Semiconductor nanocrystals or also called quantum dots exhibit outstanding optical properties compared to organic dyes. Due to the quantum confinement their emission color can be continuously tuned from the ultraviolet to the near infrared range by changing the size and chemical composition.
They exhibit a broad absorption spectrum, a narrow emission band and large absorption cross sections. Their surface can be covered by a few monolayers of different semiconductor materials in such a way that we can either improve their luminescent properties and stability or avoid the fluorescence to obtain charge carriers. The latter effect opens tremendous alternatives in photovoltaics. Due to their optical properties, semiconductor nanoparticles are studied in different disciplines, from optics to biomedicine.
Thanks to a remarkable effort in the synthetic activities in the last 20 years, we can nowadays produce nanoparticles of different materials controlling their size, shape, and surface properties. Examples of nanoparticles produced by non hydrolytic colloidal synthetic methods are CdS, CdTe, InP, GaAs, PbS, or PbSe. However, the most studied system is CdSe, with tunable emission from blue to red. Due to the synthetic approach (hot injection method), the surface of these nanoparticles is capped with an organic shell that protects them and makes them stable in non-polar organic solvents. It is also possible to controllably replace the initial organic shell for water compatible ones. The organic shell plays a relevant role in the quantum efficiency of the nanoparticles and their stability in different media. However, this shell prevents high electrical conduction.
Carbon nanotubes are another example of nanomaterials with extraordinary electrical properties. They consist of one or several rolled up graphene layers. In the case of a single layer they are called single-wall and multi-wall when several layers are rolled-up. Hybrid materials composed of semiconductor nanoparticles and carbon nanotubes combine the high absorption properties of the former and the high electrical conductivity of the latter. One of the main drawbacks in the formation of such hybrid structures focuses on the type of interaction between them. Most of the existing procedures involve the growth of nanoparticles on previous defect sites provoked on the surface or edges of carbon nanotubes by aggressive chemical means. These aggressive treatments render an oxidized nanotube surface or even structural damage that deteriorates their outstanding electrical, mechanical, and optical properties significantly. Thus, supramolecular or electrostatic functionalisations are better approaches for photovoltaic applications.
Dr Beatriz H. Juárez, from IMDEA Nanoscience, works on the preparation of hybrid materials with high coverage without modifying the electrical properties of the tubes. Furthermore, the monodispersity of the nanoparticles with high crystallographic quality and a close contact between nanoparticles and nanotubes are also under investigation. The composites show photoelectrical response, injecting charge carriers in the nanotubes upon nanoparticle excitation. Although in an initial stage, the results obtained up to now points out the high potential of these composites to build up photovoltaic devices and solar cells.
B. H. Juárez, C. Klinke, A. Kornowski, H. Weller, Nano Letters, 2007, 7, 3564
IMDEA | alfa
Further reports about: > Cells > HYBRID > Hybrid Material > Nanoscience > Photovoltaics > SOLAR > Semiconductor > Semiconductor nanocrystals > carbon nanotubes > fluorescence > hydrolytic colloidal synthetic methods > light emitting diodes > luminescent properties > nanoparticles > photovoltaic devices > solar cells
Studying fundamental particles in materials
17.01.2017 | Max-Planck-Institut für Struktur und Dynamik der Materie
Seeing the quantum future... literally
16.01.2017 | University of Sydney
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Materials Sciences
17.01.2017 | Architecture and Construction