UV-visible Spectra (uv-visible + spectrum)

Distribution by Scientific Domains
Distribution within Chemistry


Selected Abstracts


Preparation, Characterization and Magnetic Properties of PANI/La-substituted LiNi Ferrite Nanocomposites

CHINESE JOURNAL OF CHEMISTRY, Issue 12 2006
Jing Jiang
Abstract Magnetic nanocomposites containing polyaniline (PANI)-coated La-substituted LiNi ferrite (LiNi0.5La0.02Fe1.98O4) were synthesized by in situ polymerization in aqueous solution of hydrochloric acid. The nanocomposites exhibited the magnetic hysteresis nature under applied magnetic field. The saturation magnetization (MS) and coercivity (HC) varied with the ferrite content. The obtained nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), UV-Visible spectroscopy and vibrating sample magnetometer (VSM). TEM and SEM studies showed that the nanocomposites present the core-shell structure. The results of XRD patterns, FT-IR and UV-Visible spectra indicated the formation of PANI-LiNi0.5La0.02Fe1.98O4 nanocomposites and showed that the interaction existed between PANI backbone and ferrite particles in the nanocomposites. The bonding mechanism in the nanocomposites has been proposed. [source]


Preparation, Characterization and Electrocatalytic Studies on Copper Complex Dye Film Modified Electrodes

ELECTROANALYSIS, Issue 13 2007
Shen-Ming Chen
Abstract Copper complex dye (C.I. Direct Blue 200) film modified electrodes have been prepared by multiple scan cyclic voltammetry. The effect of solution pH and nature of electrode material on film formation was investigated. The optimum pH for copper complex film formation on glassy carbon was found to be 1.5. The mechanism of film formation on ITO seems to be similar to that on GC surface but completely different mechanism followed with gold electrode. Cyclic voltammetric features of our modified electrodes are in consistent with a surface-confined redox process. The voltammetric response of modified electrode was found to be depending on pH of the contacting solution. UV-visible spectra show that the nature of copper complex dye is identical in both solution phase and after forming film on electrode. The electrocatalytic behavior of copper complex dye film modified electrode towards oxidation of dopamine, ascorbic acid and reduction of SO52, was investigated. The oxidation of dopamine and ascorbic acid occurred at less positive potential on film electrode compared to bare glassy carbon electrode. Feasibility of utilizing our modified electrode in analytical estimation of dopamine, ascorbic acid was also demonstrated. [source]


Antibacterial activity of plant extracts from northwestern Argentina

JOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007
J.R. Soberón
Abstract Aims:, To determine the antibacterial and cytotoxic activities of aqueous and ethanolic extracts of northwestern Argentinian plants used in folk medicine. To compare the mentioned activities with those of five commercial antibiotics. To identify the compounds responsible for the antibacterial activity. Methods and Results:, Plant extracts were prepared according to traditional uses in northwestern Argentina. Antibacterial activity was assayed by agar dilution in Petri dishes and broth dilution in 96-well plates. Lethal dose 50 (LD50) was determined by the Artemia salina assay. Phytochemical analysis was performed by sample adsorption on silica gel, thin-layer chromatography (TLC), bioautography and UV-visible spectra. The results showed that Tripodanthus acutifolius aqueous extracts have lower minimal inhibitory concentrations (MIC) (502 and 506 ,g of extracted material (EM) per ml for infusion and decoction, respectively) than cefotaxim MIC (640 ,g ml,1) against Acinetobacterfreundii (303). These data were lower than their LD50. Tripodanthus acutifolius tincture showed lower MIC (110 ,g of EM per ml) and minimal bactericidal concentration (MBC) (220 ,g of EM per ml) than cefotaxim (MIC and MBC of 320 ,g ml,1) for Pseudomonasaeruginosa. This extract also showed a MIC/MBC of 110/220 ,g of EM per ml, lower than oxacillin (MIC/MBC of 160/220 ,g ml,1) for Staphylococcus aureus (ATCC 25923). The cytotoxicity of all extracts were compared with that of commercial antibiotics. Rutin (3,3,,4,,5,7-pentahydroxyflavone 3- , -rhamnosilglucoside), iso -quercitrin (3,3,,4,,5,7-pentahydroxyflavone 3- , -glucoside) and a terpene would be partially responsible for the antibacterial activity of T. acutifolius infusion. Conclusions:,Tripodanthus acutifolius extracts had the ability to inhibit bacterial growth. The antibacterial activity differs with the applied extractive method, and it could be partially attributed to glycoflavonoids. This paper contributes to the knowledge of antibacterial capacity of plants from northwestern Argentina. Significance and Impact of the Study:, These antibacterial activities support further studies to discover new chemical structures that can contribute to alleviate or cure some illnesses. [source]


[5-(p -alkoxy)phenyl-10, 15, 20-tri-phenyl] porphyrin and their rare earth complex liquid crystalline

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 4 2007
Miao Yu
Abstract Three series of porphyrin liquid crystalline compounds, [5-(p -alkoxy)phenyl-10, 15, 20-tri-phenyl] porphyrin and their rare earth complexes (Tb (III), Dy (III), Er (III), Yb (III)), with a hexagonal columnar discotic columnar(Colh) phase have been synthesized. These compounds were characterized by elemental analysis, molar conductances, UV-visible spectra, infrared spectra, luminescence spectra, and cyclic voltammetry. These compounds exhibit more than one mesophases, which transition points of temperature change from ,33.6 to 16.0,°C, and transition points of temperature for isotropic liquid also increase from 4.9 to 38.2,°C, with increasing chain length. Their surface photovoltage (SPV) response have also been investigated by the means of surface photovoltage spectroscopy (SPS) and field-induced surface photovoltage spectroscopy (EFISPS). It was found that their SPV bands are analogous with the UV-visible absorption spectra and derived from the same transition. Copyright © 2007 John Wiley & Sons, Ltd. [source]


Hydrazine-induced post-chemiluminescence phenomenon of permanganate,luminol reaction and its applications

LUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 6 2004
Jianxiu Du
Abstract The post-chemiluminescence phenomenon arising from the permanganate,luminol reaction induced by hydrazine and isoniazid was investigated. When hydrazine or isoniazid was injected into the mixture after the end of the reaction of permanganate with alkaline luminol, a new chemiluminescence (CL) reaction was initiated and strong CL signal was detected. A possible CL mechanism is suggested, based upon the studies of the kinetic characteristics of the CL reaction, the UV-visible spectra, the CL spectra and some other experiments. The present reactions allow the determination of 0.1,10.0 mg/L hydrazine and 0.02,1.0 mg/L isoniazid, with detection limits of 0.03 mg/L and 0.006 mg/L, respectively. The method was applied to the determination of isoniazid in pharmaceutical preparations. Copyright © 2004 John Wiley & Sons, Ltd. [source]


Synthesis and characterization of polyaniline derivative and silver nanoparticle composites

POLYMER INTERNATIONAL, Issue 10 2008
Gururaj M Neelgund
Abstract BACKGROUND: There has been a recent surge of interest in the synthesis and applications of electroactive polymers with incorporated metal nanoparticles. These hybrid systems are expected to display synergistic properties between the conjugated polymers and the metal nanoparticles, making them potential candidates for applications in sensors and electronic devices. RESULTS: Composites of polyaniline derivatives,polyaniline, poly(2,5-dimethoxyaniline) and poly(aniline-2,5-dimethoxyaniline),and silver nanoparticles were prepared through simultaneous polymerization of aniline derivative and reduction of AgNO3 in the presence of poly(styrene sulfonic acid) (PSS). We used AgNO3 as one of the initial components (1) to form the silver nanoparticles and (2) as an oxidizing agent for initiation of the polymerization reaction. UV-visible spectra of the synthesized nanocomposites reveal the synchronized formation of silver nanoparticles and polymer matrix. The morphology of the silver nanoparticles and degree of their dispersion in the nanocomposites were characterized by transmission electron microscopy. Thermogravimetric analysis and differential scanning calorimetry results indicate an enhancement of the thermal stability of the nanocomposites compared to the pure polymers. The electrical conductivity of the nanocomposites is in the range 10,4 to 10,2 S cm,1. CONCLUSION: A single-step process for the synthesis of silver nanoparticle,polyaniline derivative nanocomposites doped with PSS has been demonstrated. The approach in which silver nanoparticles are formed simultaneously during the polymerization process results in a good dispersion of the nanoparticles in the conductive polymer matrix. Copyright © 2008 Society of Chemical Industry [source]


Molecular Junctions Composed of Oligothiophene Dithiol-Bridged Gold Nanoparticles Exhibiting Photoresponsive Properties

CHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2006
Wei Huang Dr.
Abstract Three oligothiophene dithiols with different numbers of thiophene rings (3, 6 or 9) have been synthesized and characterized. The X-ray single crystal structures of terthiophene 2 and sexithiophene 5 are reported herein to show the exact molecular lengths, and to explain the difference between their UV-visible spectra arising from the different packing modes. These dithiols with different chain lengths were then treated with 2-dodecanethiol-protected active gold nanoparticles (Au-NPs) by means of in situ thiol-to-thiol ligand exchange in the presence of 1,,m gap Au electrodes. Thus the molecular junctions composed of self-assembled films were prepared, in which oligothiophene dithiol-bridged Au-NPs were attached to two electrodes by means of AuS bonded contacts. The morphologies and current,voltage (I,V) characteristics of these films were studied by SEM and AFM approaches, which suggested that the thickness of the films (3,4 layers) varied within the size of one isolated Au-NP and typical distance-dependent semiconductor properties could be observed. Temperature dependent I,V measurements for these molecular junctions were performed in which the films served as active elements in the temperature range 6,300 K; classical Arrhenius plots and subsequent linear fits were carried out to give the activation energies (,E) of devices. Furthermore, preliminary studies on the photoresponsive properties of these devices were explored at 80, 160, and 300 K, respectively. Physical and photochemical mechanisms were used to explain the possible photocurrent generation processes. To the best of our knowledge, this is the first report in which oligothiophene dithiols act as bridging units to link Au-NPs, and also the first report about functionalized Au-NPs exhibiting photoresponse properties in the solid state. [source]