In this paper, we present a novel laser-induced oxidation procedure for in situ formation of nickel oxide nanoporous structures directly onto the nickel surface as a highly sensitive nonenzymatic glucose sensor. The formation of mesoporous nickel oxide is confirmed by field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. Electrochemical properties of the pristine and laser-induced oxidized nickel (LIO-Ni) films were studied using cyclic voltammetry and electrochemical impedance spectroscopy. The unique three-dimensional mesoporous architecture of the oxide film on the LIO-Ni electrode resulted in a dramatic enhancement in electrochemical reduction/oxidation performance with a 10-fold increase in electrocatalytic activity for nonenzymatic glucose oxidation as compared to the pristine-Ni electrode. The LIO-Ni biosensor performance was successfully examined for the amperometric detection of glucose over a wide concentration range from 5 μM to 1.1 mM with a high linear sensitivity of 5222 μA mM −1 cm −2 . The limit of detection was obtained as low as 3.31 μM with a signal-tonoise ratio of 3. Furthermore, the LIO-Ni electrode showed outstanding long-term stability, reproducibility, and high selectivity in the presence of various interfering agents including uric acid, L-ascorbic acid, acetaminophen, glutamic acid, and citric acid. The demonstrated laser-induced oxidation process can be potentially adapted to the scalable manufacturing of a wide range of other easyto-use and robust metal oxide-based sensors for nonenzymatic biosensing applications.
This work describes the preparation, characterization and use of a nickel oxide/oxyhydroxide-printed carbon electrode as an efficient potentiometric phosphate sensor.
Many commercially available pH sensors are fabricated with a glass membrane as the sensing component because of several advantages of glass-based electrodes such as versatility, high accuracy, and excellent stability in various conditions. However, because of their bulkiness and poor mechanical properties, conventional glass-based sensors are not ideal for wearable or flexible applications. Here, we report for the first time the fabrication of a flexible glass-based pH sensor suitable for biomedical and environmental applications where flexibility and stability of the sensor are critical for long-term and real-time monitoring. The sensor was fabricated via a simple and facile approach using the cold atmospheric plasma technique in which a pH sensitive silica coating was deposited from a siloxane precursor onto a carbon electrode. In order to increase the sensitivity and stability of the sensor, we employed a postprocessing step which involves annealing of the silica coated electrode at elevated temperatures. This process was optimized to ensure that the crucial properties such as porosity and hydration functionality were balanced to obtain the best and most reliable sensitivity of the sensor. Our sensitivity test results indicated that these sensors exhibit excellent and stable sensitivity with a slope of about 48 mV/pH (r 2 = 0.998) and selectivity across a pH range of 4 to 10 in the presence of various cations. The optimized sensor has shown stable sensitivity for a long period of time (30 h of immersion) and in different bending conditions. We demonstrate in this investigation that this flexible cost-effective pH sensor can withstand the sterilization process resulting from ultraviolet radiation and shows repeatable sensitivity with less than ±5 mV potential drift from the sensitivity values of the standard optimized sensor.
During the γ-radiation sterilization process, the levels of radiation exposure to a medical device must be carefully monitored to achieve the required sterilization without causing deleterious effects on its intended physical and chemical properties. To address this issue, here we have demonstrated the development of an all-printed disposable low-cost sensor that exploits the change in electrical impedance of a semi-interpenetrating polymer network (SIPN) composed of poly(vinyl alcohol) (PVA) and poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) as a functional polymer composite for radiation sterilization monitoring applications. Specifically, the PEDOT:PSS acts as the electrically conductive medium, while the PVA provides the ductility and stability of the printed sensors. During irradiation exposure, chain scission and cross-linking events occur concurrently in the PEDOT:PSS and PVA polymer chains, respectively. The concurrent scissoring of the PEDOT polymer and cross-linking of the PVA polymer network leads to the formation of a stable SIPN with reduced electrical conductivity, which was verified through FTIR, Raman, and TGA analysis. Systematic studies of different ratios of PEDOT:PSS and PVA mixtures were tested to identify the optimal ratio that provided the highest radiation sensitivity and stability performance. The results showed that PEDOT:PSS/PVA composites with 10 wt % PVA produced sensors with relative impedance changes of 30% after 25 kGy and up to 370% after 53 kGy (which are two of the most commonly used radiation exposure levels for sterilization applications). This composition showed high electrical impedance stability with less than ±5% change over 18 days after irradiation exposure. These findings demonstrate the feasibility of utilizing a printing technology for scalable manufacturing of low-cost, flexible radiation sensors for more effective monitoring of radiation sterilization processes.
In this work, a scalable and rapid process is developed for creating a low‐cost humidity sensor for wireless monitoring of moisture levels within packaged goods. The sensor comprises a moisture‐sensitive interdigitated capacitor connected to a planar spiral coil, forming an LC circuit whose resonant frequency is a function of environmental humidity. The sensor is fabricated on a commercially available metallized parchment paper through selective laser ablation of the laminated aluminum (Al) film on the parchment paper substrate. The laser ablation process provides a unique one‐step patterning of the conductive Al layer on the paper while simultaneously creating high surface area Al2O3 nanoparticles within the laser‐ablated regions. The intrinsic humidity‐responsive characteristics of the laser‐induced Al2O3 nanostructures provide the wireless sensor with a tenfold higher sensitivity to humidity than a similar LC resonant sensor prepared by conventional photolithography‐based processes on FR‐4 substrates. The frequency change of the sensor is observed to be a linear function within the range of 0−85% RH, providing an average sensitivity of −87 kHz RH−1 with good repeatability and stable performance. Furthermore, the employment of scalable laser fabrication processes using commercially available inexpensive materials renders these technologies viable for roll‐to‐roll manufacturing of low‐cost wireless sensors for smart packaging applications.
Originally developed for use in controlled laboratory settings, potentiometric ionselective electrode (ISE) sensors have recently been deployed for continuous, in situ measurement of analyte concentration in agricultural (e.g., nitrate), environmental (e.g., ocean acidification), industrial (e.g., wastewater), and health-care sectors (e.g., sweat sensors). However, due to uncontrolled temperature and lack of frequent calibration in these field applications, it has been difficult to achieve accuracy comparable to the laboratory setting. In this paper, we propose a novel temperature self-calibration method where the ISE sensors can serve as their own thermometer and therefore precisely measure the analyte concentration in the field condition by compensating for the temperature variations. We validate the method with controlled experiments using pH and nitrate ISEs, which use the Nernst principle for electrochemical sensing. We show that, using temperature self-calibration, pH and nitrate can be measured within 0.3% and 5% of the true concentration, respectively, under varying concentrations and temperature conditions. Moreover, we perform a field study to continuously monitor the nitrate concentration of an agricultural field over a period of 6 days. Our temperature self-calibration approach determines the nitrate concentration within 4% of the ground truth measured by laboratory-based high-precision nitrate sensors. Our approach is general and would allow battery-free temperature-corrected analyte measurement for all Nernst principle-based sensors being deployed as wearable or implantable sensors.
Copper oxide nanostructures are widely used for various applications due to their unique optical and electrical properties that are tuneable via fabrication and deposition techniques. In this work, we demonstrate...
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