Self-Assembled Nanocube-Based Plasmene Nanosheets as Soft Surface-Enhanced Raman Scattering Substrates toward Direct Quantitative Drug Identification on Surfaces

Abstract

We report on self-assembled nanocube-based plasmene nanosheets as new surface-enhanced Raman scattering (SERS) substrates toward direct identification of a trace amount of drugs sitting on topologically complex real-world surfaces. The uniform nanocube arrays (superlattices) led to low spatial SERS signal variances (∼2%). Unlike conventional SERS substrates which are based on rigid nanostructured metals, our plasmene nanosheets are mechanically soft and optically semitransparent, enabling conformal attachment to real-world solid surfaces such as banknotes for direct SERS identification of drugs. Our plasmene nanosheets were able to detect benzocaine overdose down to a parts-per-billion (ppb) level with an excellent linear relationship (R(2) > 0.99) between characteristic peak intensity and concentration. On banknote surfaces, a detection limit of ∼0.9 × 10(-6) g/cm(2) benzocaine could be achieved. Furthermore, a few other drugs could also be identified, even in their binary mixtures with our plasmene nanosheets. Our experimental results clearly show that our plasmene sheets represent a new class of unique SERS substrates, potentially serving as a versatile platform for real-world forensic drug identification.

Dual‐Coded Plasmene Nanosheets as Next‐Generation Anticounterfeit Security Labels

“…[13][14][15] Polystyrene (PS)-capped gold nanoparticles are prepared by centrifuging the nanoparticles and redispersed in a PS-THF solution (4 mg mL −1 ). After overnight ligand exchange process, the PS-capped particles are washed thrice with chloroform and concentrated into 0.1 mL.…”

“…[13][14][15] Despite the exciting advances achieved for designing of such plasmonic nanosheets, successful self-assembly mechanisms are generally limited to simple nanoparticle shapes such as nanospheres, nanorods, and nanocubes. [ 13,14,16,17 ] In comparison, complex anisotropic shapes such as nanostars may exhibit unique novel properties.…”

“…[13][14][15] High-quality and monodispersed RD nanoparticles with a nominal edge length of ≈26.3 ± 2.1 nm were fi rst functionalized with thiolated-polystyrene, followed by an evaporation induced self-assembly process at air-water interface into plasmene nanosheets. TEM characterization revealed the assembled nanosheet to be monolayered, with the RDs lying fl at into an elongated hexagon-like shape ( Figure 1 a) and exhibiting a 2D hexagonally close-packed (hcp) ordering (Figure 1 b).…”

“…The stamping of the treated plasmene nanosheets onto silicon wafers or banknote surfaces were done with a PDMS-mediated stamping method that has been reported previously. [ 14,15 ] SERS spectra were recorded by using a Renishaw RM 2000 Confocal micro-Raman System equipped with four different excitation lasers at a laser spot size of 1 µm: 514, 633, 782, and 830 nm (laser power of 0.1, 0.1, 0.03, and 0.24 mW, respectively). All Raman spectra were recorded by fi ne-focusing a 50× microscope objective under data acquisition time of 10 s, and corrected by cubic spline baseline subtraction.…”

Self-Assembled Plasmonic Pyramids from Anisotropic Nanoparticles for High-Efficient SERS

“…This SERS effect originates from the confinement of light in interstitial spaces between noble metal nanoparticles, thus creating hot spots with excited and enhanced local electromagnetic fields [1,2]. As such, SERS technology enables detection of trace amount of molecules even down to a single-molecule level, leading to a myriad of technical applications in the fields of biology, medicine, forensics, nanophotonics and optical sensors [2][3][4][5][6][7].…”