Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Tokyo Tech researchers produce new photoactive micelles

31.01.2013
Researchers at Tokyo Institute of Technology have produced a new form of photoactive micelles with potential applications in photofunctional dyes and sensors. The research was published in Angewandte Chemie recently.

A new form of micelle, which is composed of detergents with bent aromatic panels, has been created by Michito Yoshizawa and his colleagues at Tokyo Institute of Technology. Unlike traditional micelles, the new ‘aromatic micelles’ are photoactive, and capable of encapsulating dye molecules and showing unusual fluorescence in aqueous solutions.


Figure 1: Schematic representation of spherical assemblies. a) A standard micelle composed of string-like detergents. b) An aromatic micelle composed of new detergents with bent aromatic panels.


Figure 2: a) Encapsulation of dye molecules (NR and DCM) by the aromatic micelle in aqueous solution. b) Molecular modeling of the aromatic micelle. c) Fluorescence spectra of the micelle, micelle-NR, and micelle-DCM complexes upon irradiation at 370 nm.

“The present micelles might be suitable for potential applications in the fields of photofunctional dyes, sensors, and materials owing to their ability to accommodate dye molecules and their efficient host-guest energy transfer in aqueous media,” explain the researchers. They also emphasise the straightforward synthesis, aqueous green chemistry and high stability of the aromatic micelles.

Micelles are used in a range of dissolution, separation, and preservation applications and form the basis of soap detergents. They assemble from string-like molecules in aqueous solutions as a result of different chemical components (hydrophobic and hydrophilic moieties) at either end of the strings. Michito Yoshizawa and Kei Kondo et al. replaced the hydrophobic part of the string with large aromatic panels, which are known to be photochemically active.

The new aromatic micelles form two nanometer-sized capsules that have a cavity surrounded by large aromatic panels. The selective encapsulation of fluorescent dye molecules to form photoactive guest-host complexes is the first demonstration of efficient fluorescence energy transfer from the host framework to dye ‘guest molecules’.
Background

The micelles
Micelles are typically made of string-like molecules, where one end of the string attracts water molecules (hydrophilic) and the other end repels them (hydrophobic). In aqueous solution these strings form spherical assembles like spoke on a dandelion puffball with the hydrophobic ends at the centre. These typical micelles are not photoactive, which places limitations on their potential applications.

Aromatic molecules
Aromatic molecules are carbon-based molecules with six-membered rings that have a particular type of electronic configuration, which leads to a number of specific properties. Large aromatic molecules are planar and photo- and electrochemically active, which may make them useful in applications such as liquid crystal displays. However they do not readily form discrete micelle-like assemblies.
Producing aromatic micelles
To create the aromatic micelles, the researchers made new detergents with bent aromatic panels, comprising two anthracene moieties with a spacer to connect them. The spacer was functionalized with two hydrophilic groups. The steric repulsion between the anthracene and spacer moieties gives the molecule its bent shape. With the hydrophobic bent panels and the hydrophilic groups, the detergent molecules form spherical assemblies in aqueous solution. The assembly is driven by stacking of the hydrophobic aromatic panels.
Aromatic micelle properties
The aromatic micelles had a cavity surrounded by anthracene shells with a diameter of approximately one nanometer. The shell emitted blue-green fluorescence (~500 nm). The aromatic micelles were also extremely robust. Atomic force microscopy (AFM) images showed the spherical structures persisted even after complete evaporation of water.

Dye encapsulation
The researchers demonstrated the encapsulation of two well known hydrophobic dyes, Nile red (NR) and DCM by the aromatic micelles. Stirring a suspension of the dyes in an aqueous solution of the aromatic micelles for an hour produced a clear solution. Spectroscopic observations revealed changes to the light absorption and emission properties of the micelle following encapsulation of the dyes. Strong red emission (~640 nm) from the encapsulated DCM was observed upon irradiation of the micelle-DCM complex at 370 nm. In contrast, the irradiation of DCM in the absence of the micelle at 370 nm showed almost no emission. Measurements of the fluorescence quenching profile of the anthracene panels in the micelles indicated the energy transfer efficiency as high as 97%. The work is the first demonstration of efficient fluorescent resonance energy transfer from discrete self-assembled hosts.
Next steps
The authors expect that the functionalization of the aromatic shells as well as the use of other aromatic panels will lead to new aromatic micelles with a wide range of fluorescent properties. Studies along these lines are currently in progress in their research group.

Further information
Yukiko Tokida, Miwako Kato
Center for Public Information, Tokyo Institute of Technology
2-12-1, Ookayama, Meguro-ku, Tokyo 152-8550, Japan
E-mail: kouhou@jim.titech.ac.jp
URL: http://www.titech.ac.jp/english/
Tel: +81-3-5734-2975 Fax: +81-3-5734-3661

About Tokyo Institute of Technology
As one of Japan’s top universities, Tokyo Institute of Technology seeks to contribute to civilization, peace and prosperity in the world, and aims at developing global human capabilities par excellence through pioneering research and education in science and technology, including industrial and social management. To achieve this mission, we have an eye on educating highly moral students to acquire not only scientific expertise but also expertise in the liberal arts, and a balanced knowledge of the social sciences and humanities, all while researching deeply from basics to practice with academic mastery. Through these activities, we wish to contribute to global sustainability of the natural world and the support of human life.
Website: http://www.titech.ac.jp/english/

Journal information
Reference
K. Kondo, A. Suzuki, M. Akita, and M. Yoshizawa, “Micelle-like Molecular Capsules with Anthracene Shells as Photoactive Hosts” Angewandte Chemie International Edition, 2013, DOI: 10.1002/anie.201208643 (Article first published online: 23 Jan 2013).

Funding information

Support
This research was supported by the Japan Society for the Promotion of Science (JSPS) through the “Funding Program for Next-Generation World-Leading Researchers” and by the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) through a Grant-in-Aid for Scientific Research on Innovative Areas (“Coordination Programming”).

Adarsh Sandhu | Research asia research news
Further information:
http://www.titech.ac.jp/english/
http://www.researchsea.com

More articles from Life Sciences:

nachricht How brains surrender to sleep
23.06.2017 | IMP - Forschungsinstitut für Molekulare Pathologie GmbH

nachricht A new technique isolates neuronal activity during memory consolidation
22.06.2017 | Spanish National Research Council (CSIC)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

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...

Im Focus: Climate satellite: Tracking methane with robust laser technology

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...

Im Focus: How protons move through a fuel cell

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...

Im Focus: A unique data centre for cosmological simulations

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...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

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)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>