Visible-near IR Absorption Research Articles

Simultaneous purification and oxidation of the as-synthesized MWCNTs with KMnO4 using phase transfer catalyst at three different pH medium by the hydrothermal method

Improving and streamlining current oxidation techniques for experimental is the main goal of the research described in the present article. By applying the pressure created while on the hydrothermal process to an autoclave walled with Teflon, simplifying the procedure was accomplished. By comparing the degrees of functionalization attained with the dispersibility in the substantially pure and functionalized multi-walled carbon nanotubes (MWCNTs) final product, the beneficial effect of the procedure was evaluated. In order to achieve this, the study looked at and investigated how as-synthesized MWCNTs from Fe-Mo/MgO catalyst were simultaneously purified and oxidized using the chemical vapor deposition (CVD) method. Aliquot-336 was used as phase transfer catalyst (PTC) by hydrothermal method under three different pH conditions. Following functionalization, nanotubes of carbon might easily combine with various chemical reagents to generate homogeneous dispersions or even well-aligned structures because of the functional groups linked to their surfaces. In this case, a chemical called reagent potassium permanganate (KMnO4) is necessary in order to target particular π-bonds while entirely destroying the nanotubes' graphene structures. The techniques have been explained in terms of mechanism, and the Fourier transform-infrared (FT-IR) spectroscopy has confirmed the functionalizations of the CNTs. These approaches were further explored through FT-Raman spectrum analysis, thermal assessments, energy dispersive X-ray spectroscopy (EDX), TEM (transmission electron microscopy) along with the help of EDX, and visible-near IR absorption and UV–visible absorption spectroscopy (ABS) procedures.

The donor–acceptor dyad based on high substituted fullero[70]pyrrolidine-coordinated manganese (III) phthalocyanine for photoinduced electron transfer

Donor-acceptor dyads based on manganese porphyrins/phthalocyanines and fullerene derivatives with N-basicity centers have proved as promising photoinduced electron-transfer systems for photovoltaic devices, biologically active compounds, and molecular magnetic materials. The macroheterocyclic chromophore characterized by rich UV–visible-near IR absorption is the basis for the applications above. The problem of the synthesis and the characterization of new effective dyads was solved in this work on the example of the self-organizing system consisting of (octakis-3,5-di-tert-butylphenoxy)phthalocyaninato)manganese(III) acetate, (AcO)MnPc(3,5-di-tBuPhO)8, 2′,5-di(pyridin-2′-yl)-3,4-fullero[70]pyrrolidine, Py2C70, and toluene. The phthalocyanine-fullerene dyads in the molecular and cationic form (respectively (AcO)(Py2C70)MnPc(3,5-di-tBuPhO)8 and [(Py2C70)MnPc(3,5-di-tBuPhO)8]+(AcO)-) were observed and described using the chemical kinetics/thermodynamics, UV–vis, IR, 1H NMR spectroscopy and mass spectrometry methods. The 1: 1 stoichiometry of both dyads was confirmed; the equilibrium and rate constant value, K= (4.86 ± 0.56) × 104 L mol−1 and k = (4.455 ± 3.37) × 10-5 s−1 was observed for the formation of molecular and cationic dyad, respectively. The study of (AcO)MnPc(3,5-di-tBuPhO)8 and [(Py2C70)MnPc(3,5-di-tBuPhO)8]+AcO- femtosecond transient absorption spectra points to the photoinduced electron transfer in the dyad, for which the lifetimes and the rate constants of charge separation (τCS, kCS) and charge recombination (τCR, kCR) were defined. The analysis of the relationship of the dyad physicochemical parameters with the molecular structure is represented using previously published data.

Electrochemical, spectroelectrochemical and surface photovoltage study of ambipolar C60-EDOT and C60-Carbazole based conducting polymers

Ethylenedioxythiophene (EDOT) and Carbazole (CBZ) based conducting polymers holding pendant C60 Buckminster fullerene were formed by electrochemical induced dimerization of four structurally related monomers. Electrochemical and spectroelectrochemical characterization of the thin films clearly indicates the presence of EDOT and CBZ dimers as structural building blocks of the polymeric materials. Under positive applied potentials, all the synthesized conductive materials generate UV–visible-near IR absorption bands that denote the presence of two oxidized states in the electrochemical generated dimers. Also, the four polymeric films showed reversible reduction of the C60 units. The capacity of the materials for the production of photoelectric effects was analyzed by surface photovoltage spectroscopy, showing that the illumination of C60-CBZ polymers causes preferential separation of photogenerated charge carriers in the double-cable polymeric organic films.

Efficient Solubilization of Single-Walled Carbon Nanotubes Using Tea Solutions

Here we describe the finding that oolong tea and black tea act as excellent carbon nanotube solubilizers to produce individually dissolved single-walled carbon nanotubes (SWNTs), which have been revealed using visible-near IR absorption, photoluminescence and Raman spectroscopy as well as AFM study. The oolong tea solution has a tendency to individually dissolve metallic SWNTs that can be detected by 514 nm-excition, and in solution, the (11,3)SWNTs enriched and (11,0)SWNTs that are contained in as-produced SWNTs were very few. Black tea solution shows similar tendency, while the separation performance was weaker compared to that of the oolong tea. We also used epigallocatechin gallate to solubilize the SWNTs and shed light on the mechanism of the SWNT dissolution. Tea contains numerous components with antioxidant activities; therefore biological and biomedical applications using the present soluble nanotubes might be of interest.

Individual solubilization of single-walled carbon nanotubes using totally aromatic polyimide

We report here the finding by means of visible-near IR absorption and near-IR fluorescence spectroscopies and atomic force microscopy that a total aromatic polyimide has a high potential to solubilize single-walled carbon nanotubes (SWNTs) individually in organic solutions. The solutions contained SWNTs having (7, 6), (7, 5), (8, 4), (9, 5) and (8, 6) indices. With the increasing concentrations of SWNTs, the solutions became viscous and then changed to gels that exhibited characteristic spectral features of individually dissolved SWNTs.

Synthesis and characterization of neptunyl(VI) and plutonyl(VI) orthosilicates

Summary (NpO2)2SiO4·2H2O (I) and (PuO2)2SiO4·2H2O (II) have been prepared by hydrothermal synthesis technique. Chemical composition of (I) was attributed to the compound from its isostructurality with (UO2)2SiO4·2H2O; crystal unit cell parameters of (NpO2)2SiO4·2H2O have been refined as orthorhombic, a=8.365(5)Å, b=11.089(5)Å, c=18.640(9)Å with the space group Fddd. (PuO2)2SiO4·2H2O has not been found isostructural with uranyl(VI) and neptunyl(VI) analogues. Chemical composition of (II) was determined by chemical analysis and proved by the formula volume calculated from powder X-ray data. Indexing of X-ray powder pattern of the prepared compound gave the tetragonal unit cell with a=6.912(3), c=18.563(3)Å, possible space group I41/amd. Visible-near IR and IR absorption spectra of the prepared compounds have been measured in NaCl and KBr. f–f absorption band of PuO2 2+ in the visible spectrum of crystal (PuO2)2SiO4·2H2O is not splitted but its maximum is essentially shifted (up to 858nm) to the long wave region in comparison with hydrated PuO2 2+ ions. Visible-near IR absorption spectrum of crystal (NpO2)2SiO4·2H2O is close to that of aqueous neptunyl(VI) solution. Thermal behavior of synthesized compounds has been studied up to 800°C in air.

Solid-State Polymerization of 15,17,19,21,23,25-Tetracontahexayne

A dialkyl-substituted dodecahexayne derivative of 15,17,19,21,23,25-tetracontahexayne (THY) was found to polymerize spontaneously in the solid state at ambient temperature without irradiation. The polymerization ofthe THY crystals was monitored by IR and visible-near IR absorption, 13 C NMR and ESR spectra, and X-ray diffraction. The following polymerization scheme is proposed. First, a polydiacetylene substituted by alkyl and 1,3,5,7-alkatetraynyl groups is formed by 1,4-addition polymerization of the dodecahexayne moiety. Next, polymerization occurs at the 9,12-positions (on the opposite side) of the original dodecahexayne moiety to give a ladder polymer of two polydiacetylenes bonded by butadiynylene groups

Resonance Raman evidence for tyrosine involvement in the radical site of galactose oxidase

Resonance Raman data are reported for the redox-activated form of galactose oxidase from Dactylium dendroides. Excitation within the red (659 nm) and blue (457.9 nm) absorption bands leads to strong resonance enhancement of ligated tyrosine vibrational modes at 550, 1170, 1247, 1484, and 1595 cm-1. The ring mode frequencies are unusually low, indicating a decreased bond order in the ring. The spectra clearly differ in both frequencies and relative intensities from those characteristic of known aromatic pi-radicals. Enhancement of tyrosine ring modes on excitation within absorption bands previously associated with the presence of the radical in the active site suggests that the ligated tyrosine residue is present in the radical site and may stabilize this radical species through formation of a charge transfer complex. A dramatically different Raman spectrum is observed for the N3- adduct of galactose oxidase, exhibiting a single strong 1483 cm-1 feature. The intense visible-near IR absorption bands for galactose oxidase may derive from transitions within a charge transfer complex between an aromatic free radical and a tyrosine-copper complex.

Soluble ethylmercapto-substituted polythiophenes

Abstract : Polymers of 3-ethylmercapto and 3,4-bis(ethylmercapto)thiophenes have been synthesized and characterized. These polymers are soluble in common organic solvents such as methylene chloride, chloroform and THF. Structural characterization using FT-IR and NMR spectroscopy show that these polymers have a well-defined beta-ethylmercapto substituted 2,5-(thienylene) polymeric structure. Visible-near IR absorption spectra of electrochemically doped cast films and chemically doped solutions of the polymers show that they can be oxidized to form bipolaronic species. GPC studies show a number average molecular weight of about 2500 (M w/M n approx. 5) for both polymers. Maximum electrical conductivities of 10-3/ohm/cm for the 3-ethylmercapto, and 10 to the -7th for the 3,4-bis(ethylmercapto)substituted polymers have been obtained in the oxidized state. Experimental results are correlated with theoretical calculations using the PRDDO and extended Huckel methods, which demonstrate radical-cation reactivities for the thiophene monomers, along with minimum energy conformations and band structures in these substituted polymers. Keywords: Conductive polymers; Substituted polythiophenes; Theoretical calculations; Thiophenes.