Fabrication of Amino‐Terminated Multiwalled Carbon Nanotubes via Layer‐by‐Layer Self‐Assembly Approach

MWCNT‐based composites have been successfully synthesized via layer‐by‐layer self‐assembly of crosslinked polyphosphazene nanoparticles on the surface of MWCNTs. The amino‐terminated CNTs were characterized by XPS, FT‐IR spectroscopy, EDS, XRD and TEM. The degree of functionalization could be controlled by simply changing the mass of hexachlorocyclotriphosphazene with 4,4′‐diaminodiphenyl ether. The activity of the surface amino groups was confirmed by the reaction of these groups with HAuCl₄. In addition, the effects of the mass of HCCP and ODA ratios on the content of the surface amino groups was also investigated.

     

Self-Assembly of Nanostructures on Surfaces Using Metal–Organic Coordination

Layer-by-layer (LbL) assembly of multilayers is an established method for the construction of layered nanostructures on surfaces, affording control of the thickness, composition, and organization in the vertical direction. Binding between layers is accomplished using various types of interactions, including electrostatic binding, hydrogen bonding, covalent bonding, metal–organic coordination, host–guest interactions, biospecific interactions, and others. Here we focus on LbL assembly using metal–organic coordination, and specifically on layered nanostructures based on bishydroxamate–M⁴⁺ binding. The coordination approach offers attractive features, such as a simple reaction, a defined geometry, and reversibility under certain conditions. The basic scheme includes self-assembly of a ligand (anchor) monolayer on the surface, followed by alternate binding of metal ions and multi-functional ligand layers, to form a coordination multilayer. This approach is demonstrated by the construction of a variety of coordinated nanostructures, including bilayers, multilayers, dendrimers, and nanoparticle assemblies, prepared on gold and oxide substrates.     

Targeting of Cancer Cells Using Quantum Dot–Polypeptide Hybrid Assemblies That Function as Molecular Imaging Agents and Carrier Systems

A highly tunable quantum dot (QD)–polypeptide hybrid assembly system with potential uses for both molecular imaging and delivery of biomolecular cargo to cancer cells is reported. The tunability of the assembly system, its application for imaging cancer cells, and its ability to carry a biomolecule are demonstrated. The assemblies are formed through the self‐assembly of carboxyl‐functionalized QDs and poly(diethylene glycol‐L ‐lysine)‐poly(L ‐lysine) (PEGLL‐PLL) diblock copolypeptide molecules, and they are modified with peptide ligands containing a cyclic arginine‐glycine‐aspartate [c(RGD)] motif that has affinity for αvβ3 and αvβ5 integrins overexpressed on the tumor vasculature. To illustrate the tunability of the QD‐polypeptide assembly system, it is shown that binding to U87MG glioblastoma cells can be modulated and optimized by changing either the conditions under which the assemblies are formed or the relative lengths of the PEGLL and PLL blocks in the PEGLL‐PLL molecules. The optimized c(RGD)‐modified assemblies bind integrin receptors on U87MG cells and are endocytosed, as demonstrated by flow cytometry and live‐cell imaging. Binding specificity is confirmed by competition with an excess of free c(RGD) peptide. Finally, it is shown that the QD–polypeptide assemblies can be loaded with fluorescently labeled ovalbumin, as a proof‐of‐concept for their potential use in biomolecule delivery.     

A Three‐Dimensional Nanostructured Array of Protein Nanoparticles

Here a novel technique is reported to construct a three‐dimensional (3D) array of well‐defined and controllable multilayered nanostructures of proteins that is based on alternate layer‐by‐layer assembly of bacterial protein nanoparticles and DNA on a patterned array of gold dots. This is the first report on protein‐based multilayer stacking, which has the following significant advantages over conventional multilayer assemblies: 1) avoiding hazardous chemicals, the multilayer assembly is implemented in aqueous solution under mild temperature and pH conditions over a relatively short period; 2) direct multilayer growth from designated position is possible by controlling the aspect ratio; 3) multicomponent stacking can be easily performed through alternate stacking of different building blocks (in this case protein nanoparticles); and 4) a wide variety of 3D arrays can be constructed using various functionalized protein nanoparticles that are easily prepared through a simple genetic engineering approach. In this study, as a proof of concept, the developed 3D and patterned arrays of protein nanoparticle multilayers are successfully applied to the multiplexed bioassays of breast and colorectal cancer markers.     

Fabrication and Characterization of Superhydrophobic Surfaces with Dynamic Stability

Superhydrophobic surfaces of dynamic stability are crucial for applications in water‐repellent materials. In this work, a hierarchical structure composed of a dendritic microporous surface with nanostructured porosity is demonstrated that shows robust superhydrophobicity with dynamic stability. The hierarchical structures are obtained on both copper foils and wires by a dynamic gas‐bubble template‐assisted electrochemical deposition method. The substrates can then be modified with alkyl thiols to obtain the surface superhydrophobicity. A new kind of testing, mechanical monitor‐assisted continuous water surface strokes, is developed to reveal the dynamic stability of the as‐prepared superhydrophobic copper wires. The as‐prepared superhydrophobic copper wires can exert a high propulsive force, and particularly, show little adhesive force in the process of continuous strokes on the water surface, exhibiting robust superhydrophobicity with dynamic stability. The approach allows a strategy for the fabrication of superhydrophobic surfaces with dynamic stability, and suggests a new method to evaluate the dynamic stability of superhydrophobic surfaces.     

Hydrothermal Growth: Polymer‐Templated Hydrothermal Growth of Vertically Aligned Single‐Crystal ZnO Nanorods and Morphological Transformations Using Structural Polarity (Adv. Funct. Mater. 18/2010)

Position‐configurable, vertical, single‐crystalline ZnO nanorod arrays are fabricated via a polymer‐templated hydrothermal growth method at a low temperature of 93 °C. A sol‐gel processed dense c‐oriented ZnO seed layer film is employed to grow nanorods along the c‐axis direction [0001] regardless of any substrate crystal mismatches. Here, one‐beam laser‐interference lithography is utilized to fabricate nanoscale holes over an entire 2‐in. wafer during the preparation of the polymer template. As such, vertically aligned ZnO nanorods can be grown from the seed layer exposed at the bottom of each hole. Furthermore, morphological transformations of the ZnO nanorods into pencil‐like, needle‐like, tubular, tree‐like, and spherical shapes are obtained by controlling the growth conditions and utilizing the structural polarity of the ZnO nanorods.     

Preparation,Properties,and Applications of Low-Dimensional Molecular Organic Nanomaterials

In recent years,great progress has been made in research and development of small-molecule organic materials with various low-dimensional nano-structures.This paper presents a comprehensive review of recent research progress in this field,including preparation,electronic and optoelectronic properties and applications.First,an introduction gives to the reprecipitation,soft templates methods,and progress in synthesis and morphological control of low-dimensional small-molecule organic nanomaterials.Their uniqu...     

Structural DNA nanotechnology: from design to applications

The exploitation of DNA for the production of nanoscale architectures presents a young yet paradigm breaking approach, which addresses many of the barriers to the self-assembly of small molecules into highly-ordered nanostructures via construct addressability. There are two major methods to construct DNA nanostructures, and in the current review we will discuss the principles and some examples of applications of both the tile-based and DNA origami methods. The tile-based approach is an older method that provides a good tool to construct small and simple structures, usually with multiply repeated domains. In contrast, the origami method, at this time, would appear to be more appropriate for the construction of bigger, more sophisticated and exactly defined structures.     

Green Formation of Spherical and Dendritic Silver Nanostructures under Microwave Irradiation without Reducing Agent

The rapid and green formation of spherical and dendritic silver nanostructures based on microwave irradiation time was investigated. Silver nanoparticles were successfully fabricated by reduction of Ag(+) in a water medium and using polyvinylpyrrolidone (PVP) as the stabilizing agent and without the use of any other reducing agent, and were compared with those synthesized by conventional heating method. UV-vis absorption spectrometry, transmission electron microscopy (TEM), atomic absorption spectroscopy (AAS) and photon correlation spectroscopy (PCS) measurements, indicated that increasing the irradiation time enhanced the concentration of silver nanoparticles and slightly increased the particle size. There was a lack of large silver nanoparticles at a high concentration, but interestingly, the formation and growth of silver dendrite nanostructures appeared. Compared to conventional heating methods, the silver nanoparticle suspension produced by irradiated microwaves was more stable over a six-month period in aqueous solution without any signs of precipitation.     

Polymorphism in self-assembled structures of 9-anthracene carboxylic Acid on ag(111)

Surface self-assembly process of 9-anthracene carboxylic acid (AnCA) on Ag(111) was investigated using STM. Depending on the molecular surface density, four spontaneously formed and one annealed AnCA ordered phases were observed, namely a straight belt phase, a zigzag double-belt phase, two simpler dimer phases, and a kagome phase. The two high-density belt phases possess large unit cells on the scale length of 10 nm, which are seldom observed in molecular self-assembled structures. This structural diversity stems from a complicated competition of different interactions of AnCA molecules on metal surface, including intermolecular and molecular-substrate interactions, as well as the steric demand from high molecular surface density.