Studies on polycarbazole‐modified electrode and its applications in the development of solid‐state potassium and copper(II) ion sensors

Electrochemical synthesis of polycarbazole, having better stability and electrochromic activity, in dichloromethane containing 0.1 M tetrabutyl ammonium perchlorate (TBAP) is reported at 1.4 V versus Ag/AgCl. The electrochemistry based on cyclic voltammetric measurements in dichloromethane containing TBAP show redox behavior of the polymer associated to doping and de‐doping of ClO ion within the polymer interstices. The polycarbazole matrix obtained by the potentiostatic and potentiodynamic modes of electropolymerization is characterized based on scanning electron microscopy, differential calorimetry, and infrared spectroscopy. De‐doping of the polymer is studied by electrochemical reduction in TBAP‐free dichloromethane followed by incubation of the polymer film in 1 M aqueous KCl solution for 24 h. The open circuit potential (OCP) of doped and de‐doped polycarbazole modified electrode under the present experimental conditions is found to 462 and 19 mV, respectively, versus SCE in 0.1 M NH₄NO₃. The de‐doped polymer shows remarkable sensitivity and selective to Cu(II) ion compared to its sensitivity for Fe³⁺, Ni²⁺, Co²⁺, Pb²⁺, and Cu⁺ ions. A typical response of the de‐doped polymer electrode to Cu(II) ion is reported. On the other hand, ClO doped polymer is used in the development of solid‐state K⁺ ion sensors using dibenzo‐18‐crown‐6/valinomycin as a neutral carrier–based, plasticized poly vinyl chloride matrix membrane assembled over a polymer‐modified electrode. The doped polymer under this condition helps in maintaining charge stabilization across Pt/polymer and polymer/PVC interfaces. The lowest detection limit for the potassium ion sensor is 5 × 10⁻⁵ M with a slope of 58 mV/decade for valinomycin‐based sensor and 6.8 × 10⁻⁵ M with a slope of 54 mV for dibenzo‐18‐crown‐6 carriers with a wide linearity. The typical potentiometric results on the sensitivity, detection limits, and OCP to K⁺ ion recorded using present polymer are compared with the data recorded earlier using polyindole and a similar neutral carrier–based PVC membrane. A comparison on electrode kinetics of these two polymer‐modified electrodes also has been made using the data on Tafel plots to study the relative kinetic polarizability based on ion‐exchange currents. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1749–1759, 2000     

Aqueous dispersions of DBSA‐doped polyaniline: One‐pot preparation,characterization, and properties study

Aniline was polymerized in the presence of dodecylbenzene sulfonic acid (DBSA) as a functionalized protonic acid, in an aqueous medium to directly synthesize polyaniline (PANI)‐DBSA particles. DBSA acted as a dopant and a surfactant with stabilizing PANI‐DBSA dispersions by formation of strong hydrogen bonds. The NH⁺…SO interactions between the PANI chains and the DBSA appeared at 1026 cm^?1 in Fourier transform infrared (FTIR) spectrum. Elemental analysis was used to determine the degree of sulfonation (S/N ratio) of PANI chains and resulted that the sulfur‐to‐nitrogen ratio is 0.35. Thermogravimetric analysis (TGA) technique was used to analyze thermal properties of the particles and resulted that the synthesized PANI‐DBSA particles have high thermal stability. The moisture, DBSA and PANI contents of the PANI‐DBSA were estimated from TGA curve, and then the number of aniline repeating units doped with one DBSA molecule was approximately calculated. X‐ray diffraction (XRD) analysis confirmed that a chemical crosslinking reaction occurs between the PANI chains during thermal treatment of PANI‐DBSA. The morphology of PANI‐DBSA powder was investigated by scanning electron microscopy technique and showed that the PANI particles develops from round particles to a smooth surface. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Stability of polyaniline synthesized by a doping–dedoping–redoping method

Stability, including thermal stability, conductivity stability in air and after thermal treatment (100–200°C), of the polyaniline (PANI) films synthesized by a doping–dedoping–redoping method was investigated. It was found that thermogravimetric analysis (TGA) curves undergo three steps: loss of water or solvent, dedoping and decomposition, and those depend on the counterions. Compared with PANI films doped with camphor sulfonic acid (CSA) in m‐cresol, the thermal stability of the doped PANI films is improved by the new method, and thermal stability in the order of PANI–H₃PO₄ > PANI–p‐TSA > PANI–H₂SO₄ > PANI–HCl, PANI–HClO₄ > PANI–CSA was observed. The conductivity of the doped PANI films at room temperature was reduced after thermal treatment, and it is dependent of the counterions. It was found that the conductivity stability of PANI–p‐TSA and PANI–CSA is the best below 200°C. When the doped PANI films were placed in air, their conductivity decrease slowly with time due to deproton, and also depends on the counterions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 615–621, 1999     

Synthesis and characterization of soluble polypyrrole with improved electrical conductivity

Polypyrroles doped with two dopants were prepared by chemical polymerization in aqueous solutions of pyrrole monomer. The solutions contained dodecylbenzenesulfonic acid (DBSA) as a dopant, tetraethylammonium tetrafluoroborate (TEABF₄) as a codopant, and ammonium persulfate (APS) as an oxidant. The PPy composites [polypyrrole‐dodecylbenzenesulfonates (PPy‐DBS) codoped with tetrafluoroborate (BF)—PPy‐DBS‐BF] were soluble in m‐cresol, NMP, and conditionally soluble in chloroform. Cyclic voltammetry was measured to know the electrochemical property of PPy‐DBS‐BF. The maximum electrical conductivity of room temperature for PPy‐DBS‐BF is 1.18 s/cm, which is greatly higher than that of polypyrrole doped with DBS^? (0.04 s/cm). The composition and structural characterization of PPy‐DBS‐BF were inferred from elemental analysis, nuclear magnetic resonance, and Fourier transform infrared spectroscopy. Scanning electron microscopy was performed to know the morphology of PPy‐DBS‐BF. The results of UV‐Vis spectra and electron spin resonance measurements showed that polaron and bipolaron existed as charge carrier of soluble PPy‐DBS‐BF. From the temperature dependence of the electrical conductivity, it was suggested that possible conduction mechanism for soluble PPy‐DBS‐BF should be hopping conduction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2583–2590, 2002     

Effect of Co2+, Ni2+, Cu2+, or Zn2+ on properties of polyaniline nanoparticles

Uniform polyaniline (PANI) nanoparticles with typical sizes of about 50 nm were electropolymerized on indium tin oxide surfaces in the presence of Co²⁺, Ni²⁺, Cu²⁺, or Zn²⁺. According to shaping theory, we first suggest the reason forming PANI spherical particles. Their conductivity, UV‐vis spectra, FTIR spectra, X‐ray diffraction, and thermogravimetric analysis were investigated. The conductivities and crystallinity of PANI doped with these ions are higher than those of PANI doped with HCl (PANI/HCl). Both UV‐vis absorption spectra and FTIR spectra indicate the interactions between Co²⁺, Ni²⁺, Cu²⁺, or Zn²⁺ and PANI chains. TG analysis also shows that the thermal stability of PANI doped by Co²⁺, Ni²⁺, Cu²⁺, or Zn²⁺ is lower than that of PANI/HCl. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Synthesis and characterization of ferromagnetic polyaniline with conductivity in an applied magnetic field

Ferromagnetic polyaniline (PANI) with conductivity was synthesized with peroxydisulfate as an oxidant and horseradish peroxidase as a catalyst in an N′‐a‐hydroxythylpiperazine‐N′‐ethanesulfanic acid buffer solution containing aniline, HCl, and NiCl₂·6H₂O in an applied magnetic field. The result of an electron paramagnetic resonance spectrum indicated that there were unpaired electrons in the resulting product, the spin density of which was 7.60 × 10¹⁹ spins/g. The curve of the magnetization versus the magnetic field showed that PANI had soft ferromagnetic behavior at about 300 K. The saturation magnetization and coercive force of PANI were 0.033 emu/g and 5 Oe, respectively. Ultraviolet–visible and Fourier transform infrared spectra indicated that there was interaction between Ni²⁺ and PANI chains but the structure of the backbone chains of PANI synthesized in the presence of a magnetic field hardly changed compared with that of PANI synthesized without NiCl₂·6H₂O. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Structural and dielectric properties of CuCl2 and ZnCl2 doped polyaniline

This article addresses the synthesis and characterization of polyaniline (PANI) both in pure and doped forms with various levels of CuCl₂ and ZnCl₂ in HCl medium where ammonium persulphate was used as an oxidant. Synthesized polymeric materials were characterized spectroscopically (UV‐visible spectroscopy, Fourier transform infrared spectroscopy, and Atomic absorption spectroscopy), thermally (Differential scanning calorimetry), and morphologically (Scanning electron microscopy). Free adsorption energy was calculated via Langmuir adsorption isotherm based on the quantities of Cu²⁺ and Zn²⁺ cations in both pre‐ and post‐ polymerization process where it was found that Cu²⁺ and Zn²⁺ are adsorbed physically on PANI surface. The dielectric measurements as a function of frequency and temperature showed that conductivity decreased with increasing doping levels of metal cations at high temperatures. POLYM. COMPOS., 31:1862–1868, 2010. © 2010 Society of Plastics Engineers.     

Studies on acrylate copolymer soap‐free waterborne coatings crosslinked by metal ions

Acrylate copolymers containing hydrophobic monomers (methyl methacrylate, butyl acrylate, styrene, or divinyl benzene) and hydrophilic monomer (acrylic acid) were synthesized by solution polymerization, and neutralized to form the soap‐free hydrosol. The waterborne coating was prepared from the hydrosol crosslinked by M(NH₃) (M²⁺ was Zn²⁺ , Cu²⁺, Ni²⁺ or Co²⁺). ¹³C‐NMR analysis was used to identify the copolymer. The result of GPC showed that the molecular weight of the copolymer was within the range of thermosetting resin for coating. The factors affecting the crosslinking degree of the coating films were studied by DSC and gravimetric analysis. The results indicated that the appropriate crosslinking agent was Zn(NH₃), and the optimum curing condition was heating at 80°C for 30 min. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 91–96, 1999     

Interaction between iodine and ethyl cellulose

Interaction between iodine and ethyl cellulose was investigated by immersing ethyl cellulose membranes in aqueous iodine–iodide solution (iodine doping) and incorporating iodine in the solution from which the membrane was cast. Oxygen and nitrogen permeabilities in iodine‐doped ethyl cellulose decrease with an increase in the concentration of iodine in the dopant solution up to 0.003 mol L⁻¹ and increase sharply at higher iodine concentrations, and ultraviolet–visible and far‐infrared spectra indicate formation of a charge transfer complex. Differential scanning calorimetry of both types of membrane shows changes in the characteristic phase transitions of ethyl cellulose after iodine treatment, including the crystal–liquid crystal transition that has been reported to occur in ethyl cellulose. Further evidence for liquid crystal phases has been found from circular dichroism. X‐ray photoelectron spectroscopy of iodine‐doped ethyl cellulose films indicates that the iodine is present in two different chemical states, probably l and l₂. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1303–1314, 1999     

Synthesis and properties of metal complexes of radiation grafted carboxyl containing copolymers

Metal complexes of copolymers based on polyacrylic acid radiation grafted onto films of low density polyethene were prepared by complex‐forming with solutions of salts of FeCl₃.6H₂O, CuCl₂.2H₂O, CoCl₂.6H₂O, NiCl₂.6H₂O, VOSO₄.5H₂O, Na₂MoO₄.2H₂O, Na₂WO₄.2H₂O, and NH₄VO₃. The introduction of metal ions was found to depend mainly on the degree of grafting of acrylic acid and was from 0.5 to 5.0 mass%. These complexes were characterized by IR, UV spectroscopy, and EPR. The moisture content of the materials obtained changed linearly with the degree of grafting of acrylic acid and was from 9.0 to 80.0%. The introduction of the MoO₂²⁺ and WO₂²⁺ towards carboxylic groups lead to increasing the thermal stability of the metal complexes of the copolymers compared to the initial grafted films. The modified acrylate copolymers were studied in reactions of catalytic oxidation of cyclohexene. The activities of the complexes obtained towards cyclohexene epoxidation can be arranged in the following order: PAA–MoO₂²⁺ > PAA–VO²⁺ > PAA–VO > PAA–WO₂²⁺, while for the reaction of cyclohexene hydroxylation the order was—PAA–Co²⁺ > PAA–Cu²⁺ > PAA–Fe³⁺ > PAA–Ni²⁺. The contents of cyclohexene oxide and 2‐cyclohexene‐1‐ol reached 38.5% and 7.5%, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1658–1665, 2006     

Copper chloride‐doped polyaniline/multiwalled carbon nanotubes nanocomposites: Superior electrode material for supercapacitor applications

In this study, copper chloride (CuCl₂)‐doped polyaniline (PANI)/multiwalled carbon nanotubes (MWCNTs) nanocomposite (PANI C2 CNT), CuCl₂‐doped PANI (PANI C2) and pure PANI was synthesized by in situ oxidative polymerization method, using ammonium peroxodisulfate as oxidant in HCl medium. These composites were investigated as electrode materials for supercapacitors. The interaction of metal cation (Cu²⁺) with PANI was confirmed by Fourier transform infrared spectroscopy. The morphology of the composites was characterized by field‐emission scanning electron microscopy and high‐resolution transmission electron microscopy analysis. Electrochemical characterizations of the materials were carried out by three electrode probe method, where platinum and saturated standard calomel electrode were used as counter and reference electrode, respectively. 1 M KCl solution was used as electrolyte for all the electrochemical characterizations. The transition metal ion doping enhanced the electrochemical properties of the conducting polymer. Among all the composites, CuCl₂‐doped PANI/MWCNT showed highest specific capacitance value of 724 F/g at 10 mV s⁻¹ scan rate. The Nyquist plot of the polymeric materials showed low equivalent series resistance of the electrode materials. Thermal stability of the composites was examined by thermogravimetric analysis.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Effect of some anions of some nickel salts on the aqueous polymerization of methyl methacrylate

The aqueous polymerization of methyl methacrylate in the absence and in the presence of some anions of nickel salts was carried out at temperatures of 40°C, 50°C, and 60°C using sodium bisulfite as initiator. The nitrate anion (NO) was found to have the highest catalytic effect and resulted in polymers having the least average molecular weights, while the sulfate anion (SO) was found to have the least catalytic effect and resulted in polymers having the highest average molecular weights. The apparent activation energy for the polymerization process was found to be 4.3, 3.6, 3.8, and 4.8 × 10⁴ J/mol in the absence and in the presence of Ni(NO₃)₂, NiCl₂, and NiSO₄ containing the same amount of nickel (0.00587 g). ¹³C-NMR spectra for the polymers obtained in the absence and in the presence of different nickel anions were found to result in nearly the same tacticity.     

Electrical and structural analysis of conductive polyaniline/polyimide blends

Conducting films of dodecylbenzenesulfonic (DBSA)‐doped polyaniline/polyimide (PANI/PI) blends with various compositions were prepared by solvent casting followed by a thermal imidization process. Electrical and physical properties of the blends were characterized by infrared spectroscopy, an X‐ray diffraction technique, thermal analysis, a UV‐vis spectrophotometer, a dielectrometer, and conductivity measurements. The blends exhibited a relatively low percolation threshold of electrical conductivity at 5 wt % PANI content and showed higher conductivity than that of pure DBSA‐doped PANI when the PANI content exceeded 20 wt %. A lower percolation threshold and a lower compatibility was shown between the two components in the blends than those of PANI–camphorsulfonic acid/polyamic acid (PANI–CSA/PAA). A well‐defined layered structure due to the alignment of the long alkyl chain dopant perpendicular to the PANI main chain was evidenced by WAXD spectra. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2169–2178, 1999     

Syntheses and properties of carboxymethyl chitosan/urea–formaldehyde snake‐cage resins

A series of novel snake‐cage resins were synthesized using carboxymethyl chitosan (CM‐CTS) as the snake resin and urea–formaldehyde resin (UF) as the cage resin. Such factors as the optimal synthesis conditions, content of the crosslinking agent, and sorption capacities for metal ions of the above‐mentioned resins were investigated. The experimental results show that these resins have appropriate swelling properties and good mechanical stability. They do not run off in water, HCl, and NaOH aqueous solutions. To form a stable network system, NH₄Cl was used as a crosslinking agent to crosslink urea and formaldehyde in synthesis. The sorption experiment showed that the sorption properties of the resins in the presence of the crosslinking agent NH₄Cl are better than those without a crosslinking agent. The investigation of the FTIR spectra indicated that the chelate groups, such as —OH, —CO and NHCH₂CO, in snake‐resin molecules participated in the coordination with the metal ions, but the —C?O bonds in the cage resin UF did not. The snake resin CM‐CTS in the snake‐cage resins was the major contributor of sorption. The sorption dynamics showed that the sorption was controlled by liquid film diffusion. The isotherms can be described by Freundlich and Langmuir equations. The saturated sorption capacities of the resins for Cu²⁺, Ni²⁺, Zn²⁺, and Pb²⁺ were 1.48, 0.78, 0.13, and 0.02 mmol g^?1, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 310–317, 2002; DOI 10.1002/app.10331     

Preparation,characterization, and dynamic adsorption–desorption studies on polypyrrole encapsulated TiO2 nanoparticles

Binary doped polypyrrole (PPy) encapsulated Titania (TiO₂) nanoparticles were prepared by oxidative polymerization using FeCl₃ as oxidant in presence of camphorsulfonic acid (CSA) as surfactant. Both FeCl₃ (oxidant) and camphorsulfonic acid (surfactant) also act as dopant and hence thus prepared polypyrrole/Titania (TiO₂@PPy) is termed as binary doped nanocomposite i.e. FeCl₃ dopes polypyrrole by oxidation mechanism while camphorsulfonic acid dopes polypyrrole by protonic doping mechanism. The TiO₂@PPy coreshell nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), thermogravimetry, differential scanning calorimetry (DSC), field emission‐scanning electron microscopy (FE‐SEM), and inductance‐capacitance‐resistance (LCR) measurements. The results indicated that the structural and electrical properties of the TiO₂@PPy coreshell nanocomposites were significantly influenced by the extent of TiO₂ nanoparticles loading of polypyrrole. The direct current (DC) electrical conductivity of the as‐prepared TiO₂@PPy coreshell nanocomposites was higher than that of PPy. As‐prepared TiO₂@PPy coreshell nanocomposites were also studied for their dielectric losses for alternating current (AC) which is useful characteristic for their application in the fabrication of charge storing devices. TiO₂@PPy coreshell nanocomposites showed synergistic effect of combining components in improving their alcohol sensing properties. This improvement may be attributed to the adsorption on and desorption from alcohols TiO₂@PPy interface of the nanocomposites and alcohol vapors causing decrease in depletion region. The TiO₂@PPy coreshell nanocomposites were observed to show better reproducibility of electrical conductivity and fast self‐recovery during the alcohol vapor sensing process. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43411.     

Electrical resistivity and magnetoresistivity of protonic acid (h2SO4 and HCl)‐doped polyaniline at low temperature

Electrical‐transport properties of protonic acid (H₂SO₄ and HCl)‐doped polyaniline (PANI) in an aqueous ethanol medium were investigated in the temperature range 1.8 K ≤ T ≤ 300 K and in a magnetic field up to 8 T. The room‐temperature resistivity of HCl‐doped PANI is larger than that of H₂SO₄‐doped PANI. The resistivity ratios ρ_r = ρ(1.8 K)/ρ(300 K) of the samples are high. The samples in the insulating region show a crossover from a Mott to an Efros–Shklovskii variable range hopping conduction at T = 9.8 K for H₂SO₄‐doped PANI and 8.5 K for HCl‐doped PANI. The magnetoresistivity of these samples is also explained by the variable range hopping theory. The different physical parameters were calculated from the experimental data. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1480–1486, 2000     

Doping effects of cerium ion on structure and electrochemical properties of polyaniline

Polyaniline (PANI)/Ce³⁺ and PANI/Ce⁴⁺ composites were successfully prepared by in situ polymerization in an aqueous solution of poly(2‐acrylamido‐2‐methylpropane sulfonic acid) and characterized by Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, X‐ray photoelectron spectroscopy, SEM, TEM and electrochemical methods. The results showed that the PANI/Ce ion composites had a high degree of sphericity, high electrical conductivity and good electrochemical performance. The conductivity of PANI/Ce(NO₃)₃ reaches a maximum of 46.76 S cm^?1 at 20 wt% of Ce(NO₃)₃. It is increased by 377% by comparison with that of pure PANI. In particular, the polarization results showed that the corrosion current density (0.47 µA cm^?2) and the inhibition efficiency (97%) of PANI/Ce(NO₃)₃ were better than the results for PANI and PANI/Ce(SO₄)₂ composite. This suggested that the PANI/Ce(NO₃)₃ composite has promising applications in conductive materials, anticorrosion coatings and other related fields. © 2017 Society of Chemical Industry     

Synthesis,characterization, and thermodynamic properties of poly(3‐mesityl‐2‐hydroxypropyl methacrylate)

Poly(3‐mesityl‐2‐hydroxypropyl methacrylate) (PMHPMA) was synthesized in a 1,4‐dioxane solution with 2,2′‐azobisisobutyronitrile as the initiator at 60°C. The homopolymer and its monomer were characterized with ¹H‐ and ¹³C‐NMR, Fourier transform infrared, differential scanning calorimetry, thermogravimetric analysis, size exclusion chromatography, and elemental analysis techniques. According to size exclusion chromatography analysis, the number‐average molecular weight, weight‐average molecular weight, and polydispersity index of PMHPMA were 65,864 g/mol, 215,375 g/mol, and 3.275, respectively. According to thermogravimetric analysis, the carbonaceous residue value of PMHPMA was 14% at 500°C. The values of the specific retention volume, adsorption enthalpy, sorption enthalpy, sorption free energy, sorption entropy, partial molar free energy, partial molar heat of mixing, weight fraction activity coefficient of solute probes at infinite dilution (Ω), and Flory–Huggins interaction parameter (χ) were calculated for the interactions of PMHPMA with selected alcohols and alkanes by the inverse gas chromatography method at various temperatures. According to Ω and χ, selected alcohols and alkanes were nonsolvents for PMHPMA at 423–453 K. Also, the solubility parameter of PMHPMA (δ₂) was found to be 24.24 and 26.33 (J/cm³)^0.5 from the slope and intercept of (δ/RT) ? χ/V₁ = (2δ₂/RT)δ₁ ? δ/RT at 443 K, respectively [where δ₁ is the solubility parameter of the probe, V₁ is the molar volume of the solute, T is the column temperature (K), and R is the universal gas constant]. The glass‐transition temperature of PMHPMA was found to be 386 and 385 K by inverse gas chromatography and differential scanning calorimetry techniques, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 101–109, 2006     

Polyaniline/polyimide blends as gas sensors and electrical conductivity response to CO–N2 mixtures

The effects of dopant type, doping level, polyimide (PI) content and temperature on electrical conductivity response of polyaniline (PANI) and polyaniline/polyimide (PANI/PI) blends to CO–N₂ gas mixtures were systematically investigated. At the same doping level, HNO₃‐doped PANI has a greater electrical conductivity response and sensitivity towards CO than that of camphor sulfonic acid (CSA)‐doped PANI because the former has a more ordered structure. The interaction mechanism between CO and PANI is proposed to occur at the attack site, ? N?H? or the amine nitrogen where CO withdraws an electron. Addition of PI causes a small change in electrical conductivity under atmospheric conditions when PI content is below the percolation threshold value of 55 wt%. Addition of PI reduces brittleness and improves electrical conductivity sensitivity towards CO; the effect is more pronounced at higher temperatures. Copyright © 2005 Society of Chemical Industry     

On Structure,Optical Properties and Photodegradated Ability of Aurivillius‐Type Bi3TiNbO9 Nanoparticles

Bi₃TiNbO₉ nanoparticles with an acceptor dopant of Ni²⁺ ion were prepared by the conventional Pechini sol–gel synthesis. The X‐ray polycrystalline diffraction measurements (XRD) and the Rietveld refinements of Bi₃TiNbO₉ samples were completed. The surface property of Bi₃TiNbO₉ nanoparticles was investigated by transmission electron microscope, scanning electron microscope), and N₂ adsorption–desorption isotherms. Bi₃TiNbO₉ nanoparticles showed an optical band gap with energy of 3.1 eV in the UV region. While the Ni²⁺‐doping could greatly reduce the band energy of Bi₃TiNbO₉:xNi²⁺ nanoparticles to 2.79 eV (x = 0.05) and 2.61 eV (x = 0.1). This indicates that the Ni‐doped samples could be excited by UV–visible light. The photocatalytic abilities were tested by the photodegradation on methylene blue solution (MB) and phenol solutions excited by visible light. Accordingly, the photocatalytic activity was improved by the Ni‐doping in B‐sites in this Aurivillius‐type structure. The results concluded that Bi₃TiNbO₉:Ni²⁺ would be a possible candidate as a visible light‐driven photocatalyst. The effective photocatalysis was discussed on the structure characteristic and experiment such as polarized Aurivillius (Bi₂O₂)²⁺ layers, luminescence, and decay lifetimes, etc.