Fermi level engineering of single-walled carbon nanotubes by AuCl3 doping

We investigated the modulation of optical properties of single-walled carbon nanotubes (SWCNTs) by AuCl 3 doping. The van Hove singularity transitions (E 11 (S), E 22 (S), E 11 (M)) in absorption spectroscopy disappeared gradually with an increasing doping concentration and a new peak appeared at a high doping concentration. The work function was downshifted up to 0.42 eV by a strong charge transfer from the SWCNTs to AuCl 3 by a high level of p-doping. We propose that this large work function shift forces the Fermi level of the SWCNTs to be located deep in the valence band, i.e., highly degenerate, creating empty van Hove singularity states, and hence the work function shift invokes a new asymmetric transition in the absorption spectroscopy from a deeper level to newly generated empty states.     

Synthesis of diamond-shape titanate molecular sheets with different sizes and realization of quantum confinement effect during dimensionality reduction from two to zero

Synthesis of semiconductor nanoparticles with uniform shapes, sizes, and compositions in series with a gradual size reduction has not been achieved for two-dimensional molecular sheets. We report a large-scale (>2.6 g) synthesis of 0.75-nm-thick diamond-shape lepidocrocite-type titanate molecular sheets with the sizes decreasing from (27.3, 19.1) to (7.7, 5.5), where the numbers in parentheses represent the long and short diagonal lengths, respectively, in nm. This is the first example of synthesizing semiconductor nanoparticles in series with the dimensionality reduction from two to zero, without coating the surfaces with surface-passivating ligands. The titanate molecular sheets showed three exciton-absorption bands in the 4.0-6.5 eV region, the absorption energies of which increased with decreasing the area. Contrary to the common belief, the per-unit cell oscillator strengths gradually increased with increasing area and the per-particle oscillator strengths increased in proportion to the area. The average reduced exciton masses along the two diagonal axes were 0.10 and 0.11 m e, respectively, which were much smaller than those of bulk titanates (by 60-130 times). The estimated average Bohr radii along the two-diagonal axes were 4.8 and 4.3 nm, respectively.     

Unambiguous identification of Möbius aromaticity for meso-aryl-substituted [28]hexaphyrins(1.1.1.1.1.1)

meso-Aryl-substituted [28]hexaphyrins(1.1.1.1.1.1) have been examined by (1)H, (13)C, and (19)F NMR spectroscopies, UV-vis absorption spectroscopy, magnetic circular dichroism spectroscopy, and single-crystal X-ray diffraction analysis. All of these data consistently indicate that [28]hexaphyrins(1.1.1.1.1.1) in solution at 25 degrees C exist largely as an equilibrium among several rapidly interconverting twisted M?bius conformations with distinct aromaticities, with a small contribution from a planar rectangular conformation with antiaromatic character at slightly higher energy. In the solid state, [28]hexaphyrins(1.1.1.1.1.1) take either planar or M?bius-twisted conformations, depending upon the meso-aryl substituents and crystallization conditions, indicating a small energy difference between the two conformers. Importantly, when the temperature is decreased to -100 degrees C in THF, these rapid interconversions among M?bius conformations are frozen, allowing the detection of a single [28]hexaphyrin(1.1.1.1.1.1) species having a M?bius conformation. Detailed analyses of the solid-state M?bius structures of compounds 2b, 2c, and 2f showed that singly twisted structures are achieved without serious strain and that cyclic pi-conjugation is well-preserved, as needed for exhibiting strong diatropic ring currents. Actually, the harmonic-oscillator model for aromaticity (HOMA) values of these structures are significantly large (0.85, 0.69, and 0.71, respectively), confirming the first demonstration of stable M?bius aromatic systems consisting of free-base expanded porphyrins without the assistance of metal coordination.     

Site-selective catalytic surface activation via aerosol nanoparticles for use in metal micropatterning

There is great interest in the fabrication of micro- and nanopatterned metallic structures on substrates for a wide range of electronic, photonic, and magnetic devices. One of the most widely used techniques is the electroless deposition (ELD) of metal, which requires the surface activation of the substrates with a metal catalyst. This paper introduces a method of catalytic surface activation by producing platinum aerosol nanoparticles via spark generation and then thermophoretically depositing the particles onto a flexible polyimide (PI) substrate through the pattern hole of a mask. After annealing, the catalytically activated substrate is placed into a solution for electroless silver deposition. The silver is then formed only on the activated regions of the substrate. Silver line patterns having a width of 18 microm and a height of 1 microm are created with the ability to be effectively reproduced. The average value of the resistivities is approximately 6.8 mu Omega.cm, which is almost comparable to the theoretical resistivity of bulk silver (1.6 mu Omega.cm). Other silver micropatterns containing square dot array, line, line array, Y-branched line, and tapered line using different pattern masks are also demonstrated.     

In situ detection of live cancer cells by using bioprobes based on Au nanoparticles

We fabricate the high-performance probes based on Au nanoparticles (AuNP) for detection of live cancer cell. AuNP were synthesized with narrow sized distribution (ca. 10 nm) by Au salt reduction method and deposited onto the aminated substrate as a cross-linker and hot spot. Herein, AuNP has enabled the easy and efficient immobilization of the antibody (Cetuximab), which can selectively interact with epidermal growth factor receptor (EGFR) on the surface of epidermal cancer, as detecting moiety onto the AuNP-deposited substrate without nanolithography process. After conjugation of Cetuximab with AuNP-deposited substrate, Cetuximab-conjugated probe as a live cancer cell detector (LCCD) could detect EGFR-highexpressed A431 cells related to epithelial cancer with 54-times larger specificity and sensitivity in comparison with EGFR-deficient MCF7 cells. This implies that AuNP-based probes demonstrate abundant potentials for detection and separation of small biomolecules, cells and other chemicals.     

Synthesis of water soluble PEGylated magnetic complexes using mPEG-fatty acid for biomedical applications

We report the successful fabrication of the various types of water soluble PEGylated magnetic complexes (PMCs) for magnetism-related biomedical applications. Various types of PMCs were synthesized and tested to accomplish phase transfer from organic to aqueous phase using monomethoxy polyethylene glycol (mPEG)-fatty acid amphiphilic block copolymers (PFs) through conjugation of the hydroxyl group of mPEG with the carboxyl group of fatty acids. We also carefully investigate their colloidal stabilities in aqueous phase according to the ratio of hydrophilic and hydrophobic lengths relying on different types of fatty acids. Synthesized PMCs clearly demonstrated high magnetic sensitivity under magnetic field as magnetic resonance (MR) contrast agents. Furthermore, PMCs exhibited sufficient cell viabilities and excellent cell affinities in an in vitro model. Our results demonstrated that our PMCs possessed the potential for highly efficient magnetism-related biomedical applications such as MR image agents, drug delivery and tracking of cells.     

Determination of analogs of sildenafil and vardenafil in foods by column liquid chromatography with a photodiode array detector, mass spectrometry, and nuclear magnetic resonance spectrometry

Two analogs of sildenafil and vardenafil in food were detected by column liquid chromatography (LC) with a photodiode array detector. They were isolated by preparative LC; their structures were established by mass spectrometry and nuclear magnetic resonance spectrometry. One analog was found to be methisosildenafil (compound A), 5-(5-(3,5-dimethylpiperazin-1-ylsulfonyl)-2-ethoxy-phenyl)-1-methyl-3-propyl-1H-pyrazolo[4,3-d]-pyrimidin-7(6H)-one. It is a sildenafil analog with a dimethylpiperazine ring substituted for the methylpiperazine group. The second analog, hydroxyvardenafil (compound B) is reported for the first time in this study. Hydroxyvardenafil's International Union of Pure and Applied Chemistry name is 2-(2-ethoxy-5-(4-(2-hydroxyethyl)-piperazin-1-ylsulfonyl)phenyl)-5-methyl-7-propyl-imidazo[1,5-f][1,2,4]triazin-4(3H)-one. The novel vardenafil analog has a hydroxyl group added to the ethylpiperazine group.     

Electron-transfer and acid-base properties of a two-electron oxidized form of quaterpyrrole that acts as both an electron donor and an acceptor

Electron-transfer interconversion between the four-electron oxidized form of a quaterpyrrole (abbreviated as P4 for four pyrroles) and the two-electron oxidized form (P4H2) as well as between P4H2 and its fully reduced form (P4H4) bearing analogous substituents in the alpha- and beta-pyrrolic positions was studied by means of cyclic voltammetry and UV-visible spectroelectrochemistry combined with ESR and laser flash photolysis measurements. The two-electron oxidized form, P4H2, acts as both an electron donor and an electron acceptor. The radical cation (P4H2*+) and radical anion (P4H2*-) are both produced by photoinduced electron transfer from dimeric 1-benzyl-1,4-dihydronicotinamide to P4H2, whereas the cation radical form of the compound is also produced by electron-transfer oxidation of P4H2 with [Ru(bpy)3]3+. The ESR spectra of P4H2*+ and P4H2*- were recorded at low temperature and exhibit spin delocalization over all four pyrrole units. Thus, the two-electron oxidized form of the quaterpyrrole (P4H2) displays redox and electronic features analogous to those seen in the case of porphyrins and may be considered as a simple, open-chain model of this well-studied tetrapyrrolic macrocycle. The dynamics of deprotonation from P4H2*+ and disproportionation of P4H2 were examined by laser flash photolysis measurements of photoinduced electron-transfer oxidation and reduction of P4H2, respectively.