Hypothesis: A facile, dialysis-based synthesis of stable near infrared (nIR) absorbing plasmonic gold nanoparticles (lambda(max) = 650-1000 nm) will increase the yield of nIR particles and reduce the amount of gold colloid contaminant in the product mixture. Experiments: Chloroauric acid and sodium thiosulfate were reacted using a dialysis membrane as a reaction vessel. Product yield and composition was determined and compared to traditional synthesis methods. The product particle distribution, yield, and partitioning of gold between dispersed product and membrane-adsorbed gold were determined. Findings: The synthesis results in polydisperse particle suspensions comprised of 70% spheroid-like particles, 27% triangular plates, and 3% rod-like structures with a 3% batch-to-batch variation and a prominent nIR absorption band with lambda(max) = 650-1000 nm. The amount of small gold colloid (lambda(max) = 530 nm; d < 10 nm) in the isolated product was reduced by 96% compared to traditional methods. Additionally, 91.1% of the gold starting material is retained in the solution-based nanoparticle mixture while 8.2% is found on the dialysis membrane. The synthesis results in a quality ratio (QR = Abs(nIR)/Abs(530)) of 1.7-2.4 (twice that of previous techniques) and 14.3 times greater OD(*)ml yield of the nIR-absorbing nanoparticle fraction. (C) 2014 Elsevier Inc. All rights reserved.