The Role of Etching in the Formation of Ag Nanoplates with Straight, Curved and Wavy Edges and Comparison of Their SERS Properties

Abstract

We investigate the role of etching in the formation of Ag nanoplates with different morphologies. By examining the reduction of AgNO3 with poly(vinyl pyrrolidone) in an aqueous solution under a hydrothermal condition, we confirm that etching plays an essential role in promoting the growth of Ag triangular nanoplates with straight edges at the expense of multiple twinned particles via Ostwald ripening. Once all the multiple twinned particles are gone, etching will continue at the corners of nanoplates, leading to the formation of enneahedral nanoplates with curved edges. When the nanoplates with straight edges are transferred into ethanol and subjected to a solvothermal treatment, we obtain nanoplates with wavy edges and sharp corners due to etching on the edges. A comparison study indicates that, at the same particle concentration, Ag nanoplates with wavy edges embraces a SERS enhancement factor at least 6 and 13 times stronger than those with straight and curved edges, respectively. The results from finite difference time domain calculations support our experimental observation that the sharp features on nanoplates with wavy edges are the most active sites for SERS.

Two-Step Photonic Reduction of Controlled Periodic Silver Nanostructures for Surface-Enhanced Raman Spectroscopy

“…Consistent with the results of other groups demonstrating nanoplates are superior to nanospheres for SERS [24,28], the AEF of nanoplate substrates (615 nm reduced) is at least 10 times higher than that of nanoparticles (365 nm reduced) in our results. Although Tiwari et al postulated a chemical mechanism was underlying the higher Raman signal observed with nanoplates [29], there is no evidence of differential surface absorption of particles in our experimental results, suggesting electromagnetic mechanisms may still play the dominant role.…”

“…8c) are difficult to visualize at this scale. Although these gaps are only approximately 15 nm, they are critical features of an effective SERS substrate [24].…”

Thin metal nanostructures: synthesis, properties and applications

“…Recently, hydrothermal methods have been successfully employed in the synthesis of metal nanoplates. 61,123 For example, Yan et al prepared ultrathin triangular Ru nanoplates with a thickness of ∼3.0 nm by reducing RuCl 3 · x H 2 O with HCHO (40 wt%) in the presence of PVP at 160 °C for 4 h. 61 By simply increasing the concentration of RuCl 3 · x H 2 O and PVP, irregular-shaped ultrathin Ru nanoplates with a thickness of ∼1.5 nm were obtained. Another study showed the hydrothermal synthesis of triangular Ag nanoplates with straight and curved edges from AgNO 3 in the presence of PVP at 160 °C for 4 or 6 h. 123 …”

“…Recently, Qin et al systematically studied the SERS activities of Ag nanoplates with straight, curved and wavy edges. 123 Compared to Ag nanoplates with straight and curved edges, those with wavy edges are richest in sharp corners and this can significantly enhance the localized electromagnetic field. As expected, the Ag nanoplates with wavy edges displayed the strongest SERS signal for 1,4-benzenedithiol molecules among the aforementioned three kinds of Ag nanoplates.…”

Green Intelligent Nanomaterials by Design (Using Nanoparticulate/2D-Materials Building Blocks) Current Developments and Future Trends

“…In case of silver salt, it produced triangular Ag nanoplates with sharp and curved corners [162][163][164].…”