Made available in DSpace on 2016-06-02T19:22:06Z (GMT). No. of bitstreams: 1 3661.pdf: 3457379 bytes, checksum: b8065e93e77882df9787154074c2cd19 (MD5) Previous issue date: 2010-12-17 / Financiadora de Estudos e Projetos / The fast development of the nanotechnology, and the use of this technology to develop new products to help in diagnosis diseases, drugs and treatments for many diseases is increasing. Some authors have been warning about the nanoparticles use, because the real affect, toxic or not, still unknown. Iron oxide nanoparticles have been used in contrast liquid for magnetic resonance imaging, cancer treatment, among others. The aim of this work was to analyze the possible effects of chronic treatment with these nanoparticles in adults rats. The animals were distributed in 3 groups: Control (saline 0.9% - 0.1 mL/100 of body weight), nFe 0.3 (magnetic iron oxide nanoparticles 0.3 mg/kg BW) and nFe 0.6 (magnetic iron oxide nanoparticles 0.6 mg/kg BW). The animals were treated by gastric gavage during 8 weeks, 5 days per week. The body weight of the animals from the nFe 0.6 group decreased when compared to animals from the control group, and the BW of the animals from nFe 0.3 group was not different from the control group. The animals from the nFe 0.6 group showed the higher blood levels of cholesterol, although the levels of glucose, urea, creatinine, AST, ALT and alkaline phosphatase, plus hematology were not different from the animals of control group. Moreover, the seminal gland and ventral prostate of the animals of nFe 0.6 were atrophied. All those parameters of animals from nFe 0.3 group were not different compared to control group. The bone (femur and vertebra) biometric, biomechanical and biophysical parameters were similar in the animals from the different experimental groups. These results showed that high concentrations of magnetic iron oxide nanoparticles could be toxic and dangerous to the rats when take daily, but in low concentration it could be safe. / Com o rápido desenvolvimento da nanotecnologia, o homem vem utilizando cada vez mais essa nova tecnologia para auxiliá-lo no desenvolvimento de novos produtos que auxiliem no diagnóstico de doenças, fármacos e tratamentos de inúmeras enfermidades. Alguns autores vêm chamando a atenção para o uso de nanopartículas em vários produtos comerciais, pois pouco se sabe sobre sua toxicidade. Especificamente as nanopartículas de óxido de ferro magnético vêm sendo utilizadas em líquidos de contraste de ressonância magnética, tratamento de câncer, entre outros. Com isso, o objetivo deste trabalho foi analisar os possíveis efeitos tóxicos dessas nanopartículas administradas cronicamente em ratos adultos jovens. Ratos Wistar machos foram distribuídos em 3 grupos experimentais: Controle (salina 0,9% - 0,1mL/100g MC), nFe 0,3 (nanopartículas de óxido de ferro - 0,3 mg/kg MC) e nFe 0,6 (nanopartículas de óxido de ferro - 0,6 mg/kg MC). O tratamento foi realizado por gavagem gástrica, 5 dias por semana, durante 8 semanas. As análises de massa corporal (MC) dos animais indicou que a concentração de 0,6 mg/kg MC de nanopartículas de óxido de ferro magnético levou à uma diminuição da MC dos animais em relação aos animais tratados com 0,3 mg/kg MC e aos animais tratados solução salina 0,9%. Os animais do grupo nFe 0,6 apresentaram aumento de colesterol sanguíneo, entretanto as concentrações de glicose, ferro, uréia, creatinina, AST, ALT e fosfatase alcalina, além da análise hematológica não foram diferentes dos animais do grupo controle. Além disso, as glândulas seminais e próstatas ventrais dos animais tratados com nFe 0,6 mg/kg MC atrofiaram, sendo que as dos animais do grupo nFe 0,3 não apresentaram diferença em relação as do grupo controle. Os parâmetros biométricos, biomecânicos e biofísicos dos ossos (fêmur e vértebra) foram semelhantes nos 3 grupos experimentais. Portanto, o tratamento crônico com nanopartículas na concentração de 0,6 mg/kg MC foi prejudicial à saúde dos animais, exceto no tecido ósseo, sendo que tal efeito não foi observado com a concentração mais baixa.

Iron oxide nanoparticles have received sustained interest for biomedical applications as synthetic approaches are continually developed for precise control of nanoparticle properties. This thesis presents an investigation of parameters in the benzyl alcohol synthesis of iron oxide nanoparticles. A modified seed growth method was designed for obtaining optimal nanoparticle properties for magnetic fluid hyperthermia. With a one or two addition process, iron oxide nanoparticles were produced with crystallite sizes ranging from 5-20 nm using only benzyl alcohol and iron precursor. The effects of reaction environment, temperature, concentration, and modified seed growth parameters were investigated to obtain precise control over properties affecting radiofrequency heat generation. The reaction A2-24(205)_B2-24(205) produced monodispersed (PDI=0.265) nanoparticles with a crystallite size of 19.5±1.06 nm and the highest radiofrequency heating rate of 4.48 (°C/min)/mg (SAR=1,175.56 W/g, ILP=3.1127 nHm2/kg) for the reactions investigated. The benzyl alcohol modified seed growth method offers great potential for synthesizing iron oxide nanoparticles for radiofrequency hyperthermia.

This thesis consists of two parts. The first part deals with the magnetic properties of Fe3O4 nanocrystals and their possible application in water remediation. The second part is on the delamination of layered materials and the preparation of new layered hybrids from the delaminated sheets. In recent years, nanoscale magnetic particles have attracted considerable attention because of their potential applications in industry, medicine and environmental remediation. The most commonly studied magnetic nanoparticles are metals, bimetals and metal oxides. Of these, magnetite, Fe3O4, nanoparticles have been the most intensively investigated as they are, non-toxic, stable and easy to synthesize. Magnetic properties of nanoparticles such as the saturation magnetization, coercivity and blocking temperature are influenced both by size and shape. Below a critical size magnetic particles can become single domain and above a critical temperature (T B , the blocking temperature) thermal fluctuations can induce random flipping of magnetic moments resulting in loss of magnetic order. At temperatures above the blocking temperature the particles are superparamagnetic. Magnetic nanocrystals of similar dimensions but with different shapes show variation in magnetic properties especially in the value of the blocking temperature, because of differences in the surface anisotropy contribution. The properties of magnetic nanoparticles are briefly reviewed in Chapter 1. The objective of the present study was to synthesize Fe3O4 nanocrystals of different morphologies, to understand the difference in magnetic properties associated with shape and to explore the possibility of using Fe3O4 nanocrystals in water remediation. In the present study, oleate capped magnetite (Fe3O4) nanocrystals of spherical and cubic morphologies of comparable dimensions (∼10nm) have been synthesized by thermal decomposition of FeOOH in high-boiling octadecene solvent (Chapter 2). The nanocrystals were characterized by XRD, TEM and XPS spectroscopy. The nanoparticles of different morphologies exhibit very different blocking temperatures. Cubic nanocrystals have a higher blocking temperature (T B = 190 K) as compared to spheres (T B = 142 K). From the shift in the hysteresis loop it is demonstrated that the higher blocking temperature is a consequence of exchange bias or exchange anisotropy that manifests when a ferromagnetic material is in physical contact with an antiferromagnetic material. In nanoparticles, the presence of an exchange bias field leads to higher blocking temperatures T B because of the magnetic exchange coupling induced at the interface between the ferromagnet and antiferromagnet. It is shown that in these iron oxide nanocrystals the exchange bias field originates from trace amounts of the antiferromagnet wustite, FeO, present along with the ferrimagnetic Fe3O4 phase. It is also shown that the higher FeO content in nanocrystals of cubic morphology is responsible for the larger exchange bias fields that in turn lead to a higher blocking temperature. Magnetic nanoparticles with moderate magnetization can be easily separated from dispersions by applying low intensity magnetic fields. Oleate capped spherical and cubic iron oxide nanocrystals have considerable magnetic moment and hence have the potential as host-carriers for magnetic separation in environmental remediation. These nanocrystals are, however, dispersible only in non-polar solvents like chloroform, toluene, etc. Environmental remediation requires that the nanocrystals be water dispersible. This was achieved by functionalizing the surface of the iron oxide nanocrystals by coordinating carboxymethyl-β-cyclodextrin (CMCD) cavities (Chapter 3). The hydroxyl groups located at the rim of the anchored cyclodextrin cavity renders the surface of the functionalized nanocrystal hydrophilic. The integrity of the anchored CMCD molecules are preserved on capping and their hydrophobic cavities available for host-guest chemistry. The CMCD capped iron oxide particles are water dispersible and separable in modest magnetic fields (<0.5 T). Small molecules like naphthalene and naphthol can be removed from aqueous media by forming inclusion complexes with the anchored cavities of the CMCD-Fe3O4 nanocrystals followed by separation of the nanocrystals by application of a magnetic field. The adsorption properties of the iron oxide surface towards arsenic ions are unaffected by the CMCD capping so it too can be simultaneously removed in the separation process. To extend the application of the iron oxide nanocrystals so that they can both capture and destroy organic contaminants present in water, cyclodextrin functionalized water dispersible core-shell Fe3O4@TiO2 (CMCD-Fe3O4@TiO2) nanocrystals have been synthesized (Chapter 4). The application of these particles for the photocatalytic degradation of endocrine disrupting chemicals (EDC), bisphenol A and dibutyl phthalate, in water is demonstrated. EDC molecules that may be present in water are captured by the CMCD-Fe3O4@TiO2 nanoparticles by inclusion within the anchored cavities. Once included they are photocatalytically destroyed by the TiO2 shell on UV light illumination. The magnetism associated with the crystalline Fe3O4 core allows for the magnetic separation of the particles from the aqueous dispersion once photocatalytic degradation is complete. An attractive feature of these ‘capture and destroy’ nanomaterials is that they may be completely removed from the dispersion and reused with little or no loss of catalytic activity. The second part of the thesis deals with the intercalation of surfactants in inorganic layered solids and their subsequent delamination of the functionalized solid in non-polar solvents. The solids investigated were - the anionic layered double hydroxides (LDH), the 2:1 smectite clay, montmorillonite (MMT), layered metal thiophosphates (CdPS3) and graphite oxide (GO). Layered Double Hydroxides (LDH) are lamellar solids of the general chemical formula [M0(1−x)Mx(OH)2], where M0 is a divalent metal ion and M a trivalent ion. The structure of the Mg-Al layered double hydroxide (Mg-Al LDH) may be derived from that of brucite, Mg(OH)2, by isomorphous substitution of a part of the Mg2+ by trivalent Al3+ ions with electrical neutrality maintained by interlamellar exchangeable ions like nitrate or carbonate. The ion exchange intercalation of the anionic surfactant dodecyl sulfate (DDS) in an Mg-Al LDH and the subsequent delamination of the surfactant intercalated LDH in non-polar solvent is reviewed in Chapter 5. Delamination results in a clear dispersion of neutral nanosheets. The delaminated sheets are neutral as the surfactant chains remain anchored to the inorganic sheet. On solvent evaporation, the sheets re-stack to give back the original surfactant intercalated solid. This strategy for delamination of layered solids by intercalation of an appropriate surfactant followed by dispersing in a non-polar solvent has been extended to montmorillonite (MMT) and cadmium thiophosphates (CdPS3) by ion-exchange intercalation of the cationic surfactant dioctadecyldimethylammonium bromide (DODMA) followed by sonication in non-polar solvents e.g. toluene or chloroform as in the case of the LDH (Chapter 6). The nanosheets of the MMT and CdPS3 are electrically neutral as the surfactant chains remain anchored to the inorganic sheet even after exfoliation. Graphite oxide (GO) too can be delaminated by functionalizing the sheets by covalently linking oleylamine chains to the GO sheets via an amide bond. The oleylamine functionalized GO is easily delaminated in non-polar solvents to give electrically neutral GO nanosheets. It is shown in Chapter 7 that the 1:1 mixtures of dispersions of montmorillonite-DODMA with Mg-Al LDH-DDS nanosheets can self assemble, on solvent evaporation, to give a new layered solid with periodically alternating montmorillonite and LDH layers. In this method attractive forces between the neutral exfoliated nanosheets of cationic and anionic ensures self-assembly of a perfectly periodic alternating layered structure. The method has been extended to synthesize new layered solids in which surfactant tethered cationic and anionic inorganic sheets alternate. The hybrid solids synthesized are CdPS3—MgAl-LDH, CdPS3—CoAl-LDH, GO—MgAl-LDH, GO—CoAl-LDH. The procedure outlined in Chapter 7 allows for a simple, but versatile, method for generating new periodically ordered layered hybrid solids by self-assembly.