Borem dopovaný diamant a jeho využití v elektroanalýze derivátů aromatických sloučenin

Tato práce je věnována studiu borem dopovaného diamantu jako elektrodového materiálu, jeho vlastnostem a použití v elektroanalytických metodách - ve voltametrii a následně amperometrii v kombinaci s průtokovou metodou vysokoúčinné kapalinové chromatografie. Série borem dopovaných diamantových filmů byla testována s ohledem na vliv koncentrace boru na jejich morfologii, kvalitu, elektrochemické a spektrální vlastnosti s použitím skenovací elektronové mikroskopie, mikroskopie atomárních sil, Ramanovy spektroskopie, cyklické voltametrie a diferenční pulsní voltametrie. Dále byl zkoumán vliv koncentrace boru na stanovení vybraných látek, jak jejich oxidací (2-aminobifenyl, benzofenon-3), tak jejich redukcí (5-nitrochinolin). Dále byla vyvinuta voltametrická a amperometrická metoda pro stanovení směsi aminobifenylů a aminonaftalenů s použitím borem dopované diamantové elektrody. Byly zkoumány účinky aktivačních čistících programů na signál benzofenonu-3 při použití borem dopované diamantové elektrody a dále stanovení benzofenonu-3 na borem dopované diamantové elektrodě v přítomnosti vybraného surfaktantu. Borem dopovaný diamant jako materiál na bázi uhlíku byl porovnán s dalšími vybranými uhlíkovými materiály jako skelný uhlík a uhlíkový film a jejich modifikacemi. Jejich použití bylo testováno na...This work is devoted to the study of boron doped diamond as electrode material, its properties and use in electroanalytical methods - in voltammetric and subsequently amperometric methods in combination with high performance liquid chromatography. The series of boron doped diamond films was tested with respect to the effect of boron concentration on their morphology, quality, electrochemical and spectral properties using scanning electron microscopy, atomic force microscopy, Raman spectroscopy, and cyclic voltammetry and differential pulse voltammetry. Further, the effect of boron concentration on the determination of selected substances was investigated, both for their oxidation (2-aminobiphenyl, benzophenone-3) and for their reduction (5-nitroquinoline). Furthermore, a voltammetric and amperometric method was developed for the determination of a mixture of aminobiphenyls and aminonaphthalenes using a boron doped diamond electrode. The effects of activation cleaning programs on the signal of benzophenone-3 were investigated using a boron doped diamond electrode, and the determination of benzophenone-3 on boron doped diamond electrode in the presence of the selected surfactant was studied. Boron doped diamond as carbon-based material was compared with other selected carbon materials such as glassy...Katedra analytické chemieDepartment of Analytical ChemistryPřírodovědecká fakultaFaculty of Scienc

Microextraction of Xenobiotics and Biomolecules from Different Matrices on Nano Structures

Sample preparation is the backbone of any analytical procedure; it involves extraction and pre-concentration of the desired analytes; often at trace levels. The present article describes the applications of nanomaterials (carbon based inorganic and polymeric materials) in miniaturized extraction such as solid phase micro-extraction, stir-bar sorptive extraction, liquid phase micro-extraction, and dispersive liquid phase micro-extraction in the analyses of aqueous samples. The nanoparticles used for micro-extractions are discussed on the basis of their chemical natures. The synthetic route and the preparation of nanomaterials are described along with the optimization strategies for micro-extraction. A comparison between the conventional materials and nanomaterials for micro-extraction is proposed. The key roles of the nanomaterials for the micro-extraction of different analytes such as drugs, pesticides, polycyclic aromatic hydrocarbons, proteins and peptides from aqueous samples are reported. The use of nanomaterials, combined with miniaturized micro-extraction techniques, proved to be highly promising for sample preparation of various matrices with analytes at trace levels

Electrochemically Activated Persulfate for Ciprofloxacin Degradation

Electrochemically activated persulfate (EAP) is a potential point source treatment for wastewater effluents containing high pharmaceutical content. This dissertation explores the fundamental mechanisms of EAP to better understand this technology for practical application. Ciprofloxacin, a fluoroquinolone antibiotic, was chosen as the model compound to assess parameters of EAP. Ciprofloxacin was selected for its high environmental risk factor and prevalence in hospital wastewater, a potential application for EAP. During the evaluation of EAP as a point source treatment, degradation kinetics and pathways of ciprofloxacin were elucidated.In the first stage of this study, persulfate activation by solid iron with and without applied current was characterized and applied to the degradation of ciprofloxacin. It was found that persulfate activation increased with iron surface area and increased to a plateau with increasing current. Ciprofloxacin degraded via first-order kinetics; however, applied current did not affect ciprofloxacin removal.In the second part of this study, electrochemical persulfate activation without iron, using boron-doped diamond (BDD) anodes and graphite or platinum cathodes, was examined. Sulfate radical formation at a BDD anode and persulfate activation at a graphite cathode were elucidated using different electrolytes and electrochemical set-ups. In this system, ciprofloxacin degraded via first order-kinetics, with persulfate electrolyte enhancing ciprofloxacin removal over sulfate or nitrate.In the final phase of this study, parameters such as reactor configuration, electrode surface area, persulfate concentrations and the presence of a complex matrix were examined to determine their impact on contaminant removal. Due to mass transfer limitations and relative cathode sizes, a flow-through reactor was least benefited by persulfate addition while a rotating-disk electrode reactor showed enhanced ciprofloxacin removal with persulfate electrolyte. Ciprofloxacin removal from synthetic hospital effluent using electrochemically activated persulfate was found to be less than that in pure electrolyte but still followed a first-order mechanism. Considerable total organic carbon removal of ciprofloxacin and other organic components of the effluent was achieved. Similar degradation was achieved with persulfate and sulfate electrolyte in the effluent. Chlorate, chlorite and perchlorate were formed in significant amounts during the electrochemical process, with formation independent of the presence of persulfate

Type, Sources, Methods and Treatment of Organic Pollutants in Wastewater

Persistent organic pollutants (POPs), which are synthetic organic chemical compounds, either intentionally or unintentionally produced, have widely aroused public concern in recent years. These chemicals are toxic and major environmental concern due to their persistence, long range transportability, bioaccumulation and potentially adverse effects on living organisms. Uncontrolled inputs combined with poor environmental management often result in elevated levels of persistent organic pollutants in affected estuaries. Since the Stockholm Convention on POPs was adopted, different techniques have been extensively developed. A major focus revealed the need for low cost methods that can be implemented easily in developing countries such as electrochemical techniques. Persistent organic pollutants are known to be resistant to conventional treatment methods such as flocculation, coagulation, filtration and oxidant chemical treatment. However, various advanced wastewater treatment technologies such as, activated carbon adsorption, biodegradation using membrane bioreactor and advanced oxidation processes (AOPs) have been applied in the treatment of POPs

Amperometric determination of selected persistent organic pollutants and heavy metals using horseradish peroxidase biosensor.

Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2010.Persistent organic pollutants and heavy metals are released into the environment through different anthropogenic processes. They are of concern because they tend to bioaccumulate in the food chain and show adverse health effects ranging from acute to chronic toxicity. These pollutants need therefore to be monitored to conserve the environment. Conventionally, samples are sent to a laboratory for analysis by standard techniques such as chromatography and spectroscopy. Although these conventional techniques display high accuracy and low detection limits, they are expensive, require the use of highly trained personnel and tedious sample preparation. In comparison, electrochemical methods such as biosensors are sensitive, low cost and simple to operate. In this thesis, the determination of selected persistent organic pollutants (polybrominated diphenyl ethers, polybrominated biphenyls and polychlorinated biphenyls) and heavy metals (Cd, Pb and Cu) was achieved by the use of amperometric inhibition biosensor based on horseradish peroxidase (HRP) immobilized on the surface of platinum-polyaniline modified electrode. Polyaniline (PANI) film was electrochemically deposited on the platinum electrode surface. The film was characterized by cyclic voltammetry and spectrometric techniques. The CV results proved that the PANI was electroactive and exhibited a fast reversible electrochemistry. Characteristic Ultraviolet–Visible and Fourier Transform Infrared features of the polymer film were identified. They revealed that PANI film synthesized in this study is the conductive emeraldine salt. Horseradish peroxidase based biosensor was constructed by electrostatic attachment of the enzyme onto Pt-PANI electrode surface. Spectrometric and cyclic voltammetric results indicated that the immobilized HRP retained its bioelectrocatalytic activity towards the reduction of hydrogen peroxide. The Pt/PANI/HRP biosensor showed a linear response over a concentration range of 0.05 to 3.17 mM with a detection limit of 36.8 nM. Apparent Michaelis- Menten constant ( app M K ) was calculated as 1.04 mM. This implied that the HRP biosensor had a high affinity for H2O2. Furthermore, the fabricated biosensor showed high sensitivity, good reproducibility, repeatability and long-term stability. The Pt/PANI/HRP biosensor was applied to the determination of selected persistent organic pollutants and heavy metals. The latter was found to inhibit the HRP enzyme’s activity. The percentage inhibition of the investigated persistent organic pollutants decreases in the following order: 2,2´4,4´,6-pentabrominated diphenyl ether> 2-brominated biphenyl> 2-chlorinated biphenyl> 2,2´,4,5,5´-pentachlorinated biphenyl> 2,4,4´-trichlorinated biphenyl. In the case of heavy metals, the degree of inhibition of heavy metals was highest for Cd2+, followed by Cu2+ and then Pb2+. Kinetic study for the amperometric response to H2O2, recorded in the absence and presence of persistent organic pollutants and heavy metals revealed that for polybrominated diphenyl ethers, the inhibition process corresponded to a competitive type whereas for polybrominated biphenyls, polychlorinated biphenyls and heavy metals, it corresponded to the on-competitive type. The biosensor exhibited high sensitivity towards the determination of the metals and persistent organic pollutants as pollutants in real water samples, namely tap water and landfill leachate samples

Faceted nanomaterial synthesis, characterizations and applications in reactive electrochemical membrane filtration

Facet engineering of nanomaterials, especially metals and metal oxides has become an important strategy for tuning catalytic properties and functions from heterogeneous catalysis to electrochemical catalysis, photocatalysis, biomedicine, fuel cells, and gas sensors. The catalytic properties are highly related to the surface electronic structures, surface electron transport characteristics, and active center structures of catalysts, which can be tailored by surface facet control. The aim of this doctoral dissertation research is to study the facet-dependent properties of metal or metal oxide nanoparticles using multiple advanced characterization techniques. Specifically, the novel atomic force microscope-scanning electrochemical microscope (AFM-SECM) and density functional theory (DFT) calculations were both applied to both experimentally and theoretically investigate facet dependent electrochemical properties, molecular adsorption, and dissolution properties of cuprous oxide and silver nanoparticles. To promote the facet engineered nanomaterials for environmental engineering apparitions, our research has evaluated the performances of electrochemically reactive membranes that were prepared with novel 2D nanomaterials with surface functioal modifications to enable electrochemical advanced oxidation processes (EAOPs) in membrane filtration process. Our results demonstrated many advantages such as tunable reactivity, tailored surface reactions, antifouling features, and feasibility of large-scale continuous operations. Specifically, this dissertation will introduce our electrochemical membrane synthesis, reactivity, aging, byproducts formation and electrochemical adsorption and desorption, oxidation of pollutants such as two typical per-and poly-fluoroalkyl substances (PFAS), perfluorooctanoic Acid (PFOA) and perfluorobutanoic acid (PFBA)

Cyclodextrins as Supramolecular Recognition Systems: Applications in the Fabrication of Electrochemical Sensors

Supramolecular chemistry, although focused mainly on noncovalent intermolecular and intramolecular interactions, which are considerably weaker than covalent interactions, can be employed to fabricate sensors with a remarkable affinity for a target analyte. In this review the development of cyclodextrin-based electrochemical sensors is described and discussed. Following a short introduction to the general properties of cyclodextrins and their ability to form inclusion complexes, the cyclodextrin-based sensors are introduced. This includes the combination of cyclodextrins with reduced graphene oxide, carbon nanotubes, conducting polymers, enzymes and aptamers, and electropolymerized cyclodextrin films. The applications of these materials as chiral recognition agents and biosensors and in the electrochemical detection of environmental contaminants, biomolecules and amino acids, drugs and flavonoids are reviewed and compared. Based on the papers reviewed, it is clear that cyclodextrins are promising molecular recognition agents in the creation of electrochemical sensors, chiral sensors, and biosensors. Moreover, they have been combined with a host of materials to enhance the detection of the target analytes. Nevertheless, challenges remain, including the development of more robust methods for the integration of cyclodextrins into the sensing unit

Estruturas dendríticas de ouro e sua aplicação no desenvolvimento de biossensor para determinação de bisfenol a (BPA)

Bisfenol A (BPA) é uma substância orgânica usado na produção de policarbonatos e resinas epóxi. A exposição humana ao BPA através de alimentos e água potável pode resultar em doenças cardiovasculares, diabetes, distúrbios neurológicos, câncer de mama e próstata. Este trabalho visa o desenvolvimento de um biossensor baseado na enzima tirosinase para detecção de BPA. Biossensores representam boas alternativas às técnicas convencionais; eles aproveitam a especificidade e a sensibilidade dos sistemas biológicos em dispositivos pequenos e de baixo custo. Na preparação do biossensor, optamos pelo uso de eletrodos impressos de carbono, que constituem células eletroquímicas descartáveis. O substrato à base de carbono consiste em uma mistura de grafite, solventes e ligantes poliméricos. Esta superfície, rica em grupos funcionais de oxigênio, funcionou perfeitamente para realizar a eletrodeposição de ouro a partir de uma solução de íons cloroáuricos utilizando as técnicas de voltametria cíclica e cronoamperometria independentemente. Diferentes morfologias foram observadas por microscopia eletrônica de varredura. Os eletrodos modificados foram utilizados como suporte para a imobilização da enzima tirosinase, permitindo a preparação de um biossensor altamente seletivo e sensível para a detecção do BPA. Além disso, o biossensor proposto mostrou estabilidade a longo prazo e foi aplicado para um teste de recuperação de BPA em água mineral e de torneira. Os eletrodos de grafite também provaram ser um material adequado como plataforma para o desenvolvimento de sensores eletroquímicos. Estruturas de ouro hiper-ramificadas resultaram da eletrodeposição realizada sob condições experimentais semelhantes aos eletrodos impressos de carbono. Além disso, estudos preliminares revelaram a potencial aplicabilidade do eletrodo modificado para a eletrooxidação de BPA em meio alcalino.Bisphenol A (BPA) is an organic substance used in the production of polycarbonates and epoxy resins. Human exposure to BPA through food and drinking water can result in cardiovascular disease, diabetes, neurological disorders, breast, and prostate cancer. This work aims the development of a biosensor based on the enzyme tyrosinase for BPA detection. Biosensors represent good alternatives to conventional techniques; they take advantage of the specificity and sensitivity of biological systems in small and low-cost devices. In the preparation of the biosensor, we opted for the use of carbon printed electrodes, which constitute disposable electrochemical cells. The carbon-based substrate consists of a mixture of graphite, solvents and polymeric binders. This surface, rich in functional groups of oxygen, worked perfectly to perform the electrodeposition of gold from a solution of chloroauric ions using the techniques of cyclic voltammetry and chronoamperometry independently. Different morphologies were observed by scanning electron microscopy. The modified electrodes were used as support for the immobilization of the enzyme tyrosinase, allowing the preparation of a highly selective and sensitive biosensor for the detection of BPA. Additionally, the proposed biosensor showed long-term stability and was applied for a recovery test of BPA in mineral and tap-water. Graphite pencil electrodes also proved to be a suitable material as a platform for the development of electrochemical sensors. Hyperbranched gold structures resulted from electrodeposition performed under similar experimental conditions to the carbon printed electrodes. Furthermore, preliminary studies revealed the potential applicability of the modified electrode for the electrooxidation of BPA in an alkaline medium

The Synthesis and Application of Novel Nanostructured Carbon Materials

This study presents a comprehensive investigation on synthesis of several novel carbon materials including nitrogen-doped graphene, nitrogen-doped carbon nanotubes with encapsulated iron carbide, nitrogen-doped mesoporous carbons and Co-based nanospheres supported by carbon spheres and their applications in the catalytic oxidation of phenol solution by heterogeneous activation of peroxymonosulfate. Their structures, morphologies and relevant mechanisms were studied thoroughly. These findings would open a new avenue for the development of green catalysts in environmental remediation