P.M.A.G. Araújo

Obtaining of Chitosan/ZNAL1,9EU0,05O4 Film for Application as Biomaterial

This work reports the development and characterization by SEM, XRD, FTIR, emission and excitation chisonan/ZnAl1.9Eu0.05O4 films with a mass proportion of 1:1. The powders were deagglomerated and passed 325 mesh screens and added to the diluted chitosan in 1% acetic acid. The materials were filtered and placed in petri dishes and placed in an oven at 60°C for solvent evaporation. After drying the film, a solution of 1M sodium hydroxide was added in order to obtain a film with neutral pH. With the XRD, it has been verified that the chitosan/ZnAl1.9Eu0.05O4 films presented the chitosan peaks and ZnAl2O4. Through the SEM, it has been observed that the chitosan/ZnAl1.9Eu0.05O4 presented a protruding surface. The results presented in emission and excitation spectra suggest that the film chitosan/ ZnAl1.9Eu0.05O4 exhibit good luminescence properties, and are promising to be applied as a luminescent marker in future applications in the field of biomaterials.

Synthesis and Characterization Nanoparticles ZnAl1.94(Yb:Er)0.06O4 Functionalized with Chitosan

This work aims to synthesize combustion reaction, functionalized with chitosan nanoparticles and characterize ZnAl1.94(Yb:Er)0.06O4, codoped with x = 0.06 mol in the proportion 5:1 of Yb:Er. Nanoparticles before and after functionalization were characterized by XRD, TGA/DTA, FTIR and SEM. The results show that before and after functionalization presented ZnAl2O4 majority phase and Al2Yb4O as secondary phase. Multiple bands around 1100 cm-1 and 1040 cm-1 corresponding to the asymmetric stretching Si-O confirms the functionalization of nanoparticles. Nanoparticles presented before functionalization morphology heterogeneous, consisting of clusters of particles with near-spherical shape, large particle size distribution, consisting of large clusters with size around 3 µm and smaller clusters in the shape of plates with size in order of 0.5 µm. After functionalization, the morphology shows the formation of a film consisting of amorphous phase and crystalline phase. The mass loss for the nanoparticles before and after functionalization was 7.2 and 39%, respectively.

Avaliação catalítica dos espinélios ZnAl2O4 e ZnAl1,9Eu0,1O4 na transesterificação metílica do óleo de soja

Este estudo objetivou avaliar o efeito da dopagem de europio na estrutura e na morfologia do espinelio ZnAl1,9Eu0,1O4 e seu desempenho como catalisador na transesterificacao metilica do oleo de soja. Os pos do espinelio ZnAl1,9Eu0,1O4 foram sintetizados por meio da reacao de combustao e caracterizados por difracao de raios X (DRX), espectroscopia de absorcao optica na regiao do infravermelho com transformada de Fourier (FTIR), microscopia eletronica de varredura e analise termogravimetrica. As reacoes de transesterificacao foram conduzidas a 160 e 180 oC, razao molar oleo/alcool 1:15, 2% de catalisador e tempo de reacao 3 h. Os resultados das caracterizacoes por DRX e FTIR indicaram a fase espinelio do aluminato e duas bandas de absorcao entre 450 e 700 cm-1, caracteristicas da estrutura de espinelio. Os resultados das reacoes de transesterificacao mostraram que a dopagem de ZnAl2O4 com 0,1 mol de europio favoreceu um aumento na conversao catalitica de 15,8% para 68,7%, indicando que os ions europio tornam o catalisador mais ativo. Aumentando a temperatura da reacao de 120 para 180 oC promoveu um aumento consideravel na conversao catalitica de 18,4 para 68,7%, utilizando o catalisador dopado com europio. A conversao do catalisador reutilizado ZnAl1,9Eu0,1O4 mostrou uma reducao em cerca de 31% quando foi utilizado pela terceira vez.

Nanoferrites Ni-Zn Silanized with 3-Aminopropyltrimethoxysilane Using the Reflux Method

In this paper we propose nanoferrites Ni-Zn silanization with 3-aminopropyltrimethoxysilane using the method of reflux and evaluate the effect of silanization on the structure, morphology and magnetism of the magnetic nanoparticles aimed at biological applications. The samples as synthesized and after silanization were characterized by XRD, FTIR, SEM and testing magnetic attraction. The results indicated a single phase inverse spinel Ni-Zn ferrite, high intensity of diffraction peaks and a high basal width of all reflections observed, indicating that the samples are crystalline, and formation of nanoparticles. Morphologically, for nanoferrites Ni-Zn synthesized observed formation of large agglomerates in the form of spongy blocks of frail and after silanization was observed with respect dense pellets, indicating that most particles were rigidly connected by the presence of the agent silane. The characteristic bands of the spinel were observed for the Ni-Zn nanoferrites before and after silanization, and also observed the characteristic bands of silane in confirming the ferrites silanized functionalization of ferrites with the silane agent. Nanoparticles ferrite as synthesized and after silanized were strongly attracted by the presence of a magnet, immediately after the presence thereof indicating that the silane is effective is not interfere with the magnetic particles, maintaining the same magnetic behavior.

Avaliação da fotoluminescência do TiO 2 sintetizado pelo método Pechini

Titanium dioxide (TiO2) stands out for use in various applications mainly due to its properties of thermal and chemical stability and its excellent optical properties. However, these properties are dependent on the type and phase morphology, which is related to the TiO2 processing method. Thus, this paper proposed to synthesize TiO2 nanoparticles by polymeric precursor method with different polymorphs, and evaluate the influence of these phases in the photoluminescent properties. For this, the stoichiometric molar proportions of citric acid:metallic cations of 1:1, 2:1, 3:1, 4:1 and 5:1 were investigated. The nanoparticles were characterized by X-ray diffraction (XRD), infrared spectroscopy, textural analysis, scanning electron microscopy (SEM), excitation and emission spectroscopy and determination of the band gap by UV-Vis diffuse reflectance spectroscopy. The presence of anatase and rutile was confirmed by XRD in different proportions for each sample. The agglomerate size increased with the citric acid/metal cations ratio as observed by SEM. Concerning photoluminescence, the maximum intensity in the emission spectrum occurred at the wavelength of 533 nm for the 3:1 sample and the maximum intensity in the excitation spectrum occurred for the 2:1 sample at the wavelength of 451 nm.Titanium dioxide (TiO2) stands out for use in various applications mainly due to its properties of thermal and chemical stability and its excellent optical properties. However, these properties are dependent on the type and phase morphology, which is related to the TiO2 processing method. Thus, this paper proposed to synthesize TiO2 nanoparticles by polymeric precursor method with different polymorphs, and evaluate the influence of these phases in the photoluminescent properties. For this, the stoichiometric molar proportions of citric acid:metallic cations of 1:1, 2:1, 3:1, 4:1 and 5:1 were investigated. The nanoparticles were characterized by X-ray diffraction (XRD), infrared spectroscopy, textural analysis, scanning electron microscopy (SEM), excitation and emission spectroscopy and determination of the band gap by UV-Vis diffuse reflectance spectroscopy. The presence of anatase and rutile was confirmed by XRD in different proportions for each sample. The agglomerate size increased with the citric acid/metal cations ratio as observed by SEM. Concerning photoluminescence, the maximum intensity in the emission spectrum occurred at the wavelength of 533 nm for the 3:1 sample and the maximum intensity in the excitation spectrum occurred for the 2:1 sample at the wavelength of 451 nm.

Modificação da superfície do ZnAl1,9Eu0,05O4 visando a obtenção do híbrido ZnAl1,9Eu0,05O4/SiO2 para aplicação como biossensor

This study aimed to investigate the influence of surface modification of ZnAl1.9Eu0.05O4 nanoparticles for obtaining hybrid ZnAl1.9Eu0.05O4/SiO2 for application as a biosensor. Initially ZnAl1.9Eu0.05O4 nanoparticles were synthesized by combustion reaction and, subsequently, their surfaces were modified with silane agent. The samples were characterized by X-ray diffraction, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and excitation and emission spectroscopy. The results showed formation of ZnAl2O4 as the major phase. By SEM, hard agglomerates, irregularly shaped in the form of plaques, with the presence of few irregular and variables pores were observed. The surface modification was confirmed by FTIR through the silanol and siloxane groups. The excitation and emission spectra revealed the presence of a broadband of ZnAl2O4 matrix, and fine and intense transitions from europium ion arising from doping of non-stoichiometric ZnAl2O4 with the europium. From the results of emission and excitation, it was observed that the luminescence of ZnAl1.9Eu0.05O4/SiO2 hybrid presented a small decrease in relation to the ZnAl1.9Eu0.05O4 nanoparticles. This decrease was almost insignificant in relation to the benefits of silanization caused by the introduction of functional groups that promote combination of hybrid ZnAl1.9Eu0.05O4/SiO2 with biomolecules, being this promising for application as a biosensor used in the biomedical field for the diagnosis and treatment of diseases.

Hybrid Films Photoluminescence of Chitosan/ZnAl2O4

This work reports the photoluminescence chitosan/ZnAl2O4 films in mass ratios 1:1, 1:2, 1:3, 1:4 and 1:5, respectively. The films were presented flexible, opaque, with a thickness of 0.04 mm and were characterized by XRD, FTIR, emission and excitation. The results show the presence of characteristic peaks of chitosan and ZnAl2O4, and bands related to the presence of chitosan, silanol and siloxane groups and silane agent used in surface modification ZnAl2O4, which acts as a binding agent with the chitosan all movie reviews. The excitation and emission spectra showed the presence of broadband processes associated with charge transfer from Al +3 the O-2 in all the films, and that the highest photoluminescence intensities were observed for the films 1:1 and 1:2, which showed higher concentrations than the concentrations Qs 1:3, 1:4 and 1:5. Thus, Qs acted as a binder, transferring energy to Al +3 the O- 2.

Immobilized Enzyme Gox with Ferrite CoFe2O4 and Hybrid CoFe2O4/APTS

This work aims to evaluate the immobilization of glucose oxidase (GOx) with CoFe2O4 nanoparticles and hybrids CoFe2O4/APTS. The nanoparticles were synthesized by combustion reaction and silanized using 3-aminopropyltrimethoxysilane (APTS). The samples were characterized by XRD, FTIR, magnetic measurements and immobilization of GOx. The results indicated single phase of spinel CoFe2O4 and the addition of APTS did not alter the structure of the ferrite. The characteristic bands of spinel and characteristic bands were observed in the silane silanized sample proving the silanization of nanoparticles of CoFe2O4. The CoFe2O4 nanoparticles and the hybrid had saturation magnetization of 58.0 and 53.0 emu/g and coercivity of 1.14 kOe and 1.15, indicating that the silanization does not interfere with the magnetism of the particles. The immobilized GOx was obtained with values of 0.047 and 0.050 mg/g efficiency of 84.86 and 80.30% for CoFe2O4/APTS and CoFe2O4.

ZnAl1.9Eu0.1O4 Nanoparticles Functionalized with Methylmethacrylate and Ethylenediamine Monomer Mixtures

This work aim to functionalize the ZnAl1.9Eu0.1O4 spinel with ethylenediamine and methylmethacrylate monomer mixtures. ZnAl1.9Eu0.1O4 nanoparticles were obtained according to the theory of propellants and explosives by combustion reaction. The samples were added to the silane agent 3-aminopropyltriethoxysilane. After silanized were functionalized with a monomers mixture. By X-ray diffractogram, it was observed the formation of a major phase of ZnAl2O4 cubic normal spinel and the secondary phase EuAlO3. The FTIR spectra for ZnAl1.9Eu0.1O4 exhibit absorption bands below 1000 cm -1, and after the functionalization showed two conjugate bands that were attributed to the presence of free NH2 groups and the binding of oxygen to the group NH2, and strips Si-O, originating from the silane agent. The emission spectra for samples before and after functionalization showed spectral lines 5D0 → 7F0, 7F1 → 5D0, 5D0 → 7F2, 7F3 → 5D0 and 5D0 → 7F4 and luminescence quantum yield of 58%, but the sample functionalized with a mixture monomers showed an increase in intensity on transition 5D0 → 7F2 and quantum yield of 67%.

Synthesis, Characterization and Silanization Spinel ZnAl1.9Eu0.1O4

This paper aims to synthesize by combustion reaction and silanilized of the ZnAl1.9Eu0.1O4, with silane agent 3-aminopropyltrimethoxysilane. The characterization of materials before and after silanization was investigated. Nanoparticles ZnAl1.9Eu0.1O4 was obtained according to the theory of propellants and explosives using the synthesis combustion reaction. The samples were deagglomerated and passed through a sieve of 325 mesh and added to 3-aminopropyltrimethoxysilane, followed by heat shock treatment by ultrasonic and microwave. Subsequently centrifuged and dried at 150 ° C for 24 hours. The samples before and after the silane were characterized by X-ray diffraction, infrared spectroscopy and thermogravimetric analysis. The results indicate the formation of a major phase spinel normal ZnAl2O4, and the EuAlO3 peaks as secondary phase. The FTIR spectra for ZnAl1.9Eu0.1O4 have absorption bands below 1000 cm-1, and after silanization showed bands of C = O, axial strain - CN and Si-O bands, which proves the silanization. The thermogravimetric curves showed good thermal stability, with mass loss around 30%.