Great Enhancement (great + enhancement)

Distribution by Scientific Domains

Selected Abstracts

Gold Nanorods: From Synthesis and Properties to Biological and Biomedical Applications

Xiaohua Huang
Abstract Noble metal nanoparticles are capable of confining resonant photons in such a manner as to induce coherent surface plasmon oscillation of their conduction band electrons, a phenomenon leading to two important properties. Firstly, the confinement of the photon to the nanoparticle's dimensions leads to a large increase in its electromagnetic field and consequently great enhancement of all the nanoparticle's radiative properties, such as absorption and scattering. Moreover, by confining the photon's wavelength to the nanoparticle's small dimensions, there exists enhanced imaging resolving powers, which extend well below the diffraction limit, a property of considerable importance in potential device applications. Secondly, the strongly absorbed light by the nanoparticles is followed by a rapid dephasing of the coherent electron motion in tandem with an equally rapid energy transfer to the lattice, a process integral to the technologically relevant photothermal properties of plasmonic nanoparticles. Of all the possible nanoparticle shapes, gold nanorods are especially intriguing as they offer strong plasmonic fields while exhibiting excellent tunability and biocompatibility. We begin this review of gold nanorods by summarizing their radiative and nonradiative properties. Their various synthetic methods are then outlined with an emphasis on the seed-mediated chemical growth. In particular, we describe nanorod spontaneous self-assembly, chemically driven assembly, and polymer-based alignment. The final section details current studies aimed at applications in the biological and biomedical fields. [source]

Novel Multifunctional Properties Induced by Interface Effects in Perovskite Oxide Heterostructures

Kui-juan Jin
Abstract Multilayer structures have emerged as a leading research topic and researchers expect that multilayers may lead to interesting artificial materials with novel properties. In this Research News we show that the introduction of interfaces into perovskite oxides can induce a series of novel properties including an unusual positive magnetoresistance, great enhancement of lateral photovoltage in La0.9Sr0.1MnO3/SrNb0.01Ti0.99O3, and an electrical modulation of the magnetoresistance in multi-p-n heterostructures of SrTiO3,,/La0.9Sr0.1MnO3/SrTiO3,,/La0.9Sr0.1MnO3/Si. This novel positive magnetoresistance is attributed to the creation of a space charge region at the interface where the spin of the carriers is anti-parallel to that of the carriers in the region far from the interface of manganese oxide in the heterostructures. [source]

Microwave-Accelerated Polymerization of 2-Phenoxymethyl-1,4,6-trioxaspiro[4,4]nonane with Diglycidyl Ether of Bisphenol A

Judit Canadell
Abstract The cationic copolymerization of 2-phenoxymethyl-1,4,6-trioxaspiro[4,4]nonane with DGEBA under microwave irradiation using ytterbium and lanthanum triflates as initiators is described. A comparison with thermal heating showed a great enhancement in the reaction rates and a higher SOE incorporation in the network. The double ring opening of SOE reduces the usual shrinkage of epoxy resins on curing, and it was lower under microwave irradiation. Moreover, the ytterbium triflate initiator lead to a higher incorporation of linear ester moieties in the network than lanthanum triflate. [source]

Biodegradable nanocomposites from maleated polycaprolactone/soy protein isolate blend with organoclay: Preparation, characterization, and properties

Abhisek Sasmal
New biobased, eco-friendly nanocomposites were prepared from maleated polycaprolactone/soy protein isolate blend (50/50 wt/wt) with organo-modified clay by melt compounding. The XRD, TEM, tensile, DMTA, and rheological properties of the nanocomposites were investigated. X-ray diffraction and transmission electron microscopy analysis revealed that the intercalated nanocomposite is formed and the silicate layers of the clay are uniformly dispersed at a nanometer scale in the polymer matrix. There is a great enhancement in tensile and dynamic mechanical properties of the nanocomposites. Rheological study revealed that the nanocomposite exhibits strong shear thinning behavior and clay particles form network in the melted state of the composites. POLYM. COMPOS., 2009. 2008 Society of Plastics Engineers [source]

Preparation and linear rheological behavior of polypropylene/MMT nanocomposites

Li Jian
Maleic anhydride grafted low isotactic homopolypropylene elastomer (LiPP-g-MAH) is used as a compatibilizer in the melting mixing of polypropylene (PP) and clay. The microstructures of the composites of PP/clay (PPCN) are investigated using a wide-angle X-ray diffractometer (WAXD) and transmission electron microscope (TEM) as well as parallel rheometer, which show that PPCN with different phase morphologies have been obtained. It is found that the weight ratio of LiPP-g-MAH to clay and the weight content of LiPP-g-MAH in PPCN have a strong effect on the final dispersibility of the clay. The rheological response to small amplitude oscillatory shear (SAOS) shows that the storage modulus (G,) at the low frequencies is greatly sensitive to the microstructures in comparison with WAXD measurements. The investigation further indicates that the virgin clay particles, intercalated silicate crystallites, and exfoliated layers may coexist in the matrix at the same time, resulting in the great enhancement of G, plateau at low frequency region. [source]

Simultaneous determination of eight major steroids from Polyporus umbellatus by high-performance liquid chromatography coupled with mass spectrometry detections

Ying-yong Zhao
Abstract Polyporus umbellatus is a widely used diuretic herbal medicine. In this study, a high-performance liquid chromatography coupled with atmospheric pressure chemical ionization,mass spectrometric detection (HPLC-APCI-MS) method was developed for qualitative and quantitative analysis of steroids, as well as for the quality control of Polyporus umbellatus. The selectivity, reproducibility and sensitivity were compared with HPLC with photodiode array detection and evaporative light scattering detection (ELSD). Selective ion monitoring in positive mode was used for qualitative and quantitative analysis of eight major components and ,-ecdysterone was used as the internal standard. Limits of detection and quantification fell in the ranges 7,21 and 18,63 ng/mL for the eight analytes with an injection of 10 L samples, and all calibration curves showed good linear regression (r2 > 0.9919) within the test range. The quantitative results demonstrated that samples from different localities showed different qualities. Advantages, in comparison with conventional HPLC,diode array detection and HPLC-ELSD, are that reliable identification of target compounds could be achieved by accurate mass measurements along with characteristic retention time, and the great enhancement in selectivity and sensitivity allows identification and quantification of low levels of constituents in complex Polyporus umbellatus matrixes. Copyright 2009 John Wiley & Sons, Ltd. [source]

Second-order Scattering and Frequency Doubling Scattering Spectra of Thallium(III)-Methotrexate System and Its Analytical Application

Cun-Xian XI
Abstract In pH 4.9 Britton-Robinson buffer solution, methotrexate (MTX) reacted with thallium(III) to form a 3:1 chelate. This resulted in great enhancement of second-order scattering (SOS) spectra and frequency doubling scattering (FDS) spectra and appearance of new SOS and FDS spectra. Their maximum wavelengths were located at 520 and 390 nm, respectively. The increments of scattering intensities (,I) were directly proportional to the concentrations of MTX in the ranges of 0.022,2.0 gmL,1 (SOS method) and 0.008,2.5 gmL,1 (FDS method). The methods exhibited high sensitivities. The detection limits for MTX were 7.4 ngmL,1 (SOS method) and 2.3 ngmL,1 (FDS method), respectively. The optimum conditions of the reaction, the influencing factors and the effects of coexisting substances were investigated. A highly sensitive, simple and fast method for the determination of MTX has been developed. The method can be applied satisfactorily to the determination of MTX in human serum samples. In this work, the charge distribution of MTX was calculated by a CNDO quantum chemistry method. In addition, the reaction mechanism was discussed. [source]

Determination of Potassium Ferrocyanide in Foods by Resonance Rayleigh Scattering Method with Double-Charged Triaminotriphenylmethane Dyes

Yong-Li Li
Abstract In pH 1.0 acidic medium, double-charged triaminotriphenylmethane dyes such as methyl green (MeG) and iodine green (IG) react with potassium ferrocyanide to form 2:1 ion-association complexes by virtue of electrostatic forces and hydrophobic interaction. It results in the change of absorption and the great enhancement of resonance Rayleigh scattering (RRS) and the appearance of new RRS spectra. Two systems have similar spectral characteristics and their maximum RRS wavelengths are all located at 276 nm and smaller peaks are located at 332 and 457 nm, respectively. The intensity of RRS is directly proportional to the concentration of [Fe(CN)6]4, in the range of 0.03,5.7 gmL,1 (MeG system) or 0.04,5.9 gmL,1 (IG system). The RRS method has high sensitivity and the detection limit (3,) for potassium ferrocyanide is 9.3 ngmL,1 (MeG system) or 11.2 ngmL,1 (IG system). The optimum conditions, influencing factors and effects of foreign substances are investigated. The method also has a good selectivity. A sensitive, rapid and simple RRS method for the determination of potassium ferrocyanide in salinized food and table salt has been developed. [source]