Iron(III) Catecholates for Cellular Imaging and Photocytotoxicity in Red Light

Iron(III) complexes Fe(L)(L') (NO3)]-in which L is phenyl-N, N-bis(pyridin-2-yl) methyl]methanamine (1), (anthracen-9-yl)N, N-bis(pyridin-2-yl) methyl] methanamine (2), (pyreny-1-yl)-N, N-bis(pyridin- 2-yl) methyl] methanamine (3-5), and L' is catecholate (1-3), 4-tert-butyl catecholate (4), and 4-(2-aminoethyl)benzene- 1,2-diolate (5)-were synthesized and their photocytotoxic proper-ties examined. The five electron-paramagnetic complexes displayed a FeIII/ Fe-II redox couple near similar to 0.4 V versus a saturated calomel electrode (SCE) in DMF/0.1m tetrabutylammonium perchlorate (TBAP). They showed unpre-cedented photocytotoxicity in red light (600-720 nm) to give IC50-15 mm in various cell lines by means of apoptosis to generate reactive oxygen species. They were ingested in the nucleus of HeLa and HaCaT cells in 4 h, thereby interacting favorably with calf thymus (ct)-DNA and photocleaving pUC19 DNA in red light of 785 nm to form hydroxyl radicals.

A Comparative Assessment of Hand Preference in Captive Red Howler Monkeys, Alouatta seniculus and Yellow-Breasted Capuchin Monkeys, Sapajus xanthosternos

There are two major theories that attempt to explain hand preference in non-human primates-the `task complexity' theory and the `postural origins' theory. In the present study, we proposed a third hypothesis to explain the evolutionary origin of hand preference in non-human primates, stating that it could have evolved owing to structural and functional adaptations to feeding, which we refer to as the `niche structure' hypothesis. We attempted to explore this hypothesis by comparing hand preference across species that differ in the feeding ecology and niche structure: red howler monkeys, Alouatta seniculus and yellow-breasted capuchin monkeys, Sapajus xanthosternos. The red howler monkeys used the mouth to obtain food more frequently than the yellow-breasted capuchin monkeys. The red howler monkeys almost never reached for food presented on the opposite side of a wire mesh or inside a portable container, whereas the yellow-breasted capuchin monkeys reached for food presented in all four spatial arrangements (scattered, on the opposite side of a wire mesh, inside a suspended container, and inside a portable container). In contrast to the red howler monkeys that almost never acquired bipedal and clinging posture, the yellow-breasted capuchin monkeys acquired all five body postures (sitting, bipedal, tripedal, clinging, and hanging). Although there was no difference between the proportion of the red howler monkeys and the yellow-breasted capuchin monkeys that preferentially used one hand, the yellow-breasted capuchin monkeys exhibited an overall weaker hand preference than the red howler monkeys. Differences in hand preference diminished with the increasing complexity of the reaching-for-food tasks, i.e., the relatively more complex tasks were perceived as equally complex by both the red howler monkeys and the yellow-breasted capuchin monkeys. These findings suggest that species-specific differences in feeding ecology and niche structure can influence the perception of the complexity of the task and, consequently, hand preference.

A quinazoline derivative as quick-response red-shifted reporter for nanomolar Al3+ and applicable to living cell staining

A newly synthesized and structurally characterized quinazoline derivative (L) has been shown to act as a quick-response chemosensor for Al3+ with a high selectivity over other metal ions in water-DMSO. In the presence of Al3+, L shows a red-shifted ratiometric enhancement in fluorescence as a result of internal charge transfer and chelation-enhanced fluorescence through the inhibition of a photo-induced electron transfer mechanism. This probe detects Al3+ at concentrations as low as 1.48 nM in 100 mM HEPES buffer (DMSO-water, 1 : 9 v/v) at biological pH with a very short response time (15-20 s). L was applied to biological imaging to validate its utility as a fluorescent probe for monitoring Al3+ ions in living cells, illustrating its value in practical environmental and biological systems.

Visible light assisted photocatalytic degradation of organic dyes on TiO2-CNT nanocomposites

Carbon nanotubes (CNTs) uniformly decorated with nano-anatase TiO2 particles corresponding to different TiO2-CNT weight ratios (up to 90 % TiO2:10 % CNT) were prepared by employing sol-gel process. The nanocomposites were characterized by X-ray diffraction, IR, Raman, Scanning electron microscopy, Transmission electron microscopy, Photoluminescence, BET surface area and diffuse reflectance measurements. The composites show visible light assisted photocatalytic property, for example, the 90 % TiO2-10 % CNT composite completely degrades Indigo Carmine dye within 1 h of exposure to visible light. Similarly, Orange G and Congo Red dyes were decomposed within 2 h under visible light irradiation. The excellent visible light photocatalytic property of the composite is attributed to the synergetic effect of photoexcitation and photosensitization. This is due to the special nanoarchitecture wherein TiO2 nanoparticles are anchored to CNT surface that provides high specific interfacial area for photon absorption and electron trapping. Visible light assisted degradation profile of Indigo Carmine in the presence of TiO2-CNT nanocomposite and TEM image of the TiO2-CNT nanocomposite.

Eu3+-activated SrMoO4 phosphors for white LEDs applications: Synthesis and structural characterization

We report the synthesis of Eu3+-activated SrMoO4 phosphors by the facile nitrate-citrate gel combustion method. Powder XRD and Rietveld refinement data confirmed that these phosphors have a monophasic scheelite-type tetragonal structure with space group I4(1)/a (No. 88). FESEM micrographs indicate the agglomerated spherical particles. FTIR spectra showed four stretching and bending vibrational modes (2A(u) and 2E(u)). UV-Visible absorption spectroscopy illustrated that the optical band gap energy (E-g) values increase with increase in Eu3+ concentration. The host SrMoO4 phosphor exhibited an intense blue emission under UV excitation (368 nm). The Eu3+-activated SrMoO4 phosphors revealed characteristic luminescence due to Eu3+ ion corresponding to D-5(1) -> F-7(J) (J = 1,2) and D-5(0) -> F-7(J) (J = 1,2,3,4) transitions upon 465 nm excitation. The electric dipole transition located at 615 nm (D-5(0) -> F-7(2)) was stronger than the magnetic dipole transition located at 592 nm (D-5(0) -> F-7(1)). Intensity parameters (Omega(2), Omega(4)) and radiative properties such as transition probabilities (A(T)), radiative lifetime (tau(rad)) and branching ratio (beta) of Eu3+-activated SrMoO4 phosphors were calculated using the Judd-Ofelt theory. Based on the CIE chromaticity diagram, these phosphors can be promising materials for the development of blue and orange-red component in white LEDs. (C) 2015 Elsevier B.V. All rights reserved.

Negative hyperconjugation and red-, blue- or zero-shift in X-Z center dot center dot center dot Y complexes

A generalized explanation is provided for the existence of the red-and blue-shifting nature of X-Z bonds (Z = H, halogens, chalcogens, pnicogens, etc.) in X-Z center dot center dot center dot Y complexes based on computational studies on a selected set of weakly bonded complexes and analysis of existing literature data. The additional electrons and orbitals available on Z in comparison to H make for dramatic differences between the H-bond and the rest of the Z-bonds. The nature of the X-group and its influence on the X-Z bond length in the parent X-Z molecule largely controls the change in the X-Z bond length on X-Z center dot center dot center dot Y bond formation; the Y-group usually influences only the magnitude of the effects controlled by X. The major factors which control the X-Z bond length change are: (a) negative hyperconjugative donation of electron density from X-group to X-Z sigma* antibonding molecular orbital (ABMO) in the parent X-Z, (b) induced negative hyperconjugation from the lone pair of electrons on Z to the antibonding orbitals of the X-group, and (c) charge transfer (CT) from the Y-group to the X-Z sigma* orbital. The exchange repulsion from the Y-group that shifts partial electron density at the X-Z sigma* ABMO back to X leads to blue-shifting and the CT from the Y-group to the sigma* ABMO of X-Z leads to red-shifting. The balance between these two opposing forces decides red-, zero- or blue-shifting. A continuum of behaviour of X-Z bond length variation is inevitable in X-Z center dot center dot center dot Y complexes.

Li2MnO3: a rare red-coloured manganese(IV) oxide exhibiting tunable red-yellow-green emission

An experimental assessment of Li2MnO3 has been conducted, in conjunction with related Mn(IV) oxides, to investigate its red colour and photoluminescence. Optical absorption spectra revealed strong band gap absorption, with a sharp edge at similar to 610 nm and a transparent region between similar to 610 and similar to 650 nm, giving rise to the red colour of this compound. Octahedral Mn(IV) ligand field transitions have been observed in the excitation spectra of Li2MnO3, corresponding both to Mn(IV) at ideal sites and displaced in Li sites in the rock salt-based layered structure of Li2MnO3. Optical excitation at ligand field transition energies produces tunable emission in the red-yellow-green region, rendering Li2MnO3 a unique Mn(IV) oxide. The honeycomb-ordered LiMn6] units in its structure are probably the origin of both the absorption and the photoluminescent properties of Li2MnO3.

Excitation- and power-dependent photoluminescence from oxidized Ge

Wafer/microcrystallites of oxidized Ge with holes/nanoholes synthesized by thermal oxidation strategy from Ge wafer/microcrystallites can convert one wavelength to another. Both oxidized Ge wafer and microcrystallites shows excitation- and power-dependent luminescence. Red-shift is observed as the excitation wavelength is increased, while blue-shift is observed as power density is increased. Over all, blue-green-yellow-orange luminescence is observed depending on the excitation wavelength and the morphology of oxidized Ge. The various defects level associated with germanium-oxygen vacancies in GeO2 and Ge/GeO2 interface are responsible for the excitation-dependent luminescence. Being a light-conversion material, oxidized Ge is expected to find potential applications in solid-state lighting, photovoltaic devices and photocatalysis. (C) 2013 Elsevier B.V. All rights reserved.

Biodiesel Exhaust Treatment with HFAC Plasma supported by Red Mud: Study on DeNOx and power consumption

The concentration of Nitrogen Oxides (NOx) in engines which use biodiesel as fuel is higher compared to conventional diesel engine exhaust. In this paper, an attempt has been made to treat this exhaust using a combination of High frequency AC (HFAC) plasma and an industrial waste, Red Mud which shows proclivity towards Nitrogen dioxide (NO2) adsorption. The high frequency AC source in combination with the proposed compact double dielectric plasma reactors is relatively more efficient in converting Nitric Oxide (NO) to NO2. It has been shown that the plasma treated gas enhances the activity of red mud as an adsorbent/catalyst and about 60-72% NOx removal efficiency was observed at a specific energy of 250 J/L. The advantage in this method is the cost effectiveness and abundant availability of the waste red mud in the industry. Further, power estimation studies were carried out using Manley's equation for the two reactors employed in the experiment and a close agreement between experimental and predicted powers was observed. (C) 2015 The Authors. Published by Elsevier Ltd.

Ag-doped hydroxyapatite as efficient adsorbent for removal of Congo red dye from aqueous solution: Synthesis, kinetic and equilibrium adsorption isotherm analysis

In the present study a versatile and efficient adsorbent with high adsorption capacity for adsorption of Congo red dye in aqueous solution at ambient temperature without adjusting any pH is presented over the Ag modified calcium hydroxyapatite (CaHAp). CaHAp and Ag-doped CaHAp materials were synthesized using facile aqueous precipitation method. The physico-chemical properties of the materials were determined by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Transmission electron microscopy (TEM), UV-Visible spectroscopy, N-2 physisorption and acidity was determined by n-butylamine titration and pyridine adsorption methods. XRD analysis confirmed all adsorbents exhibit hexagonal CaHAp structure with P6(3)/m space group. TEM analysis confirms the rod like morphology of the adsorbents and the average length of the rods were in the range of 40-45 nm. Pyridine adsorption results indicate increase in number of Lewis acid sites with Ag doping in CaHAp. Adsorption capacity of CaHAp was found increased with Ag content in the adsorbents. Ag (10): CaHAp adsorbent showed superior adsorption performance among all the adsorbents for various concentrations of Congo red (CR) dye in aqueous solutions. The amount of CR dye adsorbed on Ag (10): CaHAp was found to be 49.89-267.81 mg g(-1) for 50-300 ppm in aqueous solution. A good correlation between adsorption capacity and acidity of the adsorbents was observed. The adsorption kinetic data of adsorbents fitted well with pseudo second-order kinetic model with correlation coefficients ranged from 0.998 to 0.999. The equilibrium adsorption data was found to best fit to the Langmuir adsorption isotherm model. (C) 2015 Elsevier Inc. All rights reserved.

Boron-doped carbon nanoparticles: Size-independent color tunability from red to blue and bioimaging applications

Here, we report the hydrothermal synthesis of boron-doped CNPs (B-CNPs) with different size/atomic percentage of doping and size-independent color tunability from red to blue. The variation of size/atomic percentage of B is achieved by simply varying the reaction time, while the color tunability is obtained by diluting the solution. With dilution, the luminescence spectra are not only blue-shifted, the intensity increases as well. The huge blue-shift in the emission energy (similar to 1 eV) is believed to be due to the increase in the interparticle distance. The quantum yield with optimum dilution is found to increase with boron doping though it is very low as compared to CNPs and nitrogen-doped CNPs. Finally, we show that B-CNPs with a quantum yield of 0.5% can be used for bioimaging applications. (C) 2015 Elsevier Ltd. All rights reserved.

Yellow-red luminescence in ZnO nanoparticles synthesized from zinc acetylacetonate phenanthroline

ZnO powders/thin films/coatings when excited by a suitable excitation source, usually yield green luminescence in the visible wavelength range along with characteristic ultra-violet emission. We report yellow-red emission from ZnO nanoparticles synthesized within 5 min of microwave irradiation by using zinc acetylacetonate phenanthroline as the starting precursor material. The emission is strongly dependent on the typical structure of the starting precursor for ZnO synthesis, where one phenanthroline moiety is attached with zinc acetylacetonate hydrate complex. These ZnO nanoparticles could be potentially suitable phosphor for white light generation when excited by a blue laser. In contrast, the ZnO nanoparticles obtained from zinc acetylacetonate by similar method yield weak green emission. (C) 2015 Elsevier B.V. All rights reserved.

Exploring the Colour of 3d Transition-Metal Ions in Trigonal Bipyramidal Coordination: Identification of Purple-Blue (CoO5) and Beige-Red (NiO5) Chromophores in LiMgBO3 Host

In an attempt to develop new coloured inorganic oxides, we have investigated the substitution of 3d transition-metal ions in LiMgBO3 host where Mg-II has a trigonal bipyramidal (TBP) oxygen coordination]. We find that single-phase materials are formed for (LiMg1-xCoxBO3)-B-II (0 < x 1.0), (LiMg1-xNixBO3)-B-II (0 < x 0.1), (LiMg1-xCuxBO3)-B-II (0 < x 0.1) and also (Li1-xMg1-xFexBO3)-B-III (0 < x 0.1) of which the Co-II and Ni-II derivatives are strongly coloured, purple-blue and beige-red, respectively, thus identifying TBP CoO5 and NiO5 as new chromophores for these colours.

Red-emitting LaOF:Eu3+ phosphors: Synthesis, structure and their Judd-Ofelt analysis for LED applications

In the present study, we have synthesized a series of La1-xEuxOF (0.01 <= x <= 0.09) phosphors by the conventional solid-state reaction route at relatively low temperature (500 degrees C) and shorter duration of 2 h. The compounds were crystallized in the rhombohedral structure with the space group R-3m (No. 166). Upon UV excitation (254 nm), the photoluminescence spectra exhibit characteristic luminescence D-5(0) -> F-7(J) (J= 1, 2, 3, and 4) intra-4f shell Eu3+ ion transitions. An intense red emission peak at 610 nm was observed due to electric dipole (D-5(0) -> F-7(2)) transition. Judd-Ofelt theory was employed to evaluate various radiative parameters such as radiative emission rates, lifetime, branching and asymmetry ratios. CIE color coordinates confirmed the red emission of the phosphors. The luminescent results reveal that LaOF:Eu3+ phosphor can be used as potential candidate for developing red component in white LED applications. (C) 2015 Elsevier Ltd. All rights reserved.

InN Quantum Dot Based Infra-Red Photodetectors

Self-assembled InN quantum dots (QDs) were grown on Si(111) substrate using plasma assisted molecular beam epitaxy (PA-MBE). Single-crystalline wurtzite structure of InN QDs was confirmed by X-ray diffraction. The dot densities were varied by varying the indium flux. Variation of dot density was confirmed by FESEM images. Interdigitated electrodes were fabricated using standard lithography steps to form metal-semiconductor-metal (MSM) photodetector devices. The devices show strong infrared response. It was found that the samples with higher density of InN QDs showed lower dark current and higher photo current. An explanation was provided for the observations and the experimental results were validated using Silvaco Atlas device simulator.