This thesis describes observations, techniques and strategies, which contribute towards the development of nanoparticle based detection and treatment of cancer. Quantum dots and biorecognition molecules were studied towards applications in detection and microgels were used in the rational design of a targeted drug delivery vehicle. The fluorescence intensity of quantum dots was examined in buffers commonly used in molecular biology. The fluorescence intensity of ZnS-capped CdSe quantum dots (QDs) was found to vary significantly, depending on the amount of ZnS capping on the QDs or the concentration, pH and type of buffer the QDs were in. Since fluorescence cannot reliably be used to quantify QDs, an alternative quantification method was developed, which does not rely on their fluorescence. This method employs phage display to identify nanoparticle-specific bacteriophage which were then applied in an assay to quantify QDs in environments where absorbance or fluorescence spectroscopy are ineffective. Biorecognition molecules, which can direct nanoparticles to a molecular target, were also identified through phage display. Phage display on whole cells was used to identify a peptide, which was conjugated with QDs to stain HeLa (cervical cancer) cells. A high-throughput phage display screening strategy was also developed, which could enable the simultaneous identification of multiple biorecognition molecules from a single library. QD-encoded microbead barcodes were conjugated to protein targets and then used to screen a phage display library. The beads and the binding phage were then separated using flow cytometry and fluorescence assisted cell sorting. Finally, biorecognition molecules were combined with nanoparticles to create drug delivery vehicles, which were designed to protect, deliver and then release chemotherapeutic drugs through an intracellular pH trigger. PolyNIPAAm and chitosan hydrogels, under 200 nm in diameter, were loaded with chemotherapeutic drugs, conjugated to transferrin and tested in vitro on HeLa cells. These projects demonstrate the great potential in this growing field as well as some of the many challenges that have yet to be overcome.

The work presented in this thesis explores the optical properties of hierarchical structures composed of nanoscale building blocks ranging from metals to semiconductors and composites, organized through bottom-up design methods. 1) By following the dynamic generation of hot-spots in self-assembled chains of gold nanorods (NRs), we have established a direct correlation between ensemble-averaged surface-enhanced Raman scattering (SERS) and extinction properties of these nanoscale chains. Experimental results were supported by comprehensive finite-difference time-domain simulations (FDTD). The relationship established between the structure of nanorod ensembles and their optical properties provides a basis for producing dynamic, solution-based, plasmonic platforms for applications ranging from sensing to nanoelectronics. 2) We report theoretical and experimental analyses of the optical properties of side-by-side assembled gold NRs. Comprehensive FDTD simulations showed a blue shift of the surface plasmon resonance in the side-by-side assembled NR structures and a reduction of electric field intensity as the number of NRs per stack increased. These results were experimentally verified via extinction measurements and ensemble-averaged SERS spectroscopy. The experimental results and electrodynamic simulations were found to be in agreement. 3) The efficacy of hollow core photonic crystal fibers (HCPCF) as a platform for SERS spectroscopy was demonstrated. SERS measurements carried out using this platform showed the capability to monitor minute amounts of ligands on the surface of gold nanoparticles and SERS signals from HCPCF exhibited a 10-fold enhancement. Using the exchange of cetyltrimethylammonium bromide with α-methoxy-ω mercaptopolyethylene glycol on the surface of gold nanorods as an exemplary system, we showed the feasibility of using HCPCF SERS to monitor the change in surface chemistry of NRs. 4) Facile, solution-phase formation of ordered, lamellar quantum dot (QD) arrays exhibiting structural integrity and temporal stability, without the need for chemical crosslinking, was achieved. While micrometers in diameter, they are typically only two to three QD layers thick. These structures are capable of carrying a cargo of water-soluble ions, molecules, metal nanoparticles, or biomolecules. The photoluminescence of the host CdSe QDs were enhanced by the encapsulation of gold nanoparticles within the lamellae, demonstrating the ability to modulate their properties through the cargo they carry. 5) This chapter explores a bottom-up method to produce a metamaterial designed to function as an optical cloak in the visible range. A composite material consisting of an array of silver nanowires (NWs) in a dielectric host has been produced based on the theory of a non-magnetic optical cloak. The required radial array of silver NWs was achieved by electroless deposition of the metal into the channels of a porous alumina structure grown perpendicularly from the curved surface of a micrometer scale aluminum wire. The functionality of the cloak was demonstrated by partial cloaking in the visible range (540 nm).

Semiconductor quantum dots (QDs) and gold nanoparticles (AuNPs) have gained tremendous attention in the last decade as a result of their size-dependent spectroscopic properties. These nanoparticles have been a subject of intense study to bridge the gap between macroscopic and atomic behavior, as well as to generate new materials for novel applications in therapeutics, biological sensing, light emitting devices, microelectronics, lasers, and solar cells. One of the most promising areas for the use of these nanoparticles is in biotechnology, where their size-dependent optical properties are harnessed for imaging and sensing applications. However, these nanoparticles, as synthesized, are often not stable in aqueous media and lack simple and reliable means of covalently linking to biomolecules. The focus of this work is to advance the progress of these nanomaterials for biotechnology by synthesizing them, characterizing their optical properties and rendering them water-soluble and functional while maintaining their coveted optical properties. QDs were synthesized by an organometallic chemical procedure that utilizes coordinating solvents to provide brightly luminescent nanoparticles. The optical interactions of these QDs were studied as a function of concentration to identify particle size-dependent optimal concentrations, where scattering and indirection excitation are minimized and the amount light observed per particle is maximized. Both QDs and AuNPs were rendered water-soluble and stable in a broad range of biologically relevant conditions by using a series of ligands composed of dihydrolipoic acid (DHLA) appended to poly(ethylene glycol) methyl ether. By studying the stability of the surface modified AuNPs, we revealed some interesting information regarding the role of the surface ligand on the nanoparticle stability (i.e. solubility in high salt concentration, resistance to dithiothreitol competition and cyanide decomposition). Furthermore, the nanoparticles were functionalized using a series of bifunctional ligands that contain a dithiol group (DHLA) for surface binding, a PEG segment to instill water-solubility and a terminal functional group for easy bioconjugation (i.e. NH 2 , COOH, or biotin). Finally, a sensing application was demonstrated to detect the presence of microbial DNA (unmethlylated CpG) by using Toll-like receptor 9 proteins as the recognition components and the QDs as the transduction elements via Förster Resonance Energy Transfer.

Die vorliegende Arbeit beschäftigt sich mit dem Aufbau von Nanokristall-LEDs. Dazu werden der Synthese, der Abscheidung und dem Aufbau und der Charakterisierung von Nanopartikeln und LEDs Platz eingeräumt. CdTe-Nanopartikel werden über eine wässrige Synthese, die auf elektrochemisch erzeugten Tellurwasserstoff beruhte, hergestellt. Der Vorteil besteht im geringen Aufwand und der guten Reproduzierbarkeit. Es konnte festgestellt werden, dass sich ein hoher Überschuss an Cadmiumionen in der Lösung positiv auf die Wachstumsgeschwindigkeit der Nanopartikel auswirkt. Statt des anfänglich benutzten Layer-by-Layer-Tauchverfahrens wurde ein Layer-by-Layer-Sprühverfahren entwickelt, das die schnelle Herstellung homogener Filme, bestehend aus alternierenden Schichten einer Matrix und der Nanopartikel, ermöglichte. Nachteilig ist der hohe Verbrauch an Nanopartikeln gegenüber dem Tauchverfahren. Dem Tauchverfahren lastet der Umstand an, die kolloidalen Lösungen durch häufiges Eintauchen des Substrats zu verunreinigen. Dies wird beim Sprühverfahren vermieden, da alles nicht adsorbierte Material nach unten abfließt. Es wurde gezeigt, dass sich Polyelektrolyte durch anorganische Gele ersetzen lassen, die über einen Sol-Gel-Prozess darstellbar sind, wobei es möglich wurde „All inorganic“-LEDs aufzubauen mit dem Vorteil der hohen Temperaturstabilität. Wobei sich die Reinheit der dargestellten Aluminiumoxid-Sole stark auf das Bestreben Aluminiumoxid-Kristalle zu bilden, auswirkt, die die Funktionsfähigkeit der LED behindern können. Die Verwendung einer isolierenden Matrix wie Poly-(diallyldimethylammoniumchlorid) oder Aluminiumoxid als Zwischenschicht zum Aufbau von mehrlagigen Nanopartikelschichten stellte sich als unproblematisch heraus, da sich Ladungsträger über einen „hopping“-Mechanismus zwischen den Halbleiternanopartikeln bewegen können. Größere Probleme bereitete die Verwendung von Nanopartikeln größerer Bandlücken wie ZnSe (2,7eV) als Elektrolumineszenz-Emitter. Es konnte nur eine weissbläuliche Emission beobachtet werden. Mit Nanopartikeln kleiner Bandlücke wie CdTe (1,6eV) wurde eine schmalbandige rote Emission festgestellt. Vorteilhaft erwies sich die Verwendung von Kern-Schale-Teilchen wie CdSe/CdS. Mit einer Matrix aus Aluminiumoxid-Gel konnte eine LED mit sehr niedriger Onset-Spannung (2,3V) hergestellt werden, die eine Lebensdauer von 33,5h besaß und noch bei einer Temperatur von 150°C emittierte. Ein weiterer Weg Nanopartikel zu stabilisieren, stellt der Einbau in makrokristalline Einkristalle durch Mischkristallbildung in Wasser oder organischen Lösungsmitteln dar. Die erhaltenen Kristalle zeichnen sich durch hohe photochemische und thermische Stabilität aus. Sie zeigen die Emissionseigenschaften der Nanopartikel, die nach Auflösung der Matrix wieder kolloidal in Lösung gehen. Allerdings liegen die Nanopartikel in der Kristallmatrix nicht regulär verteilt vor. Die Mischkristalle wurden erfolgreich als Luminophor in einer Gasentladungslampe und als Konversionsschicht einer kommerziellen LED getestet, die die Emission der Nanopartikel aufwies.

This thesis describes the development and demonstration of a new technique for the fabrication of well-defined quantum dots in a bulk silicon substrate, for potential applications such as quantum computation in coupled quantum dots. Hall characterisation was performed on double-gated mesaMetal-Oxide- Semiconductor Field-Effect Transistors (MOSFETs) on a silicon-on-insulator (SOI) substrate, for the purpose of silicon quantum dots in etched nanowires on SOI. Carrier density and mobility results are presented, demonstrating top- and backgate control over the two inversion layers created at the upper and lower surfaces of the superficial silicon mesa. A new technique is developed enabling effective depletion gating of quantum dots in a bulk silicon substrate. A lower layer of aluminium gates is defined using electron beam lithography; the surface of these gates is oxidised using a plasma oxidation technique; and a further layer of aluminium gates is deposited. The lower gates form tunable tunnel barriers in the narrow inversion layer channel created by the upper MOSFET gate. The two layers of gates are electrically isolated by the localised layer of aluminium oxide. Low-temperature transport spectroscopy has been performed in both the many electron (∼100 electrons) and the few electron (∼10 electrons) regimes.Excited states in the bias spectroscopy provide evidence of quantum confinement. Preliminary temperature and magnetic field dependence data are presented. These results demonstrate that depletion gates are an effective technique for defining quantum dots in silicon. Furthermore, the demonstration of the first silicon radio-frequency single electron transistor is reported. The island is again defined by electrostatically tunable tunnel barriers in a narrow channel field effect transistor. Charge sensitivities of better than 10μe/√Hz are demonstrated at MHz bandwidth. These results establish that silicon may be used to fabricate fast, sensitive electrometers.

This thesis deals with electron correlation effects within low-dimensional, mesoscopic systems. We study phenomena within two different types of system in which correlations play an important role. The first involves the spectra and spin structure of small symmetric quantum dots, or &quoteartificial atoms&quote. The second is the &quote0.7 structure&quote, a well-known but mysterious anomalous conductance plateau which occurs in the conductance profile of a quantum point contact. Artificial atoms are manufactured mesoscopic devices: quantum dots which resemble real atoms in that their symmetry gives them a &quoteshell structure&quote. We examine two-dimensional circular artificial atoms numerically, using restricted and unrestricted Hartree-Fock simulation. We go beyond the mean-field approximation by direct calculation of second-order correlation terms; a method which works well for real atoms but to our knowledge has not been used before for quantum dots. We examine the spectra and spin structure of such dots and find, contrary to previous theoretical mean-field studies, that Hund's rule is not followed. We also find, in agreement with previous numerical studies, that the shell structure is fragile with respect to a simple elliptical deformation. The 0.7 structure appears in the conductance of a quantum point contact. The conductance through a ballistic quantum point contact is quantised in units of 2e^2/h. On the lowest conductance step, an anomalous narrow conductance plateau at about G = 0.7 x 2e^2/h is known to exist, which cannot be explained in the non-interacting picture. Based on suggestive numerical results, we model conductance through the lowest channel of a quantum point contact analytically. The model is based on the screening of the electron-electron interaction outside the QPC, and our observation that the wavefunctions at the Fermi level are peaked within the QPC. We use a kinetic equation approach, with perturbative account of electron-electron backscattering, to demonstrate that these simple features lead to the existence of a 0.7-like structure in the conductance. The behaviour of this structure reproduces experimentally observed features of the 0.7 structure, including the temperature dependence and the behaviour under applied in-plane magnetic fields.

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisors: Valeria Gabriela Stoleru, Dept. of Materials Science & Engineering; and S. Ismat Shah, Dept. of Materials Science. Includes bibliographical references.

Thesis (Ph. D.)--Biomedical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Nie, Shuming; Committee Member: Bao, Gang; Committee Member: Chung, Leland; Committee Member: Murthy, Niren; Committee Member: Prausnitz, Mark.

Thesis (Ph.D.)--University of Melbourne, Center for Quantum Computing Technology,School of Physics, 2007. / Typescript. Includes bibliographical references (leaves 237-257).

Thesis (Ph. D.)--Northeastern University, 2008. / Title from title page (viewed March 25, 2009). Graduate School of Arts and Sciences, Dept. of Physics. Includes bibliographical references (p. 292-298).