Y-shape structured azo dyes with self-transforming feature to zwitterionic form as sensitizer for DSSC and DFT investigation of their photophysical and charge transfer properties.

Two novel azo dyes with D-π-A-π-D structures were designed and synthesized to investigate the relationship between molecular structure and sensitizing performance on applying for dye-sensitized solar cells (DSSCs) in comparison with their linear counterparts. Introducing hydroxyl auxiliary groups and arranging π-conjugation length as two parallel and series structural architectures, Y-shape and linear, led to red shift in absorption wavelength and increase in absorption intensity for the Y-shape pattern providing an efficient charge transfer pathway and improved Jsc and η of the DSSCs. Emerging a zwitterionic form, azonium structure, of the sensitizer in parallel configuration for the dyes 1a.p and 1b.p, enhanced light absorption domain and changed anchoring fashion could engendering improved electronic overlapping. The easily-synthesized dyes were evaluated for photophysical and electrochemical properties and turned out that the parallel-decorated dyes displayed better results than the series types as photosensitizers for DSSCs. ATR and Raman spectra clearly showed the adsorption of these dyes on the TiO2 surface. Operational tests of DSSCs, coated by titled azo dyes, illustrated that decorating π-conjugation pattern as parallel structure as well as accessorizing the donor unit with hydroxyl groups improved the photovoltaic performance. Optimized band gap due to participating the azonium structure and restricted electron recombination as well as rectified dye regeneration were proposed as main elements in enhancing performance parameters. A higher solar conversion efficiency was recorded for DSSCs based on the Y-shape dyes compared to other meta azo dye-based cells that were previously reported. Computational calculations were used to corroborate the opto-electrochemical traits of the dyes with a special concern on the influence of structural pattern on photovoltaic features.

Properties of a furan ring-opening reaction in aqueous micellar solutions for selective sensing of mesalazine.

A novel and efficient non-azo formation based method was developed for trace sensing of mesalazine (MES), a pharmaceutical aromatic amine. MES was simply coupled with a Meldrum's activated furan (MAF) reagent via a furan ring opening reaction to form a colored product. The intense purple colored solution was detected at 575 nm. The reaction of MES with MAF was monitored by employing 1H NMR spectroscopy and mass spectrometry. In addition, density functional theory (DFT) was applied to optimize the structure of the colored product and its λmax (the wavelength of maximum absorbance) in dimethyl sulfoxide and water. The colored product was considered in three possible structures, and the most possible structures in dimethyl sulfoxide and in water were identified by employing the DFT calculations. Both of the most possible structures indicated only a local excitation in their λmax and no charge transfer was observed. However, one of the structures in dimethyl sulfoxide presented charge transfer properties occurring through NCCC moiety. A univariate optimization method was also used to attain the optimum condition for analysis. In addition, the dependence of the analytical response on the three main affecting parameters (reaction time (X1), Triton X-100 concentration (X2) and MAF concentration (X3)) was identified by employing a central composite design (CCD) approach. The CCD study showed that the analytical response depends complexly on the parameters. Beer's law was obeyed within the range of 0.06-9.30 µg mL-1 of MES (155 fold linearity) at 575 nm, under the optimum condition introduced by the CCD approach. Also, the limit of detection was obtained 0.04 µg mL-1 of MES. The method showed precision (as relative standard deviation) and accuracy (as recovery) within the ranges of 0.6-3.2 % and 96.3-100.8%, respectively. Various organic and inorganic species, amino-pharmaceuticals, and amino acids were tested to evaluate the selectivity of the method. The selectivity of the analytical method was satisfactory. The method was successfully applied for detection of MES in various water matrices and pharmaceutical tablets.

Melting Behavior of Bimetallic and Trimetallic Nanoparticles: A Review of MD Simulation Studies.

In recent years, bimetallic and trimetallic nanoparticles (NPs) have become attractive materials for many researchers especially in the field of catalysis due to their interesting physical and chemical properties. These unique properties arise mainly from simultaneous effects of two different metal atoms in their structure. In this review, recent theoretical studies on these NPs using molecular dynamics simulation are presented. Since investigation of thermodynamic stabilities of metallic NPs is a critical factor in their construction for catalytic applications, our focus in this review is on the thermal stability of bimetallic and trimetallic NPs. The melting behavior of these materials with different atomic arrangements including core-shell, three-shell, crown-jewel, ordered and disordered alloy, and Janus materials are discussed. Other factors including stress, strain, atomic radius, thermal expansion coefficient, cohesive energy, surface energy, size, composition, and morphology are described in detail, because these properties lead to complexity in the melting behavior of bimetallic and trimetallic NPs.

A facile and regioselective one-pot synthesis of novel pyrazolo[1[Formula: see text],5[Formula: see text]:1,2]pyrrolo[3,4-b]quinoline-2,3-dicarboxylate hybrids via intramolecular Wittig reaction.

The regioselective syntheses of novel pyrazolo[1[Formula: see text],5[Formula: see text]:1,2]pyrrolo[3,4-b]quinoline-2,3-dicarboxylates (6a-l) from pyrrolo([3,4-b]quinolin-2(3H)-yl)benzamides through an intramolecular Wittig reaction are described. This protocol takes advantages of mild conditions, simple workup and high yield which make this method attractive for the synthesis of these hybrid of pyrazolo[1[Formula: see text],5[Formula: see text]:1,2]pyrrolo[3,4-b]quinolines.

Au@void@AgAu Yolk-Shell Nanoparticles with Dominant Strain Effects: A Molecular Dynamics Simulation.

Au@void@AgAu yolk-shell nanoparticles with different morphologies were studied by classical molecular dynamics simulation. The results indicated that all of simulated yolk-shell nanoclusters with ∼3.8 nm size and different morphologies are unstable at room temperature, and collapse of the shell atoms into the void space completely fills it and creates more stable Au@AgAu core-shell structures. Also, it was observed that thermodynamic stabilities of the created core-shell structures strongly depend on the morphology of nanocluster, for which competition between strain and surface energy effects plays the key role in this phenomenon. Within this competition, strain effect is dominant and helps the stability of the created core-shell structure. Herein, the icosahedral nanocluster with the lowest strain effect exhibits the highest thermodynamic stability. By comparing the simulation results with experimental data, it was concluded that the essential factor that controls the stability of these nanoparticles is their size.

Au@Void@Ag Yolk-Shell Nanoclusters Visited by Molecular Dynamics Simulation: The Effects of Structural Factors on Thermodynamic Stability.

Au@void@Ag yolk-shell nanoclusters were studied by molecular dynamics simulation in order to study the effects of core and shell sizes on their thermodynamic stability and structural transformation. The results demonstrated that all of simulated nanoclusters with different core and shell sizes are unstable at temperatures lower than 350 K in such a way that Ag atoms are collapsed into the void space and fill it, which leads to creation of a more stable core-shell morphology, and at the melting point, only core-shell structures with altered thickness of the shell exist. Also, at higher temperatures, Au atoms tend to migrate toward the surface, and an increase of both the core and shell sizes leads to an increase of the thermodynamic stability. Moreover, a Au147@void@Ag252 nanocluster with the largest core and shell and minimum void space exhibited the most thermodynamic stability and highest melting point. Generally, the core and shell sizes affect the stability and thermal behavior of yolk-shell nanoclusters cooperatively.

Delivery of Cisplatin Anti-Cancer Drug from Carbon, Boron Nitride, and Silicon Carbide Nanotubes Forced by Ag-Nanowire: A Comprehensive Molecular Dynamics Study.

In this work, liberation of cisplatin molecules from interior of a nanotube due to entrance of an Ag-nanowire inside it was simulated by classical molecular dynamics method. The aim of this simulation was investigation on the effects of diameter, chirality, and composition of the nanotube, as well as the influence of temperature on this process. For this purpose, single walled carbon, boron nitride, and silicon carbide nanotube were considered. In order for a more concise comparison of the results, a new parameter namely efficiency of drug release, was introduced. The results demonstrated that the efficiency of drug release is sensitive to its adsorption on outer surface of the nanotube. Moreover, this efficiency is also sensitive to the nanotube composition and its diameter. For the effect of nanotube composition, the results indicated that silicon carbide nanotube has the least efficiency for drug release, due to its strong drug-nanotube. Also, the most important acting forces on drug delivery are van der Waals interactions. Finally, the kinetic of drug release is fast and is not related to the structural parameters of the nanotube and temperature, significantly.

A molecular dynamics study of the effect of the substrate on the thermodynamic properties of bound Pt-Cu bimetallic nanoclusters.

In this work confinement of the Pt708Cu707 bimetallic nanocluster in single-walled carbon, boron nitride, and silicon carbide nanotubes was investigated using molecular dynamics simulation. The results of the calculations showed that at 50% composition, a eutectic-like behavior is seen during the melting-freezing process. Also, the Pt708Cu707 bimetallic nanocluster tends to have a core-shell like structure with a Pt-rich core and a Cu-rich shell, except for boron nitride nanotubes in which the nanocluster exhibits a completely different pattern on the tube wall. The Pt-Cu nanoclusters confined in boron nitride nanotubes are extremely extended on the tube wall in such a way that most of the nanotube-nanocluster interface is covered by a monolayer metal coating which can promise unique physical and chemical properties for these types of nanocomposites. Also, extension of the nanocluster on the substrate surface reduces its melting point.

Synthesis of nano-sized stereoselective imprinted polymer by copolymerization of (S)-2-(acrylamido) propanoic acid and ethylene glycol dimethacrylate in the presence of racemic propranolol and copper ion.

A new chiral functional monomer of (S)-2-(acrylamido) propanoic acid was obtained by reaction of (l)-alanine with acryloyl chloride. The resulting monomer was characterized by FT-IR and HNMR and then utilized for the preparation of chiral imprinted polymer (CIP). This was carried out by copolymerization of (l)-alanine-derived chiral monomer and ethylene glycol dimethacrylate, in the presence of racemic propranolol and copper nitrate, via precipitation polymerization technique, resulting in nano-sized networked polymer particles. The polymer obtained was characterized by scanning electron microscopy and FT-IR. The non-imprinted polymer was also synthesized and used as blank polymer. Density functional theory (DFT) was also employed to optimize the structures of two diasterometric ternary complexes, suspected to be created in the pre-polymerization step, by reaction of optically active isomers of propranolol, copper ion and (S)-2-(acrylamido) propanoic acid. Relative energies and other characteristics of the described complexes, calculated by the DFT, predicted the higher stability of (S)-propranolol involved complex, compared to (R)-propranolol participated complex. Practical batch extraction test which employed CIP as solid phase adsorbent, indicated that the CIP recognized selectively (S)-propranolol in the racemic mixture of propranolol; whereas, the non-imprinted polymer (NIP) showed no differentiation capability between two optically active isomers of propranolol.

H2 adsorption on Ag-nanocluster/single-walled carbon nanotube composites: a molecular dynamics study on the effects of nanocluster size, diameter, and chirality of nanotube.

The H2 physisorption on AgN (with N = 32, 108, 256, 500, and 864)/carbon nanotube (CNT; in armchair and zigzag structures with diameters between 0.54 and 2.98 nm) composites were studied by molecular dynamic simulation to investigate the effect of nanocluster size, diameter, and chirality of nanotube on the adsorption phenomena. The calculations indicate that the effects of nanocluster properties are more important than those of the nanotube, in such a way that increase of nanocluster size, decreases the H2 adsorption. Also, the diameter and chirality of CNTs have considerable influence on the adsorption phenomena. As the diameter of nanotube is increased, the amount of adsorption is decreased. Moreover, H2 molecules have more tendencies to those nanoclusters located on the armchair nanotubes than the zigzag ones. Another important result is the reversibility of H2 adsorption on these materials in which the structure of composite in vacuum and after reduction of H2 pressure to zero, is not changed, considerably.

The role of nano-sized manganese oxides in the oxygen-evolution reactions by manganese complexes: towards a complete picture.

Eighteen Mn complexes with N-donor and carboxylate ligands have been synthesized and characterized. Three Mn complexes among them are new and are reported for the first time. The reactions of oxygen evolution in the presence of oxone (2KHSO5·KHSO4·K2SO4) and cerium(iv) ammonium nitrate catalyzed by these complexes are studied and characterized by UV-visible spectroscopy, X-ray diffraction spectrometry, dynamic light scattering, Fourier transform infrared spectroscopy, electron paramagnetic resonance spectroscopy, transmission electron microscopy, scanning electron microscopy, membrane-inlet mass spectrometry and electrochemistry. Some of these complexes evolve oxygen in the presence of oxone as a primary oxidant. CO2 and MnO4(-) are other products of these reactions. Based on spectroscopic studies, the true catalysts for oxygen evolution in these reactions are different. We proposed that for the oxygen evolution reactions in the presence of oxone, the true catalysts are both high valent Mn complexes and Mn oxides, but for the reactions in the presence of cerium(iv) ammonium nitrate, the active catalyst is most probably a Mn oxide.