Concentration of gold nanoparticles at near Zero-cost

Gold Nanoparticles synthesis typically delivers 0.025% of Nanoparticle solution. For lateral flow applications, this 0.025% solution is concentrated to 0.1% using ultracentrifugation at 14000 rpm for hours. This is one of the most expensive procedures in lateral flow device development, and it is recurring. We report a zero-cost solution for the concentration of gold nanoparticle solution to 0.025%-0.1%. In this approach, sodium polyacrylate (SPA) beads are used to concentrate gold NP solution. SPA beads have the capacity to absorb water, almost 100–500 times their weight. During this process, the interstitial spaces are too small to allow gold nanoparticles, and so only water is absorbed, leaving the gold nanoparticle solution. In a typical procedure, 50 mg SPA beads concentrate 500 mL of gold nanoparticle solution to 25 mL in less than two hours. The concentrated gold nanoparticle solution is shown to have the same nanoparticle size and UV absorption before concentration and after as well. The cost of commercial SPA beads of $10/kg, the solution can be viewed as a near zero-cost solution for gold nanoparticle concentration and significantly lower the capital as well as recurring costs of lateral flow technologies.