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© 2013 Macmillan Publishers Limited ; Transient precursor states are often experimentally observed for molecules adsorbing on surfaces. However, such precursor states are typically rather short-lived, quickly yielding to more stable adsorption configurations. Here we employ first-principles calculations to systematically explore the interaction mechanism for benzene derivatives on metal surfaces, enabling us to selectively tune the stability and the barrier between two metastable adsorption states. In particular, in the case of the tetrachloropyrazine molecule, two equally stable adsorption states are identified with a moderate and conceivably reversible barrier between them. We address the feasibility of experimentally detecting the predicted bistable behaviour and discuss its potential usefulness in a molecular switch. ; W.L. and S.N.F. are grateful to the Alexander von Humboldt Foundation. J.C. is a Ramón y Cajal fellow and Newton Alumnus supported by the Spanish Government and The Royal Society. J.C. is grateful for support from the Marie Curie Career Integration Grant (FP7-PEOPLE-2011-CIG NanoWGS). A.T. acknowledges support from the European Research Council (ERC Starting Grant VDW-CMAT). ; Peer Reviewed

In this work, titanium phosphate nanoparticles were modified with different electroactive metals (cadmium, bismuth, copper, silver and mercury), by a cation-exchange reaction. The amount of metal introduced into the nanoparticles depended strongly on the counter-ion used during the exchange reaction and the type of metal. Nanoparticles with a high metallic load could be generated. The electrolytic medium played an important role in the detection of these metal-modified nanoparticles, since the use of acid makes it possible to extract a large part of the introduced metal by reversing the cation-exchange reaction. The application of these nanoparticles in electrochemical detection was evaluated, the nanoparticles modified with copper and mercury proving superior in terms of sensitivity and selectivity in multiplex detection. As a proof of concept, these nanoparticles were used as labels in a multiplex electrochemical biosensor for the simultaneous detection of two analytes. ; This work has been supported by the FC-15-GRUPIN-021 project from the Asturias Regional Government and the CTQ2014-58826-R project from the Spanish Ministry of Economy and Competitiveness (MEC). ; Peer Reviewed