Bending-Insensitive Flexible SERS Sensor for Stable and Sensitive Detection on Curved Surfaces

Surface-enhanced Raman scattering (SERS) based flexible sensing technology has been considered an essential candidate for future diagnostics in diverse fields. To obtain a reliable signal from the flexible SERS sensor, signal reproducibility even when the substrates are bent is highly desirable because there are various curvatures in the practical applications. However, this remains challenging because the “hot-spots” were created between the individual nanostructures on the surface of the previous flexible SERS sensor. The distance between each nanostructure varied through the bending of the sensor, leading to an adverse effect on the unform intensity of the Raman signal. Herein, a bending-insensitive flexible SERS substrate is reported for reliable and sensitive sensing on curved surfaces. It is based on silver nanodendrites on the surface of graphene-modified PI film via electrodeposition. Numerous hot spots are created between the trunk-branch and branch-branch junctions inside individual silver dendrites. The inherent hot-spots of silver nanodendrites exhibit a uniform and extremely enhanced Raman signal under the bending of the substrate, because the morphology of silver nanodendrites is insensitive to diverse degrees of bending. Thus, the flexible SERS sensor can detect 10⁻¹² m (in buffer solution) and 10⁻⁸ m (serum-containing condition) of 6-thioguanine on arbitrary curved surfaces.