Cationic Precursor Research Articles

이온성 액체 촉매를 이용한 Tricyclopentadiene 합성에 관한 연구

Tricyclopentadiene (TCPD) as a next generation high density fuel was synthesized by Diels-Alder oligomerization reaction of DCPD. TCPD was prepared by ionic liquid (IL) catalysts with combination of cationic and anionic precursors. Two kinds of anionic precursors such as copper(I) chloride (CuCl) and iron(III) chloride () and cationic precursors such as triethylamine hydrochloride (TEAC) and 1-butyl-3-methylimidazolium chloride (BMIC) were used. The preparation of TCPD using IL catalyst was superior to that using Diels-Alder reaction in terms of DCPD conversion and TCPD yield. In addition, TCPD yield was correlated with Lewis acidity by changing the ratio of anionic and cationic precursors. The TCPD yield was higher when using CuCl as anionic precursor than that of using . Control of Lewis acidity by changing the molar ratio of anionic and cationic precursors could further improve TCPD yield as well.

First N-Heterocyclic Carbenes Relying on the Triazolone Structural Motif: Syntheses, Modifications and Reactivity.

4-Phenylsemicarbazide and 1,5-diphenylcarbazide are suitable starting materials for the syntheses of N-heterocyclic carbene (NHC) compounds with new backbone structures. In the first case, cyclisation and subsequent methylation leads to a cationic precursor whose deprotonation affords the triazolon-ylidene 2, which was converted to the corresponding sulfur and selenium adducts and a range of metal complexes. In contrast, cyclisation of diphenylcarbazide affords a neutral betain-type NHC-precursor 7, which is not in equilibrium with its carbene tautomer 7a. Precursor 7 can either be deprotonated to give the anionic NHC 8 or methylated at the N or O atom of the backbone resulting in two isomeric cationic species 16 and 20. Deprotonation of the latter two provides neutral NHC compounds with a carboxamide or carboximidate backbone, respectively. The ligand properties of the new NHC compounds were evaluated by IR and (77) Se NMR spectroscopy. Tolman electronic parameter (TEP) values range from 2050 to 2063 cm(-1) with the anionic NHC 8 being the best overall donor.

Study of Alloying Behavior of Metal Cation Precursors via Polymer Solution Route

Study of Alloying Behavior of Metal Cation Precursors via Polymer Solution Route

Stoichiometrically controlled C–(A)–S–H/N–A–S–H gel blends via alkali-activation of synthetic precursors

The extent to which the composition of the reaction mix affects the formation of a biphasic C–(A)–S–H/N–A–S–H geopolymer framework, and how the interaction of these phases affects geopolymer microstructure, can only be studied by strict stoichiometric control. Stoichiometrically controlled geopolymers containing both C–(A)–S–H and N–A–S–H gels are produced here by reaction of a sodium silicate solution with calcium aluminosilicate powders, which were synthesised via a novel solution-polymerisation method utilising polyethylene glycol as a polymer carrier to sterically inhibit movement of precursor cations. Increased Ca content in the reaction mix appears to promote greater formation of a C–(N)–(A)–S–H gel, while reduced Ca content and increased Al and Si content promote greater formation of an N–A–S–H gel in addition to the main C–(A)–S–H reaction product. The stoichiometrically controlled geopolymers constitute a chemically simplified model system through which the nature of the biphasic C–(A)–S–H/N–A–S–H gels present in alkali activated binders can be studied.

Temperature Dependence of Cationic and Anionic Precursor on Morphological Improvement of CuO Electrodes and Its Consequent Effect on Electrochemical Supercapacitive Properties

The hierarchical structures of hybrid nanostructures like CuO electrodes were investigable made-up on stainless steel via surfactant-free and inexpensive successive ionic layer adsorption and reaction (SILAR) method. Further, these CuO electrodes exhibits outstanding surface properties like uniform growth on surface, high surface area and uniform pore size distribution of CuO samples. The electrochemical properties of CuO nanostructures have been investigated by cyclic voltammetry, charge discharge and electrochemical impedance spectroscopy techniques. The electrochemical studies of the CuO samples show evident influence of surface properties on the pseudo capacitance performance. The maximum specific capacitances of nanopartical/nanoplates like CuO nanosheets are found to be 790 Fg−1 at 5 mV s−1 scan rate. Present investigation suggests the inexpensive SILAR move toward for fine modification surface properties of copper oxide materials for energy storage applications. © 2015 American Scientific Publishers. All rights reserved.

Structural and optical studies of CdS and CdS:Ag nano needles prepared by a SILAR method

Nano-crystalline CdS and Ag-doped CdS films are deposited on glass substrate by a SILAR technique at room temperature with cationic precursors of cadmium nitrate and silver nitrate, and anionic precursor of sodium sulfide with different S:Cd ratio in starting solutions. In order to fabricate samples, substrates were taken in the solutions with determined duration and immersion cycles. To investigate the structural and morphological characteristics of the samples XRD analysis and SEM were used. The X-ray diffraction patterns show that the CdS samples have cubic crystal structure with preferential orientation along the (111) plane and CdS:Ag samples have hexagonal crystal structure with preferential orientation along the (002) plane. Also the peak intensity of XRD patterns of CdS increases with increasing the number of immersion cycles. Optical reflection of the layers is measured with a spectrophotometer and their optical absorption coefficient and band gaps are calculated. The band gap energy of Ag-doped samples decreases respect to CdS samples. It seems that silver doping creates intermediate levels in the energy gap and this causes decreasing of energy gap. Making samples with different S:Cd ratio demonstrates that the sample with 3:1 ratio has highest peak intensity in the XRD pattern and best stoichiometry. It is also observed that with increasing S:Cd ratio, the band gap energy of the samples decreases.

A high efficient photoluminescence Zn–Cu–In–S/ZnS quantum dots with long lifetime

Highly Cu-rich copper indium sulfide (CuInS2, CIS) quantum dots were synthesized utilizing copper chloride (CuCl) and indium acetate (In(Ac)3) as metal cation precursors, combined with n-dodecanethiol (DDT) as a coordinating sulfur source and solvent. With excess of In(Ac)3, i.e. with Cu/In ratios of 1/4, together with Zn2+ ions post-treatment, a relatively high photoluminescence quantum yield (QY) of ∼73% with long average lifetime of ∼359ns has been obtained, which is proposed to be attributed to the Cu-rich defect states in the CIS nanocrystals (NCs) nuclei. Meanwhile, the formation of In-rich CIS–ZnS alloy, i.e. Zn–Cu–In–S (ZCIS) with high density of Cu vacancies, combined with the surface passivation of ZnS overlay resulted in a high QY. Finally, the formation mechanism of the ZCIS/ZnS with Cu-rich nuclei has been proposed.

Nonionic surfactant poly (ethane 1,2-diol)-400 assisted solvothermal synthesis of copper monosulfide (CuS) nanoplates and their structural, topographical, optical and luminescent properties

Copper monosulfide (CuS) nanoplates were prepared by a nonionic surfactant assisted solvothermal method by using a cationic precursor (copper ethanoate dehydrate), an anionic precursor (sulfocarbamide, sulfur source), water–butanol as a mixed solvent and poly (ethane 1,2-diol)-400 as a nonionic surfactant. The X-ray powder diffraction (XRD) and Selected Area Electron Diffraction studies show the formation of the hexagonal phase of CuS (covellite). The functional groups were identified by the FTIR spectrum. The morphology and sizes of the CuS powder have been studied by the Transmission Electron Microscopy analysis. A strong absorption edge was observed in the visible (infrared) region from the optical absorption spectrum, which indicates the presence of the CuS (covellite) structure. The estimated band gap energy of the CuS nanoplates is found to be 2.26eV from the optical band energy curve, which is larger than that of the bulk CuS (2.2eV), showing a blueshift occuring due to the nanosized effect. The photoluminescence emission spectrum of the CuS nanoplates was observed in the strong UV emission peak at 350nm, due to the low sulfur vacancy defect. This defect is related to the high optical quality of the nanocrystal. The possible formation mechanism of the CuS nanoplates is also proposed.

Synergetic Protein Factors That Improve rhGM-CSF Absorption via an Oral Route Exist in Silkworm Pupae.

Recent studies have demonstrated that recombinant human granulocyte macrophage colony-stimulating factor (rhGM-CSF) produced by the silkworm pupae bioreactor is absorbed into blood through oral administration and functions as an active cytokine. The aim of this study was to further examine and identify synergetic protein factors in silkworm pupae that improve rhGM-CSF absorption via an oral route. The concentrations of rhGM-CSF in serum were evaluated in mice after oral administration of rhGM-CSF using different chemical compositions of silkworm pupae as pharmaceutical excipients. The experimental data revealed that the supernatant lyophilized powder (SLP) of a homogenized slurry of silkworm pupae caused a significant increase in the rhGM-CSF level in blood when rhGM-CSF was orally administered with SLP, suggesting that synergetic protein factors that improve the oral absorption of rhGM-CSF primarily exist in SLP. As shown by scanning electron microscopy, microspheres were formed when rhGM-CSF was coated with SLP. Animal experimental data showed that the absorption of orally administered rhGM-CSF through the gastrointestinal (GI) tract primarily resulted from protein factors present in the SLP retentate obtained after 10 kDa ultrafiltration. Surface plasmon resonance spectroscopy analysis demonstrated that several protein factors present in the SLP retentate obtained after 10 kDa ultrafiltration were bound to rhGM-CSF. Proteins bound to rhGM-CSF by liquid chromatography-mass spectrometry were identified as chymotrypsin inhibitor SCI-II precursor, cationic peptide CP8 precursor, Kazal-type proteinase inhibitor, and chymotrypsin inhibitor SCI-I. These findings indicate that these proteinase inhibitors play an important role in improving rhGM-CSF absorption in the GI tract.

Cu-Deficient Plasmonic Cu2–xS Nanoplate Electrocatalysts for Oxygen Reduction

Cation deficient transition metal sulfides have attracted increased attention due to their unique properties that arise from degenerate p-doping, particularly their localized surface plasmon resonance (LSPR) and related optical properties. Here, we present the first study of their electrocatalytic activity. We developed a facile one-pot method to prepare p-doped copper sulfide nanoplates with tunable LSPR at moderate temperature (below 100 °C) without any hot injection or rapid mixing step. The doping level was controlled by varying the concentration of cation precursor (Cu2+) to finely tune the LSPR wavelength without changing the nanoplate size or morphology. Cu2–xS nanoplates with three different doping levels were tested for their electrocatalytic activity for the oxygen reduction reaction (ORR) in alkaline solution. Importantly, increasing the concentration of free holes in Cu2–xS significantly enhanced the ORR catalytic activity. Furthermore, to improve the electrical conductivity, the most heavily ...

Nazarov cyclization of divinyl and arylvinyl epoxides: application in the synthesis of resveratrol-based natural products.

New variation in the Nazarov cyclization has been developed by preparing divinyl and arylvinyl epoxides as pentadienyl cation precursors for the first time. Highly substituted cyclopentadienes, hydrindienes, and indenes were synthesized to demonstrate the compatibility of this reaction with substrates bearing a variety of substitutions and having different types of epoxides. Application of this method in the synthesis of resveratrol-based natural products was also demonstrated.

Effect of the nature of cationic precursors for SILAR deposition on the performance of CdS and PbS/CdS quantum dot-sensitized solar cells

In this work, the influences of cationic precursors on the quality of photoelectrode, consequently on the performance of the quantum dot-sensitized solar cells (QDSCs) have been studied. CdS QDSCs have been prepared using successive ionic layer absorption and reaction (SILAR) method. Three cadmium precursors including nitrate (Cd(NO3)2), chloride (CdCl2), and acetate (Cd(Ac)2) were employed for the synthesis and absorption of CdS nanoparticles on nanostructure TiO2 film. The loading amount and nanoparticle size of the CdS on mesoporous TiO2 film showed a significant difference while using various cadmium precursors in the same SILAR cycles. Both the light-harvesting ability and the obtained incident photon-to-current conversion efficiency values show the trend of deposition rate caused by cadmium precursors. Further, it was proposed that an effective cationic precursor could provide a good connection between QD sensitizer and TiO2 interface by electrochemical impedance spectroscopy analysis. Under AM 1.5 G full one sun illumination, the final power conversion efficiency of CdS QDSC based on Cd(Ac)2 was 2.10 %, and PCE values of 1.57 and 1.20 % were obtained for solar cells sensitized by CdS QDs prepared by CdCl2 and Cd(NO3)2, respectively. The cationic precursor effect was further applied in PbS/CdS co-sensitized solar cells. The PbS/CdS QDSCs based on acetate cationic precursors provide a photocurrent of 19.24 mA/cm2 and PCE of 3.23 % in comparison with 11.26 mA and 2.13 % obtained with nitrate acetate salts. Noticeably, the CdS and PbS/CdS QDSCs based on various cationic precursors prepared by SILAR exhibited good photocurrent stability under several light on–off cycles.

Role of complexing agents on chemicalbath deposited PbS thin film characterization

In the present work, lead sulphide thin films have been grown on soda lime glass substrates by chemical bath deposition technique using three different complexing agents, namely triethanolamine, diethanolamine and hexamine. Aqueous solutions of lead acetate complexed with the above mentioned ligands were used as cationic precursor and thioacetamide as anionic precursor. The structural, morphological, optical and electrical properties of the as-prepared samples were investigated and compared by means of X-ray diffraction (XRD), Scanning electron microscopy (SEM), optical and electrical studies. The films were well crystallized and highly adherent to the substrate with face centered cubic structure. The average crystallite size was found to be in the range 15-20nm. The SEM micrographs showed variations in morphology. Optical studies revealed that the direct band gap energy was in the range of 1.65-2.27eV. The transmittance and reflectance in IR region was respectively in the range of 14%-47% and 25-45%. Optical constants of all films were determined by absorbance and reflection measurements. The room temperature conductivity of the PbS thin films were in the range 9.67×10−9 (Ω-Cm)−1-3.29×10−6(Ω-Cm)−1. The optical band gap energy has inverse relation with grain size and electrical conductivity is closely related to structural parameters like grain size, crystallinity and microstrain. PbS thin film using hexamine as complexing agent was proved to be the best in structural, optical and electrical properties. In this attempt we establish that the use of different complexing agents have immense effect on structural, morphological, optoelectronic and transport properties of PbS thin films.

Controlling the Size, Shape, Phase, Band Gap, and Localized Surface Plasmon Resonance of Cu2–xS and CuxInyS Nanocrystals

We show how indium incorporation can effect the size, morphology, crystal structure, and optical properties of CIS nanocrystals (NCs) and demonstrate a robust methodology for preparing monodisperse plasmonic and nonplasmonic CIS NCs. In contrast with previous methods of producing CIS nanocrystals exhibiting localized surface plasmon resonance (LSPR), which employed expensive and hazardous bis(trimethylsilyl) sulfide, we employ sulfur dissolved in oleic acid as the sulfur donor in combination with appropriate cation precursors to allow production of monodisperse CIS NCs with broad variation of the Cu:In ratio in the products. The crystal phase of the CIS NCs is determined not only by the reactivity of the ligands but also by the cation composition. The LSPR shifted to longer wavelengths with increasing In content until it vanished, while the band gap of the CIS NCs decreased linearly from 2.1 to 1.2 eV. The manipulation of optical properties of CIS NCs with controlled and well-defined size, shape, and phase may open up new possibilities for applying I–III–VI materials in solution-processed optoelectronic devices.

Encapsulation of rat bone marrow stromal cells using a poly-ion complex gel of chitosan and succinylated poly(Pro-Hyp-Gly).

Encapsulation of stem cells into a three-dimensional (3D) scaffold is necessary to achieve tissue regeneration. Prefabricated 3D scaffolds, such as fibres or porous sponges, have limitations regarding homogeneous cell distribution. Hydrogels that can encapsulate cells such as animal-derived collagen gels need adjustment of the pH and/or temperature upon cell mixing. In this report, we fabricated a poly-ion complex (PIC) hydrogel of chitosan and succinylated poly(Pro-Hyp-Gly) and assessed its effect on cell viability after encapsulation of rat bone marrow stromal cells. PIC hydrogels were obtained successfully with a concentration of each precursor as low as 3.0-3.8 mg/ml. The maximum gelation and swelling ratios were achieved with an equal molar ratio (1:1) of anionic and cationic groups. Using chitosan acetate as a cationic precursor produced a PIC hydrogel with both a significantly greater gelation ratio and a better swelling ratio than chitosan chloride. Ammonium succinylated poly(Pro-Hyp-Gly) as an anionic precursor gave similar gelation and swelling ratios to those of sodium succinylated poly(Pro-Hyp-Gly). Cell encapsulation was also achieved successfully by mixing rat bone marrow stromal cells with the PIC hydrogel simultaneously during its formation. The PIC hydrogel was maintained in the culture medium for 7 days at 37°C and the encapsulated cells survived and proliferated in it. Although it is necessary to improve its functionality, this PIC hydrogel has the potential to act as a 3D scaffold for cell encapsulation and tissue regeneration. Copyright © 2015 John Wiley & Sons, Ltd.

Systematic Strategy for Designing Immidazolium Containing Precursors To Produce N-Heterocyclic Carbenes: A DFT Study

A series of cationic N-heterocyclic carbene (NHC) precursors that can be utilized as fluorescent chemosensors for carbon dioxide capture were investigated by density functional theory (DFT) calculations. Activation energy barriers for the reactions of the cationic NHC precursors and hydrogen carbonate (HCO3(-)) based on intrinsic reaction coordinate (IRC) profiles as well as proton affinity of the precursors were compared. The calculated proton affinity of 1-ethyl-3-methylimidazol-2-yliene was in good agreement with experimental one within the margin of error. We clarified main factors to lower the activation energy barrier based on the correlation among the number of N-heterocyclic functional group, aromatic ring size, and structural characteristics for the candidate compounds. On the basis of the results, it was verified that some of our model systems spontaneously generate NHCs without any specific catalyst.

Mesoporous alumina from colloidal biotemplating of Al clusters.

A simple and green synthesis route was disclosed for the achievement of mesoporous alumina microparticles employing polysaccharide nanoparticles (α-chitin nanorods) as templates. Pore textures can be tuned by the cationic alumina precursor. Compared to small cations, the use of Al13 and Al30 oxo-hydroxo clusters leads to better defined and elongated mesopores. Electron microscopy and spectroscopic ((13) C, (27) Al NMR, XPS) measurements demonstrated that this is related to the effective coating of α-chitin nanorods by these pre-condensed colloids.

Synthesis and Characterization of Perovskite Oxides LaAl1−x Ni x O3−δ (0 ≤ x ≤ 0.6) via Co-precipitation Method

Our contribution has focused on the synthesis and characterization of nickel-containing LaAlO3 perovskite, LaAl1−x Ni x O3−δ (0 ≤ x ≤ 0.6) by a co-precipitation method. Nano-powders were successfully synthesized using nitrate salts of lanthanum, aluminium and nickel as cations precursors and sodium hydroxide such as base precipitant by this method and calcined at low temperatures. They were characterized by several techniques: Fourier transform infrared spectroscopy, thermogravimetric and differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), scanning electron microscopy and electrochemical measurements. Thermal analysis shows that the crystallization temperature of the La (Al, Ni) O3−δ precursor gels are estimated as 780 °C by TG–DTA. The XRD patterns of the precursor gels calcined at 700 °C for 6 h have a perovskite structure and the presence of crystalline impurities is not found. The microstructure and morphology of the compounds show that the particles are nearly spherical in shape and are partially agglomerated. Electrochemical measurements indicate that the catalytic activity is strongly influenced by lanthanum doping. The highest electrode performance is achieved with large nickel content.

CuInS<sub>2</sub> Quantum Dot-Sensitized Solar Cells Fabricated via a Linker-Assisted Adsorption Approach

Colloidal chalcopyrite CuInS2 (CIS) quantum dots (aDs) were synthesized using copper(I) iodine (Cul) and indium(III) acetate (InAc3) as metal cationic precursors, and dodecanethiol (DDT) as the sulfur source and solvent. The microstructure and optical properties of the prepared CIS QDs were characterized by X-ray diffraction (XRD), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and UV-Vis absorption spectroscopy. The results showed that the CIS consisted of chalcopyrite phase and exhibited Cu-Au ordering. With prolonged reaction time, the grain sizes of the QDs became larger and the absorption edges of the CIS QDs showed a red-shift owing to the size-induced quantum confinement effect. For the first time, DDT-capped CIS QDs with narrow size distribution were connected to the inner surface of mesoporous TiO2 films via a thioglycolic acid (TGA)-assisted adsorption approach, which was simple and easy to carry out. The adsorption behaviors of both TGA and the CIS QDs on the TiO2 films were detected by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The results indicated that TGA was adsorbed onto the surface of TiO2 via COOH groups while the -SH group was exposed outside, and replaced DDT at the surface of the CIS QDs, leading to the attachment between TiO2 and CIS. It was revealed that the CIS QDs of similar to 3.6 nm in size exhibited the best light absorption capacity and photovoltaic performance. An over-coating of CdS significantly improved the performance of the QDSSCs owing to decreased electron recombination, and a power conversion efficiency of similar to 2.83% was obtained.

Size Dependent Physical Properties of Nanostructured α-Fe2O3 Thin Films Grown by Successive Ionic Layer Adsorption and Reaction Method for Antibacterial Application

Thin films of nanostructured α-Fe2O3 with thickness of 156, 203 and 251 nm were deposited by successive ionic layer adsorption and reaction (SILAR) method onto glass substrates using FeCl3·6H2O and NaOH as cationic and anionic precursors. The X-ray diffraction studies revealed that, α-Fe2O3 thin films are nanocrystalline in nature with rhombohedral structure. The morphological properties were investigated by field emission scanning electron and atomic force microscopy. The optical studies showed that α-Fe2O3 exhibits direct as well as indirect optical band gap energy. The electrical resistivity of α-Fe2O3 at 305 K decreases from 11.76 × 102 to 9.46 × 102 Ω cm as film thickness increases from 156 to 251 nm. The thermo-emf measurements confirmed that α-Fe2O3 exhibits n-type conductivity. The nanocrystalline α-Fe2O3 exhibits antibacterial character against Staphylococcus aureus and its efficiency increases from 37.50% to 87.50% depending on crystallite size.