Macroscopic Ag nanostructure array patterns with high-density hotspots for reliable and ultra-sensitive SERS substrates

Peptidoglycan-Binding Protein Metamaterials Mediated Enhanced and Selective Capturing of Gram-Positive Bacteria and Their Specific, Ultra-Sensitive, and Reproducible Detection via Surface-Enhanced Raman Scattering

“…To construct the substrate for selective and enhanced capturing of Gram-positive bacteria, an NHP with 150 nm diameter and 300 nm pitch was synthesized via thermal nanoimprint lithography. Then, the residual imprint resist was removed by sequential O 2 plasma and short wet-etching processes for surface modification. − For comparison, a bare gold wafer without NHP was also prepared (Figure S1).…”

“…The spacing between superficial PGBPs on fs-PBP and PBPMs was about 80 and 300 nm, respectively, consistent with the pitch length between the hole pattern. In addition, the height and distances were much smaller than the diameter of a bacterium (micrometer scale), thus ensuring that the captured bacteria can lie flat on the chip surface. , In contrast with bare gold wafer, NHP could concentrate 3-mercaptopropionic acid molecules inside the hole pattern because the outside was blocked by imprint resist as a template. , This leads to concentrated PGBP for the generation of protein-based metamaterials with greater height and roughness compared to fs-PBP. In addition, XPS and X-ray diffraction analysis of the substrates revealed the conserved surface elements and crystallinity of the gold surface regardless of Ni-NTA modification or protein attachment (Figures S3 and S4).…”

“…Herein, we report an efficient and Gram-positive bacteria selective capturing system aided by peptidoglycan-binding protein (PGBP)-based metamaterials (PBPMs) rather than flat and spread peptidoglycan-binding protein (fs-PBP). PGBP was selected to construct the protein metamaterials because it can specifically recognize the peptidoglycan layer, which is highly abundant in Gram-positive bacteria but insufficient in Gram-negative bacteria. − To fabricate PBPMs, a nanohole pattern (NHP) was first prepared on a gold-coated wafer via nanoimprint lithography, and residual resist was etched by a plasma and wet-etching process. − As a control, fs-PBP was fabricated on a bare gold wafer. Then, the surfaces of NHP and bare gold wafers were modified with Ni-NTA to immobilize PGBP through chelation between six histidines (6×-His) in PGBP and Ni-NTA. , In particular, Ni-NTA was concentrated inside the NHP, whereas the outside was blocked by the nanoimprint resist. , As a result, nanosized PGBP metamaterials were produced, whereas PGBP-coated bare gold wafers exhibited flat and spread surface properties.…”

Facial Fabrication of Large-Scale SERS-Active Substrate Based on Self-Assembled Monolayer of Silver Nanoparticles on CTAB-Modified Silicon for Analytical Applications

“…Based on these findings, in the past decade, there has been a lot of research focused on the fabrication of SERS "hot spots" that have an extremely high detection sensitivity. SERS "hot spots" with single-molecule detection sensitivity have also been reported [12][13][14][15][16].…”

Label-Free Protein Analysis by Pyro-Electrohydrodynamic Jet Printing of Gold Nanoparticles

“…The confinement of the plasmonic nanostructure within an area of precisely controlled size and shape provides the additional advantage of increasing the nanoparticle density, which enhances the SERS sensitivity. The micro-confinement of plasmonic nanoobjects has been approached in several ways, among which are electrospinning ( Zhang et al, 2012 ), self-assembly ( García-Lojo et al, 2019 ; Lin et al, 2019 ), and electro-deposition combined with lithography ( Lee et al, 2019 ).…”