Since the rDNA is modified with thiolated group at the 5′ end, the resulted dsDNA-GaAs surface has multiple binding sites for interaction with GNPs, thereby leading to high density GNPs assembly on GaAs substrate. By keeping the GNPs with radius of 5 ± 0.5 nm and concentration of 50 nM, but altering the ionic strength of the gold colloid, the GNPs would bind with the thiolated rDNA on dsDNA-GaAs surface. The as-resulted GaAs-dsDNA-GNPs substrates were then analyzed using steady-state PL spectroscopy. The results are averaged over 10–15 measurements on different areas for each spectra. It was found that when the thiolated dsDNA-GaAs incubated with GNPs, another ∼7-fold increase in PL intensity of GaAs was obtained (Fig. 2A). In contrast, only little PL signal change was observed when the untreated GaAs or nonthiolated dsDNA-GaAs (with nonthiolated rDNA) incubated with GNPs. Scanning electron microscopy (SEM) was used to directly characterize the GNPs attachment on GaAs surface. As shown in Fig. 2B, a typical GNPs-GaAs hybrid structure was obtained by incubating thiolated dsDNA-GaAs with GNPs. The GNPs were evenly distributed over the whole GaAs surface with a diameter of ∼5 nm. Whereas, untreated or nonthiolated dsDNA-GaAs resulted in a clean surface without any GNPs. Therefore, the functionalized DNA duplex scaffolds are responsible for GNPs attachment on GaAs substrate.