Patent ID: 6177088
Filing Date: 2001-01-23
Classification: G01N,Y10T

Abstract:
A nanometer-scale bead, having an essentially spherical shape and a diameter of from about 10 nm to about 50 nm, said nanosphere comprising:a nanometer-scale probe ion core, formed from an ionic salt consisting of any water soluble inorganic anion or cation having a labile counterion;a molecular layer of a first anionic surfactant, surrounding said probe ion core;a molecular layer of a second anionic surfactant, surrounding said probe ion core and said first aninic surfactant layer such that the surfactant molecules of said second surfactant are oriented tail-to-tail with the molecules of said first surfactant;a semi-permeable polymer shell, being formed of polymer chains formed from a polymerizable organic monomer by the addition of an initiator, and encasing said probe ion core within said shell; anda first organic acid having an acid functionality, a terminal olefin and a spacer of at least 5 .ANG. between the acid functionality and the olefin, said first organic acid being incorporated into the polymer chains of said polymer shell,the nanosphere being formed by the steps of:(a) dispersing said first anionic surfactant in a non-polar organic solvent;(b) dispersing said second anionic surfactant in an aqueous solution;(c) adding a concentrated aqueous solution of said ionic salt to said surfactant-containing organic solvent, allowing said salt to be dispersed into said first surfactant to form a reverse micelle;(d) adding said surfactant-containing organic solvent to said surfactant-containing aqueous solution, and allowing the reverse micelle to be dispersed into said second surfactant to form a double micelle;(e) evaporating said organic solvent away from said aqueous solution containing said double micelles,(f) adding to said double-micelle-containing aqueous solution said polymerizable monomer and said first organic acid having an acid functionality, a terminal olefin, and a spacer of at least 5 .ANG.;(g) then adding to said aqueous solution said initiator, and activating said initiator, while mixing said aqueous solution, and allowing a polymerization reaction to proceed until the reaction is essentially complete and said double micelles are encapsulated in polymer shells to form nanospheres wherein each nanosphere has a diameter of from about 10 nanometers to about 50 nanometers; and(h) removing said aqueous solution from the nanospheres.