J. A. Misewich

Stony Brook University, Stony Brook, NY, United States

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Publications (95)336.69 Total impact

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    ABSTRACT: Double-walled carbon nanotube (DWNT)-CdSe heterostructures with the individual nanoscale building blocks linked together by 4-aminothiophenol (4-ATP) have been successfully synthesized using two different and complementary routes, i.e. covalent attachment and non-covalent π-π stacking. Specifically, using a number of characterization methods, we have probed the effects of these differential synthetic coupling approaches on the resulting CdSe quantum dot (QD) coverage on the underlying nanotube template as well as the degree of charge transfer between the CdSe QDs and the DWNTs. In general, based on microscopy and spectroscopy data collectively, we noted that heterostructures generated by non-covalent π-π stacking interactions evinced not only higher QD coverage density but also possibly more efficient charge transfer behavior as compared with their counterparts produced using covalent linker-mediated protocols.
    Dalton Transactions 03/2014; · 3.81 Impact Factor
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    Robert M. Konik, Matthew Y. Sfeir, James A. Misewich
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    ABSTRACT: We demonstrate that a non-perturbative framework for the treatment of the excitations of single walled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. We test this theory explicitly on the data reported in NanoLetters 5, 2314 (2005) and Phys. Rev. B. 82, 195424 (2010) and so demonstrate the method works over a wide range of reported excitonic spectra.
    03/2014;
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    ABSTRACT: One means of combining the unique physical and chemical properties of both carbon nanotubes and complementary material motifs (such as metal sulfide quantum dots (QDs), metal oxide nanostructures, and polymers) can be achieved by generating carbon nanotube (CNT)-based heterostructures. These materials can be subsequently utilized as novel and interesting constituent building blocks for the assembly of functional light energy harvesting devices and because of their architectural and functional flexibility, can potentially open up novel means of using and taking advantage of existing renewable energy sources. In this review, we present the reliable and reproducible synthesis of several unique model CNT-based heterostructured systems as well as include an accompanying discussion about the charge transfer and energy flow properties of these materials for their potential incorporation into a range of practical solar energy conversion devices.
    Chemical Society Reviews 07/2013; · 24.89 Impact Factor
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    ABSTRACT: We report unidirectional charge transfer in multidimensional nanohybrids, consisting of a quantum dot, an electronically active molecular linker, and a carbon nanotube. After covalent attachment to the nanotube, only emission consistent with the negatively charged quantum dot exciton ion rather than the neutral exciton is observed, showing nearly monoexponential recombination kinetics and an average lifetime of 3.5 ns. Using kinetic models, we explain how charge transfer is biased at the expense of other decay pathways.
    Nano Letters 11/2011; 11(11):4562-8. · 13.03 Impact Factor
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    ABSTRACT: Graphene presents many distinctive optical properties that complement its attractive electronic and mechanical characteristics. We review some of the recent progress in understanding the electronic transitions and ultrafast dynamics in single and few-layer graphene crystals.
    International Quantum Electronics Conference; 08/2011
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    ABSTRACT: Multiple exciton generation (MEG) is under intense investigation as potential third-generation solar photovoltaics with efficiencies beyond the Shockley-Queisser limit. We examine PbS nanocrystals, dispersed and vigorously stirred in TCE solution, by means of supercontinuum femtosecond transient absorption (TA). TA spectra show the presence of first and second order bleaches for the 1Sh-Se and 1Ph-Pe excitonic transition while photoinduced absorption for the 1Sh,e-Ph,e transitions. We found evidence of carrier multiplication (MEG for single absorbed photon) from the analysis of the first and second order bleaches, in the limit of low number of absorbed photons (Nabs˜0.01), for energy three times and four times the Energy gap. The MEG efficiency, derived from the ratio between early-time to long-time TA signal, presents a strongly dispersive behavior with maximum red shifted respect the first absorption peak. Analysis of population dynamics shows that in presence of biexciton, the 1Sh-Se bleach peak is red-shifted indicating a positive binding energy. MEG efficiency estimation will be discussed with regards to spectral integration, correlated higher-order and first excitonic transitions, as well as the nanocrystal morphologies.
    03/2011;
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    ABSTRACT: We have measured the low-energy excitonic transitions of chiral assigned individual large-diameter semiconducting single-walled nanotubes using a high-resolution Fourier transform photoconductivity technique. When photoconductivity is complemented by Rayleigh scattering spectroscopy, as many as five optical transitions can be identified on the same individual nanotube over an energy range of 0.3–2.7 eV. We find that well-established energy scaling relations developed for nanotubes of smaller diameter are not consistent with the measured low-energy transitions in large (1.8–2.3 nm) diameter nanotubes.
    Physical review. B, Condensed matter 11/2010; 82(19). · 3.77 Impact Factor
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    ABSTRACT: The massless Dirac spectrum of electrons in single-layer graphene has been thoroughly studied both theoretically and experimentally. Although a subject of considerable theoretical interest, experimental investigations of the richer electronic structure of few-layer graphene (FLG) have been limited. Here we examine FLG graphene crystals with Bernal stacking of layer thicknesses N = 1,2,3,...8 prepared using the mechanical exfoliation technique. For each layer thickness N, infrared conductivity measurements over the spectral range of 0.2-1.0 eV have been performed and reveal a distinctive band structure, with different conductivity peaks present below 0.5 eV and a relatively flat spectrum at higher photon energies. The principal transitions exhibit a systematic energy-scaling behavior with N. These observations are explained within a unified zone-folding scheme that generates the electronic states for all FLG materials from that of the bulk 3D graphite crystal through imposition of appropriate boundary conditions. Using the Kubo formula, we find that the complete infrared conductivity spectra for the different FLG crystals can be reproduced reasonably well within the framework a tight-binding model.
    Proceedings of the National Academy of Sciences 08/2010; 107(34):14999-5004. · 9.81 Impact Factor
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    ABSTRACT: The unique electronic structure and optical properties of double-walled carbon nanotubes (DWNTs) have made them a key focus material of research in recent years. However, the incorporation of DWNTs with quantum dots (QDs) into nanocomposites via a covalent chemical approach as well as the optical properties of the composites have rarely been explored. In particular, we have been interested in this model system to investigate whether nanomaterial heterostructures can provide efficient pathways for charge separation relative to loss mechanisms such as recombination. In this specific work, the synthesis of DWNT-CdSe QD heterostructures obtained by using a conventional covalent protocol has been demonstrated. CdSe QDs with terminal amino groups have been conjugated onto the surfaces of oxidized DWNTs by the formation of amide bonds. The observed trap emission of CdSe is thought to arise from the presence of 2-aminoethanethiol capping ligands and is effectively quenched upon conjugation with the DWNT surface because of the charge transfer from CdSe to DWNTs.
    Journal of Physical Chemistry C - J PHYS CHEM C. 04/2010; 114(19).
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    ABSTRACT: We experimentally study the optical properties of double-wall carbon nanotube and quantum dot (QD) composites. The two materials are covalently linked by an aminoethanethiol ligand (AET), which, when in complex with the QD, gives a characteristic emission in the NIR originating from trap states. The magnitude of this NIR emission peak relative to the QD exciton peak is directly proportional to the quantity of linker in the solution. Studies of the AET ligand-exchanged QD alone show that it poorly passivates the surface of the QD, leading to a short and complex multiexponential exciton lifetime, characteristic of the existence of randomly distributed surface traps. In contrast, upon linking with the DWNT complex, the defect related emission disappears, leaving only exciton emission. More striking, the exciton emission recovers a nearly monoexponential behavior of ˜ 2.8 ns.
    03/2010;
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    ABSTRACT: While preserving many of the unusual features of single-layer graphene, few-layer graphene (FLG) provides a richness and flexibility of electronic structure that render this set of materials of great interest for both fundamental studies and applications. Essential for progress, however, is an understanding of the evolution of the electronic structure of these materials with increasing layer number. In this report, the evolution of the electronic structure of FLG, for N = 1 - 8 atomic layers, has been characterized by measurements of the optical conductivity spectra. For each layer thickness N, distinctive peaks are found in the infrared range, with positions obeying a simple scaling relation. The observations are explained by a unified zone-folding scheme that generates the electronic structure for all FLG materials from that of bulk graphite. Comment: 15 pages, 5 figures
    08/2009;
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    ABSTRACT: The importance of generating carbon nanotube-nanoparticle heterostructures is that these composites ought to take advantage of and combine the unique physical and chemical properties of both carbon nanotubes and nanoparticles in one discrete structure. These materials have potential applicability in a range of diverse fields spanning heterogeneous catalysis to optoelectronic device development, of importance to chemists, physicists, materials scientists, and engineers. In this critical review, we present a host of diverse, complementary strategies for the reliable synthesis of carbon nanotube-nanoparticle heterostructures using both covalent as well as non-covalent protocols, incorporating not only single-walled and multi-walled carbon nanotubes but also diverse classes of metallic and semiconducting nanoparticles (221 references).
    Chemical Society Reviews 05/2009; 38(4):1076-98. · 24.89 Impact Factor
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    ABSTRACT: Bilayers of graphene have attracted intense interest because of the possibility of tuning of their band gap by the application of a perpendicular electric field [Taisuke Ohta et al. Science 313, 951 (2006)]. Indeed, such gate electric fields induce both 1) tuning of the chemical potential and 2) modification of the bilayer electronic structure by the development of potential difference across the two layers. These effects have significant consequences for the infrared absorption, which probes the interband transitions, of bilayer samples. We have examined these issues by measuring the evolution of the optical conductivity (for photon energies of 0.2 - 0.8 eV) of graphene bilayer field-effect transistors constructed with a transparent top gate. The infrared absorption shows a significant and reproducible variation with gate voltage. The behavior for positive and negative gate voltages reveals an electron/hole asymmetry, reflecting corresponding differences in the band structure. The role of the development of a band gap in these structures and the effect of electrostatic screening will be discussed.
    03/2009;
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    ABSTRACT: Optical conductivity spectra of multi-layer graphene samples were determined for photon energies in the range of 0.2 -- 1.0 eV. The measurements were performed using synchrotron radiatiaon on well-characterized exfoliated graphene samples on a transparent substrate. We observed distinct optical conductivity spectra for different samples having precisely the same number of layers. In particular, two well-defined types of spectra were obtained in measurements of more than a dozen of four-layer samples. This result can be understood by considering the existence of two stable configurations of four-layer graphene, namely, the ABAB Bernel stacking and the ABCA rhombohedral stacking. The observed absorption features were reproduced by explicit calculations, within a tight-binding model, of the optical conductivities for the two stacking sequences. We have thus shown the possibility of identifying these different crystallographic structures optically. Further, the significant difference found in the low-energy electronic structure suggests that the // var SiteRoot = 'http://academic.research.microsoft.com'; // 0) {$('.input-box-advanced-yearquery').eq(0).show();}} else hideAdvancedSearch();}function CheckAdvInput(objName,len){var obj=document.getElementById(objName); if(obj.value.length>len){obj.value=obj.value.substring(0,len);}};function hideAdvancedSearch(){document.getElementById('advancedsearchDiv').style.display='none';delCookie('advanceTabIndex');if(document.getElementById('divYearFilter'))document.getElementById('divYearFilter').style.display = '';}//]]> Sign in Advanced Search Author | Conference | Journal | Organization | Year | DOI Look for results that meet for the following criteria: sinceequal tobeforebetweenand // Search in all fields of study Limit my searches in the following fields of study Agriculture ScienceArts & HumanitiesBiologyChemistryComputer ScienceEconomics & BusinessEngineeringEnvironmental SciencesGeosciencesMaterial ScienceMathematicsMedicinePhysicsSocial ScienceMultidisciplinary BindEventForDomainPanelButton("ctl00_SearchHeader_SearchForm_txtQuery", "ctl00_SearchHeader_SearchForm_divDomainButton"); // // var isSilverlightInstalled = false; function CheckSilverlightInstalled() { try { try { var slControl = new ActiveXObject('AgControl.AgControl'); //IE isSilverlightInstalled = true; } catch (e) { if (navigator.plugins["Silverlight Plug-In"]) //non-IE { isSilverlightInstalled = true; } } } catch (e) { } } CheckSilverlightInstalled(); $(function () { $(".ranklist-summary").css("position", "static"); $(".ranklist-summary").css("position", "relative"); }) Keywords (4) Charge Transport Electronic Structure Optical Conductivity Tight Binding Subscribe Academic PublicationsDependence of the Low Energy Electronic Structure of Multi-layer Graphene on Stacking Order Probed by Infrared Absorption Dependence of the Low Energy Electronic Structure of Multi-layer Graphene on Stacking Order Probed by Infrared Absorption,Matthew Sfeir,Kin Fai Mak,Ja Edit Dependence of the Low Energy Electronic Structure of Multi-layer Graphene on Stacking Order Probed by Infrared Absorption BibTex | RIS | RefWorks Download Matthew Sfeir, Kin Fai Mak, James Misewich, Tony Heinz Optical conductivity spectra of multi-layer graphene samples were determined for photon energies in the range of 0.2 -- 1.0 eV. The measurements were performed using synchrotron radiatiaon on well-characterized exfoliated graphene samples on a transparent substrate. We observed distinct optical conductivity spectra for different samples having precisely the same number of layers. In particular, two well-defined types of spectra were obtained in measurements of more than a dozen of four-layer samples. This result can be understood by considering the existence of two stable configurations of four-layer graphene, namely, the ABAB Bernel stacking and the ABCA rhombohedral stacking. The observed absorption features were reproduced by explicit calculations, within a tight-binding model, of the optical conductivities for the two stacking sequences. We have thus shown the possibility of identifying these different crystallographic structures optically. Further, the significant difference found in the low-energy electronic structure suggests that the charge transport behavior of multilayer graphene may also depend on stacking order. Published in 2009. Cumulative Annual View Publication The following links allow you to view full publications. These links are maintained by other sources not affiliated with Microsoft Academic Search. 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    03/2009;
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    ABSTRACT: The evolution of the electronic structure of few-layer graphene, for n = 1, 2, 3, , 8 atomic layers, was characterized by optical absorption spectroscopy. Each thickness of few-layer graphene exhibited well defined and distinct infrared absorption peaks associated with interband transitions. The positions of the peaks were found to obey a simple scaling relation with layer thickness. The principal features of the experimental spectra for all samples could be described consistently in terms of the electronic states of the parent graphite material through application of a specific zone-folding construct obtained when only nearest-layer interactions are considered. Both the experiment and analysis permit one to follow the convergence of the multilayer graphene response to that of graphite with increasing sample thickness.
    03/2009;
  • ChemInform 01/2009; 40(25).
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    ABSTRACT: Optical reflectivity and transmission measurements over photon energies between 0.2 and 1.2 eV were performed on single-crystal graphene samples on a SiO2 substrate. For photon energies above 0.5 eV, graphene yielded a spectrally flat optical absorbance of (2.3+/-0.2)%. This result is in agreement with a constant absorbance of pialpha, or a sheet conductivity of pie2/2h, predicted within a model of noninteracting massless Dirac fermions. This simple result breaks down at lower photon energies, where both spectral and sample-to-sample variations were observed. This "nonuniversal" behavior is explained by including the effects of doping and finite temperature, as well as contributions from intraband transitions.
    Physical Review Letters 12/2008; 101(19):196405. · 7.73 Impact Factor
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    ABSTRACT: The current report describes the systematic synthesis of single-crystalline alkaline-earth-metal tungstate AWO4 (A = Ca, Sr, Ba) nanorods as well as a series of their crystalline solid−solution analogues Sr1-xCaxWO4 and Ba1-xSrxWO4 (0 < x < 1) with controllable chemical composition and morphology using a modified template-directed methodology under ambient room-temperature conditions. Extensive characterization of the resulting nanorods has been performed using diffraction, X-ray photoelectron spectroscopy, electron microscopy, and optical spectroscopy. The composition-modulated luminescence properties of these alkaline-earth-metal tungstate solid−solution nanorods provide for a fundamental understanding of the intrinsic optical and optoelectronic properties of these systems, suggesting, therefore, the possibility of their rational incorporation into functional nanoscale devices.
    Chemistry of Materials - CHEM MATER. 08/2008; 20(17).
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    ABSTRACT: We present a systematic and detailed near edge X-ray absorption fine structure (NEXAFS) experimental investigation of the electronic structure and chemistry of iron-based metal oxide nanostructured (FeMONS) materials including BiFeO3, Bi2Fe4O9, α-Fe2O3, γ-Fe2O3, and Fe/Fe3O4. Correlations of the electronic structure and structural chemistry of these intriguing nanomaterials are presented, ranging from the nano to the bulk scale. In this work, variations in the shape, position, and intensity of the O K-edge and Fe L-edge NEXAFS spectra have been analyzed in terms of electronic structure and surface chemistry of the FeMONS materials as compared with that of the bulk. We hypothesize that surface imperfection and surface strain anisotropies in nanoparticles induce distortion and site inequivalency of the oxygen Oh sites around the Fe ion located close to the surface, resulting in an increase in the degree of multiplicity as well as in nonstoichiometric effects in FeMONS materials.
    The Journal of Physical Chemistry C 06/2008; · 4.84 Impact Factor
  • 04/2008: pages 130 - 166; , ISBN: 9783527619436

Publication Stats

2k Citations
336.69 Total Impact Points

Institutions

  • 2004–2013
    • Stony Brook University
      • Department of Chemistry
      Stony Brook, NY, United States
  • 2007–2010
    • Brookhaven National Laboratory
      • Biology Department
      New York City, New York, United States
  • 1999–2010
    • Columbia University
      • Department of Physics
      New York City, NY, United States
  • 2008
    • Freie Universität Berlin
      Berlín, Berlin, Germany
  • 1997
    • Oklahoma State University - Stillwater
      • School of Electrical and Computer Engineering
      Stillwater, OK, United States