Muhammad Adil Mansoor

Hexagonal structured Zn(1−x)CdxO solid solution thin films: synthesis, characterization and applications in photoelectrochemical water splitting

Hexagonal nanostructured zinc–cadmium oxide [Zn(1−x)CdxO where x = 0.08, 0.15, and 0.17] solid solution thin films were deposited on FTO coated glass substrates from a common solution of zinc acetate and a newly developed polymeric cadmium precursor by an aerosol-assisted chemical vapour deposition (AACVD) technique. The polymeric cadmium precursor [Cd3(TFA)4(OAc)2(THF)4]n (1) was synthesized by the reaction of cadmium(II)acetate dihydrate with triflouroacetic acid in THF solution and characterized by melting point, microanalysis, FTIR, 1H-NMR, thermogravimetry (TG/DTG) and single crystal X-ray analysis. The deposited thin films were characterized by powder XRD, SEM, EDX and UV-visible spectrophotometry, and tested for photoelectrochemical (PEC) water splitting to hydrogen and oxygen. The effect of various thin film deposition parameters such as solvent type, temperature and electrolyte concentration on PEC properties has been investigated. The SEM analysis illustrated that the morphology of the films changes significantly with the change of the solvent. The films deposited from THF solution have a needle-like appearance scattered vertically on the FTO-coated glass substrate. An optical band gap of 2.40 eV has been estimated by UV-visible spectrophotometry. The current–voltage characterization proved that the nanocrystalline hexagonal structured Zn0.83Cd0.17O electrodes exhibit an n-type semiconducting behaviour and the photocurrent was found to be strongly dependent on the deposition solvent, deposition temperature and electrolyte concentration. The maximum photocurrent density of 0.23 mA cm−2 at 0.55 V vs. Ag/AgCl/3 M KCl (∼1.23 V vs. RHE) was obtained for the Zn0.83Cd0.17O photoelectrode deposited at 500 °C for 45 min from 0.5 M solution of (1) and Zn(CH3COO)2·2H2O in THF.

Perovskite-structured PbTiO3 thin films grown from a single source precursor.

Perovskite-structured lead titanate thin films have been grown on FTO-coated glass substrates from a single-source heterometallic molecular complex, [PbTi(μ2-O2CCF3)4(THF)3(μ3-O)]2 (1), which was isolated in quantitative yield from the reaction of tetraacetatolead(IV), tetrabutoxytitanium(IV), and trifluoroacetic acid from a tetrahydrofuran solution. Complex 1 has been characterized by physicochemical methods such as melting point, microanalysis, FTIR, (1)H and (19)F NMR, thermal analysis, and single-crystal X-ray diffraction (XRD) analysis. Thin films of lead titanate having spherical particles of various sizes have been grown from 1 by aerosol-assisted chemical vapor deposition at 550 °C. The thin films have been characterized by powder XRD, scanning electron microscopy, and energy-dispersive X-ray analysis. An optical band gap of 3.69 eV has been estimated by UV-visible spectrophotometry.

The Gumbel-Lomax Distribution: Properties and Applications

We introduce a new four-parameter model called the Gumbel-Lomax distribution arising from the GumbelX generator recently proposed by Al-Aqtash (2013). Its density function can be right-skewed and reversed-J shaped, and can have decreasing and upside-down bathtub shaped hazard rate. Various structural properties of the new distribution are obtained including explicit expressions for the quantile function, ordinary and incomplete moments, Lorenz and Bonferroni curves, mean residual lifetime, mean waiting time, probability weighted moments, generating function and Shannon entropy. We also provide the density function for the order statistics. Some characterizations of the new distribution based on the conditional expectations of certain functions of the random variable are also proposed. The model parameters are estimated by the method of maximum likelihood and the observed information matrix is determined. The flexibility of the new model is illustrated by means of two real lifetime data sets.

Effect of synergic cooperation on optical and photoelectrochemical properties of CeO2–MnO composite thin films

CeO2–MnO composite thin films have been deposited on glass substrates, which were coated with fluorine-doped tin oxide (FTO), by aerosol-assisted chemical vapor deposition (AACVD) using a 1 : 1 mixture of the cerium complex [Ce(OCOCF3)4]−[(CH3)2NHCH2CH2OH]+ (1) and acetatomanganese(II). X-ray diffraction (XRD), Raman spectroscopy and profilometry were used to investigate the phase purity, stoichiometry and thickness of the films. EDX results confirmed that the Ce : Mn ratio was 1 : 9 in the deposited composite thin films. FEG-SEM analysis illustrated that the morphology of the fabricated films was influenced by the deposition temperature and hence the optoelectronic properties. UV-vis studies of a composite thin film fabricated from methanol solution at 475 °C demonstrate a direct band gap of 2.5 eV. From its current–voltage characteristics it is evident that a CeO2–MnO composite semiconductor electrode exhibits n-type behavior and the photocurrent was strongly dependent on the deposition temperature. A CeO2–MnO photoanode deposited at 475 °C for 45 min from a 0.023 M solution of (1) and acetatomanganese(II) in methanol gave a maximum photocurrent density of 265 μA cm−2 at 0.65 V vs. Ag/AgCl/3 M KCl using a 0.5 M NaOH electrolyte.

Single step fabrication of CuO–MnO–2TiO2 composite thin films with improved photoelectrochemical response

Novel trimetallic composite oxide CuO–MnO–2TiO2 thin films have been deposited on glass substrates, which were coated with fluorine-doped tin oxide (FTO), by aerosol-assisted chemical vapor deposition (AACVD) using a 1 : 1 : 2 non aqueous mixture of copper(II) acetate monohydrate (Cu(CH3COO)2·H2O), anhydrous manganese(II) acetate (Mn(CH3COO)2) and titanium(IV) butoxide (Ti(O(CH2)3CH3)4) in the presence of trifluoroacetic acid (TFA). Thin films were characterized by Fourier transform infrared spectroscopy (FT-IR), Raman, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS), suggesting the formation of a crystalline mixture of CuO–MnO–2TiO2 composite with well defined and evenly distributed particles. The direct band gap energy of 1.95 eV was estimated by UV-Vis spectroscopy. From its current–voltage characterization, it is evident that the nanostructured CuO–MnO–2TiO2 photoelectrode deposited at 550 °C for 45 minutes displayed enhanced photocatalytic activity in photoelectrochemical (PEC) water splitting and yielded a photocurrent of 2.21 mA cm−2 at +0.7 V vs. Ag/AgCl/3 M KCl using a 0.5 M Na2SO4 electrolyte under AM 1.5 G illumination (100 mW cm−2). The charge transfer dynamics of the thin film were also explored using an electrochemical impedance spectroscopy (EIS) technique.

The synthesis and characterization of a hexanuclear copper yttrium complex for deposition of semiconducting CuYO2 0.5Cu2O composite thin films

The copper–yttrium hexanuclear complex [Cu4Y2(dmae)6(OAc)7.85(OH)0.15(H2O)2]·2CH3C6H5 (1) (where dmae = dimethylaminoethanoato, OAc = acetato) has been synthesized and characterized by its melting point, elemental analysis, and FT-IR, thermogravimetric/differential thermogravimetric (TG/DTG) and single crystal X-ray diffraction analyses. The complex crystallizes in the triclinic space group P with cell parameters a = 9.4934(3) A, b = 13.2045(4) A, c = 14.6990(5) A, α = 76.486(2)°, β = 85.811(2)° and γ = 83.394(2)°. A thin film of a CuYO2–0.5Cu2O composite has been deposited on a FTO glass substrate by implementation of the complex (1) at 400 °C under an argon atmosphere via aerosol assisted chemical vapour deposition (AACVD). XRPD, SEM and EDX analyses reveal the formation of impurity-free crystalline mixtures of the CuYO2–0.5Cu2O composite with well-defined evenly distributed rods of Cu2O in the size range of 0.85–1.05 μm and granules of CuYO2 in the size range of 110–125 nm. UV-Vis spectrophotometric measurements and photoelectrochemical (PEC) results show an optical band gap energy of 2.6 eV and a photocurrent density of 81 μA cm−2 under illumination using a 150 W halogen lamp at a potential of 1.0 V vs. SCE.

Iron–manganese–titanium (1 : 1 : 2) oxide composite thin films for improved photocurrent efficiency

In continuation of our previous studies on the photoelectrochemical (PEC) properties of titanium-based composite oxide thin films, an effort was made to develop thin films of the 1 : 1 : 2 iron–manganese–titanium oxide composite, Fe2MnTi3O10–MnTiO3, using Fe(OAc)2 and a bimetallic manganese–titanium complex, [Mn2Ti4(TFA)8(THF)6(OH)4(O)2]·0.4THF (1), where OAc = acetato, TFA = trifluoroacetato, and THF = tetrahydrofuran by the aerosol-assisted chemical vapour deposition (AACVD) technique. The thin films after their proper characterization with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Mossbauer spectroscopy, field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), energy-dispersive X-ray (EDX) spectroscopy, UV-Vis spectrophotometery and photoluminescence (PL) spectroscopy were tested for their potential applications for the photoelectrochemical oxidation of water. The PEC results revealed that a photocurrent density (Jlight) of 1.88 mA cm−2 was obtained at a low potential of 0.20 V vs. Ag/AgCl/3MKCl inferring a promising photo-conversion efficiency of 1.56%. These observations were further endorsed by electrochemical impedance spectroscopic (EIS) studies in terms of charge transportation and its recombination time. Furthermore, the Mott–Schottky plot indicated a flat band potential of −1.0 V vs. Ag/AgCl.

A new family of distributions to analyze lifetime data

M. Mansoor1, M. H. Tahir1,†, Gauss M. Cordeiro2, Ayman Alzaatreh3, M. Zubair1,4 1Department of Statistics, The Islamia University of Bahawalpur, Bahawalpur-63100, Pakistan 2Department of Statistics, Federal University of Pernambuco, Recife, PE, Brazil 3Department of Mathematics and Statistics, American University of Sharjah, UAE 4Department of Statistics, Govt. S.E College, Bahawalpur-63100, Pakistan Emails: mansoor.abbasi143@gmail.com; †mtahir.stat@gmail.com(corresponding author); gausscordeiro@gmail.com; aalzaatreh@aus.edu; zubair.stat@yahoo.com