Metal chalcogenide nanomaterials are interesting due to their size dependent properties and potential use in numerous types of devices or applications. The synthetic methods of binary phase metal chalcogenide nanoparticles are well established, but finding simple ways to make even more complex nanostructures is important. To this end, two techniques were studied: the cation exchange of metal chalcogenide nanocrystals, CdE → MxEy (E = S, Se, Te; M = Pd, Pt) and the solution phase synthesis of ternary chalcogenide nanoparticles. The effects of cation solvation and the volume change (Delta V) of reaction on the equilibrium and the morphology change in the cation-exchange reactions of CdE → MxEy were investigated. A two-phase solvent environment was particularly efficient in increasing the thermodynamic driving force. The effect of Delta V of reaction on the morphology of the product nanocrystals was also investigated. Depending on the stress developed in the lattice during the reaction, product nanocrystals underwent varying degrees of morphological changes, such as void formation and fragmentation, in addition to the preservation of the original morphology of the reactant nanocrystals. The knowledge of the effect of ion solvation and Delta V of reaction on the equilibrium and product morphology provides a new strategy and useful guide to the application of cation-exchange reactions for the synthesis of a broader range of inorganic nanocrystals. Using a solution phase method, the morphology of CuInSe2 nanoparticles could be tuned from small 10 nm spheres to micron length nanowires by varying the relative amount of strong and weak surfactants passivating the surface. Oleylamine and trioctylphosphine oxide were chosen as the strong and weak surfactants, respectively. Small isotropic structures were formed when the oleylamine was the only surfactant with the size of the nanospheres increasing as the amount of oleylamine decreased. For the CuInSe2 nanowires, weakly-binding dioctylphosphine oxide (DOPO), an impurity in the TOPO, was found to be the key surfactant that enables the anisotropic one-dimensional growth. Detailed analysis of the structure of the nanowires indicated that they grow perpendicular to (112) planes, with twinning around the growth axis by ~60 degree rotation. The nanowires exhibit a saw-tooth surface morphology resembling a stack of truncated tetrahedral.

No description available.

Magister Scientiae - MSc (Chemistry) / Although cadmium and lead chalcogenide quantum dot have excellent optical and photoluminescent properties that are highly favorable for biological applications, there still exists increasing concerns due to the toxicity of these metals. We, therefore, report the synthesis of new aqueous soluble IrSe quantum dot at room temperature utilizing a bottom-up wet chemistry approach. NaHSe and H2IrCl6 were utilized as the Se and Ir source, respectively. High-resolution transmission electron microscopy reveals that the synthesized 3MPA-IrSe Qd are 3 nm in diameter. The characteristics and properties of the IrSe Qd are investigated utilizing, Selected Area electron diffraction, ATR- Fourier Transform Infra-Red Spectroscopy, Energy Dispersive X-ray spectroscopy, Photoluminescence, Cyclic Voltammetry and chronocoulometry. A 3 fold increase in the optical band gap of IrSe quantum dot in comparison to reported bulk IrSe is observed consistent with the effective mass approximation theory for semiconductor materials of particles sizes < 10 nm. The PL emission of the IrSe quantum dot is at 519 nm. Their electro-activity is studied on gold electrodes and exhibit reduction and oxidation at - 107 mV and +641 mV, with lowered reductive potentials. The synthesized quantum dot are suitable for low energy requiring electrochemical applications such as biological sensors and candidates for further investigation as photoluminescent biological labels.

D. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Nanoscience receives a lot of attention in the 21 century and is one of the most advancing technology in our days. It provides many new and advanced technological opportunities. This field involves many disciplines which include chemical, physical, and biological related fields. The advancement of nanoscience makes life to be better and bring about new inventions which can solve many problems in our day to day life. Although there are reservations about the use of these materials in other fields. Some researchers believe that these materials can be a problem to the environment and humanity at large. Therefore, more research needs to be done to fully understand these materials. Polymer science is another field that has been advancing every day. Many problems in our lives require material which have properties from nanomaterials and polymers. The combination of these technologies can leads to new materials which have many possibilities in solving most problems. Some researchers have taken advantage of these two powerful fields and merge them. There has been a lot of work done that involves combination of nanotechnology and polymer science. The current project is an initiative to manufacture nanofibers. These fibers are prepared using polymer solution mixed with metal oxide and metal selenide nanomaterials. The polymer solution is incorporated with nanoparticles and electrospunned to make nanofibers. The electrospinning afford the material prepared to be at nanoscale. The fact that the material formed is at nanoscale opens many possibilities to be used in various fields. The study is about fabrication of polymer nanofibers embedded with metal chalcogenide nanoparticles. The metal oxide and metal selenide nanoparticles were prepared using complexes. These complexes contain both the metal and the chalcogenide of interest. The complexes are prepared from oxygen-based (urea), and selenium-based (diphenyldiselenide) ligands. The urea complexes co-ordinates with metal using oxygen for iron, however in silver complexes both nitrogen and oxygen are used. These complexes allow easy control of reaction parameters, and thermal decomposes to form metal oxide, metal selenide, and metal. The complexes are very stable and decomposes at about 200 °C. These compounds are thermal decomposed to form metal chalcogenides, and metal nanoparticles. The complexes are characterized with FTIR, TGA, and elemental analysis. The metal chalcoginedes (copper oxide, iron oxide, silver oxide, copper selenide, iron selenide, and silver selenide) nanoparticles were prepared using thermal decomposition of a single source (complexes or metal salts). The prepared chalcogenides nanoparticles have good absorption and emission properties consistent with small sizes. These nanoparticles are composed of various phased and stoichiometry. Some metal chalcogenides have a mixture of stoichiometry and phase. The metal chalcogenides nanoparticles are dominated by spheres, and other shapes such as rods. These metal chalcogenides have a particles size in the range of 1-36 nm. The metal chalcogenides nanoparticles were tested against bacteria and fungi. These nanoparticles show highest activity in gram positive compared to gram negative bacteria. Metal oxide nanoparticles show the highest activity compared to metal selenide. All the metal chalcogenides show the highest against fungi. The nanoparticles are able to inhibit the fungi at lowest concentration. The nanoparticles are characterized with various instruments which includes UV-Vis, PL, XRD, and TEM. Nanofibers of poly(methyl methacrylate) (PMMA) incorporated with metal selenide and metal oxide nanoparticles were prepared by electrospinning. The nanofibers incorporated with metal chalcogenide are more thermal stable than PMMA nanofibers. Therefore, incorporation of metal chalcogenides nanoparticles leads to more thermal stability nanofibers. The PMMA are coordinated to the metal oxide and metal selenide through carbonyl oxygen atom. The PMMA incorporated with metal oxide and metal selenide leads to the formation of nanofibers with uneven surface with a diameter in the range of 30 to 200 nm. The prepared fibers are characterized using FTIR, TGA, SEM.

The thesis consists of eight chapters of which the first chapter presents a brief overview of inorganic nanostructures. Synthesis and magnetic properties of MnO and NiO nanocrystals are described in Chapter 2, with emphasis on the low-temperature ferromagnetic interactions in these antiferromagnetic oxides. Chapter 3 deals with the synthesis and characterizations of nanocrystals of ReO3, RuO2 and IrO2 which are oxides with metallic properties. Pressure-induced phase transitions of ReO3 nanocrystals and the use of the nanocrystals for carrying out surface-enhanced Raman spectroscopy of the molecules form Chapter 4. Use of ionic liquids to synthesize different nanostructures of semiconducting metal sulfides and selenides is described in Chapter 5. Synthesis of Mn-doped GaN nanocrystals and their magnetic properties are described in Chapter 6. A detailed investigation has been carried out on the growth kinetics of nanostructures of a few inorganic materials by using small-angle X-ray scattering and other techniques (Chapter 7). The study includes the growth kinetics of nanocrystals of Au, CdS and CdSe as well as of nanorods of ZnO. Results of a synchrotron X-ray study of the formation of nanocrystalline gold films at the organic-aqueous interface are also included in this chapter. Chapter 8 discuses the use of the organic-aqueous interface to generate Janus nanocrystalline films of inorganic materials where one side of the film is hydrophobic and other side is hydrophilic. This chapter also includes the formation of nanostructured peptide fibrils at the organic-aqueous interface and their use as templates to prepare inorganic nanotubes.

Technology scaling beyond Moore’s law demands cutting-edge solutions of the gate length scaling in sub-10 nm regime for low power high speed operations. Recently SOI technology has received considerable attention, however manufacturable solutions in sub-10 nm technologies are not yet known for future nanoelectronics. Therefore, to continue scalinginsub-10 nm region, new one(1D) and two dimensional(2D) “nano-materials” and engineering are expected to keep its pace. However, significant challenges must be overcome for nano-material properties in carrier transport to be useful in future silicon nanotechnology. Thus, it is very important to understand and modulate their electronic band structure and transport properties for low power nanoelectronics applications. This thesis tries to provide solutions for some problems in this area. In recent times, one dimensional Silicon nanowire has emerged as a building block for the next generation nano-electronic devices as it can accommodate multiple gate transistor architecture with excellent electrostatic integrity. However as the experimental study of various energy band parameters at the nanoscale regime is extremely challenging, usually one relies on the atomic level simulations, the results of which are at par with the experimental observations. Two such parameters are the band gap and effective mass, which are of pioneer importance for the understanding of the current transport mechanism. Although there exists a large number of empirical relations of the band gap in relaxed Silicon nanowire, however there is a growing demand for the development of a physics based analytical model to standardize different energy band parameters which particularly demands its application in TCAD software for predicting different electrical characteristics of novel devices and its strained counterpart to increase the device characteristics significantly without changing the device architecture. In the first part of this work reports the analytical modeling of energy band gap and electron transport effective mass of relaxed and strained Silicon nanowires in various crystallographic directions for future nanoelectronics. The technology scaling of gate length in beyond Moore’s law devices also demands the SOI body thickness, TSi0 which is essentially very challenging task in nano-device engineering. To overcome this circumstance, two dimensional crystals in atomically thin layered materials have found great attention for future nanolectronics device applications. Graphene, one layer of Graphite, is such 2D materials which have found potentiality in high speed nanoelectronics applications due to its several unique electronic properties. However, the zero band gap in pure Graphene makes it limited in switching device or transistor applications. Thus, opening and tailoring a band gap has become a highly pursued topic in recent graphene research. The second part of this work reports atomistic simulation based real and complex band structure properties Graphene-Boron nitride heterobilayer and Boron Nitride embedded Graphene nanoribbons which can improve the grapheme and its nanoribbon band structure properties without changing their originality. This part also reports the direct band-to-band tunneling phenomena through the complex band structures and their applications in tunnel field effect transistors(TFETs) which has emerged as a strong candidate for next generation low-stand by power(LSTP) applications due to its sub-60mV/dec Sub threshold slope(SS). As the direct band-to-band tunneling(BTBT) is improbable in Silicon(either its bulk or nanowire form), it is difficult to achieve superior TFET characteristics(i.e., very low SS and high ON cur-rent) from the Silicon TFETs. Whereas, it is explored that much high ON current and very low subthreshold slope in hybrid Graphene based TFET characteristics open a new prospect in future TFETs. The investigations on ultrathin body materials also call for a need to explore new 2D materials with finite band gap and their various nanostructures for future nanoelectronic applications in order to replace conventional Silicon. In the third part of this report, we have investigated the electronic and dielectric properties of semiconducting layered Transition metal dichalcogenide materials (MX2)(M=Mo, W;X =S, Se, Te) which has recently emerged as a promising alternative to Si as channel materials for CMOS devices. Five layered MX2 materials(exceptWTe2)in their 2D sheet and 1D nanoribbon forms are considered to study the real and imaginary band structure of thoseMX2 materials by atomistic simulations. Studying the complex dispersion properties, it is shown that all the five MX2 support direct BTBT in their monolayer sheet forms and offer an average ON current and subthresholdslopeof150 A/mand4 mV/dec, respectively. However, onlytheMoTe2 support direct BTBT in its nanoribbon form, whereas the direct BTBT possibility in MoS2 and MoSe2 depends on the number of layers or applied uniaxial strain. WX2 nanoribbons are shown to be non-suitable for efficient TFET operation. Reasonably high tunneling current in these MX2 shows that these can take advantage over conventional Silicon in future tunnel field effect transistor applications.

Technology scaling beyond Moore’s law demands cutting-edge solutions of the gate length scaling in sub-10 nm regime for low power high speed operations. Recently SOI technology has received considerable attention, however manufacturable solutions in sub-10 nm technologies are not yet known for future nanoelectronics. Therefore, to continue scalinginsub-10 nm region, new one(1D) and two dimensional(2D) “nano-materials” and engineering are expected to keep its pace. However, significant challenges must be overcome for nano-material properties in carrier transport to be useful in future silicon nanotechnology. Thus, it is very important to understand and modulate their electronic band structure and transport properties for low power nanoelectronics applications. This thesis tries to provide solutions for some problems in this area. In recent times, one dimensional Silicon nanowire has emerged as a building block for the next generation nano-electronic devices as it can accommodate multiple gate transistor architecture with excellent electrostatic integrity. However as the experimental study of various energy band parameters at the nanoscale regime is extremely challenging, usually one relies on the atomic level simulations, the results of which are at par with the experimental observations. Two such parameters are the band gap and effective mass, which are of pioneer importance for the understanding of the current transport mechanism. Although there exists a large number of empirical relations of the band gap in relaxed Silicon nanowire, however there is a growing demand for the development of a physics based analytical model to standardize different energy band parameters which particularly demands its application in TCAD software for predicting different electrical characteristics of novel devices and its strained counterpart to increase the device characteristics significantly without changing the device architecture. In the first part of this work reports the analytical modeling of energy band gap and electron transport effective mass of relaxed and strained Silicon nanowires in various crystallographic directions for future nanoelectronics. The technology scaling of gate length in beyond Moore’s law devices also demands the SOI body thickness, TSi0 which is essentially very challenging task in nano-device engineering. To overcome this circumstance, two dimensional crystals in atomically thin layered materials have found great attention for future nanolectronics device applications. Graphene, one layer of Graphite, is such 2D materials which have found potentiality in high speed nanoelectronics applications due to its several unique electronic properties. However, the zero band gap in pure Graphene makes it limited in switching device or transistor applications. Thus, opening and tailoring a band gap has become a highly pursued topic in recent graphene research. The second part of this work reports atomistic simulation based real and complex band structure properties Graphene-Boron nitride heterobilayer and Boron Nitride embedded Graphene nanoribbons which can improve the grapheme and its nanoribbon band structure properties without changing their originality. This part also reports the direct band-to-band tunneling phenomena through the complex band structures and their applications in tunnel field effect transistors(TFETs) which has emerged as a strong candidate for next generation low-stand by power(LSTP) applications due to its sub-60mV/dec Sub threshold slope(SS). As the direct band-to-band tunneling(BTBT) is improbable in Silicon(either its bulk or nanowire form), it is difficult to achieve superior TFET characteristics(i.e., very low SS and high ON cur-rent) from the Silicon TFETs. Whereas, it is explored that much high ON current and very low subthreshold slope in hybrid Graphene based TFET characteristics open a new prospect in future TFETs. The investigations on ultrathin body materials also call for a need to explore new 2D materials with finite band gap and their various nanostructures for future nanoelectronic applications in order to replace conventional Silicon. In the third part of this report, we have investigated the electronic and dielectric properties of semiconducting layered Transition metal dichalcogenide materials (MX2)(M=Mo, W;X =S, Se, Te) which has recently emerged as a promising alternative to Si as channel materials for CMOS devices. Five layered MX2 materials(exceptWTe2)in their 2D sheet and 1D nanoribbon forms are considered to study the real and imaginary band structure of thoseMX2 materials by atomistic simulations. Studying the complex dispersion properties, it is shown that all the five MX2 support direct BTBT in their monolayer sheet forms and offer an average ON current and subthresholdslopeof150 A/mand4 mV/dec, respectively. However, onlytheMoTe2 support direct BTBT in its nanoribbon form, whereas the direct BTBT possibility in MoS2 and MoSe2 depends on the number of layers or applied uniaxial strain. WX2 nanoribbons are shown to be non-suitable for efficient TFET operation. Reasonably high tunneling current in these MX2 shows that these can take advantage over conventional Silicon in future tunnel field effect transistor applications.

<p dir="ltr">Transitioning to a carbon-neutral future will require a broad portfolio of green energy generation and storage solutions. With the abundant availability of solar radiation across the Earth’s surface, energy generation from photovoltaics (PVs) will be an important part of this green energy portfolio. While silicon-based solar cells currently dominate the PV market, temperatures exceeding 1000 °C are needed for purification of silicon, and batch processing of silicon wafers limits how rapidly Si-based PV can be deployed. Furthermore, silicon’s indirect band gap necessitates absorber layers to exceed 100 µm thick, limiting its applications to rigid substrates.</p><p dir="ltr">Solution processed thin-film solar cells may allow for the realization of continuous, high-throughput manufacturing of PV modules. Thin-film absorber materials have direct band gaps, allowing them to absorb light more efficiently, and thus, they can be as thin as a few hundred nanometers and can be deposited on flexible substrates. Solution deposition of these absorber materials utilizing molecular precursor-based inks could be done in a roll-to-roll format, drastically increasing the throughput of PV manufacturing, and reducing installation costs. In this dissertation, solution processed synthesis and the characterization of two emerging direct band gap absorber materials consisting of earth abundant elements is discussed: the enargite phase of Cu₃AsS₄ and the distorted perovskite phase of BaZrS₃.</p><p dir="ltr">The enargite phase of Cu₃AsS₄ (ENG) is an emerging PV material with a 1.42 eV band gap, making it an ideal single-junction absorber material for photovoltaic applications. Unfortunately, ENG-based PV devices have historically been shown to have low power conversion efficiencies, potentially due to defects in the material. A combined computational and experimental study was completed where DFT-based calculations from collaborators were used inform synthesis strategies to improve the defect properties of ENG utilizing new synthesis techniques, including silver alloying, to reduce the density of harmful defects.</p><p dir="ltr">Chalcogenide perovskites are viewed as a stable alternative to halide perovskites, with BaZrS₃ being the most widely studied. With a band gap of 1.8 eV, BaZrS₃ could be an excellent wide-bandgap partner for a silicon-based tandem solar cell.Historically, sputtering, and solid-state approaches have been used to synthesize chalcogenide perovskites, but these methods require synthesis temperatures exceeding 800 °C, making them incompatible with the glass substrates and rear-contact layers required to create a PV device. In this dissertation, these high synthesis temperatures are bypassed through the development of a solution-processed deposition technique.A unique chemistry was developed to create fully soluble molecular precursor inks consisting of alkaline earth metal dithiocarboxylates and transition metal dithiocarbamates for direct-to-substrate synthesis of BaZrS₃ and BaHfS₃ at temperatures below 600 °C.</p><p dir="ltr">However, many challenges must be overcome before chalcogenide perovskites can be used for the creation of photovoltaic devices including oxide and Ruddlesden-Popper secondary phases, isolated grain growth, and deep level defects. Nevertheless, the development of a moderate temperature solution-based synthesis route makes chalcogenide perovskite research accessible to labs which do not have high temperature furnaces or sputtering equipment, further increasing research interest in this quickly developing absorber material.</p>

<div>Inorganic metal chalcogenide materials are of great importance in the semiconducting field for various electronic applications such as photovoltaics, thermoelectrics, sensors, and many others. Compared to traditional vacuum processing routes, solution processing provides an alternate cost-effective route to synthesize these inorganic materials through its ease of synthesis and device fabrication, higher material utilization, mild processing conditions, and opportunity for roll-to-roll manufacturing. One such versatile solution chemistry involving a mixture of amine and thiol species has evolved in the past few years as a common solvent for various precursor dissolutions including metal salts, metal oxides, elemental metals, and chalcogens.</div><div><br></div><div>The amine-thiol solvent system has been used by various researchers for the fabrication of inorganic materials, but without the complete understanding of the chemistry involved in this system, utilizing its full potential, and overcoming any inherent limitations will be difficult. So, to identify the organometallic complexes and their reaction pathways, the precursor dissolutions in amine-thiol solutions, specifically for elemental metals like Cu, In and chalcogens like Se, Te were studied using X-ray absorption, nuclear magnetic resonance, infrared, and Raman spectroscopy along with electrospray ionization mass spectrometry techniques. These analyses suggested the formation of metal thiolate complexes in the solution with the release of hydrogen gas in the case of metal dissolutions confirming irreversibility of the dissolution. Insights gained for chalcogen dissolutions confirmed the formation of different species like monoatomic or polyatomic clusters when different amine-thiol pair is used for dissolution. Results from these analyses also identified the role of each component in the dissolution which allowed for tuning of the solutions by isolating the complexes to reduce their reactivity and corrosivity for commercial applications.</div><div><br></div><div>After identifying complexes in metal dissolution for Cu and In metals, the decomposition pathway for these complexes was studied using X-ray diffraction and gas chromatography mass spectrometry techniques which confirmed the formation of phase pure metal chalcogenide material with a release of volatile byproducts like hydrogen sulfide and thiirane. This allowed for the fabrication of impurity-free thin-film Cu(In,Ga)S2 material for use in photovoltaic applications. The film fabrication with reduced carbon impurity achieved using this solvent system yielded a preliminary promising efficiency beyond 12% for heavy alkali-free, low bandgap CuInSe2 material. Along with promising devices, by utilizing the understanding of the chalcogen complexation, a new method for CuInSe2 film fabrication was developed with the addition of selenide precursors and elemental selenium which enabled first-ever fabrication of a solution-processed CuInSe2 thin film with thickness above 2 μm and absence of any secondary fine-grain layer.</div><div><br></div><div>Along with thin-film fabrication, a room temperature synthesis route for lead chalcogenide materials (PbS, PbSe, PbTe) with controlled size, shape, crystallinity, and composition of nanoparticle self-assemblies was demonstrated. Micro-assemblies formed via this route, especially the ones with hollow-core morphology were subjected to a solution-based anion and cation exchange to introduced desired foreign elements suitable for improving the thermoelectric properties of the material. Adopting from traditional hot injection and heat up synthesis routes, a versatile synthesis procedure for various binary, ternary, and quaternary metal chalcogenide (sulfide and sulfoselenide) nanoparticles from elemental metals like Cu, Zn, Sn, In, Ga, and Se was developed. This new synthesis avoids the incorporation of impurities like O, Cl, I, Br arising from a traditional metal oxide, halide, acetate, or other similar metal salt precursors giving an opportunity for truly impurity-free colloidal metal chalcogenide nanoparticle synthesis.</div>

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