Dr Patrick Cullen
My research focuses on scalably producing nanomaterial inks, with a view to incorporating them into devices and applications for improved performance. These materials are used as: catalysts in fuel cells, electrodes for supercapacitors, Lithium-ion and Sodium-ion batteries electrodes, redox flow cell catalysts and anti-corrosion coatings.
Creating nanomaterials from bulk materials (top down synthesis) is widely researched as bulk materials often occur naturally, providing cheap starting materials. Making nanomaterials from bulk materials within a liquid is a useful approach as these liquids can be used to manipulate the nanomaterials scalably, much like an ink; these nanomaterial inks can be painted, sprayed and printed in a variety of scalable ways.
Typically, harsh physical or chemical methods are used to break up bulk materials within liquids. This results in a suspension of damaged nanomaterials that have a wide range of shapes and sizes. Over time these suspensions settle out, leaving a liquid with some sediment at the bottom of the container. This is a process similar to one that would happen if you were to take a bottle filled with soil and water and shake it up – first you would get a “mud”, but when left over time, the soil would settle at the bottom of the bottle.
Conversely, I use methods of chemical doping in order to make “salts” of bulk materials. Once I have these bulk material salts, it is possible with certain liquids (anhydrous polar aprotic solvents), to dissolve these salts as large charged species. This can result in liquids containing undamaged, individualised nanomaterials which are homogeneous in shape and size. In this case, since the materials are dissolved (and this is thermodynamically driven), no agglomeration occurs. This is much like what would happen if you were to take a bottle filled with seawater – over time, the salt and the water do not separate.
I use these “solutions” of nanomaterials to improve performance in a variety of devices and applications. A large challenge is to get the nanomaterials to order in the correct configuration for the particular target device or application.