Journal ArticleDOI
Composition and size-dependent extinction coefficient of colloidal PbSe quantum dots
Iwan Moreels,Karel Lambert,David De Muynck,Frank Vanhaecke,Dirk Poelman,José C. Martins,Guy Allan,Zeger Hens +7 more
TLDR
In this article, inductively coupled plasma mass spectrometry (ICP-MS) was combined with UV-vis−NIR spectrophotometry and transmission electron microscopy to determine the nanocrystal composition and molar extinction coefficient ϵ of colloidal PbSe quantum dot (Q-PbSe) suspensions.Abstract:
Inductively coupled plasma mass spectrometry (ICP-MS) was combined with UV–vis−NIR spectrophotometry and transmission electron microscopy to determine the nanocrystal composition and molar extinction coefficient ϵ of colloidal PbSe quantum dot (Q-PbSe) suspensions. The ICP-MS results show a nonstoichiometric Pb/Se ratio, with a systematic excess of lead for all samples studied. The observed ratio is consistent with a faceted spherical Q-PbSe model, composed of a quasi stoichiometric Q-PbSe core terminated by a Pb surface shell. At high photon energies, we find that ϵ scales with the nanocrystal volume, irrespective of the Q-PbSe size. From ϵ, we calculated a size-independent absorption coefficient. Its value is in good agreement with the theoretical value for bulk PbSe. At the band gap, ϵ is size-dependent. The resulting absorption coefficient increases quadratically with decreasing Q-PbSe size. Calculations of the oscillator strength of the first optical transition are in good agreement with theoretical ...read more
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Towards a definition of inorganic nanoparticles from an environmental, health and safety perspective
Mélanie Auffan,Jérôme Rose,Jérôme Rose,Jean-Yves Bottero,Jean-Yves Bottero,Gregory V. Lowry,Gregory V. Lowry,Jean-Pierre Jolivet,Jean-Pierre Jolivet,Mark R. Wiesner +9 more
TL;DR: It is argued that evidence for novel size-dependent properties alone, rather than particle size, should be the primary criterion in any definition of nanoparticles when making decisions about their regulation for environmental, health and safety reasons.
Journal ArticleDOI
Deep ultraviolet photoluminescence of water-soluble self-passivated graphene quantum dots
Libin Tang,Rongbin Ji,Xiangke Cao,Jingyu Lin,Hongxing Jiang,Li Xueming,Kar Seng Teng,Chi Man Luk,Songjun Zeng,Jianhua Hao,Shu Ping Lau +10 more
TL;DR: The G QDs are capable of converting blue light into white light when the GQDs are coated onto a blue light emitting diode and the photoluminescence quantum yields were determined to be 7-11%.
Journal ArticleDOI
The surface science of nanocrystals.
Michael A. Boles,Daishun Ling,Daishun Ling,Taeghwan Hyeon,Dmitri V. Talapin,Dmitri V. Talapin +5 more
TL;DR: The role of surface ligands in tuning and rationally designing properties of functional nanomaterials and their importance for biomedical and optoelectronic applications is focused on and an assessment of application-targeted surface engineering is concluded.
Journal ArticleDOI
Size-dependent optical properties of colloidal PbS quantum dots.
Iwan Moreels,Karel Lambert,Dries Smeets,David De Muynck,Tom Nollet,José C. Martins,Frank Vanhaecke,André Vantomme,Christophe Delerue,Guy Allan,Zeger Hens +10 more
TL;DR: At high energies, the molar extinction coefficient epsilon increases with the Qdot volume d(3) and agrees with theoretical calculations using the Maxwell-Garnett effective medium theory and bulk values for the Q dot dielectric function.
Journal ArticleDOI
Building devices from colloidal quantum dots.
TL;DR: Recent progress in tailoring and combining quantum dots to build electronic and optoelectronic devices and new ligand chemistries and matrix materials have been reported that provide freedom to control the dynamics of excitons and charge carriers and to design device interfaces are reviewed.
References
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Journal ArticleDOI
Experimental Determination of the Extinction Coefficient of CdTe, CdSe, and CdS Nanocrystals
TL;DR: In this article, the extinction coefficient per mole of nanocrystals at the first exitonic absorption peak, e.g., for high-quality CdTe, CdSe, and CdS, was found to be strongly dependent on the size of the nanocrystal, between a square and a cubic dependence.
Journal ArticleDOI
Nanometer-sized semiconductor clusters: materials synthesis, quantum size effects, and photophysical properties
Ying Wang,Norman Herron +1 more
TL;DR: In this article, the size effect on the optical and photophysical properties of semiconductor clusters has been studied in the condensed phase and the current status of materials synthesis and the prospect for making monodisperse clusters of well-defined surfaces has been discussed.
Journal ArticleDOI
Quantum-size effects of interacting electrons and holes in semiconductor microcrystals with spherical shape
TL;DR: In this article, an extensive numerical calculation for the eigenvalue problem is carried out by Ritz's variational technique, and the motional state of the lowest level is classified into three regimes: the regime of exciton confinement for R/${a}_{B}^{\mathrm{*}}$\ensuremath{\gtrsim}4, the regime for individual particle confinement forR/${b}^{*}+1.2.
Journal ArticleDOI
CdS Nanoclusters: Synthesis, Characterization, Size Dependent Oscillator Strength, Temperature Shift of the Excitonic Transition Energy, and Reversible Absorbance Shift
Tobias Vossmeyer,Lynne Katsikas,Michael Giersig,Ivanka G. Popović,K. Diesner,Abdelkrim Chemseddine,Alexander Eychmueller,Horst Weller +7 more
TL;DR: In this paper, the size-dependent shift of the Is-Is excitonic transition is in agreement with the tight-binding theory and the pseudopotential theory, and as expected by quantum mechanical calculations the oscillator strength of the transition increases proportional to 1 /r3.
Journal ArticleDOI
Colloidal synthesis of nanocrystals and nanocrystal superlattices
Christopher B. Murray,Shouheng Sun,Wolfgang Gaschler,Hugh Doyle,Theodore A. Betley,Cherie R. Kagan +5 more
TL;DR: This paper provides an overview of the synthetic techniques used to prepare colloidal nanocrystals of controlled composition, size, shape, and internal structure and the methods for manipulating these Ns.