Self-assembled monolayer noble metals

Self-assembled monolayers (SAMs) [8] The layers are formed by heterologous interaction between reactive groups, such as thiols, and noble metals, such as gold or silver. Since the molecules are selectively adsorbed on these metals, film growth stops after the first monolayer is completed. The molecular aggregation is enthalpy driven, and the final structure is in thermodynamic equilibrium. 

SELF-ASSEMBLED MONOLAYERS OF THIOLS ON NOBLE METALS... 

Noble metal surfaces, particularly gold, have been usually functionalized using self-assembled monolayer (SAM) techniques [14]. The formation of stable and aligned packed monolayers is carried out directly onto the transducer surface via bifunctional molecules. Two methods are used to... 

Another possible application of chiral metal nanostructures is catalysis. For example, Kobayashi et al7 used chiral noble metal nanoparticles for asymmetric C-C bond formation. In another work Heiz et al. employed variations of the pH for the ligand N-acetyl cysteine that were subsequently bound to platinum nanoclusters to generate differences in the moieties bound to the surface of the cluster. The researchers also reported the special production of Pt nanoclusters in the presence of ethylene glycol which were then replaced with cysteine and derivatives generating chiral functionality on the particles. These nanoclusters were then be used for the enantioselective hydrogenation of butanone. Finally, Somorjai et al7 produced a chiral self assembled monolayer of gold nanoparticles in mesoporous silica which has been used to catalyse the production of cyclic propanes in high enantiomeric excess. 

A currently very fashionable recipe for the preparation of well-controlled surface layers is the use of molecules with a reactive head-group amenable to undergo a covalent bond with a complementary chemical site on the surface of the substrate to be modified. This leads to the formation of so-called self-assembled monolayers SAM [1] with structural properties similar to Langmuir layers prepared from amphiphiles at the water-air interface [2]. Examples are silanes on oxide surfaces or thiols, and monosulfides or disulfides on noble metal surfaces (see also Chapter 7). 

G. Heimel, L. Romaner, E. Zojer and J.-L. Bredas, Toward Control of the Metal — Organic Interfacial Electronic Structure in Molecular Electronics A Eirst-Principles Study on Self-Assembled Monolayers of re-Conjugated Molecules on Noble Metals, Nano Lett, 2007, 7, 932-940. 

Toward control of the metal-organic interfacial electronic structure in molecular electronics a first-principles study on self-assembled monolayers of -conjugated molecules on noble metal, G. Heimel,... 

Concomitant to the development of the trichlorosilane technique, a method for the chemisorption of monolayers of disulfides on gold was developed by Nuzzo and Allara [25]. It has been rapidly generalized to the adsorption of monolayers of alkanethiols on noble metal surfaces [22,26]. Using acid surface to a copper salt on which another thiol monolayer can adsorb, Ulman and coworkers showed that this chemical self-assembling technique is also useful for multilayers build-up [27,28]. Alternatively a, [Pg.651]

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