Molecular engineering for panchromatic absorbing oligothiophene donor-π-acceptor organic semiconductors

A series of three novel organic semiconductor molecules based on the donor-π-bridge-acceptor (D-π-A) modular design have been designed, synthesised and characterised. These small organic molecules have a common donor (triphenylamine), π-bridge (an alkylated tetrathiophene) and various acceptors to provide tuning of optical and electronic properties. The examined acceptors were dicyanovinylidene, cyanopyridone and oxoindenemalononitrile groups. These compounds were highly soluble in common organic solvents, such as chloroform, toluene and chlorobenzene. As acceptor strength increased from dicyanovinylidene to cyanopyridone to oxoindenemalononitrile groups, the wavelength of the longest wavelength absorption maximum increased (518, 587, 619 nm (solution)), the respective extinction coefficients increased (4.9×10⁴, 6.3×10⁴, 7.4×10⁴ M⁻¹ cm⁻¹) and with increasing acceptor strength the band gap narrowed (1.63, 1.42 1.38 eV). Panchromatic absorbance was observed for the compounds comprising the cyanopyridone and oxoindenemalononitrile acceptors.     

Screening for unknown compounds in complex matrices analysed by liquid chromatography: An overview

Rapid scanning UV/visible spectrophotometry, video fluorimetry, mass spectrometry and electrochemical characterization hold great promise for structure elucidation of components of complex mixtures separated by HPLC. As technology continues to improve, newer techniques, such as Fourier transform nuclear magnetic resonance and infrared spectroscopy, are emerging as alternative or complementary methods of detection.     

The interaction of fluorescent nanodiamond probes with cellular media

Fluorescent nanodiamonds (FNDs) are promising tools to image cells, bioanalytes and physical quantities such as temperature, pressure, and electric or magnetic fields with nanometer resolution. To exploit their potential for intracellular applications, the FNDs have to be brought into contact with cell culture media. The interactions between the medium and the diamonds crucially influence sensitivity as well as the ability to enter cells. The authors demonstrate that certain proteins and salts spontaneously adhere to the FNDs and may cause aggregation. This is a first investigation on the fundamental questions on how (a) FNDs interact with the medium, and (b) which proteins and salts are being attracted. A differentiation between strongly binding and weakly binding proteins is made. Not all proteins participate in the formation of FND aggregates. Surprisingly, some main components in the medium seem to play no role in aggregation. Simple strategies to prevent aggregation are discussed. These include adding the proteins, which are naturally present in the cell culture to the diamonds first and then inserting them in the full medium.

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Graphical abstract Schematic of the interaction of nanodiamonds with cell culture medium. Certain proteins and salts adhere to the diamond surface and lead to aggregation or to formation of a protein corona.

     

Two‐Dimensional Boron Hydride Sheets: High Stability,Massless Dirac Fermions,and Excellent Mechanical Properties

Two‐dimensional (2D) boron sheets have been successfully synthesized in recent experiments, however, some important issues remain, including the dynamical instability, high energy, and the active surface of the sheets. In an attempt to stabilize 2D boron layers, we have used density functional theory and global minimum search with the particle‐swarm optimization method to predict four stable 2D boron hydride layers, namely the C2/m, Pbcm, Cmmm, and Pmmn sheets. The vibrational normal mode calculations reveal all these structures are dynamically stable, indicating potential for successful experimental synthesis. The calculated Young's modulus indicates a high mechanical strength for the C2/m and Pbcm phases. Most importantly, the C2/m, Pbcm, and Pmmn structures exhibit Dirac cones with massless Dirac fermions and the Fermi velocities for the Pbcm and Cmmm structures are even higher than that of graphene. The Cmmm phase is reported as the first discovery of Dirac ring material among boron‐based 2D structures. The unique electronic structure of the 2D boron hydride sheets makes them ideal for nanoelectronics applications.     

Pharmaceutical analysis beyond compendial requirements

Recent ICH recommendations on test procedures and acceptance criteria for new drug substances of synthetic chemical origin and new drug products produced from them (Q6A) sets the frame for registration of new chemical entities. These requirements are automatically applied by all pharmaceutical companies to products in late developmental phases. Furthermore, and justifiably so, they do not provide any guideline for setting specifications other than those for residual solvents and residues of heavy metal catalysts. During development of new chemical entities, ICH requirements represent a minimum beyond which additional testing has to be carried out in order to accumulate a body of scientific data which may ultimately permit simplified testing. This information is furthermore needed for drafting of registration files. This presentation will provide information on salt and polymorph selection, as well as morphology of particles. The need for more sophisticated techniques for assay of trace impurities by LC/MS will be illustrated with examples of alkylating agents. Complementary information from techniques such as CE, orthogonal to HPLC, is often needed to ensure absence of additional impurities. Finally, beyond compendial characterisation of hydroxypropylmethylcellulose, a commonly used excipient, by size exclusion chromatography with triple detection will be described.     

Rapid quantitative determination of ephedra alkaloids in tablet formulations and human urine by microchip electrophoresis

Microchip electrophoresis with fluorescence detection has been applied for fast separation and determination of ephedra alkaloids in pharmaceutical formulations and body fluids. A custom epifluorescence microscope setup was employed and the compounds were separated within 40?s, allowing the detection of less than 200?ng/L for both analytes. Quantitation of the two stimulants was performed via a derivatization step using FITC without any extraction or preconcentration steps. The effects of different microchip types and excitation light sources were investigated and the method was successfully applied for the analysis of these compounds in tablet formulations, yielding recovery rates from 100.2 to 101.1% and relative standard deviations from 1.5 to 3.4%. Analysis of ephedrines was also carried out with human urine samples at detection limits of 500-1000?ng/L and relative standard deviations from 2.2 to 3.3% using argon ion LIF detection.     

Atom-bond connectivity index of trees

The recently introduced atom-bond connectivity (ABC) index has been applied up to now to study the stability of alkanes and the strain energy of cycloalkanes. Here, mathematical properties of the ABC index of trees are studied. Chemical trees with extremal ABC values are found. In addition, it has been proven that, among all trees, the star tree, S_n, has the maximal ABC value.     

Harnack Inequality and Hölder Regularity Estimates for a Lévy Process with Small Jumps of High Intensity

We consider a Lévy process in ? ^d (d≥3) with the characteristic exponent $$\varPhi(\xi)=\frac{|\xi|^2}{\ln(1+|\xi|^2)}-1.$$ The scale invariant Harnack inequality and a priori estimates of harmonic functions in Hölder spaces are proved.