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Moungi G. Bawendi

Bio: Moungi G. Bawendi is an academic researcher from Massachusetts Institute of Technology. The author has contributed to research in topics: Quantum dot & Nanocrystal. The author has an hindex of 165, co-authored 626 publications receiving 118108 citations. Previous affiliations of Moungi G. Bawendi include United States Department of the Navy & United States Naval Research Laboratory.


Papers
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Journal ArticleDOI
TL;DR: It is demonstrated how measuring the conductivity of nanowires during cation exchange can be used to monitor the transition from CdSe to Ag(2)Se, in situ, by imaging the same wire mat region before and after complete cation Exchange.
Abstract: Controlling the extent of cation exchange reactions is a promising route for tuning the material composition and properties of nanostructures. Here we demonstrate how measuring the conductivity of nanowires during cation exchange can be used to monitor the transition from CdSe to Ag2Se, in situ. In addition, by imaging the same wire mat region before and after complete cation exchange, we find that the shape and morphology of the nanowires are completely preserved.

29 citations

Journal ArticleDOI
TL;DR: In this paper, the authors show that only 30% of surface cadmium atoms are passivated by TOPO/TOPSe and approximately 1/3 of these native ligands occupy sites too strongly bound to be replaced by ligand exchange reactions.
Abstract: CdSe quantum dots (QDs) with several different ligands were prepared by ligand exchange reactions of trioctylphosphine oxide (TOPO)/trioctylphosphine selenide (TOPSe) passivated QDs with an excess of new ligands, such as pyridine, 4-picoline, thiophenol, 4-(trifluoromethyl)-thiophenol, and tris(2-ethylhexyl)phosphate. We find that 85~90% of ligands passivating the surface of the QDs are the newly introduced capping species and 10~15% are native TOPO/TOPSe ligands, reflecting the incomplete exchange of the QD surface. Thermal gravimetric analysis (TGA) and quantitative proton NMR measurements show that on average only 30% of surface cadmium atoms are passivated by TOPO/TOPSe. Approximately 1/3 of these native ligands occupy sites too strongly bound to be replaced by ligand exchange reactions.

29 citations

Journal ArticleDOI
TL;DR: It is shown that holes are the minority carriers in tetrabutylammonium iodide-treated PbS QD films due to the formation of a p-n junction with an ethanedithiol (EDT)-treated QD layer, whereas a heterojunction with n-type ZnO forms a weaker n+- n junction.
Abstract: Lead sulfide quantum dots (PbS QDs) are an attractive material system for the development of low-cost photovoltaics (PV) due to their ease of processing and stability in air, with certified power conversion efficiencies exceeding 11%. However, even the best PbS QD PV devices are limited by diffusive transport, as the optical absorption length exceeds the minority carrier diffusion length. Understanding minority carrier transport in these devices will therefore be critical for future efficiency improvement. We utilize cross-sectional electron beam-induced current (EBIC) microscopy and develop methodology to quantify minority carrier diffusion length in PbS QD PV devices. We show that holes are the minority carriers in tetrabutylammonium iodide (TBAI)-treated PbS QD films due to the formation of a p–n junction with an ethanedithiol (EDT)-treated QD layer, whereas a heterojunction with n-type ZnO forms a weaker n+–n junction. This indicates that modifying the standard device architecture to include a p-type ...

29 citations

Patent
30 Nov 2005
TL;DR: An optical resonator can include an optical feedback structure (130)disposed on a substrate (110), and a composite (140) including a matrix including a chromophore as discussed by the authors.
Abstract: An optical resonator can include an optical feedback structure (130)disposed on a substrate (110), and a composite (140) including a matrix including a chromophore. (150). The composite is disposed on the substrate and in optical communication with the optical feedback structure. The chromophore can be a semiconductor nanocrystal. The resonator can provide laser emission when excited.

28 citations


Cited by
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28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
TL;DR: A review of gold nanoparticles can be found in this article, where the most stable metal nanoparticles, called gold colloids (AuNPs), have been used for catalysis and biology applications.
Abstract: Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

11,752 citations

Journal ArticleDOI
16 Feb 1996-Science
TL;DR: In this article, the authors focus on the properties of quantum dots and their ability to join the dots into complex assemblies creates many opportunities for scientific discovery, such as the ability of joining the dots to complex assemblies.
Abstract: Current research into semiconductor clusters is focused on the properties of quantum dots-fragments of semiconductor consisting of hundreds to many thousands of atoms-with the bulk bonding geometry and with surface states eliminated by enclosure in a material that has a larger band gap. Quantum dots exhibit strongly size-dependent optical and electrical properties. The ability to join the dots into complex assemblies creates many opportunities for scientific discovery.

10,737 citations

Journal ArticleDOI
01 Apr 1988-Nature
TL;DR: In this paper, a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) is presented.
Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

9,929 citations

Journal ArticleDOI
21 Feb 1997-Science
TL;DR: In this article, surface-enhanced Raman scattering was used to detect single molecules and single nanoparticles at room temperature with the use of surface enhanced Raman, and the intrinsic Raman enhancement factors were on the order of 10 14 to 10 15, much larger than the ensemble-averaged values derived from conventional measurements.
Abstract: Optical detection and spectroscopy of single molecules and single nanoparticles have been achieved at room temperature with the use of surface-enhanced Raman scattering. Individual silver colloidal nanoparticles were screened from a large heterogeneous population for special size-dependent properties and were then used to amplify the spectroscopic signatures of adsorbed molecules. For single rhodamine 6G molecules adsorbed on the selected nanoparticles, the intrinsic Raman enhancement factors were on the order of 10 14 to 10 15 , much larger than the ensemble-averaged values derived from conventional measurements. This enormous enhancement leads to vibrational Raman signals that are more intense and more stable than single-molecule fluorescence.

9,609 citations