Search results for " microscopy"
showing 10 items of 1617 documents
Structural studies of dielectric polymer nanocomposites
2013
A constant need for the development of new and superior materials is always present; for example, a better electrical insulator would enable more efficient use of electrical power. Polymeric nanocomposites, i.e. nanodielectrics, are thought to have unique electrical properties. The basic chemical constitution of a material alone fails to provide an understanding of how desired properties of a material originate or predict the long term behavior of a material. We need to define the structure behind the functionality of a material. To do that, the structure of the material must be studied on several scales. This research was part of the Finnish Funding Agency for Technology and Innovation (TE…
Nanoscale mechanical characterization of polymers by atomic force microscopy (AFM) nanoindentations: Viscoelastic characterization on a model material
2009
The Atomic Force Microscope (AFM), apart form its conventional use as a microscope, is also used for the characterization of the local mechanical properties of polymers. In fact, the elastic characterization of purely elastic materials using this instrument can be considered as a well assessed technique while the challenge remains the characterization of the viscoelastic mechanical properties. In particular, one finds the mechanical behavior changing when performing indentations at different loading rates, i.e., on different time scales. Moreover, this apparent viscoelastic behavior can also be due to complex contact mechanics phenomena, with the onset of plasticity and long-term viscoelast…
Preparation of Nd:YAG Nanopowder in a Confined Environment
2007
Nanopowder of yttrium aluminum garnet (YAG, Y3Al5O12) doped with neodymium ions (Nd:YAG) was prepared in the water/cetyltrimethylammonium bromide/1-butanol/n-heptane system. Aluminum, yttrium, and neodymium nitrates were used as starting materials, and ammonia was used as a precipitating agent. Coprecipitate hydroxide precursors where thermally treated at 900 degrees C to achieve the garnet phase. The starting system with and without reactants was characterized by means of the small-angle neutron scattering technique. The system, without reactants, is constituted by a bicontinuous structure laying near the borderline with the lamellar phase region. The introduction of nitrates stabilizes th…
Impact of pharmacological and environmental manipulations on neuronal structural plasticity and dynamics
2017
El sistema nervioso de vertebrados es uno de los más estudiados, aunque peor comprendidos, del organismo de mamíferos. Desde que Ramón y Cajal postuló su teoría celular de este sistema (Ramón y Cajal 1909), la neurona se ha postulado como su unidad funcional. Sin embargo, durante las últimas décadas se ha revolucionado la visión que se tenía de éste. Una de las percepciones más asentadas era que, tras el desarrollo embrionario, el sistema nervioso se mantenía inmutable. Sin embargo, ahora sabemos que diferentes formas de plasticidad gobiernan su adaptación, que son necesarias para importantes procesos del día a día, tales como el aprendizaje y la memoria (Smythies 2002; Berlucchi and Buchte…
Thermal noise limit for ultra-high vacuum noncontact atomic force microscopy
2013
The noise of the frequency-shift signal Δf in noncontact atomic force microscopy (NC-AFM) consists of cantilever thermal noise, tip–surface-interaction noise and instrumental noise from the detection and signal processing systems. We investigate how the displacement-noise spectral density dz at the input of the frequency demodulator propagates to the frequency-shift-noise spectral density dΔf at the demodulator output in dependence of cantilever properties and settings of the signal processing electronics in the limit of a negligible tip–surface interaction and a measurement under ultrahigh-vacuum conditions. For a quantification of the noise figures, we calibrate the cantilever displacemen…
Modification of a commercial atomic force microscopy for low-noise, high-resolution frequency-modulation imaging in liquid environment.
2011
A key issue for high-resolution frequency-modulation atomic force microscopy imaging in liquids is minimizing the frequency noise, which requires a detailed analysis of the corresponding noise contributions. In this paper, we present a detailed description for modifying a commercial atomic force microscope (Bruker MultiMode V with Nanoscope V controller), aiming at atomic-resolution frequency-modulation imaging in ambient and in liquid environment. Care was taken to maintain the AFMs original stability and ease of operation. The new system builds upon an optimized light source, a new photodiode and an entirely new amplifier. Moreover, we introduce a home-built liquid cell and sample holder …
Direct Visualization of Molecule Deprotonation on an Insulating Surface
2012
Elucidating molecular-scale details of basic reaction steps on surfaces is decisive for a fundamental understanding of molecular reactivity within many fields, including catalysis and on-surface synthesis. Here, the deprotonation of 2,5-dihydroxybenzoic acid (DHBA) deposited onto calcite (101;4) held at room temperature is followed in situ by noncontact atomic force microscopy. After deposition, the molecules form two coexisting phases, a transient striped phase and a stable dense phase. A detailed analysis of high-resolution noncontact atomic force microscopy images indicates the transient striped phase being a bulk-like phase, which requires hydrogen bonds between the carboxylic acid moie…
New advances in high-resolution optical microscopy
2015
La microscopio ía tiene como nalidad observar muestras que no pueden distinguirse a simple vista por el ojo humano dado que el tamaño de ellas es menor que su l mite de resoluci on. Un microscopio produce una imagen ampliada de la muestra a analizar. Debido a que la microscopía es un instrumento b asico para la ciencia de la vida y de los materiales, en esta Tesis se desarrolla un estudio exhaustivo de la microscopía óptica. Los microscopios opticos se pueden con gurar de diferentes formas para producir im agenes con diferentes caracter sticas. El microscopio de campo amplio, el m as simple de todos, presenta algunas limitaciones que debe ser superadas para obtener im agenes de mayor calida…
Synthesis, Optical, and Morphological Studies of ZnO Powders and Thin Films Fabricated by Wet Chemical Methods
2020
Zinc oxide nanoparticles were prepared from Zn5(CO3)2(OH)6 precursor, capped with poly(vinylpyrrolidone) (PVP), and annealed at 600 °
Optical and structural properties of Al 2 O 3 /ZnO nanolaminates deposited by ALD method
2014
International audience; We report on the investigation of optical and structural properties of Al2O3/ZnO nanolaminates. The nanolaminates were deposited on Si and glass substrates by Atomic layer deposition method. Structural properties of nanolaminates were studied by SEM, GIXRD, and AFM. Optical characterization was performed by transmittance and photoluminescence spectroscopy. Complex analysis of monolayer properties was done by ellipsometry. Optical constants for Al2O3 and ZnO monolayer were calculated.