Synthesis of Ligand-Stabilized Silicon Nanocrystals with Size-Dependent Photoluminescence Spanning Visible to Near-Infrared Wavelengths

We report a chemical route to colloidal silicon (Si) nanocrystals, or quantum dots, with widely tunable average diameter, from less than 3 nm up to 90 nm and peak photoluminescence (PL) from visible wavelengths to the bulk band gap of Si at 1100 nm. The synthesis relies on the high temperature (>1100 °C) decomposition of hydrogen silsesquioxane (HSQ) to obtain Si quantum dots with good crystallinity and a narrow size distribution with tunable size embedded in SiO2. The oxide matrix is removed by hydrofluoric acid etching in the dark. Subsequent thermal hydrosilylation with alkenes yields free, solvent-dispersible Si nanocrystals with bright PL. The relationship between PL energy and size, exhaustively characterized by transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and X-ray diffraction (XRD), is reported.

[1]  S. Bhatia,et al.  Probing the Cytotoxicity Of Semiconductor Quantum Dots. , 2004, Nano letters.

[2]  T. Hasegawa,et al.  Size-tunable UV-luminescent silicon nanocrystals. , 2010, Small.

[3]  José María Ripalda,et al.  Behavior of oxygen doped SiC thin films: An x-ray photoelectron spectroscopy study , 2001 .

[4]  S. Ramesh,et al.  Colloidal Synthesis of Silicon Nanocrystals Via Inverse Micelles Microemulsion , 2009 .

[5]  J. Veinot,et al.  From phenylsiloxane polymer composition to size-controlled silicon carbide nanocrystals. , 2009, Journal of the American Chemical Society.

[6]  Michael J Sailor,et al.  Biodegradable luminescent porous silicon nanoparticles for in vivo applications. , 2009, Nature materials.

[7]  Louis E. Brus,et al.  A luminescent silicon nanocrystal colloid via a high-temperature aerosol reaction , 1993 .

[8]  Jillian M Buriak,et al.  Organometallic chemistry on silicon and germanium surfaces. , 2002, Chemical reviews.

[9]  F. Koch,et al.  Optical absorption cross sections of Si nanocrystals , 2000 .

[10]  B. Korgel,et al.  Small-angle x-ray-scattering study of silver-nanocrystal disorder-order phase transitions , 1999 .

[11]  C. Hessel,et al.  An investigation of the formation and growth of oxide-embedded silicon nanocrystals in hydrogen silsesquioxane-derived nanocomposites , 2007 .

[12]  T. Sham,et al.  Origin of Luminescence from Silicon Nanocrystals: a Near Edge X-ray Absorption Fine Structure (NEXAFS) and X-ray Excited Optical Luminescence (XEOL) Study of Oxide-Embedded and Free-Standing Systems , 2008 .

[13]  Isao Matsui,et al.  Micro-emulsion synthesis of monodisperse surface stabilized silicon nanocrystals. , 2005, Chemical communications.

[14]  Mark T. Swihart,et al.  Luminescent Colloidal Dispersion of Silicon Quantum Dots from Microwave Plasma Synthesis: Exploring the Photoluminescence Behavior Across the Visible Spectrum , 2009 .

[15]  Kirk J. Ziegler,et al.  Highly luminescent silicon nanocrystals with discrete optical transitions. , 2001, Journal of the American Chemical Society.

[16]  G. Fournet,et al.  Small‐Angle Scattering of X‐Rays , 1956 .

[17]  B. Korgel,et al.  Assembly and Self-Organization of Silver Nanocrystal Superlattices: Ordered “Soft Spheres” , 1998 .

[18]  L. De Cola,et al.  Alkyl-functionalized oxide-free silicon nanoparticles: synthesis and optical properties. , 2008, Small.

[19]  J. Heath,et al.  A Liquid-Solution-Phase Synthesis of Crystalline Silicon , 1992, Science.

[20]  J. Luther,et al.  Absolute Photoluminescence Quantum Yields of IR-26 Dye, PbS, and PbSe Quantum Dots , 2010 .

[21]  Rebecca J. Anthony,et al.  Hybrid silicon nanocrystal-organic light-emitting devices for infrared electroluminescence. , 2010, Nano letters.

[22]  Rossiĭskai︠a︡ akademii︠a︡ nauk,et al.  Soviet physics. Semiconductors , 1967 .

[23]  Grace M. Credo,et al.  Luminescent Colloidal Silicon Suspensions from Porous Silicon , 1992, Science.

[24]  Doinita Neiner,et al.  Low-temperature solution route to macroscopic amounts of hydrogen terminated silicon nanoparticles. , 2006, Journal of the American Chemical Society.

[25]  L. Canham.  Silicon quantum wire array fabrication by electrochemical and chemical dissolution of wafers , 1990 .

[26]  C. Hessel,et al.  Hydrogen Silsesquioxane: A Molecular Precursor for Nanocrystalline Si−SiO2 Composites and Freestanding Hydride-Surface-Terminated Silicon Nanoparticles , 2006 .

[27]  P. F. Szajowski,et al.  Quantum Confinement in Size-Selected, Surface-Oxidized Silicon Nanocrystals , 1993, Science.

[28]  G. Ozin,et al.  Visible colloidal nanocrystal silicon light-emitting diode. , 2011, Nano letters.

[29]  U. Kortshagen,et al.  High-yield plasma synthesis of luminescent silicon nanocrystals. , 2005, Nano letters.

[30]  O. Glatter,et al.  19 – Small-Angle X-ray Scattering , 1973 .

[31]  C. B. Carter,et al.  Air-stable full-visible-spectrum emission from silicon nanocrystals synthesized by an all-gas-phase plasma approach , 2008, Nanotechnology.

[32]  Katherine A. Pettigrew,et al.  Solution Synthesis of Alkyl- and Alkyl/Alkoxy-Capped Silicon Nanoparticles via Oxidation of Mg2Si , 2003 .

[33]  A. G. Cullis,et al.  The structural and luminescence properties of porous silicon , 1997 .

[34]  Xiaogang Peng,et al.  Experimental Determination of the Extinction Coefficient of CdTe, CdSe, and CdS Nanocrystals , 2003 .

[35]  Uwe R. Kortshagen,et al.  Silicon nanocrystals with ensemble quantum yields exceeding 60 , 2006 .

[36]  U. Kortshagen,et al.  Size-dependent intrinsic radiative decay rates of silicon nanocrystals at large confinement energies. , 2008, Physical review letters.

[37]  J. Kelly,et al.  Influence of HSiO1.5 Sol−Gel Polymer Structure and Composition on the Size and Luminescent Properties of Silicon Nanocrystals , 2009 .

[38]  J. L. Hueso,et al.  Alkyl passivation and amphiphilic polymer coating of silicon nanocrystals for diagnostic imaging. , 2010, Small.

[39]  L. Canham.  Bioactive silicon structure fabrication through nanoetching techniques , 1995 .

[40]  J. Jorné,et al.  Electronic States and Luminescence in Porous Silicon Quantum Dots: The Role of Oxygen , 1999 .

[41]  Doinita Neiner,et al.  A new solution route to hydrogen-terminated silicon nanoparticles: synthesis, functionalization and water stability , 2007, Nanotechnology.

[42]  Mark T Swihart,et al.  Efficient surface grafting of luminescent silicon quantum dots by photoinitiated hydrosilylation. , 2005, Langmuir : the ACS journal of surfaces and colloids.

[43]  Kelly P. Knutsen,et al.  Multiple exciton generation in colloidal silicon nanocrystals. , 2007, Nano letters.

[44]  Ken-Tye Yong,et al.  Biocompatible luminescent silicon quantum dots for imaging of cancer cells. , 2008, ACS nano.

[45]  Michael J. Sailor,et al.  Enhanced photoemission from short-wavelength photochemically etched porous silicon , 1993 .

[46]  M. Fleischauer,et al.  Size-dependent reactivity in hydrosilylation of silicon nanocrystals. , 2011, Journal of the American Chemical Society.

[47]  P. Trwoga,et al.  Modeling the contribution of quantum confinement to luminescence from silicon nanoclusters , 1998 .

[48]  Rebecca J. Anthony,et al.  High-efficiency silicon nanocrystal light-emitting devices. , 2011, Nano letters.

[49]  K. Kolasinski.  Etching of silicon in fluoride solutions , 2009 .

[50]  V. Bulović,et al.  1.3 μm to 1.55 μm Tunable Electroluminescence from PbSe Quantum Dots Embedded within an Organic Device , 2003 .

[51]  J. Kelly,et al.  An investigation into near-UV hydrosilylation of freestanding silicon nanocrystals. , 2010, ACS nano.

[52]  Lindsay E. Pell,et al.  Optical properties of silicon nanocrystals synthesized in supercritical fluids , 2002, SPIE Optics + Photonics.

[53]  Mark T. Swihart,et al.  Process for preparing macroscopic quantities of brightly photoluminescent silicon nanoparticles with emission spanning the visible spectrum , 2003 .

[54]  Susan M. Kauzlarich,et al.  Synthesis of Alkyl-Terminated Silicon Nanoclusters by a Solution Route , 1999 .

[55]  Paul F. Barbara,et al.  Size Tunable Visible Luminescence from Individual Organic Monolayer Stabilized Silicon Nanocrystal Quantum Dots , 2002 .

[56]  R. Weissleder.  A clearer vision for in vivo imaging , 2001, Nature Biotechnology.