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Molecular logic gates open up
30 August 2006
A chemical logic gate that combines both inorganic and organic molecules is a versatile addition to the suite of molecules that already mimic the core functions of computer chips, Chinese scientists report.
Conventional electronic logic gates are smart switches that produce an 'on' or 'off' signal depending on their input conditions. For example, an AND gate will only deliver an 'on' signal if both its inputs are also 'on'.
Their chemical cousins are generally made of either organic molecules or inorganic materials, but this new hybrid consists of a europium-based polyoxometalate surrounded by surfactant molecules that have a long carbon-based chain capped by a positively charged nitrogen atom. The nanoparticles assemble themselves, with the surfactant molecules' nitrogen sticking to the negatively-charged europium compound.
The fluorescent nanoparticles emit light at one of two different wavelengths, depending on the combination of inputs
The hybrid nanoparticles, developed by Lixin Wu and colleagues at Jilin University, Changchun, perform logic operations of combined NOR and INHIBIT gates. Their two input signals are switched on by the presence of metal ions and UV light. If these signals combine to trigger an output, the fluorescent nanoparticles will emit light at one of two different wavelengths.
'The nanoscale inorganic-organic clusters formed should be much easier to manipulate in the solid state than a single organic molecule which will facilitate the construction and integration of single molecular logic gates,' said Wu. 'Also, it should be possible to fabricate all kinds of logic gates using this hybrid model.'
Francisco Raymo, an expert in molecular devices at the University of Miami, US, said the choice of building blocks in this system makes it different to logic gates already available. 'I am not aware of any other system based on a polyoxometalate structure,' he said.
The challenge is 'to make these molecular logic gates fast, reversible, stable and, more importantly, we need to figure out how they can talk to each other,' said Raymo.
Hui Zhang, Xiankun Lin, Yi Yan and Lixin Wu, Chem. Commun., 2006