E-Tongues/Noses Based on Conducting Polymers and Composite Materials: Expanding the Possibilities in Complex Analytical Sensing

Conducting polymers (CPs) are extensively studied due to their high versatility and electrical properties, as well as their high environmental stability. Based on the above, their applications as electronic devices are promoted and constitute an interesting matter of research. This review summa- rizes their application in common electronic devices and their implementation in electronic tongues and noses systems (E-tongues and E-noses, respectively). The monitoring of diverse factors with these devices by multivariate calibration methods for different applications is also included. Lastly, a critical discussion about the enclosed analytical potential of several conducting polymer-based devices in electronic systems reported in literature will be offered

Recent advances in applications of oxidases and peroxidases polymer-based enzyme biocatalysts in sensing and wastewater treatment : a review

DATA AVAILABILITY STATEMENT : Data sharing is not applicable to this article as no new data were created or analyzed in this study.Oxidase and peroxidase enzymes have attracted attention in various biotechnological industries due to their ease of synthesis, wide range of applications, and operation under mild conditions. Their applicability, however, is limited by their poor stability in harsher conditions and their non-reusability. As a result, several approaches such as enzyme engineering, medium engineering, and enzyme immobilization have been used to improve the enzyme properties. Several materials have been used as supports for these enzymes to increase their stability and reusability. This review focusses on the immobilization of oxidase and peroxidase enzymes on metal and metal oxide nanoparticle-polymer composite supports and the different methods used to achieve the immobilization. The application of the enzyme-metal/metal oxide-polymer biocatalysts in biosensing of hydrogen peroxide, glucose, pesticides, and herbicides as well as blood components such as cholesterol, urea, dopamine, and xanthine have been extensively reviewed. The application of the biocatalysts in wastewater treatment through degradation of dyes, pesticides, and other organic compounds has also been discussed.National Research Foundation (NRF) of South Africa, Margaret McNamara Education grants (2023), the Federal Ministry of Education, Science and Research (BMBWF) through Austria’s Agency for Education and Internationalization (OeAD).https://www.mdpi.com/journal/polymersam2024Chemical EngineeringSDG-12:Responsible consumption and productio

0D and 2D nanomaterials based on Graphene Quantum Dots and MXenes: synthesis, characterization and application in sensors and supercapacitors.

ABSTRACT 0D AND 2D NANOMATERIALS BASED ON GRAPHENE QUANTUM DOTS AND MXENES APPLIED IN SENSORS AND SUPERCAPACITORS. Graphene Quantum Dots (GQDs) are small fragments of one or a few layers of graphene with lateral dimensions inferior to 100 nm. GQDs present some characteristics similar to those of graphene, such as a high surface area/volume ratio and chemical stability. In addition, GQDs present a bandgap between their valence and electronic conduction bands. This bandgap gives rise to one of the most investigated properties of GQDs: their photoluminescence, which enables their application as luminescent sensors. In this sense, in the first work, hydrothermal syntheses of GQDs from graphene oxide (GO) were studied aiming at obtaining a material with greater photoluminescence intensity for application in luminescent sensors. The synthesis temperature, pH of the GO solution, and GO concentration were evaluated to optimize the quantum yield of GQDs. An optimized value of 8.9% was obtained. The influence of each parameter on the composition and properties of the GQDs was carried out from the physical-chemical characterization of the materials. The synthesized materials were used in the detection of Fe3+ ions in aqueous solutions by luminescence quenching, obtaining a detection limit of 0.136 M. Like GQDs, the discovery of a new class of materials known as MXenes was inspired by the discovery of graphene. MXenes are 2D materials, in which transition metal layers are interleaved with carbon and/or nitrogen layers. Such materials have demonstrated high energy storage capacity, being widely exploited in devices such as supercapacitors and batteries. However, the restacking of the MXene layers and the narrow potential window usually obtained limit the performance of these materials in such applications. In another work, nanodiamonds (NDs) were used to prevent the restacking of the MXene layers during its use as a supercapacitor electrode. The pillaring effect obtained with the NDs allowed a greater diffusion of protons between the layers of the MXene Ti3C2Tx, resulting in a capacitance of 235 F/g (561 F/cm3 ) when used in 3 M AlCl3 electrolyte. Furthermore, a wide potential window of 1.2 V could be used due to the reduced water activity in the electrolyte.Advisor: Dr. Daniel Souza Corrê

Chapter 34 - Biocompatibility of nanocellulose: Emerging biomedical applications

Nanocellulose already proved to be a highly relevant material for biomedical applications, ensued by its outstanding mechanical properties and, more importantly, its biocompatibility. Nevertheless, despite their previous intensive research, a notable number of emerging applications are still being developed. Interestingly, this drive is not solely based on the nanocellulose features, but also heavily dependent on sustainability. The three core nanocelluloses encompass cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs), and bacterial nanocellulose (BNC). All these different types of nanocellulose display highly interesting biomedical properties per se, after modification and when used in composite formulations. Novel applications that use nanocellulose includewell-known areas, namely, wound dressings, implants, indwelling medical devices, scaffolds, and novel printed scaffolds. Their cytotoxicity and biocompatibility using recent methodologies are thoroughly analyzed to reinforce their near future applicability. By analyzing the pristine core nanocellulose, none display cytotoxicity. However, CNF has the highest potential to fail long-term biocompatibility since it tends to trigger inflammation. On the other hand, neverdried BNC displays a remarkable biocompatibility. Despite this, all nanocelluloses clearly represent a flag bearer of future superior biomaterials, being elite materials in the urgent replacement of our petrochemical dependence

Rapid response analytical systems based on the direct coupling of flat supports and instrumental techniques

En las últimas décadas, la Química Analítica ha estudiado en profundidad el desarrollo de metodologías capaces de proporcionar resultados fiables de manera rápida para así responder a la creciente demanda informativa de la sociedad actual. En este contexto, la etapa de tratamiento de muestra se ha visto directamente afectada debido al tiempo que requiere y, además, por ser la principal fuente de error como consecuencia del alto grado de participación humana. La simplificación, miniaturización y automatización han sido las principales fuerzas impulsoras de la evolución del tratamiento de muestra en estos años. La aplicación de estas tres tendencias ha dado lugar a la aparición de las técnicas de microextracción. La reducción del consumo de reactivos, disolventes y energía, así como de los residuos generados, responden al compromiso social y medioambiental de la Química Verde y, al mismo tiempo, contribuyen al desarrollo de metodologías simples capaces de proporcionar resultados de calidad en un tiempo reducido. Esta simplificación engloba, asimismo, a los materiales sorbentes empleados en las técnicas de microextracción. En esta línea, los dispositivos analíticos basados en papel han despertado un gran interés debido a las múltiples ventajas de este material como fase sorbente, entre las que destacan su flexibilidad, porosidad y bajo coste. Asimismo, en los últimos años, la modificación del papel con distintos materiales ha sido una tendencia estable que ha derivado en la mejora de la versatilidad de este soporte. La modificación del papel con polímeros o nanomateriales ha hecho posible el desarrollo de soportes planos con una elevada área superficial capaces de interaccionar con una gran variedad de analitos. No obstante, los procedimientos llevados a cabo para la modificación del papel a menudo son complicados y requieren un control muy estricto de las condiciones experimentales. Por este motivo, es necesario buscar alternativas capaces de solventar estas dificultades. La simplificación de la etapa de tratamiento de muestra no supondría un gran avance si las técnicas instrumentales empleadas para la determinación de los analitos no estuviesen igualmente influenciadas por esta tendencia. En este sentido, los soportes basados en papel han sido también muy útiles debido a su fácil manipulación y acoplamiento con técnicas instrumentales, como las técnicas espectroscópicas (fluorimetría, Raman, etc.) o la espectrometría de masas en la modalidad de paper-spray. Teniendo en cuenta lo anteriormente expuesto, el objetivo principal de la Tesis Doctoral presentada en esta Memoria es el desarrollo de sistemas analíticos de respuesta rápida basados en el acoplamiento directo de soportes planos basados en papel con técnicas instrumentales, tales como la fluorimetría, la espectroscopia Raman y/o la espectrometría de masas. De este objetivo principal, surgen los siguientes objetivos específicos: • Síntesis de soportes planos basados en papel compatibles con espectrometría de masas en la modalidad de infusión directa. Este objetivo se afronta en los Bloques II y III con el desarrollo de dos soportes planos basados en papel. En primer lugar, se ha explotado la capacidad sorbente intrínseca del papel (Capítulo 2). En el segundo caso, se ha modificado papel de filtro con un polímero de impresión molecular para mejorar la selectividad en el aislamiento de los analitos (Capítulo 5). • Síntesis de soportes planos basados en papel compatibles con técnicas espectroscópicas. En el Capítulo 3 de la Memoria se describe el empleo de sorbentes con una alta selectividad en diversas técnicas instrumentales. Por otro lado, se ha desarrollado un sustrato basado en papel modificado con un polímero de impresión molecular y se ha propuesto su acoplamiento con fluorimetría (Capítulo 4). • Síntesis de soportes planos basados en papel duales compatibles tanto con técnicas espectroscópicas como con espectrometría de masas. Esta investigación se desarrolla en el Bloque IV de la Memoria, donde se describen las tendencias sobre las membranas modificadas con nanomateriales (Capítulo 6). Además, se llevó a cabo la modificación de un sustrato basado en papel con nanoflores de plata para la determinación de ketoprofeno en muestra de saliva mediante espectroscopia Raman amplificada en superficie y espectrometría de masas ambiental en la modalidad de paper-spray (Capítulo 7). Por otro lado, también se han desarrollado los siguientes objetivos transversales durante el transcurso de la Tesis Doctoral: • Caracterización de los soportes sintetizados mediante diversas técnicas instrumentales. • Aplicación de los procedimientos desarrollados en el análisis de alimentos y muestras biológicas.In the last decades, the development of methodologies able to provide rapid and reliable results has been deeply investigated in order to address the growing information demand of modern society. In this context, the sample preparation field is greatly concerning, since it is one of the most time-consuming steps and the main source of errors in the analytical procedure, due to the high level of human intervention. Simplification, automation and miniaturization have been the three main tendencies followed in the sample preparation field in the past years, leading to the rise of the microextraction techniques. Furthermore, the decrease of reagents, solvents and energy consumption agrees with the Green Chemistry principles and at the same time contributes to the development of methodologies capable of providing high-quality results in a shorter time. The simplification also involves the materials used in the microextraction techniques. Paper-based analytical devices have emerged as a very promising material due to the advantages of paper as a sorbent, e.g., flexibility, porosity or costeffectiveness. Likewise, the chemical modification of paper with different materials is a steady trend that has led to the increase of the versatility of this support. The modification of paper with polymers or nanomaterials has enabled the synthesis of flat supports with a high surface area able to interact with a wide variety of analytes. However, the procedures employed to carry out these modifications are usually tedious, and a strict control of the experimental conditions is mandatory. For this reason, it is of high importance searching for alternative methods that can overcome this drawback. The simplification of the sample preparation step must consider not only the materials used, but also the instrumental techniques employed for the determination of the analytes. In this sense, paper-based analytical devices have been really useful due to their easy handling and coupling to instrumental techniques, such as spectroscopic techniques or paper-spray mass spectrometry. Based on the foregoing, the foremost aim of this Doctoral Thesis is the development of rapid response analytical systems based on the coupling of paper-based flat supports and instrumental techniques, such as fluorimetry, Raman spectroscopy or mass spectrometry, together with substrates that can be simultaneously employed in different techniques. The specific objectives derived from this general objective are as follows: • Synthesis of paper-based flat supports compatible with direct infusion mass spectrometry. This research is detailed in Blocks II and III, where two paperbased flat supports are developed. On the one hand, the intrinsic sorbent capacity of non-modified cellulose was exploited in Chapter 2. On the other hand, the obtention of a molecularly imprinted paper is explained in Chapter 5 of this Doctoral Thesis. • Synthesis of paper-based flat supports compatible with spectroscopic techniques. The employment of selectivity enhanced sorbents with different instrumental techniques is described in Chapter 3 of this Doctoral Thesis. Furthermore, a molecularly imprinted paper-based analytical device was developed and combined with fluorimetry (Chapter 4). • Synthesis of dual paper-based flat supports compatible with both spectroscopic techniques and mass spectrometry. The results of this study are shown in Block IV, where the current trends about particle loaded membranes are firstly described (Chapter 6). On the other hand, the development of a silver nanoflower-coated paper for the determination of ketoprofen in saliva samples via Surface-enhanced Raman spectroscopy and ambient pressure mass spectrometry was carried out (Chapter 7). Additionally, the following specific objectives have been treated transversally throughout the entire Doctoral Thesis: • Characterization of the supports obtained employing various instrumental techniques. • Application of the developed procedures in the analysis of food products and biological samples

Technological Solutions for Water Sustainability: Challenges and Prospects

The book provides an overview of technical sustainable water management in the Global South, mainly in India. The book is structured in five sections: (1) current state and challenges, (2) new age materials in (waste) water treatment, (3) new technologies developed for (waste) water treatment, (4) sensors, (5) urban water infrastructure. Section-1 provides the latest information about the status and challenges for sustainable water management in India, from the perspective of water quality, industrial and domestic wastewater treatment, urban water infrastructure and policy and governance towards water security. Section 2 deals with new age materials for water and wastewater treatment. This part discusses new framework solids for water purification, new materials for arsenic and fluoride removal, nanocomposites for water and wastewater treatment and removal of hazardous materials, and toxicity of these materials. Section 3 of the book presents the new technologies developed for water and wastewater treatment; dealing with pulsed power technology, constructed wetlands, nutrient recovery, low-cost filters and pollution abatement using waste derived materials. Section 4 of the book focuses on sensors, presenting the development of low-cost colorimetric sensors for eutrophying ions, sensors for conductivity and flow parameters, and multi-analyte assessment for water quality. Finally, Section 5 addresses the issues related to urban water infrastructure, sustainable urban drainage and integrated flood and water scarcity management. This section also discusses virtual water. The unique feature of this edited volume is the special perspective on emerging economies in the Global South, such as India. It provides information about adaption of technologies, development of new technologies, and management practices which are context driven and region specific. It also deals with economical and easy to use sensors for large scale monitoring of water quality and water quantity parameters

Synthesis of new pyrazolium based tunable aryl alkyl ionic liquids and their use in removal of methylene blue from aqueous solution

In this study, two new pyrazolium based tunable aryl alkyl ionic liquids, 2-ethyl-1-(4-methylphenyl)-3,5- dimethylpyrazolium tetrafluoroborate (3a) and 1-(4-methylphenyl)-2-pentyl-3,5-dimethylpyrazolium tetrafluoroborate (3b), were synthesized via three-step reaction and characterized. The removal of methylene blue (MB) from aqueous solution has been investigated using the synthesized salts as an extractant and methylene chloride as a solvent. The obtained results show that MB was extracted from aqueous solution with high extraction efficiency up to 87 % at room temperature at the natural pH of MB solution. The influence of the alkyl chain length on the properties of the salts and their extraction efficiency of MB was investigated

Electrochemical sensor based on polyamide 6/polypyrrole electrospun nanofibers coated with reduced graphene oxide for malathion pesticide detection

Abstract An electrochemical sensor based on polymeric electrospun nanofibers of polyamide 6 (PA6)/polypyrrole (PPy) surface-modified with two forms of graphene was developed for the detection of malathion, an organophosphorus pesticide. The materials were chosen considering the electrospun nanofibers possess large surface area and porosity, while reduced graphene oxide has remarkable electrical conductivity, which is a good strategy to increase sensor sensitivity and improve the limit of detection towards the pesticide. The surface modification of nanofibers with graphene was carried out using chemically (CRGO) and electrochemically reduced graphene oxide (ERGO), in order to demonstrate how the degree of reduction of graphene oxide can influence its electrical conductivity. The influence of the reduction on the conductivity properties of graphene-based films was studied through electrochemical techniques: cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The platform modified with CRGO, which presented higher electrical conductivity compared to ERGO, was used in the electrochemical detection of the pesticide malathion and exhibited a low detection limit of 0.8 ng ml−1 (S/N = 3). The results indicate that chemically reduced graphene oxide is a potential alternative for modifying electrodes surfaces designed for sensing distinct pollutants of environmental or agricultural interest.</jats:p