Synthesis, surface studies, composition and structural characterization of CdSe, core/shell and biologically active nanocrystals

Abstract

Nanostructures, with their very large surface to volume ratio and their non-planar geometry, present an important challenge to surface scientists. New issues arise as to surface characterization, quantification and interface formation. This review summarizes the current state of the art in the synthesis, composition, surface and interface control of CdSe nanocrystal systems, one of the most studied and useful nanostructures. KeywordsCadmium; Selenium; Selenide; CdSe; nanocrystal; quantum dot; nanoparticle; surface; synthesis; electron microscopy; Z-STEM; RBS; alloy; core/shell; fluorescence; quantum yield; growth mechanism; expitaxy; spectroscopy 1.0 Introduction BackgroundWe are currently witnessing an explosion of research in nanoscale science, engineering, and biotechnology. As the nano-revolution proceeds, basic research is leading to the development of true nanotechnologies which have the potential to impact fields from health care and opto-electronics to energy and the environment. One particular type of nanostructure, semiconductor nanocrystals (also known as quantum dots), may ultimately be employed in technologies in each of these fields. For example, antibody-conjugated CdSe/ ZnS core-shell nanocrystals have been used to detect respiratory syncytial virus. 1 The high brightness of the quantum dots enables the virus to be detected in a matter of minutes, whereas the previous assay required 4 days. The ramification of this new technology is that anti-viral drugs can be given early in the infection when they are most effective, reducing Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access Author ManuscriptSurf Sci Rep. Author manuscript; available in PMC 2011 April 6. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript hospitalizations and deaths. In the field of opto-electronics CdSe nanocrystals have been incorporated in light emitting diodes2 -6 and it has been demonstrated that they can serve as the gain media in a laser.7 , 8 Nanocrystals are also poised to play a role in solar energy conversion.9 -14 A specific example is a device in which elongated CdSe nanocrystals (nanorods) are mixed with a conducting polymer and sandwiched between aluminum and indium tin oxide electrodes to create a device with a power conversion efficiency of 1.7 %. 12 Nanocrystals may also have a positive impact on the environment, as it has been shown that they can be used to sequester CO 2 . 15 The spark that ignited two decades of intense research in nanocrystal synthesis, properties, and applications was Louis Brus' demonstration that qua...

Characterization of nanoparticles through medium-energy ion scattering

“…The mean energy loss ⌬E in and the squared variance ⌬W 2 in are calculated from the dE/dx and dW 2 / dx, respectively, of each cell along the inward path. ͑iv͒ In the same way, the mean energy loss ⌬E out and squared variance ⌬W 2 out are calculated for the outgoing path, given by the detection angle 2 . ͑v͒…”

“…1 The latter is usually achieved by techniques involving incident electrons or photons ͑e.g., electron microscopy, x-ray spectroscopy and diffraction, and ultraviolet-visible spectroscopy͒, and to a less extent by using incident ions ͓e.g., Rutherford backscattering spectrometry ͑RBS͔͒. 2 Determining the depth distribution of different chemical elements near and at the surface of solids is of major importance for many aspects of nanotechnology. In principle, this can be accomplished quantitatively with deep subnanometric depth resolution, using ion scattering at energies corresponding to the maximum stopping power and high-energy resolution detection systems.…”

Doping Group IIB Metal Ions into Quantum Dot Shells via the One‐Pot Decomposition of Metal‐Dithiocarbamates

“…[37,38] figure 1 and 2). [11] Quantitative EDS and XPS analysis of CdSe/ZnS-HgS QDs (2a) indicated an increase in the concentration of Hg with increased doping levels in a similar trend to that seen in 1a (see tables S2.1 and S3.1). Crucially, despite the strong affinity of Hg for Se, Cd was detected by both XPS and EDS, which rules out a complete exchange of Cd atoms in the core.…”

“…[1][2][3][4][5] The vast majority of research has been directed into improving the optical properties of quantum dots by increasing quantum yields (QYs), [6][7][8] photostability, [9,10] increasing the range of optical activity [11][12][13] and eliminating "blinking". [14][15][16] Enhancement of the optical properties and QYs relies on the reduction of surface defects in the QD lattice fringes.…”

Challenges and advances in quantum dot fluorescent probes to detect reactive oxygen and nitrogen species: A review

“…Presently, there are numerous comprehensive reviews that have focused broadly on the chemistry of group II-VI, IV-VI and III-V QDs, such as their design, synthesis, surface modifications and optical properties which readers of this article can refer to [58][59][60][61][62][63][64][65][66][67]. However, it is important to discuss certain photophysical properties of QDs that influence their surface chemistry towards sensor development in order to convey a clearer understanding of the behavioural properties of different QD-based fluorescent probes for ROS/RNS.…”