Spatial-Tunable Au Nanoparticle Functionalized Si Nanorods Arrays for Surface Enhanced Raman Spectroscopy

Abstract

<jats:p>In this study, hexagonal-packed Si nanorods (SiNRs) arrays were fabricated and conjugated with Au nanoparticles (AuNPs) in different spatial distributions for surface-enhanced Raman spectroscopy (SERS). The AuNPs were functionalized on the bottom of SiNRs (B-SiNRs@AuNPs), top of SiNRs (T-SiNRs@AuNPs) and sides of SiNRs (S-SiNRs@AuNPs), respectively. Our results demonstrated that the SiNRs conjugated with AuNPs on the sides achieved high reproducibility in detection of R6G molecules, while the AuNPs on the top of the SiNRs obtained the strongest Raman enhancement. In addition, the substrate with S-SiNRs@AuNPs obtained the highest spatial uniformity of enhancement. The finite-difference time-domain simulation gave further evidence that the incident light could be confined in the space of SiNRs arrays and yield a zero-gap enhancement coupled with the AuNPs. Our study provided a spatially tunable SiNRs@AuNPs substrate with high sensitivity and reproducibility in molecular detection.</jats:p>

Self-Assembled Au Nanoparticle Monolayers on Silicon in Two- and Three-Dimensions for Surface-Enhanced Raman Scattering Sensing

“…As expected from previous reports, the AuNPs@SiNWs samples show a large Raman signal from the analyte molecule 4-MBA. 4 , 5 , 11 , 56 The signal intensity measured on the AuNPs@SiNWs incubated for 24 h and 3 days in the 1:1 mixture of AuNP solution and absolute ethanol is much higher than on the AuNPs@SiNWs incubated for 4 h, most likely due to the higher amount of isolated AuNPs and AuNP chains that are present after longer incubation times. The AuNPs@SiNWs sample incubated for 3 days shows the highest signal enhancement, which is around twice the signal measured on the AuNPs@SiNWs incubated for 24 h and 25 times that on the AuNPs@SiNWs incubated for 4 h, respectively.…”

“…This not only increases the substrate surface area, but can also enhance the optical properties of the resulting composite to provide large and uniform E-field enhancements. 1 , 4 , 5 , 11 , 17 , 28 VA-SiNW arrays, with an average pitch, nanowire diameter, and length of 407, 135, and 1340 nm, respectively, were prepared via colloidal lithography and metal-assisted chemical etching (MACE), as previously reported from our group (more details in the Experimental Section ). 37 , 64 Functionalization with APTES was carried out using the protocol developed for the fabrication of AuNPs@APTES-Si flat substrates.…”

“…Nanostructured surfaces have unique and tunable, size-dependent physicochemical properties that enabled their use in a variety of applications, such as chemical and optical sensing, 1 − 11 nanoelectronics, 6 , 7 , 12 − 16 catalysis, 7 , 8 , 17 solar cells 6 , 8 , 18 or biomedical applications. 6 , 9 , 13 − 15 , 19 In that regard, the integration of gold nanoparticles (AuNPs) with silicon (Si) surfaces provides a range of opportunities thanks to the favorable combination of the tunable optoelectronic properties of the AuNPs and Si.…”

“… 1 , 5 , 7 , 8 , 20 − 22 Because AuNPs@Si substrates are biocompatible, can be selectively functionalized with a wide variety of molecules, and are chemically stable in many different environments, they have become a key model system for the design and study of nanostructured surfaces with tailored properties. 2 − 5 , 7 , 11 , 12 , 18 − 21 , 23 …”

“…Nanostructured surfaces have unique and tunable, size-dependent physicochemical properties that enabled their use in a variety of applications, such as chemical and optical sensing, − nanoelectronics, ,,− catalysis, ,, solar cells ,, or biomedical applications. ,,− , In that regard, the integration of gold nanoparticles (AuNPs) with silicon (Si) surfaces provides a range of opportunities thanks to the favorable combination of the tunable optoelectronic properties of the AuNPs and Si. ,,,,− Because AuNPs@Si substrates are biocompatible, can be selectively functionalized with a wide variety of molecules, and are chemically stable in many different environments, they have become a key model system for the design and study of nanostructured surfaces with tailored properties. − ,,,,− , …”