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In this work, the successful synthesis of spherical (sCuONPs) and rod-like (CuONRs) copper oxide nanoparticles was reported. Several microscopic and spectroscopic techniques were used to confirm the different morphologies (spherical and rod-like) and also different diameter sizes. Copper metal within nanomaterials had different oxidation states (Cu0, Cu+, and Cu2+) as was confirmed by X-ray photoelectron spectroscopy (XPS). The optical properties of the synthesized nanoparticles were investigated, and their reactive oxygen radical species (ROS) generation was confirmed using UV–vis spectroscopy. Copper oxide nanoparticles catalytically converted H2O2 to form ROS (HO●−, HOO●−, or O2●−). ROS generation was confirmed using UV–vis spectroscopy and 1,3-diphenylbenzofuran (DPBF, as a radical quencher) and also using electron paramagnetic resonance (EPR) spectroscopy and 2,2,6,6-tetramethylpiperidine (TEMP) as a spin trap. UV–vis spectroscopy was further used to monitor a blue color development when copper oxide nanoparticles were mixed with 3,3′,5,5′-tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2). The color changes were confirmed by UV–vis spectra with absorption maxima at 370 nm and 652 nm and naked eye for blue color development. Oxidase enzymes produce hydrogen peroxide as by-product and this property was used for the detection of biological analytes. Glucose and glucose oxidase (GOx) enzyme were used as model bioanalytical system. Copper oxide nanorods were successfully synthesized and characterized their surface properties using various techniques. The nanoparticles exhibited excellent catalytic properties towards converting hydrogen peroxide to reactive oxygen radical species (ROS). The catalytic properties were confirmed using UV–vis (DPBF, radical scavenger) and EPR spectroscopy (TEMP, spin trap). The radicals could oxidize TMB to blue products visible to the naked eye as further proof of ROS generation. [ABSTRACT FROM AUTHOR]

A polymer of tetra(4)-(4,6-diaminopyrimidin-2-ylthio) phthalocyaninatocobalt(II) (CoPyPc) has been deposited over a multiwalled carbon nanotube (MWCNT) platform and its electrocatalytic properties investigated side by side with polymerized cobalt tetraamino phthalocyanine (CoTAPc). X-ray photoelectron spectroscopy, scanning electron microscopy and cyclic voltammetry studies were used for characterization of the prepared polymers of cobalt phthalocyanine derivatives and their nanocomposites. l-Cysteine was used as a test analyte for the electrocatalytic activity of the nanocomposites of polymerized cobalt phthalocyanines and multiwalled carbon nanotubes. The electrocatalytic activity of both polymerized cobalt phthalocyanines was found to be superior when polymerization was done on top of MWCNTs compared to bare glassy carbon electrode. A higher sensitivity for l-cysteine detection was obtained on CoTAPc compared to CoPyPc. [ABSTRACT FROM AUTHOR]

This paper reports on the photophysical behavior of (2-pyridylsulfanyl)phthalocyaninato zinc(II) and 2,9(10),16(17),23(24)-tetra-(2-pyridylsulfanyl)phthalocyaninato zinc(II) in the presence of differently shaped silver nanoparticles (nanospheres, nanotriangles and nanoflowers). The presence of shaped nanoparticles increased both triplet quantum yields and lifetimes of the tetra-substituted mercaptopyridine zinc phthalocyanine in DMSO. It is apparent from this work that the shape of the silver nanoparticle used is of little consequence in influencing photophysical behavior of the phthalocyanines. [ABSTRACT FROM AUTHOR]

Abstract: Surface chemistry and electrocatalytic properties of self-assembled monolayers of metal tetra-carboxylic acid phthalocyanine complexes with cobalt (Co), iron (Fe) and manganese (Mn) as central metal ions have been studied. These phthalocyanine molecules are immobilized on gold electrode via the coupling reaction between the ring substituents and pre-formed mercaptoethanol self-assembled monolayer (Au-ME SAM). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy confirmed chemisorption of mercaptoethanol via sulfur group on gold electrode and also coupling reaction between phthalocyanines and Au-ME SAM. Electrochemical parameters of the immobilized molecules show that these molecules are densely packed with a perpendicular orientation. The potential applications of the gold modified electrodes were investigated towards l-cysteine detection and the analysis at phthalocyanine SAMs. Cobalt and iron tetra-carboxylic acid phthalocyanine monolayers showed good oxidation peak for l-cysteine at potentials where metal oxidation (MIII/MII) takes place and this metal oxidation mediates the catalytic oxidation of l-cysteine. Manganese tetra-carboxylic acid phthalocyanine monolayer also exhibited a good catalytic oxidation peak towards l-cysteine at potentials where MnIV/MnIII redox peak occurs and this redox peak mediates l-cysteine oxidation. The analysis of cysteine at phthalocyanine monolayers displayed good analytical parameters with good detection limits of the orders of 10−7 molL−1 and good linearity for a studied concentration range up to 60μmolL−1. [Copyright &y& Elsevier]

Grafting of electrodes with diazonium salts using cyclic voltammetry (CV) is a well-established procedure for surface modification. However, little is known about the effect of the concentration of the diazonium salt on the number of layers grafted on the electrode surface. In this work, the impact of concentration on the grafting of 4-carboxybenzenediazonium (4-CBD) onto a glassy carbon electrode (GCE) is elucidated. The number of layers grafted on the GCE was linearly dependent on the concentration of 4-CBD and varied between 0.9 and 4.3 when the concentration was varied between 0.050 and 0.30 mmol/L at 0.10 V.s−1. Characterization of modified glassy carbon surface with X-ray photoelectron spectroscopy (XPS) confirmed the grafting of carboxyphenyl layer on the surface. Grafting with 0.15 mmol/L 4-CBD (1 CV cycle) did not form a detectable amount of carboxyphenyl (CP) moieties at the surface, while a single scan with higher concentration (2.5 mmol/L) or multiple scans (22 cycles) gave detectable signals, indicating formation of multilayers. We also demonstrate the possibility of removing the thin layer grafted on a glassy carbon electrode by applying high oxidation potential +1.40 V. [ABSTRACT FROM AUTHOR]

An electrochemical impedimetric immunosensor was developed for the label-free detection of autoantibodies against the human P53 antigen (protein) involved in carcinogenesis. The immunosensor was based on the covalent immobilization of human P53-protein (P53ag) using amide coupling onto gold electrode pre-grafted with phenylethylamine-succinic acid (Au-PEA-SA). The non-specific binding sites on the activated Au-PEA-SA were blocked with bovine-serum albumin (BSA) to yield an Au-PEA-SA-P53ag/BSA immunosensor. The gold electrode modification steps were monitored using X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The analytical performance of Au-PEA-SA-P53ag/BSA towards the detection of anti -P53 autoantibodies showed a concentration-dependent impedimetric (R CT) response. A wide linear range (1.0 –1000 ng.mL-1) with a low detection limit of 103 pg.mL−1 and high R CT sensitivity of 0.749 kΩ.ng.mL−1.cm−2 was obtained. The Au-PEA-SA-P53ag/BSA could be regenerated (using dimethylsulfoxide/formamide) several times without the loss of covalently bound human P53ag as a sensing element. The detection signal was retained and about 92% of the original signal was recovered without damage to the immunoelectrode after the 6 regeneration cycles. The real sample detection was investigated using serum recovery method. An excellent % recovery was obtained between 84.8 and 93.7%. • Stable thin film of P53 antigenic protein immobilized onto gold surface. • Detection of anti -P53 autoantibodies exhibited excellent analytical ability. • Low detection limits better than ELISA as gold standard were obtained. • Good regeneration of the immunoelectrode without losing the signal. • Real sample analysis using % recovery was obtained with up-to 93.7%. [ABSTRACT FROM AUTHOR]

The photophysical properties of the conjugate of uridine and zinc mono carboxy phenoxy phthalocyanine (ZnMCPPc–uridine, 4 ) are reported in this work. The conjugate was also adsorbed onto single walled carbon nanotubes (ZnMCPPc–uridine–SWCNT, 5 ). The X-ray photoelectron spectroscopy of 4 showed three N 1s peaks while that of 5 showed four N 1s peak, a new peak at 399.4 eV of 5 was assigned to pyrrolidonic nitrogen, due to the interaction of the pyrrolic nitrogen of 4 with the oxygen moiety of SWCNT–COOH in 5 . The triplet lifetime, triplet and singlet oxygen quantum yields of the zinc mono carboxy phenoxy phthalocyanine increased by over 40% in the presence of uridine. SWCNTs resulted in only a small quenching of the triplet state parameters of 4 . [ABSTRACT FROM AUTHOR]

In this work, a gold electrode surface was pre-grafted with phenylethylamine (PEA) thin film for spontaneous covalent immobilization of cobalt (II) octa acyl chloride (CoOAClPc) via the nucleophilic addition reaction. Pre-grafting of PEA thin film was achieved by electrochemical reduction of 4-(2-aminoethyl) benzene diazonium (AEBD) salt. Cobalt (II) octa acyl chloride phthalocyanine (CoOAClPc) was successfully synthesized and covalently immobilized onto the pre-grafted gold electrode surface to form a thin monolayer of Au-PEA-CoOAClPc. Upon hydrolysis of the thin monolayer, the –COCl terminal functional groups were converted to -COOH to form Au-PEA-CoOCAPc. The presence of PEA and PEA-CoOCAPc was confirmed by electrochemical X-ray photoelectron spectroscopy surface characterization. The pH sensitivity of -COOH terminal groups was studied using a negatively charged [Fe(CN) 6 ]3−/4− and a positively charged [Ru(NH 3) 6 ]2+/3+ redox probes. The Au-PEA-CoOCAPc was investigated for electrocatalytic and electroanalytical properties towards the detection of catecholamine neurotransmitters (dopamine, epinephrine, and norepinephrine). The electrocatalytic oxidation of the catecholamine neurotransmitters in PBS solution (pH 7.4) was studied using differential pulse voltammetry (DPV) in a linear range up to 50 μM. The limit of detection (LOD) was determined to be 64 nM, 0.22 μM and 0.17 μM for dopamine (DA), epinephrine (EP) and norepinephrine (NOR) respectively. The limit of quantification (LOQ) was determined to be 0.21 μM, 0.73 μM and 0.56 μM for DA, EP and NOR respectively. Stable and reproducible novel method of electrode fabrication to form Au-PEA-CoOCAPc was achieved. Excellent analytical properties (sensitivity, low detection limits and limit of quantification) were obtained by using the fabricated electrochemical sensors, Au-PEA-CoOCAPc, for the determination of catecholamine neurotransmitters and screening of ascorbic acid (AA). [ABSTRACT FROM AUTHOR]

• The design of an ultrasensitive label-free detection of prostate specific antigen (PSA) was achieved. • The fabricated immunosensor used monoclonal anti-PSA antibody as capture probe on an electrografted isophthalic thin fim. • Capacitance signals were deconvoluted from the impedance plots and were sensitive to PSA concentrations. • The detection of PSA could be achieved in fg.ml −1. A rapid, low-cost, and accurate point-of-care analytical device for the determination of prostate-specific antigen (PSA) is required for the early diagnosis and prognosis of prostate cancer (PCa). In this work, an electrochemical capacitive immunosensor was developed for the label-free detection of PSA. The immunosensor was based on the covalent immobilization of monoclonal anti -PSA antibody via carbodiimide chemistry onto gold electrode (AuE) pre-modified with a thin monolayer film of isophthalic acid (IPA). A methodology based on the steric hindrance of 1,3-substituted aryldiazonium salt was adopted to control the growth of the IPA thin film on the gold electrode. The non-specific binding sites were blocked with bovine serum albumin (BSA) to afford an AuE-IPA- anti -PSA-mAb|BSA immunosensor. The immunosensor was characterized by X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The analytical performance of the developed sensor was evaluated using the capacitance Nyquist plots generated from the complex impedance data. In addition, complex capacitance was also calculated from the imaginary part of the impedance and plotted against the log of frequency. The double layer capacitance from the circuit fitting (R S C) was also used and compared the sensitive capacitance signals to the changes in PSA concentrations. The LOD values were in fg.mL −1 and distinguishable from the blank (PBS) for the Nyquist plots of capacitance, complex capacitance, and double layer capacitance signals. The developed immunosensor exhibited good stability, selectivity, low detection limits, and a wide linear range which was suitable for screening of prostate cancer using prostate-specific antigen. [ABSTRACT FROM AUTHOR]

We report the structure of four coordinate orthorhombic bis (piperidinedithiocarbamato)lead complex and its use as single source precursor for the deposition of lead sulfide thin films by aerosol assisted chemical vapour deposition (AACVD) and spin coating routes. • A crystal structure of a lead(II) complex and its use to deposit thin films is reported. • PbS nanostructures are obtained via AACVD and spin coating techniques. • Band gaps between 1.32 and 1.55 eV as controlled by change in temperature were observed for thin films. A distorted single crystal structure of bis(piperidinedithiocarbamato)lead(II) complex and its subsequent use to deposit thin films is reported. Two deposition routes namely, aerosol-assisted chemical vapour deposition (AACVD) and spin coating deposition have been employed to obtain anisotropic lead sulfide (PbS) nanostructures. The thin films displayed rod to cubic shaped crystals for AACVD, and a range of cubes, star and dendritic morphologies with variation of temperatures were displayed for spin coated films. Optical band gaps between 1.32 and 1.55 eV as controlled by the change in temperature were observed for thin films deposited by AACVD. Powder X-ray diffraction (P-XRD) studies show that the films formed are composed of cubic crystalline PbS. The X-ray photoelectron spectroscopy (XPS) was used to investigate the effect of activation temperatures (350, 400 and 450 °C) on the chemical composition and oxidation states of PbS samples. [ABSTRACT FROM AUTHOR]