The reported organic electrochemiluminescence (ECL) luminophors for the detection of various markers often suffer from intermolecular π-π stacking-induced luminophore quenching. Herein, we demonstrate one-pot synthesis of a new aggregation-induced electrochemiluminescence (AIECL) emitter (i.e., TPE@SiO2/rGO composite) for sensitive measurement of microcystin-leucine arginine (MC-LR). The TPE@SiO2/rGO composite is constructed by embedding the silica-encapsuled 1,1,2,2-tetra(4-carboxylphenyl)ethylene (TPE) in the reduced graphene oxide. In comparison with the monomer TPE, this composite exhibit high luminescence efficiency and strong ECL emission, because the AIECL phenomenon triggered by the spatial confinement effect in the SiO2 cage induces the restriction of the internal motion and vibration of molecules. Notably, this composite has distinct advantages of easy preparation, simple functionalization, and stable luminescence. Especially, the TPE@SiO2/rGO-based ECL-RET system exhibits a high quenching efficiency (ΦET) of 69.7%. When target MC-LR is present, it triggers DNA strand displacement reaction (SDR), inducing the quenching of the ECL signal of TPE@SiO2/rGO composite due to ECL resonance energy transfer between TPE@SiO2/rGO composite and methylene blue (MB). The proposed biosensor enables highly sensitive, low-cost, and robust measurement of MC-LR with a large dynamic range of 7 orders of magnitude and a detection limit of 3.78 fg/mL, and it displays excellent detection performance in complex biological matrices, holding potential applications in food safety and water monitoring.

Nowadays, global water scarcity is becoming a pressing issue, and the discharge of various pollutants leads to the biological pollution of water bodies, which further leads to the poisoning of living organisms. Consequently, traditional water treatment methods are proving inadequate in addressing the growing demands of various industries. As an effective and eco-friendly water treatment method, micro/nanorobots is making significant advancements. Based on researches conducted between 2019 and 2023 in the field of water pollution using micro/nanorobots, this paper comprehensively reviews the development of micro/nanorobots in water pollution control from multiple perspectives, including propulsion methods, decontamination mechanisms, experimental techniques, and water monitoring. Furthermore, this paper highlights current challenges and provides insights into the future development of the industry, providing guidance on biological water pollution control.

Capacitive sensors are essential to promoting modernization and intelligence in agriculture. With the continuous advancement of this sensor technology, the demand for materials with high conductivity and flexibility is rapidly increasing. Herein, we introduce liquid metal as a solution for the in-site fabrication of high-performance capacitive sensors for plant sensing. As a comparison, three pathways have been proposed for the preparation of flexible capacitors inside plants, as well as on their surfaces. Specifically, concealed capacitors can be constructed by directly injecting liquid metal into the plant cavity. Printable capacitors are prepared via printing Cu-doped liquid metal with better adhesion on plant surfaces. A composite liquid metal-based capacitive sensor is achieved by printing liquid metal on the plant surface and injecting it into the interior of the plant. While each method has limitations, the composite liquid metal-based capacitive sensor provides an optimal trade-off between signal capture capability and operability. As a result, this composite capacitor is chosen as a sensor for monitoring water changes within plants and demonstrates the desired sensing performance, making it a promising technology for monitoring plant physiology.

Saxitoxin (STX), the most widely distributed neurotoxin in marine waters and emerging cyanotoxin of concern in freshwaters, causes paralytic shellfish poisoning in humans upon consumption of contaminated shellfish. To allow for the efficient monitoring of this biotoxin, it is of high importance to find high-affinity materials for its adsorption. Herein, we report the design and synthesis of a covalent organic polymer for the efficient adsorption of STX. Two β-keto-enamine-based materials were prepared by self-assembly of 2,4,6-triformylphloroglucinol (Tp) with 2,5-diaminobenzoic acid (Pa-COOH) to give TpPa-COOH and with 2,5-diaminotoluene (Pa-CH3) to give TpPa-CH3. The carboxylic acid functionalized TpPa-COOH outperformed the methyl-bearing counterpart TpPa-CH3 by an order of magnitude despite the higher long-range order and surface area of the latter. The adsorption of STX by TpPa-COOH was fast with equilibrium reached within 1 h, and the Langmuir adsorption model gave a calculated maximum adsorption capacity, Qm, of 5.69 mg g-1, making this material the best reported adsorbent for this toxin. More importantly, the prepared TpPa-COOH also showed good reusability and high recovery rates for STX in natural freshwater, thereby highlighting the material as a good candidate for the extraction and pre-concentration of STX from aquatic environments.

Rapid and sensitive Escherichia coli (E. coli) detection is important in determining environmental contamination, food contamination, as well as bacterial infection. Conventional methods based on bacterial culture suffer from long testing time (24 h), whereas novel nucleic acid-based and immunolabelling approaches are hindered by complicated operation, the need of complex and costly equipment, and the lack of differentiation of live and dead bacteria. Herein, we propose a chemiluminescence digital microwell array chip based on the hydrolysis of 6-Chloro-4-methylumbelliferyl-β-D-glucuronide by the β-D-glucuronidase in E. coli to achieve fast single bacterial fluorescence detection. Taking the advantage of the picoliter microwells, single bacteria are digitally encapsulated in these microwells, thus the accurate quantification of E. coli can be realized by counting the number of positive microwells. We also show that the chemiluminescence digital microwell array chip is not affected by the turbidity of the test samples as well as the temperature. Most importantly, our method can differentiate live and dead bacteria through bacterial proliferation and enzyme expression, which is confirmed by detecting E. coli after pH and chlorination treatment. By comparing with the standard method of plate counting, our method has comparable performance but significantly reduces the testing time from over 24 h-2 h and 4 h for qualitative and quantitative analysis, respectively. In addition, the microfluidic chip is portable and easy to operate without external pump, which is promising as a rapid and on-site platform for single E. coli analysis in water and food monitoring, as well as infection diagnosis.

Water utilities encounter unpredictable odor issues that cannot be explained by routine water parameters during spring runoff, even in the summer and fall. Highly water-soluble organics (e.g., amino acids and saccharides) have been reported to form odorous disinfection byproducts during disinfection, but the lack of simple and practical on-site sampling techniques hampers their routine monitoring at trace levels in source water. Therefore, we have created two functionalized nested-in-sponge silica monoliths (NiS-SMs) using a one-pot synthesis method and demonstrated their application for extracting highly soluble organics in water. The NiS-SMs functionalized with the sulfonic group and phenylboronic moiety selectively extracted amino acids and monosaccharides, respectively. We further developed a spinning sampling technique using the composites and evaluated its robust performance under varying water conditions. The spinning sampling coupled to high-performance liquid chromatography tandem mass spectrometry analysis provided limits of detection for amino acids at 0.038-0.092 ng L-1 and monosaccharides at 0.036-0.14 ng L-1. Using the pre-equilibrium sampling-rate calibration, we demonstrated the applicability of the spinning sampling technique for on-site sampling and monitoring of amino acids and monosaccharides in river water. The new composite materials and rapid on-site sampling technique are unique and efficient tools for monitoring highly soluble organics in water sources.

High-resolution time-series concentrations (CTS) are very important for the investigation of the biogeochemical processes of trace metals in the aquatic environment. However, the acquisition of CTS of trace metals in water is still challenging because of the lack of suitable samplers. In this study, an osmotic sampler coupled with air segment injection and preservative addition was employed for time-series sampling of trace metals in surface waters. In the sampler, water sampling and preservative adding are both driven by osmotic pumps (OPs), while air segment injection is accomplished by a timer-controlled micro diaphragm pump. During deployment, the sampling OP continuously draws water through a filter and stores it in a narrow-bore coil. Simultaneously, a preservative OP slowly pushes 30% HNO3 (v/v) into the collected sample for in situ preservation. Periodically, the micro diaphragm pump injects air into the continuous water stream to divide it into water segments, enabling accurate time-stamping. After retrieval, the time-series samples were pumped out from the coil and re-collected to analyze the CTS of analytes. The sampler was deployed in river, reservoir, and marine waters for 26 h and one week to measure CTS of trace metals at time resolutions of 2 h and 12 h. Results showed that the recoveries of a preloaded standard mixture (1.0 μg/L) in all samplers ranged from 93.1% to 117.8%. The measured CTS of Cd, Co, Cr, Cu, Mn, and Ni in the waters only varied in small ranges. Accordingly, the measured CTS data from the sampler were consistent with the obtained concentrations from grab sampling. The relative percent differences between the measurements from two samplers were less than 37.4%. These results demonstrate the reliability and accuracy of the sampler for time-series sampling of the chosen trace metals in surface waters.

This research introduced a new low-cost and multi-parameter analyzer for in-situ measurements of typical nutrients in water bodies. The analyzer consisted of color detection and chromogenic reaction modules. The self-sampling action of the 3D printed sampling/reaction cells was achieved with the cooperative application of rubber bands and dissolvable thread. The target analytes in the collected water sample reacted with the chromogenic reagents that were diffused from the pre-placed glass wool in the cell, producing color compounds. A portable document scanner was employed as a multi-parameter in-situ detector to record the image of the colored solutions in all five cells simultaneously. Based on the image, the corrected grayscale values were derived for target analyte quantitation. The relationships between grayscale values and concentrations of target analytes were established, and the temperature effects were studied. In addition, the practicability of the analyzer was demonstrated by in-situ experiments carried out in four different sites, including a creek, a river dock, a reservoir and a secondary settling tank in a wastewater treatment facility. The results indicated that the analyzer could be used for in-situ measuring of nutrients at μmol/L levels in the water. The nutrient concentrations obtained with the analyzer were comparable with those obtained with the standard methods. The presented analyzer provided new complementary ideas and methods for in-situ rapid measurement of nutrients and other target analytes in various water systems.

Irreversible organ damage or even death frequently occurs when humans or animals unknowingly drink contaminated water. Therefore, in many countries drinking water is disinfected to ensure removal of harmful pathogens from drinking water. If upstream water treatment prior to disinfection is not adequate, disinfection byproducts (DBPs) can be formed. DBPs can exist as wide variety of compounds, but up until now, only several typical compounds have drinking water standards attributed to them. However, it is apparent that the range of DBPs present in water can comprise hundreds of compounds, some of which are at high enough concentrations to be toxic or potentially carcinogenic. Hence, it becomes increasingly significant and urgent to develop an accessible, affordable, and durable sensing platform for a broader range and more sensitive detection of DBPs. Compared with well-established laboratory detection techniques, electrochemical sensing has been identified as a promising alternative that will provide rapid, affordable, and sensitive DBP monitoring in remote water sources. Therefore, this Review covers current state-of-the-art development (within the past decade) in electrochemical sensing to detect organic DBPs in water, which covered three major aspects: (1) recognition mechanism, (2) electrodes with signal amplification, and (3) signal read-out techniques. Moreover, comprehensive quality assessments on electrochemical biosensors, including linear detection range, limit of detection (LoD) and recovery, have also been summarized.

Graphene field-effect transistor (GFET) sensors are an attractive analytical tool for the detection of water pollutants. Unfortunately, this application has been hindered by the sensitivity of such sensors to nonspecific disturbances caused by variations of environmental conditions. Incorporation of differential designs is a logical choice to address this issue, but this has been difficult for GFET sensors due to the impact of fabrication processes and material properties. This paper presents a differential GFET affinity sensor for the selective detection of water pollutants in the presence of nonspecific disturbances. This differential design allows for minimization of the effects of variations of environmental conditions on the measurement accuracy. In addition, to mitigate the impact of the fabrication process and material property variations, we introduce a compensation scheme for the individual sensing units of the sensor, so that such variations are accounted for in the compensation-based differential sensing method. We test the use of this differential sensor for the selective detection of the water pollutant 17β-estradiol in buffer and tap water. Consistent detection results can be obtained with and without interferences of pH variations, and in tap water where unknown interferences are present. These results demonstrate that the differential graphene affinity sensor is capable of effectively mitigating the effects of nonspecific interferences to enable selective water pollutant detection for water quality monitoring.