal ions can be converted to more toxic forms or can directly interfere with metabolic processes. As a result of metal toxicity, various disorders and damage due to oxidative stress triggered by metal ions have been witnessed. Toxic effects of metallic pollution coupled with the need of pure water for the survival and sanitation have thus prompted researchers to take every possible step to uphold the quality of water. In this regard, various strategies have been developed for the detection and the removal of metal ions from aqueous systems. Here we review metal-free water and methodologies used for rapid detection at low levels. Also, the application of benign materials and methods for metal removal from aqueous systems is detailed. Electrochemical methods, especially stripping and cyclic voltammetry, are commonly used methods for detection, while adsorption and ion exchange methods are quite effective for removal.

Herein, we report the electrochemical detection of heavy metal ions such as Pb(II), Cd(II) and Hg(II) ions while using glutathione coated hollow ZnO modified glassy carbon electrode (Glu-h-ZnO/GCE). An excellent voltammetric response of the modified electrode towards these metal ions was observed by different voltammetric techniques. Among the different target metal ions, a selective electrochemical response (sensitivity = 4.57 μA μM−1) for the detection of Pb(II) ions was obtained with differential pulse voltammetric (DPV) measurements. Besides, under optimal experimental conditions and in the linear concentration range of 2–18 μM, a very low detection limit of 0.42 μM was obtained for Pb(II) ion. The observed electrochemical behaviour of Glu-h-ZnO/GCE towards these metal ions is in conformity with the band gap of the composite in the presence of various test metal ions. The band gap studies of the composite and various “Composite-Metal Ion” systems were obtained by reflectance as well as by computational methods where results are in close agreement, justifying the observed electrochemical behaviour of the systems. The lowest band gap value of the “Composite-Pb” system may be the reason for the excellent electrochemical response of the Glu-h-ZnO modified GCE towards the detection of Pb(II) ion.

Efficient storage of hydrogen is one serious impediment in using H2as an alternate clean fuel, at a larger scale, in the context of alarming levels of global warming and fast depleting fossil fuel resources.Metal nitrides such as Li2N4, Na2N4 and K2N4using density functional theory at PBE1PBE and B3LYP functional using 6-31G (d,p), 6-31++G (d,p) and 6-311++G (d,p) as basis sets have revealed that doping of alkali-metal atoms on the nitride systems increases their hydrogen adsorption ability, due to electron transfer that occurs from the metal atom to the nitrogen surface. The charged surface created around the metal atom is found to enhance the hydrogen adsorption capacity of the complex from 9 to 16.79wt% with an average binding energy of0.06 to 0.30 eV/H2. Various conceptual reactivity descriptors,bond parameters, Gibbs free energy change (ΔG) and energy gap values, support the ideathat the stability of the complex increaseson hydrogen uptake.

Pollution due to heavy metals is currently a serious problems affecting water bodies. The removal of heavy metals is of great concern due to their toxicity at trace levels and accumulation in the biosystem. Here we review the technical feasibility of biosorption and ion exchange methods for the removal of various heavy metals from the aqueous media. Chemical pretreatment of low-cost biosorbents are presented. Chemically modified biosorbents exhibit far better adsorption capacities than unmodified ones. We also highlighted the effect of pH on the biosorption for maximal uptake of heavy metals, because pH modifies the surface charge of the biosorbent as well as the speciation of heavy metals.

Chitosan is an excellent polymer that has been exploited for biomedical applications ranging from antimicrobial action to targeted drug delivery and tissue engineering. Chitosan has been chiefly used to develop formulations in the form of conjugates, nanoparticles, hydrogels and scaffolds. However, being a polyelectrolyte, the charge density and various physicochemical properties, such as solubility, viscosity, mucoadhesion, and swelling of chitosan, are extremely sensitive to variation in external conditions (e.g., pH and ionic strength of the medium). This review discusses chitosan's physicochemical properties in the solution like solubility, viscosity, mucoadhesion, and swelling, which are a function of its polyelectrolytic nature. Furthermore, the effect of specific parameters like pH and ionic strength of the medium on the polymer and nanoparticle synthesis is also discussed. During formulation development process the charge density on chitosan plays a crucial role in determining the final product's efficiency. Finally, we conclude that the effectiveness of cellular adherence of chitosan hydrogels or scaffolds, the biodistribution of nanoparticles, and the antimicrobial action of chitosan are all functions of its surface charge density.

The removal of potentially toxic metal ions such as Pb(II), Zn(II), and Cr(VI) has drawn immense attention because of their persistence and acute toxicological effects. In the present work, we report the preparation of a biocompatible L -cysteine capped Fe3O4 nanoparticles (Fe3O4@ L -Cys) under sonochemical conditions and evaluate its efficiency as an adsorbent for the removal of Pb(II), Zn(II), and Cr(VI) ions from the contaminated water. The adsorbent material displays promising results for decontamination of Pb(II) and Cr(VI) ions present in water samples collected from Dal Lake. Intriguingly, Fe3O4@ L -Cys depicts a pH-guided removal of cationic (Pb2+ and Zn2+) and anionic (HCrO4-) pollutants under competitive and non-competitive optimum batch conditions. We performed density functional theory (DFT) to gain more insight into the pH-dependent site preference for the uptake of Zn(II), Pb(II), and HCrO4- ions. At pH = 3.5, HCrO4- ions interact electrostatically with protonated amine (NH3+) groups, while at pH = 6.5 Zn(II), Pb(II) ions coordinates with carboxylate and amine groups. We first time demonstrated the in-depth interaction of HCrO4- with Fe3O4@ L -Cys using DFT and X-ray photoelectron spectroscopic studies and the results confirm the reduction of HCrO4- to Cr(III) ions. The batch experimental data fitted well with the Langmuir isotherm model and pseudo-second-order kinetic model with maximum monolayer capacity (qm) of 243.14, 237.37, and 170.63 mg g−1 for Pb(II), Zn(II), and HCrO4- ions respectively. The Fe3O4@ L -Cys nanoparticles show excellent stability and reusability over multiple cycles of sorption. We strongly believe that the present study will serve as a good guiding star for future research developments in water research and technology.

Density Functional Theory at B3PW91/6-311G (d, p) level was employed to analyze the spectral properties and nonlinear optical response of the oxo and thia-bridged triarylamine heterohelicenes. The energy calculations of optimized geometries reveals that the M and P isomeric forms of heterohelicenes of 1 , 2 , 3 and 4 are enantiomers, while as for 5 , 6 and 7 they are atropisomers. The simulated Infrared and Vibrational circular dichroism spectra in the mid-infrared region (1300-1650 cm −1 ) display peaks, having contribution from out-of-phase stretching of the three fused aromatic rings and contribution from the three N C bond stretching. In addition to these peaks M-7 displays peak corresponds to bending of H C H of terminal methoxy group. In this study we have observed the oxo-bridged heterohelicenes displays higher values of hyperpolarizability as compared to thia-bridged heterohelicenes. In case of M-5 , M-6 and M-7 the calculation reveals that with increase in electron donating capacity of substituent the hyperpolarizability increase due to decrease in optical band gap. Therefore, the oxo- and thia-bridged heterohelicenes can act as good raw material for nonlinear optical device and their nonlinear optical response can be enhanced by the extension in π-conjugation or addition of electron donating substituents.

Density functional theory at CAM-B3LYP/6-311G++ (2d, 2p) level was employed to study the Triphenylboroxine derivatives (TB) containing electron donating and electron substituents, for their charge transfer and nonlinear optical properties. The results reveal that electron donating groups facilitate the rapid electron injection as compared to unsubstituted TB. It was observed that upon substitution with electron donating groups, the TB derivatives show an increased double bond character in the B3–C18 bond indicating an increase in the degree of conjugation. The Frontier molecular orbital studies indicate that highest occupied molecular orbitals of the neutral molecules delocalize primarily over the three phenyl rings and bridging oxygen atoms, whereas the lowest unoccupied molecular orbitals localize largely on the two phenyl rings and the boron atoms. Further, the TD-DFT studies indicate that the maximum absorption band results from the electron transitions from the initial states that are contributed by the HOMO and HOMO-1 to the final states that are mainly contributed by the LUMOs. In addition, we have observed that the introduction of electron donating group to the TB-7 leads to more active nonlinear performance.

The super paramagnetic iron oxide nanoparticles (SPIONs) such as magnetite (Fe3O4) appear as an emerging class of materials in the field of environmental remediation owing to its biocompatibility, high surface area, super paramagnetic properties and ease of reuse and recovery. However, susceptibility of bare Fe3O4 to oxidation and agglomeration limits its use as an adsorbent material in aqueous medium, which demands the surface capping of these Fe3O4 nanoparticles for effective adsorption performance. We have successfully capped Fe3O4 with sodium citrate with a purpose to develop a felicitous magnetic sorbent material containing abundant metal trap centers at its surface. The successful surface modification of Fe3O4 with citrate is noticeable from FT-IR, TGA, XRD, Zeta potential (DLS), SEM, EDX,TEM, DR-UV, and contact angle measurements. For the first time, we report electrical impedance spectroscopic studies on this capped magnetic nanoparticle to understand the capacitive behavior of super paramagnetic Fe3O4 and citrate@Fe3O4 nanoparticles. The cyclic voltammograms manifested the excellent electrochemical response of citrate@Fe3O4 modified glassy carbon electrode to mM concentrations of Pb2+, Cd2+ and Zn2+ ions with response in order Pb2+> Cd2+> Zn2+. Differential Pulse Voltammetry confirms the descent sensitivity towards Pb2+ ions at different concentration with a 0.3 µM detection limit. The adsorption of Pb2+ ions followed Langmuir isotherm model with maximum monolayer adsorption capacity of 58.93 mg g−1. To further validate the experimental adsorption results and the mode of interaction between Pb2+and citrate@Fe3O4, quantum calculations using density functional theory were performed which indicate a good coherence between experimental and theoretical data. The presence of abundant carboxyl and hydroxyl metal trap centers at the surface of citrate@Fe3O4 is responsible for its promising adsorption capacity for Pb2+ ions removal. Both experimental as well as theoretical results suggest that surface functionalization has a positive impact for detection of heavy metal ions and should be given prime importance while designing absorbent materials. The citrate@Fe3O4 nanoparticles exhibit outstanding stability and regeneration over various cycles of sorption.

Herein, we report the low temperature, template directed synthesis of zirconium resorcinol phosphate (ZrRP) nanocomposite material, within water-in-oil microemulsion with Tergitol-7 as a surfactant. The material was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), simultaneous thermogravimetric analysis (TGA), differential thermal analysis (DTG), energy dispersive X-ray spectrometry (EDX), and specific area electron diffraction (SAED) studies. The powder X-ray diffraction studies revealed that the material is amorphous in nature with hardly developed crystallinity. SEM and TEM micrography studies showed that the ZrRP nanocomposite has nearly spherical morphology with average particle size of 30–40 nm. Viscoelastic behavior of ZrRP gel confirms its non-Newtonian behavior which is indicative of monodisperse nature of ZrRP nanoparticles. ZrRP possesses high ion exchange capacity of 2.9...

Synthesis and characterization of a new hybrid ion exchange material Zirconiumresorcinol Phosphate (ZrRP) is reported in this study. Synthetic conditions such as reactant concentrations and mixing volume ratio were varied to optimize the ion exchange properties of this material. The material has Na+ ion exchange capacity equal to 1.7 meq/g (dry). X-ray diffraction spectra suggest that it is amorphous in nature. This ion-exchanger was also characterization by SEM, IR and TGA-DTG. Various studies such as determination of ion exchange capacity, elution behaviour and pH titration has been performed for different metal ions such as K+, Ca2+, Sr2+, Mg2+, Ni2+, Cd2+. This material has potential application for removal of these ions from the aqueous systems. Effect of anionic (SDS) and nonionic (TX-100) surfactants has also been studied on the adsorption behavior of ZrRP. The material has been found to be selective for Mg2+and Cd2+. We also found that the material showed remarkable adsorption behavior towards some dyes like malachite green and methylene blue.

Glutathione has tremendous binding potential with metal ions present in water. However, the solubility of glutathione in water limits its productivity in the removal of these toxic ions from aqueous systems. The removability of heavy ions with glutathione and the associated adsorption capability are enhanced; for this purpose, glutathione is coated over hollow zinc oxide particles. Glutathione-coated hollow zinc oxide (Glu@h-ZnO) was successfully synthesized under microwave (MW) conditions using polystyrene (PS) as the template. The as-synthesized material was characterized by Fourier transform infrared (FTIR) spectroscopy, and the results were supported by X-ray diffraction crystallography (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), differential thermal analysis (DTA), dynamic light scattering (DLS), Brunauer–Emmett–Teller (BET) studies and zeta potential (ζ) analysis. The sorption performance of Glu@h-ZnO towards the uptake of Hg2+, Cd2+ and Pb2+ ions from an aqueous medium under non-competitive batch conditions was investigated and the material was found to have the maximum affinity for Hg2+ ions with a maximum adsorption (qm) capacity of 233 mg g−1. The adsorption kinetics for Hg2+ ions and the effects of pH and ζ on the adsorption properties were also studied in detail. Finally, the experimental data were correlated with theoretical data obtained from density functional theory (DFT) studies and good agreement between the two was obtained.

Crystalline and agglomerated spherical alpha zirconium phosphate nanoparticles hereafter α-ZrP were synthesized by a facile and rapid microwave-hydrothermal (MW-HT) approach within 30 min at 120 °C in the absence of any complexing or structure directing agent (SDA). The material was characterized by Fourier-transform infrared (FT-IR), powdered X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive spectroscopic analysis (EDS) and surface area analysis (BET). It crystallizes in the monoclinic P121/n1 space group with the following cell parameters: a = 5.288, b = 9.174, c = 15.384 A and β = 102.384. Crystallite sizes in the range 3–4 nm evaluated using Scherer equation were obtained for α-ZrP. Ion exchange performance of α-ZrP towards removal of Cs+ and Sr2+ ions was examined under noncompetitive batch conditions. Distribution studies indicate higher selectivity of α-ZrP towards Sr2+ uptake (Kd ca. 4.3 × 104) in comparison with Cs+ (Kd ca. 2.4 × 103). This study suggested to agglomerated α-ZrP as potential adsorbent for the removal of radioactive Sr2+ from acidic wastewater.

In this work, a hybrid composite material, acrylamide zirconium(IV) sulphosalicylate (AaZrSs) has been synthesized by intercalating acrylamide into zirconium(IV) sulphosalicylate. The synthetic conditions were varied to optimize the ion exchange properties of the material. The characterization of the material was done using SEM, IR, XRD and TGA so as to identify the various functional groups and ion exchange sites present in the material. The ion exchange capacities of some monovalent and divalent cations were investigated in order to know the working capacity of the composite material. Quantum chemical computations at B3LYP/LanL2DZ level were performed to substantiate the structural conclusions based on instrumental techniques. Investigations into the elution behavior, ion exchange reversibility and distribution capacities of the material towards some heavy metal ions were also performed. The distribution coefficients of certain metal ions were determined in different media and following order is observed; Cd(II) > Pb(II) > Zn(II) > Co(II) > Sn(II). Its selectivity was examined by achieving some important binary separations like Co(II)–Cd(II), Pb(II)–Cd(II), Zn(II)–Cd(II) and Sn(II)–Cd(II). The extent of Cd(II) removal was tested by varying the solution parameters like adsorbent dose, adsorbate concentration, pH of the solution, contact time and temperature. The adsorption process followed second order kinetics and adsorption data was best fitted to Langmuir isotherm with correlation coefficient of 0.994. The values of various thermodynamic parameters like ΔG°, ΔS° and ΔH° were also determined. Hence the composite material can be potentially applied to remove Cd(II) from polluted waters.

The review focuses on various hydrogen producing and storing methods that can be employed for creating a hydrogen economy. The latest advancements that have been made on different hydrogen storing materials and hydrogen storing technologies which have proven useful both on gravimetric and volumetric basis, have been highlighted. The encouraging and hopeful aspect of their developments is that the most of the materials are approaching the hydrogen storing capacity requirement that have been laid down by DOE. The classification of different systems has been done on basis of their storage mechanism, keeping in mind their advantages and disadvantages while they tend to store hydrogen both in the atomic and molecular form.

We report batch adsorption studies for the removal of Malachite green from an aqueous solution using 5-sulphosalicylic acid doped tetraethoxysilane (SATEOS) composite material, prepared in our laboratory previously. Various variables studied were the initial dye concentration, adsorbent concentration, pH, contact time and temperature. The maximum percentage of colour was removed at the basic pH of 9. The removal data were fitted to Langmuir and Freundlich adsorption isotherm equations. The values of their corresponding constants were determined from the slope and intercepts of their respective plots. The monolayer adsorption capacity of SATEOS at 323 K was found to be 657.89 mg g−1. The values of various thermodynamic parameters, such as ΔG°, ΔS° and ΔH°, were also determined. A pseudo second-order kinetic model and Lagergren first-order kinetic model were also applied to study the adsorption process. The effective diffusion parameter Di values were estimated at different initial dye concentrations. The mechanism of adsorption was studied using Rechienberg's equation where a linearity test indicates a film diffusion controlled adsorption mechanism. The maximum interaction (IE = 1432.54 kJ mol−1) between SATEOS and the dye molecule, calculated using B3PW91 functional and LanL2MB basis set, was observed when the nitrogen atom of the dye lies at a distance of 1.57 A from the hydrogen of the hydroxyl group present on SATEOS molecule.

Calculations based on second-order Moller–Plesset and density functional theory (DFT) methods using different exchange and correlation functionals are performed on C2H4Nb organometallic complex for its hydrogen storage capacity. We found that this complex can store up to a maximum of 14 H2 molecules using Becke-3 Lee–Yang–Parr (B3LYP)/LanL2DZ method, with a gravimetric H2 uptake capacity of 18.92 wt% and average binding energy of 0.52 eV/H2. The evaluation of the temperature dependence of the Gibbs free energy change (ΔG) of H2 adsorption process indicates that the adsorption of H2 molecules is energetically favorable below 250 K using B3LYP (LanL2DZ) and PBEPBE (LanL2MB, LanL2DZ) level of theories. On the basis of the DFT descriptors, calculated at B3LYP (LanL2DZ) and B3PW91 (LanL2MB) level of theory, we found that the stability of the complex increases with increase in the number of H2 molecules adsorbed by the complex. © 2013 Wiley Periodicals, Inc.

Co-solubilization of the hydrophobic drugs Carbamezipine (CBZ) and Nifedipine (NFD) by micellar solutions at 25 °C, using two series of polyoxyethylene based nonionic surfactants, was measured and compared. The first series is composed of surfactants with a 12 carbon (C12) hydrophobic chain while the second series had 16 carbon (C16) hydrophobic chains. Experimental results were obtained for solubilization and co-solubilization of CBZ and NFD within the micelles at saturation and quantification was done in terms of the molar solubilization ratio and the micelle–water partition coefficient employing spectrophotometric and tensiometric techniques. The extent of micellar solubilization of CBZ is much greater than NFD. The C12 series of surfactants exhibit higher solubilization capacities for CBZ than the C16 series while the reverse is the case for NFD. Co-solubilization results showed competitive solubilization of the drugs. A synergistic effect on the solubilization of NFD was observed in the presence of CBZ in Brij30 and Brij56 surfactant systems while, in the remaining surfactants, the solubility of NFD was slightly reduced. Since the surfactants used in the present study are either nontoxic or have minimal toxicity, it is expected that they can be employed as drug delivery vehicles for co-administration of the two drugs in vivo. Both from industrial and research points of view, this paper reports a comprehensive study for co-solubilization of differently structured drugs in micellar media.

Metal ion binding affinity of three NN bidentate ligands in terms of simple parameters of the conceptual density functional theory is reported. Role of ligand framework for chelate stabilization for ethylenediamine (en) bipyridyl (bpy), and 1,10 phenanthroline (phen) is quantified on the basis of NCCN dihedral angle ( ) and N–N spatial distance. We find that the sigma (σ) donor character of three NN-bidentate ligands follow the order phen

Herein, we report our observations on voltammetric investigations about the redox behaviour of para-nitrotoluene, 1,4-benzoquinone and ferrocene, aimed at exploring the unusual aspects of ion-pairing phenomena in imidazolium-based room temperature ionic liquids (RTILs). Our observations indicate that the stabilization of electrogenerated ion/radical ion intermediates depends upon the potential of the working electrode and the overall composition of RTILs. In light of observed relative trends and quantum mechanical calculations, we propose that the ion-pair stabilization of electrogenerated charged species in RTILs is closely related to the structural organization and composition of electrode/RTIL interface. Copyright © 2012 John Wiley & Sons, Ltd.

Comparative quantitative-structure-toxicity-relationship models developed using various quantum chemical descriptors calculated at semiempirical (AM1, PM3), Hartree–Fock and density functional theory (DFT) (B3LYP) methods, are compared for predicting the toxicity (pIGC50) of 69 aliphatic compounds toward Vibrio fischeri. The multiple linear regression equations, which can assist in modeling toxicity of these compounds, are developed using molecular descriptor, log P (1-octanol/water partition coefficient) in conjunction with two quantum chemical descriptors, electrophilicity index (ω) and energy of the lowest unoccupied molecular orbital (ELUMO). The calculated toxicity values (PIGC50) based on the model equations are compared with the experimental data. In general, the stepwise model regression equations based on quantum chemical descriptor ω in combination with molecular descriptor log P, calculated at DFT(B3LYP) with 6-311G (d,p) and DGDVZP basis sets show better agreement with the experimental data. The electronic origin of the toxicity dependence on descriptors like log P, ω and ELUMO is traced to the cumulative contribution of the lipophilicity and electrophilicity of the chemical moieties to their toxic behavior. © 2012 Wiley Periodicals, Inc.

Ab initio calculations of conformational stabilities, IR absorption and vibrational circular dichroism spectra of four bridged triarylamine helicenes are reported, using DFT/B3LYP/6-31G(d, p) method. We find that the bridged triarylamine helicenes in M configuration are more stable than the helicenes in P-configuration ( Scheme 1 ). The two atropisomers, M and P of the helicene 1 and 2 as well as the two diastereomers of the camphanate derivatives, 3 and 4 , show no significant dissimilarities in the IR absorptions, but the VCD spectra of these molecules are the characteristic feature of the particular isomer and can be used for identification of absolute configuration of these chiral molecular systems, along with experimentally obtained VCD spectra.

Quantum chemical parameters such as LUMO energy, HOMO energy, ionization energy (I), electron affinity (A), chemical potential (μ), hardness (η) electronegativity (χ), philicity (ωα), and electrophilicity (ω) of a series of aliphatic compounds are calculated at the B3LYP/6-31G(d) level of theory. Quantitative structure-activity relationship (QSAR) models are developed for predicting the toxicity (pIGC50) of 13 classes of aliphatic compounds, including 171 electron acceptors and 81 electron donors, towardsTetrahymena pyriformis. The multiple linear regression modeling of toxicity of these compounds is performed by using the molecular descriptor log P(1-octanol/water partition coefficient) in conjunction with two other quantum chemical descriptors, electrophilicity (ω) and energy of the lowest unoccupied molecular orbital (ELUMO). A comparison is made towards the toxicity predicting the ability of electrophilicity (ω) versusELUMOas a global chemical reactivity descriptor in addition to log P. The former works marginally better in most cases. There is a slight improvement in the quality of regression by changing the unit ofIGC50from mg/L to molarity and by removing the racemates and the diastereoisomers from the data set.

The conformational preferences and vibrational circular dichroism of tris(ethylenediamine)ruthenium complex in two main configurations (Lambda) and (Delta), have been performed using density functional theory. We find that for the free [Ru(en)(3)](2+) ion in the Delta-configuration, the conformational stability order is Delta(deltadeltadelta)Delta(lambdadeltadelta)Delta(lambdalambdadelta)Delta(lambdalambdalambda) and that for the Lambda-configuration it is Lambda(deltadeltadelta)Lambda(lambdadeltadelta)Lambda(lambdalambdadelta)Lambda(lambdalambdalambda). The energy differences between the four conformers for both the configurations Delta and Lambda are relatively small, but the activation barriers for ring inversion from one conformation to another are significant, as compared to other such systems. We trace the origin of these results to the lower oxidation state of Ru and relatively larger Ru-N bond length. We have also studied the effect of counterions on the conformational stability for Ru(en)(3)Cl(2.) Our results indicate a reverse stability order for the associated complex, Ru(en)(3) Cl(2) and higher activation barriers for ring inversion as compared to the free complex ion Ru(en)(3)(2+). It is because of larger hydrogen bonding interactions between the three N-H bonds and the chloride ion in these two conformers as compared to other conformations, which is also evident from the VCD spectra of N-H stretching modes. We also investigate IR spectra for all conformations in Delta- and Lambda-configurations and together with energetics and VCD spectra elucidate the spectroscopic characteristics of Ru(en)(3)(2+) complexes with and without the associated counterions.

The equilibrium exchange of Na(I), K(I) and Ca(II) ions with the hydrogen form of zirconium(IV) aluminophosphate has been studied at 30 and 60 °C. On the basis of the exchange isotherms, various thermodynamic parameters such as equilibrium constants (K°), standard free energy (ΔG°), entropy (ΔS°) and enthalpy (ΔH°) changes during the exchange reaction have been calculated. A correlation has been made of these parameters with the ion exchange characteristics of the material.

This work involved the design of a new series of triarylaminehelicenes (TAH) with significant hole transport capacity and enhanced nonlinear optical response. The geometries, electronic properties and nonlinear response of TAH derivatives were studied using density functional theory at the B3PW91/6-311++G (2d, 2p) level. Charge transfer and nonlinear optical response were analyzed and correlated with modifications in geometry and energy levels. Calculations indicated that trivial changes in the torsional angle occur in TAH derivatives with electron-donating substituents as compared to those with electron-withdrawing substituents, resulting in lower reorganization energies for TAH derivatives 2-6. TAH derivatives with an -N(CH3)2 group have the greatest highest occupied molecular orbital (HOMO) level, and thus the least ionization potential, indicating significant hole transfer efficiency as compared to unsubstituted TAH. A decrease in the HOMO-LUMO gap occurs upon substitution with electron-releasing groups, whereas there is an increase in the case of -NO2, -COOH, and -CN TAH derivatives. Topological analysis of the HOMOs of the neutral molecules revealed that these orbitals are concentrated mainly in the helicene backbone, with an important contribution from fused phenyl rings, nitrogen atoms and carbonyl groups. However, the lowest unoccupied molecular orbitals (LUMO) are invariably constituted by fused phenyl rings without any contribution from the central nitrogen atom. Studying the effect of substitution on the nonlinear optical response of TAH derivatives, the calculated polarizability and hyperpolarizability at B3PW91/6-311++G (2d,2p) level of theory exhibited a prominent improvement as compared to unsubstituted TAH. Both electron-donating groups and electron-withdrawing groups result in a red shift in the electronic absorption bands of the substitution derivatives, in particular those with -N(CH3)2 and -NH2 groups.

The density functional theoretical (DFT) computations were performed at the B3LYP/6-311G++(d, p) level to calculate the equilibrium geometry, vibrational wave numbers, intensities, and various other molecular properties of brucine and strychnine, which were found in satisfactory agreement with the experimental data. The out-of-phase stretching modes of aromatic rings and carbonyl stretching modes in combination with CH stretching modes at stereogenic centers generate VCD signals, which are remarkably efficient configuration markers for these chiral molecular systems. NBOs analysis reveals that the large values of second order perturbation energy (47.24 kcal/mol for brucine and 46.93 kcal/mol for strychnine) confirms strong hyperconjugative interaction between the orbital containing the lone pair of electron of nitrogen and the neighboring C O antibonding orbital. The molecular electrostatic potential map of strychnine molecule, with no polar groups other than the lone keto group, shows less polarization, which accounts for its lower susceptibility towards electrophilic attack as compared to brucine.

The Nernst−Planck equations are applied to study the ion-exchange kinetics on the surface of zirconium(IV) aluminophosphate for Li+/H+, Na+/H+, K+/H+, Mg2+/H+, Ca2+/H+, and Sr2+/H+ exchanges in the forward and reverse directions under the conditions favoring particle diffusion. On the basis of these studies, various physical parameters such as the self-diffusion coefficient (D0), the energy of activation (Ea), and the entropy of activation (ΔS*) have been determined and a correlation has been made of these parameters with the ion-exchange characteristics of the material. The study gives an insight into the ion-exchange processes going on in the exchanger phase and its potential use in metal ion separations.

A new inorganic ion exchange sorbent, zirconium aluminophosphate, has been prepared with Na+ ion exchange capacity (iec) equal to 2.10 mequiv/dry g. Its X-ray diffraction studies suggest that it is amorphous in nature. Its characterization has also been done by IR, TGA, and DSC so as to identify various functional groups and ion exchange sites present in the material. Further, various ion exchange studies such as determination of iec, elution behavior, pH titration, and distribution behavior have been performed on this material. Distribution coefficients for some heavy metal ions have also been determined to explore its separation potential. This material shows a high selectivity for Pb(II). On this basis some possible binary separations may be Pb(II)−Cd(II) and Pb(II)−Mg(II) on a column of this material.

Density functional theory calculations were performed on [Ru(L)3]2+ (L = 1,10-phenanthroline, 2,2′-bipyridine, 2,2′-bipyrimidine, 2,2′-bipyrazine) complexes by employing B3PW91 functional and LAN2DZ basis set to predict their spectra and nonlinear optical response. The geometrical and coordination energy studies explained that the stability of [Ru(L)3]2+ metal complexes depends on the extent of interaction of the dπ orbitals of Ru2+ with the π* ligand orbitals, which is maximum for 1,10-phenanthroline. The two enantiomers of the [Ru(L)3]2+ show IR absorption peaks in the region of 1100–1800 cm−1, and a slight shift occurs to lower frequency by solvent. The vibrational circular dichroism peaks of [Ru(phen)3]2+ had major contribution from out-of-phase stretching of 1,10-phenanthroline rings and a minor contribution from H–C=C–H wagging and C=C stretching of rings. Maximum hyperpolarizability was observed for [Ru(phen)3]2+ due to stronger anharmonicity in the π-electron system. Among the [Ru(L)3]2+ (L = bpy, bpm, and bpz) complexes, [Ru(bpm)3]2+ shows enhanced hyperpolarizability due to increase in the dipole along the X-direction. In derivative Ru2+ complexes, we found that hyperpolarizability depends on electron-donating capability of the substituent. As per FMOs study, the HOMO is predominantly metal fragment based, the LUMO is primarily ligand based, and the larger value of hyperpolarizability corresponds to the lower ELUMO–EHOMO gap, reflecting that nonlinear optical response is a consequence of additive dipolar responses of charge transfer and hyperpolarizability.

We report DFT studies on some perylene-based dyes for their electron transfer properties in solar cell applications. The study involves modeling of different donor-π-acceptor type sensitizers, with perylene as the donor, furan/pyrrole/thiophene as the π-bridge and cyanoacrylic group as the acceptor. The effect of different π-bridges and various substituents on the perylene donor was evaluated in terms of opto-electronic and photovoltaic parameters such as HOMO-LUMO energy gap, λmax, light harvesting efficiency(LHE), electron injection efficiency (Oinject), excited state dye potential (Edye*), reorganization energy(λ), and free energy of dye regeneration (ΔGdyeRegen). The effect of various substituents on the dye–I2 interaction and hence recombination process was also evaluated. We found that the furan-based dimethylamine derivative exhibits a better balance of the various optical and photovoltaic properties. Finally, we evaluated the overall opto-electronic and transport parameters of the TiO2-dye assembly after anchoring the dyes on the model TiO2 cluster assembly.