DNA-modified silicon nanocrystals studied by X-ray luminescence and X-ray absorption spectroscopies: Observation of a strong infra-red luminescence band

摘要

Silicon nanocrystals (SiNCs) modified with 18-mer DNA oligonucleotides have been studied by X-ray excited optical luminescence (XEOL) and X-ray absorption spectroscopy (XAS) in photoluminescence yield (PLY) and total electron yield (TEY) modes. Luminescence spectra from the DNA-modified SiNCs under X-ray excitation display distinct differences from simple alkyl terminated SiNCs. The DNA-modified SiNCs show strong luminescence at 540 ± 10 nm under vacuum ultraviolet excitation which is assigned to nitrogen Is - σ* transitions within the DNA bases. Under excitation at 130 eV the PLY spectra from the same samples show the native nanocrystal ultraviolet emission band is suppressed, and the strongest emission peak is red shifted from 430 ± 10 nm to 489 ± 10 nm which we attribute to base nitrogen s transitions. In addition, a strong emission band in the infrared region at 815 ± 10 nm is observed. This clearly resolved strong IR band from the DNA-modified SiNCs may provide a useful luminescence signature in cell-labeling techniques and open up a range of applications for in vivo assays.