Tailored polymer-based nanorods and nanotubes by "template synthesis": From preparation to applications

Polymer nanotechnology allows manipulating materials microstructure, morphology and compositional variation on the nanometer scale. Thus, it is able to provide materials for many cutting edge applications, from photonics to medical devices to sensors. This article summarizes recent work on template-based fabrication and on the basic properties of one-dimensional polymeric nanostructures and their inherent advantages over their conventional counterparts. The chemistry and physics relevant for the design of these nanostructured materials are discussed and recent advances emphasized. In particular, highlighting the effects of nanoconfinement on material behavior and putting somewhat greater emphasis on molecular motions. Some examples of one-dimensional-based polymeric nanostructures with promising applications for example in the field of tissue engineering are also presented as well as some aspects concerning recyclability of the used templates.     

Functionalized DNA Nanostructures for Nanomedicine

DNA nanotechnology utilizes synthetic DNA strands as the building material to construct nanoscale devices, and the field has developed rapidly over the past decade. Recently, the use of DNA nanostructures for various applications, particularly biomedical ones, has drawn great interest. This review focuses on the most recent research directed at utilizing functionalized DNA devices for nanomedical applications and presents representative research progress in disease diagnosis, treatment and prevention. In addition, the safety and future clinical applications of DNA nanostructures are discussed.     

Morphology control and optical properties of SiGe nanostructures grown on glass substrate

With the rapid progress of nanotechnology, nanostructures with different morphologies have been realized, which may be very promising to enhance the performance of semiconductor devices. In this study, SiGe nanostructures with several kinds of configurations have been synthesized through a chemical vapor deposition process. By controlling growth conditions, different SiGe nanostructures can be easily tuned. Structures and compositions of the nanostructures were determined by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The optical properties of various SiGe nanostructures revealed some dependence with their morphologies, which may be suitable for solar cell applications. The control of the SiGe morphology on nanoscale provides a convenient route to produce diverse SiGe nanostructures and creates new opportunities to realize the integration of future devices.     

Self-assembled,Programmable DNA Nanodevices for Biological and Biomedical Applications

The broad field of structural DNA nanotechnology has diverged into various areas of applications ranging from computing, photonics, synthetic biology, and biosensing to in-vivo bioimaging and therapeutic delivery, to name but a few. Though the field began to exploit DNA to build various nanoscale architectures, it has now taken a new path to diverge from structural DNA nanotechnology to functional or applied DNA nanotechnology. More recently a third sub-branch has emerged-biologically oriented DNA nanotechnology, which seeks to explore the functionalities of combinatorial DNA devices in various biological systems. In this review, we summarize the key developments in DNA nanotechnology revealing a current trend that merges the functionality of DNA devices with the specificity of biomolecules to access a range of functions in biological systems. This review seeks to provide a perspective on the evolution and biological applications of DNA nanotechnology, where the integration of DNA structures with biomolecules can now uncover phenomena of interest to biologists and biomedical scientists. Finally, we conclude with the challenges, limitations, and perspectives of DNA nanodevices in fundamental and applied research.     

Towards nano-organic chemistry: perspectives for a bottom-up approach to the synthesis of low-dimensional carbon nanostructures

Low-dimensional carbon nanostructures, such as nanotubes and graphenes, represent one of the most promising classes of materials, in view of their potential use in nanotechnology. However, their exploitation in applications is often hindered by difficulties in their synthesis and purification. Despite the huge efforts by the research community, the production of nanostructured carbon materials with controlled properties is still beyond reach. Nonetheless, this step is nowadays mandatory for significant progresses in the realization of advanced applications and devices based on low-dimensional carbon nanostructures. Although promising alternative routes for the fabrication of nanostructured carbon materials have recently been proposed, a comprehensive understanding of the key factors governing the bottom-up assembly of simple precursors to form complex systems with tailored properties is still at its early stages. In this paper, following a survey of recent experimental efforts in the bottom-up synthesis of carbon nanostructures, we attempt to clarify generalized criteria for the design of suitable precursors that can be used as building blocks in the production of complex systems based on sp(2) carbon atoms and discuss potential synthetic strategies. In particular, the approaches presented in this feature article are based on the application of concepts borrowed from traditional organic chemistry, such as valence-bond theory and Clar sextet theory, and on their extension to the case of complex carbon nanomaterials. We also present and discuss a validation of these approaches through first-principle calculations on prototypical systems. Detailed studies on the processes involved in the bottom-up fabrication of low-dimensional carbon nanostructures are expected to pave the way for the design and optimization of precursors and efficient synthetic routes, thus allowing the development of novel materials with controlled morphology and properties that can be used in technological applications.     

Tecto‐GIRz: Engineered Group I Ribozyme the Catalytic Ability of Which Can Be Controlled by Self‐Dimerization

RNA is a promising biomaterial for self‐assembly of nano‐sized structures with a wide range of applications in nanotechnology and synthetic biology. Several RNA‐based nanostructures have been reported, but most are unrelated to intracellular RNA, which possesses modular structures that are sufficiently large and complex to serve as catalysts to promote sophisticated chemical reactions. In this study, we designed dimeric RNA structures based on the Tetrahymena group I ribozyme. The resulting dimeric RNAs (tecto group I ribozyme; tecto‐GIRz) exhibit catalytic ability that depended on controlled dimerization, by which a pair of ribozymes can be activated to perform cleavage and splicing reactions of two distinct substrates. Modular redesign of complex RNA structures affords large ribozymes for use as modules in RNA nanotechnology and RNA synthetic biology.     

Janus树枝分子液晶自组装结构研究进展

综述了Janus树枝分子在液晶自组装结构研究方面的进展,阐述了其在液晶材料、主-客体化学、生物医药等方面的应用,并探讨了Janus树枝自组装纳米技术的应用前景。     

Advances in DNA Origami–Cell Interfaces

The nascent field of DNA nanotechnology has undergone rapid growth since its inception. By using DNA as a biologically “safe” material, DNA nanotechnology shows great promise in applications such as drug-delivery systems. Further progress, however, relies on understanding the different ways in which DNA nanostructures behave in and interact with cells, tissues and even whole organisms. Moreover, this knowledge must then be harnessed in innovative ways to improve existing DNA nanostructures and design new ones, so that they can perform more diverse functions more effectively. There have been many developments in this regard in the past few years, and herein some of these are highlighted, with respect to both works that improve our understanding of what happens to DNA nanostructures once they are at their target site, and those that utilise clever design to accomplish desired functions.     

Strategies for Stabilizing DNA Nanostructures to Biological Conditions

DNA is one of the most promising building blocks for creating functional nanostructures for applications in biology and medicine. However, these highly programmable nanomaterials (e.g., DNA origami) often require supraphysiological salt concentrations for stability, are degraded by nuclease enzymes, and can elicit an inflammatory response. Herein, three key strategies for stabilizing DNA nanostructures to conditions required for biological applications are outlined: 1) tuning the buffer conditions or nanostructure design; 2) covalently crosslinking the strands that make up the structures; and 3) coating the structures with polymers, proteins, or lipid bilayers. Taken together, these approaches greatly expand the chemical diversity and future applicability of DNA nanotechnology both in vitro and in vivo.     

Biologically Relevant Molecular Finite Automata

Bio-Molecular Computing (BMC) has been rapidly evolving as an independent field at the interface between computer science, mathematics, chemistry, and biology. Over the years, numerous architectures of autonomous molecular computing devices have been developed in the lab on the basis of opportunities offered by molecular biology techniques. This account focuses mainly on the realization of programmable DNA-based finite-state automata that can compute autonomously upon mixing all their components in solution.The main advantage of autonomous BMC devices over electronic computers arises from their ability to interact directly with biological systems and even with living organisms without any interface. Indeed, it has been demonstrated that appropriately designed computing machines can produce output signals in the form of a specific biological function via direct interaction with living cells. Additional topics are briefly included to point at interesting opportunities in the field and to describe some of the potential applications and extension of the basic concepts. These include logic evaluators and logic gates that operate in cells, applications in developmental biology, as well as chemical encoding and processing of alphanumeric information.     

Block Copolymer Nanostructures and Their Applications: A Review

Block copolymer nanostructures are smart, intelligent, and environment sensitive nanostructures designed to respond in a controlled manner to an external stimulus. Block copolymer nanostructures are being extensively utilized in pharmaceutical field, nanotechnology, and inforensics. Upon micellization, the hydrophobic core of block copolymer nanostructures region serves as a reservoir for hydrophobic medication, which can be loaded by chemical, physical, or electrostatic means. DNA combined with synthetic block copolymer nanostructure enhances the chemical and biological behaviors of biomacromolecule and at the same time completely suppress undesirable properties. Novel Nanoelectromechanical Systems/Microelectromechanical Systems (NEMS/MEMS) devices are being realized using block copolymer nanostructures and DNA combined with inorganic material nanoparticles and small organic moieties.     

Peanut-shaped ZnO nanostructures: A driving force for enriched antibacterial activity and their statistical analysis

The nanostructures made of ZnO have a special place in nanotechnology because of the broader applications in various optoelectronic devices. The new shapes and sizes have different synergic effects on biological entities. Because of the broader applications, the current work was aimed at the synthesis, characterisation, antibacterial testing, and statistical validation of peanut-shaped ZnO nanostructures (ZnO-PNTs). They were prepared via a chemical process with precursor zinc nitrate and sodium hydroxide at ∼80 °C for 3 h with refluxing. The bacteriostatic properties of prepared nanostructures were tested on different bacterial species, namely, Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, and Klebsiella pneumoniae at various concentrations (5–45 μg/mL) of ZnO-PNTs, assessed via UV–visible spectrophotometry. The results and their assessment revealed that a minute concentration of ZnO-PNTs in the form of a solution reduces the population of bacteria effectively, and the effective concentration was found to be 5 μg/mL for all the tested pathogens. Additionally, the chemical and biological mechanism of action was explored for ZnO-PNTs toward the bacterial species under study. The ZnO-PNTs were well characterised by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and fourier transform infrared spectroscopy, which indicated that well-grown nanostructures at a very low concentration effectively inhibit the growth of bacteria (reduce their concentration), as confirmed by UV–visible spectrophotometry. On the basis of obtained results and their analysis, it is expected that ZnO-PNTs will be applied as a biofilm against various food pathogens in near future. Statistical evaluation was also conducted for the bacterial suspensions with the nano structures.     

Free-standing one-dimensional plasmonic nanostructures

The field of plasmonics has become one of the most interesting and active research areas in nanotechnology, enabling numerous fundamental studies and applications. The ability to tailor the size, shape, and environment of metal nanostructures is the key component for controlling the plasmonic properties of individual or aggregated nanostructures. In this feature article, a category of chemically nanofabricated, unique free-standing one-dimensional (1D) plasmonic nanostructures has been summarized. The dispersible plasmonic nanostructures were obtained in high yield with control over gap size and feature size. This ability was exploited to tune the emerging plasmonic properties overcoming the difficulties of other methods to do so, leading to applications in analytical detection, biological sensing, and nanoelectronics.     

Carbon nanotubes: properties,synthesis, purification,and medical applications

Current discoveries of different forms of carbon nanostructures have motivated research on their applications in various fields. They hold promise for applications in medicine, gene, and drug delivery areas. Many different production methods for carbon nanotubes (CNTs) have been introduced; functionalization, filling, doping, and chemical modification have been achieved, and characterization, separation, and manipulation of individual CNTs are now possible. Parameters such as structure, surface area, surface charge, size distribution, surface chemistry, and agglomeration state as well as purity of the samples have considerable impact on the reactivity of carbon nanotubes. Otherwise, the strength and flexibility of carbon nanotubes make them of potential use in controlling other nanoscale structures, which suggests they will have a significant role in nanotechnology engineering.     

Advances and Prospect of Nanotechnology in Stem Cells

In recent years, stem cell nanotechnology has emerged as a new exciting field. Theoretical and experimental studies of interaction between nanomaterials or nanostructures and stem cells have made great advances. The importance of nanomaterials, nanostructures, and nanotechnology to the fundamental developments in stem cells-based therapies for injuries and degenerative diseases has been recognized. In particular, the effects of structure and properties of nanomaterials on the proliferation and differentiation of stem cells have become a new interdisciplinary frontier in regeneration medicine and material science. Here we review some of the main advances in this field over the past few years, explore the application prospects, and discuss the issues, approaches and challenges, with the aim of improving application of nanotechnology in the stem cells research and development.     

The chemistry of the sulfur-gold interface: in search of a unified model

Over the last three decades, self-assembled molecular films on solid surfaces have attracted widespread interest as an intellectual and technological challenge to chemists, physicists, materials scientists, and biologists. A variety of technological applications of nanotechnology rely on the possibility of controlling topological, chemical, and functional features at the molecular level. Self-assembled monolayers (SAMs) composed of chemisorbed species represent fundamental building blocks for creating complex structures by a bottom-up approach. These materials take advantage of the flexibility of organic and supramolecular chemistry to generate synthetic surfaces with well-defined chemical and physical properties. These films already serve as structural or functional parts of sensors, biosensors, drug-delivery systems, molecular electronic devices, protecting capping for nanostructures, and coatings for corrosion protection and tribological applications. Thiol SAMs on gold are the most popular molecular films because the resulting oxide-free, clean, flat surfaces can be easily modified both in the gas phase and in liquid media under ambient conditions. In particular, researchers have extensively studied SAMs on Au(111) because they serve as model systems to understand the basic aspects of the self-assembly of organic molecules on well-defined metal surfaces. Also, great interest has arisen in the surface structure of thiol-capped gold nanoparticles (AuNPs) because of simple synthesis methods that produce highly monodisperse particles with controllable size and a high surface/volume ratio. These features make AuNPs very attractive for technological applications in fields ranging from medicine to heterogeneous catalysis. In many applications, the structure and chemistry of the sulfur-gold interface become crucial since they control the system properties. Therefore, many researchers have focused on understanding of the nature of this interface on both planar and nanoparticle thiol-covered surfaces. However, despite the considerable theoretical and experimental efforts made using various sophisticated techniques, the structure and chemical composition of the sulfur-gold interface at the atomic level remains elusive. In particular, the search for a unified model of the chemistry of the S-Au interface illustrates the difficulty of determining the surface chemistry at the nanoscale. This Account provides a state-of-the-art analysis of this problem and raises some questions that deserve further investigation.     

Controlling the Morphology of Polymeric Precursor-Derived ZnO Flower-Like Structures

The study of the mechanisms of formation and growth of ZnO nanostructures is crucial as they have the potential to find applications in opto-electronic devices. ZnO nanostructures of different morphologies have been synthesized using a low-temperature polymeric precursor process. Controlling the Zn cation and nitric acid concentrations, flower-like morphology of the ZnO nanostructures could be synthesized with excellent reproducibility. Besides chemistry, the effects of spin-coating variables on morphology were also investigated. The results show that the morphology of the flowers is controlled by Zn²⁺ ion concentration, whereas spin speed and film thickness are responsible for the size variations. All obtained ZnO structures reveal a polycrystalline hexagonal wurtzite structure and strong UV photoluminescence along with lattice defects. Polar surfaces of ZnO promoting multilayer Volmer–Weber growth play a crucial role in the development of these flower-like structures. Possible mechanisms for variations of morphology with synthesis parameters are discussed.     

Synthesis and optical properties of II-VI 1D nanostructures

1D nanostructures from II-VI semiconductors have been demonstrated to exhibit outstanding optical properties with strong promise for novel optoelectronic devices with augmented performance and functionalities. Herein, we present a comprehensive review discussing important topics pertinent to the fundamental properties and applications of II-VI 1D nanostructures. With practical applications in mind, the considerations, principles and experimental techniques on the sample preparation of high quality 1D nanostructures are highlighted. Fundamentals on the optical properties of II-VI materials, along with relevant investigation techniques and recent progress in the field, are also extensively discussed. With the steady development of their synthesis, characterization and device fabrication, it is strongly expected that II-VI 1D nanostructures will assume a unique position in future technology.     

Chemical Reactions Directed Peptide Self-Assembly

Fabrication of self-assembled nanostructures is one of the important aspects in nanoscience and nanotechnology. The study of self-assembled soft materials remains an area of interest due to their potential applications in biomedicine. The versatile properties of soft materials can be tuned using a bottom up approach of small molecules. Peptide based self-assembly has significant impact in biology because of its unique features such as biocompatibility, straight peptide chain and the presence of different side chain functionality. These unique features explore peptides in various self-assembly process. In this review, we briefly introduce chemical reaction-mediated peptide self-assembly. Herein, we have emphasised enzymes, native chemical ligation and photochemical reactions in the exploration of peptide self-assembly.     

Photoresponsive liquid crystalline block copolymers: From photonics to nanotechnology

Being one of the most fascinating multi-functional materials, photoresponsive liquid crystalline block copolymers (PLCBCs) have attracted much attention because of their light controllable properties of supramolecularly self-assembled structures. These originate from their unique features combining the advanced function of photoresponsive liquid crystalline polymers (PLCPs) with the inherent property of microphase separation of block copolymers (BCs). Benefiting from recent progresses in materials chemistry, diverse PLCBCs have been designed and synthesized by controlled polymerization using different synthetic routes and strategies. Generally, PLCBCs show different performance depending on their self-organization and molecular composition, with the PLCP blocks in the minority phase or in the majority phase. One of the most important properties of PLCBCs is supramolecular cooperative motion, resulted from the interactions between liquid crystalline elastic deformation and microphase separation, which enables them to self-assemble into regularly ordered nanostructures in bulk films with high reliability. These nanostructures contribute to improving the optical performance of polymer films by eliminating the scattering of visible light, in favor of their photonic applications. With the help of liquid crystal alignment techniques, both parallel and perpendicular patterning of nanostructures has been fabricated in macroscopic scale with excellent reproducibility and mass production, which provides nanotemplates and nanofabrication processes for preparing varieties of nanomaterials. Recent findings about PLCBCs including their synthesis, diagram of microphase separation, structure-property relationship, precise control of nanostructure as well as their applications in photonics to nanotechnology are reviewed.