Abstract:This paper describes the preparation of wavelength-tunable luminescent Au nanodots (NDs) and Au/Ag NDs at room temperature. Controlling the molar ratios of tetrakis(hydroxymethyl)phosphonium chloride (THPC) to Au ions and of Ag ions to Au ions allows the preparation of different sizes of Au and Au/Ag nanoparticles. We then used 11-mercaptoundecanoic acid (11-MUA) to react with the as-prepared nanoparticles to prepare wavelength-tunable luminescent 11-MUA–Au NDs and 11-MUA–Au/Ag NDs, respectively. Our prepared luminescent NDs exhibit a number of attractive optical properties: tunable luminescence wavelengths (456–640 nm), long lifetimes (>250 ns), and large Stokes shifts (>100 nm). These properties suggest that the as-prepared 11-MUA–Au NDs and 11-MUA–Au/Ag NDs would be suitable for use in sensing applications after bio-conjugation.