Best Practices for Real-Time in Situ Atomic Force and Chemical Force Microscopy of Crystals

Poloni, Laura N.; Zhong, Xiaodi; Ward, Michael D.; Mandal, Trinanjana

doi:10.1021/acs.chemmater.6b03082

Cited by 14 publications

(15 citation statements)

References 97 publications

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“…To conduct in situ AFM studies, growth solution is flowed over the surface of a freshly cleaved single crystal of calcite using a fluid cell containing the AFM tip. , Under carefully controlled conditions corresponding to relatively low supersaturation (supersaturation σ is defined in eq , where AP is the activity product and K sp is the equilibrium solubility product), calcite grows via addition of CaCO 3 units to hillocks, which are sources for atomic steps originating from screw dislocations within the crystal. − …”

Section: Resultsmentioning

confidence: 99%

Mechanistic Insights into Diblock Copolymer Nanoparticle–Crystal Interactions Revealed via in Situ Atomic Force Microscopy

et al. 2018

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Recently, it has become clear that a range of nanoparticles can be occluded within single crystals to form nanocomposites. Calcite is a much-studied model, but even in this case we have yet to fully understand the details of the nanoscale interactions at the organic-inorganic interface that lead to occlusion. Here, a series of diblock copolymer nanoparticles with well-defined surface chemistries were visualized interacting with a growing calcite surface using in situ atomic force microscopy. These nanoparticles comprise a poly(benzyl methacrylate) (PBzMA) core-forming block and a non-ionic poly(glycerol monomethacrylate) (Ph-PGMA), a carboxylic acid-tipped poly(glycerol monomethacrylate) (HOOC-PGMA), or an anionic poly(methacrylic acid) (PMAA) stabilizer block. Our results reveal three modes of interaction between the nanoparticles and the calcite surface: (i) attachment followed by detachment, (ii) sticking to and "hovering" over the surface, allowing steps to pass beneath the immobilized nanoparticle, and (iii) incorporation of the nanoparticle by the growing crystals. By analyzing the relative contributions of these three types of interactions as a function of nanoparticle surface chemistry, we show that ∼85% of PMAA-PBzMA nanoparticles either "hover" or become incorporated, compared to ∼50% of the HOOC-PGMA-PBzMA nanoparticles. To explain this difference, we propose a two-state binding mechanism for the anionic PMAA-PBzMA nanoparticles. The "hovering" nanoparticles possess highly extended polyelectrolytic stabilizer chains and such chains must adopt a more "collapsed" conformation prior to successful nanoparticle occlusion. This study provides a conceptual framework for understanding how sterically stabilized nanoparticles interact with growing crystals, and suggests design principles for improving occlusion efficiencies.

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Section: Resultsmentioning

confidence: 99%

Mechanistic Insights into Diblock Copolymer Nanoparticle–Crystal Interactions Revealed via in Situ Atomic Force Microscopy

et al. 2018

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“…However, for a wide range of materials, including proteins, contact angle goniometry and XPS measurements as those proposed in the literature ( 4 , 5 , 7 ) are not experimentally feasible, where similar issues limit the applicability of IGC ( 41 ). Chemical force microscopy (CFM), could be a promising tool ( 196 – 199 ) as it enables the measurement of the interactions of a specific facet with a functionalized AFM tip. Combining many functionalization groups against a specific facet, could provide a good understanding of the interactions associated with that facet.…”

Section: Comments and Perspectivesmentioning

confidence: 99%

Influences of Crystal Anisotropy in Pharmaceutical Process Development

et al. 2018

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Crystalline materials are of crucial importance to the pharmaceutical industry, as a large number of APIs are formulated in crystalline form, occasionally in the presence of crystalline excipients. Owing to their multifaceted character, crystals were found to have strongly anisotropic properties. In fact, anisotropic properties were found to be quite important for a number of processes including milling, granulation and tableting. An understanding of crystal anisotropy and an ability to control and predict crystal anisotropy are mostly subjects of interest for researchers. A number of studies dealing with the aforementioned phenomena are grounded on over-simplistic assumptions, neglecting key attributes of crystalline materials, most importantly the anisotropic nature of a number of their properties. Moreover, concepts such as the influence of interfacial phenomena in the behaviour of crystalline materials during their growth and in vivo, are still poorly understood. The review aims to address concepts from a molecular perspective, focusing on crystal growth and dissolution. It begins with a brief outline of fundamental concepts of intermolecular and interfacial phenomena. The second part discusses their relevance to the field of pharmaceutical crystal growth and dissolution. Particular emphasis is given to works dealing with mechanistic understandings of the influence of solvents and additives on crystal habit. Furthermore, comments and perspectives, highlighting future directions for the implementation of fundamental concepts of interfacial phenomena in the rational understanding of crystal growth and dissolution processes, have been provided.

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“…The highly consistent orientation of OZPN DD microcrystals on OZPN I suggests a significant influence of the underlying OZPN I crystal structure on OZPN DD nucleation and growth under quiescent conditions. The strong dependence of the orientation between the substrate crystal and grown crystals is generally presumed to be controlled by an epitaxial mechanism, however GRACE analysis 35,36,63 shows that there is no long range epitaxial match between the lattices of either dihydrate and the OZPN (100) face (ESI section 2).…”

Section: Effect Of Stirring On Ozpn Dihydrate Formation At (100)ozpni Solution Interfacementioning

confidence: 99%

Direct Observation of Templated Two-Step Nucleation Mechanism during Olanzapine Hydrate Formation

Warzecha

Guo

Bhardwaj

et al. 2017

Crystal Growth & Design

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Investigating crystal nucleation at the nanoscale is of significant interest, in particular as more complex, non-classical routes have roused questions about the classical view of homo-and hetero-nucleation processes. Here, we report the direct observation of a two-step nucleation mechanism during the transformation of anhydrous olanzapine to olanzapine dihydrate. Atomic force microscopy studies of the dominant (100)OZPNI face of olanzapine form I single crystals in contact with water show the formation and growth of dense nanodroplets concentrated around ledge sites. In unstirred solution, apparent ordering and crystallisation from these droplets occurs with olanzapine dihydrate D produced by the templating effect of the underlying olanzapine I lattice. In contrast, under stirred conditions a kinetic dihydrate polymorph, dihydrate B, nucleates probably due to the detachment of nanodroplets from the surface during stirring and a consequent loss of template effect. Computational modelling of the binding of olanzapine growth units on crystal ledges reveals many strongly bound dimer positions unrelated to either crystal structure. This impedes surface integration and contributes to the growth of disordered clusters at the ledge site. Nanocrystal modelling shows that the (100)OZPNI surface favours the nucleation of dihydrate D over the kinetic form. This work gives an important insight into heterogeneous two step nucleation where the first step, the formation of a prenucleation droplet, can in the second step, bifurcate, either to produce the stable form by templating, or the kinetic form on detachment of the nanodroplets.

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Best Practices for Real-Time in Situ Atomic Force and Chemical Force Microscopy of Crystals

Cited by 14 publications

References 97 publications

Mechanistic Insights into Diblock Copolymer Nanoparticle–Crystal Interactions Revealed via in Situ Atomic Force Microscopy

Mechanistic Insights into Diblock Copolymer Nanoparticle–Crystal Interactions Revealed via in Situ Atomic Force Microscopy

Influences of Crystal Anisotropy in Pharmaceutical Process Development

Direct Observation of Templated Two-Step Nucleation Mechanism during Olanzapine Hydrate Formation

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