SERS: Materials, applications, and the future

Surface-enhanced Raman spectroscopy (SERS) combines molecular fingerprint specificity with potential single-molecule sensitivity. Therefore, the SERS technique is an attractive tool for sensing molecules in trace amounts within the field of chemical and biochemical analytics. Since SERS is an ongoing topic, which can be illustrated by the increased annual number of publications within the last few years, this review reflects the progress and trends in SERS research in approximately the last three years. The main reason why the SERS technique has not been established as a routine analytic technique, despite its high specificity and sensitivity, is due to the low reproducibility of the SERS signal. Thus, this review is dominated by the discussion of the various concepts for generating powerful, reproducible, SERS-active surfaces. Furthermore, the limit of sensitivity in SERS is introduced in the context of single-molecule spectroscopy and the calculation of the 'real' enhancement factor. In order to shed more light onto the underlying molecular processes of SERS, the theoretical description of SERS spectra is also a growing research field and will be summarized here. In addition, the recording of SERS spectra is affected by a number of parameters, such as laser power, integration time, and analyte concentration. To benefit from synergies, SERS is combined with other methods, such as scanning probe microscopy and microfluidics, which illustrates the broad applications of this powerful technique.

Surface-enhanced Raman spectroscopy (SERS): progress and trends

This paper provides a brief overview of recent research activities concerning metal nanomaterials, including their synthesis, structure, surface plasmon absorption, surface enhanced Raman scattering (SERS), electron dynamics, emerging applications, and the historical context by which to view these subjects. We emphasize coinage metals, particularly silver and gold. Silver and gold nanostructures exhibit fascinating optical properties due to their strong optical absorption in the visible as a result of the collective oscillation of conduction band electrons, known as the surface plasmon. This is the origin of many interesting physical phenomena and related applications such as surface plasmon resonance (SPR) and SERS useful in chemical and biomedical detection and analysis. SERS offers high sensitivity and molecular specificity that are attractive for sensing and imaging applications. Electron dynamics in metal nanostructures have been studied using ultrafast laser techniques to gain fundamental insight in...

Novel Optical Properties and Emerging Applications of Metal Nanostructures

We combine nanofluidics and nanoplasmonics for surface-plasmon resonance (SPR) sensing using flow-through nanohole arrays. The role of surface plasmons on resonant transmission motivates the application of nanohole arrays as surface-based biosensors. Research to date, however, has focused on dead-ended holes, and therefore failed to harness the benefits of nanoconfined transport combined with SPR sensing. The flow-through format enables rapid transport of reactants to the active surface inside the nanoholes, with potential for significantly improved time of analysis and biomarker yield through nanohole sieving. We apply the flow-through method to monitor the formation of a monolayer and the immobilization of an ovarian cancer biomarker specific antibody on the sensing surface in real-time. The flow-through method resulted in a 6-fold improvement in response time as compared to the established flow-over method.

/pdf/nanoholes-as-nanochannels-flow-through-plasmonic-sensing-4gumrf25nv.pdf

Nanoholes as nanochannels: flow-through plasmonic sensing.

A novel, ultra low-cost surface enhanced Raman spectroscopy (SERS) substrate has been developed by modifying the surface chemistry of cellulose paper and patterning nanoparticle arrays, all with a consumer inkjet printer. Micro/nanofabrication of SERS substrates for on-chip chemical and biomolecular analysis has been under intense investigation. However, the high cost of producing these substrates and the limited shelf life severely limit their use, especially for routine laboratory analysis and for point-of-sample analysis in the field. Paper-based microfluidic biosensing systems have shown great potential as low-cost disposable analysis tools. In this work, this concept is extended to SERS-based detection. Using an inexpensive consumer inkjet printer, cellulose paper substrates are modified to be hydrophobic in the sensing regions. Synthesized silver nanoparticles are printed onto this hydrophobic paper substrate with microscale precision to form sensing arrays. The hydrophobic surface prevents the aque...

/pdf/inkjet-printed-surface-enhanced-raman-spectroscopy-array-on-4lb3pogkwg.pdf

Inkjet printed surface enhanced Raman spectroscopy array on cellulose paper.

Trace detection of the conformational transition of beta-amyloid peptide (Abeta) from a predominantly alpha-helical structure to beta-sheet could have a large impact in understanding and diagnosing Alzheimer's disease. We demonstrate how a novel nanofluidic biosensor using a controlled, reproducible surface enhanced Raman spectroscopy active site was developed to observe Abeta in different conformational states during the Abeta self-assembly process as well as to distinguish Abeta from confounder proteins commonly found in cerebral spinal fluid.

Nanofluidic biosensing for beta-amyloid detection using surface enhanced Raman spectroscopy.

Currently, no methods exist for the definitive diagnosis of AD premortem. β-amyloid, the primary component of the senile plaques found in patients with this disease, is believed to play a role in its neurotoxicity. We are developing a nanoshell substrate, functionalized with sialic acid residues to mimic neuron cell surfaces, for the surface-enhanced Raman detection of β-amyloid. It is our hope that this sensing mechanism will be able to detect the toxic form of β-amyloid, with structural and concentration information, to aid in the diagnosis of AD and provide insight into the relationship between β-amyloid and disease progression. We have been successfully able to functionalize the nanoshells with the sialic acid residues to allow for the specific binding of β-amyloid to the substrate. We have also shown that a surface-enhanced Raman spectroscopy response using nanoshells is stable and concentration-dependent with detection into the picomolar range.

Application of Surface-Enhanced Raman Spectroscopy for Detection of Beta Amyloid Using Nanoshells

An optofluidic device is reported in this paper that can highly improve the robustness of surface-enhanced Raman scattering (SERS) detection and provide fingerprint information of proteins with a concentration in the nanogram per liter range within minutes. Moreover, the conformational change of protein can also be obtained using this device. Fabricated by standard photolithography processes, the optofluidic device has a step microfluidic–nanofluidic structure, which provides robust SERS detection. The sensitivity of the device is investigated using insulin and albumin as target analytes at a concentration of 0.9 ng/L. The ability to detect conformational changes of proteins using this technology is also shown by probing these analytes before and after their denaturation.

Optofluidic device for ultra-sensitive detection of proteins using surface-enhanced Raman spectroscopy

A nano-fluidic trapping device and method of fabrication are disclosed. In one embodiment, a nano-fluidic trapping device for assembling a SERS-active cluster includes a substrate. The nano-fluidic trapping device further includes a SERS-active cluster compartment. The SERS-active cluster is formed in the SERS-active cluster compartment. In addition, the nano-fluidic trapping device includes a reservoir. The reservoir allows introduction of target molecules into the nano-fluidic trapping device. Moreover, the nano-fluidic trapping device includes a microchannel. The microchannel allows the target molecules to be introduced to the SERS-active cluster compartment from the reservoir. The nano-fluidic trapping device also includes a nanochannel. The SERS-active cluster compartment, the reservoir, the microchannel, and the nanochannel are disposed within the substrate.

Nano-fluidic Trapping Device for Surface-Enhanced Raman Spectroscopy

According to the World Health Organization, cardiovascular disease is the most common cause of death in the world. In
the US, over 115 million people visit the emergency department (ED), 5 million of which may have acute coronary
syndrome (ACS). Cardiac biomarkers can provide early identification and diagnosis of ACS, and can provide
information on the prognosis of the patient by assessing the risk of death. In addition, the biomarkers can serve as criteria
for admission, indicate possibility of re-infarction, or eliminate ACS as a diagnosis altogether. We propose a SERSbased
multi-marker approach towards a point-of-care diagnostic system for ACS. Using a nanofluidic device consisting
of a microchannel leading into a nanochannel, we formed SERS active sites by mechanically aggregating gold particles
(60 nm) at the entrance to the nanochannel (40nm×1μm). The induced capillary flow produces a high density of
aggregated nanoparticles at this precise region, creating areas with enhanced electromagnetic fields within the
aggregates, shifting the plasmon resonance to the near infrared region, in resonance with incident laser wavelength. With
this robust sensing platform, we were able to obtain qualitative information of brain natriuretic peptide (biomarker of
ventricular dysfunction or pulmonary stress), troponin I (biomarker of myocardial necrosis), and C-reactive protein
(biomarker of inflammation potentially caused by atherosclerosis).

Detection of cardiac biomarkers exploiting surface enhanced Raman scattering (SERS) using a nanofluidic channel based biosensor towards coronary point-of-care diagnostics

Melodie Benford

Papers

Nanofluidic biosensing for beta-amyloid detection using surface enhanced Raman spectroscopy.

Application of Surface-Enhanced Raman Spectroscopy for Detection of Beta Amyloid Using Nanoshells

Optofluidic device for ultra-sensitive detection of proteins using surface-enhanced Raman spectroscopy

Nano-fluidic Trapping Device for Surface-Enhanced Raman Spectroscopy

Detection of cardiac biomarkers exploiting surface enhanced Raman scattering (SERS) using a nanofluidic channel based biosensor towards coronary point-of-care diagnostics