Abstract
Upon irradiating noble metal nanoparticles with light, unique optical phenomena can occur, such as resonantly enhanced light-scattering and light-absorption, or a tremendous enhancement of the exciting optical field close to the surface of the nanoparticles. These phenomena rely on the excitations of collective oscillations of the conduction electrons within a nanoparticle. The optical properties of a nanoparticle are determined by the resonance frequency of these so-called plasmon oscillations. This resonance frequency and the light-scattering spectrum of a nanoparticle depend (among other effects) on the dielectric environment of the particle. Due to this effect, noble metal nanoparticles can be applied for local optical sensing of chemical substances. The large light-absorption properties of a nanoparticle also enable the usage of light-irradiation to deposit heat in the nanoparticle in a selective and highly localized manner. Therefore, a local temperature increase can be induced in the nanoparticle and its immediate environment. This temperature increase could be used to trigger chemical or biological reactions, or it could be used for a selective hyperthermia of biological material. These and further possible applications rely on the detection or the systematic excitation of interactions between the noble metal nanoparticle and its environment. These interactions are the central subject
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Citation Formats
Reismann, Maximilian.
Interactions of noble metal nanoparticles with their environment; Wechselwirkungen von Edelmetallnanopartikeln mit ihrer Umgebung.
Germany: N. p.,
2009.
Web.
Reismann, Maximilian.
Interactions of noble metal nanoparticles with their environment; Wechselwirkungen von Edelmetallnanopartikeln mit ihrer Umgebung.
Germany.
Reismann, Maximilian.
2009.
"Interactions of noble metal nanoparticles with their environment; Wechselwirkungen von Edelmetallnanopartikeln mit ihrer Umgebung."
Germany.
@misc{etde_21317708,
title = {Interactions of noble metal nanoparticles with their environment; Wechselwirkungen von Edelmetallnanopartikeln mit ihrer Umgebung}
author = {Reismann, Maximilian}
abstractNote = {Upon irradiating noble metal nanoparticles with light, unique optical phenomena can occur, such as resonantly enhanced light-scattering and light-absorption, or a tremendous enhancement of the exciting optical field close to the surface of the nanoparticles. These phenomena rely on the excitations of collective oscillations of the conduction electrons within a nanoparticle. The optical properties of a nanoparticle are determined by the resonance frequency of these so-called plasmon oscillations. This resonance frequency and the light-scattering spectrum of a nanoparticle depend (among other effects) on the dielectric environment of the particle. Due to this effect, noble metal nanoparticles can be applied for local optical sensing of chemical substances. The large light-absorption properties of a nanoparticle also enable the usage of light-irradiation to deposit heat in the nanoparticle in a selective and highly localized manner. Therefore, a local temperature increase can be induced in the nanoparticle and its immediate environment. This temperature increase could be used to trigger chemical or biological reactions, or it could be used for a selective hyperthermia of biological material. These and further possible applications rely on the detection or the systematic excitation of interactions between the noble metal nanoparticle and its environment. These interactions are the central subject of this thesis. Particular attention is paid to photothermal interactions. An interesting question is to what extend a nanoparticle-supported, photothermally-induced temperature rise can be applied to trigger a biomolecular reaction in a spatially confined volume. By carefully adjusting the photothermal treatment, one aims at affecting the molecules without damaging their chemical functionality. The photothermal interaction is addressed in two projects: First, networks built up by gold nanoparticles are investigated. In these networks, double-stranded DNA-molecules are used to interlink and assemble single nanoparticles. A photothermally-induced temperature rise aims at a collective breaking of these DNA-interlinkages, which results in a dissociation of the networks. Due to the high spatial particle concentration, an electromagnetic coupling of the plasmons occurs in the nanoparticles. This coupling results in a spectral shift of the light-scattering signal of the nanoparticle network with respect to the signal of spatially separated particles. This effect is used for the spectroscopic detection of network assembling and network dissociation. A second project demonstrates a nanoparticle-supported photothermal control of an enzymatic reaction. For this purpose, enzymes are chemically attached to the surface of gold nanospheres. These nanospheres then become subject to a photothermal treatment. By using the temperature-dependent catalytic activity of the enzymes, the photothermal treatment controls the reaction kinetics of an enzymatic reaction that takes place in the environment of the nanoparticles. Furthermore, this thesis deals with the dependency of the light-scattering signal of noble-metal nanoparticles on their dielectric and chemical environment. For designing sensing applications that rely on this dependency, it is of particular importance to identify the interactions that occur between a nanoparticle and its environment, and to investigate how these interactions affect the spectral characteristics of the nanoparticle. In this work, the interactions between single gold nanospheres and the sample substrate used for the deposition of the spheres are investigated. For this purpose, an optical tweezer is combined with a microspectroscopy setup. This combined setup enables to immobilize single gold nanospheres within an aqueous suspension, and to subsequently deposit the nanospheres onto a sample substrate. The changes in the light-scattering spectrum due to this deposition process can be measured on the same nanoparticle. The main advantage of the described procedure is the lack of superposition of the changes in the recorded spectra by spectral contributions of shape and size of the nanoparticle. This simplifies the interpretation of the recorded spectra considerably. An essential requirement for the application of noble-metal nanoparticles in medical technology consist of their tunability into the near-infrared spectral region. In this spectral region, the human tissue is more transparent to light irradiation than in the visible region, which allows for using light irradiation to affect nanoparticles in vivo. Elongated gold nanoparticles (nanorods) are promising candidates for this task as their resonance frequency can be tuned over a wide spectral region by varying their size and their aspect ratio. Damping of the plasmon oscillation is an important physical origin for this dependency on shape and size. In this thesis, a contribution of the plasmon damping is investigated that is caused by electronic-scattering of the oscillating conduction electrons at the nanoparticle surface. For this investigation, light-scattering spectra of single gold nanorods are recorded in a systematic approach. The large enhancement of optical fields at the surface of nanoparticles can be used to excite non linear optical phenomena, for example Raman scattering. In this thesis, the construction of a setup is presented that aims at using this enhancement effect for the detection of Raman-scattering signals. This setup is tested, and the ability to enhance the detection of Raman signals is compared to different nanostructured samples. (orig.)}
place = {Germany}
year = {2009}
month = {Dec}
}
title = {Interactions of noble metal nanoparticles with their environment; Wechselwirkungen von Edelmetallnanopartikeln mit ihrer Umgebung}
author = {Reismann, Maximilian}
abstractNote = {Upon irradiating noble metal nanoparticles with light, unique optical phenomena can occur, such as resonantly enhanced light-scattering and light-absorption, or a tremendous enhancement of the exciting optical field close to the surface of the nanoparticles. These phenomena rely on the excitations of collective oscillations of the conduction electrons within a nanoparticle. The optical properties of a nanoparticle are determined by the resonance frequency of these so-called plasmon oscillations. This resonance frequency and the light-scattering spectrum of a nanoparticle depend (among other effects) on the dielectric environment of the particle. Due to this effect, noble metal nanoparticles can be applied for local optical sensing of chemical substances. The large light-absorption properties of a nanoparticle also enable the usage of light-irradiation to deposit heat in the nanoparticle in a selective and highly localized manner. Therefore, a local temperature increase can be induced in the nanoparticle and its immediate environment. This temperature increase could be used to trigger chemical or biological reactions, or it could be used for a selective hyperthermia of biological material. These and further possible applications rely on the detection or the systematic excitation of interactions between the noble metal nanoparticle and its environment. These interactions are the central subject of this thesis. Particular attention is paid to photothermal interactions. An interesting question is to what extend a nanoparticle-supported, photothermally-induced temperature rise can be applied to trigger a biomolecular reaction in a spatially confined volume. By carefully adjusting the photothermal treatment, one aims at affecting the molecules without damaging their chemical functionality. The photothermal interaction is addressed in two projects: First, networks built up by gold nanoparticles are investigated. In these networks, double-stranded DNA-molecules are used to interlink and assemble single nanoparticles. A photothermally-induced temperature rise aims at a collective breaking of these DNA-interlinkages, which results in a dissociation of the networks. Due to the high spatial particle concentration, an electromagnetic coupling of the plasmons occurs in the nanoparticles. This coupling results in a spectral shift of the light-scattering signal of the nanoparticle network with respect to the signal of spatially separated particles. This effect is used for the spectroscopic detection of network assembling and network dissociation. A second project demonstrates a nanoparticle-supported photothermal control of an enzymatic reaction. For this purpose, enzymes are chemically attached to the surface of gold nanospheres. These nanospheres then become subject to a photothermal treatment. By using the temperature-dependent catalytic activity of the enzymes, the photothermal treatment controls the reaction kinetics of an enzymatic reaction that takes place in the environment of the nanoparticles. Furthermore, this thesis deals with the dependency of the light-scattering signal of noble-metal nanoparticles on their dielectric and chemical environment. For designing sensing applications that rely on this dependency, it is of particular importance to identify the interactions that occur between a nanoparticle and its environment, and to investigate how these interactions affect the spectral characteristics of the nanoparticle. In this work, the interactions between single gold nanospheres and the sample substrate used for the deposition of the spheres are investigated. For this purpose, an optical tweezer is combined with a microspectroscopy setup. This combined setup enables to immobilize single gold nanospheres within an aqueous suspension, and to subsequently deposit the nanospheres onto a sample substrate. The changes in the light-scattering spectrum due to this deposition process can be measured on the same nanoparticle. The main advantage of the described procedure is the lack of superposition of the changes in the recorded spectra by spectral contributions of shape and size of the nanoparticle. This simplifies the interpretation of the recorded spectra considerably. An essential requirement for the application of noble-metal nanoparticles in medical technology consist of their tunability into the near-infrared spectral region. In this spectral region, the human tissue is more transparent to light irradiation than in the visible region, which allows for using light irradiation to affect nanoparticles in vivo. Elongated gold nanoparticles (nanorods) are promising candidates for this task as their resonance frequency can be tuned over a wide spectral region by varying their size and their aspect ratio. Damping of the plasmon oscillation is an important physical origin for this dependency on shape and size. In this thesis, a contribution of the plasmon damping is investigated that is caused by electronic-scattering of the oscillating conduction electrons at the nanoparticle surface. For this investigation, light-scattering spectra of single gold nanorods are recorded in a systematic approach. The large enhancement of optical fields at the surface of nanoparticles can be used to excite non linear optical phenomena, for example Raman scattering. In this thesis, the construction of a setup is presented that aims at using this enhancement effect for the detection of Raman-scattering signals. This setup is tested, and the ability to enhance the detection of Raman signals is compared to different nanostructured samples. (orig.)}
place = {Germany}
year = {2009}
month = {Dec}
}