Characterization of sequential physical vapor deposited methylammonium lead tri-iodide perovskite thin films

Please read abstract in the article.The University of Pretoria, National Research Foundation-The World Academy of Science (NRF-TWAS) and NRF-South Africa, grant no N01156/115463 of the SARChI.http://www.journals.elsevier.com/vacuum2021-12-01hj2020ChemistryPhysic

Electrochemical studies of titanium, manganese and cobalt phthalocyanines

Syntheses, spectral, electrochemical and spectroelectrochemical studies of phenylthio and amino derivatised metallophthalocyanines complexes are reported. The complexes are immobilized onto a gold macro disk, gold ultramicroelectrode and gold coated fiber electrodes via self assembly with phenylthio MPc derivatives or onto a glassy carbon electrode via electropolymerisation with amino MPc derivatives. For the first time MPc SAMs were formed on gold coated fiber. The electrocatalytic behavior of the modified electrodes was studied for the detection of nitrite and L-cysteine, all modified electrodes showed improved electrocatalytic oxidation compared to the unmodified electrode. The MPc complexes catalyzed nitrite oxidation via a two-electron mechanism producing nitrate. Cobalt tetraaminophthalocyanine showed the best catalytic activity for nitrite oxidation in terms of overpotential lowering compared to other complexes and thus was used for nitrite detection in a food sample, the nitrite concentration was determined to be 59.13 ppm, well within the limit for cured meat products. Electrocatalytic oxidation of L-cysteine on SAM modified gold coated fiber was reported for the first time. The gold coated fiber and ultamicro cylinder electrode were less stable towards the electro-oxidation of cysteine compared to its oxidation on the gold disk. The gold disk electrode gave better catalytic performance in terms of stability and reduction of overpotential. The phenylthio cobalt phthalocyanine derivative gave the best catalytic activity for L-cysteine oxidation in terms of overpotential lowering compared to other phenylthio derivatized MPc complexes. The amount of L-cysteine in human urine was 2.4 mM, well within the urinary L-cysteine excretion range for a healthy human being

Photophysical and photochemical studies of sulfur containing phthalocyanine derivatives in the presence of folic acid

The syntheses of zinc and magnesium 9,16,23-tris-(5-trifluoromethyl-2-mercaptopyridine)-2-(carboxy)phthalocyaninato complexes are described for the first time. The photophysical and photochemical parameters of these molecules in the absence or presence of folic acid are compared to the corresponding oxygen bridged complexes and to 2,9,17,23-tetrakis-[(1,6-hexanedithiol)phthalocyaninato]zinc(II), [8,15,22-tris-(naptho)-2-(amidoethanethiol)phthalocyaninato]zinc(II) and zinc phthalocyanine tetrasulfonate. In the absence of folic acid, the complexes show relatively good triplet quantum yields (ranging from 0.52 to 0.88) in DMSO with reasonable triplet lifetime between 140 and 470 μs. The complexes showed high singlet oxygen quantum yield values ranging from 0.27 to 0.66 in the absence of folic acid. In the presence of folic acid, the triplet quantum yield values were between 0.37 and 0.75 and the lifetimes were significantly reduced (70–320 μs)

The synthesis, cyclic voltammetry and spectroelectrochemical studies of Co (II) phthalocyanines tetra-substituted at the α and β positions with phenylthio groups

Non-peripherally substituted cobalt 1,(4)-(tetraphenylthiophthalocyaninato) and peripherally substituted cobalt 2,(3)-(tetraphenylthiophthalocyaninato) complexes were synthesized. Redox processes were observed at E1/2 = −1.44 V (I), −0.39 V (II), +0.37 V (III), +0.78 V (IV) and 1.15 V (V) for the non-peripherally substituted and at E1/2 = −1.42 V (I), −0.57, −0.39 V (II), +0.27 V (III), +0.79 V (IV) and +1.10 V (V) for the peripherally substituted complexes, respectively. The couples were assigned to CoIPc−2/CoIPc−3 (I), CoIIPc−2/CoIPc−2 (II), CoIIIPc−2/CoIIPc−2 (III), and CoIIIPc−1/CoIIIPc−2 (IV) using spectroelectrochemistry. The last process (V) could not be ascertained by spectroelectrochemistry but is associated with ring oxidation. Upon reduction or oxidation, the Q band of the non-peripherally substituted complex became less red shifted compared to that of its peripherally substituted counterpart

Synthesis and characterization of electrospun composite nanofibers from Moringa oleifera biomass and metal oxide nanoparticles as potential adsorbents for the removal of lead ions

Electrospun multicomposite nanofibers synthesized from extracts of Moringa oleifera (M. oleifera) seed biomass blended with metal oxide nanoparticles (MONPs) and polyacrylonitrile (PAN) were investigated as potential adsorbents. The materials were characterized using SEM, XRD, FTIR, BET and TGA. The specific surface area of MONPs ranged between 29.75 and 60.92 m2/ g and their incorporation in the PAN/M. oleifera composite blend resulted in increased surface coarseness and larger nanofiber diameters (268 ± 21–317 ± 27 nm). The application of PAN/M. oleifera/MONPs for Pb(II) removal from aqueous solution via batch adsorption experiments was investigated based on the parameters: solution pH, contact time and initial Pb(II) ion concentration. Experimental results better fitted the Langmuir isotherm model and pseudo-second-order kinetics. Adsorption capacities ranged between 172.4 and 227.3 mg/g. These results demonstrate that low-cost indigenous materials have significance and applicability in water remediation applications.FUNDING : Open access funding provided by University of Pretoria. This work was supported by the University of Pretoria and National Research Foundation (TTK14051367221).https://www.springer.com/journal/11696am2024ChemistryNon

The formation of self-assembled monolayers of thiophthalocyanine complexes of titanium, vanadium and manganese and their use in l-cysteine electrocatalysis

Self-assembled monolayers (SAMs) based on octapentylthiophthalocyanine complexes of oxovanadium (IV) (OVOPThPc), titanium(IV) (OTiOPThPc), and manganese (III) acetate (AcMnOPThPc), and of tetraphenylthiophthalocyanine complexes of hydroxo manganese(III) (OHMnTPPc) and oxotitanium(IV) (OTiTPPc) are described. The oxidation of l-cysteine was observed at potentials which ranged from 0.52 V to 0.67 V. The detection limits for l-cysteine analysis were of the order of 10− 7 to 10− 6 M

Tuning the surface properties of CuO films using the precursor aging approach for enhanced photoelectrocatalytic reactions

DATA AVAILABILITY STATEMENT : The data that support the findings of this study are available from the corresponding author upon reasonable request.The surface properties of semiconductors have a significant influence on their photoelectrocatalytic efficiency. This research presents a precursor aging method for tuning the surface properties of CuO films, for enhanced catalytic response. A precursor solution made using copper acetate, polyethylene glycol (PEG) 400, and diethanolamine, and aged for 1, 40, 80, 120, 150, 180, and 250 days is used in each case to fabricate CuO photocathodes via the dip-coating method. The films fabricated using the 1-day-old precursor reveal compact and homogeneous nanoparticles. The films eventually get tuned to yield highly porous and rougher surfaces after aging the precursors for 180–250 days. The film's bandgap decreases by 9% after 180–250 days of precursor aging. Photocathodes prepared using the 180-day-old precursor produce the optimum photocurrent density of 1.6 mA cm−2 at 0.35 V versus reversible hydrogen electrode (RHE), representing a 196% increase relative to the films fabricated using the 1-day-old solution. They also produce an anodic onset potential shift of 260 mV. This improved photoelectrocatalytic response is due to the porous morphology of the films, which produces a larger surface area that enhances light absorption, increases active sites for catalytic reactions, and reduces charge transfer resistance at the photocathode-electrolyte interface.Externally funded UP postdoctoral fellowship program and South African Research Chairs Initiative (SARCHI).https://onlinelibrary.wiley.com/journal/21967350ChemistryPhysic

Photophysical behaviour of asymmetrically substituted metal free, Mg and Zn phthalocyanines in the presence of folic acid

This work reports on the synthesis, characterisation and photophysical properties of new asymmetric metal free, magnesium and zinc phthalocyanines containing a mono carboxylic acid group for possible linking to biological molecules via an amide bond. Successful synthesis of the phthalocyanines was achieved through the statistical condensation method. The phthalocyanines were mixed with folic acid and their photophysical properties were examined. The triplet quantum yield values for all the complexes in DMSO were between 0.49 and 0.74 and in the presence of folic acid they were between 0.37 and 0.63. The lifetimes were generally good ranging from 70 to 290 μs in the absence or presence of folic acid

Spectroscopic and physicochemical behavior of magnesium phthalocyanine derivatives mono-substituted with a carboxylic acid group

This work reports on the synthesis of novel unsymmetrically substituted magnesium phthalocyanine complexes containing one carboxyl group. The physicochemical behavior of these complexes were compared with those of their unmetallated and zinc counterparts. The MgPcs showed interesting absorption spectra with [8,15,22-Tris-(naphtho)-4,5-(3-carboxy-1,2-dioxyphenyl)phthalocyaninato]magnesium (II) showing a large split in the Q band whereas [8,15,22-Tris-(naphtho)-2-(carboxy) phthalocyaninato]magnesium(II) presented only a small splitting. The magnesium phthalocyanine derivatives displayed higher fluorescence quantum yields compared to unmetallated and zinc phthalocyanine counterparts. The latter gave admirable triplet and singlet oxygen quantum yields. These molecules can distinctly be employed in the field of photodynamic therapy in combination with fluorescence imaging

Synthesis, spectroscopic and DFT characterization of 4 β -(4-tert-butylphenoxy) phthalocyanine positional isomers for non-linear optical absorption

In this work the synthesis, spectral characterization and non-linear optical properties of metal-free 4β-(4-tert-butylphenoxy) phthalocyanine isomers are described and compared to the previously reported alpha derivative. The second-order nonlinear optical properties of the phthalocyanine isomers were investigated using the Z-scan technique and compared to the theoretical data obtained from density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations. Z-scan results indicated strong non-linear behaviour, revealing reverse saturable absorption (RSA) profiles for all four isomers. The experimental βexp values showed the following trend:C4h (9.31×10–10mMW–1)>D2h (7.89×10–10mMW–1)>Cs (7.32× 10–10 mMW–1) > C2v (1.77 × 10–10 mMW–1). These results were similar to that obtained with the 4β-(4-tert-butylphenoxy) phthalocyanines as the C2v and Cs isomers were found to have the lowest βexp values compared to other symmetries. The 4β-(4-tert-butylphenoxy) phthalocyanine C4h isomer was found toshowbetter non-linear optical properties compared to all other isomers.Keywords: Phthalocyanine, non-linear optical absorption, density functional theory, magnetic circular dichrois