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The prevalence of diabetes has increased over the past years. Therefore, developing minimally invasive, user-friendly and cost-effective glucose biosensors is necessary especially in low-income and developing countries. Cellulose paper-based analytical devices have attracted the attention of many researchers due to affordability, not requiring trained personnel, and complex equipment. This paper describes a microfluidic paper-based analytical device for the detection of glucose in tear with the naked eye. The paper-based biosensor fabricated by laser CO2, and GOx/HRP enzymatic solution coupled with TMB was utilized as reagents. A sample volume of 10 µl was needed for the biosensor operation and the results were observable within 5 minutes. To evaluate the device performance, color intensity-based and distance-based results were analyzed by ImageJ and Tracker. Distance-based results showed a linear behavior in the range of 0.1–0.6 mM with an R2 = 0.967 and LOD of 0.2 mM. The results could be perceived by the naked eye without any need to further equipment or trained personnel in a relatively short time (3–5 minutes). Moreover, glucose concentration could be obtained non-invasively by tears collected by this µPAD.

Mechanochemistry studies and explains the processes of chemical and physicochemical transformations that are generated by mechanical action on a substance. When carrying out deep mechanochemical transformations, as a rule, it is necessary to transfer to solid reagents a portion of energy comparable to the energy of interatomic bonds. For this, various machines and apparatus are used, such as extruders, in which mechanical energy is constantly transferred to the crushed material. The article discusses the interaction of two reagents in a simple chemical reaction in the state of a mixture of particles of two types, which occurs during compression of particles having a rough irregular shape, and colliding with each other, forming areas of contact. Significant stress concentrations and heating of the substance with the formation of a new phase arise in these regions. Thermal control of the mechanochemical reaction is to maintain an optimal balance of dissipative heat and heat from the coolant in the worm reactor so that the rate of flow and the final product of the reaction meet the specified specifications. The formulas provided in the article for calculating the coefficient of the rate of mechanochemical reaction, heat transfer between worm reactor and jacket channel, heat exchange between jacket and environment allows to calculate the balance conditions for thermal management. The block diagram of the technological line, which is presented in the article, is more economical in comparison with carrying out the same reaction in a solvent. The economic benefit lies in the elimination of the steps of introducing and removing the solvent from the reaction product. At the end, it is indicated that the mechanochemical reaction of the transformation of a mixture of two dispersed materials consisting of solid particles into a liquid can be realized in continuous conditions in a flow mode in a worm machine. And thermal control of the course of a mechanochemical reaction can be carried out using controlled heat exchange with a coolant in a jacket under conditions of turn-around spatial dispersion., Механохімія вивчає та пояснює процеси хімічних та фізико-хімічних перетворень, які породжуються механічним впливом на речовину. При здійсненні глибоких механохімічних перетворень, як правило, необхідно передати твердим реагентам порцію енергії, порівняну до енергії міжатомних зв’язків. Для цього використовуються різноманітні машини та апарати, такі як екструдери, в яких механічна енергія постійно передається подрібненому матеріалу. У статті розглянута взаємодія двох реагентів у найпростішій хімічній реакції у стані суміші часток двох сортів, що відбувається при стисненні часток, що мають широкувату неправильну форму та стикаються одна з одною, утворюючі області контакту. У цих областях виникають значні концентрації напружень та нагрів речовини з утворенням нової фази. Теплове управління механохімічною реакцією полягає у підтримці оптимального балансу дисипативного тепла та тепла від теплоносія у черв’ячному реакторі для того, щоб швидкість протікання та кінцевий продукт реакції задовольняли поставленим технічним умовам. Надані у статті формули для розрахунку коефіцієнту швидкості механохімічної реакції, теплообміну між черв’ячним реактором та каналом рубашки, теплообміну між рубашкою та оточуючим середовищем дозволяють розрахувати умови балансу для теплового управління. Блок-схема технологічної лінії, що представлена у статті, є економічно вигіднішою у зрівнянні з проведенням цієї ж реакції у розчиннику. Економічна вигода полягає в елімінуванні стадій введення та видалення розчинника з продукту реакції. На завершення зазначено, що механохімічна реакція перетворення суміші двох дисперсних матеріалів, що складається з твердих часток, у рідину може бути реалізована у непереривних умовах у потоковому режимі у черв’ячній машині. А теплове керування ходом механохімічної реакції можна здійснити за допомогою керованого теплообміну з теплоносієм у рубашці в умовах погілковій просторової дисперсії.

Iron gall Inks corrosion causes paper degradation (browning, embrittlement) and treatments were developed to tackle this issue. They often include resizing with gelatin to reinforce the paper and its cellulosic fibers (of diameter approx. 10 µm). This work aimed at measuring the distribution of ink components at the scale of individual paper fibers so as to give a better understanding of the impact of gelatin (re-)sizing on iron gall ink corrosion. For this purpose, scanning transmission X-ray microscopy (STXM) was used at the Canadian light source synchrotron (CLS, Saskatoon). This technique combines nano-scale mapping (resolution of 30 nm) and near edge X-ray absorption fine structure (NEXAFS) analysis. Fe L-edge measurements enabled to map iron distribution and to locate iron(II) and iron(III) rich areas. N K-edge measurement made it possible to map gelatin distribution. C K-edge measurements allowed mapping and discrimination of cellulose, gallic acid, iron gall ink precipitate and gelatin. Three fibers were studied: an inked fiber with no size, a sized fiber that was afterwards inked and an inked fiber sprayed with gelatin. Analysis of gelatin and ink ingredients distribution indicated a lower amount of iron inside the treated cellulosic fiber, which may explain the beneficial effect of gelatin on iron gall ink corrosion.

Timely and rapid detection of biomarkers is extremely important for the diagnosis and treatment of diseases. However, going to the hospital to test biomarkers is the most common way. People need to spend a lot of money and time on various tests for potential disease detection. To make the detection more convenient and affordable, we propose a paper-based aptasensor platform in this work. This device is based on a cellulose paper, on which a three-electrode system and microfluidic channels are fabricated. Meanwhile, novel nanomaterials consisting of amino redox graphene/thionine/streptavidin-modified gold nanoparticles/chitosan are synthesized and modified on the working electrode of the device. Through the biotin-streptavidin system, the aptamer whose 5'end is modified with biotin can be firmly immobilized on the electrode. The detection principle is that the current generated by the nanomaterials decreases proportionally to the concentration of targets owing to the combination of the biomarker and its aptamer. 17β-Estradiol (17β-E2), as one of the widely used diagnostic biomarkers of various clinical conditions, is adopted for verifying the performance of the platform. The experimental results demonstrated that this device enables the determination of 17β-E2 in a wide linear range of concentrations of 10 pg mL-1 to 100 ng mL-1 and the limit of detection is 10 pg mL-1 (S/N = 3). Moreover, it enables the detection of targets in clinical serum samples, demonstrating its potential to be a disposable and convenient integrated platform for detecting various biomarkers.

In the present study, and for the waste valorization, Moringa oleifera seeds-removed ripened pods (SRRP) were used for papersheet production and for the extraction of bioactive compounds. Fibers were characterized by SEM–EDX patterns, while the phytoconstituents in ethanol extract was analyzed by HPLC. The inhibition percentage of fungal mycelial growth (IFMG) of the treated Melia azedarach wood with M. oleifera SRRP extract at the concentrations of 10,000, 20,000, and 30,000 µg/mL against the growth of Rhizoctonia solani and Fusarium culmorum was calculated and compared with fluconazole (25 µg). The produced papersheet was treated with the ethanol extract (4000, 2000, and 1000 µg/mL) and assayed for its antibacterial activity against Agrobacterium tumefaciens, Erwinia amylovora, and Pectobacterium atrosepticum by measuring the inhibition zones and minimum inhibitory concentrations (MICs). According to chemical analysis of M. oleifera SRRP, benzene:alcohol extractives, holocellulose, lignin, and ash contents were 7.56, 64.94, 25.66 and 1.53%, respectively, while for the produced unbleached pulp, the screen pulp yield and the Kappa number were 39% and 25, respectively. The produced papersheet showed tensile index, tear index, burst index, and double fold number values of 58.8 N m/g, 3.38 mN m2/g, 3.86 kPa m2/g, and 10.66, respectively. SEM examination showed that the average fiber diameter was 16.39 µm, and the mass average of for elemental composition of C and O by EDX were, 44.21%, and 55.79%, respectively. The main phytoconstituents in the extract (mg/100 g extract) by HPLC were vanillic acid (5053.49), benzoic acid (262.98), naringenin (133.02), chlorogenic acid (66.16), and myricetin (56.27). After 14 days of incubation, M. oleifera SRRP extract-wood treated showed good IFMG against R. solani (36.88%) and F. culmorum (51.66%) compared to fluconazole, where it observed 42.96% and 53.70%, respectively. Moderate to significant antibacterial activity was found, where the minimum inhibitory concentration (MIC) values were 500, 650, and 250 µg/mL against the growth of A. tumefaciens, E. amylovora, and P. atrosepticum respectively, which were lower than the positive control used (Tobramycin 10 µg/disc). In conclusion, M. oleifera SRRP showed promising properties as a raw material for pulp and paper production as well as for the extraction of bioactive compounds.

In this work, we fabricated a novel origami paper-based analytical device (oPAD) assisted by the nanostructuring effect of in situ Pd decoration of Cu/Co-doped CeO2 (CuCo-CeO2-Pd) nanospheres, functionalized with their strongly enhanced electrocatalytic properties to realize an electrochemical and visual signal readout system in oPAD, for highly sensitive detection of amyloid-β (Aβ). The CuCo-CeO2-Pd nanospheres were introduced as an enhanced "signal transducer layer" on account of the electron transfer acceleration caused by catalyzing glucose to produce H2O2 for differential pulse voltammetry signal readout and further 3,3'5,5'-tetramethylbenzidine (TMB) oxidation for colorimetric analysis. Meanwhile, for achieving superior performance of the proposed oPAD, in situ growth of urchin-like gold nanoparticles (Au NPs) onto cellulose fibers was adopted to improve "the recognition layer" in favor of immobilizing antibodies for targeting Aβ through specific antigen-antibody interactions. Combined with the delicate design of oPAD, exhibiting actuation of the conversion procedure between hydrophobicity and hydrophilicity on paper tabs in the assay process, the oPAD successfully enabled sensitive diagnosis of Aβ in a linear range from 1.0 pM to 100 nM with a limit of detection of 0.05 pM (S/N = 3) for electrochemical detection, providing a reliable strategy for quantifying the Aβ protein in clinical applications. Ministry of Education (MOE) This work was financially supported by the Science and Technology Projects of University of Jinan (XKY2002), the Natural Science Foundation of Shandong Province (ZR2020MB057), the Singapore Ministry of Education (MOE AcRF Tier 1 RG176/16), the Taishan Scholars Program, the Case-by-Case Project for Top Outstanding Talents of Jinan, and the project of "20 Items of University" of Jinan (2018GXRC001).

Hypoxia is a nonphysiological oxygen tension which is common in most malignant tumors. Hypoxia stimulates complicated cell signaling networks in cancer cells, e.g., the HIF, PI3K, MAPK, and NFκB pathways. Then, cells release a number of cytokines such as VEGFA to promote the growth of peripheral blood vessels and lead to metastasis. In the current work, understanding of the internal hypoxic environment in solid tumor tissue was attempted by developing a folding paper system. A paper-based solid tumor was constructed by folding a filter paper cultured with cancer cells. The cellular response in each layer could be analyzed by disassembling the folded paper after the culture course. The result showed that an internal hypoxic environment was successfully reproduced in the paper-based solid tumor. The cells in the inner layer expressed high levels of HIF1-α and VEGFA. Hence, proliferation and migration of endothelial cells were shown to be induced by the cells located in the internal hypoxic environment. Moreover, the paper-based solid tumor was transplanted into nude mice for the study of hypoxic response and angiogenesis. The crosstalk between internal and external parts of solid tumor tissue could be analyzed by sectioning each layer of the paper-based solid tumor. This approach provides a favorable analytical method for the discovery of the interaction between cancer cells, hypoxia, and peripheral angiogenesis.

An increase in the environmental and health concerns over fluorochemical‐based, wax‐based, and extrusion‐based paper coatings has led to a growing interest in bio‐based, biodegradable, and repulpable alternatives to obtain water‐ and oil‐repellent coatings. Reported herein is a fluorine‐free, plastic‐free, and cost‐effective water and grease resistant paper coating approach that utilizes blends of corn‐starch (S) and a novel chitosan‐graft‐polydimethylsiloxane (CP) copolymer. The hydrophobic and oleophobic performance of the S/CP‐coated paper was evaluated by varying the ratio of S and CP in the overall blend. The S/CP‐coated papers were observed to have low cobb60 values (water absorptivity) of 13 ± 0.9 g m−2 and an excellent kit rating (oil resistance) of 12/12. The S/CP‐coated paper substrate surface profile was analyzed via scanning electron microscopy (SEM). The repulpability of the coated paper is also demonstrated by washing the coating materials from the paper and recovering the pulp.

Cellulose nanopaper (CNP) has been considered as a promising material with great application potential in diverse fields. However, the hydrophilic nature of CNP significantly limits its practical application. In order to improve its water resistance, we demonstrate a facile approach to functionalize CNP by impregnating it with chitosan (CS), followed by in situ polymerization of polypyrrole (PPy). The results indicate that the obtained CNP/CS/PPy shows excellent water resistance with the wet tensile strength of up to 80 MPa, which is more than 10 times higher than that of the pure CNP. Intriguingly, new features (e.g., electrical conductivity, antibacterial activity, and so forth) are achieved at the same time. The functionalized CNP/CS/PPy shows a high conductivity of 6.5 S cm-1, which can be used for electromagnetic interference shielding applications with a high shielding performance of around 18 dB. In addition, the CNP/CS/PPy exhibits good antibacterial activity toward Staphylococcus aureus and Escherichia coli, with the bacterial reductions of 99.28 and 95.59%, respectively. Thus, this work provides a simple and versatile approach to functionalize CNP for achieving multifunctional properties.

Funding Information: The financial support of the Austrian Federal Ministry of Digital and Economic Affairs and the National Foundation for Research, Technology and Development , Austria, is gratefully acknowledged. We also thank the industrial partners Mondi, Canon Production Printing, Kelheim Fibres, and SIG Combibloc for their support. Publisher Copyright: © 2021 Copyright: Copyright 2021 Elsevier B.V., All rights reserved. Hydrophobization of cellulosic materials and particularly paper products is a commonly used procedure to render papers more resistant to water and moisture. Here, we explore the hydrophobization of unsized paper sheets via the gas phase. We employed three different compounds, namely palmitoyl chloride (PCl), trifluoroacetic anhydride/acetic anhydride (TFAA/Ac2O)) and hexamethyldisilazane (HMDS) which were vaporized and allowed to react with the paper sheets via the gas phase. All routes yielded hydrophobic papers with static water contact angles far above 90° and indicated the formation of covalent bonds. The PCl and TFAA approach negatively impacted the mechanical and optical properties of the paper leading to a decrease in tensile strength and yellowing of the sheets. The HMDS modified papers did not exhibit any differences regarding relevant paper technological parameters (mechanical properties, optical properties, porosity) compared to the non-modified sheets. XPS studies revealed that the HMDS modified samples have a rather low silicon content, pointing at the formation of submonolayers of trimethylsilyl groups on the fiber surfaces in the paper network. This was further investigated by penetration dynamic analysis using ultrasonication, which revealed that the whole fiber network has been homogeneously modified with the silyl groups and not only the very outer surface as for the PCl and the TFAA modified papers. This procedure yields a possibility to study the influence of hydrophobicity on paper sheets and their network properties without changing structural and mechanical paper parameters.

In this study, the effects of the lacquer applied to the printing materials which were printed by electrophotographic printing method on printing quality were investigated. In practice, printing materials with the same weight and different optical properties were used and the study was carried out in three stages. The optical and physical properties of the printing materials used in the first part were determined, in the second part, the printing of these materials by electrophotographic printing method and printability tests were performed. In the third chapter, matte and glossy lacquers were applied to these printed materials and printability tests were repeated. As a result of the study, it was observed that the application of gloss and matte lacquer caused a decrease in the printing density values and also the application of matte lacquer caused a decrease in the gloss values.

From the moment of production, paper as a printing substrate is exposed to the process of natural ageing regardless of the type of cellulose fibres in its composition. Accordingly, the prints produced by the various printing techniques are also exposed to several factors that impair the quality of the print i.e. its colour over time. Therefore, it is very important to properly select the printing substrate for achieving a high quality of graphic products. For that purpose, three types of papers with hemp fibres were used as printing substrates which were printed with laboratory hand-operated instrument Esiproof using flexographic cyan (C), magenta (M), yellow (Y) and black (K) water-based inks. Prints were artificially aged in SunTEST XLS+ test chamber according to standard ASTM D 6789-02 for 48 and 96 hours. Based on changes in the reflectance spectra of each printed ink after exposure to electromagnetic radiation it was noticed how composition of printing substrate strongly influence on colour stability of prints due time. An increase of exposure time to electromagnetic radiation leads to a decrease in the value of the reflectance of the printing substrate and cyan, magenta and yellow prints. It was confirmed how electromagnetic radiation have the greatest impact on the reflectance of yellow print, while the black one is the most stabile regardless of the substrate it was printed on.

Novel ways to track and verify items of a high value or security is an ever-present need. Taggants made from deoxyribonucleic acid (DNA) have several advantageous properties, such as high information density and robust synthesis; however, existing methods require laboratory techniques to verify, limiting applications. Here, we leverage DNA nanotechnology to create DNA taggants that can be validated in the field in seconds to minutes with a simple equipment. The system is driven by toehold-mediated strand-displacement reactions where matching oligonucleotide sequences drive the generation of a fluorescent signal through the potential energy of base pairing. By pooling different "input" oligonucleotide sequences in a taggant and spatially separating "reporter" oligonucleotide sequences on a paper ticket, unique, sequence-driven patterns emerge for different taggant formulations. Algorithmically generated oligonucleotide sequences show no crosstalk and ink-embedded taggants maintain activity for at least 99 days at 60 °C (equivalent to nearly 2 years at room temperature). The resulting fluorescent signals can be analyzed by the eye or a smartphone when paired with a UV flashlight and filtered glasses.

On-site detection of multiple small-molecule analytes in complex sample matrixes would be highly valuable for diverse biosensing applications. Paper electrochemical devices (PEDs) offer an especially appealing sensing platform for such applications due to their low cost, portability, and ease of use. Using oligonucleotide-based aptamers as biorecognition elements, we here for the first time have developed a simple, inexpensive procedure for the fabrication of aptamer-modified multiplex PEDs (mPEDs), which can robustly and specifically detect multiple small molecules in complex samples. These devices are prepared via an ambient vacuum filtration technique using carbon and metal nanomaterials that yields precisely patterned sensing architecture featuring a silver pseudo-reference electrode, a gold counter electrode, and three gold working electrodes. The devices are user-friendly, and the fabrication procedure is highly reproducible. Each working electrode can be readily modified with different aptamers for sensitive and accurate detection of multiple small-molecule analytes in a single sample within seconds. We further demonstrate that the addition of a PDMS chamber allows us to achieve detection in microliter volumes of biological samples. We believe this approach should be highly generalizable, and given the rapid development of small-molecule aptamers, we envision that facile on-site multi-analyte detection of diverse targets in a drop of sample should be readily achievable in the near future.

Flexible paper-based sensors may be applied in numerous fields, but this requires addressing their limitations related to poor thermal and water resistance, which results in low service life. Herein, we report a paper-based composite sensor composed of carboxylic carbon nanotubes (CCNTs) and poly-m-phenyleneisophthalamide (PMIA), fabricated by a facile papermaking process. The CCNT/PMIA composite sensor exhibits an ability to detect pressures generated by various human movements, attributed to the sensor's conductive network and the characteristic "mud-brick" microstructure. The sensor exhibits the capability to monitor human motions, such as bending of finger joints and elbow joints, speaking, blinking, and smiling, as well as temperature variations in the range of 30-90 °C. Such a capability to sensitively detect pressure can be realized at different applied frequencies, gradient sagittas, and multiple twists with a short response time (104 ms) even after being soaked in water, acid, and alkali solutions. Moreover, the sensor demonstrates excellent mechanical properties and hence can be folded up to 6000 times without failure, can bear 5 kg of load without breaking, and can be cycled 2000 times without energy loss, providing a great possibility for a long sensing life. Additionally, the composite sensor shows exceptional Joule heating performance, which can reach 242 °C in less than 15 s even when powered by a low input voltage (25 V). From the perspective of industrialization, low-cost and large-scale roll-to-roll production of the paper-based sensor can be achieved, with a formed length of thousands of meters, showing great potential for future industrial applications as a wearable smart sensor for detecting pressure and temperature, with the capability of electric heating.

The plasmonic properties of gold nanoparticles (AuNPs) are a promising tool to develop sensing alternatives to traditional, enzyme-catalyzed reactions. The need for sensing alternatives, especially in underdeveloped areas of the world, has given rise to the application of nonenzymatic sensing approaches paired with cellulosic substrates to biochemical analysis. Herein, we present three individual, low-step, wet-chemistry, colorimetric assays for three target biomarkers, namely, glucose, uric acid, and free cholesterol, relevant in diabetes control and their translation into paper-based assays and microfluidic platforms for multiplexed analysis. For glucose determination, an in situ AuNPs synthesis approach was applied into the developed μPAD, giving semiquantitative measures in the physiologically relevant range. For uric acid and cholesterol determination, modified AuNPs were used to functionalize paper with a gold-on-paper approach with the optical properties changing based on different aggregation degrees and hydrophobic properties of particles dependent on analyte concentration. These paper-based assays show sensitivity ranges and limits of detection compatible for target analyte level determination and detection limits comparable to those of similar enzymatic, colorimetric systems, relying only on plasmonic transduction without the need for enzymatic activity or other chromogenic substrates. The resulting paper-based assays were integrated into a single 3D, multiplex paper-based device using paper microfluidics, showing the capability for performing different colorimetric assays with distinct requirements in terms of sample flow and sample uptake in test zones using a combination of both horizontal and vertical flows inside the same device. The presented device allows for multiparametric, colorimetric measures of different metabolite levels from a single complex sample matrix drop using digital color analysis, showing the potential for development of low-cost, low-complexity tools for diagnostics toward the point-of-care.

Microfluidic paper-based analytical devices (μPADs) have been widely explored for point-of-care testing due to their simplicity, low cost, and portability. μPADs with multiple-step reactions usually require precise flow control, especially flow-delay. This paper reports the numerical, mathematical, and experimental studies of flow delay through wax valves surrounded by PDMS walls on paper microfluidics. The predried surfactant in the sample zone diffuses into the liquid sample which can therefore flow through the wax valves. The delay time is automatically regulated by the diffusion of the surfactant after sample loading. The numerical study suggested that both the elevated contact angle and the reduced porosity and pore size in the wax printed region could effectively prevent water but allow liquids with lower contact angles (e.g., surfactant solutions) to flow through. The PDMS walls fabricated using a low-cost liquid dispenser effectively prevented the leakage of surfactant solutions. By controlling the quantity, diffusion distance, and type of the surfactant predried on the chip, the system successfully achieved a delay time ranging from 1.6 to 20 minutes. A mathematical model involving the above parameters was developed based on Fick's second law to predict the delay time. Finally, the flow-delay systems were applied in sequential mixing and distance-based detection of either glucose or alcohol. Linear ranges of 1-100 mg dL-1 and 1-40 mg dL-1 were achieved for glucose and alcohol, respectively. The lower limit detection (LOD) of glucose and alcohol was 1 mg dL-1. The LOD of glucose was only 1/11 of that detected using μPADs without flow control, indicating the advantage of controlling fluid flow. The systematic findings in this study provide critical guidelines for the development and applications of wax valves in automatic flow delay for point-of-care testing. This journal is

Nanofibrillated films based on TEMPO-oxidized cotton linters were applied to reduce the hydrophilic properties of paper. For this purpose, aqueous dispersions of nanofibrillated cellulose of different composition: 1 and 3% of nanofibrillated cellulose, up to 13% of CaCO3 and/or Al(OH)3, up to 20% of propane-1,2-diol (glycol), and up to 21% of TEMPO-oxidized cotton linters were coated on the model paper, without additional adhesive. The pristine model paper and papers coated with nanofibrillated cellulose-based composite films were characterized in terms of water absorptiveness by COBB method and water drop contact angle measurements. The surface appearance was characterized by scanning electron microscopy (SEM) and surface chemistry by infrared spectroscopy with Fourier transform and attenuated total reflection (ATR-FTIR). Additionally, optical properties, i.e. measurement of reflection curves and CIE degrees of whiteness, were determined according to appropriate standards. For all papers coated with nanofibrillated cellulose-based films, depending on the composition of the dispersions, a decrease in sorption properties was achieved, without changes in optical properties and surface morphology of the paper compared to the pristine paper.

In this study, we developed a novel, simple, rapid, and low-cost colloidal gold-based immunochromatography method, with filter paper replacing nitrocellulose membrane as the substrate. To obtain adequately immobilized protein, chitosan was used to functionalize the filter paper. After conditions and parameters were optimized, the novel immunochromatography method was applied for detection of sulfonamide residues in milk. Quantitative detection was accomplished using a smartphone and Photoshop software (Adobe Inc., San Jose, CA), allowing us to screen 13 sulfonamides with a limit of detection ranging from 0.42 to 8.64 μg/L and recovery ranging from 88.2 to 116.9% in milk. The proposed novel method performed similarly to the conventional method that uses a nitrocellulose membrane as the transport medium, and it had lower cost and better usability because of the inexpensive and easily available filter paper.

Weighing paper-assisted magnetic ionic liquid headspace single-drop microextraction using microwave distillation followed by gas chromatography-mass spectrometry was successfully developed to determine the essential oil components in lavender. The magnetic ionic liquid 1-octyl-3-methylimidazolium tetrachloroferrate was successfully synthesized and used as the optimal extraction solvent. An aliquot of 9 μL of magnetic ionic liquid could be stably suspended on the weighing paper for long time extraction. The increase of the extractant volume resulted in a significantly enhanced in extracting efficiency of the weighing paper-assisted magnetic ionic liquid headspace single-drop microextraction than traditional headspace single-drop microextraction method. In this experiment, the optimal conditions were 1-octyl-3-methylimidazolium tetrachloroferrate as the extraction solvent, extraction time of 12 min, microwave power of 600 W, cyclohexane as back-extractant and sample amount of 30 mg. The developed method was successfully applied to analyze 16 lavender samples from three different harvest years. A total of 39 compounds in lavender were identified and the principal component analysis provided a clear separation between those lavender samples harvested in different years. The results indicated that the proposed weighing paper-assisted magnetic ionic liquid headspace single-drop microextraction is a novel, fast, simple and sensitive microextration technique for the determination of the essential oil components in lavender.

There is a pressing need around the world to develop novel functional biodegradable materials to separate oil/water mixtures and emulsions completely. Recently, superhydrophilicity and underwater superoleophobicity materials have been attracted attention due to their high efficiency in oil/water separation. However, it is still a challenge to prepare materials that combine oil/water separation and water purification in an environment-friendly way. In this work, biodegradable starch-based nanospheres (SNPs) coated filter paper was prepared in a low-cost, simple, and environmentally friendly manner. The SNPs coating could not only help to change the wettability of the substrate material but also build the hierarchical micro and nano structures which are conducive to separation and purification process. After modification by coating SNPs, the filter paper exhibited excellent performance in a wide range of oil/water mixtures or emulsions separation and the wettability of the filter paper could be regulated by adjusting the pH value. The modified filter paper presented good recyclability after several separation process. Furthermore, the as-prepared filter paper could also remove water-soluble contaminants during the oil/water separation process, thus realizing to combine separation and purification process in one single step. This biodegradable starch-based separating material with good separation performance, stability and recyclability has significant application potential in practical separation and purification process.

Starch and derivatives thereof have proven their usefulness in paper coating processes. Among these derivatives, cationic starch has been widely used in the paper industry as a flocculation, dispersion and ink fixing agent. In another context, nanoscale cellulosic materials have been shown to improve the strength, retention of fillers, the barrier properties of packaging paper products, and printing qualities. This review summarizes the recent studies on the general components used in paper coating, describes the conventional and alternative synthetic processes of cationic starches and nanocellulose, and deals with their current and potential applications in papermaking, focusing primarily on surface treatments. Moreover, environmental applications have been considered to expand the understanding and usefulness of these materials. Further research on modified polysaccharides is encouraged to replace, in a feasible way, petro-based components of coating formulations, and to provide paper surfaces with new properties.

Application of barrier dispersion coatings on paperboards, which must have proper moisture and grease resistance for food applications, has always been an interesting subject for the packaging industry. In this study, paperboards were coated with a novel dispersion barrier coating prepared through mixing soy protein isolate (SPI) and polyethylene wax (PE-wax). Different characterization methods were used to study the effects of coating and its composition on the physical, mechanical, and barrier characteristics of paperboards. The results indicated that the incorporation of PE-wax into the coating formulation caused significant reduction of the viscosity of coating slurries. It had no effect on the coating weight of the samples but increased the thickness of the coated paperboards as compared with those coated with SPI only. The increase of the wax content led to a reduction of 5-16% in the tensile strength values in comparison with the uncoated paperboards. Barrier characteristics, i.e., water vapor permeability (WVP), surface wettability, and water resistance, improved by adding PE-wax. In addition, it was found that there was a critical level for the addition of PE-wax, 50% of SPI, as no oil migration was detected when the paperboards coated with SPI coatings contained less than 50% PE-wax.

Development of selective and sensitive methods for on-site assay of tetracycline (TC) is of great significance for public health and food safety. Herein, a valid ratiometric fluorescence strategy using g-C3N4 nanosheets coupled with Eu3+ is designed for the assay of TC. In this strategy, both Eu3+ and g-C3N4 nanosheets serve as the recognition units of TC. The blue fluorescence of g-C3N4 nanosheets can be quenched by TC via the inner filter effect (IFE); meanwhile, the red fluorescence of Eu3+ can be enhanced by TC through the antenna effect (AE). The synergistic effect of AE and IFE caused by TC makes the developed ratiometric fluorescent sensor display a wide linear range for TC from 0.25 to 80 μM with a detection limit of 6.5 nM and a significant fluorescence color evolution from blue to red. Given its simplicity, free-label, excellent selectivity, high sensitivity, and recognizable color change, point-of-care testing systems, including smartphones and test paper-based assays, are developed for the visual sensing of TC. The integration of smartphones and test paper on a ratiometric fluorescent sensor greatly reduces the detection cost and time, providing a promising method for the qualitative discernment and semi-quantitative assay of TC on-site. Moreover, the potential application of the approach is also verified by detecting TC in milk.

A soft body area sensor network presents a promising direction in wearable devices to integrate on-body sensors for physiological signal monitoring and flexible printed circuit boards (FPCBs) for signal conditioning/readout and wireless transmission. However, its realization currently relies on various sophisticated fabrication approaches such as lithography or direct printing on a carrier substrate before attaching to the body. Here, we report a universal fabrication scheme to enable printing and room-temperature sintering of the metal nanoparticle on paper/fabric for FPCBs and directly on the human skin for on-body sensors with a novel sintering aid layer. Consisting of polyvinyl alcohol (PVA) paste and nanoadditives in the water, the sintering aid layer reduces the sintering temperature. Together with the significantly decreased surface roughness, it allows for the integration of a submicron-thick conductive pattern with enhanced electromechanical performance. Various on-body sensors integrated with an FPCB to detect health conditions illustrate a system-level example.

A two-step process involving coagulation-flocculation followed by solar photocatalysis – based Advanced Oxidation Process (AOP) using TiO2-Reduced Graphene Oxide (TRGO) nanocomposite as catalyst ha...

As a global shift continues to occur in high burden diseases toward developing countries, the importance of medical diagnostics based on point-of-care testing (POCT) is rapidly increasing. However, most diagnostic tests that meet clinical standards rely on high-end analyzers in central hospitals. Here, we report the development of a simple, low-cost, mass-producible, highly sensitive/quantitative, automated, and robust paper/soluble polymer hybrid-based lateral flow biosensing platform, paired with a smartphone-based reader, for high-performance POCT. The testing architecture incorporates a polymeric barrier that programs/automates sequential reactions via a polymer dissolving mechanism. The smartphone-based reader with simple opto-mechanical parts offers a stable framework for accurate quantification. Analytical performance of this platform was evaluated by testing human cardiac troponin I (cTnI), a preferred biomarker for the diagnosis of myocardial infarction, in serum/plasma samples. Coupled with catalytic/colorimetric gold-ion amplification, this platform produced results within 20 min with a detection limit of 0.92 pg mL

A laminated paper-based analytical device (LPAD) for histidine detection was fabricated from a chromatography filtration paper and laminate films. Histidine recognition was effected by histidyl-tRNA synthetase (HisRS), and its detection was signaled colorimetrically based on the molybdenum blue reaction. The analytical conditions and detectable concentration range of histidine were examined. The method provided selective quantification from 1 to 100 μM histidine. LPAD fabrication is considerably simple, involving only the craft-cutting of the chromatography filtration paper and laminate film, and is cost-effective.

Insulation oil is an important dielectric in power devices, and many studies on mixed insulation oil have been conducted in recent years to improve the performance of insulation oils. To replace mineral oil directly, the authors previously developed a novel three-element mixed insulation oil successfully; the main parameters of which satisfy the IEC 60296-2012 standard for mineral oil. In the present study, the AC breakdown properties of insulation paper (pressboard) immersed by the new mixed oil and naphthenic mineral oil were compared. For both insulation oils, the increase in temperature cannot significantly reduce the breakdown strength of oil-immersed insulation paper (pressboard) at a low moisture content, and the increment of moisture content cannot reduce the breakdown voltage at a low temperature (25°C). The breakdown voltage decreases only when the two factors increase simultaneously. For the mixed and mineral oils, the AC breakdown voltage of oil-immersed paper (pressboard) with different thicknesses has significant difference. The mineral oil has a high breakdown voltage for the thin insulation paper, whereas the mixed oil has a high breakdown voltage when the thickness of the insulation paper (pressboard) exceeds 0.2 mm. This phenomenon is mainly caused by the breakdown field strength that varies with the increase of dielectric thickness and the different change trends of paper (pressboard) immersed with the mixed and the mineral oils. Moreover, the stack of thin multilayer insulation paper enables the mixed oil-immersed paper to have a higher breakdown strength than the mineral oil-immersed paper. For the AC breakdown voltage of oil-immersed pressboard with an oil-gap structure, the mixed oil is comprehensively superior to the mineral oil due to its larger relative permittivity.

A sonication of graphite in polysaccharide (pullulan, chitosan and alginate) is one of the viable methods for the preparation of few-layer graphene. However, the effect of these adsorbed polysaccharides on the electrical performance of the produced graphene so far is not yet clear. In order to investigate the present effect of pullulan, chitosan and alginate on the electrical characteristic of resulted graphene, we have produced few-layer graphene using bath sonication of graphite in pullulan, chitosan and alginate medium for the application as electrical conductive ink in strain-sensitive. Data from the TEM reveals the appearance of folded few-layer graphene flakes after sonication for 150 min while the XPS data shows that the chitosan-based graphene possesses the highest carbon-oxygen ratio of 7.2 as compared to that of the pullulan and alginate-based graphene. By subjecting the produced graphene as the ink for paper-based strain sensor, we have discovered that the chitosan-graphene has the best resistivity value (1.66 × 10-3 Ω⋅cm) and demonstrate the highest sensitivity towards strain (GF: 18.6). This result interestingly implies the potential of the reported chitosan-based conductive ink as a strain-sensitive material for future food packaging.

The use of nanocelluloses is being conducted for the most diverse applications. Their performance as coating agent has been mainly explored to improve barrier properties, as they emerge as perfect candidate for plastic substitution, but it is also important to explore their potential to improve printing quality. In the present work, the influence of different nanocelluloses, obtained through mechanical, enzymatic, TEMPO-mediated oxidation and carboxymethylation treatments, in the coating process and inkjet printability of office papers was assessed. The results revealed that the cellulose nanofibrils are better for printability than the microfibrils. But the size and charge of the former must be taken into account, since fibrils of very small size penetrate the paper structure, dragging the pigments from the surface, and very anionic nanofibrils can also have negative influence on the optical density. Besides, an interesting synergy between surface-sizing starch and the cellulose nanofibrils was found to occur as the latter closed the paper structure, which prevented starch from penetrating, while potentiating both of their positive effects on ink pigment entrapment. An additional study of characterization of inkjet pigments was also performed.

In this paper, nanochitin was used as an alternative natural nanomaterial to combine with cellulose fibers for fabricating high-strength paper. Two typical chitin nanowhiskers having contrasting sign of surface charge were compared to evaluate the enhancement performance on paper in details. The results show that nanochitin with positive charges on the surface has a significant effect on the strength properties of the prepared paper, especially on wet strength. When the dosage of chitin nanowhiskers was 2%, the wet strength index was increased to 2.48 N·m/g, which is important for paper-based analytical devices with the common use in liquid analysis. Typical colorimetric glucose assays were successfully performed, suggesting the improved analytical performance on these prepared paper.

Nanolayer and nanolayer by nanolayer deposition of nanofilms of Ag and C using cold plasma in sequences (Ag, Ag-C, Ag-Ag-C), on porous paper, were used to design three disposable stochastic sensors for the assay of amyloid polypeptide from whole blood. The nanofilms were modified with α-cyclodextrin. The test developed using the nanofilm-based disposable stochastic sensors is used for early detection of diabetes. The wider linear concentration range (1.00 × 10−6–1.00 ng mL−1) and the lower limit of quantification (1.00 × 10−6ng mL−1) were obtained using the disposable stochastic sensors based on Ag-C and Ag-Ag-C, while the highest sensitivity (3.19 × 104 s−1/μg mL−1) was recorded using the disposable stochastic sensor based on Ag-Ag-C. The screening methods were fully validated using whole blood samples from confirmed patients, when the recovery of the islet amyloid polypeptide was higher than 98.00%.

Lithium carbonate is an effective medicine for the treatment of the bipolar disorder, but the concentration of lithium in the patient's blood must be frequently monitored because of its toxicity. To date, no colorimetric methods of lithium ion detection in whole blood without pretreatment have been reported. Here, we report a colorimetric paper-based device that allows point-of-care testing in one step. This device is composed of two paper-based elements linked to each other: a blood cell separation unit and a colorimetric detection unit. After a portion of whole blood has been placed on the end of the separation unit, plasma in the sample is automatically transported to the detection unit, which displays a diagnostic color. The key feature of this device is its simple, user-friendly operation. The limit of detection is 0.054 mM and the coefficient of variance is below 6.1%, which are comparable to those of conventional instruments using the same colorimetric reaction. Furthermore, we achieved high recovery (>90%) and reproducibility (

A complete mathematical model for electromigration in paper-based analytical devices is derived, based on differential equations describing the motion of fluids by pressure sources and EOF, the transport of charged chemical species, and the electric potential distribution. The porous medium created by the cellulose fibers is considered like a network of tortuous capillaries and represented by macroscopic parameters following an effective medium approach. The equations are obtained starting from their open-channel counterparts, applying scaling laws and, where necessary, including additional terms. With this approach, effective parameters are derived, describing diffusion, mobility, and conductivity for porous media. While the foundations of these phenomena can be found in previous reports, here, all the contributions are analyzed systematically and provided in a comprehensive way. Moreover, a novel electrophoretically driven dispersive transport mechanism in porous materials is proposed. Results of the numerical implementation of the mathematical model are compared with experimental data, showing good agreement and supporting the validity of the proposed model. Finally, the model succeeds in simulating a challenging case of free-flow electrophoresis in paper, involving capillary flow and electrophoretic transport developed in a 2D geometry. Fil: Schaumburg, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Kler, Pablo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; Argentina Fil: Berli, Claudio Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

China, a big paper-making country, produced hundreds of millions of tons of waste paper which contain a lot of fiber every year. Cellulose nanocrystals were extracted from recycled waste paper which can be a high value utilization of secondary fiber. In this paper, cellulose nanocrystals were successfully extracted from waste paper fibers via two different systems, sulfuric acid hydrolysis (SCNCs) and one-step ammonium persulfate (APS) oxidation (OCNCs). This not only broadened the methods of extracting CNCs from waste paper, but also improved the dispersion and reactivity of CNCs. The CNCs products were investigated by FT-IR spectroscopy for functional group structure, X-ray diffraction for crystal structure, TG-DTG for thermal stability and scanning electron microscope, transmission electron microscope for morphology. The results showed that both OCNCs and SCNCs were a rod-like structure. The crystallinity of OCNCs and SCNCs increased to 72.45 and 77.56, but with a low yield of 22.42% and 41.22%, respectively. The result also suggested H2O2 formed by decomposition of APS, selectively oxidized the hydroxyl on the C6 in cellulose to carboxyl, introduced 0.57 mmol/g carboxyl. Successful preparation of CNCs extracted from waste paper can effectively utilize the fiber resources in waste paper, thus transforming into higher economic benefits.

Paper-based packaging is widely employed in industries ranging from food to beverages to pharmaceuticals because of its attractive advantages of biodegradability, recyclability, good strength, low cost, and lightweight. However, paper products usually have poor water barrier resistance properties because of paper and fibers porous microstructure. In this study, an ecofriendly water-resistant (hydrophobic) oil from biological origin, namely, palm kernel oil (PKO) was used to coat paper by using a facile and cost-effective dip-casting approach. PKO formulation was prepared by mixing with a solvent and furfuryl alcohol (FA). The water resistance, structural properties, and thermal and mechanical properties of the coated papers obtained under different processing conditions were reported and compared to understand the performance of coated paper. Contact angle (CA), Fourier transform infrared (FTIR), and thermal gravimetry (TGA) were used for analysis and characterization of coated papers. Data from contact angle measurements showed that the PKO formulation could considerably improve the liquid water barrier property of the paper, with a measured water contact angle (CA) of ∼120° and reduce the water vapor transmission rate (WVTR) by 22%. This novel, green, low-cost, and water-resistant paper coating made with biological and biodegradable oil is a potential candidate for replacing petroleum-based coatings used in a broad range of applications and will also be able to make an additional full use of the palm kernel oil.

Cotton is cheap, easily available and widely used as surgical material. Therefore, cotton would be good raw material to design a scaffold for tissue engineering applications. In this work, the gelatin-coated microfibrous paper scaffold was fabricated successfully by a papermaking process. Microfibers-based scaffold could overcome the limitations of nanofibrous material-based scaffold for tissue engineering application. The physicochemical and mechanical properties of the scaffolds were characterized. The results revealed that the gelatin contributed to the enhanced cell attachment and proliferation over the scaffolds, whereas cellulose as a strong backbone in the scaffold to support it for keeping its appearance. Their tensile strength and water absorption capacity were improved, but pore size and porosity were decreased after incorporation of gelatin. Hence, results suggested that fabricated scaffolds have huge prospective as a bioactive, well-designed and economical scaffold stand for tissue engineering application.

Because of numerous inherent and unrivaled features of nanofibers made of chitin, the second most plentiful natural-based polymer (after cellulose), including affordability, abundant nature, biodegradability, biocompatibility, commercial availability, flexibility, transparency, and extraordinary mechanical and physicochemical properties, chitin nanofibers (ChNFs) are being applied as one of the most appealing bionanomaterials in a myriad of fields. Herein, we exploited the beneficial properties offered by the ChNF paper to fabricate transparent, efficient, biocompatible, flexible, and miniaturized optical sensing bioplatforms via embedding/immobilizing various plasmonic nanoparticles (silver and gold nanoparticles), photoluminescent nanoparticles (CdTe quantum dots, carbon dots, and NaYF4:Yb3+@Er3+&SiO2 upconversion nanoparticles) along with colorimetric reagents (curcumin, dithizone, etc.) in the 3D nanonetwork scaffold of the ChNF paper. Several configurations, including 2D multi-wall and 2D cuvette patterns with hydrophobic barriers/walls and hydrophilic test zones/channels, were easily printed using laser printing technology or punched as spot patterns on the dried ChNF paper-based nanocomposites to fabricate the (bio)sensing platforms. A variety of (bio)chemicals as model analytes were used to confirm the efficiency and applicability of the fabricated ChNF paper-based sensing bioplatforms. The developed (bio)sensors were also coupled with smartphone technology to take the advantages of smartphone-based monitoring/sensing devices along with the Internet of Nano Things (IoNT)/the Internet of Medical Things (IoMT) concepts for easy-to-use sensing applications. Building upon the unrivaled and inherent features of ChNF as a very promising bionanomaterial, we foresee that the ChNF paper-based sensing bioplatforms will emerge new opportunities for the development of innovative strategies to fabricate cost-effective, simple, smart, transparent, biodegradable, miniaturized, flexible, portable, and easy-to-use (bio)sensing/monitoring devices., Financial support from the Chemistry & Chemical Engineering Research Centre of Iran (Tehran, Iran), Iran’s National Elites Foundation (INEF), Nano Novin Polymer Co. (Iran), and the Nano Match program of Iran Nanotechnology Initiative Council (INIC) are gratefully acknowledged. The ICN2 is funded by the CERCA Programme/Generalitat de Catalunya. The ICN2 is supported by the Severo Ochoa program of the Spanish Ministry of Economy, Industry and Competitiveness (MINECO; grant nos. SEV-2017-0706 and MAT2017-87202-P). The financial support of “the Czech Science Foundation (No. 19-00676S)” is also greatly appreciated.

Point-of-care (POC) detection is crucial in clinical diagnosis in order to provide timely and specific treatment. Combining polyamidoamine (PAMAM) dendrimer, p-phenylene diisothiocyanate (PDITC) and superparamagnetic beads, a novel method to activate the surface of filter paper to bind DNA molecules has been developed. The method is based on the primary amination of the filter paper surface with PAMAM dendrimer, followed by generation of isothiocyanate groups via PDITC, and subsequent repetition of these two steps. Different parameters of the process have been optimized, including probe printing, preparation of target DNAs and detection. The result shows that, due to the highly porous structure of filter paper, high amounts of printed probes, target DNAs and magnetic beads can provide high signal intensities in the detection area via probe/target duplex formation. This method is suitable for rapid, specific and cost-efficient DNA detection on cellulose filter paper. It can be used as a POC device, in particular for diagnosis and treatment management of infectious diseases and identification of antimicrobial drug resistance genes.

Hydrogels of TEMPO-oxidized nanocellulose were stabilized for dry-jet wet spinning using a shell of cellulose dissolved in 1,5-diazabicyclo[4.3.0]non-5-enium propionate ([DBNH][CO2Et]), a protic ionic liquid (PIL). Coagulation in an acidic water bath resulted in continuous core-shell filaments (CSFs) that were tough and flexible with an average dry (and wet) toughness of similar to 11 (2) MJ.m(-3) and elongation of similar to 9 (14) %. The CSF morphology, chemical composition, thermal stability, crystallinity, and bacterial activity were assessed using scanning electron microscopy with energy-dispersive X-ray spectroscopy, liquid-state nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetric analysis, pyrolysis gas chromatography-mass spectrometry, wide-angle X-ray scattering, and bacterial cell culturing, respectively. The coaxial wet spinning yields PIL-free systems carrying on the surface the cellulose II polymorph, which not only enhances the toughness of the filaments but facilities their functionalization.

The production of cellulose nanofibers (CNF) usually consist of two different phases. First of all, lignocellulosic fibers need to be treated by means of either chemical, enzymatic or mechanical treatments. Then, in the second phase, the treated lignocellulosic fibers need to be submitted to mechanical fibrillation. This last treatment is usually critical in terms of energy consumption, as well as for providing the appropriate characteristics to the resulting CNF. In the present work, we have investigated the effect of fibrillating lignocellulosic nanofibers (LCNF) made from eucalyptus sawdust by means of high-pressure homogenization and grinding. The obtained results showed that, to achieve the same property level of LCNF, the grinder consumed 12.86 kWh/kg, while the homogenizer, 19.07 kWh/kg, bringing to the light the suitability of grinding for LCNF production. Overall, the present work shows the feasibility of using eucalyptus sawdust, which is a residue from the pulp and paper industry, as raw material for LCNF production, at the same time that brings to the light the relevance of the fibrillation equipment in terms of energy efficiency, approaching the production of LCNF to the industry.

Real-time monitoring of neonicotinoid pesticide residues is of great significance for food security and sustainable development of the ecological environment. Herein, a paper-based surface-enhanced Raman scattering (SERS) amplified approach was proposed by virtue of multilayered plasmonic coupling amplification. The unique plasmonic SERS multilayer was constructed using three-dimensional (3D) silver dendrite (SD)/electropolymerized molecular identifier (EMI)/silver nanoparticle (AgNP) sandwich hybrids with multiple hotspots and a strong electromagnetic field in nanogaps. Dendritelike 3D silver materials with remarkably high accessible surface areas and the lightning rod effect constituted the first-order enhancement of paper-based sensors. Molecular identifiers coated upon an SD layer as the interlayer were used for target capture and enrichment. Subsequently, AgNPs featuring rough surface and local plasma resonance decorated as the top layer formed the secondary enhancement of the amplification strategy. As the most brilliant part, dendritelike 3D silver coupled with AgNPs has established double Ag layers to accomplish a multistage enhancement of SERS signals based on the superposition of their electromagnetic fields. Owning to the distinctive design of the multiple coupling amplification strategy, the fabricated SERS paper chips demonstrated impressive specificity and ultrahigh sensitivity in the detection of imidacloprid (IMI), with a detection limit as low as 0.02811 ng mL-1. More importantly, the multiple SERS enhancement paper chip holds great potential for automated screening of a variety of contaminants.

We report a smartphone–paper-based sensor impregnated with cetyltrimethylammonium bromide modified silver nanoparticles (AgNPs/CTAB) for determination of Fe3+ in water and blood plasma samples. The methodology for determination of Fe3+ is based on the change in signal intensity of AgNPs/CTAB fabricated on a paper substrate after the deposition of analyte, using a smartphone followed by processing with ImageJ software. The mechanism of sensing for detection and determination of Fe3+ is based on the discoloration of AgNPs which impregnated the paper substrate. The discoloration is attributed to the electron transfer reaction taking place on the surface of NPs in the presence of CTAB. Fe3+ was determined when the paper was impregnated with 1 mM AgNPs for 5 min of reaction time and the substrate was kept under acidic conditions. The linear range for determination of total iron in terms of Fe3+ was 50–900 μg L−1 with a limit of determination (LOD) of 20 μg L−1 and coefficient of variation (CV) of 3.2%. The good relative recovery of 91.3–95.0% and interference studies showed the selectivity of the method for determination of total iron in water and blood plasma samples. Smartphone–paper-based sensors have advantages of simplicity, rapidity, user-friendliness, low cost, and miniaturization of the method for on-site determination of total iron compared to methods that require sophisticated analytical instruments.