PCCP Blog

Paul Mulvaney and co-workers investigate the optical properties of an end-to-end assembly of gold nanorods in their recent PCCP paper.

The group from the University of Melbourne used optical and electron microscopy to study the scattering properties of colloidal gold nanorods aligned end-to-end via dithiol coupling at the single particle level. They found that the nanostructures exhibited polarization-dependant optical properties, due to selective excitation of collective bonding and antibonding modes.

The authors were interested in how the angle between plasmonic structures affects coupling. They examined the coupling between both gold nanorod dimers and rod-sphere-rod trimers as a function of subtended angles of the dimer and trimer. They found that the intensity of the resonance in dimers and trimers depends strongly on the angles within the assembled structure. Additionally, they determined that the coupled longitudinal surface plasmon resonance of coupled Au nanorods exhibited a red shift as the number of rods in the chain increased.

Read this HOT article today:

Surface plasmon coupling in end-to-end linked gold nanorod dimers and trimers
Jatish Kumar, Xingzhan Wei, Steven Barrow, Alison M. Funston, K. George Thomas and Paul Mulvaney
DOI: 10.1039/C3CP44657C

If you enjoyed this article you will enjoy our themed issue on optical studies of single metal nanoparticles. Take a look!

Emilie Ringe and co-authors have comprehensively reviewed recent progress in single particle studies of plasmonic nanostructures. They also highlight the exciting and very interdisciplinary future prospects for this field.

The authors discuss methods of characterisation of single metallic nanoparticles, covering both near-field and far-field approaches. They focus on what can uniquely be learnt from these methods, including the fundamental properties of such particles and their relation to, for example, particle shape and environment. Additionally, they explicate potential applications potential applications, notably in sensing.

Read this timely PCCP Perspective today:

Single nanoparticle plasmonics
Emilie Ringe, Bhavya Sharma, Anne-Isabelle Henry, Laurence D. Marks and Richard P. Van Duyne
DOI: 10.1039/C3CP44574G

Scientists from Japan have discovered that the synchronization of Cu and Ce valence charge in Cu/CeO2 catalysts can improve the catalytic activity for NO reduction.  They used an operando time-resolved XAFS technique at the Cu and Ce k-edges to study the catalytic NO reduction under periodic (rich-lean cycling) operation.

Read the details in this PCCP communication:

Operando XAFS study of catalytic NO reduction over Cu/CeO2: the effect of copper–ceria interaction under periodic operation
Yasutaka Nagai, Kazuhiko Dohmae, Yusaku F. Nishimura, Hitoshi Kato, Hirohito Hirata and Naoki Takahashi DOI: 10.1039/C3CP44316G

Scientists from the USA suggest that plant-derived volatile organic compounds are more likely to react with OH at the air-water interface than inside the bulk of water droplets or in the vapour phase. They carried out molecular dynamics simulations of an organic compound in green leaf volatiles, MBO, and OH radicals at air-water interfaces bringing new insight into their absorption behaviours.

Green leaf volatiles are oxygenated hydrocarbons that are emitted by plants, especially under stress conditions such as mechanical damage and local weather changes. MBO is an unsaturated alcohol which is emitted in large quantities by some species of pine and can be oxidised by radicals including OH. MBO and other green leaf volatiles can be a source of secondary organic aerosols in the atmosphere, which play an important role in climate. Currently secondary organic aerosols are not well understood, and are an important factor in the smog-fog-smog cycle.

Read more in this HOT PCCP article:

Molecular simulations of green leaf volatiles and atmospheric oxidants on air/water interfaces
Thilanga P. Liyana-Arachchi, Christopher Stevens, Amie K. Hansel, Franz S. Ehrenhauser, Kalliat T. Valsaraj and Francisco R. Hung
DOI: 10.1039/C3CP44090G

In their PCCP perspective on nanogap-enhanced SERS, Natelson, Li and Herzog discuss the rich and fascinating plasmonic physics at work in these systems.

In their recent PCCP communication, Richard Compton et al. explore gold electrocatalytic activity and report very interesting differences between the macro-and nano-scales.

The researchers from Oxford University, UK, applied the procedure of consecutive electro-oxidation and reduction cycling in sulphuric acid medium to electrodeposited nanoparticles. Whereas this method is commonly used as a cleaning and calibration procedure for gold macro-electrodes, the method was found to have a negative effect on the surface of gold nanoparticles.

It has previously been thought that this surface cleaning method can be effectively applied to gold nanoparticles on the assumption that their behaviour is the same as the bulk behaviour. Compton et al. correctly question this assumption and suggest that changes in the surface morphology and/or composition of the nanoparticles during the cycling treatment may cause the damaging effects on the gold nanoparticle-modified electrode.

Read more detail in this article today:

Surface oxidation of gold nanoparticles supported on a glassy carbon electrode in sulphuric acid medium: contrasts with the behaviour of ‘macro’ gold
Ying Wang, Eduardo Laborda, Alison Crossley and Richard G. Compton
DOI: 10.1039/C3CP44615H

In their recent PCCP Perspective, Maxim Prigozhin and Martin Gruebele from the Center for Biophysics and Computational Biology, Urbana, USA, provide an excellent overview of the recent developments in the area of protein folding on the microsecond timescale.

Their Perspective compares recent experiments and simulations that have progressed the understanding of complex problems of multiple reaction coordinates, downhill folding, and intricate underlying structures of unfolded or misfolded states.

Advances in computing power and force fields in the late 1990s made it possible to directly compare protein folding experiments and simulations on the microsecond time-scale. Since then, understanding of how small globular proteins fold has made much progress.

With the continuing developments in both computing power and experimental methodology, this article highlights that exciting things in protein science are still to come!

Read this Perspective today:

Microsecond folding experiments and simulations: a match is made
M. B. Prigozhin and M. Gruebele
DOI: 10.1039/C3CP43992E

You may be interested in our themed collection Biophysics and Biophysical Chemistry in PCCP.

Grant McIntosh from the University of Auckland, New Zealand, has shone light in the interesting problem of silicate oligomer formation kinetics. For the first time, an ab initio study has been conducted that considers all possible oligomerization reactions available to silicic acid in basic solution, up to and including tetramers. An understanding of the nucleation and growth of silica colloids is important in the comprehension of sol-gel processes and geothermal fluids.

 Including explicit water molecules in the calculations showed that these greatly affect the stability of intermediates and transition states, suggesting that some of the known pathways are more facile than previously predicted. Previously neglected bimolecular growth pathways were found to be energetically feasible, and so could significantly impact on the intial stages of silica nucleation.

Silicates are able to adopt a vast array of linear, cyclic, and branched structures, which makes it tough to experimentally monitor and identify product oligomers of silicate systems. This challenge is complicated further by the sensitivity toward temperature, ionic strength and pH. McIntosh remarks that a full picture of silicate growth will require time- and concentration dependent modelling techniques.

Read McIntosh’s article today:

Theoretical investigations into the nucleation of silica growth in basic solution part I – ab Initio studies of the formation of trimers and tetramers
Grant J. McIntosh
DOI: 10.1039/C3CP43399D