Immobilization of platinum nanoparticles on 3,4-diaminobenzoyl-functionalized multi-walled carbon nanotube and its electrocatalytic activity

Abstract  

Multi-walled carbon nanotubes (MWCNTs) are functionalized at the sp² C–H defect sites with 3,4-diaminobenzoic acid by a “direct” Friedel–Crafts acylation reaction in a mild polyphosphoric acid/phosphorous pentoxide medium. Owing to enhanced surface polarity, the resulting 3,4-diaminobenzoyl-functionalized MWCNTs (DAB-MWCNT) are highly dispersible in polar solvents, such as ethanol, N-methyl-2-pyrrolidone, and methanesulfonic acid. The absorption and emission properties of DAB-MWCNT in solution state are qualitatively shown to be sensitive to the pH in the environment. The DAB-MWCNT is used as a stable platform on which to deposit platinum nanoparticles (PNP). The PNP/DAB-MWCNT hybrid displays high electrocatalytic activity with good electrochemical stability for an oxygen reduction reaction under an alkaline condition.     

Imaging Hydrogen Sulfide in Hypoxic Tissue with [99mTc]Tc-Gluconate

Hydrogen sulfide (H₂S) is the third gasotransmitter and is generated endogenously in hypoxic or inflammatory tissues and various cancers. We have recently demonstrated that endogenous H₂S can be imaged with [^99mTc]Tc-gluconate. In the present study, we detected H₂S generated in hypoxic tissue, both in vitro and in vivo, using [^99mTc]Tc-gluconate. In vitro uptake of [^99mTc]Tc-gluconate was measured under hypoxic and normoxic conditions, using the colon carcinoma cell line CT26, and was higher in hypoxic cells than that in normoxic cells. An acute hindlimb ischemia-reperfusion model was established in BALB/c mice by exposing the animals to 3 h of ischemia and 3 h of reperfusion prior to in vivo imaging. [^99mTc]Tc-gluconate (12.5 MBq) was intravenously injected through the tail vein, and uptake in the lower limb was analyzed by single-photon emission computed tomography/computed tomography (SPECT/CT). SPECT/CT images showed five times higher uptake in the ischemic limb than that in the normal limb. The standard uptake value (SUVmean) of the ischemic limb was 0.39 ± 0.03, while that of the normal limb was 0.07 ± 0.01. [^99mTc]Tc-gluconate is a novel imaging agent that can be used both in vitro and in vivo for the detection of endogenous H₂S generated in hypoxic tissue.     

Discovery of safety biomarkers for atorvastatin in rat urine using mass spectrometry based metabolomics combined with global and targeted approach

In order to develop a safety biomarker for atorvastatin, this drug was orally administrated to hyperlipidemic rats, and a metabolomic study was performed. Atorvastatin was given in doses of either 70 mg kg⁻¹ day⁻¹ or 250 mg kg⁻¹ day⁻¹ for a period of 7 days (n = 4 for each group). To evaluate any abnormal effects of the drug, physiological and plasma biochemical parameters were measured and histopathological tests were carried out. Safety biomarkers were derived by comparing these parameters and using both global and targeted metabolic profiling. Global metabolic profiling was performed using liquid chromatography/time of flight/mass spectrometry (LC/TOF/MS) with multivariate data analysis. Several safety biomarker candidates that included various steroids and amino acids were discovered as a result of global metabolic profiling, and they were also confirmed by targeted metabolic profiling using gas chromatography/mass spectrometry (GC/MS) and capillary electrophoresis/mass spectrometry (CE/MS). Serum biochemical and histopathological tests were used to detect abnormal drug reactions in the liver after repeating oral administration of atorvastatin. The metabolic differences between control and the drug-treated groups were compared using PLS-DA score plots. These results were compared with the physiological and plasma biochemical parameters and the results of a histopathological test. Estrone, cortisone, proline, cystine, 3-ureidopropionic acid and histidine were proposed as potential safety biomarkers related with the liver toxicity of atorvastatin. These results indicate that the combined application of global and targeted metabolic profiling could be a useful tool for the discovery of drug safety biomarkers.     

Vinyl‐Type Polynorbornenes with Pendant PCBM: A Novel Acceptor for Organic Solar Cells

Vinyl addition homo‐ and copolymerization of norbornene monomer ( M1 ) functionalized with a PCBM moiety using a Pd(II) catalyst in combination with a 1‐octene chain transfer agent efficiently produces polynorbornenes with side‐chain PCBM groups. Characterization by NMR spectroscopy and elemental analysis reveals that the copolymers constitute a well‐defined polymer structure with controlled incorporation of M1 . Although the homopolymer is insoluble in organic solvents, the copolymers containing 62 mol% ( P2 ) and 50 mol% ( P3 ) of the PCBM moiety are soluble in chlorinated solvents such as o‐dichlorobenzene. The bulk‐heterojunction organic photovoltaic devices fabricated based on the P3HT: P3 blends show that P3 can adequately function as an electron acceptor, leading to a cell with a power conversion efficiency of 1.5%, which is outstanding among the polymeric rivals.     

Enhanced dispersion stability of supramolecular complexes of single-walled carbon nanotubes with fluorene-based conjugated polymers

Supramolecular complexes of single-walled carbon nanotubes (SWNTs) with poly(9,9-didodecylfluorene-2,7-diyl) (PF) derivatives were prepared using a solution dispersion process. A series of novel conjugated PF polymers with carboxyl or hydroxyl end groups at both ends were synthesized by the Yamamoto-type coupling of 2,7-dibromo-9,9-didodecylfluorene using Ni(COD)₂ as a catalyst, and further end-capped with either 4-bromobenzoic acid or 4-bromobenzyl alcohol to obtain the end-functionalized PF with different terminal groups. An α-monocarboxy-ω-mono-methoxy poly(ethylene glycol) was connected to both ends of the PF-containing hydroxyl end groups to produce triblock copolymers of poly(ethylene glycol)-b-polyfluorene-b-poly(ethylene glycol) (PEO-b-PF-b-PEO). These SWNTs were completely wrapped with the conjugated polymers through π–π interactions, which enhanced the solubility of the SWNT complexes in organic media, and prevented the aggregation of the polymer–SWNT complexes into large bundles. This indicates that the dispersion stability of SWNTs is enhanced by the addition of the conjugated polymers.