Porous carbon materials are common materials used for sensor and absorbent applications. A novel approach for functionalizing porous carbons through the impregnation of porous carbon black with benzoxazine monomers, followed by thermal polymerization is introduced herein. The method not only establishes a new avenue for the functionalization of porous carbons but also endows the resulting material with both copper ion-binding and sensing properties. We showcase the versatility of the technique by illustrating that the polymerization of phenols with benzoxazine monomers serves as an extra tool to customize absorption- and sensing properties. Experimental validation involved testing the method on carbon black as a porous substrate, which was impregnated with both bisphenol-a benzoxazine and a combination of bisphenol-a benzoxazine and alizarin. The resulting materials were assessed for their dual functionality as both an absorbent and a sensor for copper ions by varied copper ion concentrations and exposure times. The dye absorption test demonstrated a notable capacity to accumulate copper ions from dilute solutions. Electrochemical characterization further confirmed the effectiveness of the modified carbons, as electrodes produced from inks were successful in detecting copper ions accumulated from 50 μM Cu2+ solutions. With this work, we aspire to set the steppingstone towards a facile functionalization of porous carbon materials towards water purification applications. © 2024 The Authors

Water pollutants harm ecosystems and degrade water quality. At the same time, many pollutants carry potentially valuable chemical energy, measured by chemical oxygen demand (COD). This study highlights the potential for energy harvesting during remediation using photocatalytic fuel cells (PCFCs), stressing the importance of economically viable and sustainable materials. To achieve this, this research explores alternatives to platinum cathodes in photocathodes and aims to develop durable, cost-effective photoanode materials. Here, zinc oxide nanorods of high density are fabricated on carbon fiber surfaces using a low-temperature aqueous chemical growth method that is simple, cost-efficient, and readily scalable. Alternatives to the Pt cathodes frequently used in PCFC research are explored in comparison with screen-printed PEDOT:PSS cathodes. The fabricated ZnO/carbon anode (1.5 × 2 cm2) is used to remove the model pollutant used here and salicylic acid from water (30 mL, 70 μM) is placed under simulated sunlight (0.225 Sun). It was observed that salicylic acid was degraded by 23 ±0.46% at open voltage (OV) and 43.2 ± 0.86% at 1 V with Pt as the counter electrode, degradation was 18.5 ± 0.37% at open voltage (OV) and 44.1 ± 0.88% at 1 V, while PEDOT:PSS was used as the counter electrode over 120 min. This shows that the PEDOT:PSS exhibits an excellent performance with the full potential to provide low-environmental-impact electrodes for PCFCs. 

Laser-induced graphitization (LIG) is a method of converting a carbon-rich precursor into a highly conductive graphite-like carbon by laser scribing. This method has shown great promise as a versatile and low-cost patterning technique. Here we show for the first time how an ink based on cellulose and lignin can be patterned using screen printing followed by laser graphitization. Screen printing is one of the most commonly used manufacturing techniques of printed electronics, making this approach compatible with existing processing of various devices. The use of forest-based materials opens the possibility of producing green and sustainable electronics. Pre-patterning of the ink enables carbon patterns without residual precursor between the patterns. We investigated the effect of the ink composition, laser parameters, and additives on the conductivity and structure of the resulting carbon and could achieve low sheet resistance of 3.8 Ω sq-1 and a high degree of graphitization. We demonstrated that the process is compatible with printed electronics and finally manufactured a humidity sensor which uses lignin as the sensing layer and graphitized lignin as the electrodes.

Paper machine manufacturing of photocatalysts can enable low cost devices for removal of low concentratedpollutants. Lateral variations originating from the paper making process leads to variations of the catalyticactivity over the paper area. Paper machine manufactured papers made from tetrapodal ZnO whiskers and kraftpulp were investigated in this test geometry using simulated solar light. Photocatalytic ZnO papers were laminatedbetween polyethylene sheets and an indicator solution seeped into the laminated photocatalytic paper, tocreate a test geometry where the indicator ink is confined to a small volume between the polyethylene sheets.The photocatalyst papers exhibited surprisingly similar photocatalytic behavior although having different catalystloading 15, 30 and 45 wt percent. All papers exhibited lateral variations that peaked during the conversion.The results show that production of effective photocatalytic composite papers can be scaled.Further, the results show that variations must be considered for photocatalytic papers.

There is an increasing demand for compact, reliable and versatile sensor concepts for pH-level monitoring within several industrial, chemical as well as bio-medical applications. Many pH sensors concepts have been proposed, however, there is still a need for improved sensor solutions with respect to reliability, durability and miniaturization but also for multiparameter sensing. Here we present a conceptual verification, which includes theoretical simulations as well as experimental evaluation of a fiber optic pH-sensor based on a bio-compatible pH sensitive material not previously used in this context. The fiber optic sensor is based on a Mach-Zehnder interferometric technique, where the pH sensitive material is coated on a short, typically 20-25 mm thin core fiber spliced between two standard single mode fibers. The working principle of the sensor is simulated by using COMSOL Multiphysics. The simulations are used as a guideline for the construction of the sensors that have been experimentally evaluated in different liquids with pH ranging from 1.95 to 11.89. The results are promising, showing the potential for the development of bio-compatible fiber optic pH sensor with short response time, high sensitivity and broad measurement range. The developed sensor concept can find future use in many medical- or bio-chemical applications as well as in environmental monitoring of large areas. Challenges encountered during the sensor development due to variation in the design parameters are discussed. © 2019 by the authors.

A study has been made of the production of zinc oxide (ZnO) paper in a pilot paper machine. Bleached sulphate softwood pulp (70%) and bleached sulphate hardwood pulp (30%) were corefined. Cationic polyacrylamide (CPAM) was used as retention agent, while alkyl ketene dimer (AKD) was used as sizing agent for some samples. Some papers were screen printed with a conducting carbon-based ink to produce a photosensor device. Two methods were used to study the photocatalysis: immersing ZnO papers into kongo red dispersions or resazurin (Rz) based photocatalyst activity indicator ink and exposing the papers to ultraviolet (UV) light in a sunlight simulator. ZnO papers of approximately 60gsm were successfully produced on the pilot scale machine, which was run at a low speed (100m/min) and the retention of ZnO particles was good in all samples. The paper looked like an ordinary white printing paper product, but was a truly interactive material, exhibiting photoconductivity and enabling use as an excellent photosensor.

Environmental monitoring of land, water and air, is an area receiving greater attention because of human health and safety concerns. Monitoring the type of pollution and concentration levels is vital, so that appropriate contingency plans can be determined. To effectively monitor the environment, there is a need for new sensors and sensor systems that suits these type of measurements. However, the diversity of sensors suitable for low, battery powered- and large area sensor systems are limited. We have manufactured and characterized a flexible pH sensor using laser processing and blade coating techniques that is able to measure pH between 2.94 and 11.80. The sensor consists of an interdigital capacitance with a pH sensitive hydrogel coating. Thin sensors can reach 95% of their final value value within 3 min, and are stable after 4 min. Good repeatability was achieved in regard to cycling of the sensor with different pH and multiple measurements from dry state. We have also studied the relation between an interdigital capacitance penetration depth and hydrogels expansion. We believe that our passive sensor is suitable to be used in low power and large area sensor networks.

The concept of monolithic integration of electrochemical energy storage modules was tested on serially connected supercapacitor cells balanced by passive resistive dissipation. Five electrode pairs with collectors, interconnects, corrosion protection layers, electrode material and shunt resistors were printed on a single substrate. The printed patterns, lamination film, and a hot-sealing tool were designed so that upon folding, lamination, and electrolyte filling and sealing, five serial cells were formed with each having a shunt resistance. In an open circuit idling period following charge and discharge, the standard deviation of the individual cell voltages decreased, demonstrating the balancing function of this so called “modulit”, a short term proposed for a monolithically integrated electrochemical energy storage module.

The ability of acryl-terminated oligo(beta-amino esters) (AOBAE) to be coated on fibers and printed electronics without solvents and to be cross-linked to a pH-responsive coatings, makes AOBAE-based coatings a potential type of pH-sensor coating. However, there are currently no reports of AOBAEs used as a pH-responsive coating material in sensor applications. Here we present an investigation of the synthesis, curing behavior and swell tests of AOBAEs. AOBAEs were synthesized from reacting an excess of asymmetric diacrylates with piperazine without the use of any solvents. They were then cross-linked to an insoluble network by UV-curing. Nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy were used to characterize the AOBAEs. NMR was used to clarify the irregular structure of the AOBAE. FTIR was used to monitor the effects of UV-curing dose and air exposure on monomer conversion during curing. An interferometric technique was used to monitor the swelling behavior of the coating in response to pH variations. Swell experiments showed that the AOBAE also responded to pH variations after polymerization. Therefore, AOBAE is an interesting class of material with potential use as a pH responsive coating in optical-and printed electronics pH-sensors applications.

Cell voltage equalizers are an important part in electric energy storage systems comprising series-connected cells, for example, supercapacitors. Hybrid electronics with silicon chips and printed devices enables electronic systems with moderate performance and low cost. This paper presents a silicon-organic hybrid voltage equalizer to balance and protect series-connected supercapacitor cells during charging. Printed organic electrochemical transistors with conducting polymer poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) are utilized to bypass excess current when the supercapacitor cells are fully charged to desired voltages. In this study, low-cost silicon microcontrollers (ATtiny85) are programmed to sense voltages across the supercapacitor cells and control the organic electrochemical transistors to bypass charging current when the voltages exceed 1 V. Experimental results show that the hybrid equalizer with the organic electrochemical transistors works in dual-mode, switched-transistor mode or constant-resistor mode, depending on the charging current applied (0.3-100 mA). With the voltage equalizer, capacitors are charged equally regardless of their capacitances. This work demonstrates a low-cost hybrid solution for supercapacitor balancing modules at large-scale packs.