Scanning tunneling microscopy (STM) has been used to investigate the adsorption of benzoic acid on the rutile TiO2(110)(1 x 1) and the reconstructed TiO2(110)(1 x 2) surfaces. Benzoic acid binds to both surfaces dissociatively via a bridging geometry to two Ti-5c sites. At a slightly elevated sample temperature during deposition onto the (110) (1 x 1) surface, a well-ordered (2 x 1) overlayer was formed at saturated benzoate coverage. On the reconstructed (110) (1 x 2) surface, benzoate was observed to adsorb between the (1 x 2) strands leading to a (2 x 2) superstructure at higher coverage. Elongation along the [1 (1) over bar0] direction in the STM images indicates a rotation of the benzene ring of 90 degrees relative to the carboxylate group, which is reasonably explained by hydrogen bond interactions between terminating O-atoms on the surface and H-atoms of the ring.

We describe a lab-scale closed-circulating test system for photocatalytic wastewater treatment. The system comprises a UV-LED photoreactor, a microcirculating fluid pump, and an in-stream sensor unit. The reactor can hold volumes up to 250 mL and is optimized to study the degradation of pollutant concentrations in the microgram to milligram per liter range using photocatalysts fixed to a planar surface within the reactor vessel. The test pollutant used was methyl orange. The in-stream sensor unit consists of a liquid flow cell with transparent windows, allowing the transmission of light from an LED to be monitored by a photodiode. The concentration of the pollutant is evaluated in real-time. The system is lightweight, cheap, portable, and flexible, ideal for laboratory or fieldwork use, and could be easily up-scaled and used for in-line quality control monitoring in a wastewater treatment plant.

Commercial TiO2 (Hombikat, UV-100) was impregnated with different loadings of zinc nitrate solution and subsequently calcined at different temperatures in order to obtain a stable homogeneous solid composite of ZnO/TiO2. The prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), UV-vis and Raman spectroscopy, inductively coupled plasma mass spectroscopy (ICP), X-ray photoelectron spectroscopy (XPS) as well as N-2 adsorption and desorption measurements. Results show that ZnO was incorporated within the TiO2 crystals and did not form a separate bulky phase or metallic zinc. Moreover, the calcination temperature dramatically modifies the texture properties of the prepared samples compared with original Hombikat TiO2. The photocatalytic performance of the prepared samples was evaluated by monitoring the degradation of methyl orange dye under black light illumination. Three main parameters were studied; ZnO loading, surface area and initial pH of the methyl orange solution. The variation in ZnO loading appears to have less influence on the catalytic activity than either the surface area or the pH. (C) 2011 Elsevier B.V. All rights reserved.

Metallic photo-couplers utilizing surface plasmon polariton (SPP) excitation have been studied experimentally and theoretically for improving the quantum efficiency of charge sensitive infrared phototransistors (CSIP). Metallic hole arrays deposited on top of the photo-active area of CSIPs (wavelength of 14.7 ¿m) induce intensified near fields for the intersubband transition in a GaAs quantum well at 100 nm below the metal/substrate interface. Cross-hole arrays yield the highest efficiency of 7%, which is by a factor of about four higher than the previously achieved value with square patch arrays.

A passive terahertz (THz) microscope has been developed for sensitive imaging of spontaneous THz radiation. The THz microscope consisted mainly of a Ge objective lens, a confocal pinhole, Ge relay lenses, and a highly sensitive THz detector (Charge-Sensitive Infrared Phototransistor, CSIP). Then experimental examinations of the developed microscope were performed. First, THz signals, which were related to the spontaneous thermal radiation, were reasonably obtained. Next a passive THz image was successfully achieved. The lateral resolution of the microscope was derived to be 25 m, where the depth resolution was derived to be 30 m. In addition, the lateral resolution was not degraded despite the coverage of GaAs and Si. These results indicate that the THz microscope enables passive imaging with high resolution. This study opens the door to novel THz measurement technology, which can reveal physical and biological phenomena such as molecular motions, biomolecular protein interactions, and semiconductor conditions in their true colors.

A passive scanning confocal microscope in the long-wavelength infrared (LWIR) region has been developed for sensitive imaging of spontaneous LWIR radiation by utilizing an ultrahighly sensitive detector, called the charge-sensitive infrared phototransistor (CSIP). The microscope consisted of room-temperature components including a Ge objective lens and liquid helium temperature components including a confocal pinhole, Ge relay lenses, and CSIP detector. With the microscope, thermal radiation (wavelength of 14.7 μm) spontaneously emitted by the object was studied with a spatial resolution of 25 μm. Clear passive LWIR imaging pictures were obtained by scanning a sample consisting of glass, Al foil, Ag paste, and Au. Clear passive LWIR image was also obtained even when the sample surface was covered by a GaAs or Si plate. This work suggests usefulness of CSIP detectors for application of passive LWIR microscopy.

A scanning confocal long-wavelength infrared (LWIR) microscope has been developed by using a highly-sensitive, novel LWIR detector (charge-sensitive infrared phototransistor) for wavelengths -14.7 mum. Samples and Ge objective lens are placed at room temperature, while other optics including a confocal pinhole, Ge relay lenses, and the detector are cooled down to 4.2 K. Passive LWIR imaging has been achieved with a spatial resolution of 25 mum, which was kept unchanged when the sample surface was covered by a GaAs or Si plate. This work indicates the usefulness of the CSIP for application in passive LWIR microscopy.

A novel highly sensitive detector for long wavelength infrared radiation, called charge sensitive infrared phototransistor (CSIP), is described, with a stress put on the report of recent improvements in the quantum efficiency. Metallic antenna structure placed on the surface to convert incident radiation has to be optimized. In case of the CSIP, where the absorbing quantum well is very close (∼100nm) to the antenna, near field effects have to be taken into consideration. We consider several patterns based either on a double capacitive (dot) or inductive (hole) grating. We present results of a study comparing four different geometries showing that cross shape hole arrays are most promising candidates reaching efficiencies of almost 8%. Further strategies to optimize essential parameters of antennas by using finite difference time domain (FDTD) simulations are considered.

We describe a novel GaAs/AlGaAs double-quantum-well device for the infrared photon detection, called Charge-Sensitive Infrared Phototransistor (CSIP). The principle of CSIP detector is the photo-excitation of an intersubband transition in a QW as an charge integrating gate and the signal amplification by another QW as a channel with very high gain, which provides us with extremely high responsivity (10^4 -- 10^6 A/W). It has been demonstrated that the CSIP designed for the mid-infrared wavelength (14.7 um) has an excellent sensitivity; the noise equivalent power (NEP) of 7x10^-19 W/rHz with the quantum efficiency of ~2%. Advantages of the CSIP against the other highly sensitive detectors are, huge dynamic range of >10^6, low output impedance of 10^3 -- 10^4 Ohms, and relatively high operation temperature (>2K). We discuss possible applications of the CSIP to FIR photon detection covering 35 -- 60 um waveband, which is a gap uncovered with presently available photoconductors.

As a bottom-up approach toward spintronics, a network structure of gold nanoparticles connected with spin-polarized wire molecules has been studied. A spinless network is prepared as a reference system. The network of gold nanoparticles with an average diameter of 4 nm form granules (average diameter of 100 nm), which in turn, connect themselves with each other to bridge 2 mu m-gap gold electrodes. Since the charging energy of a 4-nm gold nanoparticle amounts to 160 meV, it works as a Coulomb island and the conduction through the network is dominated by Coulomb blockade effect at room temperature. Thermal-activation-type conduction is found in a temperature range of 300 K-30 K, below which cotunneling is suggested to dominate. Important findings reported here are as follows: (1) The cotunneling occurs at elevated temperatures as high as T=30 K due to the small size of gold nanoparticles: Nonlinear characteristics featured by I-V-3 are found, suggesting that the number of tunnel junctions relevant to the cotunneling is two. (2) The cotunneling current is substantially smaller in spin-polarized network than in spinless network, suggesting that spin-flip scattering caused by localized spins on wire molecules suppresses cotunneling process: The interpretation is supported by negative magnetoresistance observed in spin-polarized networks.

SmallVolume 4, Issue 4 p. 471-475 Communication Controlling Co-tunneling Currents in Nanoparticle Networks Using Spin-Polarized Wire Molecules† Patrick Nickels, Patrick Nickels Department of Basic Science, Graduate School of Arts and Sciences The University of Tokyo Komaba Meguro, Tokyo 153-8902 (Japan)Search for more papers by this authorMichio M. Matsushita, Michio M. Matsushita Department of Basic Science, Graduate School of Arts and Sciences The University of Tokyo Komaba Meguro, Tokyo 153-8902 (Japan)Search for more papers by this authorMasaru Minamoto, Masaru Minamoto Department of Basic Science, Graduate School of Arts and Sciences The University of Tokyo Komaba Meguro, Tokyo 153-8902 (Japan)Search for more papers by this authorSusumu Komiyama, Susumu Komiyama Department of Basic Science, Graduate School of Arts and Sciences The University of Tokyo Komaba Meguro, Tokyo 153-8902 (Japan)Search for more papers by this authorTadashi Sugawara, Corresponding Author Tadashi Sugawara [email protected] Department of Basic Science, Graduate School of Arts and Sciences The University of Tokyo Komaba Meguro, Tokyo 153-8902 (Japan)Department of Basic Science, Graduate School of Arts and Sciences The University of Tokyo Komaba Meguro, Tokyo 153-8902 (Japan) Fax: (+81) 354-546-997Search for more papers by this author Patrick Nickels, Patrick Nickels Department of Basic Science, Graduate School of Arts and Sciences The University of Tokyo Komaba Meguro, Tokyo 153-8902 (Japan)Search for more papers by this authorMichio M. Matsushita, Michio M. Matsushita Department of Basic Science, Graduate School of Arts and Sciences The University of Tokyo Komaba Meguro, Tokyo 153-8902 (Japan)Search for more papers by this authorMasaru Minamoto, Masaru Minamoto Department of Basic Science, Graduate School of Arts and Sciences The University of Tokyo Komaba Meguro, Tokyo 153-8902 (Japan)Search for more papers by this authorSusumu Komiyama, Susumu Komiyama Department of Basic Science, Graduate School of Arts and Sciences The University of Tokyo Komaba Meguro, Tokyo 153-8902 (Japan)Search for more papers by this authorTadashi Sugawara, Corresponding Author Tadashi Sugawara [email protected] Department of Basic Science, Graduate School of Arts and Sciences The University of Tokyo Komaba Meguro, Tokyo 153-8902 (Japan)Department of Basic Science, Graduate School of Arts and Sciences The University of Tokyo Komaba Meguro, Tokyo 153-8902 (Japan) Fax: (+81) 354-546-997Search for more papers by this author First published: 23 April 2008 https://doi.org/10.1002/smll.200700461Citations: 21 † This work was supported by a Grant-in-aid for Scientific Research on Priority Areas “Application of Molecular Spins” (Area No. 769, Proposal No. 15087101) from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT). Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat References 1 M. C. Daniel, D. Astruc, Chem. Rev. 2004, 104, 293. 10.1021/cr030698+ CASPubMedWeb of Science®Google Scholar 2 G. Schmidt, in Nanoparticles, Wiley-VCH, Weinheim 2003. 10.1002/3527602399 Google Scholar 3 T. Hasobe, H. Imahori, P. V. Kamat, T. K. Ahn, S. K. Kim, D. Kim, A. Fujimoto, T. Hirakawa, S. Fukuzumi, J. Am. Chem. Soc. 2005, 127, 12865. Google Scholar 4 A. Zabet-Khosousi, P. E. Trudeau, Y. Suganuma, A. Dhirani, Phys. Rev. Lett. 2006, 96, 156403. 10.1103/PhysRevLett.96.156403 CASPubMedWeb of Science®Google Scholar 5 J. M. Wessels, H. G. Nothofer, W. E. Ford, F. v. Wrochem, F. Scholz, T. Vossmeyer, A. Schroedter, H. Weller, A. Yasuda, J. Am. Chem. Soc. 2004, 126, 3349. 10.1021/ja0377605 CASPubMedWeb of Science®Google Scholar 6 D. K. James, J. M. Tour, Chem. Mater. 2004, 16, 4423. 10.1021/cm049648r CASWeb of Science®Google Scholar 7 L. P. Kouwenhoven, G. Schön, L. L. Sohn, Mesoscopic Electron Transport (Eds.: L. L. Sohn, L. P. Kouwenhoven, G. Schön ), Kluwer Academic Publishers, Dordrecht, The Netherlands, 1997, pp 1– 44. 10.1007/978-94-015-8839-3_1 Web of Science®Google Scholar 8 M. G. Ancona, W. Kruppa, R. W. Rendell, A. W. Snow, D. Park, J. B. Boos, Phys. Rev. B 2001, 64, 033408. 10.1103/PhysRevB.64.033408 CASWeb of Science®Google Scholar 9 T. B. Tran, I. S. Beloborodov, X. M. Lin, T. P. Bigioni, V. M. Vinokur, H. M. Jaeger, Phys. Rev. Lett. 2005, 95, 76806. 10.1103/PhysRevLett.95.076806 PubMedWeb of Science®Google Scholar 10 M. Minamoto, M. M. Matsushita, T. Sugawara, Polyhedron 2005, 24( 16–17), 2263. 10.1016/j.poly.2005.03.083 CASWeb of Science®Google Scholar 11a) J. Nakazaki, I.-G. Chung, M. M. Matsushita, T. Sugawara, R. Watanabe, A. Izuoka, Y. Kawada, J. Mater. Chem. 2003, 13, 1011; 10.1039/b211986b CASWeb of Science®Google Scholar11b) J. Nakazaki, I. Chung, R. Watanabe, T. Ishitsuka, Y. Kawada, M. M. Matsushita, T. Sugawara, Internet Electron. J. Mol. Des. 2003, 2, 112. CASGoogle Scholar 12 H. Sakurai, A. Izuoka, T. Sugawara, J. Am. Chem. Soc. 2000, 122, 9723. 10.1021/ja994547t CASWeb of Science®Google Scholar 13 W. M. H. Sachtler, G. J. H. Dorelo, A. A. Holscher, Surf. Sci. 1966, 5, 221. 10.1016/0039-6028(66)90083-5 CASWeb of Science®Google Scholar 14 D. Jones, M. Guerra, L. Favaretto, A. Modelli, M. Fabrizolo, G. Distefano, J. Phys. Chem. 1990, 94, 5761. 10.1021/j100378a030 CASWeb of Science®Google Scholar 15 J. L. Brédas, R. Silbey, D. S. Boudreaux, R. R. Chance, J. Am. Chem. Soc. 1983, 105, 6555. 10.1021/ja00360a004 CASWeb of Science®Google Scholar 16 S. Taniguchi, M. Minamoto, M. M. Matsushita, T. Sugawara, Y. Kawada, D. Bethell, J. Mater. Chem. 2006, 16, 1. 10.1039/b604732g Web of Science®Google Scholar 17 A. J. Quinn, G. Redmond, Prog. Solid State Chem. 2005, 33, 263. 10.1016/j.progsolidstchem.2005.11.048 CASWeb of Science®Google Scholar 18To estimate the number of neighboring particles n, we calculated the capacitance of two adjacent particles as Cpair = 4πεoεr(1 − r2/d2)/(2/r − 2/d) ≈ 3.0 × 10−19 F, using ε = 2, a radius r of 2 nm, and a center-to-center distance d of 5.6 nm (molecular length of 1.6 nm). The overall capacitance of one nanoparticle in the network can be expressed as Ctotal = n Cpair and n can be derived from Ec = e2/Ctotal. Google Scholar 19 H. E. Romero, M. Drndic, Phys. Rev. Lett. 2005, 95, 156801. 10.1103/PhysRevLett.95.156801 CASPubMedWeb of Science®Google Scholar 20 D. Yu, C. Wang, B. L. Wehrenberg, P. Guyot-Sionnest, Phys. Rev. Lett. 2004, 92, 216802. 10.1103/PhysRevLett.92.216802 CASPubMedWeb of Science®Google Scholar 21 B. I. Shklovskii, A. L. Efros, in Electronic Properties of Doped Semiconductors, Springer Verlag, Berlin 1984. 10.1007/978-3-662-02403-4 Google Scholar 22 M. V. Feigelman, A. S. Ioselevich, cond-mat/0502481, 2005. Google Scholar 23a) I. S. Beloborodov, K. B. Efetov, A. V. Lopatin, V. M. Vinokur, Phys. Rev. Lett. 2003, 91, 246801; 10.1103/PhysRevLett.91.246801 CASPubMedWeb of Science®Google Scholar23b) I. S. Beloborodov, A. V. Lopatin, V. M. Vinokur, Phys. Rev. B 2005, 72, 125121; 10.1103/PhysRevB.72.125121 CASWeb of Science®Google Scholar23c) I. S. Beloborodov, A. Glatz, V. M. Vinokur, Phys. Rev. B 2007, 75, 052302. 10.1103/PhysRevB.75.052302 Web of Science®Google Scholar 24 L. J. Geerlings, D. V. Averin, J. E. Mooij, Phys. Rev. Lett. 1990, 65, 3037. 10.1103/PhysRevLett.65.3037 PubMedWeb of Science®Google Scholar 25 D. V. Averin, Yu. V. Nazarov, in Coulomb Blockade Phenomena in Nanostructures (Eds.: H. Grabert, M. H. Devoret), Plenum Press and NATO Scientific Affairs Division, New York, 1992, p. 217. Web of Science®Google Scholar 26 A. A. Middleton, N. S. Wingreen, Phys. Rev. Lett. 1993, 71, 3198. 10.1103/PhysRevLett.71.3198 CASPubMedWeb of Science®Google Scholar 27 F. Guinea, Phys. Rev. B 1998, 58, 9212. 10.1103/PhysRevB.58.9212 CASWeb of Science®Google Scholar 28 S. Mitani, S. Takahashi, K. Takanashi, K. Yakushiji, S. Maekawa, H. Fijimori, Phys. Rev. Lett. 1998, 81, 2799. 10.1103/PhysRevLett.81.2799 CASWeb of Science®Google Scholar 29 C. T. Black, C. B. Murray, R. L. Sandstrom, S. Sun, Science 2000, 290, 1131. 10.1126/science.290.5494.1131 CASPubMedWeb of Science®Google Scholar 30 M. M. Maye, S. C. Chun, L. Han, D. Rabinovich, C.-J. Zhong, J. Am. Chem. Soc. 2002, 124, 4958. 10.1021/ja025724k CASPubMedWeb of Science®Google Scholar 31 M. Brust, M. Walker, D. Bethell, D. J. Schiffrin, R. Whyman, J. Chem. Soc.; Chem. Commun. 1994, 801. 10.1039/C39940000801 CASGoogle Scholar 32 O. Nagao, G. Harada, T. Sugawara, A. Sasaki, Y. Ito, Jpn. J. Appl. Phys. 2004, 43, 7742. 10.1143/JJAP.43.7742 CASWeb of Science®Google Scholar 33 M. M. Matsushita, N. Ozaki, T. Sugawara, F. Nakamura, M. Hara, Chem. Lett. 2002, 31, 596. 10.1246/cl.2002.596 Web of Science®Google Scholar Citing Literature Volume4, Issue4April 2008Pages 471-475 ReferencesRelatedInformation

Rolling circle amplification (RCA) is an elegant biochemical method by which long single-stranded DNA molecules with a repeating sequence motif can be readily synthesized. In RCA, small circular single-stranded oligonucleotides serve as templates for the polymerization of the complementary strand. A DNA polymerase with an efficient strand displacement activity can copy the circular template without stopping. This results in a long DNA strand with periodic sequence. We here demonstrate that this method, using DNA recognition and biotin-streptavidin binding, provides a simple procedure for DNA-directed nanoscale organization of matter. As an example, a 74 nucleotide (nt) long circular DNA molecule is amplified into a sequence-periodic single strand with a length up to several micrometers. Hybridization of this long periodic DNA template to the biotinylated complement of the sequence motif results in a long DNA duplex with a periodic arrangement of biotin binding sites. On this duplex, streptavidin-coated particles can be organized into one-dimensional arrays. The resulting DNA constructs are characterized by gel electrophoresis and atomic force microscopy.