Molecularly imprinted polymer-based sensors for priority pollutants

Globally, there is growing concern about the health risks of water and air pollution. The U.S. Environmental Protection Agency (EPA) has developed a list of priority pollutants containing 129 different chemical compounds. All of these chemicals are of significant interest due to their serious health and safety issues. Permanent exposure to some concentrations of these chemicals can cause severe and irrecoverable health effects, which can be easily prevented by their early identification. Molecularly imprinted polymers (MIPs) offer great potential for selective adsorption of chemicals from water and air samples. These selective artificial bio(mimetic) receptors are promising candidates for modification of sensors, especially disposable sensors, due to their low-cost, long-term stability, ease of engineering, simplicity of production and their applicability for a wide range of targets. Herein, innovative strategies used to develop MIP-based sensors for EPA priority pollutants will be reviewed. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

An enhanced safrole sensing performance of a olyacrylonitrile nanofiber-based-QCM sensor by overlaying with chitosan

We report on a method to enhance the sensing performance of polyacrylonitrile (PAN) nanofiber-based QCM sensor overlaid with chitosan. The PAN nanofibers were deposited on the QCM sensing surface by electrospinning technique followed by overlay with chitosan by a drop-casting method. The Fourier transform infrared (FTIR) spectra confirm that chitosan covers the PAN nanofibers. The SEM images show the average diameter of the produced PAN nanofibers was 236 nm, and it increased to 283 nm after overlay with chitosan. The modified QCM sensor has the sensitivity of 18.7 Hz mg-1 L, which is better than that of PAN nanofiber alone of 4.5 Hz mg-1 L. It is an increase nearly 5 times. The analytical parameters of the limit of detection (LOD), sensitivity, a time constant, and stability improved after the PAN nanofiber sensor was overlaid with chitosan. The amine groups present in chitosan interact effectively with safrole, thus increase the sensing response. The proposed device is robust, inexpensive, and convenient for detecting safrole, and can be used as an alternative to those of classical instrumental methods for the analysis of safrole as a drug precursor

Design of Electronic Nose System Using Gas Chromatography Principle and Surface Acoustic Wave Sensor

Most gases are odorless, colorless and also hazard to be sensed by the human olfactory system. Hence, an electronic nose system is required for the gas classification process. This study presents the design of electronic nose system using a combination of Gas Chromatography Column and a Surface Acoustic Wave (SAW). The Gas Chromatography Column is a technique based on the compound partition at a certain temperature. Whereas, the SAW sensor works based on the resonant frequency change. In this study, gas samples including methanol, acetonitrile, and benzene are used for system performance measurement. Each gas sample generates a specific acoustic signal data in the form of a frequency change recorded by the SAW sensor. Then, the acoustic signal data is analyzed to obtain the acoustic features, i.e. the peak amplitude, the negative slope, the positive slope, and the length. The Support Vector Machine (SVM) method using the acoustic feature as its input parameters are applied to classify the gas sample. Radial Basis Function is used to build the optimal hyperplane model which devided into two processes i.e., the training process and the external validation process. According to the result performance, the training process has the accuracy of 98.7% and the external validation process has the accuracy of 93.3%. Our electronic nose system has the average sensitivity of 51.43 Hz/mL to sense the gas samples

Síntesis y caracterización de un semiconductor ZnO dopado con Au para sensores de gas

En esta investigación se sintetizaron películas de ZnO dopadas con Au, a través del método sol-gel; evaluando el efecto del porcentaje molar (3, 5 y 7%) de dopante y de la temperatura de recocido (400, 500 y 600°C) sobre las propiedades estructurales, de absorbancia, de sensibilidad a los gases H2 y CO, y eléctricas. Las mediciones de difracción de rayos X y la intensidad de las bandas de absorción ultravioleta-visible evidencian que, con el método utilizado, las películas delgadas de ZnO presentan la fase wurtzita. El aumento del porcentaje molar de Au disminuye el tamaño del cristal, mientras que la temperatura de recocido lo hace aumentar. Así también, con el incremento de Au y de la temperatura de recocido, disminuye el ancho de la banda prohibida y desplaza el pico del excitón hacia mayores energías. Con el aumento de porcentaje de dopante y de la temperatura de recocido, se incrementa el número de portadores de carga, mientras que la movilidad disminuye; incrementando también la sensibilidad a los gases CO e H2, obteniéndose como resultado una alta respuesta a la presencia de del gas H2 en todas las temperaturas ensayadas, y una respuesta ligera a la presencia de CO

Electrospinning of composite biomaterials: incorporation of bioactive agents and formation of hierarchical nanostructures

This PhD focused on promotion of bioactivity of electrospun fibres. Two methods were used to achieve this objective: using antimicrobial agents and, creating hierar-chical structures.Antimicrobial agents, essential oils and zinc oxide nanoparticles, were encapsulat-ed in polymer nanofibres to promote antimicrobial properties. Tea tree and Manuka essential oils were encapsulated in poly (lactic acid) (PLA) by dissolving in their common solvent acetone and then electrospin. Plasticising effect of essential oils was observed in differential scanning calorimetry (DSC)test. Glass transition temperature of PLA fibres decreased with increasing essential oil concen-tration. This corresponded with mechanical results. Manuka/PLA fibres showed successful result in inhibition of E. coli in antimicrobial test.Zinc oxide nanoparticles have previously been used in electrospun fibres for anti-microbial purpose. To my knowledge, previous studies have only achieved to en-capsulate zinc oxide nanoparticles directly in electrospun fibres. In this thesis, for the first time, zinc oxide nanoparticles were first in-situ synthesised in polyethylene-imine (PEI) and then combined with zein to electrospin fibres. Resulting fibres showed better mechanical properties when compared to pure electrospun zein fi-bres.The second method, creating hierarchical structure, was achieved by phase separa-tion. An unique dual-porosity structure of electrospun poly(ethyl cyanoacry-late)/polycaprolactone (PECA/PCL) was demonstrated. Composition of fibres was confirmed by Fourier-transform infrared spectroscopy (FTIR). Hierarchical structures are believed to favour cell attachment and proliferation by increasing fibre surface roughness and surface-to-volume ratio.</div

The 1st International Electronic Conference on Chemical Sensors and Analytical Chemistry

The 1st International Electronic Conference on Chemical Sensors and Analytical Chemistry was held on 1–15 July 2021. The scope of this online conference was to gather experts that are well-known worldwide who are currently working in chemical sensor technologies and to provide an online forum for the presention and discussion of new results. Throughout this event, topics of interest included, but were not limited to, the following: electrochemical devices and sensors; optical chemical sensors; mass-sensitive sensors; materials for chemical sensing; nano- and micro-technologies for sensing; chemical assays and validation; chemical sensor applications; analytical methods; gas sensors and apparatuses; electronic noses; electronic tongues; microfluidic devices; lab-on-a-chip; single-molecule sensing; nanosensors; and medico-diagnostic testing

Enhanced Dibutyl Phthalate Sensing Performance of a Quartz Crystal Microbalance Coated with Au-Decorated ZnO Porous Microspheres

Noble metals addition on nanostructured metal oxides is an attractive way to enhance gas sensing properties. Herein, hierarchical zinc oxide (ZnO) porous microspheres decorated with cubic gold particles (Au particles) were synthesized using a facile hydrothermal method. The as-prepared Au-decorated ZnO was then utilized as the sensing film of a gas sensor based on a quartz crystal microbalance (QCM). This fabricated sensor was applied to detect dibutyl phthalate (DBP), which is a widely used plasticizer, and its coating load was optimized. When tested at room temperature, the sensor exhibited a high sensitivity of 38.10 Hz/ppb to DBP in a low concentration range from 2 ppb to 30 ppb and the calculated theoretical detection limit is below 1 ppb. It maintains good repeatability as well as long-term stability. Compared with the undecorated ZnO based QCM, the Au-decorated one achieved a 1.62-time enhancement in sensitivity to DBP, and the selectivity was also improved. According to the experimental results, Au-functionalized ZnO porous microspheres displayed superior sensing performance towards DBP, indicating its potential use in monitoring plasticizers in the gaseous state. Moreover, Au decoration of porous metal oxide nanostructures is proved to be an effective approach for enhancing the gas sensing properties and the corresponding mechanism was investigated

Enhanced Dibutyl Phthalate Sensing Performance of a Quartz Crystal Microbalance Coated with Au-Decorated ZnO Porous Microspheres

Noble metals addition on nanostructured metal oxides is an attractive way to enhance gas sensing properties. Herein, hierarchical zinc oxide (ZnO) porous microspheres decorated with cubic gold particles (Au particles) were synthesized using a facile hydrothermal method. The as-prepared Au-decorated ZnO was then utilized as the sensing film of a gas sensor based on a quartz crystal microbalance (QCM). This fabricated sensor was applied to detect dibutyl phthalate (DBP), which is a widely used plasticizer, and its coating load was optimized. When tested at room temperature, the sensor exhibited a high sensitivity of 38.10 Hz/ppb to DBP in a low concentration range from 2 ppb to 30 ppb and the calculated theoretical detection limit is below 1 ppb. It maintains good repeatability as well as long-term stability. Compared with the undecorated ZnO based QCM, the Au-decorated one achieved a 1.62-time enhancement in sensitivity to DBP, and the selectivity was also improved. According to the experimental results, Au-functionalized ZnO porous microspheres displayed superior sensing performance towards DBP, indicating its potential use in monitoring plasticizers in the gaseous state. Moreover, Au decoration of porous metal oxide nanostructures is proved to be an effective approach for enhancing the gas sensing properties and the corresponding mechanism was investigated