Chiral Assembly of Gold–Silver Core–Shell Plasmonic Nanorods on DNA Origami with Strong Optical Activity

Abstract

The spatial organization of metal nanoparticles has become an important tool for manipulating light in nanophotonic applications. Silver nanoparticles, particularly silver nanorods have excellent plasmonic properties, but are prone to oxidation and are therefore inherently unstable in aqueous solutions and salt containing buffers. Consequently, gold nanoparticles have often been favored, despite their inferior optical performance. Bimetallic, i.e. gold-silver core-shell nanoparticles can resolve this issue. We present a method for synthesizing highly stable gold/silver core-shell NRs that are instantaneously functionalized with DNA, enabling chiral self-assembly on DNA origami. The silver shell gives rise to an enhancement of plasmonic properties, reflected here in strongly increased circular dichroism, as compared to pristine gold nanorods. Gold-silver nanorods are ideal candidates for plasmonic sensing with increased sensitivity as needed in pathogen RNA or antibody testing, for non-linear optics and light-funneling applications in surface enhanced Raman spectroscopy. Furthermore, the control of interparticle orientation enables the study of plasmonic phenomena, in particular synergistic effects arising from plasmonic coupling of such bimetallic systems.

Programmable and Site‐Specific Patterning on DNA Origami Templates with Heterogeneous Condensation of Silver and Silica

“…biosensing. [12][13][14][15][16][17][18][19][20][21][22][23][24][25] While these researches have clearly shown the power of DNA nanostructures as breadboards for bottomup nanofabrication, there still exist multiple roadblocks before reaching the maturity of this approach.…”

Recent developments in the chiroptical properties of chiral plasmonic gold nanostructures: bioanalytical applications

“…The Ag shell thickness can be used as a parameter for tuning the LSPR. The DNA origami platform holds great promise for synthesizing bimetallic nanoparticles [35]. The chiral core-satellite silver nanorod (Ag NR)-gold nanoparticle nanostructure has been fabricated by using L-cysteine and D-cysteine as bridging molecules.…”

Broadband Enhanced Chirality with Tunable Response in Hybrid Plasmonic Helical Metamaterials

“…Recently, several efforts have been devoted to boost the weak chiral light‐matter interactions in different frequency ranges by using artificially engineered structures, such as optical metamaterials, molecular self‐assembled chiral plasmonic nanoparticles, and thin films based on enantiomer molecules. [ 7–30 ] However, all of these approaches were limited to relatively low and narrowband experimentally obtained g‐ factors, with the maximum values obtained mainly in infrared (IR) frequencies and not the visible or ultraviolet (UV) spectrum. In addition, the majority of the highest reported narrowband optical activity values are possible by using chiral molecules or other structures embedded in aqueous solutions, [ 8 ] which make them incompatible to on‐chip nanophotonic‐based circuit applications.…”

“…Moreover, most of the chiral metamaterial structures are built based on top‐down, complicated, and costly fabrication methods, prone to fabrication imperfections, limiting their flexibility, reproducibility, and, as a result, their practical applications. Finally, several chiral structures presented in the literature are based on single chiral resonator elements, [ 9–16 ] leading to weak output optical signals, mainly generated from extinction coefficient or luminescent measurements; and their chiral response is not broadband and cannot be tuned along different frequencies, spanning the UV, visible, and IR range. Hence, planar ultrathin nanophotonic structures to achieve extremely strong, broadband, and tunable chiral light‐matter interactions at visible and UV frequencies still remain elusive.…”