Seed-mediated synthesis of gold nanorods: control of the aspect ratio by variation of the reducing agent

Abstract

Seed-mediated growth methods involving reduction of tetrachloroaurate(III) with ascorbic acid are common for the synthesis of gold nanorods. This study shows, however, that simply by appropriate choice of the reducing agent a drastic influence on the aspect ratio can be attained. Weaker reducing agents, such as dihydroxybenzene isomers (hydroquinone, catechol or resorcinol) or glucose can increase the aspect ratio of the nanorods by an order of magnitude, up to values as high as 100 (nanowires). The increase in aspect ratio is mainly a consequence of an increase in length of the particles (up to 1-3 lm). This effect is probably associated with a decrease in the reduction rate of gold(III) species by dihydroxybenzenes or glucose compared to ascorbic acid. The reduction potential of the reducing agents strongly depends on the pH value, and related effects on the dimensions of the nanoparticles are also reflected in this study. The nanorods exhibited penta-twinned nature without noteworthy defects (e.g. stacking faults and dislocations).

Investigation of electro-oxidation of glucose at gold nanoparticles/carbon composites prepared in the presence of halide ions

“…This method is based on two major steps, such as the selection of reducing agents in order to reduce Au 3+ or Au + ions to Au°, and stabilizing agents with the aim to stabilize NPs against aggregation by controlling their growth rate, size and shape. Among the vast majority of reducing agents, such as borohydrides and hydrazine, citric, oxalic or ascorbic acids, sugars (including glucose), polyols, hydrogen peroxide and sulfites have been tested and widely reviewed [26,27,[29][30][31]. Meanwhile, stabilizing agents count in such materials as trisodium citrate dihydrate, sulfur or phosphorus ligands, polymers, surfactants (in particular cetyltrimethylammonium bromide (CTAB)), and others [25,30,31].…”

Synthesis and Crystal Structures of Gold Nanowires with Gemini Surfactants as Directing Agents

“…[26] Recently, a systematic approach to synthesize gold NWs with tunable lengths has been reported. [32] However, the synthesis of gold NWs above 3 mm with moderate diameters ( % 30 nm) has rarely been reported. In another modified method, NWs with lengths of up to several micrometers were obtained by using fewer seeds in the last step of the multiple-step growth process.…”

“…We tried to choose ligands on the basis of current theoretical predictions and experimental results. [32] Both approaches mentioned above have demonstrated that the growth of longer NWs/NRs may result from a very slow reaction rate. [34] On the other hand, it was found that the hydrocarbon part of the surfactants had a tremendous influence on producing gold NRs, and longer tail The preparation of crystalline gold nanowires (NWs) by using gemini surfactants as directing agents through a three-step seed-mediated method is reported.…”

“…Recently, NWs of 1-3 mm with controllable widths ( % 30 nm) have been obtained by variation of the reducing agent. [32] However, the synthesis of gold NWs above 3 mm with moderate diameters ( % 30 nm) has rarely been reported.…”

“…Alternatively, replacing ascorbic acid with more mild reducing agents makes the reduction slower. [32] Both approaches mentioned above have demonstrated that the growth of longer NWs/NRs may result from a very slow reaction rate.…”