Nonlinear ptychographic coherent diffractive imaging.

Ptychographic Coherent diffractive imaging (PCDI) is a significant advance in imaging allowing the measurement of the full electric field at a sample without use of any imaging optics. So far it has been confined solely to imaging of linear optical responses. In this paper we show that because of the coherence-preserving nature of nonlinear optical interactions, PCDI can be generalised to nonlinear optical imaging. We demonstrate second harmonic generation PCDI, directly revealing phase information about the nonlinear coefficients, and showing the general applicability of PCDI to nonlinear interactions.

Metal-organic fireworks: MOFs as integrated structural scaffolds for pyrotechnic materials.

A new approach to formulating pyrotechnic materials is presented whereby constituent ingredients are bound together in a solid-state lattice. This reduces the batch inconsistencies arising from the traditional approach of combining powders by ensuring the key ingredients are 'mixed' in appropriate quantities and are in intimate contact. Further benefits of these types of material are increased safety levels as well as simpler logistics, storage and manufacture. A systematic series of new frameworks comprising fuel and oxidiser agents (group 1 and 2 metal nodes & terephthalic acid derivatives as linkers) has been synthesised and structurally characterised. These new materials have been assessed for pyrotechnic effect by calorimetry and burn tests. Results indicate that these materials exhibit the desired pyrotechnic material properties and the effect can be correlated to the dimensionality of the structure. A new approach to formulating pyrotechnic materials is proposed whereby constituent ingredients are bound together in a solid-state lattice. A series of Metal-organic framework frameworks comprising fuel and oxidiser agents exhibits the desired properties of a pyrotechnic material and this effect is correlated to the dimensionality of the structure.

Polymorphism in 2,4,6-trinitrotoluene crystallized from solution.

An examination has been made of the role of solvent type in the definition of the polymorphic nature of 2,4,6-trinitrotoluene precipitated from solution. A combination of calorimetric and structural techniques including in situ crystallization studies using synchrotron radiation has shown that the variations in polymorphic form following precipitation from solution do not arise specifically from any stereospecific guidance that the nature of the solvent might impose on the structural form. Rather the differences are linked to the variations in solubility and hence supersaturation which might build up prior to nucleation and growth and to the isolation of the metastable orthorhombic phase from the solvent. The final conclusion is that the changes fit well with Ostwald's Law of Stages with the orthorhombic form always precipitating initially followed by its conversion to the stable monoclinic form. The previously observed tendency for some solvents to yield one or the other form then becomes attributable to kinetics in solution rather than structural control. It can be associated with the solubility of the material in the solvent used and the role of this factor in a solvent-mediated phase transformation. On this basis rules can be formulated for the isolation of the metastable forms of this and similarly related polymorphic systems.