Superhydrophobic ZnO-Au nanocomposite over polydimethylsiloxane tubes for efficient photocatalytic dye degradation

Multiplexed Gas Sensor: Fabrication Strategies, Recent Progress, and Challenges

Due to miscellaneous toxic gases in the vicinity, there is a burgeoning need for advancement in the existing gas sensing technology not only for the survival of mankind but also for the industries based in various fields such as beverage, forestry, health care, environmental monitoring, agriculture, and military security. A gas sensor must be highly selective toward a specific gas in order to avoid incorrect signals while responding to nontarget gases. This may lead to complex scenarios depicting sensor defects, such as low selectivity and cross-sensitivity. Therefore, a multiplex gas sensor is required to address the problems of cross selectivity by combining different gas sensors, signal processing, and pattern recognition techniques along with the currently employed gas sensing technologies. The different sensing materials used in these sensor arrays will produce a unique response signal for developing a set of identifiers as the input that can be used to recognize a specific gas by its "fingerprint". This review provides a comprehensive review of chemiresistive-based multiplex gas sensors, including various fabrication strategies from expensive to low-cost techniques, advances in sensing materials, and a gist of various pattern recognition techniques used for both rigid and flexible gas sensor applications. Finally, the review assesses the current state-of-the-art in multiplex gas sensor technology and discusses various challenges for future research in this direction.

A simple approach to develop a paper-based biosensor for real-time uric acid detection

The current work reports the development of an inexpensive real-time sensing module for uric acid detection on a simple, disposable paper substrate. Detection is based on a capacitive measurement system using functional ZnO hexagonal rods on pulse-electrodeposited Cu interdigitated electrodes (IDEs) over hydrophobic A4 paper. Both the prepared hydrophobic A4 paper and ZnO hexagonal rods are well characterized using field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), UV-visible spectrophotometry (UV-Vis), Raman spectroscopy, and contact angle measurement. Arduino IDE software is used to configure the Arduino Mega board to evaluate the change in the capacitance value and to display the corresponding uric acid concentration on a liquid crystal display (LCD) screen. The experimental result shows the linear relationship in the range of 0.1 mM-1 mM concentration of uric acid with a high sensitivity of 9.00 μF mM^-1 cm^-2 at 0.1 mM. The results indicate that the developed capacitance measurement unit can be employed for the early screening of uric acid in real samples for clinical applications. The reported proof-of-concept has huge potential towards the development of a disposable and inexpensive biosensor platform.

Paper-based multiplex biosensors for inexpensive healthcare diagnostics: a comprehensive review

Multiplex detection is a smart and an emerging approach in point-of-care testing as it reduces analysis time and testing cost by detecting multiple analytes or biomarkers simultaneously which are crucial for disease detection at an early stage. Application of inexpensive substrate such as paper has immense potential and matter of research interest in the area of point of care testing for multiplexed analysis as it possesses several unique advantages. This study presents the use of paper, strategies adopted to refine the design created on paper and lateral flow strips to enhance the signal, increase the sensitivity and specificity of multiplexed biosensors. An overview of different multiplexed detection studies performed using biological samples has also been reviewed along with the challenges and advantages offered by multiplexed analysis.

Nd-Doped ZnO Nanostructures with Enhanced Photocatalytic Performance for Environmental Protection

Neodymium (Nd)-doped ZnO nanostructures with different amounts of Nd were obtained by the electrospinning-calcination method. X-ray diffraction measurements indicated that the prepared nanostructures have a wurtzite structure without undesirable impurities. Nd doping changes the mean crystallite size as well the lattice strain, as proved by Williamson-Hall plots. The ZnO-based nanostructures were tested as photocatalysts for methylene blue (MB) dye and ciprofloxacin (CIP) drug pollutant degradations under visible light irradiation. Corroborating the obtained results, it was found that the reaction rate constant increased almost linearly with the mean crystallite size (from 2.235 × 10^-2 to 3.482 × 10^-2 min^-1) with a variation in the mean crystallite size from 24.2 to 42.1 nm. Furthermore, the best catalyst sample (0.1% Nd-doped ZnO) was used to optimize the photodegradation process of ciprofloxacin, taking into account the pollutant concentration as well as the catalyst dose. The removal efficiency after 120 min was about 100%, with the rate constant of k = 5.291·10^-2 min^-1 (CIP) and k = 4.780·10^-2 min^-1 (MB) for the established optimal conditions. Considering the value of the rate constant, the half-life of the reaction (τ_1/2 = ln2/k) was evaluated to be about τ_1/2 =13 min for CIP and 14.5 min corresponding to MB. Several catalytic cycles were successfully performed without any loss of photocatalytic activity using these nanostructures, demonstrating that the obtained nanostructures have good stability in the leaching processes.