Shape and size dependent nonlinear refraction and absorption in citrate-stabilized, near-IR plasmonic silver nanopyramids

Abstract

Using a combination of a mild stabilizer and a mild reductant, sodium citrate and hydrazine hydrate, anisotropic silver nanocrystals (NCs) were synthesized with tunable plasmon peaks at 550 nm, 700 nm, 800 nm, 900 nm and 1010 nm (the samples are named Ag-550, Ag-700, Ag-800, Ag-900 and Ag-1010, respectively). TEM investigations revealed that Ag-550 NCs were pentagonal nanoplates while the other four samples were nanopyramids with a pentagonal base with the edge length varying between 15 and 30 nm. The non-linear optical (NLO) properties of these NCs were studied by the Z-scan technique using the CW He-Ne laser (632.8 nm, 15 mW). The shape change from 2D nanoplates (Ag-550) to 3D nanopyramids (Ag-700) resulted in sign reversal of the non-linear refractive index, n, from a negative (-3.164 × 10 cm W) to a positive one (1.195 × 10 cm W). This corresponds to a change from a self-defocussing effect to a self-focussing one. Besides shape, the size effect is also prominently observed. Amongst nanopyramids, as the edge length increases, n increases linearly and reaches a maximum of 3.124 × 10 cm W. Doubling the edge length from 15 nm to 30 nm resulted in 162% increase in n. On moving from Ag-550 to Ag-900 NCs, with the increasing plasmon wavelength, the non-linear absorption (NLA) coefficient increased exponentially to a high value of 8.52 × 10 cm W. However, Ag-1010 showed 29% decrease in NLA which is attributed to twinning present in the crystal structure as seen in the HR-TEM images. Due to the tunable NLO properties, these anisotropic Ag NCs hold great potential for applications in optical limiting, switching and data storage.

Self-Saturable Absorption and Reverse-Saturable Absorption Effects in Diamond-Like Carbon Films with Embedded Copper Nanoparticles

“…However, for these samples, no surface plasmon resonance effect was reported. Recently, reverse-saturable absorption at low exciting optical power density was reported for Ag nanoprisms [21]. However, in that study, continuous wave laser was used.…”

Photochemical Synthesis of Silver Nanodecahedrons under Blue LED Irradiation and Their SERS Activity

“…The UV-Vis results in Figure 2 show the formation of silver nanoseeds (at 0 h) which presented an absorption peak at 400 nm (peak 1). A yellow color indicated the presence of spherical silver nanoparticles in the solution [4][5][6][7][8][9]. After irradiating with LEDs for 6 h, this peak showed a red shift to 407 nm, and another peak (peak 2) appeared at 460 nm, corresponding to the vibration of dipole resonance of AgNDs [6][7][8][9].…”

“…In particular, AgNDs with multihedral structure display a remarkable scattering ability [3,4]. So far, AgNDs have been synthesized by a chemical method using hydrazine as a reductive agent and trisodium citrate as a stabilizer [5]. However, only few AgNDs are obtained with this method.…”

Assessment of optical, mechanical and nonlinear properties of potassium acid phthalate single crystal: a potential candidate for optoelectronic applications

“…The grown crystal of KAP is one of the potential materials for second harmonic generation (SHG) applications and its efficiency is 1.13 times higher than that of standard Potassium Dihydrogen Orthophosphate (KDP) single crystal [34]. In addition to the above said property, it also obeys the third order nonlinear optical behavior which is measured by Z-scan technique which is a simple and famous experimental method for the precise measurements of intensity dependent nonlinear susceptibilities, nonlinear refractive index and the nonlinear absorption (NLA) coefficient and based on the principles of spatial beam distortion [35][36][37][38]. It is a single-beam method employed to find out the real and imaginary parts of nonlinear optical susceptibility of a material.…”