The precise atomic structure of the recently synthesized "magic cluster" Au(20)(SR)(16) is predicted using ab initio calculations and global-minimum searches. The cluster contains a prolate Au(8) core and four level-3 extended staple motifs (-RS-Au-RS-Au-RS-Au-RS-). The simulated optical absorption spectra of the lowest-energy structures are in good agreement with the measured spectrum. The Au(20)(SR)(16) cluster, with a low Au/SR ratio of 1.25:1, may represent a structural evolution from core-free homoleptic clusters [Au(SR)](N) to core-stacked clusters.

Using the CO oxidation as a chemical probe, we perform a comprehensive ab initio study of catalytic activities of subnanometer gold clusters. Particular attention is placed on 12 different clusters in the size range of Au(16)-Au(35), whose atomic structures in the anionic state have been resolved from previous experiments. Adsorption energies of a single CO or O(2) molecule as well as coadsorption energies of both CO and O(2) molecules on various distinctive surface sites of each anionic cluster and their neutral counterpart are computed. In general, the anionic clusters can adsorb CO and O(2) more strongly than their neutral counterparts. The coadsorption energies of both CO and O(2) molecules decrease as the size of gold clusters increases with the exception of Au(34) (an electronic "magic-number" cluster). Besides the known factor of low coordination site, we find that a relatively small cone angle (<110°) associated with each surface site is another key geometric factor that can enhance the binding strength of CO and O(2). For the subnanometer clusters, although the size effect can be important to the strength of CO adsorption, it is less important to the activation energy. Using Au(34) as a prototype model, we show that strong CO and O(2) adsorption sites tend to yield a lower reaction barrier for the CO oxidation, but they have little effect on the stability of the reaction intermediate. Our calculations support the notion that CO and O(2) adsorption energies on the gold clusters can be an effective indicator to assess catalytic activities of subnanometer gold clusters. This systematic study of the site- and size-dependent adsorption energies and reaction pathways enables a quantitative assessment of the site-size-activity relationship for the CO oxidation on subnanometer gold clusters.

The structural evolution of negatively charged gold clusters (Au(n)(-)) in the medium size range for n = 27-35 has been investigated using photoelectron spectroscopy (PES) and theoretical calculations. New PES data are obtained using Ar-seeded He supersonic beams to achieve better cluster cooling, resulting in well-resolved spectra and revealing the presence of low-lying isomers in a number of systems. Density-functional theory calculations are used for global minimum searches. For each cluster anion, more than 200 low-lying isomers are generated using the basin-hopping global minimum search algorithm. The most viable structures and low-lying isomers are obtained using both the relative energies and comparisons between the simulated spectra and experimental PES data. The global minimum structures of Au(n)(-) (n = 27, 28, 30, and 32-35) are found to exhibit low-symmetry core-shell structures with the number of core atoms increasing with cluster size: Au(27)(-), Au(28)(-), and Au(30)(-) possess a one-atom core; Au(32)(-) features a three-atom triangular core; and Au(33)(-) to Au(35)(-) all contain a four-atom tetrahedral core. The global searches reveal that the tetrahedral core is a popular motif for low-lying structures of Au(33)(-) to Au(35)(-). The structural information forms the basis for future chemisorption studies to unravel the catalytic effects of gold nanoparticles.

Further development of high-voltage lithium-ion batteries requires electrolytes with electrochemical windows greater than 5 V. Sulfone-based electrolytes are promising for such a purpose. Here we compute the electrochemical windows for experimentally tested sulfone electrolytes by different levels of theory in combination with various solvation models. The MP2 method combined with the polarizable continuum model is shown to be the most accurate method to predict oxidation potentials of sulfone-based electrolytes with mean deviation less than 0.29 V. Mulliken charge analysis shows that the oxidation happens on the sulfone group for ethylmethyl sulfone and tetramethylene sulfone, and on the ether group for ether functionalized sulfones. Large electrochemical windows of sulfone-based electrolytes are mainly contributed by the sulfone group in the molecules which helps lower the HOMO level. This study can help understand the voltage limits imposed by the sulfone-based electrolytes and aid in designing new electrolytes with greater electrochemical windows.

Current standard of care dressings are unsatisfactorily inefficacious for the treatment of chronic wounds. Chronic inflammation is the primary cause of the long‐term incurable nature of chronic wounds. Herein, an absorbable nanofibrous hydrogel is developed for synergistic modulation of the inflammation microenvironment to accelerate chronic diabetic wound healing. The electrospun thioether grafted hyaluronic acid nanofibers (FHHA‐S/Fe) are able to form a nanofibrous hydrogel in situ on the wound bed. This hydrogel degrades and is absorbed gradually within 3 days. The grafted thioethers on HHA can scavenge the reactive oxygen species quickly in the early inflammation phase to relieve the inflammation reactions. Additionally, the HHA itself is able to promote the transformation of the gathered M1 macrophages to the M2 phenotype, thus synergistically accelerating the wound healing phase transition from inflammation to proliferation and remodeling. On the chronic diabetic wound model, the average remaining wound area after FHHA‐S/Fe treatment is much smaller than both that of FHHA/Fe without grafted thioethers and the control group, especially in the early wound healing stage. Therefore, this facile dressing strategy with intrinsic dual modulation mechanisms of the wound inflammation microenvironment may act as an effective and safe treatment strategy for chronic wound management.

A total structural determination of the Au(102)(p-MBA)(44) nanocluster has been recently achieved via successful crystallization of the thiolated-protected gold nanocluster (Jadzinsky et al. Science 2007, 318, 430). The embedded Au(102) cluster may be viewed as a multilayered structure described as Au(54)(penta-star)@Au(38)(ten wings)@Au(10)(two pentagon caps), where the inner Au(54) "penta-star" consists of five twinned Au(20) tetrahedral subunits. To gain more insight into high stability of the Au(102)(p-MBA)(44) nanocluster, we have performed ab initio calculations to study electronic properties of a homologue Au(102)(SCH(3))(44) nanocluster, an Au(102)(SCH(3))(42) nanocluster (with two SCH(3) groups less), and an "effectively isoelectronic" Au(104)(SCH(3))(46) nanocluster with a more symmetric embedded Au(104) structure. Electronic structure calculations suggest that the Au(102)(SCH(3))(44) nanocluster possesses a reasonably large gap (approximately 0.54 eV) between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO-LUMO gap), which is comparable to the measured HOMO-LUMO gap (approximately 0.65 eV) of the bare Au(58) cluster. Likewise, the Au(104)(SCH(3))(46) nanocluster has a HOMO-LUMO gap of approximately 0.51 eV, comparable to that of Au(102)(SCH(3))(44) nanocluster. In contrast, the Au(102)(SCH(3))(42) nanocluster has a zero HOMO-LUMO gap. These results confirm that high stability of the Au(102)(p-MBA)(44) nanocluster may be attributed in part to the electronic shell closing of effective 58 (= 102 - 44) valence electrons, as in the case of Au(25)(SCH(2)CH(2)Ph)(18)(-) cluster whose high stability may be attributed to the electronic shell closing of effective 8 (= 26 -18) valence electrons.

We present an ab initio investigation of structural, electronic, catalytic, and selective properties of the ligand-covered gold nanoparticle Au55(PPh3)12Cl6 and associated model clusters. The catalytic activity of the Au55(PPh3)12Cl6 nanoparticle in the presence of O2 stems from a combined effect of triphenylphosphine ligands and surface structure of the "magic-number" quasi-icosahedral Au55 core, which entails numerous ligand-encompassed triangle Au6 faces as the active sites. Under the Eley-Rideal mechanism, the "triangle-socket" active site not only can accommodate one pre-adsorbed O2 (which is subsequently activated to the superoxo species) with one styrene molecule at a time but also can provide spatial confinement which favors the formation of an oxametallacycle intermediate that leads to unique selectivity in styrene oxidation.

Structural and catalytic properties of the gold alloy nanocluster Au(43)Cu(12) are investigated using a density-functional method. In contrast to the pure Au(55) nanocluster, which exhibits a low-symmetry C(1) structure, the 55-atom "crown gold" nanocluster exhibits a multishell structure, denoted by Au@Cu(12)@Au(42), with the highest icosahedral group-symmetry. In addition, density functional calculations suggest that this geometric magic-number nanocluster possesses comparable catalytic capability as a small-sized Au(10) cluster for the CO oxidation, due in part to their low-coordinated Au atoms on vertexes. The gold alloy nanocluster also shows higher selectivity for styrene oxidation than the bare Au(111) surface.