We appreciate the support of research in our lab by:
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
We are based at the
Weizmann Institute of Science
M.Sc. rotation, M.Sc. and Ph.D. positions available. Postdoc positions available for outstanding candidates.
Please inquire with Dr. Rafal Klajn.
Congratulations and good luck to former group members Ji-Woong Lee and Pintu Kumar Kundu as they embark on their new positions as Assistant Professors at the SRM University and the University of Copenhagen, respectively!
DYNAMICALLY SELF-ASSEMBLING CONFINED ENVIRONMENTS
We show that as light-responsive nanoparticles self-assemble, are can efficiently occlude various small molecules
from the surrounding solution. In the presence of these dynamically self-assembling nanoparticles, various chemical
reactions can be accelerated, often proceeding with stereoselectivities different than in bulk solution. See also
News & Views
Project leader: Dr. H. Zhao
CONGRATULATIONS TO HUI!
Dr. Hui Zhao wins one of three ACS Nano poster awards (out of 600+ posters) at the ChinaNANO 2015 conference in Beijing!
Hui Zhao (center) along with Kerui Li and Jing Cao receiving the award from ACS Nano Editor-in-Chief Prof. Paul S. Weiss and Associate Editors Profs. Warren Chan, Wolfgang Parak, and Ali Khademhosseini (photo credit: Prof. Tao He)
Make sure not to miss Mark Peplow's
excellent piece on molecular switches in Nature!
Credit: Karl-Heinz Ernst
HOW TO CONTROL THE ASSEMBLY OF NON-PHOTORESPONSIVE NANOPARTICLES USING LIGHT?
We show that nanoparticles that do not respond to light
can be made to assemble in a reversible fashion
- using light
- when placed in a light-sensitive medium. As they assemble, the particles can efficiently remove
selected molecules from solution - and subsequently release them using light. Performing the assembly
process in thin films of gels allowed us to draw images
that spontaneously disappeared
a specific period of time.
See highlights at:
Project leader: Dr. P. K. Kundu (Image by Ella Marushchenko)
SELF-ASSEMBLY OF HELICAL NANOPARTICLE SUPERSTRUCTURES
We discovered the ability of cubic
nanocrystals of magnetite
to self-assemble into helical superstructures. Large arrays of enantiopure helices can
be assembled under weak magnetic fields. Nanoscale interactions involved in the self-assembly process were analyzed in collaboration with the
Petr Král group at UIC.
Project leader: Dr. G. Singh
See also highlights at:
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
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, Dr. S. Das
DYNAMIC MATERIALS BASED ON SPIROPYRAN
Our new Review Article is now out! The paper discusses 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
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