Sensors For Environmental Monitoring Research Articles

Laser-induced graphene gas sensors for environmental monitoring.

Artemesia tridentata is a foundational plant taxon in western North America and an important medicinal plant threatened by climate change. Low-cost fabrication of sensors is critical for developing large-area sensor networks for understanding and monitoring a range of environmental conditions. However, the availability of materials and manufacturing processes is still in the early stages, limiting the capacity to develop cost-effective sensors at a large scale. In this study, we demonstrate the fabrication of low-cost flexible sensors using laser-induced graphene (LIG); a graphitic material synthesized using a 450-nm wavelength bench top laser patterned onto polyimide substrates. We demonstrate the effect of the intensity and focus of the incident beam on the morphology and electrical properties of the synthesized material. Raman analyses of the synthesized LIG show a defect-rich graphene with a crystallite size in the tens of nanometers. This shows that the high level of disorder within the LIG structure, along with the porous nature of the material provide a good surface for gas adsorption. The initial characterization of the material has shown an analyte response represented by a change in resistance of up to 5% in the presence of volatile organic compounds (VOCs) that are emitted and detected by Artemisia species. Bend testing up to 100 cycles provides evidence that these sensors will remain resilient when deployed across the landscapes to assess VOC signaling in plant communities. The versatile low-cost laser writing technique highlights the promise of low-cost and scalable fabrication of LIG sensors for gas sensor monitoring.

Assessing Wear Characteristics of Sprayable, Diacetylene-Containing Sensor Formulations.

This work extends recent developments in diacetylene-based, sprayable sensors by identification and assessment of formulations which facilitate their use for wearable sensing. Diacetylene-based spray-on sensors have the potential to be a widely deployed sensing technology, as they require no power and can be applied as thin coatings onto surfaces to provide a colorimetric response to target exposure. In responding to radiation, liquid-phase targets, or gas-phase targets specifically determined by the formulation of the sprayable sensor used, this technology is amenable to wearable sensors for measuring exposure to different environmental risks. Here, we provide the means to improve wear resistance, reduce false-positive signals due to wetting, and enhance color fastness for coatings of sprayable, diacetylene-based sensor formulations on cotton fabric. These sensor formulations possess polymethyl methacrylate (PMMA), which enhances the coating stability to only 8% color loss due to wear compared to 18-25% without PMMA, while maintaining the inherent ability of diacetylene-component formulations to detect radiation as well as gas or liquid phase analytes. This represents a significant step toward the use of diacetylene-based sensing formulations for wearable sensing. In the future, the form of spray-on sensor materials demonstrated here may find use in wearable sensing applications for detection of cumulative exposure to UV radiation, hydrogen peroxide vapors, or solvent exposure. We expect trends toward applications toward other wearable sensors for environmental monitoring given the well-known customizability in target response of diacetylene-containing monomers by modifying their headgroup chemistry.

Electrochemical Sensing Strategies for Synthetic Orange Dyes.

This review explores electrochemical sensing strategies for synthetic orange dyes, addressing the growing need for sensitive and selective detection methods in various industries. We examine the fundamental principles underlying the electrochemical detection of these compounds, focusing on their redox behavior and interaction with electrode surfaces. The review covers a range of sensor designs, from unmodified electrodes to advanced nanomaterial-based platforms. Chemically modified electrodes incorporating polymers and molecularly imprinted polymers are discussed for their enhanced selectivity. Particular attention is given to nanomaterial-based sensors, including those utilizing carbon nanotubes, graphene derivatives, and metal nanoparticles, which have demonstrated exceptional sensitivity and wide linear ranges. The potential of biological-based approaches, such as DNA interaction sensors and immunosensors, is also evaluated. Current challenges in the field are addressed, including matrix effects in complex samples and long-term stability issues. Emerging trends are highlighted, including the development of multi-modal sensing platforms and the integration of artificial intelligence for data analysis. The review concludes by discussing the commercial potential of these sensors in food safety, environmental monitoring, and smart packaging applications, emphasizing their importance in ensuring the safe use of synthetic orange dyes across industries.

Design of low-cost humidity sensor based on chipless RFID

It is of great significance to design a low-cost chipless radio frequency identification(RFID) sensor for environmental humidity monitoring. To this end, polyvinyl alcohol (PVA) film is used as a humidity sensitive material, and the overall size of the rectangular substrate is 18 mm × 18 mm ×0.5 mm. Through the humidity sensing principle and simulation analysis, the change of environmental humidity causes the change of the dielectric constant of the humidity sensitive material PVA, which in turn affects the resonant frequency offset of the entire sensor. The simulation results show that the relative humidity working range of the designed humidity sensor is 21.9% ∼ 52.5%, the corresponding sensor resonant frequency range is 2.76 ∼ 2.51GHz, the total offset reaches 250 MHz, and the average sensitivity at the maximum relative humidity is 23.08MHz/% . The designed humidity sensor has the advantages of miniaturization, simple structure and low cost, and can be used for humidity monitoring in various target environments. Keywords.low cost; chipless RFID humidity sensor; polyvinyl alcohol; humidity monitoring; humidity sensitive material.

Chemical Sensor Technologies for Sustainable Development: Recent Advances, Classification, and Environmental Monitoring

AbstractOne of the significant issues of concern in recent times is detecting, quantifying, and monitoring various chemical contaminants in the environment. Numerous inorganic and organic substances are discharged into the environment from various anthropogenic activities, thereby polluting the ecosystems' air, water, soil, and other components. These contaminants have been documented to have deleterious effects on humans, animals, and the environment. Therefore, the need for monitoring and continual quantification of the contents of these contaminants in various environmental matrices becomes paramount. Many diverse sensors are fabricated for multiple utilizations, including liquids and gas sensors, wireless sensors, electronic tongues, and noses for detecting volatile airborne substances, pollutants, and effluents. This review focuses on cutting‐edge technology used in chemical sensors for environmental protection and sustainable development. It also discusses the fabrication and development of chemical sensors and their working principles. In addition, highlights about the applications of chemical sensors in environmental monitoring are also elaborated. This review article discusses emerging sensor technologies and their application in ecological monitoring. Further, the recognition of chemical warfare agents and homeland security applications with the help of bioelectronic nose and tongue is discussed. Finally, some challenges associated with chemical sensors and future trends are also attempted.

III-nitride MQW-based optoelectronic sensors for multifunctional environmental monitoring

This work presents an integrated multi-quantum well (MQW) optoelectronic sensor leveraging III-nitride materials for multifunctionality on a monolithic chip. Fabricated using standard microfabrication techniques, the sensor adopts identical InGaN/GaN MQWs, enabling simultaneous emission and detection. The sensor features a double concentric circle structure, supporting both on-chip and off-chip detection mechanisms, capable of detecting environmental parameters like rotational speed, proximity, and sucrose concentration. It exhibits stable photocurrent response to rotational speed up to 8000 rpm, a 3 cm vertical detection range, and a linear response with 3.9 nA/% sensitivity to changes in sucrose concentration, demonstrating potential for diverse applications including industrial and biomedical fields.

Performance Study of Collection Tree Protocol in Mobile Wireless Sensor Network

The Mobile Wireless Sensor Networks (MWSN) are defined as the successor of Wireless Sensor Networks (WSN); geographically distributed autonomous mobile sensors for physical and environmental conditions monitoring. Mobile sensor networks are more flexible than static sensor networks as they can cope with rapid topology changes. Sensor networks are deployed by having their sensors collect information reliably and then relay the sensor readings to a central base station using wireless multi-hop transmission. Multi-hop routes within a rapid-changed topology requires a routing protocol that can adapt to network changes with an efficient communication mechanism among the nodes; to comply with the energy-constraint nature of the wireless sensor networks. Through significant simulation on this study using the AVRora simulator, the Collection Tree Protocol’s (CTP) capacity to respond to MWSN’s changing network topology was assessed by analysing the performance indicators; specifically, the average of packet loss and energy use of mobile nodes with different circumstances considering varied quantities of mobile nodes in the simulation region, with different velocities and network density. In several circumstances, the implementation of CTP in MWSN indicates a rise in energy usage because of broken linkages along with regular tree regeneration brought on by node mobility.

Rational design of carbon dot nanozymes for ratiometric dual-signal and smartphone-assisted visual detection of nitrite in food matrices

Developing reliable nitrite (NO2−) sensors is essential for food safety and reducing health risks from NO2− exposure. In this study, we strategically designed nitrogen-doped carbon dot (N-CD) nanozymes to establish an accessible dual-signal ratiometric sensing system for detecting NO2− in food matrices. This system utilizes the photoluminescence and enzyme-like properties of N-CD nanozymes combined with NO2−-triggered diazotization reactions of substrates such as o-phenylenediamine (OPD) or 3,3',5,5'-tetramethylbenzidine (TMB). The resulting N-CD/OPD and N-CD/TMB composites provide dual-mode detection—fluorescence and colorimetric—with high selectivity for NO2− and excellent resistance to interference. These sensors exhibit clear color changes under both ultraviolet and visible light, and can be combined with smartphones for visual, on-site detection of NO2−. By incorporating a ratiometric strategy, dual-signal output, and smartphone compatibility, our system achieved a low detection limit (≤ 1.92μM) and satisfactory recovery rates (85.6~115%) in environmental water and food samples. This highlights the potential of smartphone-assisted sensors for environmental monitoring and food safety applications. Our carbon dot-based platform offers a practical and effective solution for on-site NO2− detection, contributing valuable insights to the field.

Machine Learning Approach for Spatiotemporal Multivariate Optimization of Environmental Monitoring Sensor Locations

Abstract Long-term environmental monitoring is critical for managing the soil and groundwater at contaminated sites. Recent improvements in state-of-the-art sensor technology, communication networks, and artificial intelligence have created opportunities to modernize this monitoring activity for automated, fast, robust, and predictive monitoring. In such modernization, it is required that sensor locations be optimized to capture the spatiotemporal dynamics of all monitoring variables as well as to make it cost-effective. The legacy monitoring datasets of the target area are important to perform this optimization. In this study, we have developed a machine-learning approach to optimize sensor locations for soil and groundwater monitoring based on ensemble supervised learning and majority voting. For spatial optimization, Gaussian process regression (GPR) is used for spatial interpolation, while the majority voting is applied to accommodate the multivariate temporal dimension. Results show that the algorithms significantly outperform the random selection of the sensor locations for predictive spatiotemporal interpolation. While the method has been applied to a four-dimensional dataset (with two-dimensional space, time, and multiple contaminants), we anticipate that it can be generalizable to higher-dimensional datasets for environmental monitoring sensor location optimization.

Hierarchical Porous Biowaste‐Based Dual Humidity/Pressure Sensor for Robotic Tactile Sensing, Sustainable Health, and Environmental Monitoring

A crucial tradeoff between material efficacy and environmental impact is often encountered in the development of high‐performance sensors. The use of rare‐earth elements or intricate fabrication techniques is sometimes needed for conventional sensing materials, posing concerns regarding sustainability. Exploring the potential of tomato peel (TP) as a dual‐purpose sensing dielectric layer for pressure and humidity monitoring is a paradigm shift, capitalizing on its porous structure and hygroscopic nature. TP‐based humidity sensor (TP‐HS) exhibits impressive results, with a wide humidity sensing range (5%–95%), fast response/recovery time (6.5/9 s), a high sensitivity (12 500 pF %RH−1), and a high stability (30 days). Additionally, TP‐based pressure sensor (TP‐PS) also shows excellent performance in accurately sensing pressure changes in a wide range (0–196 kPa). TP‐HS can easily distinguish between breathing rates (normal, fast, and slow) and moisture content present in different moisturizers (aloe vera and sanitizer) along with its successful use for proximity sensing. Alternatively, TP‐PS demonstrates weight measurement (490 and 980 N), grip recognition (measuring the pressure exerted by each finger), and gesture detection (by monitoring multiple bending angles 0°, 30°, 50°, and 80°). A wearable, biocompatible dual sensor based on a promising sustainable material for environmental, robotic, and health monitoring applications is successfully demonstrated.

Sediment microbial fuel cells capable of powering outdoor environmental monitoring sensors

In this study, Sediment Microbial Fuel Cells (SMFCs) prototypes have been developed to operate under open-air conditions and power sensors for environmental monitoring. Two SMFCs with a volume of 50 l each, consisting of two types of anodic materials – graphite and coke, were operated on-field for over a year. The electrical outputs have been recorded and compared with the measured environmental parameters such as temperature, light illumination, atmospheric pressure, humidity, etc. The statistical analysis of the obtained data shows that temperature changes between 0 and 14 °C do not affect the power achieved. On the contrary, the sunlight irradiation showed a second-order polynomial correlation with the current generated by the SMFCs, increasing the latter during the days. The cathode reactions significantly impacted the power density achieved by both explored SMFCs and the system's sustainability. The metallurgical coke is suggested to be used as an inexpensive and convenient anode material for SMFCs giving compatible results to the widely used graphite.

Towards Integrating Pressure-Sound Piezo Energy Generator in Sports Facility Energy Mix

The paper examines the evolving landscape of energy sources within sports facilities. Traditionally reliant on electrical power and other forms of power from non-renewable resources such as coal, petroleum, and natural gas, these facilities face the inevitability of resource depletion and environmental repercussions. In response, this paper advocates for the adoption of new avenues, including energy conservation, emission reduction, energy recovery, and embracing renewable energy sources. A pioneering focus is on the implementation of a piezoelectric power generation system, tapping into typically wasted sources such as sound and human locomotion. An experimental approach explored the feasibility of such a system in order to ascertain its reliability, efficiency, and sustainability. With applications ranging from powering low-power electronic devices to environmental monitoring sensors, the successful integration of this technology promises a substantial advancement in the use of other renewable energy sources, diminishing reliance on non-renewable sources albeit on a small scale. The paper endeavours to shed light on the potential application of piezoelectric power generation in the electricity production field, aligning with the overarching objective of harvesting energy from unconventional sources and converting it into usable electrical energy. Moreover, it aims to shed light on the potential integration of piezoelectric and audio-electric generators in the energy or renewable energy mix of sports facilities, and address emerging technologies, societal impacts, and strategies to overcome barriers to adoption.

Microbial bioelectronic sensors for environmental monitoring

Microbial bioelectronic sensors for environmental monitoring

Laser-Induced Graphene for Electrochemical Analysis of Food and Agricultural Contaminants

Carbon-nanomaterial sensors offer promising routes toward low-cost, high-throughput electrochemical sensors. Carbon nanomaterials, such as graphene and carbon nanotube (CNT), have been studied with various fabrication methods to produce sensors, including high-quality thin film graphene and CNT by chemical vapor deposition. However, the complexity and cost associated with their fabrication have hindered their implementation into single-use test strip sensors. Even high-yield mechanical and/or chemical exfoliation of graphene from graphite followed by solution phase printing of electrodes can be costly due to the complexity of ink formulation and the need for post-print annealing requirements. However, laser-induced graphene (LIG) avoids the need to exfoliate graphene from graphite or to create a solution-phase graphene ink by converting sp3 carbon found in carbon-rich substrates into conductive sp2-hybridized carbon found in graphene through a laser scribing technique. The resulting LIG also exhibits a high surface area and is porous with a high density of edge plane sites, which are beneficial for biofunctionalization and heterogeneous charge transport during electrochemical sensing. Furthermore, we have demonstrated that the surface area and wettability of the LIG can be tuned to greatly improve the sensitivity of electrochemical enzymatic biosensors (detection limits down to the picomolar range) and reduce the water layer buildup between the ion-selective membrane and the electrode, which improves the accuracy of the sensor readings. The fabricated LIG electrodes have been used in a wide variety of electrochemical sensing applications, including in food safety (foodborne pathogens and other contaminants), environmental monitoring (agrochemicals), and health monitoring sensors (salivary potassium and lactate, and urinary potassium and ammonium). Different electroanalytical methods are used, including amperometric, potentiometric, coulometric, and impedimetric, to quantify the analytes. We demonstrate how the ISE (ion-selective electrodes) can be functionalized with PVC-based ion-selective membranes for potassium, nitrate, nitrite, ammonium, sodium, and pH in various biological solutions, including soil and water for nutrient/fertilizer monitoring in farm fields. Additionally, we demonstrate how the hydrophilic LIG graphene can be used to create other highly sensitive electrochemical biosensors including enzymatic pesticide biosensors and Salmonella spp. immunosensors. All these electroanalytical sensors were validated in real-world samples and demonstrated to have limits of detection and linear sensing ranges that are relevant to their sensing applications. Results demonstrate the utility of LIG-based sensors for rapid and sensitive electrochemical measurement of contaminants as a readily modified platform for scalable production of electroanalytical devices applied toward point-of-service environmental and food monitoring.

A highly sensitive of electrochemical biosensor based on new aptamer sequence for 17α-ethinylestradiol detection in water

The remarkable features of aptamer as biological agent in detecting various compound with high binding affinity could be useful in monitoring of 17α-ethinylestradiol (EE2). EE2 is considered as an endocrine disrupting compound due its ecotoxicity and has widespread in the aquatic ecosystem due to improper disposal. Hence, there is a pressing requirement for sensitive and selective detection of EE2. In this study, we developed a new electrochemical biosensor based on modified DNA aptamers and gold nanoparticles/poly(n-butyl acrylate-co-N-acryloxysuccinimide) microspheres (Au/P(nBA-NAS)). The DNA aptamers was truncated from a 76-mer sequence to 39-mer sequences via computational method, has showed improved binding affinity and stability for EE2. The biosensor was fabricated by attaching the aptamers to the Au/P(NBA-NAS) microspheres, which is provided a large surface area and enhanced electron transfer for the immobilization and signal amplification of the aptamers. The detection principle of the [Fe(CN)6]−3/−4 redox probe in differential pulse voltammetry (DPV) measurement by the presence of aptamer-EE2 complexes on the electrode surface. The biosensor exhibited a linear relationship between the current decrease and the EE2 concentration in the range of 1 × 10−6 M to 1 × 10−12 M, with a detection limit of 1.7 × 10−13 M. The biosensor exhibited excellent selectivity, repeatability, and recovery for detecting EE2 in real samples, with results that closely matched those obtained using the high-performance liquid chromatography (HPLC) technique. This study provided a promising alternative for developing aptamer-based sensors for onsite environmental monitoring.

Monitoring Soil Temperature and Humidity in an IoT-Based Green House to Improve Plant Management

This study aims to develop and validate a soil temperature and humidity monitoring system using DHT 11 and YL 69 sensors connected to an ESP 8266 microcontroller. Calibration was performed by comparing sensor data with a reference instrument, followed by regression analysis to determine sensor accuracy. Validation involved calculating the standard deviation and accuracy of the sensor measurements. Temperature and soil humidity monitoring was conducted over five days in September, with average temperature measurements ranging from 22.4°C to 32.6°C and soil humidity ranging from 66.47% to 88.78%. The results showed that the temperature sensor had an average accuracy of 99.19%, while the humidity sensor had an average accuracy of 97.95%. The low standard deviation values for both sensors indicate good measurement consistency. These findings align with the literature emphasizing the importance of high-performance sensors for environmental monitoring in smart agriculture systems. The implementation of this system is expected to enhance the efficiency and effectiveness of agricultural management and support the sustainability of agricultural practices.

Novel solution-gated transistor sensor-based SnO2 epitaxial thin films grown by pulsed laser deposition for nitrite detection.

A solution-gate controlled thin-film transistor with SnO2 epitaxial thin films (SnO2-SGTFT) is successfully utilized for highly sensitive detection of nitrite. The SnO2 films are deposited as channel materials on a c-plane sapphire (c-Al2O3) substrate through pulsed laser deposition (PLD), with superior crystal quality and out-of-plane atomic ordering. PtAu NPs/rGO nanocomposites are electrodeposited on agold electrode to function as a transistor gate to further enhance the nitrite catalytic performance of thedevice. The change in effective gate voltage due to the electrooxidation of nitrite on the gate electrode is the primary sensing mechanism of the device. Based on the inherent amplification effect of transistors, the superior electrical properties of SnO2, and the high electrocatalytic activity of PtAu NPs/rGO, the SnO2-SGTFT sensor has a low detection limit of 0.1nM and a wide linear detection range of 0.1nM ~ 50mM at VGS = 1.0V. Furthermore, the sensor has excellent characteristics such as rapid response time, selectivity, and stability. The practicability of the device has been confirmed by the quantitative detection of nitrite in natural lake water. SnO2 epitaxial films grown by PLD provide a simple and efficient way to fabricate nitrite SnO2-SGTFT sensors in environmental monitoring and food safety, among others. It also provides a reference for the construction of other high-performance thin-film transistor sensors.

Fingerprinting DNAzyme Cross-Reactivity for Pattern-Based Detection of Heavy Metals.

Heavy metal contamination in food and water is a major public health concern because heavy metals are toxic in minute amounts. DNAzyme sensors are emerging as a promising tool for rapid onsite detection of heavy metals, which can aid in minimizing exposure. However, DNAzyme activity toward its target metal is not absolute and has cross-reactivity with similar metals, which is a major challenge in the wide-scale application of DNAzyme sensors for environmental monitoring. To address this, we constructed a four DNAzyme array (17E, GR-5, EtNA, and NaA43) and used a pattern-based readout to improve sensor accuracy. We measured cross-reactivity between three metal cofactors (Pb2+, Ca2+, and Na+) and common interferents (Mg2+, Zn2+, Mn2+, UO22+, Li+, K+, and Ag+) and then used t-SNE analysis to identify and quantify the metal ion. We further showed that this method can be used for distinguishing mixtures of metals and detecting Pb2+ in environmental soil samples at micromolar concentrations.

Bismuth-MXene nanocomposite: A low-cost portable solution for zinc (II) detection in water for safer environmental monitoring

The development of a portable and cost-effective sensor for detecting zinc ions (Zn (II)) in water addresses a crucial need for real-time monitoring of heavy metal environmental contamination. To this, here, a novel bismuth-MXene (Bi2S3-MXene) nanocomposite-based sensor is developed for the rapid and selective detection of Zn (II) ions with a simple procedure. The exceptionally selective nanocomposites were capable of detecting Zn (II) through the square-wave anodic stripping voltammetry (SWASV) technique in a linearity range of up to 3 µg/mL, achieving limit of detection (LOD) of 7 ng/mL and limit of quantification (LOQ) of 22 ng/mL with a correlation coefficient of R2 =0.9825. Subsequently, the content of Zn (II) in real tap water and sea water was successfully determined for sensitivity and practical applicability. The developed sensor demonstrated several advantages for detecting Zn (II) in water, including a rapid setup process, fast detection times, high sensitivity, more selectivity and portability. While this study focuses on Zn (II) detection, the developed platform suggests it could potentially be adapted for detecting other heavy metals in future research. This work broadens the potential applications of portable nanomaterial-based sensors for regular environmental monitoring.

Eco-friendly triboelectric nanogenerator for self-powering stacked In2O3 nanosheets/PPy nanoparticles-based NO2 gas sensor

As atmospheric issues and energy crises worsen, developing environmentally friendly, low-cost, high-performance self-powered gas sensing systems for gas pollutant monitoring is crucial for the development of ecological civilization. In this work, an eco-friendly self-powered nitrogen dioxide (NO2) sensor (EFNS) system based on an eco-friendly triboelectric nanogenerator (EF-TENG) is reported. The system comprises a power supply unit (EF-TENG) and a sensing unit (In2O3/PPy sensor), connected through a signal stabilization circuit. EF-TENG utilizes eco-friendly and biodegradable gelatin and PLA/PBAT as the friction layer. By introducing leaf structures on the gelatin surface using a template method, the output voltage and current of EF-TENG were increased by 1.44 and 1.67 times, respectively. The peak power density and root mean square power density of EF-TENG reached 1386 mW m−2 and 185.35 mW m−2, respectively. Additionally, EF-TENG exhibited excellent long-term stability, maintaining a stable output voltage (∼24 V) after rectification and voltage stabilization treatment under conditions of 15–55°C and 40–80 % RH. Additionally, an In2O3/PPy heterostructure sensor was prepared, and the EFNS system was constructed through impedance matching effects, revealing the NO2 response mechanism of the In2O3/PPy heterostructure. This achieved a wide detection range and highly sensitive (Vg/Va = 355 %@30 ppm) detection of NO2. This work provides insights into eco-friendly self-powered gas sensors and sensing mechanisms, offering ideas for the development of environmental monitoring sensors and clean energy harvesting devices.