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[Display omitted] • A novel filter paper patterning method based on parylene C. • A paper-based colorimetric sensor for detection of Al (III) using a smartphone platform. • The detection range of the sensor for Al (III) detection is 0.05 to 10 mg/mL. The detection limit is 0.05 mg/mL. • The assembled paper-based smartphone sensor platform has the potential to detect other biochemical molecules. The paper-based analytical platforms have been applied in biochemical detection and environmental monitoring due to their low cost and easy operation. Despite their advantages, the complexity of fabrication has limited their further application. Here, a simple and innovative approach using parylene C, a material commonly used in semiconductors, is reported to fabricate paper-based chips and construct a point-of-care testing (POCT) platform through smartphones. Parylene C is deposited on the filter paper through a polydimethylsiloxane (PDMS) clamp and forms a hydrophobic barrier. A three-channel paper-based chip was utilized to detect aluminum (Al) ions on a smartphone platform by the chromogenic method. The color change after Al3+ detection is represented with △E which was photographed and calculated by app on smartphone. The detection limit is 0.05 mg/L and the detection range is from 0.05 mg/L to 10 mg/L which indicates the application potential in the field of biochemical detection. This new paper-based sensing method and smartphone-based portable detection platform are simple, low-cost, fast, and highly sensitive, and provides a potential application for on-site, visual detection of ions and even other substances. [ABSTRACT FROM AUTHOR]

Sensor arrays, which draw inspiration from the mammalian olfactory system, are fundamental concepts in high-throughput analysis based on pattern recognition. Although numerous optical sensor arrays for various targets in aqueous media have demonstrated their diverse applications in a wide range of research fields, practical device platforms for on-site analysis have not been satisfactorily established. The significant limitations of these sensor arrays lie in their solution-based platforms, which require stationary spectrophotometers to record the optical responses in chemical sensing. To address this, this review focuses on paper substrates as device components for solid-state sensor arrays. Paper-based sensor arrays (PSADs) embedded with multiple detection sites having cross-reactivity allow rapid and simultaneous chemical sensing using portable recording apparatuses and powerful data-processing techniques. The applicability of office printing technologies has promoted the realization of PSADs in real-world scenarios, including environmental monitoring, healthcare diagnostics, food safety, and other relevant fields. In this review, we discuss the methodologies of device fabrication and imaging analysis technologies for pattern recognition-driven chemical sensing in aqueous media. [Display omitted] • Cross-reactive sensors are applied to paper-based arrays for simultaneous detection. • Portable digital recorders can be used for detecting various responses. • Imaging analysis techniques can accelerate accurate data processing. [ABSTRACT FROM AUTHOR]

Microfluidic paper-based point-of-care assays are a highly valuable technology with many promising applications in public health and environmental monitoring. High-sensitivity detection of certain trace substances is one of the critical important considerations for practical usage of microfluidic point-of-care techniques. Over the past decade, luminescence nanoprobes have been increasingly emerged as powerful toolboxes to achieve exceptional sensitivity and low detection limits for many chemical sensors. In this Review, we provide an overview of the fundamental principles underlying paper-based microfluidic point-of-care detection. We highlight various luminescence nanoprobes, including nano-diamonds, upconversion luminescent nanoparticles, inorganic quantum dots, and carbon dots, along with their corresponding sensing mechanisms. In subsequent sections, we emphasize the requisite utilization of specialized readout equipment for the effective implementation of fluorescence detection. Moreover, we summarize key microfluidic design strategies capable of achieving enhanced precision in the detection processes. We also discuss future research directions and the main challenges to be addressed for fluorescence nanoprobes-inspired paper-based microfluidic point-of-care technology. • Microfluidic point-of-care paper-based Luminescence assays. • Luminescence nanoprobes and corresponding mechanism. • Portable devices for signal readout and diagnosis. [ABSTRACT FROM AUTHOR]

Point-of-care testing (POCT) technology is urgently required owing to the prevalence of the Internet of Things and portable electronics. In light of the attractive properties of low background and high sensitivity caused by the complete separation of excitation source and detection signal, the paper-based photoelectrochemical (PEC) sensors, featured with fast in analysis, disposable and environmental-friendly have become one of the most promising strategies in POCT. Therefore, in this review, the latest advances and principal issues in the design and fabrication of portable paper-based PEC sensors for POCT are systematically discussed. Primarily, the flexible electronic devices that can be constructed by paper and the reasons why they can be used in PEC sensors are expounded. Afterwards, the photosensitive materials involved in paper-based PEC sensor and the signal amplification strategies are emphatically introduced. Subsequently, the application of paper-based PEC sensors in medical diagnosis, environmental monitoring and food safety are further discussed. Finally, the main opportunities and challenges of paper-based PEC sensing platforms for POCT are briefly summarized. It provides a distinct perspective for researchers to construct paper-based PEC sensors with portable and cost-effective, hoping to enlighten the fast development of POCT soon after, as well as benefit human society. • The merits of functionalized paper for PEC sensor are introduced. • Photosensitive material and signal amplification strategy of paper-based PEC sensor are discussed. • The application of paper-based PEC sensor in the field of POCT is highlighted. • The limitations and challenges of paper-based PEC sensor are summarized. [ABSTRACT FROM AUTHOR]

Nowadays, great efforts are made in developing new technology for rapid detection of specific DNA sequences, for environmental monitoring, forensic analysis and rapid biomedical diagnosis applications. Microfluidic paper-based analytical devices are suitable platforms for the development of point of care devices, due to their simple fabrication protocols, ease of use and low cost. Herein, a methodology for in situ detection of single strand DNA by using a colorimetric assay based on the formation of a DNAzyme within a paper substrate was developed. A DNAzyme that could only be formed in the presence of a specific sequence of the Y human amelogenin gene was designed. The performance of the DNAzyme was followed colorimetrically first in solution and then in paper substrates. The reaction was found to be specific to the Y fragment selected as analyte. The DNAzyme reaction on paper enabled the unequivocal colorimetric identification of the Y single strand DNA fragment both qualitatively, with the naked eye (143 ng), and quantitatively by image analysis (45.7 ng). As a proof of concept, a microfluidic paper-based device, pre-loaded with all DNAzyme reagents, was characterized and implemented for the simultaneous detection of X and Y single strand DNA fragments. Image 1 • Optimized methodology for in situ DNA detection in a paper device format. • Detection based on a DNAzyme using Y human amelogenin fragment. • Presents a non-enzymatic, colorimetric and rapid way to detect DNA sequences. • Detection: quantitatively by calculating the grey intensity values. • Detection: qualitatively by the presence of a green color "coffee ring". [ABSTRACT FROM AUTHOR]

Pathogens cause various infectious diseases and high morbidity and mortality which is a global public health threat. The highly sensitive and specific detection is of significant importance for the effective treatment and intervention to minimise the impact. However, conventional detection methods including culture and molecular method gravely depend on expensive equipment and well-trained skilled personnel, limiting in the laboratory. It remains challenging to adapt in resource-limiting areas, e.g., low and middle-income countries (LMICs). To this end, low-cost, rapid, and sensitive detection tools with the capability of field testing e.g., a portable device for identification and quantification of pathogens, has attracted increasing attentions. Recently, paper-based microfluidic analytical devices (μPADs) have shown a promising tool for rapid and on-site diagnosis, providing a cost-effective and sensitive analytical approach for pathogens detection. The fast turn-round data collection may also contribute to better understanding of the risks and insights on mitigation method. In this paper, critical developments of μPADs for in-field detection of pathogens both for clinical diagnostics and environmental surveillance are reviewed. The future development, and challenges of μPADs for rapid and onsite detection of pathogens are discussed, including using the cross-disciplinary development with, emerging techniques such as deep learning and Internet of Things (IoT). [Display omitted] • The state-of-the-art on μPAD is critically reviewed. • μPAD enables onsite detections of biochemical markers from molecules to organisms. • Insights is provided highlighting on multidisciplinary aspects. [ABSTRACT FROM AUTHOR]

Dissolved sulfide tends to species transformation and loss upon leaving the matrix, thus the development of a practical on-site determination of sulfide is crucial for environmental monitoring and human health. In this work, a novel paper-based ratiometric fluorescence sensor was developed for the field analysis of sulfide, which system was constructed by the inner filter effect (IFE) of CdS quantum dots (QDs) toward carbon dots (C-dots). Instead of an aqueous phase system, the conversion of sulfide to its hydride would induce the in-situ formation of CdS QDs on the paper, which acted as an energy acceptor to quench the emission of C-dots, leading to a variation of ratiometric fluorescence from blue to yellow with the increasing concentration of sulfide. Moreover, we proposed a smartphone-based fluorescence capture device integrated with a programmed Python program, accomplishing both color recognition and accurate detection of sulfide. Under the optimal condition, this ratiometric fluorescence sensor allowed for the on-site analysis of sulfide with a limit of detection of 0.05 μM. The accuracy of the sensor was validated via the successful field analysis of environmental water samples with satisfactory recoveries. Compared to other fluorescence methods used for sulfide analysis, this developed system retains the advantages of label-free, low-cost, ease of operation, and miniaturization, showing great potential for the measurement of sulfide on-site, as well as environmental monitoring. [Display omitted] • A paper-based fluorescence sensor was developed for the field analysis of sulfide. • Sulfide induced the IFE between C-dots and CdS QDs and caused fluorescence change. • The portable device for sulfide analysis is low-cost and easy to operate. • The developed system shows great potential for the measurement of sulfide on-site. [ABSTRACT FROM AUTHOR]

The simultaneous detection of free chlorine, hydrogen sulfide and formaldehyde in wastewater samples was performed. In this report, we designed and fabricated functionalized paper test strips featuring detection zones that use 3-aminopropyltriethoxysilane (APTES) for the immobilization of chromogenic substrates to detect free chlorine, hydrogen sulfide and formaldehyde. After multiple chromogenic reactions, red, blue and purple colors were obtained on the detection zones and analyzed using a smartphone. Under optimum conditions, the paper test strips showed 1.7, 1.8 and 1.7 orders of magnitude for free chlorine, hydrogen sulfide and formaldehyde, respectively. This sensitivity is caused by the formation of homogeneous complexes on detection zones resulting from the chromogenic reagents immobilized on the detection zone via APTES. Through this strategy, free chlorine, hydrogen sulfide and formaldehyde analysis was achieved within 5 min with detection limits of 0.08, 0.14 and 0.13 mg L−1, respectively. The developed paper test strip was able to selective detection of free chlorine, hydrogen sulfide and formaldehyde even in the presence of common interfering agents therefore, the test strip was highly selective. In a further demonstration, the developed functionalized paper test strip was successfully used for simultaneous detection of free chlorine, hydrogen sulfide and formaldehyde in wastewater in the field and exhibited with high precision and accuracy in detecting free chlorine, hydrogen sulfide and formaldehyde in wastewater samples. Compared to other methods, this assay was advantageous in terms of its low detection limit, time savings, good stability and highly portable format, which facilitates rapid on-site environmental monitoring with a smartphone. Image 1 • A functionalized paper strip test enables two-fold improvement of detection limit. • Simultaneous detection of free chlorine, hydrogen sulfide and formaldehyde was achieved within 5 min with low detection limits. • A platform integrating functionalized paper strip test with a smartphone was successfully applied for ready-to-use for detection of free chlorine, hydrogen sulfide and formaldehyde in wastewater samples. [ABSTRACT FROM AUTHOR]

Here, an inkjet printed paper electrode (PPE) decorated with graphene (Gr)-silver (Ag) nanocomposite was exploited as an electrochemical sensing probe for analysis of 4-nitrophenol (4-NP) in environmental water samples. In this work, 4% Gr-Ag nanocomposite ink (NI) was prepared in ethanol, ethylene glycol, and glycerol in the ratio of 50:45:5, which possess surface tension and viscosity of 36 mN m−1 and 11 mPa s, respectively. The office inkjet printer was employed to print formulated Gr-Ag NI on digital photo paper, followed by sintered at 200 °C for 30 min to make effective conducting tracks for the sensing of 4-NP. Gr-Ag NI-based PPE was used as a working electrode in cyclic voltammetry. The working principle of detection is based on the electrocatalytic reduction process of 4-NP on the electrode surface. A good linearity range of 3.125–100 μM was observed, achieving a detection limit of 2.7 μM to measure 4-NP. Thus, the developed PPE holds considerable potential and offers an economical, biodegradable, and user-friendly sensor for future applications in the monitoring of 4-NP in environmental water samples. [Display omitted] • Printed paper electrode (PPE) with graphene (Gr)-silver (Ag) was used as electrochemical sensing for 4-nitrophenol (4-NP). • Inkjet printer was employed to print formulated Gr-Ag NI on photo paper and sintered at 200 °C for 30 min to make electrode. • Gr-Ag/PPE was used as a working electrode in cyclic voltammetry for 4-NP determination. • Gr-Ag/PPE provides a low cost, decomposable, and user-friendly sensor for monitoring of 4-NP in environmental water sample. [ABSTRACT FROM AUTHOR]

Abstract Paper-based immunosensors are regarded as attractive analytical tools for performing point-of-care and in-field assays in medical diagnostics, environmental monitoring and food safety control. In this review, we provide a general overview of the types and applied detection techniques of paper-based immunosensors published in recent years and analyse the current trends in these two aspects. The first section introduces the background of paper-based immunosensors and critically discusses the necessity and distinct features of existing paper-based immunosensors. The second section summarizes the types of current paper-based immunosensors, including paper-based lateral-flow assays (LFAs), microfluidic paper-based analytical devices (μPADs) and some other device types. In the third section, we describe various detection techniques currently applied in paper-based immunosensors, covering optical, electrochemical and some multiple detection techniques. Finally, current trends and future perspectives are also discussed. We hope this review will be a helpful reference for readers of various fields. Highlights • The application value of paper-based immunosensors is emphasized. • Current paper-based immunosensors are outlined according to two aspects. • Representative examples of paper-based immunosensors are elaborated. • The current trends and prospect of paper-based immunosensors are discussed. [ABSTRACT FROM AUTHOR]

Pressure sensor, as one of the most common components in the sensing systems, has attracted plenty of attention in recent years with urgent needs. Herein, a highly sensitive flexible pressure sensor based on conducting polymer (CP)-coated paper is developed via an ultra-simple approach of synthesis and fabrication. This paper-based sensor displays an ultra-low detection limit as low as 0.3 Pa level, and outstanding sensitivity (∼2 kPa −1 , P  ≤ 75 Pa), which can rank the top among that of the reported pressure sensors. The advantages based on paper framework such as low cost, portability, and easy disposability further enhance its feasibility. Meanwhile, combining its rapid and precise response at room temperature and the recognized stability of PPy in the ambient environment, the sensor would ensure direct and continuous environment monitoring with low energy consumption. [ABSTRACT FROM AUTHOR]

The development of cost-effective sensing system for Hg2+ quantitation is highly demanded for environmental monitoring. In this work, we reported an on-site, rapid and portable smartphone-based Hg2+ sensing system integrating coumarin-modified paper as a probe and smartphone readout device as a processing platform. For fluorescent sensing of Hg2+, the modified paper was fabricated by chemically grafting a coumarin-based probe N-((7-hydroxy-coumarin-3-yl)carbamothioyl)acetamide (HCCA) onto paper, and its physicochemical properties and sensing performance were characterized by elemental analysis, FTIR, XPS, SEM, and fluorescence spectral analysis. The modified paper displayed high selectivity and sensitivity for Hg2+, accompanied with a distinct fluorescence color change. For portable detection of the fluorescent sensors, a smartphone readout device was designed, consisting of a removable 3D-printed hardware device and an application. Remarkably, the smartphone readout device in cooperation with the modified paper is highly selective and sensitive to Hg2+ with the limit of detection (LOD) of 0.46 ppb, which avoids the requirement of sophisticated equipment and complex operation. The cost-effective sensing system based on smartphone shows a great potential for monitoring of Hg2+ in environmental water. [Display omitted] • A coumarin-modified paper was fabricated by chemical grafting. • The modified paper showed good fluorescent sensing performance for Hg2+. • A smartphone readout device was designed containing hardware and software. • The smartphone-based sensing system could quantify Hg2+ reliably and portably. [ABSTRACT FROM AUTHOR]

Highlights • Definition of passive envelope indexes and caracterization of libraries in La Plata. • Environmental monitoring: achievement of preventive conservation indexes. • Correlation between passive envelope indexes and preventive conservation indexes. • Determination of the most influential passive envelope indexes for the achievement of preventive conservation indexes. Abstract The common approach for libraries to preserve their paper-based collections from irreversible deterioration is by controlling quantitative parameters, such as temperature and relative humidity. Variations of these parameters for preventive conservation can be expressed by the "performance index" (PI) and the "amplitude index" (AI). Building envelope is the first filter of the external climate, buffering the external weather fluctuations and maintaining the building's indoor climate stable. Its shape, window areas and envelope materials are the most influential parameters. As they capture the relationship of a few geometric and physical variables with the building's performance, the envelope characteristics can be expressed as certain passive envelope indexes. This paper studies the relationship of certain passive envelope indexes and the preventive conservation indexes for books for several libraries and archives located in La Plata, Argentina. The results show the impact of every passive envelope index upon the preventive conservation indexes. The compactness, heaviness, adjacency to spaces and adjacency to ground have a positive linear correlation meanwhile transparency and global transmittance are parameters with a negative correlation. In general, the most influential parameter is the relative area adjacent to other spaces, followed by global transmittance, transparency, heaviness, relative area adjacent to ground and compactness. [ABSTRACT FROM AUTHOR]

A fluorescence sensing system based on supramolecular assembly of a perylene probe (PDI-BTMA) has been constructed to rapidly and accurately quantify TNP via smartphone. [Display omitted] • Smartphone-assisted fluorescence sensor based PDI-BTMA probe was constructed for TNP. • Visual sensing of TNP was accomplished rapidly in aqueous media with LOD of 9 nM. • Optical responses of PDI-BTMA were caused by the formation of supramolecular complex. • The sensor can detect TNP quantitatively with sensitivity in environmental samples. 2,4,6-trinitrophenol (TNP) is an environmentally deleterious substance with high toxicity and explosibility. It is of great significance for environmental protection and public health to establish a rapidly on-site monitoring method for perilous TNP. Current methods for detecting TNP mainly rely on traditional laboratory analysis lacking rapid detection through intelligent modes. Herein, we construct a smartphone recognition based fluorescence sensing system via the supramolecular assembly of a perylene probe to quantify TNP. The sensing platform consists of a fluorescent probe based on quaternary ammonium functionalized perylene (PDI-BTMA), as the TNP-response recognition element, and smartphones as optical signals receptors bringing simpleness, celerity, and portability for TNP monitoring. The sensor reveals dual output signals of color and fluorescence in response to TNP. The results show that the optical responses of PDI-BTMA can be attributed to the formation of the supramolecular complex (PDI-BTMA/TNP) via non-covalent interactions including static electricity, hydrophobic interaction, charge transfer, and π-π stacking. It shows a wide linear range for TNP of 200–1200 nM with a detection limit of 9 nM. In addition, we successfully made portable PDI-BTMA fluorescence paper. The RGB value of fluorescence color was also collected by using the smartphone-assisted sensing platform, and the G/B channel values show a linear relationship with TNP concentration in 0.1–50 μM, with the lowest detection concentration of 48.4 nM. Additionally, it could be successfully utilized for quantitative TNP monitoring in environmental water and soil samples, which achieved a greater recovery rate in the range of 99–110%. This research integrating the PDI-BTMA probe with a smartphone firstly presents a new strategy for real-time and on-site monitoring of TNP in the environment. [ABSTRACT FROM AUTHOR]

Microfluidic paper-based analytical devices (microPADs) are an emerging platform for point-of-care assays with potential applications ranging from medical diagnostics to environmental monitoring. A standard approach for signal generation and amplification on microPADs is the use of enzymes and chromogenic substrates, which produce colored products and enable the qualitative and quantitative detection of analytes. Horseradish peroxidase (HRP) is one of the most commonly used enzymes for this application. While a wide variety of chromogenic substrates and substrate solutions are available for HRP, these were all originally developed and optimized for other platforms and have not been systematically compared on microPADs. In this work, 33 chromogenic substrate solutions for HRP containing one of six different substrate molecules were evaluated in a standardized colorimetric assay and compared on the basis of limit of detection (LOD), lower limit of quantitation (LLOQ), upper limit of quantitation (ULOQ), sensitivity, dynamic range, stability, and cost. While the substrates tetramethylbenzidine (TMB) and o-phenylenediamine (OPD) were found to achieve the best overall analytical performance, each substrate had characteristics that may make them appealing for specific applications. The results of this work will facilitate the selection of substrate molecules and the formulation of substrate solutions for future colorimetric paper-based assays involving HRP. • Six chromogenic substrates for HRP in 33 different formulations were evaluated on microPADs. • TMB and OPD provided the best overall LOD, LLOQ and sensitivity. • ABTS provided the best ULOQ and dynamic range. • Results will facilitate the selection of suitable substrates for future applications. [ABSTRACT FROM AUTHOR]

Volatile organic compound (VOC) detection is critical for controlling industrial and commercial emissions, environmental monitoring, and public health. Simple, portable, rapid and low-cost VOC sensing platforms offer the benefits of on-site and real-time monitoring anytime and anywhere. The best and most practically useful approaches to monitoring would include equipment-free and power-free detection by the naked eye. In this work, we created a novel, paper-based cantilever sensor array that allows simple and rapid naked-eye VOC detection without the need for power, electronics or readout interface/equipment. This simple VOC detection method was achieved using (i) low-cost paper materials as a substrate and (ii) swellable thin polymers adhered to the paper. Upon exposure to VOCs, the polymer swelling adhered to the paper-based cantilever, inducing mechanical deflection that generated a distinctive composite pattern of the deflection angles for a specific VOC. The angle is directly measured by the naked eye on a 3-D protractor printed on a paper facing the cantilevers. The generated angle patterns are subjected to statistical algorithms (linear discriminant analysis (LDA)) to classify each VOC sample and selectively detect a VOC. We classified four VOC samples with 100% accuracy using LDA. Graphical abstractfx1Highlights· We created a novel, paper-based cantilever gas sensor array. · It allowed simple and rapid naked-eye VOC detection. · Upon exposure to VOCs, the mechanical deflection of the cantilevers was monitored. [ABSTRACT FROM AUTHOR]

Since 2007, the world of microfluidics saw an emergence of a new era of low cost, simple, quick fabrication, abundantly available, and environmentally friendly microfluidic paper-based analytical devices (μPADs) capable of clinical diagnostics, food quality control as well as environmental monitoring. Although many fabrication techniques have evolved as a result of its broad application spectrum and ease of use, the technology has still barely scratched the surface of its potential in terms of its underlying fundamental principle, i.e., fluid flow analysis. In this study, we report the comparison of flow profile attained by using two of the most promising techniques of photolithography and wax printing from a hydrodynamic point of view. A modified protocol for synthesizing an epoxy based negative photoresist (SU-8) channel and wax-based channel was created by optimizing a few process parameters of our equipment. Water and oil (oleic acid) are selected as the hydrophilic and hydrophobic fluids, respectively, and their flow was analyzed in straight channels using a paper device. A new approach to vary the flow velocity is described in detail involving cylindrical dots as the resistance inside the paper channel. Observing the length-time curve for the two fluids, it becomes evident that both follow the Lucas–Washburn equation if the width of the channel is large enough. Various configurations of dots indicate that different longitudinal flow velocity implying its application in simultaneous addition of chemicals without the need to change the channel width or length. [ABSTRACT FROM AUTHOR]

Paper-based analytical devices are lightweight, inexpensively produced, effective, and easily disposable; allowing for their suitable implementation in resource-limited areas. They allow effective handling of quantitative analysis in a diverse range of areas, from standard healthcare and environmental monitoring to water quality monitoring. Nonetheless, such devices often require an energy source for their complex assays or readings, preventing their effective use. Most commonly, conventional batteries are integrated into the device to serve as an energy source. However, considering its non-environmentally friendly approach to energy generation and its difficulty of being effectively disposed, a search for a new power source has begun. In light of the newly found potential of cellulose-based entities in the energy field, attention has been drawn towards a supposedly unlikely material: paper. Considering the potentials of such technology, this manuscript aims to describe the benefits of current and future technologies of paper-based devices in the energy sector. Here, we discuss the role of paper as a main platform or part of energy storage and conversion devices such as fuel cells, lithium-ion batteries, and alkaline batteries thoroughly. [ABSTRACT FROM AUTHOR]

This paper describes the development of a new system for amperometric determination of phenolic compounds, and its application for monitoring these compounds in paper mill effluent. The method was based on a flow system, a dialysis sampler, and a laccase-based biosensor. The performance of this system was investigated with respect to pH, ionic strength, working potential, and flow-rate dependence. The biosensor showed an excellent long-term stability allowing measurements for over than 3 months. The sensitivity of laccase-based biosensor was tested for phenol, p-chlorophenol, guaiacol and chloroguaiacol; the detector presented selective measurements of micromolar concentration of these compounds. The integration of a dialysis membrane sampling in the system protected the biosensor surface from fouling and gave independence of sample conditions that commonly influence the biosensor performance. These favorable characteristics allowed its application for direct measurements in complex media with no sample pretreatment. This ability was confirmed employing this system in a continuous analysis of phenolic compounds during the remediation of paper mill effluent by ozonization process. [Copyright &y& Elsevier]

• This manuscript reviews the history and new developments of ePADs from 2016 to 2021. • This review focuses on construction and representative applications of ePADs. • The limiting factors and future development of ePADs have been discussed. Integration of electrochemical detection methods into paper-based analytical devices (PADs) provides a powerful tool for the area of point-of-care testing (POCT) because the electrochemical PADs (termed as ePADs) enable to rapidly determine a broad spectrum of analytes from ions to living cells in a miniaturized, cost-effective and user-friendly manner. Recently, nanomaterials and their composites were extensively introduced in ePADs for improvement of their detection performance. This review attempts to provide a comprehensive information on the ePADs including a general aspect of ePADs and recent development of ePADs by highlighting selected publication. We mainly focus on the fabrication of ePADs, enhancement strategies of nanomaterials and potential applications of ePADs in the fields of environmental monitoring, food safety management and disease diagnosis. Based on the limitations and challenges associated with the development of ePADs, the future perspectives of this research field are proposed. [ABSTRACT FROM AUTHOR]

Lateral flow assays (LFAs) hold great promise for point-of-care testing, especially in resource-poor settings. However, the poor sensitivity of LFAs limits their widespread applications. To address this, we developed a novel device by integrating dialysis-based concentration method into LFAs. The device successfully achieved 10-fold signal enhancement in Human Immunodeficiency Virus (HIV) nucleic acid detection with a detection limit of 0.1 nM and 4-fold signal enhancement in myoglobin (MYO) detection with a detection limit of 1.56 ng/mL in less than 25 min. This simple, low-cost and portable integrated device holds great potential for highly sensitive detection of various target analytes for medical diagnostics, food safety analysis and environmental monitoring. [ABSTRACT FROM AUTHOR]

[Display omitted] • A portable nanocluster-modified paper analytical device integrated with a syringe for highly sensitive Hg2+ detection. • The CMC-EDC/NHS method attaches AuNCs to the substrate, preventing the AuNCs from leaching. • This platform accumulates the signal of Hg2+ by flowing with increased solution volume. • The platform can complete the detection of Hg2+ ions within 30 min, with a detection limit as low as 1.2 nM. To minimize the need for complex testing procedures, sophisticated instrumentation, and electricity for on-site testing, we demonstrate a simple and portable gold nanocluster (AuNC)-modified paper analytical device integrated with syringe-driven fluid flow to enable highly sensitive mercury ion (Hg2+) detection for environmental monitoring. The device is composed of a paper substrate modified with fluorescent AuNCs (AuNC-paper), which is held within a reusable cartridge connected to a syringe, thus allowing users to flow a large volume of the sample solution through the paper test for greater accumulation of the analyte signal. The metallophilic d10-d10 interaction of Hg2+ with Au+ on the surface of the AuNC-paper induces fluorescence quenching, which can be monitored using a smartphone. Importantly, the red-emitting AuNCs avoid interference with the background fluorescence of the paper substrate. Additionally, the AuNCs are strongly-attached to the paper substrate via carbodiimide coupling, which helps prevent the AuNCs from leaching and enables a large amount of solution to interact with the test (up to 2.5 mL) to increase the amount of the target ions that react with the AuNC-paper. As a result, without the need for preconcentrating the test solution, this paper device can provide the highly sensitive detection of Hg2+ ions, including a 26-fold higher sensitivity than the AuNC-modified test paper without a fluidic cartridge, at a low level of down to nM. The paper platform can complete the detection of Hg2+ ions within 30 min, with a detection limit as low as 1.2 nM, which is less than the United States Environmental Protection Agency's regulatory limit for drinking water. This highly sensitive, selective, portable, and easy-to-operate platform may be valuable for on-site mercury pollution monitoring in resource-constrained settings. [ABSTRACT FROM AUTHOR]

Abstract: The preparation and evaluation of a simple paper-based device for the determination of reactive phosphate in natural and soil waters based on the formation of phosphomolybdenum blue is reported. Hydrophilic reagent zones were defined by printing filter paper with a hydrophobic paper-sizing agent using an inkjet printer. The molybdate/potassium antimony(III)-tartrate reagent and ascorbic acid reductant merged together from adjacent hydrophilic zones after spotting the liquid sample onto the paper. The colour intensity of the phosphoantimonylmolybdenum blue complex produced was measured using a flat bed scanner. Under optimal conditions, the paper-based device is characterised by a working range of 0.2–10mgL−1 P, limits of detection and quantitation of 0.05 and 0.16mgL−1 P, respectively, and repeatability of less than 2% RSD at 1 and 5mgL−1 P (n=10 and 8). There was no significant difference between the results obtained using the paper-based device and reference methods (t=0.0135, P (T≤t) two-tail=0.9892, df=38). In its optimum form, the paper-based device was stable for up to 15 day under ambient conditions, and up to 122day when stored at ≤−20°C. The small dimensions, minimal reagent consumption, low cost (a few cents), ease of operation and favourable analytical performance make the proposed paper-based device attractive for on-site environmental monitoring and analysis. [Copyright &y& Elsevier]

• Stationery, Pencils, Papers for fabricating paper-based analytical devices. • Hydrophobic barriers, Cutting and Electrode fabrication. • Robust and Easy-to-use methodology. • Deployable to resource limited settings and scalable for point-of-care diagnostics and detection. Paper-based devices for an analytical application have gained great interest among researchers due to their portability, versatility and facile interpretation. The popularity of these analytical devices is supplemented by their myriad of applications, in point-of-care health systems, environmental monitoring and food safety. However, relatively sophisticated manufacturing techniques used to create complex multiplexed systems, pose barrier between the widespread adoption of the such methods in low-cost settings. Recently, researchers have taken significant efforts towards the development of paper-based analytical devices with more emphasis on novel fabrication approaches costing <1$. Such an approach was achieved by implementing Do-It-Yourself (DIY) path by employing readily available stationaries for fabrication. Here in this review, we categorise such Do-It-Yourself (DIY) approaches and explore their further developments and challenges. Moreover, we discuss the use of various low cost or off-the-shelf equipments for the fabrication of (i) hydrophobic barriers on plain paper (ii) electrodes in detection devices, and (iii) devices porting old detection techniques on to more DIY friendly housings. Additionally, this paper also explores amalgamation of multiple DIY fabrication methods, emerging trends and prospects in the past five years. [ABSTRACT FROM AUTHOR]

The development of low-cost analytical devices for on-site water quality monitoring is a critical need, especially for developing countries and remote communities in developed countries with limited resources. Microbial electrochemical cell-based (MXC) biosensors have been quite promising for quantitative and semi-quantitative (often qualitative) measurements of various water quality parameters due to their low cost and simplicity compared to traditional analytical methods. However, conventional MXC biosensors often encounter challenges, such as the slow establishment of biofilms, low sensitivity, and poor recoverability, making them unable to be applied for practical cases. In response, MXC biosensors assembled with paper-based materials demonstrated tremendous potentials to enhance sensitivity and field applicability. Furthermore, the paper-based platforms offer many prominent features, including autonomous liquid transport, rapid bacterial adhesion, lowered resistance, low fabrication cost (<$1 in USD), and eco-friendliness. Therefore, this review aims to summarize the current trend and applications of paper-based MXC biosensors, along with critical discussions on their field applicability. Moreover, future advancements of paper-based MXC biosensors, such as developing a novel paper-based biobatteries, increasing the system performance using an unique biocatalyst, such as yeast, and integrating the biosensor system with other advanced tools, such as machine learning and 3D printing, are highlighted. [Display omitted] • Studies related to paper-based MXC biosensors are summarized and reviewed. • Benefits of using paper-based platforms over traditional materials are listed. • Current applications and challenges of paper-based MXC biosensors are provided. • Field applicability of paper-based MXC biosensors is highlighted. • Opportunities to integrate 3D printing and machine learning are discussed. [ABSTRACT FROM AUTHOR]

Paper mill effluents may contain polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) that are normally generated due to chlorinated bleaching of pulp and paper. We used the semipermeable membrane device (SPMD) to monitor PCDD/F levels upstream and downstream of a paper mill on the Androscoggin River, in Jay (ME). Following the 36 day deployment, SPMD dialysis and cleanup, the samples were analyzed by HRGC/HRMS. Total concentrations of PCDD/Fs in SPMDs (sum of all tetra-through octachlorinated congeners) ranged from 4.71pgg−1 to 26.26pgg−1. Five out of the targeted 17 toxic congeners were detected, including: 2,3,7,8-TCDF; 1,2,3,7,8-PeCDF; 2,3,4,7,8-PeCDF; 1,2,3,4,6,7,8-HpCDD and OCDD. Permeability reference compounds (PRCs) were used for in situ calibration of the SPMD sampling rate (R s). In all sites, water concentrations were the highest for OCDD (0.081–0.103pgl−1), and the lowest for 1,2,3,7,8-PeCDF (0.005–0.009pgl−1). There was not a consistent pattern of upstream–downstream gradient in the PCDD/F levels. This suggested that processes other than the mill in Jay (multiple sources, river dynamics) governed the flux of PCDD/Fs in the sampling locations. The SPMD results were validated by comparison to other studies on the Androscoggin River and elsewhere, confirming the potential of the device as a useful monitoring technique for PCDD/Fs in large river systems. [Copyright &y& Elsevier]

In this paper, a bifunctional tri-site fluorescent probe was designed for the first time not only for visualization and quantitative analysis of sensing H 2 S in wastewater by coupling paper strip and smartphone (Color recognizer, Xiyi Technology) but also for sensitively monitoring GSH in living cells, which relied on different emission channels and the pH of solutions. The recognition properties of GH towards H 2 S/GSH were satisfactorily demonstrated through fluorescence, UV–vis, 1H NMR and DFT calculations. More importantly, integrated with the paper strip, portable smartphone-sensing platform with a color recognizer app would accomplish cost-effective and rapid assays for colorimetric water quality testing, which displayed huge application potential in fields of environmental monitoring. ga1 • GH could simultaneously detect H 2 S in wastewater and GSH in living cells. • The mechanism of GH towards H 2 S/GSH was demonstrated through fluorescence, UV–vis, 1H NMR and DFT calculations. • Portable fluorescent paper strips are widely used in field inspections. • Fluorescent paper strips of GH integrated with smartphone can realize quantitative monitor of H 2 S in wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • Distinctive hydrophilic-hydrophobic SERS substrates have been fabricated utilizing ordinary papers loaded with Ag nanowires. • Remarkable SERS activity with an enhancement factor (EF) up to 2.63 × 106 was achieved. • An in-situ detection of trace furazolidone on fish under the interference of malachite green was realized. As a typical membrane matrix with attractive flexibility, paper has exhibited great feasibility to serve as surface-enhanced Raman scattering (SERS) substrate in the environmental monitoring and surveillance. In this research, we have designed and fabricated a distinctive hydrophilic-hydrophobic SERS substrate utilizing several ordinary papers loaded with Ag nanowires (Ag NWs). Remarkable SERS activities with an enhancement factor (EF) up to 2.63 × 106 was successfully achieved in the assembly Ag NWs with the optimal amount of nanotips and overlaps. The hydrophilic-hydrophobic strategy could contribute to anchoring microdroplets and thus enrich analytes to improve the homogeneity of substrate with a low relative standard deviation of 10.6%. Furthermore, the sophisticated SERS substrate was also applied in the in-situ detection of trace furazolidone on fish under the interference of malachite green and the reliable recovery rates were demonstrated as well. [ABSTRACT FROM AUTHOR]

• Metabolic biomarker profiles were used for the prediction of clinical diagnoses. • k-NN classifiers were fitted to demonstrate the reliability of µPADs derived data. • Predictors were associated with glucose, lactate, and uric acid concentrations. • Metabolic disorders were suitably predicted with 95.0% overall accuracy. • The modeling addressed here proved that the µPADs could be applied in telemedicine. The development of microfluidic devices for point-of-care (POC) testing has been widely applied for food quality control, environmental monitoring, and clinical diagnoses. Regarding the latter, microfluidic paper-based analytical devices (µPADs) have a great potential in developing portable and disposable platforms for fast disease-relevant biomarker detection in remote areas. In this work, k-nearest neighbors (k-NN) classifiers were applied to demonstrate the reliability of using chemical data obtained from µPADs for diagnosis of diseases like diabetes mellitus and hyperuricemia. Predictors based on glucose, lactate, and uric acid biomarkers were evaluated to reach this goal. Healthy adults were differentiated from the diagnosed patients with a perfect success rate. Metabolic disorders were suitably predicted with 95.0% overall accuracy. This model also showed sensitivities and specificities in the ranges 75–100% and 93–100%, respectively, indicating that the classification protocol is robust. The k-NN modeling proved the potential of the µPADs to be applied in telemedicine for reliable off-site diagnoses. [ABSTRACT FROM AUTHOR]

This work describes a novel, simple and inexpensive pen-on-paper (PoP) method for patterning hydrophobic structures in paper substrates aiming the production of paper-based analytical devices (PADs). This fabrication protocol uses a commercially available plastic welding kit that can be easily acquired and is sold as a repair tool. It consists of an acrylate-based resin which is deposited on the paper and then cured using a UV led, or even the sunlight, for creation of the hydrophobic barriers. The protocol is instrument-free and can be easily implemented in any laboratory. To the best of our knowledge, this is the first report of the use of this material for production of analytical devices. The developed PADs were fully characterized and exhibited better chemical resistance than other recently reported PoP approaches regarding organic media and surfactants. Moreover, the fabrication method demonstrated good analytical versatility since it allowed the production of flexible devices, flow-based devices and pencil-drawn electrochemical devices. These findings are very interesting since overcome some limitations related by other PoP reports and expand the possibilities of using this technology in several aqueous and non-aqueous applications. Lastly, the analytical usefulness of the developed devices was successfully explored through colorimetric determination of nitrite. A detection limit of 0.14 mg L−1 was achieved and several samples of natural waters were analyzed. The results showed good agreement when compared with a reference technique. So, considering the simplicity and the results presented here, this fabrication method shows great potential for use in analytical chemistry. Image 1 • An instrumentless method for fabrication of paper analytical devices is proposed. • The hydrophobic barriers are created with a UV-curable resin used as repair tool. • The use of this material for fabrication of analytical devices is first described. • This material showed better chemical compatibility than other similar approaches. • Colorimetric and electrochemical applications were successfully explored. [ABSTRACT FROM AUTHOR]

Paper-based lateral-flow assays (LFAs) have achieved considerable commercial success and continue to have a significant impact on medical diagnostics and environmental monitoring. Conventional LFAs are typically performed by examining the color changes in the test bands by naked eye. However, for critical biochemical markers that are present in extremely small amounts in the clinical specimens, this readout method is not quantitative, and does not provide sufficient sensitivity or suitable detection limit for a reliable assay. Diverse technologies for high-sensitivity LFA detection have been developed and commercialization efforts are underway. In this review, we aim to provide a critical and objective overview of the recent progress in high-sensitivity LFA detection technologies, which involve the exploitation of the physical and chemical responses of transducing particles. The features and biomedical applications of the technologies, along with future prospects and challenges, are also discussed. • High-sensitivity detection methods for paper-based LFA are reviewed. • Operating principles, features, and applications of diverse LFA detection methods are described. • Future perspectives for high-sensitivity LFA detection methods are presented. [ABSTRACT FROM AUTHOR]

• A new boronic acid functionalized MoS 2 QDs (B-MoS 2 QDs) was synthesized. • B-MoS 2 QDs as a fluorescent mode used for ultra-selectivity analysis of Hg2+. • A unique quenching mechanism of the sensor for Hg2+ detection was studied in detail. • The relevant test paper can use to detect the trace amounts of Hg2+ under UV lamp. • This method has potentially applied in on-site monitoring of environmental Hg2+. In this study, the B-MoS 2 QDs, boronic acid functionalized MoS 2 quantum dots, are synthesized by a simple aminoacylation reaction between MoS 2 QDs and 3-aminobenzeneboronic acid (APBA). It not only exhibits excellent thermo-stability, photo-stability and good salt tolerance, but shows excellent fluorescence stability even under industrial wastewater with high concentration. These good characters can be used to construct a new fluorescence sensor for sensitive and selective detection of mercury ions (Hg2+). The fluorescence intensity of B-MoS 2 QDs linearly decreases with the increase of Hg2+ concentration ranging from 0.005 to 41 μmol L−1, and the limit of detection as low as 1.8 nmol L−1. Due to the mercury ion-promoted transmetalation reaction of aryl boronic acid, this proposed method exhibits fast response, ultra-sensitivity and high selectivity for analysis of Hg2+ in different environmental water, and which also uses to online monitoring of Hg2+. The B-MoS 2 QDs–based test paper can be used to detect the trace amounts of Hg2+ under UV lamp by naked eyes, suggesting that the proposed method has potential application in on-site monitoring of environmental Hg2+. [ABSTRACT FROM AUTHOR]

Microfluidic paper-based analytical devices (μPADs) have experienced rapid growth over the past decade due to their simple design, low cost, minimal sample requirement, and good sensitivity, selectivity and accuracy. While designed originally for point-of-care medical diagnostics, biological, and food safety applications, μPADs are now used increasingly for environmental monitoring purposes. This review provides a detailed overview of the μPADs developed over the past ten years for the environmental analysis of soil, air, ecology (pesticides) and river water. The review commences by introducing the fabrication techniques and detection methods used in μPAD technology. A detailed description of the main μPAD frameworks proposed in the past decade for environmental monitoring is then provided. The review concludes by examining the challenges facing μPADs for environmental monitoring and identifying probable avenues of future research. [ABSTRACT FROM AUTHOR]

• A colorimetric and ratiometric fluorescence dual-mode responsive chemosensor was prepared to detect toxic oxalyl chloride. • The chemosensor could determine oxalyl chloride with high sensitivity (LOD: ∼95 nM), high selectivity and fast response. • The flexible and portable AC-HPD-based test strip could semi-quantitatively determine oxalyl chloride vapor. • The AC-HPD-based kit could respond toward oxalyl chloride vapor with obvious color and fluorescence alteration. The screening of highly toxic chemical vapor is critical for environmental monitoring and human health maintenance. Herein, we reported a chemosensor (AC-HPD) for rapid and specific detection of highly toxic oxalyl chloride vapor, which adopted anthracene carboxyimide as a fluorophore and 3-aminopropanol as the reaction site. Upon coupling of oxalyl chloride with NH and OH groups, AC-HPD exhibited remarkable colorimetric and ratiometric fluorescence dual-mode responses towards oxalyl chloride via the intramolecular charge transfer effect. AC-HPD could determine oxalyl chloride with features of rapid response, excellent specificity, low detection limit (95 nM), as well as obvious color and fluorescence change. Furthermore, AC-HPD-embedded test strip was successfully fabricated and used as a flexible sensing device for rapid, sensitive and visible monitoring oxalyl chloride vapor. [ABSTRACT FROM AUTHOR]

Water contamination by heavy metals poses a significant threat to human health and to the environment. Cr3+ is a common contaminant in aqueous media; therefore, innovative sensing technologies for reliable detection are in demand. In this study, we demonstrate that NaGdF 4 : Yb3+, Er3+ up-converting nanoparticles can be used as ratiometric luminescence probes to detect low concentrations of Cr3+ contaminating ions in water. Excitation in the near-infrared region provides a fluorescence-based detection method with large depth penetration and is autofluorescence-free. Based on this ability, a paper-based sensor was manufactured in which the incorporated up-converting nanoparticles allowed a limit of detection of Cr3+ ion concentrations as low as 2 nM. This represents a new step towards the practical application of rare-earth-doped nanoparticles in environmental monitoring, addressing the critical need for efficient detection methods of contaminating ions in water. • Conventional water pollutant measurement often needs functionalized sensing probes or multiple probes. • This work presents a simple method to measure Cr3+ concentration in water using luminescent rare-earth-doped nanoparticles. • Detecting Cr3+ in water with Yb, Er-NPs does not require functionalization or combination with other nanoparticles. • Integrating Yb, Er-NPs into paper substrates enables simple, quick ratiometric paper-based water quality sensors. • The ratiometric paper-based sensors used in this work shows a limit of detection of 2.4 nM. [ABSTRACT FROM AUTHOR]

Phosphate rock is mined on a large scale as a source material for fertilizers and other phosphorous containing products, such as phosphoric acid and gypsum. The potential problem of high concentrations of naturally occurring radionuclides in the phosphate industry has been recognized for many years. The industry is responsible for the production of millions of tons of phosphogypsum waste, which is usually stockpiled and might impact the surrounding environment. The presented study aims to assess the natural radioactivity concentrations in raw and waste sub-products from phosphate mining and fertilizer production in South Africa and determine the potential radiological risk associated with the industry. Activity concentrations of 238U, 226Ra and 232Th in phosphate rock, phosphogypsum, tailings, fertilizer, soil and sediment were found to be similar to values reported in previous studies conducted in South Africa. Concentrations of the 232Th decay series were higher than those of the 238U series in rock and ore. The low concentrations of 238U and 226Ra in rock and ore, compared to other countries, makes it more suitable to be used for fertilizer production, and therefore increases the demand for export of rock phosphate and fertilizer from South Africa. 228Ra concentrations in phosphogypsum were higher than 226Ra. The activity of 228Ra was also enriched compared to 232Th, with a ratio of 0.45–19.8. Similar equilibria as described in literature were observed, with almost all the 228Ra and 226Ra present in the phosphate rock observed in the phosphogypsum. Only a low percentage of 232Th present in the original rock remained in the phosphogypsum, with more than 60% present in the fertilizer. The activity concentrations of all nuclides in the analysed samples from the phosphate industry were less than the 1000 Bq kg−1 exclusion value proposed internationally for regulation of NORM. With the exception of phosphate rock samples, concentrations in all solids were lower than the 500 Bq kg−1 limit proposed by the National Nuclear Regulator in South Africa. The obtained values of Ra eq for all phosphogypsum, tailings and soil samples were less than the recommended limit of 370 Bq kg−1. The gamma index for the majority of samples was less than 0.5. The index exceeded the limit of unity only for phosphate rock and fertilizer samples, indicating some radiological risk to people living in the vicinity of the industry. The results suggested that members of the public were unlikely to receive any significant dose from the use of phosphate rocks and fertilizers, with an annual effective dose of less than 0.5 mSv.a−1. The highest external dose of 0.45 mSv a−1 is expected from phosphate rock. The suitability of use of phosphogypsum as building material was evaluated. Based on the calculated gamma index [ I γ = 0.52 ± 0.14] use of phosphogypsum as building material is permitted. • Characterization of natural radioactivity in samples from the phosphate fertilizer production industry in South Africa. • Comparison of measured activity concentrations in these samples with those in similar products worldwide. • Evaluation of the radiological impact associated with the phosphate industry in South Africa. • Evaluation of utilization of by-products such as phosphogypsum as building material. [ABSTRACT FROM AUTHOR]

In the recent Comment on our paper ‘Life cycle environmental impacts of UK shale gas’ ( Applied Energy 134 (2014) 506–518), Westaway et al. ( Applied Energy , available online 20th March 2015) allege that we exaggerated the potential impacts of shale gas extraction in the UK. They first take an issue with our inclusion of worst case scenarios despite our clear declaration in several places in the paper that this is indicative of what could happen within the confines of a very ill-defined and highly variable future reality. Secondly, Westaway et al. claim that key assumptions in the modelling reflect illegal practices that would not occur, when in fact this is an exaggeration of the legal situation and these practices are still viable. This rebuttal addresses some of the claims made by Westaway et al. while welcoming further open and impartial discourse in this area. [ABSTRACT FROM AUTHOR]

The Internet of Things (IoT) is an innovative technology used in manufacturing, environmental monitoring, home automation, human health applications, and other fields. IoT devices, however, are susceptible to various security risks. Cyber-attacks on IoT systems can halt the entire system, resulting in data loss. Intrusion Detection Systems (IDS) can quickly identify malicious activity that could have compromised the network's performance. Effective IDS and Intrusion Prevention System (IPS) are necessary to protect IoT systems. Blockchain technology presents another innovative method to strengthen security systems against the latest attacks. This paper focuses on conducting a Systematic Literature Review (SLR) on Blockchain-based Intrusion Detection/Prevention Systems in IoT Networks. We reviewed several relevant blockchain-based IDS and IPS proposed for IoT networks and their mechanisms. The most recent research articles, published between 2017 and 2022, were selected from several databases. Consequently, a comprehensive review of these selected papers sheds light on their techniques, advantages, and drawbacks. [ABSTRACT FROM AUTHOR]

• A 3D Europium-based Metal-organic framework (ZEuMOF), was synthesized and characterized using various analytical and computational techniques. • ZEuMOF demonstrated excellent selectivity and sensitivity towards important bioflavonoid quercetin. • The limit of detection (LOD) for quercetin was remarkably low (9.86 × 10−7 M). • Performance of ZEuMOF was compared with high-performance liquid chromatography with ultraviolet detection (HPLC–UV) for quercetin determination in a green tea sample. • Quercetin detection using ZEuMOF could be visualized by the naked eye under 254 nm UV light using test filter papers. In this study, we present the synthesis and characterization of a metal-organic framework (MOF) named ZEuMOF, which was prepared through a solvothermal method using pamoic acid and Eu(NO3) 3 ·6H 2 O. The MOF was characterized using various analytical techniques and computational studies. One of the noteworthy findings of this study is that the ZEuMOF exhibits excellent selectivity and sensitivity towards quercetin, an important bioflavonoid. The limit of detection (LOD) of quercetin was found to be as low as 9.86 × 10−7 M. In addition, we compared the performance of ZEuMOF with that of high-performance liquid chromatography with ultraviolet detection (HPLC–UV) for determining the quercetin content in a green tea sample. The results were satisfactory, and the detection of quercetin could even be visualized by the naked eye under 254 nm UV light using a test filter paper. These findings suggest that ZEuMOF could serve as a portable luminescent sensor for the detection of quercetin. Overall, this study sheds light on the potential application of ZEuMOF as a highly selective, sensitive, recyclable, and portable sensor for quercetin, which could have significant implications in various fields, including environmental monitoring and food quality control. [Display omitted] [ABSTRACT FROM AUTHOR]

Marine intelligent net tank aquaculture monitoring plays an important role in improving aquaculture efficiency, environmental monitoring efficiency, and environmental safety. The underwater environment has complex light, often with problems such as scattering and absorption, resulting in poor image quality, making it difficult to accurately analyze and judge the aquaculture environment. Improving marine intelligent net tank aquaculture monitoring has the following three advantages: 1) better observation and monitoring of the aquaculture process, timely detection of problems and abnormalities, to protect the benefits of aquaculture and product quality. 2) more convenient and rapid monitoring of the aquaculture environment, improving monitoring efficiency and reducing monitoring costs. 3) effective monitoring of the underwater environment around the farm, and timely detection of foreign pollution, harmful substances, and other problems, to protect the safety of the aquaculture environment. Therefore, in order to solve the two degradation problems of scattering and absorption in the process of marine smart net farm monitoring, we propose a marine smart net farm monitoring method using multiple scattering models and multiple spatial transformations, called MINM. Specifically, inspired by the image chromatic aberration correction method, we design a color correction method in the multicolor space, which is implemented by using the Lab and RGB color space by performing contrast-constrained adaptive histogram equalization and gray world assumptions, respectively, to correct color shifts in different color models. Based on this, we propose a de-scattering method using a multi-scattering model, which eliminates the effect of scattering on underwater imaging by embedding a complete multi-scattering underwater imaging model to guide the extraction of different features in the multi-scattering model. To obtain more qualified results, we also propose an efficient perceptual fusion to mix the output of the de-scattering and color correction. Thus, our method can take advantage of multiple scattering models and multiple spatial transformations to effectively improve the visual quality of underwater images, producing enhanced results that fit the complete underwater imaging model and have bio-visual characteristics. In extensive experimental demonstrations, our MINM method has shown higher performance than the state-of-the-art methods in terms of both visual quality and quantitative metrics. All experimental results and datasets in this paper are available from the following website: https://github.com/An-Shunmin/MINM. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of environmental information disclosure on firm pollution behavior by leveraging an exogenous shock which allow Chinese environmental non-governmental organizations (ENGOs) to disclose pollution information. Using a difference-in-differences approach comparing firms in disclosed cities versus undisclosed cities, we find ENGO information disclosure significantly reduces manufacturing firm COD emissions. We explore several potential mechanisms and find that the reduction effect was primarily driven by "higher-level government supervision" rather than "public supervision." Heterogeneous analysis reveals significant effects only for firms facing high reduction pressure, low governance costs, weak local protection, and in heavy-polluting industries. Our findings provide insights into supplementing inadequate regulations with informal institutions to achieve environmental aims within a decentralized economy. [ABSTRACT FROM AUTHOR]

• The EEMPW significantly curbs firms' hypocritical greenwashing behaviors. • Firms in cleaner production industries, highly-developed green finance regions are more restrained in greenwashing. • Firms in highly environmentally regulated areas, and state-owned firms are more restrained in greenwashing. • Financially constrained firms reduce their likelihood of greenwashing behavior by compressing costs, and facilitating green innovation behaviors. To address ecological, climate and environmental issues in sustainable growth, local ecological environmental monitoring power withdrawal (EEMPW) by the Chinese State Council has been implemented since 2015. This paper aims to comprehensively investigate how the centralization of national environmental quality monitoring policy via the EEMPW affects corporate greenwashing behavior, and evaluate the reacting mechanisms. The empirical findings derived by the continuous difference-in-differences models show that the EEMPW significantly curbs firms' hypocritical greenwashing behaviors, and by increasing financial constraint level, the greenwashing behaviors can be significantly reduced. This paper finds that firms in cleaner production industries, firms in regions with highly developed green finance, firms in highly environmentally regulated areas, and state-owned enterprises are more restrained in greenwashing. Furthermore, our mechanism analyses show that financially constrained firms reduce their likelihood of greenwashing behavior by compressing management and financial costs, and facilitating green innovation efficiency behaviors. Our findings provide suggestions for curbing greenwashing behaviors and for improving the efficiency of the government regulation of ecological, climate and environmental targets in economic growth. [ABSTRACT FROM AUTHOR]

Abstract: This Letter aimed to develop an efficient method for the determination of cyanide ion (CN−). A novel colorimetric chemosensor 4-[(1E)-2-(4-hydroxyphenyl)ethenyl]-1-allylpyridinium bromide (HPEAPB) was synthesized. HPEAPB displayed good selectivity toward CN− over other competing anions in ethanol. A color change from yellow to red was immediately observed upon the addition of CN− and the limit of detection (LOD) was 3.4×10−6 molL−1. The sensing mechanism was discussed by UV–vis, 1H NMR titration, and a comparison study. Colorimetric test paper for CN− was prepared by attaching HPEAPB to a chromatography paper, which could be used to detect CN− in environmental samples as simply as a pH-indicator paper for pH value. The LOD of the test paper for CN− was 2.0×10−4 molL−1. This detection method for CN− has potential applications in cyanide ion containing fields by combination of rapid and real-time advantages. [Copyright &y& Elsevier]

This paper contributes to the growing debate about the role of board-level sustainability committees, focusing on whether they leverage sustainability expertise for impactful environmental initiatives or purely serve as symbolic actions aimed at greenwashing. Using a large set of firms from 35 countries over the 2010–2017 period, we find that the presence of a sustainability committee is positively associated with higher-quality GHG emissions disclosure. This finding is robust to endogeneity and sample selection bias concerns. The sustainability committee effect is more pronounced when external environmental institutions are too weak to properly monitor corporate environmental disclosure. Our findings suggest that sustainability committees are not a symbolic management tool, but play a crucial role in enhancing corporate environmental disclosure. [ABSTRACT FROM AUTHOR]

Clustering and routing algorithms are critical to collecting and processing data sensed by nodes of wireless sensor networks deployed in various missions including environmental monitoring, tracking, and rescue operations. In this paper, a clustering algorithm is presented for wireless sensor networks with balanced cluster size resulting in energy efficiency. The algorithm is based on forming clusters using topology of the network and routing aggregated data from each cluster head to the base station. The cluster formation phase involves using tree-based traversals on the underlying sensor network graph. Using simulations, it is demonstrated that clusters of similar sizes are obtained for networks of varying sensor radii. It is demonstrated that the time to death of the first node of this clustering algorithm is superior to well-known clustering algorithm for random networks. [ABSTRACT FROM AUTHOR]

More and more sensor nodes which are deployed in smart cities for data collection and analysis form the ubiquitous urban Internet of Things. Energy saving and rapid data collection play a key role in environmental monitoring, military search, medical care, and general city management in smart cities. Therefore, it is a very meaningful and challenging work to design an energy efficient and fast routing protocol to collect data. Although the widely used duty cycle mechanism can effectively save energy, it brings greater delay to routing. Using wake-up radio enable nodes can effectively reduce the delay, but it will bring a large network deployment cost. So how to reduce the deployment cost and quickly route data is a challenge issue for sensor-based system. In this paper, Pre-Awake for Wake-up Radio Enable Sensor based system (PA-WuRES) routing protocol is proposed to reduce delay and deployment cost. The main contribution of our work are as follows: (a) A novel PA-WuRES protocol is proposed which requires much less WuR(WuR,Wake-up Radio) enable nodes, so its deployment cost is lower. (b) Using WuR enable nodes will increase a certain amount of energy consumption. Therefore, this paper proposes a differentiated service data routing mechanism to minimize energy consumption. (c) Full theoretical analysis and experimental results show that the proposed PA-WuRES protocol reduces the deployed WuR enable nodes by 80%, but sensitive-data routing delay is reduced by 48.4%. [ABSTRACT FROM AUTHOR]

A dual-p K a values pH fluorescent probe by combining mechanisms of PET and fluorescent conversion between monomer and excimer of pyrene shows advantage of a widely pH detected range and high sensitivity in extremely and weakly acidic solutions. [Display omitted] • Probe MPCA has two p K a values, a p K a 1 of 1.88 and a p K a 2 of 5.81. • Probes MPCA has high sensitivity and fast response time. • Probes MPCA has strong good photostability and anti-ion interference ability. • Probes MPCA can measure pH of the environmental water samples. • Probes MPCA can be made into pH fluorescent test paper. A dual-p K a values pH fluorescence probe based on pyrene, N-(2′-morpholinoethyl)-pyrene-1-carboxamide (MPCA), was fabricated through facile one-step reaction. Interestingly, MPCA showed a p K a 1 of 1.88 under extremely acidic conditions and a p K a 2 of 5.81 under weak acidic conditions in deionized water, which indicate that MPCA has a high sensitivity to change of pH value. When the pH value was decreased further from 4.05 to 0.52, the fluorescence response of MPCA was quenched by 93.8% due to quenching of fluorescence emission of the pyrene monomer and apparent conversion of monomer/excimer of pyrene group. The results show that pyrene excimer of MPCA can be produced in extremely acidic environment. When the pH value of the solution was decreased from 7.03 to 4.05, the fluorescence response of MPCA was enhanced due to the inhibition of photoinduced electron transfer (PET) from N atom on morpholine ring to pyrene fluorophore. In addition, MPCA has a short response time, good repeatability and anti-cation interference for pH monitoring. MPCA was then applied successfully to monitor the acidity of environmental water systems (tap water and Pearl River water) and the living GS cells of epinepheluscoioides. Finally, a fluorescence pH test paper based on the colorful changes of MPCA at different pHs was developed, which can conveniently monitor the pHs of aqueous solutions. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel variant of the Covering Tour Problem (CTP), called the Covering Tour Problem with Varying Coverage (CTP-VC). We consider a simple graph G = (V , E) , with a measure of importance assigned to each node in V. A vehicle with limited battery capacity visits the nodes of the graph and has the ability to stay in each node for a certain period of time, which determines the coverage radius at the node. We refer to this feature as stay-dependent varying coverage or, in short, varying coverage. The objective is to maximize a scalarization of the weighted coverage of the nodes and the negation of the cost of moving and staying at the nodes. This problem arises in the monitoring of marine environments, where pollutants can be measured at locations far from the source due to ocean currents. To solve the CTP-VC, we propose a mathematical formulation and a heuristic approach, given that the problem is NP-hard. Depending on the availability of solutions yielded by an exact solver, we evaluate our heuristic approach against the exact solver or a constructive heuristic on various instance sets and show how varying coverage improves performance. Additionally, we use an offshore CO 2 storage site in the Gulf of Mexico as a case study to demonstrate the problem's applicability. Our results demonstrate that the proposed heuristic approach is an efficient and practical solution to the problem of stay-dependent varying coverage. We conduct numerous experiments and provide managerial insights. • Stay-dependent coverage in Covering Tour Problem improves the efficiency. • Time spent in a node influences the area of coverage or covering set. • Adaptive metaheuristic algorithm tackles the increased complexity. • The problem is applied to environmental monitoring of offshore Carbon Capture and Storage site. [ABSTRACT FROM AUTHOR]

Supramolecular gels with metal ion-responsiveness are an important kind of smart materials due to their potential application in environmental monitoring. In this study, a novel l -glutamine-contained 1,8-naphthalimide derivative (NDG) has been designed and synthesized as an organogelator. NDG could self-assemble into stable supramolecular organogels in different kind of solvents, and the gelation process showed bright blue aggregation-induced emission (AIE). The self-assembly behavior, morphology and structure of NDG gels were thoroughly studied by various techniques. Interestingly, the obtained NDG organogel exhibited a fluorescence "turn-off" response for Fe3+ and formed a stable metallogel NDG -Fe3+. The detection limit (LOD) of NDG in diluted solution and gel states for Fe3+ was calculated to be 30.8 nM and 11.5 nM, respectively, indicating high sensitivity. In addition, the blue fluorescence emission of the gel system was restored in the presence of ascorbic acid and then quenched again with oxygen, which showed reversible fluorescence sensing effect and employed as a logic gate at the molecular level. Furthermore, xerogel-based film of NDG emitted strong blue emission and could be utilized as paper-based chemosensor to detect Fe3+. And also, the NDG gel had potential application in fluorescence display material. [Display omitted] • A l -glutamine-contained 1,8-naphthalimide gelator was synthesized with AIE effect. • The organogel exhibited a fluorescence response for Fe3+ by gel-gel transition. • The gel system was potentially constructed as a molecular logic gate. • Paper-based gel film was used in Fe3+ recognition and as display material. [ABSTRACT FROM AUTHOR]

The detection of underwater fish targets is critical for ecological monitoring and marine biodiversity research. However, underwater fish detection is typically constrained by problems including low image quality and variable underwater surroundings. On behalf of further improving the underwater fish detection accuracy in complex underwater environments, this paper proposes a dual-path (DP) Pyramid Vision Transformer (PVT) feature extraction network named DP-FishNet. The backbone network DP-PVT composed from the PVT Network is made up of two feature extraction paths. The first represents the Vision Transformer path, which extracts global features to enhance the distinction between the foreground and background of underwater images. The second is the convolutional neural network path, which enhances the accuracy of detecting small targets by extracting local features. Additionally, to more effectively utilize the feature information extracted by the network, this paper provides a promising solution to employ the content-aware reassembly of features (Carafe) in the feature pyramid network (FPN). The seesaw loss is utilized as a classification loss to address the problem of unbalanced samples caused by the gap in the number of fish populations. According to the experimental findings, the AP and AP50 of the DP-FishNet are 76.0% and 95.2%, respectively. In comparison to currently available advanced two-stage detection algorithms, the quantity of computation and parameters is reduced by approximately 40%. DP-FishNet strengthens the ability to extract global and local features from underwater images and enhances feature reuse. DP-FishNet can be utilized to detect fish targets in actual and complicated underwater habitats. [ABSTRACT FROM AUTHOR]