Newly Developed Chip Can Sense Homemade Bombs

A very small and inexpensive chip which is capable of sensing trace amounts of hydrogen peroxide used in common homemade explosives has been developed by researchers at the University of California, San Diego. About the size of a penny, the chip is capable of detecting hydrogen peroxide vapor in the parts-per-billion range. The chip operates by monitoring the varying electrical conductivity contained in thin films of “metal phthalocyanines”. In general, when these films are exposed to an oxidizing agent such as chlorine, there is an increase in electric current, whereas a reducing agent would cause a reduction in current. Depending on the type of metal used in the thin films however, the presence of hydrogen peroxide causes current to either increase or decrease. By combining different metals with both of these properties, researchers were able to produce a unique signature when in the presence of hydrogen peroxide. Hydrogen peroxide was used in the July 7, 2005 London Transit bombing and again in London in the failed July 21 attempt.