From the Shelf to the Particle: Preparation of Highly Organic-Functionalized Magnetic Composites via 4-Nitrophenyl Reactive Ester.

Preparation of chemically tunable magnetic nanoparticles (MNPs) is of great interest in many technological fields. Although numerous methods have been developed to prepare MNPs coated with functional organic moieties, most of them are complex, multistep, and involve the preparation of a specific ligand to be inserted on the particle surface. Herein, we describe the preparation of MNPs covered with reactive polymer poly(4-nitrophenyl methacrylate). The composite was prepared by the dispersion polymerization of 4-nitrophenyl methacrylate in the presence of magnetite nanoparticles stabilized by oleic acid. The novel material can be easily modified with amines to give chemically stable amide bonds without installation of pH-dependent features in the link. The extent of particle modification is readily monitored by the release of 4-nitrophenol from the polymer using UV-vis spectrophotometry. Good agreement between the degree of functionalization assessed by colorimetry and elemental analysis was obtained, and functionalization up to 3 mmol g-1 is easily attained. To illustrate the applicability of the method for catalyst development, we prepared imidazole-covered MNPs that accelerate the hydrolysis of a model organophosphate, with rate constants approximately 105-fold higher than the spontaneous hydrolysis. The catalyst can be recovered by a magnet and recycled without appreciable loss of catalytic activity.

Pheomelanin-coated iron oxide magnetic nanoparticles: a promising candidate for negative T2 contrast enhancement in magnetic resonance imaging.

We describe herein a novel type of monodisperse water-soluble magnetite nanoparticle coated with pheomelanin using an environmentally-friendly approach in aqueous medium. The results indicate superparamagnetic behaviour at room temperature and show improved negative contrast in T2-weighted MRI with a transverse relaxivity of 218 mM(-1) s(-1).

Solid-state evaluation and polymorphic quantification of venlafaxine hydrochloride raw materials using the Rietveld method.

Venlafaxine hydrochloride (VEN) is an antidepressant drug widely used for the treatment of depression. The purpose of this study was to carry out the preparation and solid state characterization of the pure polymorphs (Forms 1 and 2) and the polymorphic identification and quantification of four commercially-available VEN raw materials. These two polymorphic forms were obtained from different crystallization methods and characterized by X-ray Powder Diffraction (XRPD), Diffuse Reflectance Infrared Fourier Transform (DRIFT), Raman Spectroscopy (RS), liquid and solid state Nuclear Magnetic Resonance (NMR and ssNMR) spectroscopies, Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopy (SEM) techniques. The main differences were observed by DSC and XRPD and the latter was chosen as the standard technique for the identification and quantification studies in combination with the Rietveld method for the commercial raw materials (VEN1-VEN4) acquired from different manufacturers. Additionally Form 1 and Form 2 can be clearly distinguished from their (13)C ssNMR spectra. Through the analysis, it was possible to conclude that VEN1 and VEN2 were composed only of Form 1, while VEN3 and VEN4 were a mixture of Forms 1 and 2. Additionally, the Rietveld refinement was successfully applied to quantify the polymorphic ratio for VEN3 and VEN4.

Effect of reaction parameters on the formation and properties of ZnO nanocrystals synthesized via a rapid solochemical processing.

ZnO nanocrystals were successfully prepared under mild conditions by solochemical method from sodium hydroxide and zinc nitrate hexahydrate in 3 h refluxing. In this process the dependence of the morphologies, sizes and formation mechanisms of the ZnO nanocrystals on the reaction temperature was investigated. The samples were analyzed by X-ray diffraction (XRD), including Rietveld analyses, transmission electron microscopy (TEM), Raman spectroscopy and UV-Visible absorption spectroscopy. The X-ray diffraction patterns revealed that the formed products are pure ZnO with hexagonal (wurtzite) structure. Rietveld analyses of the XRD patterns showed anisotropic effects on the size and microstrain of ZnO nanocrystals. The anisotropy on the crystallite size decreases as the reaction temperature increases. The microstrain remains constant up to 90 degrees C when reached highest values in all directions. The transmission electron microscopy images showed short ZnO nanorods and rounded shape nanoparticles for all samples. The average size (length by diameter) ratio of the ZnO nanorod increased from 1.5 to 2.4 when reaction temperature was raised from 50 degrees C to 80 degrees C and decreased to 1.4 as the temperature was further increased to 90 degrees C. The HRTEM image of the sample prepared at 90 degrees C showed that ZnO nanocrystals have their c-axes as the primary growth direction. The wurtzite structure in ZnO nanorods has been verified by its characteristic E2 mode in the Raman spectra of all samples. All Raman peaks (especially for E2 mode) observed for the sample prepared at 90 degrees C showed huge intensity reduction and linebroadening, except for the second order Raman mode at about 1068 cm(-1) which presented a very huge and unusual increase on intensity. All samples presented a blue shift in the excitonic absorption compared to ZnO bulk that increases alongside with reaction temperature. In addition a mechanism for the synthesis of ZnO nanocrystals using zinc nitrate hexahydrate and sodium hydroxide by the solochemical method has also been proposed.

Morphology study of progesterone polymorphs prepared by polymer-induced heteronucleation (PIHn).

In this article, morphology of progesterone polymorphs prepared by polymer-induced heteronucleation (PIHn) technique was studied. Hydroxypropyl methylcellulose(HPMC), such as dextran T-500 and gelatin G-9382, polyisoprene (PI), and acrylonitrile/butadiene copolymer (NBR) were used as substrates. The crystallizations were performed by solvent evaporation at room temperature from 0.5, 10, and 40 mg/ml solutions in chloroform and acetone. Progesterone polymorphs were identified by X-ray diffraction. Differential scanning calorimetry and total attenuated reflectance infrared spectroscopy were used as complementary techniques in the identification. Depending on the polymeric matrix and the concentration used, form 1, form 2, or mixture of both polymorphs were obtained. Scanning electron microscopy pictures evidenced difference in morphology and in homogeneity of the two progesterone polymorphs. These polymorphs prepared by PIHn, did not present a distinctive morphology that allows identifying polymorph by its crystal habit. Hence, polymeric matrix induced the crystallization, affecting polymorphism and morphology.

Solid-state characterization and dissolution properties of Fluvastatin sodium salt hydrates.

The present study reports the solid-state properties of Fluvastatin sodium salt crystallized from different solvents for comparison with crystalline forms of the commercially available raw material and United States Pharmacopeia (USP) reference standard. Fluvastatin (FLV) samples were characterized by several techniques; such as X-ray powder diffractometry, differential scanning calorimetry, thermogravimetry, liquid and solid-state nuclear magnetic resonance spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, and scanning electron microscopy. In addition, intrinsic dissolution rate (IDR) of samples was performed in order to study the influence of crystalline form and other factors on rate and extent of dissolution. Three different forms were found. The commercial raw material and Fluvastatin-Acetonitrile (ACN) were identified as "form I" hydrate, the USP reference standard as "form II" hydrate and an ethanol solvate which presented a mixture of phases. Form I, with water content of 4%, was identified as monohydrate.

Effects of reaction temperature on structural properties of ZnO nanocrystals prepared via solochemical technique.

In this research, ZnO nanocrystals were prepared in a few hours by solochemical processing using sodium hydroxide and zinc nitrate hexahydrate as raw materials. Different reaction temperatures have been investigated and revealed their effects on the crystallite size, morphology and crystalline phase of ZnO nanocrystals. Materials synthesized by this technique were investigated employing X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, UV-Visible spectroscopy and Rietveld method. XRD and TEM showed that the ZnO samples are formed by a single hexagonal phase of wurtzite structure containing predominantly rod-like particles, except for the sample obtained at 90 degrees C that is basically formed by rounded nanometric particles. The sample obtained at 90 degrees C presented the smallest average crystallite size (approximately 20 nm) and the highest blue shift between the UV-Vis absorption spectra of the samples when compared to that of ZnO bulk. These size/disorder effects can also explain the attenuation of the ZnO Raman spectrum with increase of reaction temperature.

The rapid preparation of ZnO nanorods via low-temperatures solochemical method.

Substantial efforts have been devoted towards researching routes that provide an appropriate and simple approach for the production of zinc oxide (ZnO) nanocrystals. Here, a rapid and inexpensive solochemical method was employed to synthesize ZnQ nanocrystals through the decomposition of zinc chloride (ZnCl2) and sodium hydroxide (NaOH) at 50 degrees C, 70 degrees C and 90 degrees C. The powders were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy. The products showed high purity, nearly uniform rod-like morphology and nanometric crystallite sizes. With increasing reaction temperature, the crystallites become smaller and rounded. The Raman results reveal correlations between Raman line widths and intensities with ZnO nanorods dimensions. More specifically, the line widths are large and therefore less intense as the nanorod becomes smaller.

Tristriazolotriazines: a core for luminescent discotic liquid crystals.

The synthesis and structural, thermal, optical and theoretical characterization of new tris[1,2,4]triazolo[1,3,5]triazines were performed to support their application as liquid crystals and advanced materials.