In Situ Focused Beam Reflectance Measurement (FBRM), Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) and Raman Characterization of the Polymorphic Transformation of Carbamazepine

The objective of this work was to study the polymorphic transformation of carbamazepine from Form II to Form III in 1-propanol during seeded isothermal batch crystallization. First, the pure Form II and Form III were obtained and characterized. Then their solubilities and metastable zone limits were measured by in-situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and focused beam reflectance measurement (FBRM). A transition temperature at about 34.2 °C was deduced suggesting the enantiotropic nature of this compound over the studied temperature range. To quantify the polymorph ratio during the transformation process, a new in-situ quantitative method was developed to measure the fraction of Form II by Raman spectroscopy. Successful tracking of the nucleation of the stable form and the transformation from Form II to Form III during isothermal crystallization was achieved by Raman spectroscopy and FBRM. The results from these three in-situ techniques, FBRM, FTIR and Raman were consistent with each other. The results showed a strong dependency on the amount of seeds added during isothermal crystallization.

Transparent nanostructured coatings with UV-shielding and superhydrophobicity properties

Visible light transparent, UV-shielding and superhydrophobic nanostructured coatings have been successfully fabricated through a facile layer-by-layer deposition of TiO(2) and SiO(2) nanoparticles. The coatings are composed of an underlying UV-shielding TiO(2) layer and a top fully covered protective SiO(2) layer. The resulting coatings can block 100% of UVB and UVC and almost 85% of UVA. The fabricated surfaces have contact angles exceeding 165° after coating with organic PTES (1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane) molecules. The transparent superhydrophobic surfaces exhibit extremely strong UV stability. All coatings retain the initial UV-shielding and superhydrophobic properties even after exposure to 275 nm UV light with a light intensity of 75 mW cm(-2) for 12 h.

An innovative approach to synthesize highly-ordered TiO2 nanotubes

An innovative route to prepare highly-ordered and dimensionally controlled TiO2 nanotubes has been proposed using a mild sonication method. The nanotube arrays were prepared by the anodization of titanium in an electrolyte containing 3% NH4F and 5% H2O in glycerol. It is demonstrated that the TiO2 nanostructures has two layers: the top layer is TiO2 nanowire and underneath is well-ordered TiO2 nanotubes. The top layer can easily fall off and form nanowires bundles by implementing a mild sonication after a short annealing time. We found that the dimensions of the TiO2 nanotubes were only dependent on the anodizing condition. The proposed technique may be extended to fabricate reproducible well-ordered TiO2 nanotubes with large area on other metals.

Chiral discrimination in diastereomeric salts of chlorine-substituted mandelic acid and phenylethylamine

The crystal structures of diastereomeric salts of chloromandelic acid and phenylethylamine were determined and are presented herein. The structure comparison between less soluble salts and more soluble salts shows that weak interactions such as CH/pi interactions and van der Waals gain importance and contribute to chiral recognition when the hydrogen bonding patterns are very similar.

Fabrication of titania nanotube arrays in viscous electrolytes

This study probes the dependence of titania nanotube arrays nanoarchitecture on different synthesis parameters in viscous electrolytes. Titania nanotube arrays were synthesized in glycerol, ethylene glycol and carboxymethylcellulose as base materials. The effects of anodization voltage and time, as well as chemical composition and pH of the electrolyte bath were studied. Nanotube arrays with an inner diameter ranging from 16 to 91 nm, and wall thickness ranging from 7 to 29 nm were fabricated in a glycerol-water electrolyte. Water content of 5 wt% or higher was found to be essential for nanotubes fabrication in glycerol electrolyte. Diameter and length were influenced by varying water content above 5 wt%. Nanotube length was found to be time dependent at high pH values. A pH value of 6 was favorable for fabrication of highly ordered and continuous nanotube arrays with length up to 900 nm. Using modified ethylene glycol (containing 2 wt% and 0.5 wt% NH4F) instead of glycerol, resulted in nanotube length up to 430 nm after 1.5 hr anodization time. With a minor modification of electrochemical anodization cell, we successfully fabricated double-sided titania nanotube arrays layers with a total thickness of 9.5 microm for the first time. Nantube arrays were successfully fabricated in 2 wt% sodium carboxy mythylcellulose aqueous electrolyte (CMC electrolyte). These nanotube arrays had an inner diameter of 42 nm similar to those fabricated in 2 wt% urea-ethylene glycol electrolyte but their length was 450 nm.

Diastereomeric resolution of p-chloromandelic acid with (R)-phenylethylamine

The optical resolution of p-chloromandelic acid using (R)-alpha-phenylethylamine as resolving agent was presented. The effect of solvents, molar ratio of racemate to the resolving agent, filtration temperature as well as the amount of solvent on resolution was investigated by orthogonal experimentation. The binary melting point phase diagram and crystal structure analysis of diastereomeric salts rationalized the success of the resolution.

The fabrication of highly ordered and visible-light-responsive Fe-C-N-codoped TiO2 nanotubes

A one-step method for the fabrication of Fe-C-N-codoped TiO2 nanotubes by electrochemical anodization is reported. The proposed method is both simple and efficient. The prepared samples were annealed at 550 degrees C for 3 h. The resulting nanotubes were characterized by SEM, XRD, XPS, EDX and UV-vis spectrophotometer. The results showed that the average tube diameter of the nanotubes was 70 nm and wall thickness was 20 nm and the average tube length was 2.4 microm. The doped TiO2 nanotubes exhibited strong absorption in the visible-light region. The maximum photocurrent efficiency measured under solar simulator was 2.7%.

Transition metal ions effect on the properties and photocatalytic activity of nanocrystalline TiO2 prepared in an ionic liquid

TiO(2) and transition metal (Cr, Mn, Fe, Co, Ni, Cu, and Zn) doped TiO(2) nanoparticles were synthesized by the sol-gel method using 2-hydroxylethylammonium formate as an ionic liquid. All the prepared samples were calcined at 500 degrees C and characterized by X-ray diffraction (XRD), BET surface area determination, energy dispersive X-ray (EDX) analysis, diffuse reflectance spectroscopy (DRS), and Fourier transformed infrared (FT-IR) techniques. The studies revealed that transition metal (TM) doped nanoparticles have smaller crystalline size and higher surface area than pure TiO(2). Dopant ions in the TiO(2) structure caused significant absorption shift into the visible region. The results of photodegradation of Acid Blue92 (AB92) in aqueous medium under UV light showed that photocatalytic activity of TiO(2) nanoparticles was significantly enhanced by the presence of some transition metal ions. Chemical Oxygen Demand (COD) of dye solutions were done at regular intervals gave a good idea about mineralization of dye.

Polymorphism and crystallization of active pharmaceutical ingredients (APIs)

Active pharmaceutical ingredients (APIs), frequently delivered to the patient in the solid-state as part of an approved dosage form, can exist in such diverse solid forms as polymorphs, pseudopolymorphs, salts, co-crystals and amorphous solids. Various solid forms often display different mechanical, thermal, physical and chemical properties that can remarkably influence the bioavailability, hygroscopicity, stability and other performance characteristics of the drug. Hence, a thorough understanding of the relationship between the particular solid form of an active pharmaceutical ingredient (API) and its functional properties is important in selecting the most suitable form of the API for development into a drug product. In past decades, there have been significant efforts on the discovery, selection and control of the solid forms of APIs and bulk drugs. This contribution discusses the thermodynamics and kinetics of polymorphic systems, the characterization of polymorphs, and the transformation between polymorphs. The major techniques for polymorph discovery and control developed in the past years are discussed as well.