Three-dimensional hybrid silicon nanostructures for surface enhanced Raman spectroscopy based molecular detection (original) (raw)
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Three-dimensional silver nanoparticles decorated vertically aligned Si nanowires (Si NWs) are effective surface-enhanced Raman spectroscopy (SERS) substrates for molecular detection at low concentration levels. The length of Si NWs prepared by silver assisted electroless etching is increased with an increase in etching time, which resulted in the reduced optical reflection in the visible region. These substrates were tested and optimized by measuring the Raman spectrum of standard dye Rhodamine 6G (R6G) of 10 nM concentration. Further, effective SERS enhancements of 105and10 5 and 105and10 4 were observed for the cytosine protein (concentration of 50 lM) and ammonium perchlorate (oxidizer used in explosives composition with a concentration of 10 lM), respectively. It is established that these three-dimensional SERS substrates yielded considerably higher enhancement factors for the detection of R6G when compared to previous reports. The sensitivity can further be increased and optimized since the Raman enhancement was found to increase with an increase in the density of silver nanoparticles decorated on the walls of Si NWs. Published by AIP Publishing. https://doi.org/10.1063/1.5000994
Applied Spectroscopy
In this work, we combined a hierarchical nano-array effect of silicon nanowires (SiNWs) with a metallic surface of silver nanoparticles (AgNPs) to design a surface-enhanced Raman spectroscopy (SERS) scattering substrate for sensitive detection of Rhodamine 6G (R6G) which is a typical dye for fluorescence probes. The SiNWs were prepared by Metal-Assisted Chemical Etching (MACE) of n-Si (100) wafers. The Doehlert design methodology was used for planning the experiment and analyzing the experimental results. Thanks to this methodology, the R6G SERS response has been optimized by studying the effects of the silver nitrate concentration, silver nitrate and R6G immersion times and their interactions. The immersion time in R6G solution stands out as the most of influential factor on the SERS response.
Silicon Nanowires as Sensory Material for Surface-Enhanced Raman Spectroscopy
Silicon, 2018
This paper shows steps for silicon nanowires substrates synthesis in detail. The research is focused on experimental techniques optimization while the targeted application was a fabrication of highly sensitive substrates for surface-enhanced Raman spectroscopy (SERS). Horizontal silicon nanowires on top of two-inch wafers were obtained by vapour-liquid-solid growth inside the low-pressure chemical vapour deposition reaction tube. The silicon nanowires morphology was monitored by scanning electron microscope after a short and long growth period which defined an adequate deposition time for SERS applications. Surface-enhanced Raman spectroscopy features were tested on silver nanoparticles decorated substrates and the detection concentration limit of 10 −9 M of rhodamine 6G molecules was reached. Raman spectroscopy showed that the 532 nm laser excitation powers of less than 4 mW (∼0.57 kW/cm 2) do not widen the phonon peak or shift its frequency and the nanostructure distribution parameter of 3.7 nm was calculated. The horizontally placed Ag decorated nanowires are proved to be sensitive substrates for surface-enhanced Raman spectroscopy only if the silicon nanowires thickness, length, volume density as well as metal nanoparticle size and distribution are carefully designed.
Croatica Chemica Acta, 2017
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 production obtained for 5 M hydrofluoric acid and 30 mM silver nitrate etching solution. The results show SERS detection limit of 10-8 M rhodamine in aqueous solution.
ACS Applied Materials & Interfaces, 2009
Silver nanoparticles (Ag NPs) were chemically deposited on silicon nanowires (SiNWs), prepared using the vapor-liquid-solid (VLS) growth mechanism, using an in situ electroless metal deposition technique. The resulting SiNWs/Ag NPs composite interfaces showed large Raman scattering enhancement for rhodamine 6G (R6G) with a detection limit of 10 -14 M and an enhancement factor of 2.3 × 10 8 . This large enhancement factor was attributed to the presence of "hot" spots on the SiNWs/Ag NPs substrate.
Photobleaching effect is an immense problem in optical spectroscopy, especially when fluorophores are adsorbed on metal nanoparticles (NPs). Nevertheless, little effort has been assigned to the study of fluorophore photostability under this condition. In this paper, the effect of photobleaching on the Raman signal enhancement factor (RS-EF) of dye molecules on Ag-modified silicon nanowire (SiNW) substrates is investigated. For this purpose, SiNWs are fabricated by using the vapor-liquid-solid growth mechanism and decorated with Ag NPs by means of electroless deposition method. This process provides the possibility of forming uniformly and tightly packed Ag NPs on SiNWs. The effect of photostability of the crystal violet as analyte molecules on surface-enhanced Raman spectroscopy is investigated as a function of time evolution and laser power. The influence of Ag NP deposition time on Raman signal enhancement is explored. Our work shows how we can optimize the excitation power for achievement of higher RS-EF and, consequently, lower detectable concentration. Time evolution of surface-enhanced Raman spectroscopy signal shows an exponential decay behavior, which indicates an almost uniform distribution of EFs. Capability of our nanostructure is assessed for different concentration, and subsequently, limit of detection of 10 pm with RS-EF of 2.4×10 9 is obtained.
International Journal of Nanotechnology
In this paper, we present the use of silver nanoparticles coated silicon nanowire (SiNW) arrays in surface-enhanced Raman scattering (SERS) measurements with emphasis on the use of obliquely instead of vertically aligned SiNW arrays. The obliquely aligned SiNW arrays were fabricated on Si(111) substrate, and the SiNWs were coated with silver nanoparticles with sizes in the 20-40 nm range. The results showed that with the use of obliquely instead of vertically aligned SiNW arrays, the Raman enhancement factor (REF) is increased by more than one order of magnitude and can reach 10 14 when malachite green is used as test sample. The mechanism causing the improvement of the REF is also discussed.
Nanomaterials, 2021
In this study, we developed highly sensitive substrates for Surface-Enhanced-Raman-Scattering (SERS) spectroscopy, consisting of silicon nanowires (SiNWs) decorated by silver nanostructures using single-step Metal Assisted Chemical Etching (MACE). One-step MACE was performed on p-type Si substrates by immersion in AgNO3/HF aqueous solutions resulting in the formation of SiNWs decorated by either silver aggregates or dendrites. Specifically, dendrites were formed during SiNWs’ growth in the etchant solution, whereas aggregates were grown after the removal of the dendrites from the SiNWs in HNO3 aqueous solution and subsequent re-immersion of the specimens in a AgNO3/HF aqueous solution by adjusting the growth time to achieve the desired density of silver nanostructures. The dendrites had much larger height than the aggregates. R6G was used as analyte to test the SERS activity of the substrates prepared by the two fabrication processes. The silver aggregates showed a considerably lowe...
MATERIALS TRANSACTIONS, 2014
Metal nanoparticles with nanoscale spacing are promising materials for the detection of single molecules through surface-enhanced Raman scattering. To increase the sensitivity of nanoparticles through the use of a nanoscale substrate, we fabricated various Ag NPdecorated silicon nanowalls for the Raman spectroscopic detection of rhodamine 6G (R6G). The sensitivity of detection was affected by the nanowall depth and was influenced by several parameters: the AgNO 3 concentration for metal-assisted etching, the HF/H 2 O 2 etching time for nanowall formation, and the Ag evaporation time for nanoparticle growth. For an approximately 400-nm-deep nanowall substrate having the optimal surface filling ratio and etching depth, we obtained an ultrahigh enhancement factor of 1.1 © 10 9 for the detection of R6G at a concentration of 10 ¹11 M.