The emerging field of nanotechnology, which spans diverse areas such as nanoelectronics, medicine, chemical and pharmaceutical industries, biotechnology and computation, focuses on the development of devices whose improved performance is based on the utilization of self-assembled nanoscale components exhibiting unique properties owing to their miniaturized dimensions. The first phase in the conception of such multifunctional devices based on integrated technologies requires the study of basic principles behind the functional mechanism of nanoscale components, which could originate from individual nanoobjects or result as a collective behaviour of miniaturized unit structures. The comprehensive studies presented in this thesis encompass the mechanical, dynamical and photophysical aspects of three nanoscale systems. A newly developed europium sulfide nanocrystalline material is introduced. Advances in synthetic methods allowed for shape control of surface-functionalized EuS nanocrystals and the fabrication of multifunctional EuS-CdSe hybrid particles, whose unique structural and optical properties hold promise as useful attributes of integrated materials in developing technologies. A comprehensive study based on a new class of multifunctional nanomaterials, derived from the basic unit of barcoded metal nanorods is presented. Their chemical composition affords them the ability to undergo autonomous motion in the presence of a suitable fuel. The nature of their chemically powered self-propulsion locomotion was investigated, and plausible mechanisms for various motility modes were presented. Furthermore functionalization of striped metallic nanorods has been realized through the incorporation of chemically controlled flexible hinges displaying bendable properties. The structural aspect of the light harvesting machinery of a photosynthetic cryptophyte alga, Rhodomonas CS24, and the mobility of the antenna protein, PE545, in vivo were investigated. Information obtained through a combination of steady-state and time-resolved spectroscopy in conjunction with quantum chemical calculations aided in the elucidation of the dynamics and the mechanism of light harvesting in the multichromophoric phycobiliprotein phycocyanin PC645 in vitro. Investigation of the light-harvesting efficiency and optimization of energy transfer with respect to the structural organization of light-harvesting chromophores on the nanoscale, can provide us with fundamental information necessary for the development of synthetic light-harvesting devices capable of mimicking the efficiency of the natural system.

The emerging field of nanotechnology, which spans diverse areas such as nanoelectronics, medicine, chemical and pharmaceutical industries, biotechnology and computation, focuses on the development of devices whose improved performance is based on the utilization of self-assembled nanoscale components exhibiting unique properties owing to their miniaturized dimensions. The first phase in the conception of such multifunctional devices based on integrated technologies requires the study of basic principles behind the functional mechanism of nanoscale components, which could originate from individual nanoobjects or result as a collective behaviour of miniaturized unit structures. The comprehensive studies presented in this thesis encompass the mechanical, dynamical and photophysical aspects of three nanoscale systems. A newly developed europium sulfide nanocrystalline material is introduced. Advances in synthetic methods allowed for shape control of surface-functionalized EuS nanocrystals and the fabrication of multifunctional EuS-CdSe hybrid particles, whose unique structural and optical properties hold promise as useful attributes of integrated materials in developing technologies. A comprehensive study based on a new class of multifunctional nanomaterials, derived from the basic unit of barcoded metal nanorods is presented. Their chemical composition affords them the ability to undergo autonomous motion in the presence of a suitable fuel. The nature of their chemically powered self-propulsion locomotion was investigated, and plausible mechanisms for various motility modes were presented. Furthermore functionalization of striped metallic nanorods has been realized through the incorporation of chemically controlled flexible hinges displaying bendable properties. The structural aspect of the light harvesting machinery of a photosynthetic cryptophyte alga, Rhodomonas CS24, and the mobility of the antenna protein, PE545, in vivo were investigated. Information obtained through a combination of steady-state and time-resolved spectroscopy in conjunction with quantum chemical calculations aided in the elucidation of the dynamics and the mechanism of light harvesting in the multichromophoric phycobiliprotein phycocyanin PC645 in vitro. Investigation of the light-harvesting efficiency and optimization of energy transfer with respect to the structural organization of light-harvesting chromophores on the nanoscale, can provide us with fundamental information necessary for the development of synthetic light-harvesting devices capable of mimicking the efficiency of the natural system.

abstract: Locomotion of microorganisms is commonly observed in nature. Although microorganism locomotion is commonly attributed to mechanical deformation of solid appendages, in 1956 Nobel Laureate Peter Mitchell proposed that an asymmetric ion flux on a bacterium's surface could generate electric fields that drive locomotion via self-electrophoresis. Recent advances in nanofabrication have enabled the engineering of synthetic analogues, bimetallic colloidal particles, that swim due to asymmetric ion flux originally proposed by Mitchell. Bimetallic colloidal particles swim through aqueous solutions by converting chemical fuel to fluid motion through asymmetric electrochemical reactions. This dissertation presents novel bimetallic motor fabrication strategies, motor functionality, and a study of the motor collective behavior in chemical concentration gradients. Brownian dynamics simulations and experiments show that the motors exhibit chemokinesis, a motile response to chemical gradients that results in net migration and concentration of particles. Chemokinesis is typically observed in living organisms and distinct from chemotaxis in that there is no particle directional sensing. The synthetic motor chemokinesis observed in this work is due to variation in the motor's velocity and effective diffusivity as a function of the fuel and salt concentration. Static concentration fields are generated in microfluidic devices fabricated with porous walls. The development of nanoscale particles that swim autonomously and collectively in chemical concentration gradients can be leveraged for a wide range of applications such as directed drug delivery, self-healing materials, and environmental remediation. / Dissertation/Thesis / Ph.D. Mechanical Engineering 2011

Self-propelled microjet engines (microbots) can transport multiple cells into specific locations in a fluid. The motion is externally controlled by a magnetic field which allows to selectively load, transport and deliver the cells. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Small devices capable of self-propulsion have potential application in areas of nanoscience where autonomous locomotion and programmability are needed. The specific base-pairing interactions that arise from DNA hybridisation permit the programmed assembly of matter and also the creation of controllable dynamical systems. The aim of this thesis is to use the tools of DNA nanotechnology to design synthetic active matter at the micro and nano scales. In the first section, DNA was used as an active medium capable of transporting information faster than diffusion in the form of chemical waves. DNA waves were generated experimentally using a DNA autocatalytic reaction in a microfluidic channel. The propagation velocity of DNA chemical waves was slowed down by creating concentration gradients that changed the reaction kinetics in space. The second section details the synthesis of chemically-propelled particles and the use of DNA as a 'programmable glue' to mediate their interactions. Janus micromotors were fabricated by physical vapour deposition and a wet-chemical approach was demonstrated to synthesise asymmetrical catalytic Pt-Au nanoparticles that function as nanomotors. Dynamic light scattering measurements showed nanomotor activity that depends on H₂O₂ concentration, consistent with chemical propulsion. Gold nanoparticles/Origami hybrids were assembled in 2D lattices of different symmetries arranged by DNA linkers. The third section details the design process and synthesis of nanomotors using DNA as a structural scaffold. 3D DNA Origami rectangular prisms were functionalised site-specifically with bioconjugated catalysts, i.e. Pt nanoparticles and catalase. Enzymatic nanomotors were also conjugated to various cargoes and their motor activity was demonstrated by Fluorescence Correlation Spectroscopy. In the final section, control mechanisms for autonomous nanomotors are studied, which includes the conformational change of DNA aptamers in response to chemical signals, as well as a design for an adaptive dynamical system based on DNA/enzyme reaction networks.

Self-propelled microjet engines (microbots) can transport multiple cells into specific locations in a fluid. The motion is externally controlled by a magnetic field which allows to selectively load, transport and deliver the cells. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.