KL performed the statistical analysis. All authors carried out the manuscript drafting. find more All authors read and approved the final manuscript.”
“Background In the last decades, it has been demonstrated that metallic nanostructures are a powerful means to attain the subwavelength control of electromagnetic field thanks to the so-called surface plasmon (SP) effect supported by them [1, 2]. Confining the oscillating collective excitations at the interface of a metal and a dielectric introduces the prospect of optical devices with new functionalities by enhancing inherently weak physical processes, such as fluorescence  and Raman scattering which the latter
is nominally called surface-enhanced Raman scattering (SERS) . Surface plasmon and electrooptical properties can be effectively and intentionally regulated by the size and shape of the nanostructure. Various morphology-controlled noble metal structures have been synthesized among which flower-like silver nanostructures raise much attention and are promising candidates as SERS substrate owing
to silver-intrinsic outstanding properties than other metals , the existence of abundance of ‘hot spots’ in sharp tips and nanoparticle junctions resembling intuitively selleck chemicals nanoscale optical antenna [6, 7]. Nowadays, many approaches including chemical reduction [8, 9], light irradiation , galvanic replacement , evaporation , and anisotropic etching  have been developed to prepare flower-like noble metal nanostructures. Metal nanostructures with well-controlled shape, size, and uniquely designed optical properties can be finely prepared with multistep methods such as double-reductant method, etching technique, 2-hydroxyphytanoyl-CoA lyase and construction of core-shell nanostructures . In comparison, although single-step reduction needs to be regulated carefully and improved intentionally, this method can be more efficient. In the solution-phase synthesis, nanocrystals of common face-centered
cubic (FCC) metals tend to take a polyhedral shape ; therefore, highly branched Ag nanostructures are thermodynamically unfavorable. In our previous research, flower-like silver nanostructures were synthesized employing CH2O or C2H4O as a moderate-reducing agent [15, 16]. The reaction is finished in less than 1 min; thus, the growth rate is beyond the thermodynamically controlled regime, which leads to anisotropic growth due to a faster rate of atomic addition than that of adatom diffusion. However, kinetic-controlled growth alone cannot interpret the occurrence of unusual and rare hexagonal close-packed (HCP) silver nanostructures apart from common FCC ones as noted in our previous report . To our knowledge, HCP crystal structures appear in silver nanowires prepared by electrochemical deposition [17–19] or by simply heating or evaporating Enzalutamide chemical structure FCC-Ag nanowires or nanoparticles [20, 21].