Nanostructured Colloidal Solutions of Malachite Green Formulated: Nonlinear Optical Properties and Simulation

Journal of Fluorescence - Malachite green (MG) is a dye that has been presented to use as photosensitizers for photodynamic therapy (PDT). Nonlinear absorption coefficient (β) and nonlinear...     

Analysis of ordered categorical data to develop control charts for monitoring customer loyalty

In the highly competitive business environment of today, the cost to attract new customers is much higher than the cost required to maintain the existing ones. To keep the balance between the acquisition rate and defection rate through executing offensive and defensive marketing policies, it is required to have real time information using an efficient method to monitor customer loyalty. The relationship between customer loyalty and customer satisfaction should be kept in mind when one develops a method for loyalty monitoring. This paper presents several control charts classified in two groups based on the scale used to assess customer loyalty. In the first group of control charts, customer loyalty is considered as a binary random variable modeled by Bernoulli distribution whilst in the second group, an ordinal scale is considered to report loyalty level. Performance comparison of the proposed techniques using ARL criterion indicates that chi‐square and likelihood‐ratio control charts developed based on Pearson chi‐square statistic and ordinal logistic regression model respectively are able to rapidly detect the significant changes in loyalty behavior. To show how to apply the procedures and how to interpret their results, two illustrative synthetic cases are also explained. Copyright © 2009 John Wiley & Sons, Ltd.     

Catalytic study of the copper-based magnetic nanocatalyst on the aerobic oxidation of alcohols in water

A copper-based magnetic nanocatalyst has been prepared by co-precipitation method and characterized by FESEM, EDS, TEM, XRD, XRF, ICP–OES, FTIR, and BET analysis. This new nanocatalyst displays a good activity toward the aerobic oxidation of a wide range of alcohols in water. Moreover, it is recyclable up to five following runs by simple filtration without any significant loss of its catalytic activity.

     

Graphene Quantum Dots Incorporated into β-cyclodextrin: a Novel Polymeric Nanocomposite for Non-Enzymatic Sensing of L-Tyrosine at Physiological pH

Graphene quantum dot-β-cyclodextrin modified glassy carbon electrode was used as a new nanosensor for determination of L-tyrosine (L-Tyr). It was found that graphene quantum dot-β-cyclodextrin has been stably electrodeposited on glassy carbon electrode modified by simple technique. The cyclic voltammograms of the modified electrode in an aqueous solution displayed a pair of well-defined, stable and irreversible reductive/oxidation redox systems. The apparent electron transfer rate constant (k_s) and transfer coefficient (α) determined by cyclic voltammetry were approximately equal to 8.0 s^–1 and 0.7, respectively. The modified electrode showed excellent catalytic activity towards the oxidation of L-Tyr at positive potential in buffer solution. The nanosensor also displayed fast response time, high sensitivity, low detection limit and a remarkably positive potential oxidation of L-Tyr that decreased the effect of interferences in analysis.     

An efficient synthesis of 5‐benzoyloxazolines by regio‐ and stereo‐controlled reaction of N‐substituted 2‐benzoylaziridines under microwave irradiation

Several N‐acyl‐2‐benzoylaziridines were prepared conveniently in good to high yields (71‐93%) and used in the preparation of 5‐benzoyloxazolines (76‐91%) by a regio‐ and stereo‐controlled reaction in the presence of Nal as an efficient catalyst under microwave irradiation in short reaction times (5‐10 mins). The structure of the regioisomeric product was confirmed by X‐ray analysis.     

Syntheses,crystal structures and solvatochromic properties of dinuclear oxalato-bridged copper(II) complexes

Three dinuclear copper(II) complexes, [Cu₂(L¹)₂(μ-ox)](ClO₄)₂?2(CH₃CN), [Cu₂(L²)₂(μ-ox)](ClO₄)₂?H₂O, and [Cu₂(L³)₂(μ-ox)](ClO₄)₂ where ox = oxalato; L = N,N-dimethyl,N′-benzylethane-1,2-diamine, L¹, N,N-diethyl,N′-benzylethane-1,2-diamine, L², N,N-diisoprophyl,N′-benzylethane-1,2-diamine, L³, were prepared and characterized by elemental analyses, spectral (IR, UV–Vis) data and molar conductance measurements. The crystal structures of [Cu₂(L¹)₂(μ-ox)](ClO₄)₂?2(CH₃CN) and [Cu₂(L³)₂(μ-ox)](ClO₄)₂ have been determined by single-crystal X-ray analysis. Solvatochromic behaviors were investigated in various solvents, showing positive solvatochromism. The effect of steric hindrance around the copper ion imposed by N-alkyl groups of the diamine chelates on the solvatochromism property of the complexes is discussed. Solvatochromism was also studied with different solvent parameter models using stepwise multiple linear regression method.     

Chemical composition and antioxidant activity of the essential oil and various extracts of Haplophyllum robustum Bge

This study was designed to examine the chemical composition and in vitro antioxidant activity of the essential oil and various extracts of Haplophyllum robustum. GC-MS analysis of the oil resulted in the identification of 30 compounds, representing 99.2% of the oil; 1,8-cineole (38.1%), myrcene (10.7%), α-pinene (8.5%), 4-terpineol (7.0%) and sabinene (6.1%) were the main components. The antioxidant potential of the oil and extracts was evaluated using three separate methods: inhibition of the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH), β-carotene-linoleic acid assay and reducing power systems. The essential oil of the plant was able to reduce the stable free radical DPPH with an IC(50) of 72.0?±?1.2?μg?mL(-1) (the IC(50) for ascorbic acid was determined as 5.8?±?0.4?μg?mL(-1)). The essential oil also showed strong reducing power. The level of total phenolics was highest in the essential oil (179.5?±?2.1?μg?mg(-1)).     

DOX delivery based on chitosan-capped graphene oxide-mesoporous silica nanohybride as pH-responsive nanocarriers

Journal of Sol-Gel Science and Technology - pH-responsive chitosan-coated graphene oxide-mesoporous silica nanoparticles (GMSN-Cs) was synthesized as a core–shell nanosheets to be used as DOX...     

Studies on the Synthesis and Dynamic NMR Properties of 2-(Benzylidene amino)-N-[(R)-2-hydroxy-2-methyl-1-phenylpropyl]acetamide

An efficient method was employed for the preparation of 2-(benzylideneamino)-N-[(R)-2-hydroxy-2-methyl-1-phenylpropyl] acetamide utilizing optically pure (R)-5,5-dimethyl-4-phenyloxazolidin-2-one. This product showed interesting dynamic NMR properties for the methylene protons adjacent to the azomethine group (ΔG^? = 15.1 ± 0.1 kcal mol^-1).