Engineered Nanoparticles Generation, Characterization and Applications

It is predicted that novel nanometer-sized structures incorporating nanoparticles will have a considerable impact on our lives during the coming decades. Engineered nanoparticles are already found in a number of commercially available products. However, many applications of these nanoparticles have only reached the stage of promising ideas or research demonstrations. The number of nanoparticle-based products on the market is therefore expected to increase considerably during the coming decades. For engineered nanoparticles to be useful in different commercial applications, it is important that their generation can be controlled. This means a stable generation process resulting in reproducible, high-quality nanoparticles with properties tailored for specific applications. In order to develop such production methods, thorough characterization of the particles generated is essential. In addition, since the impact of nanoparticles on human health and the environment has not been fully explored, the entire lifecycle of engineered nanoparticles must be thoroughly investigated. Engineered nanoparticles should not cause any harm to human health or the environment, during manufacturing or use of the product, or during disposal of the product after use. This thesis describes the manufacture of engineered nanoparticles, mainly by inert gas evaporation using a spark discharge generator and an evaporation/condensation furnace. Considerable effort has been put into investigating how different generation parameters affect particle production, so that the particle properties can be controlled and tailored to meet specific applications. To achieve this, the as-generated nanoparticles have been systematically characterized by various methods; transmission electron microscopy being the key characterization tool. The nanoparticles generated were then used in three different areas of application: as seed particles for so-called nanowires which may be useful in future devices, as model catalyst systems to provide deeper knowledge about the atomic-scale mechanisms involved in catalysis, and finally for research in the area of nano safety to learn how nanoparticles should be handled in a safe and sustainable manner

Multiple exciton generation in nano-crystals revisited: Consistent calculation of the yield based on pump-probe spectroscopy

Multiple exciton generation (MEG) is a process in which more than one exciton is generated upon the absorption of a high energy photon, typically higher than two times the band gap, in semiconductor nanocrystals. It can be observed experimentally using time resolved spectroscopy such as the transient absorption measurements. Quantification of the MEG yield is usu- ally done by assuming that the bi-exciton signal is twice the signal from a single exciton. Herein we show that this assumption is not always justified and may lead to significant errors in the estimated MEG yields. We develop a methodology to determine proper scaling factors to the signals from the transient absorption experiments. Using the methodology we find modest MEG yields in lead chalcogenide nanocrystals including the nanorods

Looking and listening in a technical world : Effects of discontinuity in work schedules on nurses’ work activity

The structure of work schedules and its effects on the work activity of health care workers in a short-term care facility were analyzed in a context of changes to the Québec health care system. The analysis revealed short patient stays and a great discontinuity in work periods for nursing personnel : 60 % of health care workers in one department worked for fewer than five shifts per month in this department. Thus, the workers often have little information on patients, and the constant changes in the work teams can affect the strategies that they use to remedy the situation. Since the “technical” aspects of the work cannot be reduced, the more “human” aspects can be compressed. Could this type of work organization diminish caring, thus depriving patients of important human contact and health care workers of their sense of the meaning of their work. Could this loss of meaning affect the absenteeism rate, which is known to be high among nurses ?La structure des horaires et ses effets sur le travail des infirmières et infirmières auxiliaires d’un hôpital de soins de courte durée ont été analysés dans un contexte de modifications du réseau québécois de la santé. L’analyse montre de courts séjours chez les patients et une très grande discontinuité des périodes de travail chez le personnel infirmier : 60 % de celles qui travaillaient dans un département cumulent moins de cinq quarts par mois dans ce département. Ainsi, elles ont souvent peu d’information sur les patients et la constante recomposition des équipes peut affecter leurs stratégies pour pallier cette situation. Les aspects « techniques » du travail ne pouvant être escamotés, les aspects « humains » deviennent compressibles. Cette organisation du travail peut-elle diminuer le caring, privant d’une part les patients de contacts importants et entraînant d’autre part, chez les soignantes, une perte du sens de leur travail ? Est-ce que cette perte de sens aurait un effet sur le taux d’absence, très élevé dans cette population ?La estructura de los horarios y sus efectos sobre el trabajo de las enfermeras y enfermeras auxiliares en un hospital de atención a corto plazo fueron analyzados en un contexto de modificaciones de la red quebequense de la salud. El análisis enseña estancias cortas de los pacientes y una discontinuidad muy grande de los periodos de trabajo del personal enfermero : 60 % de las que trabajaban en un departamento cumulaban menos de cinco turnos por més en este departamento. Así, a menudo tenían poca información sobre los pacientes y la constante recomposición de los equipos puede afectar las estrategias para paliar la situación. Como no se puede minimizar los aspectos « técnicos » del trabajo, se comprime los aspectos « humanos ». ¿ Puede esta organización de trabajo disminuir la atención, privando por una parte los pacientes de contactos importantes, y llevando por otra parte, una pérdida del sentido del trabajo para el personal sanitario ? ¿ Tendría esta pérdida un efecto sobre la tasa de ausencia, muy elevada en esta población 

Écouter et voir dans un monde technique : Effets de la discontinuité des horaires sur l’activité de travail des infirmières

La structure des horaires et ses effets sur le travail des infirmières et infirmières auxiliaires d’un hôpital de soins de courte durée ont été analysés dans un contexte de modifications du réseau québécois de la santé. L’analyse montre de courts séjours chez les patients et une très grande discontinuité des périodes de travail chez le personnel infirmier : 60 % de celles qui travaillaient dans un département cumulent moins de cinq quarts par mois dans ce département. Ainsi, elles ont souvent peu d’information sur les patients et la constante recomposition des équipes peut affecter leurs stratégies pour pallier cette situation. Les aspects « techniques » du travail ne pouvant être escamotés, les aspects « humains » deviennent compressibles. Cette organisation du travail peut-elle diminuer le caring, privant d’une part les patients de contacts importants et entraînant d’autre part, chez les soignantes, une perte du sens de leur travail ? Est-ce que cette perte de sens aurait un effet sur le taux d’absence, très élevé dans cette population ?The structure of work schedules and its effects on the work activity of health care workers in a short-term care facility were analyzed in a context of changes to the Québec health care system. The analysis revealed short patient stays and a great discontinuity in work periods for nursing personnel : 60 % of health care workers in one department worked for fewer than five shifts per month in this department. Thus, the workers often have little information on patients, and the constant changes in the work teams can affect the strategies that they use to remedy the situation. Since the “technical” aspects of the work cannot be reduced, the more “human” aspects can be compressed. Could this type of work organization diminish caring, thus depriving patients of important human contact and health care workers of their sense of the meaning of their work. Could this loss of meaning affect the absenteeism rate, which is known to be high among nurses ?La estructura de los horarios y sus efectos sobre el trabajo de las enfermeras y enfermeras auxiliares en un hospital de atención a corto plazo fueron analyzados en un contexto de modificaciones de la red quebequense de la salud. El análisis enseña estancias cortas de los pacientes y una discontinuidad muy grande de los periodos de trabajo del personal enfermero : 60 % de las que trabajaban en un departamento cumulaban menos de cinco turnos por més en este departamento. Así, a menudo tenían poca información sobre los pacientes y la constante recomposición de los equipos puede afectar las estrategias para paliar la situación. Como no se puede minimizar los aspectos « técnicos » del trabajo, se comprime los aspectos « humanos ». ¿ Puede esta organización de trabajo disminuir la atención, privando por una parte los pacientes de contactos importantes, y llevando por otra parte, una pérdida del sentido del trabajo para el personal sanitario ? ¿ Tendría esta pérdida un efecto sobre la tasa de ausencia, muy elevada en esta población 

Gas-borne particles with tunable and highly controlled characteristics: for nanotoxicology studies

For nanotoxicology investigations of air-borne particles to provide relevant results it is ever so important that the particle exposure of, for example cells, closely resembles the “real” exposure situation, that the dosimetry is well defined, and that the characteristics of the deposited nanoparticles are known in detail. By synthesizing the particles in the gas-phase and directly depositing them on lung cells the particle deposition conditions in the lung is closely mimicked. In this work we present a setup for generation of gas-borne nanoparticles of a variety of different materials with highly controlled and tunable particle characteristics, and demonstrate the method by generation of gold particles. Particle size, number concentration and mass of individual particles of the population are measured on-line by means of differential mobility analyzers (DMA) and an aerosol particle mass analyzer (APM), whereas primary particle size and internal structure are investigated by transmission electron microscopy. A method for estimating the surface area dose from the DMA-APM measurements is applied and we further demonstrate that for the setup used, a deposition time of around 1 h is needed for deposition onto cells in an air–liquid interface chamber, using electrostatic deposition, to reach a toxicological relevant surface area dose

Parameter space mapping of InAs nanowire crystal structure

Crystal structure and defects have been shown to have a strong impact on III-Vnanowire properties. Recently, it was demonstrated that the issue of random stacking and polytypism in semiconductornanowires can often be controlled using accessible growth parameters (such as temperature, diameter, and V/III ratio). In addition, it has been shown that crystal phase can be tuned selectively between cubic zinc blende and hexagonal wurtzite within individual nanowires of III-V materials such as InAs. In order for such results to be generally applied to different growth setups, it is necessary to fully explore and understand the trends governing crystal phase dependencies on all accessible growth parameters, including how they relate to each other. In this study, the authors have systematically investigated the influence of temperature, diameter, V/III ratio, and total mass flow on the crystal structure of InAsnanowiresgrown by metal-organic vapor phase epitaxy over a broad parameter range. The authors observed that each of these accessible parameters can affect the resulting crystal structure, and that the trends for each parameter are affected by the magnitude of the others. The authors also noted that most of the parameter dependencies are nonlinear and, in fact, exhibit threshold values at which structure changes discontinuously. By optimizing each of the growth parameters, it is shown that pure ZB or pure WZ phase can be achieved for several different sets of growth conditions. The roles of nucleation kinetics, thermodynamics, and precursor chemistry are also discussed to compare the results to current nanowiregrowth models. The results in this work should facilitate comparison of data and transfer of knowledge between different growth systems and techniques, which, in turn, should lead to greater understanding of polytypism in nanowires and greater control and freedom in nanowire crystal phase engineering.This work was supported by the Nanometer Structure Consortium at Lund University nmC@LU, the Swedish Foundation for Strategic Research SSF, the Swedish Research Council VR, and the Knut and Alice Wallenberg Foundation