RESUMO
Superparamagnetic iron oxide nanoparticles (MNPs) with appropriate surface chemistry exhibit many interesting properties that can be exploited in a variety of biomedical applications such as magnetic resonance imaging contrast enhancement, tissue repair, hyperthermia, drug delivery and in cell separation. These applications required that the MNPs such as iron oxide Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) having high magnetization values and particle size smaller than 100 nm. This paper reports the experimental detail for preparation of monodisperse oleic acid (OA)-coated Fe3O4 MNPs by chemical co-precipitation method to determine the optimum pH, initial temperature and stirring speed in order to obtain the MNPs with small particle size and size distribution that is needed for biomedical applications. The obtained nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray fluorescence spectrometry (EDXRF), thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), and vibrating sample magnetometer (VSM). The results show that the particle size as well as the magnetization of the MNPs was very much dependent on pH, initial temperature of Fe²âº and Fe³âº solutions and steering speed. The monodisperse Fe3O4 MNPs coated with oleic acid with size of 7.8 ± 1.9 nm were successfully prepared at optimum pH 11, initial temperature of 45°C and at stirring rate of 800 rpm. FTIR and XRD data reveal that the oleic acid molecules were adsorbed on the magnetic nanoparticles by chemisorption. Analyses of TEM show the oleic acid provided the Fe3O4 particles with better dispersibility. The synthesized Fe3O4 nanoparticles exhibited superparamagnetic behavior and the saturation magnetization of the Fe3O4 nanoparticles increased with the particle size.
Assuntos
Materiais Biocompatíveis/química , Compostos Férricos/química , Nanopartículas de Magnetita/química , Materiais Biocompatíveis/administração & dosagem , Portadores de Fármacos , Compostos Férricos/administração & dosagem , Nanopartículas de Magnetita/administração & dosagem , Microscopia Eletrônica de Varredura , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
The title compound, C(17)H(16)N(2)O(3), has an E conformation about the azobenzene (-N=N-) linkage. The benzene rings are twisted slightly with respect to each other [6.79â (9)°], while the dihedral angle between the plane through the carb-oxy group and the attached benzene ring is 3.2â (2)°. In the crystal, mol-ecules are oriented with the carb-oxy groups head-to-head, forming O-Hâ¯O hydrogen-bonded inversion dimers. These dimers are connected by C-Hâ¯O hydrogen-bonds into layers lying parallel to the (013) plane.
RESUMO
This study investigates the effects of calcium carbonate (CaCO(3)) nanoparticles on the mechanical and thermal properties and surface morphology of polycaprolactone (PCL)/chitosan nanocomposites. The nanocomposites of PCL/chitosan/CaCO(3) were prepared using a melt blending technique. Transmission electron microscopy (TEM) results indicate the average size of nanoparticles to be approximately 62 nm. Tensile measurement results show an increase in the tensile modulus with CaCO(3) nanoparticle loading. Tensile strength and elongation at break show gradual improvement with the addition of up to 1 wt% of nano-sized CaCO(3). Decreasing performance of these properties is observed for loading of more than 1 wt% of nano-sized CaCO(3). The thermal stability was best enhanced at 1 wt% of CaCO(3) nanoparticle loading. The fractured surface morphology of the PCL/chitosan blend becomes more stretched and homogeneous in PCL/chitosan/CaCO(3) nanocomposite. TEM micrograph displays good dispersion of CaCO(3) at lower nanoparticle loading within the matrix.
Assuntos
Carbonato de Cálcio/química , Quitosana/química , Nanopartículas/química , Poliésteres/química , Resistência à Tração/fisiologia , Teste de Materiais , Fenômenos Mecânicos , Microscopia Eletrônica de Transmissão , Nanocompostos/química , Propriedades de SuperfícieRESUMO
A new class of biocomposites based on oil palm empty fruit bunch fiber and poly(butylene adipate-co-terephthalate) (PBAT), which is a biodegradable aliphatic aromatic co-polyester, were prepared using melt blending technique. The composites were prepared at various fiber contents of 10, 20, 30, 40 and 50 wt% and characterized. Chemical treatment of oil palm empty fruit bunch (EFB) fiber was successfully done by grafting succinic anhydride (SAH) onto the EFB fiber surface, and the modified fibers were obtained in two levels of grafting (low and high weight percentage gain, WPG) after 5 and 6 h of grafting. The FTIR characterization showed evidence of successful fiber esterification. The results showed that 40 wt% of fiber loading improved the tensile properties of the biocomposite. The effects of EFB fiber chemical treatments and various organic initiators content on mechanical and thermal properties and water absorption of PBAT/EFB 60/40 wt% biocomposites were also examined. The SAH-g-EFB fiber at low WPG in presence of 1 wt% of dicumyl peroxide (DCP) initiator was found to significantly enhance the tensile and flexural properties as well as water resistance of biocomposite (up to 24%) compared with those of untreated fiber reinforced composites. The thermal behavior of the composites was evaluated from thermogravimetric analysis (TGA)/differential thermogravimetric (DTG) thermograms. It was observed that, the chemical treatment has marginally improved the biocomposites' thermal stability in presence of 1 wt% of dicumyl peroxide at the low WPG level of grafting. The improved fiber-matrix surface enhancement in the chemically treated biocomposite was confirmed by SEM analysis of the tensile fractured specimens.
Assuntos
Arecaceae/química , Frutas/química , Teste de Materiais , Poliésteres/química , Esterificação , Resistência à TraçãoRESUMO
In this work, the oil palm empty fruit bunch (EFB) fiber was used as a source of lignocellulosic filler to fabricate a novel type of cost effective biodegradable composite, based on the aliphatic aromatic co-polyester poly(butylene adipate-co-terephtalate) PBAT (Ecoflex™), as a fully biodegradable thermoplastic polymer matrix. The aim of this research was to improve the new biocomposites' performance by chemical modification using succinic anhydride (SAH) as a coupling agent in the presence and absence of dicumyl peroxide (DCP) and benzoyl peroxide (BPO) as initiators. For the composite preparation, several blends were prepared with varying ratios of filler and matrix using the melt blending technique. The composites were prepared at various fiber contents of 10, 20, 30, 40 and 50 (wt %) and characterized. The effects of fiber loading and coupling agent loading on the thermal properties of biodegradable polymer composites were evaluated using thermal gravimetric analysis (TGA). Scanning Electron Microscopy (SEM) was used for morphological studies. The chemical structure of the new biocomposites was also analyzed using the Fourier Transform Infrared (FTIR) spectroscopy technique. The PBAT biocomposite reinforced with 40 (wt %) of EFB fiber showed the best mechanical properties compared to the other PBAT/EFB fiber biocomposites. Biocomposite treatment with 4 (wt %) succinic anhydride (SAH) and 1 (wt %) dicumyl peroxide (DCP) improved both tensile and flexural strength as well as tensile and flexural modulus. The FTIR analyses proved the mechanical test results by presenting the evidence of successful esterification using SAH/DCP in the biocomposites' spectra. The SEM micrograph of the tensile fractured surfaces showed the improvement of fiber-matrix adhesion after using SAH. The TGA results showed that chemical modification using SAH/DCP improved the thermal stability of the PBAT/EFB biocomposite.
Assuntos
Resinas Compostas/química , Frutas/química , Óleos de Plantas/química , Poliésteres/química , Polímeros/química , Anidridos Succínicos/química , Peróxido de Benzoíla/química , Compostos de Benzil/química , Biodegradação Ambiental , Esterificação , Lignina/química , Fenômenos Mecânicos , Microscopia Eletrônica de Varredura/métodos , Óleo de Palmeira , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Temperatura , Resistência à Tração , Termogravimetria/métodosRESUMO
In the title compound, C(13)H(19)NO(2), the dihedral angle between the benzene ring and the plane throught the non-H atoms of the amide group is 29.3â (1)°. The benzene ring and the alkane carbon skeleton plane are twisted slightly with respect to each other [5.40â (5)°]. In the crystal, mol-ecules are oriented with the amide groups head-to-head, forming N-Hâ¯O hydrogen-bonded dimers. The dimers are connected by further N-Hâ¯O hydrogen bonds into a ladder-like motif along the b axis.
RESUMO
In the title compound, C(19)H(29)NO, the C-C and C-N bond distances of the benzonitrile group are 1.445â (2) and 1.157â (2)â Å, respectively. The aliphatic fragment adopts a bent zigzag arangement which differs from the planar zigzag arrangement normally observed in n-alkanes or long-chain alkyl-benzenes. In the crystal, inversion dimers linked by pairs of C-Hâ¯O hydrogen bonds occur. A C-Hâ¯N inter-action also occurs. In the crystal, mol-ecules are packed with the nitrile and aliphatic groups oriented in a head-to-tail fashion involving, forming a ripple-like motif along the a axis.