Статті в журналах з теми "Macromolecular Building Blocks - Nanoscale Dimensions"

Nanotechnology, a much abused term, refers to the fabrication and assembly of functional objects of nanometer dimensions. In this article, we will refer only to specific aspects of chemical nanotechnology, meaning by this the production of structures of nanometer dimensions by chemical means. In particular, we will center the discussion on the use of metal nanoparticles as chemical building blocks.

ABSTRACTHigh-index materials such as silicon and III-V compounds have recently gained a lot of interest as a promising material platform for efficient photonic nanostructures. Because of the high refractive index, nanoparticles of such materials support Mie resonances and enable efficient light control and its confinement at the nanoscale. Here we propose a design of nanostructure with multipole resonances where optical nanoantennas are made out of transition metal dichalcogenide, in particular, tungsten disulfide WS2. Transition metal dichalcogenide (TMDCs) possess a high refractive index and strong optical anisotropy because of their layered structure and are promising building blocks for next-generation photonic devices. Strong anisotropic response results in different components of TMDC permittivity and the possibility of tailoring nanostructure optical properties by choosing different axes and adjusting dimensions in design. The proposed periodic array of TMDC nanoantennas can be used for controlling optical resonances in the visible and near-infrared spectral ranges and engineering efficient ultra-thin optical components with nanoscale light confinement.

Molecules provide versatile building blocks, with a vast palette of functionalities and an ability to assemble via supramolecular and covalent bonding to generate remarkably diverse macromolecular systems. This is abundantly displayed by natural systems that have evolved on Earth, which exploit both supramolecular and covalent protocols to create the machinery of life. Importantly, these molecular assemblies deliver functions that are reproducible, adaptable, finessed and responsive. There is now a real need to translate complex molecular systems to surfaces and interfaces in order to engineer 21st century nanotechnology. ‘Top-down’ and ‘bottom-up’ approaches, and utilisation of supramolecular and covalent assembly, are currently being used to create a range of molecular architectures and functionalities at surfaces. In parallel, advanced tools developed for interrogating surfaces and interfaces have been deployed to capture the complexities of molecular behaviour at interfaces from the nanoscale to the macroscale, while advances in theoretical modelling are delivering insights into the balance of interactions that determine system behaviour. A few examples are provided here that outline molecular behaviour at surfaces, and the level of complexity that is inherent in such systems.

One-dimensional (1D) nanostructures are ideal systems for investigating the dependence of electrical transport, optical properties and mechanical properties on size and dimensionality. They are expected to play an important role as both interconnects and functional components in the fabrication of nanoscale electronic and optoelectronic devices. This article presents an overview of current research activities that center on nanowires whose lateral dimensions fall anywhere in the range of 1–200 nm. It is organized into three parts: The first part discusses various methods that have been developed for generating nanowires with tightly controlled dimensions, orientations, and well-defined properties. The second part highlights a number of strategies that are being developed for the hierarchical assembly of nanowire building blocks. The third part surveys some of the novel physical properties (e.g., optical, electrical, and mechanical) of these nanostructures. Finally, we conclude with some personal perspectives on the future research directions in this field.

Systems with nanoscale dimensions have attracted great attention for many decades since they manifest interesting size-dependent behavior and have many possible technological applications. While significant progress has been made toward the experimental and theoretical understanding of various phenomena at nanoscale, much is yet is to be explored in fully comprehending how the interplay of several parameters such as shape, size and dimensionality affects the resulting properties. In this work, we study the nature of the interaction in a nanosystem consisting of a charged nanoplate and a charged nanowire. The two constituent nanostructures of this nanosystem represent important building blocks for bottom-up assembly processes. We consider a specific orientation of the two nanostructures and calculate exactly their interaction energy as a function of shape, size and relative distance. With help from suitable though nontrivial mathematical transformations, we are able to derive a closed form exact expression for such an interaction energy. It is shown that the interaction energy of this configuration is very sensitive to shape and depends in a nontrivial way on size and separation distance.

AbstractThe emergence of micro- and nanoscale science and engineering has provided new avenues for engineering materials with macromolecular and even molecular-scale precision, leading to diagnostic and therapeutic technologies that will revolutionize the way healthcare is administered. Biomaterials have evolved from off-the-shelf products to materials designed with molecular precision to exhibit the desired properties for a specific application, often mimicking biological systems. Controlling interactions at the level of natural building blocks, from proteins to cells, facilitates the novel exploration, manipulation, and application of living systems and biological phenomena. In addition, polymer networks with precisely engineered binding sites have been created via molecular imprinting, where functional monomers are preassembled with a target molecule and then the structure is locked with network formation. Nanoscale science and engineering have accelerated the development of novel drug delivery systems and led to enhanced control over how a given pharmaceutical is administered, helping biological potential to be transformed into medical reality. Micro- and nanoscale devices have been fabricated using integrated-circuit processing techniques, enabling strict temporal control over drug release. The advantages of these microdevices include simple release mechanisms, very accurate dosing, the capability of complex release patterns, the potential for local delivery, and possible biological drug stability enhancement by means of storage in a microvolume that can be precisely controlled. In particular, the development of polymer systems that are able to interact with their environment in a thermodynamically responsive manner has led to novel intelligent biomaterials and applications. Intelligent biomedical materials can be used for the delivery of drugs, peptides, and proteins; as targeting agents for site-specific delivery; or as components for the preparation of protein or drug conjugates. These intelligent materials are attractive options as functional components in micro- and nanodevices because of the ease with which recognition and actuation properties can be precisely tailored. Recent developments in intelligent materials and nano- or microdevices for drug delivery systems are the emphasis of this review, which addresses the use of intelligent biomedical materials as carriers for the development of novel pharmaceutical formulations.

ABSTRACTTo realize applications based on nanowires, the development of methods that allow the organization of nanostructures into integrated arrangements is crucial. While many different methods exist, the direct synthesis of complex nanowire structures is one of the most suitable approaches to efficiently connect numerous nanostructures to the macroscopic world. The fabrication of various 3D nanowire assemblies including arrays, networks, and hierarchical structures by combining specifically designed template materials with electrochemical deposition is demonstrated. The ion track template method is extended to create more complex structures by changing template production and electrodeposition parameters. In contrast to current synthesis routes, it is possible to independently control many of the parameters defining both (i) characteristics of individual nanowires (including dimensions and composition) and (ii) the arrangement of the nanoscale building blocks into nanowire assemblies determined by nanowire orientation and integration level. Results that highlight the benefits arising from the design of advanced 3D nanowire architectures are presented.

AbstractSince the development of the light microscope in the 16th century, optical device size and performance have been limited by diffraction. Optoelectronic devices of today are much bigger than the smallest electronic devices for this reason. Achieving control of light—material interactions for photonic device applications at the nanoscale requires structures that guide electromagnetic energy with subwavelength-scale mode confinement. By converting the optical mode into nonradiating surface plasmons, electromagnetic energy can be guided in structures with lateral dimensions of less than 10% of the free-space wavelength. A variety of methods—including electron-beam lithography and self-assembly—have been used to construct both particle and planar plasmon waveguides. Recent experimental studies have confirmed the strongly coupled collective plasmonic modes of metallic nanostructures. In plasmon waveguides consisting of closely spaced silver rods, electromagnetic energy transport over distances of 0.5 m has been observed. Moreover, numerical simulations suggest the possibility of multi-centimeter plasmon propagation in thin metallic stripes. Thus, there appears to be no fundamental scaling limit to the size and density of photonic devices, and ongoing work is aimed at identifying important device performance criteria in the subwavelength size regime. Ultimately, it may be possible to design an entire class of subwavelength-scale optoelectronic components (waveguides, sources, detectors, modulators) that could form the building blocks of an optical device technology—a technology scalable to molecular dimensions, with potential imaging, spectroscopy, and interconnection applications in computing, communications, and chemical/biological detection.

In electronics field, researchers and industries have been working to fabricate low-cost optoelectronic devices by using less materials in the fabrication process. Thus, miniaturization concept has been used in the design and synthesis of the fabricated materials and devices based on nano-dimension. However, reducing the used materials would affects the overall performance of the devices and new building blocks materials are needed to pass the performance capacity limits of current silicon-based materials. Quantum Dots DQs have been introduced and attracted much attention among researchers because of their unique characteristics that are necessary for many potential applications by using nano-dimensions structures. These properties include size-tunable optical and other electronic characteristics that are not found in the current bulk materials. Although there has been interested QDs experimental studied that have been already carried out, different theoretical efforts must be introduced in order to provide good understanding of the possible and different QDs applications. In this work, therefore, optoelectronic properties of Double Quantum Dots DQDs system were studied theoretically to provide important information about the possibility of using this system in photoelectric applications. A tight-binding framework was adopted to describe the system, and all the calculations were carried out based on the steady state formalism. The proposed DQD structure was connected to metallic leads and studied to investigate the QD size dependent. The transmission calculation presented first through the electron transport mechanism. Tunneling current and conductance were then presented to provide general understanding about the behavior of the proposed system. A correlation of transmission, current and conductance results with QD radius R, incident photon energy Eph, Temperature and bias voltage have been identified. Therefore, this correlation is strongly supporting the proposal of using DQD system in fabricating nanoscale photovoltaic devices, particularly, solar cells.

Magnetic nanomaterials play an important role in emerging industries, specializing in the study of objects (natural or artificially synthesized) with nanoscale building blocks. The wide use of magnetic nanomaterials (especially for biological applications) is constrained by the following reasons: difficulties in obtaining monodisperse ferromagnet particles with stable reproducible characteristics, high cost of large-capacity production However, nanomaterials with magnetic properties are increasingly used in everyday practice. Some companies have already established the production of the first samples of nanomaterials. The time to conduct of a large-scale search for the ways of practical use of magnetic materials has come. Ferrofluids or so-called magnetic fluids are suspensions of magnetic nanoparticles stabilized with a surfactant, in liquid media. Magnetite and ferrites can act as the magnetic phase in the ferrofluids. The liquid phase is water or an organic liquid. The dimensions of the magnetic nanoparticles are 5-10 nm. The market supplied magnetic fluids contain mostly magnetite. Such magnetic fluids are used as a separation medium, polarized external inhomogeneous magnetic field in the gold mining industry to recover the fractions containing 90-97% native gold. A method for the preparation of a colloidal solution with a narrow distribution of magnetite particles according to the size by the heterogeneous condensation method according to R. Zigmondi has been developed. Condensation is carried out on seeds, which is brought into the solution of nanoparticles of magnetite. Getting monodisperse sol is achieved by injecting a concentrated solution of one component in a very dilute solution of another, with vigorous stirring (typically Veimarn). A method called "double additive" proposed G.J. Fleer and J. Lyklema is used to stabilize the sol. The method reduces to the fact that the source unprotected magnetite sol stabilizer is added to a certain volume of a colloidal solution of magnetite, on the surface of which stabilizer is physically and chemically sorbed.

Background: The trend for the fabrication of electrical circuits with nanoscale dimensions has led to impressive progress in the field of molecular electronics in the last decade. However, a theoretical description of molecular contacts as the building blocks of future devices is challenging, as it has to combine the properties of Fermi liquids in the leads with charge and phonon degrees of freedom on the molecule. Outside of ab initio schemes for specific set-ups, generic models reveal the characteristics of transport processes. Particularly appealing are descriptions based on transfer rates successfully used in other contexts such as mesoscopic physics and intramolecular electron transfer. However, a detailed analysis of this scheme in comparison with numerically exact solutions is still elusive. Results: We show that a formulation in terms of transfer rates provides a quantitatively accurate description even in domains of parameter space where strictly it is expected to fail, e.g., at lower temperatures. Typically, intramolecular phonons are distributed according to a voltage driven steady state that can only roughly be captured by a thermal distribution with an effective elevated temperature (heating). An extension of a master equation for the charge–phonon complex, to effectively include the impact of off-diagonal elements of the reduced density matrix, provides very accurate solutions even for stronger electron–phonon coupling. Conclusion: Rate descriptions and master equations offer a versatile model to describe and understand charge transfer processes through molecular junctions. Such methods are computationally orders of magnitude less expensive than elaborate numerical simulations that, however, provide exact solutions as benchmarks. Adjustable parameters obtained, e.g., from ab initio calculations allow for the treatment of various realizations. Even though not as rigorously formulated as, e.g., nonequilibrium Green’s function methods, they are conceptually simpler, more flexible for extensions, and from a practical point of view provide accurate results as long as strong quantum correlations do not modify the properties of the relevant subunits substantially.

Artikel review ini memberikan informasi tentang aplikasi polianilina (PANI) dan kompositnya sebagai sensor gas berbahaya khususnya amonia (NH3). Kajian yang dibahas pada artikel ini meliputi sifat gas NH3, material komposit, kinerja sensor, serta limit deteksi. Tinjauan sensor gas amonia berbasis polimer konduktif polianilina secara menyeluruh diambil dari referensi sepuluh tahun terakhir. Sebagai contoh, komposit polianilina dengan turunan karbon seperti reduced Graphene Oxide (rGO) dan Carbon Nanotube menunjukkan limit deteksi hingga 46 ppb dengan waktu pemulihan hanya 75 detik. Selain itu, komposit PANI dengan logam seperti Ag, Sr dan sebagainya, menunjukkan limit deteksi yang lebih besar yaitu 1 ppm, namun terdapat keunggulan dimana waktu pemulihan hanya 4 deti. Oleh sebab itu, polimer konduktif polianilina menjadi material yang sangat menjanjikan untuk mendeteksi keberadaan gas NH3. Terakhir, mekanisme penginderaan gas amonia terhadap material PANI juga dibahas pada tulisan ini. 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Abstract Light-harvesting complexes in natural photosynthetic systems, such as those in purple bacteria, consist of photo-reactive chromophores embedded in densely packed “antenna” systems organized in well-defined nanostructures. In the case of purple bacteria, the chromophore antennas are composed of natural J-aggregates such as bacteriochlorophylls and carotenoids. Inspired by the molecular composition of such biological systems, we create a library of organic materials composed of densely packed J-aggregates in a polymeric matrix, in which the matrix mimics the optical role of a protein scaffold. This library of organic materials shows polaritonic properties which can be tuned from the visible to the infrared by choice of the model molecule. Inspired by the molecular architecture of the light-harvesting complexes of Rhodospirillum molischianum bacteria, we study the light–matter interactions of J-aggregate-based nanorings with similar dimensions to the analogous natural nanoscale architectures. Electromagnetic simulations show that these nanorings of J-aggregates can act as resonators, with subwavelength confinement of light while concentrating the electric field in specific regions. These results open the door to bio-inspired building blocks for metamaterials from visible to infrared in an all-organic platform, while offering a new perspective on light–matter interactions at the nanoscale in densely packed organic matter in biological organisms including photosynthetic organelles.

AbstractCovalent organic frameworks (COFs) as a type of porous and crystalline covalent organic polymer are built up from covalently linked and periodically arranged organic molecules. Their precise assembly, well-defined coordination network, and tunable porosity endow COFs with diverse characteristics such as low density, high crystallinity, porous structure, and large specific-surface area, as well as versatile functions and active sites that can be tuned at molecular and atomic level. These unique properties make them excellent candidate materials for biomedical applications, such as drug delivery, diagnostic imaging, and disease therapy. To realize these functions, the components, dimensions, and guest molecule loading into COFs have a great influence on their performance in various applications. In this review, we first introduce the influence of dimensions, building blocks, and synthetic conditions on the chemical stability, pore structure, and chemical interaction with guest molecules of COFs. Next, the applications of COFs in cancer diagnosis and therapy are summarized. Finally, some challenges for COFs in cancer therapy are noted and the problems to be solved in the future are proposed.

Abstract As devices approach the single-nanoparticle scale, the rational assembly of nanomaterial heterojunctions remains a persistent challenge. While optical traps can manipulate objects in three dimensions, to date, nanoscale materials have been trapped primarily in aqueous solvents or vacuum. Here, we demonstrate the use of optical traps to manipulate, align, and assemble metal-seeded nanowire building blocks in a range of organic solvents. Anisotropic radiation pressure generates an optical torque that orients each nanowire, and subsequent trapping of aligned nanowires enables deterministic fabrication of arbitrarily long heterostructures of periodically repeating bismuth-nanocrystal/germanium-nanowire junctions. Heat transport calculations, back-focal-plane interferometry, and optical images reveal that the bismuth nanocrystal melts during trapping, facilitating tip-to-tail “nanosoldering” of the germanium nanowires. These bismuth-semiconductor interfaces may be useful for quantum computing or thermoelectric applications. In addition, the ability to trap nanostructures in oxygen- and water-free organic media broadly expands the library of materials available for optical manipulation and single-particle spectroscopy.

Abstract Nanowires offer unprecedented flexibility as nanoscale building blocks for future optoelectronic devices, especially with respect to nanowire solar cells and light-emitting diodes. A relatively new concept is that of charge carrier diffusion-induced light-emitting diodes, for which nanowires offer an interesting architecture by use of particle-assisted core-branch growth. The branches should be homogenously distributed along the cores. However, most deposition techniques, such as aerosol particle deposition, mainly yield particles at the nanowire tips for dense nanowire arrays. In this study, we demonstrate a liquid-based approach for homogeneously distributed formation of catalytic Au particles on the core nanowire sidewalls which is cost and time-efficient. Subsequently, we demonstrate the synthesis of dispersed nanowire branches. We show that by changing the deposition parameters, we can tune the number of branches, their dimensions, and their growth direction.

Micro- and nanoelectromechanical systems have numerous applications in sensing and signal transduction. Many properties benefit from reducing the system size to the nanoscale, such as increased responsivity, enhanced tunability, lower power consumption, and higher spatial density. Two-dimensional (2D) materials represent the ultimate limit of thickness, offering unprecedented new capabilities due to their natural nanoscale dimensions, high stability, high mechanical strength, and easy electronic integration. Here, we review the primary design principles, properties, applications, opportunities, and challenges of 2D materials as the building blocks of NEMS (2D NEMS) with a focus on nanomechanical resonators. First, we review the techniques used to design, fabricate, and transduce the motion of 2D NEMS. Then, we describe the dynamic behavior of 2D NEMS including vibrational eigenmodes, frequency, nonlinear behavior, and dissipation. We highlight the crucial features of 2D NEMS that enhance or expand the functionalities found in conventional NEMS, such as high tunability and rich nonlinear dynamics. Next, we overview the demonstrated applications of 2D NEMS as sensors and actuators, comparing their performance metrics to those of commercial MEMS. Finally, we provide a perspective on the future directions of 2D NEMS, such as hybrid quantum systems, integration of active 2D layers into nanomechanical devices, and low-friction interfaces in micromachines.

AbstractNanoparticles, nanowires, nanorods and other kinds of nanostructures have been of great interest to scientific field. Semiconducting nanowires have attracted much attention due to the fact that reduced dimensional confinement of electrons, holes and photons make them particularly attractive as potential building blocks for nanoscale optoelectronic devices, highly quantum efficient lasers and non-linear optical converters. It is generally accepted that the low dimensional structures (where the size in one direction is equivalent to or smaller than the de Broglie wavelength) are useful materials for investigating the dependence of electrical and thermal transport or mechanical properties on the dimensionality and quantum confinement. Nanomaterials also play an important role as functional units in fabricating the electromechanical devices. Semiconductor nanostructures of different materials and shapes are investigated due to their size dependent electronic properties observable at dimensions comparable to or less than Bohr radius of exciton in these materials. Especially various oxides and sulphides have generated interests in variety of applications. In this paper, the recent progress in various nanostructures, paradigms in implementation and technology hurdles in implementing nanostructures are discussed

AbstractMagnetic particles of optimized nanoscale dimensions can be utilized as building blocks to generate colloidal nanocrystal assemblies with controlled size, well-defined morphology, and tailored properties. Recent advances in the state-of-the-art surfactant-assisted approaches for the directed aggregation of inorganic nanocrystals into cluster-like entities are discussed, and the synthesis parameters that determine their geometrical arrangement are highlighted. This review pays attention to the enhanced physical properties of iron oxide nanoclusters, while it also points to their emerging collective magnetic response. The current progress in experiment and theory for evaluating the strength and the role of intra- and inter-cluster interactions is analyzed in view of the spatial arrangement of the component nanocrystals. Numerous approaches have been proposed for the critical role of dipole-dipole and exchange interactions in establishing the nature of the nanoclusters’ cooperative magnetic behavior (be it ferromagnetic or spin-glass like). Finally, we point out why the purposeful engineering of the nanoclusters’ magnetic characteristics, including their surface functionality, may facilitate their use in diverse technological sectors ranging from nanomedicine and photonics to catalysis.