Current Issue

Volume 4 Issue 9 (September 2008)

Cover Picture

Cover Picture: Small 9/2008 (p NA)
Changxin Chen, Yang Lu, Eric S. Kong, Yafei Zhang, Shuit-Tong Lee
Published Online: Sep 1 2008 5:11AM
DOI: 10.1002/smll.200890038

	The cover picture shows a series-parallel array of single-walled carbon nanotube (SWNT) solar photovoltaic microcells. In this SWNT solar microcell, the directed semiconducting SWNTs are ultrasonically nanowelded onto two asymmetric metal electrodes with high and low work functions, respectively, resulting in a strong built-in electric field in SWNTs for efficient separation of photogenerated electron-hole pairs. Under solar-light illumination, the device shows photovoltaic effects. A high power-conversion efficiency of 12.6% can be achieved by the monolayer SWNT solar microcell. The results demonstrate the great application potential for SWNTs as the photosensitive material of solar cells. For more information, please read the Communication Nanowelded Carbon-Nanotube-Based Solar Microcells by C. Chen et al., beginning on page 1313.

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Contents

Contents: Small 9/2008 (p 1255-1265)

Published Online: Sep 1 2008 5:11AM
DOI: 10.1002/smll.200890039

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News

News from the micro-nano world (p 1268-1269)

Published Online: Sep 1 2008 5:11AM
DOI: 10.1002/smll.200801187

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Review

Liquid crystals

Carbon Nanotubes as Liquid Crystals (p 1270-1283)
Shanju Zhang, Satish Kumar
Published Online: Aug 27 2008 6:55AM
DOI: 10.1002/smll.200700082

	Liquid crystals have only recently entered the carbon-nanotube (CNT) arena. The intrinsic self-assembling nature of CNT liquid crystals (see image) is promising in achieving macroscopic alignments of CNT-based materials. This Review highlights recent developments of nanotubes as liquid crystals by addressing the current approaches for fabricating liquid-crystal phases and exploiting the liquid-crystal routes for making aligned CNT materials.

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Communications

Carbon nanotubes

Optical Identification of a DNA-Wrapped Carbon Nanotube: Signs of Helically Broken Symmetry (p 1284-1286)
Stacy E. Snyder, Slava V. Rotkin
Published Online: Aug 6 2008 5:11AM
DOI: 10.1002/smll.200800114

	Optical absorption of a DNA-wrapped single-walled carbon nanotube is simulated for perpendicularly polarized light. The helical wrap causes circular dichroism of an achiral nanotube and alters the absorption spectrum (see image). These effects may allow direct optical identification of the wrap.

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Reversible assembly

pH-Controlled Reversible Assembly and Disassembly of Gold Nanorods (p 1287-1292)
Zhenhua Sun, Weihai Ni, Zhi Yang, Xiaoshan Kou, Li Li, Jianfang Wang
Published Online: Aug 6 2008 5:11AM
DOI: 10.1002/smll.200800099

	pH-Controlled assembly and disassembly of gold nanorods in both end-to-end and side-by-side fashions are demonstrated using bifunctional molecules that contain a thiol group at one end and a different functional group at the other end (see image). The assembly and disassembly processes are reversible and can be repeated for many cycles.

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NMR

Supramolecular Interactions at the Picomole Level Studied by ¹⁹F NMR Spectroscopy in a Microfluidic Chip (p 1293-1295)
M. Victoria Gómez, David N. Reinhoudt, Aldrik H. Velders
Published Online: Aug 14 2008 3:39AM
DOI: 10.1002/smll.200701306

	Small-scale chips: 19F NMR spectroscopy is performed on nanoliter volumes in a microfluidic chip equipped with a planar microcoil (see picture). The high resolution and sensitivity allow the detection of small chemical shift variations, which enables investigation of the supramolecular interaction between NaPF6 and -cyclodextrin.

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Nanostructures for SERS

Individual Nanometer Hole-Particle Pairs for Surface-Enhanced Raman Scattering (p 1296-1300)
Hong Wei, Ulf Håkanson, Zhilin Yang, Fredrik Höök, Hongxing Xu
Published Online: Aug 21 2008 5:39AM
DOI: 10.1002/smll.200701135

	Holed up: Individual nanometer hole-particle pairs are prepared by self-assembly and their optical properties studied. A single nanoparticle is located in a single nanohole, which creates hot sites between them, thus greatly enhancing Raman signals of probe molecules. The enhancement is shown to depend on the spacing between the particle and hole. This new system has great potential for SERS studies in general and biosensor applications in particular.

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Core/Shell nanostructures

Facile One-Pot Synthesis of Self-Assembled Silver@Polypyrrole Core/Shell Nanosnakes (p 1301-1306)
David Muñoz-Rojas, Judith Oró-Solé, Omar Ayyad, Pedro Gómez-Romero
Published Online: Aug 19 2008 2:38AM
DOI: 10.1002/smll.200701199

	Snakes on a plane TEM grid! Tortuous core/shell nanostructures are produced by a simple, additive-free, one-pot hydrothermal reaction at 120-150 °C. Electron diffraction and high-resolution transmission electron microscopy indicate that the inner silver core is coherent. The nanosnakes (see image) form through self-assembly of reduced silver particles inside a polypyrrole matrix.

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Imaging

Protease-Triggered Unveiling of Bioactive Nanoparticles (p 1307-1312)
Todd J. Harris, Geoffrey von Maltzahn, Matthew E. Lord, Ji-Ho Park, Amit Agrawal, Dal-Hee Min, Michael J. Sailor, Sangeeta N. Bhatia
Published Online: Aug 8 2008 8:09AM
DOI: 10.1002/smll.200701319

	The ability to reveal bioactive domains on the surface of nanoparticles in response to microenvironmental cues in tumors could provide a powerful means for targeting their activity. The feasibility of such a design is demonstrated by veiling nanoparticles with protease-removable polymer coatings (see image). Multimodal visualization and quantification of this model system establishes the utility of these coatings to improve nanoparticle delivery and direct the unveiling of bioactive surface groups in solid tumors.

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Photovoltaic cells

Nanowelded Carbon-Nanotube-Based Solar Microcells (p 1313-1318)
Changxin Chen, Yang Lu, Eric S. Kong, Yafei Zhang, Shuit-Tong Lee
Published Online: Aug 14 2008 3:39AM
DOI: 10.1002/smll.200701309

	A novel carbon-nanotube (CNT) solar photovoltaic cell is constructed by nanowelding of semiconducting single-walled CNTs onto two asymmetric metal electrodes for efficient separation of photogenerated electron-hole pairs (see image). Under solar-light illumination, high internal power-conversion efficiency up to 12.6% is achieved for monolayer CNT cells.

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Heterostructured nanorods

ZnSe Quantum Dots Within CdS Nanorods: A Seeded-Growth Type-II System (p 1319-1323)
Dirk Dorfs, Asaf Salant, Inna Popov, Uri Banin
Published Online: Aug 4 2008 4:42AM
DOI: 10.1002/smll.200800084

	CdS nanorods with ZnSe seeds are developed. Rod growth is achieved for a seed with a zinc blende structure. Due to the type-I potential profile in this anisotropic nanoheterostructure, charge-carrier separation occurs in the excited state of the nanorod. Structural characterization is shown as well as static and time-resolved optical spectroscopy. A fluorescence quantum yield of 45% is achieved, demonstrating the exceptional optical properties of these structures.

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Peptide nanoarrays

Controlled Growth of Peptide Nanoarrays on Si/SiO_x Substrates (p 1324-1328)
Xiaozhu Zhou, Yanhong Chen, Bing Li, Gang Lu, Freddy Y. C. Boey, Jan Ma, Hua Zhang
Published Online: Aug 19 2008 9:14AM
DOI: 10.1002/smll.200701267

	PAMAM dendrimer nanopatterns on Si/ SiOx substrates generated by dip-pen nanolithography are used as anchoring scaffolds for the growth of peptides in situ by ring-opening polymerization of tryptophan-N-carboxyanhydrides. This new method for the fabrication of peptide nanoarrays (see image) on a solid substrate is unique in that the growth of peptide nanostructures is controlled by the reaction time and the concentration of the tryptophan species.

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DNA

Complexity Emerges from Lattice Overlapping: Implications for Nanopatterning (p 1329-1331)
Yu He, Seung Hyeon Ko, Ye Tian, Alexander E. Ribbe, Chengde Mao
Published Online: Aug 21 2008 5:39AM
DOI: 10.1002/smll.200701051

	The overlapping of self-assembled, two-dimensional DNA crystal lattices generates complex Moiré nanopatterns (see image). This work suggests a novel hierarchical self-assembly approach for nanopatterning, which could potentially greatly increase the pattern complexities.

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Nanocrystals

Photostable Second-Harmonic Generation from a Single KTiOPO₄ Nanocrystal for Nonlinear Microscopy (p 1332-1336)
Loc Le Xuan, Chunyuan Zhou, Abdallah Slablab, Dominique Chauvat, Cédric Tard, Sandrine Perruchas, Thierry Gacoin, Philippe Villeval, Jean-François Roch
Published Online: Aug 21 2008 5:39AM
DOI: 10.1002/smll.200701093

	Single KTiOPO4 nanocrystals, isolated from a flux-grown powder, efficiently generate a perfectly stable and blinking-free second-harmonic field under non-resonant femtosecond optical excitation (see image). For each individual nanocrystal, size and three-dimensional orientation are determined using combined atomic force microscopy and optical techniques.

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Gas sensors

Synthesis of Polyhedral ZnSnO₃ Microcrystals with Controlled Exposed Facets and Their Selective Gas-Sensing Properties (p 1337-1343)
Baoyou Geng, Caihong Fang, Fangming Zhan, Nan Yu
Published Online: Aug 21 2008 5:39AM
DOI: 10.1002/smll.200701177

	A sensitive face: Polyhedral ZnSnO3 microcrystals with controlled exposed facets are selectively synthesized in high yield by a convenient, repeatable, and low-temperature process (see image). The polyhedral ZnSnO3 particles have good gas-sensing properties and show high sensitivity to H2S, HCHO, and C2H5OH, as well as good reproducibility and short response/recovery times. Different shapes of ZnSnO3 polyhedra have unique gas sensitivity to the detected gases because of their different active facets.

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Quantum dots

Chiral Recognition of Amino Acids Based on Cyclodextrin-Capped Quantum Dots (p 1344-1350)
Cuiping Han, Haibing Li
Published Online: Aug 21 2008 5:39AM
DOI: 10.1002/smll.200701221

	Water-soluble and stable semiconductor CdSe/ZnS quantum dots (QDs) are prepared by using - and -cyclodextrin (CD) as surface-coating agents by using a simple sonochemical method, which allows highly enantioselective fluorescent recognition of amino acids (see image). When CD-QDs are treated with L-amino acids (see image), a much greater fluorescence enhancement is observed than that with D-amino acids.

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Nanorods

Two-Component Nanorod Arrays by Glancing-Angle Deposition (p 1351-1354)
Chunming Zhou, Daniel Gall
Published Online: Aug 8 2008 8:09AM
DOI: 10.1002/smll.200701289

	Simultaneous deposition of two distinct materials A and B from opposite sides onto nanospheres leads to the formation of nanorod arrays with vertically separated components. This is demonstrated for the case of 220-nm-wide Si-Ta two-component rods (see image), which exhibit a measured and simulated vertical interface width of 28 nm.

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Nanoclusters

The Creation of Nanostructures on an Au(111) Electrode by Tip-Induced Iron Deposition from an Ionic Liquid (p 1355-1358)
Yi-Min Wei, Xiao-Shun Zhou, Jin-Gang Wang, Jing Tang, Bing-Wei Mao, Dieter M. Kolb
Published Online: Aug 14 2008 3:39AM
DOI: 10.1002/smll.200800037

	High-precision nanostructuring with an STM combined with electrodeposition of a reactive metal allows the creation of iron clusters in an ionic liquid. This type of structuring would not be possible in an aqueous solution. The image shows a ring of 48 iron clusters on an Au(111) electrode surface. The diameter of the ring is 120 nm and the average height of the clusters is 0.6 nm.

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Nanoporous structures

Nanoporous Structures: Smaller is Stronger (p 1359-1362)
Gang Ouyang, Guowei Yang, Changqing Sun, Weiguang Zhu
Published Online: Aug 8 2008 8:09AM
DOI: 10.1002/smll.200800129

	It's what's inside that counts! Nanoporous materials with large internal surface area have been extensively employed as host materials in nanotechnology. Since the lower co-ordination of atoms of nanoporous structures can lead to the redistribution of electronic charge and change the cohesive energy of single atoms in the matrix (see image), the mechanical responses differ from those of atoms in the bulk counterpart.

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Full Papers

Antitumor therapy

Carbon Nanotubes Conjugated to Tumor Lysate Protein Enhance the Efficacy of an Antitumor Immunotherapy (p 1364-1370)
Jie Meng, Jie Meng, Jinhong Duan, Hua Kong, Li Li, Chen Wang, Sishen Xie, Shuchang Chen, Ning Gu, Haiyan Xu, Xian-Da Yang
Published Online: Aug 21 2008 5:39AM
DOI: 10.1002/smll.200701059

	Multi-walled carbon nanotubes are conjugated to tumor protein (see image) and injected into tumor-bearing mice. The treatment enhances the tumor-cure rate of an antitumor immunotherapy and the cellular immune reaction against the tumor cells.

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Dielectrophoresis

Microtubule Alignment and Manipulation Using AC Electrokinetics (p 1371-1381)
Maruti Uppalapati, Ying-Ming Huang, Thomas N. Jackson, William O. Hancock
Published Online: Aug 21 2008 5:39AM
DOI: 10.1002/smll.200701088

	AC electric fields generated by microfabricated electrodes result in both dielectrophoresis and electrohydrodynamic flow. Using these forces, microtubules are aligned along the centerline of electrodes (see image, left) or assembled into structures mimicking the mitotic spindle in dividing cells (right). These tools can be used for microscale transport applications or for investigating the biological function of kinesin motors and microtubules.

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Growth simulations

Understanding the Kinetics and Nanoscale Morphology of Electron-Beam-Induced Deposition via a Three-Dimensional Monte Carlo Simulation: The Effects of the Precursor Molecule and the Deposited Material (p 1382-1389)
Daryl A. Smith, Jason D. Fowlkes, Philip D. Rack
Published Online: Aug 21 2008 5:39AM
DOI: 10.1002/smll.200701133

	The electron-beam-induced deposition of silicon oxide from tetraethyorthosilicate and tungsten from tungsten hexafluoride is simulated via a Monte Carlo simulation. Pseudo one-dimensional nanopillars are grown (see image) and a comparison of vertical and lateral growth rate and pillar morphology is correlated to the precursor and deposited material parameters. The primary and secondary electrons (type I) dominate the vertical growth rate and the lateral growth rate is dominated by forward and secondary electrons (type II).

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Crystal growth

Biomimetic Synthesis of Gold Nanocrystals Using a Reducing Amphiphile (p 1390-1398)
Ferdinand Gonzaga, Sherdeep Singh, Michael A. Brook
Published Online: Aug 19 2008 2:38AM
DOI: 10.1002/smll.200701163

	A single reactive amphiphile derived from citric acid and silicones induces gold ion reduction, particle nucleation, and further directs gold crystal growth (see image). The process, both pH and light dependent, occurs through lipid-directed assembly of metal ions, their reduction and subsequent lipid-directed growth to yield ultrathin (ca. 7 nm thick) quasi-2D gold nanocrystals.

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Molecular junctions

High-Fidelity Formation of a Molecular-Junction Device Using a Thickness-Controlled Bilayer Architecture (p 1399-1405)
Gyeong Sook Bang, Hojong Chang, Ja-Ryong Koo, Takhee Lee, Rigoberto C. Advincula, Hyoyoung Lee
Published Online: Aug 21 2008 5:39AM
DOI: 10.1002/smll.200701232

	A bilayered film with a thickness of 4-5 nm and free thiol-terminated bilayer self-assembled monolayers is a breakthrough for reducing the effect of the surface roughness (1.4 nm) of the bottom electrode as well as for preventing the penetration of the top electrode of molecular-electronic devices (see image). This structure can be an effective way to regulate the generation of electrical shorts in this type of device.

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Quantum dots

Functionalized-Quantum-Dot-Liposome Hybrids as Multimodal Nanoparticles for Cancer (p 1406-1415)
Wafa' T. Al-Jamal, Khuloud T. Al-Jamal, Paul H. Bomans, Peter M. Frederik, Kostas Kostarelos
Published Online: Aug 19 2008 2:38AM
DOI: 10.1002/smll.200701043

	Functionalized quantum-dot-liposome (f-QD-L) hybrids are engineered by encapsulation of fluorescent poly(ethylene glycol)-coated QD in the internal aqueous phase of lipid vesicles (see image). Cationic f-QD-L hybrids have shown dramatic improvements in cellular binding and deeper penetration into three-dimensional multicellular tumor spheroids, without the need for conjugation chemistry on the QD surface.

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Cell proliferation

Contractility-Dependent Modulation of Cell Proliferation and Adhesion by Microscale Topographical Cues (p 1416-1424)
Rahul G. Thakar, Matthew G. Chown, Anuj Patel, Lily Peng, Sanjay Kumar, Tejal A. Desai
Published Online: Aug 19 2008 2:38AM
DOI: 10.1002/smll.200701302

	On a square peg: Scanning electron microscopy shows that cells are attracted to micropegs (25 × 25 × 15 µm) in an array (see image of attached fibroblasts). Contact with a micropeg leads to a decrease in proliferation as the contractility increases.

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Green chemistry

Soybeans as a Phytochemical Reservoir for the Production and Stabilization of Biocompatible Gold Nanoparticles (p 1425-1436)
Ravi Shukla, Satish K. Nune, Nripen Chanda, Kavita Katti, Swapna Mekapothula, Rajesh R. Kulkarni, Wade V. Welshons, Raghuraman Kannan, Kattesh V. Katti
Published Online: Jul 18 2008 8:47AM
DOI: 10.1002/smll.200800525

	A green nanotechnological process for the production of gold nanoparticles using phytochemicals in soybeans is described. The interaction of sodium tetrachloroaurate with soybeans or soybean extract in water results in the production of nontoxic gold nanoparticles of spherical shape. No man-made chemicals, other than the gold salts, are used, thus satisfying the fundamental principles of green chemistry.

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Macrophage detection

An ApoA-I Mimetic Peptide High-Density-Lipoprotein-Based MRI Contrast Agent for Atherosclerotic Plaque Composition Detection (p 1437-1444)
David P. Cormode, Karen C. Briley-Saebo, Willem J. M. Mulder, Juan Gilberto S. Aguinaldo, Alessandra Barazza, Yanqing Ma, Edward A. Fisher, Zahi A. Fayad
Published Online: Aug 19 2008 9:14AM
DOI: 10.1002/smll.200701285

	The synthesis and characterization of synthetic high-density lipoprotein labeled with Gd3+ and rhodamine is reported. As can be seen in the figure, MRI images of the aorta of apoE mice (a model of atherosclerosis) show 93% enhancement. In addition, confocal microscopy of the aorta proves the agent to be macrophage specific.

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Imaging

Mesoporous Silica Nanoparticles as a Delivery System of Gadolinium for Effective Human Stem Cell Tracking (p 1445-1452)
Jong-Kai Hsiao, Chih-Pin Tsai, Tsai-Hua Chung, Yann Hung, Ming Yao, Hon-Man Liu, Chung-Yuan Mou, Chung-Shi Yang, Yao-Chang Chen, Dong-Ming Huang
Published Online: Aug 4 2008 4:42AM
DOI: 10.1002/smll.200701316

	Designer Label: Dual-functional Gd-FITC mesoporous silica nanoparticles (Gd-Dye@MSN) displaying green fluorescence and paramagnetism are developed as a label for human mesenchymal stem cells (hMSCs). Labeled hMSCs can be easily MRI-detected in vivo with a clinical 1.5-T MRI system (see image).

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Magnetite nanoparticles

Modified PVA-Fe₃O₄ Nanoparticles as Protein Carriers into Sperm Cells (p 1453-1458)
Shirly Ben-David Makhluf, Riam Abu-Mukh, Sara Rubinstein, Haim Breitbart, Aharon Gedanken
Published Online: Aug 4 2008 4:42AM
DOI: 10.1002/smll.200701308

	Bovine sperm cells are incubated with APS-PVA-magnetite nanoparticles conjugated with anti-PKC, for 1 h at 37 °C in NKM, fixed, and labeled by secondary antibody antirabbit IgG conjugated Cy-3 (see figure). The magnetic nature of the nanoparticles conjugated with antibody provides a novel and simple method for specific protein separation.

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Carbon nanotubes

Phase Behavior and Shear Alignment in SWNT-Surfactant Dispersions (p 1459-1467)
Einat Nativ-Roth, Rachel Yerushalmi-Rozen, Oren Regev
Published Online: Sep 1 2008 5:11AM
DOI: 10.1002/smll.200800082

	Surfactant-dispersed single-walled nanotubes (SWNTs) nucleate ordering and elongation of micelles under shear. The shear-induced structure (SIS), imaged by cryo-TEM (see picture), is found in the presence of minute amounts of SWNTs. The effect is exclusive to SWNTs and does not occurin dispersions of other carbonaceous additives.

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DNA

An AFM/Rotaxane Molecular Reading Head for Sequence-Dependent DNA Structures (p 1468-1475)
Brian A. Ashcroft, Quinn Spadola, Shahid Qamar, Peiming Zhang, Gerald Kada, Rouvain Bension, Stuart Lindsay
Published Online: Aug 4 2008 4:42AM
DOI: 10.1002/smll.200800233

	A method for studying DNA secondary structure is developed using an atomic force microscope (AFM; see image). --CD forms a rotaxane on a nonstick surface, is covalently bound to an AFM tip via a flexible linker, and pulled up and over tethered DNA. The formation and mechanical operation of the system is confirmed by measuring the forces required to unfold hairpins.

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Carbon nanotubes

Towards an Ultrasensitive Method for the Determination of Metal Impurities in Carbon Nanotubes (p 1476-1484)
Taras Kolodiazhnyi, Martin Pumera
Published Online: Aug 4 2008 4:42AM
DOI: 10.1002/smll.200800125

	Purity test: Residual catalyst metal nanoparticles remain obstacles for the utilization of carbon nanotubes in many areas. A comparative study of magnetic susceptibility, EPR, EDX, XPS, and TGA techniques show that the most sensitive method for the detection of metal impurities in carbon nanotubes is magnetic susceptibility, which allows the detection of traces of magnetic metal impurities embedded in carbon nanotubes(see image), whereas other methods provide false impurity-free information.

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Hydrogels

EPR Spectroscopy Reveals Nanoinhomogeneities in the Structure and Reactivity of Thermoresponsive Hydrogels (p 1485-1493)
Matthias J. N. Junk, Ulrich Jonas, Dariush Hinderberger
Published Online: Aug 4 2008 4:42AM
DOI: 10.1002/smll.200800127

	Using EPR spectroscopy, it is found that a simple statistical copolymer network shows remarkable complexity on the nanoscale. These hydrogels show structural inhomogeneities that lead to the coexistence of network regions that significantly enhance a chemical reaction (nanoreactors) and shield molecules from the reaction (nanoshelters; see image).

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Self-assembly

An Investigation into the Interactions Between Self-Assembled Adenine Molecules and a Au(111) Surface (p 1494-1500)
Ross E. A. Kelly, Wei Xu, Maya Lukas, Roberto Otero, Manuela Mura, Young-Joo Lee, Erik Lægsgaard, Ivan Stensgaard, Lev N. Kantorovich, Flemming Besenbacher
Published Online: Aug 4 2008 4:42AM
DOI: 10.1002/smll.200800172

	Two-phased lier! Two self-assembled molecular surface nanostructures of the DNA base adenine (A) on Au(111) are observed. The left panel shows one of the monolayer phases observed by using STM and the corresponding molecular model. The right panel represents a DFT calculation of an A pair lying (involved in the monolayer on the left) on the Au(111) surface. The surface has a negligible effect on the hydrogen bonding between the molecules.

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Steam purification and shortening

Steam Purification for the Removal of Graphitic Shells Coating Catalytic Particles and the Shortening of Single-Walled Carbon Nanotubes (p 1501-1506)
Belén Ballesteros, Gerard Tobias, Lidong Shao, Eva Pellicer, Josep Nogués, Ernest Mendoza, Malcolm L.H. Green
Published Online: Aug 14 2008 3:39AM
DOI: 10.1002/smll.200701283

	Steam-cleaning for nanotubes: Purification and shortening of single-walled carbon nanotubes is carried out by treatment with steam. During the steam purification the graphitic shells coating the catalytic metal particles are removed (see image). The exposed catalytic particles can now be easily dissolved by treatment with hydrochloric acid. No damage of the carbon nanotube tubular structure is observed, even after prolonged treatment with steam.

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Gold nanowires

Microtubule-Based Gold Nanowires and Nanowire Arrays (p 1507-1515)
Jing C. Zhou, Yao Gao, Alfredo A. Martinez-Molares, Xiaoye Jing, Dong Yan, Joseph Lau, Toshikazu Hamasaki, Cengiz S. Ozkan, Mihrimah Ozkan, Evelyn Hu, Bruce Dunn
Published Online: Aug 27 2008 6:55AM
DOI: 10.1002/smll.200701187

	Microtubule protein filaments are used as templates to fabricate gold nanowires and nanowire arrays. Colloidal gold is directly seeded on microtubules (MTs) which are immobilized on Si wafers. Photochemical reduction is used to achieve continuous Au coverage. Conductivity of these MT-templated nanowires is reported. Conductive AFM studies reveal an interesting memory-like behavior.

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Photoluminescence

Photoactivation of CdSe/ZnS Quantum Dots Embedded in Silica Colloids (p 1516-1526)
Sofia Dembski, Christina Graf, Tim Krüger, Uwe Gbureck, Andrea Ewald, Anne Bock, Eckart Rühl
Published Online: Aug 19 2008 9:14AM
DOI: 10.1002/smll.200700997

	CdSe/ZnS quantum dots (QD) embedded in silica colloids show significant photoluminescence enhancement by irradiation with UV or visible radiation in various solvents (see image). The photoluminescence of the embedded QD is enhanced up to ten times and is strongly dependent on the local environment. The permeability of the silica shell controls the influence of the outer media on the QD.

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Lithography

Positive and Negative ZnO Micropatterning on Functionalized Polymer Surfaces (p 1527-1536)
Peng Yang, Shengli Zou, Wantai Yang
Published Online: Aug 19 2008 2:38AM
DOI: 10.1002/smll.200700859

	Chemical solution growth of ZnO rods (see image) is conducted on functionality-patterned polymer surfaces to fabricate positive and negative ZnO micropatterns. The ZnO film is selectively obtained on sulfated and hydroxylated biaxially oriented poly(propylene) surfaces, giving rise to positive patterns, providing an effective solution toward microfabrication on inert polymer substrates. For PET, the ZnO pillars selectively remain on the unexposed original regions creating negative patterns.

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Cancer treatment

Enhancement of Radiation Cytotoxicity in Breast-Cancer Cells by Localized Attachment of Gold Nanoparticles (p 1537-1543)
Tao Kong, Jie Zeng, Xiaoping Wang, Xiaoyan Yang, Jing Yang, Steve McQuarrie, Alexander McEwan, Wilson Roa, Jie Chen, James Z. Xing
Published Online: Aug 19 2008 9:14AM
DOI: 10.1002/smll.200700794

	Functional nanoparticles with modified surface properties achieve targeted delivery at the subcellular level and selective binding with the cell membrane or localization to the cytoplasm (see image). Results show that the nanoparticles significantly increase the cytotoxicity of 200 kVp X-rays. Targeted nanoparticles can be used as an agent for cancer therapy.

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Keywords

Keywords Index Small 9/2008 (p 1544)

Published Online: Sep 1 2008 5:11AM
DOI: 10.1002/smll.200890040

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Authors

Authors Index Small 9/2008 (p 1545-1546)

Published Online: Sep 1 2008 5:11AM
DOI: 10.1002/smll.200890041

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Published Online: Sep 1 2008 5:11AM
DOI: 10.1002/smll.200890042

Abstract | Full Text: PDF (Size: 78K)
Save Article