Thesis (Ph. D.)--University of Chicago, Department of Chemistry, June 2002. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Albert E. Stiegman, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Sept. 24, 2004). Includes bibliographical references.

The hetero-bimetallic mixed valence metal polycyanides (Prussian Blue analogues (PBAs)) with formula AxMII[M’III(CN)6]y (where A= alkali-metal cation and M, M’= transition-metal cations respectively) are archetypal examples of molecule-based magnets, exhibiting a wealth of exotic electronic and magnetic behaviours. Similar intriguing electronic and magnetic properties are anticipated in nanoscale structures employing the PBA molecular building block. Herein investigations of multifunctional molecular magnets based on the PBA building block, with varying dimensionalities, are reported. Synthesis and characterisation of a novel family of mixed ferri-ferromagnets, RbNizMn(1-z)[Fe(CN)6] (0<z<1), illustrates how relatively minor changes in chemical composition can induce significant changes in the magnetic properties. Selected members of this series show photo-induced electronic transitions and pressureinduced magnetic pole inversions. The rare phenomenon of a double magnetic pole inversion is observed when FeII is introduced as a third MII ion. PBAs incorporating the Cu2+ ion are studied with the aim of establishing the influence of Jahn-Teller distortions on the photo-induced electron transfer which has been observed in a number of PBAs. X-ray powder diffraction and absorption measurements of CsCu[Fe(CN)6] under laser illumination reveal an unusual and unexpected behaviour, with photo-irradiation initiating a simultaneous reduction of both transition metal centres, which is proposed to occur via a chemical reaction. Superparamagnetic nanoparticles based on the CuII-NC-CrIII and Mn-NC-CrIII moieties are prepared by polymer protected synthesis, a method based upon spatial confinement. Control over the particle size, and consequently magnetic properties, of the isolated polymer-capped nanoparticles is achieved by altering the polymer concentration. The relaxation dynamics of the polymer-capped nanoparticles are studied using AC susceptibility.

Glucose-6-phosphate (G6P) plays an important role in carbohydrate metabolism of all living organisms. Compared to the conventional analytical methods available for estimation of G6P, the biosensors having relative simplicity, specificity, low-cost and fast response time are a promising alternative. We have reported a G6P biosensor based on screen-printed electrode utilizing Prussian Blue (PB) nanoparticles and enzymes, glucose-6-phosphate dehydrogenase and glutathione reductase. The PB nanoparticles acted as a mediator and thereby enhanced the rate of electron transfer in a bi-enzymatic reaction. The Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy study confirmed the formation of PB, whereas, the atomic forced microscopy revealed that PB nanoparticles were about 25-30 nm in diameter. Various optimization studies, such as pH, enzyme and cofactor loading, etc. were conducted to obtain maximum amperometric responses for G6P measurement. The developed G6P biosensor showed a broad linear response in the range of 0.01-1.25 mM with a detection limit of 2.3 mM and sensitivity of ­63.3 mA/mM at a signal-to-noise ratio of 3 within 15 s at an applied working potential of -100 mV. The proposed G6P biosensor also exhibited good stability, excellent anti-interference ability and worked well for serum samples.

L’électrochromisme est le changement réversible de couleur d’un matériau lors de son oxydation ou de sa réduction électrochimique. Cette thèse porte sur l’étude d’électrolytes à base de liquide ionique (BMIPF6 et BMITFSI), de sel de lithium (LiTFSI) et de polymère (PMMA) et sur la préparation de systèmes électrochromes à base de ces électrolytes et du PEDOT, du Bleu de Prusse ou d'InHCF comme matériaux électrochromes. La conduction ionique mesurée par EIS, les analyses thermo gravimétriques, les spectroscopies IR et Raman et la mesure des coefficients de diffusion informent sur les interactions entre les espèces dans l'électrolyte. Les matériaux électrochromes (PEDOT, BP, InHCF) sont ensuite étudiés dans un électrolyte modèle LiTFSI 0.03 / BMITFSI 0.97. Enfin, des systèmes électrochromiques flexibles sont réalisés et leur propriétés de coloration et de cyclage étudiées. / Electrochromism is the reversible colour change of a material upon electrochemical oxidation or reduction. This thesis will focus on the study of ionic liquid (BMIPF6 and BMITFSI), lithium salt (LiTFSI) and polymer (PMMA) based electrolytes and on the preparation of electrochromic devices with PEDOT, Prussian Blue or one of its analogues InHCF, as electrochromic materials. The measurement of ionic conductivity by EIS, thermo-gravimetric analysis, IR and Raman spectroscopy and measurement of diffusion coefficients of these electrolytes highlight the interactions between the different species of the electrolyte. Electrochromic materials (PEDOT, BP, InHCF) are then studied in a model electrolyte (LiTFSI 0.03 / 0.97 BMITFSI), their electrochromic properties are detailed. Finally, flexible electrochromic devices are made and their properties of colouration and cycling are presented.

Prussian blue (PB) nanoparticles were synthesized from FeCl3.6H2O, K4[Fe(CN)6].3H2O, and from Fe(NO3)3.9H2O and K4[Fe(CN)6].3H2O, and then characterized by Fourier transform infrared (FT-IR), Ultraviolet-visible spectroscopy, X-ray diffraction (XRD), Energy dispersive spectroscopy (EDS), Scanning electron microscopy (SEM), Raman spectroscopy and thermogravimetric analysis. Graphene oxide and carbon nanotubes were also synthesized and characterized. PB nanoparticles, carbon nanotubes (CNT), graphene oxide (GO) and cetyltrimethylammonium bromide (CTAB) were sequentially deposited onto glassy carbon electrode surface to form chemically modified electrode for the detection of hydrogen peroxide (H2O2) and dopamine. The following electrodes were fabricated, GC-PB, GC-MWCNT, GCGO, GC-CTAB, GC-MWCNT-PB, GC-GO-PB and GC-CTAB-PB. Cyclic and Square wave voltammetric techniques were used to measure the hydrogen peroxide detectability of the electrodes at pH ranges of (3 - 7.4) in 0.1M phosphate buffer solution, in the absence or presence of 25 μL of H2O2. The GC-CNT-PB, GC-GO-PB,GC-CTAB-PB electrodes showed a good response for the detection of hydrogen peroxide in both acidic and neutral media while the GCPB electrode only showed good response in acidic media.

De acordo com a literatura recente, a eletroquímica de partículas magnéticas e fenômenos de colisões em superfícies eletródicas resultam em curvas voltamétricas e amperométricas com perfis completamente destoados do convencional. Alguns modelos teóricos propõem explicações, no entanto, ainda se observa a necessidade de aquisição de mais dados experimentais. Visando contribuir com esta área, esta Dissertação de Mestrado aborda a manipulação de micropartículas e nanopartículas de magnetita modificadas com azul da Prússia (Fe3O4-PB), bem como o estudo das propriedades eletroquímicas das partículas na presença de um campo magnético externo. Filmes constituídos por micropartículas sobre eletrodos de carbono (grafite) foram obtidos por duas técnicas distintas, drop coating e magneto-deposição. Para ambos os métodos, os filmes apresentaram dois picos nos voltamogramas, um de oxidação (0,12 V) e outro de redução (-0,05 V), que estão associados ao par redox azul da Prússia/branco da Prússia. Para o filme obtido via drop coating, observaram-se correntes de pico mais elevadas. Também, micropartículas de Fe3O4-PB individuais foram isoladas (single particle) com auxílio de um microscópio óptico e analisadas por voltametria, onde se verificou o aparecimento de picos com os mesmos valores de potenciais. Utilizando os dois estados de comutação de campo (0,2 Tesla), ligado e desligado, foi possível controlar a presença e a ausência da partícula no eletrodo. Também, observaram-se diferenças nos valores de densidade de corrente nos cronoamperogramas para cada micropartícula de Fe3O4-PB e que a morfologia da micropartícula interfere significativamente na resposta eletroquímica. Por fim, e agora se tratando da eletroquímica de nanopartículas de Fe3O4-PB sobre um ultramicroeletrodo (UME) de ouro, controlaram-se as colisões das mesmas em diferentes condições experimentais, como na presença e na ausência de um campo magnético externo paralelo a superfície do eletrodo e com intensidades variadas (0,1 e 0,2 Tesla). Na ausência do campo, as nanopartículas que chegaram ao UME colidiram e se acumularam, gerando sinais eletroquímicos do tipo corrente staircase. Na presença de um campo de 0,1 T, observaram-se vários transientes de correntes (spikes) associados às colisões das nanopartículas, eventos esses não observados frequentemente na presença do campo de 0,2 T. Assim, esses resultados abrem a discussão da necessidade de se aperfeiçoarem os modelos que explicam os perfis das curvas voltamétricas e amperométricas para esses sistemas. / According to recent literature, the electrochemistry of magnetic particles and collision phenomena on surfaces result in unconventional voltammetric and amperometric responses. Some theoretical models has been proposed; however, experimental data are required for improve that. In order to contribute to this research area, this Master\'s Dissertation describes the manipulation of microparticles and nanoparticles of magnetite modified with Prussian blue (Fe3O4-PB), as well as the study of electrochemical properties of them in presence of an external magnetic field. Carbon (graphite) electrodes modified with microparticles were obtained by using two different techniques, (i) magneto-deposition and (ii) drop coating. For both, two peaks in the voltammograms were observed, related to oxidation (0.12 V) and reduction (-0.05 V), which are associated with redox couple Prussian blue / Prussian white. Higher peaks currents were observed for the film obtained via drop coating. Also, individual Fe3O4-PB microparticles (single particles) were isolated by using an optical microscope and analyzed by voltammetry, where there was the appearance of peaks with the same potential values. However, using two commutations magnetic states, \"switch on\" and \"switch off\", it was possible to monitor the presence and the absence of the particle on electrode. Also, there were differences in the values of current density in the chronoamperograms for each Fe3O4-PB microparticle, and the morphology of the microparticle significantly interfered in the electrochemical response. Finally, it was performed several electrochemical experiments regarding to collisions of Fe3O4-PB nanoparticles on a gold ultramicroelectrode. Controlled collisions in different experimental conditions were carried out, such as in the presence and absence of an external magnetic field parallel to the surface electrode, and also with intensities fields of 0.1 and 0.2 Tesla. In the absence of the field, the nanoparticles reached the UME and collided, resulting in electrochemical signals of this type staircase, due to accumulation of them. On the other hand, in the presence of a 0.1 T, we observed several transient currents (spikes) associated with the collisions of the nanoparticles. These events were not observed in the presence of the field of 0.2 T. Thus, these findings allow us to the discussion for improvements on the models for these systems, in order to explain the profiles of voltammetric and amperometric responses.

Cette thèse se compose de deux parties qui peuvent être considérées comme deux aspects différents de l'électronique moléculaire avec pour point commun les moyens de nanofabrication mis en jeu pour réaliser des dispositifs de mesures électriques à bas courant. La première partie de la thèse concerne l'assemblage de nano-aimants entre électrodes à nanogap. Le besoin croissant de processeurs toujours plus performants et celui d’une densité de stockage toujours plus grande ont poussé la technologie CMOS couramment utilisée dans l'industrie à ses limites physiques vis-à-vis de sa miniaturisation. L'électronique moléculaire et la spintronique moléculaire se révèlent être des alternatives prometteuses à cette technologie pour les futurs dispositifs nanoélectroniques. Mes principaux travaux dans ce domaine ont porté sur l'assemblage entre des électrodes à nanogap, de nano-aimants moléculaires à base de bleu de Prusse ou de son analogue Cs–Co–Cr. Le but était ainsi de faire les premiers pas vers la construction de dispositifs en spintronique moléculaire. Des nanogaps de ~ 7 à 50 nm ont été fabriqués en palladium ou en or sur un substrat Si/SiO₂ par lithographie électronique et lift-off. Les nano-aimants ont été placés dans le gap par diélectrophorèse à courant alternatif (AC DEP). À température ambiante, un courant négligeable a été mesuré sur les jonctions utilisant des nanoparticules de Cs–Co–Cr alors qu’un courant de ~ 30 pA a été mesuré sur celles avec les nanoparticules en bleu de Prusse pour une tension de ~ 1 V. J’ai montré qu‘en fait, l’eau piégée dans les nanogaps altérait sérieusement les mesures de courants et nécessitait un recuit préalable. Pour optimiser la localisation des nanoparticules entre les électrodes, j’ai proposé un programme de simulation de la DEP ne tenant pas compte du mouvement brownien et de la dynamique des fluides. La deuxième partie de la thèse concerne la fabrication de dispositifs de type nanopatch-clamp planaire pour l'enregistrement de courants ioniques à travers les canaux ioniques des protéines membranaires. Les canaux de ces protéines incorporées dans les membranes cellulaires sont des composantes essentielles de toutes les cellules vivantes et sont à la base de divers processus physiologiques tels que ceux dans la communication nerveuse, la contraction musculaire, la sensation tactile, etc. Les mesures de transport d'ions sont maintenant utilisées dans diverses applications telles que le criblage de médicaments dans l'industrie pharmaceutique et les biocapteurs médicaux. La méthode classique pour effectuer des mesures de transport d'ions consiste à utiliser un système patch-clamp. Cependant, cette méthode nécessite d’importantes compétences, des équipements lourds et coûteux et présente une faible efficacité de mesure. Pour pallier ces inconvénients, une solution est de développer des patch-clamps planaires, qui sont modulables, automatisés et faciles d’utilisation. La fabrication du dispositif a consisté en la réalisation d’une piste conductrice constituée d’un empilement de couches Au/Ag sur un substrat de silicium oxydé. Cette piste a été passivée et isolée électriquement par une couche de Si₃N₄/SiO₂ dans laquelle j’ai gravé des micro-trous et j’ai ensuite converti la couche d’Ag en AgCl pour les mesures électriques. Afin de valider le fonctionnement du dispositif sans la membrane, j’ai procédé à des mesures de courant en fonction du temps pour diverses tensions, ce qui m’a ensuite permis de proposer un schéma équivalent électrique. / This thesis consists of two parts. The two parts correspond to two different subjects but with a common feature which is the fabrication of nanometer scale devices for low current measurements. The first part investigated the assembly of Prussian blue and Cs–Co–Cr Prussian blue analogue molecular nanomagnets into nano-patterned electrodes. The ever growing need for higher performance processors and higher storage densities has pushed the CMOS technology commonly used in industry to its physical limitations toward its miniaturization. Molecular electronics and molecular spintronics prove to be promising alternatives for the CMOS in future nanoelectronic devices. Pd or Au gaps with ~ 7–50 nm width were fabricated on a Si/SiO₂ substrate using standard electron beam lithography, metal deposition and lift-off. Nanomagnets were positioned between the gaps via AC dielectrophoresis (DEP). At room temperature, the Cs–Co–Cr Prussian blue analogue nanoparticles exhibited negligible current whereas junction with Prussian blue nanoparticles exhibited ~ 30 pA at ~ 1 V. Water trapped in nanogaps was found to seriously alter current measurements. This problem was solved by heating samples prior to measurements. A simplified DEP simulation program using Delphi was developed, which neglected Brownian motion and fluid dynamics but allowed us to better understand the DEP process. The second part of the thesis investigated the fabrication of devices for measuring electrical currents through membrane protein channels. Membrane-embedded protein channels are the basis of various physiological processes like nervous communication, muscular contraction, tactile sensation, and so on. Electrical measurements are used in different applications such as drug screening in pharmaceutical industry and biosensors. The standard method to perform such measurements is the use of patch-clamp. However, this method requires intense skill and heavy equipment while it exhibits low measurement efficiency. A solution to these drawbacks is the development of planar patch clamps, which are scalable, automated and easier to use. The first device fabrication step was the patterning of Au/Ag electrodes on thermally oxidized Si substrate by optical lithography, metallization and lift-off. Secondly, a passivation layer of Si₃N₄/SiO₂ was deposited on top of electrodes by PECVD. Then micro-holes were formed inside the Si₃N₄/SiO₂ passivation layer stack using Raith-150 e-beam lithography and reactive ion etching. Finally, Ag layer was converted to AgCl using bleach. The test of electrical current was done using Axopatch patch-clamp amplifier. Current versus time measurements for different voltages were recorded without membrane covering the holes, and an electrical model has been developed for the fabricated devices.

The main purpose of this work is study of electrochemical hydrogen peroxide and ascorbate reactions on electrodes modified by Prussian blue (PB), with the aim to apply these electrodes in creation of sensors and biosensors. For this purpose, a detailed study of electrochemical reduction of hydrogen peroxide, as well as of oxidation of ascorbate at Prussian blue modified rotating disk electrode. In view of the results obtained, a mechanism for hydrogen peroxide reduction at PB modified electrode has been proposed. In accordance with this mechanism, electron transfer appears to be rate-limiting step. The kinetics of decomposition of PB modified electrode in the course of a cathodic reduction of hydrogen peroxide has been studied, and the influence of different factors to this process has been determined. Prototypes of sensors and biosensors, for different analytes have been elaborated and tested. / Darbo tikslas yra elektrocheminių vandenilio peroksido ir askorbato reakcijų tyrimas ant Berlyno mėlynuoju (BM) modifikuotų elektrodų, siekiant pritaikyti šiuos elektrodus jutiklių ir biojutiklių kūrimui. Ištirta vandenilio peroksido redukciją ir askorbato oksidaciją naudojant sukamojo disko elektrodą. Gauti rezultatai galimai įrodo stadijinį vandenilio peroksido katodinės redukcijos mechanizmą vykstantį ant BM modifikuoto elektrodo. Detaliai ištirta BM sluoksnio irimo kinetika vandenilio peroksido elektroredukcijos metu, ir nustatyti faktoriai, įtakojantys irimo proceso greitį. Sukurti jutiklių ir biojutiklių prototipai, kurie galėtų būti panaudoti biologiškai aktyvių medžiagų (vandenilio peroksido, askorbato, gliukozės) nustatymui.

Darbo tikslas yra elektrocheminių vandenilio peroksido ir askorbato reakcijų tyrimas ant Berlyno mėlynuoju (BM) modifikuotų elektrodų, siekiant pritaikyti šiuos elektrodus jutiklių ir biojutiklių kūrimui. Ištirta vandenilio peroksido redukciją ir askorbato oksidaciją naudojant sukamojo disko elektrodą. Gauti rezultatai galimai įrodo stadijinį vandenilio peroksido katodinės redukcijos mechanizmą vykstantį ant BM modifikuoto elektrodo. Detaliai ištirta BM sluoksnio irimo kinetika vandenilio peroksido elektroredukcijos metu, ir nustatyti faktoriai, įtakojantys irimo proceso greitį. Sukurti jutiklių ir biojutiklių prototipai, kurie galėtų būti panaudoti biologiškai aktyvių medžiagų (vandenilio peroksido, askorbato, gliukozės) nustatymui. / The main purpose of this work is study of electrochemical hydrogen peroxide and ascorbate reactions on electrodes modified by Prussian blue (PB), with the aim to apply these electrodes in creation of sensors and biosensors. For this purpose, a detailed study of electrochemical reduction of hydrogen peroxide, as well as of oxidation of ascorbate at Prussian blue modified rotating disk electrode. In view of the results obtained, a mechanism for hydrogen peroxide reduction at PB modified electrode has been proposed. In accordance with this mechanism, electron transfer appears to be rate-limiting step. The kinetics of decomposition of PB modified electrode in the course of a cathodic reduction of hydrogen peroxide has been studied, and the influence of different factors to this process has been determined. Prototypes of sensors and biosensors, for different analytes have been elaborated and tested.