Reaction of Pyrrole and Chlorauric Acid A New Route to Composite Colloids

Abstract

Composite colloids of gold and polypyrrole were prepared using two different methods: 1, using pyrrole colloid, created by the oxidation of pyrrole by ferric chloride, to subsequently reduce chlorauric acid and, 2, oxidizing pyrrole monomer with chlorauric acid in a sodium dodecylbenzene sulfonate solution. In each case, the polypyrrole colloid consisted of irregularly shaped particles approximately 500 nm in diameter. The gold produced in each case was in the form of irregular spheres, approximately 407 nm in diameter in method 1 and 13 nm in method 2. X-ray photoelectron spectroscopy was used to determine the oxidation state of the species present. Transmission electron microscopy and light scattering data were used to determine the particle sizes of both gold and polypyrrole colloids. Energy dispersed spectrum X-ray analysis and electron diffraction were used to confirm the presence of metallic gold in the composite colloids. The second-order rate constant for the reaction of chlorauric acid with pyrrole in dilute solution was found to be 13 M Ϫ1 s Ϫ1 . Aqueous solutions of palladium, platinum, rhodium, cobalt, tin, silver, zinc, nickel, titanium, cadmium, mercury, arsenic, and selenium were also examined for their potential to act as oxidants to produce composite polypyrrole colloids. Palladium, platinum, and rhodium salts were suitable oxidants, producing polypyrrole in less than 12 h.Methods for the preparation of colloidal gold have been known for hundreds of years. 1 Over this time, colloidal metals have found applications in biochemistry, 2 cytology, 3 microscopy, 4 and catalysis 5 as described in recent reviews. Most of the procedures used to prepare colloidal metals rely on micelles as a stabilizer containing either metal salts or a reductant, thereby acting as microreactors to control the size distribution of the metal particles produced. The various morphologies that can be produced by this method have been described as ''cherries'' ͑one central metal particle͒, ''raspberries'' ͑multiple internal particles͒, ''strawberries'' ͑a layer of metal particles outside the micelle boundary͒, and ''red currant'' or ''ginger root'' ͑a dendritic type with strings of metal particles radiating away from the central micelle͒. 6 Under conditions in which the reductant is a monomer that undergoes oxidative polymerization, a polymer/metal composite colloid can be formed. These are unique materials, with interesting electronic, 7 magnetic, 8,9 optical, 10 and nonlinear optical properties, 11 depending on the metal and polymer employed. The metal thus supported can also be catalytically 6,12,13 or electrochemically 14-16 useful, especially with a conducting polymer as part of the system. Especially in terms of catalysis, polymer-supported precious metals have many applications. For example, polymer-supported platinum and rhodium catalysts have been used to carry out hydrogenation reactions. 12 The polymer allows the control of the environment around the metal center, thus influencing selectivity of the hydrogenation rea...

Oxidation and photo-induced oxidation of glucose at a polyaniline film modified by copper particles

“…In recent years there have been many reported studies on the incorporation of metal particles within a conducting polymer matrix, such as polyaniline or polypyrrole [1][2][3][4][5][6][7]. This incorporation can be achieved readily by the reduction of the appropriate metal salt at the conducting polymer interface.…”

Conducting Polymer-Metal Nanocomposite Coating on Fibers

“…Chen et al (Chen et al, 2005;Chen et al, 2005) and the present authors (Fujii et al, 2007) have demonstrated a one-step facile and versatile synthetic route to PPy-Ag nanocomposites by chemical oxidative polymerization using AgNO 3 as an oxidant in aqueous media. Henry et al (Henry et al, 2001) and the present authors suggested that PdCl 2 acts as an efficient oxidant for pyrrole to form PPy-Pd composite in aqueous media (Scheme 1). More recently, Vasilyeva et al (Vasilyeva et al, 2008) described the synthesis of PPy-Pd nanocomposites via direct redox reaction between Pd(II) acetate and pyrrole in acetonitrile.…”

“…The coating of such conducting polymer-metal nanocomposite on the substrates typically requires more than two steps including purification steps: (i) coating of the substrates with a conductive polymer and (ii) application of metal nanoparticles onto the conducting polymer shells. Recently, it was reported that conducting polymer-noble metal nanocomposites can be synthesized by a one-step chemical oxidative polymerization using metal salts as an oxidant (Scheme 1) (Selvan et al, 1998;Chen et al, 2005;Chen et al, 2005;Fujii et al, 2007;Freund et al, 2001;Vasilyeva et al, 2008;. It was demonstrated that chemical oxidative polymerization using metal salts such as hydrogen tetrachloroaurate(III), silver nitrate (AgNO 3 ), palladium(II) chloride (PdCl 2 ), and hydrogen hexachloroplatinate(IV) (H 2 PtCl 6 ), which act both as an oxidant and as a source of metal atoms, yielded well-dispersed metal nanoparticles in/on bulk conducting polymers.…”

Stability and particle size of polypyrrole dispersion using sodium dodecylbenzenesulfonate as surfactant

“…On the other hand, the size distributions of sterically stabilized PPy colloids were determined based on a charge-velocity analysis with various steric stabilizers [18]. Apart from that, dynamic light scattering (DLS) being an effective way to determine the particle size of colloids has also been used for the measurement of the particle size of the PPy colloids and it showed that the results based on DLS were in agreement with those from the observation of transmission electron microscopy [19]. However, there are few reports systemically discussing the change of the particle size of PPy dispersion from different preparation conditions.…”