Ratna Chauhan

Synthesis, structure and light-harvesting properties of some new transition-metal dithiocarbamates involving ferrocene.

Nine new transition-metal dithiocarbamates involving ferrocene (Fc), namely, [M(FcCH(2)Bzdtc)(2)] (M=Ni(II) (1), Cu(II) (2), Cd(II) (3), Hg(II) (4), Pd(II) (5), Pt(II) (6) and Pb(II) (7); Bzdtc=N-benzyl dithiocarbamate) and [M(FcCH(2)Bzdtc)(3)] (M=Co(II) (8) and UO(2) (VI) (9)), have been synthesised and characterised by micro analyses, IR spectroscopy, (1)H and (13)C NMR spectroscopy, and in three cases by single-crystal X-ray analysis. The peak broadening in the (1)H spectrum of the copper complex indicates the paramagnetic behaviour of this compound. A square-planar geometry around the nickel and copper complexes and distorted linear geometry around the mercury complex have been found. The latter geometry is attributed to the bulkiness of the methylferrocenyl and benzyl groups. The observed single quasi-reversible cyclic voltammograms for complexes 2, 8 and 9 indicate the stabilisation of a metal centre other than Fe in their characteristic oxidation state. These complexes have been used as a photosensitiser in dye-sensitised solar cells.

Application of π-Extended Ferrocene with Varied Anchoring Groups as Photosensitizers in TiO2-Based Dye-Sensitized Solar Cells (DSSCs)

Two new compounds, FcCH=NC(6)H(4)COOH (1) and FcCH=NCH(2)CH(2)OH (2) (Fc=C(5)H(4)FeC(5)H(5)), have been synthesized and characterized by elemental analyses, IR and (1)H NMR spectroscopy, and ESI-MS. Attempt has been made to explain their quasi-reversible redox behavior evidenced by cyclic voltammetry using density functional theory (DFT) calculations. Light-harvesting properties of both the compounds and also the starting material, FcCHO (3), have been studied using these compounds as photosensitizers in TiO(2)-based dye-sensitized solar cells having either a propylene carbonate-based electrolyte or ionic liquid electrolyte, namely, 1-propyl-3-methyl imidazolium iodide (PMII). Long-term stability of the photocurrent output of the cell using compound 1 as photosensitizer has been monitored periodically over 1400 h.

Light harvesting properties of some new heteroleptic dithiocarbimate–diamine/diimine complexes of Ni, Pd and Pt studied as photosensitizer in dye-sensitized TiO2 solar cells

This contribution describes the light harvesting efficiencies of new heteroleptic complexes of the form [M(L)(L′)] where L = p-tolylsulfonyldithiocarbimate (p-CH3C6H4SO2NCS22−); M = Ni(II), L′ = 2,2′-bipyridine (bpy) (1) or 1,10-phenanthroline (phen) (2) or N,N,N′,N′-tetramethylethylenediamine (tmed) (3); M = Pd(II), L′ = bpy (4) or phen (5) or tmed (6); and M = Pt(II), L′ = bpy (7) or phen (8) or tmed (9). These have been characterized by elemental analysis, IR, 1H and 13C NMR and UV-visible spectroscopies, and 1, 4 and 6 by single crystal X-ray diffraction. UV-visible absorption, electrochemical behavior and structural features of the ligand aromatic sulfonyldithiocarbimate containing free sulfonyl oxygen atoms serving as a typical anchoring group on TiO2 semiconductor electrode of the nickel complexes enable them to act as potential photosensitizers for solar energy conversion. This study widens the scope for square planar heteroleptic complexes with a suitable combination of metal ions and ligands to be explored as photosensitizers.

Synthesis, characterization and light harvesting properties of Sb(III) and Bi(III) ferrocenyl dithiocarbamate complexes

New Sb(III) and Bi(III) ferrocenyl dithiocarbamate complexes viz. [Sb(FcCH2Bzdtc)3] (Sb) and [Bi(FcCH2Bzdtc)3] (Bi) (Fc=C5H5FeC5H4-; Bz=C6H5CH2-) have been synthesized and characterized by elemental analyses, IR, (1)H and (13)C NMR spectroscopies. The optical, electrochemical and photovoltaic properties of the synthesized complexes were investigated. The light harvesting properties of both of the compounds have been studied using these compounds as photosensitizers in TiO2-based DSSCs. The photovoltaic devices fabricated by Sb and Bi showed a maximum current conversion efficiency of 1.51% and 0.97%, respectively under 1.5 AM illumination (100 mW cm(-2)) and having incident photon to current efficiency (IPCE) of 38% and 31%, respectively. The reason for the higher efficiency of Sb is due its higher dye loading.

Ferrocenyl chalcones with phenolic and pyridyl anchors as potential sensitizers in dye-sensitized solar cells

Five ferrocenyl chalcones viz. (E)-1-(3′-hydroxyphenyl)-3-ferrocenylprop-2-en-1-one (H-1), (E)-1-(4′-hydroxyphenyl)-3-ferrocenylprop-2-en-1-one (H-2), (E)-1-(2′-hydroxyphenyl)-3-ferrocenylprop-2-en-1-one (H-3), (E)-1-(4-pyridyl)-3-ferrocenylprop-2-en-1-one (H-4) and (E)-1-(2-pyridyl)-3-ferrocenylprop-2-en-1-one (H-5) having hydroxyl or pyridyl as the anchoring group have been synthesized and characterized using microanalyses, IR, 1H and 13C NMR, and in three cases, using single-crystal X-ray diffraction. UV-vis spectroscopic studies indicates that in comparison to ferrocene the electronic absorption bands of the synthesized dyes H-1–H-5 are bathochromically shifted up to 530 nm with concomitant enhancement in their intensities. The synthesized dyes have been exploited as photosensitizers in TiO2-based dye-sensitized solar cells (DSSCs). The photovoltaic performances and charge transport properties (EIS spectra) were studied to evaluate the synthesized dye performances in DSSCs. Amongst all the ferrocenyl chalcone dyes, those with the hydroxyl linker H-1–H-3 showed relatively superior photovoltaic performance in comparison to the dyes having a pyridyl anchor. The superior performances of H-1–H-3 are probably due to the better electronic communication between the ferrocene and the six-membered aromatic ring with anchoring group as well as the high dye loading abilities of these compounds on the TiO2 surface, which suppress charge recombination, prolong electron lifetime, and decreases the total resistance of DSSCs. The assembly fabricated using H-2 showed the best performance with an overall conversion efficiency η of 6.55%, Jsc of 11.99 mA cm−2 and Voc of −0.74 V. The long term stability of the photocurrent output of the cell using H-2 as photosensitizer has been monitored during 700 h which shows 92% retention of the cell parameters. Also, H-2 showed better thermal stability than the state-of-the-art N719 dye and also has a comparable lifetime of electrons in the conduction band.

Crystalline to amorphous phase transition of tin oxide nanocrystals induced by SHI at low temperature

Tin oxide (SnO2) thin films were deposited using pulsed laser deposition (PLD) technique on Si substrates. The as-deposited films were irradiated using 100 MeV Ag ions at different fluences ranging from 3×1013 to 3×1014 ions/cm2 at an incidence angle of 75° with respect to surface normal at liquid nitrogen (LN2) temperature. The as-deposited and irradiated films have been characterized using X-ray diffraction (XRD) and atomic force microscopy (AFM) techniques to study the modifications in structural and surface morphological properties. Nanocrystalline film become completely amorphous and nanograins of tin oxide disappeared from the surface as indicated by XRD spectra and AFM micrographs respectively.

1,2-Bis(diphenylphosphino)ethane nickel(ii) O,O'-dialkyldithiophosphates as potential precursors for nickel sulfides

In this work, three heteroleptic Ni(II)dppe dithiophosphate complexes, [Ni{S2P(OC2H5)2}(dppe)]B(C6H5)4 (1), [Ni{S2P(OCH(CH3)2)2}(dppe)]PF6 (2) and [Ni{S2P(OCH(CH3)2)2}(dppe)]B(C6H5)4 (3) (dppe=1,2-bis(diphenylphosphino)ethane), have been synthesized and characterized by analytical and spectroscopic techniques (microanalysis, IR, UV-Vis, 1H, 13C and 31P NMR spectroscopy) as well as single crystal X-ray crystallography. The crystal structures of all complexes displayed a distorted square planar geometry around the Ni(II) center bonded through two sulfur atoms of the dithiophosphate ligand and two phosphorus atoms of dppe. The TGA results indicated that all three compounds display loss of solvents at the outset and decompose to Ni–S phase systems and hence may act as potential precursors for nickel sulfides. Investigations indicated that the bulkiness of counteranions as well as the alkyl fragment of the dithiophosphate ligands do not have any effect on the morphologies of as-synthesized nickel sulfides.

Ferrocenyl benzimidazole with carboxylic and nitro anchors as potential sensitizers in dye-sensitized solar cells

Two ferrocenyl benzimidazoles with carboxylic (1) and nitro (2) anchors have been synthesized and characterized using microanalyses, IR, 1H and 13C NMR spectroscopy, and in one case using single crystal X-ray diffraction. UV-Vis spectroscopic studies indicate that in comparison to ferrocene the electronic absorption bands of the synthesized 1 and 2 dyes are bathochromically shifted up to 530 nm with concomitant enhancement in their intensities. The synthesized dyes have been exploited as a photosensitizer in TiO2-based dye-sensitized solar cells (DSSCs). The photovoltaic performances and charge transport properties (EIS spectra) were studied to evaluate the synthesized dye performance in DSSCs. Amongst both the dyes, the one with the carboxylic anchor showed relatively superior photovoltaic performance in comparison to the dye with a nitro anchor. The superior performance of 1 is probably due to the better anchorage and superior dye loading capability on the TiO2 surface, which suppresses charge recombination, prolongs electron lifetime, and decreases the total resistance of the DSSC. The assembly fabricated using 1 showed the best performance with an overall conversion efficiency η of 5.81%, Jsc of 12.74 mA cm−2, and Voc of −0.648 V. The obtained efficiency is ∼84% of the cell efficiency compared with the state-of-the-art N719 dye in similar conditions.

Comparison of optical and photovoltaic properties of ZnO chemically synthesized by using different hydrolyzing agents

AbstractTwo zinc oxide (ZnO) nanoparticles ZS with hexagonal sheet and ZN having nanorod-like morphologies were prepared by precipitation technique using two different hydrolyzing agents viz. water (ZS) and ethanol (ZN). The physicochemical properties of both of the as-synthesized ZnO nanoparticles were investigated by UV–vis, powder X-ray diffraction (pXRD) and field emission scanning microscopy (FESEM). The as-synthesized ZnO nanoparticulates were successfully employed as photoanode material in dye-sensitized solar cells (DSSCs). The photoanode fabricated by using ZN in DSSC showed two times better cell efficiency with enhanced photocurrent and open circuit potential in comparison to the photoanode fabricated using ZS. The improved efficiency of ZN over ZS is due to high active surface area for greater dye loading. Graphical abstractThe enhanced efficiency has been obtained by employing ZnO nanostructures (nanosheets and short rods) as photoanode in dye-sensitized solar cells.

Investigation of energetic ion-induced mixing in Bi/Ge system

The present study is carried out for the investigation of energetic ion beam mixing in the Bi/Ge system, induced by electronic excitation. The system Ge/Bi/C was deposited on Si substrate at room temperature in the high vacuum deposition system and irradiated using Au ions of 120 MeV at the fluences 1 × 1013, 5 × 1013 and 1 × 1014 ions/cm2. The top layer of carbon was deposited as the protecting layer to avoid oxidation. The swift heavy ions (SHI)-induced interface mixing was studied by Rutherford backscattering spectroscopy (RBS) for depth profiles and compositions, grazing incidence X-ray diffraction (GIXRD) for phase identification and atomic force microscopy (AFM) for surface roughness. We have calculated the mixing rate, mixing efficiency and inter-diffusion coefficient for the Bi/Ge system. We observed that the thickness of the mixed region increased with increasing fluence. In the GIXRD pattern, no new crystalline phase formation was observed after irradiation, the mixed region may be in an amorphous form. The mixing effect is explained in the framework of the thermal spike model.