Epitaxial 2D nucleation of the stable polymorphic form of the steroid 7αMNa on the metastable form: Implications for Ostwald's rule of stages

Stoica, Cristina; Verwer, P.; Meekes, Hugo; Vlieg, E.; Hoof, P.J.C.M. van; Kaspersen, Frans M.

doi:10.1016/j.ijpharm.2005.10.041

Cited by 23 publications

(33 citation statements)

References 16 publications

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“…Recently, increasing research work has shown that the nucleation of the stable polymorph tends to occur on the surfaces of an unstable polymorph existing in solution 13. Generally, 2D nucleation has a lower energy barrier than the homogeneous nucleation in solution 5, 12, 14, 15. An in‐depth understanding of the surface‐induced nucleation mechanism will help to accelerate or prevent the formation of a more stable polymorph by controlling the 2D nucleation.…”

Section: Introductionmentioning

confidence: 99%

Transition Metal (Mn, Fe, Co, Ni)‐Doped Graphene Hybrids for Electrocatalysis

Toh

Poh

Sofer

et al. 2013

Chemistry An Asian Journal

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The development of electrocatalysts is crucial for renewable energy applications. Metal-doped graphene hybrid materials have been explored for this purpose, however, with much focus on noble metals, which are limited by their low availability and high costs. Transition metals may serve as promising alternatives. Here, transition metal-doped graphene hybrids were synthesized by a simple and scalable method. Metal-doped graphite oxide precursors were thermally exfoliated in either hydrogen or nitrogen atmosphere; by changing exfoliation atmospheres from inert to reductive, we produced materials with different degrees of oxidation. Effects of the presence of metal nanoparticles and exfoliation atmosphere on the morphology and electrocatalytic activity of the hybrid materials were investigated using electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry. Doping of graphene with transition metal nanoparticles of the 4th period significantly influenced the electrocatalysis of compounds important in energy production and storage applications, with hybrid materials exfoliated in nitrogen atmosphere displaying superior performance over those exfoliated in hydrogen atmosphere. Moreover, nickel-doped graphene hybrids displayed outstanding electrocatalytic activities towards reduction of O2 when compared to bare graphenes. These findings may be exploited in the research field of renewable energy.

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Section: Introductionmentioning

confidence: 99%

Transition Metal (Mn, Fe, Co, Ni)‐Doped Graphene Hybrids for Electrocatalysis

Toh

Poh

Sofer

et al. 2013

Chemistry An Asian Journal

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“…In another study of the same steroid, epitaxial nucleation of the stable polymorph on a specific face of the metastable form was observed, indicating that the presence of the metastable form was essential for the nucleation and growth of the stable form. 40 Interestingly, the order of the metastable zones for the two polymorphic forms was reversed for epitaxial growth as opposed to nucleation in bulk solutions.…”

Section: Studies Of Preparative and Isolation Methodsmentioning

confidence: 99%

Polymorphism and Solvatomorphism 2006

Brittain¹

2008

Journal of Pharmaceutical Sciences

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“…24,29 Incorporating an optical microscope and motorized stage into the Raman instrument for spectroscopic chemical imaging by obtaining spectra for a defined 2-dimensional area with a resolution down to 1 μm 12 has further expanded Raman spectroscopy's utility in various structural and molecular investigations. These direct and quantitative Raman chemical imaging ( Figure 3) and mapping ( Figure 4) investigations include biomaterial nanotubes (providing a spatial resolution of~25 nm), 30 drug-polymer-controlled drug delivery systems, 31,32 solid-state polymorphic transformations, [33][34][35][36][37] and drug disposition research. 24,[38][39][40][41][42] The combination of scanning electron microscopy (SEM) and Raman spectroscopy has been applied in single-crystal hydration studies of carbamazepine, in the absence and presence of excipients, where it was demonstrated that defect structures were of greater importance in the initiation of the hydration process than the crystal face.…”

Section: Surface-enhanced Raman Spectroscopymentioning

confidence: 99%

Raman characterization and chemical imaging of biocolloidal self-assemblies, drug delivery systems, and pulmonary inhalation aerosols: A review

Mansour

Hickey

2007

AAPS PharmSciTech

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This review presents an introduction to Raman scattering and describes the various Raman spectroscopy, Raman microscopy, and chemical imaging techniques that have demonstrated utility in biocolloidal self-assemblies, pharmaceutical drug delivery systems, and pulmonary research applications. Recent Raman applications to pharmaceutical aerosols in the context of pulmonary inhalation aerosol delivery are discussed. The "molecular fingerprint" insight that Raman applications provide includes molecular structure, drug-carrier/ excipient interactions, intramolecular and intermolecular bonding, surface structure, surface and interfacial interactions, and the functional groups involved therein. The molecular, surface, and interfacial properties that Raman characterization can provide are particularly important in respirable pharmaceutical powders, as these particles possess a higher surface-area-to-volume ratio; hence, understanding the nature of these solid surfaces can enable their manipulation and tailoring for functionality at the nanometer level for targeted pulmonary delivery and deposition. Moreover, Raman mapping of aerosols at the micro-and nanometer level of resolution is achievable with new, sophisticated, commercially available Raman microspectroscopy techniques. This noninvasive, highly versatile analytical and imaging technique exhibits vast potential for in vitro and in vivo molecular investigations of pulmonary aerosol delivery, lung deposition, and pulmonary cellular drug uptake and disposition in unfixed living pulmonary cells.

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Epitaxial 2D nucleation of the stable polymorphic form of the steroid 7αMNa on the metastable form: Implications for Ostwald's rule of stages

Cited by 23 publications

References 16 publications

Transition Metal (Mn, Fe, Co, Ni)‐Doped Graphene Hybrids for Electrocatalysis

Transition Metal (Mn, Fe, Co, Ni)‐Doped Graphene Hybrids for Electrocatalysis

Polymorphism and Solvatomorphism 2006

Raman characterization and chemical imaging of biocolloidal self-assemblies, drug delivery systems, and pulmonary inhalation aerosols: A review

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