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Paper-based test film material is widely used in a variety of test instruments for different applications. The enzyme activity test paper sheet is one of the most popularly used test papers. Here we present a novel fabrication of paper-based enzyme activity test paper without cationic resin added in. The chemical pulping fibers were first beaten to different degrees (from 14.6 to 41.5°SR) with a PFI beater. After that, the fibers were modified with a cationic agent (3-chloro-2-hydroxypropyl trimethyl ammonium chloride) under the system of alkali and water solution. Finally, the test papers were made with the modified fiber by a regular paper former in lab. The results showed that beating is beneficial for the improvement of the cationization reaction which is indicated by the Zeta potential, FTIR and EDS. The main mechanisms involved are the destruction of crystalline zone, increase of free hydroxyl group and defibrillation. This hypothesis was supported by the SEM, XRD and fiber analyzer. Beating under the optimized condition, the wet strength and liquid absorbability of test paper can meet the application requirement, and the test results of enzyme activity are quite close to those of commercial test papers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

This review provides an in-depth examination of recent progress in the development of chemosensors, with a particular emphasis on colorimetric and fluorescent probes. It systematically explores various sensing mechanisms, including metal-to-ligand charge transfer (MLCT), ligand-to-metal charge transfer (LMCT), photoinduced electron transfer (PET), intramolecular charge transfer (ICT), and fluorescence resonance energy transfer (FRET), and elucidates the mechanism of action for cation and anion chemosensors. Special attention is given to phenothiazine-based fluorescence probes, highlighting their exceptional sensitivity and rapid detection abilities for a broad spectrum of analytes, including cations, anions, and small molecules. Phenothiazine chemosensors have emerged as versatile tools widely employed in a multitude of applications, spanning environmental and biomedical fields. Furthermore, it addresses existing challenges and offers insights into future research directions, aiming to facilitate the continued advancement of phenothiazine-based fluorescent probes., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Selective and sensitive detection of halides in water is critically important in the diagnosis of diseases and assessment of aquatic ecosystems. The recognition is usually carried out by numerous analytical techniques such as ion chromatography, fluorescence, near-infrared spectroscopy, ion-selective electrode and light scattering. Although these methods offer high sensitivity, they are expensive and time-consuming. Therefore, great efforts have been focused on the sensing of halide anions in water through a simple, fast, low-cost and portable paper-based colorimetric platform. In particular, the sensing process with silver nanoparticles interacting with analytes is of great chemical and biological interest. In this work, anisotropic silver nanoparticles in size and shape embedded in epoxy resin were prepared and subsequently printed on filter papers of cellulose. The influence of water and halide anions (Cl−, Br− and I−) on the morphology of these nanoparticles are investigated by scanning electron microscopy, Raman shift and diffuse reflectance spectroscopy. The mechanism involves aggregation of faceted silver nanoparticles induced by interactions between carbonyl groups of the resin and water. Subsequently, the interaction between halide anions and the aggregated silver nanoparticles causes oxidative etching on their surface, shape conversion (faceted to quasi-spherical shapes), decreasing in the particle size and formation of chain–like or compact aggregates resulting in strong interparticle plasmonic coupling. This selective mechanism was tested for the naked-eye colorimetric recognition of chloride anions in a complex simulated physiological system, whose results show promising perspectives to develop diagnostic-sensing devices. [ABSTRACT FROM AUTHOR]

When the degree of closure of the paper machine wet end waters increases, wet end problems also become more difficult to control without specific and selective on-line measurements. The need to measure the concentrations of individual compounds in order to explain wet end phenomena is growing. This study was performed to set up a CE system to a paper machine and to determine soluble inorganic and organic ions in different locations of pulp and paper process waters with real time analyses by two on-line CE methods. A reconstructed commercial CE apparatus was connected to a papermaking machine via an apparatus, which was a combined sampling and sample pretreatment instrument, the role of which was to filter and dilute the samples before on-line determination by CE. The on-line procedures were optimized for simultaneous determination of anions as chloride, sulfate, oxalate, formate and acetate and for determination of cations as potassium, calcium, sodium, magnesium and traces of aluminium. The quantification was performed with external standard methods using the programs available in the commercial CE instrument. The concentrations of the ions were transferred by using a computerized transfer algorithm exporting the results from the analysis instrument to the process control unit. The developed on-line procedures were tested three times in paper and paperboard mills for 1 month at a time. Correlations were observed between the CE results and changes in the processes.

The simultaneous discrimination and detection of multiple anions in an aqueous solution has been a major challenge due to their structural similarity and low charge radii. In this study, we have constructed a supramolecular fluorescence sensor array based on three host-guest complexes to distinguish five anions (F - , Cl - , Br - , I - , and ClO - ) in an aqueous solution using anionic-induced fluorescence quenching combined with linear discriminant analysis. Due to the different affinities of the three host-guest complexes for each anion the anion quenching efficiency for each host-guest complex was likewise different, and the five anions were well recognized. The fluorescence sensor array not only distinguished anions at different concentrations (0.5, 10, and 50 µM) with 100% accuracy but also showed good linearity within a certain concentration range. The limit of detection (LOD) was < 0.5 µM. Our interference study showed that the developed sensor array had good anti-interference ability. The practicability of the developed sensor array was also verified by the identification and differentiation of toothpaste brands with different fluoride content and the prediction of the iodine concentration in urine combined with machine learning., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

The ability to link criminal activity and identity using validated analytical approaches can be of great value to forensic scientists. Herein, the factors affecting the recovery and detection of inorganic and organic energetic material residues within chemically or physically enhanced fingermarks on paper and glass substrates are presented using micro-bore anion exchange chromatography with suppressed conductivity detection. Fingermarks on both surfaces were enhanced using aluminium powder or ninhydrin after spiking with model test mixtures or through contact with black-powder substitutes. A quantitative study of the effects of environmental/method interferences, the sweat matrix, the surface and the enhancement technique on the relative anion recovery of forensically relevant species is presented. It is shown that the analytical method could detect target analytes at the nanogram level even within excesses of enhancement reagents and their reaction products when using solid phase extraction and/or microfiltration. To our knowledge, this work demonstrates for the first time that ion chromatography can detect anions in energetic materials within fingermarks on two very different surfaces, after operational enhancement techniques commonly used by forensic scientists and police have been applied., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

An epoxy-silver nanocomposite printed on paper was prepared for colorimetric detection of chloride anions (Cl−) in aqueous solution. This paper-based sensor provides a promising platform with attractive advantages such as simple fabrication, intense colors, fast naked-eye response, and high specificity toward Cl− detection. The sensor undergoes a color change from yellow-orange to chestnut-brown in the presence of water and turns to green–brown in the presence of Cl−. A good linear relationship (R2 = 0.9754) between logarithmic Cl− concentration and the extinction intensity difference at 515 nm was observed at concentrations in the 20–400 mM range with a limit of detection (LOD) of 14 mM, far beyond the usual concentrations at which most of the Cl− colorimetric sensors are limited. It was also proposed a sensing mechanism based on the oxidative etching of anisotropic silver nanoparticles (from 20 to 250 nm) by Cl− and subsequent formation of chain-like aggregates, resulting in strong interparticle plasmonic coupling. This paper-based sensor can distinguish Cl− from other ions such as F−, OH−, NO3−, SO42−, HPO42−, H2PO4−, H+, K+, Na+, NH4+, Zn2+, and Co2+ and from mixtures of these ions. The nanosensor was also tested to recognize Cl− in seawater and a commercial electrolyte solution, even using volumes as small as 4 µL, suggesting its easy inclusion in portable devices. This novel colorimetric platform is undoubtedly useful for recognizing Cl− in environmental and physiological systems. Epoxy-silver nanocomposite printed on paper for colorimetric detection of chloride anions in water. The paper-based sensor shows intense colors, fast naked-eye response, and high specificity toward Cl− detection at high concentrations (mM) [ABSTRACT FROM AUTHOR]

We report a paper-based chemosensor array device (PCSAD) for the quantitative detection of oxyanions including the herbicide glyphosate (GlyP) in aqueous media. The mechanism of the oxyanion detection relies on a coordination-binding-based sensor array. In this study, the competitive coordination binding among Zn2+, four catechol dyes, and seven oxyanions caused noticeable colour changes. The colour changes were employed for qualitative and quantitative analyses using an in-house automated image-processing algorithm with pattern recognition for digital images. A linear discrimination analysis discerned similarly structured oxyanions with 100% accuracy. The regression analysis allowed the accurate quantification of GlyP in the herbicide products with a limit of detection of 16 mg/L, which is lower than the health advisory value for children (20 mg/L) stipulated by the environmental protection agency (EPA). PCSAD is a powerful sensor device for the on-site quantification of aqueous anions for environmental assessment. [ABSTRACT FROM AUTHOR]

Negative ion mode paper spray mass spectrometry (PS-MS) suffers from intense background noise and unstable MS signal. For the first time, we reported fluorinated boron nitride nanosheet (h-FBN) assisted negative ion PS-MS for the detection of a series of molecules. We demonstrated that the introduction of h-FBN can greatly improve the detection sensitivity and signal stability in the negative ion mode. [ABSTRACT FROM AUTHOR]

Electrospray ionization mass spectrometry (ESI-MS) analysis in the negative ion mode is adversely affected by ionization suppression caused by electrical discharge and the presence of salts. Paper spray mass spectrometry (PS-MS) also suffers from the above phenomenon, being built on principles similar to those of ESI. Herein, we report the use of a paper substrate modified by 1-[3-(trimethoxysilyl)propyl]urea to improve the sensitivity of quantitative PS-MS analysis in the negative ion mode. The obtained results demonstrated that the urea modified paper substrate can effectively bind anions and highly polar compounds in the sample solution, decreasing competitive ionization in the negative ion mode of PS-MS and significantly reducing the signal intensity of Cl − adducts. In addition, the analyte responses were also significantly improved owing to the decreased electrical discharge observed for the less polar surface to decrease electrical discharge. Compared to non-modified PS-MS, urea-modified PS-MS exhibits a much higher sensitivity, showing 2−109 times improved signal-to-noise ratio (S/N). In real sample analysis, the limits of detection (LODs) of salicylic acid in urine and terpene lactones in Ginkgo biloba extract (EGb) were improved 10-fold and 2–40-fold, respectively, compared to that of non-modified PS-MS. [ABSTRACT FROM AUTHOR]

A general anion-sensing platform is reported based on a portable and cost-effective ion-selective optode and a smartphone detector equipped with a color analysis app. In contrast to traditional anion-selective optodes using a hydrophobic polymer and/or plasticizer to dissolve hydrophobic sensing elements, the new optode relies on hydrophilic cellulose paper. The anion ionophore and a lipophilic pH indicator are inkjet-printed and adsorbed on paper and form a 'dry' hydrophobic sensing layer. Porous cellulose sheets also allow the sensing site to be modified with dried buffer that prevents any sample pH dependence of the observed color change. A highly selective fluoride optode using an AlIII-porphyrin ionophore is examined as an initial example of this new anion sensing platform for measurements of fluoride levels in drinking water samples. Apart from Lewis acid-base recognition, hydrogen bonding recognition is also compatible with this sensing platform. [ABSTRACT FROM AUTHOR]

This experiment studies the use of an available azo dye, calmagite (CAL), for the recognition of carbonate ion in running water. The linear range of carbonate, derived from the results of this simple, selective, sensitive and rapid determination, was 1.2 × 10−8–5.4 × 10−6 mol L−1 with the detection limit of 1.6 × 10−8 mol L−1. In the examined cases, the coexisting cation, anions and weak acids (NO3−, NO2−, SO42−, SO32−, HSO3−, OAc−, I−, Br−, F−, Cl−, SCN−, CO32−, HCO3−, H2PO4−, HPO42−, Cit3−), (Ascorbate, K+, Na+, Mg2+ <6.9 × 10−4 mol L−1) did not restrict the analysis by causing interference. The recoveries which were in the range of 97.3–101.4% established the evidence of the validity of the method for real water samples. The obtained results manifested good proof of the accuracy of the method to be comparable with acid-base titration. In general, the method was cost-effective and fast, with the uncomplicated operation, which made the receptor suitable for rapid detection of carbonate ion in freshwater in the field. On the other hand, having regard to the modifications calmagite made in the filter paper strips, this chemosensor revealed the great potential to be applied as a carbonate solid-state colorimetric indicator. [ABSTRACT FROM AUTHOR]

The electrochromic (EC) polymer poly (3,4‐(2,2‐dimethylpropylenedioxy)thiophene) (PProDOT‐Me2) is expected to be used in flexible e‐paper displays because of its great optical modulation ability and inherent flexibility. While the EC effect is primarily determined by the anions and cations in the electrolyte, yet suffers from inorganic salt based on monovalent Li+ cations and corresponding anions, such as lithium perchlorate(LiClO4), lithium bis(trifluoromethane sulfonyl) imide (LiTFSI), and lithium trifluoromethane sulfonate (LiTRIF), which may impact the overall EC performance of the EC device caused by insufficient ion doping/de‐doping processes. Herein, the divalent viologen cation‐based ionogel (VGE) is developed to tackle the challenge. Owing to its more anions design, the doping/de‐doping process in the PProDOT‐Me2 is more sufficient, thereby enhancing the optical modulation range (ΔR = 39.4%) of PProDOT‐Me2, compared to monovalent Li+ cation‐based ionogel (ΔR = 13.3%). Meanwhile, the VGE has good interface contact with PProDOT‐Me2 and the flexible electrode, which makes the VGE‐based EC device (V‐ECD) exhibit commendable mechanical stability. To demonstrate the potential application in flexible e‐paper displays, the simple eight‐digit EC display device is assembled from seven V‐ECDs, each of which hasa high switching speed, robust cycling stability, and low operating energy consumption. [ABSTRACT FROM AUTHOR]

In this work, we report atomic-scale reconstruction processes in Fe-Ce oxide-based composites (hydrothermally precipitated at Fe-to-Ce dosage ratios of 1:0, 2:1, 1:1, 1:2, and 0:1), upon treatment at 300 °C. The structural changes are correlated with the adsorptive removal of arsenate, phosphate, fluoride, bromide, and bromate. The presence of the carbonate-based Ce-component and surface sulfate in precursor samples creates favorable conditions for phase transformation, resulting in the formation of novel (unknown) layered compounds of Fe and Ce. These compounds are of the layered double hydroxide type, with sulfate in the interlayer space. In spite of general awareness of the importance of surface area in adsorptive removal, the increase in surface area upon thermal treatment did not increase adsorption of the studied anions. However, EXAFS simulations and the adsorption tests provided evidence of regularities between local structures of Fe in composites obtained at 80 and 300 °C and adsorption performance of most studied anions. The best adsorption of tetrahedral anions was demonstrated by samples whose simulated outer Fe shells resulted from oscillations from both O and Fe atoms. In contrast, the loss of extended x-ray absorption fine structure was correlated with the decrease of adsorptive removal. Both Fe K-edge and Ce L 3 -edge EXAFS suggested the formation of solid solutions. For the first time, the utilization of extended x-ray absorption fine structure is suggested as a methodological approach (first expressed in the companion paper) to estimate the surface reactivity of inorganic materials intended for use as anion exchange adsorbents. [ABSTRACT FROM AUTHOR]