Gold nanoparticles for bio-molecule detection in body fluid and systems therefor

A method for synthesis of gold nanoparticles dispersed in solution, comprising the steps of:

• (1) mixing a sodium citrate solution and a first chloroauric acid solution to form a first solution, wherein the concentration of sodium citrate of said first solution is 0.05-0.1 M prior to reaction;
• (2) dilute said first solution with purified water, then mixing the diluted solution with a hydroxylammonium chloride solution to form a second solution, wherein the concentration of gold ions of said second solution is 0.08-0.2 M and the concentration of hydroxylammonium chloride of said second solution is 0.05-0.2 M prior to reaction;
• (3) preparing a third solution by adding a second chloroauric acid solution to said second solution;
• (4) preparing a fourth solution by adding a metal hydroxide solution to said third solution, wherein the concentration of metal hydroxide of the fourth solution is 0.5-2 M prior to reaction;
• and
• (5) adding an alcohol into said fourth solution to form said gold nanoparticles dispersed in solution;
• wherein 80% of said gold nanoparticles have a diameter between 25 nm to 40 nm.