Volume 12 Issue 8, August 2013

In spite of substantial progress over the past 35 years, underfunding and lack of evaluation are preventing Greek research and technology from reaching its true potential. A coordinated effort between government, academia and industry could lead to viable solutions to the current crisis.

The recent economic crisis has drastically affected research and development in Greece, but competitive research goes on, says Eleftherios Economou, a founder of the Foundation of Research and Technology Hellas (FORTH) research centre in Greece, and former General Secretary for research and technology.

Experiments and simulations show that coherent twin boundaries, commonly believed to be perfect, are riddled with kinks and other defects.

In addition to manipulating the charge or spin of electrons, another way to control electric current is by using the 'valley' degree-of-freedom of electrons. The first demonstration of the generation, transport and detection of valley-polarized electrons in bulk diamond now opens up new opportunities for quantum control in electronic devices.

Elucidating the relationship between the structure and magnetism of quasicrystals has long been a challenge. The discovery of an extended family of binary icosahedral quasicrystals with localized magnetic moments may be an important step in shedding light on this issue.

The entropic repulsion between tethered molecular brushes at fluid interfaces templates the mixing of otherwise incompatible macromolecules.

A general approach for decorating nanoparticles with a highly dense shell of DNA linkers expands the range of building blocks that can be used for DNA-mediated nanoparticle self-assembly.

Coherent twin boundaries, which usually form during the growth, deformation or annealing of crystalline solids, are widely described as perfect interfaces. Experiments and simulations now show that as-grown coherent twin boundaries in nanotwinned copper consist of incoherent segments and partial dislocations, and significantly affect the material’s mechanical behaviour and deformation mechanisms.

Results suggesting the onset of magnetism at the interface between LaAlO₃ and SrTiO₃ have been among the more intriguing associated with this system. Using element-specific techniques such as X-ray magnetic circular dichroism, direct signatures of in-plane ferromagnetic order occurring at the interface are now reported.

Iridate materials are at present the focus of interest because the combination of strong spin–orbit effects and many-body electronic correlations makes their physics non-trivial. Now, the density of states of Sr₃Ir₂O₇ is mapped out spatially using scanning tunnelling microscopy and spectroscopy, yielding insights into the influence of nanoscale heterogeneities on the electronic structure.

At present, there are no known examples of binary icosahedral quasicrystals featuring localized magnetic moments. Now, a family of magnetic binary icosahedral quasicrystals is discovered, offering the possibility of studying the behaviour of coupled magnetic interactions in the presence of aperiodic structural order.

The conversion efficiency of heat to electricity in thermoelectric materials depends on both their thermopower and electrical conductivity. It is now reported that, unlike their inorganic counterparts, organic thermoelectric materials show an improvement in both these parameters when the volume of dopant elements is minimized; furthermore, a high conversion efficiency is achieved in PEDOT:PSS blends.

Although the coarsening of catalytically active metal clusters can be accelerated by the presence of gases, the role played by gas molecules is difficult to ascertain. Carbon monoxide-induced coalescence of Pd adatoms supported on a Fe₃O₄ surface is now investigated at room temperature, and Pd-carbonyl species are shown to be responsible for their mobility.

Understanding the distribution of internal local strains within zeolites is important for catalytic applications because they can affect the rates of adsorption and diffusion of guest molecules. A ‘triangular’ deformation-field distribution in ZSM-5 zeolites is now observed, showing the presence of a strain within the crystal that arises from the heterogeneous core–shell structure.

Surface-active macromolecules that are chemically different can be mixed at fluid interfaces if the molecules attract each other, or if they have complementary shapes and a net attraction is induced by a depletant. Now, a strategy that eludes the need for complementarity between the molecules, where tethered molecular brushes induce an entropic net repulsion between like species, achieves long-range arrays of perfectly mixed macromolecules.

Progress in DNA-mediated nanoparticle self-assembly has been hampered by the lack of a general method to control the bonding of nanoparticles of different chemical composition into lattices by means of DNA linkers. An approach that makes possible the functionalization of any nanoparticle that has hydrophobic capping ligands with a dense monolayer of DNA, and allows for independent control of composition, particle size and lattice parameters for a variety of lattices, is now demonstrated.

A highly selective and efficient approach to covalently bond complementary DNA strands in solution and on surfaces on demand is shown. The approach involves the substitution of a pair of complementary bases by cinnamate-based crosslinks, which can be activated on exposure to ultraviolet light, and allows chemical patterning of flat and curved surfaces down to micrometre and potentially submicrometre resolutions.

The controlled vapour phase synthesis of molybdenum disulphide atomic layers and a fundamental mechanism for the nucleation, growth and grain boundary formation in its crystalline monolayers are now reported. Using high-resolution electron microscopy imaging, the atomic structure of the grains and their boundaries in the polycrystalline molybdenum disulphide atomic layers are examined, and the primary mechanisms for grain-boundary formation are evaluated.

Electronic devices usually rely on the charge or spin of electrons to encode information. A less exploited route is to manipulate the valley quantum number of electrons. It is now shown that the generation, macroscopic transport and detection of valley-polarized electrons in bulk diamond can be achieved with a relaxation time of 300 ns at 77 K, forming a basis for valleytronic devices.

Although site-dependent metal surface segregation in bimetallic nanoalloys affects catalytic activity and stability, segregation on shaped nanocatalysts and their atomic-scale evolution is largely unexplored. Pt_xNi_1−x alloy nanoparticle electrocatalysts with unique activity for oxygen reduction reactions exhibit an unexpected compositional segregation structure across the {111} facets.

Greek science has been badly hit by the ongoing economic crisis in Europe. In this focus issue, we highlight the main challenges that are now facing Greek research, and examine the possible avenues that should be explored to maintain its existing competitive research facilities.