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 HKUST researchers discover ways to regenerate corticospinal tract axons
06.07.2015 | Hong Kong University of Science and Technology

nachricht Southampton researchers go with the flow to help protect endangered European eel
06.07.2015 | University of Southampton

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Viaducts with wind turbines, the new renewable energy source

Wind turbines could be installed under some of the biggest bridges on the road network to produce electricity. So it is confirmed by calculations carried out by a European researchers team, that have taken a viaduct in the Canary Islands as a reference. This concept could be applied in heavily built-up territories or natural areas with new constructions limitations.

The Juncal Viaduct, in Gran Canaria, has served as a reference for Spanish and British researchers to verify that the wind blowing between the pillars on this...

Im Focus: X-rays and electrons join forces to map catalytic reactions in real-time

New technique combines electron microscopy and synchrotron X-rays to track chemical reactions under real operating conditions

A new technique pioneered at the U.S. Department of Energy's Brookhaven National Laboratory reveals atomic-scale changes during catalytic reactions in real...

Im Focus: Iron: A biological element?

Think of an object made of iron: An I-beam, a car frame, a nail. Now imagine that half of the iron in that object owes its existence to bacteria living two and a half billion years ago.

Think of an object made of iron: An I-beam, a car frame, a nail. Now imagine that half of the iron in that object owes its existence to bacteria living two and...

Im Focus: Thousands of Droplets for Diagnostics

Researchers develop new method enabling DNA molecules to be counted in just 30 minutes

A team of scientists including PhD student Friedrich Schuler from the Laboratory of MEMS Applications at the Department of Microsystems Engineering (IMTEK) of...

Im Focus: Bionic eye clinical trial results show long-term safety, efficacy vision-restoring implant

Patients using Argus II experienced significant improvement in visual function and quality of life

The three-year clinical trial results of the retinal implant popularly known as the "bionic eye," have proven the long-term efficacy, safety and reliability of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

World Conference on Regenerative Medicine in Leipzig: Last chance to submit abstracts until 2 July

25.06.2015 | Event News

World Conference on Regenerative Medicine: Abstract Submission has been extended to 24 June

16.06.2015 | Event News

MUSE hosting Europe’s largest science communication conference

11.06.2015 | Event News

 
Latest News

Aluminum Clusters Shut Down Molecular Fuel Factory

06.07.2015 | Power and Electrical Engineering

Veja Mate Offshore orders 67 wind turbines including record long-term service

06.07.2015 | Press release

The quantum middle man

06.07.2015 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>