Chemical Communications Blog

A mesoporous material functionalised with aggregation-induced emission (AIE) luminogens serves as an efficient and recyclable fluorescent sensor to detect picric acid (PA) in water

A reusable fluorescent sensor that detects explosives in groundwater or seawater could aid antiterrorist activities and environmental protection, say scientists in China.

Many techniques have been used to detect explosives, including gas chromatography, Raman spectroscopy and fluorescence spectroscopy. The latter is considered the most useful because of its simplicity, high sensitivity and low cost. With this technique, fluorescent dyes are incorporated into a solid matrix on which they interact with the explosive molecules, causing them to fluoresce.

However, the dyes often aggregate within the matrix, leading to a substantial decrease in fluorescence, known as quenching. This loss of efficiency and sensitivity motivated the discovery of molecules whose fluorescence is turned on by aggregation rather than suppressed. Materials based on such aggregation-induced emission (AIE) luminogens (luminescent compounds) have shown promise in explosive detection in organic solvents. Dispersion in aqueous solution has, until recently, proven difficult.

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Supersensitive detection of explosives by recyclable AIE luminogen-functionalized mesoporous materials
Dongdong Li, Jianzhao Liu, Ryan T. K. Kwok, Zhiqiang Liang, Ben Zhong Tang and Jihong Yu
Chem. Commun., 2012, Advance Article, DOI: 10.1039/C2CC31890C, Communication

Field emission-scanning electron microscopy image of a single walled carbon nanotube forest

UK scientists have shown that the sidewalls and closed ends of carbon nanotubes can support fast electron transfer, challenging the belief that they are electrochemically inert.

Carbon nanotubes (CNTs) have wide ranging electrochemical applications for sensing and energy. Forests of vertically aligned CNTs have been proposed for use as electrodes, but it was thought that the inert sidewalls would have to be insulated and the ends opened to allow electron transfer.

Scientists from the University of Warwick have now challenged this position by showing that the sidewalls and closed ends of CNTs can support fast electron transfer.

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Electrochemistry at carbon nanotube forests: sidewalls and closed ends allow fast electron transfer
Thomas S. Miller, Neil Ebejer, Aleix G. Güell, Julie V. Macpherson and Patrick R. Unwin
Chem. Commun., 2012, Advance Article, DOI: 10.1039/C2CC32890A, Communication

The tattoo incorporates a sensor that could be used to detect environmental hazards

Scientists in the US have developed an electrochemical sensor incorporated into a temporary transfer tattoo (T3) to be used as a device to warn the wearer of any health or security threats. Not only is the sensor non-invasive, it can also be concealed in an inconspicuous tattoo design, without compromising its resolution or performance.

Joseph Wang and his colleagues from the University of California, San Diego, have combined their expertise in printing flexible chemical sensors with commercially-available temporary tattoo paper. Integrating the electrochemical sensor within T3 maximises its contact with skin, including all epidermal irregularities, thanks to the elasticity of the T3 material. In addition to this, the team dispersed carbon fibre (CF) segments into the tattoo ink, providing an interlinked conductive backbone that enhances the sensor’s electrochemical behaviour. The CF constituents also help to counteract cracking and provide the mechanical reinforcement needed to protect the sensor against routine wear-and-tear while on the skin. The team also showed that the T3 sensor (on pig skin) could be used for detecting explosives like 2,4,6-trinitrotoluene (TNT), in connection with square wave voltammetry.

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Electrochemical Sensing Based on Printable Temporary Transfer Tattoos
Joseph Wang
Chem. Commun., 2012, Accepted Manuscript, DOI: 10.1039/C2CC32839A, Communication

The trap captures and retains light hydrocarbons for longer than current traps

A trap that adsorbs exhaust emission gases given off during the first two minutes after firing up an internal combustion engine has been developed by scientists in Spain. It’s during this cold start period that 50–80% of the total hydrocarbon emissions are produced, they say, so the trap could minimise levels of harmful exhaust gases pumped into the atmosphere.

Current traps are made from porous zeolites. They work well for the heavy hydrocarbons in fuel, which are retained until the engine’s temperature reaches 200–300oC (the light-off temperature), at which point, they are released and oxidised to carbon dioxide and water in a catalytic converter before being expelled into the atmosphere. But lighter hydrocarbons, such as ethane and propene, desorb from the trap before this temperature is reached and escape, unoxidised.

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Molecular simulation design of a multisite solid for the abatement of cold start emissions
B. Puértolas, M. Navlani-García, J. M. López, T. García, R. Murillo, A. M. Mastral, M. V. Navarro, D. Lozano-Castelló, A. Bueno-López and D. Cazorla-Amorós
Chem. Commun., 2012, Advance Article, DOI: 10.1039/C2CC30688C, Communication