Nano News: 09/09/15

Bioelectronic nose can sniff out contamination in drinking water

A bioelectronic nose that mimics the human nose can detect traces of bacteria in water by smelling it, without the need for complex equipment and testing. According to a study published in ("Real-time monitoring of geosmin and 2-methylisoborneol, representative odor compounds in water pollution using bioelectronic nose with human-like performance") the technology works by using the smell receptors in the human nose. The sensor is simple to use and it can detect tiny amounts of contamination in water, making it more sensitive than existing detection methods. The authors of the study, from Seoul National University, say this could make the technology even more useful in the field. There are two main problems caused by bacteria and other microbes in water: they can make the water toxic, and make it smell bad. At high concentrations, bacteria can be toxic in drinking water. But at lower levels – virtually undetectable by current culturing techniques – they can cause an “off flavor,” putting people off from drinking it. The new study shows how technology that mimics the human nose can sniff out low levels of bacteria and other microbes by detecting the off flavor they give off. “Water that smells bad isn’t necessarily toxic,” said Professor Tai Hyun Park, who has been leading the study. “Imagine you don’t do your laundry; it’s not that toxic but you don’t want to wear it because the smell is bad. With drinking water, if there’s off flavor, even if the water isn’t toxic, you don’t want to drink it. We wanted to develop a way to detect and remove this kind of contamination, so people are happy to drink water.” Traditionally, water was tested for contamination with bacteria by taking a sample and trying to grow the bacteria in the lab. When the bacteria grow, scientists can count the number of colonies and calculate the concentration of bacteria in the water. Another approach is to detect the smells directly; this is usually done using techniques that require large scientific equipment, such as gas chromatography or mass spectroscopy. “These are good ways to detect smell molecules, but they require a large amount of work before the sample is even ready to test,” said Prof. Park. “And all of these tests need to be done in a laboratory with expensive equipment – they’re just not suitable for the field.” Prof. Park and the team wanted to develop a more convenient, compact device for testing water that is suitable for using on-site. In addition to contamination of drinking water, bacteria and other microbes can also contaminate rivers and lakes – for example, the algal blooms in Hong Kong. Catching this kind of contamination early means it’s easier to control. We have five senses – sight, hearing, touch, smell and taste. Among these five senses, we have devices that catch the information for three of them: sight (video cameras) hearing (audio recorders) and touch (tablet PCs). But there is not yet a device that successfully captures information for smell or taste. Bacteria that contaminate water give off particular smells that are associated with a handful of smell molecules. Two typical odors - earthy and musty – are caused by to different molecules: geosmin (GSM) and 2-methylisoborneol (MIB). The new nose-like device can detect these smells at very low concentrations of just 10ng per liter of water. It’s also very sensitive, and can spot a particular smell in a cloud of others. Since their concern is the bad smell, Prof. Park and his colleagues naturally thought about how the human nose works and adapted its function as a sensor element. The human nose is more complicated than receptors for two smell molecules, so to make a true smelling device, the researchers will need to scale up their efforts. “Our eventual goal is to develop a real human nose-like bioelectronic nose,” said Prof. Park. “In the human nose, there are about 400 different olfactory receptors. If we could develop our technology to include all of these, we would have a device that could smell anything we can, at lower concentrations. The technology has many other applications, say the researchers. A smelling device could be very useful for the smell industry, such as perfume, cosmetics, wine and coffee. Certain diseases, such as lung cancer, can cause patients to give off particular smells; dogs have been known to detect these, and a bioelectronic nose opens the path to diagnosis through smell. There’s also a role for security, for example in drug searches at airports. More fundamentally though, the researcher say it could help them build something that’s never existed before: a smell classification system. “We don’t have a system for the classification of smell yet; it all still depends on our human sensory system. With our bioelectronic device, we can systematically detect and label smells, perhaps coming up with a universal smell code we can use to communicate in the future.

One step towards faster organic electronics

For years we have believed that ordered polymer chains increase the conductivity of plastic. And a new generation of polymers has been developed. It is true that these new polymers are more conductive, but for completely different reasons – according to researchers from Linköping University and Stanford University, in an article in ("Experimental evidence that short-range intermolecular aggregation is sufficient for efficient charge transport in conjugated polymers"). Organic electronics has many advantages: it is inexpensive, flexible and lightweight it does not consume any scarce resources[SF1] . In terms of applications, we are only limited by our imaginations. There has been a lot of development in polymers since the phenomenon of conducting and semi-conducting plastics was discovered and in 2000 awarded a Nobel Prize. Their weakness is still speed; plastics conduct a charge slowly, compared to silicon, for instance. A polymer consists of long chains of hydrocarbon, where other elements are bound, which give the particular plastic its properties. Research is underway, and researchers and developers in the chemical industry have developed new polymers that conduct better. ”The charge is transported two to three times faster in the latest generation polymers,” explains Dr Simone Fabiano, researcher at the Laboratory of Organic Electronics, Linköping University, Campus Norrköping. He is the lead author of the article being published in the , PNAS. Until now people have tried to get the polymer chains to lie as well ordered as possible. The idea is that it should be easy for the charge to jump between the chains if they are organised in rows. Dr Fabiano compares the polymer chains to spaghetti, that you try to line up next to each other, instead of all tangled up, like when it has been tipped from a pot. But to their surprise, the researchers observed during their experiments that the charge seems to travel as quickly in an unordered polymer as in an ordered, crystalline one. Together with colleagues at the Laboratory of Organic Electronics in Norrköping and in Stanford, California, Dr Fabiano has discovered why this occurs. They have shown that crystallinity, the degree of structural order in a solid, actually does not play a part in how quickly a polymer conducts. ”We see that the new generation of polymers has such small defects that the charge moves faster along the chain instead of jumping between the chains. For the charge carrier, it takes less energy to travel along the chain than to jump to the adjacent one. So the polymer is a faster conductor,” explains Simone Fabiano. Instead, the ideal situation seems to be that the polymer has some a degree of disorder and that the polymer chains aggregate from time to time, that is, they cross each other, to make the transition easier. To further increase conductivity in the conducting and semiconducting polymers, and to develop faster electronic components, Dr Fabiano now places his hope on the chemists. ”It is about design at the molecular level. That they can continue to reduce the defects and focus on enabling the polymer chains to make better contact with each other, rather than forming large crystalslying in order.”

Using natural nanoparticles to remove perfluorinated compounds from polluted soils

Perfluorinated compounds (PFC) are a new type of pollutants found in contaminated soils from industrial sites, airports and other sites worldwide. PFC can induce adverse health effects, nerve problems and other health problems to humans and animals as well as long-term effects to the environment.

Transmission electron microscopy image of the natural nanoparticle. The particle size is 200 nm in diameter, and is magnified 57,000 times with transmission electron microscope (TEM). (Image: Fjordforsk AS) Recent reports show that PFC have been detected in groundwater in Sweden, Norway and many other countries in Europe. In Norway, The Environment Agency has published a plan to eliminate PFOS from the environment by 2020. In other countries such as China and the United States, the levels are far higher, and several studies show accumulation of PFOS in fish and animals, however no concrete measures have been taken. The Norwegian company, Fjordforsk AS, which specializes in nanosciences and environmental methods, has developed a method to remove PFOS from soil by binding them to natural minerals. This method can be used to extract PFOS from contaminated soil and prevent leakage of PFOS to the groundwater.

Transmission electron microscopy image of t nanoparticle after adsorbing perfluoroheptanoic acid

Transmission electron microscopy image of the natural nanoparticle after adsorbing perfluoroheptanoic acid (PFC). PFC coating on nanoparticles is visible as a light and transparent layer on the surface. The particles are in the range of 100-200nm and are magnified 57.000 times with transmission electron microscopy (TEM). (Image: Fjordforsk AS) Electron microscopy images show that the minerals have the ability to bind PFOS on the surface of the natural nanoparticles. The proprietary method uses saltwater and does not contaminated the treated grounds with chemicals or other parts from remediation process.