Patent ID: 7347974

Claim:
An article of manufacture suitable for use in determining whether or in what amount a chemical species is present in a target environment, which article comprises a multiplicity of particles in three-dimensional close-packed orientation, said particles having a core of conductive metal or conductive metal alloy, in each said particle such core being of 0.8 to 40.0 nm in maximum dimension and deposited on said core a ligand shell of thickness from 0.4 to 4.0 nm and composed of an encapsulating monomolecular layer of ligand shell molecules that are not coupling agents, each molecule having a head-tail type structure, the head being a functional group possessing a bonding interaction with metal atoms in the core surface, and the tail having a structure and composition designed to provide additional stabilization of metal clusters against irreversible agglomeration, induce solubility in solvents, and promote interactions with chemical species of interest, and having a tail functional group capable of selective interactions that discriminate between chemical species of interest, the tail selected from the group consisting of a heterofunctional group, an aromatic group, a secondary aliphatic group, an araliphatic group, and a tertiary aliphatic group, the ligand shell being capable of interacting with a chemical species in a target environment such that an electrical property of said multiplicity of particles is altered; and a substrate suitably configured for supporting the multiplicity of particles and presenting the multiplicity of particles to contact with said environment; wherein the particles are substantially free of coupling agents, and the multiplicity of particles is deposited by a method comprising spraying on the substrate a solution comprising the multiplicity of particles and a solvent, the substrate being at a temperature such that the solvent is flashed away or rapidly evaporated; or wherein the particles are linked to each other and to the substrate by coupling agents.