Probing the very early stages of nucleation and colloidal growth
Nucleation and early-stage growth processes are the central, most important stages in the evolution of solid materials. These determine the morphology, composition and molecular/crystal structure of embryonic particles, which act to dictate the ultimate nature of the end products, i.e. their size, structure, crystallinity, homogeneity, etc. However, despite being studied for more than a century, these very early stages of colloidal evolution are still not fully understood. This knowledge gap exists because experimental access immediately before and after nucleation events has been largely unavailable. We are developing techniques to overcome these barriers, and glimpse into these earliest stages of colloidal evolution.
In situ X-ray Spectroscopy
Collaborating with colleagues at the Phoenix Beamline of the Paul Scherrer Institute in Switzerland, we developed easy to implement techniques to probe reacting solutions as they first come into contact, and, study the very first milliseconds of their reaction in real-time through X-ray Absorption Spectroscopy (XAS). The devices use polydimethylsiloxane (PDMS) microfluidic channels sandwiched between ultrathin, x-ray transparent silicon nitride observation windows and rigid substrates. The new approach has three key advantages:
i) Owing to the assembly techniques employed, the devices are suitable for both high energy and tender (1-5keV) x-rays;
ii) they can operate in a vacuum environment (a must for low energy x-rays) and
iii) they are robust enough to survive a full 8-hour shift of continuous scanning with a micro-focused beam, providing higher spatial and thus greater time resolution than previous was possible.
In- situ Optical Spectroscopy
In collaboration with our colleagues at Monash Materials Engineering we have developed a unique microspectrometry facility which can measure absorption and emission properties of materials down to a 0.2 μm spot size, and when combined with our microfluidic modules can take time resolved measurements with a 10 microsecond time resolution at a spectral range of 250-1100nm. The platform can conduct and analyse large numbers of experiments and evaluate the entire evolution cycle of a class of materials in the same time taken for a single batch reaction!
