Gold nanoparticles (Au NPs) have paid much attention due to their exceptional properties which make them suitable for a wide range of applications [1]. Moreover, gold nanoparticles have a broad Surface Plasmon Resonance (SPR) band in the visible region of the electromagnetic spectrum, which is suitable for designing new (bio) sensing devices. However, these properties directly depend on the dimensions and size distribution of the NPs and so, a strict control of the synthesis parameters is required to obtain well-defined nanomaterials. Nanoparticles are usually prepared by means of batch processes, which have limited reproducibility due to the difficult control of some steps such us the addition of reagents and injection volume being difficult to obtain a colloidal suspension with the same characteristics in different batches [2]. In the present work, Au NPs have been synthesized by a simple one-phase reaction in which gold (III) chloride solution was reduced by sodium borohydride. The volume of sodium borohydride was added by syringe pump. Synthesis repeatability was characterized using the SPR band intensity and shift, as the specification parameters. The obtained results indicated that the approach with the use of a syringe pump was superior because it has higher repeatability than the original method (Fig. 1).

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