Ultralarge Area Sub-10 nm Plasmonic Nanogap Array by Block Copolymer Self-Assembly for Reliable High-Sensitivity SERS

Abstract

Effective surface enhancement of Raman scattering (SERS) requires strong near-field enhancement as well as effective light collection of plasmonic structures. To this end, plasmonic nanoparticle (NP) arrays with narrow gaps or sharp tips have been suggested as desirable structures. We present a highly dense and uniform Au nanoscale gap array enabled by the customized design of NP shape and arrangement employing block copolymer self-assembly. Block copolymer selfassembly in thin films offers uniform hexagonally packed nanopost template arrays over the entire surface of a 2 in. wafer. Conventional evaporative metal deposition over the nanotemplate surface allows precise geometric control and positional arrangement of metal NPs, constituting tunable, strong plasmonic near-field enhancement particularly at the "hot spots" near interparticular nanoscale gaps. Underlying field distribution has been investigated by a finite-difference timedomain simulation. In the detection of thiophenol, our Au nanogap array shows a remarkable enhancement of Raman intensity greater than ∼10 4 , a standard deviation as small as 12.3% compared to that of the planar Au thin film. In addition, adenine biomolecules can be detected with a detection limit as low as 100 nM. Our approach proposes highly sensitive and reliable SERS on the basis of a scalable, low-cost bottom-up strategy.

Reaction Kinetics‐Mediated Control over Silver Nanogap Shells as Surface‐Enhanced Raman Scattering Nanoprobes for Detection of Alzheimer's Disease Biomarkers

“…This results in a huge enhancement in Raman scattering of up to 10 15 orders of magnitude . Several studies have been reported for the creation of “hot spots” based on nanosized gap junctions (called nanogaps) between metal nanoparticles . Most of the nanogap approaches have relied on microarray fabrication techniques involving multiple‐step lithographic processes, which are time‐consuming and complicated .…”

“…Several studies have been reported for the creation of “hot spots” based on nanosized gap junctions (called nanogaps) between metal nanoparticles . Most of the nanogap approaches have relied on microarray fabrication techniques involving multiple‐step lithographic processes, which are time‐consuming and complicated . In addition, these lithographic approaches would not be suitable for designing nanoparticle‐based SERS probes emitting SERS signals, which can be used as an alternative to conventional fluorescent probes for the detection of target molecules.…”

Directed Self-Assembly of Block Copolymers for the Fabrication of Functional Devices

“…Many of these fields are low demanding regarding BCP defectivity levels and, in many cases, self-assembly does not require to be directed, but rather take place on a free surface without guidance. Applications include, but are not restricted to, hard-disk drive and magnetic storage devices [ 126 , 132 , 133 , 134 , 135 ], nanophotonics and plasmonics materials [ 136 , 137 , 138 ], or chemical sensors [ 139 ]. Most often, BCPs are still used as templates for patterning, as in the case of graphene structuring [ 140 , 141 , 142 , 143 ], the fabrication of nanoporous membranes [ 144 , 145 , 146 , 147 , 148 ] or energy storage, photovoltaics and batteries [ 149 , 150 , 151 , 152 ].…”

Hyperbolic Metamaterials via Hierarchical Block Copolymer Nanostructures

“…Among the various nanopatterning methods, self-assembly (SA) of block copolymers (BCPs) has emerged as a cost-effective and scalable bottom-up approach, with a high throughput and able to provide highly dense and periodic patterns at the nanometric scale [16][17][18] . The extensive research over the last years has proved self-assembly of BCPs as a valid alternative to conventional nanopatterning techniques for many different applications including optics 19,20 , biosensing 21 , lithography 22,23 , and electronics 24,25 .…”