Red Emitting Monoazo Disperse Dyes with Phenyl(1H-benzoimidazol-5-yl) Methanone as Inbuilt Photostabilizing Unit: Synthesis,Spectroscopic, Dyeing and DFT Studies

Synthesis of three novel phenyl(1H-benzoimidazol-5-yl)methanone based fluorescent monoazo disperse dyes and their characterization by spectroscopic methods (¹H NMR, ¹³C NMR, IR and MS) are presented. Insertion of phenyl(1H-benzoimidazol-5-yl)methanone moiety bring about induced fluorescence properties and enhanced photostability as compared to the previously reported analogues (CI Solvent Yellow 14, 4-diethylamino-2-hydroxy-1-diazobenzene and 7-(diethylamino)-4-hydroxy-3-(phenyldiazenyl)-2H-chromen-2-one). Synthesized phenyl(1H-benzoimidazol-5-yl)methanone based dyes exhibited red-shifted absorption maxima (497–516 nm), high molar extinction coefficients and are emitting in the far-red region (565–627 nm). Moreover, naphthalene-comprising dyes showed negative solvatochromism while N,N-diethylamine comprising dyes showed positive solvatochromism and are in good agreement with solvent polarity graphs and the computed energy levels of highest occupied and lowest unoccupied molecular orbitals. Synthesised dyes have better photostability (light fastness) and sublimation fastness on dyed polyester and nylon compared to reported analogues. DFT calculated energies, electrophilicity index and Frontier Molecular Orbitals (FMO’s) enabled to evaluate the stabilities of azo and hydrazone forms of the dyes.     

Far field photoluminescence imaging of single AlGaN nanowire in the sub‐wavelength scale using confinement of polarized light

Till now the nanoscale focusing and imaging in the sub‐diffraction limit is achieved mainly with the help of plasmonic field enhancement by confining the light assisted with noble metal nanostructures. Using far field imaging technique, we have recorded polarized spectroscopic photoluminescence (PL) imaging of a single AlGaN nanowire (NW) of diameter ～100 nm using confinement of polarized light. It is found that the PL from a single NW is influenced by the proximity to other NWs. The PL intensity is proportional to 1/(l×d), where l and d are the average NW length and separation between the NWs, respectively. We suggest that the proximity induced PL intensity enhancement can be understood by assuming the existence of reasonably long lived photons in the intervening space between the NWs. A nonzero non‐equilibrium population of such photons may cause stimulated emission leading to the enhancement of PL emission with the intensity proportional to 1/(l×d). The enhancement of PL emission facilitates far field spectroscopic imaging of a single semiconductor AlGaN NW of sub‐wavelength dimension.

     

Unitary parametrization of perturbations to tribimaximal neutrino mixing

Current experimental data on neutrino mixing are very well described by tribimaximal mixing. Accordingly, any phenomenological parametrization of the Maki-Nakagawa-Sakata-Pontecorvo matrix must build upon tribimaximal mixing. We propose one particularly natural parametrization, which we call "triminimal." The three small deviations of the Particle Data Group angles from their tribimaximal values, and the PDG phase, parametrize the triminimal mixing matrix. As an important example of the utility of this new parametrization, we present the simple resulting expressions for the flavor-mixing probabilities of atmospheric and astrophysical neutrinos. As no foreseeable experiment will be sensitive to more than second order in the small parameters, we expand these flavor probabilities to second order.     

Structural, optical and electrochromic properties of Nb-doped MoO3 thin films

Niobium (Nb) doped molybdenum trioxide (MoO₃) thin films have been synthesized using spray pyrolysis deposition technique. The structural changes were observed with the help of X-ray diffraction technique. With increasing Nb concentration, the structure of MoO₃ undergoes a phase transformation from α-orthorhombic to amorphous with nano-sized grains. The thread like reticulated morphology is converted into spongy like structure at higher Nb concentration (9 at% Nb). It is seen that Nb doping can lead to significant surface morphology changes in MoO₃ films. It was found that the coloration efficiency increases with doping concentration. With increasing Nb concentration charge capacity, reversibility and electrochemical stability increases. The improvement is attributed to the amorphous structure of the doped samples that favors easy intercalation and deintercalation processes. Hence, we have successfully demonstrated formation of an adequate host for electrochromic devices with Nb (9 at%) doped MoO₃ samples.     

Effect of residual oxygen on ionization processes of Si and Si sputtered from Si(1 1 1)-7 × 7 surface

The effect of residual oxygen impurity on ionization processes of Si⁺ and Si²⁺ has been studied quantitatively. In this study, ion sputtering experiments were carried out for a Si(1 1 1)-7 × 7 surface, irradiated with 9-11 keV Ar⁰ and Kr⁰ beam. Even if the oxygen concentration is less than the detection limit of Auger electron spectrometry, SiO⁺ and SiO₂⁺ ions have been appreciably observed. Moreover, as the SiO⁺ and SiO₂⁺ yields increases, the Si⁺ yield is slightly enhanced, whereas the Si²⁺ yield is significantly reduced. From the incidence angle dependence of secondary ion yields, it is confirmed that Si⁺* (Si⁺ with a 2p hole) created in the shallow region from the surface exclusively contributes to Si²⁺ formation. By assuming that the SiO⁺ and SiO₂⁺ yields are proportional to the residual oxygen concentration, these observations are reasonably explained: The increase of Si⁺ with the increase of residual oxygen is caused by a similar effect commonly observed for oxidized surfaces. The decrease of Si²⁺ yield can be explained by the inter-atomic Auger transition between the residual oxygen impurity and Si⁺*, which efficiently interferes the Si²⁺ formation process.     

Chemical machine learning with kernels: The impact of loss functions

Machine learning promises to accelerate materials discovery by allowing computational efficient property predictions from a small number of reference calculations. As a result, the literature has spent a considerable effort in designing representations that capture basic physical properties. Our work focuses on the less-studied learning formulations in this context in order to exploit inner structures in the prediction errors. In particular, we propose to directly optimize basic loss functions of the prediction error metrics typically used in the literature, such as the mean absolute error or the worst case error. In some instances, a proper choice of the loss function can directly reduce reasonably the prediction performance in the desired metric, albeit at the cost of additional computations during training. To support this claim, we describe the statistical learning theoretic foundations, and provide supporting numerical evidence with the prediction of atomization energies for a database of small organic molecules.     

Highly Efficient Synthesis and Assay of Protein‐Imprinted Nanogels by Using Magnetic Templates

We report an approach integrating the synthesis of protein‐imprinted nanogels (“plastic antibodies”) with a highly sensitive assay employing templates attached to magnetic carriers. The enzymes trypsin and pepsin were immobilized on amino‐functionalized solgel‐coated magnetic nanoparticles (magNPs). Lightly crosslinked fluorescently doped polyacrylamide nanogels were subsequently produced by high‐dilution polymerization of monomers in the presence of the magNPs. The nanogels were characterised by a novel competitive fluorescence assay employing identical protein‐conjugated nanoparticles as ligands to reversibly immobilize the corresponding nanogels. Both nanogels exhibited K_d<10 pM for their respective target protein and low cross‐reactivity with five reference proteins. This agrees with affinities reported for solid‐phase‐synthesized nanogels prepared using low‐surface‐area glass‐bead supports. This approach simplifies the development and production of plastic antibodies and offers direct access to a practical bioassay.     

One-pot four-component domino reaction for the synthesis of bifunctionalized spiro[indazolo[3,2-b]quinazoline-7,3′-indoline hybrids: A green approach

An efficient tandem route to obtain novel spiro[indazolo[3,2-b]quinazoline-7,3′-indolines has been explored. The one-step domino reaction proceeds via in situ generation of the 1H-indazol-3-amines followed by its reaction with the cyclic 1,3-dicarbonyls and isatin derivatives to furnish complex N-fused spiro-polyheterocyclic frameworks. This protocol describes a valuable route to concisely and feasibly obtain spiro[indazolo[3,2-b]quinazoline-7,3′-indolines from isatin derivatives. The present protocol is particularly attractive because of the following features: group-assisted-purification (GAP) chemistry process, low-cost solvent, convenience of operation, excellent atom economy, and high yields.     

Solid‐contact Acetate‐selective Electrode Based on a 1,3‐bis(carbazolyl)urea‐ionophore

The construction and study of solid‐contact acetate‐selective electrodes is described using a 1,3‐bis(carbazolyl)urea derivative as a neutral hydrogen‐bonding ionophore and poly(3,4‐ethylenedioxythiophene) as the solid contact. It was shown recently that this ionophore binds acetate (logK_ass=4.98) that is used as primary ion in this study. The electrodes show linearity over the activity range of 10^?4.50–10^?1.10 with a sub‐Nernstian slope of ?51.3 mV per decade and a detection limit of 10^?5.00. The anion‐selectivity pattern of these electrodes deviates markedly from the Hofmeister pattern. When adding ionophore to the membrane the logarithm of the selectivity coefficient (logK) for SCN^? decreased from 6.5 to 1.2, logK for I^? decreased from 5.7 to 0.9, logK for NO₃^? decreased from 4.3 to 0.6 and logK for Br^? decreased from 3.3 to 0.1. The selectivity coefficients of hydrophilic anions such as Cl^?, F^?, HPO₄^2?, and SO₄^2? are significantly lower than in case of the ionophore‐free membrane. It was discovered that the constructed electrodes are also relatively selective to bicarbonate. This work is an important step towards the further development of solid‐contact anion‐selective electrodes.