Ordered Ag/Si nanowires array: wide-range surface-enhanced Raman spectroscopy for reproducible biomolecule detection.
Surface-enhanced Raman scattering (SERS) systems utilizing the interparticle nanogaps as hot spots have demonstrated ultrasensitive single-molecule detection with excellent selectivity yet the electric fields are too confined in the small nanogaps to enable reproducible biomolecule detections. Here, guided by finite-difference-time-domain simulation, we report hexagonal-packed silver-coated silicon nanowire (Ag/SiNW) arrays as a nanogap-free SERS system with wide-range electric fields and controlled interwire separation. Significantly, the system achieves a SERS detection of long double-strand DNA of 25-50 nm in length with a relative standard deviation (RSD) of 14% for measurements of above 4000 spots over an area of 200 × 200 μm(2). The high reproducibility in the SERS detection is attributed to (1) the large interwire spacing of 150 nm that allows access and excitation of large biomolecules; and (2) 600 nm wide-range electric field generated by propagating surface plasmons along the surface of continuous Ag coating on a SiNW. Moreover, a reproducible multiplex SERS measurement is also demonstrated with RSDs of 7-16% with an enhancement factor of ~10(6). The above results show that the ordered Ag/SiNW array system may serve as an excellent SERS platform for practical chemical and biological detection.
Center of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, China.
Jian-An
JA
Huang
Ying-Qi
YQ
Zhao
Xue-Jin
XJ
Zhang
Li-Fang
LF
He
Tai-Lun
TL
Wong
Ying-San
YS
Chui
Wen-Jun
WJ
Zhang
Shuit-Tong
ST
Lee
D008855:Microscopy, Electron, Scanning; D053770:Nanowires; D015203:Reproducibility of Results; D012825:Silicon / Q000737:chemistry*; D012834:Silver / Q000737:chemistry*; D013059:Spectrum Analysis, Raman / Q000379:methods*
D012834:Silver; D012825:Silicon