Dielectrics represent a new frontier for surface-enhanced Raman scattering. They can serve as either a complement or an alternative to conventional, metal-based SERS, offering key advantages in terms of low invasiveness, reproducibility, versatility, and recyclability. In comparison to metals, dielectric systems and, in particular, semiconductors are characterized by a much greater variety of parameters and properties that can be tailored to achieve enhanced Raman scattering or related effects. Light-trapping and subwavelength-focusing capabilities, morphology-dependent resonances, control of band gap and stoichiometry, size-dependent plasmons and excitons, and charge transfer from semiconductors to molecules and vice versa are a few examples of the manifold opportunities associated with the use of semiconductors as SERS-active materials. This review provides a broad analysis of SERS with dielectrics, encompassing different optical phenomena at the basis of the Raman scattering enhancement and introducing...

Enhanced Raman Scattering with Dielectrics.

Silicon nanomaterials are an important class of nanomaterials with great potential for technologies including energy, catalysis, and biotechnology, because of their many unique properties, including biocompatibility, abundance, and unique electronic, optical, and mechanical properties, among others. Silicon nanomaterials are known to have little or no toxicity due to favorable biocompatibility of silicon, which is an important precondition for biological and biomedical applications. In addition, huge surface-to-volume ratios of silicon nanomaterials are responsible for their unique optical, mechanical, or electronic properties, which offer exciting opportunities for design of high-performance silicon-based functional nanoprobes, nanosensors, and nanoagents for biological analysis and detection and disease treatment. Moreover, silicon is the second most abundant element (after oxygen) on earth, providing plentiful and inexpensive resources for large-scale and low-cost preparation of silicon nanomaterials f...

Silicon Nanomaterials Platform for Bioimaging, Biosensing, and Cancer Therapy

Herein, a reliable surface-enhanced Raman scattering (SERS)-active substrate has been prepared by synthesizing gold nanoparticles (AuNPs)-decorated MoS2 nanocomposite. The AuNPs grew in situ on the surface of MoS2 nanosheet to form efficient SERS hot spots by a spontaneous redox reaction with tetrachloroauric acid (HAuCl4) without any reducing agent. The morphologies of MoS2 and AuNPs-decorated MoS2 nanosheet were characterized by TEM, HRTEM, and AFM. The formation of hot spots greatly depended on the ratio of MoS2 and HAuCl4. When the concentration of HAuCl4 was 2.4 mM, the as-prepared AuNPs@MoS2-3 nanocomposite exhibited a high-quality SERS activity toward probe molecule due to the generated hot spots. The spot-to-spot SERS signals showed that the relative standard deviation (RSD) in the intensity of the main Raman vibration modes (1362, 1511, and 1652 cm–1) of Rhodamine 6G were about 20%, which displayed good uniformity and reproducibility. The AuNPs@MoS2-based substrate was reliable, sensitive, and re...

Creating SERS Hot Spots on MoS2 Nanosheets with in Situ Grown Gold Nanoparticles

Surface-enhanced Raman scattering (SERS) systems utilizing the interparticle nanogaps as hot spots have demonstrated ultrasensitive single-molecule detection with excellent selectivity yet the electric fields are too confined in the small nanogaps to enable reproducible biomolecule detections Here, guided by finite-difference-time-domain simulation, we report hexagonal-packed silver-coated silicon nanowire (Ag/SiNW) arrays as a nanogap-free SERS system with wide-range electric fields and controlled interwire separation Significantly, the system achieves a SERS detection of long double-strand DNA of 25–50 nm in length with a relative standard deviation (RSD) of 14% for measurements of above 4000 spots over an area of 200 × 200 μm2 The high reproducibility in the SERS detection is attributed to (1) the large interwire spacing of 150 nm that allows access and excitation of large biomolecules; and (2) 600 nm wide-range electric field generated by propagating surface plasmons along the surface of continuous

Ordered Ag/Si Nanowires Array: Wide-Range Surface-Enhanced Raman Spectroscopy for Reproducible Biomolecule Detection

This article provides an overview of recent developments and applications of surface-enhanced Raman scattering (SERS) nanosensors and nanoreporters in our laboratory for use in biochemical monitoring, medical diagnostics, and therapy. The design and fabrication of different types of plasmonics-active nanostructures are discussed. The SERS nanosensors can be used in various applications including pH sensing, protein detection, and gene diagnostics. For DNA detection the 'Molecular Sentinel' nanoprobe can be used as a homogenous bioassay in solution or on a chip platform. Gold nanostars provide an excellent multi-modality theranostic platform, combining Raman and SERS with two-photon luminescence (TPL) imaging as well as photodynamic therapy (PDT), and photothermal therapy (PTT). Plasmonics-enhanced and optically modulated delivery of nanostars into brain tumor in live animals was demonstrated; photothermal treatment of tumor vasculature may induce inflammasome activation, thus increasing the permeability of the blood brain-tumor barrier. The imaging method using TPL of gold nanostars provides an unprecedented spatial selectivity for enhanced targeted nanostar delivery to cortical tumor tissue. A quintuple-modality nanoreporter based on gold nanostars for SERS, TPL, magnetic resonance imaging (MRI), computed tomography (CT), and PTT has recently been developed. The possibility of combining spectral selectivity and high sensitivity of the SERS process with the inherent molecular specificity of bioreceptor-based nanoprobes provides a unique multiplex and selective diagnostic modality. Several examples of optical detection using SERS in combination with other detection and treatment modalities are discussed to illustrate the usefulness and potential of SERS nanosensors and nanoreporters for medical applications.

SERS nanosensors and nanoreporters: golden opportunities in biomedical applications.

Silicon-based active and reproducible surface-enhanced Raman scattering (SERS) substrate, i.e., silver nanoparticles decorated-silicon wafers (AgNPs@Si), is employed for constructing high-performance sensors. Significantly, the AgNPs@Si, facilely prepared via in situ AgNPs growth on silicon wafers, features excellent SERS reproducibility and high enhancement factor. Our experiment further demonstrates such resultant silicon-based SERS substrate is efficacious for multiplex, sensitive, and specific DNA detection. In particular, single-base mismatched DNA with low concentrations is readily discriminated by using the AgNPs@Si. Moreover, the silicon-based sensor exhibits adequate multiplexing capacity, enabling unambiguous identification of the dual-target DNA detection.

Z. Y. Jiang

Papers

Silicon-based reproducible and active surface-enhanced Raman scattering substrates for sensitive, specific, and multiplex DNA detection