An exciting discovery in the area of heterogeneous catalysis is the observation that nanoparticles of gold on high-surfacearea supports exhibit high activity for oxidation of CO with O 2 (CO + 1/2 O 2 !CO 2 ) at room temperature. [1,2] This discovery is of particular relevance for the production of fuel-cell-grade hydrogen, since carbon monoxide must be removed from hydrogen streams generated by catalytic reforming of hydrocarbons.[3] The origins for the unique catalytic properties of supported gold catalysts are still unresolved. These properties have been related to changes in the electronic properties, the presence of defect sites, and the existence of strain for metallic gold nanoparticles. [4][5][6][7][8] Unique catalytic properties have also been related to the presence of sites associated with the catalyst support, such as cationic gold species, and sites at gold-support interfaces. [9,10] Here we show that it is possible to study the catalytic properties of metallic gold, without interference from a catalyst support, by using nanotubes of gold in polycarbonate membranes. These nanotubes exhibit catalytic activity for the oxidation of carbon monoxide by O 2 at room temperature, and this activity is enhanced by liquid water, promoted by increasing the pH of the solution, and increased using H 2 O 2 as the oxidizing agent. The rate can also be increased by depositing KOH within these nanotubes. These rates are comparable with those found in heterogeneous catalysis studies with gold nanoparticles on oxide supports, which suggests that the high activity of these latter catalysts may be related to the promotional effect of hydroxyl groups.Gold nanotubes of uniform size were prepared via a template-synthesis method by electroless deposition of gold [11] within the pores of a 10-mm-thick, track-etched polycarbonate membrane containing 220-nm-diameter pores.[12] All surfaces of the template membrane were first sensitized with a Sn II salt, activated by formation of a metallic Ag layer, followed by electroless deposition of gold for a period of 2 h. The gold nanotubes were cleaned with a 25 % HNO 3 solution for 15 h.[13] Hydrophobic or hydrophilic selfassembled monolayers were formed on gold nanotubes by rinsing the samples in ethanol for 20 min, followed by immersion for 17 h in solutions of ethanol containing HS(CH 2 ) 15 CH 3 or HS(CH 2 ) 15 COOH, respectively. [14] Gold nanotubes embedded within the pores of the polycarbonate template membranes were exposed by reactive ion etching (RIE) using an oxygen plasma to selectively etch approximately 2.3 mm of polycarbonate, leaving the gold nanotubes intact.[15] Figure 1 shows images from field-emission scanning electron microscopy (SEM) of the top surface of a template membrane after electroless deposition of gold followed by RIE. The images in Figure 1 reveal a high level of surface roughness; the length scale is % 53 nm. The membrane reactor used to study CO oxidation over gold nanotubes is shown schematically in Figure 2.[12] Table 1 shows results for the rate of...

An exciting discovery in the area of heterogeneous catalysis is the observation that nanoparticles of gold on high-surfacearea supports exhibit high activity for oxidation of CO with O 2 (CO + 1/2 O 2 !CO 2 ) at room temperature. [1,2] This discovery is of particular relevance for the production of fuel-cell-grade hydrogen, since carbon monoxide must be removed from hydrogen streams generated by catalytic reforming of hydrocarbons.[3] The origins for the unique catalytic properties of supported gold catalysts are still unresolved. These properties have been related to changes in the electronic properties, the presence of defect sites, and the existence of strain for metallic gold nanoparticles. [4][5][6][7][8] Unique catalytic properties have also been related to the presence of sites associated with the catalyst support, such as cationic gold species, and sites at gold-support interfaces. [9,10] Here we show that it is possible to study the catalytic properties of metallic gold, without interference from a catalyst support, by using nanotubes of gold in polycarbonate membranes. These nanotubes exhibit catalytic activity for the oxidation of carbon monoxide by O 2 at room temperature, and this activity is enhanced by liquid water, promoted by increasing the pH of the solution, and increased using H 2 O 2 as the oxidizing agent. The rate can also be increased by depositing KOH within these nanotubes. These rates are comparable with those found in heterogeneous catalysis studies with gold nanoparticles on oxide supports, which suggests that the high activity of these latter catalysts may be related to the promotional effect of hydroxyl groups.Gold nanotubes of uniform size were prepared via a template-synthesis method by electroless deposition of gold [11] within the pores of a 10-mm-thick, track-etched polycarbonate membrane containing 220-nm-diameter pores.[12] All surfaces of the template membrane were first sensitized with a Sn II salt, activated by formation of a metallic Ag layer, followed by electroless deposition of gold for a period of 2 h. The gold nanotubes were cleaned with a 25 % HNO 3 solution for 15 h.[13] Hydrophobic or hydrophilic selfassembled monolayers were formed on gold nanotubes by rinsing the samples in ethanol for 20 min, followed by immersion for 17 h in solutions of ethanol containing HS(CH 2 ) 15 CH 3 or HS(CH 2 ) 15 COOH, respectively. [14] Gold nanotubes embedded within the pores of the polycarbonate template membranes were exposed by reactive ion etching (RIE) using an oxygen plasma to selectively etch approximately 2.3 mm of polycarbonate, leaving the gold nanotubes intact.[15] Figure 1 shows images from field-emission scanning electron microscopy (SEM) of the top surface of a template membrane after electroless deposition of gold followed by RIE. The images in Figure 1 reveal a high level of surface roughness; the length scale is % 53 nm. The membrane reactor used to study CO oxidation over gold nanotubes is shown schematically in Figure 2.[12] Table 1 shows results for the rate of ...

In the last few years gold nanoparticles (AuNPs) became extremely interesting materials due to their enhanced optical, chemical and electrical properties. With the intention of taking advantage of those properties, the use of AuNPs has spread into a wide variety of areas such as physics, chemistry, biology, industry and medicine. More interestingly, their ability to form robust conjugates with biomolecules has given proteomics a new tool to improve aspects where the current methods to study proteins and their interactions in living cells cannot achieve the success required. In this review we present some of the current methods for AuNPs synthesis, the tailoring of their surface with ligands to improve stability and strategies to conjugate with biomolecules. Lastly, we also discuss their application in proteomic methods and recent developments in clinical diagnosis.

Adsorption of enzymes to nanoparticles and the mechanisms responsible for enzyme activity modulation of adsorbed enzymes are not well understood. In this work, gold nanoparticles were used for electrostatic adsorption of a plant-derived laccase. Adsorption constants were determined by four independent techniques: dynamic light scattering, electrophoretic light scattering, agarose gel electrophoresis and fluorescence quenching. Stable bionanoconjugates were formed with log K in the range 6.8-8.9. An increase in enzyme activity was detected, in particular at acidic and close to neutral pH values, a feature that expands the useful pH range of the enzyme. A model for the adsorption was developed, based on geometrical considerations and volume increase data from dynamic light scattering. This indicates that enzymes adsorbed to gold nanoparticles are ca. 9 times more active than the free enzyme.

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