**6. Conclusions and outlook**

In summary, the synthesis of precisely controllable anisotropic NPs, with high uniformity and yield, plays the significant role in the SERS detection and imaging. This chapter has demonstrated that the recent research efforts to synthesize the anisotropic noble metal NPs with different morphologies, the E-field distribution, the key morphological parameters to achieve the strong E-field and ultra-sensitive SERS detection. The biggest influence of SERS performance is the effective near-field Raman scattering enhancement, which can be achieved by tuning the LSPR wavelength of the anisotropic noble metal NPs matching with the excitation light wavelength to induce the strong plasmon oscillation. In addition, the anisotropic NPs with high curvature give rise to the highest polarizability at the corners and edges. Many other factors can also powerfully impact the SERS signal output, for example, the binding affinities of analytes to the SERS active materials, the stability of the analyte-NPs system and so on. The interplay of these factors offers a huge potential for the NPs used as SERS active material, and the multifunctional design of the anisotropic noble metal NPs can be applied for the specific application and creates the next generation SERS substrate.

[8] Chen H, Shao L, Li Q, Wang J. Gold Nanorods and Their Plasmonic Properties Chemical

Precisely Controllable Synthesized Nanoparticles for Surface Enhanced Raman Spectroscopy

http://dx.doi.org/10.5772/intechopen.73086

65

[9] Jana NR, Gearheart L, Murphy CJ. Wet Chemical Synthesis of Silver Nanorods and Nanowires of Controllable Aspect Ratio Chemical Communications. 2001:617

[10] Nikoobakht B, El-Sayed MA. Preparation and Growth Mechanism of Gold Nanorods (NRs) Using Seed-Mediated Growth Method Chemistry of Materials. 2003;**5**:1957

[11] Ye X, Zheng C, Chen J, Gao Y, Murray CB. Preparation and Growth Mechanism of Gold Nanorods (NRs) Using Seed-Mediated Growth Method Nano Letters. 2013;**13**:765

[12] Reguera J, Langer J, de Aberasturiab DJ, Liz-Marzán LM. Anisotropic Metal Nanoparticles for Surface Enhanced Raman Scattering Chemical Society Reviews. 2017;**46**:3866

[13] Chu MW, Myroshnychenko V, Chen CH, Deng JP, Mou CY, García de Abajo FJ. Probing Bright and Dark Surface-Plasmon Modes in Individual and Coupled Noble Metal

[14] Guiton BS, beriV I, Li S, Leonard DN, Parish CM, Kotula PG, Varela M, Schatz GC, Pennycook SJ, Camden JP. Correlated Optical Measurements and Plasmon Mapping of

[15] Orendorff CJ, Gearheart L, Jana NR, Murphy CJ. Aspect Ratio Dependence on Surface Enhanced Raman Scattering Using Silver and Gold Nanorod Substrates Physical

[16] Huang JF, Zhu YH, Lin M, Wang QX, Zhao L, Yang Y, Yao KX, Han Y. Site-specific growth of Au−Pd alloy horns on Au nanorods: A platform for highly sensitive monitoring of catalytic reactions by surface enhancement Raman spectroscopy. Journal of the

[17] Scarabelli L, Coronado-Puchau M, Giner-Casares JJ, Langer J, Liz-Marzán LM. Monodisperse Gold Nanotriangles: Size Control, Large-Scale Self-Assembly, and Performance in

[18] Yang Y, Zhong XL, Zhang Q, Blackstad LG, Fu ZW, Li ZY, Qin D. The Role of Etching in the Formation of Ag Nanoplates with Straight, Curved and Wavy Edges and Comparison

[19] Qian H, Xu M, Li W, Ji M, Cheng L, Shoaib A, Liu J, Jiang L, Zhu H, Zhang JT. Surface Micro/nanostructure Evolution of Au–Ag Alloy Nanoplates: Synthesis, Simulation, Plasmonic Photothermal and Surface-enhanced Raman Scattering ApplicationsNano

[20] Tan T, Tian C, Ren Z, Yang J, Chen Y, Sun L, Li Z, Wu A, Yin J, Fu H. LSPR-dependent SERS Performance of silver Nanoplates with Highly Stable and Broad Tunable LSPRs Prepared through an Improved Seed-mediated Strategy Physical Chemistry Chemical

Nanoparticles Using an Electron Beam Nano Letters. 2009;**9**:399

Silver Nanorods Nano Letters. 2011;**11**:3482

Chemistry Chemical Physics. 2006;**8**:165

American Chemical Society. 2013;**135**:8552

of Their SERS PropertiesSmall. 2014;**10**:1430

Research. 2016;**9**:876

Physics. 2013;**15**:21034

Surface-Enhanced Raman Scattering. ACS Nano. 2014;**8**:5833

Society Reviews. 2013;**42**:2679
