This report highlights recent progress in the fabrication of vertically aligned carbon nanotubes (VA‐CNTs) on silicon‐based materials. Research into these nanostructured composite materials is spurred by the importance of silicon as a basis for most current devices and the disruptive properties of CNTs. Various CNT attachments methods of covalent and adsorptive nature are critically compared. Selected examples of device applications where the VA‐CNT on silicon assemblies are showing particular promise are discussed. These applications include field emitters, filtration membranes, dry adhesives, sensors and scaffolds for biointerfaces.
Microelectrode arrays have unique electrochemical properties such as small capacitive‐charging currents, reduced iR drop, and steady‐state diffusion currents. These properties enable the use of microelectrode arrays and have captured much interest in the field of electrochemistry. Techniques for the fabrication of such arrays are reviewed. The relative features and merits of different techniques are also discussed.
In this Progress Report, we discuss our recent achievements in design and synthesis of new functional molecules towards information processing at the molecular level and high‐density information storage. These include: 1) new molecular switches, logic gates, and combinational logic circuits based on molecules and ensembles with photochromic spiropyran units that undergo reversible structural transformation among multistates, in response to external inputs such as light, protons, and metal ions; 2) high‐density information storage, mainly focusing on nanometer‐scale electrical recording based on the conductance transition of organic molecules, and multimode data storage on multiresponsive molecules. Relevant progress and an outlook in this area are also discussed.
The wide variety of core materials available, coupled with tunable surface properties, make nanoparticles an excellent platform for a broad range of biological and biomedical applications. This Review provides an introduction to nanoparticle–biomolecular interactions as well as recent applications of nanoparticles in biological sensing, delivery, and imaging of live cells and tissues.
Molecular imaging contributes to future personalized medicine dedicated to the treatment of cardiovascular disease, the leading cause of mortality in industrialized countries. Endoscope‐compatible optical imaging techniques would offer a stand‐alone alternative and high spatial resolution validation technique to clinically accepted imaging techniques in the (intravascular) assessment of vulnerable atherosclerotic lesions, which are predisposed to initiate acute clinical events. Efficient optical visualization of molecular epitopes specific for vulnerable atherosclerotic lesions requires targeting of high‐quality optical‐contrast‐enhancing particles. In this review, we provide an overview of both current optical nanoparticles and targeting ligands for optical molecular imaging of atherosclerotic lesions and speculate on their applicability in the clinical setting.
Dip‐pen nanolithography (DPN) is a powerful method to pattern nanostructures on surfaces by the controlled delivery of an “ink” coating the tip of an atomic force microscope upon scanning and contacting with surfaces. The growing interest in the use of nanoparticles as structural and functional elements for the fabrication of nanodevices suggests that the DPN‐stimulated patterning of nanoparticles on surfaces might be a useful technique to assemble hierarchical architectures of nanoparticles that could pave methodologies for functional nanocircuits or nanodevices. This Review presents different methodologies for the nanolithographic patterning of metallic, semiconductor, and metal oxide nanostructures on surfaces. The mechanisms involved in the formation of the nanostructures are discussed and the effects that control the dimensions of the resulting patterns are reviewed. The possible applications of the nanostructures are also addressed.
Over the past two decades, advances in modern biology and nanotechnology have enabled a rapid development in the design and building of biomimetic functional materials. ATP synthase is one of the most extensively studied molecular machines because it can be used as a rotary motor in the design of novel nanodevices and it can also continuously synthesize ATP in an artificial environment. A lot of research efforts have focused on assembling ATP synthase in biomimetic systems so that a complex cellular process can be constructed in a controllable manner. As we summarize here, layer‐by‐layer assembled microcapsules have proved to be a suitable cellular mimetic structure, which can be applied for engineering active biomimetic systems with a cellular process. An added benefit is that these assembled microcapsules can be used as bioenergy containers and thus ATP supply on demand.
The subtle performance of a virus is closely related to its specific hierarchical structure, which is composed of a rigid shell and transverse, responsive, nanometer‐sized channels. Virus‐like structured colloids are of great interest for their potential applications, for example in drug delivery. Adequate knowledge of the structure and composition control of both colloids and mesoporous materials is significant in the design and synthesis of hierarchically structured colloids to mimic viruses. Some recent developments in the synthesis of composite colloids and mesoporous materials are summarized. Template synthesis is a major tool to control both the macroscopic morphology and microstructures of these composites, in which gel colloids and supramolecular structures from amphiphilic species are used as templates.
It is now well‐known that the size, shape, and composition of nanomaterials can dramatically affect their physical and chemical properties, and that technologies based on nanoscale materials have the potential to revolutionize fields ranging from catalysis to medicine. Among these materials, anisotropic particles are particularly interesting because the decreased symmetry of such particles often leads to new and unusual chemical and physical behavior. Within this class of particles, triangular Au and Ag nanoprisms stand out due to their structure‐ and environment‐dependent optical features, their anisotropic surface energetics, and the emergence of reliable synthetic methods for producing them in bulk quantities with control over their edge lengths and thickness. This Review will describe a variety of solution‐based methods for synthesizing Au and Ag triangular prismatic structures, and will address and discuss proposed mechanisms for their formation.
The interaction of nanomaterials with cells and lipid bilayers is critical in many applications such as phototherapy, imaging, and drug/gene delivery. These applications require a firm control over nanoparticle–cell interactions, which are mainly dictated by surface properties of nanoparticles. This critical Review presents an understanding of how synthetic and natural chemical moieties on the nanoparticle surface (in addition to nanoparticle shape and size) impact their interaction with lipid bilayers and cells. Challenges for undertaking a systematic study to elucidate nanoparticle–cell interactions are also discussed.
Bacteria are microscopic, single‐celled organisms that utilize a variety of nanofluidic structures. One of the best known and widely used nanofluidic structures that are derived from bacteria is the α‐hemolysin pore. This pore, which self‐assembles in lipid bilayers, has been used for a wide variety of sensing applications, most notably, DNA sensing. Synthetic pores drilled in a wide variety of materials, such as silicon nitride and polymers have been developed that use inspiration from the α‐hemolysin pore. Higher‐aspect‐ratio nanofluidic structures, akin to nanotubes, are also synthesized by bacteria. Examples of such structures include those that are associated with bacterial transport apparatus, such as pili, and are used by bacteria to facilitate the transfer of genetic material from one bacterium to another. Flagella, and its associated structures, such as the rod and hook, are also tubular nanostructures, through which the protein, flagellin, travels to assemble the flagellum. Genetic engineering allows for the creation of modified bacterial nanopores and nanotubes that can be used for a variety of medical and engineering purposes. Frontispiece images reproduced with permission from References 55 . Copyrights 1996, American Association for the Advancement of Scicnce, 2009, Elsevier, and 2007, Institute of Physics, respectively.
One of the greatest challenges for our society is providing powerful electrochemical energy conversion and storage devices. Rechargeable lithium‐ion batteries and fuel cells are amongst the most promising candidates in terms of energy densities and power densities. Nanostructured materials are currently of interest for such devices because of their high surface area, novel size effects, significantly enhanced kinetics, and so on. This Progress Report describes some recent developments in nanostructured anode and cathode materials for lithium‐ion batteries, addressing the benefits of nanometer‐size effects, the disadvantages of ‘nano’, and strategies to solve these issues such as nano/micro hierarchical structures and surface coatings, as well as developments in the discovery of nanostructured Pt‐based electrocatalysts for direct methanol fuel cells (DMFCs). Approaches to lowering the cost of Pt catalysts include the use of i) novel nanostructures of Pt, ii)new cost‐effective synthesis routes, iii) binary or multiple catalysts, and iv) new catalyst supports.
One of the most promising applications of nanotechnology is that of drug delivery, and in particular the targeted delivery of drugs using nanotubes. Functionalized nanotubes might be able to target specific cells, become ingested, and then release their contents in response to a chemical trigger. This will have significant implications for the future treatment of patients, particularly those suffering from cancer, for whom presently the nonspecific nature of chemotherapy often kills healthy normal cells. Research to date has largely been through experiments investigating toxicity, biocompatibility, solubility, functionalization, and cellular uptake. More recently, the loading and unloading of molecular cargo has gained momentum from both experimental and theoretical investigations. This Review focuses on the loading and unloading of molecular cargo and highlights recent theoretical investigations, which to date have received very little attention in the review literature. The development of nanotube drug‐delivery capsules is of vital concern for the improvement of medical treatment, and mathematical modeling tends to facilitate such development and provides a quicker route to applications of the technology. This Review highlights the latest progress in terms of theoretical investigations and provides a focus for the development of the next generation of medical therapeutics.
The aim of this review is to explore the fundamental and technological incentive for the molecular design, synthesis, and aggregation behavior of conjugated organic molecules with photo‐electronic activity, and the fabrication of low‐dimensional organic conjugated nanomaterials by self‐assembly techniques. The properties of large oriented nanostructure arrays of organic charge transfer complexes based on conjugated molecules are also discussed. The dimension‐dependent emission properties have been observed, and conductivity, field emission properties, and sensing properties have been studied for the low dimensional nanostructures of nanoparticles, nanowires, nanorods, and nanostructure arrays.
Interconnect formation is critical for the assembly and integration of nanocomponents to enable nanoelectronics‐ and nanosystems‐related applications. Recent progress on joining and interconnect formation of key nanomaterials, especially nanowires and carbon nanotubes, into functional circuits and/or prototype devices is reviewed. The nanosoldering technique through nanoscale lead‐free solders is discussed in more detail in this Review. Various strategies of fabricating lead‐free nanosolders and the utilization of the nanosoldering technique to form functional solder joints are reviewed, and related challenges facing the nanosoldering technique are discussed. A perspective is given for using lead‐free nanosolders and the nanosoldering technique for the construction of complex and/or hybrid nanoelectronics and nanosystems.
This Review presents a discussion of the electromagnetic properties of nanoscale electrical conductors, which are quantum mechanical one‐dimensional systems. Of these, carbon nanotubes are the most technologically advanced example, and are discussed mainly in this paper. The properties of such systems as transmission electron microscopy waveguides for on‐chip signal propagation and also the radiation properties of such systems are discussed. This work is primarily aimed at microwave, nanometer‐wave, and THz electronics. However, the use of nanotubes as antennas in the IR and optical frequency range is not precluded on first principles and remains an open research area.
Despite the fact that we live in a 3D world and macroscale engineering is 3D, conventional submillimeter‐scale engineering is inherently 2D. New fabrication and patterning strategies are needed to enable truly 3D‐engineered structures at small size scales. Here, strategies that have been developed over the past two decades that seek to enable such millimeter to nanoscale 3D fabrication and patterning are reviewed. A focus is the strategy of self‐assembly, specifically in a biologically inspired, more deterministic form, known as self‐folding. Self‐folding methods can leverage the strengths of lithography to enable the construction of precisely patterned 3D structures and “smart” components. This self‐assembly approach is compared with other 3D fabrication paradigms, and its advantages and disadvantages are discussed.
The growing demand for analysis of the genomes of many species and cancers, for understanding the role of genetic variation among individuals in disease, and with the ultimate goal of deciphering individual human genomes has led to the development of non‐Sanger reaction‐based technologies towards rapid and inexpensive DNA sequencing. Recent advancements in new DNA sequencing technologies are changing the scientific horizon by dramatically accelerating biological and biomedical research and promising an era of personalized medicine for improved human health. Two single‐molecule sequencing technologies based on fluorescence detection are already in a working state. The newly launched and emerging single‐molecule DNA sequencing approaches are reviewed here. The current challenges of these technologies and potential methods of overcoming these challenges are critically discussed. Further research and development of single‐molecule sequencing will allow researchers to gather nearly error‐free genomic data in a timely and inexpensive manner.
