Synthesis, Surface Functionalization, and Properties of Freestanding Silicon Nanocrystals
Department of Chemistry, University of Alberta, Edmonton, AB, Canada. Chemical Communications
(Impact Factor: 6.83).
11/2006; 38(40):4160-8. DOI: 10.1039/b607476f
Freestanding silicon nanoparticles (FS-nc-Si) have intriguing chemical and optical properties. The present contribution outlines known synthetic methodologies and protocols for surface functionalization. Recent advancements in tailoring the photoluminescence properties of FS-nc-Si and future research directions will be briefly discussed.
Available from: Tianyuan Guan
- "Liquidphase synthesis has been used to produce II–VI and III–V nanoparticles with controlled size and surface chemistry. For SiNPs, metal reduction and precursor thermal decomposition have been used . A proven solid-phase approach has involved sputtering films of silicon rich oxide, nitride or silicon carbide followed by a high temperature anneal to nucleate and grow randomly dispersed SiNPs . "
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ABSTRACT: Quantum confined silicon nanoparticles (SiNPs) may allow for the fabrication of an all silicon multiple junction photovoltaic cell, or novel photovoltaic cells that surpasses the single junction limitations. One method of growing SiNPs is by PECVD where the plasma is confined to a quartz tube. To further understand this technique, computational fluid dynamic calculation were coupled with experimental growths, which allows for the development of a phase diagram based around the reactor pressure, and gas flow. SiNP size and crystallinity were evaluated using a combination of Raman scattering, X-ray diffraction, and transmission electron microscopy (TEM), these results were used to further the develop the phase diagram. For residence times less than 1 ms, SiNPs were produced a band gap of >1.6 eV, but very low crystallinity. By maintaining a constant low gas flow (100 sccm) and increasing reactor pressure, crystallinity and size of the SiNPs were improved and increased, respectively. For SiNPs grown with a constant residence time (~2 ms), we observe a reduction in the crystallinity with increased gas flow. Closer inspection by TEM showed a significant amount of a-Si with the SiNPs. Using this growth technique we can reliably grow SiNPs with diameters from 3 nm to 8 nm, relating to a photoluminescence peak position from 1.6 eV to 1.3 eV. This range is ideal for the development of an all silicon tandem photovoltaic cell.
Solar Energy Materials and Solar Cells 05/2014; 124:1–9. DOI:10.1016/j.solmat.2014.01.026 · 5.34 Impact Factor
Available from: Susan M Kauzlarich
- "Microwave synthesis leads to highly reproducible results and reaction efficiency . Si nanoparticles can be produced by several different routes, including laser pyrolysis, heat treatment under a reducing atmosphere, plasma decomposition, and colloidal synthesis            . While these methods of producing Si nanoparticles are effective, improvements towards greener chemistry include eliminating the use of HF and reducing the processing steps. "
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ABSTRACT: Silicon nanoparticles can be considered a green material, especially when prepared via a microwave-assisted method without the use of highly reactive reducing agents or hydrofluoric acid. A simple solution synthesis of hydrogen-terminated Si- and Mn-doped Si nanoparticles via microwave-assisted synthesis is demonstrated. The reaction of the Zintl salt, Na(4)Si(4), or Mn-doped Na(4)Si(4), Na(4)Si(4(Mn)), with ammonium bromide, NH(4)Br, produces small dispersible nanoparticles along with larger particles that precipitate. Allylamine and 1-amino-10-undecene were reacted with the hydrogen-terminated Si nanoparticles to provide water solubility and stability. A one-pot, single-reaction process and a one-pot, two-step reaction process were investigated. Details of the microwave-assisted process are provided, with the optimal synthesis being the one-pot, two-step reaction procedure and a total time of about 15 min. The nanoparticles were characterized by transmission electron microscopy (TEM), x-ray diffraction, and fluorescence spectroscopies. The microwave-assisted method reliably produces a narrow size distribution of Si nanoparticles in solution.
Nanotechnology 07/2012; 23(29):294006. DOI:10.1088/0957-4484/23/29/294006 · 3.82 Impact Factor
Available from: Vytas Reipa
- "Such a procedure is typically used to prepare highly photoluminescent SNs; however, a rather polydisperse mixture is produced after sonication, leading to inhomogeneous broadening of the photoluminescence spectrum as a result of distributed bandgap energies and 0957-4484/08/085715+08$30.00 © 2008 IOP Publishing Ltd Printed in the UK varying degrees of surface passivation. It has been speculated that sonication does not produce individual Si nanoparticles, but rather nanocrystalline domains that may be trapped in micron-sized silicon pieces . From a technological point of view, a homogeneous nanoparticle size mixture would be highly desirable, as it narrows the optical bandwidth. "
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ABSTRACT: We have determined the particle size distribution profiles of octane-terminated silicon nanoparticle suspensions, produced using the sonication of electrochemically etched Si wafers. Small-angle neutron scattering data was analyzed separately in high (0.4 nm(-1)<q<3.0 nm(-1)) and low (q<0.4 nm(-1)) scattering vector ranges. Data in the high q range is consistent with the log-normal distribution of isolated spherical particles with median diameter d = 3 ± 0.2 nm. Particle sizes were also indirectly assessed from photoluminescence and optical transmission spectroscopy using the size/bandgap relation: E(g) = 3.44d(-0.5), where E(g) is in eV and d in nm. Both measurements were consistent with the particle size distribution profiles, estimated from ANS data fitting and TEM image analysis. A subpopulation of larger, irregular shape structures in the size range 10-50 nm was also indicated by neutron scattering in the low q range and HRTEM images. However, further studies are warranted to explain a relationship between the slope of scattering intensity versus scattering vector dependence in the intermediate scattering vector range (0.4 nm(-1)<q<1.0 nm(-1)) and the role of non-geometrical Si nanoparticle characteristics (mutual interaction forces, surface termination, etc).
Nanotechnology 02/2008; 19(8):085715. DOI:10.1088/0957-4484/19/8/085715 · 3.82 Impact Factor
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