Influence of TX-100 on the size controlled synthesis of gold colloid

Gold colloids were synthesized via mixing the aqueous solution of HAuCl(4) and Triton X-100 at room temperature. The gold sol samples were quickly obtained during first 2h then the samples were placed for 8h to ensure they were completely stable. The colour of most samples turned to violet red. But the sample with 0.5ml TX-100 remained colorless. During synthesizing, UV-vis absorption spectra were recorded every 10s. By studying the synthesis time-dependent surface plasmon resonance (SPR), we found that the growth of gold colloids presented an exponential increase form. By analyzing the TX-100 concentration dependence of absorption peak, the effect of TX-100 concentration on gold colloid diameter was studied and the gold colloid's final dimension was resulted from competition between reducing speed and coating speed.