The importance of studying the physico-chemical properties of nano-dimensional materials has gained significant attention in the fields of semiconductors, pharmaceuticals, materials science, and atmospheric chemistry owing to the differences in physical properties between macro- and nano-dimensional solids. Nonetheless, direct studies of physical properties of materials at nanoscale is limited in part due to their inherent size constraints and experimental limitations. However, development of atomic force microscopy (AFM) led to the implementation of methods to characterize a wide range of physical properties, including – but not limited to – mechanical properties, electrical properties, viscoelastic properties, and surface tension. Herein, the dissertation focuses on AFM-based method development for characterization of atmospheric particles as well as understanding the relationship between structure and physical properties of organic solids at both macro- and nano-dimensions. In the atmospheric chemistry realm, the combined aerosol effect on the climate and environment has significant uncertainty in part due to lack of direct characterization of their physico-chemical properties. The difficulty in assessing the physical and chemical properties arises due to the presence of diversified aerosol sources, which in turn influences the size, morphology, phase states and chemical compositions. Sea spray aerosols (SSAs) are the second-largest source of aerosols in the atmosphere. Studying SSAs – especially in submicrometer-dimensions – requires high-resolution microscopy techniques such as AFM. AFM can be used for imaging of individual aerosols, quantifying organic volume fraction for core-shell morphologies, measuring water uptake, quantifying surface tension of individual droplets, and measuring mechanical and viscoelastic properties of materials. Herein, we employed AFM-based morphology and force spectroscopy studies to correlate the 3D morphology, phase state, and viscoelastic properties of selected single-component chemical systems found in sea spray aerosol (SSA). We established a quantitative framework toward differentiation of the solid, semisolid and liquid phase states of individual particles by utilizing both relative indentation depth (RID) and viscoelastic response distance (VRD) data obtained from the force−distance plots. Moreover, we established a semi-quantitative and quick phase assessment by measuring the aspect ratio (AR) that refers the extent of particle spreading as a result of impaction. Overall, the established AFM-based quantitative and semi-quantitative phase identification method can be utilized to assess the phases of aerosols irrespective of chemical identity. Next, we investigated the factors that may control the electrical and mechanical properties of pharmaceutical and organic semiconducting materials in nano- and macro-dimensions. Understanding the structure-property relationship of materials, especially in the nano-dimension, is necessary for proper drug design and development of organic semiconducting materials. In this context, cocrystals provide a means to modulate the physico-chemical properties of organic solids. For example, the modulation of the mechanical properties is important in the pharmaceutical industry for improving the tabletability. The mechanical properties may be affected by packing arrangement, interaction strength and type, and atomic and chemical composition. Herein, we report the influence of alkane and alkene functional groups on the mechanical properties of organic solids based on salicylic acid (SA). The approach affords both isostructural and polymorphic solids. The isostructural alkane functional solid exhibits a two-fold larger Young’s modulus (YM) compared to the cocrystal with the alkene, where the YM refers to the stiffness of the material. Here, the higher YM values are attributed to the presence of a bifurcated weak C-H···O interactions involving the alkane and neighboring SA molecules. On the other hand, in the case of alkene polymorphisms, molecular packing with column arrangement shows higher YM values compared to the herringbone arrangements. Thus, functional groups and crystal arrangements influence the stiffness of the solid organic cocrystals. Moreover, we report the modulation of mechanical properties of salicylic acid (SA) through cocrystallization by variation of propane and butane functionality with bipyridine coformers. We show that the variation of propane and butane functionality in bipyridine coformer with salicylic acid leads to synthesis of cocrystal and salt-cocrystal, respectively. The AFM nanoindentation study revealed that the Young’s modulus values follow the order salicylic acid < cocrystal << salt-cocrystal. The highest Young’s modulus values of the salt-cocrystal, among the studied systems, are attributed to the presence of strong N+–H···O– and O–H···O– interactions. On the other hand, higher Young’s modulus values of the propane-based cocrystal compared to the macro-dimensional salicylic acid are attributed to the stronger O–H ···N hydrogen bonding. Thus, homologous alkane functional groups can influence the mechanical properties of the organic solid crystals. Additionally, in situ solid-solid polymorphic phase transformation and nucleation of a metastable and elusive polymorph of SA cocrystals in combination with 4,4’-bipyridine were studied. Understanding the solid-solid phase transformations and nucleation mechanisms are important for proper control over the parameters associated with the synthesis of targeted crystalline solids with desired crystal structure. Using in situ powder X-ray diffraction (PXRD) and terahertz time domain spectroscopy (THz-TDS) data we showed that the Form II polymorph transforms to Form I over time. AFM imaging and nanoindentation techniques were utilized to follow and quantify in real-time the solid-solid polymorphic transformation of the metastable Form II to the thermodynamically stable Form I on a single crystal basis. AFM in situ single crystal data revealed that the metastable Form II has a rod-shaped morphology and relatively high elasticity (Young’s modulus), which transforms to prism-shaped nanocrystals of much smaller sizes with significantly reduced elasticity. The AFM imaging reveals that the single crystals on the order of 80-150 nm to undergo catastrophic changes in morphology that are consistent with cracking and popping owing to a release of mechanical stress during the transformation. The nucleation mechanism for the polymorphic transformation is not spatially localized and occurs over the entire crystal surface. The higher mechanical properties of the metastable Form II is due to the presence of the additional interlayer C-H···O interactions. Furthermore, we have studied the electrical properties of boron-based cocrystals. More specifically, cocrystallization of a nonconductive 2,4-difluorophenylboronic ester catechol adduct of a 4,4’-bipyridine (BEA) host with two aromatic semiconducting guests (pyrene and tetrathiafulvalene) generated conductive cocrystals with variable charge carrier mobilities. Charge carrier mobilities of the cocrystals with either pyrene or tetrathiafulvalene were measured using conducting probe AFM (CP-AFM). The incorporation of π-rich aromatic guests through face-to-face and edge-to-face π-contacts results in electrically conductive cocrystals. The cocrystal with tetrathiafulvalene as a guest shows approximately 7 times higher charge carrier mobility than the cocrystal with pyrene. Overall, the current dissertation demonstrates the AFM-based method development and applications towards materials characterization to measure the morphological, electrical, mechanical, and phase-states at both nano- and macro-dimensions. The high spatial precision of the methods developed enables us to better understand the controlling factors for materials design and processing across nano- and macro-dimensions.

This dissertation is related to the understanding of catalytic reactions of metal oxides. For several decades, the surfaces and bulk of materials have been probed to determine additional properties that relate to photocatalytic applications. This investigation furthers these efforts by the (a) modification of a metal oxide surface to isolate known influences of chemical properties and (b) proposing and utilizing a novel methodology for attribution of photocatalytic activity to a discernable influence. For the first effort, by effectively utilizing a known technique for a new application on a metal oxide, such isolations can be made despite unfavorable states. For the second effort, a reduction in the influence of surface states for metal oxides is effectively performed, providing the isolation of influences originating from the bulk. The challenge with such a proposal is verifying such bulk states have been adequately isolated as external influences would obviously distort any conclusions. Thus, techniques to both create such bulk states and eliminate unwanted combinations thereof are additionally required and must be provided for. Lastly, a determination of the photocatalytic activity is made to these states and results are provided.

Perylene-based materials, including charge-transport discotic liquid crystals and charge-transfer long-wavelength absorbing chromophores, for potential organic electronic and optoelectronic applications, were designed, synthesized and characterized. Two types of discotic liquid crystals, perylene diimides and coronene diimides, can form columnar liquid crystalline phases over a wide temperature range; many of them can have room-temperature liquid crystalline phases after cooling from isotropic liquid. Their charge transport properties were studied by space-charge limited current method; high charge carrier mobilities, with the highest being up to 6.6 cm2/Vs, were found in liquid crystalline phases of these materials under ambient conditions. Structural variables, including aromatic cores and side groups, were examined to get a certain degree of understanding of charge transport properties in these discotic liquid crystals. It was found that mesophase order can have an important effect on charge carrier mobilities. The discotic liquid crystals with high charge carrier mobilities are serious candidates for use in large-area low-cost applications such as solar cells. Long-wavelength, highly absorbing chromophores, featuring donor-substituted perylene diimides, were generated by a combination of charge-transfer process and conjugation extension. The charge-transfer chromophores are expected to lead to further investigation on their potentials as sensitizers in Grtzel solar cells.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第19007号 / 工博第4049号 / 新制||工||1623 / 31958 / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 伊藤 紳三郎, 教授 赤木 和夫, 教授 辻井 敬亘 / 学位規則第4条第1項該当

Due to their unique properties organic semiconductors may be used for various applications in organic optoelectronic devices: light emitting devices, lasers, field-effect transistors, photovoltaic cells and etc. Despite high perspectives of organic semiconductors they are still upstaged by their inorganic counterparts. Development of organic electronics requires better understanding of electrooptical properties of organic semiconductors and relationships between their structure and functions. The main goal of this thesis is a detailed investigation of ultrafast exciton and charge carrier processes in pure organic semiconductors and their blends with fullerene derivatives. Investigated organic or silicon organic semiconductors were poly-di-n-hexylsilane (PDHS), polyfluorenes F8BT and PSF-BT, merocyanine MD376. C60 fullerene and its derivative PCBM were used in blends. Ultrafast transient absorption, fluorescence, and integral mode photocurrent measurements were used for investigations. The investigation of PDHS nanocomposites revealed that PDHS incorporation into nanopores can be used for improvement of fluorescence properties. Formation of intramolecular charge transfer state was proposed for PSF-BT neat films. Charge transfer scheme of the formation of long-lived charge pair state in PSF-BT/PCBM blend was presented. The charge pair and free charge carrier generation scheme in merocyanine blends with fullerene derivatives were discussed in detail. Analysis of measurement... [to full text] / Dėl savo unikalių savybių organiniai puslaidininkiai gali būti plačiai pritaikyti įvairiuose optoelektroniniuose prietaisuose: organiniuose šviestukuose, organiniuose lazeriuose, organiniuose tranzistoriuose ir organiniuose šviesos elementuose. Visi šie pritaikymai yra galimi dėl organinių molekulių laidumo. Nepaisant didelių organinių puslaidininkių perspektyvų, jie vis dar yra nukonkuruojami neorganinių puslaidininkių. Pagrindinis šių tezių tikslas yra detaliai ištirti eksitonų ir krūvininkų dinamikos procesus grynuose organiniuose puslaidininkiuose ir jų mišiniuose su fulereno dariniais. Buvo matuoti organiniai ir silicio organiniai puslaidininkiai: poli-di-n-heksilsilanas (PDHS), polifluoreno dariniai F8BT ir PSF-BT, merocianinas MD376. Mišiniuose naudoti fulerenai buvo C60 ir jo darinys PCBM. Tyrimams buvo naudoti ultraspartūs skirtuminės sugerties, fluorescencijos ir integralinės fotosrovės matavimai. PDHS tyrimai atskleidė, kad neorganinės matricos sumažina nespindulinį relaksacijos kanalą. PDHS nanokompozitai gali būti naudojami polimero fluorescencijos savybių: stabilumo, kvantinio našumo pagerinimui. Polifluorenų F8BT ir PSF-BT grynų plėvelių tyrimų metu nustatyti eksitonų-eksitonų anihiliacijos ir eksitonų migracijos skirtumai. Vidumolekulinės krūvio pernašos būsenos formavimasis buvo pasiūlytas PSF-BT grynoms plėvelėms. Pristatyta ilgi gyvuojančių krūvininkų porų formavimosi schema PSF-BT/PCBM mišiniuose. Krūvio pernašos būsenų formavimasis buvo ištirtas... [toliau žr. visą tekstą]

Dėl savo unikalių savybių organiniai puslaidininkiai gali būti plačiai pritaikyti įvairiuose optoelektroniniuose prietaisuose: organiniuose šviestukuose, organiniuose lazeriuose, organiniuose tranzistoriuose ir organiniuose šviesos elementuose. Visi šie pritaikymai yra galimi dėl organinių molekulių laidumo. Nepaisant didelių organinių puslaidininkių perspektyvų, jie vis dar yra nukonkuruojami neorganinių puslaidininkių. Pagrindinis šių tezių tikslas yra detaliai ištirti eksitonų ir krūvininkų dinamikos procesus grynuose organiniuose puslaidininkiuose ir jų mišiniuose su fulereno dariniais. Buvo matuoti organiniai ir silicio organiniai puslaidininkiai: poli-di-n-heksilsilanas (PDHS), polifluoreno dariniai F8BT ir PSF-BT, merocianinas MD376. Mišiniuose naudoti fulerenai buvo C60 ir jo darinys PCBM. Tyrimams buvo naudoti ultraspartūs skirtuminės sugerties, fluorescencijos ir integralinės fotosrovės matavimai. PDHS tyrimai atskleidė, kad neorganinės matricos sumažina nespindulinį relaksacijos kanalą. PDHS nanokompozitai gali būti naudojami polimero fluorescencijos savybių: stabilumo, kvantinio našumo pagerinimui. Polifluorenų F8BT ir PSF-BT grynų plėvelių tyrimų metu nustatyti eksitonų-eksitonų anihiliacijos ir eksitonų migracijos skirtumai. Vidumolekulinės krūvio pernašos būsenos formavimasis buvo pasiūlytas PSF-BT grynoms plėvelėms. Pristatyta ilgi gyvuojančių krūvininkų porų formavimosi schema PSF-BT/PCBM mišiniuose. Krūvio pernašos būsenų formavimasis buvo ištirtas... [toliau žr. visą tekstą] / Due to their unique properties organic semiconductors may be used for various applications in organic optoelectronic devices: light emitting devices, lasers, field-effect transistors and photovoltaic cells and etc. Despite high perspectives of organic semiconductors they are still upstaged by their inorganic counterpart. The efficiency of electrooptical properties of organic semiconductors is tried to increase. The main goal of this thesis is a detailed investigation of ultrafast exciton and charge carrier processes in pure organic semiconductors and their blends with fullerene derivatives. Measured organic or silicon organic semiconductors were poly-di-n-hexylsilane (PDHS), polyfluorenes F8BT and PSF-BT, merocyanine MD376. Fullerenes used in blends were C60 and its derivative PCBM. Ultrafast transient absorption, fluorescence, and integral mode photocurrent measurements were used for investigations. The investigation of PDHS revealed that PDHS nanocomposites can be used for improvement of neat PDHS films fluorescence properties. The formation of intramolecular charge transfer state was proposed for PSF-BT neat films. Charge transfer scheme of the formation of long-lived charge pair state in PSF-BT/PCBM blend was presented. The formation of charge transfer states was explored in neat merocyanine films and blends with fullerene derivatives. The scheme of generation of charge pairs and free charge carriers in merocyanine blends with fullerene derivatives was discussed in... [to full text]

Orientador: Fernando Galembeck / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-13T18:39:32Z (GMT). No. of bitstreams: 1 Burgo_ThiagoAugustodeLima_M.pdf: 5433149 bytes, checksum: 072a8a59c85a99f30a12ff303fcdb4e1 (MD5) Previous issue date: 2009 / Resumo: Neste trabalho estudou-se o comportamento de potenciais induzidos em celulose pela aproximação de um corpo eletrificado e também a dissipação de cargas (positivas e negativas) em polietileno de baixa densidade (PEBD) geradas por descarga corona. As medidas de determinação do potencial eletrostático foram feitas utilizando eletrodos de Kelvin acoplados a voltímetros eletrostáticos. Os resultados mostraram que a umidade relativa (UR) tem papel decisivo tanto sobre a indução e dissipação de cargas em celulose quanto sobre a dissipação de cargas em polietileno. Nos experimentos de dissipação de carga em PEBD (virgem e oxidado) os potenciais são mais rapidamente dissipados em umidade elevada. O polietileno sempre apresenta um potencial negativo no equilíbrio (¿4,6 ±0,7V), independente do sinal do potencial medido após a eletrização inicial, positivo ou negativo. A atmosfera se mostrou decisiva tanto para a aquisição quanto para a dissipação de cargas nos materiais e os resultados foram interpretados de acordo com um modelo no qual a atmosfera atua como reservatório de cargas uma vez que o equilíbrio da água sob um potencial eletrostático V mostra excesso de concentração de íons H(H2O)n se V < 0 e excesso de concentração de OH(H2O)m se V > 0, de acordo com a definição de potencial eletroquímico. De acordo com este modelo, a atmosfera é um importante e provavelmente decisivo reservatório de íons na eletrização e dissipação de cargas de dielétricos / Abstract: The objective of this study is the verification of a model for electrostatic charge induction and dissipation in dielectrics. Experiments aimed at 1) the determination of electrostatic potential induced and dissipated in cellulose by the approximation of a charged body and 2) the determination of electrostatic potential dissipation by low-density polyethylene (LDPE) charged with corona pulses. Measurements were made using Kelvin electrodes coupled to electrostatic voltmeters with spatial resolution at the macroscopic and nanometric scales. In cellulose, positive and negative charge induction follow the same kinetics with similar time constants but positive corona-induced potentials in LDPE are dissipated faster than negative corona potentials. LDPE surface oxidation causes an increase in the rate of corona potential decay that increases with the degree of oxidation. Relative humidity (RH) is decisive for both charge acquisition and dissipation and the present results cannot be explained by the usual assumption of surface conductivity as the main charge/discharge mechanism. On the other hand, experimental results are interpreted assuming that the atmospheric water is a charge reservoir for dielectrics and charge acquisition and dissipation is the result of adsorption and desorption of H and OH ions from adsorbed water, under the effect of external or internal fields. LDPE in equilibrium under a moist nitrogen atmosphere is not electroneutral, showing an equilibrium potential equal to ¿4.6±0.7 V / Mestrado / Físico-Química / Mestre em Química

No description available.

La photocatalyse se base sur l’excitation d’un semi-conducteur par des photons d’énergie supérieure ou égale à son gap, générant des paires électron-trous. Celles-ci sont très réactives et susceptibles de réagir à l’interface pour réaliser par exemple l’oxydation totale d’un composé organique. Cette méthode peut être appliquée sur des eaux usées pour éliminer totalement les polluants organiques qui y sont présents. Dans la perspective d’une utilisation du soleil comme source de lumière, cette méthode peut s’avérer très économique et écologique pour le traitement de l’eau.L’interaction lumière-semi-conducteur et la dynamique des porteurs de charge sont des processus physico-chimiques primordiaux pour la photocatalyse, et il est nécessaire de bien les comprendre pour maîtriser le procédé et développer des matériaux plus efficaces. La Time Resolved Microwave Conductivity (TRMC) est une technique qui se base sur la réflexion des micro-ondes sur un semi-conducteur excité qui est directement reliée avec le nombre de porteurs de charge photo-générés. Il s’agit d’un moyen de sonder en temps réel la dynamique des porteurs de charge dans les semi-conducteurs.Ce travail s’inscrit dans le cadre du projet ANR PhotoNorm. Il consiste en une étude par TRMC de dioxyde de titane TiO2 utilisé pour la dépollution de l’eau par photocatalyse. Une partie de cette étude concerne la caractérisation des propriétés opto-électroniques des matériaux, pour lesquels la dynamique des porteurs de charge sera comparée à l’activité photocatalytique. L’effet bénéfique en photocatalyse de la déposition de nanoparticules d'or, d'argent ou bimetallique or-cuivre sur des TiO2 commerciaux sera relié à une capture d’électrons libres observée en TRMC. L’effet bénéfique sur la photocatalyse en lumière visible a été relié à une injection d’électrons dans le TiO2 par des nanoparticules de bismuth. L’autre partie de ce travail consiste en une étude plus fondamentale de la dynamique des porteurs de charge dans des TiO2 commerciaux ou synthétisés dans le cadre du projet PhotoNorm. Il y sera montré l’importance de la longueur d’onde et de l’intensité d’excitation du matériau sur le rendement de génération de porteurs de charge. L’importance des effets de surface et de l’environnement seront aussi mis en évidence de plusieurs façons. La première consiste simplement en un traitement chimique de la surface (lavage), qui peut avoir une grande influence à la fois sur la dynamique des porteurs de charge et sur la photocatalyse, sûrement en lien avec la présence d’impuretés de surface. La seconde consiste à imprégner le TiO2 par des colorants organiques présentant une forte absorption en lumière visible. Les mesures de TRMC sur ces systèmes permettent de mettre en évidence l’interaction entre le semi-conducteur et les molécules extérieures adsorbées à sa surface, notamment l’injection d’électrons du colorant excité vers le semi-conducteur, mais aussi des effets de recombinaison accrus. La troisième méthode consiste à modifier l’atmosphère de travail en TRMC. Il y est observé notamment l’importance de l’oxygène sur la dynamique des porteurs de charge, et notamment les effets de captures d’électrons, phénomènes qui entrent en jeu dans le processus de photocatalyse.Au final, la TRMC s’avère être un bon moyen d’étude de la durée de vie des porteurs de charge dans les semi-conducteurs, qui peut permettre de mieux comprendre les processus fondamentaux associés à la photocatalyse. / The photocatalysis is based on the excitation of semiconductor by photons with an energy superior or equal to the gap, generating electron-hole pairs. These are very reactive and able to react at the interface, involving for exemple the total oxidation of an organic compound. This method can be used on wastewater to eliminate the organic pollutants. With a view to use the sun as a light source this method may become an economical and ecological way for the water treatment. Light interaction between light and semiconductor and the charge-carrier dynamics are fundamental processes for photocatalysis and it is necessary to understand them in order to manage with this process and develop more efficient materials. The Time Resolved Microwave Conductivity (TRMC) is a method based on the reflexion of microwaves on an excited semiconductor which is linked to the number of photo-generated charge-carriers. This method allows us to probe in real time the charge-carrier dynamics in semiconductor. This work is included in the ANR Photonorm project. It consists in a TRMC study on titanium dioxyde TiO2 used for water depollution by photocatalysis. One part of this study consists in the characterization of the opto-electronic properties of materials for which the charge-carrier dynamics will be compared with the photocatalytic activity. The beneficial effect of nanoparticles deposition of gold, silver or gold-copper bimetallics on commercial TiO2 will be linked to the observation of free electrons observed by TRMC . The beneficial effect on photocatalysis in visible light was linked to an electron injection in TiO2 by bismuth nanoparticles. The second part of this work consists in a more fundamental study of charge-carrier dynamics on commercial or synthetized for the Photonorm project. I will be shown the importance of excitation wavelength and intensities on charge carrier generation. The importance of surface effect and environment will be emphasized by several ways. The first one just consist in surface treatment which can have a major importance on charge-carrier dynamics and photocatalysis, probably in connection with the presence or not of impurities on the surface. The second way consists in impregnating TiO2 by organic dyes which show a strong visible light absorption. The TRMC measurements highlight the interaction between the adsorbed molecules and the semiconducteur, including the electron injection from the excited dye to the TiO2 but also an increased recombination effect. The third method consist in modified the working atmosphere in TRMC. The major role of oxygen is so observed on charge-carrier dynamics, with an effect of electron capture, involving in photocatalytic mechanism.Finally TRMC proves to be a convenient method for studying charge-carrier dynamics in semiconductors, which allow a better understanding of fundamental processes bound to photocatalysis.

Tato práce je zaměřena na studium vlastností organických polovodivých materiálů se zaměřením na jejich vodivost a pohyblivost nosičů náboje. Hlavním cílem této práce je objasnit vztah mezi chemickou strukturou organických polovodičů a jejich vlastnostmi. Teoretická část práce je zaměřena na základy organických polovodičů, transport náboje a přehled vlastností organických polovodivých materiálů, které vedly k jejich aplikaci v polních a elektrochemických tranzistorech. Experimentální část představuje přehled použitých materiálů, způsoby jejich přípravy a charakterizační metody. V rámci výsledkové části bylo vyvinuto nebo optimalizováno několik metod pro přípravu tenkých vrstev a následně byl studován jejich vliv na výkon organických polem řízených tranzistorů. Byly charakterizovány a diskutovány relevantní vlastnosti nových organických polovodivých materiálů se zaměřením na pohyblivost nosičů náboje. Byla charakterizována a diskutována biokompatibilita několika organických polovodičů. Elektrické vlastnosti, stabilita a biokompatibilita elektroaktivních polymerních inkoustů na bázi PEDOT:PSS byla charakterizována a diskutována s ohledem na jejich možné použití v bioelektronice. Nakonec byl zkonstruován organický bioelektronický senzor pro detekci fyziologické odpovědi kardiomyocytů na základě studovaných materiálů.