Earth-abundant quaternary chalcogenides are promising candidate materials for thin-film solar cells. Here we have synthesized Cu2NiSnS4 nanocrystals and thin films in a novel zincblende type cubic phase using a facile hot-injection method. The structural, electronic, and optical properties are studied using various experimental techniques, and the results are further corroborated within first-principles density functional theory based calculations. The estimated direct band gap ∼ 1.57 eV and high optical absorption coefficient ∼ 106 cm–1 indicate potential application in a low-cost thin-film solar cell. Further, the alignments for both conduction and valence bands are directly measured through cyclic voltametry. The 1.47 eV electrochemical gap and very small conduction band offset of −0.12 eV measured at the CNTS/CdS heterojunction are encouraging factors for the device. These results enable us to model carrier transport across the heterostructure interface. Finally, we have fabricated a CNTS solar cell device for the first time, with high open circuit voltage and fill factor. The results presented here should attract further studies.

We present detailed observations of MRC 0116+111, revealing a luminous, miniradio halo of ∼240-kpc diameter located at the centre of a cluster of galaxies at redshift z = 0.131. Our optical and multiwavelength Giant Metrewave Radio Telescope and Very Large Array radio observations reveal a highly unusual radio source: showing a pair of giant (∼100-kpc diameter) bubble-like diffuse structures, that are about three times larger than the analogous extended radio emission observed in M87 -the dominant central radio galaxy in the Virgo cluster. However, in MRC 0116+111 we do not detect any ongoing active galactic nucleus (AGN) activity, such as a compact core or active radio jets feeding the plasma bubbles. The radio emitting relativistic particles and magnetic fields were probably seeded in the past by a pair of radio jets originating in the AGN of the central cD galaxy. The extremely steep high-frequency radio spectrum of the north-western bubble, located ∼100 kpc from cluster centre, indicates radiation losses, possibly because having detached, it is rising buoyantly and moving away into the putative hot intracluster medium. The other bubble, closer to the cluster centre, shows signs of ongoing particle re-acceleration. We estimate that the radio jets which inflated these two bubbles might have also fed enough energy into the intracluster medium to create an enormous system of cavities and shock fronts, and to drive a massive outflow from the AGN, which could counter-balance and even quench a cooling flow. Therefore, this source presents an excellent opportunity to understand the energetics and the dynamical evolution of radio jet inflated plasma bubbles in the hot cluster atmosphere.

Publication informationChemical Physics Letters, Publisher Elsevier Item record/more information http://hdl.handle.net/10197/4903 Publisher's statementThis is the author's version of a work that was accepted for publication in Chemical Physics Letters. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Chemical Physics Letters (572, , (2013) An experimental and a hybrid density functional theory study of the photo-active and optical properties of bismuth ferrite are presented. Phase-pure photo-catalytically active BFO was prepared experimentally with a 28% degradation of methyl orange observed over a 7-hour period. Direct and indirect band gaps were measured to be 2.10 and 1.92 eV, respectively. BFO was also studied computationally with the use of hybrid density functional theory, quite suitable for such a multiferroelectric material. This led to excellent, semiquantitative agreement between hybrid DFT and experimental approaches for absorption coefficients.

No abstract

The dynamical properties of physically and chemically adsorbed water molecules at pristine hematite-(001) surfaces have been studied by means of equilibrium Born-Oppenheimer molecular dynamics (BOMD) in the NVT ensemble at 298 K. The dissociation of water molecules to form chemically adsorbed species was scrutinised, in addition to 'hopping' or swapping events of protons between water molecules. Particular foci have been dynamical properties of the adsorbed water molecules and OH -and H 3 O + ions, the hydrogen bonds between protons in water molecules and the bridging oxygen atoms at the hematite surface, as well as the interactions between oxygen atoms in adsorbed water molecules and iron atoms at the hematite surface. Experimental results for photoelectrical current generation complement simulation findings of water dissociation.

The hydrogen storage capacity of C 2 H 4 V organometallic complex and its cation was obtained using second order Møller-Plesset (MP2) and density functional theory methods with different exchange and correlation functionals. A maximum of five and six hydrogen molecules can be adsorbed on C 2 H 4 V and C 2 H 4 V + compounds with gravimetric H 2 uptake capacities of 11.32 and 13.28 wt %, respectively. The effect of temperature and different exchange and correlation functionals on the adsorption energy of C 2 H 4 V(5H 2 ) and C 2 H 4 V + (6H 2 ) complexes was studied. The superiority of C 2 H 4 V + as a possible hydrogen storage material over C 2 H 4 V and other vanadium containing organometallic compounds was observed. Similar to isolated C 2 H 4 V and C 2 H 4 V + , after adsorption of a maximum of H 2 molecules on C 2 H 4 V and C 2 H 4 V + also, V as well as V + remain strongly bound to the C 2 H 4 substrate. Many-body analysis was carried out to study the nature of interactions between different molecules in a complex, and the contribution from different many-body energies to the binding energy of a complex.

No abstract

No abstract