Generation of gold nanoparticles according to procedures described in the eighteenth century

Abstract

Gold nanoparticles have received much attention in recent years due to their unique size-dependent properties, as they find useful applications in materials science [Mayoral et al. (Nanoscale 2:335-342, 2010) [Sperling et al. (Chem Soc Rev 37:1896-1908, 2008]. The preparation of such nanoparticles benefits from modern chemical knowledge, and a large variety of several procedures have been developed aiming at controlling the size and shape of these metal nanoparticles. Here, we show that two eighteenth-century recipes (Online Resource 1) used at that time to prepare drinkable solutions of gold, used as drugs, actually generate gold nanoparticles, clusters and even monoatomic species of gold. These simple methods involve the dissolution of gold in a solution of ammonium chloride in nitric acid (aqua regia) and the mixing of the resulting solution with rosemary or cinnamon essential oils. The complex mixture of compounds resulting from the fast reaction between aqua regia and the essential oils behave simultaneously as reductants and stabilisers of the nascent gold particles. These results not only prove that historical speculations on the presence of finely divided gold particles floating in these solutions were basically correct but they could also serve as a source of inspiration for new experimental approaches procuring the generation of stable sub-nanometer gold nanoparticles. Keywords Gold nanoparticles . STEM . Eighteenth-century recipes . Essential oilThere is a general agreement that the first scientific approach to the nature of what are now known as solutions of colloidal gold can be traced back to the works of the British scientist Michael Faraday. In a seminal paper published in 1857 [1, 2], he clearly concluded that the ruby or purple colours exhibited by solutions containing gold were due to the presence of very small particles of this metal, so small that they were invisible to the human eye, yet they could be easily detected by their effect in dispersing incident light.As important as this publication is as pioneering the foundation of modern colloid chemistry, Faraday was not the first in preparing such ruby-coloured solutions neither in suggesting the presence in them of gold in such an extremely divided state.There is a long tradition behind the preparation of colloidal gold, which can be briefly summarised as follows. Historically, two main research lines were developed aiming at two different purposes. One of them was directed toward the preparation of colloidal gold to be used for colouring the transparent glass into red colour, resulting in the much sought, valuable and beautiful ruby glass [3]. The second approach belongs to the field of medicine, where the goal was to prepare a gold drinkable solution which behaved as a powerful drug able to cure even the most severe ailments, the so-called potable gold, known in old Latin texts as aurum potabile [4,5]. Although its origin can be traced back to the Middle Ages, Electronic supplementary material The online version of this article

Modulation of the Activity of Gold Clusters Immobilized on Functionalized Mesoporous Materials in the Oxidation of Cyclohexene via the Functional Group. The Case of Aminopropyl Moiety

“…These observations evidence that the gold entities aggregate in the oily phase, through a slow process that takes several days. By comparing these results with those reported for the same two-liquid phase system in which a more concentrated solution of gold was used [13], it can be concluded that a decrease of the gold concentration in aqua regia changes the selectivity of the gold-reduction process toward the By comparing these results with those reported for the same two-liquid phase system in which a more concentrated solution of gold was used [13], it can be concluded that a decrease of the gold concentration in aqua regia changes the selectivity of the gold-reduction process toward the preferential formation of small gold clusters and isolated gold atoms over that of AuNPs, although the latter are still present. These results corroborate the efficiency of this simple two-liquid system to render small gold aggregates and isolated gold atoms.…”

“…Gold clusters were prepared from a two-liquid phase system following a procedure previously described [13][14][15]. A gold lump of 0.3290 g (99.99%, Royston Hertfordshire, UK) was dissolved under gentle stirring in 105.2 g of aqua regia, prepared by mixing (4:1, w/w) concentrated nitric acid (65 wt%, Panreac Química SLU, Castellar del Vallès, Spain) and ammonium chloride (Sigma-Aldrich, >98%, Merck KGaA, Darmstadt, Germany), while heating at 40 • C in a sand bath.…”

“…− species present in the latter are spontaneously reduced at the oil-water interphase and transferred to the essential oil. The presence of finely divided gold in the oil phase of these ancient preparations was already hypothesized by authors contemporary with the invention of the recipe, but only the modern replication of the procedure has confirmed the actual existence of AuNPs together with very small gold clusters and even isolated gold atoms, though the former dominate [13]. Following this procedure but using a gold concentration in aqua regia lower than that originally reported, we have been able to immobilize gold clusters prepared according to that procedure in ordered mesoporous materials (SBA-15) functionalized with mercaptopropyl groups.…”

“…Experimental and fitted29 Si MAS NMR (a) and13 C CP/MAS NMR spectra (b) of samples 0.11-E (top), 0.11-Au-17d (middle) and 0.20-ox-Au-8d (bottom).…”

Gold Nanoparticles in the Past: Before the Nanotechnology Era

“…Recently, a group of Spanish researchers has been able to reproduce a recipe of Aurum potabile of the eighteenth century and to probe the presence of gold nanoparticles in the solution. 6 A gold cordial was advocated in the seventeenth century for the treatment of ailments caused by a decrease in the vital spirits, such as melancholy, fainting, fevers and falling sickness. Later in the nineteenth century, a mixture of gold chloride and sodium chloride was used to treat syphilis.…”