Photochemical transformation of silver nanoparticles by combining blue and green irradiation

Abstract

Spherical silver nanoparticles (diameter 3 nm) were transformed by means of photochemical synthesis using superluminescent LEDs. Flat rounded (21 nm) and decahedral nanoparticles (78 nm) were, respectively, obtained when the colloid was exposed to green and blue radiation. Furthermore, by changing from blue to green radiation at different exposure times, various morphologies and sizes were obtained. Exposure times shorter than 30 min of blue radiation followed by green radiation resulted on different morphologies such as twine rounded (42 nm), flat elongated (peanuts, 17 nm), and flat rounded nanoparticles (11 and 24 nm). Times longer than 45 min produced decahedral nanoparticles with corners ranging from rounded to sharp (size 71-78 nm). Additionally, these results showed that by controlling morphologies and sizes through the combination of blue and green light at different exposure times, it was possible to tune the plasmon band from 511 to 594 nm. Moreover, controlling the morphology of nanoparticles is of prime importance in order to exploit their properties as part of novel emerging technologies.

The sensitive detection of methylene blue using silver nanodecahedra prepared through a photochemical route

“…5 LSPR occurs through a strong interaction between incident light and free electrons in the nanostructures. Therefore, many groups developed a variety of solution-based strategies to synthesize silver nanodecahedra, including photochemical process, [6][7][8] chemical reduction under the assistance of large-molecular-mass surfactants, 9 photoassisted chemical reduction, 10,11 seed-mediated plasmon-driven regrowth, 12 shape evolution in DMF (dimethylformamide, (CH 3 ) 2 N-CHO) solution 13 or in the presence of polyvinyl alcohol (PVA, (C 2 H 4 O) n ), 14 etc. Recently, there has been remarkably rapid progress in the development of photocatalytic reactions sensitized by high-brightness light-emitting diodes (LEDS).…”

Demonstrating the Photochemical Transformation of Silver Nanoparticles

“…Increasing the size of the spherical silver NPs will lead to a red shift of the plasmon band, but as size increases, colloidal stability is compromised. In the case of silver colloids, a second plasmon band around 550 nm appears when aggregation of the silver NPs occurs. , Experimentally, anisotropic noble metal NPs, such as rods, cubes, decahedra, disks, prisms, and plates, will present two plasmon bands; ,, in the case of silver nanorods, the second plasmon band can be fine-tuned from 500 to 750 nm, depending on their aspect ratio (width/length) . In silver nanoprisms (of 34 nm in edge length and 4 nm in thickness), the second plasmon band is located at 730 nm. , This red shift will be impossible to achieve by using spherical NPs.…”

“…This experiment will introduce students to nanotechnology, and it shows that anisotropic nanoparticle synthesis methods are not limited to chemical reduction or seed regrowth. Students will synthesize silver nanospheres and transform them into other anisotropic morphologies (decahedral and disks) by means of a photochemical process. − …”

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

“…However, only few AgNDs are obtained with this method. The synthesis of AgNDs using a photochemical method based on irradiation by light-emitting diodes (LEDs) for a better control of their shape has gained much attention [3,4,[6][7][8][9][10]. One of the first researchers to study AgNDs were Stamplecoskie and Scaiano.…”

“…They studied the mechanism of AgNDs formation but did not consider the surface plasmon effect, one of the important surface properties of silver nanomaterials [9]. Cardoso-Avila et al also applied LED irradiation on quartz cuvettes containing AgNPs to synthesize AgNDs; however, neither the reaction mechanism nor the SERS effects were thoroughly investigated [10,11].…”