Directed Assembly of One-Dimensional Nanostructures into Functional Networks
26 Jan 2001-Science (American Association for the Advancement of Science)-Vol. 291, Iss: 5504, pp 630-633
TL;DR: It is shown that nanowires can be assembled into parallel arrays with control of the average separation and, by combining fluidic alignment with surface-patterning techniques, that it is also possible to control periodicity.
Abstract: One-dimensional nanostructures, such as nanowires and nanotubes, represent the smallest dimension for efficient transport of electrons and excitons and thus are ideal building blocks for hierarchical assembly of functional nanoscale electronic and photonic structures. We report an approach for the hierarchical assembly of one-dimensional nanostructures into well-defined functional networks. We show that nanowires can be assembled into parallel arrays with control of the average separation and, by combining fluidic alignment with surface-patterning techniques, that it is also possible to control periodicity. In addition, complex crossed nanowire arrays can be prepared with layer-by-layer assembly with different flow directions for sequential steps. Transport studies show that the crossed nanowire arrays form electrically conducting networks, with individually addressable device function at each cross point.
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TL;DR: Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects.
Abstract: Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects. Some of these applications are now realized in products. Others are demonstrated in early to advanced devices, and one, hydrogen storage, is clouded by controversy. Nanotube cost, polydispersity in nanotube type, and limitations in processing and assembly methods are important barriers for some applications of single-walled nanotubes.
9,693 citations
TL;DR: The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties are equally important.
Abstract: The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102
6,852 citations
TL;DR: Self-assembling processes are common throughout nature and technology and involve components from the molecular to the planetary scale and many different kinds of interactions.
Abstract: Self-assembly is the autonomous organization of components into patterns or structures without human intervention. Self-assembling processes are common throughout nature and technology. They involve components from the molecular (crystals) to the planetary (weather systems) scale and many different kinds of interactions. The concept of self-assembly is used increasingly in many disciplines, with a different flavor and emphasis in each.
6,491 citations
TL;DR: The small size and capability of these semiconductor nanowires for sensitive, label-free, real-time detection of a wide range of chemical and biological species could be exploited in array-based screening and in vivo diagnostics.
Abstract: Boron-doped silicon nanowires (SiNWs) were used to create highly sensitive, real-time electrically based sensors for biological and chemical species. Amine- and oxide-functionalized SiNWs exhibit pH-dependent conductance that was linear over a large dynamic range and could be understood in terms of the change in surface charge during protonation and deprotonation. Biotin-modified SiNWs were used to detect streptavidin down to at least a picomolar concentration range. In addition, antigen-functionalized SiNWs show reversible antibody binding and concentration-dependent detection in real time. Lastly, detection of the reversible binding of the metabolic indicator Ca2+ was demonstrated. The small size and capability of these semiconductor nanowires for sensitive, label-free, real-time detection of a wide range of chemical and biological species could be exploited in array-based screening and in vivo diagnostics.
5,841 citations
TL;DR: The facile assembly of key electronic device elements from well-defined nanoscale building blocks may represent a step toward a "bottom-up" paradigm for electronics manufacturing.
Abstract: Because semiconductor nanowires can transport electrons and holes, they could function as building blocks for nanoscale electronics assembled without the need for complex and costly fabrication facilities. Boron- and phosphorous-doped silicon nanowires were used as building blocks to assemble three types of semiconductor nanodevices. Passive diode structures consisting of crossed p- and n-type nanowires exhibit rectifying transport similar to planar p-n junctions. Active bipolar transistors, consisting of heavily and lightly n-doped nanowires crossing a common p-type wire base, exhibit common base and emitter current gains as large as 0.94 and 16, respectively. In addition, p- and n-type nanowires have been used to assemble complementary inverter-like structures. The facile assembly of key electronic device elements from well-defined nanoscale building blocks may represent a step toward a "bottom-up" paradigm for electronics manufacturing.
3,143 citations
References
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TL;DR: A procedure that makes it possible to design and fabricate microfluidic systems in an elastomeric material poly(dimethylsiloxane) (PDMS) in less than 24 h by fabricating a miniaturized capillary electrophoresis system is described.
Abstract: This paper describes a procedure that makes it possible to design and fabricate (including sealing) microfluidic systems in an elastomeric materialpoly(dimethylsiloxane) (PDMS)in less than 24 h. A network of microfluidic channels (with width >20 μm) is designed in a CAD program. This design is converted into a transparency by a high-resolution printer; this transparency is used as a mask in photolithography to create a master in positive relief photoresist. PDMS cast against the master yields a polymeric replica containing a network of channels. The surface of this replica, and that of a flat slab of PDMS, are oxidized in an oxygen plasma. These oxidized surfaces seal tightly and irreversibly when brought into conformal contact. Oxidized PDMS also seals irreversibly to other materials used in microfluidic systems, such as glass, silicon, silicon oxide, and oxidized polystyrene; a number of substrates for devices are, therefore, practical options. Oxidation of the PDMS has the additional advantage that it ...
5,491 citations
TL;DR: In this paper, the fabrication of a three-terminal switching device at the level of a single molecule represents an important step towards molecular electronics and has attracted much interest, particularly because it could lead to new miniaturization strategies in the electronics and computer industry.
Abstract: The use of individual molecules as functional electronic devices was first proposed in the 1970s (ref 1) Since then, molecular electronics2,3 has attracted much interest, particularly because it could lead to conceptually new miniaturization strategies in the electronics and computer industry The realization of single-molecule devices has remained challenging, largely owing to difficulties in achieving electrical contact to individual molecules Recent advances in nanotechnology, however, have resulted in electrical measurements on single molecules4,5,6,7 Here we report the fabrication of a field-effect transistor—a three-terminal switching device—that consists of one semiconducting8,9,10 single-wall carbon nanotube11,12 connected to two metal electrodes By applying a voltage to a gate electrode, the nanotube can be switched from a conducting to an insulating state We have previously reported5 similar behaviour for a metallic single-wall carbon nanotube operated at extremely low temperatures The present device, in contrast, operates at room temperature, thereby meeting an important requirement for potential practical applications Electrical measurements on the nanotube transistor indicate that its operation characteristics can be qualitatively described by the semiclassical band-bending models currently used for traditional semiconductor devices The fabrication of the three-terminal switching device at the level of a single molecule represents an important step towards molecular electronics
5,258 citations
TL;DR: The assembly of functional nanoscale devices from indium phosphide nanowires, the electrical properties of which are controlled by selective doping are reported, and electric-field-directed assembly can be used to create highly integrated device arrays from nanowire building blocks.
Abstract: Nanowires and nanotubes carry charge and excitons efficiently, and are therefore potentially ideal building blocks for nanoscale electronics and optoelectronics. Carbon nanotubes have already been exploited in devices such as field-effect and single-electron transistors, but the practical utility of nanotube components for building electronic circuits is limited, as it is not yet possible to selectively grow semiconducting or metallic nanotubes. Here we report the assembly of functional nanoscale devices from indium phosphide nanowires, the electrical properties of which are controlled by selective doping. Gate-voltage-dependent transport measurements demonstrate that the nanowires can be predictably synthesized as either n- or p-type. These doped nanowires function as nanoscale field-effect transistors, and can be assembled into crossed-wire p-n junctions that exhibit rectifying behaviour. Significantly, the p-n junctions emit light strongly and are perhaps the smallest light-emitting diodes that have yet been made. Finally, we show that electric-field-directed assembly can be used to create highly integrated device arrays from nanowire building blocks.
3,280 citations
TL;DR: In this article, the authors discuss the development of a general approach to rational synthesis of crystalline nanowires of arbitrary composition, and illustrate solutions to these challenges with measurements of the atomic structure and electronic properties of carbon nanotubes.
Abstract: Dimensionality plays a critical role in determining the properties of materials due to, for example, the different ways that electrons interact in three-dimensional, twodimensional (2D), and one-dimensional (1D) structures.1-5 The study of dimensionality has a long history in chemistry and physics, although this has been primarily with the prefix “quasi” added to the description of materials; that is, quasi-1D solids, including square-planar platinum chain and metal trichalcogenide compounds,2,6 and quasi2D layered solids, such as metal dichalcogenides and copper oxide superconductors.3-5,7,8 The anisotropy inherent in quasi-1D and -2D systems is central to the unique properties and phases that these materials exhibit, although the small but finite interactions between 1D chains or 2D layers in bulk materials have made it difficult to address the interesting properties expected for the pure low-dimensional systems. Are pure low-dimensional systems interesting and worth pursuing? We believe that the answer to this question is an unqualified yes from the standpoints of both fundamental science and technology. One needs to look no further than past studies of the 2D electron gas in semiconductor heterostructures, which have produced remarkably rich and often unexpected results,9,10 and electron tunneling through 0D quantum dots, which have led to the concepts of the artificial atom and the creation of single electron transistors.11-15 In these cases, lowdimensional systems were realized by creating discrete 2D and 0D nanostructures. 1D nanostructures, such as nanowires and nanotubes, are expected to be at least as interesting and important as 2D and 0D systems.16,17 1D systems are the smallest dimension structures that can be used for efficient transport of electrons and optical excitations, and are thus expected to be critical to the function and integration of nanoscale devices. However, little is known about the nature of, for example, localization that could preclude transport through 1D systems. In addition, 1D systems should exhibit density of states singularities, can have energetically discrete molecularlike states extending over large linear distances, and may show more exotic phenomena, such as the spin-charge separation predicted for a Luttinger liquid.1,2 There are also many applications where 1D nanostructures could be exploited, including nanoelectronics, superstrong and tough composites, functional nanostructured materials, and novel probe microscopy tips.16-29 To address these fascinating fundamental scientific issues and potential applications requires answers to two questions at the heart of condensed matter chemistry and physics research: (1) How can atoms or other building blocks be rationally assembled into structures with nanometer-sized diameters but much longer lengths? (2) What are the intrinsic properties of these quantum wires and how do these properties depend, for example, on diameter and structure? Below we describe investigations from our laboratory directed toward these two general questions. The organization of this Account is as follows. In section II, we discuss the development of a general approach to the rational synthesis of crystalline nanowires of arbitrary composition. In section III, we outline key challenges to probing the intrinsic properties of 1D systems and illustrate solutions to these challenges with measurements of the atomic structure and electronic properties of carbon nanotubes. Last, we discuss future directions and challenges in section IV.
3,218 citations
TL;DR: In this article, the self-organization of CdSe nanocrystallites into three-dimensional semiconductor quantum dot superlattices (colloidal crystals) is demonstrated.
Abstract: The self-organization of CdSe nanocrystallites into three-dimensional semiconductor quantum dot superlattices (colloidal crystals) is demonstrated. The size and spacing of the dots within the superlattice are controlled with near atomic precision. This control is a result of synthetic advances that provide CdSe nanocrystallites that are monodisperse within the limit of atomic roughness. The methodology is not limited to semiconductor quantum dots but provides general procedures for the preparation and characterization of ordered structures of nanocrystallites from a variety of materials.
1,996 citations