Reinforced cluster optical sensors

An optical sensor comprising an electrically conducting, electromagnetic waves reflecting layer, said reflecting layer being made of metal or electrically-conducting colloid particles, an inert interlayer, and analyte-interacting linkers immobilized on a surface of said inert interlayer at a distance of less than 500 nm from said reflecting layer, said analyte-interacting linkers including a number of electrically-conducting colloid particles having a diameter of less than 500 nm bound thereto, interaction of an analyte with said optical sensor causing changes in the number of electrically-conducting colloid particles bound to said analyte-interacting linkers and thus leading to characteristic color changes of said optical sensor, said inert interlayer providing a constant distance between the electromagnetic wave-reflecting layer and the linker-bound colloid particles.