AgBi(SO4)(IO3)2: aliovalent substitution induces structure dimensional upgrade and second harmonic generation enhancement.

A new 3D noncentrosymmetric mixed-metal sulfate iodate, AgBi(SO4)(IO3)2, has been designed based on a 2D iodate of AgBi(IO3)4via the aliovalent substitution of [IO3]- groups by [SO4]2- groups. Enhancement of the second harmonic generation response (3.0 × KDP to 3.9 × KDP) has been achieved while retaining a favorable NLO framework. This is a novel strategy to upgrade structural dimensions.

Pb3(SeO3)Br4: a new nonlinear optical material with enhanced SHG response designed via an ion-substitution strategy.

Using an ion-substitution strategy, herein, a new polar material, Pb3(SeO3)Br4, with a greatly enhanced SHG response has been successfully designed and synthesized through a hydrothermal reaction. Pb3(SeO3)Br4 crystallizes in the NCS space group P212121 and consists of a three-dimensional framework formed by interconnecting one-dimensional chains, with a good thermal stability up to 230 °C. This compound exhibits a phase-matchable SHG response as strong as that of KH2PO4 (KDP) and a relatively wide mid-infrared (mid-IR) transparent window. Moreover, the optical band gap of Pb3(SeO3)Br4 reaches about 3.35 eV, thus leading to a high laser damage threshold (LDT) of 67 MW cm-2, which is over 12 times that of AgGaS2 (<5 MW cm-2) measured under the same condition. All these findings suggest that Pb3(SeO3)Br4 would be a candidate for an NLO material in the mid-IR region.

ABi2 (IO3 )2 F5 (A=K, Rb, and Cs): A Combination of Halide and Oxide Anionic Units To Create a Large Second-Harmonic Generation Response with a Wide Bandgap.

A family of nonlinear optical materials that contain the halide, oxide, and oxyhalide polar units simultaneously in a single structure, namely ABi2 (IO3 )2 F5 (A=K (1), Rb (2), and Cs (3)), have been designed and synthesized. They crystallize in the same polar space group (P21 ) with a two-dimensional double-layered framework constructed by [BiF5 ]2- and [BiO2 F4 ]5- units connected to each other by four F atoms, in which two [IO3 ]- groups are linked to [BiO2 F4 ]5- unit on the same side. A hanging Bi-F bond of [BiF5 ]2- unit is located on the other side via ionic interaction with the layer-inserted alkali metal ions to form three-dimensional structure. The well-ordered alignments of these polar units lead to a very strong second-harmonic generation response of 12 (1), 9.5 (2), and 7.5 (3) times larger than that of potassium dihydrogen phosphate under 1064 nm laser radiation. All of them exhibited a wide energy bandgap over 3.75 eV, suggesting that they will have a high laser damage threshold.

Colorimetric and fluorescent probes for real-time naked eye sensing of copper ion in solution and on paper substrate.

In this paper, BT ((E)-2-(4-(4-(bis(pyridin-2-ylmethyl)amino)styryl)-3-cyano-5,5-dimethylfuran-2(5H)-ylidene)malononitrile) with strong donor-π-acceptor structure was synthesized, which showed both colorimetric and fluorescent sensing ability toward Cu2+ with high selectivity and sensitivity. Job plot and mass spectra measurement revealed a 1 : 1 coordination mode between Cu2+ and probe BT in ethanol/HEPES (1 : 4 v/v) buffer (pH 7.2) solution, and the binding constant was calculated to be 3.6 × 104 M-1. The colour of BT solution (10 µM) immediately turned from purple red to yellow and the red fluorescence was quenched obviously when a certain amount of Cu2+ was added, which enabled a dual-channel detection of Cu2+. A paper strip pre-stained with BT solution was further fabricated and it also showed excellent sensing ability toward Cu2+ with a detection limit as low as 10-6 M with the naked eye, which represents better portability and operation simplicity that is favourable for on-site analysis of Cu2+ in water.

Rb2SeOCl4·H2O: a polar material among the alkali metal selenite halides with a strong SHG response.

An alkali metal selenite chloride, Rb2SeOCl4·H2O, has been hydrothermally synthesized and structurally characterized. It is the first example of an alkali metal selenite halide in the literature. The compound crystallizes in the noncentrosymmetric (NCS) space group, Cmc21(36), of the orthorhombic system with a = 10.342(3) Å, b = 10.124(3) Å, c = 9.158(3) Å, and α = ß = γ = 90°. The anionic [SeOCl4]2- groups are arranged in the crystal in nearly the same direction, giving rise to a relatively large macroscopic dipole moment, causing the compound to display second harmonic generation (SHG) eight times as strong as that of KDP, measured using the Kurtz-Perry method on powders. First-principle density functional theory (DFT) calculations were carried out to interpret the relationship between the crystal structure and properties.

Dramatically enhancing the yield of carbon nanotubes by simply adding oxygen-containing molecules in solid-state synthesis.

By adding just a small amount of commercially available oxygen-containing molecules (OCMs), organometallic precursors could be easily converted to CNTs with high yield and high quality through the solid-state pyrolysis (SSP) process, although only nanospheres were obtained under the same conditions without the presence of OCMs, providing a convenient approach for the preparation of CNTs.

A relay strategy for the mercury (II) chemodosimeter with ultra-sensitivity as test strips.

A relay strategy has been proposed to design a new Hg(2+) chemodosimeter (TPE-S), by coupling Hg(2+)-promoted deprotection reaction with ketone-enol isomerization, realizing the multistage amplifying effect. Changes in both of color and fluorescence could occur immediately, and TPE-S displayed high selectivity for Hg(2+), other metal ions (Ag(+), Fe(3+), Cu(2+), Pb(2+), Co(2+), Cr(3+), Al(3+), Cd(2+), Mg(2+), Mn(2+), Ba(2+), Fe(2+), Ca(2+), Ni(2+), Zn(2+), Li(+), K(+) and Na(+)) gave nearly no disturbance to the sensing process. When fabricated as test strips similar to pH-indicator papers, immediate color change from colorless to purple could be visually observed by naked-eyes without the aid of any additional equipment, with the detection limit as low as 1 × 10(-7) M (Hg(2+) in aqueous solution). Due to its easy synthesis, high selectivity and sensitivity, combined with the portable test strips, TPE-S could be developed as a convenient and cost-effective tool for the detection of Hg(2+) in on-site inspections.

Adamantane-based wide-bandgap host material: blue electrophosphorescence with high efficiency and very high brightness.

An adamantane-based host material, namely, 4-{3-[4-(9H-carbazol-9-yl)phenyl]adamantan-1-yl}benzonitrile (CzCN-Ad), was prepared by linking an electron-donating carbazole unit and an electron-accepting benzonitrile moiety through an adamantane bridge. In this approach, two functional groups were attached to tetrahedral points of adamantane to construct an "sp(3)" topological configuration. This design strategy endows the host material with a high triplet energy of 3.03 eV due to the disruption of intramolecular charge transfer. Although CzCN-Ad has a low molecular weight, the rigid nonconjugated adamantane bridge results in a glass transition temperature of 89 °C. These features make CzCN-Ad suitable for fabricating blue phosphorescent organic light-emitting diodes (PhOLEDs). The devices based on sky-blue phosphor bis[(4,6-difluorophenyl)pyridinato-N,C(2')](picolinato)iridium(III) (FIrpic) achieved a high maximum external quantum efficiency (EQE) of 24.1%, which is among the best results for blue PhOLEDs ever reported. Furthermore, blue PhOLEDs with bis(2,4-difluorophenylpyridinato)-tetrakis(1-pyrazolyl)borate iridium(III) (FIr6) as dopant exhibited a maximum EQE of 14.2% and a maximum luminance of 34 262 cd m(-2). To the best of our knowledge, this is the highest luminance ever reported for FIr6-based PhOLEDs.

White polymer light-emitting diodes based on star-shaped polymers with an orange dendritic phosphorescent core.

A series of new star-shaped polymers with a triphenylamine-based iridium(III) dendritic complex as the orange-emitting core and poly(9,9-dihexylfluorene) (PFH) chains as the blue-emitting arms is developed towards white polymer light-emitting diodes (WPLEDs). By fine-tuning the content of the orange phosphor, partial energy transfer and charge trapping from the blue backbone to the orange core is realized to achieve white light emission. Single-layer WPLEDs with the configuration of ITO (indium-tin oxide)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/polymer/CsF/Al exhibit a maximum current efficiency of 1.69 cd A(-1) and CIE coordinates of (0.35, 0.33), which is very close to the pure white-light point of (0.33, 0.33). To the best of our knowledge, this is the first report on star-shaped white-emitting single polymers that simultaneously consist of fluorescent and phosphorescent species.

Amino-modified tetraphenylethene derivatives as nucleic acid stain: relationship between the structure and sensitivity.

A series of new amino-functionalized tetraphenylethene (TPE) derivatives were designed and synthesized to study the effect of molecular structures on the detection of nucleic acid. Contrastive studies revealed that the number of binding groups, the length of hydrophobic linking arm and the configuration of TPE molecule all play important roles on the sensitivity of the probes in nucleic acid detection. Z-TPE3 with two binding amino groups, long linking arms, and cis configuration was found to be the most sensitive dye in both solution and gel matrix. Z-TPE3 is able to stain dsDNA with the lowest amount of 1 ng and exclusively stain 40 ng of short oligonucleotide with only 10 nt. This work is of important significance for the further design of TPE probes as biosensors with higher sensitivity.

The influence of pentafluorophenyl groups on the nonlinear optical (NLO) performance of high generation dendrons and dendrimers.

With the aim to make the influence of pentafluorophenyl groups in the periphery of high generation dendrons and dendrimers on their NLO performance clearly, some NLO dendrons and dendrimers with different chromophore moieties or different end-capped groups were carefully designed and investigated in detail. The results demonstrated that some strong Ar-Ar(F) interactions between the pentafluorophenyl groups in the periphery and the normal phenyl rings of the donors, could influence the topological structures of dendrons or dendrimers, and then affect their NLO performance. Furthermore, the optical transparency and the stability of the dendrons and dendrimers with pentafluorophenyl groups as end-capped moieties were all improved, in comparison with normal dendrons and dendrimers containing phenyl ones as the end-capped groups.

Exploration of new second-order nonlinear optical materials of the Cs-Hg-Br-I system.

A first example of a Cs-Hg-Br-I system, namely Cs2Hg2Br2I4·H2O (1), has been synthesized by reaction in solution. It belongs to the polar monoclinic space group pc with a = 7.460(5) Å, b = 13.458(9) Å, c = 8.891(6) Å, and ß = 92.448(9)°. The basic anionic group in the crystal is non-centrosymmetric [Hg2Br2I4](2-), and the groups are aligned in the same direction in the crystal. As a result, 1 exhibits a phase-matchable second harmonic generation (SHG) response as strong as 6 times that of KH2PO4 (KDP). For the purpose of comparison, the known compound Cs2Hg3I8·H2O (2) was also synthesized and its SHG properties were studied for the first time. Band structure and optical property calculations for the two compounds based on DFT methods were also performed. The comprehensive properties of 1 and 2 as well as their analog, Cs2HgCl2I2, have been compared and discussed.

A tetraphenylethene-based zinc complex as a sensitive DNA probe by coordination interaction.

We developed a new DNA probe by utilizing the coordination interaction of Zn(2+) with DNA and the consequent emission. Because the coordination interactions do not depend on the length of the DNA, the new probe exhibited much higher sensitivity for the detection of short ssDNA than the corresponding probe based on electrostatic interactions.

A highly sensitive nucleic acid stain based on amino-modified tetraphenylethene: the influence of configuration.

We designed and synthesized a new amino-functionalized tetraphenylethene (TPE) derivative as a highly sensitive dye for the detection of dsDNA and oligonucleotide in both solution and a gel matrix. We further revealed that the cis configuration dye showed a much higher sensitivity than its trans isomer for the first time.

Rb2CdBr2I2: a new IR nonlinear optical material with a large laser damage threshold.

This paper describes the synthesis, crystal structure, and photophysical properties of a new compound Rb2CdBr2I2. It crystallizes in the noncentrosymmetric space group Ama2. In the crystal, all the distorted tetrahedron [CdBr2I2](2-) groups are arranged in a way such that all the Cd-I bonds are located in the same side of the Cd atoms resulting in a net polarization. Rb2CdBr2I2 showed a powder second harmonic generation (SHG) response 4 times that of KH2PO4 (KDP). The preliminary measurement indicated that it exhibits a large laser-induced damage threshold (LDT) of 190 MW/cm(2) which is 6 times that of AgGaS2. It also exhibits a wide transparent region (0.37-14 µm) with a relatively high (up to 490 °C) thermal stability. All these indicate that Rb2CdBr2I2 is a new promising candidate for NLO materials in the IR region.

A new approach to prepare efficient blue AIE emitters for undoped OLEDs.

Two aggregation-induced emission active luminogens (TPE-pTPA and TPE-mTPA) were successfully synthesized. For comparison, another six similar compounds were prepared. Because of the introduced hole-dominated triphenylamine (TPA), fluorene groups with high luminous efficiency, and unconjugated linkages, the π conjugation length of the obtained luminogens is effectively restricted to ensure their blue emission. The undoped organic light-emitting diodes based on TPE-pTPA and TPE-mTPA exhibited blue or deep-blue emissions, low turn-on voltages (3 V), and high electroluminescence efficiencies with Lmax, ηC,max, and ηP,max values of up to 26,697 cd m(-2), 3.37 cd A(-1), and 2.40 Lm W(-1).

Using an organic molecule with low triplet energy as a host in a highly efficient blue electrophosphorescent device.

To achieve high efficiencies in blue phosphorescent organic light-emitting diodes (PhOLEDs), the triplet energies (T1) of host materials are generally supposed to be higher than the blue phosphors. A small organic molecule with low singlet energy (S1) of 2.80 eV and triplet energy of 2.71 eV can be used as the host material for the blue phosphor, [bis(4,6-difluorophenylpyridinato-N,C(2'))iridium(III)] tetrakis(1-pyrazolyl)borate (FIr6; T1=2.73 eV). In both the photo- and electro-excited processes, the energy transfer from the host material to FIr6 was found to be efficient. In a three organic-layer device, the maximum current efficiency of 37 cd A(-1) and power efficiency of 40 Lm W(-1) were achieved for the FIr6-based blue PhOLEDs.

Dendrimers with large nonlinear optical performance by introducing isolation chromophore, utilizing the Ar/ArF self-assembly effect, and modifying the topological structure.

By the combination of divergent and convergent approach, a new series of NLO dendrimers (G1-PFPh-NS-GL to G3-PFPh-NS-GL) was conveniently prepared with satisfied yields through the powerful "click chemistry" reaction, in which perfluoroaromatic rings were introduced in the periphery, two types of chromophores were arranged with regular AB structure, and their topological structure was improved to a more spherical shape. All the dendrimers demonstrated good processability, and G1-PFPh-NS-GL exhibited the highest NLO effect of 221 pm/V among the three dendrimers.

A promising nonlinear optical material in the Mid-IR region: new results on synthesis, crystal structure and properties of noncentrosymmetric ß-HgBrCl.

This paper reports, for the first time, the nonlinear optical property of ß-HgBrCl, which was synthesized by a reaction of Hg2Cl2 and Br2 in EtOH. This reaction also gave α-HgBrCl. And the single crystal structures of both α- and ß-HgBrCl are presented and compared. ß-HgBrCl shows phase-matchable powder second harmonic generation (SHG) effect of about 2 times that of KH2PO4 (KDP). Its absorption edge in UV-vis spectrum locates at 366 nm, implying a wide band gap and therefore higher laser damage threshold. It also exhibits a relatively wide transparent window (from 0.4 to 20 µm) and relatively good thermal stability.

The utilization of isolation chromophore in an "A3 +B2 " type second-order nonlinear optical hyperbranched polymer.

In this paper, a new nonlinear optical (NLO) hyperbranched polymer P1 is designed and synthesized successfully through one-pot "A3 +B2 " approach via a simple Sonogashira coupling reaction, in which isolation chromophore is introduced to improve its comprehensive performance such as NLO activity, optical transparency, and stability. For comparison, its analogs, P2 and P3, just containing one type of chromophore, are also prepared. Although P1 cannot be well poled under our test conditions, its NLO coefficient is still much higher than its analogs P2, P3, and the linear polyaryleneethynylene P4, which also contains isolation chromophore, indicating the advantages of isolation chromophore and the three-dimensional (3D) spatial isolation from the highly branched structure in the NLO field.