Role of the Surfactant Structure in the Behavior of Hydrophobic Ionic Liquids within Aqueous Micellar Solutions

The behavior of an ionic liquid (IL) within aqueous micellar solutions is governed by its unique property to act as both an electrolyte and a cosolvent. The influence of the surfactant structure on the properties of aqueous micellar solutions of zwitterionic SB‐12, nonionic Brij‐35 and TX‐100, and anionic sodium dodecyl sulfate (SDS) in the presence of the “hydrophobic” IL 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim][PF₆]) is assessed along with the possibility of forming oil‐in‐water microemulsions in which the IL acts as the “oil” phase. The solubility of [bmim][PF₆] within aqueous micellar solutions increases with increasing surfactant concentration. In contrast to anionic SDS, the zwitterionic and nonionic surfactant solutions solubilize more [bmim][PF₆] at higher concentrations and the average aggregate size remains almost unchanged. The formation of IL‐in‐water microemulsions when the concentration of [bmim][PF₆] is above its aqueous solubility is suggested for nonionic Brij‐35 and TX‐100 aqueous surfactant solutions.     

Solventless protocol for efficient bis-N-boc protection of adenosine, cytidine, and guanosine derivatives

A solvent-free reaction employing a simple low-energy ball mill apparatus converts the amino groups of adenosine, 2-deoxyadenosine, cytidine, 2-deoxycytidine, guanosine, and 2-deoxyguanosine as well as some of their ribosyl O-protected derivatives to the corresponding bis-N-Boc carbamates. In the case of guanosine compounds, the carbonyl group of the base moiety was also blocked as its O-Boc enol carbonate. A variation of this approach using transient in situ O-silylation permitted the preparation of bis-N-Boc nucleosides in which the sugar hydroxyls were unprotected. The ball mill reactions were rapid, convenient, and very high-yielding except in the case of the guanosine compounds. This highly efficient method protects the amino groups of these nucleosides with a base stable and acid labile group suitable for further synthetic manipulation.     

Growth and morphological studies of NiO/CuO/ZnO based nanostructured thin films for photovoltaic applications

At present, inorganic semiconducting materials are the most economical and viable source for the renewable energy industry. The present work deals with the morphological and optical characterization of copper oxide (CuO) and zinc oxide (ZnO) thin films fabricated by layer by layer deposition on nickel oxide (NiO) coated indium tin oxide (ITO) glass by solution processing methods, mainly chemical bath deposition (CBD) and hydrothermal deposition (HTD) processes at room temperature. As a whole, the above inorganic composite materials (NiO/CuO/ZnO) can be applied in photovoltaic cells. An attempt has been made to study structural, morphological and absorption characteristics of NiO/CuO/ZnO heterojunction using state of the art techniques like X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV spectroscopy. The energy band gaps of CuO and ZnO have also been calculated and discussed based on the UV spectroscopy measurements.     

Helicenoid-based bis-1,2,3-triazole tweezer: Synthesis and selective iodide sensing

Abstract

Novel helicenoid based 1,2,3-triazole tweezer 4 was synthesized using a multistep synthetic protocol with high yields from 2,7-Dihydroxynaphtlene 3 as a precursor. This helicenoid-based bis-1,2,3-triazole tweezer 4 selectively causes non-covalent interaction with iodide anion. The UV-vis absorption exhibited enhancement while fluorescence spectra exhibited significant quenching. ¹H NMR titration showed shift of 1,2,3-triazole C-H signal with an increase in iodide concentration. Association constant of 3.818?×?10⁴ M^?1 was recorded for the host interaction with iodide ions. This value of association constant for iodide sensing using 1,2,3-triazole is the best reported so far for hosts with 1,2,3-triazole moiety and suggests that the helicenoid geometry is responsible for this remarkable behavior.     

Proton‐Transfer Reactions of Acridine in Water‐Containing Ionic‐Liquid‐Rich Mixtures

To assess the potential of ionic liquids (ILs) as a solubilizing media that facilitates proton‐transfer reactions, acridine prototropism is investigated using UV/Vis molecular absorbance as well as steady‐state and time‐resolved fluorescence with different ILs in the presence of a small amount of dilute acid or base. It is found that protonation and deprotonation of acridine, when dissolved in different ILs, can be triggered by the addition of a small amount of dilute aqueous HCl and NaOH, respectively, in both the ground and excited states, irrespective of the identity of the IL. However, the amount of dilute acid/base needed to protonate/deprotonate acridine dissolved in different ILs is found to vary from one IL to another. Steady‐state fluorescence measurements also imply the presence of interactions between the acidic proton(s) of IL cation and excited acridine. The interconversion of neutral and protonated acridine, as well as the presence of a weakly fluorescent complex between excited acridine and the acidic proton(s) of the IL cation, is further corroborated by the parameters recovered from the fitting of the excited‐state intensity‐decay data. It is established that ILs as solubilizing media readily support facile proton transfer in both ground and excited states.     

Au Nanoparticles Modified with Pt,Ru and SnO2 as Electrocatalysts for Ethanol Oxidation Reaction in Acids

The anodic reaction in direct ethanol fuel cells (DEFCs), ethanol oxidation reaction (EOR) faces challenges, such as incomplete electrooxidation of ethanol and high cost of the most efficient electrocatalyst, Pt in acidic media at low temperature. In this study, core‐shell electrocatalysts with an Au core and Pt‐based shell (Au@Pt) are developed. The Au core size and Pt shell thickness play an important role in the EOR activity. The Au size of 2.8 nm and one layer of Pt provide the most optimized performance, having 6 times higher peak current density in contrast to commercial Pt/C. SnO₂ as a support also enhances the EOR activity of Au@Pt by 1.73 times. Further modifying the Pt shell with Ru atoms achieve the highest EOR current density that is 15 and 2.5 times of Pt/C and Au@Pt. Our results suggest the importance of surface modification in rational design of advanced electrocatalysts.     

Polymers incorporating backbone thiophene,furan, and alcohol functionalities formed through chemical modifications of alternating olefin–carbon monoxide copolymers

The reaction of the alternating ethylene–carbon monoxide copolymer with Lawesson's reagent resulted in the conversion of 75% of the carbonyl groups to thiophene units. A few thioketone groups were also present in the derived polymer. A polymer with furan units in the backbone was formed upon treatment of the alternating propylene–carbon monoxide copolymer with P₂O₅. Depending on the reaction conditions, up to 90% of the carbonyl groups were converted. Finally, 1,4-polyalcohols were prepared from the alternating propylene-carbon monoxide copolymer by reduction. Hydrogenation using Raney nickel as catalyst resulted in the reduction of 60% of the carbonyl groups, whereas reaction with LiAlH₄ at room temperature caused the reduction of 85% of the carbonyl groups. The glass transition temperature was found to increase monotonically with increasing concentration of hydroxyl groups in the polymer backbone. © 1994 John Wiley & Sons, Inc.     

A branch and price solution approach for order acceptance and capacity planning in make-to-order operations

Make-to-order (MTO) operations have to effectively manage their capacity to make long-term sustainable profits. This objective can be met by selectively accepting available customer orders and simultaneously planning for capacity. We model a MTO operation of a job-shop with multiple resources having regular and non-regular capacity. The MTO firm has a set of customer orders at time zero with fixed due-dates. The process route, processing times, and sales price for each order are given. Since orders compete for limited resources, the firm can only accept some orders. In this paper a Mixed-Integer Linear Program (MILP) is proposed to aid an operational manager to decide which orders to accept and how to allocate resources such that the overall profit is maximized. A branch-and-price (B&P) algorithm is devised to solve the MILP effectively. The MILP is first decomposed into a master problem and several sub-problems using Dantzig-Wolfe decomposition. Each sub-problem is represented as a network flow problem and an exact procedure is proposed to solve the sub-problems efficiently. We also propose an approximate B&P scheme, Lagrangian bounds, and approximations to fathom nodes in the branch-and-bound tree. Computational analysis shows that the proposed B&P algorithm can solve large problem instances with relatively short time.     

Contrasting behavior of classical salts versus ionic liquids toward aqueous phase J-aggregate dissociation of a cyanine dye

The effect of addition of ionic liquids (ILs) on the aggregation behavior of a cyanine dye, 5,5',6,6'-tetrachloro-1,1'-diethyl-3,3'-di(4-sulfobutyl)-benzimidazolocarbocyanine (TDBC), was investigated. In basic aqueous buffer solutions (pH ≥ 10), TDBC preferably exists in its J-aggregated form. Addition of hydrophilic ILs > 5 wt % is observed to disrupt the TDBC J-aggregates, converting them to monomer form most likely because of the interaction between bulky IL cation and the J-aggregates in a time-dependent fashion. This is evidenced by the observed increase in monomer band absorbance at the expense of the absorbance band due to J-aggregates over time. Inorganic salts at similar molar concentrations do not cause this phenomenon but instead induce TDBC precipitation. At low concentrations (<5 wt %), the added IL acts similarly to the inorganic salts, reducing the overall absorbance of TDBC in the solution most likely due to cation exchange causing TDBC precipitation. Addition of a molecular solvent, ethanol, at 15 wt % results in an initial increase in monomer absorbance, albeit to a much lesser extent than for the corresponding molar fraction of IL, which then decreases over time with recovery of J-aggregate absorbance--quite opposite the time-dependent behavior seen for TDBC in PB at pH 12.0 with >5 wt % IL. The unique and dual behavior of ILs as an additive toward affecting cyanine dye aggregation is demonstrated.     

Electrifying the nitrogen cycle: An electrochemical endeavor

The advent of the Haber–Bosch (HB) process has made accessible all forms of nitrogenous derivatives (ammonia, nitrates, nitrites, and amines), revolutionizing the chemical industry. However, the depleting natural resources and growing environmental concerns demand a shift toward an energy-abated and environment-friendly alternative to the HB process, hence the shift in the recent research focus. The electrochemical reduction pathway offers one of the most alluring prospects as a carbon-free, environment-friendly, energy-abated alternative to the HB process. In this context, we provide a holistic overview of the electrochemical pathways for nitrogen fixation into its activated forms and categorically discuss the energetical and technological challenges that researchers encounter, simultaneously highlighting commendable contributions in the field. We also propose research targets that can serve as a benchmark to measure progress toward the practical realization of the electrochemical nitrogen reduction reaction.