Polymeric foams as the matrix of voltammetric sensors for the detection of catechol, hydroquinone, and their mixtures

Producción CientíficaPorous electrodes based on polymethylmethacrylate and graphite foams (PMMA_G_F) have been developed and characterized. Such devices have been successfully used as voltammetric sensors to analyze catechol, hydroquinone, and their mixtures. The presence of pores induces important changes in the oxidation/reduction mechanism of catechol and hydroquinone with respect to the sensing properties observed in nonfoamed PMMA_graphite electrodes (PMMA_G). The electropolymerization processes of catechol or hydroquinone at the electrode surface observed using PMMA_G do not occur at the surface of the foamed PMM_G_F. In addition, the limits of detection observed in foamed electrodes are one order of magnitude lower than the observed in the nonfoamed electrodes. Moreover, foamed electrodes can be used to detect simultaneously both isomers and a remarkable increase in the electrocatalytic properties shown by the foamed samples, produces a decrease in the oxidation potential peak of catechol in presence of hydroquinone, from +0.7 V to +0.3 V. Peak currents increased linearly with concentration of catechol in presence of hydroquinone over the range of 0.37·10−3 M to 1.69·10−3 M with a limit of detection (LOD) of 0.27 mM. These effects demonstrate the advantages obtained by increasing the active surface by means of porous structures.Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (project AGL2015-67482-R)Junta de Castilla y Leon - Fondo Europeo de Desarrollo Regional (project VA-011U16

Conducting Polymers and Natural Molecular Materials for Bioelectronics and Energy Storage

La découverte de la conduction électronique dans les matériaux organiques, dans les années 70, est à l’origine du développement des technologies optoélectroniques organiques. La remarquable propriété que présentent les semiconducteurs organiques de conduire les ions, en plus des porteurs de charge électroniques, a permis l’émergence d’un nouveau domaine de l’optoélectronique organique, c’est à dire la bioélectronique. La bioélectronique organique ouvre de nouvelles opportunités d’interface entre l’électronique organique et la biologie, avec la promesse d’applications dans des domaines aussi variés que les biocapteurs, la livraison de médicament, l’enregistrement et la stimulation neural. Combiner un transport ionique et électronique dans les semiconducteurs organiques utilisés pour les transistors représente une tentative intéressante pour parvenir à des dispositifs bioélectroniques efficaces. Ces dispositifs opèrent à faible polarisation de l’électrode de grille, grâce à la formation d’une double couche électrique au niveau de l’interface électrode/électrolyte. Les capacitances de double couches résultantes ont des valeurs qui dépassent de plusieurs ordres de grandeurs celles typiques des interfaces métal/diélectrique, en raison de la faible épaisseur (ca. 3nm) des doubles couches électriques. Par conséquent, les capacitances de double couche peuvent mener à de plus fortes modulations en courant pour des différences de potentiel de grille plus faibles (~1 V), compatibles avec les milieux aqueux. Le coeur de cette thèse de doctorat est dévoué à une meilleure compréhension des mécanismes d’opération d’une classe importante de dispositifs bioélectroniques organiques, c’est-à-dire les transistors électrochimiques organiques (OECTs), dans le but d’optimiser leurs performances et de concevoir de nouveaux dispositifs bioélectroniques. Les OECTs sont formés d’un canal en polymère conducteur ainsi que d’une électrode de grille mis en contact avec le canal au travers d’un électrolyte. L’application d’une différence de potentiel électrique au niveau de la grille entraîne l’inclusion d’ions de l’électrolyte à l’intérieur de la couche mince en polymère en qui changent sa conducitvité initiale. Dans cette thèse, nous nous sommes concentrés sur le poly(3,4- éthylènedioxythiophène) dopé avec du poly(styrène sulfonate) (PEDOT:PSS) en tant que matériau actif dans le canal de OECTs. Nous avons utilisé différentes épaisseurs de canal ainsi que deux électrolytes différents : le bromure de cétyltriméthyl-ammonium (CTAB), un surfactant apte à former des micelles, et du NaCl. Les rapports ON/OFF les plus élevés ont été obtenus pour de transistors utilisant de faibles épaisseurs (~ 50 nm) de la couche mince et le CTAB comme électrolyte. La voltammétrie cyclique suggère qu’une réaction rédox entre les molécules d’oxygène dissoutes dans l’électrolyte et le PEDOT:PSS mène à de faibles ratios ON/OFF quand le NaCl est utilisé comme électrolyte. La voltammétrie cyclique et la spectroscopie d’impédance électrochimique révèlent que le dopage/dédopage du canal devient plus lent à des épaisseurs relativement élevés de la couche mince et en présence d’ions de plus grande taille. Les caractéristiques de l’électrode de grille ont des effets significatifs sur le comportement des OECTs. Dans cette thèse, du carbone activé (AC) avec une importante surface spécifique a été utilisé comme matériau pour l’électrode de grille dans les OECTs basés sur le PEDOT:PSS. L’utilisation d’électrodes de grille en AC de grande surface, a mené à une importante modulation en courant drain-source dans les OECTs et à la limitation des réactions électrochimiques indésirables. La biocompatibilité et la biodégradabilité des matériaux utilisés en bioélectronique organique sont essentiels. Ces propriétés sont importantes même pour des dispositifs alimentant les dispositifs bioélectroniques. La mélanine est un biopigment abondant en nature et doté d’activité redox. Ce biopigment peut être mis en forme à température ambiante et est donc un matériau extrêmement intéressant pour le développement de dispositifs de stockage de l’énergie biocompatibles et « verts ». L’eumélanine est une des formes de la mélanine qui est particulièrement étudiée par les chercheurs en science de matériaux. Celle-ci se retrouve dans de nombreuses parties du corps humain, dont la peau, les cheveux, l’oreille interne et le cerveau. L’eumélanine réalise de nombreuses fonctions dans le corps humain comme l’absorption dans une large bande du spectre UV-visible ou encore la chélation métallique. Dans cette thèse, nous rapportons les propriétés de stockage d’énergie électrochimique de la part d’électrodes basées sur l’eumélanine, en configuration supercondensateur. L’eumélanine est formée de monomères faits de 5,6-dihydroxyindole (DHI) et d’acide 5,6-dihydroxyindole carboxylique (DHICA), présents sous différentes formes redox (hydroxyquinone, semiquinone et quinone). La synergie entre l’activité redox des monomères et la capacité de plusieurs de leurs fonctionnalités à lier des cations de façon réversible permet l’utilisation de l’eumélanine dans des dispositifs de stockage d’énergie fonctionnant en mode pseudocapacitif. En partant de la démonstration des supercondensateurs basés sur l’eumélanine, nous avons utilisé une approche non-conventionnelle pour fabriquer des micro-condensateurs flexibles sur substrats plastiques. ---------- The discovery of electronic conduction in carbon-based materials, in the 1970s, is the basis of the development of organic optoelectronics technologies. The remarkable property of organic semiconductors to conduct ions, in addition to electronic charge carriers, has recently offered a new emerging direction in organic optoelectronics, called organic bioelectronics. Organic bioelectronics opens the opportunity to interface organic electronics with biology with promising applications such as biosensing, drug delivery, neural recording and stimulation. Combining ionic and electronic transport in organic semiconductors into transistor architectures represents an interesting attempt to achieve efficient bioelectronics devices. These devices operate at low gate biases, due to the formation of electrical double layers at electrode/electrolyte interfaces. The resultant double layer capacitances are a few orders of magnitude higher compared to capacitances typical of metal/dielectric interfaces, due to the low thickness (ca. 3 nm) of the electrical double layers, which consequently leads to higher current modulations at lower gate voltage (~1 V). The core of this Ph.D. thesis is devoted to a better understanding of the operational mechanism of an important class of organic bioelectronics devices, i.e. organic electrochemical transistors (OECTs), to optimize their performance and to design novel bioelectronics devices. OECTs consist of a conducting polymer channel and a gate electrode in contact with an electrolyte. The application of a gate electrical bias triggers the inclusion of electrolyte ions into the polymer film thus changing its initial conductivity. In this thesis we focus on poly(3,4-ethylenedioxythiophene) doped with polystyrenesulfonate (PEDOT:PSS) as the active material in OECTs. We employed various channel thicknesses and two different electrolytes: the micelle-forming surfactant cetyltrimethyl ammonium bromide (CTAB) and NaCl. The highest transistor ON/OFF ratios were achieved at low film thicknesses (~ 50 nm), using CTAB as the electrolyte. Cyclic voltammetry suggested that a redox reaction between molecular oxygen dissolved in the electrolytes and PEDOT:PSS leads to low ON/OFF ratios when NaCl was used as the electrolyte. Cyclic voltammetry and electrochemical impedance spectroscopy revealed that doping/dedoping of the channel becomes slower at relatively high film thickness and in the presence of bulky ions. The characteristics of the gate electrode have significant effects on the behavior of OECTs. In this thesis, high specific surface area activated carbon (AC) was used as gate electrode material in OECTs based PEDOT:PSS. The use of high surface area carbon gate electrodes led to the high drain-source current modulation in OECT and limited undesirable electrochemical processes. The biocompatibility and biodegradability property of the materials used in organic bioelectronics is of course of primary importance. These features are important even for devices powering the bioelectronics devices. Melanin is a redox active biopigment abundant in nature. The biopigment can be processed at room temperature and, as such, it is an extremely attractive material for environmentally and human friendly energy storage solutions. A form of melanin highly investigated by materials scientists is eumelanin, found in many parts of the human body including skin, hair, inner ear and brain. Eumelanin has many functions in the human body, such as strong broad-band UV-visible absorption and metal chelation. In this thesis, we report the ion storage property of eumelanin-based electrodes assembled in supercapacitors. Eumelanin is based on 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole carboxylic acid (DHICA) building blocks, present in different redox forms (hydroxyquinone, semiquinone and quinone). The synergy between the redox activity of the building blocks and the capability of several of their functionalities to reversibly bind cations constitutes the foundation for the use of melanin in pseudocapacitive energy storage systems. Capitalizing on the demonstration of eumelanin-based supercapacitors, we used an unconventional patterning approach to fabricate binder-free flexible micro-supercapacitors on plastic substrates

Applications and immobilization strategies of the copper-centred laccase enzyme : a review

DATA AVAILABILITY STATEMENT: No data was used for the research described in the article.Laccase is a multi-copper enzyme widely expressed in fungi, higher plants, and bacteria which facilitates the direct reduction of molecular oxygen to water (without hydrogen peroxide production) accompanied by the oxidation of an electron donor. Laccase has attracted attention in biotechnological applications due to its non-specificity and use of molecular oxygen as secondary substrate. This review discusses different applications of laccase in various sectors of food, paper and pulp, waste water treatment, pharmaceuticals, sensors, and fuel cells. Despite the many advantages of laccase, challenges such as high cost due to its non-reusability, instability in harsh environmental conditions, and proteolysis are often encountered in its application. One of the approaches used to minimize these challenges is immobilization. The various methods used to immobilize laccase and the different supports used are further extensively discussed in this review.The National Research Foundation (NRF) of South Africa.https://www.cell.com/heliyonChemical Engineerin

Fundamentals and scopes of doped carbon nanotubes towards energy and biosensing applications

Since their first allusion, carbon nanotubes have attracted significant research interest, especially with respect to composite manufacturing as a filler material for enhancing their mechanical and electrical properties. Several methods have been developed for modifying the electrical properties of carbon nanotubes such as CNTs wall's carbon atoms substitution with other appropriate atoms including engineering of their outer surfaces by covalent and noncovalent molecules, such as CNTs channel filling and nano-chemical reactions therein. CNTs with tailored electrical conduction open large perspectives for their applicabilities in advanced technologies. Taking into consideration the innovative advantages of pure and hybrid CNTs, in this article we have comprehensively reviewed the latest state-of-art research developments in the direction of different synthesis strategies, structure-property relationships, and advanced applications towards energy storage, supercapacitors, electrodes, catalytic supports, as well as biosensing

Novel amperometric enzyme biosensors of environmental interest

The performance and characteristics of amperometric enzyme-based biosensors for environmental monitoring are described in detail in Chapter 1. The concept of enzyme inhibition is also outlined including detailed theoretical evaluation of inhibitor type. The inhibition of one or more enzymes in a metabolic pathway can have detrimental effects in vivo. Inhibitors range from food constituents, pesticides, halide, azide and cyanide compounds, drug and related therapeutic agents, respiratory poisons, oxides and peroxides. In Chapter 2 the use of screen printing is described as a disposable tyrosinase based biosensor for the monitoring of selected inhibitors. The characterisation and attractive performance of single use inhibitor biosensor strips is presented. Exploitation of mushroom tissue electrodes for the convenient monitoring of tyrosinase inhibitors is also outlined, including detailed elucidation of inhibitor type using native tyrosinase enzyme. Tyrosinase as a polyphenol oxidase is also an ideal candidate for the biosensing of phenolic compounds. The use of several hydrocarbon pasting liquids for improved tyrosinase-based carbon paste phenol biosensors is demonstrated in Chapter 3. Much interest has evolved in recent years on the use of sol-gel glasses in sensor manufacturing. Chapter 4 addresses this area with a sol-gel carbon composite electrode as an amperometric detector for catecholamines in liquid chromatography. An example of a sol-gel amperometric biosensor for the analysis of phenolics is also described. The most recent advancement in amperometric biosensing models, has been the proposed use of cytochrome P450 enzyme for environmental monitoring. Cytochrome P450s are heamthiolate monooxygenase enzymes that result in the hydroxylation of a wide range of substances. This novel biosensing technique is presented in Chapter 5 in relation to the encapsulation of the P450 enzyme along with membrane vesicles, within a methyltriethoxysilane gel. The behaviour of this biosensor for the analysis of polyaromatic hydrocarbons is evaluated. The thesis concludes in Chapter 6 with a critical assessment of the work performed there-in, along with suggestions for future work

Chemistry, structures, and advanced applications of nanocomposites from biorenewable resources

Researchers have recently focused on the advancement of new materials from biorenewable and sustainable sources because of great concerns about the environment, waste accumulation and destruction, and the inevitable depletion of fossil resources. Biorenewable materials have been extensively used as a matrix or reinforcement in many applications. In the development of innovative methods and materials, composites offer important advantages because of their excellent properties such as ease of fabrication, higher mechanical properties, high thermal stability, and many more. Especially, nanocomposites (obtained by using biorenewable sources) have significant advantages when compared to conventional composites. Nanocomposites have been utilized in many applications including food, biomedical, electroanalysis, energy storage, wastewater treatment, automotive, etc. This comprehensive review provides chemistry, structures, advanced applications, and recent developments about nanocomposites obtained from biorenewable sources

Applications of Nanoporous Gold to Drug Release and Glycoscience

Nanoporous gold (NPG) is a versatile material because of its three-dimensional nanoscale network, facile surface functionalization, biocompatibility, and potential usage in biotechnology applications. The field of glycoscience is growing in significance as the importance of glycans in human health and disease becomes more fully understood at the molecular level. NPG can be applied to several needs in the field of glycoscience. Our lab has applied NPG to applications in glycoscience including the capture and release of glycoproteins, and the detection of glycoprotein interactions by using either electrochemical methods or localized surface plasmon spectroscopy (LSPR). The capture of glycoproteins onto high surface area NPG is demonstrated using both lectin-glycan interactions and interaction between glycoproteins and NPG modified with boronic acid functional groups. Thermogravimetric analysis and use of a UV-visible HPLC detector in a flow cell containing monoliths of NPG were applied to monitor the capture of glycoprotein and its elution by the flow of free ligand. The modification of NPG by self-assembled monolayers (SAMs) with terminal boronic acid groups has been used together with LSPR to monitor the capture of glycoprotein by the induced shift in the LSPR peak wavelength. Square-wave voltammetry methods can also be applied to monitor the binding of glycoproteins to NPG modified either by SAMs with terminal boronic acid groups or by conjugated lectins. Thiolated β-cyclodextrin modified NPG wire was used for the pH-sensitive release of doxorubicin (DOX) in a controlled manner, with an ultra-high DOX payload. Thiolated β-cyclodextrins are attractive macrocycles as they can form supramolecular inclusion complexes with doxorubicin affording the possibility of altering the controlled release behavior. Doxorubicin is one of the most potent anti-tumor drugs used in the treatment of different cancers. The binding of thiolated β-cyclodextrin with the anti-cancer drug doxorubicin has been examined with the use of spectroscopy and electrochemistry. Moreover, the prepared structure exhibited excellent properties for controlled drug release outlining the potential of a pH-sensitive drug implant or carrier for biomedical application. This delivery system could improve localized targeting of the drug as well as alter the rate of release of the doxorubicin near a tumor

Effect of the air pressure on electro-Fenton process

Electro-Fenton process is considered a very promising tool for the treatment of waste waters contaminated by organic pollutants refractant or toxic for microorganisms used in biological processes [1-6]. In these processes H2O2 is continuously supplied to an acidic aqueous solution contained in an electrolytic cell from the two-electron reduction of oxygen gas, directly injected as pure gas or bubbled air. Due to the poor solubility of O2 in aqueous solutions, two dimensional cheap graphite or carbon felt electrodes give quite slow generation of H2O2, thus resulting in a slow abatement of organics. In this context, we report here a series of studies [7-9] on the effect of air pressure on the electro-generation of H2O2 and the abatement of organic pollutants in water by electro-Fenton process. The effect of air pressure, current density, mixing and nature of the organic pollutant was evaluated. [1] E. Brillas, I. Sirés, M.A. Oturan, Chem. Rev., 109 (2009) 6570-6631. [2] C.A. Martínez-Huitle, M.A. Rodrigo, I. Sirés, O. Scialdone, Chem. Rev. 115 (2015) 13362–13407. [3] M. Panizza, G. Cerisola, Chem. Rev. 109 (2009) 6541–6569. [4] I. Sirés, E. Brillas, M.A. Oturan, M.A. Rodrigo, M. Panizza, Environ. Sci. Pollut. Res. 21 (2014) 8336–8367. [5] C.A. Martínez-Huitle, S. Ferro, Chem. Soc. Rev. 35 (2006) 1324–1340. [6] B.P.P. Chaplin, Environ. Sci. Process. Impacts. 16 (2014) 1182–1203. [7] O. Scialdone, A. Galia, C. Gattuso, S. Sabatino, B. Schiavo, Electrochim. Acta, 182 (2015) 775-780. [8] J.F. Pérez, A. Galia, M.A. Rodrigo, J. Llanos, S. Sabatino, C. Sáez, B. Schiavo, O. Scialdone, Electrochim. Acta, 248 (2017) 169-177. [9] A.H. Ltaïef, S. Sabatino, F. Proietto, A. Galia, O. Scialdone, O. 2018, Chemosphere, 202, 111-118

Pressurized CO2 Electrochemical Conversion to Formic Acid: From Theoretical Model to Experimental Results

To curb the severely rising levels of carbon dioxide in the atmosphere, new approaches to capture and utilize this greenhouse gas are currently being investigated. In the last few years, many researches have focused on the electrochemical conversion of CO2 to added-value products in aqueous electrolyte solutions. In this backdrop, the pressurized electroreduction of CO2 can be assumed an up-and-coming alternative process for the production of valuable organic chemicals [1-3]. In this work, the process was studied in an undivided cell with tin cathode in order to produce formic acid and develop a theoretical model, predicting the effect of several operative parameters. The model is based on the cathodic conversion of pressurized CO2 to HCOOH and it also accounts for its anodic oxidation. In particular, the electrochemical reduction of CO2 to formic acid was performed in pressurized filter press cell with a continuous recirculation of electrolytic solution (0.9 L) at a tin cathode (9 cm2) for a long time (charge passed 67’000 C). It was shown that it is possible to scale-up the process by maintaining good results in terms of faradaic efficiency and generating significantly high concentrations of HCOOH (about 0.4 M) [4]. It was also demonstrated that, for pressurized systems, the process is under the mixed kinetic control of mass transfer of CO2 and the reduction of adsorbed CO2 (described by the Langmuir equation), following our proposed reaction mechanism [5]. Moreover, the theoretical model is in good agreement with the experimental results collected and well describes the effect of several operating parameters, including current density, pressure, and the type of reactor used. 1. Ma, S., & Kenis, P. J. (2013). Electrochemical conversion of CO2 to useful chemicals: current status, remaining challenges, and future opportunities. Current Opinion in Chemical Engineering, 2(2), 191-199. 2. Endrődi, B., Bencsik, G., Darvas, F., Jones, R., Rajeshwar, K., & Janáky, C. (2017). Continuous-flow electroreduction of carbon dioxide. Progress in Energy and Combustion Science, 62, 133-154. 3. Dufek, E. J., Lister, T. E., Stone, S. G., & McIlwain, M. E. (2012). Operation of a pressurized system for continuous reduction of CO2. Journal of The Electrochemical Society, 159(9), F514-F517. 4. Proietto, F., Schiavo, B., Galia, A., & Scialdone, O. (2018). Electrochemical conversion of CO2 to HCOOH at tin cathode in a pressurized undivided filter-press cell. Electrochimica Acta, 277, 30-40. 5. Proietto, F., Galia, A., & Scialdone, O. (2019) Electrochemical conversion of CO2 to HCOOH at tin cathode: development of a theoretical model and comparison with experimental results. ChemElectroChem, 6, 162-172

Carbon-Based Material for Environmental Protection and Remediation

Carbon-Based Material for Environmental Protection and Remediation presents an overview of carbon-based technologies and processes, and examines their usefulness and efficiency for environmental preservation and remediation. Chapters cover topics ranging from pollutants removal to new processes in materials science. Written for interested readers with strong scientific and technological backgrounds, this book will appeal to scientific advisors at private companies, academics, and graduate students