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Next-generation in vivo optical imaging with short-wave infrared quantum dots

For in vivo imaging, the short-wavelength infrared region (SWIR; 1,000–2,000 nm) provides several advantages over the visible and near-infrared regions: general lack of autofluorescence, low light absorption by blood and tissue, and reduced scattering. However, the lack of versatile and functional SWIR emitters has prevented the general adoption of SWIR imaging by the biomedical research community. Here, we introduce a class of high-quality SWIR-emissive indium-arsenide-based quantum dots that are readily modifiable for various functional imaging applications, and that exhibit narrow and size-tunable emission and a dramatically higher emission quantum yield than previously described SWIR probes. To demonstrate the unprecedented combination of deep penetration, high spatial resolution, multicolour imaging and fast acquisition speed afforded by the SWIR quantum dots, we quantified, in mice, the metabolic turnover rates of lipoproteins in several organs simultaneously and in real time as well as heartbeat and breathing rates in awake and unrestrained animals, and generated detailed three-dimensional quantitative flow maps of the mouse brain vasculature.

Video of Magnetic Separation of Magneto-Fluorescent Supernanoparticles

Magneto-fluorescent core-shell supernanoparticles (red emission) can be separated from non-magnetic silica-coated quantum dots (green emission) using a magnetic column.

Video of Nanocrystal Synthesis

Synthesis of CdSe nanocrystals by injection of cadmium and selenium precursors into a high boiling point coordinating solvent at 360 degrees C. Intense color results from the quantum confinement effect on the electron as a result of the nanocrystal size being less than the Bohr radius of the exciton. Thus, larger particle size results in a red-shift in the emission. A size series was generated by allowing the crystals to grow at 280 degrees C. Over a period of 2 minutes, the fluorescence spectrum from 515 nm to 635 nm was covered.

Museum of Science Talk - Boston

Professor Moungi Bawendi from MIT demystifies the "Quantum Magic in Nanocrystals" at NanoDays 2011 celebrated at the Museum of Science Boston on March 26th. He explains what quantum dots are, how they work, and some current and potential future applications for this nanomaterial.

An interview podcast that describes the science and technology of Quantum Dots, given by Moungi at the Museum of Science Boston (starts at 8:30 in the above video).

In the Press

A long-sought goal of creating particles that can emit a colorful fluorescent glow in a biological environment, 
and that could be precisely manipulated into position within living cells, has been achieved by a team of 
researchers at MIT and several other institutions. The finding is reported in the journal Nature Communications 
by Prof. Moungi Bawendi and lead author Dr. Ou Chen and others.

Mastering the impact of surface chemistry on the electronic properties and stability of colloidal quantum dots 
enables the realization of architectures with enhanced photovoltaic performance and air stability.

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Quantum-dot photovoltaics set new record for efficiency in such devices, could unlock new uses.

The new work represents a significant leap in overcoming those limitations, increasing the current flow 
in the cells and thus boosting their overall efficiency in converting sunlight into electricity.
The development is described in a paper, published in the journal Nature Materials, by MIT professors 
Moungi Bawendi and Vladimir Bulović and graduate students Chia-Hao Chuang and Patrick Brown.

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Quantum dots — tiny particles that emit light in a dazzling array of glowing colors — have the potential for 
many applications, but have faced a series of hurdles to improved performance. But an MIT team says that it has
succeeded in overcoming all these obstacles at once, while earlier efforts have only been able to tackle them one 
or a few at a time.  This research is published in the journal Nature Materials by MIT chemistry postdoc Ou Chen,
the Lester Wolfe Professor of Chemistry, Moungi Bawendi, and several others

The in vivo behaviour of nanoparticles is known to be dependent on many physical properties including size,
shape and charge. Less is understood, however, about the relationship between biological properties and the
spatial arrangement of charge on the nanoparticle surface. Now, Han et al. synthesize zwitterionic quantum
dots with varying charge distributions and analyse their in vitro and in vivo behaviour.
...researchers have now introduced an unconventional pH sensor that makes it possible to monitor changes in pH
values in living cells over longer periods of time, with previously unobtainable spatial resolution.
..Researchers at MIT say they have found ways of making defect-free patterns of nanocrystal films where the
shape and position of the films are controlled with nanoscale resolution, potentially opening up a significant
area for research and possible new applications.
Researchers led by an MIT postdoc have analyzed an artificial system that models the light-capturing method 
used by deep-sea bacteria. Further advances in understanding fundamental light-harvesting processes may yield 
entirely new approaches to capturing solar energy, the researchers say. Their results were reported July 1 in
the journal Nature Chemistry.
What does cancer research have in common with sculpting or writing or dancing? When it comes to the creative 
process, a lot. From committing to an idea and following passion at all costs, to finding inspiration in 
unexpected places and being undeterred by critics, many traits are universal among those who create.

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For the past two decades, researchers have been manipulating tiny clumps of atoms to exploit their quantum 
mechanical properties in computing, optics, and electronics. Now Moungi G. Bawendi envisions uses for these
quantum dots as alternatives to fluorescent organic dyes and proteins for labeling, imaging, and monitoring
biological systems and for better understanding and battling cancer.

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According to a recent SciFinder search, Moungi G. Bawendi's seminal paper - in which he and his students
reported the first method for synthesizing quantum dots while simultaneously maintaining precise control
over their size (J. Am. Chem. Soc. 1993, 115, 8706) - has been cited more than 3,000 times. "This publication
represents the beginning of a whole new subfield of materials chemistry - the study of defined semiconductor
nanocrystals," says Timothy M. Swager, head of the chemistry department at Massachusetts Institute of Technology.

Targeting diseases with nanotechnology-based therapies supposes precise knowledge of where nanodevices go
when released in the human body. Yet current knowledge is anything but precise.

John Frangioni of Beth Israel Deaconess Medical Center in Boston, Massachusetts, Moungi Bawendi of the
Massachusetts Institute of Technology in Cambridge and their colleagues went looking for answers in rats.
They used near-infrared-emitting semiconductor nanoparticles coated with a polymer...

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Today, The Tech features an interview with Moungi G. Bawendi, a professor in the Department of Chemistry who 
teaches 5.112 (Principles of Chemical Science), among other courses. Bawendi discusses his background and 
research, and his experience advising students.

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"...Moungi Bawendi, Ph.D., and colleagues at the Massachusetts Institute of Technology have also developed 
an EGFR-targeted quantum dot capable of imaging live cells..."
"...The most common probes are the rainbow of fluorescent proteins such as green fluorescent protein (GFP) or
yellow fluorescent protein (YFP). These probes have the advantage that they can be genetically encoded as a 
fusion protein attached to the target protein, thereby circumventing the delivery challenge. However, their 
signals are relatively weak, they blink, and their color quickly fades when exposed to light. Most scientists 
have learned to live with these drawbacks.

To solve this problem, Alice Y. Ting and Moungi G. Bawendi of Massachusetts Institute of Technology have 
synthesized quantum dots that are half the hydrodynamic diameter of those that are commercially available. Ting 
can use these smaller quantum dots to study synaptic receptors; the commercial quantum dots don't fit in the 
neuronal synapse..."

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"Five MIT faculty members are among the 72 newly elected members and 18 foreign associates of the National 
Academy of Sciences--an honor that recognizes their distinguished and continuing achievements in original 

Election to membership in the National Academy of Sciences (NAS) is considered one of the highest honors in 
American science or engineering. Those elected today bring the total number of active members to 2,025."

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"Two MIT professors are among eight winners of the 2007 Ernest Orlando Lawrence Award from the U.S. Department 
of Energy.The award, which consists of a gold medal, a citation and an honorarium of $50,000, honors scientists 
and engineers at mid-career for exceptional contributions in research and development that support the 
Department of Energy (DOE) and its mission to advance the national, economic and energy security of the 
United States." 

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