Some previous studies suggested that hydrophobic molecules might interact with nanodiamonds, so we speculated that they might actually be beneficial when combined with the typical surfactant mixtures used for removing lipids. This turned out to be the case.
Dr Andrew Marsh
A new study has found that nanodiamonds could increase the cleaning potential of low temperature washing. As part of the ‘Cold Water Cleaning Initiative’, funded by the Engineering and Physical Sciences Research Council (EPSRC) and P&G plc, researchers from the University of Warwick and Aston University have discovered that the inclusion of these minute pieces of carbon enables detergents to operate effectively at temperatures of 25°C and below.
It can be difficult to remove certain types of dirt and fat from clothing at low temperatures, even when using modern biological washing powders. This forces many consumers to regularly wash garments at temperatures between 60°C and 90°C, resulting in a significant energy burden.
The findings, published in the journal ACS Applied Materials and Interfaces
, show how nanodiamonds help to loosen crystallised fat, allowing washing powders to remove dirt at environmentally friendly temperatures.
I spoke to the project’s leader Dr Andrew Marsh, Associate Professor of Chemistry at Warwick’s Department of Chemistry, to find out whether nanodiamonds could become ingrained within the fabric of future detergents. I opened our conversation by asking Dr Marsh what first caused him and his colleagues to suspect that nanodiamonds might be well suited to the removal of fats and dirt from clothing.
"That’s a really interesting question," he began. "Some previous studies suggested that hydrophobic molecules might interact with nanodiamonds, so we speculated that they might actually be beneficial when combined with the typical surfactant mixtures used for removing lipids. This turned out to be the case."
I went on to ask Dr Marsh to what extent his team understood the mechanisms involved in this process.
"Well, we believe that the size of these particles is important, as well as the nature of the surface to which the dirt is attached," he explained. "Also, the positive or negative electrostatic charge that is carried on the surface seems to play a role in the removal process. Even so, we would really like to find out more about the mechanisms involved in the process."
When investigating the cleaning potential of nanodiamonds, the team chose what to some, might seem like an odd test surface. However, as Dr Marsh explained, their selection is not as strange as it might appear.
"We examined lipids, like tristearin, coated on to gold surfaces," he said. "This sounds unusual, but it is actually a fairly standard test that is used when investigating the removal of fat molecules from surfaces. We opted for gold as it allowed us to use an instrument called a Quartz Crystal Microbalance. This instrument enabled us to study the tiny amounts of material that are typically removed during such experiments."
One of the most common factors associated with diamonds is their costliness, but is this also true of nanodiamonds? I asked Dr Marsh whether these tiny pieces of carbon would increase the prices of detergents in which they were included.
"Nanodiamonds themselves are certainly not as costly as the sort of diamonds that you might find in jewellery," he explained. "Having said that, they are not completely inexpensive either. Even so, there is scope for their price to be brought down further. These are the typical sorts of negotiations that take place between suppliers and those who want to use a material for a particular application.
"It could well be that nanodiamonds are not the optimal material to use for this particular application. We have made some very interesting and exciting physical and chemical observations concerning the properties of nanodiamonds, but we would like to expand our research in order to optimise the technology."
I suggested to Dr Marsh that whilst the initial price of new detergents containing nanodiamonds might be heightened, this could be to some degree offset by reduced energy bills.
"Absolutely," he replied. "This was the fundamental issue that we set out to address. Consumers, both in the United Kingdom and around the world, have to resort to the classic boil wash in order to remove crystallised fat from their laundry, and we wanted to change this situation. We want to eliminate the need to heat water to 90°C. Anything that can be done to improve the efficiency and efficacy of current commercial preparations will be beneficial."
Dr Marsh has said that the physical and chemical insight gained from this study could pave the way for future research into how this unique behaviour can be exploited in other ways. I concluded by asking him what other ways he had in mind.
"There are all sorts of other applications for which the improved ability to remove fat from surfaces would be advantageous," he responded. "These applications might be in engineering, for example, but it would also be nice have the ability to more effectively remove fat from surfaces around the home."