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Nanofibras de ZnO foram produzidas a partir de precursores à base de poli(álcool vinílico) (PVA) e acetato de zinco (AcZn) obtidos por eletrofiação, nas proporções mássicas de PVA/AcZn 1:1; 2:1 e 4:1, e posterior calcinação. Bandas características da ligação Zn-O e de transições eletrônicas do ZnO foram detectadas nos espectros de infravermelho (FTIR) e absorção fotoacústica (PAS) das nanofibras. Picos cristalinos característicos da estrutura wurtzita e fase hexagonal do ZnO foram detectados nos difratogramas de raios-X (DRX) das amostras produzidas. Os valores de energia de gap (Eg) estimados para as nanofibras de ZnO produzidas após calcinação dos precursores PVA/AcZn 1:1; 2:1 e 4:1 foram de 2,95; 3,15 e 3,02 eV, respectivamente, e a área específica (SBET) destas respectivas amostras foi de 25,26 m²/g; 20,95 m²/g e 23,79 m²/g. As imagens de MEV e MET das amostras de ZnO revelaram que após calcinação, a morfologia de fibra foi mantida apenas para aquelas produzidas a partir dos nanofios precursores de PVA/AcZn 1:1 e 4:1. Todas as amostras de ZnO exibiram excelente desempenho fotocatalítico, degradando cerca de 99% do corante Azul de Metileno, em ambos pH 7,0 e 9,0, e após 240 minutos de irradiação UV-visível.

Rice husks (RH) are a known agricultural residue due to their abundance of silicon, that can be extracted for the production of materials with added high-value. Although part of RH can be converted into useful products, most of it is incinerated generating a large amount of toxic compounds, being of particular importance to find economically and environmentally viable alternatives to promote the full use of RH. In this study, mesoporous silica nanoparticles (MSNs) were synthesized, considering the green chemistry principles, using sodium silicate extracted from RH as a silica source. The capacity of MSNs for loading and release the doxorubicin (DOX) chemotherapeutic drug was evaluated, in order to assess their use in drug delivery systems (DDS). MSNs exhibited attractive textural properties and colloidal stability, that contributed to a high encapsulation efficiency of DOX and to a release rate of about 40% in both simulated intestinal fluid (SIF) and simulated gastric fluid (SGF). The in vitro cytotoxicity assays assured that our eco-friendly MSNs are not cytotoxic for healthy fibroblast cells, whilst MSNs-DOX killed about 70% of colorectal cancerous cells (Caco-2) after 72 h, demonstrating that MSNs produced from RH may have a valuable application in the pharmaceutical area as a promising platform for cancer therapy.

Nano-catalysts based on ZnO-Ca x% (with x = 0, 0.1, 0.3, 0.5, 0.7, and 1.0 mol % Ca2+) were synthesized with a bio-friendly adaptation of the sol-gel method using gelatin as template. These materials were characterized by Fourier Transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Micro-Raman, transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 physisorption, photoacoustic absorption spectroscopy (PAS), and photoluminescence spectroscopy (PL). The Raman results indicated that the signal, attributed to an E1(LO) mode at 580 cm−1, was characteristic of oxygen vacancies that decreased with the increased Ca2+ content in doped oxides. This agreed with the PL results, which showed that the green emission centered at 510 nm and attributable to structural defects in ZnO decreased for Ca-doped ZnO. Our oxides are constituted by nanoparticles with rod-like and spherical morphologies. All the nano-catalysts exhibited the band gap characteristics of semiconductor materials around 3.0 eV. ZnO-Ca 1.0% exhibited the best photocatalytic performance for degradation of Methyl Orange (MO) model dye, degrading about 82% after 240 min of UV–Vis irradiation at pH 7.0. The reaction mechanism was influenced by hydroxyl ( OH) and superoxide (O2 -) radicals and mainly by active holes (h+). This doped oxide also demonstrated efficiency in wastewater disinfection against heterotrophic bacteria and total coliforms, exhibiting a potential use as an antimicrobial agent for the treatment of hospital wastewater. Furthermore, our nanoparticles did not show significant cytotoxic effects on L929 fibroblast cells.

Al2O3-Zn x% NPs, with x = 0, 1, 3, 5 or 10 mol% Zn2+ were synthesized by a modified sol–gel method. The influence of the insertion of Zn2+ dopant on the crystal lattice, morphology, optical and cytotoxic properties of Al2O3 was investigated. Rietveld refinement applied to DRX data revealed that the oxides are constituted by four crystalline phases: α-Al2O3, θ-Al2O3, δ-Al2O3 and α-Al2O3(*), and that the doping promoted changes in unit cell volume for all the crystalline phases. Raman signals indicated that the insertion of Zn2+ caused changes in the vibrations of bonds Al–O, mainly in tetrahedral sites of transition phases of Al2O3, which are preferentially occupied by Zn ions. The oxides exhibited photoluminescence emission in the visible and near-infrared region, but Al2O3-Zn 10% showed increased emission intensity in the visible region. The nanoparticles with spherical and elongated morphologies did not exhibit cytotoxic effects on L929 fibroblast cells. Zn-doped Al2O3 nanoparticles were synthesized by a modified sol-gel method. The influence of the insertion of Zn2+ dopant on the crystal lattice, morphology, optical and cytotoxic properties of Al2O3 was investigated.

Inorganic nanoparticles incorporation in polymer membranes for filtration processes has attracted the attention of researchers in order to improve in some ways their performance. In this work, AgNPs were synthesized "in situ" in cellulose acetate (CA) membrane by chemical reduction of a silver salt. The membranes were prepared by the nonsolvent induced phase inversion method. Asymmetric membranes without (CA-M) and with adsorbed AgNPs (CA-Ag-M) were obtained. Ultrafiltration properties were confirmed for both membranes (16 nm of average pore diameter) and average crystallite size of 21 nm for the adsorbed AgNPs was computed. Contact angle measured with Milli-Q water and dry CA-Ag-M is near zero while for the CA-M is around 80°. The CA-M showed water permeability of 214 Lh-1m-2, while the CA-Ag-M permeability was 1651 Lh-1m-2.

ZnO-Al x% nanoparticles (NPs), with x = 0, 1, 3, 5 or 10 mol% Al3+, were synthesized by a modified sol-gel method. The effects of Al3+ content on the structure, morphology and optical properties of Al-doped ZnO were investigated by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, photoacoustic absorption spectroscopy (PAS), photoluminescence spectroscopy (PL) and specific surface area determination. A single crystalline phase characteristic of ZnO with wurtzite structure was detected for all synthesized oxides. With increasing dopant content, the average crystallite size of the NPs decreased from 25 to 7 nm. ZnO-Al x% NPs exhibited enhanced optical properties with the absorption slightly shifted to the visible region and with the band gap energy (Eg) decreased from 3.12 (undoped ZnO) to 2.95 eV (ZnO-Al 3%). Undoped ZnO showed intense PL above 430 nm, which was considerably decreased with the insertion of Al3+. Despite the increase of the surface area with Al3+ doping of ZnO NPs, its catalytic activity in the decomposition reaction of Congo red showed a decrease with doping. Research has shown that ZnO NPs can selectively target and kill cancer cells and that its cytotoxicity is dependent of the concentration. The doping can be a method of shape the cytotoxicity of ZnO NPs and their optical and photocatalytic properties. In-vitro cytotoxicity studies showed that both undoped ZnO and Al-doped ZnO NPs synthesized were highly cytotoxic for fibroblast cells, suggesting that these nanomaterials could be promising anticancer agents.

Hybrid materials based on cuprous oxide nanoparticles (Cu2ONPs) adsorbed on cotton fabric (CF) fibers were synthesized by in situ Cu2+ reduction. Ascorbic acid (AsA) or hydroxylamine (HA) was used as chemical reducing agent in the presence of polyvinylpyrrolidone (PVP) or lactose (Lac) as protective agent. UV-Vis diffuse reflectance spectra of the samples showed absorption bands in the region of 400–600 nm, attributed to Cu2O. Band gap energy estimated for Cu2O were about 2.5 eV and 2.2 eV for samples synthesized with AsA and HA, respectively. X-ray diffractograms showed characteristic peaks to cellulose I and Cu2O. AsA provided Cu2O with smaller particle size, better covering of the fibers as observed by scanning electron microscope and confirmed by contact angle measurements. CF-Cu2O nanocomposites exhibited interesting activity against S. aureus bacteria.

This work describes the synthesis of ferrite nanoparticles and the zinc and cobalt doping effect on tuning their magnetic properties. The zinc doping led to formation of a secondary crystalline phase (ZnO), which meant that the Zn and Co individual ions show different physical-chemical affinities for the two types of lattice sites. Zero-field cooling and field cooling curves were elaborated to study the magnetization unblocking process of these nanoparticles. The metal doping effect led to large differences in the magnetization curves. The zinc-doped samples were shown to exhibit classical magnetization unblocking, being superparamagnetic below the room temperature. The cobalt doping increased the blocking temperature to above room temperature. The amount of cobalt did not change the coercive field of the doped samples. The coercive field of zinc-doped samples followed the same trend, but with a much lower value (0.6 kOe) when compared with cobalt-doped samples (18 kOe), showing a great change in magnetic anisotropy. The current synthesis approach offered a facile way to synthesize ferrite nanoparticles with metal doping-tunable magnetic properties by an environmentally friendly and facile sol-gel approach using water as solvent. This finding motivated us to think these ferrite nanoparticles can be attractive for biomedical and/or technological applications, although further studies other than these are still required.

Chromium-doped $$\alpha$$ - $$\hbox {Al}_{2}\hbox {O}_{3}$$ powder was synthesized by a modified sol–gel method using poly(vinyl alcohol) aqueous solutions and metal nitrate precursors. The synthesis process is simple, is of low cost and produced final crystals with cubic shape as confirmed by X-ray diffraction. The morphology of the samples verified by scanning electron microscopy showed slabs with thickness below 1 $$\upmu {\mathrm{m}}$$ , formed by interconnected long grains of typical thickness of around 200 $${\mathrm{nm}}$$ , showing growth of the grains as followed by thermogravimetric analysis. Luminescence characteristics of $$\hbox {Cr}^{3+}$$ were detected and analyzed as a function of the concentration of chromium using photoacoustic and photoluminescence spectroscopies.

Films and fibers of PMMA/ZnO nanocomposites (100/0, 99/01, 97/03, 95/05, 90/10, and 85/15 wt.%) were produced by casting and electrospinning, respectively. Their structural, thermal, and optical properties were investigated by XRD, SEM, TGA, PAS, and PL. The incorporation of ZnO NPs reduced the diameter of PMMA fibers and the presence of beads. The surfaces of the fibers exhibited greater hydrophobicity, compared to the films, with contact angles of around 120° and 94°, respectively. PMMA films containing ZnO exhibited higher thermal stability than the pure polymer, while the corresponding fibers did not show any changes in thermal stability. The dispersion of the ZnO NPs at the surface and in the bulk of the nanocomposites appeared to be relatively homogeneous. ZnO improved the optical properties of the PMMA, with an intense absorption band near 370 nm observed for all the nanocomposites, which also exhibited luminescence with emission in the near-UV region, both attributed to ZnO. Biological tests demonstrated that fibers and films with up to 1% of ZnO exhibited good performance in the proliferation of fibroblast cells, indicating their potential for applications in tissue engineering. The fibers provided higher cell viability than the films, presumably due to their greater surface area and/or more suitable surface morphology. Nanocomposites with 15% ZnO inhibited cell proliferation, due to the cytotoxicity of the ZnO NPs. Although several applications of PMMA have been suggested by biomedical researchers, until now there have been no reports on the specific uses of fibers and films of PMMA/ZnO nanocomposites as scaffolds for fibroblast cell proliferation.

Mn-doped ZnO nanoparticles were successfully synthesized through the sol–gel technique. X-ray diffraction results showed that Mn doping did not disturb the hexagonal wurtzite structure of ZnO and no secondary phases were identified. Raman studies indicated the presence of defects in the form of oxygen vacancy clusters created due to Mn doping. Ferromagnetic-like curves were determined at room temperature for the sample with low doping (2% Mn). The results indicate that the observed ferromagnetism at room temperature can essentially be attributed to interactions mediated by magnetic impurities throughout the large number of oxygen vacancies created by Mn ions.

Silver nanoparticles (AgNPs) have attracted great attention due to its optical, electrical and thermal properties. Cellulosic supports for these nanoparticles are of particular interest because of its availability, flexibility and biocompatibility. In this work, AgNPs were synthesized using two cellulosic materials, cellophane (CP) and filter paper (FP), as matrix support. Cellulosic materials were immersed in an aqueous solution of silver nitrate containing polyvinylpyrrolidone (PVP) and then reduced with hydroxylamine. The obtained nanocomposites (CP-AgNPs and FP-AgNPs) were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (DRX) and scanning electron microscopy (SEM). AgNPs of near 15nm anchored onto cellulosic surfaces were detected. The thermal properties of these materials were investigated through thermogravimetry (TG). Their kinetic of thermal decomposition was studied by the Vyasovkin method of dynamic isoconvertion, which indicated a catalytic effect of AgNPs in the cellulose thermal decomposition reaction.

Fe2O3 nanoparticles (as maghemite and hematite mixtures) were prepared using adapted sol-gel method from a polyvinylpyrrolidone (PVP) aqueous solution in various Fe3+ : PVP monomer ratios. Analysis of X-ray diffraction was obtained to evaluate the crystalline state, average crystallite size, and composition of iron oxide phases. The morphology and average nanoparticles size were evaluated by electronic transmission microscopy. Magnetic properties of iron oxide were analyzed at low and room temperatures. Optical characteristics were evaluated by UV-Vis photoacoustic spectroscopy and the Mössbauer spectrum was obtained in order to evaluate subtle changes in the nuclear environment of the iron atoms.

It is becoming progressively more understandable that different phytochemicals isolated from edible plants interfere with specific stages of carcinogenesis. Cancer cells have evolved hallmark mechanisms to escape from death. Concordant with this approach, there is a disruption of spatiotemproal behaviour of signaling cascades in cancer cells, which can escape from apoptosis because of downregulation of tumor suppressor genes and over- expression of oncogenes. Genomic instability, intra-tumor heterogeneity, cellular plasticity and metastasizing potential of cancer cells all are related to molecular alterations. Data obtained through in vitro studies has convincingly revealed that curcumin, EGCG, resveratrol and quercetin are promising anticancer agents. Their efficacy has been tested in tumor xenografted mice and considerable experimental findings have stimulated researchers to further improve the bioavailability of these nutraceuticals. We partition this review into different sections with emphasis on how bioavailability of curcumin, EGCG, resveratrol and quercetin has improved using different nanotechnology approaches.

Pure and Co-doped ZnO nanoparticles were synthesized with different cobalt levels (1–10 mol%) via adapted sol–gel method using water as solvent and characterized by X-ray diffraction, transmission electron microscopy, Raman spectroscopy and photoacoustic absorption spectroscopy. The results showed that all the samples have hexagonal wurtzite structure, with no evidence of any secondary phases until 10 mol% of the dopant. The average crystallite size of the samples was in the range of 25–50 nm, do not showing significant differences with the increase of the dopant level. However, the band gap energy of the nanoparticles decreases from 2.98 eV (pure ZnO) to 1.95 eV (10 mol% of Co). The photocatalytic activity of the samples was evaluated on the removal of methylene blue under visible light irradiation, which revealed an efficiency reduction by Co-doping ZnO. The antibacterial property was carried out indicating activity of the prepared samples against gram-positive bacteria.

In this work, Fe-doped and mixed ZnO nanoparticles were synthesized via a modified sol–gel method using water as unique solvent. The structural properties were analyzed by X-ray diffraction and the results showed the existence of wurtzite ZnO structure. The XRD results also indicate a phase segregation in the samples with more than 2 mol% of Fe. UV–Vis diffuse reflectance spectra showed that Fe-doped ZnO exhibited a red-shift of the band-edge and a decrease in band gap energy, as compared to pure ZnO. The surface area increased significantly with the iron addition, and TEM analysis revealed hexagonal nanoparticles.

The acetone-soluble lignin fraction (ASLF) of sugar cane bagasse, from a sugar and alcohol factory residue, was obtained after extraction with formic acid and used to prepare blends with poly(vinyl acetate) (PVAc) by casting. PVAc and ASLF/PVAc blends were irradiated with ultraviolet light (Hg lamp). Blend formation and the irradiation effects were examined through thermal analysis (TG and DSC), scanning electron microscopy, and atomic force microscopy. The DSC results show PVAc glass transition temperature (T g) shifts because of both, irradiation and ASLF incorporation. Non-irradiated pure PVAc presented a smooth surface, while after UV irradiation, light surface spots are observed. ASLF/PVAc 10/90 and 5/95 blends did not exhibit differences before and after UV irradiation, suggesting that lignin protects PVAc from photochemical degradation.

Estudou-se neste trabalho, a cinetica de adsorcao e o equilibrio de adsorcao do azul de metileno (AM) em lignina formica reticulada (LFR) obtida do bagaco de cana de acucar. O processo de adsorcao e dependente do pH, temperatura e forca ionica (µ) e obedece ao modelo de Langmuir. Algumas condicoes como a alta capacidade e velocidade de adsorcao foram determinadas. Observouse rapida adsorcao (12 horas) e alta capacidade de adsorcao (34,20 mg.g-1) em pH = 5,8 (tampao aceta-to de sodio-acido acetico), 50oC e 0,1 de forca ionica. Para alcancar o equilibrio de adsorcao, o sistema foi termostatizado com tempos de 1 a 10 dias, com agitacao ocasional.

Numerous investigations are dedicated to the research and development of new polymer materials destined for innovation in pharmaceutical forms. The application of these technological resources has allowed the commercialization of new therapeutic systems for modified drug release. This investigation aimed to evaluate the association of modified chondroitin sulfate with an insoluble polymer, Eudragit® RS 30 D, widely available in the pharmaceutical market. Isolated films were prepared by the evaporation process using a Teflon® plate. The aqueous dispersions (4% m/v) of synthetic polymer received the addition of modified chondroitin sulfate at different ratios. The interactions of the polymer chains in the blends were physicochemically characterized by means of Fourier transform infrared spectroscopy, thermal analyses, differential scanning calorimetry, thermogravimetry and scanning electron microscopy combined with hydration and assays in alkaline pH. The results showed appropriate properties of the coating materials for solid oral forms intended for drug deliver in specific environments.

Iron oxide nanoparticles (ION) have been studied for essential applications, like detection of biological constituents (virus, bacterials, cell, nucleic acids, protein, enzyme, etc.), magnetic bioseparation and clinic therapy and diagnosis (such as MRI magnetic fluid and hyperthermia). In this work, γ-Fe2O3 has been synthetized by a adapted sol-gel method and entraped in poly e-caprolactone (PCL) nanocapsules. The superparamagnetic nanocapsules have been formulated by double emulsion evaporation method. Some variables affecting the polydispersity index, zeta potential surface and size of nanocapsules were studied aiming optimize the formulation process of maghemite-loaded PCL nanocapsules. The following parameters were selected: sonication time, PCL concentration in organic phase, PVA concentration in external aqueous phase and maghemite/PCL weight ratio. Under these experimental conditions, the resulting nanocapsules displayed a mean size of about 346 nm and a maghemite content of about 7.5 µg/mg of nanocapsules and superparamagnetic behaviour at room temperature.

Alkaline lignin was isolated from sugar cane bagasse for polyblends preparation with three poly (vinyl alcohol) (PVAl) samples (80, 87 and 98% hydrolyzed). Blends preparation was carried out by thorough manual grinding the solid polymer powders, and for one system a comparison was made with blends prepared without grinding. The resulting blends were studied by thermal analysis (TGA and DSC). Miscibility evaluation by T g determination was possible only in some extent because it was not clearly detected in all cases. These results suggest at least some miscibility of the lignin/PVAl80 and lignin/PVAl87 systems and immiscibility of the lignin/PVAl98 blend. Differences were observed in the properties of the blends prepared with and without grinding. Apparent activation energy of pyrolysis reaction ( E a ) were evaluated from TGA curves for pure polymers and blends. E a of PVAl increases with increasing acetate group content. E a of the blends suggest a dependence of thermal stability on the hydrolysis degree of the PVAl. Other parameters obtained from TGA and DSC curves were also analysed.

Magnetic nanoparticles have been proposed as interesting tools for biomedical purposes. One of their promising utilization is the MRI in which magnetic substances like maghemite are used in a nanometric size and encapsulated within locally biodegradable nanoparticles. In this work, maghemite has been obtained by a modified sol–gel method and encapsulated in polymer-based nanospheres. The nanospheres have been prepared by single emulsion evaporation method. The different parameters influencing the size, polydispersity index and zeta potential surface of nanospheres were investigated. The size of nanospheres was found to increase as the concentration of PLGA increases, but lower sizes were obtained for 3 min of sonication time and surfactant concentration of 1%. Zeta potential response of magnetic nanospheres towards pH variation was similar to that of maghemite-free nanospheres confirming the encapsulation of maghemite within PLGA nanospheres. The maghemite entrapment efficiency and maghemite content for nanospheres are 12% and 0.59% w/w respectively.

Cellulose from a cotton residue was isolated, characterized and used for benzylcellulose preparation. A comparative study was done using a commercial cellulose. IR, DSC and TGA were used to characterize celluloses and benzylcelluloses. Experimental data showed that the cotton residue cellulose has a different thermal behavior compared to other celluloses. On the other hand the infrared spectra are identical. Benzylcelluloses with high substitution degree obtained by reaction of celluloses with benzylchloride, showed very similar thermal behavior, but a little higher thermal stability of the commercial cellulose derivatives was always observed.

The separation of cupric ions from aqueous solution by adsorption onto modified corncobs (hemicellulose-free) was studied. The adsorption process was found to take ∼ 15 minutes to attain equilibrium in experiments with continuous agitation at 35°C. The process was found to be pH-dependent, with increasing adsorption as pH increases up to 6.00. There is evidence that the adsorption mechanism is an ion-exchange one involving carboxylate groups, and that two binding sites may be present at the adsorbent. The adsorption was found to fit a Langmuir isotherm, and the parameters n s (adsorbent capacity) and b (adsorption intensity) were calculated. The results obtained show that corncobs are an interesting adsorbent because they are available in large quantities at several places in the world at little or no cost, and they retain cupric ions rapidly. The corncobs studied also contain aliphatic and phenolic hydroxyl groups that allow for the incorporation of other functional groups and thus increase the ...

Latex-based adhesives and paints can be fractionated by isopycnic sedimentation in density gradients, generated by osmocentrifugation. Fractions were obtained from a PVA-based adhesive, which differed in tacticity, as observed by 1H NMR; calcium carbonate was easily identified in another product, after fractionation. In an acrylic-based latex paint the pigments contained PVA, although this polymer was not detected in other fractions. These results show that low-speed isopycnic sedimentation in density gradients is a convenient, gentle, inexpensive, and powerful method to fractionate complex particle admixtures. A marked advantage of this method is its ability to give fractions large enough for examination by other analytical techniques.

Microcrystalline cellulose (MCC) is a very important product in pharmaceutic, food, cosmetic and other industries. In this work, MCC was prepared from soybean husk, produced in large quantities in soybean oil processing industries. It was characterized through various techniques (scanning electron microscopy (SEM), infrared spectroscopy (FTIR), thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC)) and compared with a commercial MCC. The results obtained show that the prepared sample has similar crystallinity and lower particle size than the commercial MCC. Both MCC samples were treated with organic solvents (chloroform, acetone, ethanol and ethyl ether), for structural modifications to be introduced, and used as acetylsalicylic acid (ASA) carrier. Pretreated MCC and MCC/ASA 1:1 mixtures were analyzed through FTIR and thermal analysis. The drug release was evaluated in buffer solution of pH 4.5 and in pure water, at 37 degrees C. The MCC pretreated with different solvents show different thermal properties and ASA release rates, each MCC showing a particular behavior.

Fe2O3 nanoparticles with sizes ranging from 15 to 53 nm were synthesized by a modified sol-gel method. Maghemite particles as well as particles with admixture of maghemite and hematite were obtained and characterized by XRD, FTIR, UV-Vis photoacoustic and Mossbauer spectroscopy, TEM, and magnetic measurements. The size and hematite/maghemite ratio of the nanoparticles were controlled by changing the Fe:PVA (poly (vinyl alcohol)) monomeric unit ratio used in the medium reaction (1:6, 1:12, 1:18, and 1:24). The average size of the nanoparticles decreases, and the maghemite content increases with increasing PVA amount until 1:18 ratio. The maghemite and hematite nanoparticles showed cubic and hexagonal morphology, respectively. Direct band gap energy were 1.77 and 1.91 eV for A6 and A18 samples. Zero-field-cooling–field-cooling curves show that samples present superparamagnetic behavior. Maghemite-hematite phase transition and hematite Neel transition were observed near 700 K and 1015 K, respectively. Magnetization of the particles increases consistently with the increase in the amount of PVA used in the synthesis. Mossbauer spectra were adjusted with a hematite sextet and maghemite distribution for A6, A12, and A24 and with maghemite distribution for A18, in agreement with XRD results.

Polymer latexes can be fractionated by size and by chemical composition through osmocentrifugation. Density gradients are formed by centrifuging Ficoll and Percoll solutions in dialysis cells; mixed polymer latex zones are layered over these gradients and centrifuged again, leading to separated latex bands from which polymer may be collected and further analyzed. Zone migration rates in the osmocentrifugation experiment are faster than in standard centrifugation tubes.

A novel ultrafiltration device is described. It consists of a vertical dialysis cell in which the semipermeable membrane is supported by a metal or plastic porous, rigid sheet. The dialysis cell is mounted in a centrifuge swinging bucket, or rotor hole, with the membrane parallel to the centrifuge radius. Experiments are performed by filling one dialysis cell compartment with the liquid sample to be treated and by spinning it in a centrifuge. Effluent is collected from the other (initially empty) compartment of the dialysis cell. Membranes used in these cells have similar permeabilities but better retention than those used in unstirred ultrafiltration cells for small filtrate volumes.

Orientador : Fernando Galembeck Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica Doutorado

Activated carbons were prepared and characterized using flamboyant pods by chemical a, activation with NaOH under conditions of activation temperature of 700°C, activation time of 1.5 h and three different ratios NaOH/charcoal: 1:1 (CA-1), 2:1 (CA-2) and 3:1 (AC-3). The properties of these materials, including BET surface area, total pore volume, micropore volume, mesopore volume, pore diameter and pore size distribution were obtained from N2 adsorption and desorption isotherms. The activated carbons obtained were essentially microporous. Thermogravimetric analysis, Fourier transform infrared spectroscopy and solid state 13C nuclear magnetic resonance spectroscopy, allowed identify the lignocellulosic structure of the precursor and the presence of heteroaromatic groups on the surface of activated carbons. Scanning electron microscopy images showed a high pore development by the process. The process optimization of the best conditions of temperature, time and ratio NaOH/charcoal was performed using the response surface methodology. In this methodology, a central composite rotatable design of three factors and five levels was developed to know the optimum values of the responses; BET surface area and yield. Statistical analysis showed that the ratio NaOH/charcoal and temperature are the factors that most affect the responses mentioned above. The best conditions of temperature (761.70°C), time (0.86h) and ratio NaOH/charcoal (3.46:1), showed a BET surface area of 2854 m² g-1 and yield of 10.8%. The results indicated the potential use of flamboyant pods as a precursor material in the preparation of low-cost activated carbon. Carvões ativados foram preparados e caracterizados usando vagens de Flamboyant mediante ativação química com NaOH em condições de temperatura de ativação de 700°C, tempo de ativação de 1,5 h e três diferentes razões NaOH/carvão: 1:1 (CA-1), 2:1 (CA-2) e 3:1 (CA-3). As propriedades destes materiais, incluindo área superficial BET, volume total dos poros, volume de microporos, volume de mesoporos, diâmetro do poro e distribuição dos poros foram obtidas a partir das isotermas de adsorção e dessorção de N2. Os carvões ativados obtidos foram essencialmente microporosos. Análises termogravimétricas, espectroscopia no infravermelho com transformada de Fourier e ressonância magnética nuclear de 13C no estado sólido, permitiram identificar os componentes lignocelulósicos do precursor e a presença de grupos heteroaromáticos na superfície dos carvões ativados. As imagens de microscopia eletrônica de varredura mostraram um alto desenvolvimento de porosidade durante o processo. Um processo de otimização das melhores condições de temperatura, tempo e razão NaOH/carvão foi realizado utilizando a metodologia de superfície de resposta. Nesta metodologia, um planejamento composto central rodável de três fatores e cinco níveis foi desenvolvido para conhecer os valores ótimos das respostas; área superficial BET e rendimento. As análises estatísticas mostraram que a razão NaOH/carvão e a temperatura são os fatores que mais afetam as respostas mencionadas anteriormente. As melhores condições de temperatura (761,70°C), tempo (0,86h) e razão NaOH/carvão (3,46:1), apresentaram uma área superficial BET de 2854 m² g-1 e rendimento de 10,8 %. Os resultados indicam que a vagem de Flamboyant é um precursor com um alto potencial para ser utilizado na produção de carvão ativado de baixo custo. 87 f