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

Gold colloids were synthesized via mixing the aqueous solution of HAuCl4 and Triton X-100 at room temperature. The gold sol samples were quickly obtained during first 2 h then the samples were placed for 8 h to ensure they were completely stable. The colour of most samples turned to violet red. But the sample with 0.5 ml TX-100 remained colorless. During synthesizing, UV–vis absorption spectra were recorded every 10 s. 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.