Silicon Microchannel-Driven Raman Scattering Enhancement to Improve Gold Nanorod Functions as a SERS Substrate toward Single-Molecule Detection

Abstract

The investigation of enhanced Raman signal effects and the preparation of high-quality, reliable surface-enhanced Raman scattering (SERS) substrates is still a hot topic in the SERS field. Herein, we report an effect based on the shape-induced enhanced Raman scattering (SIERS) to improve the action of gold nanorods (AuNRs) as a SERS substrate. Scattered electric field simulations reveal that bare V-shaped Si substrates exhibit spatially distributed interference patterns from the incident radiation used in the Raman experiment, resulting in constructive interference for an enhanced Raman signal. Experimental data show a 4.29 increase in Raman signal intensity for bare V-shaped Si microchannels when compared with flat Si substrates. The combination of V-shaped microchannels and uniform aggregates of AuNRs is the key feature to achieve detections in ultra-low concentrations, enabling reproducible SERS substrates having high performance and sensitivity. Besides SIERS effects, the geometric design of V-shaped microchannels also enables a “trap” to the molecule confinement and builds up an excellent electromagnetic field distribution by AuNR aggregates. The statistical projection of SERS spectra combined with the SIERS effect displayed a silhouette coefficient of 0.83, indicating attomolar (10 –18 mol L –1 ) detection with the V-shaped Si microchannel.

Hybrid Surface-Enhanced Raman Scattering Substrates for the Trace Detection of Ammonium Nitrate, Thiram, and Nile Blue

“… 6 , 11 − 14 Recently, a few novel strategies have been demonstrated for patterned SERS substrates coated with NPs of various shapes for the detection of diverse analytes. 15 − 18 The patterned substrates along with NPs with diverse shapes have demonstrated a significant improvement in the detection sensitivity due to the embedded NPs, along with the patterned areas acting as hotspot regions and increasing the SPR strength, resulting in strong electric fields at the confined regions. 18 − 20 Abundant fabrication procedures have been established for fabricating patterned substrates on countless materials, among which short/ultrashort laser ablation is a simple, fast, and efficient fabrication tool for the generation of distinct surface structures on various substrates.…”

“… 15 − 18 The patterned substrates along with NPs with diverse shapes have demonstrated a significant improvement in the detection sensitivity due to the embedded NPs, along with the patterned areas acting as hotspot regions and increasing the SPR strength, resulting in strong electric fields at the confined regions. 18 − 20 Abundant fabrication procedures have been established for fabricating patterned substrates on countless materials, among which short/ultrashort laser ablation is a simple, fast, and efficient fabrication tool for the generation of distinct surface structures on various substrates. 21 − 26 Since the past 2 decades, substantial improvements have been made in achieving diverse nanostructures (NSs) on a wide range of materials such as metals, semiconductors, insulators, and polymers by varying the short/ultrashort laser ablation parameters (pulse duration, wavelength, fluence, number of pulses, and focusing conditions) and surrounding environments (air, gas, and liquid).…”

SERS for Detection of Proteinuria: A Comparison of Gold, Silver, Al Tape, and Silicon Substrates for Identification of Elevated Protein Concentration in Urine

“…A possible way to improve the accuracy of a direct SERS assay of urine with an Al substrate, which we plan to attempt in the future, is to test substrates based on Al film or the glossy side of Al foil, which have significantly lower surface roughness and lower diffusive reflectivity. Comparable performance of the silicon substrate vs. gold substrate (similar average AUC of 0.79 and 0.80, respectively) is NOT surprising, since silicon has been reported as an efficiently good SERS active substrate in a number of works [ 57 , 58 , 59 ]. In fact, the lower non-specific binding of proteins to silicon is expected in comparison with non-specific binding to gold [ 23 ].…”

Ti–Si–Zr–Zn Nanometallic Glass Substrate with a Tunable Zinc Composition for Surface-Enhanced Raman Scattering of Cytochrome c

“…The heme-containing protein Cyt c is chosen because the structural, thermodynamic, and kinetic properties of this water-soluble protein are well known in detail, including its electron transfer reactions. , As previously reported, the electron transfer would be optimized associating with enhanced SERS signals, if the adsorbed Cyt c has a preferred orientation with its heme group close and perpendicular to the surface of the SERS substrate . Titanium (Ti), zirconium (Zr), and zinc (Zn) are employed for creating a Raman sensing substrate at a low cost combined with sufficient biocompatibility and high stability. , Silicon (Si) is an extensively used Raman-active substrate and building block material for electronic devices. , Besides, Si with its small size fits well in Ti–Zr–Zn facilitating a formation of an amorphous structure …”