Abstract:Abstract:The silicon based substrates for surface enhanced Raman spectroscopy (SERS) have been synthesized and tested. The silver-assisted electroless wet chemical etching method has been utilized for silicon nanowires production which has been proved as the promising SERS substrate. The morphology of the silicon nanowires coated with silver nanoparticles has been examined by scanning electron microscopy. The SERS measurements tested on rhodamine 6G molecules indicated the optimal silicon nanowire substrate pr… Show more
“…The AgNPs density at the top of the sensor surface is lower also breaking of nanowires was witnessed for higher etching times of 30 and 35 min ( Fig. 3 (g, h)) and could be of add-on reasons for lower signal of Raman spectra of R6G [39] . Figure 4 (a) and (b) Effect of the etching times on the Raman spectra of R6G deposited on SiNWs/AgNPs (The immersion time for AgNPs decoration is set constant for 30 s).…”
Severe acute respiratory syndrome SARS-CoV-2 virus led to notable challenges amongst researchers in view of development of new and fast detecting techniques. In this regard, surface-enhanced Raman spectroscopy (SERS) technique, providing a fingerprint characteristic for each material, would be an interesting approach. The current study encompasses the fabrication of a SERS sensor to study the SARS-CoV-2 S1 (RBD) spike protein of the SARS-CoV-2 virus family. The SERS sensor consists of a silicon nanowires (SiNWs) substrate decorated with plasmonic silver nanoparticles (AgNPs). Both SiNWs fabrication and AgNPs decoration were achieved by a relatively simple wet chemical processing method. The study deliberately projects the factors that influence the growth of silicon nanowires, uniform decoration of AgNPs onto the SiNWs matrix along with detection of Rhodamine-6G (R6G) to optimize the best conditions for enhanced sensing of the spike protein. Increasing the time period of etching process resulted in enhanced SiNWs’ length from 0.55 to 7.34 µm. Furthermore, the variation of the immersion time in the decoration process of AgNPs onto SiNWs ensued the optimum time period for the enhancement in the sensitivity of detection. Tremendous increase in sensitivity of R6G detection was perceived on SiNWs etched for 2 min (length=0.90 µm), followed by 30s of immersion time for their optimal decoration by AgNPs. These SiNWs/AgNPs SERS-based sensors were able to detect the spike protein at a concentration down to 9.3 × 10
−12
M. Strong and dominant peaks at 1280, 1404, 1495, 1541 and 1609 cm
−1
were spotted at a fraction of a minute. Moreover, direct, ultra-fast, facile, and affordable optoelectronic SiNWs/AgNPs sensors tuned to function as a biosensor for detecting the spike protein even at a trace level (pico molar concentration). The current findings hold great promise for the utilization of SERS as an innovative approach in the diagnosis domain of infections at very early stages.
“…The AgNPs density at the top of the sensor surface is lower also breaking of nanowires was witnessed for higher etching times of 30 and 35 min ( Fig. 3 (g, h)) and could be of add-on reasons for lower signal of Raman spectra of R6G [39] . Figure 4 (a) and (b) Effect of the etching times on the Raman spectra of R6G deposited on SiNWs/AgNPs (The immersion time for AgNPs decoration is set constant for 30 s).…”
Severe acute respiratory syndrome SARS-CoV-2 virus led to notable challenges amongst researchers in view of development of new and fast detecting techniques. In this regard, surface-enhanced Raman spectroscopy (SERS) technique, providing a fingerprint characteristic for each material, would be an interesting approach. The current study encompasses the fabrication of a SERS sensor to study the SARS-CoV-2 S1 (RBD) spike protein of the SARS-CoV-2 virus family. The SERS sensor consists of a silicon nanowires (SiNWs) substrate decorated with plasmonic silver nanoparticles (AgNPs). Both SiNWs fabrication and AgNPs decoration were achieved by a relatively simple wet chemical processing method. The study deliberately projects the factors that influence the growth of silicon nanowires, uniform decoration of AgNPs onto the SiNWs matrix along with detection of Rhodamine-6G (R6G) to optimize the best conditions for enhanced sensing of the spike protein. Increasing the time period of etching process resulted in enhanced SiNWs’ length from 0.55 to 7.34 µm. Furthermore, the variation of the immersion time in the decoration process of AgNPs onto SiNWs ensued the optimum time period for the enhancement in the sensitivity of detection. Tremendous increase in sensitivity of R6G detection was perceived on SiNWs etched for 2 min (length=0.90 µm), followed by 30s of immersion time for their optimal decoration by AgNPs. These SiNWs/AgNPs SERS-based sensors were able to detect the spike protein at a concentration down to 9.3 × 10
−12
M. Strong and dominant peaks at 1280, 1404, 1495, 1541 and 1609 cm
−1
were spotted at a fraction of a minute. Moreover, direct, ultra-fast, facile, and affordable optoelectronic SiNWs/AgNPs sensors tuned to function as a biosensor for detecting the spike protein even at a trace level (pico molar concentration). The current findings hold great promise for the utilization of SERS as an innovative approach in the diagnosis domain of infections at very early stages.
“…The voids between SiNWs grow larger when etching time exceeds 1 h. The appearance of voids described by Bontempi et al [31] was attributed to mechanical damage because SiNWs became brittle. The procedures of electroless chemical etching and metalassisted chemical etching refer to mainly the same procedure, sometimes without hydrogen peroxide H 2 O 2 and sometimes exchanging HF with NH 4 F [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. Occasionally nanowires get entangled or joined at the top.…”
Modern diagnostic tools ever aim to reduce the amount of analyte and the time needed for obtaining the result. Surface-enhanced Raman spectroscopy is a method that could satisfy both of these requirements, provided that for each analyte an adequate substrate is found. Here we demonstrate the ability of gold-sputtered silicon nanowires (SiNW) to bind p-mercaptobenzoic acid in 10, 10 and 10M and adenine in 30 and 100μM concentrations. Based on the normal mode analysis, presented here for the first time, the binding of p-mercaptobenzoic acid is deduced. The intensity enhancement of the 1106cm band is explained by involvement of the CS stretching deformation, and the appearance of the broad 300cm band attributed to SAu stretching mode. Adenine SERS spectra demonstrate the existence of the 7H tautomer since the strongest band observed is at 736cm. The adenine binding is likely to occur in several ways, because the number of observed bands in the 1200-1600cm interval exceeds the number of observed bands in the normal Raman spectrum of the free molecule.
“…As such, different designs have been implemented for SERS measurements such as the colloidal mixture of MNPs and target molecule and drop-coating deposition, or the immobilizing MNPs on three-dimensional porous matrices of high surface-to-volume ratio [8][9][10]. In this context, tremendous research works have been dedicated to look after optimized matrices with ultra sensitivity and high specificity for SERS applications [11][12][13][14].…”
Surface enhanced Raman scattering (SERS) is an important analytical tool for the optochemical detection of molecules. The enhancement is commonly achieved by engineering (i) novel types and morphologies of plasmonic nanomaterials, and (ii) patterned or roughened supporting substrates of high surface area for increased light scattering and molecule adsorption. Si substrates can be easily and reproducibly textured for effective SERS applications. In this work, silver nanoprisms (AgNPr) coated silicon nanowire (SiNWs) of different morphologies have been prepared by metal-assisted chemical etching and tested for SERS detection of R6G dye. By varying the etching time from 5 to 30 min, the nanowires’ lengths increased from 2.4 to 10.5 µm and resulted in a variable topological morphology of the substrates in terms of bundles and valleys. We found that an optimum of 10 min etching time led to the highest SERS enhancement of R6G on AgNPr/SiNWs at 612 cm−1 Raman shift (30× compared to R6G/Si and 2× compared to R6G/AgNPr/Si), with a detection limit comparable to that of state-of-the-art performances (down to 5×10−10 M of R6G). Such an enhancement is attributed to a middle ground between increased overall surface area of SiNWs, and the available bundle tops trapping the AgNPr and R6G molecules.
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