Semiconducting polymers for gas detection

Conjugated polyenes, and polyesters containing phthalocyanine in their backbone, were synthesized. These polymers were characterized by chemical analysis, thermogravimetric analysis, spectral analysis, and X-ray diffraction studies for crystallinity, as well as for their film-forming capability and gas/polymer interactions. Most of the polymers were relatively insensitive to water vapor up to 50 percent relative humidity, but the polyester/phthalocyanine (iron) polymer was relatively insensitive up to 100 percent RH. On the other hand, poly(p-dimethylaminophenylacetylene) was too conductive at 100 percent RH. Of the gases tested, the only ones that gave any evidence of interacting with the polymers were SO2, NOx, HCN and NH3. Poly(imidazole)/thiophene responded to each of these gases at all relative humidities, while the other polymers gave varying response, depending upon the RH. Thus, since most of these gases were electron-accepting, the electron-donating character of poly(imidazole)/thiophene substantiates the concept of electronegativity being the operating principle for interaction effects. Of the six polymers prepared, poly(imidazole)/thiophene first showed a very good response to smoldering cotton, but it later became nonresponsive; presumably due to oxidation effects

Chemical Polymerization Kinetics of Poly-O-Phenylenediamine and Characterization of the Obtained Polymer in Aqueous Hydrochloric Acid Solution Using K 2

The oxidative chemical polymerization of o-phenylenediamine (OPDA) was studied in hydrochloric acid solution using potassium dichromate as oxidant at 5°C. The effects of potassium dichromate, hydrochloric acid, and monomer concentrations on the polymerization reaction were investigated. The order of reaction with respect to potassium dichromate, hydrochloric acid, and monomer concentration was found to be 1.011, 0.954, and 1.045, respectively. Also, the effect of temperature on the polymerization rate was studied and the apparent activation energy of the polymerization reaction was found to be 63.658 kJ/mol. The obtained polymer was characterized using XPS, IR, UV-visible, and elemental analysis. The surface morphology of the obtained polymers was characterized by X-ray diffraction and transmission electron microscopy (TEM). The TGA analysis was used to confirm the proposed structure and number of water molecules in each polymeric chain unit. The ac conductivity (σac) of (POPDA) was investigated as a function of frequency and temperature. The ac conductivity was interpreted as a power law of frequency. The frequency exponent (s) was found to be less than unity and decreased with the increase of temperature, which confirms that the correlated barrier hopping model was the dominant charge transport mechanism

Metal ion and pH Sensors based on Carbon Nanotubes

The sensitive and selective detection of metal ions and pH levels is important in environmental and biomedical applications. Conventional methods are limited in their potential due to high cost, big size, and lack of portability. A new system incorporating single-walled carbon nanotubes (SWNTs) modified with polymers or proteins has been developed to create a cost-effective, easy-to-use metal ion/pH sensing platform. This system utilized SWNTs modified with metal ion/pH sensitive materials because pristine SWNTs are only sensitive to high concentrations of metal ions (> 1 mM), and strong base (pH > 12) or acid (pH < 2), and lack selectivity as well. This work uses noncovalent functionalization approaches to chemically modify SWNTs because noncovalent modifications do not disrupt SWNT electronic properties. When the modified-SWNT system encounters metal ions or pH solutions, the alteration in modified layers, such as conformational change or charge transfer, initiates signal transduction processes, thus changing the electrical and optical properties of the underlying SWNTs. The properties of modified SWNTs were characterized by a variety of techniques including optical spectroscopy, and electrical transport measurements in solid state or liquid state, through which the transduction mechanism of the system was investigated. The modified SWNT-based metal ion/pH sensors offer promise in applications and provide a platform for fundamental understanding of the transduction mechanism that help us to develop better chemical sensors in the future

Molecularly imprinted polymers combined with electrochemical sensors for food contaminants analysis

Detection of relevant contaminants using screening approaches is a key issue to ensure food safety and respect for the regulatory limits established. Electrochemical sensors present several advantages such as rapidity; ease of use; possibility of on-site analysis and low cost. The lack of selectivity for electrochemical sensors working in complex samples as food may be overcome by coupling them with molecularly imprinted polymers (MIPs). MIPs are synthetic materials that mimic biological receptors and are produced by the polymerization of functional monomers in presence of a target analyte. This paper critically reviews and discusses the recent progress in MIP-based electrochemical sensors for food safety. A brief introduction on MIPs and electrochemical sensors is given; followed by a discussion of the recent achievements for various MIPs-based electrochemical sensors for food contaminants analysis. Both electropolymerization and chemical synthesis of MIP-based electrochemical sensing are discussed as well as the relevant applications of MIPs used in sample preparation and then coupled to electrochemical analysis. Future perspectives and challenges have been eventually given

Molecularly Imprinted Sensors — New Sensing Technologies

In this chapter we discus molecular imprinting technology (MIT), molecular imprinted polymers (MIPs), and their compatibility on a proper transducer to construct a sensing system. Molecularly imprinted sensors (MISens), in other words, artificial receptor-based sensors synthesized in the presence of the target molecule, are capable of sensing target molecules by using their specific cavities and are compatible with the target molecule. This MIP technology is a viable alternative of artificial receptor technology, and the sensor technology is capable of detecting any kind of molecule without pre-analytic preparations. In this chapter, you can find examples, sensor construction techniques and fundamentals of MIP and sensor combinations to look forward in your studies. For sensor technology, we explained and discussed the new sensing technologies of MIP-based electrochemical, optical (especially surface plasmon resonance, SPR), and piezoelectric techniques. Therefore, this chapter presents a short guideline of MISens

The rational development of molecularly imprinted polymer-based sensors for protein detection.

The detection of specific proteins as biomarkers of disease, health status, environmental monitoring, food quality, control of fermenters and civil defence purposes means that biosensors for these targets will become increasingly more important. Among the technologies used for building specific recognition properties, molecularly imprinted polymers (MIPs) are attracting much attention. In this critical review we describe many methods used for imprinting recognition for protein targets in polymers and their incorporation with a number of transducer platforms with the aim of identifying the most promising approaches for the preparation of MIP-based protein sensors (277 references)

Development of a skin-like sensor for monitoring an inflammatory biomarker for wound care application

Globally, wound management poses a massive challenge with a great impact on social-economic and healthcare systems. In a post-Covid era, at-home diagnostic and monitoring devices gained a crucial role in our lives, boosting the development of novel skin patch sensors targeted for health monitoring. In this context, one of the most important requirements concerns the creation of flexible and conformable conductive platforms that can be employed as skin-like sensors. Thus, the main goal of this dissertation consists in the development of a flexible electrochemical biosensing device for the detection of an inflammation biomarker, interleukin-6 (IL-6). The 3-electrode gold pattern was standardized by e-beam evaporation on a 6 μm polyimide membrane, a transparent and biocompatible polymeric material. Subsequently, protein-printed sensors were electrochemically fabricated on the gold-modified electrodes for IL-6 detection. This biorecognition is accomplished with molecularly-imprinted polymers (MIPs) that were synthesized on the electrode surface by electropolymerization of a mixture of two monomers, pyrrole and carboxylated pyrrole. Along this process, several electropolymerization parameters were optimized like the potential range and number of cycles, as well as the pH conditions of the medium and the removal of the imprinted protein, to create the cavities responsible for the rebinding event. Electrochemical sensing features were then investigated to demonstrate the imprinting effect and the optimized biosensor exhibited a linear electrochemical response in the 0.5 ng/mL to 500 ng/mL concentration range. Moreover, chemical, and morphological characterizations, such as XPS, SEM and FTIR confirmed the surface modifications on the gold surface. The final biosensing device demonstrated great potential in terms of sensitivity, stability, and reproducibility, making it a simpler and more cost-effective portable solution for the remote monitoring of chronic wounds. Finally, the incorporation of the sensing component directly on biocompatible flexible polymers enables new monitoring and treatment tools that can be more accurate, less invasive, and more comfortable for the patient.Globalmente, a monitorização de feridas representa um enorme desafio com grande impacto nos sistemas socio-económicos e de saúde. Numa era pós-Covid, os dispositivos de diagnóstico e monitorização a partir de casa adquiriram um papel crucial nas nossas vidas, impulsionando o desenvolvimento de novos sensores flexíveis para a pele para monitorização da saúde. Nesse contexto, um dos requisitos mais importantes diz respeito à criação de plataformas condutoras flexíveis e conformáveis que possam ser utilizadas como sensores para pele. Assim, o principal objetivo desta dissertação consiste no desenvolvimento de um dispositivo biossensor eletroquímico flexível para a deteção de um biomarcador de inflamação, interleucina-6 (IL-6). O padrão de 3 elétrodos de ouro foi padronizado por evaporação por feixe eletrónico numa membrana de poliimida com 6 μm de espessura, um material polimérico transparente e biocompatível. Posteriormente, os biossensores foram fabricados eletroquimicamente nos elétrodos modificados com ouro para deteção de IL-6. Este bioreconhecimento é realizado através de polímeros de impressão molecular (MIPs) que foram sintetizados na superfície do elétrodo por eletropolimerização de uma mistura de dois monómeros, pirrol e pirrol carboxilado. Ao longo deste processo, vários parâmetros de eletropolimerização foram otimizados tais como a gama de potencial aplicado e o número de ciclos, as condições de pH do meio e a remoção da proteína impressa, a fim de criar as cavidades responsáveis pelo evento de religação. As características de deteção eletroquímica foram então investigadas para demonstrar o efeito de impressão e o biossensor otimizado exibiu uma resposta eletroquímica linear na gama de concentrações de 0.5 ng/mL a 500 ng/mL. Além disso, caracterizações químicas e morfológicas, tais como XPS, SEM e FTIR confirmaram as modificações químicas na superfície do eléctrodo. O dispositivo biossensor final demonstrou potencial em termos de sensibilidade, estabilidade e reprodutibilidade, tornando-se uma solução portátil, simples e económica para a monitorização remota de feridas crónicas. Por fim, a incorporação do componente sensor diretamente em polímeros flexíveis biocompatíveis permite novas ferramentas de monitorização e tratamento que podem ser mais precisas, menos invasivas e mais confortáveis para o paciente

Recent Developments in the Field of Explosive Trace Detection

Explosive trace detection (ETD) technologies play a vital role in maintaining national security. ETD remains an active research area with many analytical techniques in operational use. This review details the latest advances in animal olfactory, ion mobility spectrometry (IMS), and Raman and colorimetric detection methods. Developments in optical, biological, electrochemical, mass, and thermal sensors are also covered in addition to the use of nanomaterials technology. Commercially available systems are presented as examples of current detection capabilities and as benchmarks for improvement. Attention is also drawn to recent collaborative projects involving government, academia, and industry to highlight the emergence of multimodal screening approaches and applications. The objective of the review is to provide a comprehensive overview of ETD by highlighting challenges in ETD and providing an understanding of the principles, advantages, and limitations of each technology and relating this to current systems