Sorting nanoparticles by centrifugal fields in clean media

The on-demand availability of nanomaterials with selected size and well-defined chemical/physical properties is of fundamental importance for their widespread application. We report two clean, rapid, and non-destructive approaches for nanoparticle (NP) size selection in centrifugal fields. The first exploits rate zonal separation in a high viscosity gradient. The second exploits selective sedimentation of NPs with different sizes. These methods are here applied to metallic nanoparticles (MNPs) with different compositions and surface chemistry, dispersed either in water or organic solvents. The approach is general and can also be exploited for the separation of NPs of any material. We selectively sort both Au and AgNPs with sizes in the 10-30 nm range, achieving chemical-free MNPs with low polydispersivity. We do not use solutes, thus avoiding contamination, and only require low centrifugal fields, easily achievable in benchtop systems. © 2013 American Chemical Society.

Electroluminescence of hole block material caused by electron accumulation and hole penetration

In this study, we investigated the electroluminescence (EL) mechanisms and processes of hole block material in the multilayer devices with Eu(TTA)(3)phen (TTA = thenoyltrifluoroacetone, phen = 1,10-phenanthroline) doped CBP (4,4'-N,N'-dicarbazolebiphenyl) as the light-emitting layer (EML). First, the hole block ability of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) was experimentally confirmed by comparing the EL spectra. With increasing hole injection, BCP emission emerges and increases gradually due to the increasing hole penetration from EML into the hole block layer (HBL).

Ultrathin-film growth of para-sexiphenyl (I): Submonolayer thin-film growth as a function of the substrate temperature

The para-sexiphenyl (p-6P) monolayer film induces weak epitaxy growth (WEG) of disk-like organic semiconductors, and their charge mobilities are increased dramatically to the level of the corresponding single crystals [Wang et al., Adv. Mater. 2007, 19, 2168]. The growth behavior and morphology of p-6P monolayer film play decisive roles on WEG. Here, we investigated the growth behavior of p-6P submonolayer film as a function of the substrate temperature. Its growth exhibited two different mechanisms at high and low substrate temperature.

Weak epitaxy growth of metal-free phthalocyanine on p-sexiphenyl monolayer and double-layer films

Weak epitaxy growth (WEG) can afford high-mobility thin films of disk-like organic semiconductor of which mobility is up to the level of the corresponding single crystals. We investigated the WEG behavior and mechanism of planar phthalocyanine in the model system of metal-free phthalocyanine (H2Pc) grown on p-sexiphenyl (p-6P) ultrathin films (monolayers and double layers). Highly oriented H2Pc films with molecules standing up exhibited two kinds of different in-plane orientations, i.e., three sets of in-plane orientations and only one set of in-plane orientation, on p-6P monolayer and double-layer films, respectively.

Effect of secondary ligands' size on energy transfer and electroluminescent efficiencies for a series of europium(III) complexes, a density functional theory study

In this paper, a quantum chemistry method was used to investigate the effect of different sizes of substituted phenanthrolines on absorption, energy transfer, and the electroluminescent performance of a series of Eu(TTA)(3)L (L = [1,10] phenanthroline (Phen), Pyrazino[2,3-f][1,10]phenanthroline (PyPhen), 2-methylprrazino[2,3-f][1,10] phenanthroline(MPP), dipyrido[3,2-a:2',3'-c]phenazine(DPPz), 11-methyldipyrido[3,2-a:2',3'c]phenazine(MDPz), 11.12-dimethyldipyrido[3,2-a:2',3'-c]phenazine(DDPz), and benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (BDPz)) complexes. Absorption spectra calculations show that different sizes of secondary ligands have different effects on transition characters, intensities, and absorption peak positions.

Synthesis, Spectroscopic Properties, and Stabilities of Ternary Europium Complex in SBA-15 and Periodic Mesoporous Organosilica: A Comparative Study

Ternary europium complex Eu(tta)(3)phen was covalently bonded with the general mesoporous. material SBA-15 and SBA-15-type of periodic mesoporous organosilica (PMO) material via impregnation of Eu(tta)(3)center dot 2H(2)O into phen-S15 and phen-PMO, respectively, through a ligand exchange reaction. The parent materials of phen-S15 and phen-PMO were synthesized by co-condensation of tetraethylorthosilicate (TEOS) or 1,2-bis(triethoxysilyl)ethane (BTESE) and the functionalized chelate ligand 5-(N,N-bis(3-triethoxysilyl)propyl)ureyl-1,10-phenanthroline (phen-Si) in the presence of Pluronic P123 surfactant as template, which were confirmed by SEM, XRD, FTIR, Si-29 CP-MAS NMR, and N-2 adsorption measurements.

Novel Near-Infrared Luminescent Hybrid Materials Covalently Linking with Lanthanide [Nd(III), Er(III), Yb(III), and Sm(III)] Complexes via a Primary beta-Diketone Ligand: Synthesis and Photophysical Studies

A series of novel, colorless, and transparent sot-gel derived hybrid materials Ln-DBM-Si covalently grafted with Ln(DBM-OH)(3)center dot 2H(2)O (where DBM-OH = o-hydroxydibenzoylmethane, Ln = Nd, Er, Yb, and Sin) were prepared through the primary beta-diketone ligand DBM-OH. The structures and optical properties of Ln-DBM-Si were studied in detail. The investigation results revealed that the lanthanide complexes were successfully in situ grafted into the corresponding hybrids Ln-DBM-Si. Upon excitation at the maximum absorption of ligands, the resultant materials displayed excellent near-infrared luminescence.

Luminescent and Mesoporous Europium-Doped Bioactive Glasses (MBG) as a Drug Carrier

Luminescent and mesoporous europium-doped bioactive glasses (MBG:Eu) were successfully synthesized by a two-step acid-catalyzed self-assembly process combined with hydrothermal treatment in an inorganic-organic system. The obtained MBG was performed as a drug delivery carrier to investigate the drug storage/release properties using ibuprofen (IBU) as a model drug. The structural, morphological, textural and optical properties were well characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N-2 adsorption/desorption, and photoluminescence (PL) spectra, respectively. The results reveal that the MBG exhibit the typical ordered characteristics of the hexagonal mesostructure. This composite shows sustained release profile with ibuprofen as the model drug. The IBU-loaded samples still show red luminescence of Eu3+ (D-5(0)-F-7(1, 2)) under UV irradiation, and the emission intensities of Eu3+ in the drug carrier system vary with the released amount of IBU, thus making the drug release be easily tracked and monitored by the change of the luminescence intensity.

Shape and Phase-Controlled Synthesis of KMgF3 Colloidal Nanocrystals via Microwave Irradiation

In this paper, we present a facile one-step route to controlled synthesis of colloidal KMgF3 nanocrystals via the thermolysis of metal trifluoroacetate precursors in combined solvents (OA/OM) using microwave irradiation. X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric and differential thermal analysis (TG-DTA), Fourier transform infrared (FT-IR) spectra, and photoluminescence (PL) spectra were employed to characterize the samples. Only through the variation of the OA/OM ratio, can the phase and shape of nanocrystals be readily controlled, resulting in the formation of well-defined near-spherical nanoparticles, and nanoplates of cubic-phased KMgF3, as well as nanorods of tetragonal-phased MgF2, and a possible mechanism has been proposed to elucidate this effect. Furthermore, all these samples in this system can be well dispersed in nonpolar solvents such as cyclohexane to form stable and clear colloidal solutions, due to the successful coating of organic surfactants (OA/OM) on the nanocrystal surface.

LaF3, CeF3, CeF3 : Tb3+, and CeF3 : Tb3+@LaF3 (core-shell) nanoplates: Hydrothermal synthesis and luminescence properties

LaF3. CeF3, CeF3:Tb3+, and CeF3:Tb3+ @LaF3 (core-shell) 2D nanoplates have been successfully synthesized by a facile and effective hydrothermal process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra as well as kinetic decays were used to characterize the samples. The experimental results indicate that the organic additive, trisodium citrate (Cit(3-)), as a shape modifier has the dynamic effect by adjusting the growth rate of different crystal facets, resulting in forming the anisotropic geometries of the final products. The possible formation mechanisms for different products have been presented. The CeF3, CeF3:Tb3+, and CeF3:Tb3+ @LaF3 (core/shell) nanoplates show characteristic emission of Ce3+ (5d-4f) and Tb3+ (f-f), respectively.

Shape-controllable synthesis and upconversion properties of lutetium fluoride (doped with Yb3+/Er3+) microcrystals by hydrothermal process

Lutetium fluorides with different compositions, crystal phases, and morphologies, such as beta-NaLuF4 hexagonal microprisms, microdisks, mirotubes, alpha-NaLuF4 submicrospheres, LuF3 octahedra, and NH4Lu2F7 icosahedra, prolate ellipsoids and spherical particles have been successfully synthesized via a facile hydrothermal route. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction, and photoluminescence spectra were used to characterize the samples. The intrinsic structural feature of lutetium fluorides, the solution pH values, F- sources, and organic additives (Cit(3-) and EDTA) account for the ultimate shape evolutions of the final products. The possible formation mechanisms for products with various architectures have been presented. Additionally, we investigated the upconversion luminescence properties of beta-NaLuF4: 20% Yb3+/2% Er3+ with different morphologies.

Nonconjugated Carbazoles: A Series of Novel Host Materials for Highly Efficient Blue Electrophosphorescent OLEDs

A series of carbazole derivatives was synthesized and their electrical and photophysical properties were investigated. It is shown that the triplet energy levels of these hosts are higher than that of the most popular blue phosphorescent material iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C-2'] picolinate (FIrpic) and the most extensively used phosphorescent host material 4,4'-N,N'-dicarbazole-biphenyl (CBP). These new host materials also showed good thermal stability and high glass transition temperatures (T-g) ranging from 78 to 115 degrees C as the linkage group between the carbazoles was altered. Photophysical measurements indicate that the energy transfer between these new hosts and FIrpic is more efficient than that between CBP and FIrpic. Devices incorporating these novel carbazole derivatives as the host material doped with FIrpic were fabricated with the configurations of ITO/NPB (40 nm)/host:FIrpic (30 nm)/BCP (15 nm)/AlQ (30 nm)/LiF (1 nm)/Al (150 nm). High efficiencies (up to 13.4 cd/A) have been obtained when 1,4-bis (4-(9H-carbazol-9-yl)phenyl)cyclohexane (CBPCH) and bis(4-(9H-carbazol-9-yl)phenyl) ether (CBPE) were used as the host, respectively.

Uniform Lanthanide Orthoborates LnBO(3) (Ln = Gd, Nd, Sm, Eu, Tb, and Dy) Microplates: General Synthesis and Luminescence Properties

A variety of uniform lanthanide orthoborates LnBO(3) (Ln = Gd, Nd, Sm, Eu, Tb, and Dy) microplates have been successfully prepared by a general and facile conversion method. One-dimensional (ID) lanthanide hydroxides were first prepared through a simple hydrothermal process. Subsequently, uniform LnBO(3) microplates were synthesized at the expense of the ID precursors during a hydrothermal conversion process. The whole process in this method was carried out in aqueous condition without the use of any organic solvents, surfactant, or catalyst. The as-obtained rare earth ions doped GdBO3 and TbBO3 microplates show strong light emissions with different colors coming from different activator ions under ultraviolet excitation or low-voltage electron beam excitation, which might find potential applications in fields such as light phosphor powders and advanced flat panel display devices.

Effects of polar group saturation on physical gelation of Amphiphilic polymer solutions

Monte Carlo simulation on the basis of the comblike coarse grained nonpolar/polar (NP) model has been carried out to study the polar group saturation effect on physical gelation of amphiphilic polymer solutions. The effects of polar group saturation due to hydrogen bonding or ion bridging on the sol-gel phase diagram, microstructure of aggregates, and chain conformation of amphiphilic polymer solutions under four different solvent conditions to either the nonpolar backbone or the polar side chain in amphiphilic polymer chains have been investigated. It is found that an increase of polar group saturation results in a monotonically decreased critical concentration of gelation point, which can be qualitatively supported by the dynamic theological measurements on pectin aqueous solutions. Furthermore, various solvent conditions to either the backbone or the side chain have significant impact on both chain conformation and microstructure of aggregates. When the solvent is repulsive to the nonpolar backbone but attractive to the polar side chain, the polymer chains are collapsed, and the gelation follows the mechanism of colloidal packing; at the other solvent conditions, the gelation follows the mechanism of random aggregation.

Sequential deprotonation of meso-(p-hydroxyphenyl)porphyrins in DMF: From hyperporphyrins to sodium porphyrin complexes

Sequential deprotonations of meso-(p-hydroxyphenyl)porphyrins (p-OHTPPH2) in DMF + H2O (V/V = 1:1) mixture have been verified to result in the appearance of hyperporphyrin spectra. However, when the deprotonations of these p-OHTPPH2 are carried out in DMF, the spectral changes differ considerably from those in the mixture mentioned above. At low [OH-], the optical spectra in the visible region are still considered to have characteristics of hyperporphyrin spectra. Further deprotonation at much higher basicity makes the optical spectra form three-banded spectra similar to those in the acidic solution. To clarify the molecular origins of these changes, UV-vis, resonance Raman (RR), proton nuclear magnetic resonance (H-1 NMR) experiments are carried out. Our data give evidence that p-OHTPPH2 in DMF can be further deprotonated of pyrrolic-H by higher concentrated NaOH, due to an aprotic medium like DMF effectively weakening the basicity of the porphyrin relative to that of the NaOH, and coordinates with two sodium ions (except the sodium ions that interact with the peripherial phenoxide anions) to form the sodium complexes of p-OHTPPH2 (Na2P, to lay a strong emphasis on the sodium ions that coordinate with the central nitrogen atom), which can be regarded as the porphyrin anions being perturbed by the sodium cations due to their highly ionic character.