Chemical barcodes made from MOFs

US researchers have made metal-organic frameworks (MOFs) with 'rainbow barcodes' built directly into their structure. By varying the amount of luminescent lanthanides in the framework, the novel MOFs are coded to emit a unique spectrum of light that can be read like a fingerprint. 

It is hoped that these materials could find uses as invisible and harmless security tags to prevent theft or fraud, for example by integrating them into money, credit cards and parcels.   More...

http://www.rsc.org/chemistryworld/News/2009/December/02120901.asp