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In the realm of electrochemical nitrite detection, the potent oxidizing nature of nitrite typically necessitates operation at high detection potentials. However, this study introduces a novel approach to address this challenge by developing a highly sensitive electrochemical sensor with a low reduction detection potential. Specifically, a copper metal nanosheet/carbon paper sensitive electrode (Cu/CP) was fabricated using a one-step electrodeposition method, leveraging the catalytic reduction properties of copper's high occupancy d-orbital. The Cu/CP sensor exhibited remarkable performance in nitrite detection, featuring a low detection potential of −0.05 V vs. Hg/HgO, a wide linear range of 10~1000 μM, an impressive detection limit of 0.079 μM (S/N = 3), and a high sensitivity of 2140 μA mM−1cm−2. These findings underscore the efficacy of electrochemical nitrite detection through catalytic reduction as a means to reduce the operational voltage of the sensor. By showcasing the successful implementation of this strategy, this work sets a valuable precedent for the advancement of electrochemical low-potential nitrite detection methodologies. [ABSTRACT FROM AUTHOR]

Lithium–sulfur (Li–S) batteries are expected to be one of the next generations of high-energy-density battery systems due to their high theoretical energy density of 2600 Wh kg−1. Embracing the trends toward flexibility, lightweight design, and cost-effectiveness, paper-based electrodes offer a promising alternative to traditional coated cathodes in Li–S batteries. Within paper-based electrodes, conductive fibers such as carbon nanotubes (CNTs) play a crucial role. They help to form a three-dimensional network within the paper matrix to ensure structural integrity over extended cycling while mitigating the shuttle effect by confining sulfur within the cathode. Herein, we explore how variously functionalized CNTs, serving as conductive fibers, impact the physical and electrochemical characteristics of paper-based sulfur cathodes in Li–S batteries. Specifically, graphitized hydroxylated carbon nanotubes (G-CNTs) exhibit remarkable capacity at low currents owing to their excellent conductivity and interaction with lithium polysulfide (LiPS), achieving the highest initial specific capacity of 1033 mAh g−1 at 0.25 C (1.1 mA cm−2). Aminated multi-walled carbon nanotubes (NH2-CNTs) demonstrate an enhanced affinity for LiPS due to the -NH2 groups. However, the uneven distribution of these fibers may induce electrode surface passivation during charge–discharge cycles. Notably, hydroxylated multi-walled carbon nanotubes (OH-CNTs) can establish a uniform and stable 3D network with plant fibers, showcasing superior mechanical properties and helping to mitigate Li2S agglomeration while preserving the electrode porosity. The paper-based electrode integrated with OH-CNTs even retains a specific capacity of approximately 800 mAh g−1 at about 1.25 C (5 mA cm−2), demonstrating good sulfur utilization and rate capacity compared to other CNT variants. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor for paraquat determination was facilely developed using nanocomposites of cellulose incorporated with manganese oxide (MnO2@cellulose) modified screen-printed carbon electrode (SPCE). In this study, SPCE was fabricated on a low-cost poster paper, and nanocellulose from sugarcane bagasse was employed to enhance the electrode's surface area and improve the dispersion of MnO2. The MnO2@cellulose modified poster-SPCE exhibited a high electrochemical response toward paraquat. Various influencing factors, including differential pulse voltammetric parameters and accumulation time, were systematically explored. Under the optimal conditions, the cathodic peak current was linearly proportional to paraquat concentration in a range of 2 to 200 µM, featuring a low detection limit of 1 µM. The proposed sensor offers cost-effectiveness and can be readily prepared via a simple procedure. Moreover, this method exhibits excellent reproducibility, high selectivity, and a short analysis time. The portable electrochemical sensor was able to determine paraquat in water samples with acceptable recoveries from 95.45 to 109.20%, indicating that the sensor based on MnO2@cellulose/SPCE is reliable for paraquat quantification. [ABSTRACT FROM AUTHOR]

Paper-based electrochemical sensors have the characteristics of flexibility, biocompatibility, environmental protection, low cost, wide availability, and hydropathy, which make them very suitable for the development and application of biological detection. This work proposes electrospun cellulose acetate nanofiber (CA NF)-decorated paper-based screen-printed (PBSP) electrode electrochemical sensors. The CA NFs were directly collected on the PBSP electrode through an electrospinning technique at an optimized voltage of 16 kV for 10 min. The sensor was functionalized with different bio-sensitive materials for detecting different targets, and its sensing capability was evaluated by CV, DPV, and chronoamperometry methods. The test results demonstrated that the CA NFs enhanced the detection sensitivity of the PBSP electrode, and the sensor showed good stability, repeatability, and specificity (p < 0.01, N = 3). The electrochemical sensing of the CA NF-decorated PBSP electrode exhibited a short detection duration of ∼5–7 min and detection ranges of 1 nmol mL−1–100 μmol mL−1, 100 fg mL−1–10 μg mL−1, and 1.5 × 102–106 CFU mL−1 and limits of detection of 0.71 nmol mL−1, 89.1 fg mL−1, and 30 CFU mL−1 for glucose, Ag85B protein, and E. coli O157:H7, respectively. These CA NF-decorated PBSP sensors can be used as a general electrochemical tool to detect, for example, organic substances, proteins, and bacteria, which are expected to achieve point-of-care testing of pathogenic microorganisms and have wide application prospects in biomedicine, clinical diagnosis, environmental monitoring, and food safety. [ABSTRACT FROM AUTHOR]

• Preparation of ZIF-67/PEDOT/CP self-supporting electrodes using simple in situ hydrothermal. • The addition of PEDOT to ZIF-67 helps to achieve high electrical conductivity and large specific surface area. • The sensor has a high detection performance for CGA. • ZIF-67/PEDOT/CP provided a new sensor for the detection of CGA in real sample. The design of efficient electrocatalysts for the determination of chlorogenic acids (CGA) is crucial in the biological and medical fields. In this paper, ZIF-67/poly(3,4-ethylenedioxythiophene) (PEDOT) nanocomposites were synthesised. The introduction of PEDOT increased the electrical conductivity of the ZIF-67/PEDOT composites, inhibited the Co atom agglomeration, led to the exposure of more active sites and increased the transport channels. An ultrasensitive CGA sensor based on ZIF-67/PEDOT nanocomposite modified carbon paper (CP) electrode was developed. The nanomaterials were characterised using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction spectroscopy (XRD). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to study the electrochemical properties of the modified CP electrode. In addition, the effects of different experimental conditions such as pH, scan rate and concentration on the peak current of CGA were investigated. Under the optimised conditions, the linear range of ZIF-67/PEDOT/CP for the determination of CGA was 0.1 ∼ 40 μM, and the limit of detection (LOD) was as low as 0.003 μM (S/N = 3). Furthermore, the sensor was successfully used for the quantitative analysis of CGA in real samples. [ABSTRACT FROM AUTHOR]

The development of nanohybrid with high electrocatalytic activity is of great significance for electrochemical sensing applications. In this work, we develop a novel and facile method to prepare a high-performance flexible nanohybrid paper electrode, based on nitrogen-doped carbon (NC) wrapped Bi nanoparticles (Bi-NPs) assembly derived from Bi-MOF, which are decorated on a flexible and freestanding graphene paper (GP) electrode. The as-obtained Bi-NPs encapsulated by an NC layer are uniform, and the active sites are increased by introducing a nitrogen source while preparing Bi-MOF. Owing to the synergistic effect between the high conductivity of GP electrode and the highly efficient electrocatalytic activity of Bi-NPs, the NC wrapped Bi-NPs (Bi-NPs@NC) modified GP (Bi-NPs@NC/GP) electrode possesses high electrochemically active area, rapid electron-transfer capability, and good electrochemical stability. To demonstrate its outstanding functionality, the Bi-NPs@NC/GP electrode has been integrated into a handheld electrochemical sensor for detecting heavy metal ions. The result shows that Zn2+, Cd2+, and Pb2+ can be detected with extremely low detection limits, wide linear range, high sensitivity, as well as good selectivity. Furthermore, it demonstrates outstanding electrochemical sensing performance in the simultaneous detection of Zn2+, Cd2+, and Pb2+. Finally, the proposed electrochemical sensor has achieved excellent repeatability, reproducibility, stability, and reliability in measuring real water samples, which will have great potential in advanced applications in environmental systems. [ABSTRACT FROM AUTHOR]

The need for disposable, simpler, and accurate paper‐based analytical devices represents an open research field that is focused on simpler fabrication methods. To achieve this, four feasible methodologies are proposed for the direct printing of an electrochemical sensor on a biodegradable paper substrate using commercial gold and silver inks, which are compatible with inkjet printing technology. Four substrate treatment strategies are evaluated: printing the active elements directly on the hydrophilic bare paper, a hydrophobic gas‐phase coating over all the substrate, a hydrophobic silane ink that is selectively printed on the paper, and a hydrophobic coating that is selectively printed and blocks the surface porosity. Thanks to the ability of the inks to conform the cellulose fibers, the resulting working electrodes tune their electrochemical active area, showing higher active electrochemical areas when the roughness is increased. The most planar consideration is achieved blocking the paper porosity with SU‐8 and the direct printing on bare paper maximizes the electrochemical response with the smallest geometric area, with current values 2.7‐times higher than the theoretical one. Although all methods allow a functional electrochemical sensor, the highest reproducible results are accomplished with the blocked paper, consequently allowing a higher controlled and robust manufacturing approach. [ABSTRACT FROM AUTHOR]

Herein, we evaluated the use of paper towel, waxed paper, and Parafilm M® (Heathrow Scientific, Vernon Hills, IL, USA) as alternative substrates for screen-printed sensor manufacturing. Morphological study was performed to evaluate the adhesion of the ink on these uncommon substrates, as well as the morphology of the working electrode. The electrochemical characterization was carried out using ferricyanide/ferrocyanide as redox couple. To enhance the electrochemical properties of the developed sensors, the nanomaterial carbon black was used as nanomodifier. The modification by drop casting of the working electrode surface, using a stable dispersion of carbon black, allows to obtain a sensor with improved electrochemical behavior in terms of peak-to-peak separation, current intensity, and the resistance of charge transfer. The results achieved confirm the possibility of printing the electrode on several cost-effective paper-based materials and the improvement of the electrochemical behavior by using carbon black as sustainable nanomaterial. [ABSTRACT FROM AUTHOR]

The effective integration of nanomaterials with underlying current collectors is a key factor affecting the performance of nonenzymatic glucose sensors, where an inappropriate integration structure often leads to poor electron transport and instability. In this work, a seamless integrated electrode was constructed by the in situ immobilizing of a nickel-based metal-organic framework (Ni-MOF) on a three-dimensional (3D) conductive nickel foam (NF) for highly sensitive and durable glucose sensing. Facilitated by a rapid microwave-assisted reaction, a robust interfacial interaction between the Ni-MOF and the substrate was established through in situ conversion from nickel oxide (NiO). The fabricated Ni-MOF/NF electrode exhibits an excellent limit of detection (LOD) of 2.65 μM and an impressive sensitivity (14.31 mA cm-2 mM-1) within the linear range (4-576 μM), which is significantly boosted compared with that of an electrode prepared by a typical drop-casting method (3.56 mA cm-2 mM-1 in 4-1836 μM). Characterization and electrochemical tests reveal that this integrated structure on the one hand contributes to fast electron transport and thus has enhanced sensitivity and on the other hand leads to exceptional durability with its structural integrity maintained under bending, shaking, and ultrasonication. Moreover, this seamless integration method was also employed to immobilize the Ni-MOF converted from the pre-chemically deposited NiO layer on another type of substrate, 3D carbon paper (CP), demonstrating the versatility of this facile strategy in creating diverse electrochemical electrodes for applications beyond glucose sensing. [ABSTRACT FROM AUTHOR]

The fabrication of the Screen‐Printed Electrode (SPE) was performed using the graphite ink to print the working (WE) and counter electrodes (CE), and silver/silver chloride path as reference electrode (RE). All the electrodes are printed in a paper substrate using screen‐printing technique. The resulting SPE is characterized using scanning electron microscopy, showing all the ink layer, and subsequently optimized. The paper sample presented the cellulose fibers entanglement, extremely rough, with highly porous network. Then the graphite ink was deposited and the surface became flat, thinner and very smooth. When the silver ink was painted on top of the graphite ink, the spherical silver particles, ranged from 2–3.5 μm in size, were observed. And finally, the silver ink was covered with a AgCl layer and the particle size becomes larger with an irregular sphere‐like phase. The images showed that the layers appear to be homogeneously distributed with good coverage. Then fabrication process was optimized concerning type of paper, the sanding process, the hydrophobic barrier, the electrode design and size. In summary, the optimized values included using the previously sanded matte paper with a mineral spirit layer. The design and size of the electrode were also tested to achieve the best electrochemical performance (design 3 with 3.5 cm). The final SPE was a miniaturized and flexible paper‐based electrochemical electrode. In order to evaluate the electrical properties, the ohmic resistance of each ink was tested using a multimeter and the obtained values were 2.18 kΩ for the graphite ink, 2.27 Ω for the silver ink and 38.33 kΩ for the silver/silver chloride ink. That can indicate the good conductivity of each ink used in the fabrication of the electrode and the correct deposition of Ag/AgCl. Finally, the electrode was used to measure the electrochemical response of K4[Fe(CN)6] in different concentrations. Then a calibration curve was obtained from the voltammograms and a linearity was observed between the current and concentration in the range of 0.50–2.00 mM. That indicates that the SPE has potential to be used as a voltammetric electrode. [ABSTRACT FROM AUTHOR]

Laser irradiation to induce networks of graphene-based structures toward cost-effective, flexible device fabrication is a highly pursued area, with applications in various polymeric substrates. This work reports the application of this approach toward commonly available, eco-friendly, low-cost substrates, namely, chromatographic and office papers. Through an appropriate chemical treatment with sodium tetraborate as a fire-retardant agent, photothermal conversion to porous laser-induced graphene (LIG) on paper is achieved. Raman peaks are identified, with I2D/IG and ID/IG peak ratios of 0.616 ± 0.095 and 1.281 ± 0.173, showing the formation of multilayered graphenic material, exhibiting sheet resistances as low as 56.0 Ω sq-1. Coplanar, LIG-based, three-electrode systems (working, counter and reference electrodes) are produced and characterized, showing high current Faradaic oxidation and reduction peaks, translating in high electrochemical active area, doubling the geometric area. Good electron transfer kinetics performed exclusively with on-chip measurements are reached, with k0 values as high as 7.15 x 10-4 cm s-1. Proof-of-concept, amperometric, enzymatic glucose biosensors are developed, exhibiting good analytical performance in physiologically relevant glucose levels, with results pointing to the applicability of paper-based LIG toward efficient, disposable electrochemical sensor development, increasing their sustainability and accessibility, while simplifying their production and reducing their cost. [ABSTRACT FROM AUTHOR]

Abstract With the legalization of recreational cannabis use, there is a need to develop a rapid and accurate roadside test that can be used to analyze human saliva samples for Δ9-tetrahydrocannabinol (THC), the main psychoactive ingredient in cannabis. Here we demonstrate a novel drug detection method where THC is infused into carbon paper electrodes followed by electrochemical detection in a pH 10 aqueous solution. This method produces a linear, sensitive (down to ∼ 1 pmol), dose-dependent change in the oxidation peak current that varies with THC surface densities. These results, as well as the peak charge per real carbon surface area and linear current/scan-rate dependence, support a model for the distribution of THC on the carbon surface in a thin-layer configuration, facilitating the oxidation of the deposited drug. We also demonstrate electro-oxidation of the two major metabolites of THC, the psychoactive 11-hydroxy-tetrahydrocannabinol (OH-THC), and the non-psychoactive 11-nor-9-carboxy-tetrahydrocannabinol (COOH-THC), that also produce linear, dose-dependent changes in peak charge. However, COOH-THC exhibits a much lower Faradaic efficiency than OH-THC and THC, suggesting that variations in the THC functional groups affect the electro-oxidation of the cannabinoids. Overall, this work illustrates a novel, reproducible, and sensitive method for the analysis of THC and oxidation properties of its common metabolites that could be adapted for use with human saliva samples in future work. [ABSTRACT FROM AUTHOR]

Electrochemical dilatometry is used to investigate Li plating/stripping on Cu foil and porous carbon paper substrates. Experiments are performed in standard electrolyte for Li–S batteries at a current density of 1 mA cm−2 with a Li plating charge fixed at 1 mAh cm−2. A fully dense Li film (4.8 μm thick) is initially electrodeposited on the Cu electrode. However, from the 2nd Li plating/stripping cycle, Li deposit becomes porous to reach a thickness of 9.6 µm at the 27th cycle, corresponding to a film porosity of 50%, favoring its collapse during the subsequent cycles. When a carbon paper with a low surface area (0.02 m2 g−1) is used as a substrate, Li deposition occurs preferentially in the pores of the carbon paper during the first few cycles. However, this does not prevent the formation of Li dendrites, which progressively extend on the top of the substrate, resulting in the degradation of the electrode cyclability after about 40 cycles. The use of a carbon paper with a higher surface area (4.2 m2 g−1) favors Li deposition inside the electrode, with no apparent loss of cyclability after 50 cycles. However, this does not prevent the formation of dead Li, as suggested by the continuous and irreversible expansion of the electrode over cycling at a mean rate of 1.3 μm per cycle. Additionally, a large and irreversible expansion of 38 μm is observed during the first cycle, which is attributed to the lithium-solvent co-intercalation in the graphitic part of the carbon paper substrate. [ABSTRACT FROM AUTHOR]

• First use of graphite and polycaprolactone composite electrode for electrochemical study of NBOHs;. • Proposal of a mechanism for the oxidation of 25H-NBOH and 25B-NBOH using cyclic voltammetry. • Quantification of 25H-NBOH and 25B-NBOH in synthetic urine and blotting paper without the need for complex sample preparation. The dramatic escalation in the quantity of new synthetic drugs in recent years has prompted the pursuit of novel methods for identifying and quantifying these substances. Notably among them are the substituted phenethylamines known as NBOHs and NBOMes. Electrochemical study and quantification of new psychoactive substances (NPS) 25H-NBOH and 25B-NBOH in synthetic urine and synthetic blotting papers are presented using differential pulse voltammetry (DPV) on a composite electrode (CE) made of graphite and polycaprolactone (PCL). Based on the cyclic voltammetry (CV) results, we propose that the drug oxidation mechanism comprises two main steps. Initially, it involves the oxidation of the secondary amine, necessitating the removal of one electron from the amino-nitrogen atom, leading to dealkylation. Subsequently, bromine or methoxy substitution takes place. Under the optimized experimental conditions for the differential pulse voltammetry (DPV) studies, analytical curves were obtained in the range of 100 to 800 ng mL−1 for 25H-NBOH and 100 to 700 ng mL−1 for 25B-NBOH (r² = 0.999), with detection limits of 19 ng mL−1 and 23 ng mL−1, respectively, and quantification limits of 64 ng mL−1 and 76 ng mL−1. The proposed method was employed for quantification of the drugs in synthetic urine and synthetic blotting papers, with recovery values between 95 % and 106 %, demonstrating no interference from the matrices. [Display omitted] [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) are, arguably, one of the most promising candidates for post-lithium ion battery era. The success of sodium-ion batteries is dependent on electrode materials developed. We reported here the facile preparation of carbonized filter paper decorated with Sn@C nanospheres as negative electrode materials for SIBs. The carbonized filter paper decorated with Sn@C nanospheres were obtained by in-situ carbonization of the cellulose paper fibers and the reduction of SnO 2 to metallic Sn which were encapsulated with carbon sheaths by chemical vapor deposition (CVD). Particularly, both the carbon sheaths and the encapsulated Sn cores are spherical. The formation mechanism of the spherical Sn@C nanospheres was proposed based on unique properties of molten tin with high surface tension forming spherical droplets. The carbonized filter paper decorated with Sn@C nanospheres in the form of slices can be directly assembled into electrochemical cells without any further treatment or additives. Higher capacities and better Coulombic efficiencies than that of bare carbonized filter paper were achieved. The mechanism of capacity fading was investigated systematically by cyclic voltammetry (CV) and post-test analysis. This understanding will be helpful to design better Sn based electrodes for SIBs. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li-S) batteries appear to be one of the most promising energy-storage devices owing to the unparalleled theoretical specific energy, relatively inexpensive price and abundant resources. Despite these attractive features, the practical performances of sulfur cathode still remain a lot of challenges, such as the electrical insulating nature of S and Li 2 S, huge volume change during cycling, notorious shuttle effect of lithium polysulfide intermediates (LiPSs), sluggish redox kinetics and construction of thick electrodes with high sulfur loading. Here, CoFe 2 O 4 nanoparticles anchored on the carbon nanotube (CNT) paper is proposed as free-standing sulfur host to address the issues. The cross-linking CNT network can serve as conductive matrix and accommodate volume change upon cycling simultaneously. Meanwhile, the CoFe 2 O 4 nanoparticles are capable of effectively anchoring LiPSs to suppress the shuttle effect and accelerating LiPSs conversion to boost redox kinetics. Moreover, the free-standing paper electrode without any binder is conducive to constructing stable cathode with high sulfur loading. In consequence, the well-designed S/CoFe 2 O 4 /CNT paper cathodes deliver impressive electrochemical performance, demonstrating an initial discharge capacity of 755.3 mAh g−1 and remaining a high reversible capacity of 642.6 mAh g−1 after 400 cycles at 2 C with an inconspicuous decay of 0.04% per cycle. The bimetallic oxide CoFe 2 O 4 nanoparticles anchored on the carbon nanotube paper is proposed as free-standing sulfur host with enhanced polysulfide trapping and catalytic effects for advanced Li-S batteries. [Display omitted] • Binder-free host realizes high sulfur loading and energy density for Li-S battery. • CoFe 2 O 4 /CNT paper inhibits the polysulfide shuttling via strong chemical interaction. • CNT-anchored CoFe 2 O 4 catalytically promotes the polysulfide conversion kinetics. • The Li-S battery with S/CoFe 2 O 4 /CNT cathode exhibits enhanced capacity and stability. [ABSTRACT FROM AUTHOR]

Arsenic contamination is widespread in water bodies and poses a significant risk to human health, thus developing a rapid and inexpensive in situ method for the detection of arsenic is urgently needed. In this study, a chitosan-catechol carbon paper electrode was fabricated by electrodeposition of chitosan on a conductive carbon paper and subsequential electro-oxidative grafting of catechol. This chitosan-catechol modified electrode demonstrated good performance in detecting trace amounts of arsenic, which is mainly due to the significantly amplification of oxidation signals generated by ferrocene (Fc) on chitosan-catechol hydrogel. The interaction of As(III) with quinone and semiquinone radicals results in the decrease of electronic transmission nodes. The modified electrode exhibited a good detection capability of low concentration As(III) with a detection limit 0.82 ppb by differential pulse voltammetry (DPV). In addition, the chitosan-catechol modified sensor has the merits of high reproducibility, durability and strong resistance to ionic interference. Further successful detection of As(III) in actual rice and soil samples suggests its good potential in the field of in situ detection. [Display omitted] • Modified paper sensor was constructed by catechol grafting without gold modification. • The redox of catechol allows a significant amplification of oxdation signals. • Modified paper sensor achieves a LOD of 0.82 ppb for As(III) detection. • Actual rice and soil samples can be analyzed by the modified paper sensors. [ABSTRACT FROM AUTHOR]

Globe Thistles-Like NiCo 2 S 4 and rGO grow on flexible paper for the detection of H 2 O 2. [Display omitted] • To paper as the basement, successfully developed a low cost and biodegradable flexible electrochemical sensor electrode materials. • NiCo 2 S 4 microspheres with unique globe thistles-like structure was prepared for the first time. • The NiCo 2 S 4 /rGO/FP electrode has high sensitivity, low LOD, and wide linear range. The Globe Thistles-Like (GTL) NiCo 2 S 4 nanostructures were supported on reduced graphene oxide modified filter paper (FP). The prepared GTL NiCo 2 S 4 /rGO/FP is investigated as a disposable and flexible electrode for the electrochemical detection of H 2 O 2 in alkaline media. Owing to the rich redox active sites, the synergistic effect between Co3+ and Ni2+, and the rapid electron transportation of substituting sulfur (S) for oxygen (O) in NiCo 2 O 4 , the GTL NiCo 2 S 4 /rGO/FP exhibits considerable enzyme-free H 2 O 2 sensing performance with wide linear H 2 O 2 ranging from 38.8 to 37306.8 μM, high sensitivity of 2.4326 mA mM−1 cm−2, and low detection limit of 0.08 μM. The GTL NiCo 2 S 4 /rGO/FP electrode has stable sensing performance and is highly selective toward analyte for physiological interfering species. The excellent electrochemical performance of GTL NiCo 2 S 4 /rGO/FP composite is attributed to the GTL structure of NiCo 2 S 4. By studying the hydrothermal reaction time, electrochemical active surface area, and hydrophilic-hydrophobic surfaces of GTL NiCo 2 S 4 /rGO/FP composite, the relationship between the microstructure and sensing performance of the composite was elucidated. Surely this study opens up new possibilities for the application of low-cost, biodegradable flexible electrode materials in wearable sensors in the near future. [ABSTRACT FROM AUTHOR]

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

Free standing electrodes have grabbed attention among the researchers around the globe due to its ease of fabrication, scale‐up and flexibility for stack development. In the present communication, we have described a novel approach to improve the areal capacitance of graphite fiber paper (GP) from 4.5 ×10−3 F cm−2 to 0.677 F cm−2 by surface modification. Surface functionalised graphite paper (Oxd‐GP) and its chemically reduced counterpart (Red‐GP) are explored as electrode materials for supercapacitors. The materials synthesized are structurally characterized by X‐ray diffraction (XRD), Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), Energy dispersive analysis of X‐rays (EDAX) and field emission scanning electron microscopy (FESEM). The electrochemical performance of the electrodes is assessed using cyclic voltammetry (CV), galvanostatic charge‐discharge (GC) analysis and electrochemical impedance spectroscopy (EIS) where both Oxd‐GP and Red‐GP exhibit appreciable areal capacitance while Red‐GP shows excellent cycle life over 2600 cycles. Red‐GP showed an increment in capacitance over 1000 cycles while attaining stability. This work suggests that modified graphite paper can be a low‐cost and free‐standing electrode for high performance energy storage devices. [ABSTRACT FROM AUTHOR]

Due to highly conducting and extraordinary stable nature, carbon based materials expand the arms of energy storage devices in terms of supercapacitor. Hence, emphasis has been made to use flexible and free-standing multi-walled carbon nanotubes (MWCNTs) bucky paper synthesized by chemical vapor deposition for electrochemical supercapacitive electrode. The high specific capacitance of 270 F/g (2 mV/s) with superb stable behavior (88% at 10000 cycles) of bucky paper has promised as decent electrode in energy storage application. Aqueous symmetric supercapacitor (ASSC) device developed through bucky paper exhibits voltage frame of 1.6 V yielding specific capacitance of 91 F/g along with specific energy of 32 Wh/kg at a current density of 1 mA/cm 2 with trustworthy stability of 107% at 6000 cycles. The hands-on practicability to light up a red LED offers its promising approach in energy storage domain. [ABSTRACT FROM AUTHOR]

Purified paper was prepared from UHT milk packaging waste and firstly applied as a novel electrochemical sensor by chemical modification using alkali treatment, whereas 0.25–1 g of aluminum foil was dissolved into solvent. The purified paper was then immersed into aluminum solution. The existence of aluminum was found on purified cellulose paper. The mapping experiment was reported the aluminum was uniformly distributed onto purified cellulose. It was thermally stable up to 200 °C. The surface roughness of conductive paper was found to be 20–30 micron. A significant conductivity enhancement of purified cellulose was caused by the presence of aluminum. 1 g of aluminum in solution provided the excellent electrochemical conductivity measured by both cyclic voltammetry and electrochemical impedance spectroscopy, verifying that this material might be an alternative candidate as a novel paper-based electrode in electrochemical sensor. [ABSTRACT FROM AUTHOR]

Abstract In this study, cathodic electrodeposition of manganese oxide onto reduced graphene oxide paper is carried out to prepare flexible and binder-free electrodes for electrochemical capacitors. Effects of electrodeposition potential and the amount of deposited mass on the electrochemical performance are examined. Hausmannite phase manganese oxide coated electrodes exhibit promising performance in charge-discharge and cyclic voltammetry measurements with specific capacitance of 546 F g−1 at current density of 0.5 A g−1 and 308 F g−1 at scan rate of 1 mV s−1, respectively. During potential cycling, phase transformation of Mn 3 O 4 to mixed-valent MnO x is observed. Consequently, MnO x nanostructures on self-standing reduced graphene oxide electrodes have 154% capacitance retention at 10000 cycles of cyclic voltammetry. Graphical abstract Image [ABSTRACT FROM AUTHOR]

This research introduces the design of a gas-diffusional cathode employing bilirubin oxidase (BOx) immobilized on a complex matrix composed of carbon nanotube (CNT) modified Toray paper (TP) and, encapsulated in silica-gel. The developed enzymatic cathode consists of two layers. One is the hydrophobic gas-diffusional layer (GDL) and the other a hydrophilic catalytic layer (CL) which were combined by pressing at 1000 psi for five minutes. The GDL (35% weight teflonized Vulcan carbon powder (XC35)) that is exposed to air has hydrophobic and porous properties that facilitate oxygen diffusion. The CL consists of a thin, high surface area, 3D CNT/silica-gel matrix where the 3D-enzymatic structure is immobilized and preserved. The nanostructured architecture of the CL was designed to improve conductivity and surface area. Such a design was achieved by modifying the TP surface with CNTs. CNTs are grown on TP by chemical vapor deposition which is possible by electrodepositing Ni seeds via pulse chronoamperometry. Entrapment of BOx was achieved by using tetramethyl orthosilicate (TMOS), a highly volatile compound that results in a polymeric condensation reaction with H2O at room temperature. TMOS polymerization of the cathode surface was performed in a chemical vapor deposition process to form a silica-gel matrix. The gas diffusional cathode was assembled to a capillary driven microfluidic system to be electrochemically characterized. The characterization was performed from electrolyte pH 5 to pH 8 with increments 0.5 in pH. The best performance was observed at pH 5.5 showing a current output of 655.07 ± 146.18 µA.cm-2 and 345.36 ± 30.04 µA.cm-2 at 0 V and 0.3 V, respectively. At a pH of 7.5 the current generated was 287.05 ± 20.37 µA.cm-2 and 205.37 ± 1.57 µA.cm-2 at 0 V and 0.3 V, respectively. The results show the stability of the enzymatic structure, subject to various pH, is maintained within the 3D-CNT silica-gel matrix for pH lower than 8. Future work will focus on storage life and stability over time. [ABSTRACT FROM AUTHOR]

Current 3D printed electrodes suffer from insufficient multiscale transport speed, which limits the improvement of electrochemical performance of 3D printed electrodes. Herein, a bioinspired hierarchical fast transport network (HFTN) in a 3D printed reduced graphene oxide/carbon nanotube (3DP GC) electrode demonstrating superior electrochemical performance is constructed. Theoretical calculations reveal that the HFTN of the 3DP GC electrode increases the ion transport rate by more than 50 times and 36 times compared with those of the bulk GC electrode and traditional 3DP GC (T‐3DP GC) electrode, respectively. Compared with carbon paper, carbon cloth, bulk GC electrode, and T‐3DP GC electrode, the HFTN in 3DP GC electrode endows obvious advantages: i) efficient utilization of surface area for uniform catalysts dispersion during electrochemical deposition; ii) efficient utilization of catalysts enables the high mass activity of catalysts and low overpotential of electrode in electrocatalytic reaction. The cell of 3DP GC/Ni‐NiO||3DP GC/NiS2 demonstrates a low voltage of only 1.42 V to reach 10 mA cm−2 and good stability up to 20 h for water splitting in alkaline conditions, which is superior to commercialized Pt/C||RuO2. This work demonstrates great potential in developing high‐performance 3D printed electrodes for electrochemical energy conversion and storage. [ABSTRACT FROM AUTHOR]

Abstract: Modification of cellulosic paper with carbon nanotubes (CNT) was studied for the development of electronic and analytical devices. Interesting results were published by using a CNT aqueous solution and the capillary forces of filter paper to make conductive tracks, supercapacitors, potentiometric electrodes and chemometric sensors. In this report, we show for the first time an electrochemical characterization of CNT‐CS‐SDS paper electrodes constructed with an ink containing optimized proportions of multi‐wall CNT, chitosan (CS) and sodium dodecyl sulfate (SDS), and we compared our data with CNT‐SDS paper electrodes constructed with a previously reported ink. We achieved better reversibility (ΔE=131±14 mV, CVs) and reproducibility (RSD=3.63 %) with CNT‐CS‐SDS paper electrodes, when compared to CNT‐SDS paper electrodes (ΔE=249±7 mV; RSD=6.8 %) used as controls. When electrodes were fold at 90° angle, CNT‐CS‐SDS paper electrodes showed lower RSD than CNT‐SDS paper electrodes, 8.43 % and 21.5 % respectively. These results are in concordance with SEM analysis indicating a dense CS film in CNT‐CS‐SDS paper electrodes. As a proof of concept, we determine dopamine concentration by DPV in the presence of ascorbic and uric acids, the limit of detection calculated was 6.32 μM. Moreover, a bismuth‐film was prepared by in situ plating of Bi into CNT‐CS‐SDS paper electrodes. ASV allowed us to detect Pb in the presence of Bi (10–200 ppb) with a limit of detection of 6.74 ppb. [ABSTRACT FROM AUTHOR]

• In-situ growth of MoS 2 over MnCO 3 inhibits formation of Mn-oxides/hydroxide. • MnCO 3 transforms to Mn(OH) 2 in aqueous KOH and stores charge by redox processes. • Mn(OH) 2 and MoS 2 afford low diffusion and charge transfer resistances, respectively. • MnCO 3 @MoS 2 hybrid utilized as negative electrode in asymmetric supercapacitor. This article puts forward a novel approach of combining the battery-type charge storage material, Mn(OH) 2 , indirectly with the two-dimensional material, MoS 2 , to develop the composite MnCO 3 @MoS 2 (designated as MCMS). A single-step facile hydrothermal method is described here for the synthesis of MCMS on a low-cost graphite substrate. Furthermore, this as-synthesized binder-free electrode is utilized as the negative electrode of an all-solid state asymmetric alkaline supercapacitor, employing NiCo 2 O 4 as the high specific energy positive electrode material. The overall asymmetric cell is shown to achieve a high specific energy of 48.97 W.h.kg −1 at 600 W.kg −1 and a high specific power of 12 kW.kg −1 at 11.33 W.h.kg −1, within a potential window of 1.2 V. Also, the composite electrode notably retains 86.5% of its gravimetric discharge capacity after 10,000 cycles with complete retention of its coulombic efficiency. The present work contributes to the development of a facile strategy for the preparation of non-carbonaceous hybrid materials suitable for high specific energy negative electrodes. [ABSTRACT FROM AUTHOR]

Abstract: Paper‐based analytical devices, which are suited to point‐of‐care diagnostics and on‐site detection because of cheap price and portability, have attracted increasing attention for improving global health and in other applications. Here, we constructed one carbon nanotube paper‐based electrode (CNTPE) for the detection of neurochemicals in brain microdialysate. CNTPE was directly fabricated through filter depositing CNT dispersion onto the surface of filter paper. The fabricated CNTPE have good electrochemical performance with advantage of CNT, which not only facilitate ascorbic acid (AA) oxidation, also could as a good platform to functionalize. As a proof, we demonstrate that the CNTPE act as electrode to detect AA directly and detect glucose with further modified CNTPE through electrodeposited Prussian blue (PB). The results show that the easily prepared CNTPE can be used for the selective measurement of AA without interference from dopamine and other electrochemical active substances; what's more, PB and glucose oxidase (GOx) modified CNTPE has good performance towards the specific detection of glucose. Therefore, we believe that CNTPE would have great potential application in detection of chemicals to understand the function of brain. [ABSTRACT FROM AUTHOR]

A simple and inexpensive procedure of paper-based electrode (PE) fabrication using A4 size conventional paper, nail polish and carbon powder is reported. The device was prepared by spreading the carbon conductive ink directly onto the paper substrate using a paint-brush. The best composition of the conductive ink was 80:20% (m:m) carbon powder: nail polish and the best device was obtained with 100 mg (2.5 mg cm −2 ) of carbon conductive ink spread on the paper piece. The proposed device showed satisfactory stability in acidic, neutral and alkaline medium in presence of ferrocyanide ion used as electrochemical probe. Dopamine was selected as a target compound to evaluate the possibility of using the proposed device for electroanalytical purposes. Differential pulse voltammetry was used in these studies and dopamine detection was achieved at +0.13 V vs. Ag/AgCl sat in phosphate buffer solution pH = 7 with a detection limit of 5.2 μmol L −1 . The proposed device represents an interesting advance in the field of PE construction since it combines satisfactory electrochemical stability and electroanalytical performance with simplicity and widely available low-cost materials. Moreover, chemical modifiers can be easily added to the conductive ink. Therefore, this versatile device brings exciting possibilities for future electroanalytical applications mainly for those that require small and/or flexible devices, such as the amperometric detection in microfluidic systems. [ABSTRACT FROM AUTHOR]

This paper demonstrates, for the first time, the use of paper-based electrochemical devices coupled to external solid working electrodes. The paper-based electrochemical cells were fabricated using inexpensive and largely available office paper, according to a simple protocol that consists on the creation of hydrophobic barriers using paraffinized paper and preheated metal stamp. The counter and reference electrodes were integrated to the paper platform through the deposition of carbon and silver inks, respectively. The electrochemical paper analytical device (ePAD) was coupled to external glassy carbon rod electrode modified with reduced graphene oxide doped with Cu nanoparticles through meniscus configuration. The analytical usefulness of this electrochemical approach was demonstrated through the simultaneous determination of paracetamol and caffeine in biological samples. The analytes were successfully quantified in real urine samples and limits of detection of 24.6 nM (paracetamol) and 36.1 nM (caffeine) were obtained. The paper platform showed good stability (RSD of 1.07 % for the peak currents and 1.43 % for the peak potentials) and satisfactory performance. The use of solid electrodes coupled to paper electrochemical devices, firstly demonstrated here, opens new possibilities for the utilization of ePADs in electrochemistry and electroanalytical chemistry and offers advantages such as the extremely reduced consumption of reagents and the minimal generation of wastes. [ABSTRACT FROM AUTHOR]

In this work, MgAl-layered double hydroxide nanosheets arrays in-situ grown on commercial carbon paper (MA-LDH/CP) have been successfully fabricated via a facile one-pot hydrothermal method, which shows a hierarchical flower-like structure. The as-prepared MA-LDH/CP is used as a free-standing electrode for electrochemical detection of nitrite in aqueous media, showing high sensitivity with a low detection limit of 0.03 μM, and good anti-interference to other species. Moreover, it exhibits outstanding electrochemical stability without any deactivation in almost two months. The superior performance of MA-LDH/CP for nitrite determination is attributed to the 3D hierarchical architecture of MA-LDH nanolayers and a large number of exposed surface sites, which facilitate the electron transfer and nitrite adsorption. Flower-like MgAl-layered double hydroxide nanosheets arrays grown on carbon paper have been successfully fabricated and used as high-performance free-standing electrode for electrochemical nitrite detection with high sensitivity, selectivity, and stability. Image 1 • MgAl-layered double hydroxide nanosheets arrays on carbon paper (MA-LDH/CP) is prepared via a facile hydrothermal method. • MA-LDH/CP serves as a free-standing electrochemical sensor for nitrite detection. • High sensitivity, stability, and anti-interference to other species toward nitrite sensing are achieved. • 3D hierarchical architecture of MA-LDH enhances electrochemical active area, electron transfer, and nitrite adsorption. [ABSTRACT FROM AUTHOR]

In this paper, a facile and low-cost “pencil-drawing” method is exploited for writing electrodes on filter paper to fabricate an electrochemical paper-based analytical device. Unlike other techniques using inks or pastes, the three-electrode system can be prepared directly by drawing with nothing more than pencils and paper. The optimization using ferricyanide as the redox probe showed that the device fully drawn with 6B grade pencil possesses excellent electrochemical properties and sensor-to-sensor reproducibility in spite of its truly simple fabrication process. Experimental results demonstrated that the proposed device could be utilized for quantification of dopamine with high sensitivity and no interference from ascorbic acid and uric acid, which are normally present in biological fluids. Human urine and blood serum samples were analyzed using the proposed device as proof of concept. Such fully-drawn sensors are flexible, portable and disposable, represent a cheap and environmentally friendly approach that can be rapidly and easily fabricated without any specialized materials, affording great convenience for practical use in resource-limited or emergency situations. [ABSTRACT FROM AUTHOR]

In this article, we detail a paper-based three-electrode electrochemical biosensor using a mitochondria modified Toray carbon paper working electrode. Cyclic voltammetry performed on the paper-based biosensor and similar electrodes in a common laboratory setup (not in an integrated paper-based device) compare favorably. In addition, instant detection of malathion with a detection limit of 20 nM by cyclic voltammetry is demonstrated, showing the device can potentially be used as a portable platform for pesticides detection. [ABSTRACT FROM AUTHOR]

Electrochemical techniques are attractive for nitrite detection owing to their intrinsic advantages. However, traditional electrochemical sensors often suffer from the effects of fouling due to the adsorption of oxidation products on the electrode surface. In this work, a paper-based, inexpensive, disposable electrochemical sensing platform was developed for nitrite analysis based on a simple and efficient vacuum filtration system. Taking advantage of the physicochemical properties of graphene nanosheets and gold nanoparticles, the mass transport regime of nitrite at the paper-based electrode was thin layer diffusion rather than planar diffusion. In comparison with the electrochemical responses of commercial gold electrodes and glassy carbon electrodes (GCE), a considerably larger current signal was seen at the paper-based sensing interface, which significantly improved its sensitivity for nitrite detection. In particular, the paper-based electrode was a disposable sensing device, so that it effectively avoided the fouling effect arising from the adsorption of oxidation products. Moreover, the paper-based sensing platform made it possible to determine nitrite in environmental and food samples in an accurate, convenient, inexpensive, and reproducible way, indicating that the proposed system is promising for practical applications in environmental monitoring and public health. [ABSTRACT FROM AUTHOR]

A novel three-dimensional paper-based electrochemical impedance device (3D-PEID) is first introduced for measuring multiple diabetes markers. Herein, a simple 3D-PEID composed of a dual screen-printed electrode on wax-patterned paper coupled with a multilayer of magnetic paper was fabricated for label-free electrochemical detection. The results clearly demonstrated in a step-wise manner that the haptoglobin (Hp)-modified and 3-aminophenylboronic acid (APBA)-modified eggshell membranes (ESMs) were highly responsive to a clinically relevant range of total (0.5–20 g dL −1 ; r 2 = 0.989) and glycated haemoglobin (HbA1c) (2.3%–14%; r 2 = 0.997) levels with detection limits (S/N = 3) of 0.08 g dL −1 and 0.21%, respectively. The optimal binding frequencies of total haemoglobin and HbA1c to their specific recognition elements were 5.18 Hz and 9.99 Hz, respectively. The within-run coefficients of variation (CV) were 1.84%, 2.18%, 1.72%, and 2.01%, whereas the run-to-run CVs were 2.11%, 2.41%, 2.08%, and 2.21%, when assaying two levels of haemoglobin and HbA1c, respectively. The CVs for the haemoglobin and HbA1c levels measured on ten independently fabricated paper-based sheets were 1.96% and 2.10%, respectively. These results demonstrated that our proposed system achieved excellent precision for the simultaneous detection of total haemoglobin and HbA1c, with an acceptable reproducibility of fabrication. The long-term stability of the Hp-modified eggshell membrane (ESM) was 98.84% over a shelf-life of 4 weeks, enabling the possibility of storage or long-distance transport to remote regions, particularly in resource-limited settings; however, for the APBA-modified ESM, the stability was 92.35% over a one-week period. Compared with the commercial automated method, the results demonstrated excellent agreement between the techniques (p-value < 0.05), thus permitting the potential application of 3D-PEID for the monitoring of the glycaemic status in diabetic patients. [ABSTRACT FROM AUTHOR]

[Display omitted] • Computer numerical control printed disposable paper electrodes for electrochemical sensing. • Proof-of-concept demonstrated by detecting Pseudomonas aeruginosa virulence factor pyocyanin. • Satisfactory analytical performance and validated with gold standard. Disposable paper electrodes (PPE) have significant advantages in biosensor research considering the cost-effectiveness, simplicity, and easy batch manufacturing opportunity. An increase in communicable and non-communicable diseases demands for custom-made sensor platforms. Herein, we report an alternative method for the fabrication of PPE through simple and rapid computer numerical controlled (CNC) printing technique. The fabricated electrodes were electrochemically characterised, and by detecting antibiotic resistant pathogen, Pseudomonas aeruginosa virulence factor pyocyanin, the sensing application is demonstrated. Finally, the sensor is validated with a gold-standard culture-based assay. [ABSTRACT FROM AUTHOR]

We propose here a quick and easy procedure for preparing pencil leads doped with Ag and AgCl suitable for the reproducible and easy drawing on paper or other porous supports of carbon based Ag/AgCl conductive lines for the use as reference electrodes. They were prepared by careful electrodeposition of silver and silver chloride on carbon powder (conductive material) which was then mixed with sodium bentonite (binding agent) and sodium silicate (hardening agent). Extrusion at room temperature of these mixtures from a suitable die allowed thin rods to be obtained, which were then inserted in commercial lead holders to facilitate their use for drawing electrodes on paper. Their performance was evaluated by voltammetric measurements conducted by using hexacyanoferrate(II) and 1,2-hydroxybenzene as probe species known to display a reversible electrochemical behaviour. The results found pointed out that the potential exhibited by these drawn reference electrodes was fully reliable only when small but controlled amounts of chloride ions can be added to assayed samples, without interfering investigated processes. Conversely, a poorer reliability characterise these reference electrodes when chlorides cannot be added, in that they display potentials higher of about 100–150 mV than their theoretical value. Their reproducibility (± 0.02 V), controlled on a series of different PEDs wetted with the same sample, was however so narrow for voltammetric investigations as to make their use preferable to usual pseudo-reference electrodes whose potential is remarkably affected by the different components present in assayed samples. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li-S) batteries are a very appealing power source with extremely high energy density. But the use of a metallic-Li anode causes serious safety hazards, such as short-circuiting and explosion of the cells. Replacing a sulfur cathode with a fully-lithiated lithium sulfide (Li2S) to pair with metallic-Li-free high-capacity anodes paves a feasible way to address this issue. However, the practical utility of Li2S cathodes faces the challenges of poor conductivity, sluggish activation process, and high sensitivity to moisture and oxygen that make electrode production more difficult than dealing with sulfur cathodes. Here, an efficient but low-cost strategy for easy production of freestanding flexible Li2S-based paper electrodes with very high mass and capacity loading in terms of in situ carbonthermal reduction of Li2SO4 by electrospinning carbon is reported. This chemistry enables high loading but strong affinity of ultrafine Li2S nanoparticles in a freestanding conductive carbon-nanofiber network, meanwhile greatly reducing the manufacturing complexity and cost of Li2S cathodes. Benefiting from enhanced structural stability and reaction kinetics, the areal specific capacities of such cathodes can be significantly boosted with less sacrificing of high-rate and cycling capability. This unique Li2S-cathode design can be directly applied for constructing metallic-Li-free or flexible Li-S batteries with high-energy density. [ABSTRACT FROM AUTHOR]

An electrochemical paper-based analytical device (ePAD) was developed for quasi-steady flow detection at microwire electrodes, for the first time. The device implements a fan shaped geometry connected to an analysis channel whereby solution is pulled from an inlet, through a channel, and into the steadily increasing capillary network of the fan. The network counteracts the decrease in solution flow rate associated with increasing viscosity within the channel, generating quasi-steady flow within tlie analysis channel. Microwire electrodes were embedded between two paper layers within the analysis channel, such that solution flow occurred on both sides of the wire electrodes. The quasi-steady flow ePAD increased the current by 2.5 times and 0.7 times from a saturated channel with no flow and from a single-layer paper device with flow, respectively. Amperometric detection was used for flow injection analysis (FIA) of multiple analytes at both Au and Pt microwire working electrodes, both of which provided similar sensitivity (ca. 0.2 mM-1) when normalized to the same standard. The two-layer paper devices provided a detection limit of 31 μM for p-aminophenol (PAP) using Pt electrodes and was also used to detect enzyme activity for tlie reaction of β-galactosidase with p-aminophenyl-galactopyranoside (PAPG). Measured enzyme kinetics provided similar Vmax (0.079 mM/min) and Km (0.36 mM) values as those found in the literature. This device shows great promise toward use in enzyme-linked immunosorbent assays or other analytical techniques where flow or washing steps are necessary. The developed sensor provides a simple and inexpensive device capable of performing multiple injection analysis with steady-flow and online detection that would normally require an external pump to perform. [ABSTRACT FROM AUTHOR]

This work reports a new type of disposable electrochemical sensor for the determination of bisphenol A (BPA). The working electrodes were fabricated by sputtering gold nanoparticles on commercial art paper and then modifying the gold layer with multi-walled carbon nanotubes (MWCNTs). The electrode in their intermediated and final stage was characterized by atomic force microscope, scanning electron microscope and electrochemical techniques. To perform electrochemical analysis, the resulting electrode was integrated with a homemade paper-based analytical device, which could also ensure the immobilization of MWCNTs on the electrode surface without any functionalization. The determination of BPA was investigated by linear sweep voltammetry (LSV). A wide linearity in the range from 0.2 to 20 mg/L with a detection limit of 0.03 mg/L (S/N = 3) was obtained. The between-sensor reproducibility was 5.7% (n = 8) for 0.5 mg/L BPA. The proposed sensor showed good resistance against interferences and was applied to detect BPA leached from real plastic samples with satisfying results. This disposable sensor is readily mass-produced and has been verified to serve as an attractive alternative to screen-printed electrodes for practical applications. [ABSTRACT FROM AUTHOR]

The New Journal of Chemistry, published by The Royal Society of Chemistry and the Centre National de la Recherche Scientifique, contains a variety of articles on different topics in chemistry. The articles cover areas such as polydimethylsiloxane coatings, water oxidation, lithium-ion batteries, and photocatalytic reactions. The journal provides valuable insights for those interested in chemistry and covers a diverse range of research areas. The document is a list of research papers published in the journal Chemistry in 2024, including topics such as the electrocatalytic degradation of tetracycline, the construction of a supramolecular system for imaging nematic mesophase and nematode cells, insights into hydrogen bond strengths in microhydrated clusters, and the development of macrophage-red blood cell hybrid membranes for eliminating pathogens, endotoxins, and heavy metal ions from blood. [Extracted from the article]

Large-capacitance and ultrahigh-rate electrochemical supercapacitors (UECs) with frequency response up to kilohertz (kHz) range are reported using light, thin, and flexible freestanding electrodes. The electrode is formed by perpendicularly edge oriented multilayer graphene/thin-graphite (EOG) sheets grown radially around individual fibers in carbonized cellulous paper (CCP), with cellulous carbonization and EOG deposition implemented in one step. The resulted ∼10 μm thick EOG/CCP electrode is light and flexible. The oriented porous structure of EOG with large surface area, in conjunction with high conductivity of the electrode, ensures ultrahigh-rate performance of the fabricated cells, with large areal capacitance of 0.59 mF cm −2 and 0.53 mF cm −2 and large phase angle of −83° and −80° at 120 Hz and 1 kHz, respectively. Particularly, the hierarchical EOG/CCP sheet structure allows multiple sheets stacked together for thick electrodes with almost linearly increased areal capacitance while maintaining the volumetric capacitance nearly no degradation, a critical merit for developing practical faraday-scale UECs. 3-layers of EOG/CCP electrode achieved an areal capacitance of 1.5 mF cm −2 and 1.4 mF cm −2 at 120 Hz and 1 kHz, respectively. This demonstration moves a step closer to the goal of bridging the frequency/capacitance gap between supercapacitors and electrolytic capacitors. [ABSTRACT FROM AUTHOR]

The challenge of heavy metal detection for environmental, industrial and medical purposes has led to the development of many analytical techniques. Stripping voltammetry is a very sensitive electrochemical method and has been widely used for heavy metal detection. Carbon nanotubes, a well-studied carbon material with physical and chemical properties suited for electrode material is commonly employed for sensitive and selective metal detection in electrochemistry. This article reviews the recent (2011-2016) applications of carbon nanotubes as an electrode or electrode surface modifier for heavy metals detection with stripping voltammetry. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we demonstrate up to 30% increase in power density of carbon paper electrodes for vanadium redox flow batteries (VRFB) by introducing perforations into the structure of electrodes. A CO2 laser was used to generate holes ranging from 171 to 421 μm diameter, and hole densities from 96.8 to 649.8 holes cm−2. Perforation of the carbon paper electrodes was observed to improve cell performance in the activation region due to thermal treatment of the area around the perforations. Results also demonstrate improved mass transport, resulting in enhanced peak power and limiting current density. However, excessive perforation of the electrode yielded a decrease in performance due to reduced available surface area. A 30% increase in peak power density (478 mW cm−2) was observed for the laser perforated electrode with 234 μm diameter holes and 352.8 holes cm−2 (1764 holes per 5 cm2 electrode), despite a 15% decrease in total surface area compared to the raw un-perforated electrode. Additionally, the effect of perforation on VRFB performance was studied at different flow rates (up to 120 mL min−1) for the optimized electrode architecture. A maximum power density of 543 mW cm−2 was achieved at 120 mL min−1. [Copyright &y& Elsevier]

As the most promising anode material for sodium-ion batteries (SIBs), elemental phosphorus (P) has recently gained a lot of interest due to its extraordinary theoretical capacity of 2596 mAh/g. The main drawback of a P anode is its low conductivity and rapid structural degradation caused by the enormous volume expansion (>490%) during cycling. Here, we redesigned the anode structure by using an innovative methodology to fabricate flexible paper made of nitrogen-doped graphene and amorphous phosphorus that effectively tackles this problem. The restructured anode exhibits an ultrastable cyclic performance and excellent rate capability (809 mAh/g at 1500 mA/g). The excellent structural integrity of the novel anode was further visualized during cycling by using in situ experiments inside a high-resolution transmission electron microscope (HRTEM), and the associated sodiation/desodiation mechanism was also thoroughly investigated. Finally, density functional theory (DFT) calculations confirmed that the N-doped graphene not only contributes to an increase in capacity for sodium storage but also is beneficial in regards to improved rate performance of the anode. [ABSTRACT FROM AUTHOR]

• A molecularly imprinted conducting polymer-based electrochemical sensor was developed to determine 2,4-DCP. • Hydrogen bonding of analyte to conducting polymer was utilized for imprinting and the template was electrochemically removed. • MIP-PEDOT/CFP has exhibited high selectivity towards 2,4-DCP. • Effective sensor with nanomolar-level detection of 2,4-DCP in real water samples. A highly selective electrochemical sensor has been developed for the determination of the pesticide molecule, 2,4-dichlorophenol (2,4-DCP) using molecularly imprinted conducting polymer. 2,4-dichlorophenol imprinted polymer films were prepared by electropolymerising 3,4-ethylenedioxythiophene (EDOT) on surface of carbon fiber paper electrode (CFP) in presence of 2,4-dichlorophenol. Electrochemical over-oxidation was carried out for the controlled release of 2,4-DCP templates and to generate definite imprinting sites. Surface morphology of the imprinted electrode was analysed by Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometry, Fourier Transform Infrared and Raman spectroscopy. In optimized conditions, the voltammetric sensor gave a linear response in the range of 0.21 nM – 300 nM. The significantly low detection limit (0.07 nM) demonstrates the ultra-low sensitivity of the method. The imprinted sensor displayed higher affinity and selectivity towards the target 2,4-DCP over similar structural analogical interference than the non-imprinted sensor. MIP sensor was efficaciously employed for the selective determination of 2,4-DCP in real samples of water. [ABSTRACT FROM AUTHOR]

• Development of low-cost paper based disposable printed electrodes with silver nano-ink using desktop inkjet printer. • Fabricated paper electrode exploited as a counter electrode in cyclic voltammetry (CV) analysis. • Printed paper electrode is demonstrated to used as a working electrode for analysis of nitrate in CV. Development of low-cost paper based disposable electrodes printed with silver nano-ink using desktop inkjet printer is reported in this work. A stable nano-ink was prepared by dissolving 3% silver nanoparticles (AgNPs) capped with polyvinylpyrrolidone (PVP) in ethanol as a dispersing solvent. Highly stable silver nano-ink with surface tension of 21.1 mN/M and viscosity of 2.6 mPa.S was prepared for printing on photo paper that can be used as an electrode for electrochemical analyses. The fabricated paper electrode was exploited as a counter electrode in cyclic voltammetry (CV) analysis of potassium ferricyanide with better stability and reproducibility (relative standard deviation (RSD) 1.6%) for multiple times of analyses (n = 60) and compared with the results of conventional electrodes. Further, the printed paper electrode was demonstrated to be used as a working electrode for analysis of nitrate by CV. The use of paper electrode is found to be simple, rapid, user-friendly and can be applied at the sample source for determination of nitrate from different samples. [ABSTRACT FROM AUTHOR]

• A flexible Cobalt-based metal-organic frameworks/reduced graphene oxide (CoMOF/rGO) composite paper was prepared. • The characterization of the CoMOF/rGO composite paper was performed. • Finger-like long-chain structures on the as-prepared CoMOF/rGO composite paper were shown high catalytic performance. • The CoMOF/rGO composite paper was used for the electrochemical determination of Resorcinol (RS). • The CoMOF/rGO composite paper showed a wide linear range, high sensitivity, and a low detection limit for RS detection. The flexible, free-standing, 3-dimensional (3D) Cobalt-based metal-organic frameworks/reduced graphene oxide (CoMOF/rGO) composite paper was prepared with a facile electrochemical deposition of CoMOF on the surface of rGO paper electrode. Structural, chemical and morphological characterization of the CoMOF/rGO composite paper electrode was performed by using various techniques. Finger-like long-chain structures on the as-prepared CoMOF/rGO composite paper electrode surface were determined to greatly enhance the catalytic performance of the electrode for the electrochemical detection of Resorcinol (RS) with a large linear range (0.1–800 μM) and a low detection limit (1.9 × 10−8 M). Furthermore, stability tests performed with CoMOF/rGO paper were exhibited that this composite electrode has great potential for flexible sensor applications with high stability, flexibility, and durability. [ABSTRACT FROM AUTHOR]

We investigated the electrochemical performance of reduced graphene oxide (rGO)/carbon nanotube (CNT) hybrid papers as binder-free anodes for potassium-ion batteries. RGO/CNT hybrid papers were fabricated by vacuum filtration and thermal reduction. The potassium-ion storage ability of rGO paper was significantly enhanced by CNT incorporation and the electrochemical performance of the hybrid papers was related to the weight ratio of CNTs. The optimal rGO/CNT-30% paper can deliver an initial reversible discharge capacity of 351 and 223 mA h g−1 at a current density of 10 and 50 mA g−1, respectively. A capacity of 148 mA h g−1 was achieved after 200 cycles at a current density of 50 mA g−1. The enhanced performance of rGO/CNT hybrid papers is attributed to the formation of a 3D conductive carbon network, in which the graphene layers are bridged by CNTs. Such a structure could effectively facilitate the transport of electrons and potassium ions and provide more storage sites for potassium ions. Image 1 • RGO/CNT hybrid papers were fabricated by vacuum filtration and thermal reduction. • The potassium-ion storage ability of rGO paper was significantly enhanced by CNT incorporation. • RGO/CNT-30% paper delivered a reversible capacity of 232 mA h g−1 at a current density of 50 mA g−1, respectively. • The enhanced performance of rGO/CNT hybrid papers was attributed to the formation of a 3D conductive carbon network. [ABSTRACT FROM AUTHOR]