Highly Stable, Graphene-Wrapped, Petal-like, Gap-Enhanced Raman Tags

Gap-enhanced Raman tags (GERTs) were widely used in cell or biological tissue imaging due to their narrow spectral linewidth, weak photobleaching effect, and low biological matrix interference. Here, we reported a new kind of graphene-wrapped, petal-like, gap-enhanced Raman tags (GP-GERTs). The 4-Nitrobenzenethiol (4-NBT) Raman reporters were embedded in the petal-like nanogap, and graphene was wrapped on the surface of the petal-like, gap-enhanced Raman tags. Finite-difference time-domain (FDTD) simulations and Raman experimental studies jointly reveal the Raman enhancement mechanism of graphene. The SERS enhancement of GP-GERTs is jointly determined by the petal-like interstitial hotspots and electron transfer between graphene and 4-NBT molecules, and the total Raman enhancement factor (EF) can reach 10(10). Mesoporous silica was grown on the surface of GP-GERTs by tetraethyl orthosilicate hydrolysis to obtain Raman tags of MS-GP-GERTs. Raman tag stability experiments showed that: MS-GP-GERTs not only can maintain the signal stability in aqueous solutions of different pH values (from 3 to 12) and simulated the physiological environment (up to 72 h), but it can also stably enhance the signal of different Raman molecules. These highly stable, high-signal-intensity nanotags show great potential for SERS-based bioimaging and multicolor imaging.

Automated summary

In this study, a new type of graphene-wrapped, petal-like, gap-enhanced Raman tags (GP-GERTs) were reported for cell or biological tissue imaging. These nanotags showed narrow spectral linewidth, weak photobleaching effect, and low biological matrix interference. The Raman enhancement mechanism of graphene was revealed through simulations and experimental studies. The GP-GERTs achieved a high total Raman enhancement factor (EF) of 10(10) through petal-like interstitial hotspots and electron transfer between graphene and 4-NBT molecules. The modification of mesoporous silica on GERTs further enhanced their stability and signal intensity, making them suitable for SERS-based bioimaging and multicolor imaging.