Properties of nanocrystals are extremely sensitive to their sizes when their sizes are smaller or of the order of the excitonic diameter due to the quantum confinement effect. The interest in this field has been concentrated basically in understanding the size-property relations of nanocrystals, for example, the pronounced variation in the bandgap of the material or the fluorescence emission properties, by tuning the sizes of the nanocrystals. Thus, the optical and electronic properties of semiconductor nanocrystals can be tailor-made to suit the needs of the specific application and hence is of immense importance. One of the major aspects necessary for the actual realization of the various applications is the ability to synthesize nanocrystals of the required size with a controlled size distribution. The growing demand to obtain such nanocrystals with the required size and controlled size distribution is met largely by the solution route synthesis of nanocrystals, that constitutes an important class of synthesis methods due to their ease of implementation and the high degree of flexibility. The main difficulty of this method is that the dependence of the average size and the size distribution of the generated particles on parameters of the reaction are not understood in detail and therefore, the optimal reaction conditions are arrived at essentially in an empirical and intuitive manner. From a fundamental point of view, understanding the growth kinetics of various nanocrystals can provide a deeper insight into the phenomena. The study of growth kinetics can be experimentally achieved by measuring the time evolution of diameter using several in-situ techniques like UV-absorption and small angle X-ray scattering. Having understood the mechanism of growth of nanocrystals, it is possible to obtain the required size of the nanocrystal using optimized synthesis conditions. The properties of these high quality nanocrystals can be further tuned by doping with a small percentage of magnetic ions. The optical and magnetic properties of these nanocrystals play an important role in the various technological applications. The first part of the thesis concentrates on the theoretical methods to study the electronic structure of semiconductor nanocrystals. The second part describes the studies performed on growth of various nanocrystal systems, both in the presence and absence of capping agents. The third part of the thesis describes the studies carried out on ZnO and doped ZnO nanocrystals, synthesized using optimal conditions that were obtained in the earlier part of the thesis. The thesis is divided into five chapters which are described below. Chapter 1 provides a brief overall perspective of various interesting properties of semiconductor nanocrystals, including various concepts relevant for the study of such systems. Chapter 2 describes experimental and theoretical methods used for the study of nanocrystals reported in this thesis. In Chapter 3 of this thesis, we report results of theoretical studies carried out on III-V and II-VI semiconductors using the tight-binding (TB) methodology. Chapter 4 presents the investigations on the growth kinetics of several nanocrystal systems. Chapter 5 presents experimental investigations carried out on undoped and various transition metal (TM) doped ZnO nanocrystals. In summary, we have performed electronic structure calculations on various nanocrystal systems, devised a novel method to obtain the size distribution from UV-absorption spectrum and studied the mechanism of growth in the presence and absence of capping agents in various II-VI semiconductors. Using the optimal conditions obtained from the growth studies, we prepare high quality ZnO nanocrystals of required size, both in free-standing and capped states and doped it with small percentages of various transition metals like Mn, Cu and Fe. We have then studied their optical and magnetic properties.

Materials science today is a multidisciplinary effort comprising an accelerated convergence of diverse fields spanning the physical, applied, and engineering sciences. This diversity promises to deliver the next generation of advanced functional materials for a wide range of specific applications. In particular, the past decade has seen a growing interest in the development of nanoscale materials for sophisticated technologies. Aqueous colloidal microgels have emerged as a promising class of soft materials for multiple biotechnology applications. The amalgamation of physical, chemical and mechanical properties of microgels with optical properties of nanostructures in hybrid composite particles further enhances the capabilities of these materials. This work covers the general areas of responsive polymer microgels and their composites, and encompasses methods of fabricating microgel-based drug delivery systems for controlled and targeted therapeutic applications. The first part of this thesis is devoted to acquainting the reader with the fundamental aspects of the synthesis, functionalization and characteristic properties of stimulus-responsive microgels constructed from poly(N-isopropylacrylamide) (poly(NIPAm)) and other functional comonomers. In particular, the role of electrostatics on the swelling-deswelling transitions of polyampholyte microgels upon exposure to a range of environmental stimuli including pH, temperature, and salt concentration are discussed. The templated synthesis of bimetallic gold and silver nanoparticles in zwitterionic microgels is also described. The latter part of this thesis focuses on the rational development of microgel-based drug delivery systems for controlled and targeted drug release. Specifically, the development of a biofunctionalized, pH-responsive drug delivery system (DDS) is illustrated, and shown to effectively suppress cancer cells when loaded with an anticancer agent. In another chapter, the design of tailored hybrid particles that combine the thermal response of microgels with the light-sensitive properties of gold nanorods to create a DDS for photothermally-induced drug release is discussed. The photothermally-triggered volume transitions of hybrid microgels under physiological conditions are reported, and their suitability for the said application evaluated. In another component of this work, it is explicitly shown that electrostatic interactions were not needed to deposit gold nanorods on poly(NIPAm)-derived particles, thereby eliminating the need for incorporation of charged functional groups in the microgels that are otherwise responsible for large, undesirable shifts and broadening of the phase transition.

Noble metal nanostructures possess unique properties including large near-field enhancement and strong light scattering and absorption due to their plasmon resonance - the collective coherent oscillation of the metal free electrons in resonance with the electromagnetic field of light. The effect of nanostructure size, shape, composition, and environment on the plasmon resonance frequency and plasmonic enhancement is well known. In this thesis, we describe the effect of inter-particle coupling in assembled plasmonic nanostructures on their radiative and non-radiative properties. When metal nanoparticles assemble, plasmon oscillations of neighboring particles couple, resulting in a shift in the plasmon resonance frequency. Our investigation of plasmon coupling in gold nanorods shows that the coupling between the plasmons is "bonding" in nature when the plasmon oscillations are polarized along the inter-particle axis, whereas an "anti-bonding" interaction results when the polarization is perpendicular. We studied the distance-dependence of plasmon coupling using electrodynamic simulations and experimental plasmon resonances of lithographically fabricated gold nanoparticle pairs with systematically varying inter-particle separations. The strength of plasmon bonding, reflected by the fractional plasmon shift, decays near-exponentially with the inter-particle separation (in units of particle size) according to a universal trend independent of the nanoparticle size, shape, metal type, or medium. From the universal scaling model, we obtain a "plasmon ruler equation" which calculates (in good agreement with the experiments of Alivisatos and Liphardt) the inter-particle separation in a gold nanosphere pair from its plasmon resonance shift, making it applicable to the determination of inter-site distances in biological systems. Universal size-scaling is valid also in the metal nanoshell structure, a nanosphere trimer, and pairs of elongated nanoparticles, thus making it a generalized fundamental model, which is useful in optimizing plasmon coupling for achieving tunable plasmon resonances, enhanced plasmonic sensitivities, and large SERS cross-sections. Ultrafast laser pump-probe studies of non-radiative electronic relaxation in coupled metal nanospheres in aggregates and in gold nanospheres conjugated to thiol SAMs are also reported. We also show that the relative contribution of scattering (radiative) to absorption (non-radiative) part of the plasmon relaxation, respectively useful in optical and photothermal applications, can be increased by increasing the nanostructure size.

Orientador: Daniela Zanchet / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-26T07:36:24Z (GMT). No. of bitstreams: 1 Kokumai_TathianaMidori_M.pdf: 2185484 bytes, checksum: f809cfde78398806bc98554749cf01c8 (MD5) Previous issue date: 2014 / Resumo: Nanobastões de céria (CeO2) funcionalizados com grupos amino foram utilizados como suporte em catalisadores de cobre para a reação de deslocamento gás-água (WGS). A funcionalização da superfície do óxido foi realizada visando uma melhor dispersão da fase metálica no suporte, através da interação entre o grupo amino e o precursor Cu2+, com a posterior correlação entre esta modificação e a atividade do catalisador. Utilizou-se o método hidrotérmico para a síntese dos nanobastões, que foram posteriormente funcionalizados com 3-(aminopropil)trimetoxisilano. A adição do precursor Cu2+ ao suporte foi feita via impregnação, seguida de calcinação e redução (ativação do catalisador), etapa na qual se formaram as nanopartículas metálicas (Cu0) suportadas. Comparando os catalisadores com suporte de céria pura e de céria funcionalizada, observou-se que de fato a funcionalização resultou na maior dispersão do Cu2+ na superfície. No entanto, ela causou a menor dispersão do metal (Cu0) após a redução, a diminuição da redutibilidade da céria superficial, a fragmentação dos bastões e o menor desempenho catalítico frente à reação de WGS. Visando a compreensão destes sistemas, verificou-se que a calcinação após a adição de Cu2+ na amostra funcionalizada formou uma camada de SiO2 na superfície da céria, o que diminui a atividade por reduzir as interações Cu-CeO2 (formação de Cu-O-Si), corroborando a grande influência desta interface no desempenho destes catalisadores. Além disso, a menor dispersão de Cu0 na superfície funcionalizada após a redução demonstrou a importância da céria também na estabilização da fase metálica. Desta maneira, a funcionalização da superfície se mostrou uma abordagem interessante no que se refere à dispersão do precursor metálico no suporte / Abstract: Amino functionalized ceria nanorods were explored as support on copper catalysts for the water-gas shift (WGS) reaction. The purpose of the design of a functionalized oxide surface was to obtain a better metal phase dispersion on the support provided by amino-Cu2+ interaction, in addition to further correlation between this modification and the catalyst activity. The hydrothermal method was used to synthetize the nanorods, which were subsequently functionalized with 3-(aminopropyl)trimethoxysilane. The Cu2+ precursor was added to the support by impregnation, followed by calcination and reduction (catalyst activation), when the supported metallic (Cu0) nanoparticles were formed. By comparison of the catalysts obtained with pure ceria and functionalized ceria supports it was observed that the functionalization indeed caused a greater Cu2+ dispersion on the oxide surface. However, it gave rise to a lower metal dispersion (Cu0) after reduction step, along with the decrease of surface ceria reducibility, nanorods fragmentation and inferior catalytic performance towards WGS reaction. In order to understand these systems, it was confirmed that the calcination step (after Cu2+ addition) on functionalized sample created a SiO2 layer above ceria surface, therefore lowering the activity due to the decrease of Cu-CeO2 interactions (formation of Cu-O-Si), which corroborated the great influence of Cu-CeO2 interface on the activity. Also, the lower Cu0 dispersion on the functionalized surface after reduction showed the importance of ceria on the metallic phase stabilization. Hence, the surface functionalization demonstrated to be an interesting approach to the dispersion of metal precursor on the catalyst support / Mestrado / Quimica Inorganica / Mestra em Química

De par leurs nombreuses applications potentielles, de nombreux efforts de recherche ontété poursuivis dans le domaine de la synthèse de nanoparticules. Cependant le mécanisme àl'origine des formes anisotropes de nanoparticules d'or, pour une taille et une structure biendéfinies, reste encore un sujet controverse.L'objectif général de cette thèse est de comprendre l'origine de cette anisotropie, lors dela formation de nanoparticules d'or, en particulier sous la forme de nano-bâtonnets d'or, enphase liquide. Parmi les nombreux procédés de synthèse existants, la "synthèse de particulesanisotropes par croissance à partir de germes" a été retenu, car il permet un contrôle précis dela taille et de la structure des nanoparticules. Lors de la synthèse de nanoparticules, les germesjouent un rôle de précurseur et permettent ainsi de maitriser la structure cristalline desnanoparticules finales. Si le rôle crucial des germes a déjà pu être étudié par différentsgroupes de recherche, une étude systématique sur la genèse de l'anisotropie par rapport à lataille et la structure initale des germes restait à réaliser. Ce travail a ainsi pour objectif derépondrre aux deux questions :i. Comment contrôler la structure cristalline et de la taille des germes?ii. Quelles sont les influences de la taille des germes et de leur structure sur la cinétique dela croissance? / Between the ongoing research on various type of nanomaterials to tune the particle sizeand crystal design in nanoscale for their potential applications, anisotropic gold nanoparticleshas attracted the most intention not only because of their divine color but also their enhancedcatalytic activities, optical properties and electrical conductivities. Event though, many effortshave been already made in the field of synthesis of anisotropic gold nanoparticles, withdefined sizes and structures, growth mechanism of many unique anisotropic shapes is still acontroversial subject.Overall objective of this thesis is to understand the origin of anisotropy during theformation of anisotropic gold nanoparticles, especially gold nanorods, in liquid phase. For ourenvisaged aim, between numerous synthetic methods developed for production ofnanoparticles, seed mediated approach is chosen for the fabrication of final anisotropic goldnanoparticles from small seeds which is grown into final nanoparticle later on. During thesynthesis of nanoparticles, those seeds play critical role as precursors to control the yield ofand the crystal structure of final anisotropic nanoparticle. Here we offer a systematical studyon the origin of anisotropy with respect to “seed size” and “crystal morphology”. Since thesesmall particles are the genesis of anisotropic metal nanoparticle synthesis, in this thesis weanswer following questions to explain the origin of anisotropy;i. How to control the crystal structure and the size of the seeds?ii. What are the influences of controlled seed size and structure on the kinetics ofnanoparticle growth?

Recently, efforts have been made for self-powering the batteries and portable electronic devices by piezoelectric nanogenerators. The piezoelectric nanogenerators can work as a power source for nano-systems and also as an active sensor. The piezoelectric nanogenerator is a device that converts random mechanical energy into electrical energy by utilizing the semiconducting and piezoelectric properties. Also, the mechanical energy is always available in and around us for powering these nano devices. The aim of the present thesis work is to explore 1D and 2D ZnO nanostructures (nanorods and nanosheets) on metal alloy substrates for the development of piezoelectric nanogenerators in energy harvesting and sensors applications. Hydrothermal synthesis method was adopted for the growth of ZnO nanostructures. The nanogenerators were fabricated by using the optimized synthesis parameters and subsequently studied their performance for power generation and as an active speed sensor. These 1D and 2D nanostructures based nanogenerators have opened up a new window for the energy harvesting applications and sensors development. The thesis is divided into following six chapters. Chapter 1: This chapter gives a general introduction about energy harvesting devices such as nanogenerators, available energy sources, mechanical energy harvesting, ZnO material and the details on hydrothermal synthesis process. A brief literature survey on different applications of piezoelectric nanogenerators is also included. Chapter 2: A novel flexible metal alloy (Phynox) and its properties along with its applications are discussed in this chapter. Details on the synthesis of 1D ZnO nanorods on Phynox alloy substrate by hydrothermal method are presented. Further, the optimization of parameters such as growth temperature, seed layer annealing and substrate temperature effects on the synthesis of ZnO nanorods are discussed in detail. As-synthesized ZnO nanorods have been characterized using XRD, FE-SEM, TEM and XPS. Chapter 3: It reports on the fabrication of piezoelectric nanogenerator on Phynox alloy substrate as power generating device by harvesting the mechanical energy. Initially, the performance of the nanogenerator for power generation due to finger tip impacts was studied and subsequently its switching polarity test was also carried out. Output voltage measurements were carried out using the in-house developed experimental setup. Stability test was also carried out to see the robustness of the nanogenerator. Finally, the output voltage response of the nanogenerator was studied for its use as an active speed sensor. Chapter 4: Synthesis of Al doped 2D ZnO nanorsheets on Aluminum alloy (AA-6061) substrate by hydrothermal method is reported in this chapter. The optimized parameters such as growth temperature and growth time effects on the synthesis of ZnO nanosheets are discussed. As-synthesized ZnO nanosheets were characterized using XRD, FE-SEM, TEM and XPS. The Al doping in ZnO is confirmed by EDXS and XPS analysis. Chapter 5: Cost effective fabrication of Al doped 2D ZnO nanosheets based nanogenerator for direct current (DC) power generation is reported in this chapter. The performance of the nanogenerator for DC power generation due to finger tip impacts was studied and subsequently its switching polarity test was also carried out. Output voltage measurements were carried out using the in-house developed experimental setup. Stability test was also carried out to see the robustness of the nanogenerator. Finally, the DC output voltage response of the nanogenerator was studied for its use as an active speed sensor. Chapter 6: The first section summarizes the significant features of the work presented in this thesis. In the second section the scope for carrying out the further work is given.

Diplomová práce se zabývá výrobou a využitím zlatých koloidních nanotyčinek v biomedicínských aplikacích. Konkrétně se zaměřuje na tři základní funkce nanočástic v analýze - transportní, separační a především zobrazovací. V části o využití nanočástic pro zobrazování je hlavní zájem věnován zejména povrchové plazmonové rezonanci zlatých nantyčinek. Dále je práce zaměřena na využití nanotyčinek pro termální terapii. Následující část je věnována vhodným modifikacím povrchu, hlavně za účelem zmírnění toxicity částic. Závěrem teoretické části jsou způsoby přípravy zlatých koloidních nanotyčinek a techniky jejich následné analýzy. V navazující experimetální části jsou uvedeny postupy, podmínky a výsledky provedených pokusů.

abstract: Tissue approximation and repair have been performed with sutures and staples for centuries, but these means are inherently traumatic. Tissue repair using laser-responsive nanomaterials can lead to rapid tissue sealing and repair and is an attractive alternative to existing clinical methods. Laser tissue welding is a sutureless technique for sealing incised or wounded tissue, where chromophores convert laser light to heat to induce in tissue sealing. Introducing chromophores that absorb near-infrared light creates differential laser absorption and allows for laser wavelengths that minimizes tissue damage. In this work, plasmonic nanocomposites have been synthesized and used in laser tissue welding for ruptured porcine intestine ex vivo and incised murine skin in vivo. These laser-responsive nanocomposites improved tissue strength and healing, respectively. Additionally, a spatiotemporal model has been developed for laser tissue welding of porcine and mouse cadaver intestine sections using near-infrared laser irradiation. This mathematical model can be employed to identify optimal conditions for minimizing healthy cell death while still achieving a strong seal of the ruptured tissue using laser welding. Finally, in a model of surgical site infection, laser-responsive nanomaterials were shown to be efficacious in inhibiting bacterial growth. By incorporating an anti-microbial functionality to laser-responsive nanocomposites, these materials will serve as a treatment modality in sealing tissue, healing tissue, and protecting tissue in surgery. / Dissertation/Thesis / Doctoral Dissertation Chemical Engineering 2019

Title: Optical Responses of Biomolecules on Regular Metal Plasmonic Nanostructures Author: Martin Šubr Department: Institute of Physics of Charles University Supervisor of the doctoral thesis: prof. RNDr. Marek Procházka, Dr., Institute of Physics of Charles University Abstract: Adsorption of molecules on metal plasmonic nanostructures leads to significant enhancement of many optical processes, such as Raman scattering (surface-enhanced Raman scattering - SERS) or fluorescence (surface-enhanced fluorescence - SEF). Two groups of substrates were tested within this thesis: (i) Silver nanorods prepared by oblique angle vapor deposition, and (ii) silver and gold nanoislands growing on magnetron-sputtered polytetrafluoroethylene film. Step-by- step optimization process was performed on the nanoislands in order to obtain optimum SERS sensitivity and reproducibility. Detailed SERS intensity profiles were obtained using gradient nanostructures with the localized surface plasmon resonance (LSPR) condition varying across the sample and three different excitation wavelengths. It was also found that spectral position and height of the LSPR band can be controlled simultaneously using mixed gold/silver nanoislands. Detailed investigation of polarization- and angular- dependences of anisotropic silver nanorods was...

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