Individual porphyrin molecules have been covalently linked together onto a copper surface by scientists in the UK and Spain.

David Amabilino from the Institut de Ciència de Materials de Barcelona (CSIC), Rasmita Raval from Liverpool University, UK and colleagues have developed a method to deposit porphyrins onto a copper surface and induced covalent coupling by using a thermal annealing method. The resulting reaction leads to a mixture of products, which can be individually imaged using scanning tunnelling microscopy (STM). 

The organisation of molecules on surfaces into strong and defined structures has potential application in a range of technologies, from molecular electronics, catalysis, sensors, smart materials to optical devices. 

Raval has shown that it is possible to form highly functional surface arrays that have strong, stable and, most importantly, covalently bonded structures attached. Further investigations are being carried out by the group on a range of molecules, surfaces and general reaction conditions to afford other macromolecules grafted onto surfaces. This may lead towards surfaces with different molecular functionalities, such as molecular recognition, catalytic properties and specific electronic/magnetic responses.

'This is a clean and powerful method for introducing both complexity and robustness into the design of molecular nanostructures at surfaces,' says Raval. However, there are still many challenges to overcome with this work with regards to characterisation of the individual nanostructures and their individual electronic, chemical and optical responses using STM and other techniques. Raval says the biggest challenge is 'to make sophisticated surfaces with multi-functional, multi-tasking capabilities.'

Emma Shiells