33 research outputs found
Electrocatalytic behavior of cobalt phthalocyanine complexes immobilized on glassy carbon electrode towards the reduction of dicrotophos pesticide
Electrocatalytic properties of cobalt phthalocyanine (CoPc), cobalt tetra-carboxy phthalocyanine (CoTCPc) and cobalt octa-carboxy (CoOCPc), towards the detection of dicrotophos have been studied. Catalytic behavior towards the reduction of dicrotophos was found to be dependent on the pH, as well as the substitution on the phthalocyanine ring. Strong electron withdrawing groups on the phthalocyanine ring yielded best catalysis as evidenced by the enhancement of the reduction peak current, (~5 fold) compared to the bare glassy carbon electrode. The analysis gave a good detection limit of 1.25 Ă 10-7 M, and good linearity for the studied concentration range. A high Tafel slope value was obtained, indicating a strong interaction between dicrotophos and the cobalt phthalocyanine complex
Histological comparison of three apatitic bone substitutes with different carbonate contents in alveolar bone defects in a beagle mandible with simultaneous implant installation
Since bone apatite is a carbonate apatite containing carbonate in an apatitic structure, carbonate content may be one of the factors governing the osteoconductivity of apatitic bone substitutes. The aim of this study was to evaluate the effects of carbonate content on the osteoconductivity of apatitic bone substitutes using three commercially available bone substitutes for the reconstruction of alveolar bone defects of a beagle mandible with simultaneous dental implant installation. NEOBONEÂź, Bio-OssÂź, and CytransÂź that contain 0.1 mass%, 5.5 mass%, and 12.0 mass% of carbonate, respectively, were used in this study. The amount of newly formed bone in the upper portion of the alveolar bone defect of the beagleâs mandible was 0.7%, 6.6%, and 39.4% at 4 weeks after surgery and 4.7%, 39.5% and 75.2% at 12 weeks after surgery for NEOBONEÂź, Bio-OssÂź, and CytransÂź, respectively. The results indicate that bone-to-implant contact ratio was the largest for CytransÂź. Additionally, the continuity of the alveolar ridge was restored in the case of CytransÂź, whereas the continuity of the alveolar ridge was not sufficient when using NEOBONEÂź and Bio-OssÂź. Both CytransÂź and Bio-OssÂź that has a relatively larger carbonate content in their apatitic structure was resorbed with time. We concluded that carbonate content is one of important factors governing the osteoconductivity of apatitic bone substitutes
Tuning the physico-electrochemical properties of novel cobalt (II) octa [(3, 5-biscarboxylate)-phenoxy] phthalocyanine complex using phenylamine-functionalised SWCNTs
The integration of phenylamine-functionalised SWCNTs (SWCNT-phenylamine) with a novel cobalt (II) octa[(3,5-biscarboxylate)-phenoxy] phthalocyanine (CoOBPPc) complex has been described. The physical and electrochemical properties of the CoOBPPc-SWCNT-phenylamine hybrid were evaluated using spectroscopy (IR and UVâvis), field emission scanning electron microscopy and electrochemistry (cyclic voltammetry and electrochemical impedance spectroscopy). Integration of SWCNT-phenylamine resulted in the physical transformation of the CoOBCPPc from the usually bluish colour of cobalt phthalocyanine complexes to a beautiful bright green colour. In addition, the heterogeneous electron transfer kinetics and electrocatalytic properties of the CoOBCPPc were greatly enhanced following the attachment of the SWCNT-phenylamine. The potential electrocatalytic application of the hybrid was tested using ÎČ-nicotinamide adenine dinucleotide (NADH) as a model biological analyte. Interestingly, the onset oxidation potential of this analyte was significantly reduced (300 mV) by this hybrid compared to the bare electrode
Electrocatalytic behavior of cobalt phthalocyanine complexes immobilized on glassy carbon electrode towards the reduction of dicrotophos pesticide
Electrocatalytic properties of cobalt phthalocyanine (CoPc), cobalt tetra-carboxy phthalocyanine (CoTCPc) and cobalt octa-carboxy (CoOCPc), towards the detection of dicrotophos have been studied. Catalytic behavior towards the reduction of dicrotophos was found to be dependent on the pH, as well as the substitution on the phthalocyanine ring. Strong electron withdrawing groups on the phthalocyanine ring yielded best catalysis as evidenced by the enhancement of the reduction peak current, (~5 fold) compared to the bare glassy carbon electrode. The analysis gave a good detection limit of 1.25 Ă 10-7 M, and good linearity for the studied concentration range. A high Tafel slope value was obtained, indicating a strong interaction between dicrotophos and the cobalt phthalocyanine complex
Iron(II) tetrakis(diaquaplatinum)octacarboxyphthalocyanine supported on multi-walled carbon nanotube platform : an efficient functional material for enhancing electron transfer kinetics and electrocatalytic oxidation of formic acid
A novel platinum-based macrocycle, iron(II) tetrakis(diaquaplatinum)octacarboxyphthalocyanine
(PtFeOCPc), was synthesised and characterised. The heterogeneous electron transfer and
electrocatalytic properties of this functional material towards the oxidation of formic acid have been explored on a graphite electrode platform pre-modified with or without acid-functionalised multiwalled carbon nanotubes (MWCNTs). We prove that PtFeOCPc supported on a MWCNT platform (MWCNTâPtFeOCPc) exhibits enhanced electrochemical response in terms of (i) electron transfer towards outer-sphere redox probe, (ii) catalytic rate constant, and (iii) tolerance towards CO poisoning during formic acid oxidation. The results clearly suggest that the MWCNTâPtFeOCPc is a promising platform for potential application as an electrocatalyst for direct formic acid fuel cell
Influence of Intramolecular fâf Interactions on Nuclear Spin Driven Quantum Tunneling of Magnetizations in Quadruple-Decker Phthalocyanine Complexes Containing Two Terbium or Dysprosium Magnetic Centers
Nuclear spin driven quantum tunneling
of magnetization (QTM) phenomena,
which arise from admixture of more than two orthogonal electronic
spin wave functions through the couplings with those of the nuclear
spins, are one of the important magnetic relaxation processes in lanthanide
single molecule magnets (SMMs) in the low temperature range. Although
recent experimental studies have indicated that the presence of the
intramolecular f-f interactions affects their magnetic relaxation
processes, little attention has been given to their mechanisms and,
to the best of our knowledge, no rational theoretical models have
been proposed for the interpretations of how the nuclear spin driven
QTMs are influenced by the f-f interactions. Since quadruple-decker
phthalocyanine complexes with two terbium or dysprosium ions as the
magnetic centers show moderate f-f interactions, these are appropriate
to investigate the influence of the f-f interactions on the dynamic
magnetic relaxation processes. In the present paper, a theoretical
model including ligand field (LF) potentials, hyperfine, nuclear quadrupole,
magnetic dipolar, and the Zeeman interactions has been constructed
to understand the roles of the nuclear spins for the QTM processes,
and the resultant Zeeman plots are obtained. The ac susceptibility
measurements of the magnetically diluted quadruple-decker monoterbium
and diterbium phthalocyanine complexes, [TbâY] and [TbâTb],
have indicated that the presence of the f-f interactions suppresses
the QTMs in the absence of the external magnetic field (<i>H</i><sub>dc</sub>) being consistent with previous reports. On the contrary,
the faster magnetic relaxation processes are observed for [TbâTb]
than [TbâY] at <i>H</i><sub>dc</sub> = 1000 Oe, clearly
demonstrating that the QTMs are rather enhanced in the presence of
the external magnetic field. Based on the calculated Zeeman diagrams,
these observations can be attributed to the enhanced nuclear spin
driven QTMs for [TbâTb]. At the <i>H</i><sub>dc</sub> higher than 2000 Oe, the magnetic relaxations become faster with
increasing <i>H</i><sub>dc</sub> for both complexes, which
are possibly ascribed to the enhanced direct processes. The results
on the dysprosium complexes are also discussed as the example of a
Kramers system
Observation of Exceptionally Low-Lying ÏâÏ* Excited States in Oxidized Forms of Quadruple-Decker Phthalocyanine Complexes
Spectroscopic investigations have been performed for
the oxidized
forms of two quadruple-decker phthalocyanine complexes in order to
clarify the electronic structures of multiply stacked Ï-systems.
Up to three-electron-oxidized species were isolated by using phenoxaÂthiin
hexachloroantimonate as the oxidant. As the oxidations proceed, the
Q-bands in the visible region shift bathochromically along with the
clear isosbestic points. The one- and three-electron-oxidized species
exhibited typical Ï-radical signals in the ESR spectra, while
the neutral and two-electron oxidized species gave no indication of
the presence of Ï-radicals. The electronic transitions observed
for the oxidized species reach even into the so-called fingerprint
region in IR spectroscopy (âŒ1000 cm<sup>â1</sup>). With
the aid of theoretical calculations, these bands can be assigned to
the ÏâÏ* transitions. Our results provide new insights
into Ï-electronic systems having exceptionally small MO energy
gaps
Metal (Co, Fe) tribenzotetraazachlorinâfullerene conjugates: Impact of direct Ï-bonding on the redox behaviour and oxygen reduction reaction
Novel hexabutylsulphonyltribenzotetraazachlorinâfullerene (C60) complexes of iron (FeHBSTBTACâC60) and cobalt (CoHBSTBTACâC60) have been synthesized and their electrochemistry and oxygen reduction reaction (ORR) compared with their octabutylsulphonylphthalocyanine analogues (FeOBSPc and CoOBSPc). It is proved that electron-withdrawing substituents (âSO2Bu and C60) on phthalocyanine macrocycle exhibit distinct impact on the solution electrochemistry of these metallophthalocyanine (MPc) complexes. The more electron-withdrawing C60 substituent suppressed ORR compared to the âSO2Bu in alkaline medium. FeOBSPc showed the best ORR activity involving a direct 4-electron mechanism, a rate constant of âŒ1 Ă 108 cm3 molâ1 sâ1 and a Tafel slope of â171 mV decâ1. Keywords: Metal (Fe, Co) phthalocyanineâC60, Cyclic voltammetry, RDE experiment, Oxygen reductio
Tuning the physico-electrochemical properties of novel cobalt (II) octa [(3, 5-biscarboxylate)-phenoxy] phthalocyanine complex using phenylamine-functionalised SWCNTs
The integration of phenylamine-functionalised SWCNTs (SWCNT-phenylamine) with a novel cobalt (II) octa[(3,5-biscarboxylate)-phenoxy] phthalocyanine (CoOBPPc) complex has been described. The physical and electrochemical properties of the CoOBPPc-SWCNT-phenylamine hybrid were evaluated using spectroscopy (IR and UVâvis), field emission scanning electron microscopy and electrochemistry (cyclic voltammetry and electrochemical impedance spectroscopy). Integration of SWCNT-phenylamine resulted in the physical transformation of the CoOBCPPc from the usually bluish colour of cobalt phthalocyanine complexes to a beautiful bright green colour. In addition, the heterogeneous electron transfer kinetics and electrocatalytic properties of the CoOBCPPc were greatly enhanced following the attachment of the SWCNT-phenylamine. The potential electrocatalytic application of the hybrid was tested using ÎČ-nicotinamide adenine dinucleotide (NADH) as a model biological analyte. Interestingly, the onset oxidation potential of this analyte was significantly reduced (300 mV) by this hybrid compared to the bare electrode