Thermal decomposition of solid state compounds of lanthanide and yttrium benzoates in CO2 atmosphere

Solid-state Ln-Bz compounds, where Ln stands for trivalent lanthanides and Bz is benzoate have been synthesized. Simultaneous thermogravimetric and differential thermal analysis in a CO2 atmosphere were used to study the thermal decomposition of these compounds.

Defects in Persistent Luminescence Materials

Persistent luminescence materials can store energy from solar radiation or artificial lighting and release it over a period of several hours without a continuous excitation source. These materials are widely used to improve human safety in emergency and traffic signalization. They can also be utilized in novel applications including solar cells, medical diagnostics, radiation detectors and structural damage sensors. The development of these materials is currently based on methods based on trial and error. The tailoring of new materials is also hindered by the lack of knowledge on the role of their intrinsic and extrinsic lattice defects in the appropriate mechanisms. The goal of this work was to clarify the persistent luminescence mechanisms by combining ab initio density functional theory (DFT) calculations with selected experimental methods. The DFT approach enables a full control of both the nature of the defects and their locations in the host lattice. The materials studied in the present work, the distrontium magnesium disilicate (Sr₂MgSi₂O₇) and strontium aluminate (SrAl₂O₄) are among the most efficient persistent luminescence hosts when doped with divalent europium Eu²⁺ and co-doped with trivalent rare earth ions R³⁺ (R: Y, La-Nd, Sm, Gd-Lu). The polycrystalline materials were prepared with the solid state method and their structural and phase purity was confirmed by X-ray powder diffraction. Their local crystal structure was studied by high-resolution transmission electron microscopy. The crystal and electronic structure of the nondoped as well as Eu²⁺, R^2+/3+ and other defect containing materials were studied using DFT calculations. The experimental trap depths were obtained using thermoluminescence (TL) spectroscopy. The emission and excitation of Sr₂MgSi₂O₇:Eu²+,Dy³⁺ were also studied. Significant modifications in the local crystal structure due to the Eu²⁺ ion and lattice defects were found by the experimental and DFT methods. The charge compensation effects induced by the R³⁺ co-doping further increased the number of defects and distortions in the host lattice. As for the electronic structure of Sr₂MgSi₂O₇ and SrAl₂O₄, the experimental band gap energy of the host materials was well reproduced by the calculations. The DFT calculated Eu²⁺ and R^2+/3+ 4fn as well as 4f^n-15d¹ ground states in the Sr₂MgSi₂O₇ band structure provide an independent verification for an empirical model which is constructed using rather sparse experimental data for the R³⁺ and especially the R²⁺ ions. The intrinsic and defect induced electron traps were found to act together as energy storage sites contributing to the materials’ efficient persistent luminescence. The calculated trap energy range agreed with the trap structure of Sr₂MgSi₂O₇ obtained using TL measurements. More experimental studies should be carried out for SrAl₂O₄ to compare with the DFT calculations. The calculated and experimental results show that the electron traps created by both the rare earth ions and vacancies are modified due to the defect aggregation and charge compensation effects. The relationships between this modification and the energy storage properties of the solid state materials are discussed.

Influenza in children – Diagnosis, treatment and prevention

Background: The burden of influenza on children is substantial. Although mortality rates are low, the incidence of influenza is highest in children, among whom also complications are frequent. A more accurate recognition of influenza in children could enable the rational use of antiviral drugs and help to avoid unnecessary courses of antibiotics. Limited data exists on the efficacy of oseltamivir treatment and the trivalent inactivated influenza vaccine (TIV) in children. Aims and methods: We sought for signs and symptoms that could help clinicians to diagnose influenza on clinical grounds in a case-control study in children <13 years of age. We further assessed the feasibility of different diagnostics methods during the early stage of the illness in children aged 1-3 years. The efficacy of early oseltamivir treatment (started <24h from the onset of symptoms) was evaluated in a randomized controlled trial (RCT) conducted in children 1-3 years of age, and the effectiveness of TIV to prevent laboratory-confirmed influenza was determined in a prospective, observational cohort study conducted among children aged 9 months to 3 years of age. Results: Fever was the only symptom predicting influenza in children. The sensitivity of conventionally used laboratory methods to detect influenza during the first 24h of illness was 92%. The sensitivity of the influenza rapid test in the same setting was 90% for influenza A and 25% for influenza B. Early oseltamivir treatment shortened the duration of the illness in children with influenza A by 3.5-4.0 days, but no efficacy was observed against influenza B. The effectiveness of TIV was 84% against the wellmatched influenza A, while no effectiveness against the mismatched influenza B was observed. Conclusions: Laboratory diagnostics are needed for a reliable diagnosis of influenza in children and were found sensitive already during the early stage of the illness. Early oseltamivir treatment was highly effective against influenza A, but no efficacy was seen against influenza B. TIV is effective also in young children if a good match between the vaccine and circulating strain is achieved.

Elektrolyyttinen nanopinnoitus

Diplomityö on osa Savonia-amk:n hallinnoimaa ENC- pinnoitushanketta, jossa tutkitaan uuden teknologian elektrolyyttisiä kromi (III) -nanopinnoitteita. Tavoitteena oli selvittää uudella menetelmällä saavutettavat parannukset pinnoitteiden mekaanisiin ominaisuuksiin. Työ toteutettiin rakentamalla pinnoitustutkimuksen toimintaympäristö osaksi Savo-nia-amk:n materiaalitekniikan laboratorioita sekä tutkimalla eri koe- ja sovelluspinnoitteiden mekaanisia ominaisuuksia eri pinnoitusparametreilla. Työssä tutkittiin, miten nanopartikkelit sekä erilaiset pinnoitusparametrit vaikuttavat kromipinnoitteiden rakenteeseen sekä mekaaniseen suorituskykyyn.

Electrochemical Treatment of Wastewaters

Electrocoagulation is a process in which wastewater is treated under electrical current. Coagulant is formed during the process through the metal anode dissolution to respective ions which react with hydroxyl ions released in cathode. These metal hydroxides form complexes with pollutant ions. Pollutants are removed among metal hydroxide precipitates. This study was concentrated on describing chemistry and device structures in which electrochemical treatment operations are based on. Studied pollutants were nitrogen compounds, sulphate, trivalent and pentavalent arsenic, heavy metals, phosphate, fluoride, chloride, and bromide. In experimental part, removal of ammonium, nitrate, and sulphate during electrochemical treatment was studied separately. Main objective of this study was to find suitable metal plate material for ammonium, nitrate, and sulphate removal, respectively. Also other parameters such as pH of solution, concentration of pollutant and sodium chloride, and current density were optimized. According to this study the most suitable material for ammonium and sulphate removal by electrochemical treatment was stainless steel. Respectively, iron was the optimum material for nitrate removal. Rise in the pH of solution at the final stage of electrochemical treatment of ammonium, nitrate, and sulphate was detected. Conductivities of solutions decreased during ammonium removal in electrochemical processes. When nitrate and sulphate were removed electrochemically conductivities of solutions increased. Concentrations of residual metals in electrochemically treated solutions were not significant. Based on this study electrochemical treatment processes are recommended to be used in treatment of industrial wastewaters. Treatment conditions should be optimized for each wastewater matrix.

NIR-Vis Up-Conversion Luminescence in the Yb3+,Er3+ Doped Y2O2S, ZrO2, and NaYF4 Nanomaterials

Since the discovery of the up-conversion phenomenon, there has been an ever increasing interest in up-converting phosphors in which the absorption of two or more low energy photons is followed by emission of a higher energy photon. Most up-conversion luminescence materials operate by using a combination of a trivalent rare earth (lanthanide) sensitizer (e.g. Yb or Er) and an activator (e.g. Er, Ho, Tm or Pr) ion in a crystal lattice. Up-converting phosphors have a variety of potential applications as lasers and displays as well as inks for security printing (e.g. bank notes and bonds). One of the most sophisticated applications of lanthanide up-conversion luminescence is probably in medical diagnostics. However, there are some major problems in the use of photoluminescence based on the direct UV excitation in immunoassays. Human blood absorbs strongly UV radiation as well as the emission of the phosphor in the visible. A promising way to overcome the problems arising from the blood absorption is to use a long wavelength excitation and benefit from the up-conversion luminescence. Since there is practically no absorption by the whole-blood in the near IR region, it has no capability for up-conversion in the excitation wavelength region of the conventional up-converting phosphor based on the Yb3+ (sensitizer) and Er3+ (activator) combination. The aim of this work was to prepare nanocrystalline materials with high red (and green) up-conversion luminescence efficiency for use in quantitative whole-blood immunoassays. For coupling to biological compounds, nanometer-sized (crystallite size below 50 nm) up-converting phosphor particles are required. The nanocrystalline ZrO2:Yb3+,Er3+, Y2O2S:Yb3+,Er3+, NaYF4:Yb3+,Er3+ and NaRF4-NaR’F4 (R: Y, Yb, Er) materials, prepared with the combustion, sol-gel, flux, co-precipitation and solvothermal synthesis, were studied using the thermal analysis, FT-IR spectroscopy, transmission electron microscopy, EDX spectroscopy, XANES/EXAFS measurements, absorption spectroscopy, X-ray powder diffraction, as well as up-conversion and thermoluminescence spectroscopies. The effect of the impurities of the phosphors, crystallite size, as well as the crystal structure on the up-conversion luminescence intensity was analyzed. Finally, a new phenomenon, persistent up-conversion luminescence was introduced and discussed. For efficient use in bioassays, more work is needed to yield nanomaterials with smaller and more uniform crystallite sizes. Surface modifications need to be studied to improve the dispersion in water. On the other hand, further work must be carried out to optimize the persistent up-conversion luminescence of the nanomaterials to allow for their use as efficient immunoassay nanomaterials combining the advantages of both up-conversion and persistent luminescence.

Development of a Glycocluster Adjuvant Mimicking Natural Yeast beta-(1,2)-Structures

Allergy is characterized by T helper (Th) 2-type immune response after encounter with an allergen leading to subsequent immunoglobulin (Ig) E-mediated hypersensitivity reaction and further allergic inflammation. Allergen-specific immunotherapy (SIT) balances the Th2-biased immunity towards Th1 and T regulatory responses. Adjuvants are used in allergen preparations to intensify and modify SIT. β-(1,2)-oligomannoside constituents present in Candida albicans (C. albicans) cell wall possess Th1-type immunostimulatory properties. The aim of this thesis was to develop a β-(1,2)-linked carbohydrate compound with known structure and anti-allergic properties to be applied as an adjuvant in SIT. First the immunostimulatory properties of various fungal extracts were studied. C. albicans appeared to be the most promising Th1-inducing extract, which led to the synthesis of various mono- or divalent oligomannosides designed on the basis of C. albicans. These carbohydrates did not induce strong cytokine production in human peripheral blood mononuclear cell (PBMC) cultures. In contrast to earlier reports using native oligosaccharides from C. albicans, synthetic -(1,2)-linked mannotetraose did not induce any tumor necrosis factor production in murine macrophages. Next, similarities with synthesized divalent mannosides and the antigenic epitopes of β-(1,2)-linked C. albicans mannan were investigated. Two divalent compounds inhibited specific IgG antibodies binding to below 3 kDa hydrolyzed mannan down to the level of 30–50% showing similar antigenicity to C. albicans. Immunomodulatory properties of synthesized carbohydrate assemblies ranging from mono- to pentavalent were evaluated. A trivalent acetylated dimannose (TADM) induced interleukin-10 (IL-10) and interferon-γ responses. TADM also suppressed birch pollen induced IL-4 and IL-5 responses in allergen (Bet v) stimulated PBMCs of birch pollen allergic subjects. This suppression was stronger with TADM than with other used adjuvants, immunostimulatory oligonucleotides and monophosphoryl lipid A. In a murine model of asthma, the allergen induced inflammatory responses could also be suppressed by TADM on cytokine and antibody levels.

Environmental assessment and biomonitoring of the Twelve Mile Creek watershed, Niagara Peninsula, Ontario

In light of the heavy reliance of the people of the Niagara Peninsula on the T\\'elve Mile Creek (TMC) watershed for recreational activities and for municipal and industrial uses ( e.g., drinking water, shipping and discharge of effluents), it was deemed prudent to assess the envirol1tnental health of the system by analysing the sediments total and exchangeable metal, and TPH contents. The MOEE has set guidelines with limits for the protection and management of aquatic sediments, and the sediments from the headwaters of the TMC have total metal and TPH (subset of O&G) contents well below the lower provincial limits. Areas of environmental concern where total metal contents in sediments, either individually or collectively, exceed the guideline, are the south side of Lake Gibson, the Old WeIland Canal, a segment of TMC just south of the QEW and Martindale Pond. The total metal content of sediments does not in all instances identify areas of biological concern. Instead, it has been found that the exchangeable metal fraction of sediments is a better indicator of metal availability and thus potential accumulation in organisms. In some instances, the exchangeable metal fraction agrees with the total metal fraction defining areas of environmental concern, but it does vary from site to site reflecting the natural variability of the ambient environment. Overall, the exchangeable metal fraction of sediments appears to be a better indicator of anthropogenic pollution and ecosystem impact. A histochemical study of Anodon.ta sp., Elliptio sp. and zebra mussels (Dreissena polyn'101pha) was done in conjunction with passive biomonitoring of zebra and quagga mussels (Dreissena bugensis) from the Twelve Mile Creek watershed and Lake 51. Clair (Jeanette's Creek, Chatham, Ontario). The highest concentrations of divalent metals such as Cu, Ni, Cd, and Zn, and trivalent Al appear to accumulate in gill and kidney tissues. Metal contents of organ tissues in Anodonta sp. vary with size class. Organ metal content varies among size classes, thus requiring consideration of size in biomonitoring studies. Shucked zebra and quagga mussel tissues, exhibited similar size class to Al content trends. In addition they reflected the Al content trends of top (approximately 10 cm) most sediments in the Twelve Mile Creek watershed. Quagga mussels appear to have higher Al concentrations than zebra mussels, thus suggesting that quagga mussels may be better passive biomonitors of AI. Cd content in zebra mussel tissues, seemed to increase with size class trends. This was not demonstrated in the quagga mussel tissues. This suggests that Cd may be regulated by quagga mussels and not by zebra mussels, and that zebra mussels may be better passivebiomonitors of Cd than are quagga mussels. Zebra mussel, quagga mussel, Anodonta sp., and Elliptio sp. were used in a two part, active (translocated) biomonitoring study of the Twelve Mile Creek watershed. There was no statistical difference in death rates between zebra and quagga mussels after 65 days of biomonitoring. However there does appear to be a difference of death rates between sites. Unfortunately the data base did not permit us to differentiate between sites. Relative to Port Colborne Harbour (Port Colborne, Ontario), the Twelve Mile Creek watershed appears to be elevated in bioavailable AI. An area near the terminus of the Twelve Mile Creek appears to be an area of environmental concern since mussels seemed to have accumulated relatively large concentrations of Cd, Zn, and Pb. In addition to possible metal loading from a nearby outfalls, or possible upstream outfalls, road salt runoff from storm sewers may have contributed to metal accumulation through cation exchanges processes. Similar trends in cumulative quagga mussel metal concentrations during the two time periods (65 and 159 days), suggest that quagga mussels may reach equilibrium within 65 days of translocation. Differences in bioaccumulated metal concentrations of the two dreissenid species demonstrate that active biomonitoring studies must use a variety of organisms to adequately assess the environmental situation of specific waterways and/or bodies.

Investigation into the determination of arsenic by direct current plasma atomic emission spectrometer

Improvements have been made on the currently available hydride generator system manufactured by SpectraMetrics Incorporated, because the system was found to be unsatisfactory with respect to the following: 1. the drying agent, anhydrous calcium chloride, 2. the special sample tube, 3. the direction of argon flow through the Buchner funnel when it came to dealing with real sample, that is, with reference only to aqueous extracts of soil samples. Changes that were made on the system included the replacement of anhydrous calcium chloride with anhydrous calcium sulphate and the replacement of the special sample tube with a modified one made from silica. Re-directing the flow of argon through the top of the Buchner funnel appeared to make the system compatible with aqueous extracts of soil samples. The interferences from 1000 ~g/mL of nickel(II) , cobalt(II), iron(III), copper(II) have been eliminated with the aid of 1.4 M hydrochloric acid and 1% (weight/volume) L-cystine. Greater than 90% recovery of 0.3 ~g/mL arsenic signal was achieved in each case. Furthermore, 103% of arsenic signal was accomplished in the presence of 1000 ~g/mL cadmium with 5 M Hel. tVhen each of the interferents was present in solution at 1000 ppm, a recovery of 85% was achieved by using 5 M hydrochloric acid and 3% (weight/volume) L-cystine. Without L-cystine and when 1.4 M hydrochloric acid was used, the recoveries were 0% (Ni), 0% (Co), 88% (Fe), 15% (Cu), 18% (Cd). Similarly, a solution containing 1000 ppm of each interferent gave a zero percent recovery of arsenic. The reduction of trivalent and pentavalent arsenic at a pH less than one has also been investigated and shown to be quantitative if peak areas are measured. The reproducibility determination of a 0.3 Vg/mL standard arsenic solution by hydride generation shows a relative standard deviation of 3.4%. The detection limits with and without Porapak Q have been found to be 0.6 ng/mL and 1.0 ng/mL, respectively.

POCN-type Pincer Complexes of NiII and NiIII : synthesis, reactivities, catalytic activities and physical properties

Cette thèse décrit la synthèse, la caractérisation, les réactivités, et les propriétés physiques de complexes divalents et trivalents de Ni formés à partir de nouveaux ligands «pincer» de type POCN. Les ligands POCN de type amine sont préparés d’une façon simple et efficace via l’amination réductrice de 3-hydroxybenzaldéhyde avec NaBH4 et plusieurs amines, suivie par la phosphination de l’amino alcool résultant pour installer la fonction phosphinite (OPR2); le ligand POCN de type imine 1,3-(i-Pr)2PC6H4C(H)=N(CH2Ph) est préparé de façon similaire en faisant usage de PhCH2NH2 en l’absence de NaBH4. La réaction de ces ligands «pincer» de type POCN avec NiBr2(CH3CN)x en présence d’une base résulte en un bon rendement de la cyclométalation du lien C-H situé en ortho aux fonctions amine et phosphinite. Il fut découvert que la base est essentielle pour la propreté et le haut rendement de la formation des complexes «pincer» désirés. Nous avons préparé des complexes «pincer» plan- carrés de type POCN, (POCNRR΄)NiBr, possédant des fonctions amines secondaires et tertiaires qui démontrent des réactivités différentes selon les substituants R et R΄. Par exemple, les complexes possédant des fonctions amines tertiaires ArCH2NR2 (NR2= NMe2, NEt2, and morpholinyl) démontrent des propriétés rédox intéressantes et pourraient être convertis en leurs analogues trivalents (POCNR2)NiBr2 lorsque réagis avec Br2 ou N-bromosuccinimide (NBS). Les complexes trivalents paramagnétiques à 17 électrons adoptent une géométrie de type plan-carré déformée, les atomes de Br occupant les positions axiale et équatoriale. Les analyses «DSC» et «TGA» des ces composés ont démontré qu’ils sont thermiquement stables jusqu’à ~170 °C; tandis que la spectroscopie d’absorption en solution a démontré qu’ils se décomposent thermiquement à beaucoup plus basse température pour regénérer les complexes divalents ne possédant qu’un seul Br; l’encombrement stérique des substitutants amines accélère cette route de décomposition de façon significative. Les analogues NMe2 et N(morpholinyl) de ces espèces de NiIII sont actifs pour catalyser la réaction d’addition de Kharasch, de CX4 à des oléfines telles que le styrène, tandis qu’il fut découvert que l’analogue le moins thermiquement stable (POCNEt2)Ni est complètement inerte pour catalyser cette réaction. Les complexes (POCNRH)NiBr possédant des fonctions amines secondaires permettent l’accès à des fonctions amines substituées de façon non symétrique via leur réaction avec des halogénures d’alkyle. Un autre avantage important de ces complexes réside dans la possibilité de déprotonation pour préparer des complexes POCN de type amide. De telles tentatives pour déprotoner les fonctions NRH nous ont permis de préparer des espèces dimériques possédant des ligands amides pontants. La nature dimérique des ces complexes [P,C,N,N-(2,6-(i-Pr)2PC6H3CH2NR)Ni]2 (R= PhCH2 et Ph) fut établie par des études de diffraction des rayons-X qui ont démontré différentes géométries pour les cœurs Ni2N2 selon le substituant N : l’analogue (PhCH2)N possède une orientation syn des substitutants benzyles et un arrangement ressemblant à celui du cyclobutane du Ni et des atomes d’azote, tandis que l’analogue PhN adopte un arrangement de type diamant quasi-planaire des atomes du Ni et des atomes d’azote et une orientation anti des substituants phényles. Les espèces dimériques ne se dissocient pas en présence d’alcools, mais elles promouvoient l’alcoolyse catalytique de l’acrylonitrile. De façon intéressante, les rendements de ces réactions sont plus élevés avec les alcools possédant des fonctions O-H plus acides, avec un nombre de «turnover» catalytique pouvant atteindre 2000 dans le cas de m-cresol. Nous croyons que ces réactions d’alcoolyse procèdent par activation hétérolytique de l’alcool par l’espèce dimérique via des liaisons hydrogènes avec une ou deux des fonctions amides du dimère. Les espèces dimériques de Ni (II) s’oxydent facilement électrochimiquement et par reaction avec NBS ou Br2. De façon surprenante, l’oxydation chimique mène à l’isolation de nouveaux produits monomériques dans lesquels le centre métallique et le ligand sont oxydés. Le mécanisme d’oxydation fut aussi investigué par RMN, «UV-vis-NIR», «DFT» et spectroélectrochimie.

INVESTIGATIONS ON THE SOLVENT EXTRACTION AND LUMINESCENCE OF LANTHANOIDS WITH MIXTURES OF HETEROCYCLIC β- DIKETONE S AND VARIOUS NEUTRAL OXO-DONORS

The thesis entitled “ Investigations on the solvent extraction and luminescence of lanthanoids with mixtures of heterocyclic β-diketone S and various neutral oxo-donors” embodies the results of investigations carried out on the solvent extraction of trivalent lanthanoids with various heterocyclic β-diketones in the presence and absence of neutral oxo-donors and also on the luminescent studies of Eu3+-heterocyclic β-diketonate complexes with Lewis bases. The primary objective of the present work is to generate the knowledge base, especially to understand the interactions of lanthanoid-heterocyclic β-diketonates with various macrocyclic ligands such as crown ethers and neutral organophosphorus extractants , with a view to achieve better selectivity. The secondary objective of this thesis is to develop novel lanthanoid luminescent materials based on 3-phenyl-4-aroyl-5-isoxazolones and organophosphorus ligands, for use in electroluminescent devices. In the beginning it describes the need for the development of new mixed-ligand systems for the separation of lanthanoids and the development and importance of novel luminescent lanthanoid- β-diketonate complexes for display devices. The syntheses of various para substituted derivatives of 4-aroyl-5-isoxazolones and their characterization by various spectroscopic techniques are described. It also investigate the solvent extraction behaviour of trivalent lanthanoids with 4-aroyl-5-isoxazolones in the presence and absence of various crown ethers such as 18C6, DC18C6, DB18C6 and B18C6. Elemental analysis, IR and H NMR spectral studies are used to understand the interactions of crown ethers with 4-aroyl-5-isoxazolonate complexes of lanthanoids. The synergistic extraction of trivalent lanthanoids with sterically hindered 1-phenyl-3-methyl-4-pivaloyl-5-pyrazolone in the presence of various structurally related crown ethers are studied. The syntheses, characterization and photyphysical properties of Eu3+-4-aroyl-5-isoxazolonate complexes in the presence of Lewis bases like trictylphosphine oxide or triphenylphosphine oxide were studied.

A PVC plasticized membrane sensor for nickel ions

A new PVC membrane sensor, which is highly selective towards Ni (II) ions, has been developed using a thiophene-derivative Schiff base as the ionophore. The best performance was exhibited by the membrane having the composition percentage ratio of 5:3:61:31 (ionophore:NaTPB:DBP:PVC) (w=w), where NaTPB is the anion excluder, sodium tetraphenylborate and DBP is the plasticizing agent (dibutyl phthalate). The membrane exhibited a good Nernstian response for nickel ions over the concentration range of 1.0 10 1– 5.0 10 6M (limit of detection is 1.8 10 6 M) with a slope of 29.5 1.0mV per decade of activity. It has a fast response time of<20 s and can be used for a period of 4 months with good reproducibility. The sensor is suitable for use in aqueous solutions of a wide pH range of 3.2–7.9. The sensor shows high selectivity to nickel ions over a large number of mono-, bi- and trivalent cations. It has been successfully used as an indicator electrode in the potentiometric titration of nickel ions against EDTA and also for direct determination of nickel content in real samples – wastewater samples from electroplating industries and Indian chocolates.

A PVC Plasticized Membrane Sensor for Nickel Ions

A new PVC membrane sensor, which is highly selective towards Ni (II) ions, has been developed using a thiophene-derivative Schiff base as the ionophore. The best performance was exhibited by the membrane having the composition percentage ratio of 5:3:61:31 (ionophore:NaTPB:DBP:PVC) (w=w), where NaTPB is the anion excluder, sodium tetraphenylborate and DBP is the plasticizing agent (dibutyl phthalate). The membrane exhibited a good Nernstian response for nickel ions over the concentration range of 1.0 10 1– 5.0 10 6M (limit of detection is 1.8 10 6 M) with a slope of 29.5 1.0mV per decade of activity. It has a fast response time of<20 s and can be used for a period of 4 months with good reproducibility. The sensor is suitable for use in aqueous solutions of a wide pH range of 3.2–7.9. The sensor shows high selectivity to nickel ions over a large number of mono-, bi- and trivalent cations. It has been successfully used as an indicator electrode in the potentiometric titration of nickel ions against EDTA and also for direct determination of nickel content in real samples – wastewater samples from electroplating industries and Indian chocolates.

The Effect of Dopants on the Microwave Dielectric Properties of Ba (Mg 0.33 Ta 0.67) O3 Ceramics

The effect of dopants with different valencies and ionic radii on the densification, structural ordering, and microwave dielectric properties of Ba(Mg1/3Ta2/3)O3 (BMT) is investigated. It is found that dopants such as Sb2O5, MnO, ZrO2, WO3, and ZnO improve the microwave dielectric properties of BMT. Addition of trivalent dopants is detrimental to the cation ordering and dielectric properties of BMT. A correlation between the microwave dielectric properties of BMT and ionic radii of the dopant has been established. The variation of the dielectric properties of pure and doped BMT at cryogenic temperatures is also discussed.