Preparation of Silver Nanostructures from Bicontinuous Microemulsions

Abstract

Precipitation of silver nanoparticles at 70°C was carried out by dosing a 1.3 M sodium borohydride aqueous solution over bicontinuous microemulsions formed with a mixture of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and sodium dodecylsulfate (SDS) as surfactants, a 0.5 M silver nitrate aqueous solution, and toluene. Weight ratios of 2.5/1 and 3/1 AOT/SDS were used in the precipitation reactions. Silver nanoparticles were characterized by transmission electronic microscopy, X-ray diffraction, and atomic absorption spectroscopy. A mixture of isolated spheroidal nanoparticles (≈15 wt.%) with an average diameter around 10 nm and wormlike structures (≈85 wt.%) with an average length close to 480 nm and an average diameter ca. 40 nm was obtained, regardless of the AOT/SDS ratio. Higher yields were obtained compared with those reported when reverse microemulsions were employed. Formation of wormlike structures was ascribed to one-dimensional aggregation of crystal and particles within the channels of bicontinuous microemulsions, which performed as templates.

Silver Nanoparticles Obtained by Semicontinuous Chemical Reduction Using Carboxymethyl Cellulose as a Stabilizing Agent and Its Antibacterial Capacity

“…A slight change of the transparent solution to a yellowish color was an indication that the CMC acted as a reduction agent to form AgNPs [17]. When the addition of the NaBH 4 started, the solution began to turn black because of the reduction of the Ag + ions [10], and at the end of the addition a black and very stable colloidal solution was obtained. The product (a grayish-black powder) was recovered, obtaining conversions between 82 and 87% (see Table 2).…”

“…Figure 4 depicts representative micrographs of samples S1 and S5, along with their corresponding particle average diameters and histograms obtained by measuring over 500 particles; Table 2 shows the average diameter for the samples. The particles were quasi-spherical and the histograms indicate that there is a unique population, which suggests that each nanoparticle is formed of a single crystal [10]. The AgNPs obtained using the different formulations were quasi-spherical and presented similar histograms.…”

“…Journal of Nanomaterials AgNPs can be obtained by chemical, physical, and biological methods. In the chemical routes, silver ions in aqueous solutions are reduced, with or without stabilizing agents, by using electrochemical reduction, photoreduction in reverse and bicontinuous micelles, and chemical reduction [6,[8][9][10]. The physical methods include evaporation-condensation and laser ablation [11].…”

Preparation of Spherical Ultrafine Silver Particles Using Y-Type Microjet Reactor

“…Various methods can be used to prepare silver powders, including physical, chemical, and biological methods [ 7 ]. Common physical preparation methods include the high-energy ball-milling method [ 8 ], spray thermal decomposition method [ 9 ], plasma evaporation condensation method [ 10 ], liquid phase reduction method [ 11 , 12 ], microemulsion method [ 13 , 14 ], liquid–solid phase reduction method [ 15 ], and microbial reduction [ 16 ]. The chemical method is widely used in large-scale industrial production because of its low equipment requirements and energy consumption.…”

Self‐seeding synthesis of silver nanosheets with binary reduction in poly(vinylpyrrolidone)–sodium dodecyl sulphate aggregation microreactor

“…Introduction: Anisotropic silver (Ag) nanostructures have received wide and intensive interest [1][2][3][4][5][6][7][8][9][10][11]. In recent years, various synthetic approaches have been applied in the controlled fabrication or morphology modulation of Ag nanostructures, including hydrothermal [12], NaBH 4 reduction using citrate and poly(vinylpyrrolidone) (PVP) as stabilisers [1], polyol reduction [13] or UV [2,14]/microwave radiation [15] reduction, electrochemical deposition [16], microemulsion [17] and vapour deposition [18]. However, the preparation strategies for two-dimensional (2D) Ag nanostructures were relatively limited.…”