Synthesis of inorganic nanomaterials

Synthesis forms a vital aspect of the science of nanomaterials. In this context, chemical methods have proved to be more effective and versatile than physical methods and have therefore, been employed widely to synthesize a variety of nanomaterials, including zero-dimensional nanocrystals, one-dimensional nanowires and nanotubes as well as two-dimensional nanofilms and nanowalls. Chemical synthesis of inorganic nanomaterials has been pursued vigorously in the last few years and in this article we provide a perspective on the present status of the subject. The article includes a discussion of nanocrystals and nanowires of metals, oxides, chalcogenides and pnictides. In addition, inorganic nanotubes and nanowalls have been reviewed. Some aspects of core-shell particles, oriented attachment and the use of liquid-liquid interfaces are also presented.     

Effect of TiO2/reduced graphene oxide composite thin film as a blocking layer on the efficiency of dye-sensitized solar cells

Journal of Solid State Electrochemistry - The objective of the present work was to study the change in efficiency of dye-sensitized solar cells due to introduction of a thin blocking composite...     

Synthesis of dimeric pyridinium bromide under silica supported approach

Abstract

Synthesis of dimeric substituted ester derivative of pyridinium salt with flexible linker units under conventional/silica supported approach. Solid-phase approach is much superior to the conventional method due to nontoxic, solvent free, easy work up procedure, and lesser reaction period. Synthesized dimeric ester derivative of pyridinium salts is showed excellent catalytic response for the preparation of oxizinone derivatives under conventional/approach.     

A new method of preparing single-walled carbon nanotubes

A novel method of purification for single-walled carbon nanotubes, prepared by an arc-discharge method, is described. The method involves a combination of acid washing followed by high temperature hydrogen treatment to remove the metal nanoparticles and amorphous carbon present in the as-synthesized singlewalled carbon nanotubes. The purified single-walled carbon nanotubes have been characterised by low-angle X-ray diffraction, electron microscopy, thermo-gravi-metric analysis and Raman spectroscopy. Dedicated to Professor C N R Rao on his 70th birthday     

Use of fluorous chemistry in the solubilization and phase transfer of nanocrystals, nanorods, and nanotubes

Fluorous chemistry, involving the use of a fluorous label for the functionalization of a substrate and a fluorous solvent for extraction of the functionalized substrate, is shown to be effective in solubilizing gold and CdSe nanoparticles in a fluorous medium, through phase transfer from an aqueous or a hydrocarbon medium. While these nanoparticles were functionalized with a fluorous thiol, single-walled carbon nanotubes and ZnO nanorods could be solubilized in a fluorous medium by reacting them with a fluorous amine. Fluorous chemistry enables the solubilization of the nanostructures in the most nonpolar liquid medium possible.     

Photoluminescence and photoconducting properties of ZnO nanoparticles

Photoluminescence and photoconducting properties of thinfilms of colloidal ZnO nanoparticles have been investigated by annealing them in an oxygen atmosphere at different temperatures. The changes in the defect-related emission and the photoconducting properties with the annealing temperature have been examined in detail.     

GC–MS method for the determination of paraben preservatives in the human breast cancerous tissue

The general presumption that the preservative laden personal care products may be one of the causative agents for breast cancer, has remained a matter of controversy during this decade. Extensive studies have not been carried out to either prove or disprove the role of preservatives in breast cancer incidences. In this study we have developed a new method for the identification and quantification of the preservatives such as methyl paraben (MeP), ethyl paraben (EtP), propyl paraben (PrP) and butyl paraben (BuP) in breast tissue using Gas Chromatography and Mass Spectrometry (GC–MS). Tissue was extracted by using acetone:n-hexane mixture (1:1 v/v) and derivatized with N-Methyl-N-(trimethylsilyl) trifluoroacetamide (MSTFA). The extent of reaction time and the amount of MSTFA to attain greater derivatization were optimized. The developed method yielded good recovery (mean ± SD) of 99.8 ± 5.1, 96 ± 4.4, 107 ± 17 and 113 ± 13% with relative standard deviations (RSDs) of 5.1, 4.6, 15.6 and 13%, and the limits of detection (LOD) of 2.02, 1.05, 1.71 and 3.75 ng g^{− 1} for MeP, EtP, PrP and BuP, respectively. The method was successfully validated for the determination of parabens including butyl paraben (log K_ow = 3.57) in cancerous breast tissues; this could be a promising one for screening of breast tissues and also the environment for paraben residues. As far as our knowledge goes this is the first GC–MS method for the determination of parabens in human tissue.     

Essential Oil Microemulsions Inactivate Antibiotic-Resistant Bacteria on Iceberg Lettuce during 28-Day Storage at 4 °C

The objective of this study was to investigate the antimicrobial activities of essential oil-based microemulsions in the wash water against Escherichia coli O157:H7 and Pseudomonas fluorescens on Iceberg lettuce. Evaluated wash microemulsions included oregano oil, lemongrass oil, and cinnamon oil, along with a plant-based emulsifier for improved solubility. Iceberg lettuce was inoculated for 2 min with E. coli O157:H7 (6.0 log CFU/g) or P. fluorescens (6.0 log CFU/g) and then dip-treated in a phosphate buffered saline (PBS) control, 50 ppm chlorine, 3% hydrogen peroxide treatment or a 0.1%, 0.3%, or 0.5% microemulsion solution. Treated leaves were stored at 4 °C, and analyzed for surviving bacteria on days 0, 3, 7, 10, 14, 21, and 28. Efficacies of the antimicrobials were concentration and storage-time dependent. There was a 1.26–4.86 log CFU/g reduction in E. coli O157:H7 and significant reductions (0.32–2.35 log CFU/g) in P. fluorescens during storage at days 0–28 (p < 0.05). The 0.1% oregano oil microemulsion resulted in the best visual appeal in Iceberg leaves inoculated with E. coli O157:H7 and showed better improvement in the quality of the Iceberg leaves inoculated with spoilage bacteria P. fluorescens. The results suggest that 0.5% cinnamon and 0.3% oregano oil treatments have the potential to provide natural, eco-friendly, and effective alternatives to chemicals for the decontamination of leafy greens, eliminating E. coli O157:H7 and P. fluorescens.     

Controllability Results for Nonlinear Fractional-Order Dynamical Systems

This paper establishes a set of sufficient conditions for the controllability of nonlinear fractional dynamical system of order 1<α<2 in finite dimensional spaces. The main tools are the Mittag–Leffler matrix function and the Schaefer’s fixed-point theorem. An example is provided to illustrate the theory.     

A supervisory control paradigm for real-time control of flexible manufacturing systems

Most of the current academic flexible manufacturing system (FMS) scheduling research has focused on the derivation of algorithms or knowledge-based techniques for efficient FMS real-time control. Here, the limitations of this view are outlined with respect to effective control of actual real-time FMS operation. A more realistic paradigm for real-time FMS control is presented, based on explicit engineering of human and automated control functions and system interfaces. To illustrate design principles within the conceptual model, an example of algorithmic and operator function models for a specific real-time FMS control problem are developed.Portions of this paper have appeared in: Proc. 2nd ORSA/TIMS Conf. on Flexible Manufacturing Systems: Operations Research Models and Applications, Ann Arbor, Michigan, August 12–15, 1986, and Proc. 1986 Int. Conf. on Systems, Man, and Cybernetics, Atlanta, Georgia, October 14–17, 1986.This research was supported in part by the New Faculty Research Program of the Georgia Institute of Technology.