Thermal, electrical, and mechanical characteristics of heated cantilevers were experimentally studied in various conditions. Experiments investigated thermal, mechanical, and coupled behaviors of the heated cantilevers under DC, AC, and transient electrical heating. Raman spectroscopy measured local temperature and qualitative intrinsic stress with high spatial resolution. Based on the thorough understanding from device characterization, cantilever type micro hotplates and small array of heated cantilevers with integrated piezoresistive sensors were fabricated and characterized. Well characterized cantilever sensors were applied to heat transfer study and microfludic research. Heated microcantilevers were suggested to study sub-continuum heat transfer from a micro heater to ambient gas environment in a wide range of pressure. Microcantilever sensors were employed to study the free microjets emanated from microfabricated nozzles. Piezoresistive cantilevers measured jet thrust, velocity, and break-up distance of the liquid microjets and heated cantilevers investigated heat transfer characteristics and phase change phenomena during the microjet impingement.

<p>The electronic and geometrical structure of free neutral clusters and liquids have been studied using synchrotron-radiation based photoelectron and Auger electron spectroscopy in combination with lineshape modeling. A novel experimental setup has been developed for studies of liquids, based on the liquid microjet technique. Theoretical lineshapes have been computed using both classical (molecular dynamics) and quantum mechanical (mainly density functional theory) methods.</p><p>Clusters are finite ensembles of atoms or molecules, ranging in size from a few to several thousand atoms. Apart from being fundamentally interesting, clusters are also promising as building blocks for nano-technology. In this thesis results are presented for rare-gas and molecular clusters, ranging from weakly van-deer-Waals bonded to hydrogen bonded. It is shown that the combination of core-level photoelectron spectroscopy (XPS) and lineshape modeling can be used to estimate the sizes of clusters. A model for treating the effect of inter-molecular nuclear relaxation upon ionization is proposed. The structure of single-component molecular clusters are investigated by molecular dynamics simulations, validated against XPS data. Finally, the radial structure of a two-component molecular cluster is investigated by XPS.</p><p>Liquids have been studied for centuries, but still many questions remain regarding the microscopic properties. With the recent development of the liquid microjet technique, new insight into the atomic structure can be obtained. In this thesis we study aqueous solutions using photoelectron and Auger electron spectroscopy (AES). We investigate the structure of surface active molecules by XPS, study the Auger decay after core-level ionization in aqueous potassium chloride (KCl), and follow the changes in molecular structure of glycine as a function of pH.</p>

The electronic and geometrical structure of free neutral clusters and liquids have been studied using synchrotron-radiation based photoelectron and Auger electron spectroscopy in combination with lineshape modeling. A novel experimental setup has been developed for studies of liquids, based on the liquid microjet technique. Theoretical lineshapes have been computed using both classical (molecular dynamics) and quantum mechanical (mainly density functional theory) methods. Clusters are finite ensembles of atoms or molecules, ranging in size from a few to several thousand atoms. Apart from being fundamentally interesting, clusters are also promising as building blocks for nano-technology. In this thesis results are presented for rare-gas and molecular clusters, ranging from weakly van-deer-Waals bonded to hydrogen bonded. It is shown that the combination of core-level photoelectron spectroscopy (XPS) and lineshape modeling can be used to estimate the sizes of clusters. A model for treating the effect of inter-molecular nuclear relaxation upon ionization is proposed. The structure of single-component molecular clusters are investigated by molecular dynamics simulations, validated against XPS data. Finally, the radial structure of a two-component molecular cluster is investigated by XPS. Liquids have been studied for centuries, but still many questions remain regarding the microscopic properties. With the recent development of the liquid microjet technique, new insight into the atomic structure can be obtained. In this thesis we study aqueous solutions using photoelectron and Auger electron spectroscopy (AES). We investigate the structure of surface active molecules by XPS, study the Auger decay after core-level ionization in aqueous potassium chloride (KCl), and follow the changes in molecular structure of glycine as a function of pH.

This dissertation offers demonstrations of autonomous catalytic microtubes (microjet engines) with tunable diameters ranging from micro- to nanoscale and lengths from 50 μm to 1 mm. These results open the door to effective microengines and represent the entry in the Guinness Book of World Records for “the smallest man-made jet engine.” Several attractive methodologies of machine-based functions at the micro- and nanoscale are shown. For instance, catalytic Ti/Cr/Pt microjets, which are integrated on a planar substrate, can operate as “on chip” chemical micropumps by decomposition of hydrogen peroxide fuel into oxygen bubbles and water. When released from a substrate, microjets self-propel autonomously in solution. The incorporation of ferromagnetic layer (Fe) into the rolled-up geometry enables their remote control using external magnetic field. Such microjets were used to load, transport, deliver and assemble multiple cargo particles, including biological cells in bulk solutions and microfluidic channels. Furthermore, it is demonstrated that for microjets that are fixed to or self-propelled above a platinum patterned surface, the microengine power/speed can be controlled using a white lightsource. A change in intensity of the white light leads to a controllable switching “off” and “on” of the microengine power on demand. Light degrades a local concentration of the hydrogen peroxide fuel and surface tension and subsequently suppresses the generation of oxygen microbubbles. In the next step, the diameter of the microjets was rigorously reduced to 250 nm by using hybrid heteroepitaxial/catalytic InGaAs/GaAs/Cr/Pt nanotubes. Due to asymmetry of the rolled-up layers, these nanojets move in corkscrew-like motions and act as “self-propelled nanotools,” which were used in the next step to transport yeast cells and drill into fixed cancer Hela cells. Although it is well-known that hydrogen peroxide cannot be used to sustain viable cellular function, it is however conceivable that alternative fuels, such as glucose, might enable operation of such nanotools under biologically compatible conditions. As a first step to achieve this goal, demonstrations were made using metal-enzyme biocatalytic Ti/Au/SAM/Catalase microengines. Synthetic components with competing interactions are well-suited to study the emergence of their collective behavior, such as swarms of large numbers of individuals. Microengines’ self-organization in bistable swarms is shown at the air-liquid interface of the mixture of propylene carbonate and hydrogen peroxide. Microengines act as “water striders.” Buoyed by oxygen bubbles, they self-propel via the microbubble recoiling mechanism and, depending on the bubbles’ sizes, self-organize into swarms due to the meniscus climbing effect. These reversible swarms depend on the microengine power, which competes against attracting surface tension force. The demonstrated microjet engines show great promise for emerging applications, including biomedical, on-chip, environmental, and robotic micromachines. Furthermore, a key method discovered, entitled “rolled-up nanotechnology on polymers,” allowed for the fabrication of highly parallel arrays of microtubes with multiple functionalities and aimed for different purposes.

Mechanical forces have been observed to affect various aspects of life, for example, cell differentiation, cell migration, locomotion and behavior of multicellular organisms etc. Such forces are generated either by external entities such as mechanical touch, fluid flow, electric and magnetic fields or by the living organisms themselves. Study of forces sensed and applied by living organisms is important to understand the interactions between organisms and their environment. Such studies may reveal molecular mechanisms involved in mechanosensation and locomotion. Several techniques have been successfully applied to measure forces exerted by single cells and cell monolayers. The earliest technique made use of functionalized soft surfaces and membranes as substrates on which cell monolayers were grown. The forces exerted by the cells could be measured by observing deformation of the substrates. Atomic Force Microscope (AFM) is another sensitive instrument that allows one to exert and measure forces in pico-Newton range. Advances in micromachining technology have enabled development of miniature force sensors and actuators. Latest techniques for mechanical force application and measurement use micromachined Silicon cantilevers in single as well as array form and micropillar arrays. Micropillar arrays fabricated using soft lithography enabled the use of biocompatible materials for force sensors. Together, these techniques provide access to a wide range of forces, from sub micro-Newton to milli-Newton. In the present work, types of forces experienced in biological systems and various force measurement and actuation techniques will be introduced. This will be followed by in depth description of the two major contributions of this thesis, 1) ―Colored polydimethylsiloxane micropillar arrays for high throughput measurements of forces applied by genetic model organisms‖. Biomicrofluidics, January 29, 2015. doi: 10.1063/1.4906905 2) ―Air microjet system for non-contact force application and the actuation of micro-structures‖. Journal of micromechanics and microengineering, December 15, 2015. doi: 10.1088/0960-1317/26/1/017001 Device developed for force measurement consists of an array of micropillars made of a biocompatible polymer Poly Dimethyl Siloxane (PDMS). Such devices have been used by researchers to measure traction forces exerted by single cells and also by nematode worm Caenorhabditis elegans (C. elegans). C. elegans is allowed to move in between the micropillars and the locomotion is video recorded. Deflection of the micropillar tips as the worm moves is converted into force exerted. Transparent appearance of C. elegans and PDMS poses difficulties in distinguishing micropillars from the worm, thus making it challenging to automate the analysis process. We address this problem by developing a technique to color the micropillars selectively. This enabled us to develop a semi-automated graphical user interface (GUI) for high throughput data extraction and analysis, reducing the analysis time for each worm to minutes. Moreover, increased contrast because of the color also delivered better images. Addition of color changed the Young‘s modulus of PDMS. Thus the dye-PDMS composite was characterized using hyper-elastic model. The micropillars were also calibrated using commercial force sensor. Analysis of forces exerted by wild type and mutant C. elegans moving on an agarose surface was performed. Wild type C. elegans exerted a total average force of 7.68 µN and an average force of ~1 µN on an individual pillar. We show that the middle of C. elegans exerts more force than its extremities. We find that C. elegans mutants with defective body wall muscles apply significantly lower force on individual pillars, while mutants defective in sensing externally applied mechanical forces still apply the same average force per pillar compared to wild type animals. Average forces applied per pillar are independent of the length, diameter, or cuticle stiffness of the animal. It was also observed that the motility of the worms with mechanosensation defects, lower cuticle stiffness, and body wall muscle defects was reduced with worms that have defective body wall muscle having the largest degree. Thus, we conclude that while reduced ability to apply forces affects the locomotion of the worm in the micropillar array, the reduced motility/locomotion may not indicate that the worm has reduced ability to apply forces on the micropillars. We also used the colored micropillar array for the first time to measure forces exerted by Drosophila larvae. Our device successfully captured the peristaltic rhythm of the body wall muscles of the larva and allowed us to measure the forces applied on each deflected pillar during this motion. Average force exerted by 1st instar wild type Drosophila larvae was measured to be ~ 1.5 µN per pillar. We demonstrated that a microjet of air can be used to apply forces in micro-Newton range. We developed a standalone system to generate a controlled air microjet. Microjet was generated using a controlled electromagnetic actuation of a diaphragm. With a nozzle diameter of 150 µm, the microjet diameter was maintained to a maximum of 1 mm at a distance of 5 mm from the nozzle. The force generated by the microjet was measured using a commercial force sensor to determine the velocity profile of the jet. Axial flow velocities of up to 25 m/s were obtained at distances as long as 6 mm. The microjet exerted a force up to 1 µN on a poly dimethyl siloxane (PDMS) micropillar (50 µm in diameter, 157 µm in height) and 415 µN on a PDMS membrane (3 mm in diameter, 28 µm thick). We also demonstrate that from a distance of 6 mm our microjet can exert a peak pressure of 187 Pa with a total force of about 84 µN on a flat surface with 8 V operating voltage. Next, we demonstrated that the response of C. elegans worms to the impinging air microjet is similar to the response evoked using a manual gentle touch. This contactless actuation tool avoids contamination and mechanical damage to the samples. Out of the cleanroom fabrication and robust design make this system cost effective and durable. Magnetic micropillars have been used as actuators. We fabricated magnetic micropillar arrays and designed actuation mechanisms using permanent magnet and a pulsed electromagnet. Force of about 19 µN was achievable using a permanent magnet actuation. In a pulsed electromagnetic field micropillar exerted a force of about 10 µN on a commercial force sensor. These techniques have promising applications when actuation needs to be controlled from long distances.

Die vorliegende Arbeit entstand im Zeitraum 12/2014 bis 02/2018 im erweiterten Rahmen des BMWi-Projekts „NeoKarII“ in Kooperation mit der Umicore AG & Co. KG. Das Projekt befasste sich mit der Suche nach neuartigen, oxidischen Elektrodenmaterialien für Polymerelektrolytmembranbrennstoffzellen (PEM-FC). Im Rahmen dieser Arbeit wurden Niob- und Tantal-dotierte Zinnoxide mit verschiedenen Dotiergraden (hauptsächlich 1 bis 10 %) über Sol-Gel Synthesen, Imprägnierungen und Co-Fällung hergestellt. Für die Co-Fällungen wurde eine MicroJet-Reaktor Anlage entwickelt und aufgebaut. Die Materialien wurden anschließend röntgenografisch untersucht und auf ihre Eignung für die Anwendung als Katalysatorträgermaterial in PEM-FC geprüft. Als Zielgrößen dienten die BET-Oberfläche und spezifische Leitfähigkeit, welche mit einem eigens entwickelten Leitfähigkeitsmessstand ermittelt wurde.:1 Einleitung 1.1 Brennstoffzellen 1.2 Methoden zur Synthese der Mischoxide 1.3 Eigenschaften von Zinnoxiden 1.4 Zielsetzung 2 Ergebnisse und Diskussion 2.1 Synthesen und Beobachtungen 2.2 Röntgenfluoreszenzanalyse 2.3 Pulver-Röntgendiffraktometrie 2.4 BET-Oberfläche 2.5 Leitfähigkeit 2.6 Röntgenphotoelektronenspektroskopie 3 Experimenteller Teil 3.1 Synthesen 3.2 Analytische Methoden 4 Zusammenfassung und Ausblick 4.1 Zusammenfassung 4.2 Ausblick 5 Anhang / This thesis was developed between 12/2014 and 02/2018 in an extended framework of BMWi project „NeoKarII “ in cooperation with Umicore AG & Co. KG. The project was concerned with the search for novel oxidic electrode materials for polymer electrolyte fuel cells (PEM-FC). In this work we prepared niobium- and tantalum-doped tin oxides with different doping levels (mainly 1 to 10 %) by sol-gel synthesis, impregnation and co-precipitation. For co-precipitation we developed and built a MicroJet reactor plant. We analysed the materials by X-ray diffraction and tested them for suitability for use as catalyst support material in PEM-FC. Target values were BET surface area and specific conductivity, which was determined using a specially developed conductivity measurement setup.:1 Einleitung 1.1 Brennstoffzellen 1.2 Methoden zur Synthese der Mischoxide 1.3 Eigenschaften von Zinnoxiden 1.4 Zielsetzung 2 Ergebnisse und Diskussion 2.1 Synthesen und Beobachtungen 2.2 Röntgenfluoreszenzanalyse 2.3 Pulver-Röntgendiffraktometrie 2.4 BET-Oberfläche 2.5 Leitfähigkeit 2.6 Röntgenphotoelektronenspektroskopie 3 Experimenteller Teil 3.1 Synthesen 3.2 Analytische Methoden 4 Zusammenfassung und Ausblick 4.1 Zusammenfassung 4.2 Ausblick 5 Anhang

This dissertation offers demonstrations of autonomous catalytic microtubes (microjet engines) with tunable diameters ranging from micro- to nanoscale and lengths from 50 μm to 1 mm. These results open the door to effective microengines and represent the entry in the Guinness Book of World Records for “the smallest man-made jet engine.” Several attractive methodologies of machine-based functions at the micro- and nanoscale are shown. For instance, catalytic Ti/Cr/Pt microjets, which are integrated on a planar substrate, can operate as “on chip” chemical micropumps by decomposition of hydrogen peroxide fuel into oxygen bubbles and water. When released from a substrate, microjets self-propel autonomously in solution. The incorporation of ferromagnetic layer (Fe) into the rolled-up geometry enables their remote control using external magnetic field. Such microjets were used to load, transport, deliver and assemble multiple cargo particles, including biological cells in bulk solutions and microfluidic channels. Furthermore, it is demonstrated that for microjets that are fixed to or self-propelled above a platinum patterned surface, the microengine power/speed can be controlled using a white lightsource. A change in intensity of the white light leads to a controllable switching “off” and “on” of the microengine power on demand. Light degrades a local concentration of the hydrogen peroxide fuel and surface tension and subsequently suppresses the generation of oxygen microbubbles. In the next step, the diameter of the microjets was rigorously reduced to 250 nm by using hybrid heteroepitaxial/catalytic InGaAs/GaAs/Cr/Pt nanotubes. Due to asymmetry of the rolled-up layers, these nanojets move in corkscrew-like motions and act as “self-propelled nanotools,” which were used in the next step to transport yeast cells and drill into fixed cancer Hela cells. Although it is well-known that hydrogen peroxide cannot be used to sustain viable cellular function, it is however conceivable that alternative fuels, such as glucose, might enable operation of such nanotools under biologically compatible conditions. As a first step to achieve this goal, demonstrations were made using metal-enzyme biocatalytic Ti/Au/SAM/Catalase microengines. Synthetic components with competing interactions are well-suited to study the emergence of their collective behavior, such as swarms of large numbers of individuals. Microengines’ self-organization in bistable swarms is shown at the air-liquid interface of the mixture of propylene carbonate and hydrogen peroxide. Microengines act as “water striders.” Buoyed by oxygen bubbles, they self-propel via the microbubble recoiling mechanism and, depending on the bubbles’ sizes, self-organize into swarms due to the meniscus climbing effect. These reversible swarms depend on the microengine power, which competes against attracting surface tension force. The demonstrated microjet engines show great promise for emerging applications, including biomedical, on-chip, environmental, and robotic micromachines. Furthermore, a key method discovered, entitled “rolled-up nanotechnology on polymers,” allowed for the fabrication of highly parallel arrays of microtubes with multiple functionalities and aimed for different purposes.

Im Rahmen der vorliegenden Arbeit wurden Metallchalkogenid-Nanopartikel bzw. Quantum Dots größenselektiv mittels kontinuierlicher MicroJet-Reaktor-Technologie in wässrigem Medium erzeugt. Aufgrund der sehr kurzen Mischzeiten im µs- bis ms-Bereich können Keimbildung und -wachstum im MicroJet-Reaktor zeitlich voneinander separiert werden. Die Begrenzung des Partikelwachstum durch den Einsatz von Stabilisatoren oder geringer Präkursorkonzentrationen ermöglichten die Synthese von monodispersen, nanokristallinen Produkten mit sehr schmaler Partikelgrößenverteilung. Ausgehend von den wasserlöslichen Präkursoren Cadmiumnitrat und Natriumsulfid wurde sowohl eine Synthesestrategie für elektrostatisch- als auch Liganden-stabilisierte CdS-Nanopartikel entwickelt. Es wurden zahlreiche Reaktionsparameter wie Temperatur, Präkursorverhältnis, Konzentration oder Fällungsmittel variiert und der Einfluss auf die Partikelgröße überprüft. In weiteren Untersuchungen konnte die Übertragbarkeit der MicroJet-Reaktor-Synthese auf die Metallchalkogenide Cadmiumzinksulfid, Silbersulfid und Silberindiumsulfid validiert werden. Auch komplexere Systeme wie Core/Shell Partikel sind mittels postsynthetischer Beschichtung der im MicroJet-Reaktor hergestellten Nanopartikel möglich. Erste Experimente zur Synthese von CdSe bestätigten die Eignung des kontinuierlichen Verfahrens zur Fällung höherer Chalkogenide.:1 Einleitung 1 1.1 Halbleiternanopartikel 3 1.1.1 Bandstruktur des Festkörpers 3 1.1.2 Interbandübergänge in direkten und indirekten Halbleitern 7 1.1.3 Quantum Confinement 15 1.2 Fällung von Nanopartikeln im MicroJet-Reaktor 20 1.2.1 Partikelbildung durch Kristallisation 20 1.2.2 Funktionsprinzip des MicroJet-Reaktors 22 1.2.3 State of the Art 25 1.3 Nanoskalige Metallchalkogenide 29 1.3.1 Cadmiumchalkogenide 29 1.3.2 Near-Infrared Quantum Dots 31 1.3.3 Core/Shell-Partikel 34 1.4 Zielsetzung 37 2 Ergebnisse und Diskussion 39 2.1 Allgemeines 39 2.2 Cadmiumchalkogenide 47 2.2.1 Hydrothermalsynthese von CdS im Laborautoklaven 47 2.2.1.1 Wiederholbarkeit 48 2.2.1.2 Einfluss des Präkursorverhältnis 50 2.2.1.3 Versuchsplanung zur Untersuchung ausgewählter Reaktionsparameter 51 2.2.1.4 Effektberechnung zur Untersuchung ausgewählter Einflussfaktoren 54 2.2.1.5 Beobachtungen und Charakterisierung 56 2.2.2 Kontinuierliche Synthese von CdS im MicroJet-Reaktor 62 2.2.2.1 MJR-Synthese von CdS aus Cd(NO3)2 und Na2S 62 2.2.2.2 MJR-Synthese von CdS aus Cd(NO3)2 und Thioacetamid 71 2.2.3 CdS/ZnS Core/Shell und Cd1-xZnxS Quantum Dots 76 2.2.3.1 CdS/ZnS Core/Shell Quantum Dots 77 2.2.3.2 Cd1-xZnxS Quantum Dots 88 2.2.4 Hydrothermalsynthese von CdSe im Laborautoklaven 99 2.2.4.1 Wiederholbarkeit 99 2.2.4.2 Präkursorverhältnis Cd2+:Se2- 101 2.2.4.3 Versuchsplanung zur Untersuchung ausgewählter Reaktionsparameter 104 2.2.4.4 Effektberechnung zur Untersuchung ausgewählter Einflussfaktoren 108 2.2.4.5 Beobachtungen und Charakterisierung 111 2.2.5 Kontinuierliche Synthese von CdSe im MicroJet-Reaktor 116 2.3 Near-Infrared Quantum Dots 121 2.3.1 Kontinuierliche Synthese von AgS2 im MJR-Reaktor 121 2.3.1.1 Elektrostatisch stabilisierte Ag2S Quantum Dots 121 2.3.1.2 Ag2S/ZnS Core/Shell Quantum Dots 138 2.3.1.3 Ligandenstabilisierte Ag2S Quantum Dots 143 2.3.2 Kontinuierliche Synthese von Indiumsilbersulfid im MJR-Reaktor 152 3 Experimenteller Teil 165 3.1 Synthesen 165 3.1.1 Verwendete Chemikalien 165 3.1.2 Hydrothermalsynthese im Laborautoklaven 166 3.1.2.1 Versuchsaufbau 166 3.1.2.2 Cadmiumsulfid 167 3.1.2.3 Cadmiumselenid 168 3.1.2.4 Silbersulfid 169 3.1.3 Kontinuierliche Synthese im MicroJet-Reaktor 169 3.1.3.1 Versuchsaufbau und Durchführung der MicroJet-Reaktor-Synthese 169 3.1.3.2 Synthese Liganden-stabilisierter Metallsulfide 171 3.1.3.3 Synthese elektrostatisch stabilisierter Metallsulfide 171 3.1.3.4 Synthese von Cadmiumselenid 172 3.1.3.5 Synthese von Core-Shell-Partikeln 172 3.2 Analytische Methoden 173 3.2.1 Dynamische Lichtstreuung (DLS) 173 3.2.2 Statische Lichtstreuung (SLS) 173 3.2.3 UV/Vis-Absorptionsspektroskopie 173 3.2.4 Photolumineszenz (PL)-Spektroskopie 174 3.2.5 Transmissionselektronenmikroskopie (TEM) 174 3.2.6 Rasterelektronenmikroskopie (REM) 175 3.2.7 Optische Emissionsspektroskopie mit induktiv gekoppeltem Plasma (ICP-OES) 175 3.2.8 Röntgenfluoreszenzanalyse (RFA) 176 3.2.9 Pulver-Röntgendiffraktometrie (PXRD) 176 3.2.10 RAMAN-Spektroskopie 177 3.2.11 Abgeschwächte Totalreflexions-Infrarotspektroskopie (ATR-FTIR) 177 4 Zusammenfassung und Ausblick 179 5 Literatur 182 6 Anhang 195 / In the present work, metal chalcogenide nanoparticles or Quantum Dots were obtained size-selectively using continuous MicroJet Reactor technology. Due to the short mixing times in the µs to ms range, crystallite nucleation and crystal growth are well separated and enable concentration-limited particle growth. Alternatively, particle growth can be limited by stabilizers. Starting from the water-soluble precursors Cd(NO3)2 and Na2S, a synthesis strategy for both electrostatic and ligand stabilized CdS nanoparticles in aqueous medium was developed. The nanocrystalline products obtained were characterized by a narrow, monodisperse particle size distribution. Examining the influence of the particle size, numerous reaction parameters e. g. temperature, ratio of precursors, concentration or precipitant were varied. In further investigations, the transferability of the MicroJet Reactor synthesis to the metal chalcogenides (Cd,Zn)S, Ag2S and AgInS2 was validated. By means of post-synthetic coating of the nanoparticles produced in the MicroJet Reactor, more complex systems such as CdS/ZnS or Ag2S/ZnS core/shell particles are accessible. Initial experiments on the synthesis of CdSe confirmed the suitability of the continuous process for precipitation of selenides.:1 Einleitung 1 1.1 Halbleiternanopartikel 3 1.1.1 Bandstruktur des Festkörpers 3 1.1.2 Interbandübergänge in direkten und indirekten Halbleitern 7 1.1.3 Quantum Confinement 15 1.2 Fällung von Nanopartikeln im MicroJet-Reaktor 20 1.2.1 Partikelbildung durch Kristallisation 20 1.2.2 Funktionsprinzip des MicroJet-Reaktors 22 1.2.3 State of the Art 25 1.3 Nanoskalige Metallchalkogenide 29 1.3.1 Cadmiumchalkogenide 29 1.3.2 Near-Infrared Quantum Dots 31 1.3.3 Core/Shell-Partikel 34 1.4 Zielsetzung 37 2 Ergebnisse und Diskussion 39 2.1 Allgemeines 39 2.2 Cadmiumchalkogenide 47 2.2.1 Hydrothermalsynthese von CdS im Laborautoklaven 47 2.2.1.1 Wiederholbarkeit 48 2.2.1.2 Einfluss des Präkursorverhältnis 50 2.2.1.3 Versuchsplanung zur Untersuchung ausgewählter Reaktionsparameter 51 2.2.1.4 Effektberechnung zur Untersuchung ausgewählter Einflussfaktoren 54 2.2.1.5 Beobachtungen und Charakterisierung 56 2.2.2 Kontinuierliche Synthese von CdS im MicroJet-Reaktor 62 2.2.2.1 MJR-Synthese von CdS aus Cd(NO3)2 und Na2S 62 2.2.2.2 MJR-Synthese von CdS aus Cd(NO3)2 und Thioacetamid 71 2.2.3 CdS/ZnS Core/Shell und Cd1-xZnxS Quantum Dots 76 2.2.3.1 CdS/ZnS Core/Shell Quantum Dots 77 2.2.3.2 Cd1-xZnxS Quantum Dots 88 2.2.4 Hydrothermalsynthese von CdSe im Laborautoklaven 99 2.2.4.1 Wiederholbarkeit 99 2.2.4.2 Präkursorverhältnis Cd2+:Se2- 101 2.2.4.3 Versuchsplanung zur Untersuchung ausgewählter Reaktionsparameter 104 2.2.4.4 Effektberechnung zur Untersuchung ausgewählter Einflussfaktoren 108 2.2.4.5 Beobachtungen und Charakterisierung 111 2.2.5 Kontinuierliche Synthese von CdSe im MicroJet-Reaktor 116 2.3 Near-Infrared Quantum Dots 121 2.3.1 Kontinuierliche Synthese von AgS2 im MJR-Reaktor 121 2.3.1.1 Elektrostatisch stabilisierte Ag2S Quantum Dots 121 2.3.1.2 Ag2S/ZnS Core/Shell Quantum Dots 138 2.3.1.3 Ligandenstabilisierte Ag2S Quantum Dots 143 2.3.2 Kontinuierliche Synthese von Indiumsilbersulfid im MJR-Reaktor 152 3 Experimenteller Teil 165 3.1 Synthesen 165 3.1.1 Verwendete Chemikalien 165 3.1.2 Hydrothermalsynthese im Laborautoklaven 166 3.1.2.1 Versuchsaufbau 166 3.1.2.2 Cadmiumsulfid 167 3.1.2.3 Cadmiumselenid 168 3.1.2.4 Silbersulfid 169 3.1.3 Kontinuierliche Synthese im MicroJet-Reaktor 169 3.1.3.1 Versuchsaufbau und Durchführung der MicroJet-Reaktor-Synthese 169 3.1.3.2 Synthese Liganden-stabilisierter Metallsulfide 171 3.1.3.3 Synthese elektrostatisch stabilisierter Metallsulfide 171 3.1.3.4 Synthese von Cadmiumselenid 172 3.1.3.5 Synthese von Core-Shell-Partikeln 172 3.2 Analytische Methoden 173 3.2.1 Dynamische Lichtstreuung (DLS) 173 3.2.2 Statische Lichtstreuung (SLS) 173 3.2.3 UV/Vis-Absorptionsspektroskopie 173 3.2.4 Photolumineszenz (PL)-Spektroskopie 174 3.2.5 Transmissionselektronenmikroskopie (TEM) 174 3.2.6 Rasterelektronenmikroskopie (REM) 175 3.2.7 Optische Emissionsspektroskopie mit induktiv gekoppeltem Plasma (ICP-OES) 175 3.2.8 Röntgenfluoreszenzanalyse (RFA) 176 3.2.9 Pulver-Röntgendiffraktometrie (PXRD) 176 3.2.10 RAMAN-Spektroskopie 177 3.2.11 Abgeschwächte Totalreflexions-Infrarotspektroskopie (ATR-FTIR) 177 4 Zusammenfassung und Ausblick 179 5 Literatur 182 6 Anhang 195

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