9 October 2013

The bright side of carbon

By Dr Ng Sing Muk

Whether we realise it or not we are surrounded by carbon-based materials. From fossil fuel as a source of energy to diamond jewellery, the core component of these matters is carbon.

Biologically, carbon is the basic building blocks of living organisms including man, animals, plants and microorganisms. Combined with other elements such as oxygen, nitrogen, sulphur and hydrogen, carbon forms complex biological macro-molecules such as enzymes, proteins and cells all of which have their own functions. Carbon can be in many forms but is commonly associated physically as a black coloured substance such as charcoal and the soot that forms on the walls after the burning of a candle.

But in spite of all the bad press it has been getting, carbon has a unique physical property. It was recently found that carbon could emit light, like a fluorescent lamp, under controlled conditions. However, this only works when it is crushed into minute, nanometre-sized form. For the sake of comparison, a strain of hair is about 100,000 nanometres in diameter. It is so tiny that we will need a powerful microscope such as an atomic force microscope to view a nanometre particle. To make this nano material, crush carbon matter such as charcoal into fine, powdery particles. Putting this under UV light activates the fluorescence. It is similar to viewing a RM50 note where some of the features brighten up. Studies from different parts of the globe show that waste materials such as burned water melon peels and candle soot work just as well for this purpose. This shows that it is possible to create fluorescent material easily and at an extremely low cost.

Following this discovery, carbon is being seen in the same league as other advanced materials that has an endless potential for a diverse range of applications. All this is fine and good, but how can we put it to use, you might ask. Well, let’s imagine that you have an area so small that even the most advanced and smallest bulb available in the market could not reach. We are talking about an area the size of human cells, thousands of times smaller than the full stop at the end of this sentence. This is where carbon nanoparticles could be used to light up the spot under an optical microscope, for example. The nanoparticles will diffuse into the cells, lighting up the cell from the inside out. This will be much brighter compared to light from an external source. This imaging technique will be extremely useful in helping medical practitioners identify abnormal or foreign cells. And since carbon is by nature nontoxic, the issue of toxicity is a moot point.

Another area where the fluorescent property of carbon could be utilised is in the field of chemical optical sensor application. An optical sensor is a tool that measures substances or chemical constituents such as heavy metals, simple molecules and pesticides in the environment and human system. It converts light rays into electronic signals, making it possible to measure the changes in light beam intensity. Since carbon nanoparticles in nature are fluorescing, it can act as the sensing platform. The details on how this works is rather technical but very simply, the substance being investigated will interact with the nanoparticles. Once this is happens the intensity of light rays will drop, indicating the presence and concentration of the substance of interest. There have been many cases where the use of carbon nanoparticles for detecting heavy metal ions such as lead, tin and mercury has proven successful.

Sometimes it takes only a touch of innovation to turn a material which we take for granted into a new class of matter that could be used for other purposes, for instance in the case of the carbon matter discussed here. On that note, it is my belief that when the technology for carbon nanoparticles is better refined and utilised, sustainability and green technologies can be promoted. This is because cheap carbon-rich wastes, especially those from plantations such as tree trunks, leaves, stems and husks, could be turned into high value commodities as carbon nanoparticles which could be used for various applications. Such an approach not only reduces and recycles waste into something useful, but it also contributes towards building the national economy. Who knows, carbon could be used for life-saving procedures in future.

Dr Ng Sing Muk is a lecturer with the Faculty of Engineering, Computing and Science at Swinburne University of Technology Sarawak Campus. He is contactable at smng@swinburne.edu.my