PCCP Blog

A recent theoretical study by Zhijan Wu, Aimin Ren and co-workers predicts novel BODIPY derivatives with interesting and potentially very useful nonlinear optical properties.

The group studied a series of aza-BODIPY fluorophores with structures expected to have large two-photon cross-sections at telecommunication wavelengths. They found that it is possible to finely tune the linear and non-linear optical properties by chemical modification of the aza-BODIPY core and peripheral moieties, resulting in excellent, original candidates for nonlinear transmission and fluorescent labelling materials.

Read the full paper:

New insights into two-photon absorption properties of functionalized aza-BODIPY dyes at telecommunication wavelengths: a theoretical study
Xiaoting Liu, Jilong Zhang, Kai Li, Xiaobo Sun, Zhijian Wu, Aimin Ren and Jikang Feng
DOI: 10.1039/C3CP44435J

Janina Kneipp and co-authors report SERS spectra of hemoglobin using silver and gold nanoparticles in red blood cells in their recent PCCP paper, which shed light on the interactions of nanoparticles with red blood cells.

The group used small nanoparticle concentrations compared to the concentration of hemoglobin molecules, similar to the situation upon nanoparticle entry into the hemoglobin-rich environment of the red blood cell. They demonstrated the dependence of the SERS spectra on the type and size of nanoparticle used as the SERS substrate. They confirmed that the nanoparticles interact with blood cells via interaction with hemoglobin and are also in contact with many other red blood cell components. Interestingly, the evidence shows nanoparticle-induced structural changes in the lipid bilayer of the red blood cells.

Understanding these interactions are of great importance, as silver nanoparticles, found everywhere in everyday life, display high cytotoxicity. The uptake of nanoparticles into red blood is also intriguing as it does not occur by endocytosis.

Read the detail in this article today:

SERS reveals the specific interaction of silver and gold nanoparticles with hemoglobin and red blood cell components
Daniela Drescher, Tina Büchner, Don McNaughton and Janina Kneipp
DOI: 10.1039/C3CP43883J

If you enjoyed this article, keep an eye out for our themed issue on plasmonics and spectroscopy, which is soon to be published.

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!

Doping various mineral oxides with lanthanide ions is one of the big trends at the moment. Possibly because of the wide application of lanthanide ions in lighting, bioanalysis and telecommunication, possibly because all you need is an oven and a big laser in order to study something as interesting as the processes in the lanthanide excited state manifold.

Singh and co-workers have doped an yttrium titanium oxide with erbium an ytterbium and studied the luminescence following energy up-conversion. Subsequently, they used laser ablation to pulverise the mineral and studied the powder. Most intriguing, they find that the amount of red and green light emitted vary as a function of laser power.

Lanthanide luminescence, originating from f–f transitions, where the only the f-electron configuration changes, is intriguing as it can occur all across the spectrum, from numerous excited states to multiple other excited states, some of which may even be emissive as well.

While organic chromophores have one ground state, one excited state and a triplet state wherein the molecule may stay for more than picoseconds, lanthanide ions have several if not many. Ytterbium is the only exception, with only one; a consequence of the nearly full f-shell. The shielded nature of the f-orbitals allow for slow processes in the excited state manifold, where the excited states are only quenched by high-energy phonon or vibrational modes in the surroundings. Thus, although energy up-conversion is possible through several pathways, excited state absorption usually dominates.

“Structural and up-conversion properties of Er³⁺ and Yb³⁺ co-doped Y₂Ti₂O₇ phosphors” by B. P. Singh , A. K. Parchur , R. K. Singh , A. A. Ansari , P. Singh and S. B. Rai is a comprehensive study of the photophysics of erbium and ytterbium doped in a solid state lattice. For the full account see issue 10 of PCCP: Phys. Chem. Chem. Phys., 2013,15, 3480-3489.

by Dr Thomas Just Sørensen