DNA-Mediated Wirelike Clusters of Silver Nanoparticles: An Ultrasensitive SERS Substrate

Abstract

Stable metal nanoclusters (NCs) with uniform interior nanogaps reproducibly offer a highly robust substrate for surface-enhanced Raman scattering (SERS) because of the presence of abundant hot spots on their surface. The synthesis of such an SERS substrate by a simple route is a challenging task. Here, we have synthesized a highly stable wirelike cluster of silver nanoparticles (Ag-NPs) with an interparticle gap of ~1.7 ± 0.2 nm using deoxyribonucleic acid (DNA) as the template by exploiting an easy and inexpensive chemical route. The red shift in the surface plasmon resonance (SPR) band of Ag-NCs compared to SPR of a single Ag-NP confirms the strong interplasmonic interaction. Methylene Blue (MB) is used as a representative Raman probe to study the SERS effect of the NCs. The SERS measurements reveal that uniform, reproducible, and strong Raman signals were observed up to the single-molecule level. The intensity of the Raman signal is not highly dependent on the polarization of the excitation laser. The DNA-based Ag-NCs as a substrate show better isotropic behavior for their SERS intensity compared to the dimer, as confirmed from both the experimental and theoretical simulation results. We believe that in the future the DNA-based Ag-NCs might be useful as a potential SERS substrate for ultrasensitive trace detection, biomolecular assays, NP-based photothermal therapeutics, and a few other technologically important fields.

Enhanced catalytic and SERS activities of CTAB stabilized interconnected osmium nanoclusters

“…5 Recently, Kundu et al studied that aggregated Ag NCs can generate better SERS as compared to a monomer or a dimer and the results were compared to theoretical calculations. 57 Most of the previous studies on SERS however, mainly focus on a few noble metal NPs like Au, Ag, Cu, Pd, Pt, etc., and a vast study is centered on Au and Ag only. Very recently, Os nanostructures were also tested in SERS studies.…”

“…It was reported previously that when noble metal NPs aggregate, they provide a greater number of surface active 'hot spots' at the junction of the aggregates. [54][55][56][57] The plasmonic coupling effect at those junctions or 'hot spots' creates a very high intensity local electromagnetic field and consequently leads to strong Raman cross-section enhancement. So we also believe that the self-assembled aggregated structure of Os NPs was responsible for the generation of a highly stable and reproducible SERS signal.…”

In situ regulation nanoarchitecture of Au nanoparticles/reduced graphene oxide colloid for sensitive and selective SERS detection of lead ions

“…Surface-enhanced Raman scattering (SERS), based on the magnitude of the electromagnetic field around a roughened gold or silver surface [10], is a promising technique for chemical sensing [11,12], bio-sensing [13,14] and bioimaging [15,16] due to its high sensitivity and noninvasiveness [17]. To date, there are some researches for the detection of Pb 2+ using SERS probes [18][19][20][21] [20].…”

Nanosilver-based surface-enhanced Raman spectroscopic determination of DNA methyltransferase activity through real-time hybridization chain reaction

“…Accordingly, the unmethylated S1/S2 hybrids would be digested by HpaII when no enough M. SssI was available, and released from the reaction solution in the present of external magnetic fields. Streptavidin-coated AgNPs (AgNPs-SA) that can recognize the biotin moiety of dsDNA was then applied as the enhancement substrate, followed by the supplementary of methylene blue (MB) (Scheme 1A), which is an aromatic cationic dye showing optically and representative Raman active properties that usually binds to DNA via intercalation (Majumdar et al 2013). To avoid the potential false positive response by the DNA residues that are tethered to the MMPs, base sequences of S1 and S2 were designed thoughtful, and the melting temperature of hybridized double strands before and after HpaII treatment is 51.1°C and 25.1°C, respectively, according to the results with the utilization of IDT Oligo Analyzer.…”