Silica encapsulation of quantum dots and metal clusters

The use of nanometre thick silica shells as a means to stabilize metal clusters and semiconductor particles is discussed, and its potential advantages over conventional organic capping agents are presented. Shell deposition depends on control of the double layer potential, and requires priming of the core particle surface. Chemical reactions are possible within the core, via diffusion of reactants through the shell layer. Quantum dots can be stabilized against photochemical degradation through silica deposition, whilst retaining strong fluorescence quantum yields and their size dependent optical properties. Ordered 3D and 2D arrays of a macroscopic size with uniform particle spacing can be created. Thin colloid films can also be created with well-defined interparticle spacing, allowing controlled coupling of exciton and surface plasmon modes to be investigated. A number of future core–shell nanocomposite structures are postulated, including quantum bubbles and single electron capacitors based on Au@SiO2.

[1]  L. Liz‐Marzán,et al.  Synthesis and Optical Properties of Gold-Labeled Silica Particles , 1995 .

[2]  L. Liz‐Marzán,et al.  Au@SiO2 colloids: effect of temperature on the surface plasmon absorption , 1998 .

[3]  M. Grätzel,et al.  A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films , 1991, Nature.

[4]  Norman Herron,et al.  Optical properties of CdS and PbS clusters encapsulated in zeolites , 1987 .

[5]  E. Matijević,et al.  Stability of colloidal silica: I. Effect of simple electrolytes , 1969 .

[6]  R. Doremus.  Optical Properties of Small Silver Particles , 1965 .

[7]  T. D. Harris,et al.  Surface derivatization and isolation of semiconductor cluster molecules , 1988 .

[8]  Jan K. G. Dhont,et al.  A time resolved static light scattering study on nucleation and crystallization in a colloidal system , 1992 .

[9]  Ying Wang,et al.  PbS in polymers. From molecules to bulk solids , 1987 .

[10]  Paul Mulvaney,et al.  Surface Plasmon Spectroscopy of Nanosized Metal Particles , 1996 .

[11]  A. I. Ekimov,et al.  Quantum size effect in semiconductor microcrystals , 1985 .

[12]  N. Kotov,et al.  Layer-by-Layer Self-Assembly of Polyelectrolyte-Semiconductor Nanoparticle Composite Films , 1995 .

[13]  Hirokazu Miyoshi,et al.  Adsorption and Encapsulation of Fluorescent Probes in Nanoparticles , 1999 .

[14]  P. Mulvaney,et al.  Measurement of the forces between gold surfaces in water by atomic force microscopy , 1994 .

[15]  I. Larson,et al.  Electrokinetic and Direct Force Measurements between Silica and Mica Surfaces in Dilute Electrolyte Solutions , 1997 .

[16]  A. Henglein,et al.  Electrochemistry of multilayer colloids : preparation and absorption spectrum of gold-coated silver particles , 1993 .

[17]  M. Matsumura,et al.  Splitting of water by electrochemical combination of two photocatalytic reactions on TiO2 particles , 1998 .

[18]  Horst Weller,et al.  Photochemistry of colloidal semiconductors. 20. Surface modification and stability of strong luminescing CdS particles , 1987 .

[19]  Vos,et al.  Preparation of photonic crystals made of air spheres in titania , 1998, Science.

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

[21]  P. Mulvaney.  Nucleation and stabilization of quantized AgI clusters in aqueous solution , 1993 .

[22]  Albert P. Philipse,et al.  Preparation and properties of nonaqueous model dispersions of chemically modified, charged silica spheres , 1989 .

[23]  P. Mulvaney,et al.  Double-Layer Interactions between Self-Assembled Monolayers of ω-Mercaptoundecanoic Acid on Gold Surfaces , 1998 .

[24]  J. W. Jansen,et al.  Preparation and characterization of spherical monodisperse silica dispersions in nonaqueous solvents , 1981 .

[25]  Arthur J. Nozik,et al.  Highly efficient band‐edge emission from InP quantum dots , 1996 .

[26]  Alan Campion,et al.  Size quantization effects in cadmium sulfide layers formed by a Langmuir-Blodgett technique , 1988 .

[27]  A. Stein,et al.  Synthesis of macroporous minerals with highly ordered three-dimensional arrays of spheroidal voids , 1998, Science.

[28]  Marc A. Anderson,et al.  Semiconductor clusters in the sol-gel process: quantized aggregation, gelation, and crystal growth in concentrated zinc oxide colloids , 1991 .

[29]  E. Matijević,et al.  Preparation and Properties of Uniform Coated Inorganic Colloidal Particles: 8. Silica on Iron , 1993 .

[30]  A. Fujishima,et al.  New Mesostructured Porous TiO2 Surface Prepared Using a Two-Dimensional Array-Based Template of Silica Particles , 1998 .

[31]  D. Furlong,et al.  Size-quantised semiconductor cadmium chalcogenide particles in Langmuir–Blodgett films , 1992 .

[32]  A. Imhof,et al.  Ordered macroporous materials by emulsion templating , 1997, Nature.

[33]  J. Heath,et al.  Cooperative Phenomena in Artificial Solids Made from Silver Quantum Dots: The Importance of Classical Coupling , 1998 .

[34]  Luis M. Liz-Marzán,et al.  Formation and Stabilization of Silver Nanoparticles through Reduction by N,N-Dimethylformamide , 1999 .

[35]  Stella M. Marinakos,et al.  Gold Nanoparticles as Templates for the Synthesis of Hollow Nanometer-Sized Conductive Polymer Capsules** , 1999 .

[36]  L. Motte,et al.  Self-Assembled Monolayer of Nanosized Particles Differing by Their Sizes , 1995 .

[37]  A. V. Rao,et al.  Processing and characterization of PbS nanocrystallites in TMOS silica xerogels , 1997 .

[38]  A. Maitra,et al.  Nanometer Silica Particles Encapsulating Active Compounds: A Novel Ceramic Drug Carrier , 1998 .

[39]  Cherie R. Kagan,et al.  Electronic energy transfer in CdSe quantum dot solids. , 1996, Physical review letters.

[40]  Paul Mulvaney,et al.  Effect of the Solution Refractive Index on the Color of Gold Colloids , 1994 .

[41]  R. Murray,et al.  Water-Soluble, Isolable Gold Clusters Protected by Tiopronin and Coenzyme A Monolayers , 1999 .

[42]  Louis E. Brus,et al.  Nucleation and Growth of CdSe on ZnS Quantum Crystallite Seeds and Vice Versa, in Inverse Micelle Media , 1990 .

[43]  T. Healy,et al.  Effect of particle size on colloid stability , 1970 .

[44]  Caruso,et al.  Nanoengineering of inorganic and hybrid hollow spheres by colloidal templating , 1998, Science.

[45]  A. Henglein,et al.  Surface chemistry of colloidal gold : deposition of lead and accompanying optical effects , 1992 .

[46]  Paul Mulvaney,et al.  Synthesis of Nanosized Gold−Silica Core−Shell Particles , 1996 .

[47]  C. Zukoski,et al.  STUDY OF ANION ADSORPTION AT THE GOLD-AQUEOUS SOLUTION INTERFACE BY ATOMIC-FORCE MICROSCOPY , 1994 .

[48]  A. Bard,et al.  Use of Atomic Force Microscopy for the Study of Surface Acid-Base Properties of Carboxylic Acid-Terminated Self-Assembled Monolayers , 1997 .

[49]  L. Liz‐Marzán,et al.  Stabilization of CdS semiconductor nanoparticles against photodegradation by a silica coating procedure , 1998 .

[50]  Paul Mulvaney,et al.  Controlled Method for Silica Coating of Silver Colloids. Influence of Coating on the Rate of Chemical Reactions , 1998 .