The effect of triethylamine on dye-sensitized upconversion luminescence and its application in nanoprobes and photostability.

Triethylamine (TEA) is an effective medium for inhibiting dye aggregation and improving the luminescence of dye-sensitized lanthanide-doped upconversion nanoparticles (UCNPs). However, excessive TEA will cause quenching of upconversion luminescence. In this paper, the possible mechanism of TEA affecting upconversion luminescence is discussed. It is found that TEA can enhance the nucleophilicity of the solvent, leading to dye shedding from the nanoparticles. Reducing the dielectric constant of the solvent can make TEA play a more positive role in upconversion luminescence and photostability of dye-sensitized UCNPs. When heptanol is selected as the solvent for CyBSO-sensitized ß-NaYF4:20%Yb3+,2%Er3+ (UNs), TEA can increase the upconversion luminescence by 6.0 times relative to that in methanol. More importantly, the optimal content of TEA in heptanol is 3700 times more than that in methanol. Under the action of large amounts of TEA in heptanol, a novel upconversion nanoprobe for detecting ascorbic acid is developed with a limit of detection of 0.103 µM and high selectivity over potential interfering species. Meanwhile, the high concentration of TEA in heptanol can improve the photostability of CyBSO-sensitized UNs by 10.4 times, which is of paramount importance for the practical application of dye-sensitized UCNPs.

Picosecond mid-infrared optical parametric amplifier based on LiInSe2 with tenability extending from 3.6 to 4.8 µm.

A picosecond (ps) mid-infrared (MIR) optical parametric amplifier (OPA) with LiInSe2 crystal was demonstrated for the first time. The MIR OPA was pumped by a 30 ps 1064 nm Nd:YAG laser and injected by a barium boron oxide (BBO)-based widely tunable near-infrared seed. A maximum idler pulse energy of 433 µJ at 4 µm has been obtained under a pump energy of 17 mJ, and the corresponding pulse duration was estimated to be ~13 ps. To our knowledge, this is the highest single pulse energy generated by LiInSe2 crystal. Furthermore, an idler spectrum tuning from 3.6 to 4.8 µm was investigated at fixed pump energy of 15 mJ.

A14MgBi11 (A = Ca, Sr, Eu): Magnesium Bismuth Based Zintl Phases as Potential Thermoelectric Materials.

A series of new magnesium bismuth Zintl phases, A14MgBi11 (A = Ca, Sr, Eu), have been synthesized, and their thermoelectric properties were systematically evaluated. These novel phases belong to the well-known Yb14MnSb11 family, whose structure adopts the tetragonal space group I41/acd (No. 142) with cell parameters of a = 17.0470(17)/17.854(2)/17.6660(7) Å and c = 22.665(5)/23.580(6)/23.2446(18) Å for Ca14MgBi11, Sr14MgBi11, and Eu14MgBi11, respectively. Without intentional optimization, these materials exhibit high potential as new thermoelectric candidates. Especially for Sr14MgBi11, a high zT value of 0.72 has been approached at 1073 K. The discovery of these new Zintl series is very interesting, which implies the high possibility of extending the 14-1-11 thermoelectric system to the bismuth analogues in the development of highly efficient thermoelectric materials. Density functional theory (DFT) calculations were incorporated as well to help better understand the properties of these important compounds.

Structure, Magnetism, and Thermoelectric Properties of Magnesium-Containing Antimonide Zintl Phases Sr14MgSb11 and Eu14MgSb11.

New Mg-containing antimonide Zintl phases, Sr14MgSb11 and Eu14MgSb11, were synthesized from high-temperature solid-state reactions in Ta tubes at 1323 K. Their structures can be viewed as derived from the Ca14AlSb11 structure type, which adopt the tetragonal space group I41/acd (No. 142, Z = 8) with the cell parameters of a = 17.5691(14)/17.3442(11) Å and c = 23.399(4)/22.981(3) Å for the Sr- and Eu-containing compounds, respectively. The corresponding thermoelectric properties were probed, which demonstrated high potential of these compounds as new thermoelectrics for their very low thermal conductivity and moderate Seebeck coefficient. Magnetism studies and theoretical calculations were conducted as well to better understand the structure-and-property correlation of these materials.

Structural variability versus structural flexibility. A case study of Eu9Cd4+xSb9 and Ca9Mn4+xSb9 (x ≈ (1)/2).

The focus of this article is on the synthesis and structural characterization of the new ternary antimonides Eu(9)Cd(4+x)Sb(9) and Ca(9)Mn(4+x)Sb(9) (x ≈ (1)/2). Although these compounds have analogous chemical makeup and formulas, which may suggest isotypism, they actually belong to two different structure types. Eu(9)Cd(4.45(1))Sb(9) is isostructural with the previously reported Eu(9)Zn(4.5)Sb(9) (Pbam), and its structure has unit cell parameters a = 12.9178(11) Å, b = 23.025(2) Å, and c = 4.7767(4) Å. Ca(9)Mn(4.41(1))Sb(9) crystallizes in the orthorhombic space group Pnma with unit cell dimensions a = 12.490(2) Å, b = 4.6292(8) Å, and c = 44.197(8) Å and constitutes a new structure type. The two structures are compared and contrasted, and the structural relationships are discussed. Exploratory work aimed at the arsenic-based analogues of either type led to the identification of Ca(9)Zn(4.46(1))As(9), forming with the latter structure [a = 11.855(2) Å, b = 4.2747(8) Å, and c = 41.440(8) Å]. Differential thermal analysis and electrical resistivity measurements, performed on single crystals of Ca(9)Zn(4+x)As(9), indicate high thermal stability and semiconducting behavior. Magnetic susceptibility measurements on Eu(9)Cd(4+x)Sb(9) samples confirm the expected Eu(2+) ([Xe]4f(7)) ground state.

Sr14Sn3As12 and Eu14Sn3As12: enantiomorph-like Zintl compounds.

Two new chiral Zintl compounds, Sr14Sn3As12 and Eu14Sn3As12, were synthesized from tin-flux reactions, and the structures were determined by using single-crystal X-ray diffraction. Both compounds crystallize in the trigonal space group R3 (No. 146, Z = 3) with the anion structures containing various units: dumbbell-shaped [Sn2As6](12-) dimers, [SnAs3](7-) triangular pyramids, and isolated As(3-) anions. Very interestingly, these two compounds exhibit opposite chirality in the observed crystal structures, resembling enantiomorphs. Detailed structure analyses suggest possible steric effects among the anion clusters, and on the basis of the calculated electronic structures, substantial electron lone pairs exist on the anions of both compounds, which may provide a hint to understanding the origination of chirality in these intermetallic compounds.

Ca(1-x)RE(x)Ag(1-y)Sb (RE = La, Ce, Pr, Nd, Sm; 0 ≤ x ≤ 1; 0 ≤ y ≤ 1): interesting structural transformation and enhanced high-temperature thermoelectric performance.

For materials used in high-temperature thermoelectric power generation, the choices are still quite limited. Here we demonstrate the design and synthesis of a new class of complex Zintl compounds, Ca(1-x)RE(x)Ag(1-y)Sb (RE = La, Ce, Pr, Nd, Sm) (P63mc, No. 186, LiGaGe-type), which exhibit a high figure of merit in the high-temperature region. Compared with the parent structure that is based on CaAgSb (Pnma, No. 62, TiNiSi-type), an interesting structural relationship is established which suggests that important size and electronic effects govern the formation of these multinary phases. According to theoretical calculations, such a structural transformation from the orthorhombic TiNiSi-type to the hexagonal LiGaGe-type also corresponds to an obvious modification in the electronic band structure, which explains the observed significant enhancement of the related thermoelectric properties. For an optimized p-type material, Ca(0.84)Ce(0.16)Ag(0.87)Sb, a figure of merit of ~0.7 can be achieved at 1079 K, which is comparable to that of Yb14MnSb11 at the same temperature. In addition, due to the excellent thermal stability and high electrical conductivity, these materials are very promising candidates for high-temperature thermoelectric power generation.

High-efficiency femtosecond Yb:Gd3Al(0.5)Ga(4.5)O12 mode-locked laser based on reduced graphene oxide.

A diode-pumped Yb-doped Gd(3)Al(0.5)Ga(4.5)O(12) mode-locked bulk laser based on chemically reduced graphene oxide (RGO) has been demonstrated for the first time to our best knowledge. Pulses with duration of 643 fs were produced at the central wavelength of 1041.1 nm. A maximum average output power of 0.8 W was obtained from the RGO mode-locked laser, corresponding to a slope efficiency of 20.1% and a peak power of 27.6 kW. The results indicate that RGO is suitable for obtaining high-power and high-efficiency ultrafast lasers.

New anthracene derivatives as triplet acceptors for efficient green-to-blue low-power upconversion.

Three new anthracene derivatives [2-chloro-9,10-dip-tolylanthracene (DTACl), 9,10-dip-tolylanthracene-2-carbonitrile (DTACN), and 9,10-di(naphthalen-1-yl)anthracene-2-carbonitrile (DNACN)] were synthesized as triplet acceptors for low-power upconversion. Their linear absorption, single-photon-excited fluorescence, and upconversion fluorescence properties were studied. The acceptors exhibit high fluorescence yields in DMF. Selective excitation of the sensitizer Pd(II)octaethylporphyrin (PdOEP) in solution containing DTACl, DTACN, or DNA-CN at 532 nm with an ultralow excitation power density of 0.5 W cm(-2) results in anti-Stokes blue emission. The maximum upconversion quantum yield (Φ(UC) =17.4%) was obtained for the couple PdOEP/DTACl. In addition, the efficiency of the triplet-triplet energy transfer process was quantitatively studied by quenching experiments. Experimental results revealed that a highly effective acceptor for upconversion should combine high fluorescence quantum yields with efficient quenching of the sensitizer triplet.

Ba13Si6Sn8As22: a quaternary Zintl phase containing adamantane-like [Si4As10] clusters.

A new quaternary arsenide Zintl phase, Ba13Si6Sn8As22, has been synthesized from the Sn-flux reactions, and the structure was determined by the single-crystal X-ray diffraction methods. The compound crystallizes in the tetragonal non-centrosymmetric space group I42m (No. 121) with unit cell parameters of a = b = 14.4857(3) Å, c = 13.5506(7) Å, V = 2843.40(17) Å(3). Its polyanion structure can be viewed as composed of [Si4As10] adamantane-like clusters and SiAs4 tetrahedra, which are linked via the [Sn2As4] groups built through two edge-sharing SnAs3 triangular pyramids. Differential thermal analysis and thermogravimetry measurements indicate that Ba13Si6Sn8As22 has good thermal stability, and does not melt or decompose below 1045 K under Ar atmosphere. Density functional calculations were performed on Ba13Si6Sn8As22 and the results suggest a band gap of around 1.0 eV for Ba13Si6Sn8As22, confirmed by the diffuse reflectance spectrum measurement. In addition, the extensively existing lone pairs of electrons on the p-orbitals of As and Sn may also hint interesting nonlinear optical properties considering the noncentrosymmetric structure.

A5Sn2As6 (A = Sr, Eu). Synthesis, crystal and electronic structure, and thermoelectric properties.

Two new ternary Zintl phases, Sr(5)Sn(2)As(6) and Eu(5)Sn(2)As(6), have been synthesized, and their structures have been accurately determined through single-crystal X-ray diffraction. Both compounds crystallize in orthorhombic space group Pbam (No. 55, Z = 2) with cell parameters of a = 12.482(3)/12.281(5) Å, b = 14.137(3)/13.941(5) Å, and c = 4.2440(10)/4.2029(16) Å for Sr(5)Sn(2)As(6) (R1 = 0.0341; wR2 = 0.0628) and Eu(5)Sn(2)As(6) (R1 = 0.0324; wR2 = 0.0766), respectively. Their structure belongs to the Sr(5)Sn(2)P(6) type, which can be closely related to the Ca(5)Ga(2)As(6) type. Electronic band structure calculations based on the density functional theory reveal an interesting electronic effect in the structure formation of these two types of Zintl phases, which substantially affect their corresponding electronic band structure. Related studies on the thermal stability, magnetism, and thermoelectric properties of Eu(5)Sn(2)As(6) are presented as well.

Redetermination of Ba(2)CdTe(3) from single-crystal X-ray data.

The previous structure determination of the title compound, dibarium tritelluridocadmate, was based on powder X-ray diffraction data [Wang & DiSalvo (1999 ▶). J. Solid State Chem.148, 464-467]. In the current redetermination from single-crystal X-ray data, all atoms were refined with anisotropic displacement parameters. The previous structure report is generally confirmed, but with some differences in bond lengths. Ba(2)CdTe(3) is isotypic with Ba(2)MX(3) (M = Mn, Cd; X = S, Se) and features (1) (∞)[CdTe(2/2)Te(2/1)](4-) chains of corner-sharing CdTe(4) tetra-hedra running parallel [010]. The two Ba(2+) cations are located between the chains, both within distorted monocapped trigonal-prismatic coordination polyhedra. All atoms in the structure are located on a mirror plane.

C-H⋠⋠⋠π interaction-modulated solid-state packing and carrier mobility in thienyl and thieno[3,2-b]thienyl end-capped distyrylarylene derivatives.

Research on structure-property relationships in distyrylarylene derivatives is far behind their wide applications in optoelectronic devices due to the absence of crystal structure information. Herein, the single crystals of 4,4'-bis(2-thienylvinyl)biphenyl (1) and 4,4'-bis(2-thieno[3,2-b]thienylvinyl)biphenyl (2) were successfully grown by the vapor transport method. Both molecules adopt the typical herringbone packing motif. However, the intermolecular C-H⋅⋅⋅π interaction in compound 2 is much stronger than that in compound 1. The correlations of interchain interaction with film morphology, optical and electronic properties were studied. Compound 2 formed higher crystalline films with (001) and (111) orientations. The organic field-effect transistor properties of both materials were investigated. Compound 2 showed better performance with a hole mobility higher than 0.01 cm(2) V(-1) s(-1) and an on/off current ratio over 10(6) . These results reveal that the intensity of C-H⋅⋅⋅π interactions can exert dramatic influences on the optical and electronic properties of distyrylarylene-based materials.

Synthesis, crystal and electronic structures, and properties of the new pnictide semiconductors A2CdPn2 (A = Ca, Sr, Ba, Eu; Pn = P, As).

A series of ternary Zintl phases, Ca(2)CdP(2), Ca(2)CdAs(2), Sr(2)CdAs(2), Ba(2)CdAs(2), and Eu(2)CdAs(2), have been synthesized through high temperature metal flux reactions, and their structures have been characterized by single-crystal X-ray diffraction. They belong to the Yb(2)CdSb(2) structure type and crystallize in the orthorhombic space group Cmc2(1) (No. 36, Z = 4) with cell dimensions of a = 4.2066(5), 4.3163(5), 4.4459(7), 4.5922(5), 4.4418(9) Å; b = 16.120(2), 16.5063(19), 16.904(3), 17.4047(18), 16.847(4) Å; c = 7.0639(9), 7.1418(8), 7.5885(11), 8.0526(8), 7.4985(16) Å for Ca(2)CdP(2) (R1 = 0.0152, wR2 = 0.0278), Ca(2)CdAs(2) (R1 = 0.0165, wR2 = 0.0290), Sr(2)CdAs(2) (R1 = 0.0238, wR2 = 0.0404), Ba(2)CdAs(2) (R1 = 0.0184, wR2 = 0.0361), and Eu(2)CdAs(2) (R1 = 0.0203, wR2 = 0.0404), respectively. Among these, Ca(2)CdAs(2) was found to form with another closely related structure, depending on the experimental conditions--monoclinic space group Cm (No. 8, Z = 10) with lattice constants a = 21.5152(3) Å, b = 4.30050(10) Å, c = 14.3761(2) Å and ß = 110.0170(10)° (R1 = 0.0461, wR2 = 0.0747). UV/vis optical absorption spectra for both forms of Ca(2)CdAs(2) show band gaps on the order of 1.0 eV, suggesting semiconducting properties, which have also been confirmed through electronic band structure calculations based on the density-functional theory. Results from differential scanning calorimetry measurements probing the thermal stability and phase transitions in the two Ca(2)CdAs(2) polymorphs are discussed. Magnetic susceptibility measurements for Eu(2)CdAs(2), indicating divalent Eu(2+) cations, are presented as well.

[(Dibenzo[b,d]thio-phen-4-yl)tellan-yl]methane-thiol.

In the title compound, C(13)H(10)S(2)Te, the dibenzothio-phene moiety is almost planar, the maximum atomic deviation being 0.055 (5) Å. The two Te-C bonds are nearly perpen-dicular to each other with a C-Te-C bond angle of 93.0 (2)°. An inter-molecular C-H⋯π inter-action is present between the methyl-ene group and thio-phene ring.

[Two-photon sensors for proton derived from 7-pyridinylbenzo[c] [1,2,5]thiadiazole receptor].

Two new chromophores with carbazole as molecular focal point bearing either one o-pyridine-benzothiadiazole unit or two o-pyridine-benzothiadiazole units at the periphery respectively, named as 2,8-(o-pyridine-benzothiadiazole)-N-ethyl-carbazole (CPTZ1) and 2,8-bis(o-pyridine-benzothiadiazole)-N-ethyl-carbazole (CPTZ2), were synthesized and characterized by IR spectra, 1H NMR spectra and MS. The influence of proton upon one-photon and two-photon fluorescence about these two compounds was discussed. Stern-Volmer equation gives that the S-V constants (k(SV)(1P)) of one-photon fluorescence (1PF) of CPTZ1 and CPTZ2 are 0.04 and 0.10 L mol(-1), respectively; while the k(SV)(2P) of two-photon fluorescence (2PF) of CPTZ1 and CPTZ2 are 0.20 and 0.22 L mol(-1), respectively. Obviously, two-photon (2P) fluorescence detection presented more sensitivity than one-photon (1P) fluorescence response, which exhibits the potential application of two-photon sensor in PH detection.

V3+:YAG as the saturable absorber for a diode-pumped quasi-three-level dual-wavelength Nd:GGG laser.

The performance of a diode-end-pumped passively Q-switched dual-wavelength Nd:GGG laser operating at 932.9 and 936.5 nm with V(3+):YAG as the saturable absorber was demonstrated for the first time to the best of our knowledge. The maximum dual-wavelength average output power of 150 mW was achieved with a T = 2% output coupler under the absorbed pump power of 2.55 W, corresponding to the optical-to-optical conversion and slope efficiency of 5.9% and 8.0%, respectively. The minimum pulse width was 395 ns with the pulse repetition frequency of 140 kHz, which was attained with a T = 5% output coupler under the absorbed pump power of 2.55 W.

Various unique coordination patterns of Hg and DFT calculations to determine the formation of a 3-D supramoleculer framework by covalent and noncovalent interactions.

By combining a large pi-conjugated bidentate ligand L: 3,6-dipyrazole-N-ethylcarbazole with HgI(2), an extraordinary supramolecular coordination polymer, [Hg(4)L(2)I(8)](infinity), has been prepared. The crystal structures of the ligand and its coordination polymer were determined by X-ray crystallography, which shows three varied coordination modes especially the rare asymmetric quadruply bridged trinuclear moieties in [Hg(4)L(2)I(8)](infinity). Density functional theory (DFT) calculations (ADF) performed on model dimers show the roles of covalent and noncovalent interactions in establishing the three-dimensional architecture.

(E)-2-{3-[4-(Diphenyl-amino)styr-yl]-5,5-dimethyl-cyclo-hex-2-enyl-idene}-malono-nitrile.

In the title compound, C(31)H(27)N(3), the cyclo-hexene ring has an envelope configuration. In the crystal structure, there is an 34 Å(3) void around the inversion center, but the low electron density (0.13 e Å(-3)) in the difference Fourier map suggests no solvent mol-ecule occupying this void. No hydrogen bonding is found in the crystal structure.

Conjugated chromophore near the quantum-confined cadmium sulfide cluster: quenched photoluminescence and enhanced two-photon absorption.

Quenching effect of the photoluminescence of 1,2,4,5-tetrakis(4-pyridylvinyl)benzene in the presence of CdS colloids stabilized by inverse micelles was observed. The observed regularities of luminescence quenching by the quenchers of different size were studied. An increase in the two-photon absorption cross section (6.5 times higher) and in the two-photon-induced fluorescence intensity was observed for the composite solution when pumped by 740-nm laser irradiation. The results are in accord with theoretical prediction of enhancement of third-order optical nonlinearity of quantum-confined semiconductor.