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Protected Metallic Clusters, Quantum Wells and Metal-Nanocrystal Molecules This Special Issue is based on a symposium “Protected Metallic Clusters, Quantum Wells and Metal-Nanocrystal Molecules” during the 238th ACS National Meeting in Washington, DC, August 16-20, 2009, co-organized by Dr. Ignacio Garzon and Dr. Theodore Goodson III. We would like to thank the invited speakers of the meeting, many of whom agreed to contribute to this Issue, as well as those contributing authors who were not able to travel to the meeting. In our opinion, this Special Issue1 succeeds well in giving a snapshot of the diverse and dynamic research area of metal clusters and nanoparticles made and stabilized by wet chemical methods. Ligand-monolayer-protected nanometer-sized gold clusters continue to attract significant interest that is intensified by the recent breakthroughs in total-structure-determination and accompanied theoretical understanding of thiolate-protected Au25(SR)18, Au38(SR)24, and Au102(SR)44 (for concise overviews of the recent progress, see Introduction of refs 2 and 3). In this Issue, reactivity studies of the well-known Au25(SR)18-1 cluster with metal ions are reported,4 with a motivation to understand mechanisms by which bimetal cores can be formed. Thiolate-protected gold clusters are luminescent; emission of Au38 and Au55 clusters are discussed here.5,6 A refined composition assignment is reported from MALDI experiments for the 11 kDa gold cluster.2 Chemistries to stabilize gold nanoparticles with calixarenes,7 cyclodextrins,8 and chiral BINAS molecules9 are explored and place-exchange reactions on a large nanoparticle surface are reported.10 Nanometer-size gold clusters are gaining advantage for bioimaging and biolabeling; here formation and stabilization of luminescent nanoclusters in Good’s buffers are reported,11 and the rigidity of protein-bound Au144 clusters is discussed.12 Finally, laser-induced formation kinetics and surfactant-modified particle size distributions of gold nanoparticles in aqueous solutions are reported.13 Theoretical work on small ligand-protected gold clusters has progressed hand-in-hand with many of the experiments, enjoying the firm ground of resolved atomic structures of Au25, Au38, and Au102.3,14-19 In this Issue, material systems made out of the known Au25(SR)18 cluster are investigated,3 plausible structures of the yet-unknown Au44(SR)282- cluster are explored,14 and solvation effects around a passivated and redox-active ligated Au55 cluster with hypothetical structures are studied.15 For the smallest clusters, theory is now able to reveal thiolate-for-thiolate ligand-exchange mechanisms,16 or predict properties of “superhalogen” coinage-metal complexes.17 The detailed atomic structure of the metal-thiolate interface of other noble metal (Cu, Ag) clusters continues to be an unsolved issue; a computational study here makes a contribution by comparing structures and energetics of thiolate-SAMs on Au(111) and Cu(111).18 Silver nanoclusters are interesting due to their optical properties, but problems in long-term stability have impeded their precise compositional assignments. This Issue contains four reports on synthesis of ligand-protected silver clusters from the small size (less than 2 nm)20-22 to colloidal particles.23 Of particular interest are the chiroptical response, found as “as-prepared”20,22 or as induced by complexation to chiral molecules.21 Synthesis of stable copper and silver clusters is likely to draw more attention in the near future, here an
electrochemical method for making stable few-atom copper clusters is reported.24 The bulk of the research on the passivated noble metal clusters relies on the controllable chemistry of the metal-thiol(ate) or metal-phosphine bonds. Nanoparticles or clusters stabilized by other metal-ligand bonds have received less attention. Here, synthesis of stable alkyne-protected ruthenium nanoparticles, featuring direct metal-carbon bonds is reported.25 Stability of metal clusters, both in gas phase and as stabilized by ligands, is intimately related to the electronic structure. A combined experimental and theoretical work investigates here the stability of mixed bismuth-indium clusters in gas phase.26 Finally, this Issue highlights also work on larger-scale nanoand mesostructures. Wet chemical methods are applied to synthesize magnetic Au/Ni, Au/Co, and Au/Pt/Ni “mesoflowers”.27 A technique for measuring the extinction cross section of anisotropic nanomaterials is described.28 In the theoretical front, nonlocal dielectric effects in core-shell nanowires are numerically studied.29 References and Notes (1) The papers in this Issue are indicated by the DOI number in lieu of the page numbers. (2) Tsukuda, T.; et al. J. Phys. Chem. C 2010, [Online early access]. DOI: 10.1021/jp101741a. (3) Häkkinen, H.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp1015438. (4) Murray, R.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp9101114. (5) Merijerink, A.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp1018372. (6) Goodson, T., III; et al. J. Phys. Chem. C 2010, [Online early access]. DOI: 10.1021/jp101420g. (7) Katz, A.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp104122m. (8) Choi, M.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp101571k. (9) Burgi, T.; et al. J. Phys. Chem. C 2010, [Online early access]. DOI: 10.1021/jp910800m. (10) Pinedaresa, T.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp9122387. (11) Martinez, J.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp909580z. (12) Ackerson, C.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp101970x. (13) Buntine, M.; et al. J. Phys. Chem. C 2010, [Online early access]. DOI: 10.1021/jp9118315. (14) Jiang, D.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp9097342. (15) Remacle, F.; et al. J. Phys. Chem. C 2010, [Online early access]. DOI: 10.1021/jp9119827. (16) Aikens, C.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp911054e. (17) Jena, P.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp101807s. (18) Gro¨nbeck, H.; et al. J. Phys. Chem. C 2010, [Online early access]. DOI: 10.1021/jp100278p. (19) Gascon, J.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp102585n. (20) Fitaev, V.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp101764q. (21) Yao, H.; et al. J. Phys. Chem. C 2010, [Online early access]. DOI: 10.1021/jp910875s. (22) Markovich, G.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp911968x. (23) Bigioni, T.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp911316e. (24) Vilar-Vidal, N.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp911380s.
10.1021/jp107501p 2010 American Chemical Society Published on Web 09/23/2010
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J. Phys. Chem. C, Vol. 114, No. 38, 2010
(25) Chen, S.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp101053c. (26) Castelman, A. W.; et al. J. Phys. Chem. C 2010, [Online early access]. DOI: 10.1021/jp1000754. (27) Pradeep, T. P. R.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp103198e. (28) Hartman, G.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp101891a. (29) McMahon, J. M.; et al. J. Phys. Chem C 2010, [Online early access]. DOI: 10.1021/jp910899b.
Ha¨kkinen and Whetten
Hannu Ha¨kkinen UniVersity of JyVa¨skyla¨ Robert L. Whetten Georgia Institute of Technology JP107501P
