Synthesis and Characterization of Nanoparticles

Inhaltsangabe:Introduction: The development of small and smallest particle is one of today s key features in modern science. The goal is to form materials with improved properties than their classical ancestors with just a fractional amount of raw material. Another key feature of nanoparticles is their different, and sometimes unexpected, behavior concerning reactivity, compared with their bulk materials. Because of this, nanoparticles have a wide range of applications, especially in the field of catalysis. Here, characteristics of nanoparticles - more edges, corners, defects or oxygen vacancies are used to obtain a high performance of the catalysts. Nanoscaled particles also exhibit larger surface area and higher metal dispersion, which further contributes to the catalytic possibilities. To gain such particles, two different pathways are given: first, there is the so-called top down pathway, considered as further developments of micro technology, where physical preparation methods like lithography are used. The second way is the bottom up method where self-assembling systems, formed by surfactants, are used. Concerning gold nanoparticles, it is reported that the use of C16TAB at specified conditions, gives gold nanorods with a sharp size-distribution because the direction of growth is predetermined. Being a cationic surfactant, C16TAB affects the electrochemical potentials and introduces bromide-ions as an additional species to the reaction. To achieve gold nanoparticles from aqueous HAuCl4-solutions, the above-mentioned method needs a separate reducing agent such as ascorbic acid (Asc0), NaBH4 or N2H4. A way of synthesizing spherical gold nanoparticles is the use of Nd:YAG laser with a salt induced agglomeration. By modifying the formulation of the salt solution, different sizes are obtained. This way of synthesis, a combination of physical top-down and self-assembling bottom-up processes, can be modified by adding surfactants, like PEG, to optimize size distribution and physical characteristics, like UV-Vis absorption. This method is an elegant way of synthesis; however, problems may occur by functionalizing the particles, because of a high salt content. Here, a high influence of purity, concentration and composition to the size and shape of gold nanoparticles might be given. Therefore, a route of synthesis is needed, which shows high efficiency in producing gold nanoparticles and in stabilizing them with a manageable amount of [...]

Résumé
Inhaltsangabe:Introduction:The development of small and smallest particle is one of today’s key features in modern science. The goal is to form materials with improved properties than their ‘classical’ ancestors with just a fractional amount of raw material. Another key feature of nanoparticles is their different, and sometimes unexpected, behavior concerning reactivity, compared with their bulk materials. Because of this, nanoparticles have a wide range of applications, especially in the field of catalysis.Here, characteristics of nanoparticles - more edges, corners, defects or oxygen vacancies – are used to obtain a high performance of the catalysts. Nanoscaled particles also exhibit larger surface area and higher metal dispersion, which further contributes to the catalytic possibilities.To gain such particles, two different pathways are given: first, there is the so-called ‘top down’ pathway, considered as further developments of micro technology, where physical preparation methods like lithography are used. The second way is the ‘bottom up” method where self-assembling systems, formed by surfactants, are used. Concerning gold nanoparticles, it is reported that the use of C16TAB at specified conditions, gives gold nanorods with a sharp size-distribution because the direction of growth is predetermined. Being a cationic surfactant, C16TAB affects the electrochemical potentials and introduces bromide-ions as an additional species to the reaction. To achieve gold nanoparticles from aqueous HAuCl4-solutions, the above-mentioned method needs a separate reducing agent such as ascorbic acid (Asc0), NaBH4 or N2H4. A way of synthesizing spherical gold nanoparticles is the use of Nd:YAG laser with a salt induced agglomeration. By modifying the formulation of the salt solution, different sizes are obtained. This way of synthesis, a combination of physical top-down and self-assembling bottom-up processes, can be modified by adding surfactants, like PEG, to optimize size distribution and physical characteristics, like UV-Vis absorption. This method is an elegant way of synthesis; however, problems may occur by functionalizing the particles, because of a high salt content. Here, a high influence of purity, concentration and composition to the size and shape of gold nanoparticles might be given. Therefore, a route of synthesis is needed, which shows high efficiency in producing gold nanoparticles and in stabilizing them with a manageable amount of []