Bicontinuous microemulsion as confined reaction media for the synthesis of plasmonic silver self-assembled hierarchical superstructures

Abstract

Plasmonic superstructures may concentrate hot spots both on the external surface and within the inner gaps of the assembly. However, these materials are usually obtained by two-steps procedures from synthesis of plasmonic nanoparticles to their 3D assembly. The interconnected nano-network of water and oil channels in a bicontinuous microemulsion (BµE) may act as a preorganized reaction system giving reticulated materials. In this work, a silver hierarchical superstructure (HSS-AgCt) was obtained in the water channels of a BµE in a one-pot procedure. The characterization of the morphology and crystalline structure revealed that this superstructure is composed of silver nanoparticles embedded in polymeric silver citrate forming a 3D mesh of interconnected fibers with mean width of 30 nm. The aging of HSS-AgCt in the BµE allowed the degradation of the citrate fibers giving rise to interconnected spherical silver nanoparticles (HSS-Ag) of 8 nm as measured from TEM images. Rhodamine 6-G was detected by SERS up to 10 -12 M with an analytical enhancement factor of 10 9 for both materials using a 633 nm laser operating at 0.85 mW (5% of the nominal power). These results introduce a novel route to obtain highly sensitive SERS substrates in one-pot procedures by using BµE as a nanoreactor and template.

From Nanoparticle Heteroclusters to Filament Networks by Self-Assembly at the Water–Oil Interface of Reverse Microemulsions

“…XPS characterization can provide a detailed analysis about the functionalization of the respective nanostructures from each nanoparticle dispersion. 38 For this purpose, samples were dried after solvent removal from the original dispersions and from the L 2 phase to examine the effect of the AOT surfactant on the nanoparticles, which should remain after solvent evaporation. Particle interactions can be affected not only by their surface functionalization but also by the concentration of AOT as charge control agent.…”

“…Other similar structures have been previously reported by AOT microemulsions as template phases in the presence of silver nanoparticle precursors with reducing agents to induce asymmetric shapes. 38,41 In our case, the shape-directing properties should be based on the synergistic effect of combining two types of nanoparticles, each of them dispersible in different liquid phases, at the water−oil interface. 23 A comparison of the nanoparticle structures from the WPII mixtures in the presence of each nanoparticle combination demonstrates that both types of nanoparticles (MNPs + Au(PEI)NPs) are necessary to form the organized patterns of interest (Figure S12).…”

Hierarchical Nanobiosensors at the End of the SARS-CoV-2 Pandemic

“…The existing improvements found when assembling nanostructures are versatile, and they open new methods for different technologies to control their structure and combine physicochemical properties [121][122][123][124][125][126][127][128][129][130][131]. On the other hand, some nanostructured systems based on organic polymers have been proposed [132], and applications for spectrochemical biosensing have been demonstrated.…”

Biomimetic Hierarchical Superstructures: Approaches Using Bicontinuous Microemulsions and Electrodeposition

“…The synthesis of this material is carried out in a bicontinuous microemulsion composed of Synperonic 91/5, isooctane, and water. The ethoxylated groups of the nonionic surfactant reduce the silver ions incorporated into the aqueous phase from the moment the microemulsion is formed (Adesuji et al, 2020c). The size of the plasmonic Ag nanoparticles can be controlled by varying the reaction time.…”