Fabrication of QD–silica–Au NCs ternary hybrid sphere-based fluorescence bar codes by a post-encoding method

We fabricated QD–silica–Au NC hybrid spheres, in which the solid silica core contained QDs while the mesostructured silica shell contained Au NCs, by a two-step synthesis procedure. The hybrid spheres were further characterized by high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and nitrogen adsorption–desorption analysis to confirm the formation of the ternary hybrid structure. The as-prepared ternary hybrid spheres showed an interesting fluorescence spectrum variation and further could be developed as a precursor for fabricating multicolor fluorescence bar codes by using L-cysteine (L-Cys) as an effective post-encoding adjuster. A small variation of the concentration of L-Cys led to a prominent change of the precursor's fluorescence intensity ratio, which could correspond to a series of distinguishable multicolor fluorescent bar codes. Furthermore, the multicolour fluorescence bar codes fabricated by the post-encoding method showed excellent non-reversibility, batch-to-batch reproducibility of the intensity ratios, photophysical and thermal stability properties and anti-interference capabilities, which are important virtues for them to be used in high-throughput bio-labelling and imaging.