Tailoring Plasmon Gold Nanoparticles: Influence of Reducing Agents on Shape and Size

Citrate, borohydride, a mixture of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), and alpha- or beta-cyclodextrin (CD) were utilized to synthesize plasmonic gold nanoparticles. The absorbance spectra revealed the nature of the plasmon band, while the IR spectra identified the functional groups of the reducing agents. Colloidal gold nanoparticles are produced in ruby and blue colors, exhibiting spherical, rod, and prism shapes. The diameters of AuNPs were measured as follows: AuNPs@Cit (11.8 +/- 0.2 nm), AuNPs@Cit-OH (11.1 +/- 0.8 nm), AuNPs@BH4 (5.9 +/- 0.27 nm), AuNPs@H-CTAB/SDS (21.1 +/- 1.2 nm), AuNPs@L-CTAB/SDS (19.3 +/- 2.4 nm), AuNPs@alpha-CD (8.4 +/- 0.2 nm), and AuNPs@beta-CD (7.8 +/- 0.3 nm). Furthermore, the CV spectra exhibited a stronger Au0 reduction signal for larger gold nanoparticles present on the electrode surface. Finally, electron transfer between Au3+ ions and all reducing agents was observed, with borohydride being identified as the most active and efficient among them.