Photochemical synthesis of crown-shaped platinum nanoparticles using aggregates of G4-NH₂PAMAM dendrimer as templates

Abstract

Crown-shaped platinum nanoparticles were synthesized by UV irradiation in the presence of G4-NH 2 PAMAM dendrimers in water. Aggregates of the dendrimers, which were formed in the aqueous solution, served as templates for the formation of such nonspherical nanoparticles. This is the first report on the preparation of structure-controlled platinum nanoparticles by photoreduction. This methodology to use dendrimer aggregates as templates is powerful for the production of shape-controlled nanostructures.

Effect of solvent-controlled aggregation on the intrinsic emission properties of PAMAM dendrimers

“…J-type and H-type aggregates are reported for anionic porphyrin derivatives in the presence of amine terminated PAMAM dendrimers [40]. Recent study of Luo and Imae [27] has shown that fourth-generation, amine terminated PAMAM dendrimers aggregate in aqueous solution to form templates for platinum nanoparticles. They have suggested that the motive force for the formation of aggregates is intermolecular hydrogen bonding.…”

“…Theoretical and experimental works have confirmed that PAMAM dendrimers exhibit conformational flexibility induced by solvents, pH and salt concentration [15][16][17][18][19][20]23]. Among them, role of solvents in altering the structural features of PAMAM dendrimers has been investigated in detail [24][25][26][27]. For example, Stechemesser and Eimer [24] have shown that the change in the solvent media leads to significant swelling in PAMAM dendrimers, which in turn can affect the host-guest chemistry of the dendrimer.…”

“…In another elegant work, Goddard and co-workers [26] have shown through molecular dynamic simulations that the presence of solvent leads to considerable size alterations in PAMAM dendrimers. A pioneering work by Luo and Imae [27] has recently shown that PAMAM dendrimers aggregate in aqueous solutions, resulting alterations in their normal size, which assist the template-based synthesis of platinum nanoparticles.…”

Bimetallic Dendrimer-encapsulated Nanoparticle Catalysts

“…Normal metal nanoparticles such as Ag and Pt nanoparticles are synthesized by chemical reduction of their "parent" metal species (metal salts or complexes) with reducing agents (e.g., NaBH 4 , N 2 H 4 / H 2 O 2 , H 2 , or LiBH(C 2 H 5 ) 3 ) under conditions of thermal decomposition or UV/ microwave/ultrasound irradiation. [39][40][41][42] Metal oxide nanoparticles such as CoO and ZnO are prepared by oxidation reactions of their metal compounds using H 2 O 2 or CO 2 as oxidants at high pH value. 43 Semiconductor metal halide nanoparticles can be prepared by many ways such as (i) the decomposition of organometallic compounds under the influence of heat or radiation; 44 (ii) the interaction of a metal oxide with elemental sulfur, selenium and tellurium; 45 and (iii) the interactions of divalent metal cations (e.g., Ca 2C , Cd 2C , Cu 2C , and Pb 2C ) with doubly charged chalcogen halide anions (e.g., S 2¡ , Se 2¡ , and Te 2¡ ).…”

Self‐assembly of nanorod/nanoparticle mixtures in polymer brushes

“…Unlike spherical NPs, the nonspherical NPs, such as nanowires, nanocubes, crowns, and nanorods (NRs), can display anisotropic behavior in optical and electronic properties and this special property mainly comes from the additional orientation entropy caused by their anisotropic shapes. For the organized NR superlattices, it may be possible to optimize photoelectric properties simultaneously and independently by varying the NR diameter and length.…”