Decoration of silicon nanowires with silver nanoparticles for ultrasensitive surface enhanced Raman scattering

Abstract

Silicon nanowires (Si NWs), produced by the chemical etching technique, were decorated with silver nanoparticles (NPs) produced at room temperature by the pulsed laser deposition (PLD) technique. Silver NPs were obtained by means of nanosecond pulsed laser ablation of a target in the presence of a controlled Ar atmosphere. Two different laser pulse numbers and Si NWs having different lengths were used to change the NP number density on the Si NW surface. The resulting Ag NP morphologies were studied by scanning electron microscopy imaging. The results show that this industrially compatible technological approach allows the coverage of the Si NW walls with Ag NPs with a strong control of the NP size distribution and spatial arrangement. The obtained Ag NP decorated Si NWs are free from chemicals contamination and there is no need of post deposition high temperature processes. The optical properties of Si NW arrays were investigated by reflectance spectroscopy that showed the presence of a plasmon related absorption peak, whose position and width is dependent on the Ag NP surface morphology. Coupling the huge surface-to-volume ratio of Si NW arrays with the plasmonic properties of silver nanoparticles resulted in a 3D structure suitable for very sensitive surface enhanced Raman scattering (SERS) applications, as demonstrated by the detection of Rhodamine 6G in aqueous solution at a concentration level of 10(-8) M.

Catalytic Activity of Silicon Nanowires Decorated with Gold and Copper Nanoparticles Deposited by Pulsed Laser Ablation

“…This trend is in very good agreement with the results demonstrated for AgNPs [38] and AuNPs shown in Figure 2, in fact for CuNPs the radius distribution decreases along the NW from the top to the bottom. …”

“…The structural properties of these materials were investigated by scanning electron microscopy (SEM) as reported in Figure 2 and Figure 3, respectively. As already demonstrated [38], the SiNW arrays are not damaged during the PLD decoration process that was optimized in order to fully decorate the NW sidewalls. Figure 2 displays the SEM cross-section images of the (a) top, (b) center and (c) bottom regions of the Au decorated NWs.…”

“…Preparation of silicon nanowires and their decoration with gold and copper nanoparticles by PLD technique were accomplished by previously reported protocols [38], and are briefly described into the paragraph on the structural properties of catalysts nanocomposites (results and discussion section).…”

“…), a uniform and dense decoration of silicon nanowires was obtained with a tight control of size, distribution, and mutual distance among NPs. In the case of silver NPs, this material has been successfully used for Surface Enhanced Raman Spectroscopy (SERS) applications [36,37,38]. …”

Three-dimensional hybrid silicon nanostructures for surface enhanced Raman spectroscopy based molecular detection

“…[20][21][22][23][25][26][27][28] Among all the conventional techniques, the silver-assisted electroless (SAE) etching is an easy and inexpensive wet chemical process adopted to synthesize Si NWs in a wide scale range. [29][30][31][32][33][34][35][36][37][38] Specifically, in current research, metal nanoparticles (NPs) decorated three-dimensional (3 D) semiconductor nanostructures (NSs) have been recognized as the promising SERS substrates for molecular detection. [39][40][41][42][43] The superior performance of 3D SERS substrates is basically attributed to their large surface to volume ratio, which is beneficial for the formation of hotspots, and the capture of target analytes at lower concentration levels.…”