Abstract Upconversion (UC) refers to nonlinear optical processes in which the sequential absorption of two or more photons leads emission light at shorter wavelength than excitation (anti‐Stokes type emission). In contrast other based on multiphoton absorption, upconversion can be efficiently excited even low densities. The most efficient UC mechanisms are present solid‐state materials doped with rare‐earth ions. development nanocrystal research has evoked increasing interest synthesis...

Highly monodisperse CdSe nanocrystals were prepared in a three-component hexadecylamine-trioctylphosphine oxide-trioctylphosphine (HDA-TOPO-TOP) mixture. This modification of the conventional organometallic synthesis TOPO-TOP provides much better control over growth dynamics, resulting absence defocusing particle size distribution during growth. The room-temperature quantum efficiency band edge luminescence can be improved to 40-60% by surface passivation with inorganic (ZnS) or organic...

Highly efficient photon upconversion in solution is demonstrated for the first time. Transparent colloidal solutions of Yb/Er and Yb/Tm doped NaYF4 nanocrystals show bright emission red, green, blue spectral region by excitation around 1 μm with a laser moderate power (see Figure). These new systems substantial improvement on order 108 compared to previously reported systems. Supporting information this article available WWW under http://www.wiley-vch.de/contents/jc_2089/2004/c0772_s.pdf or...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhotochemistry of colloidal semiconductors. 20. Surface modification and stability strong luminescing CdS particlesLubomir Spanhel, Markus Haase, Horst Weller, Arnim HengleinCite this: J. Am. Chem. Soc. 1987, 109, 19, 5649–5655Publication Date (Print):September 1, 1987Publication History Published online1 May 2002Published inissue 1 September 1987https://doi.org/10.1021/ja00253a015Request reuse permissionsArticle...

Reduction of platinum acetylacetonate and thermodecomposition cobalt carbonyl in the presence 1-adamantanecarboxylic acid were employed different coordinating mixtures to produce monodisperse, highly crystalline CoPt(3) nanoparticles. The mean particle size can be varied from 1.5 7.2 nm by controlling reaction conditions type mixture. As-synthesized particles represent single crystal domains have chemically disordered face-centered cubic (fcc) structure. Nearly spherical nanocrystals found...

The evolution of a nanosized particle in colloidal solution has been studied theoretically. model developed is based on the size dependence activation energies growth and dissolution processes takes into account mass transport dynamics. Using this model, Monte Carlo simulations an ensemble growing nanoparticles during Ostwald ripening have performed, conditions leading to either "focusing" or "defocusing" distribution were found. stationary inherent process ensembles less than 5 nm radius...

High quality CoPt3 nanocrystals were synthesized via simultaneous reduction of platinum acetylacetonate and thermodecomposition cobalt carbonyl in the presence 1-adamantanecarboxylic acid hexadecylamine as stabilizing agents. The high flexibility reproducibility synthesis allows us to consider a model system for hot organometallic metal nanoparticles. Different experimental conditions (reaction temperature, concentration agents, ratio between precursors, etc.) have been investigated reveal...

Advanced colloidal syntheses enable the preparation of monodisperse semiconductors and magnetic alloy nanocrystals. They can be further used as building blocks for fabrication ordered assemblies: two-dimensional three-dimensional arrays supercrystals. This article reviews our recent activities in these fields. A theoretical description evolution an ensemble nanoparticles a solution is applied to problem control over nanocrystal monodispersity.

The distribution of properties within ensembles colloidally grown II-VI and III-V semiconductor nanocrystals was studied. A drastic difference in the photoluminescence efficiencies size-selected fractions observed for both organometallically prepared CdSe InAs colloids CdTe synthesized aqueous medium, indicating a general character phenomenon observed. is attributed to different averaged surface disorder originating from Ostwald ripening growth mechanism when larger particles ensemble grow...

Oxide materials doped with lanthanide ions are technologically important, for example as laser and in lighting applications. Here the wet-chemical synthesis of lanthanide-doped nanomaterials, which may eventually find applications new optoelectronic devices, is reported. It shown that LaPO4 nanomaterials can be prepared high-temperature monazite phase two morphologies—particles fibers—via a low-temperature synthesis. The symmetry main dopant site was determined from Eu3+ emission to same bulk LaPO4.

Colloidal solutions and redispersible powders of nanocrystalline, lanthanide-doped YVO4 have been prepared via a hydrothermal method at 200 °C. High-resolution transmission electron micrographs size-selected samples show highly crystalline particles ranging in size from about 10 to 30 nm. The exhibit the tetragonal zircon structure known for bulk material. Upon UV excitation vanadate host, energy is transferred lanthanide ion strong luminescence (f−f transitions) observed. By analyzing line...

Light converter: The emission of visible light (Vis) upon excitation in the near-infrared (NIR) has been observed for first time a transparent solution. Excitation at 975 nm (marked red picture) optically clear colloidal solutions LuPO4:Yb3+, Tm3+, and YbPO4:Er3+ nanocrystals chloroform leads to upconversion luminescence blue, green, or spectral regions.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhotochemistry and radiation chemistry of colloidal semiconductors. 23. Electron storage on zinc oxide particles size quantizationMarkus Haase, Horst Weller, Arnim HengleinCite this: J. Phys. Chem. 1988, 92, 2, 482–487Publication Date (Print):January 1, 1988Publication History Published online1 May 2002Published inissue 1 January 1988https://pubs.acs.org/doi/10.1021/j100313a047https://doi.org/10.1021/j100313a047research-articleACS...

Quantum leap: Very high quantum yields, thought to be impossible for nanocrystalline phosphor materials, were achieved with CePO4:Tb/LaPO4 core–shell nanoparticles (see picture). Because the LaPO4 shell reduces energy losses at particle surface, transparent colloidal solutions of these 8-nm particles are highly photoluminescent.

Abstract Upconversion core/shell nanocrystals with different mean sizes ranging from 15 to 45 nm were prepared via a modified synthesis procedure based on anhydrous rare‐earth acetates. All particles consist of core NaYF 4 :Yb,Er, doped 18 % Yb 3+ and 2 Er , an inert shell the thickness being equal radius particle. Absolute measurements photoluminescence quantum yield at series excitation power densities show that is already very close microcrystalline upconversion phosphor powder. Smaller...

The synthesis of bifunctional Au/Pt/Au nanoraspberries for use in quantitative situ monitoring platinum-catalyzed reactions by surface-enhanced Raman scattering (SERS) is presented. Highly convolved SERS spectra reaction mixtures can be decomposed into the contributions distinct molecular species multivariate data analysis.

We report different approaches to the synthesis of size series highly luminescent CdSe/CdS core−shell nanocrystals. The mixture hexadecylamine (HDA)−trioctylphosphine oxide (TOPO)−trioctylphosphine (TOP) as stabilizing solvent was found be very suitable for one-pot nearly monodisperse CdSe nanocrystals followed by growing CdS shell a desired thickness. obtained exhibited narrow PL band (fwhm ∼27−35 nm) with reproducible room-temperature quantum yields high 50−85%. emission color is tunable...

Nanoparticles with high photoluminescence quantum yield have been recently considered as possible biolabels and emitters in optoelectronic devices. Now gram amounts of nontoxic, chemically stable LaPO4 :Ce,Tb nanocrystals obtained a coordinating solvent. These nanoparticles can be easily redispersed polar solvents to give scatter-free colloids that exhibit yields up 61 %.

Highly luminescent CdTe nanocrystals were synthesized by reacting dimethylcadmium with different tellurium sources in mixtures of dodecylamine and trioctylphosphine as the coordinating size-regulating solvent. Colloids crystalline nanoparticles zinc blende lattice displaying mean particle sizes between 2.5 7 nm prepared at temperatures from 150 to 220 °C characterized powder XRD, HRTEM, absorption, luminescence spectroscopy. The particles show strong band-edge photoluminescence shifting...

Nanocrystals of LaPO4:Eu and CePO4:Tb with a mean particle size 5 nm narrow distribution have been prepared by reacting the corresponding metal chlorides, phosphoric acid, base at 200 °C in tris(ethylhexyl) phosphate. Highly crystalline material was obtained as confirmed X-ray powder diffraction measurements high-resolution transmission electron microscopy. Successful doping europium evident from splitting intensity pattern luminescence lines. Luminescence lifetime were used to confirm...

The growth of colloidal crystals CdSe via controlled oversaturation is reported by these authors. In individual 3D quantum dot arrays formed in this manner, nanocrystals play the role building blocks—artificial atoms next level hierarchy (see also cover). Two different types crystals— irregular and perfectly faceted hexagonal Figure)—can be prepared, depending on speed nucleation.

A variety of redispersible Eu(3+)-doped LaPO(4) nanoparticles have been prepared in a high-boiling coordinating solvent mixture, and the Eu(3+) lattice sites these materials investigated by luminescence line-narrowing measurements. In this spectroscopic method, ions occupying different are selectively excited with tunable narrow-bandwidth laser system distinguished their spectra ("site-selective spectroscopy"). Depending on concentration dopant, up to three could be identified interior...

The photoluminescence efficiency of InP nanocrystals prepared via the dehalosilylation reaction between indium chloride and tris-(trimethylsilyl)phosphine in mixtures trioctylphosphine oxide can be drastically improved by etching with fluorine compounds, as proposed several years ago Micic et al. A systematic study reported this communication revealed pure photochemical nature process allowed to improve considerably its reproducibility reliability. Applying HF treatment combination...

Abstract KYF 4 /Yb 3+ , Er nanocrystals with a mean diameter of approximately 13 nm were synthesized at 200 °C in the high boiling organic solvent N ‐(2‐hydroxyethyl)ethylenediamine (HEEDA). The particles crystallize cubic phase known from α ‐NaYF and form transparent colloidal solutions tetraethylene glycol (TEG) or propanol. Solutions containing 1 wt % TEG display visible upconversion emission upon continuous wave (CW) excitation 978 nm. Growing undoped on surface increases efficiency by...