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The dissertation presents theoretical and experimental studies on the physical origin of the signal in photothermal microscopy of single particles. This noninvasive optical far field microscopy scheme allows the imaging and detection of single absorbing nanoparticles. Based on a heat-induced pertur- bation in the refractive index in the embedding medium of the nanoscopic absorber, a corresponding probe beam modification is measured and quantified. The method is well established and has been applied since its first demonstration in 2002 to the imaging and characterization of various absorbing particle species, such as quantum dots, single molecules and nanoparticles of different shapes. The extensive theoretical developments presented in this thesis provide the first quantitative assess- ment of the signal and at the same time enlarge its phenomenology and thereby its potential. On the basis of several approximation schemes to the Maxwell equations, which fundamentally gov- ern the interaction of light with inhomogeneities, several complementing models are devised which describe the photothermal signal both qualitatively and quantitatively. In succession an interdepen- dent and self-consistent set of theoretical descriptions is given and allows important experimental consequences to be drawn. In consequence, the photothermal signal is shown to correspond to the action of a nanoscopic (thermal) lens, represented by the spherically symmetric refractive index pro- file n(r) which accompanies the thermal expansion of the absorber’s environment. The achieved quantification allows the direct measurement of absorption cross-sections of nanoparticles. Further, a qualitatively new phenomenology of the signal is unraveled and experimentally demonstrated. The separate roles of the probing and the heating beams in photothermal microscopy is dismantled and the influence of their relative alignment shown to allow for a controlled adjustment of the effective detection volume. For the first time, both positive and negative signals are demonstrated to occur and to be the characteristic signature of the lens-like action on the probe beam. The detection of the probe beam’s modification is also shown to sensitively depend on the aperture used in the detection chan- nel, and a signal optimization is shown to be feasible. Also, a generalization of the detectable signal via the use of a quadrant photodiode is achieved. Specifically, measuring the far field beam deflec- tion the result of the beam passing the lens off-center manifests in a laterally split detection volume. Hereby, finally each classical photothermal spectroscopic techniques has been shown to possess its microscopic counterpart. Central to the understanding of this generalized and new phenomenology is a scalar wave-optical model which draws an analogy between the scattering of a massive particle wave-packet by a Coulomb potential and the deflection of a focused beam by a photonic potential connected with the thermal lens. The significance of the findings is demonstrated by its methodological implications on photother- mal correlation spectroscopy in which the diffusion dynamics of absorbing colloidal particles can be studied. The unique split focal detection volumes are shown to allow the sensitive measurement of a deterministic velocity field. Finally, the method is supplemented by a newly introduced sta- tistical analysis method which is capable of characterizing samples containing a heterogeneous size distribution.

Multifunctional plasmonic nanoparticles have shown extraordinary potential for near infrared photothermal and triggered-therapeutic release treatments of solid tumors. However, the accumulation rate of the nanoparticles in the target tissue, which depends on their capacity to escape the immune system, and the ability to efficiently and accurately track these particles in vivo are still limited. To address these challenges, we have created two different systems. The first one is a multifunctional nanocarrier in which PEG-coated gold nanorods were grouped into natural cell membrane vesicles from lung cancer cell membranes (A549) and loaded with β-lap (CM-β-lap-PEG-AuNRs). Our goal was to develop specific multifunctional systems for cancer treatment by using the antigens and the unique properties of the cancer cell membrane combined with photothermal properties of AuNRs and anticancer activity of β-lap. The results confirmed the assembly of PEG-AuNRs inside the vesicles and the irradiation with NIR laser led to disruption of the vesicles and release of the PEG-AuNRs and β-Lap. In vitro studies revealed an enhanced and synergic cytotoxicity against A549 cancer cells, which can be attributed to the specific cytotoxicity of β-Lap combined with heat generated by laser irradiation of the AuNRs. No cytotoxicity was observed in absence of laser irradiation. In the second system, MRI-active Au nanomatryoshkas were developed. These are Au core-silica layer-Au shell nanoparticles, where Gd(III) ions are encapsulated within the silica layer between the inner core and outer Au layer of the nanoparticle (Gd-NM). This theranostic nanoparticle retains its strong near infrared optical absorption properties, essential for in vivo photothermal cancer therapy, while simultaneously providing increased T1 contrast in MR imaging by concentrating Gd(III) within the nanoparticle. Measurements of Gd-NM revealed a substantially enhanced T1 relaxivity (r1 ~ 17 mM-1 s-1) even at 4.7 T, surpassing conventional Gd(III)-DOTA chelating agents (r1 ~ 4 mM-1 s-1) currently in clinical use. The observed relaxivities are consistent with Solomon-Bloembergen-Morgan (SBM) theory, describing the longer-range interactions between the Gd(III) and protons outside the nanoparticle. These novel multifunctional systems open the door for the development of more efficient nanoplatforms for diagnosis and treatment of cancer. / Nanopartículas plasmônicas multifuncionais têm revelado elevado potencial para fototermia na região (NIR) do infravermelho e liberação controlada de fármacos para o tratamento de tumores sólidos. No entanto, a taxa de acumulação das nanoparticulas no tecido alvo, que depende da capacidade delas de escapar do sistema imunológico, e a habilidade de rastrear de maneira efetiva essas partículas in vivo ainda são limitadas. Para superar essas barreiras, dois sistemas diferentes foram desenvolvidos. O primeiro corresponde a um nanocarreador multifunctional, onde nanobastões de ouro funcionalizados com PEG foram agrupados dentro de vesículas de membranas de células naturais originarias de células cancerígenas de pulmão (A549) conjugadas com β-Lap (CM-β-lap-PEG-AuNRs). Nosso principal objetivo foi desenvolver um sistema multifuncional especifico para tratamento de câncer utilizando os antígenos e propriedades únicas da membrana das células cancerígenas combinados com as propriedades fototérmicas dos AuNRs e a atividade anticancerígena da β-Lap. Os resultados confirmaram o agrupamento dos PEG-AuNRs dentro das CM e irradiação com o laser no NIR levou ao rompimento das vesículas e liberação dos AuNRs e β-Lap. Estudos in vitro revelaram uma elevada e sinérgica citotoxicidade contra células A549, que pode ser atribuída a combinação da especifica toxicidade da β-Lap com o calor gerado pelos AuNRs por meio da irradiação com laser. Nenhuma citotoxicidade significativa foi observada na ausência de irradiação com laser. No segundo sistema, nanomatryoshkas de Au ativas em MRI foram desenvolvidas. Elas consistem em um núcleo de Au, uma camada intersticial de sílica, onde os íons de Gd(III) são encapsulados, e uma camada externa de Au (Gd-NM). Esta nanopartícula teranóstica mantém as propriedades de elevada absorção óptica no NIR, enquanto simultaneamente fornece um elevado contraste T1 em imagem por ressonância magnética por meio da concentração dos íons de Gd(III) dentro da nanoparticula. Medidas de Gd-NM revelaram uma relaxividade elevada (r1 ~ 17 mM-1 s-1 ) a 4,7 T, superando os convencionais agentes quelantes de Gd(III)-DOTA (r1 ~ 4 mM-1 s-1) utilizados clinicamente. As relaxividades observadas são consistentes com a teoria Solomon-Bloembergen-Morgan (SBM), descrevendo as interações de longo alcance entre Gd(III) e prótons de H fora da partícula. Os novos sistemas multifuncionais desenvolvidos abrem oportunidades para o desenvolvimento de nanoplataformas mais eficientes para o diagnóstico e tratamento de câncer.

A espectroscopia foto-térmica tem sido largamente usada na investigação de propriedades térmicas e ópticas de materiais sólidos. Neste trabalho, desenvolvemos novas câmaras foto-térmicas as quais foram adaptadas para os estudos de materiais poliméricos. Estendemos o modelo desenvolvido por Mandelis para a espectroscopia fotopiroelétrica (PPES), incluindo nele um termo devido à reflexão de luz na interface amostra-detetor. A aplicação da técnica PPES em filmes de Poli(3-Butiltiofeno) não dopado nos permitiu obter sua condutividade e difusividade térmicas, como também seu gap de energia. Também aplicamos a técnica fotoacústica, com um flash de laser He-Ne, ao estudo de filmes de polímeros transparentes. Finalmente, desenvolvemos um método semi-empírico o qual significa a análise do sinal foto-térmico, quando ele é, principalmente, devido à difusão térmica. / Photothermal spectroscopies have been largely used in the investigation of thermal and optical properties of solids materials. In this work we developed new photothermal cells which were adapted for the study of polymerics materials. We also extended the model developed by Mandelis for the Photopyroeletric Spectroscopy (PPES), including in it a term due to the reflected light in the sample-detector interface. The application of the PPES technique in films of undopedpoly(3-butylthiophene) allowed us to obtain its thermal conductivity and diffusivity, as well as its gap energy. We also applied the photoacoustic technique, with a flash of He-Ne laser to study of transparent films of polymers. Finally we developed a semi-empiric method which simplifies the analysis of the photothermal signal, when it is mainly due to the thermal diffusion.

Orientador: Antonio Manoel Mansanares / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-09-26T17:20:21Z (GMT). No. of bitstreams: 1 Soffner_MaxErik_D.pdf: 4836506 bytes, checksum: af3488da1f4fb5e63235f4be7bcfa8bd (MD5) Previous issue date: 2010 / Resumo: O efeito magnetocalórico (EMC) tem sido amplamente estudado devido à sua possível aplicação em refrigeração magnética. A busca por materiais adequados se intensificou na última década, havendo demanda não só pela preparação de novos materiais como por sua completa caracterização. O objetivo deste trabalho é a aplicação das técnicas fototérmicas na caracterização de materiais que apresentam o efeito magnetocalórico. Primeiramente, versaremos sobre a Magnetoacústica. Trata-se de uma adaptação da técnica Fotoacústica e que se revelou promissora na área devido à sua alta sensibilidade e por deixar de lado questões sobre a validade da teoria envolvida nos métodos tradicionais. Recentemente, a detecção acústica do EMC foi explorada em outro trabalho do grupo, sendo proposto um modelo simples para determinar a variação adiabática de temperatura (? Tad). Aqui, exploramos a técnica em uma abordagem diferente, tendo como principal objetivo a determinação da variação isotérmica de entropia (? ST) para diferentes variações de campos magnéticos. A utilização de técnicas fototérmicas para a determinação do ? ST é a novidade deste trabalho. Os materiais analisados foram o gadolínio, que apresenta transição de fase magnética de 2a ordem e um composto da família Gd5 (Ge1-x Si x) 4, que apresenta transição de fase magnética-cristalográfica de 1a ordem. Os resultados positivos mostraram uma maneira alternativa na caracterização do EMC, trazendo vantagens sobre os métodos tradicionais em várias situações. Em paralelo, a técnica de ressonância ferromagnética fototermicamente modulada (PM-FMR) foi utilizada no estudo de filmes finos de gadolínio. O crescente interesse em filmes finos nos dias de hoje requer novos estudos sendo propícia a caracterização dos mesmos por diferentes técnicas. Através da PM-FMR, foi possível observar as transições de fase magnéticas para filmes com diferentes espessuras e tratamentos térmicos, depositados sobre substratos de quartzo e silício. Os resultados foram comparados com medidas tradicionais de ressonância ferromagnética e de magnetização. Apesar dos resultados serem, de modo geral, conhecidos o maior interesse está na evolução da técnica. Por possuir resolução espacial na escala de micrometros, permite obter imagens magnéticas, as quais não são possiveis pelos métodos tradicionais / Abstract: The magnetocaloric effect (MCE) has been widely studied because of its possible application in magnetic refrigeration. The search for suitable materials has intensified over the last decade, with a demand not only for the preparation of new materials but also for their complete characterization. The aim of this work is to apply the photothermal techniques to the characterization of materials with magnetocaloric effects. First, we will discuss the Magnetoacoustic technique. This is an adaptation of the Photoacoustic techinique, and it has proved to be promising in the magnetocaloric field due to its high sensitivity. Moreover, this technique is not limited by the validity of the theories involved in traditional methods. Recently, the acoustic detection of MCE was explored in another work of this research group and a simple model for determining the adiabatic temperature variation (? Tad) was proposed. Here, we used a different approach to determine the isothermal entropy change ( ? ST ) the ? ST is the novelty of this work. The analyzed materials were gadolinium, which shows a second order magnetic phase transition, and a Gd5 (Ge1-x Six) 4 family compound, which has a first order magnetic-crystallographic phase transition. The positive results showed an alternative way to characterize the MCE, proving to have advantages over traditional methods in many cases. In parallel, the photothermally modulated ferromagnetic resonance technique (PMFMR) was used in the study of thin films of gadolinium. Currently, there is a growing interest in thin films, and this has encouraged researches to use different characteriza tion techniques. Using PM-FMR, we observed the magnetic phase transitions for the films with different thicknesses and thermal treatments, deposited on quartz and silicon substrates. Our findings were compared with traditional results of ferromagnetic resonance and magnetization. Although the overall results are known, the main interest is in the evolution of the technique. The spatial resolution in the micrometer scale allows for magnetic images, which are not possible using traditional methods / Doutorado / Física da Matéria Condensada / Doutor em Ciências

To investigate the interaction between nanoparticles and electromagnetic waves, a numerical simulation model based on FEM was built in this thesis. Numerical simulation is an important auxiliary research method besides experiments. The optical properties of nanoparticles consist of scattering, absorption, and extinction, and in the case of nanoparticle suspension, the transmission is also involved. This thesis addressed two typical applications based on the established model, one was regarding the nanofluids for solar energy harvesting, and the other was regarding the optical properties of atmospheric soot. In the case of the nanofluids solar energy harvesting, the established model provided a convenient and rapid screening of potential nanoparticles and nanofluids candidates for solar energy harvesting. A core-shell structure nanoparticle, using Cu as the core material in a diameter of 90 nm coated with 5 nm thickness graphene, exhibited a better photothermal property under the solar radiation. In the second case regarding atmospheric soot, the established model provided an efficient method for understandings on the optical properties and warming effects of realistic soot particles. It was found that the sizes and material characteristics of soot, would greatly affect their scattering and absorption of light. Moreover, two submodels were introduced and integrated, which can better predict behaviors of real atmospheric soot involving their core-shell structures (moisture or organic condensates) and their fractal agglomerate structures. In conclusion, the established model helps to understand the interaction between nanoparticles and electromagnetic waves, which shows great potentials of wide applications.

The research in this dissertation presents Pulsed-Laser Excited photothermal studies of optical glasses and cylindrical sample cell. First, a study of a photothermal lens experiment and the finite element analysis modeling for commercial colored glass filters is done. The ideal situation of a semiinfinite cylinder approximate model used to describe the photothermal lens experiment requires the boundary condition that there is no transfer of heat from the glass to surrounding when the glass is excited with a laser. The finite element analysis modeling for photothermal signal with coupling heat with surrounding shows the thermal heat transfer between the glass surface and the coupling fluid. This work shows that the problem can be resolved by using pulsed laser excitation where the signal decay is faster than the heat diffusion to the surrounding, and finite element analysis modeling to correct the likely deviation from semi-infinite cylinder approximate models. Second, finite element analysis modeling of a photothermal lens signal also shows that there are slow and fast components of signals, which are detected by using a fast response detector and is explained to be due to the axial and radial transfer of heat. A semi-analytical theoretical description of the mode-mismatched continuous and pulsedlaser excitation thermal lens effect that accounts for heat coupling both within the sample and out to the surrounding is presented. The results are compared with the finite element analysis solution and found to be an excellent agreement. The analytical model is then used to quantify the effect of the heat transfer from the sample surface to the air coupling fluid on the thermal lens signal. The results showed that the air signal contribution to the total photothermal lens signal is significant in many cases. Third, surface deformation phenomena are quite common when glasses are excited by laser. Finite element analysis modeling of a surface deformation phenomenon is done. A thermal lens reflection experiment is carried out and results are compared with modeling. The effect of coupling fluid on sample is taken in to account to make more accurate measurement of thermophysical properties of solid sample. Fourth, a novel apparatus for performing photothermal lens spectroscopy is described which uses a low-volume cylindrical sample cell with a pulsed excitation laser. Finite element analysis modeling is used to examine the temperature profile and the photothermal signal. The result of finite element analysis is compared with the experimental result. The experimental photothermal lens enhancement has been found to be that predicted from theory within experimental error.

In frequency-domain photothermal radiometry (FD-PTR) a low-power intensity-modulated optical excitation generates thermal-wave field inside the sample and the subsequent infrared radiation from the sample is analyzed to detect material’s inhomogeneities. The non-contact nature of FD-PTR makes it very suitable for non-destructive evaluation of broad range of materials. Moreover, the methodology is based on intrinsic contrast of light absorption which can be used as a diagnostic tool for inspection of malignancy in biological tissues. Nevertheless, the bottom line is that the physics of heat diffusion allows for a highly damped and dispersive propagation of thermal-waves. As a result, the current FD-PTR modalities suffer from limited inspection depth and poor axial/depth resolution. The main objective of this thesis is to show that using alternative types of modulation schemes (such as linear frequency modulation and binary phase coding) and radar matched filter signal processing, one can obtain localized responses from inherently diffuse thermal wave fields. In this thesis, the photothermal responses of turbid, transparent, and opaque media to linear frequency modulated and binary phase coded excitations are analytically derived. Theoretical simulations suggest that matched-filtering in diffusion-wave field acts as constructive interferometry, localizing the energy of the long-duty excitation under a narrow peak and allowing one to construct depth resolved images. The developed technique is the diffusion equivalent of optical coherence tomography and is named thermal coherence tomography. It was found that the narrow-band binary phase coded matched filtering yields optimal depth resolution, while the broad-band linear frequency modulation can be used to quantify material properties through the multi-parameter fitting of the experimental data to the developed theory. Thermophotonic detection of early dental caries is discussed in detail as a potential diagnostic application of the proposed methodologies. The performance of the diagnostic system is verified through a controlled demineralization protocol as well as in teeth with natural caries.