O presente trabalho tem o objetivo de investigar a obtenção de hidrogênio a partir de soluções de etanol em água, por fotocatálise, usando-se catalisadores a base de óxido de zinco (ZnO). Nestes estudos foram empregados cinco catalisadores ZnO, sendo um comercial e os demais preparados através de diferentes metodologias encontradas na literatura. Os catalisadores foram caracterizados por área BET, DRX e FRX, e a investigação preliminar da atividade destes catalisadores foi feita através de ensaios de degradação fotocatalítica de rodamina B em reator slurry em batelada, onde foram avaliadas a taxa de reação e a remoção de corante. Os ensaios para a produção fotocatalítica de hidrogênio foram realizados em um reator de quartzo, operado em batelada com catalisador em suspensão e atmosfera inerte de nitrogênio. A solução foi irradiada por uma série de seis lâmpadas compactas de luz negra. Ao longo dos testes, amostras das fases líquida e gasosa foram coletadas e analisadas para identificação do consumo de etanol e produção de hidrogênio usando-se, respectivamente, Carbono Orgânico Total (TOC) e Cromatografia Gasosa (GC). Resultados preliminares mostraram que os catalisadores ZnO comercial e sintetizado (ZnO Merck e ZnO-B) apresentam atividade fotocatalítica e desempenho similares aos do TiO2 para a degradação da rodamina B. Contudo, estes mesmos catalisadores mostraram-se pouco ativos para a produção fotocatalítica de hidrogênio, com desempenho bastante inferior ao do TiO2 nas mesmas condições. Foi possível observar que o maior rendimento em hidrogênio ocorre para baixas concentrações de catalisador (0,05 gL[elevado a potência menos]1) e elevadas concentrações de etanol, sendo pouco dependente do pH. / This work aims to investigate the hydrogen production from ethanol-water solutions through photocatalysis, using zinc oxide catalysts (ZnO). Five ZnO catalysts were employed in this work; one was a commercial catalyst, while the others were prepared according to different methodologies reported in the literature. The catalysts were characterized by BET, XRD and XRF, and the preliminary investigation of their activity was done by photocatalytic degradation of rhodamine B, through the evaluation of the reaction rate and dye removal. Tests for photocatalytic hydrogen production were carried out in a quartz slurry batch reactor under nitrogen, irradiated by a set of six compact UV light bulbs. During the tests, gas and liquid samples were collected and analyzed in order to identify the consumption of ethanol and hydrogen production using, respectively, Total Organic Carbon (TOC) and Gas Chromatograph (GC). Preliminary results showed that the synthesized and commercial ZnO catalysts (ZnO-B and ZnO Merck) present photocatalytic activity and performance similar to TiO2 for the rhodamine B degradation. However, the ZnO catalysts presented lower performance when compared with TiO2 for hydrogen production, under the same conditions. It was observed that the highest hydrogen yield occurs for low concentrations of catalyst (0.05 gL1) and high concentrations of ethanol, being less dependent on pH.

In this dissertation, we construct a temperature controlled sample stage that is compatible with high numerical aperture objective optical microscope, and perform single molecule experiments under the system. Mixing dilute fluorophore (CdSe/ZnS quantum dot, DiI, Rhodamine B) into the liquid crystal matrix (5CB), we monitor the fluorescence dynamics of the individual fluorophore at various temperature. Different from the thermodynamic states of conventional materials, those specific class of materials which we called ¡§liquid crystals¡¨ are attracted for their existence of unique liquid crystal phase, which exhibits a solid-state like higher orientation ordering, and a liquid-state like liquidity. Probe individual fluorophore allows us to monitor the nanometer length scale local structural and dynamic heterogeneity in the solid, liquid crystal and liquid phases. The operating temperature of the platform covers more than 20 oC to 40 oC range with stability much better than 0.1 oC. Quantum dot in PMMA exhibits a clear on-off blinking behavior, and the single exponential fluorescence lifetime relaxation. While in the solid phase of the liquid crystal matrix, quantum dot exhibits similar behavior, which indicates the quantum dot is confined in the matrix. However, there exists slightly difference in decay lifetime. On the contrary, in the liquid crystalline phase as well as the liquid phase, quantum dot exhibits bi-exponential relaxation behavior. Besides a similar time scale relaxation dynamics, there exists additional fast decay behavior, which is from the feasible rotational rotation in the non-rigid matrix. In particular, the anisotropic decay dynamics in the liquid crystalline phase indicates the orientation preference of the liquid crystal molecules. Fluorescence Correlation Spectroscopy (FCS) provides the information of local dynamics of various time scales. FCS results exhibit an unclear transition that crossovers several decades in time scale, which indicates the highly heterogeneity of the liquid crystal. The results of DiI exhibits different rising time in the fluorescence lifetime measurement, which implies the forming of aggregation due to the limited solubility of the DiI molecules in the liquid crystal matrix. Results of Rhodamine B exhibit a clear rotational diffusion dynamics at ~ microsecond scale and the corresponding translational diffusion dynamics at ~ mini-second scale. Moreover, the transition time scale of translational diffusion exhibits a temperature dependence. At higher temperature, it shifts to a shorter time scale.

The motion of dye molecules in the solution is highly influenced by the Brownian motion caused by the stochastic collisions with the solvents, and it results the fluorescence intensity fluctuation. The thesis study the fluorescence intensity fluctuation of dilute dye molecule (Rhodamine B) in methanol solution ( - ), under confocal and total internal reflection (TIR) microscopy configurations. Five parameters are used to probe the fluorescence characteristics: (1) the difference between confocal and the TIR configurations. The configuration influences the laser focusing area and consequently the intensity distribution. The effective focusing area in confocal configuration is an ellipsoid shape, while that of TIR configuration is a disk shape around the interface with depth 100-200 nm. It results the TIR configuration less background and higher concentration capability. (2) concentration. We control the concentration from much less than one molecule to more than one molecule in the effective focusing area, and we observe the change of burst intensity distribution. (3) the focus position. By changing the focusing position, we study the effective focusing region changes. (4) excited intensity, and (5) fluorescence correlation spectroscopy (FCS). Our results indicate that TIR configuration exhibits lower background, and is suitable to higher concentration solution. In addition, when the dye concentration in the focusing area is much less than 1, the FCS amplitude is no longer follow 1/N, but rather be proportional to N, where N is the concentration.

PdCl2/Bi2WO6 and Pd/Bi2WO6 composite photocatalysts were synthesized via a template free hydrothermal process and the respective photocatalytic activities were investigated by degradation of Rhodamine B. The new catalyst composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet visible (UV-vis) light diffuse reflectance spectra, respectively. By XRD, it was found that the loaded Pd species did not alter the crystal lattice of Bi2WO6 photocatalyst. Through the XPS spectra, it was found that the PdCl2/Bi2WO6 was successfully reduced by chemical reducing agents CH2O and N2H4, respectively, and palladium was present in the form of both metallic Pd and Pd ion spe-cies (Pd0 and Pd2+), while the Pd species in a NaBH4-reduced composite exhibited only metallic Pd species (Pd0). For the SEM images, it was observed that both classes of composites were constructed from plenty of nanoplates, which were closed packed with hierarchical structures. Furthermore, the removal efficiency of Rhodamine B was found to be influenced by parameters such as catalyst dosage, pollutant concentration and solution pH.

O presente trabalho tem o objetivo de investigar a obtenção de hidrogênio a partir de soluções de etanol em água, por fotocatálise, usando-se catalisadores a base de óxido de zinco (ZnO). Nestes estudos foram empregados cinco catalisadores ZnO, sendo um comercial e os demais preparados através de diferentes metodologias encontradas na literatura. Os catalisadores foram caracterizados por área BET, DRX e FRX, e a investigação preliminar da atividade destes catalisadores foi feita através de ensaios de degradação fotocatalítica de rodamina B em reator slurry em batelada, onde foram avaliadas a taxa de reação e a remoção de corante. Os ensaios para a produção fotocatalítica de hidrogênio foram realizados em um reator de quartzo, operado em batelada com catalisador em suspensão e atmosfera inerte de nitrogênio. A solução foi irradiada por uma série de seis lâmpadas compactas de luz negra. Ao longo dos testes, amostras das fases líquida e gasosa foram coletadas e analisadas para identificação do consumo de etanol e produção de hidrogênio usando-se, respectivamente, Carbono Orgânico Total (TOC) e Cromatografia Gasosa (GC). Resultados preliminares mostraram que os catalisadores ZnO comercial e sintetizado (ZnO Merck e ZnO-B) apresentam atividade fotocatalítica e desempenho similares aos do TiO2 para a degradação da rodamina B. Contudo, estes mesmos catalisadores mostraram-se pouco ativos para a produção fotocatalítica de hidrogênio, com desempenho bastante inferior ao do TiO2 nas mesmas condições. Foi possível observar que o maior rendimento em hidrogênio ocorre para baixas concentrações de catalisador (0,05 gL[elevado a potência menos]1) e elevadas concentrações de etanol, sendo pouco dependente do pH. / This work aims to investigate the hydrogen production from ethanol-water solutions through photocatalysis, using zinc oxide catalysts (ZnO). Five ZnO catalysts were employed in this work; one was a commercial catalyst, while the others were prepared according to different methodologies reported in the literature. The catalysts were characterized by BET, XRD and XRF, and the preliminary investigation of their activity was done by photocatalytic degradation of rhodamine B, through the evaluation of the reaction rate and dye removal. Tests for photocatalytic hydrogen production were carried out in a quartz slurry batch reactor under nitrogen, irradiated by a set of six compact UV light bulbs. During the tests, gas and liquid samples were collected and analyzed in order to identify the consumption of ethanol and hydrogen production using, respectively, Total Organic Carbon (TOC) and Gas Chromatograph (GC). Preliminary results showed that the synthesized and commercial ZnO catalysts (ZnO-B and ZnO Merck) present photocatalytic activity and performance similar to TiO2 for the rhodamine B degradation. However, the ZnO catalysts presented lower performance when compared with TiO2 for hydrogen production, under the same conditions. It was observed that the highest hydrogen yield occurs for low concentrations of catalyst (0.05 gL1) and high concentrations of ethanol, being less dependent on pH.

O presente trabalho tem o objetivo de investigar a obtenção de hidrogênio a partir de soluções de etanol em água, por fotocatálise, usando-se catalisadores a base de óxido de zinco (ZnO). Nestes estudos foram empregados cinco catalisadores ZnO, sendo um comercial e os demais preparados através de diferentes metodologias encontradas na literatura. Os catalisadores foram caracterizados por área BET, DRX e FRX, e a investigação preliminar da atividade destes catalisadores foi feita através de ensaios de degradação fotocatalítica de rodamina B em reator slurry em batelada, onde foram avaliadas a taxa de reação e a remoção de corante. Os ensaios para a produção fotocatalítica de hidrogênio foram realizados em um reator de quartzo, operado em batelada com catalisador em suspensão e atmosfera inerte de nitrogênio. A solução foi irradiada por uma série de seis lâmpadas compactas de luz negra. Ao longo dos testes, amostras das fases líquida e gasosa foram coletadas e analisadas para identificação do consumo de etanol e produção de hidrogênio usando-se, respectivamente, Carbono Orgânico Total (TOC) e Cromatografia Gasosa (GC). Resultados preliminares mostraram que os catalisadores ZnO comercial e sintetizado (ZnO Merck e ZnO-B) apresentam atividade fotocatalítica e desempenho similares aos do TiO2 para a degradação da rodamina B. Contudo, estes mesmos catalisadores mostraram-se pouco ativos para a produção fotocatalítica de hidrogênio, com desempenho bastante inferior ao do TiO2 nas mesmas condições. Foi possível observar que o maior rendimento em hidrogênio ocorre para baixas concentrações de catalisador (0,05 gL[elevado a potência menos]1) e elevadas concentrações de etanol, sendo pouco dependente do pH. / This work aims to investigate the hydrogen production from ethanol-water solutions through photocatalysis, using zinc oxide catalysts (ZnO). Five ZnO catalysts were employed in this work; one was a commercial catalyst, while the others were prepared according to different methodologies reported in the literature. The catalysts were characterized by BET, XRD and XRF, and the preliminary investigation of their activity was done by photocatalytic degradation of rhodamine B, through the evaluation of the reaction rate and dye removal. Tests for photocatalytic hydrogen production were carried out in a quartz slurry batch reactor under nitrogen, irradiated by a set of six compact UV light bulbs. During the tests, gas and liquid samples were collected and analyzed in order to identify the consumption of ethanol and hydrogen production using, respectively, Total Organic Carbon (TOC) and Gas Chromatograph (GC). Preliminary results showed that the synthesized and commercial ZnO catalysts (ZnO-B and ZnO Merck) present photocatalytic activity and performance similar to TiO2 for the rhodamine B degradation. However, the ZnO catalysts presented lower performance when compared with TiO2 for hydrogen production, under the same conditions. It was observed that the highest hydrogen yield occurs for low concentrations of catalyst (0.05 gL1) and high concentrations of ethanol, being less dependent on pH.

PdCl2/Bi2WO6 and Pd/Bi2WO6 composite photocatalysts were synthesized via a template free hydrothermal process and the respective photocatalytic activities were investigated by degradation of Rhodamine B. The new catalyst composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet visible (UV-vis) light diffuse reflectance spectra, respectively. By XRD, it was found that the loaded Pd species did not alter the crystal lattice of Bi2WO6 photocatalyst. Through the XPS spectra, it was found that the PdCl2/Bi2WO6 was successfully reduced by chemical reducing agents CH2O and N2H4, respectively, and palladium was present in the form of both metallic Pd and Pd ion spe-cies (Pd0 and Pd2+), while the Pd species in a NaBH4-reduced composite exhibited only metallic Pd species (Pd0). For the SEM images, it was observed that both classes of composites were constructed from plenty of nanoplates, which were closed packed with hierarchical structures. Furthermore, the removal efficiency of Rhodamine B was found to be influenced by parameters such as catalyst dosage, pollutant concentration and solution pH.

Este trabalho investigou a fotodegradação do corante Rodamina-B com o auxílio do catalisador semicondutor Dióxido de Titânio, utilizando como fonte de irradiação pulsos de 40 fs gerados por um sistema laser de Titânio - Safira. Os pulsos laser foram formatados espectralmente (modulação senoidal), gerando trens de pulsos cuja separação foi escolhida para ser ressonante com um modo Raman intenso do catalisador. A fotodegradação da Rodamina-B foi monitorada através de medidas de fluorescência excitada via absorção de dois fótons. Não observamos fotodegradação do corante mediante a irradiação com pulsos ultracurtos, mesmo na presença do catalisador, tanto para o pulso de menor duração alcançada quanto para os trens de pulsos com diferentes separações temporais. Contudo, observamos uma diminuição no espalhamento da luz de excitação devido às nanopartículas de Dióxido de Titânio. Este processo foi estudado com mais detalhes, tendo sido analisada a influência da formatação espectral senoidal no resultado da medida. A relação entre a irradiação com pulsos de femtossegundos e a quebra de aglomerados de nanopartículas foi intuída a partir dos resultados obtidos, sendo fortalecida por medidas de microscopia eletrônica de varredura de um filme das amostras. / This work investigated the photodegradation of Rhodamine-B assisted by Titanium Dioxide semiconductor catalyst, using as irradiation source a Ti:Sapphire laser system delivering 40 fs pulses. The laser pulses were spectrally shaped (sinusoidal modulation), generating pulse trains whose separation was chosen to be resonant with an intense catalysts Raman mode. The Rh-B photodegradation was monitored by two photon excited fluorescence measurements. We have not observed dye photodegradation by the ultrashort pulses irradiation, in the absence of the catalyst, neither with the shortest pulse obtained, nor with pulse trains. Nevertheless, we observed a decrease in the excitation light scattering due to the Titanium Dioxide nanoparticles. Such process was studied by analyzing the influence of sinusoidal spectral phase mask in the signal. The results indicate a relationship between femtosecond pulse irradiation and the breaking of nanoparticles clusters, which was also corroborated by scanning electron microscopy measurements.

Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2016-08-10T12:27:01Z No. of bitstreams: 1 PDF - Geovânia Cordeiro de Assis.pdf: 2354639 bytes, checksum: ce1618c95a4673199ee7b5895baa2e85 (MD5) / Made available in DSpace on 2016-08-10T12:27:01Z (GMT). No. of bitstreams: 1 PDF - Geovânia Cordeiro de Assis.pdf: 2354639 bytes, checksum: ce1618c95a4673199ee7b5895baa2e85 (MD5) Previous issue date: 2016-02-26 / Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq / Much of the pollution potential adjunct to human activities is related to the emission of large volumes of household and industrial waste, which, even if treated by conventional methods available, have resistant and toxic chemical species that contaminate the water environment. As a result, many efforts have been devoted to the development of alternative technologies, especially the advanced oxidation processes and, in this context, for heterogeneous photocatalysis. The tin dioxide (SnO2) stands out as an excellent photocatalytic activity material. The objective was to study the photodegradation of rhodamine B mediated by UV irradiation / SnO2 and SnO2 impregnated polystyrene nanofoams in order to evaluate the use of the catalyst impregnated polystyrene nanofoams and its reuse. The nanoparticles of SnO2 were synthesized by the polymeric precursor method, based on the Pechini method, calcination temperatures investigated oxide were 700, 800 and 900 ° C. SnO2 nanoparticles were characterized by X-ray diffraction (XRD), Diffuse Reflectance Spectroscopy (DRS), surface area analysis (B.E.T) and Transmission Electron Microscopy (TEM). The nanoparticles of SnO2 were impregnated in nanofoams polystyrene by Thermally Induced Phase Separation mechanism (TIPS), forming the photocatalysts PS/SnO2-700; PS/SnO2-800 and PS/SnO2-900 ° C. The nanofoams PS/SnO2 were characterized by XRD, B.E.T and Scanning Electron Microscopy (SEM). The dye used for testing these photocatalysts is Rhodamine B. The tests showed the effectiveness of these catalysts in the degradation of rhodamine B dye, wherein the impregnation with the polystyrene matrix increased a little photocatalytic activity of all the catalysts and the photocatalyst that obtained the best results with 94% tin dioxide was calcined at 700 ° C and the nanofoams PS/SnO2-700 ° C with 98%. Reuse tests were made that catalyst calcined at 700 ° C powder and impregnated, where it was proven that besides having a photocatalytic activity nanofoams PS/SnO2 can be removed more easily, which facilitates the separation of solution and photocatalyst. / Grande parte do potencial poluente adjunto às atividades antrópicas está relacionado com a emissão de grandes volumes de resíduos domésticos e industriais, os quais, mesmo tratados pelos métodos convencionais disponíveis apresentam espécies químicas resistentes e tóxicas que contaminam o meio hídrico. Em função disso, muitos esforços têm sido dedicados ao desenvolvimento de tecnologias alternativas, com destaque para os processos de oxidação avançada e, dentro deste contexto, para a fotocatálise heterogênea. Dentre os óxidos metálicos aplicados na fotocatalise heterogênea, destaca- se o dióxido de estanho (SnO2) na forma nanoestruturada que apresenta propriedades que favorecem a atividade fotocatalítica. O objetivo do trabalho foi preparar nanoespumas de poliestireno e impregnar nanopartículas de SnO2 para degradação fotoquímica da Rodamina B. As nanopartículas de SnO2 foram sintetizadas através do método dos precursores poliméricos, baseado no método de Pechini, as temperaturas investigadas de calcinação do óxido foram 700, 800 e 900 °C. As nanopartículas de SnO2 foram caracterizadas através de Difração de Raio-X, Espectroscopia de Reflectância Difusa (DRS), Análise de área superficial (B.E.T) e Microscopia Eletrônica de Transmissão (TEM). As nanopartículas de SnO2 foram impregnadas em nanoespumas de poliestireno através do mecanismo de Separação de Fases Induzido Termicamente (TIPS), formando os fotocatalisadores PS/SnO2-700; PS/SnO2-800 e PS/SnO2-900 °C. As nanoespumas PS/SnO2 foram caracterizadas através de DRX , B.E.T e Microscopia Eletrônica de Varredura (MEV). O corante utilizado para os testes desses fotocatalisadores foi a Rodamina B. Os ensaios mostraram a eficiência desses catalisadores na degradação do corante rodamina B, sendo que a impregnação na matriz de Poliestireno aumentou um pouco a atividade fotocatalítica de todos os catalisadores e o fotocatalisador que obteve o melhor resultado com 94 % foi o dióxido de estanho calcinado a 700 °C, bem como a nanoespuma PS/SnO2-700 °C com 98 %. Foram feitos ensaios de reuso desse catalisador, calcinado a 700 °C em pó, e impregnado, onde foi comprovado que além de ter uma atividade fotocatalítica a nanoespuma PS/SnO2 pode ser removida com mais facilidade, o que favorece a separação entre a solução e o fotocatalisador.

Submitted by Jaqueline Silva (jtas29@gmail.com) on 2014-09-15T19:44:43Z No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Chelry Fernanda Alves de Jesus.pdf: 3412626 bytes, checksum: 196a769a0f857f15c408d233116a895b (MD5) / Approved for entry into archive by Jaqueline Silva (jtas29@gmail.com) on 2014-09-15T19:45:11Z (GMT) No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Chelry Fernanda Alves de Jesus.pdf: 3412626 bytes, checksum: 196a769a0f857f15c408d233116a895b (MD5) / Made available in DSpace on 2014-09-15T19:45:11Z (GMT). No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Chelry Fernanda Alves de Jesus.pdf: 3412626 bytes, checksum: 196a769a0f857f15c408d233116a895b (MD5) Previous issue date: 2014-04-04 / In this study, maghemite nanoparticles associated to dextran were synthesized (crystallites with average diameters of 5.6 and 5.3 nm) from the precipitation of iron salts in an alkaline medium in the presence of dextran of molecular weights of 250 kDa and 75 kDa. Aqueous colloidal dispersions of maghemite/dextran reacted with different amounts of epichlorohydrin aiming at the crosslinking of dextran. The characteristics of the samples were evaluated by X-ray diffraction, high resolution electron microscopy, infrared spectroscopy, thermogravimetric analysis, iron determination, hydrodynamic diameter and zeta potential. One of the maghemite/dextran samples was treated with an ammonium hydroxide solution for different times, seeking the functionalization of dextran with NH2 groups, whose content was determined by potentiometric titration. The maghemite/dextran-NH2 system was conjugated to rhodamine B fluorophore (RodB) under different reaction conditions, being the content of RodB determined by absorption spectrophotometry in the visible region. Photoluminescent characteristics of maghemite/dextran-RodB systems were evaluated by fluorescence microscopy, fluorescence spectrometry and flow cytometry. The results of the analyses and experiments showed that the molecular mass and the crosslinking of dextran did not influence significantly the characteristics of the colloidal systems, since the hydrodynamic diameter values were in the range of 110 and 138 nm and zeta potential was of -4.54 the -10.76 mV. However, the profile of the thermogravimetric curves of the solids was influenced by the crosslinking of dextran, as well as by the presence of the polymer not associated to the nanoparticles. The treatment with ammonia was proved efficient, increasing the number of NH2 groups per particle from 45 to 71. The conjugation of RodB to the maghemite/dextran-NH2 system was more efficient at a pH of 8.5, using a greater amount of carbodiimide and N-hydroxysuccinimide. The maghemite/dextran-RodB system presented different photoluminescent properties according to the content of NH2 groups with in the sample used in the conjugation reaction. The sample treated with the ammonia solution, containing 71 NH2-groups/particle, although it presented less amount of conjugated RodB (2.2 RodB/particle) showed greater fluorescence intensity than the sample showing the highest amount of RodB (2.8 Rod/particle), but that was not treated with ammonia (45-NH2/particle). This result was interpreted considering that the system treated with ammonia favored the RodB conjugation via covalent bond, while the untreated system favored the formation of aggregates of RodB via electrostatic interactions. / Neste trabalho, foram sintetizadas nanopartículas de maghemita (cristalitos com diâmetros médios de 5,6 e 5,3 nm) associadas à dextrana a partir da precipitação de sais de ferro em meio alcalino na presença de dextrana de massas moleculares de 250 kDa e 75 kDa. As dispersões coloidais aquosas de maghemita/dextrana reagiram com diferentes quantidades de epicloridrina visando à reticulação da dextrana. As características das amostras obtidas foram avaliadas por difração de raios-x, microscopia eletrônica de alta resolução, espectroscopia no infravermelho, análises termogravimétricas e medidas de teor de ferro, diâmetro hidrodinâmico e potencial zeta. Uma das amostras de maghemita/dextrana foi tratada com solução de hidróxido de amônio por diferentes tempos, visando à funcionalização da dextrana com grupos -NH2, cujo teor foi determinado por titulação potenciométrica. O sistema maghemita/dextrana-NH2 foi conjugado ao fluoróforo rodamina B (RodB) em diferentes condições reacionais, sendo o teor de RodB determinado por espectrofotometria de absorção na região do visível. As características fotoluminescentes dos sistemas maghemita/dextrana-RodB foram avaliadas por microscopia de fluorescência, espectrometria de fluorescência e citometria de fluxo. Os resultados das análises e experimentos mostraram que a massa molecular e a reticulação da dextrana não influenciaram, significativamente, nas características dos sistemas coloidais, já que os valores de diâmetro hidrodinâmico ficaram na faixa de 110 a 138 nm e os de potencial zeta de -4,54 a -10,76 mV. Entretanto, o perfil das curvas termogravimétricas dos sólidos foi influenciado pela reticulação da dextrana, assim como pela presença de polímero não associado às nanopartículas. O tratamento com amônia mostrou-se eficiente, incrementando o número de grupos -NH2 por partícula de 45 para 71. A conjugação da RodB ao sistema maghemita/dextrana-NH2 foi mais eficiente em pH 8,5, empregando-se maior quantidade de carbodiimida e N-hidroxisuccinimida. O sistema maghemita/dextrana-RodB apresentou propriedades fotoluminescentes distintas em função do teor de grupos –NH2 superficiais na amostra empregada na reação de conjugação. A amostra tratada com solução de amônia, contendo 71 grupos NH2/partícula, embora tenha apresentado menor quantidade de RodB conjugada (2,2 RodB/partícula) mostrou maior intensidade de fluorescência do que a amostra com maior quantidade de RodB (2,8 Rod/partícula), mas que não foi tratada com amônia (45 –NH2/partícula). Este resultado foi interpretado considerando-se que o sistema tratado com amônia favoreceu a conjugação de RodB via ligação covalente, enquanto que o sistema não tratado favoreceu a formação de agregados de RodB via interações eletrostáticas.