Multicolor Gold–Silver Nano-Mushrooms as Ready-to-Use SERS Probes for Ultrasensitive and Multiplex DNA/miRNA Detection

Poly-cytosine-mediated nanotags for SERS detection of Hg2

Highly sensitive and selective detection of heavy metal ions, such as Hg²⁺, is of great importance because the contamination of heavy metal ions has been a serious threat to human health. Herein, we have developed poly-cytosine (polyC)-mediated surface-enhanced Raman scattering (SERS) nanotags as a sensor system for rapid, selective, and sensitive detection of Hg²⁺ based on thymidine-Hg²⁺-thymidine (T-Hg²⁺-T) coordination and polyC-mediated Raman activity. The SERS nanotags exploit the mismatched T-T base pairs to capture Hg²⁺ form T-Hg²⁺-T bridges, which induce the aggregation of nanotags giving rise to the drastic amplification in the SERS signals. Moreover, this polyC not only provides the anchoring function to induce the formation of intrinsic silver-cytosine coordination but also engineers the Raman-activity of SERS nanotags by mediating its length. As a result, the polyC-mediated SERS nanotags show an excellent response for Hg²⁺ in the concentration range from 0.1 to 1000 nM and good selectivity over other metal ions. Given its simple principle and easy operation, the polyC-mediated SERS nanotags, therefore, could serve as a promising sensor for practical use.

Seed-mediated synthesis and SERS performance of graphene oxide-wrapped Ag nanomushroom

A facile seed-mediated method was developed to modify core-shell Ag nanosphere@PSPAA with another Ag layer for achieving an enhancement of their surface-enhanced Raman scattering (SERS) activity. Interestingly, an Ag bridge in the polymer shell connected the inner and outer Ag layers, resulting in a mushroom-like nanostructure. The outer Ag grew around the polymer shell to form the cap of the nanomushrooms (NMs) with the extension of the reaction time. The epitaxial growth mechanism of this novel nanostructure was investigated by tuning the type of seed from nanosphere to nanocube and nanorod. With the growth of the outer Ag cap, the SERS intensity of these Ag NMs increased significantly together with the red-shifting and broadening of their typical localized surface plasmon resonance band. Such a phenomenon can be attributed to the formation of SERS hotspots between the inner and outer Ag layers. The Ag NMs were then wrapped with a graphene oxide (GO) shell via static interactions. The GO-wrapped Ag NMs exhibited a further better SERS performance in terms of sensitivity, homogeneity and stability compared with non-wrapped ones, indicating that the heterostructure could be potentially useful for SERS-based immunoassay.

Droplet-Confined Electroless Deposition of Silver Nanoparticles on Ordered Superhydrophobic Structures for High Uniform SERS Measurements

Surface-enhanced Raman scattering spectroscopy (SERS) is a nondestructive testing technique. To increase reproducibility of the SERS measurement is the key issue for improving the performance of SERS. In this article, we demonstrate an efficient method to improve the reproducibility, using confined silver nanoparticles (AgNPs) as a substrate. The AgNPs are formed uniformly on the tops of the prepared nanopillars by droplet-confined electroless deposition on the hydrophobic Si nanopillar arrays. The AgNPs present an excellent reproducibility in Raman measurement; the relative standard deviation is down to 3.40%. There exists a great linear correlation between the concentration of Rhodamine 6G (R6G) and the Raman intensity in the log-log plot; R² is 0.998, indicating that this SERS substrate can be applied for the quantitative SERS analysis. Meanwhile, the minimum detection concentration is down to 10^-11 M on the hydrophobic substrate, with R6G as a probe molecule.

SERS detection of microRNA biomarkers for cancer diagnosis using gold-coated paramagnetic nanoparticles to capture SERS-active gold nanoparticles

A highly sensitive magnetic-capture SERS assay for detecting cancer-related microRNAs was developed by enhancing the formation of SERS “hot spots”.