Nowadays it is attached to a major effort to study applications of nanoparticles in biosensors technology. We studied the effect of gold nanoparticles on the surface of the electrodes by Electrochemical Impedance Spectroscopy method and Cyclic Voltammetry. For impedance measurements was proposed substitute electrical model and cyclic voltammetry method was used to determine the electroactive surface of electrodes.

Nowadays, nanostructures fixed on solid substrates and colloidal nanoparticles permeate through all areas of human life, in area of sensors and detection as well. This dissertation thesis deals with the fabrication of nanostructures on the surface of planar electrodes via self-ordered nanoporous template of aluminum trioxide. The nanofabrication, as one of many possible techniques, is used to increase the active surface area of electrodes by creating unique surface types with specific properties. These electrodes are very perspective in the applications, such as biomolecules electrochemical detection and measurement. The transformation of aluminum layer into non-conductive nanoporous template in the process of anodic oxidation is a fundamental technique employed to obtain the array of nanostructures in this thesis. The fabrication of high quality nanoporous membranes with narrow pore size distribution on various types of metallic multilayers is one of the key experimental parts in this work. Several problems associated with the production of the thin-film systems, including the dissolving the barrier oxide layer, are discussed and solved. Another part of this work deals with the use of nanoporous membrane as a template for the production of metallic nanostructures via electrochemical metal ions deposition directly into the pores. The obtained nanostructures as nanowires, nanorods or nanodots are characterized by the scanning electron microscopy and energy-dispersive or wavelength X-ray spectroscopy. The electrode surface, modified by gold nanostructures suitable for the detection of biomolecules, has been chosen for the electrochemical measurements, due to the gold biocompatibility. The nanostructured electrodes were characterized by electrochemical impedance spectroscopy and cyclic voltammetry. The effect of nanostructured surface geometrical parameters, including the size of the electrochemically active area, on the results of electrochemical measurements has been observed and compared to flat gold electrodes. Two model biomolecules, namely guanine and glutathione, have been chosen for the study of potential application of these nanostructures in biosensors.

Contrast agents for magnetic resonance imaging (MRI) are but one of a variety of nanosystems that have incredible potential for the detection and diagnosis of cancer. Nanosystems share a common disadvantage: they are quickly sequestered by biological processes that clear foreign material from the body, requiring ever larger doses to accumulate in targets, and reducing their overall effectiveness and viability. This thesis explores a pair of strategies for nanomaterials to boost their evasiveness from these defensive systems in the context of lanthanide MRI contrast agents, in an attempt to increase their probability to collect in cancerous tissue. Chapter 1 provides precedent and rationale for the modification of two parameters regarding novel nanosystem design: aspect ratio and zeta potential. Chapter 2 details the controlled syntheses and analysis of sodium dysprosium fluoride nanomaterials at a range of aspect ratios. Chapter 3 concerns the construction of tunable zwitterionic polymer coatings for synthesized nanomaterials to demonstrate control over the zeta potential in aqueous dispersion. Chapter 4 tests polymer-coated spherical nanoparticles and nanorods for internalization into or adsorbance onto a cancerous cell line. Chapter 5 summarizes the work of the previous chapters and suggests future research approaches. Though internalization or adsorbance onto HeLa cells was not observed for prepared nanomaterials, control over their aspect ratio at the synthetic level and zeta potential via constructed zwitterionic polymers was demonstrated, with implications for application to a plethora of nanosystems. / Graduate

No description available.

Micro-and nanorobots have the potential to perform non-invasive drug delivery, sensing, and surgery in living organisms, with the aid of diverse medical imaging techniques. To perform such actions, microrobots require high spatiotemporal resolution tracking with real-time closed-loop feedback. To that end, photoacoustic imaging has appeared as a promising technique for imaging microrobots in deep tissue with higher molecular specificity and contrast. Here, we present different strategies to track magnetically-driven micromotors with improved contrast and specificity using dedicated contrast agents (Au nanorods and nanostars). Furthermore, we discuss the possibility of improving the light absorption properties of the employed nanomaterials considering possible light scattering and coupling to the underlying metal-oxide layers on the micromotor’s surface. For that, 2D COMSOL simulation and experimental results were correlated, confirming that an increased spacing between the Au-nanostructures and the increase of thickness of the underlying oxide layer lead to enhanced light absorption and preservation of the characteristic absorption peak. These characteristics are important when visualizing the micromotors in a complex in vivo environment, to distinguish them from the light absorption properties of the surrounding natural chromophores.

Noble metal nanoparticles such as gold and silver are of interest because of the unique electro-optical properties (e.g., localized surface plasmon resonance [LSPR]) that originate from the collective behavior of their surface electrons. These nanoparticles are commonly developed and used for biomedical and industrial application. A recent report has predicted that the global market for gold nanoparticles will be over 12.7 tons by year 2020. However, these surface-functionalized nanoparticles can be potential environmental persistent contaminants post-use due to their high colloidal stability in the aquatic systems. Despite, the environmental risks associated with these nanoparticles, just a few studies have investigated the effect of nanofeature factors such as size and shape on the overall fate/transport and organismal uptake of these nanomaterials in the aquatic matrices. This study presents a comprehensive approach to evaluate the colloidal stability, fate/transport, and organismal uptake of these nanoparticles while factoring in the size and shape related properties. We demonstrate the importance and effect of anisotropicity of a gold nanoparticle on the colloidal behavior and interaction with ecologically susceptible aquatic biota. We also show how readily available characterization techniques can be utilized to monitor and assess the fate/transport of this class of nanoparticles. We further describe and investigate the relationship between the aspect ratio (AR) of these elongated gold nanoparticles with clearance mechanisms and rates from the aquatic suspension columns including aggregation, deposition, and biopurification. We illustrate how a fresh water filter-feeder bivalve, Corbicula fluminea, can be used as a model organism to study the size and shape-selective biofiltration and nanotoxicity of elongated gold nanoparticles. The results suggest that biofiltration by C. fluminea increases with an increase in the size and AR of gold nanoparticle. We develop a simple nanotoxicity assay to investigate the short-term exposure nanotoxicity of gold nanoparticles to C. fluminea. The toxicity results indicate that for the tested concentration and exposure period that gold nanoparticles were not acutely toxic (i.e., not lethal). However, gold nanoparticles significantly inhibited the activities of some antioxidant enzymes in gill and digestive gland tissues. These inhibitions could directly affect the resistance of these organisms to a secondary stressor (temperature, pathogens, hypoxia etc.) and threaten organismal health. / Ph. D.

No / The latest advances in mesocrystal formation and non-classical crystallization of pre-synthesised nanoparticles have been reviewed with the focus on providing a fuller description of a number of complex systems and their properties and applications through examination of the crystallisation mechanisms at work. Two main crystallization principles have been identified; classical crystallization and particle based aggregation modes of non-classical pathways. To understand the non-classical pathways classical crystallization and its basics are introduced before non-classical pathways, such as oriented attachment and mesocrystal formation, are examined. In particular, the various destabilization mechanisms as applied to the pre-synthesized building blocks in order to form mesocrystalline materials as well as the interparticular influences providing the driving forces are analyzed and compared to the mechanisms at work within classical crystallization. Furthermore, the new properties of the mesocrystalline materials that derive from the collective properties of the nanoparticular building units, and their applications potential are presented. It is shown that this new class of materials has the potential to impact in a number of important areas such as sensor applications, energy conversion, photonic crystals as well as for energy storage, optoelectronics and heterogeneous catalysis or photocatalysis.

Catalysis using nanostructures has been a topic of substantial interest for fundamental studies and for practical applications in energy and environmental sectors. The growing demand for production of energy and in the cleaning of polluting hazardous vehicles/industrial wastes has led to several studies in catalysis. Despite the substantial growth of heterogeneous catalytic technologies in last decade, they are still far from reaching their full potential in terms of efficiency, selectivity as well as durability. It is often difficult to simultaneously tackle all the mentioned issues with single component catalysts. Most of these challenges are being overcome with heterostructures/supported hybrid catalysts by modifying their interfaces. The properties of heterostructures hybrids arises not only from the individual contributions of the individual components but also from strong synergetic effect arising from the interface. Engineering the interfaces provides pathways to promote the catalytic performance and hence has been explored. In this regard, we have focused on the progress in investigating the active interfaces that affect the performance of metal oxide-metal, semiconductor-metal and coupled semiconductor nanocatalyst hybrids. We explored a wide spectrum of their applications in photo catalytic, electrocatalytic as well as gas-phase reactions and highlighted the importance of the interface for overall performance. The entire study reported in the thesis is organized as follows: Chapter 1 is a general introduction of hybrid nanocatalyst and their role in wide spectra of catalytic reactions in photo/electro catalysis as well as gas-phase reactions. This chapter describes the motivation behind modulating the interface between two or more nanostructures to obtain multifunctional nanocatalysts. Nan catalysts to achieve high throughput with active interfaces are elaborated while indicating the role of morphology, internal induced state, charge transfer, geometric, support, as well as electronic effect for enhanced performance. Motivation behind specific nanocatalyst hybrid, synthesis routes as well as characterization techniques are detailed in the respective chapters. Specific details for different hybrids are described in the following chapters. Chapter 2 describes the synthesis of high dense ultrathin Au wires on ZnO nanorods for electrocatalytic oxidation of ethanol, where the prerequisite step is the formation of amine-modified support. Oleylamine modification not only serves to anchor Au nanowires on ZnO but also passivates surface defects of ZnO, which in turn enhances the photocurrent. In addition to the stability, the support induces electronic effect on Au nanowires, which facilitates redox process at low potential. Most importantly, the support promotes the activity of Au nanowires upon photoirradiation, and thus leading to synergy between electro and photooxidation current. This is of immense importance for photofuel cell technologies. Moreover, the method enabled the first time electrocatalysis on these nanowires that revealed ultrathin nanowires are potentially interesting systems for catalysis applications provided they are stabilized by a suitable support. Chapter 3 deals with the growth of ultrathin Au nanowires on metal oxide (TiO2) coupled with graphene hybrid support in order to overcome the low conductivity of metal oxide. Oleylamine, used for growth of Au nanowires simultaneously functionalizes the support and leads to room temperature GO reduction. With respect to catalytic activity, we also synthesized the binary counterparts (rGO/Au, TiO2/Au ultrathin nanowires) to delineate the contribution of each of the components to the overall electrocatalytic oxidation of ethanol. Comparative analysis of photo and electrocatalytic activity between the different binary and ternary hybrids provides interesting information. Both, electronic effect of TiO2 and electrical conductivity of rGO add their specific beneficial to the nanowires, leading to superior ternary system. Chapter 4 rGO supported ultrathin Au nanowires exhibits high electrocatalytic performance for oxidation of borohydride with a lower onset potential compared to rGO/Au nanoparticles. Electrochemical impedance spectroscopy measurements display abnormal inductive behavior of the synthesized hybrids, indicative of Au surface reactivation. DFT calculations indicate that the origin of the high activity stems from the shift in the position of the Au d-band center. Chapter 5 Different aspect ratio ZnO nanostructures are obtained by varying the solvothermal reaction time. We observed a direct correlation between observed photocatalytic activity, measured photocurrent and length of the ZnO nanorods. Furthermore, photoresponse of the high aspect ratio ZnO nanorods are improved by attaching Au nanoparticles, intimate contact of two components leads to band bending. Thus, the synthesized ZnO/Au heterostructure favors for prominent separation of photogenerated charge carriers. Chapter 6 TiO2 and PbO/TiO2 hybrids are synthesized via non–hydrolytic sol–gel combustion method. Hybrid exhibits higher photocatalytic activity for the degradation of dye than TiO2. The estimated photogenerated species reveals that the origin of enhanced activity stems from the direct oxidization of dye via photogenerated hole rather than radicals. The semiconductors are matched based on their band edge positions, for the formation of energetic radicals to degrade the pollutants. Based on this study, we infer that semiconductors should not neglected (for example Si) based on calculated mismatch of their valence band edges position for photooxidation reaction via radicals. Chapter 7 describes the Pd dopant associated band engineering, a strategy for tuning the optoelectronic properties of ZnO towards enhanced photocatalytic activity. Incorporated Pd heterocation induces internal energy states within the ZnO band gap. The created energy level leads to trends mismatch between photocatalytic activity and measured photocurrent. Formed energy level arrests the photogenerated electrons, which make them not contribute for the photocurrent generation. Hence, the isolated photogenerated hole efficiently oxidizes the pollutants through hydroxyl radicals, and thus leads to enhanced photocatalytic activity. Chapter 8 employed Pd-substituted zinc stannate for CO oxidation as heterogeneous catalyst for the first time. Compared with SnO2 support, zinc stannate based materials exhibits abnormal sudden light-off profiles at selective temperatures. On the basis of DRIFT studies under relevant conditions, we find that the initially formed product gets adsorbed over the catalyst surface. It leads to the accumulation of carbonates as a consequence, both lattice oxygen mobility and further CO interactions are disabled. As soon as Sn redox nature dominates over the accumulated carbonates, this leads to sudden release of lattice oxygen, and thus leads to a sudden full conversion. Therefore, choosing the suitable support material greatly influences the nature of the light-off CO oxidation profile. Chapter 9 Although, reducible oxide supported gold nanostructures exhibits the highest CO oxidation activity; they still suffer from problems such as limited selectivity towards CO in the presence of H2. Both ex-situ and in-situ experiments demonstrate that, Au nanoparticles supported on Zn2SnO4 matrix selectively oxidizes CO. DRIFT experiments revealed that the involvement of OH groups leads to the formation of hydroxycarbonyl under PROX conditions. Chapter 10 This chapter discusses the conclusions for the previous chapters and highlights the possibilities for future scope for the developed nanocatalysts hybrids for energy and environmental applications.

Cellular internalization of large therapeutic agents such as proteins or nucleic acids is a challenging task because of the presence of the plasma membrane. One strategy to facilitate intracellular drug uptake is to induce transient pores in the cell membrane through physical delivery strategies. Physical approaches are attractive as they offer more generic applicability compared with viral or biochemical counterparts. Pulsed laser light can induce the endothermic carbon-steam reaction in carbon-nanoparticle suspensions to produce explosive photoacoustic effects in the surrounding medium. In this study, for the first time, these photoacoustic forces were used to transiently permeabilize the cell membrane to deliver macromolecules into cells. Intracellular delivery using this method was demonstrated in multiple cell types for uptake of small molecules, proteins and DNA. At optimized conditions, uptake was seen in up to 50% of cells with nearly 100% viability and in 90% of cells with ≥90% viability, which compared favorably with other physical methods of drug delivery. Cellular bioeffects were shown to be a consequence of laser-carbon interaction and correlated with properties of the carbon and laser, such as carbon concentration and size, laser pulse duration, wavelength, intensity and exposure time. Similar results were observed using two different lasers, a femtosecond Ti: Sapphire laser and a nanosecond Nd: YAG laser. Uptake was also shown in murine skeletal muscles in vivo with up to 40% efficiency compared to non-irradiated controls. This synergistic use of nanotechnology with advanced laser technology could provide an alternative to viral and chemical-based drug and gene delivery.

Water drops that nucleate and grow over an evaporating polymer solution exposed to a current of moist air remain noncoalescent and self-assemble into close packed arrays. The hexagonally close packed, nearly monodisperse drops, eventually evaporate away, leaving a polymer film, with ordered array of pores. Meanwhile, typical breath figures or dew that form when moist air contacts cold surfaces involve coalescence-assisted growth of highly polydisperse, disordered array of water drops. This dissertation provides the first quantitative attempt aimed at the elucidation of the mechanism of the breath figure templated assembly of the ordered arrays of pores in polymer films. The creation and evolution of a population of close packed drops occur in response to the heat and mass fluxes involved in water droplet condensation and solvent evaporation. The dynamics of drop nucleation, growth, noncoalescence and self-assembly are modeled by accounting for various transport and thermodynamic processes. The theoretical results for the rate and extent of evaporative cooling and growth are compared with experiments. Further, the dissertation describes a rich array of experimental observations about water droplet growth, noncoalescence, assembly and drying that have not been reported in the published literature so far. The theoretical framework developed in this study allows one to rationalize and predict the structure and size of pores formed in different polymer-solvent systems under given air flow conditions. While the ordered arrays of water drops present an example of dynamics, growth and assembly of spherical particles, the study on colloidal gold nanorods focuses on the behavior of rodlike particles. A comprehensive set of theoretical arguments based on the shape dependent hydrodynamics of rods were developed and used for centrifugation-assisted separation of rodlike particles from nanospheres that are typical byproducts of seed mediated growth of nanorods. Since the efficiency of shape separation is assessed using UV-Vis-NIR spectroscopy and transmission electron microscopy (TEM), the present dissertation elucidates the shape dependent parameters that affect the optical response and phase behavior of colloidal gold nanorods. The drying of a drop of colloidal gold nanorods on glass slides creates coffee ring like deposits near the contact line, which is preceded by the formation of a liquid crystalline phase. The assemblies of rods on TEM grids are shown to be the result of equilibrium and non-equilibrium processes, and the ordered phases are compared with two dimensional liquid crystals. The methodology of pattern characterization developed in this dissertation is then used to analyze the structure of the exocuticle of iridescent beetle Chrysina gloriosa. The patterns were characterized using Voronoi analysis and the effect of curvature on the fractions on hexagonal order of tiles was determined. Further, these patterns were found to be analogous to the focal conic domains formed spontaneously on the free surface of a cholesteric liquid crystal. In summary, the dissertation provides the crucial understanding required for the widespread use of breath figure templated assembly as a method for manufacturing porous films, that requires only a drop of polymer solution (dilute) and a whiff of breath! Further, the dissertation establishes the physical basis and methodology for separating and characterizing colloidal gold nanorods. The dissertation also suggests the basis for the formation and structure of tiles that decorate the exoskeleton of an iridescent beetle Chrysina gloriosa.