Ultrafast optical spectroscopy of surface-modified silicon quantum dots: unraveling the underlying mechanism of the ultrabright and color-tunable photoluminescence

Ultrafast spectroscopy shows that novel surface states give rise to ultrabright photoluminescence from surface-modified silicon quantum dots. Specifically, researchers from Jilin University and Fudan University in China used femtosecond transient absorption spectroscopy in combination with time-resolved fluorescence spectroscopy to investigate the underlying mechanism for the ultrabright, colour-tunable photoluminescence, which they had previously observed from nitrogen-containing, colloidal silicon quantum dots passivated by organic ligands. They discovered that the mechanism was related to exciton wave functions being modulated by surface molecular engineering. Based on this insight, they produced surface-modified silicon quantum dots that had identical sizes and yet whose emissions ranged in colour from deep blue to orange. This novel approach involves tailoring the surfaces of nanoparticles in contrast to the conventional approach of varying the nanoparticle size.

[1]  Ruiqin Q. Zhang,et al.  Photo and pH stable, highly-luminescent silicon nanospheres and their bioconjugates for immunofluorescent cell imaging. , 2009, Journal of the American Chemical Society.

[2]  T. Gregorkiewicz,et al.  Red spectral shift and enhanced quantum efficiency in phonon-free photoluminescence from silicon nanocrystals. , 2010, Nature nanotechnology.

[3]  Snejana Bakardjieva,et al.  Brightly luminescent organically capped silicon nanocrystals fabricated at room temperature and atmospheric pressure. , 2010, ACS nano.

[4]  A. Sa’ar.  Photoluminescence from silicon nanostructures: The mutual role of quantum confinement and surface chemistry , 2009 .

[5]  Zhenhui Kang,et al.  Small-sized silicon nanoparticles: new nanolights and nanocatalysts. , 2011, Nanoscale.

[6]  H. Wiggers,et al.  Femtosecond transient absorption spectroscopy of silanized silicon quantum dots , 2008 .

[7]  S. Cloutier,et al.  Optical gain and stimulated emission in periodic nanopatterned crystalline silicon , 2005, Nature materials.

[8]  M. Dasog,et al.  Size vs surface: tuning the photoluminescence of freestanding silicon nanocrystals across the visible spectrum via surface groups. , 2014, ACS nano.

[9]  Bai Yang,et al.  Direct Observation of Quantum‐Confined Graphene‐Like States and Novel Hybrid States in Graphene Oxide by Transient Spectroscopy , 2013, Advanced materials.

[10]  C. Tsang,et al.  Water‐Soluble Silicon Quantum Dots with Wavelength‐Tunable Photoluminescence , 2009 .

[11]  Stephan Lüttjohann,et al.  Silicon nanoparticles: Absorption, emission, and the nature of the electronic bandgap , 2007 .

[12]  Rebecca J. Anthony,et al.  Photoluminescence quantum yields of amorphous and crystalline silicon nanoparticles , 2009 .

[13]  Hong Ding,et al.  In vivo targeted cancer imaging, sentinel lymph node mapping and multi-channel imaging with biocompatible silicon nanocrystals. , 2011, ACS nano.

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

[15]  N. Browning,et al.  Femtosecond ligand/core dynamics of microwave-assisted synthesized silicon quantum dots in aqueous solution. , 2011, Journal of the American Chemical Society.

[16]  Yi Luo,et al.  The realistic domain structure of as-synthesized graphene oxide from ultrafast spectroscopy. , 2013, Journal of the American Chemical Society.

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

[18]  Lindsay E. Pell,et al.  Electrochemistry and Electrogenerated Chemiluminescence from Silicon Nanocrystal Quantum Dots , 2002, Science.

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

[20]  Hybertsen.  Absorption and emission of light in nanoscale silicon structures. , 1994, Physical review letters.

[21]  Ultrafast Excitation Energy Transfer in Vinylpyridine Terminated Silicon Quantum Dots , 2011 .

[22]  Ilsoo Kim,et al.  Two-dimensionally grown single-crystal silicon nanosheets with tunable visible-light emissions. , 2014, ACS nano.

[23]  Junwei Wei,et al.  Synthesis of Ligand-Stabilized Silicon Nanocrystals with Size-Dependent Photoluminescence Spanning Visible to Near-Infrared Wavelengths , 2012 .

[24]  N. Shirahata.  Colloidal Si nanocrystals: a controlled organic-inorganic interface and its implications of color-tuning and chemical design toward sophisticated architectures. , 2011, Physical chemistry chemical physics : PCCP.

[25]  Jian Chang,et al.  Surface-modified silicon nanoparticles with ultrabright photoluminescence and single-exponential decay for nanoscale fluorescence lifetime imaging of temperature. , 2013, Journal of the American Chemical Society.

[26]  L. Wheeler,et al.  Hypervalent surface interactions for colloidal stability and doping of silicon nanocrystals , 2013, Nature Communications.

[27]  S. Campbell,et al.  Room-temperature atmospheric oxidation of Si nanocrystals after HF etching , 2007 .

[28]  George C Schatz,et al.  On the origin of photoluminescence in silicon nanocrystals: pressure-dependent structural and optical studies. , 2012, Nano letters.

[29]  I. Balberg,et al.  Doping and quantum confinement effects in single Si nanocrystals observed by scanning tunneling spectroscopy. , 2013, Nano letters.

[30]  Lei Wang,et al.  Transient Absorption Spectroscopic Study on Band-Structure-Type Change in CdTe/CdS Core-Shell Quantum Dots , 2011, IEEE Journal of Quantum Electronics.

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

[32]  Susan M. Kauzlarich,et al.  Chemical insight into the origin of red and blue photoluminescence arising from freestanding silicon nanocrystals. , 2013, ACS nano.

[33]  D. Haarer,et al.  Excited-State Relaxation Dynamics of 3-Vinylthiophene-Terminated Silicon Quantum Dots , 2010 .

[34]  S. Kauzlarich,et al.  Red States versus Blue States in Colloidal Silicon Nanocrystals: Exciton Sequestration into Low-Density Traps , 2013 .

[35]  H. Vach.  Ultrastable silicon nanocrystals due to electron delocalization. , 2011, Nano letters.

[36]  Shui-Tong Lee,et al.  Photoluminescence of silicon quantum dots in nanospheres. , 2012, Nanoscale.

[37]  Qidai Chen,et al.  Internal structure-mediated ultrafast energy transfer in self-assembled polymer-blend dots. , 2013, Nanoscale.

[38]  W. Shen,et al.  Identification and control of the origin of photoluminescence from silicon quantum dots , 2008, Nanotechnology.

[39]  Lorenzo Pavesi,et al.  Optical gain in silicon nanocrystals , 2001 .

[40]  G Van Tendeloo,et al.  Classification and control of the origin of photoluminescence from Si nanocrystals. , 2008, Nature nanotechnology.

[41]  Yao He,et al.  One-pot microwave synthesis of water-dispersible, ultraphoto- and pH-stable, and highly fluorescent silicon quantum dots. , 2011, Journal of the American Chemical Society.

[42]  T. Krauss,et al.  Silicon nanostructures for photonics and photovoltaics. , 2014, Nature nanotechnology.

[43]  J. Valenta,et al.  Direct Bandgap Silicon: Tensile‐Strained Silicon Nanocrystals , 2014 .

[44]  X. Wen,et al.  Intrinsic and Extrinsic Fluorescence in Carbon Nanodots: Ultrafast Time‐Resolved Fluorescence and Carrier Dynamics , 2013 .

[45]  Daniel C. Hannah,et al.  Ultrafast Photoluminescence in Quantum-Confined Silicon Nanocrystals Arises from an Amorphous Surface Layer , 2014 .

[46]  Yong‐Lai Zhang,et al.  Hierarchical self-assembly of CdTe quantum dots into hyperbranched nanobundles: suppression of biexciton Auger recombination. , 2011, Nanoscale.

[47]  Bai Yang,et al.  Common origin of green luminescence in carbon nanodots and graphene quantum dots. , 2014, ACS nano.

[48]  J. Valenta,et al.  Microscopic origin of the fast blue-green luminescence of chemically synthesized non-oxidized silicon quantum dots. , 2012, Small.

[49]  D. M. Kroll,et al.  Ensemble brightening and enhanced quantum yield in size-purified silicon nanocrystals. , 2012, ACS nano.

[50]  Bai Yang,et al.  Unraveling Bright Molecule‐Like State and Dark Intrinsic State in Green‐Fluorescence Graphene Quantum Dots via Ultrafast Spectroscopy , 2013 .

[51]  L. Mitas,et al.  Observation of a magic discrete family of ultrabright Si nanoparticles , 2002 .

[52]  Haotong Wei,et al.  Unraveling Charge Separation and Transport Mechanisms in Aqueous‐Processed Polymer/CdTe Nanocrystal Hybrid Solar Cells , 2014 .

[53]  Tom Gregorkiewicz,et al.  Surface brightens up Si quantum dots: direct bandgap-like size-tunable emission , 2013, Light: Science & Applications.

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

[55]  U. Kortshagen,et al.  Optimization of Si NC/P3HT Hybrid Solar Cells , 2010 .