Tunable,dual-wavelength interferometrically coupled continuous-wave parametric source

Generation of dual-wavelength continuous-wave (cw) radiation with independent and arbitrarily tuning, and indefinitely close spacing, using two cw optical parametric oscillators (OPOs) coupled with an anti-resonant ring interferometer is reported. The singly resonant OPOs, based on identical 30-mm-long MgO:sPPLT crystals, are pumped by a single cw laser at 532 nm. Two pairs of signal and idler wavelengths can be independently and arbitrarily tuned, with each signal (idler) pair tuned through degeneracy and beyond. Frequency separation between two distinct resonant signal waves from 7 down to 0.8 THz is demonstrated, and their overlap at 951 nm providing a frequency difference as small as ~220 MHz is shown. The OPOs independently provide a signal (idler) wavelength coverage across 870–1,000 nm (1,040–1,370 nm) and simultaneously generate idler powers of >1 W.     

DFT studies of squarylium and core‐substituted squarylium dye derivatives: understanding the causes of the additional shorter wavelength absorption in the latter

Recent reports indicate that the core‐substituted squarylium (CSQ) dyes (obtained when one oxygen atom of the SQ moiety is replaced by an electron withdrawing group or sulfur) show bathochromic shift of the absorption maxima and an additional shorter wave length absorption in visible when compared to parent SQ dyes. To investigate this interesting property of these dyes which will be more suitable for applications in DSSC, a comparative study using computational techniques of some selected SQ and CSQ derivatives has been carried out. The effect of this core substitution on geometries is studied. The ground state charge distribution is analyzed by natural population analysis. It is noticed that the biradical character, which is normally large in SQ derivatives, is reduced in CSQ due to the substitution and the zwitterionic character is increased. The absorption maxima for both parent SQ and CSQ dyes obtained with TD‐DFT methods using various functional like B3LYP, M06‐2X and CAM‐B3LYP methods do not match the experimental results. However, results obtained using SAC‐CI method are better. Charge transfer (CT) data based on Mulliken charges of both ground and excited states is obtained from SAC/SAC‐CI studies. It is seen that on excitation substantial CT from the side groups to the central core is taking place in parent SQ molecules. In contrast, intense CT occurs from –X to side groups through central core in the case of CSQ molecules. This study will be helpful in designing and synthesizing new CSQ dyes which makes them suitable for solar cell applications. Copyright © 2012 John Wiley & Sons, Ltd.     

Cover Picture: Compartmentalization of Chemically Separated Components into Droplets (Angew. Chem. Int. Ed. 15/2009)

Electroosmotic‐flow‐driven droplet generation integrated with capillary electrophoresis (CE) allows the molecular components separated by CE to be compartmentalized into a stream of droplets, as reported by D. T. Chiu and co‐workers in their Communication on page 2719 ff. and illustrated on the cover picture. After separation and droplet compartmentalization, the droplet‐confined bands either can be docked and studied on‐chip or removed off‐chip for a second‐dimension separation and further analysis.

     

Ferromagnetism driven by intrinsic point defects in HfO(2)

In view of recent experimental reports of unexpected ferromagnetism in HfO(2) thin films, we carried out first-principles investigations looking for magnetic order possibly brought about by the presence of small concentrations of intrinsic point defects. Ab initio electronic structure calculations using density functional theory show that isolated cation vacancy sites in HfO(2) lead to the formation of high-spin defect states. Furthermore these appear to be ferromagnetically coupled with a rather short range magnetic interaction, resulting in a ferromagnetic ground state for the whole system. More interestingly, the occurrence of these high-spin states and ferromagnetism is in the low symmetry monoclinic phase of HfO(2). This is radically different from other systems previously known to exhibit point defect ferromagnetism, warranting a closer look at the phenomenon.     

Investigation of n-type donor defects in Co-doped ZnO

We investigate using density functional theory (DFT) the electronic structure of (∼3%) Co-doped ZnO in the presence of native n-type donor defects such as V_O and Zn_I. In particular, we apply a pseudopotential-based self-interaction correction (pseudo-SIC) scheme as an improvement to the local spin-density approximation (LSDA). This overcomes major short comings of the LSDA in describing Co-doped ZnO. Donor+dopant pair complexes such as Co–V_O and Co–Zn_I are studied as relevant magnetic centres for long-range magnetic interactions at low-dopant concentrations. We find that complex formation is energetically favourable but the inter-complex magnetic coupling is too weak to account for room temperature ferromagnetism in ZnO:Co     

How aromatic are large (4n + 2)pi annulenes?

[structure: see text] While the total aromatic stabilization energies (ASE) of the [n]annulenes, from C(6)H(6) to C(66)H(66), converge to ca. 22 kcal/mol, the ASEs per pi-electron decrease markedly. Bond length alternation (which depends on the theoretical level) only reduces stabilization somewhat but influences the magnetic properties (NICS, proton chemical shifts, and magnetic susceptibilities) considerably. Nevertheless, these magnetic criteria, when based on the most realistic structures, agree that the aromaticities of the larger annulenes decrease and then nearly vanish.     

TSP aerosol source apportionment in the urban region of the Indian steel city,Rourkela

Steel industries are a major contributor to aerosols in steel cities like Rourkela.We designed an air quality sampling program to characterize total suspended particulate(TSP) aerosol in urban areas of Rourkela and to identify their steel-related and other sources.Monitoring was carried out over 8 h,twice per week from January 2011 to December 2012.Metallic species of TSP aerosols were analyzed using an atomic absorption spectrophotometer;ionic species using the IS 3025 method;and carbonaceous species using a total organic carbon analyzer.Enrichment factor and Spearman’s rank correlation analysis were carried out on compositional data.Significant seasonal variations were observed for TSP with totals in summer>spring>winter>monsoon.Low concentrations during monsoon reflected wet scavenging,while high concentrations during summer were related to wind turbulence and low humidity.The chemical mass balance model CMB8.2 was applied to apportion sources.Particles related to steel production,road dust,and soil were dominant in all seasons.A fertilizer plant was found to contribute particles in summer and monsoon.Wood combustion,diesel exhaust,and liquefied petroleum gas contributed significantly in spring and winter.While diesel exhaust,industrial manufacturing,solid waste burning,cement kilns,and construction were found to contribute to TSP at various times throughout the year.     

Correction to: Sorption of plutonium from aqueous medium containing oxalate using zero-valent iron nano particles

Journal of Radioanalytical and Nuclear Chemistry -     

Tunable Surface Wrinkling by a Bio‐Inspired Polyamine Anion Coacervation Process that Mediates the Assembly of Polyoxometalate Nanoclusters

A bio‐inspired method is used to render controlled wrinkling surface patterns on supramolecular architectures assembled from polyoxometalate (POM) clusters. It involves a polyamine‐multivalent anion interaction generating positively charged coacervates, which while dictating the assembly of POM into spherical structures further facilitate an interesting surface morphogenesis with wrinkling patterns. This spontaneous surface wrinkling depends on the type of multivalent anion and the pH. As the polyamine‐anion interaction becomes stronger, the wrinkles turn denser with lesser depth, which eventually undergoes post‐buckling to engender a complex surface pattern. Interestingly, the order of influence exerted by different anions on the morphology follows the Hofmeister series. Moreover, the mild synthesis conditions keep the functional POM units dispersed in the sphere with a structural transformability to their lacunary form.