Potassium Ferrocyanide Research Articles

Influence of ferrocyanide on the long-term stability of poly(butyl viologen) thin film based electrochromic devices

High bleaching/coloring electrochemical reversibility is crucial for practical applications of an electrochromic material. In this study, ferrocyanide-containing poly(butyl viologen) (PBV:fc) thin films were prepared by electropolymerization, and subsequently investigated and compared their redox properties by using the electrolyte with and without the addition of potassium ferrocyanide (K4Fe(CN)6). Electrochemical and electrochromic properties of the PBV:fc thin films were studied by using cyclic voltammetry (CV) and UV–Vis spectroscopy techniques. The mass changes of the PBV:fc thin films during their redox reactions were studied by using electrochemical quartz crystal microbalance (EQCM) technique. In addition, the scanning electrochemical microscope (SECM) studies confirmed the stable anion insertion/extraction of Fe(CN)64− within a PBV:fc thin film. The obtained results indicate that the redox reversibility of the PBV:fc thin film can be effectively improved by the addition of K4Fe(CN)6 in the electrolyte. It is deduced that the enhancement of bleaching/coloring stability of the PBV:fc thin film is affected by Fe(CN)64− charge balance during the reactions. Complementary electrochromic devices (ECDs) using the PBV:fc and Prussian blue (PB) thin films were fabricated. Finally, the ECD with the electrolyte containing K4Fe(CN)6 shows the superior transmittance modulation stability than the one without K4Fe(CN)6.

OPTIMIZATION OF THE REAGENT METHOD OF CLEANING OF COPPER (II) -STATER WATER

Sewage water of electrochemical manufactures that exist at almost every machine and instrument making enterprise are the main source of the heavy metals that flow into the reservoir. The greatest interest is the purification of sewage from ions of copper (II).From the variety of available methods for purifying water from heavy metal ions, the most potentially suitable are traditional reagent methods as they are versatile, easy to operate and cheap. But they do not always provide theadmissible concentrations. All this necessitates the development and implementation of new modern technologies that allow ensuring high efficiency of the processes of purification from heavy metal ions. This also gives possibility of creating integrated technologies with a closed cycle of water consumption on their basis.Recently, the interest in derivatives of iron-synthetic acid has increased considerably; ferrocyanides acquire a rapidly growing practical value. It is known that ferrocyanides of heavy metals have very low solubility, therefore it was suggested to use potassium ferocyanide as a precipitant in order to remove copper ions from the researched solutions.Since the copper (II) ferrocyanides can form stable colloidal systems, settling solutions will be a long-term and technologically not always justifiable solution, because of its inappropriate usage as an independent method of purification. Typically, this method is combined with the filtering method.In this work, the effectiveness of the flocculantZetag 7547 was investigated.The purpose of this work is to study the features of sewage purification from copper ions (II) applying precipitation method using potassium ferrocyanide and water soluble polyelectrolyte Zetag 7547.To achieve this goal, the following tasks need to be solved: increase the depth of the deposition reaction; intensify the processes of aggregation and sedimentation of particles of the dispersed phase.To reach the optimal conditions for reagent treatment of wastewater, preliminary studies of the pH solution influence on the solubility of the formed copper (II) ferrocyanates have been made. Studies have shown that optimal pH values of precipitation of Cu (II) are within the range of 6.5 to 7.5.In order to intensify the reagent water purification, it was suggested to make its processed flocculation. When used in low concentrations, Zetag-7547 flocculant decreases potassium ferrocyanide significantly from aqueous solutions. From obtained results list of ratios of concentrations of potassium ferrocyanide and flocculant, which should be used to purify water from ions copper (II) were selected. After settling in the solution, a part of coarse dispersed impuritiesremain. They were removed by filtration, which increased the degree of purification up to 99%.Thus, in current research the processes of formation of copper (II) ferrocyanides complexes depending on the pH environment are analyzed, the conditions of reagent treatment of water using Zetag 7547 flocculantare set. The most effective methods of controlling the process of flocculation are shown. The amount of solid waste is reduced.

Iron and Nitrogen Co‐Doped Mesoporous Carbon‐Based Heterogeneous Catalysts for Selective Reduction of Nitroarenes

AbstractA facile fabrication of Fe and N co‐doped mesoporous carbon (MC), as an efficient heterogeneous catalyst for the highly selective reduction of nitroarenes, is described. The Fe and N co‐doped MC nanosheets are easily synthesized via a hydrothermal reaction between citrate acid and magnesium citrate, followed by calcination in the presence of melamine and potassium ferrocyanide. The Fe−N complex provides a unique active site for the selective reduction of 1‐chloro‐4‐nitrobenzene, leading to the production of (E)‐1,2‐bis(4‐chlorophenyl)diazene with a selectivity of >96%, in <40 mins. Control experiments based on non‐doped, N‐doped, and Fe‐doped MC nanosheets demonstrate that selectivity greatly depends on the catalyst active component type, and that non‐doped MC significantly contributes to the high efficiencies observed in the selective synthesis of azoxy compound intermediates. A broad range of substrates, including extra‐functional groups on the nitroarenes rings, were successfully converted to the corresponding azo compounds at mild conditions with high selectivity.magnified image

Detection of sensitisation on aged lean duplex stainless steel with different electrochemical methods

Ageing at 600 °C (from 0.1 h up to 20 h) leads to the formation of precipitations at the ferrite-ferrite (α/α) and ferrite-austenite (α/γ) grain boundaries of the lean duplex stainless steel (LDSS) X2CrNiN22-2. This leads to sensitisation due to chromium depletion and decreased pitting corrosion resistance proven by the results of various electrochemical methods (DL-EPR and determination of CPT, Epit). These results were compared with the KorroPad method, which uses an agar-based gel-electrolyte for the detection of stainless steel surfaces prone to pitting corrosion. However, the standard configuration of the KorroPad showed no differentiation for the various ageing conditions. Therefore, modified versions of the KorroPad with two, five and ten times higher NaCl and potassium ferrocyanide III (K3[Fe(CN)6]) concentrations were successfully used to visualise the behaviour detected by DL-EPR, Epit and CPT. Therefore, the KorroPad method can also detect a microstructure related reduction of pitting corrosion resistance, which can drastically reduce the experimental effort to generate sensitisation diagrams for stainless steels.

An Exfoliated Graphite-Bismuth Vanadate Composite Photoanode for the Photoelectrochemical Degradation of Acid Orange 7 Dye

This work investigates the removal of acid orange 7 dye from aqueous solution through photo electrochemical technique using a composite of exfoliated graphite and bismuth vanadate (EG-BiVO4) as photoanode. Monoclinic sheelite BiVO4 nanoparticles were synthesised through the hydrothermal route and subsequently added to prepared EG to form a composite. The EG-BiVO4 composite was fully characterised through XRD, SEM and FTIR. The cyclic voltammograms of the EG-BiVO4 electrodes were obtained in potassium ferricyanide and ferrocyanide redox probe. The XRD result revealed that the BiVO4 has a monoclinic sheelite crystal lattice with particle size of 74.17 nm. The EG-BiVO4 photoanode was applied for the photoelectrochemical degradation of acid orange 7 dye. Concentration decay of the dye was monitored using the UV-Vis spectrophotometer. The photo-assisted process gave improved degradation efficiency of 88% within 90 min. Kinetics study revealed that the process followed the pseudo first-order kinetics and fast with apparent rate constant of 1.60 × 10−2 min−1. The results of this investigation reveal the potential application of BiVO4 photoanode in the photoelectrochemical treatment of dye contaminated water.

Chitosan-based biosorbents: immobilization of metal hexacyanoferrates and application for removal of cesium radionuclide from aqueous solutions

Composite M (M—Cu, Ni) potassium ferrocyanide chitosan-based materials were prepared via co-precipitation methods using chitosan as a matrix for adsorption of cesium from alkaline solutions. The materials were fabricated using a suspension or in situ formation of ferrocyanides of transition metals in a chitosan matrix with simultaneous chitosan deposition. The synthesis products were characterized by the methods of scanning electron microscopy with energy-dispersive analysis (SEM–EDX) and X-ray diffraction (XRD). In the process of sorption of radiocesium from alkaline solutions under static conditions, the stability of composite sorbents compared with the pristine powders of transition metal ferrocyanides was estimated. The boundary values of the pH and time, at which the destruction of the composite sorbent is observed, are determined. The stabilizing effect of chitosan on the resistance of Ni-K ferrocyanide (FCN) complexes in alkaline mineralized solutions has been shown on the example of Ni-K FCN/chitosan composite sorbents.

Morphometric analysis in mouse scleral fibroblasts using focused ion beam/scanning electron microscopy

The sclera as well as the cornea forms the principal part of the outer fibrous coat of the eye, with a primary function of protecting the intraocular contents and maintaining the shape of the globe. However, the exact morphometric arrangement of scleral fibroblasts remains unclarified. The aim of this study was to observe the three-dimensional structure of the mouse scleral fibroblasts by focused ion beam/scanning electron microscopy (FIB/SEM). Four eyes from C57BL/6J mice were fixed using a mixture of glutaraldehyde and formaldehyde. The sclera was cut out at the equatorial portion and the posterior pole, and postfixed with potassium ferrocyanide, osmium, thiocarbohydrazide, uranyl acetate and lead aspartate. Specimens were then dehydrated and embedded in an epoxy resin. Serial block face images were obtained using FIB/SEM. Three-dimensional image reconstruction and segmentation of the image stack were created using computer software (Amira v6.0.1, FEI). Scleral fibroblasts were arranged in collagenous layers. The cells frequently showed a cellular junction with the neighboring cells and formed cellular networks. Compared with equatorial fibroblasts, there was a more complicated cellular arrangement of the posterior scleral fibroblasts.

Characterization and evaluation of synthesized ammonia triethyl amide (ATEA) for removing sodium chloride deposition

Ammonia triethyl amide (ATEA) was synthesized by a new facile one-step method using chloroacetamide and ammonia as raw materials, and its structure was characterized by FTIR and 1HNMR. TGA showed that the decomposition temperature of compounds was about 110 °C, which had good thermal stability. Its performance of inhibiting salt deposition was evaluated and the mechanism of salt inhibition was analyzed systematically. On the one hand, the optimal concentration of ATEA was 10 kg/m3 and the dispersion rate at this concentration was 79.6%. XRD and SEM analysis confirmed that the structure of NaCl crystal was not changed, but it had a tendency to grow into star-shaped crystal. On the other hand, with the increase of aging time and temperature, the solubilization rate decreased, and with the increase of pH value, the solubilization rate increased first and then decreased. At a concentration of 10 kg/m3, the solubilization rate was 6.58% after aging 16 days, was 6.35% when pH = 10 and was 5.43% at 95 °C. The maximum dispersion rate (88.35%) and the maximum solubilization rate (10.38%) were achieved when the mass concentration ratio of ammonia triethyl amide to potassium ferrocyanide were 6:4 and 7:3, respectively. The experimental results showed that ammonia triethyl amide had good synergy effect with potassium ferrocyanide for removing sodium chloride deposition.

Wall to Bed Mass Transfer in the Presence of Double Cone Promoter in a Three Phase Fluidized Bed with Conical Entry of Electrolyte

Abstract Investigations have been carried out experimentally to study the effect on wall-to-bed mass transfer coefficient in presence of double cone promoter in a three-phase fluidized bed with a conical entry of electrolyte. The system chosen was an electrolyte as liquid phase, glass spheres of different diameters as solid phase and inert nitrogen as gas phase. The electrolyte was an equimolar solution of potassium ferricyanide and potassium ferrocyanide each of 0.01 N with 0.5 N sodium hydroxide as indifferent electrolyte. The reaction considered was the reduction of ferricyanide ion. The experiment had been carried out at temperature range of 36 to 38 o C at which the physical property values of the electrolyte were known from literature. The mass transfer coefficient was computed from the measured limiting current. It was found that the mass transfer coefficient was relatively independent of liquid velocity within the range covered in the present experiment. The k L increased marginally with increasing gas velocity. The k L was not influenced significantly by particle size and diameter of promoter within the present study range. The entire experimental data have been correlated in terms of Coulburn j D -factor and particle Reynolds number. Keywords: Mass transfer coefficient based on liquid side, k L, Coulburn j D -factor, particle Reynolds number, Rep , Froude number based on gas velocity, Fr g , Schmidt number, Sc

Red blood cells collision with the wall in human coronary arteries promotes oxidative stress in early stage atheroma

Among the various actors involved in the coronary atherosclerosis (CAD), erythrocytes (RBC), have been little studied but they are rich in atherogenic components (cholesterol, phospholipids, Iron). RBC collision with the aortic wall has recently reported as an important source of oxidation process in early human aortic atheroma. The objective was to extend these data to human coronary arteries (CAs) at different stages of CAD, with integrating hemodynamic conditions to better describe this novel mechanism and consequences on atherogenesis. Thirty-nine human hearts were collected with the agreement of the French Medicine Agency. Epicardial CAs were dissected and longitudinal sections were performed to integrate flow direction and shear stress vectors in histological analysis. Both iron ionic forms were studied by a co-staining with potassium ferrocyanide and H2O2/diamino-benzydine polymerization. RBC membranes were identified by glycophorin-A immuno-staining. An in vivo model of RBC collision was performed in rabbits producing an experimental carotid stenosis using a 3D printed cuff. A high resolution MRI (7 Tesla) was performed on coronary samples to better define the intra-parietal iron distribution. Iron-induced oxidative stress was evaluated in vitro by a co-culture of vascular smooth muscle cells (vSMC) with RBC. Among the 88 coronary samples analyzed, 72% had intraparietal iron found inside the foam cells. Redox-active Fe++ was the predominante ionic form and was observed in subendothelial level, even in healthy CAs. High resolution MRI allowed a good detection of iron in human coronaries. Multimodal analysis showed that RBC collision predominated in the post-stenotic part. RBC were phagocytosed by the vSMC inducing a cytotoxic effect on them. Intimal RBC infiltration may be an initial trigger of foam cells formation and intraparietal oxidation in CAs. Their collision with CAs wall depends on the local hemodynamic conditions.

“Click” Chemistry on Gold Electrodes Modified with Reduced Graphene Oxide by Electrophoretic Deposition

The coating of electrical interfaces with reduced graphene oxide (rGO) films and their subsequent chemical modification are essential steps in the fabrication of graphene-based sensing platforms. In this work, electrophoretic deposition (EPD) of graphene oxide at 2.5 V for 300 s followed by vapor treatment were employed to coat gold electrodes uniformly with rGO. These interfaces showed excellent electron transfer characteristics for redox mediators such as ferrocene methanol and potassium ferrocyanide. Functional groups were integrated onto the Au/rGO electrodes by the electro-reduction of an aryldiazonium salt, 4-((triisopropylsilyl)ethylenyl)benzenediazonium tetrafluoroborate (TIPS-Eth-ArN) in our case. Chemical deprotection of the triisopropylsilyl function resulted in propargyl-terminated Au/rGO electrodes to which azidomethylferrocene was chemically linked using the Cu(I) catalyzed “click” chemistry.

In Situ Generation of Prussian Blue with Potassium Ferrocyanide to Improve the Sensitivity of Chemiluminescence Immunoassay Using Magnetic Nanoparticles as Label.

Using magnetic nanoparticles (MNPs) as a label in immunoassay (IA) possesses advantages such as high specific surface area, simple modification process. However, the catalytic activity of MNPs is low, which limits their applications in IA. The present study found it interesting that potassium ferrocyanide reacts with MNPs, leading to the in situ generation of Prussian blue. The produced Prussian blue shows high catalytic activity on a luminol chemiluminescent (CL) reaction. Therefore, a simple and sensitive immunoassay for rabbit IgG (rIgG) as model analyte using MNPs as label was developed. The CL intensity had a linear increase with the concentration of rIgG that ranged from 0.625 to 20 ng mL-1. The limit of detection was calculated to be 0.59 ng mL-1. In addition, the applicability of this method was evaluated using the standard addition method. The recovery ranged from 80.0% to 115.0%. What's more, the proposed CLIA method based on in situ generation of Prussian blue with MNPs was also applied to the detection of carcinoembryonic antigen (CEA) and hepatitis B virus (HBV)-related sequence-specific DNA. The LOD for the detection of CEA and sequence-specific DNA was estimated to be 0.28 ng mL-1 and 0.044 pmol, respectively.

Determination of potassium ferrocyanide in table salt and salted food using a water-soluble fluorescent silicon quantum dots

The addition of potassium ferrocyanide (K4[Fe(CN)6]) in table salt as anti-caking agent has a crucial role in preventing the formation of lumps. However, the excess of K4[Fe(CN)6] and its decomposers are harmful to both human health and environment. To date, there are still lack of suitable methods for simple and rapid analysis of K4[Fe(CN)6] in table salt and salted food. Herein, a novel fluorescent Si QDs probe for sensitive, selective and rapid detection of K4[Fe(CN)6] was synthesized by facile one-step strategy. Notably, the fluorescence of Si QDs could be remarkably quenched by K4[Fe(CN)6] via electrostatic interaction. Based on this phenomenon, a new method of determination of K4[Fe(CN)6] was established. A wide linear range was obtained from 0.05 to 8.0 µg/mL with a detection limit of 30 ng/mL. The established fluorescent new method was suitable for detecting K4[Fe(CN)6] in table salt and salted food samples with satisfactory results.

DEVELOPMENT AND CHARACTERIZATION OF A SENSOR BASED ON CARBON NANOFIBERS: APPLICATION TO ACETAZOLAMIDE DETERMINATION IN PHARMACEUTICALS AND BIOLOGICAL FLUIDS

Acetazolamide (ACZ) is a carbonic anhydrase inhibitor that exhibits diuretic activity. In medicine, it is principally used in open-angle glaucoma, for prevention or amelioration of symptoms associated with acute high-altitude sickness and as an adjunct to other anticonvulsants in centrencephalic epilepsies. Furthermore, ACZ is sometimes used by athletes to mask the presence of doping substances, so its use has been banned in competitions. The aim of this work was the development of a sensor to determine ACZ in pharmaceuticals, as quality control way, and serum, for clinical and doping analyzes. The sensor has been developed modifying a glassy carbon electrode with carbon nanofibers. The electrochemical characterization of the sensor was performed by cyclic voltammetry using the redox mediator potassium ferrocyanide. ACZ electrochemical behavior was studied as well. Measurements were performed in a conventional three electrodes cell using differential pulse voltammetry. The influence of some experimental variables involved in the preparation and performance of the sensor –amount of modifier, supporting electrolyte, pH, scan rate and pulse amplitude– were optimized. This methodology provided a linear calibration plot for ACZ in the 1 – 17 μM concentration range. Furthermore, the proposed sensor exhibited suitable analytical properties, with detection and quantification limits of 0.06 μM and 0.2 μM respectively; analytical sensitivity of 1.142 μA/μM, repeatability of 0.72 %, and it was applied to determine ACZ in pharmaceuticals (tablets) and spiked human serum, being an excellent tool to perform quality control and antidoping control.

Electrochemical investigation of amino acids Parkia seeds using the composite electrode based on copper/carbon nanotube/nanodiamond

An electrochemical biosensor comprising copper, nano-diamond (ND) and carbon nanotube (CNT) has been fabricated to detect the amino acids of Parkia speciosa (PS) seeds. Parkia speciosa (stink bean), a Southeast Asian legume, is composed of medicinal chemicals which exhibit biological activities. The electro-catalytic activity of three electrodes Cu/CNT/ND, Zn/CNT/ND and NiO/CNT/ND was studied using 5 mM potassium ferrocyanide in 0.1 MKCl. The Zn/CNT/ND electrode exhibited irreversible reaction free oxidation with reduction peaks at −1 V, whereas, a pair redox peaks was observed for Cu/CNT/ND electrode. The immobilization of l-amino acid oxidase on the Cu/CNT/ND electrode was carried out to catalyze the amino acids detection. It was observed that the anodic and cathodic peak currents increased linearly with both the square root of the scan rate (ν1/2) and scan rate (ν) over the studied scan range of 0.01–0.1 V/s with high correlation coefficients and following both the adsorption and the diffusion-controlled mechanisms. The developed biosensor displayed a very good electro-catalytic activity toward the oxidation of the amino acid to release H2O2 and NH3 as a result of the reaction between the active sites and the Parkia speciosa component. This was also confirmed by a drop in the pH value from 6.8 to 6.5 and a change in the color of the solution from green to yellow (releasing H2S). The impedance results indicated an inductance behavior due to the co-formation of the hydrogen peroxide (H2O2) and the water via the adsorption on the electrode surface.

Is the Cooking Salt Safe in China? Assessment of Chemical Contaminants in Cooking Salt.

Global environmental pollution is becoming more serious, and most dietary salts come from nature. We postulated that chemical pollutants could affect the quality of salt. Forty-five different types of salt were collected from supermarkets, convenience stores, and online retailers in Shanghai, 2015. These comprised more than 90% of all cooking salts consumed in Shanghai, China. We measured and analyzed heavy metal elements, fluoride, potassium ferrocyanide, and 16 phthalate plasticizers. Lead was detected in only two types of salt at concentrations recorded of 0.047mg/kg and 0.077mg/kg. The concentrations of total arsenic, total mercury, cadmium, and barium were under limit of detection (LOD) in all samples. The maximum fluoride concentration of salts was 2.50mg/kg. The median fluoride concentration of domestic salts was significantly lower than foreign-produced salts, and it was significantly higher in sea salt than in other types of salt (P < 0.05). The maximum potassium ferrocyanide concentration in 12 types of salts was 9.20mg/kg, which was under the Chinese national standard. Just three salt types had low levels of diethylhexyl phthalate concentrations that were above the LOD, at 0.208mg/kg, 0.375mg/kg, and 0.380mg/kg, respectively. All other phthalate indicators were below the LOD in all samples. The level of chemical pollutants in salt is either very low or under LOD. We believe that dietary salt products are safe at retail, and the long-term dietary exposure of cooking salts will not pose any significant health risk.

Reformation of the surface of powdered activated carbon (PAC) using covalent organic polymers (COPs) and synthesis of a Prussian blue impregnated adsorbent for the decontamination of radioactive cesium

Prussian blue (PB) is known to selectively adsorb cesium (Cs), with a high adsorption efficiency. However, it is difficult to collect it after adsorption, which increases the risk of secondary environmental pollution. In this study, covalent organic polymers (COPs) were used to reform the surface of powdered activated carbon (PAC) particles in order to stably immobilize PB, with the aim of developing an adsorbent impregnated with PB (COP-PAC-PB). PAC particles reformed with COPs (COP-PAC) were analyzed using TEM (EDS) and FT-IR techniques, and it was found that COPs were successfully synthesized on the surface of COP-PAC particles. COP-PAC-PB particles were synthesized by reacting PAC particles with iron(III) chloride and potassium ferrocyanide solutions in order, to synthesize PB within the pores of COPs (in situ). COP-PAC-PB particles were analyzed using XRD and FT-IR techniques, and peaks showing the general characteristics of PB were observed, which indicated that PB existed on the surface of COP-PAC-PB particles. PB was synthesized on the surface of the non-reformed groups (PAC and Ox-PAC) using the same method. In addition, UV–vis analysis was performed to compare the characteristics of PB desorbed from the non-reformed and reformed groups immediately after synthesizing and washing them. In the non-reformed groups (PAC-PB and Ox-PAC-PB), a large amount of PB was desorbed while they were washed 6 times. For COP-PAC-PB, however, a small amount of PB was desorbed during the first washing, but no desorbed PB was observed thereafter. The maximum Cs adsorption capacity of COP-PAC-PB particles was 19 mg/g, and its removal efficiency of radioactivity cesium (Cs-137, 60 Bq/kg) was 97.3%. In this study, the surface of PAC particles was effectively reformed using COPs, and an adsorbent to which PB was stably immobilized was developed.

Synthesis, structure, magnetism and photocatalysis of α-Fe2O3 nanosnowflakes.

In this work, a simple one-step hydrothermal method was developed to synthesize high-quality α-Fe2O3 nanoparticles with a snowflake-like microstructure. First, a series of binary supramolecular aggregates were prepared by a non-covalent combination between a polymer such as polyvinylpyrrolidone (PVP) and a complex such as potassium ferrocyanide (PF). Then, the aggregates were used as the precursors of the one-step hydrothermal reactions. The snowflake-like nanostructure has six-fold symmetry as a whole, and each petal is symmetric. This synthesis method has the characteristics of simplicity, rapidity, reliance, and high yield, and can be used for creating high-quality α-Fe2O3 nanoparticles. Moreover, our results show that the molar ratio of PVP to PF, reaction time and temperature play important roles in the generation of a complete snowflake structure from different angles. Also, the snowflake-like α-Fe2O3 nanostructure exhibits a much higher coercivity (2997 Oe) compared to those reported by others, suggesting a strong hysteresis behaviour, which promises potential applications in memory devices, and other fields. Further, the α-Fe2O3 nanosnowflakes show a much higher photocatalytic degradation activity for cationic organic dyes such as crystal violet, rhodamine 6G than for anionic dyes such as methyl orange. A possible photocatalytic mechanism was proposed for explaining the selectivity of the photocatalytic oxidation reaction of organic dyes. We believe that this study provides a direct link among coordination compounds of transition metals, their supramolecular aggregates with polymers, and controlled hydrothermal synthesis of high-quality inorganic metal oxide nanomaterials.

Photoelectrochemical Properties of α-PbO Films Prepared by Spray Pyrolysis

Thin films of photoactive α-PbO have been prepared on fluorine doped tin oxide substrates using spray pyrolysis in the range of 380°C to 470°C. SEM showed the formation of interconnected PbO grains with increase in grain size at elevated temperature. The Raman peak at 147 cm−1 shows the formation of phase pure α-PbO. XPS indicates the phase purity of α-PbO as well as its stoichiometric nature. Photoelectrochemical studies of as-deposited α-PbO in 0.1 M potassium ferrocyanide (K4Fe(CN)6) or potassium iodide (KI) at pH 9.2 under visible light irradiation showed photoanodic and photocathodic current, indicating nearly intrinsic behavior. Photocurrent spectra showed the presence of a semiconductor with an indirect bandgap of 1.9 eV. Doping by inducing oxygen deficiency through annealing in hydrogen and addition of 2 at. % In, shifted the onset potential to more negative values (down to −0.5 vs. Hg/HgO) in KI, indicating successful conversion into n-type semiconducting material. The In doped hydrogen annealed α-PbO shows a flatband potential of −0.58 V vs. Hg/HgO. The IPCE (incident photon to current conversion efficiency) in KI electrolyte was found to be 0.016 in the plateau region (0.6 V vs. Hg/HgO) at an incident wavelength of 532 nm.

Design and Finite Element Model of a Microfluidic Platform with Removable Electrodes for Electrochemical Analysis

A microfluidic platform for hydrodynamic electrochemical analysis was developed, consisting of a poly(methyl methacrylate) chip and three removable electrodes, each housed in 1/16” OD polyether ether ketone tube which can be removed independently for polishing or replacement. The working electrode was a 100-μm diameter Pt microdisk, located flush with the upper face of a 150 μm × 20 μm × 3 cm microchannel, smaller than previously reported for these types of removable electrodes. A commercial leak-less reference electrode was utilized, and a coiled platinum wire was the counter electrode. The platform was evaluated electrochemically by oxidizing a potassium ferrocyanide solution at the working electrode, and a typical limiting current behavior was observed after running linear sweep voltammetry and chronoamperometry, with flow rates 1−6 μL/min. While microdisk channel electrodes have been simulated before using a finite difference method in an ideal 3D geometry, here we predict the limiting current using finite elements in COMSOL Multiphysics 5.3a, which allowed us to easily explore variations in the microchannel geometry that have not previously been considered in the literature. Experimental and simulated currents showed the same trend but differed by 41% in simulations of the ideal geometry, which improved when channel and electrode imperfections were included.