CHIMIE DOUCE: SOFT CHEMISTRY Synthesis of new metastable phases Materials not usually accessible by other methods Synthesis strategy often involves precursor method Often a close relation structurally between precursor phase and product Topotactic transformations

CHIMIE DOUCE: SOFT CHEMISTRY Tournaux synthesis of a new form of TiO2 Beyond Rutile, Anatase, Brookite and Glassy form!!! KNO3 (ToC)  K2O (source) K2O + 4TiO2 (rutile, 1000oC)  K2Ti4O9 K2Ti4O9 + HNO3 (RT)  H2Ti4O9.H2O H2Ti4O9.H2O (500oC)  4TiO2 (new slab structure) + 2H2O

KIRKENDALL EFFECT IN TOURNAUX SYNTHESIS OF SLAB FORM OF TiO2 16K + - 4Ti4+ + 36TiO2  8K2Ti4O9 4Ti4+ - 16K+ + 9K2O  K2Ti4O9 Overall reaction stoichiometry 9K2O + 36TiO2  9K2Ti4O9 RHS/LHS = 8/1 Kirkendall Ratio

RUTILE CRYSTAL STRUCTURE z x y

SEEING THE 1-D CHANELS IN RUTILE

Different to rutile, anatase or brookite forms of TiO2 NEW METASTABLE POLYMORPH OF TiO2 BASED ON K2Ti4O9 SLAB STRUCTURE - (010) PROJECTION SHOWN 1 Topotactic loss of H2O from H2Ti4O9 to give “Ti4O8” (TiO2 slabs) plus H2O, where two bridging oxygens in slab are protonated (TiOHTiOTiOH) 1 1/2 1/2 x2 1 1/3 x2 1 1/3 1/3 x2 1/3 1/2 1/3 x2 1/3 K+ at y = 3/4 1/2 K+ at y = 1/4 Different to rutile, anatase or brookite forms of TiO2

CHIMIE DOUCE: SOFT CHEMISTRY Figlarz synthesis of new WO3 WO3 (cubic form) + 2NaOH  Na2WO4 + H2O Na2WO4 + HCl (aq)  gel Gel (hydrothermal)  3WO3.H2O 3WO3.H2O (air, 420oC)  WO3 (hexagonal tunnel structural form of tungsten trioxide) More open tunnel form than cubic ReO3 form of WO3

Slightly tilted cubic polymorph of WO3 with corner sharing Oh WO6 building blocks, only protons and smaller alkali cations can be injected into cubic shaped voids in structure to form bronzes like NaxWO3 and HxWO3 1-D hexagonal tunnel polymorph of WO3 with corner sharing Oh WO6 building blocks, can inject larger alkali and alkaline earth cations into structure to form bronzes like RbxWO3 and BaxWO3 as well as HxWO3 a 1D proton conductor having mobile protons diffusing from O site to site along channels

Structure of h-WO3 showing large 1-D tunnels Apex sharing WO6 Oh building blocks Hexagonal tunnels Injection of larger M+ cations like K+ and Ba2+ than maximum of Li+ and H+ in c-WO3 Structure of h-WO3 showing large 1-D tunnels

Functional device, LED, laser, sensor, biolabel Ligand capping arrested growth of nanocluster core Growth and ligand capping of nanocluster core High T solvent, ligand, protection, amphiphilic amines, carboxylic acids, phosphines, phosphine oxides, phosphonic acids Inorganic precursor, oxides, sulphides, metals, nucleation of nanocluster seed

nMe2Cd + nnBu3PSe + mnOct3PO  (nOct3PO)m(CdSe)n + n/2C2H6 + nnBu3P Arrested nucleation and growth synthetic method for making semiconductor nanoclusters in a high-boiling solvent. Adding a non-solvent causes the larger nanocrystals to precipitate first, allowing size-selective precipitation and nanocluster scaling laws to be defined nMe2Cd + nnBu3PSe + mnOct3PO  (nOct3PO)m(CdSe)n + n/2C2H6 + nnBu3P

ARRESTED GROWTH OF MONODISPERSED NANOCLUSTERS Hydrophobic sheath of alkane chains of surfactant make the nanoclusters soluble in non-polar solvents - crucial for achieving purification and size selective crystallization of the nanoclusters. nMe2Cd + nnBu3PSe + mnOct3PO  (nOct3PO)m(CdSe)n + n/2C2H6 + nnBu3P Tributylphosphine selenide in a syringe is rapidly injected into a 300C solution of dimethyl cadmium in trioctylphosphine oxide surfactant-ligand-solvent, known as TOPO.

SIZE SELECTIVE CRYSTALLIZATION OF LIGAND CAPPED NANOCLUSTERS Gradually add non-solvent acetone to a toluene solution of capped nanoclusters Causes larger crystals to precipitate then smaller and smaller crystals as the non-solvent concentration increases. Smaller ones more soluble because of easier solvation of less dense packed alkanethiolate chains.

SIZE SELECTIVE CRYSTALLIZATION OF LIGAND CAPPED NANOCLUSTERS When non-solvent added, nc-nc contacts become more favorable than nc-solvent interactions. Larger diameter capped nanoclusters interact via the chains of the alkanethiolate capping ligands more strongly than the smaller ones due to the smaller curvature of their surface and the resulting greater interaction area. As a result they are caused to flocculate that is aggregate and crystallize first.

SIZE SELECTIVE CRYSTALLIZATION OF LIGAND CAPPED NANOCLUSTERS Process repeated to obtain next lower size nanoclusters and procedure repeated to obtain monodispersed alkanethiolate capped gold nanoclusters. Further narrowing of nanocluster size distribution achieved by gel electrophoresis – an electric field driven size exclusion separation stationary phase.

BASICS OF NANOCLUSTER NUCLEATION, GROWTH, CRYSTALLIZATION AND CAPPING STABILIZATION Addition of reagent Gb > Gs supersaturation nucleation aggregation capping and stabilization nMe2Cd + nnBu3PSe + mnOct3PO  (nOct3PO)m(CdSe)n + n/2C2H6 + nnBu3P

CAPPED MONODISPERSED SEMICONDUCTOR NANOCLUSTERS EgC = EgB + (h2/8R2)(1/me* + 1/mh*) - 1.8e2/R Quantum localization term Coulomb interaction between e-h CAPPED MONODISPERSED SEMICONDUCTOR NANOCLUSTERS nMe2Cd + nnBu3PSe + mnOct3PO  (nOct3PO)m(CdSe)n + n/2C2H6 + nnBu3P

SIZE DEPENDENT OPTICAL ABSORPTION SPECTRA OF CAPPED CDSE NANOCLUSTERS, SYNTHESIS AND CHARACTERIZATION OF NEARLY MONODISPERSE CdE (E = S, Se, Te) SEMICONDUCTOR NANOCRYSTALLITES, MURRAY CB, NORRIS DJ, BAWENDI MG, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 115 (19): 8706-8715 SEP 22 1993)

SIZE AND COMPOSITION DEPENDENCE OF THE OPTICAL EMISSION SPECTRA OF CAPPED InAs (RED), InP (GREEN) AND CdSe (BLUE), BRUCHEZ, M.JR; MORONNE, M.; GIN, P.; WEISS, S.; ALIVISATOS, A.P. SEMICONDUCTOR NANOCRYSTALS AS FLUORESCENT BIOLOGICAL LABELS, SCIENCE 1998, 281, 2013

PXRD, MALDI-MS, TEM CHARACTERIZATION OF CLUSTER CORE, CLUSTER SEPARATION LIGAND SHEATH, Nanocluster Synthetic Control – size, shape, composition, surface chemical and physical properties, separation, amorphous, crystalline Do it yourself quantum mechanics – synthetic design of optical, electrical, magnetic properties

nMe2Cd + nnBu3PSe + mnOct3PO  (nOct3PO)m(CdSe)n + n/2C2H6 + nnBu3P ARRESTED GROWTH OF MONODISPERSED NANOCLUSTERS CRYSTALS, FILMS AND LITHOGRAPHIC PATTERNS nMe2Cd + nnBu3PSe + mnOct3PO  (nOct3PO)m(CdSe)n + n/2C2H6 + nnBu3P

MONODISPERSED CAPPED CLUSTER SINGLE CRYSTALS Rogach AFM 2002 methanol 2-propanol toluene MONODISPERSED CAPPED CLUSTER SINGLE CRYSTALS

TRI-LAYER SOLVENT DIFFUSION CRYSTALLIZATION OF CAPPED NANOCLUSTER SINGLE CRYSTALS. MeOH TOP LAYER, TOLUENE BOTTOM LAYER, 2-PROPANOL MIDDLE BUFFER LAYER - OMITTING THE BUFFER LAYER CREATED ILL-DEFINED CRYSTALS, A NEW APPROACH TO CRYSTALLIZATION OF CdSe NANOPARTICLES INTO ORDERED THREE-DIMENSIONAL SUPERLATTICES, TALAPIN DV, SHEVCHENKO EV, KORNOWSKI A, GAPONIK N, HAASE M, ROGACH AL, WELLER H, ADVANCED MATERIALS, 13 (24): 1868, 2001

GOLD ATOMIC DISCRETE STATES GOLD CLUSTER DISCRETE MOLECULE STATES GOLD QUANTUM DOT CARRIER SPATIAL AND QUANTUM CONFINEMENT GOLD COLLOIDAL PARTICLE SURFACE PLASMON – 1850 MICHAEL FARADAY ROYAL INSTITUTION GB PIONEER OF NANO!!! BULK GOLD PLASMON

SELF-ASSEMBLING AUROTHIOL CLUSTERS Diagnostic cluster size dependent optical plasmon resonance originating from dipole oscillations of conduction electrons spatially confined in nanocluster – wavelength plasmon depends on size, type of capping ligand and nature of the environment of nanocluster – also size dependent electrical conductivity – hopping from cluster to cluster - useful in nanoelectronic devices and nanooptical sensors – Faraday would be pleased!!! HAuCl4(aq) + Oct4NBr (Et2O)  Oct4NAuCl4 (Et2O) nOct4NAuCl4(Et2O) + mRSH (tol) + 3nNaBH4  Aun(SR)m (tol)

Relationship between alkanethiolate polymer, nanocluster and self-assembled monolayer

SIZE SELECTIVE CRYSTALLIZATION OF SELF-ASSEMBLING AUROTHIOL CLUSTERS Aun(SR)m Gradually adding a non-solvent such as acetone to a toluene solution of capped gold nanoclusters first causes larger crystals to precipitate, then smaller and smaller crystals, as the non-solvent concentration increases. Smaller ones more soluble because of easier solvation of less dense packed alkanethiolate chains. When non-solvent added, nc-nc contacts become more favorable than nc-solvent interactions. Larger diameter capped gold nanoclusters interact via the chains of the alkanethiolate capping ligands more strongly than the smaller ones due to the smaller curvature of their surface and the resulting greater interaction area. As a result they are caused to flocculate that is aggregate and crystallize first. Process repeated to obtain next lower size nanoclusters and procedure repeated to obtain monodispersed alkanethiolate capped gold nanoclusters.

CAPPED METAL CLUSTER CRYSTAL CLUSTER SELF-ASSEMBLY DRIVEN BY HYDROPHOBIC INTERACTIONS BETWEEN ALKANE TAILS OF ALKANETHIOLATE CAPPING GROUPS ON GOLD NANOCRYSTALLITES U.Landman AM 1996

Plasmonics Basics – Size Effects

Plasmonics Basics – Size Effects What is the the surface plasmon resonance of gold nanostructures. On the top left corner is shown how the electron cloud of free-electrons in the gold respond to an oscillating electromagnetic field, depending on the shape and orientation of the particle. The formation of a dipole causes the emergence of a resonance at a specific wavelength, as shown on the right by the representative absorbance spectra. In the case of spherical particles the plasmon resonance occur at a single frequency, while for elongated nanocrystals you can have two resonance frequencies related with the two dipole oscillation modes (longitudinal or transverse). In the bottom part of the Figure is shown the origin of the absorbance features according to the Mie theory. The absorbance A is expressed as the product of two terms. The first term is scattering-related and has a 1/l dependence, while the second term is exclusively dependent on the dielectric constants of the metal and the surrounding medium. This last term represent the resonant plasmon mode which is shown as a peak centered at the surface plasmon resonance wavelength lSPR. The product of the two terms is the spectrum observed experimentally.

SURFACE PLASMON RESONANCE MIE THEORY Extinction coefficient from Mie theory is the exact solution to Maxwell’s electromagnetic field equations for a plane wave interacting with a homogenous sphere of radius R with the same dielectric constant as bulk metal (scattering and absorption contributions). em is the dielectric constant of the surrounding medium – sensitive to environment e = e1 + ie2 is the complex dielectric constant of the particle Resonance peak occurs whenever the condition e1 = -2em is satisfied – sensitive to change in em of environment hence use as a surface plasmon sensor This is the SPR peak which accounts for the brilliant colors of various metal nanoparticles – form factors can be introduced to account for non-spherical shape – Gans modification of Mie theory.

Extinction spectra calculated using Mie theory for gold nanospheres with diameters varying from 5 nm to 100 nm.

Detecting Biomolecules with Gold Nanocrystals Self Assembly and Plasmon Coupling

Detecting Biomolecules with Gold Nanocrystals Self Assembly and Plasmon Coupling The coupling of plasmons can be used for the detection of oligonucleotides in solution. Gold nanocrystals can be produced with thiol-functionalized oligonucleotides bound to their surface – a construct which we call the probe. The oligonucleotides on the nanocrystals are synthesized to be complementary to the ones one wants to detect. The ultraspecific binding of oligonucleotides for their complementary strand allows the particles to bind very efficiently to the analytes in solution. Such binding of two nanocrystals to the same analyte brings the nanocrystals very close together thus enabling the coupling of the plasmons. As shown in the diagram below, once the nanocrystals are close the dipole can extend over the ensemble of the two nanocrystals (as in resonance r2) while for single isolated particle the dipole is confined to the particle itself (resonance r1). The simultaneous presence of r1 and r2 resonances leads to an effective red shift of the absorbance peak of the nanocrystals thus changing their color, as shown in the photos thereby enabling detection of a specific oligonucleotide which shows complementary Watson-Crick base pairing.

Gold Nanocrystals to Gold Nanorods Gold nanocrystal ncAu seed mediated growth of gold nanorods nrAu ncAu seeds obtained by aqueous sodium borohydride reduction of HAuCl4 with sodium citrate surface stabilization nrAu obtained by surfactant (trimethylcetylammonium bromide CTAB) directed re-growth of ncAu seeds using ascorbic acid mild reducing agent of HAuCl4

Non-Spherical Shapes -Gans Modified Mie Theory

Au Nanorods – Shape Selective Additives Aspect Ratio Tunes Longitudinal NOT Transverse SPR Modes (a) L = 46 nm, w = 22 nm; (b) L = 61 nm, w = 22 nm; (c) L = 73 nm, w = 22 nm; (d) L = 75 nm, w = 22 nm; (e) L = 89 nm, w = 22 nm; (f) L = 108 nm, w = 22 nm. The right panel shows a representative TEM image of the sample corresponding to spectrum-f. Calculated Gans Theory Gold Nanorod w = 20 nm

NANOCHEMISTRY CURES CANCER Gold Nanorods Aspect Ratio Tunes Longitudinal NOT Transverse SPR Modes NANOCHEMISTRY CURES CANCER CANCER CELL TARGETED GOLD NANOROD ATTACHMENT BURN AWAY THOSE NASTY CANCER CELLS BY NANORODS ABSORBING NIR PLASMON AND TRANSFERING HEAT TO CANCER CELL – PHOTOTHERMAL CANCER THERAPY

Nano Medicine - Photothermal Cancer Therapy Using Gold Nanorods

Nano Medicine Photothermal Cancer Therapy Using Gold Nanorods In the top part of the Figure you can see how the plasmons relax back to the equilibrium state after being excited at their resonance. The relaxation occurs through emission of heat that can be used for killing cells to which they are selectively attached. In the middle part of the Figure is shown from the left the absorption/scattering spectrum of the biological tissues and water; the windows of low absorbance are indicated by the pink areas. In the next spectrum is shown how the different absorbances of the tissues at different wavelengths affect the intensity of light propagating in them; as it is shown in the graph the light with wavelength 1000 nm will propagate further than light 500 nm, which is instead strongly absorbed. On the right is a representative absorbance spectrum of gold nanorods highlighting how the second resonance peak can be made to fit in the biological window, thus increasing its potential for photothermal therapy. In the bottom part of the Figure are shown three different lines of cells (nonmalignant HaCat, malignant HSC and malignant HOC cells) after having exposed them to a strong NIR laser light (the circle highlights the area of exposure). The gold nanorods were made to bind selectively to the malignant cells thanks to an active targeting protocol. As you can see the nonmalignant cells were not harmed since they were not targeted by the nanorods. The malignant cells instead suffered strong damage because they were targeted by the nanorods and because the nanorods heated up upon irradiation with the laser.

CAPPED FePt FERROMAGNETIC NANOCLUSTER SUPERLATTICE HIGH-DENSITY DATA STORAGE MATERIALS

NANOMAGNETIC SEPARATIONS OF BIOLOGICAL MOLECULES