Phosphate Electrolyte Solution Research Articles

Palladium-Copper Bimetallic Aerogel as New Modifier for Highly Sensitive Determination of Bisphenol A in Real Samples.

In this study, a bimetallic palladium-copper aerogel was synthesized and used for modification of a graphite paste electrode (Pd-Cu/GPE), allowing the sensitive determination of bisphenol A (BPA). Different techniques, such as SEM, TEM, XPS, and AFM, were used for characterization of the Pd-Cu aerogel. To elucidate the properties of the Pd-Cu/GPE, the electrochemistry methods such as differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy were used. DPV measurements were conducted in phosphate electrolyte and buffer solution (0.2 M PBS, pH 5) at a potential range from 0.4 to 0.9 V vs. Ag/AgCl. The DPVs peaks currents increased linearly with BPA concentrations in the 0.04-85 and 85-305 µM ranges, with a limit of detection of 20 nM. The modified electrode was successfully used in real samples to determine BPA, and the results were compared to the standard HPLC method. The results showed that the Pd-Cu/GPE had good selectivity, stability, and sensitivity for BPA determination.

Microfluidic flow injection analysis system for the electrochemical detection of dopamine using diazonium-grafted copper nanoparticles on multi-walled carbon nanotube-modified surfaces

In this proof-of-concept study, a microfluidic flow injection analysis (FIA) system was developed using multi-walled carbon nanotube-modified screen-printed carbon electrodes (CNTSPEs) that were modified with copper nanoparticles (CuNPs) following the electrodeposition of the diazonium salt of 4-aminothiophenol to form 4-thiophenol-conjugated CuNPs (CuNPs-CNTSPE). Transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) were used to characterize the size of CuNPs, morphology and elemental analysis of CuNPs-CNTSPE, respectively. Using electrochemical impedance spectroscopy (EIS), the charge-transfer resistance (Rct) of CuNPs-CNTSPE was found to be 20-fold lower than that of CNTSPE. The CuNPs-CNTSPE displayed an oxidation peak for dopamine at −0.08 V which is ∼80 mV lower than the one detected using CNTSPE. The modified electrode was used in microfluidic flow injection analysis and offline systems for sensitive detection of dopamine (DA). The pH, flow rate, loop volume, concentration, and type of surfactant were all optimized for on-chip detection. Under the optimal conditions, using phosphate electrolyte solution (pH 6) containing 0.05% (w/v) Tween 20® as the carrier at a flow rate of 0.6 mL min−1 and a loop volume of 50 μL, the calibration curve was linear from 1.5 to 500 nM with a limit of detection of 0.33 nM. This technique was used for the successful detection of DA in real samples with recovery ranging from 96.5% to 103.8%. The microfluidic FIA system described here has the potential to be used as an electrochemical point-of-care device for rapid DA detection with high sensitivity and reproducibility.

Utilization of polyvinyl butyral-zirconium alkoxide hybrid hollow tube as an enzyme immobilization carrier

We developed a Polyvinyl butyral (PVB)-zirconium alkoxide hybrid hollow tube by air-gap spinning. Enzyme (β-galactosidase and lipase) was physically entrap-immobilized and disseminated throughout the hollow tube architecture. The enzyme immobilized PVB-Zr hybrid tube shown its stability in phosphate buffer solution, electrolyte solution, and other organic solvents. The apparent Michaelis constant Km for immobilized β-galactosidase (IβG) was 0.079 mol/l compared to 0.067 mol/l for free enzyme. The maximum velocity Vmax was 4.9 μmol.min−1, whereas it was 11.5 μmol.min−1 for free enzyme. The preserved activity of IβG was found to be 90%, after ten reaction cycles. Moreover, up to 70% conversion for citronellyl acetate after 50 h. was achieved by immobilized lipase (IL) in hexane solution. The activity of IL was found to be 62% after 8 repeated uses where free enzyme retained 15% activity. Overall, it was considered that the enzyme activity employed both in the interior and the vicinity of the hollow tube surface.

Prussian blue-doped nanosized polyaniline for electrochemical detection of benzenediol isomers.

Simultaneous speciation of benzenediol isomers (BDIs), 1,2-benzenediol (catechol, CC), 1,3-benzenediol (resorcinol, RS), and 1,4-benzenediol (hydroquinone, HQ), was investigated by differential pulse voltammetry (DPV) using a graphite paste electrode (GPE) modified with Prussian blue-polyaniline nanocomposite. The modified GPE showed good stability, sensitivity, and selectivity properties for all the three BDIs. Prussian blue-doped nanosized polyaniline (PBNS-PANI) was synthesized first by using mechanochemical reactions between aniline and ferric chloride hexahydrate as the oxidants and then followed by the addition of potassium hexacyanoferrate(II) in a solid-state and template-free technique. The material was characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The DPV measurements are performed in phosphate electrolyte solution with pH4.0 at a potential range of - 0.1 to 1.0V. The proposed modified electrode displayed a strong, stable, and continuous three well-separated oxidation peaks towards electrooxidation at potentials 0.20, 0.31, and 0.76V for HQ, CC, and RS, respectively. The calibration curves were linear from 1 to 350.5μM for both HQ and CC, while for RS, it was from 2 to 350.5μM. The limit of detection was determined to be 0.18, 0.01, and 0.02μM for HQ, CC, and RS, respectively. The analytical performance of the PBNS-PANI/GPE has been evaluated for simultaneous determination of HQ, CC, and RS in creek water, commercial hair dye, and skin whitening cream samples with satisfactory recoveries between 90 and 106%. Overall, we demonstrated that the presence of NS-PANI and PB resulted in a large redox-active surface area that enabled a promising analytical platform for simultaneous detection of BDIs. Graphical abstract.

Microstructural, protective, inhibitory and semiconducting properties of PEO coatings containing CeO2 nanoparticles formed on AZ31 Mg alloy

The aim of this study is to investigate the effects of presence of cerium oxide nanoparticles on the microstructure, protective properties and inhibitory properties, while also enquiring into plasma electrolytic oxidation (PEO) coatings semiconductors properties, which were formed in a phosphate electrolyte solution, applied on AZ31 Mg alloy. According to the SEM/elemental map, Ce has been deposited in the oxide coating structure, and results in the changing of the morphology and coating thickness. According to the results of potentiodynamic polarization (PDS) and electrochemical impedance spectroscopy (EIS), during the short and long immersion period of up to 16 days, the presence of optimum level of CeO2 in the phosphate electrolyte solution (3 g/l) results in the highest protection properties for PEO coating. Furthermore, the EIS test following the PDS, indicated the inhibitory effects of the cerium products, while the results of Mott-Schottky (M-S) test indicated a decrease in the donor concentration with presence of optimum CeO2 and thus, a drop in the tendency to undergo corrosion reactions. Thermodynamic investigations have shown that the formation of corrosion products which contain Ce is possible and stable, hence leading to the improvement of the protective properties of PEO coatings.

Lithium-Ion Intercalation by Calcium-Ion Addition in Propylene Carbonate-Trimethyl Phosphate Electrolyte Solution

Electrochemical intercalation of lithium ions was investigated in propylene carbonate (PC)-trimethyl phosphate (TMP) electrolyte solution. Intercalation of lithium ions took place in 1 mol dm−3 lithium bis(trifluoromethanesulfonyl)amide (LiTFSA)/PC:TMP by adding a certain amount of calcium ions. When the molar ratio of PC:TMP:Li+ was 6:6:1, lithium-ion intercalation took place when the molar ratio of Ca2+/Li+ was 1.2. The criteria was Ca2+/Li+ = 0.8 when the molar ratio of the electrolyte was PC:TMP:Li+ = 2:10:1. It was suggested from Raman spectra that the solvation structure of lithium ions were altered from the four coordinated tetrahedral configuration in the case that intercalation reaction occurred. This change in the lithium-ion solvation structure was caused by adding calcium ions, which has stronger Lewis acidity than lithium ions. Different criteria of Ca2+/Li+ molar ratio for lithium-ion intercalation by the difference of PC:TMP:Li+ molar ratio shows that the lithium-ion solvation structure was also affected by the electrolyte composition.

In-situ synthesis of Ag-Pi oxygen-evolving catalyst in phosphate environment for water splitting

An efficient Ag-Pi oxygen-evolving catalyst was fabricated in situ in a phosphate electrolyte solution (pH 12.4). The catalyst approaches an amorphous structure, unlike the reported Ag-based oxygen-evolving catalysts. The catalytic activity for water oxidation of the Ag-Pi catalyst is 11.1 μmol h−1 cm−2 and it has a modest oxygen-evolution overpotential of 457.0 mV at 1 mA cm−2 in 0.1 M K3PO4 electrolyte. The effects of different electrolytes on the formation of the Ag-Pi catalyst were investigated. The active component of the Ag-Pi oxygen-evolving catalyst as a water-splitting catalyst is the AgO phase as determined by X-ray diffractometry and X-ray photoelectron spectroscopy analysis. A Ag-Pi mechanism that includes the Ag(I) and Ag(III) cycles is proposed to explain the electrocatalytic oxygen evolution.

AZ91Dマグネシウム合金のトライボロジー特性に及ぼすリン酸塩・アンモニウム塩混合溶液からの陽極酸化処理およびPTFE 粒子複合化の影響

AZ91Dマグネシウム合金のトライボロジー特性に及ぼすリン酸塩・アンモニウム塩混合溶液からの陽極酸化処理およびPTFE 粒子複合化の影響

Layer-by-Layer Assembly and Characterization of Multilayers of a Manganese Porphyrin Linked Poly(4-vinylpyridinium) Derivative and Poly(styrenesulfonic acid-o-maleic) Acid

Multilayers of manganese(III) porphyrin-linked poly(vinylpyridinium) (MnTMPyP-PVPMe) polyelectrolyte and poly(styrenesulfonic acid-o-maleic) acid (PSS) have been assembled on gold, quartz, and indium tin oxide surfaces by a layer-by-layer (LBL) technique. The assembly process was monitored by measuring their absorption spectra and frequency change after each assembly, both of which confirmed the formation of three-dimensional MnTMPyP-PVPMe/PSS multilayers. The Soret absorption band of porphyrin red shifted about 8 nm in the multilayer compared with that in the dilute aqueous solution. The average mass changes for each assembly of MnTMPyP-PVPMe and PSS were estimated to be about 2.9 and 0.25 μg/cm(2), respectively. X-ray photoelectron spectra revealed that the as-prepared multilayers were composed of S 2p, C 1s, N 1s, O 1s, and Mn 2p, corresponding to polymers of MnTMPyP-PVPMe and PSS. A rough surface was observed after the assembly of MnTMPyP-PVPMe on the gold surface, but it became smoother when the PSS layer was adsorbed. The significant difference in the mass change and film morphology after the assembly of MnTMPyP-PVPMe compared to those after the assembly of PSS was ascribed to the reason that the MnTMPyP-PVPMe polyelectrolyte contained large metalloporphyrin macrocycles, which were axially coordinated to the pyridyl substituents of the PVP polymeric backbones. The cyclic voltammograms revealed two couples of redox waves in the phosphate electrolyte solution at pH 11, which corresponded to the electron-transfer processes of Mn(II)/Mn(III) and Mn(III)/Mn(IV) of polymeric manganese porphyrin MnTMPyP-PVPMe. The charge-transfer process was also investigated. Finally, the present MnTMPyP-PVPMe/PSS multilayers were used as a heterogeneous catalyst for the decoloration of an azo dye.

Surface Heat Treatment of Magnesium Alloys by Plasma Electrolysis from Phosphate Electrolytic Solution

This study examined the possibility of surface heat treatment by the plasma electrolysis from phosphate electrolytic solution on magnesium alloys. Effects of the anodic plasma electrolysis onto various AZ series magnesium alloys on the mechanical properties and microstructure were examined.The tensile test revealed that the anodic electrolytic treatment at final bias voltage from 250 V to 400 V influenced the tensile strength. The tensile strength of AZ61 and AZ91D substrate after anodic electrolytic treatment increased or decreased, and this change of tensile strength is attributable to the precipitation of intermetallic compound (β phase, Mg17Al12) as sparks occurred due to dielectric breakdown during anodic electrolysis. These results demonstrate the utility of this electrolytic treatment on AZ61 and AZ91D magnesium alloys.

Application of Laser Removal Processing on Magnesium Alloy Anodized from Phosphate Solution

Effects of the laser removal processing on corrosion resistance and conductivity for the magnesium alloy products anodized from the phosphate electrolytic solution were examined. The area where anodized coating was removed under the appropriate laser irradiated condition showed the excellent corrosion performance as well as good conductivity. This improvement of the conductivity is attributable to the removal of the anodized coatings whose conductivity is not good, and molten sputter then formed from the magnesium alloy substrate by means of the laser thermo processing becomes covered with the anodized coatings. Furthermore, this excellent corrosion resistance is based on the sacrifice corrosion protection by anodizing from the phosphate electrolytic solution.

Friction and Wear Properties on AZ91D Magnesium Alloy Treated by Anodizing from Phosphate Electrolytic Solution

Friction and Wear Properties on AZ91D Magnesium Alloy Treated by Anodizing from Phosphate Electrolytic Solution

Diagnostic assay of carcinoembryonic antigen tumor markers using a fluorine immobilized biosensor with handmade voltammetric circuit

The tumor marker carcinoembryonic antigen (CEA) was investigated using a graphite pencil electrode (PE) and fluorine immobilized onto a graphite pencil carbon electrode (FPE). The optimum diagnostic conditions for square wave (SW) stripping voltammetry and cyclic voltammetry were searched. The voltammograms indicated three other detection ranges of 0.4-1.6 μg/l cyclic voltammetry (PE) seven points, 0.2-1.2 μg/l SW (PE) cathodic six points, and better sensitive ranges of 0.05-0.45 μg/l SW (FPE). These were obtained within a diagnostic accumulation time of 120 s in 0.1 mol/l ammonium phosphate electrolyte solution of pH 5.0. Under optimum SW conditions, the detection limit (S/N) approached 0.08 μg/l CEA, and the relative standard deviation at 10 mg/l CEA was 0.074% in 15 measurements. The proposed method can be applied in tumor assay using cancer patient urine.

Determination of aconitine and hypaconitine in Gucixiaotong Ye by capillary electrophoresis with field-amplified sampleinjection

To set up a capillary electrophoresis method with field-amplified sample injection for the determination f aconitine and hypaconitine in Gucixiaotong Ye. An uncoated fused-silica capillary column (50 microm x 50 cm, effective length 42 cm) was used as the separation channel. The running buffer was 50 mmol x L(-1) phosphate electrolyte solution (pH 9)-m nol (90:10) , the running voltage was 10 kV and the capillary inlet was dipped in methanol for 5 s prior to electrokinetic injection (12 kV, 30 s), the detection wavelength was set at 235 nm. Aconitine and hypaconitine were linear in the concentration ranges of 17.2-275 microg x L(-1) and 34. 4-550 microg x L(-1), respectively. The average recovery was more than 93.9% with the RSD of 3.8%. This method could enrich 500 fold of aconitine alkaloid. The method is simple, rapid and specific with high stacking efficiency, it provides a new reliable means for production and quality control of Gucixiaotong Ye.

Development of Laser Surface Treatment with Excellent Corrosion Resistance and Conductivity Performance on Magnesium Alloy Products

Effects of the laser processing on corrosion resistance and conductivity for the magnesium alloy products anodized from the phosphate electrolytic solution were examined. The area where anodized coating was removed under the appropriate laser processing condition showed the excellent corrosion performance as well as good conductivity. This improvement of the conductivity is attributable to the removal of the anodized coatings whose conductivity is not good, and excellent corrosion resistance is based on the sacrifice corrosion protection by anodizing from the phosphate electrolytic solution.

Friction and wear properties on AZ91D magnesium alloy treated by anodizing from phosphate electrolytic solution

The effects of various surface treatments on the friction and wear properties of AZ91D magnesium alloy substrate against the SUJ2 steel ball were evaluated by using a horizontal reciprocating friction and wear test apparatus. The friction and wear properties greatly changed due to the type of surface treatment in spite of being under equal friction and wear testing conditions. Wear loss of AZ91D magnesium alloy anodized from the phosphate solution was greatly reduced in comparison with the other surface treatments such as Dow17, conversion coatings and also no surface treatment. The above results suggest that anodizing from the phosphate solution should improve the friction and wear properties of magnesium alloy used for sliding parts.

Study on the preparation of nano-flaky anatase titania layer and their photovoltaic application

Titania (TiO 2), known to have wide energy band gap, can greatly absorb dye if specific surface area can significantly be increased and hence the photovoltaic efficiency. Dye-sensitized solar cells (DSSC) based on mesoporous titania has been drawn much attention over the past few years. An attempt in this study is to employ micro-arc oxidation (MAO) process and alkali treatment to develop titania layer with very high specific surface area on pure titanium surface. Specimens were applied an anodic dc voltage at 400–500 V in a phosphate electrolytic solution during MAO process, followed by the alkali treatment in 1.25 M NaOH solution to produce nano-flaky anatase TiO 2 on surface, with nano-flakes about 50 nm in dimension thus largely increase specific surface area. Result of photovoltaic efficiency measurement of the assembled DSSC device show that ultimate efficiency (0.23%) can be obtained for the specimen post-alkali treated in 1.25 M NaOH solution, which exhibits the highest surface area and thus the enhanced dye-absorbing efficiency.

Assay of diazinon pesticides in cucumber juice and in the deep brain cells of a live carp

An electrochemical assay for diazinon pesticides was developed using cyclic voltammetry and square-wave anodic and cathodic stripping voltammetry. The method has a linear working range from 6 to 62 ng L−1. The detection limit is 0.5 ng L−1 (1.64 pM), and the relative standard deviation at a diazinon concentration of 6.0 mg L−1 was 0.06% (n = 15) in an 0.1 M ammonium phosphate electrolyte solution. The results of the application of the sensor were compared with those of other common spectrometric and electrochemical methods. The method was also applied to cucumber juice and the deep brain cells of a live carp in real conditions.

Entrap-immobilization of biocatalysts on cellulose acetate-inorganic composite gel fiber using a gel formation ofcellulose acetate–metal (Ti, Zr) alkoxide

We developed a new entrap-immobilization method, using a gel formationof cellulose acetate and metal (Ti, Zr) alkoxide. Several biocatalysts(β-galactosidase, α-chymotrypsine, invertase, urease, lipase andSaccharomyces cereviciae) were successfullyentrap-immobilized on this composite gel fiber. The immobilization process wassimple and the resultant immobilized biocatalysts on the gel fiber were easy tohandle. It is considered that the biocatalysts are physically entrapped amongthe gel networks and distribute throughout the gel fiber. The gel fiber wasstable in phosphate buffer solution, electrolyte solution and organic solvent,because the gel formation was due to coordination interaction between celluloseand transition metal. Therefore, it can be applicable as a support for abiotransformation in various reaction media. We examined some enzyme reactionsand biotransformation using the immobilized biocatalysts on this gel fiber andevaluated this immobilization matrix in the reactions compared to the resultsobtained by the other immobilization method. The immobilized biocatalyst showedstable activity for repeated cycles and over a long period of time. Moreover,continuous reaction could be carried out in a column reactor packed with thisimmobilized biocatalyst.

Separation of phenolic acids in soil and plant tissue extracts by co-electroosmotic capillary electrophoresis with direct UV detection

A capillary zone electrophoretic method for the analysis of phenolic acids in soil and plant extracts was developed with direct UV detection using a phosphate electrolyte solution. The electrophoretic separation required the phenolic acids to be charged at a pH above their pKa in order to achieve their migration towards the anode. Electroosmotic flow (EOF) was reversed in direction by adding tetradecyltrimethylammonium bromide (TTAB). Factors affecting the separation selectivity, including the buffer pH and EOF modifiers, were investigated systematically. Eight phenolic acids were separated and detected in 10 min using an electrolyte containing 25 mM phosphate, 0.5 mM TTAB and 15% acetonitrile (v/v) at pH of 7.20. Linear plots for the test phenolic acids were obtained in a concentration range of 0.01–1 mM with detection limits in the range of 1.0–7.0 μM. The recoveries ranged from 92.8 to 102.3% in soil and plant tissues samples spiked at 100 μM and the relative standard deviation based on the peak area were ranged 2.0 to 4.5%. The proposed method was used for the determination of phenolic acids in plant tissue and soil extracts with direct injection.