RAFAL KLAJN GROUP
NANOCHEMISTRY LABORATORY
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Welcome!

We are a new lab investigating chemical and physical properties of matter at the nanoscale. We are particularly interested in:

* New approaches to the synthesis of nanocrystals
* Self-assembly of nanoparticles
* Organic nanostructures
* Supramolecular chemistry
* Chemical reactivity in confined spaces
* Molecular switches
* Stimuli-responsive materials


Available positions:

Rotation, M.Sc. and Ph.D. positions available. Postdoc positions available for outstanding candidates.
Please inquire with Dr. Rafal Klajn.


News:




ANNOUNCING A NEW GORDON RESEARCH CONFERENCE SERIES
Artificial Molecular Switches & Motors

Mark your calendars! The first conference of the series to be held June 7-12, 2015, at Stonehill College, Easton, MA.


CONTROLLING ELECTRICAL CONDUCTANCE USING LIGHT

In collaboration with the
David Cahen group, we developed novel devices whose electron transport properties can be controlled by light. The key components of these devices are electrode-molecule-electrode junctions incorporating various azobenzene derivatives. Upon exposure to UV, the planar trans-azobenzene undergoes isomerization to the distorted cis isomer. The poor electronic conjugation in the latter isomer results in the conductance decreasing as much as 30 times when the device is exposed to UV light.



Project leaders: T. Ely, S. Das


DYNAMIC MATERIALS BASED ON SPIROPYRAN

Our new Review Article is now out! The paper discuss how the switchable molecule spiropyran can be employed to construct a variety of stimuli-responsive materials. These materials can find unique applications ranging from light-controlled drug delivery to detection of mechanical stress (for example, in climbing ropes or bridges) prior to catastrophic failure.




HOW TO GUIDE DIAMAGNETIC PARTICLES USING WEAK MAGNETS

We show that diamagnetic particles can be remotely manipulated by a magnet after minute amounts of our dual-responsive nanoparticles are adsorbed onto their surface. Adsorption occurs upon exposure to UV light and can be reversed by ambient light. The resulting diamagnetic core-paramagnetic shell assemblies can be remotely guided to desired locations, where the diamagnetic "cargo" can be released simply by exposure to visible light, which "strips off" the monolayers of superparamagnetic nanoparticles. A movie demonstrating the delivery and release of gold nanoparticles using this technique can be found here.


Project leaders: O. Chovnik, R. Balgley


DUAL-RESPONSIVE NANOPARTICLES

We have designed nanoparticles capable of responding to two types of external stimuli - light and magnetic field - in an orthogonal fashion. The ability to respond to magnetic fields is "encoded" in the superparamagnetic cores of the nanoparticles whereas the interactions with light are governed by the self-assembled monolayers comprising the photoswitchable azobenzene groups. The resulting "dual-responsive" nanoparticles can be assembled into various higher-order structures, depending on the relative contributions of the two external stimuli. The formation of these assemblies is fully reversible and they can be disassembled into individual nanoparticles when the UV light and/or magnetic field are removed.


Project leader: Dr. S. Das


WORLD'S SMALLEST METALLIC BOWLS?

We have developed a solution synthesis of metallic nanoparticles with a unique shape of tiny bowls. These "nanobowls" have cavities just few nanometers across and can be used to "trap" other nanosized objects. The picture below is a collage made of several tomograms reconstructed from data collected using scanning transmission electron microscopy. This is how the nanobowls really look like in three dimensions!


Project leader: Y. Ridelman

We greatly appreciate the support of research in our lab by: