Plasmonic Gold Nanohole Array for Surface-Enhanced Raman Scattering Detection of DNA Methylation.

Surface-enhanced Raman spectroscopy (SERS), which utilizes nanogaps between noble-metal nanostructures as hot spots to yield ultrasensitive SERS signals, is an outstanding label-free and straightforward tool for DNA methylation analysis. Herein, a plasmonic gold nanohole array (PGNA) with well-controlled hot spots and an open surface was designed as a SERS substrate for DNA methylation detection. A finite-difference time-domain (FDTD) simulation was first employed to investigate the electric field distributions of the PGNA as a function of the geometric parameters.

Sensitive Bacterial Detection via Dielectrophoretic-Enhanced Mass Transport Using Surface-Plasmon-Resonance Biosensors.

The performance of surface plasmon resonance (SPR)-based bacterial biosensors is often compromised as a result of diffusion-limited mass transport of bacteria to the sensing surface. In this work, dually functional interdigitated electrodes (IDEs) were developed to sustain SPR and increase bacterial mass transport through external application of dielectrophoresis (DEP). IDEs were defined into 50 nm Au films with fixed electrode gaps ( E = 5 μm) and varied electrode widths ( E = 10, 20, and 100 μm),  referred to as interdigitated SPR (iSPR) chips.

Surface-Enhanced Raman Scattering for Rapid Detection and Characterization of Antibiotic-Resistant Bacteria.

As the prevalence of antibiotic-resistant bacteria continues to rise, biosensing technologies are needed to enable rapid diagnosis of bacterial infections. Furthermore, understanding the unique biochemistry of resistance mechanisms can facilitate the development of next generation therapeutics. Surface-enhanced Raman scattering (SERS) offers a potential solution to real-time diagnostic technologies, as well as a route to fundamental, mechanistic studies.

Long-range surface plasmon resonance and surface-enhanced Raman scattering on X-shaped gold plasmonic nanohole arrays.

A multilayered architecture including a thin Au film supporting an X-shaped nanohole array and a thick continuous Au film separated by a Cytop dielectric layer is reported in this work. Long-range surface plasmon resonance (LR-SPR) was generated at the top Au/water interface, which also resulted in a long-range surface-enhanced Raman scattering (LR-SERS) effect. LR-SPR originates from the coupling of surface plasmons (SPs) propagating along the opposite sides of the thin Au film embedded in a symmetric refractive index environment with Cytop (n = 1.

Multi-functional, thiophenol-based surface chemistry for surface-enhanced Raman spectroscopy.

Surface-enhanced Raman spectroscopy (SERS) has been recognized as one of the most sensitive sensing technologies and has been used for a variety of chemical, biological and medical applications. Compared to traditional direct SERS detection using a bare metal SERS-active substrate, surface chemistries and surface modifications on SERS-active substrates are becoming more and more important to achieve the detection of target analytes with a small surface affinity or weak Raman activity. As one special class of surface chemistries and modifications for SERS-active substrates, the thiophenol-based molecules offer new functions, increased sensitivity, and improved specificity to SERS-based sensing.

Hierarchical zwitterionic modification of a SERS substrate enables real-time drug monitoring in blood plasma.

Surface-enhanced Raman spectroscopy (SERS) is an ultrasensitive analytical technique with molecular specificity, making it an ideal candidate for therapeutic drug monitoring (TDM). However, in critical diagnostic media including blood, nonspecific protein adsorption coupled with weak surface affinities and small Raman activities of many analytes hinder the TDM application of SERS. Here we report a hierarchical surface modification strategy, first by coating a gold surface with a self-assembled monolayer (SAM) designed to attract or probe for analytes and then by grafting a non-fouling zwitterionic polymer brush layer to effectively repel protein fouling.

Stealth surface modification of surface-enhanced Raman scattering substrates for sensitive and accurate detection in protein solutions.

Reliable surface-enhanced Raman scattering (SERS) based biosensing in complex media is impeded by nonspecific protein adsorptions. Because of the near-field effect of SERS, it is challenging to modify SERS-active substrates using conventional nonfouling materials without introducing interference from their SERS signals. Herein, we report a stealth surface modification strategy for sensitive, specific and accurate detection of fructose in protein solutions using SERS by forming a mixed self-assembled monolayer (SAM).

Optofluidic microsystem with quasi-3 dimensional gold plasmonic nanostructure arrays for online sensitive and reproducible SERS detection.

Practical applications of chemical and biological detections through surface-enhanced Raman scattering (SERS) require high reproducibility, sensitivity, and efficiency, along with low-cost, straightforward fabrication. In this work, we integrated a poly-(dimethylsiloxane) (PDMS) chip with quasi-3D gold plasmonic nanostructure arrays (Q3D-PNAs), which serve as SERS-active substrates, into an optofluidic microsystem for online sensitive and reproducible SERS detections. The Q3D-PNA PDMS chip was fabricated through soft lithography to ensure both precision and low-cost fabrication.