Single Walled Carbon Nanotubes Assembly: Nanohybrids toward Photodetection and Junction Engineering.

PhD ThesesBy synergistically combining the individual properties of more than one nanoscale component, novel features of hybrid structure assemblies represent a key motivation for making future functional nanomaterials. In this thesis, the successful construction of a multiplexed photo-responsive chip from DNA-wrapped single walled carbon nanotubes (DNA-CNTs) and DNA-CNT templated inorganic-organic hybrid structures is first demonstrated. The effective assembly of the hybrids was characterized by atomic force microscopy (AFM) and the corresponding device performance as well as the key mechanisms behind were investigated. Then a facile approach for the fabrication of end-to-end SWCNT junctions exploiting oligonucleotides as molecular linkers is presented. The assembled junctions show clear stimuli-responsive features stemming from the designed sequences of oligonucleotides; this grants the SWCNTs the ability to self-assemble and disassemble under specific conditions in aqueous solutions. The junction formation was confirmed by Atomic Force Microscopy (AFM) and time-dependent fluorescence analysis. Moreover, an efficient strategy to sort DNA-wrapped SWCNTs (DNA-CNTs) by length via a gel electrophoresis technique was developed (confirmed by AFM). In addition to the application of oligonucleotides, the use of diazonium salts not only as a molecular linker but also the major reactive agent for CNT junction formation was also explored. In conclusion, by integrating DNA-CNTs with other active components, we have achieved the assembly for organic-inorganic nanohybrids of multiplexed photo-sensing capabilities and the assembly of reconfigurable SWCNT junctions with stimuli-responsive features. Moreover, the facile and efficient strategies developed in our work can contribute to the controlled assembly of CNT based functional nanohybrids

DEVELOPING NANOPORE ELECTROMECHANICAL SENSORS WITH TRANSVERSE ELECTRODES FOR THE STUDY OF NANOPARTICLES/BIOMOLECULES

This study concerns development of a technology of utilizing metallic nanowires for a sensing element in nanofluidic single molecular (nanoparticle) sensors formed in plastic substrates to detect the translocation of single molecules through the nanochannel. We aimed to develop nanofluidic single molecular sensors in plastic substrates due to their scalability towards high through and low cost manufacturing for point-of-care applications. Despite significant research efforts recently on the technologies and applications of nanowires, using individual nanowires as electric sensing element in nanofluidic bioanalytic devices has not been realized yet. This dissertation work tackles several technical challenges involved in this development, which include reduction of nanowire agglomerates in the deposition of individual nanowires on a substrate, large scale alignment/assembly of metallic nanowires, placement of single nanowires on microelectrodes, characterization of electrical conductance of single nanowire, bonding of a cover plate to a substrate with patterned microelectrodes and nanowire electrodes. Overcoming the abovementioned challenges, we finally demonstrated a nanofluidic sensor with an in-plane nanowire electrode in poly(methyl methacrylate) substrates for sensing single biomolecules. In the first part of this study, we developed the processes for separation and large-scale assembly of individual NiFeCo nanowires grown using an electrodeposition process inside a porous alumina template. A method to fabricate microelectrode patterns on plastic substrates using flexible stencil masks was developed. We studied electrical and magnetic properties of new composite core-shell nanowires by measuring the electrical transport through individual nanowires. The core-shell nanowires were composed of a mechanically stable FeNiCo core and an ultrathin shell of a highly conductive Au gold (FeNiCo-Au nanowires). In the second part of this study, we simulated the effects of the nanopore geometry on the current drop signal of the translocation through a nanopore via finite element method using COMSOL. Using the above techniques, we developed for the fabrication and alignment of the microelectrodes and nanowires, we studied the optimum conditions to integrate the transverse nanoelectrode with the nanochannel on plastic substrates. The main challenge was to find the conditions to embed the micro-/nanoelectrodes into the nanochannel substrate as well as the nanochannel cover sheet

Solution-Processable Carbon Nanotube Molecular Junctions

PhDNanotechnology is the manipulation of matter at the supramolecular, molecular and atomic scale. As a result, nanotechnology is included in various fields of science including surface science, organic chemistry, molecular biology, semiconductor physics, microfabrication and molecular engineering. One of the ambitions for nanotechnology is to develop electrical devices where the active component is a single molecule or nanomoiety. In order to fabricate such devices, it is of paramount importance to develop strategies beyond the current top-down lithographic approaches typically employed in the semiconductor industry. In this regard, the ability to control the assembly of single-molecules and individual nanomoieties directly in solution can allow for the development of solution-processable approaches in nanotechnology, towards the fabrication of single-molecule devices. In this thesis, it will be discussed how molecular junctions with functional single molecules are fabricated in aqueous solutions employing single-walled carbon nanotubes as potential nanoelectrodes. Furthermore, it will be demonstrated how the assembly of molecular junctions can facilitate other functions and the construction of both nanostructures and microstructures. To begin, relevant work will be discussed that has been done in this field to date and outline clear ambitions of the study presented here. Subsequently, the key characterisation techniques that underpin all the results in this study will be described. In this work, it will be reported how metallic carbon nanotubes can act as nanoelectrodes in molecular junction assemblies and how conductive measurements of individual molecules are performed. Therefore, for the first time, the molecular junction conductance of a series of oligophenyls were successfully measured, which were formed via a solution-based assembly method. Measured molecular conductance values of the series of oligophenyls resulted in a β value of 0.5 Å−1. Furthermore, it will be described how the approach outlined previously can be extended to the synthesis of tri-amine molecular linkers as well as the formation of three-terminal junctions as the foundation of carbon nanotube-based single-molecule electronic devices. This research resulted in an increase in the formation of Y-shape molecular junctions by ~25%. Next, this report will outline the formation of molecular junctions in two-dimensional structures, which can allow for the development of electrical devices into networks. Utilising modified DNA sequences, “click” chemistry can lead to nanotube network with dimensions ranging into the micrometre scale. Building on this work, it will be further report on the change in physical properties when these two-dimensional superstructures are embedded into polymeric thin films. Finally, conclusions of the research will be drawn and it will be discussed how the findings obtained in this work can contribute to the development of novel single-molecule electronic devices

Nanofluidic Pathways for Single Molecule Translocation and Sequencing -- Nanotubes and Nanopores

abstract: Driven by the curiosity for the secret of life, the effort on sequencing of DNAs and other large biopolymers has never been respited. Advanced from recent sequencing techniques, nanotube and nanopore based sequencing has been attracting much attention. This thesis focuses on the study of first and crucial compartment of the third generation sequencing technique, the capture and translocation of biopolymers, and discuss the advantages and obstacles of two different nanofluidic pathways, nanotubes and nanopores for single molecule capturing and translocation. Carbon nanotubes with its constrained structure, the frictionless inner wall and strong electroosmotic flow, are promising materials for linearly threading DNA and other biopolymers for sequencing. Solid state nanopore on the other hand, is a robust chemical, thermal and mechanical stable nanofluidic device, which has a high capturing rate and, to some extent, good controllable threading ability for DNA and other biomolecules. These two different but similar nanofluidic pathways both provide a good preparation of analyte molecules for the sequencing purpose. In addition, more and more research interests have move onto peptide chains and protein sensing. For proteome is better and more direct indicators for human health, peptide chains and protein sensing have a much wider range of applications on bio-medicine, disease early diagnoses, and etc. A universal peptide chain nanopore sensing technique with universal chemical modification of peptides is discussed in this thesis as well, which unifies the nanopore capturing process for vast varieties of peptides. Obstacles of these nanofluidic pathways are also discussed. In the end of this thesis, a proposal of integration of solid state nanopore and fixed-gap recognition tunneling sequencing technique for a more accurate DNA and peptide readout is discussed, together with some early study work, which gives a new direction for nanopore based sequencing.Dissertation/ThesisDoctoral Dissertation Physics 201

Design, Fabrication, Testing of CNT Based ISFET and Characterization of Nano/Bio Materials Using AFM

A combination of Carbon Nanotubes (CNTs) and Ion Selective Field Effect Transistor (ISFET) is designed and experimentally verified in order to develop the next generation ion concentration sensing system. Micro Electro-Mechanical System (MEMS) fabrication techniques, such as photolithography, diffusion, evaporation, lift-off, packaging, etc., are required in the fabrication of the CNT-ISFET structure on p-type silicon wafers. In addition, Atomic Force Microscopy (AFM) based surface nanomachining is investigated and used for creating nanochannels on silicon surfaces. Since AFM based nanomanipulation and nanomachining is highly controllable, nanochannels are precisely scratched in the area between the source and drain of the FET where the inversion layer is after the ISFET is activated. Thus, a bundle of CNTs are able to be aligned inside a single nanochannel by Dielectrophoresis (DEP) and the drain current is improved greatly due to CNTs` remarkable and unique electrical properties, for example, high current carrying capacity. ISFET structures with or without CNTs are fabricated and tested with different pH solutions. Besides the CNT-ISFET pH sensing system, this dissertation also presents novel AFM-based nanotechnology for learning the properties of chemical or biomedical samples in micro or nano level. Dimensional and mechanical property behaviors of Vertically Aligned Carbon Nanofibers (VACNFs) are studied after temperature and humidity treatment using AFM. Furthermore, mechanical property testing of biomedical samples, such as microbubbles and engineered soft tissues, using AFM based nanoindentation is introduced, and the methodology is of great directional value in the area

Production, processing and assembly of carbon nanotubes

This dissertation reports the development of a method to achieve continuous production of carbon nanotubes. The as produced carbon nanotubes were purified and further processed to tune their properties. Then dielectrophoresis as a versatile technique was used to manipulate and assemble carbon nanotubes into functional structures. In the processing part, purified carbon nanotubes are treated with strong acid then annealed at different temperatures. Combined TEM and NMR studies show that tips of SWNTs in bulk quantities can be uniformly opened by oxidation and closed by vacuum annealing at a surprisingly low temperature. The results provide a guideline on how the SWNTs should be processed for potential energy storage applications. In the assembly part, first, the results of a systematic study on the interactions of CNTs suspended in media of various viscosities and ionic conductivities with an AC field of different frequencies were reported. Then the feasibility of utilizing the dielectrophoresis for controlled assembling of functional CNT structures was explored. Finally, the automated process of assembling CNT fibrils unto sharp probes was realized and a precise control over the process was especially studied

Electrogenerated chemiluminescence : from mechanistic insights to bioanalytical applications

Electrogenerated chemiluminescence (ECL) is a powerful analytical technique exploited for clinical, industrial and research applications. The high sensitivity and good selectivity, makes ECL a tool-of-choice analytical method for a broad range of assays, most importantly for a large number of commercialized bead-based immunoassays. In the present thesis, we aimed to study the ECL phenomenon and its application in development of new analytical methods.In the first part of this work, we used an imaging technique to investigate the ECL mechanisms operating in bead-based assays. Spatial reactivity mapping at the level of a single functionalised bead provides a new strategy to test the co-reactant efficiency and shows associated optical focusing effects.In the second part, the design of a novel anti-transglutaminase ECL immunoassay for celiac disease diagnostic is shown using nanoelectrode ensembles as bioelectroanalytical platforms. We also studied the characteristics of ECL generated by arrays of boron-doped-diamond nanoelectrodes (BDD NEAs) as a promising materials for bioapplications. The ECL efficiency of two co-reactants at BDD NEAs was investigated.Finally, bipolar electrochemistry is a ‘‘wireless’’ process that was exploited for the controlled motion of conductive objects exposed to an electric field in the absence of direct ohmic contact. In the third part of the thesis, we report ECL coupled to bipolar electrochemistry for tracking the autonomous trajectories of swimmers by light emission. We further expanded this concept for dynamic enzymatic sensing of glucose concentration gradient using ECL light emission as an analytical readout.La chimiluminescence électrogénérée (ECL) est une technique analytique puissante exploitée pour la détection autant au niveau industriel que dans le domaine de la recherche scientifique ou du diagnostic clinique. La sensibilité élevée et la bonne sélectivité de cette technique font de l'ECL une méthode analytique de choix pour un large éventail d'applications, dont la plus importante est son utilisation commerciale dans un grand nombre de tests immunologiques à base de billes fonctionnalisées. Dans cette thèse, nous avons cherché à étudier le phénomène ECL et son application pour le développement de nouvelles techniques analytiques.Dans la première partie de ce travail, nous utilisons les techniques d'imagerie pour étudier les mécanismes ECL se produisant sur les billes utilisées pour les tests immunologiques. La cartographie de la réactivité au niveau d'une seule microparticule fonctionnalisée avec un complexe de ruthénium fournit une nouvelle stratégie visant à tester l'efficacité du co-réactif et montre des effets optiques associés de focalisation.Dans la deuxième partie, la conception d'un test immunologique pour la détection de l'anti-transglutaminase pour le diagnostic de la maladie coeliaque est présentée en utilisant des ensembles de nanoélectrodes comme plates-formes bioélectroanalytiques. Nous avons également étudié les caractéristiques de l'ECL générée par des réseaux de nanoélectrodes dopées au bore-diamant en tant que matériaux prometteurs pour des applications biologiques ainsi que l'efficacité ECL de deux co-réactifs sur ces réseaux.L'électrochimie bipolaire est un processus sans contact que nous avons exploité pour contrôler le mouvement d'objets conducteurs exposés à un champ électrique en l'absence de contact ohmique direct. Dans la troisième partie de ma thèse, nous présentons l'ECL couplée à l'électrochimie bipolaire pour le suivi d’objets autonomes luminescents. Nous avons élargi ce concept à la détection enzymatique dynamique de glucose en utilisant l'émission de lumière ECL comme signal analytique