Au(SR) Nanocluster and a Periodic Pattern from Six to Fourteen Free Electrons in Core Size Evolution.

An Au(S-Bu) nanocluster (NC) is synthesized using the bulky -butyl thiol as the ligand. Single-crystal X-ray crystallography reveals that it has an Au core which evolves from the Au core in the previously reported Au(S-Bu), and the Au core is protected by longer staple-like surface motifs. The new Au NC extends the members of the face-centered cubic structural evolution by adding an Au triangle and an Au tetrahedron unit.

Dissecting Critical Factors for Electrochemical CO Reduction on Atomically Precise Au Nanoclusters.

This work investigates the critical factors impacting electrochemical CO reduction reaction (CO RR) using atomically precise Au nanoclusters (NCs) as electrocatalysts. First, the influence of size on CO RR is studied by precisely controlling NC size in the 1-2.5 nm regime.

High current density electroreduction of CO into formate with tin oxide nanospheres.

In this study, we demonstrate three-dimensional (3D) hollow nanosphere electrocatalysts for CO conversion into formate with excellent H-Cell performance and industrially-relevant current density in a 25 cm membrane electrode assembly electrolyzer device. Varying calcination temperature maximized formate production via optimizing the crystallinity and particle size of the constituent SnO nanoparticles. The best performing SnO nanosphere catalysts contained ~ 7.

The role of ligands in atomically precise nanocluster-catalyzed CO electrochemical reduction.

Ligand effects are of major interest in catalytic reactions owing to their potential critical role in determining the reaction activity and selectivity. Herein, we report ligand effects in the CO2 electrochemical reduction reaction at the atomic level with three unique Au25 nanoclusters comprising the same kernel but different protecting ligands (-XR, where X = S or Se, and R represents the carbon tail). It is observed that a change in the carbon tail shows no obvious impact on the catalytic selectivity and activity, but the anchoring atom (X = S or Se) strongly affects the electrocatalytic selectivity.

Boosting CO Electrochemical Reduction with Atomically Precise Surface Modification on Gold Nanoclusters.

Thiolate-protected gold nanoclusters (NCs) are promising catalytic materials for the electrochemical CO reduction reaction (CO RR). In this work an atomic level modification of a Au NC is made by substituting two surface Au atoms with two Cd atoms, and it enhances the CO RR selectivity to 90-95 % at the applied potential between -0.5 to -0.

A Mono-cuboctahedral Series of Gold Nanoclusters: Photoluminescence Origin, Large Enhancement, Wide Tunability, and Structure-Property Correlation.

The origin of the near-infrared photoluminescence (PL) from thiolate-protected gold nanoclusters (Au NCs, <2 nm) has long been controversial, and the exact mechanism for the enhancement of quantum yield (QY) in many works remains elusive. Meanwhile, based upon the sole steady-state PL analysis, it is still a major challenge for researchers to map out a definitive relationship between the atomic structure and the PL property and understand how the Au(0) kernel and Au(I)-S surface contribute to the PL of Au NCs. Herein, we provide a paradigm study to address the above critical issues.

Efficient electrochemical CO2 conversion powered by renewable energy.

The catalytic conversion of CO2 into industrially relevant chemicals is one strategy for mitigating greenhouse gas emissions. Along these lines, electrochemical CO2 conversion technologies are attractive because they can operate with high reaction rates at ambient conditions. However, electrochemical systems require electricity, and CO2 conversion processes must integrate with carbon-free, renewable-energy sources to be viable on larger scales.

Tuning the Magic Size of Atomically Precise Gold Nanoclusters via Isomeric Methylbenzenethiols.

Toward controlling the magic sizes of atomically precise gold nanoclusters, herein we have devised a new strategy by exploring the para-, meta-, ortho-methylbenzenethiol (MBT) for successful preparation of pure Au130(p-MBT)50, Au104(m-MBT)41 and Au40(o-MBT)24 nanoclusters. The decreasing size sequence is in line with the increasing hindrance of the methyl group to the interfacial Au-S bond. That the subtle change of ligand structure can result in drastically different magic sizes under otherwise similar reaction conditions is indeed for the first time observed in the synthesis of thiolate-protected gold nanoclusters.

Synthesis of ultrasmall platinum nanoparticles and structural relaxation.

We report the synthesis of ligand-protected, ultrasmall Pt nanoparticles of ∼1 nm size via a one-phase wet chemical method. Using matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), we determined the mass of the nanoparticles to be ∼8 kDa. Characterization of the Pt nanoparticles was further carried out by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), optical absorption spectroscopy, and X-ray photoelectron spectroscopy (XPS).

Photomediated Oxidation of Atomically Precise Au25(SC2H4Ph)18(-) Nanoclusters.

The anionic charge of atomically precise Au25(SC2H4Ph)18(-) nanoclusters (abbreviated as Au25(-)) is thought to facilitate the adsorption and activation of molecular species. We used optical spectroscopy, nonaqueous electrochemistry, and density functional theory to study the interaction between Au25(-) and O2. Surprisingly, the oxidation of Au25(-) by O2 was not a spontaneous process.

Experimental and computational investigation of Au25 clusters and CO2: a unique interaction and enhanced electrocatalytic activity.

Atomically precise, inherently charged Au(25) clusters are an exciting prospect for promoting catalytically challenging reactions, and we have studied the interaction between CO(2) and Au(25). Experimental results indicate a reversible Au(25)-CO(2) interaction that produced spectroscopic and electrochemical changes similar to those seen with cluster oxidation. Density functional theory (DFT) modeling indicates these changes stem from a CO(2)-induced redistribution of charge within the cluster.

Graphene versus carbon nanotubes for chemical sensor and fuel cell applications.

Graphene, an atomically thin layer of sp(2) hybridized carbon, has emerged as a promising new nanomaterial for a variety of exciting applications including chemical sensors and catalyst supports. In this article, we survey modern methods of graphene production and functionalization with an emphasis on the development of chemical sensors and fuel cell electrodes with brief comparisons to state-of-the-art carbon nanotube-based systems.

Understanding the sensor response of metal-decorated carbon nanotubes.

We have explored the room temperature response of metal nanoparticle decorated single-walled carbon nanotubes (NP-SWNTs) using a combination of electrical transport, optical spectroscopy, and electronic structure calculations. We have found that upon the electrochemical growth of Au NPs on SWNTs, there is a transfer of electron density from the SWNT to the NP species, and that adsorption of CO molecules on the NP surface is accompanied by transfer of electronic density back into the SWNT. Moreover, the electronic structure calculations indicate dramatic variations in the charge density at the NP-SWNT interface, which supports our previous observation that interfacial potential barriers dominate the electrical behavior of NP-SWNT systems.

Electrocatalytic activity of nitrogen-doped carbon nanotube cups.

The electrochemical activity of stacked nitrogen-doped carbon nanotube cups (NCNCs) has been explored in comparison to commercial Pt-decorated carbon nanotubes. The nanocup catalyst has demonstrated comparable performance to that of Pt catalyst in oxygen reduction reaction. In addition to effectively catalyzing O(2) reduction, the NCNC electrodes have been used for H(2)O(2) oxidation and consequently for glucose detection when NCNCs were functionalized with glucose oxidase (GOx).

Decorated carbon nanotubes with unique oxygen sensitivity.

The relatively simple and robust architecture of microelectronic devices based on carbon nanotubes, in conjunction with their environmental sensitivity, places them among the leading candidates for incorporation into ultraportable or wearable chemical analysis platforms. We used single-walled carbon nanotube (SWNT) networks to establish a mechanistic understanding of the solid-state oxygen sensitivity of a Eu(3+)-containing dendrimer complex. After illumination with 365 nm light, the SWNT networks decorated with the Eu(3+) dendrimer show bimodal (optical spectroscopic and electrical conductance) sensitivity towards oxygen gas at room temperature under ambient pressure.

Carbon nanotube gas and vapor sensors.

Carbon nanotubes have aroused great interest since their discovery in 1991. Because of the vast potential of these materials, researchers from diverse disciplines have come together to further develop our understanding of the fundamental properties governing their electronic structure and susceptibility towards chemical reaction. Carbon nanotubes show extreme sensitivity towards changes in their local chemical environment that stems from the susceptibility of their electronic structure to interacting molecules.

Electronically monitoring biological interactions with carbon nanotube field-effect transistors.

The year 2008 marks the 10th anniversary of the carbon nanotube field-effect transistor (NTFET). In the past decade a vast amount of effort has been placed on the development of NTFET based sensors for the detection of both chemical and biological species. Towards this end, NTFETs show great promise because of their extreme environmental sensitivity, small size, and ultra-low power requirements.

Single-walled carbon-nanotube spectroscopic and electronic field-effect transistor measurements: a combined approach.

Spectroscopic and electronic field-effect transistor measurements reveal complimentary information about molecular interactions with single-walled carbon nanotubes (SWNTs). Here we demonstrate how these two complimentary techniques can be combined to further understand electronic modifications of the SWNTs. The complimentary nature of these techniques stems from the perturbation of the electronic structure of SWNTs upon electronic interaction with an electron-donating, or -accepting species.

Chemically induced potential barriers at the carbon nanotube-metal nanoparticle interface.

Single-walled carbon nanotube (SWNT) field effect transistors were electrochemically decorated with Pt, Pd, Au, and Ag nanoparticles. Upon exposure to 10 ppm NO gas in N2 a trend was found wherein the magnitude of electron transfer into the SWNT valence band scaled with the work function of the individual metal. This trend gives experimental support for the formation of a metal work function dependent potential barrier at the SWNT--nanoparticle interface.