Nanogap-Rich Surface-Enhanced Raman Spectroscopy-Active Substrate Based on Double-Step Deposition and Annealing of the Au Film over the Back Side of Polished Si

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a highly sensitive and rapid detection technique that is used for detection of various analytes in trace quantities. We present a sensitive, large-area, and nanogap-rich SERS-active substrate by altering a thin gold (Au) film on the unpolished side of a single-side polished silicon wafer by repeated thermal deposition and annealing in an argon environment. The repeated thermal deposition and annealing process was compared on both sides of a one-side-polished silicon wafer; however, the rear side (etched/ unpolished side) demonstrated a more enhanced Raman signal owing to the larger effective area. The proposed substrate can be fabricated easily, having a high density of hotspots distributed uniformly all over the substrate. This ensures easy, rapid, and sensitive detection of analytes with a high degree of reproducibility, repeatability, and acceptable uniformity. The optimized substrate shows a high degree of stability with time when exposed to the ambient environment for a longer duration of 148 days. The reported substrate can detect up to 10 −11 M concentrations of 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT), with limits of detection (LODs) of 1.22 and 1.26 ng/L, respectively. This work not only presents the efficient and sensitive SERS-active substrate but also shows the advantages of using the rear side of a one-side-polished silicon substrate as a SERS-active chip.

α-MoO3 Microflakes Decorated with Gold Nanoislands as SERS-Active Substrates

“…Twenty μL of a 10 –6 to 10 –10 mol/L concentration of TNT solution, prepared by serial dilution, was drop-casted, and SERS spectra were recorded, as shown in Figure a. Peaks at 1078, 1202 cm –1 (CH 3 stretching), 1355 cm –1 (symmetric stretching vibration of NO 2 ), 1527 cm –1 (asymmetric stretching vibration of NO 2 ), and 1609 cm –1 (aromatic stretching vibration of CC) were observed. , It can be observed that the intensity decreased with the decrease in concentration. The 1355 cm –1 Raman peak was selected to plot the calibration curve of SERS signal intensity as a function of logarithmic TNT concentration (ng/L), as shown in Figure b.…”

Tuning LSPR of Thermal Spike-Induced Shape-Engineered Au Nanoparticles Embedded in Si3N4 Thin-Film Matrix for SERS Applications

“…It is believed that the suggested substrate may meet the requirements for plasmonic resonance or coupling at an excitation laser of 785 nm wavelength, which may be explained by the size of the NPs and the interparticle distance or gap between them. For the subsequent bands, the Raman fingerprint of Rhodamine 6G at a concentration of 10 –6 M has been seen: In-plane vibrations of the C–C–C ring occur at 612 cm –1 , C–H vibrations occur at 775 cm –1 , C–H vibrations occur at 1183 cm –1 , N–H vibrations occur at 1313 cm –1 , and aromatic C–C stretching occurs at 1364, 1514, and 1653 cm –1 …”

“…For the subsequent bands, the Raman fingerprint of Rhodamine 6G at a concentration of 10 −6 M has been seen: In-plane vibrations of the C−C−C ring occur at 612 cm −1 , C−H vibrations occur at 775 cm −1 , C−H vibrations occur at 1183 cm −1 , N−H vibrations occur at 1313 cm −1 , and aromatic C−C stretching occurs at 1364, 1514, and 1653 cm −1 . 70 The broad peak, which is located at approximately 950 cm −1 , is the silicon substrate's second-order peak. The observed SERS results are explained in the following manner:…”

Meso-Au/BN Nanosensor for Trinitrotoluene Based on Fluorescence Resonance Energy Transfer and Surface-Enhanced Raman Spectroscopy Mechanisms

“…However, these methods often face problems such as complex sample preparation, time-consuming measurement, and difficulties in analyzing samples. 11 Currently, the development of surface chemistry and nanosynthesized techniques provides convenience for the fabrication of various functional materials, such as the modification of material surfaces, 12,13 the synthesis of template materials, 14 the substrates of distinct materials, 15 and so on. 16 The surface-enhanced Raman substrate is a prime example in the field of functional materials fabrication.…”

“…22 These substrates possess robust SERS properties and durability in intricate environments. The SERS substrate was created by modifying either the precious metals Au 11 or Ag 23,24 onto a silicon wafer. This results in a high density of SERS hotspots that have an excellent Raman enhancement effect on the TNT.…”