Producing the Ultimate High Energy Density Material

Nitrogen is a truly unique element. As a diatomic molecule, N2, is extremely stable and features the strongest homoatomic bond. However, under the application of extreme pressures and temperatures, the N2 molecule breaks apart and nitrogen transforms into a 3D polymeric solid called cubic gauche polymeric nitrogen (cg-N). This solid, comprised solely of single-bonded nitrogen atoms, is the ultimate high energy density material. It can store and release about 10x more energy than the best compounds and is 100% environmentally friendly. A small problem remains: cg-N cannot be recovered to ambient conditions.

In this talk, we will explore a variety of experimental high-pressure high-temperature paths to produce alternatives to cg-N. An unexpectedly large zoology of nitrogen species is discovered, with many exotic and exciting properties, including materials highly energetic and fully recoverable to ambient conditions.

Room 2511 JCMB

Feb 27, 2023 Leave a Comment

Interfacial rheology – measuring mechanical properties of complex-liquid interfaces

In this presentation, I will introduce colloidal, micron-sized particles at liquid interfaces. These are interesting 2D model systems, but they are also interesting for (potential) applications e.g. particle-stabilized aka Pickering emulsions and bijels (bicontinuous Pickering emulsions). The mechanical properties of the particle-laden interfaces are challenging to measure, but they are important, for example to explain Pickering-emulsion stability. I will summarize some of our past and recent work on measuring and interpreting the mechanical properties of particle-laden liquid interfaces, including our recent development of ‘contactless’ interfacial rheology.

Today at 4:00 pm, back in JCMB room 2511.

Feb 20, 2023 Leave a Comment

Biomimetic crystallization of biomorphs and chemical gardens: Understanding their formation and studying their self-motion

Abiotic crystallization is typically described by classical models to form geometric shapes with flat faces, sharp edges, and well defined angles. This is in stark contrast to crystallization routes used by living systems which instead grows smoothly curved shapes such as teeth, bone, and nacre. Such morphological distinctions have been applied to determine the biogenicity of structures found in ancient rocks. However, laboratory experiments in far-from-equilibrium systems are able to precipitate similar curvilinear morphologies previously only prescribed to living organisms thus blurring the line between structures derived from biotic and abiotic origins. The first example I will discuss is the crystallization of metal carbonate and silica microstructures known as “biomorphs”. They are composed of thousands of coaligned nanorods that self-organize into larger life-like shapes such as leaf-like sheets, helices, funnels, and flowers. At the nanoscale, the growing crystallization front forms from the addition of smaller nanodot building units that merge into the elongated rod shape. At the microscale, the pseudo two-dimensional sheet shape can be simulated using reaction-diffusion equations. Finally, the hierarchical ordering is extended into the centimeter scale with the merging of neighbouring biomorphs at the air-solution interface. The second example is chemical gardens. Formed from steep chemical gradients between a metal salt and a solution of silicate, the final result is hollow tubes which resemble filaments found in many geological settings. This quick and easy production process for generating tubes can be exploited by controlling the composition of the final material to create self-moving chemical gardens.

Feb 13, 2023 Leave a Comment

“Polymer physics of cancer genomes”

While every cell in our bodies contains the same genome, different sets of genes are active in different types of cell, and the “switching on and off” of specific genes must be tightly controlled as cells develop. Gene regulation is tightly related to the spatial organisation of the chromosomes within the cell nucleus. A number of physical mechanisms through which this organisation is controlled have been identified, and polymer physics models have proved extremely useful for understanding these. I will present recent work in which polymer models were used to understand genome rearrangements in cancer. There are several methods which the cell employs to repair the genome should the DNA get broken, however these sometimes do not work correctly, and genome rearrangements can arise. For example, two different broken chromosomes could get joined together; this changes the spatial organisation, disrupts gene regulation, and can give rise to disease. Our polymer simulations were able to predict the changes in gene expression which result from genome rearrangements commonly found in B-cell cancers, shedding light on this poorly understood process. The results also allowed us to identify specific sites on the DNA which drive oncogene overexpression after the rearrangement. We are now performing genome editing experiments which target these sites with a view to reversing the over-expression; this will provide new understanding which could eventually lead to new therapies.

Feb 6, 2023 Leave a Comment