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We report the design, structure, and performance of a planar paper-based ion-sensing platform that utilizes colloid-imprinted mesoporous (CIM) carbon as a solid contact, with a redox buffer as the internal reference. This device contains an all-solid-state ion-selective electrode and an all-solid-state reference electrode that are integrated into the paper substrate with a symmetrical cell design. To ensure calibration-free sensor operation, each interfacial potential within the device is well-defined by the use of a redox buffer added to the sensing and reference membranes that controls the interfacial potentials at the CIM carbon/sensing membrane and CIM carbon/reference membrane interfaces. Two types of redox buffers were evaluated for this purpose, i.e., one based on the tetrakis(pentafluorophenyl)borate salts of cobalt(II/III) tris(4,4′-dinonyl-2,2′-bipyridyl) and one consisting of 7,7,8,8-tetracyanoquinodimethane and its corresponding anion radical. The feasibility of the design was demonstrated wit...

Filter paper has been sequentially enchased with titania (TiO2) nanoparticles and coated by a cobalt-porphyrin/dansyl piperazine complex. A series of “turn on” fluorescence sensors are demonstrated to show high sensitivity and fast response for ammonia gas.

The oxygen reduction reaction (ORR) is a vitally important process in fuel cells. The development of high-performance and low-cost ORR electrocatalysts with outstanding stability is essential for the commercialization of the electrochemical energy technology. Herein, we report a facile synthesis of cobalt (Co) and nitrogen (N) co-doped carbon nanotube@porous carbon (Co/N/CNT@PC-800) electrocatalyst through a one-step pyrolysis of waste paper, dicyandiamide, and cobalt(II) acetylacetonate. The surface of the hierarchical porous carbon supported a large number of carbon nanotubes (CNTs), which were derived from dicyandiamide through the catalysis of Co. The addition of Co resulted in the formation of a hierarchical micro/mesoporous structure, which was beneficial for the exposure of active sites and rapid transportation of ORR-relevant species (O2, H+, OH−, and H2O). The doped N and Co formed more active sites to enhance the ORR activity of the electrocatalyst. The Co/N/CNT@PC-800 material exhibited optimal ORR performance with an onset potential of 0.005 V vs. Ag/AgCl and a half-wave potential of –0.173 V vs. Ag/AgCl. Meanwhile, the electrocatalyst showed an excellent methanol tolerance and a long-term operational durability than that of Pt/C, as well as a quasi-four-electron reaction pathway. The low-cost and simple synthesis approach makes the Co/N/CNT@PC-800 a prospective electrocatalyst for the ORR. Furthermore, this work provides an alternative approach for exploring the use of biomass-derived electrocatalysts for renewable energy applications.

Molybdenum disulfide (MoS2) is considered as a promising candidate to Pt-based catalysts. Literatures report the active centers of MoS2 locate at its edges, while the perfect in-plane domains are not active. In this study, a simple Co Mo S precursor decomposition approach is used to synthesize Co-doped MoS2 in-situ grown graphite paper (GP) substrate. Electrochemical analyses reveal the Co-doped MoS2 possesses excellent electrocatalytic activity comparable to Pt. Density functional theory (DFT) calculations indicate the inert in-plane S atoms neighboring the doped Co atoms become active towards triiodide reduction, as revealed by the adsorption energies (Ead) of iodine atom decreasing from 0.36 eV to −0.52 eV, identical with value obtained from Pt (−0.52 eV). Due to increased active sites, highly conductive of GP, and excellent electrical connection between Co-doped MoS2 and GP substrate, the dye-sensitized solar cell fabricated using Co-doped MoS2/GP as counter electrode (CE) shows higher photoelectric conversion efficiency (7.26%) than those based on MoS2/GP CE (6.57%) and platinized F-doped tin oxide (Pt/FTO) electrode (6.87%).

In this work, a highly sensitive colorimetric paper-based optode for the determination of thiocyanate in urine samples was developed for the first time. The cocktail solution of the optode was composed of 5,10,15,20-tetrakis(4-octyloxyphenyl)porphyrin cobalt(II) complex (L), tridodecylmethylammonium chloride (TDMACl), 2-nitrophenyl octyl ether, and polyvinyl chloride as an ionophore, an ion exchanger, a plasticizer, and a polymer, respectively. The paper-based optode responded to thiocyanate by increasing the blue component in the RGB index and a visible change, with the naked-eye, of the optode color from pink to green was observed. From the central composite design, the optimized conditions that yielded the highest sensitivity were 4.70 mmol/kg TDMACl and 13.75 mmol/kg L. The developed optode sensor was highly selective and responded to thiocyanate over other anions, with a working range of 0.001–5 mM and with a coefficient of determination (R2) of 0.9915. The limits of detection using naked-eye and camera were determined to be 50.0 μM and 1.26 μM, respectively. In addition, the LOD and LOQ estimated from the standard deviation of the blank were 0.65 and 1.87 μM, respectively. Furthermore, this sensor was successfully applied to the detection of thiocyanate in urine samples from non-smokers and smokers. The results were in good agreement with the standard ion chromatography (IC) technique. This developed paper-based optode sensor was simple, low-cost, portable, and easy to use as a sensing device without any complicated instrument.

As one of the most toxic contaminants, arsenic (As) is well-known for diverse types of adversary effects on the life of living beings. Unfortunately, as the conventional methods of its detection generally suffer from several demerits (e.g., long duration, high cost, and complexity), the engineering of advanced materials could be a solution for the development of next generation sensors. In an effort to validate such proposition, we developed a molybdenum based metal–organic framework (Mo-MOF) by modifying a common form of [(Mo2O6)(4,4′–bpy)]n) as a new sensing platform for As. We have successfully developed and characterized a mixed metal (Co/Mo) MOF for the specific, sensitive, and expeditious detection of As(V) metal ions. The color changing capacity (from purple to blue) of Co/Mo-MOF is found to maintain a good linear relationship with changes in the concentration of As(V) from 0.05 ppb to 1000 ppm. This Mo-based MOF sensor, when bound with spectroscoptic and paper-based methods, offered exceptionally low limits of detection (LOD) for As(V) ions such as 0.02 and 0.04 ppb, respectively.

Fabricating low-cost and high-efficiency oil-water separation superwetting materials for the demand of oil spilling treatment remains a great challenge. Herein, a superwetting aluminosilicate fiber paper decorated by flower-like nickel-cobalt carbonate hydroxide (NiCo-CH) nanostructures was prepared via the hydrothermal method and chemical modification with stearic acid (SA) or 1H, 1H, 2H, 2H-Perfluoroalkyltriethoxysilane (FAS-17). The superhydrophilic multi-layers nanoflowers combing with nanoflakes were uniformly distributed on the surface of aluminosilicate fiber. The superhydrophilic aluminosilicate fiber was then modified by the SA to obtain the superhydrophobic aluminosilicate fiber (SA-NiCo-CH@Al2SiO5 FP). The SA-NiCo-CH@Al2SiO5 FP revealed high separation efficiency (> 95.4%) for both light oils and heavy oils, and high oil flux (417 L m−2 h−1–71,656 L m−2 h−1). Furthermore, the SA-NiCo-CH@Al2SiO5 FP can also remain superhydrophobicity under various harsh conditions, such as dust, sand impact, acid or alkali, and low-temperature environments. This study revealed an inexpensive and simple-fabricated multifunctional superwetting material, which provides promising avenue for future applications in oil-water separation.

Cobalt-based nanomaterials have received considerable attention in electric energy-storage devices due to their outstanding electrochemical characteristics. However, multiple time- and energy-consuming steps and complex reduction processes for producing cobalt and cobalt oxide nanostructures are disrupting their substantive commercialization. Here, we propose a facile, ultra-fast, and versatile method for the fabrication of cobalt and cobalt oxide nanostructures using an intense pulsed white light (IPWL) photothermal reduction technique. The mechanism of the IPWL photothermal reduction of cobalt and cobalt oxide is firstly studied by measuring the in-situ temperature of the Co(NO3)2-coated carbon fiber paper (CFP) substrate during IPWL irradiation and analyzing the crystal structures of the IPWL-irradiated samples. Cobalt nanoflakes and cobalt oxide nanoparticles are synthesized on the surface of the CFP substrate by irradiating IPWL for 10 ms at ambient temperature and pressure with various energy densities from 10 to 30 J cm−2. The Co3O4 nanoparticle/CFP and Co nanoflake/CFP samples are further utilized as an electrode, and each electrode exhibits high specific capacity of 29 and 73 mA h g−1, respectively, at a current density of 1 A g−1. Since this novel photothermal reduction technique is applicable to other transition metals and metal oxides, it is a promising method for not only energy storage systems, but also for energy generation applications, filters, sensors, and catalysis systems.

Quantitative indication of the process of forming a complex comes from the evaluation of the stability constants, which characterize the equilibria corresponding to the successive addition of ligands. A method, involving the use of paper electrophoretic technique is described for the study of binary complex system in solution. Present method is based upon the migration of a spot of metal ions on a paper strip at different pH’s of background electrolyte. A graph of pH against mobility gives information about the binary complexes and permits calculation of their stability constants. The first and second stability constants of [Be(II)-homoserine] and [Co(II)-homoserine] complexes were found to be (7.13 ± 0.02; 6.11 ± 0.09) and (4.27 ± 0.07; 3.47 ± 0.11) (logarithm stability constant values) for Be(II) and Co(II) complexes, respectively, at ionic strength of 0.1 mol/L and a temperature of 35 °C.

We present a high-capacity pseudocapacitor based on a hierarchical network architecture consisting of Co(3)O(4) nanowire network (nanonet) coated on a carbon fiber paper. With this tailored architecture, the electrode shows ideal capacitive behavior (rectangular shape of cyclic voltammograms) and large specific capacitance (1124 F/g) at high charge/discharge rate (25.34 A/g), still retaining ~94% of the capacitance at a much lower rate of 0.25 A/g. The much-improved capacity, rate capability, and cycling stability may be attributed to the unique hierarchical network structures, which improves electron/ion transport, enhances the kinetics of redox reactions, and facilitates facile stress relaxation during cycling.

A new chemosensor 1 was synthesized by reacting rhodamine B hydrazide and 2,3,4-trihydroxybenzaldehyde, which was then characterized by spectroscopic techniques and single crystal X-ray crystallography. Sensor 1 has the ability to sense Co2+/Cu2+ ions by “naked-eye” with an apparent colour change from colourless to pink in different solvent system, MeCN and DMF respectively. Furthermore, it can selectively detect Co2+/Cu2+ among wide range of different metal ions, and it exhibits low detection limit of 4.425 × 10−8 M and 1.398 × 10−7 M respectively. Binding mode of the two complexes were determined to be 1:1 stoichiometry for Co2+ complex and 1:2 stoichiometry for Cu2+ complex through Job’s plot, IR spectroscopy, mass spectrometry and 1H NMR spectroscopy. Moreover, reversibility of the sensor 1 as copper (II) ion detector was determined by using EDTA and the results showed that sensor 1 can be reused for at least 6 cycles. Other than that, a low cost chemosensor test strips were fabricated for the convenient “naked-eye” detection of Co2+ and Cu2+ in pure aqueous media. The MTT assay was conducted in order to determine the cytotoxicity of sensor 1 towards human cell lines.

Catalytic performances of isopropanol combustion and bed pressure drop in structured fixed bed reactor composed of cobalt oxides modified ZSM-5 zeolite membrane catalysts on paper-like stainless steel fibers (Co/ZSM-5/PSSF) and traditional granular ZSM-5 zeolites catalysts were investigated in this paper. Both of the catalyst samples were fabricated by wetness impregnation method and were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectrometer (EDS) mapping and the N 2 adsorption/desorption isotherm analyses. The result of EDS mapping revealed that cobalt oxides dispersed well on ZSM-5/PSSF. The Co/ZSM-5/PSSF catalyst display superior catalytic activity to granular Co/ZSM-5 catalyst, 50% and 90% isopropanol conversion temperatures over Co/ZSM-5/PSSF reduced 107 °C and 51 °C, respectively, compared with those over granular Co/ZSM-5 catalysts. The apparent activation energy for isopropanol combustion over Co/ZSM-5/PSSF (90 kJ/mol) was much lower than that over granular Co/ZSM-5 (134 kJ/mol). When the face velocity increased to 14.9 cm/s, the bed pressure drop of reactor filled with only Co/ZSM-5/PSSF catalysts was 9.5% of that of reactor filled with only granular Co/ZSM-5 catalysts. The ZSM-5 zeolite membrane on paper-like stainless steel fibers support provide good dispersion for cobalt oxides and Co/ZSM-5/PSSF show superior catalytic efficiency of isopropanol combustion and produced lower bed pressure drop in reactor compared with granular ZSM-5 zeolites.

A spraymethod is proposed to improve the catalytic properties of ceramic papers to be used as catalytic lters for removing diesel soot particles. Small particles of Ce and Co oxides, acting as active centers for the combustion of the soot retained by the lter, are efciently and homogeneously deposited. On the contrary, the application of the conventional dripmethod results in bigger particlesmainly agglomerated at the crossings between the bers of the ceramic paper. As a result, catalytic papers prepared by the spraymethod exhibitmuch higher performance with soot combustion temperatures decreased by ~30 °C. Fil: Tuler, Fernando Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Gaigneaux, Eric M.. Université Catholique de Louvain; Bélgica Fil: Miro, Eduardo Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Milt, Viviana Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Debecker, Damien P.. Université Catholique de Louvain; Bélgica

This paper describes the synthesis of novel material and its application to fabricate a sensing tool for the diagnosis of vitamin D deficiency. A simple and economical route for the synthesis of novel composite material based on silver-cobalt (Co-Ag) doped polyaniline-polypyrrole (PANI-PPY) copolymer and ionic liquid (IL) has been described and used as sensing material for vitamin D3 detection. The synthesized composite was characterized using structural, morphological and electrochemical techniques. Co-Ag/PANI-PPY/IL was first used to modify the glassy carbon electrode (GCE) and applied for vitamin D3 detection. Later a conductive ink of the proposed material was prepared and a handmade paper sensor was fabricated. Co-Ag/PANI-PPY/IL@GCE and paper electrode showed excellent electrochemical behavior towards vitamin D3 oxidation within the concentration range of 0.0125–22.5 µM and 0.025–0.125 µM with the acceptable detection limit of 0.0073 µM and 0.015 µM respectively. Co-Ag/PANI-PPY/IL@GCE and paper electrode were successfully applied for the detection of vitamin D3 in serum and urine samples.

The properties of the interlayer and outer layer of Ti/Co/SnO2-Sb2O5 electrode were studied, and the electrochemical behavior was examined as well. As a result of unsatisfactory treatment using Ti/Co/SnO2-Sb2O5 electrode, electrochemical disposal of paper mill wastewater employing three-dimensional electrodes, combining active carbon granules serving as packed bed particle electrodes, with Ti/Co/SnO2-Sb2O5 anode, was performed. The outcome demonstrates that efficient degradation was achieved. The residual dimensionless chemical oxygen demand (COD) concentration reached 0.137, and color removal 75% applying 167 mA cm(-2) current density at pH 11 and 15 g l(-1) NaCl. The instant current efficiency, energy cost, electrochemical oxidation index (EOI) and kinetic constant of the reaction were calculated. At the same time, the influence of pH and current density on COD abatement and decolorization was also investigated, respectively.

The electrochemical oxidation of pulp and paper making wastewater assisted by transition metal (Co, Cu) modified kaolin in a 200 ml electrolytic batch reactor with graphite plate as electrodes was investigated. H(2)O(2), which produced on the surface of porous graphite cathode, would react with the catalysts to form strong oxidant (hydroxyl radicals) that can in turn destroy the pollutants adsorbed on the surface of kaolin. The transition metal (Co, Cu) modified kaolin was also characterized by XRD and SEM before and after the modification and the results showed that the transition metals were completely supported on kaolin and formed a porous structure with big BET surface. The mechanism was proposed on the basis of XPS analysis of the catalyst after the degradation process. Series of experiments were also done to prove the synergetic effect of the combined oxidation system and to find out the optimal operating parameters such as initial pH, current density and amount of catalyst. From the results it can be founded that when the initial pH was at 3, current density was 30 mA cm(-2); catalyst dose was 30 g dm(-3), COD (chemical oxygen demand) removal could reach up to 96.8% in 73 min.

Water splitting associated with the conversion and storage of renewable energy is considered to be the most significant strategy to create hydrogen. Herein, an efficient self-supported electrode was developed by in-situ growth of interlayer expanded lamellar cobalt diselenide (CoSe2) nanosheets (NS) on carbon paper (CP) substrate (CoSe2 NS@CP). The analyses of TEM, SEM and XRD confirmed that the CP is homogeneously coated by few stacking layers of interlayer expanded lamellar structured CoSe2. This rationally designed nanostructure can provide more active sites for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The bifunctional electrode exhibits high electrocatalytic performance with −128 mV vs. RHE onset potential for the HER in 0.5 mol dm−3 H2SO4 and +1521 mV vs. RHE for the OER in 1.0 mol dm−3 KOH. Besides, small electrolysis potentials of −201.1 mV vs. RHE and +1636 mV vs. RHE are needed to drive the HER and OER at current density of 100 mA cm−2. Finally, a small overall cell voltage (ca. +1.75 V) was used to drive the water splitting reaction in 1.0 mol dm−3 KOH. The CoSe2 NS@CP electrode showed both excellent catalytic activity with overall current density of 100 mA cm−2 at 2.13 V and tremendous durability with negligible decrease in potential at a constant current of 20 mA cm−2 for more than 30 hours. Thus this rationally designed electrode material can be readily applied for large-scale water splitting process.

Here, we demonstrate that nonprecious CoFe-based oxide nanoarrays exhibit excellent electrocatalytic activity and superior stability for electrochemical oxygen evolution reaction (OER) at large current densities (>500 mA cm-2). Carbon fiber paper (CFP) with three-dimensional macroporous structure, excellent corrosion resistance, and high electrical properties is used as the support material to prevent surface passivation during the long-term process of OER. Through a facile method of hydrothermal synthesis and thermal treatment, vertically aligned arrays of spinel Co xFe3- xO4 nanostructures are homogeneously grown on CFP. The morphology and the Fe-doping content of the CoFe oxide nanoarrays can be controlled by the Fe3+ concentration in the precursor solution. The arrays of CoFe oxide nanosheets (NSs) grown on CFP (Co2.3Fe0.7O4-NSs/CFP) deliver lower Tafel slope (34.3 mV dec-1) than CoFe oxide nanowire (NW) arrays grown on CFP (Co2.7Fe0.3O4-NWs/CFP) in alkaline solution, owing to higher Fe-doping content and larger effective specific surface area. The Co2.3Fe0.7O4-NSs/CFP electrode exhibits excellent stability for OER at large current densities in alkaline solution. Moreover, the morphology and structure of CoFeO nanoarrays are well preserved after long-term testing, indicating the high stability for OER.

The high-energy Li S battery suffers from poor cycling performance due to the shuttle effect of the polysulfides. Strategies must be adopted to suppress the diffusion of polysulfides into the electrolyte in Li S battery. In this work, for the first time, we adopt hydrophilic carbon paper anchored by hierarchically porous cobalt disulfides as the interlayer for capturing polysulfides through physical absorption and chemical bonding. Hierarchical pores can physically adsorb polysulfides, and moreover cobalt disulfide can trap the polysulfides by forming strong chemical interaction. The sulfur-graphene composite with a sulfur content of 70.5% delivers a high initial capacity of 1239.5 mAh g−1 at 0.2 C and retains a reversible capacity of 818 mAh g−1 after 200 cycles. In spite of a little capacity contribution by the insertion of lithium ions into cobalt disulfide for the initial cycles, it disappears in the subsequent cycling. Therefore, the as-developed porous transition metal disulfides on carbon paper as the interlayer could significantly enhance the cycling performance of Li S batteries.

The self-standing electrode materials with large surface area and high electronic conductivity have attracted intensive attention in energy storage devices. Herein, the expanded graphite paper (EGP) is fabricated via a controlled cathodic expansion in acetonitrile with tetrabutylammonium bromide at 10 V. The as-prepared EGP exhibits a three-dimensional porous structure with large specific surface area and high electronic conductivity, which is a favorable support for in situ growing nickel cobalt carbonate hydroxide (NiCo-CH) nanowires via a simple hydrothermal method. The as-prepared NiCo-CH@EGP composite achieves high areal capacity of 2.55 C cm−2 at 0.5 mA cm−2, and still remains 1.38 C cm−2 even at 60 mA cm−2. The assembled NiCo-CH@EGP//activated carbon asymmetric supercapacitor exhibits the maximum energy density of 0.30 mWh cm−2 at a power density of 0.92 mW cm−2, and a suitable cyclic stability with the capacity retention of 78.1 % after 10,000 cycles at 20 mA cm−2. The results indicate that the self-standing NiCo-CH@EGP is a potential electrode material for energy storage devices.

Cobalt telluride branched nanostructures on carbon fiber paper (CFP) with two different morphologies were synthesized via solution-based conversion reaction. Both the CoTe2 with nanodendrite and CoTe with nanosheet morphologies on the CoTe2 nanotube (CoTe2 NDs/CoTe2 NTs and CoTe NSs/CoTe2 NTs) supported by CFP exhibit high activities toward hydrogen evolution reaction (HER). Particularly, the CoTe NSs/CoTe2 NTs only require an overpotential of 230.0 mV to deliver the current density of 100 mA cm(-2) in acid solution. After cycling for 5000 cycles or 20 h continual electrolysis, only a small performance loss is observed.

Paper folding techniques are used in order to compact a Li-ion battery and increase its energy per footprint area. Full cells were prepared using Li4Ti5O12 and LiCoO2 powders deposited onto current collectors consisting of paper coated with carbon nanotubes. Folded cells showed higher areal capacities compared to the planar versions with a 5 × 5 cell folded using the Miura-ori pattern displaying a ∼14× increase in areal energy density.

Catalytic co-pyrolysis of biomass and plastics (HDPE (high density polyethylene), PP (polypropylene) and PET (polyethylene terephthalate)) has been performed in a fixed-bed reactor in presence of cobalt based alumina, ceria and ceria-alumina catalysts to analyze the product distribution and selectivity. Catalysts are synthesized using co-precipitation method and characterized by BET (Brunauer-Emmett-Teller) surface area and XRD analysis. The effect of catalytic co-pyrolysis at different temperature with product distribution has been evaluated. The results have clearly shown the synergistic effect between biomass and plastics, the liquid products gradually increases forming with rise in the plastic content in the blend. Gaseous products have yielded most during pyrolysis of blend having biomass/plastics ratio of 5:1 with the presence of 40% Co/30% CeO2/30% Al2O3 catalyst with hydrogen gas production touched its peak of 47 vol%. Catalytic performance enhanced with increase with the cobalt loading, with best performance attributing to 40% Co/30% CeO2/30% Al2O3 catalyst. (C) 2016 Elsevier Ltd. All rights reserved.

A new method paper electrophoresis, involving the use of a ionophoretic technique is described for the study of Be(II) and Co(II) biologically important binary complexes with norvaline in solution. The stability constants of ML and ML 2 complexes of Be(II) – norvaline and Co(II) – norvaline systems have been found to be (7.19 ± 0.02, 5.93 ± 0.09) and (4.61 ± 0.12, 2.83 ± 0.05) (logarithm stability constant values), respectively at ionic strength of 0.1 mol L -1 and a temperature of 35 0 C. Keywords : Paper electrophoresis technique; Overall mobility; Beryllium(II) complexes; cobalt(II) complexes; Norvaline; stability constants. e-mail: brijtew@yahoo.com INTRODUCTION For the general case of the complex ML n , the stepwise formation or stability constants (K n ) are:where M and L are metal cation and ligand anion, respectively. For the calculation of total concentration of final complex product (ML n ), the overall formation constant is used. [ML n ]b n =