Indirect Electroanalysis of 3-Methyl-4-Nitrophenol in Water Using Carbon Fiber Microelectrode Modified with Nickel Tetrasulfonated Phthalocyanine Complex

Electrochemical detection of 3-methyl-4-nitrophenol (MNP) in direct phenol oxidation occurs at high potentials and generally leads to progressive passivation of the electrochemical sensor. This study describes the use of a carbon fiber microelectrode modified with a tetrasulfonated nickel phthalocyanine complex for the detection of MNP at a lower potential than that of direct phenol oxidation. The MNP voltammogram showed the presence of an anodic peak at -0.11 V vs SCE, corresponding to the oxidation of the hydroxylamine group generated after the reduction of the nitro group. The effect of buffer pH on the peak current and SWV parameters such as frequency, scan increment, and pulse amplitude were studied and optimized to have better electrochemical response of the proposed sensor. With these optimal parameters, the calibration curve shows that the peak current varied linearly as a function of MNP concentration, leading to a limit of detection (LoD) of 1.1 μg/L. These results show an appreciable sensitivity of the sensor for detecting the MNP at relatively low potentials, making it possible to avoid passivation phenomena.

A Simple and Rapid Method for the Detection of Non-Ionic Surfactants

A spectrophotometric approach for the detection of non-ionic surfactant (Triton X-100) has been proposed in this paper. This method does not involve extraction of the ion-associate with harmful solvents, but employs adhesion of the ion-association of potassium/non-ionic surfactants complex and tetraphenylporphyrin tetrasulfonic acid obtained by vigorous shaking. The adhered ion-associate was dissolved with water and its absorbance was measured. The sensitivity for Triton X-100 was determined to be 0.146 (expressed as absorbance of 1 mg/L solution). The adhesion tendency of ion-associate was found to be dependent on the water contact angle, which in turn was influenced by a high adhesion of the ion-associate and by low blank values. In this respect, a tetrafluo-roethylene vessel was found to be the most suitable for the detection of non-ionic surfactants. This spectrophotometrical method is simply and rapidly performed by a procedure based on mechanical shaking and can be employed to detect non-ionic surfactants containing more than 7 polyethylene oxide units.

Effect of H-type Aggregation on the Photoelectric Conversion of Tetrasulfonated Phthalocyanine Adsorbed on Nanostructured TiO_2 Electrode

Tetrasulfonated Zn,Co,Ga,In,TiO and metal free phthalocyanine (MTsPc) mainly exist as dimers on the nanostructured TiO 2 electrode and mostly exist as monomers in dimethyl sulfoxide. The photocurrent action spectra of the liquid junction based on the MTsPc/TiO 2 nanostructured electrode show that only the absorbance of the MTsPc monomer contributes to a photocurrent while that of the MTsPc face to face dimer does not generate a photocurrent.

Didodecyldimethylammonium Bromide Films Containing Cobalt Phthalocyanine Tetrasulfonate for Electrochemical Catalysis

Electrochemistry of didodecyldimethylammonium (DDAB) films containing cobalt phthalocyanine tetrasulfonate (CoPcTS4-) was examined. CoPcTS4--DDAB film electrode showed stable cyclic voltammetric responses in buffers and could catalyze reductions of trichloroacetic acid.

Chemical Degradation of Indigo Potassium Tetrasulfonate Dye by Advanced Oxidation Processes

The experimental degradation of a water soluble dye, potassium indigo tetrasulfonate salt, has been studied using stand-alone ozonation and photocatalytic oxidation process. Progress of the dye oxidation was followed by UV-VIS spectrophotometric measurements at controlled operating conditions. The organic content of reaction samples was measured to verify the process efficiency in dye mineralization. According to current results, almost complete color removal was obtained for ozonation within about 1 h reaction time. The reduction of the organic load was almost 80% from its original while initial sulphur content decreased to 32.5%. Dye conversion of 100% was obtained by means of a photocatalytic process using TiO2 as catalyst at 294 nm irradiated UV light. This complete color removal for the catalytic process was observed within 7 min of reaction time. The calculated initial rate of reaction of photocatalysis treatment was 8 times faster than that of ozonolysis. However, the remaining organic load of photocatalysis was almost 88% from its original while the final sulphur content was 27.3%. This contrasting behavior of the performance of the type of oxidation process stressed importance of physicochemical phenomena and intermediates molecules present during dye degradation. An insightful and mechanistic aspect of the dye oxidation was developed by performing quantumchemical calculations.

A NEW STAINING METHOD FOR THE MEASUREMENT OF PROTEIN USING TETRAPHENYLPORPHYRIN TETRASULFONATE(TPPS_4)

A new dye-staining method for protein assay is described.The reaction between TPPS_4 and protein molecule causes a shift in the absorption of TPPS_4 from 435 nm to 488nm.The absorbance at 488 nm is proportional to the concentration of protein.The range of Beer's law was 1-5 ug/ml and the Sandell's sensitivity was 0.0087 ug/cm^2.

Electrochemical Sensors Based on Modification of Carbon Fiber Microelectrode by Nickel Phthalocyanine Polymer for 3-Methyl-4-Nitrophenol Analysis in Water

3-methyl-4-nitrophenol (MNP) is the main by-product of the organophosphate insecticide fenitrothion (FT), used in locust control. MNP is highly toxic because it is an endocrine disruptor and then may cause adverse in the biological systems. Then, it is necessary to develop analytical methods for determination of this pollutant in the environment. In this sense, we reported herein the development of an electrochemical sensor for the detection of 3-methyl-4-nitrophenol (MNP), one of the metabolites of fenitrothion (FT), by using naked and modified carbon fiber microelectrode (CFME) by nickel tetrasulfonated phthalocyanine polymer (CFME/p-NiTSPc). The voltammogram showed that MNP presents one irreversible anodic peak corresponding to the oxidation of the phenol group at 0.9 V vs Ag/AgCl. The effect of pH of the buffer on the peak current and SWV parameters such as frequency, scan increment and pulse amplitude were investigated in order to optimize the electrochemical response of the sensor. The obtained results lead to the following optimum value: pH = 6;frequency = 25 Hz, pulse amplitude = 50 mV, scan increment = 10 mV. With these optimum values, the calibration curves show that the peak current varied linearly upon MNP concentration leading to a limit of detection (LoD) for naked CFME close to 3 μg/L whereas for CFME modified by p-NiTSPc, it reaches 0.75 μg/L. This results prove that the presence of p-NiTSPc increasing the sensitivity of the sensor could be used to monitor 3-methyl-4-nitrophenol residue in real matrix.

Photocatalytic degradation of rhodamine B by dye-sensitized TiO_2 under visible-light irradiation

Perylene tetracarboxylic diimide (PTCDI),widely used in organic photovoltaic devices,is an n-type semiconductor with strong absorption in the visible-light spectrum.There has been almost no study of the PTCDI-sensitized TiO2 composite used to photocatalytically degrade pollutants.In this study,PTCDIand copper phthalocyanine tetrasulfonic acid (CuPcTs)-sensitized TiO2 composites were prepared using a hydrothermal method.The morphologies and structures of the two composites were characterized by X-ray diffraction,transmission electron microscopy,ultraviolet-visible spectroscopy,and fluorescence spectroscopy.The visible-light photocatalytic activities of the composites were evaluated using the degradation of rhodamine B as a model reaction.Results showed that dye-sensitized TiO2 samples had a wider absorption spectrum range and higher visiblelight photocatalytic activity compared to TiO2 samples.The double dye-sensitized (or co-sensitized) TiO2 composite with efficient electron collection exhibited higher photocatalytic activity than did the single dye-sensitized TiO2 composite.The electron transfer processes of single and double dye-sensitized TiO2 composites were illustrated according to band theory.

A polyoxometalate based electrochemical sensor for efficient detection of L-cysteine

L-cysteine(L-cys),as an important sulfur-containing amino acid,plays an indispensable role in biological systems.Too low and excessively high ratio of L-cys will cause harm to the function of human organs.Therefore,it is very necessary to develop efficient methods to detect it in multifarious samples.This paper has built an electrochemical sensor by combining Keggin-type polyoxometalate(PMo9V3)and cobalt tetrasulfonate(Ⅱ)phthalocyanine(CoTsPc)on indium tin oxide electrodes using the layer-level self-assembly technology for efficiently detection of L-cys.The assembly process and surface morphology of the modified electrode was characterized by ultraviolet–visible spectroscopy,X-ray photoelectron spectroscopy,scanning electron microscope,and atomic force microscopy.The conditions of electro-catalysed oxidation of L-cys were optimized by cyclic voltammetry,and the kinetic electrochemical parameters were also evaluated by electrochemical impedance spectra.Furthermore,the sensing performance of the modified electrode was explored using amperometry.The proposed electrochemical L-cys sensor was found to have superior sensing performance with a range of linear response of 2.5×10^(−7) to 1.7×10^(−4) mol·L^(−1) and 1.7×10^(−4) to 39.5×10^(−4) mol·L^(−1),the detection limit of 1.0×10^(−7) mol·L^(−1)(signal/noise=3),and satisfactory anti-interference ability.Consequently,the fabricated sensor has the potential to be applied in laboratory practices for L-cys deterimination in commercial drinks.