DNA nanotechnology-enabled chiral plasmonics: from static to dynamic

In this Account, we discuss a variety of static and dynamic chiral plasmonic nanostructures enabled by DNA nanotechnology. In the category of static plasmonic systems, we first show chiral plasmonic nanostructures based on spherical AuNPs, including plasmonic helices, toroids, and tetramers. To enhance the CD responses, anisotropic gold nanorods with larger extinction coefficients are utilized to create chiral plasmonic crosses and helical superstructures. Next, we highlight the inevitable evolution from static to dynamic plasmonic systems along with the fast development of this interdisciplinary field. Several dynamic plasmonic systems are reviewed according to their working mechanisms.Comment: 7 figure

Coarse-Grained Simulations of the Self-Assembly of DNA-Linked Gold Nanoparticle Building Blocks

The self-assembly of nanoparticles (NPs) of varying shape, size, and composition for the purpose of constructing useful nanoassemblies with tailored properties remains challenging. Although progress has been made to design anisotropic building blocks that exhibit the required control for the precise placement of various NPs within a defined arrangement, there still exists obstacles in the technology to maximize the programmability in the self-assembly of NP building blocks. Currently, the self-assembly of nanostructures involves much experimental trial and error. Computational modeling is a possible approach that could be utilized to facilitate the purposeful design of the self-assembly of NP building blocks into a desired nanostructure. In this report, a coarse-grained model of NP building blocks based on an effective anisotropic mono-functionalization approach, which has shown the ability to construct six building block configurations, was used to simulate various nanoassemblies. The purpose of the study was to validate the model’s ability to simulate the self-assembly of the NP building blocks into nanostructures previously produced experimentally. The model can be programmed to designate up to six oligonucleotides attached to the surface of a Au NP building block, with a modifiable length and nucleotide sequence. The model successfully simulated the self-assembly of Au NP building blocks into a number of previously produced nanostructures and demonstrated the ability to produce visualizations of self-assembly as well as calculate interparticle distances and angles to be used for the comparison with the previous experimental data for validation of the model. Also, the model was used to simulate nanoassemblies which had not been produced experimentally for its further validation. The simulations showed the capability of the model to use specific NP building blocks and self-assemble. The coarse-grained NP building block model shows promise as a tool to complement the purposeful experimental design of functional nanostructures

Nano-electronic components built from DNA templates

Building metal nanomaterials with tailored electrical properties is in high demand for electronic device fabrication. However, scalable and inexpensive fabrication of such metallic structures with nanometer precision remains a challenge. DNA origami is a versatile and robust self-assembly method which allows fabrication of arbitrary structures at the nanoscale. In this thesis, DNA origami templated metal nanostructure fabrication method is introduced. Continuous metal nanostructures with controlled geometry as well as the selective deposition of multi-nanomaterials (metals and semiconductors) at specific sites on origami templates play an im-portant role in the fabrication of DNA based nanoelectronics system. A mold DNA origami with quadratic cross-section was constructed and used as template for the gold nanoparticles metal growth. Each individual mold element acted as a lego-brick in this modular mold system. (1) Linear metallic nanostructures with controlled length and programmable patterns were fabricat-ed at superior yields by systematically investigating the interface of each mold element. (2) A versatile fabrication modular mold platform for metallic nanostructures with complex shapes was further developed by integrating particular molds with different diameters, additional dock-ing sites, and junctions. Caged metal nanostructures, constrained gold growth and branched structures with extensions in two dimensions were successfully realized. (3) Micrometer long, homogeneous and continuous gold nanowires were obtained with exceeding quality. Using elec-tron-beam lithography and low-temperature conductance measurements, ohmic behavior of such nanowires were observed, confirming metallic conductive property. (4) A method for the synthesis and DNA functionalization of semiconducting nanorods was established. Metal-semiconductor heterostructures were fabricated based on the modular mold system. Semicon-ducting nanorods, as well as gold nanoparticles, were placed at defined positions on the DNA modular platform and a direct metal-semiconductor interface was achieved after the electroless metal deposition. (5) An improved and optimized metallization of DNA origami templated gold nanowires were further developed to increase the conductivity performance. Various reaction parameters were investigated and the obtained gold nanowires with a reduced number of AuNPs achieved an anisotropic growth. This developed DNA origami template mold modular platform addresses the size, pattern, and geometry controls over the metallic nanostructures. For the ap-plication prospect, the conductivity of such metallic nanostructures and controlled placement of different nanomaterials enable an important step towards the nanodevices and systems fabrica-tion based on DNA.Der Aufbau metallischer Nanomaterialien mit angepassten elektrischen Eigenschaften ist für die Verwendung in elektronischen Bauteilen von großer Bedeutung. Dabei ist die skalierbare und günstige Herstellung metallischer Strukturen im Nanometerbereich weiterhin eine Herausforderung. Die DNA Origami Technik bietet hier eine vielseitig einsetzbare und stabile Methode zur Selbstassemblierung, welche die Herstellung beliebiger nanoskalierter Strukturen ermöglicht. In dieser Arbeit wird ein neuer Ansatz zur Herstellung metallischer Nanostrukturen mit Hilfe von DNA Origami Templaten vorgestellt. Kontinuierliche Metallnanostrukturen mit einer definierten Geometrie, sowie die selektive Anbindung verschiedener Nanomaterialien (Metalle und Halbleiter) an spezifischen Anbindungsstellen des Origamitemplates spielen eine wichtige Rolle bei der Herstellung DNA basierter nanoelektrischer Systeme. Ein DNA Origami Mold mit einem quadratischen Querschnitt wurde als Templat für die Metallisierung von Goldnanopartikeln verwendet. Das legostein-artige Design der einzelnen Origami Molds ermöglicht die Assemblierung in einem modularen System. (1) Lineare metallische Nanostrukturen mit kontrollierter Länge und programmierbarem Muster wurden mit hohen Ausbeuten assembliert, indem das Interface der einzelnen Origamistrukturen systematisch untersucht wurde. (2) Weiterhin wurde eine vielseitige, sowie modulare Plattform für metallische Nanostrukturen mit komplexen Formen entwickelt. Dabei wurden spezielle Origamistrukturen mit unterschiedlichem Durchmesser, sowie zusätzlichen Anbindungsstellen und Verzweigungen integriert. Die erfolgreiche Metallisierung linearer und verzweigter Nanostrukturen in zwei Dimensionen wurde durch ein restriktives Goldwachstum im Inneren der Origamistrukturen realisiert. (3) Homogene und kontinuierliche Goldnanodrähte mit Mikrometerlänge und außerordentlicher Qualität wurden fabriziert. Mit Hilfe von Elektronenstrahllithographie wurde die Leitfähigkeit der Strukturen im Niedrigtemperaturbereich untersucht, wobei ein ohmsches Ladungstransportverhalten der Nanodrähte nachgewiesen werden konnte, welches die metallische Leitfähigkeit der Strukturen bestätigte. (4) Eine Methode zur Synthese und DNA Funktionalisierung von Halbleiternanostäbchen wurde eingeführt. Zudem konnten Metall-Halbleiterheterostrukturen hergestellt werden, basierend auf dem entworfenen modularen Origamisystem. Halbleiternanostäbchen und Goldnanopartikel wurden an definierten Positionen der DNA Origami platziert. Durch eine anschließende Metallisierung konnte ein direktes Metall-Halbleiterinterface hergestellt werden. (5) Eine verbesserte und optimierte Metallisierung der DNA Origami basierten Goldnanodrähte zur Erhöhung der Leitfähigkeit wurde entwickelt. Dazu wurden verschiedene Reaktionsparameter optimiert, so dass ein anisotropes Wachstum mit einer reduzierten Anzahl von Goldnanopartikel ermöglicht werden konnte. Die, in dieser Arbeit entwickelte DNA Origami Plattform ermöglicht die Kontrolle über Größe, Struktur und Geometrie metallischer Nanostrukturen. Die ohmsche Leitfähigkeit dieser Nanostrukturen und die zusätzliche Assemblierung verschiedener Nanomaterialien stellen dabei einen wichtigen Schritt für eine potentielle Verwendung in elektrischen Nanogeräten dar

Semi-Biosynthesis of DNA Nanostructures

Nanotechnology refers to all technologies aiming to build objects, make measurements, and carry out processes on the nanometer length scale. In particular molecular nanotechnology exemplifies the so-called bottom up approach, which is briefly defined as the ability to build useful nanostructures with molecular precision, such as molecular machinery. Such capability for controlling matter at the molecular scale has always been the dream of scientists. All living things are nanofoundries. Billions of years ago, nature perfectly provided all living things with the most accurate biological nanotechnology systems. Cellular internal dynamics, communicative resonance in protein conformational states, viruses as microreplicators, nanoscale life mechanisms, (e.g. repairing and replication) and nanoscale energy exchanges are examples of these systems. It is clear that learning and using some biological techniques (DNA replication), or even using some of the molecular tools provided by nature (enzymes) will be most relevant to nanotechnology development. In this project we demonstrate how we can derive benefit from employing biological techniques, such as Rolling Circle Amplification, Polymerase Chain Reaction, and cloning to address the challenge of emplacing DNA nanoarrays at pre-determined locations on a surface. In vitro, rolling Circle amplification (RCA) driven by DNA polymerization was first reported by Eric T. Kool and coworkers in 1995. DNA products resulting from RCA are repeating head-to-tail multimeric copies of the DNA template. We report the design and synthesis of both single stranded circular DNA (used as a template) and a multimeric product. Using the RCA technique, long tandem repeats, consisting of multiple copies of a 95 base pair sequence have been produced. We incorporated two specific, unique sequences at each end of these synthesized DNA strands, which can be used as recognition sites for surface hybridization. For the first time, heterogeneity has been introduced into a repetitive system to yield a modular nanostructured macromolecule. This product was further cloned into bacterial host cells. The DNA fragments were extracted and sequenced. The results not only confirm success in these particular experiments, but they also verify the general validity of this technique for generating nano-constructs semi- biosynthetically. In order to demonstrate applicability of the RCA product to nanotechnology, we used these strands as scaffolds for gold nanoparticle patterning

Block copolymer self-assembly for nanophotonics

The ability to control and modulate the interaction of light with matter is crucial to achieve desired optical properties including reflection, transmission, and selective polarization. Photonic materials rely upon precise control over the composition and morphology to establish periodic interactions with light on the wavelength and sub-wavelength length scales. Supramolecular assembly provides a natural solution allowing the encoding of a desired 3D architecture into the chemical building blocks and assembly conditions. The compatibility with solution processing and low-overhead manufacturing is a significant advantage over more complex approaches such as lithography or colloidal assembly. Here we review recent advances on photonic architectures derived from block copolymers and highlight the influence and complexity of processing pathways. Notable examples that have emerged from this unique synthesis platform include Bragg reflectors, antireflective coatings, and chiral metamaterials. We further predict expanded photonic capabilities and limits of these approaches in light of future developments of the field

Transfer of molecular recognition information from DNA nanostructures to gold nanoparticles

DNA nanotechnology offers unparalleled precision and programmability for the bottom-up organization of materials. This approach relies on pre-assembling a DNA scaffold, typically containing hundreds of different strands, and using it to position functional components. A particularly attractive strategy is to employ DNA nanostructures not as permanent scaffolds, but as transient, reusable templates to transfer essential information to other materials. To our knowledge, this approach, akin to top-down lithography, has not been examined. Here we report a molecular printing strategy that chemically transfers a discrete pattern of DNA strands from a three-dimensional DNA structure to a gold nanoparticle. We show that the particles inherit the DNA sequence configuration encoded in the parent template with high fidelity. This provides control over the number of DNA strands and their relative placement, directionality and sequence asymmetry. Importantly, the nanoparticles produced exhibit the site-specific addressability of DNA nanostructures, and are promising components for energy, information and biomedical applications

Manufacturing polyacrylonitrile nanowires and nanofibers for sensing and energy storage applications

A novel flow guided assembly approach is presented to well align and accurately position nanowire arrays in pre-defined locations with high throughput and large scale manufacturing capability. In this approach, polyacrylonitrile (PAN)/N, N-dimethylformamide (DMF) solution is first filled in an array of microfluidic channels. Then a gas flow is introduced to blow out most solutions while pushing a little leftover against the channel wall to assemble into polymer nanowires. In this way, highly-ordered nanowires are conveniently aligned in the flow direction and patterned along both sides of the microchannels. In this study, we demonstrated this flow-guided assembly process by producing millimeter-long nanowires across 5 mm x 12 mm area in the same orientation and with basic I-shape , T-shape , and cross patterns. The assembled polymer nanowires were further converted to conductive carbon nanowires through a standard carbonization process. After integrated into electronic sensors, high sensitivity was found in model protein sensing tests. This new nanowire manufacturing approach is anticipated to open new doors to the fabrication of nanowire-based sensing systems and serve as the Good Manufacturing Practices (GMP) (a system for ensuring that products are consistently produced and controlled according to quality standards) for its simplicity, low cost, alignment reliability, and high throughput. By using the same polymer solution (polyacrylonitrile (PAN)/N, N- dimethylformamide (DMF) solution), a new, simple, and low-cost method has been developed in the production of porous composite nanofibers via a one-step foaming and electrospinning process. Sublimable aluminum acetylacetonate (AACA) was dissolved into polyacrylonitrile (PAN)/N, N-dimethylformamide (DMF) solution as the foaming agent. Silicon nanoparticles were then added and the resulting suspension solution was further electrospun to produce PAN/silicon composite nanofibers. The PAN nanofibers were then foamed during a thermal stabilization treatment and further carbonized into carbon/silicon composite nanofibers. Such mesoporous composites nanofiber mats were explored as the anode material for lithium ion batteries. Within this composite of nanofiber electrode, carbon nanofibers serve as the conductive media, while silicon nanoparticles ensure high lithium ion capacity and electrical density. The inter-fiber macrovoids and intra-fiber mesopores provide the buffering space to accommodate the huge volume expansion and consequent stress in the composite anode during the alloying process to mitigate electrode pulverization. Its high surface-to-volume ratio helps facilitate lithium ion transport between electrolytes and the active materials. Our electrochemical tests demonstrated higher reversible capacity and better capacity retention with this porous carbon/silicon composite nanofiber anode when compared with that made of nonporous composite nanofibers and CNF alone with similar treatments

ZnO Nanostructures: Low-Temperature Synthesis, Characterisation, Their Potential Application as Gene-Delivery Tools

Among metal oxide nanomaterials, zinc oxide (ZnO) nanostructures are one of the most important nanomaterials in today’s nanotechnology research. Over the past several decades, ZnO nanostructures have been extensively investigated for their extraordinary physical and chemical characteristics and also for their prominent performance in various novel applications such as photonics, optics, electronics, drug delivery, cancer treatment, bio-imaging, etc. However, the functionality of theses nanomaterials is eventually dictated by the capability to govern their properties including shape, size, position, and crystalline structure on the nanosized scale. This thesis investigates the solution-based synthesis of ZnO nanostructures and their morphological and structural properties. Importantly, in order to achieve the promising structure of ZnO, a systematic investigation of the influence of processing parameters, including solution concentration, time and temperature of growth reaction on the resultant materials was addressed. The other main point for this work is not only to effectively control the morphology, size, uniformly distribution, and orientation of ZnO nanomaterials, but also to build a good comprehension of the mechanism of the fabrication process to raise their performance in future nanoscale applications. Furthermore, the catalytic effect of RF sputtered gold (Au) thin layer on Si substrate prior to ZnO growth was investigated to demonstrate the contributory for the remarkable catalytic activity of Au nanoparticles in the formation of high-quality ZnO nanostructures. Furthermore, we introduce an effective, inexpensive lithographic patterning method to consistently control the position of solution-processed ZnO nanowires. Nanosphere lithography technique (NSL) utilizes a catalyst-assisted pattern generated by employing colloidal self-assembled crystal of polystyrene spheres (PS) on the substrate surface to guide the hydrothermal growth of ZnO nanowires. Further, we fabricate 3D NFs and branched NFs of ZnO on a silicon substrate via a simple and cost-effective solution growth method, incorporating with seed ZnO nanoparticles deposition. The synthesis of 3D branched ZnO nanostructure could potentially exploit for applications in optoelectronics, catalysis, sensing, and photovoltaics. In addition to the synthesis of 1D and 3D ZnO nanostructures, their morphology and distribution have been analysed via scanning electron microscopy (SEM) while the surface topography was analysed by atomic force microscopy (AFM). The crystalline structure, phase purity, and particle size of ZnO nanomaterials have been investigated using X-ray diffraction (XRD). The outcomes from all these efforts have been integrated for cellular investigation via fluorescence microscopy technique (FM) to demonstrate the potential application of ZnO nanostructures as a gene delivery/-tissue engineering tool in different expression systems.Libyan Governmen