Gold nanoparticles are under consideration for a number of biomedical applications, such as tumor treatment. A German-American research team at Carnegie Mellon University in Pittsburgh, Hunter College in New York, and the RWTH Aachen has now developed a new method for the production of nanoscopic gold rods.
In contrast to previous methods, they have achieved this without the use of cytotoxic additives. As they report in the journal Angewandte Chemie, the synthesis is not carried out in water, but in an ionic liquid, a “liquid salt”.
Cancer cells are relatively temperature-sensitive. This is exploited in treatments involving overheating of parts of the cancer patient’s body. One highly promising method is photoinduced hyperthermia, in which light energy is converted to heat. Gold nanoparticles absorb light very strongly in the near infrared, a spectral region that is barely absorbed by tissue. The absorbed light energy causes the gold particles to vibrate and is dissipated into the surrounding area as heat. The tiny gold particles can be functionalized so that the specifically bind to tumor cells. Thus, only cells that contain gold particles are killed off.
The problem? Ordinary spherical gold particles do not efficiently convert the light energy into heat; only rod-shaped particles will do. Unfortunately, the additives needed to crystallize the rod-shaped particles from aqueous solutions are cytotoxic.
The team headed by Michael R. Bockstaller is now pursuing a new strategy: instead of aqueous solution, they chose to use an ionic liquid as their medium of crystallization. Ionic liquids are “liquid salts”, organic compounds that exist as oppositely charged ions, but in the liquid state. In this way, the researchers have been able to produce gold nanorods without the use of any cytotoxic additives.
In the first step, seed crystals are produced in the form of tiny spherical gold particles. These crystals are added to a “secondary growth solution” containing monovalent gold ions, silver ions, and the weak reducing agent ascorbic acid. The solvent is an imidazolium-based ionic liquid. In this medium, the crystals don’t continue to grow into spheres; instead they form rods with the round crystallization nuclei as “heads”. The mechanism is presumed to involve the various, energetically inequivalent surfaces of the crystal lattice: the aromatic, nitrogen-containing five-membered rings of the ionic liquid prefer to accumulate at the highly energetic facets of gold surfaces. They thus stabilize crystal shapes that have fewer low-energy facets than the normal spherical equilibrium form. This results in long rods.
Author: Michael R. Bockstaller, Carnegie Mellon University, Pittsburgh (USA), http://neon.mems.cmu.edu/people/bockstaller.htm
Title: Imidazolium-Based Ionic Liquids as Efficient Shape-Regulating Solvents for the Synthesis of Gold Nanorods
Angewandte Chemie International Edition 2008, 47, No. 40, doi: 10.1002/anie.200802185
Study shines light on brain cells that coordinate movement
26.06.2017 | University of Washington Health Sciences/UW Medicine
New insight into a central biological dogma on ion transport
26.06.2017 | Aarhus University
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
26.06.2017 | Life Sciences
26.06.2017 | Physics and Astronomy
26.06.2017 | Information Technology