Novel carbazole/anthracene hybrids for efficient blue organic light-emitting diodes

Two novel carbazole/anthracene hybrided molecules, namely 2-(anthracen-9-yl)-9-ethyl-9H-carbazole (AnCz) and 2,7-di(anthracen-9-yl)-9-ethyl-9H-carbazole (2AnCz), were designed and synthesized via palladium catalyzed coupling reaction. The anthracene was attached either at the 2-site (AnCz) or at both 2,7-sites (2AnCz) of the central carbazole core to tune the conjugation state and the optoelectronic properties of the resultant molecules. Both of them show good solubility in common organic solvents. They also possess relatively high HOMO levels (−5.39 eV, −5.40 eV) that would facilitate efficient hole injection and be favorable for high power efficiencies when used in organic light-emitting devices (OLEDs). AnCz and 2AnCz were used as non-doped emitter to fabricate OLEDs by vacuum evaporation. Good performance was achieved with maximum luminance efficiency of 2.61 cd A⁻¹ and CIE coordinates of (0.15, 0.12) for AnCz, and 9.52 cd A⁻¹ and (0.22, 0.37) for 2AnCz.     

A highly selective triphenylamine-based indolylmethane derivatives as colorimetric and turn-off fluorimetric sensor toward Cu detection by deprotonation of secondary amines

A new triphenylamine-based fluorogenic probe bearing an indolylmethane unit (R1) was developed as a fluorescent chemosensor with high selectivity toward Cu²⁺ over other cations tested. The new probe R1 only sensed Cu²⁺ among heavy and transition metal (HTM) ions in CH₃CN/H₂O (70/30, v/v) solution. The capture of Cu²⁺ by the receptor resulted in deprotonation of the secondary amine conjugated to the triphenylamine, so that the electron-donation ability of the “N” atom would be greatly enhanced; thus sensor showed a 250 nm change in the new absorption band (from 291 nm to 541 nm) and a large colorimetric response, it also exhibited the large decrease in fluorescence intensity at 378 nm and affinity to Cu²⁺ over other cations such as Hg²⁺, Fe³⁺, Pb²⁺, Zn²⁺, Cd²⁺, Ni²⁺, Co²⁺ and Mn²⁺ make this compound a useful chemosensor for Cu²⁺ detection in CH₃CN/H₂O (70/30, v/v) mixture. The probe R1 (c = 1.0 × 10⁻⁶ M) displayed significant fluorescence change and colorimetric change upon addition of Cu²⁺ among the metal ions examined.     

Salicylaldehyde based colorimetric and “turn on” fluorescent sensors for fluoride anion sensing employing hydrogen bonding

Two salicylaldehyde based colorimetric and fluorescent chemosensors 1 and 2 were developed. Both receptors 1 and 2 showed unique selectivity for the fluoride anions over other anions in DMSO solution. [TBA] OH and ¹H NMR titration experiments revealed that the F⁻-induced colorimetric and “turn on” fluorescence response were driven by hydrogen bonding interaction between the OH protons and F⁻.     

Imine-functionalized, turn-on fluorophore for DCP

A monopyrene-imine derivative 1 is a highly selective and sensitive “turn-on” fluorogenic probe for diethyl chlorophosphate (DCP), a stimulant for organophosphorus nerve agents. Upon addition of DCP to a solution of 1, a phosphoramidate was formed which exhibited an enhanced fluorescence emission at 425 nm. When exposed to DCP in the vapor phase, 1 impregnated on silica gel showed a sky-blue fluorescence.     

Fe-selective fluorescent probe based on rhodamine B and its application in bioimaging

A Rhodamine-based fluorescent and colorimetric chemosensor for Fe³⁺ ion, acetyl rhodamine-hydroxamate (ARH), was designed and synthesized. Upon mixed with Fe³⁺ in CH₃CN-H₂O (1:1, v/v), the spirolactam of ARH was opened, which resulted in the dramatic enhancement of both fluorescence and absorbance intensity as well as the color change of the solution. Background metal ions showed small or no interference with the detection of Fe³⁺. The Job's plot indicated the formation of 1:1 complex between ARH and Fe³⁺. Confocal laser scanning microscopy experiments showed that ARH could be used to detect Fe³⁺ in living cells.     

Enhanced chemosensing of ammonia based on the novel molecular semiconductor-doped insulator (MSDI) heterojunctions

A series of new molecular semiconductor-doped insulator (MSDI) heterojunctions as conductimetric transducers to NH₃ sensing were fabricated based on a novel semiconducting molecular material, an amphiphilic tris(phthalocyaninato) rare earth triple-decker complex, Eu₂[Pc(15C5)₄]₂[Pc(OC₁₀H₂₁)₈], quasi-Langmuir-Shäfer (QLS) film, as a top-layer, and vacuum-deposited and cast film of CuPc as well as copper tetra-tert-butyl phthalocyanine (CuTTBPc) QLS film as a sub-layer, named as MSDIs 1, 2 and 3, respectively. MSDIs 1-3 and respective sub-layers prepared from three different methods were characterized by X-ray diffraction, electronic absorption spectra and current-voltage (I-V) measurements. Depending on the sub-layer film-forming method used, α-phase CuPc film structure, β-phase CuPc crystallites and H-type aggregates of CuTTBPc have been obtained, respectively. An increasing sensitivity to NH₃ at varied concentrations in the range of 15-800 ppm, follows the order MSDI 2 < MSDI 3 < MSDI 1, revealing the effect of sub-layer film structures on sensing performance of the MSDIs. In particular, the time-dependent current plot of the MSDI 1, with α-phase CuPc film as a sub-layer, clearly shows an excellent separation of the different ammonia concentration levels and nearly complete reversibility and reproducibility even at room temperature, which is unique among the phthalocyanine-based ammonia sensors thus far reported in the literature. This provides a general method to improve sensor response of organic heterojunctions by controlling and tuning the film structure of sub-layer with appropriate fabrication techniques. On the other hand, the enhanced sensitivity, stability and reproducible response of the MSDI 1 heterostructure in comparison with the respective single-layer films have also been obtained. A judicious combination of materials and molecular architectures has led to enhanced sensing properties of the MSDI 1, in which control at the molecular level can be achieved.     

Four-arc approximation to ellipses: The best in general

So far, the four-arc approximations to an ellipse E are made under the condition that the major and minor axes keep strictly unchanged. In general, however, this condition is unnecessary. Then the fitting can be further improved. Considering a representative quadrant of E, we first draw two auxiliary circular arcs tangent to E at the axes but having a gap ε at their boundary, such that the small arc S lies outside the large arc L. Meanwhile the extreme errors of S and L w.r.t. E are ε and −ε respectively. Giving the radii of S and L a decrement −ε/2 and an increment ε/2 brings them to join smoothly. Thus, reducing the overall error to minimum, an analytic solution in implicit form is derived.     

Connected sum of digital closed surfaces

During the past 20 years the research of digital surfaces has proceeded to find their properties in the digital space Zⁿ, such as a topological number, a simple k-point, the 3D-Jordan theorem, a k-separating set, a boundary detecting algorithm and so on. Actually, unlike surfaces in a continuous space, the features of digital surfaces have different characteristics. The aim of this paper is to introduce the notion of a digital closed k-surface in Zⁿ, n ? 3, with the general k-adjacency relations as a generalization of Malgouyres’ and Morgenthaler’s k-surfaces in Z³, to establish some minimal simple closed k-surfaces in Z³ and to find their digital topological properties in relation with the k-fundamental group and k-contractibility. Moreover, a connected sum of two digital closed surfaces is introduced and its digital topological properties are investigated.     

A dual K-Na selective Prussian blue nanotubes sensor

A strategy for dual sensing of Na⁺ and K⁺ ions using Prussian blue nanotubes via selective inter/deintercalation of K⁺ ion and competitive inhibition by Na⁺ ion, is reported. The analytical signal is derived from the cyclic voltammetry cathodic peak position E_pc of Prussian blue nanotubes. Na⁺ and K⁺ levels in a sample solution can be determined conveniently using one Prussian blue nanotubes sensor. In addition, this versatile method can be applied for the analysis of single type of either Na⁺ or K⁺ ions. The dual-ion sensor response towards Na⁺ and K⁺ can be described using a model based on the competitive inhibition effects of Na⁺ on K⁺ inter/deintercalation in Prussian blue nanotubes. Successful application of the Prussian blue nanotubes sensor for Na⁺ and K⁺ determination is demonstrated in artificial saliva.     

A highly sensitive and selective colorimetric and off-on fluorescent chemosensor for Cu based on rhodamine B derivative

A new rhodamine B derivative colorimetric and fluorescent sensor (1) was synthesized by condensation reaction of rhodamine B hydrazide and 2,4-dihydroxybenzaldehyde, which showed reversible and highly selective and sensitive recognition toward Cu²⁺ over other examined metal ions. Upon addition of Cu²⁺, sensor 1 exhibits remarkably enhanced absorbance intensity and color change from colorless to pink in DMSO and MeCN aqueous buffer solution or pure MeCN, and shows significant off-on fluorescence accompanied by color changes from colorless to orange in MeCN. The sensor 1 was also successfully applied to the determination of Cu²⁺ in water samples.     

A simple band ratio technique to quantify the colored dissolved and detrital organic material from ocean color remotely sensed data

Spectral reflectances of the ocean, R, as derived from ocean color remote sensing data at four wavelengths (412, 443, 490, and 555 nm), can be used to form two ratios of spectral reflectance, namely R(412)/R(443), and R(490)/R(555), thereafter denoted R₄₄₃⁴¹² and R₅₅₅⁴⁹⁰. The former is mainly sensitive to the colored dissolved organic material (CDOM), albeit influenced by the algal content as depicted by the chlorophyll concentration, ([Chl]); in contrast, the latter is essentially depending on [Chl], although it is also influenced by CDOM. Therefore the signatures of CDOM and [Chl] which are not truly separable, can nevertheless be identified by considering simultaneously the two ratios. The concomitant variations in these ratios can be established via a bio-optical model developed for Case 1 waters. This model implicitly includes a “mean” relationship between CDOM and [Chl], and thus produces a unique curve relating R₄₄₃⁴¹² to R₅₅₅⁴⁹⁰. Deviations with respect to this mean relationship can be introduced through a factor Φ, with Φ > 1 (excess) or < 1 (deficit), applied to the CDOM-[Chl] ratio. A family of R₄₄₃⁴¹²-R₅₅₅⁴⁹⁰ curves is thus generated, in correspondence with the discrete values given to Φ; this “grid” (or numerically, a 2-D lookup table) allows the Φ-[Chl] couple to be unambiguously derived for any R₄₄₃⁴¹²-R₅₅₅⁴⁹⁰ couple. By applying this straightforward algorithm to actual reflectance ratios derived from ocean color imagery, the relative anomalies in CDOM with respect to its standard (Chl-related) values can be efficiently assessed. Within the global ocean (discarding the coastal zones), the Φ factor is widely varying, between at least ? and 3, and is roughly log-normally distributed around ~ 1 (no anomaly). The spatial distributions of the Φ factor in the whole ocean are strongly featured according to latitude, season, and hydrographic regimes, and these features are regularly reproducible, from year to year (2002-2007). This simple method is also validated against available in situ data, and its results compare favorably, for instance, to those of the GSM (Garver-Siegel-Maritorena) inversion method, in terms of retrieved CDOM concentrations and distribution patterns.     

A new acridine derivative as a highly selective ‘off-on’ fluorescence chemosensor for Cd in aqueous media

A new acridine fluoroionophore containing two diethanolamine ligands, 4,5-bis(N,N-di (2-hydroxyethyl)iminomethyl)acridine (BHIA), was designed and synthesized based on the fluorophore-spacer-receptor format. And its fluorescent sensing behavior towards metal ions was investigated in buffered aqueous media. The presence of Cd²⁺ induces the formation of a 1:1 ligand/metal complex at neutral pH, which exhibits enhanced emission at 454 nm. The fluorescence intensity is linear with the Cd²⁺ concentration in the range of 1.0 × 10⁻⁶ to 3.0 × 10⁻⁵ M (R = 0.9967). Experimental results show a low interference response towards other metal ions. The selective switch-on fluorescence response of BHIA to Cd²⁺ makes it suitable for sensing of Cd²⁺ in aqueous solution. The detection limit is 1.3 × 10⁻⁷ M. Moreover, the results indicated that BHIA was a reversible chemosensor for Cd²⁺, which makes it attractive for sensing applications.     

Per-6-ammonium-β-cyclodextrin/p-nitrophenol complex as a colorimetric sensor for phosphate and pyrophosphate anions in water

Using per-6-ammonium-β-cyclodextrin (per-6-NH₃⁺-β-CD) as an anion binding site and p-nitrophenol as a spectroscopic probe, a colorimetric sensor is developed for phosphate and pyrophosphate anions in water. Per-6-NH₃⁺-β-CD forms a 1:2 inclusion complex with p-nitrophenol as characterized by NOESY and ESI-MS spectra and it undergoes a distinct color change from colorless to intense yellow upon exposure to phosphate or pyrophosphate anions over other anions including perchlorate, ATP²⁻, ADP²⁻ and AMP²⁻. The seven ammonium groups of 1, bind phosphate (characterized by ESI-MS) or pyrophosphate anions specifically by electrostatic interaction. This naked eye sensing is significant for very low concentration (5 × 10⁻⁵ M) of anion with 1:2 ratio of host and guest.     

Embedding hamiltonian paths in hypercubes with a required vertex in a fixed position

Assume that n is a positive integer with n?2. It is proved that between any two different vertices x and y of Qn there exists a path Pl(x,y) of length l for any l with h(x,y)?l?n²−1 and 2|(l−h(x,y)). We expect such path Pl(x,y) can be further extended by including the vertices not in Pl(x,y) into a hamiltonian path from x to a fixed vertex z or a hamiltonian cycle. In this paper, we prove that for any two vertices x and z from different partite set of n-dimensional hypercube Qn, for any vertex y∈V(Qn)−{x,z}, and for any integer l with h(x,y)?l?n²−1−h(y,z) and 2|(l−h(x,y)), there exists a hamiltonian path R(x,y,z;l) from x to z such that dR(x,y,z;l)(x,y)=l. Moreover, for any two distinct vertices x and y of Qn and for any integer l with h(x,y)?l?²n−1 and 2|(l−h(x,y)), there exists a hamiltonian cycle S(x,y;l) such that dS(x,y;l)(x,y)=l.     

pocrm: An R-package for Phase I trials of combinations of agents

This paper presents the R package pocrm for implementing and simulating the partial order continual reassessment method (PO-CRM; 0005 and 0010) in Phase I trials of combinations of agents. The aim of this article is to illustrate, through examples of the pocrm package, how the PO-CRM works and how its operating characteristics can inform clinical trial investigators. This should promote the use of the PO-CRM in designing and conducting dose-finding Phase I trials of combinations of agents.     

Feynman graph generation and calculations in the Hopf algebra of Feynman graphs

Two programs for the computation of perturbative expansions of quantum field theory amplitudes are provided. feyngen can be used to generate Feynman graphs for Yang–Mills, QED and φ^k${\phi }^k$ theories. Using dedicated graph theoretic tools feyngen can generate graphs of comparatively high loop orders. feyncop implements the Hopf algebra of those Feynman graphs which incorporates the renormalization procedure necessary to calculate finite results in perturbation theory of the underlying quantum field theory. feyngen is validated by comparison to explicit calculations of zero dimensional quantum field theories and feyncop is validated using a combinatorial identity on the Hopf algebra of graphs.     

Rotation-minimizing osculating frames

An orthonormal frame (_f1,_f2,_f3)$({\mathbf{f}}_1,{\mathbf{f}}_2,{\mathbf{f}}_3)$ is rotation-minimizing   with respect to _fi${\mathbf{f}}_i$ if its angular velocity ω   satisfies ω⋅_fi≡0$\mathit{\omega }\cdot {\mathbf{f}}_i\equiv 0$ — or, equivalently, the derivatives of _fj${\mathbf{f}}_j$ and _fk${\mathbf{f}}_k$ are both parallel to _fi${\mathbf{f}}_i$. The Frenet frame (t,p,b)$(\mathbf{t},\mathbf{p},\mathbf{b})$ along a space curve is rotation-minimizing with respect to the principal normal p, and in recent years adapted frames that are rotation-minimizing with respect to the tangent t have attracted much interest. This study is concerned with rotation-minimizing osculating   frames (f,g,b)$(\mathbf{f},\mathbf{g},\mathbf{b})$ incorporating the binormal b, and osculating-plane vectors f, g that have no rotation about b. These frame vectors may be defined through a rotation of t, p by an angle equal to minus the integral of curvature with respect to arc length. In aeronautical terms, the rotation-minimizing osculating frame (RMOF) specifies yaw-free rigid-body motion along a curved path. For polynomial space curves possessing rational Frenet frames, the existence of rational RMOFs is investigated, and it is found that they must be of degree 7 at least. The RMOF is also employed to construct a novel type of ruled surface, with the property that its tangent planes coincide with the osculating planes of a given space curve, and its rulings exhibit the least possible rate of rotation consistent with this constraint.     

New fluorescent probes for mercury(II) with simple structure

Based on the protection reaction between ethanethiol and aldehyde, a novel fluorescent probe (2) for Hg²⁺ ions, with the simplest structure reported so far, was designed, which displayed high sensitivity and selectivity towards Hg²⁺ and Ag⁺ over other metal ions with detectable fluorescent signals, due to distinct deprotection reaction of dithioacetal. Compound 2 was further utilized to construct the chemical reaction-based conjugated polymer probes (P2 and P4) for Hg²⁺ ions. More importantly, the effect of the molecular weight of conjugated polymers on the sensitivity of the probes towards Hg²⁺ ions was carefully studied.