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The coating technique, supposedly invented by Chinese papermakers no later than the 3rd century AD, greatly improved paper sheets’ qualities of color, texture, writability, and printability. Alongside the dispersal of papermaking and surface-treatment techniques beyond China, coated papers were manufactured and used in many other regions of the world. Understanding the manufacture of coated papers, therefore, is crucial for perceiving how surface treatments were developed to meet the need for paper with enhanced properties. However, the characterization of coating and coating pigments on ancient Chinese papers has long remained an unsolved issue, and previous studies on this topic have often produced inconclusive results. To explore a non-invasive methodology that can more reliably characterize coated papers and the coating pigment on them, this article presents the results of a pilot study that applied micro-computed tomography (micro-CT) and Raman spectroscopy to samples of three Qing Dynasty (1644–1911 AD) papers and two handmade papers manufactured in China in the 1990s. Micro-CT revealed the coating layer(s) on Lajian (waxed coated paper) and Lengjinjian (gold-dusted paper) of the Qing Dynasty and characterized the modern raw xuan and bamboo papers as uncoated. Raman spectroscopy, together with handheld X-ray fluorescence analysis, identified the mineral-based pigment in the coating layer, suggesting the use of lead white or kaolin as the coating pigment. Additionally, Raman analysis confirmed the use of other mineral pigments (red lead and cinnabar), beeswax, and organic dyes (gamboge, kermesic acid, and possibly purpurin) in the manufacture of Lajian and Lengjinjian papers. The combination of micro-CT and Raman spectroscopy, it is therefore suggested, is a practical, more reliable approach for non-invasive investigation of coating and coating pigments on ancient Chinese paper specimens.

An optical colorimetric and smartphone-integrated paper device (SIPD) is demonstrated for determination of As (III) in water and soil samples using sucrose modified gold nanoparticles (AuNPs/Suc) as a nanoprobe. The mechanism for determination of As(III) is experimentally validated by performing UV-Vis, transmission electron microscope (TEM), Fourier transforms infra-red spectroscopy (FTIR) and dynamic light scattering (DLS) measurements. The density function theory (DFT) calculations using B3LYP with 6-311G (2d,2p) and LANL2DZ basis sets is used to theoretically prove the mechanism for determination of As(III). In addition, the paper fabricated with AuNPs/SuC was used as a nanoprobe for quantitative determination of As(III) using smartphone and ImageJ software. Calibration plot was linear over 10–800 μgL−1 for colorimetric determination of As(III) with limit of detection (LOD) of 4 μgL−1 acquired when the absorbance ratio obtained at 594 nm/515 nm. The linearity range of 50–3000 μgL−1 with LOD of 20 μgL−1 was determined using smartphone-integrated paper device. AuNPs/Suc is successfully employed for determination of As (III) from contaminated water and soil samples in colorimetry and SIPD.

In paper containing multilayer composite structures and laminates, polarization is usually investigated under dry environmental conditions. The aim of this research is to determine polarization dependence of paper and paper-dielectric structures on environmental relative humidity (RH). The role of each component was identified. The obtained and recorded data are used for identification and clarification of the physical mechanism of polarization. The polarization was studied by applying a dosed charging and forced discharge method and was evaluated by a depolarization potential and its formation kinetics. The polarization level of investigated structures increases with RH and is determined mainly by the paper (cellulose) and moisture content in it. In composite structures of the paper between dielectric films and dielectric on paper the polarization dependence on RH correlates with moisture absorption isotherm. It was found that the surface electrical conductivity of paper distorts the results of the paper and structure paper on dielectric. Analysis of the formation kinetics of the depolarization potential together with the potential decay of the charged paper has determined the role of orientation polarization and space charges. The formation of space charges is faster than orientation polarization and dominates in polarization process at higher RH. The process modeling by superposition of two exponents confirms this polarization mechanism.

A paper-based colorimetric assay for the determination of bilirubin has been developed. The method is based on the in-situ reduction of chloroauric acid to form gold nanoparticles. A chromatographic paper was patterned using a wax printer. Chloroauric acid was drop-cast onto the reagent zone. In the presence of bilirubin, gold(III) ions are reduced and form gold nanoparticles. This leads to a color change from yellow to purple. The intensity of the purple color (peak at 530 nm) increases with bilirubin concentration in the 5.0 to 1000 mg L−1 range. The detection limit is 1.0 mg L−1. For the quantification of bilirubin, images were captured using a digital camera, and data were processed with the help of machine learning-based supervised prediction using Random Forest classification. The method was applied to the determination of bilirubin in urine samples. The spiked urine samples exhibit more than 95% recovery.

This study proposed a novel method for the rapid fabrication of paper-based microfluidic devices using a roll-to-roll wax transfer method. In this approach, a custom-made device was designed and fabricated for the direct roll-to-roll wax transfer from commercially available wax ribbon to the surface of paper substrate. After wax transfer, a thermal reflow process was conducted to enable the melt wax penetration through the whole thickness of the hydrophilic paper substrate to form hydrophobic wax barriers. Compared with the conventional approaches for paper-based microfluidics (wax printing, photolithography, and inkjet printing), the proposed fabrication technique for paper-based microfluidic devices is suitable for the batch fabrication of paper-based microfluidic chips at high production speed. Additional advantages including simple fabrication process, low material and fabrication cost, low-energy consumption, and without the requirement of cleanroom environment or facilities. The paper-based microfluidics fabricated with the proposed roll-to-roll wax transfer method is widely adaptable for microfluidic applications in biological and chemical fields.

Chemical and biomolecular analysis form an integral part of food contamination testing and healthcare diagnostics. The majority of the currently established detection methods are expensive, sophisticated and time consuming. Microfluidic-based lab-on-a-chip systems offer a promising alternative in this regard by enabling the development of simpler and relatively cost-effective platforms for analytical applications. In this work, we report the fabrication of a portable sensor platform using selective wax impregnation of cellulosic paper. The application of the fabricated paper-based lab-on-a-chip device is demonstrated for the qualitative and quantitative detection of starch contamination in milk using colorimetry. Integration of a detection procedure with smartphone imaging allows for on-the-spot data collection, thus overcoming the challenges of sample storage, handling and transportation to lab facilities. This approach offers a versatile method for diagnostic and sensing applications in resource-limited areas, especially in developing and underdeveloped countries.

Paper is a widely used support for use in devices for point-of-care testing (POCT) in clinical diagnosis, food safety monitoring and environmental pollution. Paper is inexpensive, biocompatible, biodegradable and allows a sample fluid to flow by capillary force. Numerous method have been developed recently for chemical modification of papers in order to introduce different functionalities. This review (with 148 refs.) summarizes the recent progress in paper-based POCT devices. The introduction summarizes the state of the art of paper-based POCT devices and the physicochemical properties of existing unmodified materials (including cellulose, cellulose-based composites, cotton fibers, glass fibers, nitrocellulose, thread). Methods for paper modification for sample pretreatment are summarized next, with subsections on sample storage and collection, sample separation, nucleic acid extraction and sample preconcentration. Another main section covers approaches for paper modification for improving POCTs, with subsections on assays for proteins, nucleic acids, drugs, ion and organic molecules. The advantages and disadvantages of these approaches are compared. Several tables are presented that summarize the various modification techniques. A concluding section summarizes the current status, addresses challenges and gives an outlook on future perspectives of POCTs. Graphical abstract This review summarizes the progress that has been made in paper based point-of-care testing (POCT) and lateral flow assays (LFAs), quite often by using advanced nanomaterials for paper modification.

A hot topic in paper-based microfluidics is the achievement of capillary-driven flows much faster than the ones theoretically allowed by the hydrodynamic permeability of common filter papers. Recent works have experimentally shown that the flow rates can be substantially improved by using multilayer paper systems instead of single-layer papers. The present work discusses a theoretical assessment of fluid transport in multilayer paper-based microfluidic devices. The proposed model effectively predicts a series of experimental observations, namely: the occurrence of fluid velocities 2 orders of magnitudelarger than those measured in single-layer paper; the variation of fluid velocity as a function of the gap thickness, whichpresents a particular maximum; the effects of gravity on the filling dynamics, which is unexpected for single-layer paper; and the effect of the sample volume size, which leads to non-trivial filling dynamics. It is worth mentioning that these effects cannot be described by Lucas?Washburn model for single layers, because they arise from the interplay among the coupled flow domains in the multilayer system, together with the action of the gravitational force. The proposed model provides clues to understand the fundamentals behind the capillary-driven flow in multilayer systems, and hence to better design paper-based microfluidics devices for specified flow rates and time-stepped functions. 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: 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

A paper-based electrochemical sensor is described that is based on the use of thiol-terminated poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC-SH) that was self-assembled on a gold nanoparticle-modified screen-printed electrode (SPE). The SPE sensor was used for label-free detection of C-reactive protein (CRP). Gold nanoparticles (AuNPs) were first electrodeposited on the SPCE, followed by the self-assembly of PMPC-SH on gold. The electrochemical response of the modified SPE to CRP was measured by differential pulse voltammetry (DPV). If the CRP on the paper device is contacted with Ca (II) ions, the current (measured by using hexacyanoferrate as the electrochemical probe) decreases. The signal drops in the 5 to 5000 ng·mL−1 CRP concentration range, and the lower detection limit (at 3 SD/slope) is 1.6 ng·mL−1. The use of a PMPC-modified surface also reduces the nonspecific adsorption of proteins. The sensor is not interfered by bilirubin, myoglobin and albumin. It was successfully applied to CRP detection in certified human serum. This sensor is applicable as an attractive protocol for an inexpensive, highly sensitive, and disposable material for electrochemical detection of CRP.

Cystinuria, is an autosomal recessive genetic disorder involving increasingly high levels of poorly soluble cysteine in urine leading to formation of stones. Developing a facile, low-cost, point-of-care and selective sensor for diagnosis of cysteine is imperative. Accordingly, for the detection of cysteine, the present study demonstrates an inexpensive colorimetric, paper-based vertical flow plasmonic micro-well device with a two-minute turn-around time. The method encompasses the use of microbially-synthesized silver nanoparticles (AgNPs) that change from light brown / yellow to dark brown upon binding with Sulphur present in cysteine. This technique allows for visual detection up to 1 × 10−5 mM cysteine and can be easily offered as a rapid diagnostic test even at setups with minimal resources.

The cellulose colloidal particles with good photochromic and photoluminescent performances had been developed in aqueous solution based on a spiropyran-grafted filter paper cellulose (SP–cellulose) in this study. The insoluble filter paper cellulose dramatically became soluble in ethanol after grafting a spiropyran derivative onto its backbone via esterification. During this process, the optical properties of the spiropyran had been successfully inherited. With the aid of ultraviolet and visible light, the obtained SP–cellulose colloidal particles showed light-induced tunability on both photochromism and photoluminescence, corresponding to the significant change of the spiropyran between weak polar ring-closed spiropyran and strong polar ring-opened zwitterionic merocyanine. Based upon this result, the SP–cellulose colloidal particles were finally obtained in water by follow-up dialysis process. In comparison to the pure spiropyran showing poor optical properties in mixed solvent of ethanol/water, the obtained SP–cellulose colloidal particles in water showed good photochromic and photoluminescent performances as well as fine stability. Considering also the raw material of filter paper being cheap and easy to get as well as the facile preparation process of the functional colloidal particles, our experimental results may bring about more promising applications of spiropyran species and water-insoluble cellulose in aqueous medium.

A wet clutch synchronizes the speed and transmits power from an engine or motor to a drive train by mechanical coupling between a friction disk and a separate disk. The performance of a wet clutch may be significantly dependent on the friction and wear characteristics of paper-based friction materials. In this work, the wear characteristics of paper-based friction materials were experimentally investigated using a pin on reciprocating plate tribo-tester. In particular, the wear characteristics of paper-based friction materials with and without carbon fibers were assessed in a boundary lubrication state with respect to normal force and sliding speed. The tests found that the wear rate of paper-based friction materials increased with increasing normal force and sliding speed. The wear rates were found to vary in the range of 10-6-10-4 mm3/(N·cycle). In addition, paper-based friction material with carbon fiber exhibited relatively larger friction and wear characteristics than those without carbon fibers. It was observed that the carbon fibers were broken due to the sliding contact, which may have contributed to the wear progression. The outcomes of this work may be helpful in gaining a better understanding of the tribological characteristics of paper-based friction materials in order to enhance the lifetimes of wet clutches.

Cellulose-based paper is a versatile material with a diverse array of applications. While paper is not commonly thought of as a material that shrinks, here we present a method for miniaturizing paper via periodate oxidation. Chromatography paper was exposed to varying concentrations of periodate (0.1–0.5 M) over a 96-h period. Following optimization of miniaturization parameters, fourteen different types of paper were miniaturized and reductions in surface area ranging from 60 to 80% were observed. All cellulose paper types, but not cellulose-derivatives, displayed successful miniaturization. Results were highly tunable dependent upon periodate concentration and reaction time. Potential applications of the technique are discussed, including its use as a microfabrication method.

The governing international standard for the development of prosthetic heart valves is International Organization for Standardization (ISO) 5840. This standard requires the assessment of the thrombus potential of transcatheter heart valve substitutes using an integrated thrombus evaluation. Besides experimental flow field assessment and ex vivo flow testing, computational fluid dynamics is a critical component of this integrated approach. This position paper is intended to provide and discuss best practices for the setup of a computational model, numerical solving, post-processing, data evaluation and reporting, as it relates to transcatheter heart valve substitutes. This paper is not intended to be a review of current computational technology; instead, it represents the position of the ISO working group consisting of experts from academia and industry with regards to considerations for computational fluid dynamic assessment of transcatheter heart valve substitutes.

On-site rapid monitoring of nitrite as an assessment indicator of the environment, food, and physiological systems has drawn extensive attention. Here, electrokinetic stacking (ES) was combined with colorimetric reaction on a paper-based device (PAD) to achieve colorless nitrite detection with smartphone. In this paper, nitrite was stacked on the paper fluidic channel as a narrow band by electrokinetic stacking. Then, Griess reagent was introduced to visualize the stacking band. Under optimal conditions, the sensitivity of nitrite was 160-fold increased within 5 min. A linear response in the range of 0.075 to 1.0 μg mL−1 (R2 = 0.99) and a limit of detection (LOD) of 73 ng mL−1 (0.86 μM) were obtained. The LOD was 10 times lower than the reported PAD, and close to that achieved by a desktop spectrophotometer. The applicability was demonstrated by nitrite detection from saliva and water with good selectivity, adding 100 times more concentrated co-ions. High recovery (91.0~108.7%) and reasonable intra-day and inter-day reproducibility (RSD

The urgent demand for portable electronics has promoted the development of high-efficiency, sustainable, and even stretchable self-charging power sources. In this work, we propose a flexible self-charging power unit based on folded carbon (FC) paper for harvesting mechanical energy from human motion and power portable electronics. The present unit mainly consists of a triboelectric nanogenerator (FC-TENG) and a supercapacitor (FC-SC), both based on folded carbon paper, as energy harvester and storage device, respectively. This favorable geometric design provides the high Young’s modulus carbon paper with excellent stretchability and enables the power unit to work even under severe deformations, such as bending, twisting, and rolling. In addition, the tensile strain can be maximized by tuning the folding angle of the triangle-folded carbon paper. Moreover, the waterproof property of the packaged device make it washable, protect it from human sweat, and enable it to work in harsh environments. Finally, the as-prepared self-charging power unit was tested by placing it on the human body to harvest mechanical energy from hand tapping, foot treading, and arm touching, successfully powering an electronic watch. This work demonstrates the impressive potential of stretchable self-charging power units, which will further promote the development of high Young’s modulus materials for wearable/portable electronics.

Point-of-use system is an appropriate choice in emergency situation because this system is efficient, easy to use, and highly portable. The present study aimed to determine the optimal parameter values associated with the preparation of cellulose paper coated with silver nanoparticles using response surface methodology via Box–Behnken Design (BBD) for the purpose of finding the appropriate filter material in point-of-use water purification system. In this case, the efficiency of cellulose paper coated with silver nanoparticles was investigated based on the optimal parameter values and tested using different types of water samples (tapwater, rainwater, and surface water) by taking into account the drinking water guidelines and health risks. Finally, the cellulose paper coated with silver nanoparticles was compared with other point-of-use technologies in determining its suitability during emergency situation. Box Behnken Design results showed that quadratic model was capable of describing the effects of parameters (silver nitrate solutions, sodium borohydride; silver nitrate ratio and immersion time) on the responses (E. coli removal efficiency). Moreover, second order polynomial equations, ANOVA, and three-dimensional surface plots were developed to evaluate the effects of each parameter on E. coli removal efficiency. The findings show that optimal parameters are found in silver nitrate concentration of 0.035 M and sodium borohydride: silver nitrate ratio of 5 with insignificant immersion time. The field testing results show that cellulose papers coated with silver nanoparticle is suitable for low-turbidity water as it meets the drinking water guidelines with low health risks. The comparison with other point-of-use technologies indicated that cellulose paper coated with silver nanoparticle is suitable to be used as a filter to supply clean drinking water in emergency situation.

Biomolecules in human body serve as biomarker for diagnosis of diseases, and paper-based biochips have become of much interest for development of biomolecule sensing. Cellulose micro-/nanofiber matrices consisting of paper allow not only capillary-driven flow without external pumping owing to abundant micro-/nanopores but also three-dimensional (3D) hierarchical micro-/nanostructures as 3D templates for microfluidic bioassays. Besides, colloidal and thermal evaporated metal nanoparticles on cellulose fibers offer huge opportunities in nanoplasmonic biosensing. Here, we review paper-based biochips including microfluidic paper-based assays and nanoplasmonic biosensors and further discuss micro-/nanofabrication of paper-based biochips and their applications in biomolecule detection.

Paper-based devices are continuing to grow rapidly. However, conventional paper patterning methods are mostly restricted to the fabrication of two-dimensional (2D) patterns. Here, we present a novel patterning method for the fabrication of 2D and 3D paper-based devices. For the first time, a 3D fluidic channel network with multiple crossings of fluidic channels is successfully fabricated on a layer of paper without sophisticated procedures. The proposed method utilizes a commercially available inkjet printer to print water pattern as a protective mask onto both sides of a paper substrate and followed by soaking the sample into a non-polar solution which contains a hydrophobic substance to form hydrophobic barriers on the paper substrate. The printed water mask helps preventing the adsorption of the non-polar solution into the printed water area resulting in the formation of hydrophobic and hydrophilic areas. This opens up a new route towards the development of 2D and 3D paper-based devices using low-cost equipment and a variety of materials.

Simple, low-cost and portable microfluidic paper-based analytical devices (μPADs) for determination of creatinine in urine samples were developed. The methodology was based on Jaffé reaction between the creatinine and picric acid in alkaline conditions, generating a colorimetric creatinine-alkaline picrate complex. The product exhibits an orange color that is clearly visible on the μPADs. The color intensity of the complex, which is indicative of the concentration of creatinine, is then quantitatively determined using ImageJ software. Various experimental parameters were optimized to achieve the best performance of the μPADs. Under the optimum conditions, a wide linear range was obtained in the range of 0.2 - 1 mM with a limit of detection and limit of quantitation of 0.08 and 0.26 mM, respectively. The accuracy of the proposed method was in good agreement with the standard Jaffé method. Finally, the developed devices were successfully applied for the determination of creatinine in urine samples.

Educational evaluation helps to improve the learning and teaching process. The learning process can be assessed by the examination system. In the examination system, the learners have to answer a set of questions. The learning assessment ensures improved performance in the educational system. The success of the learning assessment is highly dependent on the listening and understanding ability of each student. The assessment of the question paper can be at two levels—cognitive level assessment and difficulty level. The cognitive level assessment is purely based on Bloom’s Taxonomy and the difficulty level assessment is purely based on the examination marks of each student. This article presents a technical method called Question Paper’s Difficulty Level (QPDL) that helps to identify the difficulty level of each question in the question paper. The QPDL method is incorporate in the implementation of ‘QAUDIT’ web application to assess the difficulty level of the question paper systematically. The systematic analysis to identify the difficulty level of the question paper is made for 239 question papers. Each question paper can be recognized based on three difficulty levels such as High, Moderate and Low.

A colorimetric paper-based enzyme-coupled antimony tin oxide nanoparticle (ATONP) nanobiosensor for selective detection of Cd2+ ions in clams and mussels is presented. Alkaline phosphatase (ALP) was immobilized on ATONPs via 16-phosphonohexadecanoic acid (16-PHA) to develop ATONP-ALP nanobiosensor. The biosensor was characterized using XPS, Raman spectroscopy, SEM, and EDX. ATONP-ALP nanobiosensor exhibited high selectivity towards detection of Cd2+ ion with a LOD 0.006 μg L−1 and linear range of detection 0.005–1 μg L−1. The developed biosensor was further integrated into a low-cost paper-based format. A visual color change was obtained for Cd2+ ion in the range 0.1–10 μg L−1. The developed biosensor was successfully demonstrated for the analysis of Cd2+ ions in clams with recoveries 101–104%. The ATONP-ALP nanobiosensor was validated using mussel tissue (BCR-668) and the conventional ICP-OES and ICP-MS techniques.

To support the safe operation of the novel three-element mixed insulation oil (TEMO) transformer, gas generation behaviors of the TEMO oil–paper insulation system under overheating faults and discharge faults were investigated. Results show that that the content of H2 and C2H6 generated by TEMO–paper insulation system is much higher than that in conventional mineral oil (MO)–paper insulation system under different overheating temperatures. Under partial discharge fault, the content of H2 dissolved in oil changes distinctly, while the content of C2H2 also increases with the discharge time. Under surface flashover breakdown, AC breakdown and lightning impulse breakdown fault, the content of H2 and C2H2 changes greatly compared to other gases, while the concentration of total hydrocarbon gases in TEMO–paper insulation system is smaller than that in MO–paper insulating system after the same breakdown times. The diagnosis model of overheating and discharge faults for the TEMO–paper insulation system was proposed based on the oil dissolved gas analysis, while H2, C2H2 and C2H4 were chosen as the characteristic gases and the boundary settings were determined. The verified result for the low-temperature overheating, lightning impulse and surface flashover fault for the TEMO–paper insulation system presents that the new diagnosis model is effective.

This paper examines various ways of combining paper and glass as a laminate and the effects on transparency. Laminate in this context means a layer of paper sandwiched in between layers of glass held together with an adhesive. Different kinds of papers and adhesives were used to study the potentials of glass-paper-laminates as related to transparency and translucency. These laminates may find applications in building construction, safety glass, printed electronics and more. Utilizing a variety of adhesives and papers, qualitative evidence found that epoxy achieves the best with regards to transparency and adheres most effectively.

To effectively utilize paper sludge and allow for energy recovery, the thermal behaviors of two paper sludge (PS) were studied by thermogravimetric analysis (TGA). The kinetic analysis was conducted according to Coats-Redfern (CR) method. The evolution of pore structure and surface morphology was investigated by N2 adsorption and scanning electron microscopy (SEM), respectively. The mineral transformation was analyzed by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Derivative thermogravimetry (DTG) curves of PS show two different stages. The first stage was due to devolatilization (200–400 °C) and the second stage (650–800 °C) accounted for the mineral decomposition and char degradation. It was found that a large number of pores formed during pyrolysis because of char fragmentation. The specific surface areas increased from 5.161 to 22.894 m2 g−1 for PSA and from 9.007 to 16.126 m2 g−1 for PSB with the increase of temperature. The intense absorption bands of calcite (1426, 875 and 712 cm−1) in raw material indicated that calcite was the main mineral of PS. The decomposition of calcite at 700 °C and the further production of gehlenite (916 cm−1) at 900 °C, and the dehydration of kaolinite at 500 °C and further transformation into mullite (996 cm−1) at 900 °C were observed by both FTIR and XRD. The XRD results were generally consistent with FTIR analyses.

Presently synthesis of edible oil for resin formation and using scrap paper as reinforcement for composite fabrication is still not carried out. In this work, acrylate epoxidized mustard oil (AEMO) was used after blending with a crosslinker N-Vinyl-2-Pyrrolidone (NVP) to fabricate scrap paper reinforced green composites. Mustard oil (MO), Epoxidized mustard oil (EMO) and acrylate epoxidized mustard oil (AEMO) were characterized using iodine value, oxirane content, acid value, FTIR, NMR and viscosity properties. The composites were fabricated using 50:50 ratio of AEMO: NVP and paper loading of 15%, 30% and 60% along with the neat sample. With an increase in paper loading, there was a significant improvement in mechanical properties giving 158.9, 150, 233, 566.66 and 140% improvement in tensile, young’s, flexural strength, flexural moduli and impact strength at 60% loading. The elongation at break showed a value of 20% due to the stiff nature of composite. Biodegradability testing proved an increase in weight loss of composite with time, recording the highest weight loss of 7% for 60% composite sample. Dimensional stability showed excellent result for the neat and lower loaded composite samples. Thermogravimetric and differential scanning colorimetry analysis indicated improvement in thermal stability with higher loading %. Morphological analysis confirmed excellent interfacial adhesion and bonding with higher paper loading %. Dynamic mechanical analysis demonstrated a significant rise in storage modulus (E') and loss modulus (E'') and decline in tan δ with broadening of the peak for maximum loading. Chemical resistance was poor for the highest loaded samples with respect to acids and bases.

Necessary optimality conditions for a bilevel optimization problem are given in the paper by Kohli (J Optim Theory Appl 152: 632–651, 2012). Recently, the same author corrected his results in the note (J Optim Theory Appl 181:706–707, 2019). In this work, we have pointed out that some of the new modifications are wrong. We correct the flaws and present an alternative proof for the main result.

Mitigation of the peroxide explosive threat, specifically triacetone triperoxide (TATP) and hexamethylene triperoxide diamine (HMTD), is a priority among the law enforcement community, as scientists and canine (K9) units are constantly working to improve detection. We propose the use of paper spray ionization–high-resolution mass spectrometry (PSI-HRMS) for detection of peroxide explosives in biological matrices. Occurrence of peroxide explosives and/or their metabolites in biological samples, obtained from urine or blood tests, give scientific evidence of peroxide explosives exposure. PSI-HRMS promote analysis of samples in situ by eliminating laborious sample preparation steps. However, it increases matrix background issues, which were overcome by the formation of multiple alkali metal adducts with the peroxide explosives. Multiple ion formation increases confidence when identifying these peroxide explosives in direct sample analysis. Our previous work examined aspects of TATP metabolism. Herein, we investigate the excretion of a TATP glucuronide conjugate in the urine of bomb-sniffing dogs and demonstrate its detection using PSI from the in vivo sample.

Herein we are reporting, the in-situ synthesis of polydopamine capped silver nanoparticles (PDA-AgNPs) and its cysteamine (CYS) and tetracycline (TC) drugs sensor applications. The synthesized PDA-AgNPs was characterized by UV–Visible, Fourier Transformed–Infrared, X-Ray Diffraction, Zeta Potential, and High Resolution-Transmission Electron Microscope techniques. We have utilized PDA-AgNPs as probes for the detection of CYS and TC by spectrophotometry method. The addition of CYS has led to a decrease in the absorption of PDA-AgNPs. The yellow color solution becomes colorless and observed the aggregated particles in the TEM image. In contrast, the addition of TC, into the same solution, absorption of PDA-AgNPs was increased. The color of the solution became dark yellow and the particles are obtained de-aggregation. Based on the Surface Plasmon Resonance (SPR) band absorption changes, the detection limit of CYS and TC was calculated to be 180 nM and 17 nM, respectively. Interestingly, 600-fold of common interferences did not interfere with the detection of CYS and TC. PDA-AgNPs was successfully utilized to detect CYS and TC in serum, urine, and drug samples. Finally, we have prepared a paper-based colorimetric kit for on-site monitoring of CYS and TC.

Transition metal–based catalysts are considered to be promising materials to replace noble metal catalysts for electrocatalytic water splitting. Herein, a flexible electrode composed of Co-Ni-P ternary catalysts and carbon fiber paper substrate (Co-Ni-P/CFP) was successfully fabricated and applied in water electrolysis. The Co-Ni-P coatings were deposited on CFP by a one-step cyclic voltammetric electrodeposition method and the surface of the composite material exhibits nano-reticular structure. The formation mechanism was also discussed according to the results of material characterization. Notably, the Co-Ni-P/CFP flexible electrode exhibited superior catalytic performance for both hydrogen and oxygen evolution reactions in alkaline media, which could achieve 10 mA/cm2 current density with overpotential of 89 mV for HER and 320 mV for OER. Moreover, the Co-Ni-P/CFP electrode could also be used as both anode and cathode electrode to drive overall water splitting and required only 1.64 V to achieve a current density of 10 mA/cm2, which was very close to that of the commercial combination of Pt/C and IrO2. This affordable and easily obtained electrode offers a new avenue to develop earth-abundant resource catalysts for water electrolysis system.

Herein we report a quantitative, multiplex assay for disease markers in plasma based on an integrated setup of a portable scanner and a disposable paper-based analytical device (PAD). The quantitative analysis relies on the digital colorimetric reading of the three-layer PAD with 30 assay sites for performing respective chromogenic reactions for plasma uric acid, glucose, and triglyceride, which are considered as important risk factors for cardiovascular diseases. A portable scanner with WiFi transmission capability was used to produce high-quality color images of the PADs and wirelessly transfer them to a smartphone or other mobile devices for data processing. The concentrations of biomarkers in both standard solutions and plasma samples can be directly obtained using a custom-designed smartphone app that is also capable of constructing calibration curves. The detection limits of uric acid, glucose, and triglyceride were determined to be 0.50 mg/dL, 0.84 mmol/L, and 14 mg/dL, respectively, which are below the normal limits and adequate for clinical validation. Owing to the distinct advantages—simple, portable, and cost-effective—this mobile assay protocol can be used for point-of-care (POC) settings or resource-limited situations, and potentially for the diagnosis and prevention of infectious diseases.

Starch is one of the most popular biodegradable polymers in nature, which is gaining increasing attention because of its abundant availability and low cost. However, starch film itself is very brittle and its barrier property is poor for many applications. Polyvinyl alcohol (PVA), a versatile polymer in paper industry, is used to improve the barrier property of starch film. In this study, painting paper with exceptional barrier properties against organic solvents is successfully prepared for art creation purpose by coating a thin layer of environmentally friendly starch/PVA film on its surface. The coated paper can resist the penetration of the ink from marker pens. Furthermore, the solvent resistance and mechanical flexibility of freestanding starch/PVA hybrid film were investigated in detail. It found that the excellent barrier properties of the coated painting paper against solvents are due to the superior solvent resistance and mechanical flexibility of starch/PVA hybrid film. Therefore, the biodegradable and cost-effective strategy in this study provides a promising approach to enhance the barrier property of painting paper against solvents, which can find potential applications in painting field.

In this work, the commercial carbon paper was firstly peeled in K2CO3 solution and then was further treated in a KNO3 solution to form functional exfoliation graphene (FEG) on the commercial carbon paper. The FEG/carbon paper was characterized by Raman spectra and scanning electron microscopy, confirming that some typical layered fold graphenes were successfully peeled off and stood on the carbon paper matrix. Then, Fe3O4 nanoparticles (NPs) were grown on the surface of FEG/carbon paper and the as-prepared Fe3O4 NPs/FEG/carbon paper was directly used as supercapacitor electrode. The specific capacitance of Fe3O4 NPs/FEG/carbon paper was about 316.07 F g−1 at a current density of 1 A g−1. Furthermore, the FEG/carbon papers were also functionalized by benzene carboxylic acid to form FFEG/carbon papers, and then the Fe3O4 NPs were grown on the surface of FFEG/carbon paper. The specific capacitance of Fe3O4 NPs/FFEG/carbon paper was 470 F g−1 at a current density of 1 A g−1, superior to some previous reported results. This work might provide a new strategy to prepare various nanostructures on FFEG/carbon papers for future applications.

The production of high filler-loaded recycled papers is often affected by high values of linting and low values of strength. In the first case, the accumulation of lint particles from paper’s surface on the printing blanket affects the quality of the printed paper and the pressroom’s productivity. In the second case, increasing the use of fillers and recycling cycles lead to poor paper strength. Cellulose nanofibers (CNFs) are receiving a great deal of attention due to their potential as a reinforcement aid for high filler-loaded papers through filler–fiber interaction and interfiber bonding. It is already proven that high quality CNFs can reduce linting, although their industrial application is limited by their high production cost. The objective of this research is, therefore, to quantify the effect of applying lower grade, more sustainable CNFs on linting phenomena and on the mechanical properties of recycled papers. Eucalyptus, pine and triticale residues were used as cellulose sources, and the CNFs were produced minimizing the chemical pretreatment before homogenization. Addition of 3 wt% of CNFs from pine residues into the recycled paper with 15.7 wt% of total filler reduced linting by 40% and increased tensile strength by 15.1%; further improvements on linting and mechanical properties were achieved at 5 wt%. Moreover, the increase in drainage time can be overcome by the addition of a retention aid, in this case a coagulant-cationic polyacrylamide-bentonite system, commonly used in paper mills.

A high quality graphene paper has been fabricated using drop-casting of a custom developed stable ink mixture. The graphene/ethyl cellulose mixture can produce graphene paper coating on Kapton substrate at fairly large scales by finely adjusting the viscosity of the ethyl cellulose solvent blend. It was possible to produce a morphologically intact 300 nm-thick stacked structures of high purity graphene platelets after annealing at 300 °C, as characterized by SEM, Raman Spectroscopy and AFM. The electrical resistivity of a large batch of samples was measured and the results thoroughly evaluated, using a design of experiments approach. The resistivity values achieved were found to be lower or comparable to the best results reported in the literature. As expected, resistivity is inherently related to the concentration of the as-prepared ink and subsequent annealing conditions. However, prolonged annealing time can deteriorate mechanical properties as determined by cyclic bending and shear tests. It is anticipated that the present graphene paper has potential use in flexible electronics applications since the lowest resistivity and structure achieved were generally unaffected by the range of mechanical loadings studied.

The use of nanocelluloses as strength-enhancing additives in papermaking is widely known since both cellulose nanofibers (CNF) and nanocrystals (CNC) present similar composition than paper but their exceptional properties in the nanometer scale confers a paper quality enhancement. However, some agglomeration problems in CNF and CNC through hydrogen bonding cause a lower improvement of mechanical properties of paper. Therefore, a better dispersion of both nanocelluloses can maximize their effect on paper properties, thus reducing the needed dose to get the same increment in tensile strength and then reducing material costs. To ease the implementation of these nanocelluloses in the production process of recycled paper, typically used operations of these industries have been used. Among them, those devoted to improve the homogeneous mixture of nanocellulose in the pulp suspension have been assessed. Firstly, pulping conditions were studied, including pulping time, temperature and need for soaking as variables. Secondly, some dispersing agents used in papermaking were considered, studying the effect of different types and doses. The highest tensile strength of paper was achieved by applying long pulping times (60 min), getting increments up to 30% with the use of soaking and polyacrylamide as retention system. However, with the use of a low dose of a dispersing agent (0.003%), tensile index can be still increased up to 20.6% avoiding these long times. This study can be of great interest of those researchers trying to implement the use of nanocelluloses as strength additive in papermaking.

Lignocellulosic–plastic composites are materials widely used in the construction industry; however, their mechanical performance and durability constitutes a serious issue due to the nature of the lignocellulosic component which makes it prone to biological degradation. This article gives account of the protective performance of a novel eco-friendly solvent based coating obtained from recycled expanded polystyrene dissolved with Limonene, and three different coating systems used generally for outside wood protection, applied on a Kraft paper for potential structural use. Three aspects were evaluated, namely coating interaction with the lignocellulosic substrate, water absorption and resistance to Nasutitermes corniger termite attack. Scanning electron microscopy revealed two types of interaction namely—adsorption and absorption—of the coatings systems in the fibrous structure. Coating absorption revealed better protection for water absorptiveness of the paper structure. After biotic exposure, sample weight loss and damaged structure were observed, highlighting the aggressiveness of this type of termites which attack any kind of material studied here, in order to reach their food source.

Fiber length and fiber-to-fiber bonding effects on tensile strength and fracture toughness of kraft paper have experimentally been investigated. Laboratory sheets were made from kraft pulp, each with a distinct set of fiber lengths. Additionally, the fiber–fiber bond strength was improved by carboxymethyl (CMC) grafting. The tensile strength and work of fracture toughness results were compared to predictions from a shear-lag model which considers the fiber–fiber bond shear strength, the fiber tensile strength and fiber pull-out work. The tensile strength and fracture work for papers with weak fiber–fiber bonds increased with fiber length consistent with the shear-lag model. CMC-treated fibers provided strong fiber–fiber bonds. Papers made from such fibers displayed high strength and work of fracture independent of fiber length which indicates that the failure process is governed by fiber failures rather than bond failures. The fracture toughness, expressed as the critical value of the J-integral, increased strongly with fiber length for both untreated and CMC-treated papers. The results show that long fibers and CMC addition are extremely beneficial for improving the fracture toughness.

To protect forest resources and increase the value of agro-industrial residues, it would be helpful to produce paper-based materials from non-woody or recycled fiber resources. This study investigated the reinforcement mechanism of bacterial cellulose (BC) on paper sheets made from different sources including softwood, hardwood, sugarcane bagasse, bamboo, wheat straw, and recycled fiber, which represent a selection of high quality, medium quality, and low quality fibers. The results showed that by maintaining BC addition at a low level of 0.5–1.5% (total paper dry weight), the paper sheets made from high and medium quality fibers have the maximum tensile index improvement, with 5–25%. The tensile index of low quality fiber including wheat straw pulp and recycled fiber pulp increased slightly and gradually with the level of BC addition; at 5% BC addition, the tensile indexes increased by 9 and 40%, respectively. To investigate the BC reinforcement mechanism, different fiber characteristics, SEM images of BC reinforced paper, BC retention rate on paper, and the effects of dispersant addition were evaluated. It was found that high BC addition or retention rate in paper sheets do not necessarily result in good BC reinforcement effects but that proper dispersion of BC is important.

Pulp and paper wastewater (PPW) is classified as complex wastewater that contains high concentrations of recalcitrant pollutants. In this study, the integration of coagulation process and electro-activated peroxymonosulfate (PMS) were tested to treat PPW. FeCl3, aluminum sulfate and poly aluminum chloride were examined for chemical oxygen demand (COD) removal from PPW. Amongst the coagulants, FeCl3 showed higher performance compared to other coagulants in which 55% of COD was removed under the conditions of natural pH of 6.9 and FeCl3 dosage of 100 mg L−1. Coagulation-treated wastewater by FeCl3 was treated by electro-activated PMS. Under the condition of 0.75 mA cm−2 current density, 6.0 mM PMS and 60 min reaction time, 53% of COD was further eliminated. To compare with electro-Fenton, electro-activated PMS provided higher COD removal and specific oxidant efficiency. Integration of coagulation (FeCl3) and electro-activated PMS enhanced the biodegradability of PPW based on biochemical oxygen demand/COD index. The results showed that integrated chemical and electrochemical processes can be used as a pretreatment for biological process.

The need for research into the use of alternative raw materials for the production of paper results from the anticipated shortages in the supply of raw-materials to the wood-based paper-industry. Although Burdwan town is vested with different types of algae, literally no work has been done for valorization of such biomass. Start of such bioprocess involves optimization of resource-utilization that is the main topic in this paper. Burdwan town was surveyed for collection of algae that were identified by morphologic characteristics under the microscope. Cellulose, hemicelluloses, lignin, ash-content, water-retention-value, total carbohydrate and starch concentration of these algae were determined for assessing their feasibility in handmade-paper production. Element content in these algae was determined from energy-dispersive-X-ray-spectroscopy. Breaking-length and tensile-strength were the two parameters tested to assess hand-made-paper quality obtained from pulp extracted from the collected algae species. Data obtained were statistically evaluated with one-way analysis-of-variance followed by Tukey’s HSD (honest-significant-difference) test. Paper made from pure algae pulp was also tested for inter-fiber bonding with scanning-electron-microscopic-imaging. All experiments were repeated with Eucalyptus sp. pulp (wood) as control to assess the suitability of algal pulp as an alternative to the conventional wood pulp. Five algal species: Pithophora sp., Lyngbya sp., Hydrodiction sp., Cladophora sp. and Rhizoclonium sp. were collected. Although here were no statistically-significant differences (p = 0.8137) in biomass-compositional values from the studied algae species and Eucalyptus sp. pulp, paper quality parameters (Breaking-length and tensile-strength) varied significantly (p

Applicability of super-insulating silica aerogel materials for thermal insulation is still restricted by limited mechanical strength. We report on a systematic improvement of silica aerogels in respect to shrinkage, density and thermal conductivity by varying sol-gel parameters as the molar ratios of TEOS:EtOH:H2O or the hydrolysis time. The received silica aerogels can be combined with paper-based honeycomb structures to improve the mechanical strength. We successfully manufactured such silica aerogel paper honeycomb composites. The challenges in the preparation are the must to prevent shrinkage of the silica aerogels during synthesis, to avoid cracks by supercritical drying, and to get a perfect bonding at the paper–silica interface. The composite materials are characterized with respect to their compression modulus, thermal conductivity, and flammability.

Generation of efficient and reusable superhydrophobic and superoleophilic coatings for oil–water separation have received substantial interest in material science. In the present work, porous superhydrophobic and superoleophilic LLDPE and SiO2 + LLDPE coatings on cellulosic filter papers were fabricated using a solution casting technique. Surface morphology, water contact angle, and chemical composition of uncoated and coated filter papers were characterized. SiO2 + LLDPE coating on filter paper shows the maximum water contact angle of 167.8° ± 1.4° and sliding angle of 3.8° ± 0.5°. In addition, thermal, chemical, and mechanical stability of the coatings were also studied. Additionally, water-drop impact dynamics for the superhydrophobic coatings were also studied. Further, efficiency and reusability of coated filter papers to remove petroleum ether and benzene from an oil–water mixture were also characterized.

The present work proposes the recycling of expanded polystyrene (EPS) waste, in order to contribute to reduce the excessive accumulation of this material in sanitary landfills in Mexico. The recovery process of EPS is proposed using a biosolvent (Lemon limonene-LL) to prepare a polymeric solution (EPS-LL), and its subsequent evaluation as a coating on a lignocellulosic Kraft paper of 200 g/m2 and a Gurley porosity of 15–30 seg/100 ml. The effect of different resin concentrations and resin coating layers on the compressive and tensile strength was tested, as well as the resistance of the treated paper to water absorption. Results indicated that the coating layers gradually increased the mechanical strength of the Kraft paper, both tensile and compressive, but only up to a certain grammage of resin applied. Regarding to water absorptiveness, the treated paper showed a significant reduction of water absorption, from 230 g/m2 with one resin layer to 23 g/m2 with three resin layers. The results demonstrate the potential of recycling EPS to obtain a composite material with good hydrophobic characteristics and mechanical strength. This study also intends to provide an added value of this recycled polymer, rather than continuing the current custom of discarding it in sanitary landfills.

Bacterial cellulose (BC) was used to reinforce paper sheets made from non-woody fibers, e.g. sugarcane bagasse. BC produced from static and agitated fermentation methods was mixed with bleached sugarcane bagasse pulp (BSBP) to produce composite paper sheets. BC from static culture had a higher degree of polymerization, crystallinity, and crystallite width. Adding BC at a low ratio (

A voltammetric method for fast and high sensitive determination of Bisphenol A (BPA) using glassy carbon electrode (GC) modified with carbon black nanoparticles (CB) was developed. Cyclic voltammetry study in the 0.1 M phosphates of pH = 7.0 gave single anodic peak at 578 mV. Adsorption-controlled oxidation of BPA was found to be irreversible with the participation of two electrons and two protons. The proposed CB/GC electrode significantly improved the oxidation peak current of BPA compared to the bare electrode. Under the optimum conditions, calibration curve was linear in the concentration of BPA from 0.01 to 3 × 10−6 mol L−1 with the detection limit of 3.4 × 10−9 mol L−1. Moreover, the proposed method was successfully validated by studying the recovery of BPA in commonly available samples: thermal paper (receipt, ticket) and food/beverages packaging. This paper introduces carbon black as a new, perspective material for electrode modification used in voltammetry.

Paper curls in printers should be prevented since they cause paper jams and degradation of printing quality. Moisture transport due to high temperature in the fuser nip of a printer is one of main reasons for paper curls. In order to predict and control the paper curls, it is therefore essential to understand the mechanisms of heat and moisture transport in paper. In this paper, we derived a coupled heat and moisture transport model and applied it to the situation where a paper sheet moves between two rollers having different temperatures in a fuser nip. A series of simulations were carried out with varying parameters related to the characteristics of printer paper, the environment, and paper/environment interfaces. The simulation results provided a deep understanding of the moisture transport mechanisms and identified several key variables affecting changes of moisture profiles as a function of time. The time-dependent moisture contents data will be fed into a mechanical model to obtain the quantitative amount of the nip curl.

A disposable surface-enhanced Raman scattering (SERS) substrate was prepared by successively spraying silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) onto commercial filter paper using an inexpensive consumer sprayer. The strong surface enhancement of AgNPs and chemical stability of AuNPs can be advantageously combined. The substrate exhibited excellent SERS activity for malachite green (MG), methylene blue (MB), and crystal violet (CV) under 785-nm excitation, with limits of detection (LODs) of 4.3 × 10−9, 2.0 × 10−8, and 8.1 × 10−8 M, respectively. The substrate exhibited long-term stability, and it can be stored under ambient conditions for 4 weeks with a relative standard deviation of less than 3% among peak intensities. The substrate also showed good reproducibility with a relative standard deviation of 7.1% among different substrate peak intensities. The substrates enable on-site determination of residual fishery drugs and distinguish MG, MB, and CV mixtures in spiked fish within 5 min, and the average recoveries in fish scales and fish meat were better 90.1% and 76.9%, respectively. The method exhibited rapidity, simplicity, and high sensitivity and is expected to be used for the screening of additives in food.

Nanoparticle (NP)-loaded filter paper (FP)-based surface-enhanced Raman scattering (SERS) substrates have been prepared using differently shaped gold (Au) NPs. The shape of Au NPs plays a significant role in the amplification of SERS signal. Here, two differently shaped Au NPs were synthesized using two different techniques: (a) femtosecond (fs) laser ablation in liquid and (b) chemical method. Spherical shaped Au NPs were obtained using fs ablation of a bulk Au target in distilled water and Au nanostars (NSs) were achieved through chemical process utilizing N-vinyl-2-pyrrolidone as a reducing/capping agent. The size and shapes of these synthesized NPs and NSs were investigated meticulously using different characterization techniques such as transmission electron microscopy, field emission scanning electron microscopy and X-ray diffraction. Both the NPs and NSs were subsequently loaded onto commercially available FP by simple drop casting method. To achieve higher number of hot spots, the aggregated spherical NPs were obtained by addition of NaCl. The non-aggregated spherical, aggregated spherical, and star Au NPs loaded on FP were used for the detection of a dye (Nile blue) and an explosive molecule (Picric acid).

Graphite materials are widely used as electrode materials for electrochemical energy storage. N-doping is an effective method for enhancing the electrochemical properties of graphite. A novel one-step N-doping method for complete and compact carbon paper was proposed for molten salt electrolysis in the LiCl-KCl-Li3N system. The results show that the degree of graphitization of carbon paper can be improved by the electrolysis of molten salts, especially at 2.0 V. Nitrogen gas was produced at the anode and nitrogen atoms can substitute carbon atoms of carbon paper at different sites to create nitrogen doping during the electrolysis process. The doping content of N in carbon paper is up to 13.0wt%. There were three groups of nitrogen atoms, i.e. quaternary N (N-Q), pyrrolic N (N-5), and pyridinic N (N-6) in N-doping carbon paper. N-doping carbon paper as an Al-ion battery cathode shows strong charge-recharge properties.