Diacidic ionic liquid supported on magnetic-silica nanocomposite: a novel,stable, and reusable catalyst for selective diester production

Abstract

Supported diacidic ionic liquid on magnetic silica nanoparticles (SDAIL@magnetic nanoSiO₂) was successfully prepared through a multi-step approach. 2,2- bis ((3- methylimidazolidin-1-yl) methyl) propane- 1,3- diol bromide salt was immobilized onto the surface of magnetic silica nanoparticles via covalent bonding to prepare a novel powerful acidic catalyst. The synthesized catalyst was characterized by FT-IR, SEM, TGA, VSM, N₂ adsorption–desorption measurements and acid-base titration. The catalytic activity of the prepared SDAIL@magnetic nanoSiO₂ was investigated for the selective diesterification of alcohols by phthalic anhydride to afford corresponding dialkyl plasticizers under solvent-free conditions. The nature of two acidic counter anions as well as the presence of Lewis acidic species (Fe₃O₄) on the magnetic nanosilica and high surface area of the nanosilica influenced the behavior of the catalyst. Surperisingly, the high acidic character of the catalyst facilitates the reaction with a short reaction time. Furthermore, TG analysis strongly demonstrates that major content of IL is still stable on the support up to 290 °C, so catalyst has a good thermal stability. Under the optimized conditions, the conversion of phthalic anhydride was 100% and diester plasticizers were obtained with excellent yields (80–100%). The SDAIL@magnetic nanoSiO₂ catalyst showed a good reusability and could be easily separated from the reaction mixture using an external magnet thanks to its superparamagnetic behavior and reused for several runs without significant activity loss. An important advantage of the SDAIL@magnetic nanoSiO₂ was its high-hydrophilicity resulted in excellent selectivity towards the formation of only diesters which are commonly used plasticizers in different industries.Graphical abstract

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Nanocrystalline ruthenium oxide and ruthenium in sensing applications – an experimental and theoretical study

In this project, we have explored RuO₂ and Ru nanoparticles (∼ ∼10 and ∼ ∼5 nm, respectively, estimated from XRD data) to be used as gate material in field effect sensor devices. The particles were synthesized by wet chemical procedure. The capacitance versus voltage characteristics of the studied capacitance shifts to a lower voltage while exposed to reducing gases. The main objectives are to improve the selectivity of the FET sensors by tailoring the dimension and surface chemistry of the nanoparticles and to improve the high temperature stability. The sensors were characterized using capacitance versus voltage measurements, at different frequencies, 500 Hz to 1 MHz, and temperatures at 100–400°C. The sensor response patterns have been found to depend on operating temperature. X-ray photoelectron spectroscopy (XPS) analyses were performed to investigate the oxidation state due to gas exposure. Quantum-chemical computations suggest that heterolytic dissociative adsorption is favored and preliminary computations regarding water formation from adsorbed hydrogen and oxygen was also performed.     

Periodic behavior of a nonlinear dynamical system

Nonlinear dynamical systems, being more of a realistic representation of nature, could exhibit a somewhat complex behavior. Their analysis requires a thorough investigation into the solution of the governing differential equations. In this paper, a class of third order nonlinear differential equations has been analyzed. An attempt has been made to obtain sufficient conditions in order to guarantee the existence of periodic solutions. The results obtained from this analysis are shown to be beneficial when studying the steady-state response of nonlinear dynamical systems. In order to obtain the periodic solutions for any form of third order differential equations, a computer program has been developed on the basis of the fourth order Runge-Kutta method together with the Newton-Raphson algorithm. Results obtained from the computer simulation model confirmed the validity of the mathematical approach presented for these sufficient conditions.     

Periodicity and chaos in a flexible crank-rocker mechanism

In this paper we introduce a crank-rocker mechanism at which the rocker is flexible. Using Hamilton’s principle we obtain the governing equations of motion for the elastic mode of the rocker. By applying the Bubnov–Galerkin global averaging method, we reduce the governing equations of motion to an ordinary differential equation which is Duffing’s oscillator with time varying coefficients. Through the application of Banach’s fixed-point theorem we predict the periodic solutions. Then we study the geometrical features of the motion near the 1 : 1, 1 : 2 and 2 : 1 commensurabilities. It is also shown that homoclinic and heteroclinic orbits can exist for the system.     

V(HSO_4)_3 promoted oxidation of alcohols and trimethylsilyl,tetrahyropyranyl and methoxymethyl ethers with Cu(NO_3)_2·3H_2O in the absence of solvent

V(HSO_4)_3 has been found to be an efficient reagent for the promotion of the oxidation of alcohols and trimethylsilyl, tetrahydropyranyl and methoxymethyl ethers to their corresponding carbonyl compounds with Cu(NO_3)_2·3H_2O in the absence of solvent.     

On inner automorphisms and certain central automorphisms of groups

Let G be a group, let M and N be two normal subgroups of G. We denote by Aut _N ^M (G), the set of all automorphisms of G which centralize G/M and N. In this paper we investigate the structure of a group G in which one of the Inn(G) = Aut _N ^M (G), Aut _N ^M (G) ≤ Inn(G) or Inn(G) ≤ Aut _N ^M (G) holds. We also discuss the problem: “what conditions on G is sufficient to ensure that G has a non-inner automorphism which centralizes G/M and N”.     

Immunogenic Potential and Therapeutic Efficacy of Multi-Epitope Encapsulated Silk Fibroin Nanoparticles against Pseudomonas aeruginosa-Mediated Urinary Tract Infections

Pseudomonas aeruginosa (P. aeruginosa) causing urinary tract infections (UTIs) are a major concern among hospital-acquired infections. The need for an effective vaccine that reduces the infections is imperative. This study aims to evaluate the efficacy of a multi-epitope vaccine encapsulated in silk fibroin nanoparticles (SFNPs) against P. aeruginosa-mediated UTIs. A multi-epitope is constructed from nine proteins of P. aeruginosa using immunoinformatic analysis, expressed, and purified in BL21 (DE3) cells. The encapsulation efficiency of the multi-epitope in SFNPs is 85% with a mean particle size of 130 nm and 24% of the encapsulated antigen is released after 35 days. The vaccine formulations adjuvanted with SFNPs or alum significantly improve systemic and mucosal humoral responses and the cytokine profile (IFN-γ, IL-4, and IL-17) in mice. Additionally, the longevity of the IgG response is maintained for at least 110 days in a steady state. In a bladder challenge, mice treated with the multi-epitope admixed with alum or encapsulated in SFNPs demonstrate significant protection of the bladder and kidneys against P. aeruginosa. This study highlights the promising therapeutic potential of a multi-epitope vaccine encapsulated in SFNPs or adjuvanted with alum against P. aeruginosa infections.     

New approach for the synthesis of novel acenaphtho[1,2-b]furan-8-amines

A new approach for the preparation of new 9-(alkyl or aryl)acenaphtho[1,2-b]furan-8-(alky or aryl) amine derivatives has been reported by the catalyst-free one-pot cyclocondensation of (acenaphthylen-1-yloxy)trimethylsilane, alkyl and aryl aldehydes, and aryl and alky isocyanides in refluxing DMF.     

On the existence of periodic solutions for the quasi‐linear third order system of O.D.Es

In this paper we concern with the nonlinear third order quasi‐linear system of ordinary differential equations as: X′′′ + Λ X′ = ϵ F(X, X′, X″) where X ∈ ℝⁿ and Λ is a diagonal matrix. We obtain some simple sufficient conditions for the existence of periodic solution using theorem of Brouer's degree. As we showed earlier [1], the scalar form the (1) can be treated by the Implicit Function Theorem instead of Brouer degree. Also because of the possibility of rewriting a 2n + 1 order equation into a third order system by a simple transformation [2], we can obtain useful results for such equations too. The main problem for this kind of equations is the validity of the results for the parameter free problem, i.e. when ϵ = 1. We consider it by study of dynamic of curves formed by the initial conditions that force the system be periodic when ϵ starts to increase.