Biomimetic modulation of crystal morphology using gel: From nano to micron-scale architectures

Various in vitro studies have been used to elucidate the roles of matrix molecules in the processes of biomineralization. Among these, gel-diffusion–precipitation methodology is unique. This effective method is capable of characterizing the effects of matrix molecules on mineralization while only using very small quantities of material. Here we discuss the versatility of agar–agar and agarose gel in morphosynthesis of different calcium and barium minerals. Crystalline nano to micron-scale superstructures of these minerals were characterized by means of scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), FT-IR, thermo gravimetric analysis (TGA) and differential scanning calorimetric (DSC) analysis.     

Electrospun self‐assembled nanofiber yarns

A technique for making self‐assembled electrospun (E‐spun) nanofiber yarns from poly(acrylonitrile) in a single step is described. The process involved formation of the nanofiber yarn directly within the electrospinning zone and its removal before it can reach the counter‐electrode. The yarn is presumably formed due to splitting of the main jet into numerous nanojets and their reassembly into a single entity midway between the two electrodes. The process was found to occur at a particular field strength, which varied considerably with the concentration of the polymer dope. The gross morphology of yarns and the alignment of nanofibers in the yarn were evaluated by scanning electron microscopy (SEM). The rationale behind the formation of the yarn like structure has been explained. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Ce–Nd codoping effect on the structural and optical properties of TiO2 nanoparticles

We report the changes in the structural and optical property of TiO₂ nanoparticles on codoping Ce–Nd ions. X-ray diffraction clearly demonstrates the structural changes occurring in the codoped TiO₂ nanoparticle. Oxygen defects disturb the TiO bonds in the TiO₆ octahedra and result in the shifting and broadening of the Raman E_g peak. Pure TiO₂ nanoparticles show absorption peak in the UV region. However, codoped TiO₂ nanoparticles exhibit absorption peaks in the visible region corresponding to the f–d and f–f electronic transition of Ce³⁺ and Nd³⁺ in the crystalline environment of TiO₂. The visible emission peaks of pure and codoped TiO₂ nanoparticles are mainly associated with oxygen vacancies. Incorporation of cerium intensifies the visible emission peaks of TiO₂ nanoparticles. On the other hand, codoping of Nd forms some non radiative recombination centres and increases the possibility of emission energy transfer among dopants, defects, thereby quenching the intensity of the visible emission peaks.     

Recent Advances in Transition Metal‐Catalyzed Methylation Reactions

Methylation is one of the most fundamental synthetic transformations in organic chemistry, but usually employs hazardous and toxic reagents, such as methyl iodide, dimethyl sulfate, diazomethane and dimethyl carbonate. In order to address sustainable development and green strategies, synthetic chemists have devoted much effort to the discovery and development of new methylating reagents, which are successfully being applied in transition metal‐catalyzed cross‐coupling reactions. In this review, recent advances in this area are summarized, mainly including C‐methylation, N‐methylation and O‐methylation. The respective reaction mechanisms are also discussed.

     

Tuning temperature-dependent microstructural properties of tungsten oxide thin films for acetone sensor

Journal of Materials Science: Materials in Electronics - In this paper, the physical properties of thermally evaporated tungsten oxide thin films and their performance towards acetone sensors are...     

Improved Chaotic Dynamics of a Fractional-Order System,its Chaos-Suppressed Synchronisation and Circuit Implementation

This paper presents (1) a new and improved fractional-order chaotic system (FOCS); (2) design of controllers for suppression of chaos for commensurate and incommensurate orders in the regions: \(0<\alpha \le 1\) and \(1<\alpha <2\); (3) synchronisation between the new FOCS (as master) and a non-identical FOCS (as slave) when the master is in either chaotic mode or chaos-suppressed mode and finally (4) analog circuit implementation to validate the numerical simulation results. The rich variety of complex nonlinear dynamical behaviour is explored by varying the parameters as well as the fractional orders. Effective control strategies are designed to suppress chaos in the new system. In addition to this, the paper contributes the idea of synchronisation of the FOCS when it switches between chaotic and chaos-suppressed mode. The control scheme put forward in the paper is able to synchronise the slave with the switching master effectively in spite of change in dynamics. The paper compares the improved features of the newly proposed FO model with a class of well-known FOCSs and elaborates its capability to enhance the performance of secure communication. Circuit implementation results for all the above are in perfect agreement with those obtained through theoretical analyses and numerical simulations and thus reveal that the objectives of the paper are successfully achieved.