Synthesis And Multicolor Encoding Applications Of Gap-enhanced Raman Tags

Surface-enhanced Raman scattering(SERS)tags have the function of optical labeling as fluorescent dyes.SERS tags have been widely used in biomedical field due to high specificity,high sensitivity,narrow linewidth and non-invasion.However,conventional SERS tags have poor reproducibility and limited enhancement factor.Therefore,it is necessary to develop a novel SERS tag with stronger signals and good reproducibility.Photostability is fundamental to optical tags.Generally speaking,SERS tags tend to be more photostable than conventional fluorescent probes.However,very limited research has been reported on SERS photostability.Multiplexing detection of biomolecules can play significant roles in reflecting complicated biochemical processes.SERS tags have quite narrow linewidth so that they have great potentials in multicolor encoding.A five-color coding has been reported to be successfully achieved.However,the encoding capacity could be further increased.In addition,it is hard to encode in terms of Raman intensity owing to the bad signal reproducibility of conventional SERS tags.In our work,a novel SERS tag called gap-enhanced Raman tags(GERTs)has been fabricated through metal ion reduction.GERTs have strong Raman intensity and good reproducibility.We first explore the photostability of GERTs,and find some rules by comparing the photostability results of different GERTs.Then we successfully synthesize various GERTs with unique spectral profiles by embedding different reporters into the gap,and apply their multicolor encoding ability to physically unclonable anticounterfeiting labels.With the aid of non-negative least square method,ten-color encoded labels have been realized.In addition to the type of GERTs,the labels are also encoded through the other two dimensions-the pixel position and the Raman intensity,and consequently,an ultra-high encoding capacity up to 3.2?10¹⁵⁰⁵¹is acquired.Therefore,GERTs are demonstrated to be excellent nanoprobes with high sensitivity,specificity,safety,photostability and good multiplexing ability,thus showing great application prospects in biomedicine.