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Background: Efficient monitoring of glucose concentration in the human body necessitates the utilization of electrochemically active sensing materials in nonenzymatic glucose sensors. However, prevailing limitations such as intricate fabrication processes, lower sensitivity, and instability impede their practical application. Herein, ternary Cu-Co-Ni-S sulfides nanoporous network structure was synthesized on carbon fiber paper (CP) by an ultrafast, facile, and controllable technique through on-step cyclic voltammetry, serving as a superior self-supporting catalytic electrode for the high-performance glucose sensor. Results: The direct growth of free-standing Cu-Co-Ni-S on the interconnected three-dimensional (3D) network of CP boosted the active site of the composites, improved ion diffusion kinetics, and significantly promoted the electron transfer rate. The multiple oxidation states and synergistic effects among Co, Ni, Cu, and S further promoted glucose electrooxidation. The well-architected Cu-Co-Ni-S/CP presented exceptional electrocatalytic properties for glucose with satisfied linearity of a broad range from 0.3 to 16,000 μM and high sensitivity of 6829 μA mM− 1 cm− 2. Furthermore, the novel sensor demonstrated excellent selectivity and storage stability, which could successfully evaluate the glucose levels in human serum. Notably, the novel Cu-Co-Ni-S/CP showed favorable biocompatibility, proving its potential for in vivo glucose monitoring. Conclusion: The proposed 3D hierarchical morphology self-supported electrode sensor, which demonstrates appealing analysis behavior for glucose electrooxidation, holds great promise for the next generation of high-performance glucose sensors. [ABSTRACT FROM AUTHOR]

Developing new forms of flexible zinc–air (Zn–air) batteries is crucial to economic growth. Nevertheless, the absence of an oxygen evolution reaction catalyst with high catalytic efficiency and low-cost causes instability of Zn–air battery cycling and economic unviability, respectively. In this paper, a leaf-like N-doped carbon structure with CoS2 nanoparticles self-supported on carbon fiber paper (CoS2-CZ@CFP) was developed as an air electrode for Zn–air batteries, which not only uses nonprecious metal elements, but also has a self-supporting configuration, enhancing the contact between the catalyst and electrode while facilitating the transfer of electrons. Sulfur as the source gas was introduced into Co-doped metal–organic skeletons (Co-ZIFs) anchored on carbon fiber paper (CFP) for in situ vulcanizing transition metal Co, which successfully ensures the uniform distribution of sulfide particles in the carbon matrix, hence enriching active catalyst sites. The CoS2-CZ@CFP demonstrated an overpotential of 1.611 V at J = 50 mA cm−2, superior to RuO2@CFP (1.814 V). A Zn–air battery fabricated using the synthesized CoS2-CZ@CFP exhibited an extended life cycle of 117 h. This research paves the way for a novel method of designing self-supporting configurations of sulfides and carbon matrix composites as promising air electrodes applicable to Zn–air batteries. [ABSTRACT FROM AUTHOR]

A portable paper-based enzyme-linked biosensor that integrates a multi-enzyme cascade reaction, natural enzyme, and nanozyme with filter paper, combined with smartphones, is proposed for the detection of xanthine (XA) and sarcosine (SA) in urine. The primary biological component of the sensor is horseradish peroxidase (HRP). By chemically modifying cellulose filter paper (CFP) the HRP in horseradish crude extract is specifically immobilized through boron affinity and metal chelation techniques. Furthermore, the incorporation of UiO-66 on CFP had a good synergistic effect on the electron transfer of HRP and the detection of H 2 O 2 , significantly increasing the sensor's sensitivity. Under optimized experimental conditions, the sensor demonstrated a dynamic response range of 8–400 μmol L−1 for SA with a minimum detection limit (LOD) of 5 μmol L−1, and a dynamic response range of 10–400 μmol L−1 with an LOD of 8 μmol L−1 for XA. Additionally, the well-designed detection area of the portable test strip simplifies the detection operation, reduces the detection time, and enables rapid on-site analysis. UV-Vis analysis further confirmed the sensor's accuracy in detecting disease markers in urine. The sensing platform has good reproducibility, specificity and stability, suitable for the detection of SA and XA in real human urine samples, and the sensor has the advantages of simple manufacturing, easy operation, strong portability, low reagent consumption, and low cost benefit. Therefore, the development of this paper-based enzyme-linked biosensor offers a novel approach to the detection of disease markers in urine and has potential applications in medical testing. [Display omitted] • Paper-based enzyme-linked biosensor was successfully prepared. • Smartphone-assisted test paper detected xanthine and sarcosine in urine. • The sensor immobilizes HRP from horseradish by modifying the filter paper. • The addition of UiO-66 had good synergistic effect on the HRP's electron transfer. • The portable test paper can realize the simultaneous detection of multiple copies. [ABSTRACT FROM AUTHOR]

Technological advancements in flexible and wearable electronics have driven a boom in high-performance flexible electrodes. In this study, a simple and low-cost bio-inspired filter paper (FP) template method using the interfacial-aided polyethyleneimine-functionalized filter paper (FP-PEI) was developed to fabricate highly flexible silver-based conductive films. The FP was modified through amination to obtain FP-PEI with the rigid cellulose backbone and the flexible side chain of grafted amino groups, which played a key role as an interfacial layer during the chemical deposition of fractal-structured silver particles (FSSPs). The naturally porous and rough network structures of FP templates provided structural support and network for the deposition of conductive materials. In addition, the high porosity of FP facilitated the effective transfer of electrons, and its nano- or micro-scale rough surface structure promoted the formation of strong adhesion between the cellulose substrate and the conductive layer, which was crucial for the conductive stability of the device. The obtained conductive films (FP-PEI/FSSPs) exhibited a low sheet resistance of 1.47 Ω sq−1, a conductivity of 3401 S m−1, and good mechanical properties with a stress strength of 6.17 MPa. Moreover, FP-PEI/FSSPs exhibited a stable electrical conductivity (the sheet resistance only increased by 0.06 Ω sq–1 through 500 bending cycles), thermal stability (the maximum thermal decomposition rate increased from 349.3 to 357.8 °C), and oxidation resistance (the sheet resistance increased by only 0.04 Ω sq–1 after FP was exposed to the air for 15 days). The results indicate that FP-PEI/FSSP conductive films can be a potential green flexible electronic material. [ABSTRACT FROM AUTHOR]

Functional laser scribing carbon paper (LSCP) decorated with highly uniform Ni nanoparticles were constructed through a facile electroless plating. The nanocomposites were characterized by high resolution scanning electron microscope, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and chronoamperometry. The results showed high electron transferring kinetics of this sensor, which can be ascribed to their excellent properties such as rich pore channels, excellent structural durability, and large surface area. These properties facilitated mass transfer and electron conductions. Notably, a systematical response surface methodology simulating-modeling-predicting-optimizing design was employed to simulate, model and optimize processing parameters to gain the optimal conductivity of 8.52 × 106 S m−1. The obtained sensor owned high electrochemical activity and wide linear responses (0.80 μM–2.50 mM and 4.50 mM–15.20 mM), low detection limit of 20 nM (S/N = 3) to the glucose detection. The glucose determination in human serum and perspiration samples are also successful. Therefore, LSCP/NN provides an excellent sensing platform towards flexible biosensors in monitoring physical conditions. Disposable, Non-enzymatic and Ultrasensitive Carbon Fiber Paper-based Glucose Sensor has been Constructed by A Theoretical Box-Behnken Modeling-Predicting-Optimizing Design. Image 1 • A disposable, ultrasensitive and highly flexible LSCP/NN glucose biosensor is firstly constructed. • Novel nanoporous Ni networks are integrated with pulsed laser-scribed carbon paper via a rational Box-Behnken modeling-predicting-optimizing design. • The enzyme-free and binder-free LSCP/NN biosensor exhibits a wide linear glucose determination range (0.80 μM–2.50 mM; 4.5 mM–15.2 mM). • Excellent sensitivity (3415 μA mM−1 cm−2), a fast response (<1 s) and ultra-low limit of detection (20 nM). • Favorable flexibility, good accuracy and satisfactory specificity for glucose quantification in human serum and perspiration are indicated by the LSCP/NN biosensor. [ABSTRACT FROM AUTHOR]

A Eu-TDCA-Phen probe was employed for the detection of Nitrofurantoin (NFT) through a fluorescence quenching mechanism. Simultaneously, a smartphone-assisted fluorescence paper strip detection platform was designed for the visual and intelligent detection of NFT in real honey samples. [Display omitted] • A Eu-TDCA-Phen probe was synthesized and characterized. • Red fluorescence of Eu-TDCA-Phen was quenched by Nitrofurantoin (NFT). • Smartphone-assisted paper-based probe was developed for NFT detection. • A logic gate device was developed to simplify the detection process. The development of a rapid and convenient detection method for nitrofurantoin (NFT) residual is of great significance for food safety. Herein, a new fluorescent probe (Eu-TDCA-Phen) was developed for the visual and sensitive assay of NFT through the fluorescence quenching effect of inner filter effect (IFE) and photo-induced electron transfer (PET). The probe suspension demonstrates a wide linear range (0–0.16 mM), low detection limit (90 nM), high sensitivity, and rapid response time (2 min) in the "turn-off" process. To quantify the visual detection process, a smartphone-assisted test paper sensing platform was established and was applied for NFT determination in real honey samples, achieving satisfactory recovery rate ranges from 98.04 % to 105.04 %. Furthermore, a logic gate device was integrated with the sensing platform to streamline the visual detection process. The sensing platform offers several merits, including simpleness, quantification, portability and cost-effectiveness, making it highly suitable for real-time and on-site detection of antibiotics in food samples. [ABSTRACT FROM AUTHOR]

One of the most important problems in dark fermentative hydrogen production is the need for the regulation of the ambient pH due to the formation of volatile fatty acids. For this purpose, alkaline chemicals are usually used; however, alkaline addition to the media increases salt formation, which negatively affects microbial activity. In this study, pH adjustment was performed by providing direct current as an alternative to alkali addition. Experiments were carried out batchwise and electricity was only applied to neutralize the acidic pH value. The waste paper hydrolysate was used as a substrate and the effects of applied voltage (0.25–3 V), substrate concentration (4.8–41.2 g/L at 1 V) and electrode distance (0.3–1.3 cm at 1 V) on hydrogen production performance was investigated. Voltages less than 1 V required too much time to keep the pH convenient and voltages more than 1.5 V adversely affected hydrogen production performance. Providing direct current to the fermentation media significantly reduced the adaptation phase. Conditions for optimal pH adjustment and hydrogen production were obtained at 1 V, 20 g glucose/L and 0.5 cm electrode distance. • Most convenient H 2 production was obtained at 1 V, 20 g glucose/L and 0.5 cm electrode distance. • H 2 was efficiently produced up to 29.1 g glucose/L with DC assistance. • Proper electrode distance enables sufficient electron transfer for pH regulation. [ABSTRACT FROM AUTHOR]

• Developing a microfluidic paper-based analysis device (μ-PAD) for β-LG detection. • Using BPNSs@MWCNTs-COOH to improve the electron transfer rate on sensing interface. • The μ-PAD offered an effective strategy for detecting β-LG in milk matrices. • The BPNSs@MWCNTs-COOH-based μ-PAD can detect β-LG with a LOD of 0.12 ng mL−1. This study prepared a novel, portable and cost-effective microfluidic paper-based electrochemical analysis device (μ-PAD) using black phosphorus nanosheets@carboxylated multi-walled carbon nanotubes (BPNSs@MWCNTs-COOH) nanocomposites for β-lactoglobulin (β-LG) detection. At the appreciate ratio, the synthesized BPNSs@MWCNTs-COOH was demonstrated to not only serve as a high-quality substrate for the specific aptamer immobilization, but also improve the electron transfer capability of the sensing interface. The μ-PADs, utilizing BPNSs@MWCNTs-COOH and aptamer recognition, exhibited a wider detection range (10–1000 ng mL−1) and lower detection limit (LOD: 0.12 ng mL−1) for β-LG, and demonstrated enhanced specificity, satisfactory anti-interference ability and stability. When applied to the β-LG determination in dairy samples, the μ-PAD yielded β-LG concentrations highly correlated with those obtained using the HPLC method (R 2: 0.9982). These results emphasized the reliable performance of the developed μ-PADs in β-LG allergen quantification, highlighting their potential as an efficient platform for the rapid screening of β-LG allergens. [ABSTRACT FROM AUTHOR]

The technique of using biochar-based catalysts in persulfate activation is a promising alternative to remov emerging and refractory pollutants (e.g., tetracycline-) in wastewater. However, the situation of biochars derived from waste pulp/paper mill sludge is still unclear. The pulp/paper mill sludge biochars (SBC300, SBC500, and SBC700) were obtained and characterized at pyrolysis temperatures of 300, 500, and 700 °C. Tetracycline degradation using peroxydisulfate activated by SBCs was investigated. The results demonstrated the removal efficiencies of tetracycline in SBC300-, SBC500- and SBC700-peroxydisulfate systems, which increased with the pyrolysis temperatures and were 4.3, 4.8, and 5.0 times that of a system with peroxydisulfate alone. The experiments of free radical quenching, singlet oxygen quenching, and electrochemistry indicated that the degradation of tetracycline in SBC-peroxydisulfate systems was mainly not a free radical pathway, but a non-radical pathway. Singlet oxygen (1O2) and electron transfer could play main roles in the degradation removal of tetracycline. The removal efficiencies of tetracycline in the SBC-peroxydisulfate systems could be up to 96.0% (SBC700-peroxydisulfate) under the optimum dosage of SBC, the molar ratio of peroxydisulfate to tetracycline and the solution pH value. The results indicate that a SBC700-peroxydisulfate system could be an effective "trash-to-treasure" treatment technique for wastewater containing antibiotics. [ABSTRACT FROM AUTHOR]

Laser-induced graphene from paper (paper-LIG) was applied in non-enzymatic electrochemical sensing of uric acid (UA) in human urine. Paper-LIG was formed by CO 2 laser modification of paper into a 3D graphene arrangement. Kinetic analysis of paper-LIG electrodes returned effective heterogeneous electron transfer standard rate constants of 1.4 × 10−3 cm s−1 and 7.8 × 10−4 cm s−1 for [Ru(NH 3) 6 ]2+/3+ and [Fe(CN) 6 ]4−/3− redox probes, respectively. These electrodes were able to detect and quantify uric acid in PBS within the 10–300 μM range at pH between 5.6 and 7.4. At pH 7.4, a linear response (R2 = 0.999) from 10 to 250 μM was achieved, with a limit of detection of 3.97 μM and a sensitivity of 0.363 μA cm−2 μM−1. Paper-LIG electrodes denoted adequate selectivity in synthetic urine as well as in ascorbic acid (AA) and dopamine (DA)-containing electrolytes. Determination of urinary UA content in human samples returned a concentration of c.a. 1.8–1.9 mM, within the range for healthy individuals. Recoveries of samples spiked with 50 and 100 μM UA were 100.6% and 95.4%, respectively, with satisfactory reproducibility and stability. These cheap, lightweight, flexible, and eco-friendly paper-LIG biosensors for non-enzymatic quantification of UA in human urine pave the way to widespread application in the detection of other important biomarkers. [Display omitted] • "Green" graphene electrodes by CO 2 laser irradiation of paper ("paper-LIG"). • Uric acid (UA) quantification at clinically relevant concentrations and pH (5.6–7.4). • Limit of detection of 3.97 μM and a sensitivity of 0.363 μA cm−2 μM−1 (pH = 7.4). • Adequate selectivity in synthetic urine, as well as in ascorbic acid and dopamine-containing electrolytes. • Recoveries of 100.6% and 95.4% for human urine samples spiked with 50 and 100 μM UA. [ABSTRACT FROM AUTHOR]

[Display omitted] • Paper mill sludge-based biochar (PSBC) is synthesized for PDS activation. • High BPA removal efficiency can be achieved by the PSBC950/PDS process. • Both radical and non-radical pathways are involved in BPA degradation. • Fe(Ⅱ), O V , C O, and graphitized sp2-C with defects were identified as active sites. • The enhancement effects of C O and defects to the electron transfer were confirmed. Paper mill sludge generated from the pulp and papermaking industries has inherent iron and carbon contents. Herein, the biochar derived from paper mill sludge (PSBC) was synthesized via simple pyrolysis processes and applied as an efficient persulfate (PDS) activator for the removal of Bisphenol A (BPA) in water. The unique properties of PSBC endowed it with multiple active sites including Fe(II) species, oxygen vacancy, C O, and graphite sp2-C with defects, owing to which, the PSBC/PDS process presented satisfactory performance with BPA removal efficiency up to 98 % within 60 min. Both of the radical and non-radical pathways were revealed to be involved in the BPA degradation. Based on the results of theoretical calculation, the existences of some special structures in PSBC effectively facilitated the electron transfer process of PDS activation. The process also exhibited a high anti-interference capability to coexisting substances and the universality toward various organic contaminants degradation. And the used PSBC can be recovered by simple thermal treatment. This work provided a promising heterogeneous PDS activator with plentiful active sites and satisfactory efficiency, which can be beneficial to the cost reduction of wastewater treatment and promotes the application of paper mill sludge in the area of environmental remediation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A highly active 2e-WOR electrocatalyst was prepared by modifying CFP with SAMs. • SAMs modified CFP achieves a high H 2 O 2 yield of 79.8 μmol min−1 cm−2 at 2.1 V. • SAMs modification enriches the 2e-WOR active site and reduces the OER active site by modulating the ΔG*OH. • Carbon atoms adjacent to O=C-M are active sites for efficient 2e-WOR. • O=C-M are rooted from the reaction between the functional group on CFP and SAMs. Two-electron water oxidation (2e-WOR) is an attractive method for the electrosynthesis of hydrogen peroxide (H 2 O 2). However, its practical application is limited by the viable 2e-WOR catalysts that can ensure high selectivity and high H 2 O 2 yield. In this paper, a highly active 2e-WOR electrocatalyst was prepared by modifying carbon fiber paper (CFP) with a self-assembled membrane (SAMs). The SAMs modified CFP can achieve an H 2 O 2 yield of 79.8 μmol min−1 cm−2 and an H 2 O 2 selectivity of 82.5% at a low potential (2.1 V vs. RHE). The DFT calculation reveals that SAMs modification can modulate the *OH binding energy of the active site on CFP, thus leading to a significantly improved selectivity and production rate of H 2 O 2. Moreover, the 2e-WOR performance is found to be independent of the functional tail groups of SAMs because the electron transfer during the 2e-WOR occurs through direct electron transfer via the carbon atoms adjacent to the O=C-M on carbon fiber rather than the well-known electron tunneling through SAMs. This study provides a new strategy for surface modification of 2e-WOR carbon-based catalysts and opens a new way for efficient electrosynthesis of H 2 O 2. [ABSTRACT FROM AUTHOR]

The use of fossil energy has caused a serious burden on the environment, so it is urgent to find new and developable energy sources. H 2 O 2 as a new type of clean fuel for fuel cell has received widespread attention. In this paper, a novel graphite modified paper based cobalt-cobalt oxalate-nickel (FG@Co–CoC 2 O 4 –Ni) electrode is fabricated by the simple "pencil depicting-electrodeposition-oxalic acid etching-electrodeposition" process for the electrooxidation of H 2 O 2 in alkaline environment. The as-prepared FG@Co–CoC 2 O 4 –Ni electrode owns a novel and special three-dimensional (3D) porous structure, which can greatly increase the diffusion of reactants (NaOH and H 2 O 2) during the electrochemical reaction process and lead a high catalytic activity for the electrooxidation of H 2 O 2. More importantly, three main nanomaterial (Co, CoC 2 O 4 and Ni) and some new generated substances during the CV test in NaOH solution (e.g. Ni(OH) 2 , NiOOH, Co(OH) 2 , CoOOH, Co 3 O 4 and Co 2 O 3 etc.) are on the surface of paper, which will enhance the electrocatalytic activity of the FG@Co–CoC 2 O 4 –Ni electrode to a great extent due to their synergistic effect. When the reaction solution contains 1.0 mol dm−3 NaOH and 0.2 mol dm−3 H 2 O 2 , the FG@Co–CoC 2 O 4 –Ni electrode exhibits a much higher oxidation current density (270.6 mA cm−2) than the FG, FG@Co, FG@Ni, FG@Co–Ni and FG@Co–CoC 2 O 4 electrodes. Besides, the whole preparation process for the FG@Co–CoC 2 O 4 –Ni electrode doesn't use any organic binder, ensuring the electrode owns good conductivity and stability for the electrochemical reaction. At last, the electrocatalytic mechanism for the electrooxidation of H 2 O 2 is discussed. The Ni compounds and Co compounds are believed as the main catalytic substances, and the metallic Co core provides a fast route for the transfer of electrons. The super catalytic activity makes the prepared electrode in this study to be a promising material for the electrooxidation of H 2 O 2 and the novel design idea gives some guidance for the fabrication of electrode materials in the field of fuel cell. [Display omitted] • The environmentally and inexpensive filter paper is used as electrode support. • The 3D porous electrode structure can improve the catalytic performance. • The synergistic effect among complex substances can enhance the performance. • The as-prepared electrode has high catalytic activity at low H 2 O 2 concentration. • The as-prepared electrode has a fast electron transfer path. [ABSTRACT FROM AUTHOR]

In this study, the performance of a paper-based, screen-printed biofuel cell with mesoporous MgO-templated carbon (MgOC) electrodes was improved in two steps. First, a small amount of carboxymethyl cellulose (CMC) was added to the MgOC ink. Next, the cathode was modified with bilirubin prior to immobilizing the bilirubin oxidase (BOD). The CMC increased the accessibility of the mesopores of the MgOC, and subsequently, the performance of both the bioanode and biocathode. CMC also likely increased the stability of the electrodes. The pre-modification with bilirubin improved the orientation of the BOD, which facilitated direct electron transfer. With these two steps, an open circuit potential of 0.65 V, a maximal current density of 1.94 mA cm−2, and a maximal power density of 465 μW cm−2 was achieved with lactate oxidase as bioanode enzyme and lactate as fuel. This is one of the highest reported performances for a biofuel cell. [ABSTRACT FROM AUTHOR]

The detection of hydrogen peroxide and the control of its concentration are important tasks in the biological and chemical sciences. In this paper, we developed a simple and quantitative method for the non-enzymatic detection of H2O2 based on the selective etching of Au@Ag nanorods with embedded Raman active molecules. The transfer of electrons between silver atoms and hydrogen peroxide enhances the oxidation reaction, and the Ag shell around the Au nanorod gradually dissolves. This leads to a change in the color of the nanoparticle colloid, a shift in LSPR, and a decrease in the SERS response from molecules embedded between the Au core and Ag shell. In our study, we compared the sensitivity of these readouts for nanoparticles with different Ag shell morphology. We found that triangle core–shell nanoparticles exhibited the highest sensitivity, with a detection limit of 10−4 M, and the SERS detection range of 1 × 10−4 to 2 × 10−2 M. In addition, a colorimetric strategy was applied to fabricate a simple indicator paper sensor for fast detection of hydrogen peroxide in liquids. In this case, the concentration of hydrogen peroxide was qualitatively determined by the change in the color of the nanoparticles deposited on the nitrocellulose membrane. [ABSTRACT FROM AUTHOR]

Prussian blue analogues (PBAs) are promising materials due to their rich active sites and straightforward synthesis. However, their limited conductivity and electron transfer inefficiency hinder practical applications. This study utilizes a simple one-pot synthesis approach to produce a tungsten-disulfide (WS 2) and iron-cobalt Prussian blue analogue composite (WS 2 -PBA), enhancing conductivity and electron transfer rate performance. Through the inclusion of sodium citrate into the solution, the S-edge site concentration of WS 2 increases. This augmentation introduces additional active sites and defects into the catalyst, enhancing its catalytic activity. The effectiveness of the WS 2 -PBA 3D-Origami paper device for lactate detection in sweat is also evaluated for biomedical applications. The device demonstrated a robust relationship between the lactate concentration and current intensity (R2 = 0.997), with a detection limit of 1.83 mM. Additionally, this platform has successfully detected lactate in clinical sweat, correlating with the high-performance liquid chromatography test results, suggesting promising prospects for clinical diagnosis. In the future, the excellent catalytic and R ct performance of the WS 2 -PBA will enable its use in biomedical applications. [ABSTRACT FROM AUTHOR]

• The sulfate radicals were in-situ generated via photoelectrocatalytic activating sulfate ions originally exist in water without adding any extra expensive oxidants. • Carbon paper with large surface area and high electrical conductivity as an excellent support for BiPO 4 is beneficial to improve the reutilization, electron transfer and photocatalytic performance of BiPO 4. • BiPO 4 with large bandgap has sufficient redox capacity to produce not only ·OH, superoxide radical (·O 2 −), but also SO 4 −·, which is crucial for photocatalytic pollutant degradation. • The photocatalytic, electrocatalytic and advanced oxidation process technologies were combined to in-situ produce crucial free radicals and realize the low-cost and eco-friendly degradation of pefloxacin. In recent years, advanced oxidation processes (AOP) based on sulfate free radicals (SO 4 −·) have attracted considerable attention due to the excellent advantages of SO 4 −· compared with hydroxyl radical (·OH). However, SO 4 −· generally produced by activating extra persulphates, which causes high cost and risk of secondary pollution. In this work, BiPO 4 modified carbon paper electrode (BiPO 4 /CP) successfully fabricated via simple method can be used as a photocatalyst to effectively activate sulfate originally existed in wastewater to generated sulfate radicals in-situ without adding any extrinsic chemical oxidants. Pefloxacin (PFX) was degraded effectively on BiPO 4 /CP with the help of applied potential. CP with large surface area and high electrical conductivity as an excellent support for BiPO 4 is beneficial to improve the reutilization, electron transfer and photocatalytic performance of BiPO 4. Moreover, BiPO 4 with large bandgap has sufficient redox capacity to produce not only ·OH, superoxide radical (·O 2 −), but also SO 4 −·, which is crucial for photocatalytic pollutant degradation. Detailed characterizations give strong evidences of the successful fabrication of photocatalyst, thermodynamic feasibility of SO 4 −· in-situ formation, the generation of free radicals, and the possible mechanism. Consequently, under the optimal conditions (pH=5.6, +1.0 V (vs.SCE), [SO 4 2−]=10 mM, 61 μW cm−2 UV light irradiation, 33 mg BiPO 4 loaded on CP), the degradation efficiency of PFX (10 mg/L) was 87.8% in 120 min, which was 5.1 ad 8.2 times higher than that in photocatalytic and electrocatalytic system and 3.3 times higher than that without SO 4 2−. Meanwhile, BiPO 4 /CP maintains high level of degradation efficiency of PFX after 6 cycles under the optimal conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

Owing to the challenge of irregular morphology, the impact of compressed carbon fiber paper (CFP) on fuel cell performance and durability is intricate. As a carbon-carbon composite, the internal contact state of CFP directly determines its mechanical and physical properties. In this paper, fiber distribution and intersection of uncompressed CFP are achieved by X-ray computed tomography. Then we established an analytical model of bulk resistance based on the electron transfer path and provided a function to describe the internal contact state with strain. The results imply that the increasing number of electron paths and the variation of the contact state are the main factors for the decrease in bulk resistance under compression. The turning points in the contact state curve divide the range of pressure into fiber contact, elastic-plastic deformation and fiber fracture region, which can be used to assess the mechanical properties of CFP and determine the optimal pressure for fuel cell assembly. [Display omitted] • Fiber distribution and intersection of uncompressed CFP is given. • The effect of contact resistance between fibers on bulk resistance is evaluated. • The structural information to electric and mechanical properties is connected. [ABSTRACT FROM AUTHOR]

This paper developed a portable microfluidic paper-based analysis device (μ-PAD) combined with the electrochemical technique for efficient and sensitive detection of peanut allergen Ara h1. The proposed μ-PAD works based on the variation of differential pulse voltammetry (DPV) response current induced by peanut allergen Ara h1. Black phosphorus (BP)–Au nanocomposites were introduced both to improve the electron transfer rate at the electrode interface for signal amplification, and to immobilize the specific Ara h1 aptamers through Au–S bonding to recognize the target in food matrices. This μ-PAD had good specificity and detection stability for Ara h1 allergen and could complete the entire analysis process within 20 min, achieving a wide linear response range (25–800 ng mL−1) and a low detection limit (LOD, 11.8 ng mL−1). In the Ara h1 allergen detection applied to real peanut products (cookies, milk, and bread), the constructed μ-PAD obtained acceptable recoveries (93.50%–101.86%) with relative standard deviations (RSDs) of 0.36–2.97% (n = 3), with a good correlation with the ELISA results (R 2 = 0.9956). Therefore, the portable μ-PAD based on BP-Au nanocomposites was demonstrated to provide an effective strategy for rapid analysis and screening of Ara h1 allergen in food, which has broad application prospects. [Display omitted] • A microfluidic paper-based analysis device for quantitative detection of peanut allergen Ara h1 was developed. • The BP-Au nanocomposites were introduced to improve the electron transfer rate of the working electrode for signal amplification, and were employed to fix specific Ara h1 aptamers through Au–S bonding for recognizing the target in food matrices. • This μ-PAD combined with electrochemical detection technique showed good performance in peanut allergen Ara h1 detection with a LOD of 11.8 ng mL−1. [ABSTRACT FROM AUTHOR]

• A simple and scalable synthesis of exfoliated graphite carbon paper. • ExGCP potential for nonenzymatic glucose sensor. • A high sensitivity of about ∼5.93 µA mM−1 cm−2. • Diffusion controlled sensing reaction in ExGCP. The continuous real-time monitoring of glucose is essential for patients suffering from diabetes. Therefore, the low-cost and flexible glucose sensor is necessary, showing enhanced sensitivity and limit of detection. We report results of studies resulting in developing a nanostructured exfoliated graphite carbon paper (ExGCP) based efficient electrode for application to a nonenzymatic glucose sensor. This glucose sensor showed ∼ sensitivity as 5.93 µA mM−1 cm−2 with a linear response in the 2–8 mM concentration range and ∼0.812 mM as the limit of detection. The diffusion-controlled sensing reaction on ExGCP reduces electron transfer resistance with increasing glucose concentration, revealing ExGCP as an efficient and flexible electrode material for glucose sensing applications. [ABSTRACT FROM AUTHOR]

Selecting different metal ions, two novel complexes {[Zn(BCbpy)(m‐BDC)(H2O)] ⋅ 2H2O}n (1) and [Co(H2O)6]0.5[Co0.5(BCbpy)(H2O)2](m‐BDC) ⋅ 3H2O ⋅ DMF (2) have been prepared and structurally characterized in the presence of the viologen ligand 1‐(4‐carboxybenzyl)‐4,4′‐bipyridinium (BCbpy) and 1,3‐benzenedicarboxylic acid (m‐H2BDC). The crystal structures and photochromic properties of two complexes have been investigated in this article. 1 possesses a two‐dimensional (2D) layered structure, while the structure of 2 is zero‐dimensional (0D). As expected, 1 and 2 were discovered to be photochromic accompanying electron transfer (ET). Interestingly, 1 can be dissolved in ethanol solution and deposited on filter paper, applied to a printing medium without ink. [ABSTRACT FROM AUTHOR]

Herein, an inkjet-printed paper electrode (PPE) with gold nanoparticle (AuNP)-ink as a non-enzymatic electrochemical sensor for detection of glucose in blood serum is reported. In this work, a green method is used for the synthesis of the aqueous AuNP-ink and the electrode is fabricated on a paper substrate using an office desktop inkjet-printer. The developed AuNP-ink is stable and has a surface tension and viscosity of 70.2 mN m−1 and 2.1 mPa s (2% aqueous AuNP ink). The PPE with AuNPs is sintered at 100 °C for 30 min to obtain a conductive film for electrochemical sensing. The prepared AuNP-PPE is employed as a working electrode in cyclic voltammetry (CV) for the sensitive measurement of glucose in blood serum. The fabricated AuNP-PPE demonstrated excellent electrochemical activity and rapid electron transfer kinetics towards the oxidation of glucose. A wide linear range, 0.05–35 mM, with a limit of detection of 10 μM is observed for the determination of glucose. The advantages of using the AuNP-PPE in electrochemical measurements are that it is flexible, user-friendly, biodegradable, economic and enzyme-free with respect to the commercially available electrochemical sensors. [ABSTRACT FROM AUTHOR]

A new strategy for the fluorescent and colorimetric sensing of hydrogen peroxide (H 2 O 2) and glucose based on the metal oxide – carbon-dot hybrid structure was investigated. The sensing system is related to the catalytic oxidation reaction of glucose-by-glucose oxidase (GOx) to H 2 O 2. In this study, a metal oxide hybrid with nitrogen-doped carbon dots (MFNCDs) that showed intrinsic peroxidase-like activity was synthesized and used as a catalyst instead of GOx to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to blue-emitting oxidized TMB (oxTMB) in the presence of hydrogen peroxide (H 2 O 2). The fluorescence of MFNCDs/TMB at 405 nm was quenched in the presence of H 2 O 2 through the inner filter effect (IFE) and electron transfer within MFNCDs, oxTMB, and glucose system. Therefore, the fluorescence and absorbance intensity can be applied to the quantitative determination of the concentration of H 2 O 2 and glucose with a wide linear range. The detection limit for H 2 O 2 and glucose based on the colorimetric method were as low as 84 nM and 0.41 μM, respectively. In contrast, the detection limit for H 2 O 2 and glucose based on the fluorescent method were as low as 97 nM and 0.85 μM, respectively. Furthermore, the colorimetric readout on the paper device based on the changing color of the solution could also be integrated with a smartphone platform to conduct the on-site analysis of glucose without the use of the spectrometer. In addition, this dual sensor can be applied to detect glucose in real serum with highly accurate results, making it a good candidate for biosensor applications. Image 1 • Metal oxide hybrid with N-doped carbon dots (MFNCDs) as a peroxidase-like catalyst was fabricated by a hydrothermal method. • A colorimetric and fluorescent sensor for H 2 O 2 and glucose was developed. • The MFNCDs exhibited excellent selectivity towards glucose. • MFNCDs showed low cytotoxicity and excellent biocompatibility. [ABSTRACT FROM AUTHOR]

A disposable paper-based glucose biosensor with direct electron transfer (DET) of glucose oxidase (GOX) was developed through simple covalent immobilization of GOX on a carbon electrode surface using zero-length cross-linkers. This glucose biosensor exhibited a high electron transfer rate (ks, 3.363 s−1) as well as good affinity (km, 0.03 mM) for GOX while keeping innate enzymatic activities. Furthermore, the DET-based glucose detection was accomplished by employing both square wave voltammetry and chronoamperometric techniques, and it achieved a glucose detection range from 5.4 mg/dL to 900 mg/dL, which is wider than most commercially available glucometers. This low-cost DET glucose biosensor showed remarkable selectivity, and the use of the negative operating potential avoided interference from other common electroactive compounds. It has great potential to monitor different stages of diabetes from hypoglycemic to hyperglycemic states, especially for self-monitoring of blood glucose. [ABSTRACT FROM AUTHOR]

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The invention of paper as a writing material greatly promoted the development and spread of civilization. However, its large-scale production and utilization has also brought about huge environmental and sustainability concerns. It is desirable to develop a strategy for paper that can be used in a reprintable manner. In this work, ZnO-based photocatalytic reactions have been applied in preparing a reprintable paper that works through the color conversion of methylene blue. The resulting paper does not require additional ink and can be repeatedly printed for 20 cycles keeping over 77% of the initial contrast ratio. The reprintable raw materials can be retained for more than 2 months in the ambient environment. A fast color-switching time of about 10 s has been achieved, which can be attributed to the high photo-induced electron transfer rate from the ZnO to the dyes. [ABSTRACT FROM AUTHOR]

• The 1D/2D MnO 2 /MXene heterostructures generate built-in electric fields that greatly accelerating the ionic and electronic diffusion/transport kinetics. • The synergistic mechanism generated by 1D/2D heterostructures achieve the balance between high energy storage activity and high active substance proportion of MnO 2 /MXene flexible electrode. • The quasi-solid-state FZIBs with MnO 2 /MXene paper-like film provide high total specific capacity and stability in flexible applications. Paper-like flexible electrode plays a critical importance role in booming the development of flexible energy storage devices. One-dimensional manganese dioxide (1D MnO 2) shows immense advantage in flexible zinc-ion batteries (FZIBs) on account of renowned tunnel crystal structure and high operating voltage. However, inherent inferior electrical conductivity and sluggish reaction kinetics seriously hinder the practical application of FZIBs, resulting in unsatisfactory rate capability and cycle performance. Herein, 1D/2D MnO 2 /MXene-5 heterostructure materials were constructed by electrostatic self-assembly, which were then prepared into paper-like membrane with high energy storage active substance ratio (95.2 %) towards high capacity and ultrastable FZIBs. The built-in electric field induced by the heterostructure accelerates the electron transfer, reduces the charge transfer resistance and promotes ion diffusion, enabling the 1D/2D phase collaboration to improve the zinc ion storage of the paper-like electrode. The design achieves a high total specific capacity (based on the total cathode mass) of 314.7 mAh g−1 at 0.1 A g−1 and ultrastable of 8000 cycles at 5 A g−1 with a retention of 81.1 %. Remarkably, quasi-solid-state FZIBs with MnO 2 /MXene-5 membrane can deliver an outstanding reversible capacity of 273.5 mAh g−1 at 0.1 A g−1 and maintain 500 cycles at 1 A g−1 across various bending angles without decay, demonstrating excellent stability. This work provides a novel approach for the targeted design of self-standing flexible electrodes. [Display omitted] [ABSTRACT FROM AUTHOR]

Porous carbon encapsulated non-precious metal nanocatalysts have recently opened the ways towards the development of high-performance water remediation and energy conversion technologies. Herein, we report a facile, scalable and green synthetic methodology to fabricate porous carbon encapsulated transition metal nanocatalysts (M@TP: M = Cu, Ni, Fe and Co) using commercial tissue paper. The morphology, crystalline structure, chemical composition and textural properties of the M@TP nanocatalysts were thoroughly characterized. The catalytic activity of the M@TP nanocatalysts was investigated for the degradation of Congo red (CR) via peroxymonosulfate activation. Co@TP-6 was found to be the most active catalyst allowing 97.68% degradation in 30 min with a higher rate constant of 0.109 min−1. The nanocatalysts also displayed a carbon shell thickness-dependent electrocatalytic hydrogen evolution reaction (HER) activity, most likely due to the shielding effect of the carbon layers over the electron transfer (ET) processes at the metal core/carbon interfaces. Remarkably, the Ni@TP-6 electrocatalyst, with the smaller carbon shell thickness, showed the best electrocatalytic performance. They delivered an ultralow onset potential of −30 mV vs RHE, an overpotential of 105 mV at a current density of 10 mA·cm−2 and an excellent electrochemical stability to keep the 92% of the initial current applied after 25000 s, which is comparable with the HER activity of the state-of-the-art Ni-based catalysts. [ABSTRACT FROM AUTHOR]

Screen printed carbon electrodes (SPCEs) are widely used in the field of electrochemical sensors, especially in the areas of food, water, environmental quality, and healthcare applications. In this context, microband SPCEs were fabricated on Whatman paper, overhead projection (OHP) sheet and cotton textile substrates for the development of cost-effective electrochemical biosensors. The fabricated electrodes were subjected to three consecutive processes such as thermal, electrochemical and oxygen plasma treatment. Surface morphologies of SPCEs after each treatment stage were observed using scanning electron microscope for process standardization. Electrochemical performances of the fabricated SPCEs were analyzed using cyclic voltammetry. SPCEs on OHP substrate exhibited a single electron transfer rate at ΔEp of 57 mV and ipa/ipc = 1 (n = 3) with significant repeatability and reproducibility compared to SPCEs on paper and textile substrates. The role of activation of edge plane pyrolytic graphite of SPCEs in achieving the reversible reaction with single electron transfer characteristics has been analysed and reported. The effectiveness of the activated SPCEs on the OHP substrate was tested by detecting 1 mM of uric acid and ascorbic acid with KCl as an electrolyte. [ABSTRACT FROM AUTHOR]

A novel platform of microfluidic paper-based analytical devices (μPADs) for dual detection of bisphenol A (BPA), a model analyte, was fabricated using an electronic digital plotter to create the stacked layer of μPADs and generate the lateral-flow channel without using an external pump. Two detection techniques, including electrochemical detection and laser desorption ionization mass spectrometric detection (LDI-MS), were used complementarily to improve the precision in the detection of BPA. The fluid sample was delivered to both detection zones by the capillary action, automatically generated from the fabricated microfluidic device. For an electrochemical sensor, two ballpoint pens filled with silver nanoparticles (AgNPs) and multiwall carbon nanotube (MWCNT) ink were used to print onto the paper with a contact printing method using a digital plotter. To further improve the sensitivity, zinc oxide (ZnO) was used to modify both electrochemical and LDI-MS detection zones. For BPA detection, high electrocatalytic properties and strong UV absorption of ZnO promote the electron transfer in the electrochemical sensor and ionization efficiency in LDI-MS with low interferences compared with a conventional organic matrix. Under optimal conditions, this platform showed a dual detection capability for BPA with a detection limit of 0.35 μM for electrochemical detection and with an ultralow detection limit of 0.01 pM for LDI-MS. This novel platform might be very useful for trace analyses requiring high precision detection of various analytes. [ABSTRACT FROM AUTHOR]

The loss and sluggish kinetics of intermediate polysulfides in electrochemical processes seriously reduce electrochemical activity of sulfur in lithium-sulfur batteries (LSBs). Herein, we design and synthesize freestanding graphitized carbon interlayers decorated with Fe/Fe 3 C nanocatalysts by thermal treatment of cellulose paper with adsorbed ferric nitrate at 1000 °C, during which the freestanding carbon network derives from the cellulose paper while the Fe results from the reduction of Fe3+ with a carbothermal reduction process; simultaneously, the in situ formed Fe boosts graphitization of carbon to enhance electrical conductivity of the interlayer, and the carbon network effectively helps confine and accommodate Fe/Fe 3 C nanoparticles. Therefore, the well dispersed Fe/Fe 3 C nanoparticles catalytically accelerate electrochemical conversion of polysulfides, while the enhanced conductive network of carbon benefits the electron transfer during the electrocatalytic process. The cell with an optimal carbon/Fe/Fe 3 C interlayer delivers excellent cyclability and rate performances. At current densities of 0.2C and 2C, the specific capacities are close to 1000 and 735 mA h g−1, respectively. Even after 200 cycles at 1C, the reversible specific capacity is still 772 mA h g−1. Such a synergistic catalytic interlayer with an enhanced conversion kinetic towards polysulfides provides a new approach for improving electrochemical performances of LSBs. Image 1 [ABSTRACT FROM AUTHOR]

One challenge in capitalizing on the affordability, sustainability, and accessibility of biohybrid solar energy conversion, including devices based on Photosystem I (PSI), is the identification of metal‐free electrode materials to replace the inorganic substrates commonly found in solar cell development. Herein, commercially available Toray carbon paper (CP) is investigated as a high surface area, carbon electrode for the development of photoactive bioelectrodes consisting of PSI and poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). Mediated anodic photocurrent is achieved at both PSI multilayer and PSI–polymer composite films on CP electrodes subjected to flame pretreatment. Film preparation is optimized by utilizing potential sweep voltammetry in place of potentiostatic conditions for polymerization. The optimized PSI–PEDOT:PSS films achieve a threefold increase in polymer growth under potential sweep conditions, quantified through net charge consumed during electropolymerization, resulting in a fourfold increase in photocurrent density (−53 vs −196 nA cm−2). The ability to prepare photoactive PSI‐polymer films on metal‐free CP electrodes opens the door to a rapidly scalable system for biohybrid energy production ultimately leading to more affordable, sustainable, and accessible energy. [ABSTRACT FROM AUTHOR]

Simultaneous detection of multiple tumor biomarkers in body fluids could facilitate early diagnosis of lung cancer, so as to provide scientific reference for clinical treatment. This paper depicted a multi-parameter paper-based electrochemical aptasensor for simultaneous detection of carcinoembryonic antigen (CEA) and neuron-specific enolase (NSE) in a clinical sample with high sensitivity and specificity. The paper-based device was fabricated through wax printing and screen-printing, which enabled functions of sample filtration and sample auto injection. Amino functional graphene (NG)-Thionin (THI)- gold nanoparticles (AuNPs) and Prussian blue (PB)- poly (3,4- ethylenedioxythiophene) (PEDOT)- AuNPs nanocomposites were synthesized respectively. They were used to modify the working electrodes not only for promoting the electron transfer rate, but also for immobilization of the CEA and NSE aptamers. A label-free electrochemical method was adopted, enabling a rapid simple point-of-care testing. Experimental results showed that the proposed multi-parameter aptasensor exhibited good linearity in ranges of 0.01–500 ng mL−1 for CEA (R2 = 0.989) and 0.05–500 ng mL−1 for NSE (R2 = 0.944), respectively. The limit of detection (LOD) was 2 pg mL−1 for CEA and 10 pg mL−1 for NSE. In addition, the device was evaluated using clinical serum samples and received a good correlation with large electrochemical luminescence (ECL) equipment, which would offer a new platform for early cancer diagnostics, especially in those resource-limit areas. • The aptasensor could enable simultaneous detection of two tumor markers in a single sample with high sensitivity. • The aptasensor had a fast response time as a label-free electrochemical detection method was adopted. • The aptasensor was fabricated by wax printing and screen-printing, which could be mass-produced easily with low cost. [ABSTRACT FROM AUTHOR]

In this work, we present a multiplexed (eight simultaneous measurements) paper-based electrochemical device developed in a very simple way and using low-cost materials, such as paper, carbon ink and multifunctional connector headers. Meanwhile, we have also combined the paper-based electrochemical platform with a glass-fiber strip in order to integrate easily a sampling step. Both approaches, simultaneous measuring and sampling, have been applied to the determination of glucose using bienzymatic biosensors. They are fabricated by adsorbing the mixture of enzymes (glucose oxidase and horseradish peroxidase), as well as the ferrocyanide, mediator of the electron transfer, on the paper-based electrode. After drying, the measuring solution (containing either glucose standards or samples) is added and the eight corresponding chronoamperograms are recorded. In the case of the microfluidic approach for sampling purposes, the glass-fiber pad (sampler) is immersed in a container with the solution, which flows by capillarity until it reaches the working electrode. The integration of one more step of the analytical process advances towards real and useful lab-on-a-chip devices. With these designs, a linear range comprised between 0.5 and 15 mM was achieved for glucose determination, with an excellent precision. If the sampler is employed, it is not necessary to use micropipettes and, nevertheless, precise measurements are obtained. The RSD of the slopes obtained for different calibrations performed in different days, with different arrays of electrochemical cells and different solutions is ca. 1%. Accurate results are obtained in the determination of glucose in real samples (orange fruit and cola beverages). Image 1 • Precise sampling is integrated in a paper-based electroanalytical device for glucose biosensing. • Adding a sampler to a paper-based enzymatic sensor advances towards lab-on-paper platforms. • A paper-based simple electrochemical device for eight simultaneous measurements is presented. • A low-cost paper-based sensor samples which analyzes food samples with 8 simultaneous measurements is developed. • Accurate results are obtained for glucose determination in orange fruits and cola beverages. [ABSTRACT FROM AUTHOR]

Inspired by the design of folding greeting cards and tissue drawing covers, a photoelectrochemical (PEC) lab-on-paper device with a controllable fluid separator, producing both reaction zone and detection zone, was explored for ultrasensitive detection of adenosine 5′-triphosphate (ATP) via mimic peroxidase-transfer enhancement of photocurrent response. To realize it, the DNA1, aptamer, and DNA2 as well as the mimic peroxidase of G-quadruplex/hemin modified Au nanocubes were linked on the graphene oxide-functionalized reaction zone via the DNA hybridization. Meanwhile, three-dimensional CuO nanoflowers (CuO NFs) as a photoactive material with outstanding electron transfer ability and absorption of light were grown in situ on the detection zone, providing a PEC active interface. Besides, an innovative fluid separator was elaborately designed by assembling a strip of paper with a hydrophilic channel, providing an effective way to bridge the gap between the two zones with a controllable drawing way, which could successfully avoid the signal interference caused by modifying biomolecules layer by layer on photosensitive materials. In the presence of ATP, the G-quadruplex/hemin modified in the reaction zone was dissociated due to the specific recognition of ATP with aptamer and released into the detection zone with the assistance of controllable fluid separator. The free G-quadruplex/hemin could catalyze hydrogen peroxide to generate oxygen for the consumption of photo-induced electrons from CuO NFs, which could further promote the electron-hole carriers separation efficiency, and eventually resulting in the enhancement of PEC signal. The proposed PEC lab-on-paper device could be employed for specific detection of ATP in the range from 5.0 to 3.0 × 103 nM with a detection limit of 2.1 nM. • The CuO nanoflowers were grown in situ on rGO-modified detection zone. • The lab-on-paper microfluidic systems simplify the analytical processes. • The modification of biomolecules was separated from the PEC transducer. • The fluid separator was designed as a bridge between two functional zones. • The device was applied to detect ATP with high sensitivity, stability and selectivity. [ABSTRACT FROM AUTHOR]

More than 65% of bacterial infections are caused by biofilms. However, standard biofilm susceptibility tests are not available for clinical use. All conventional biofilm models suffer from a long formation time and fail to mimic in vivo microbial biofilm conditions. Moreover, biofilms make it difficult to monitor the effectiveness of antibiotics. This work creates a powerful yet simple method to form a target biofilm and develops an innovative approach to monitoring the antibiotic's efficacy against a biofilm-associated infection. A paper-based culture platform can provide a new strategy for rapid microbial biofilm formation through capillary action. A combined electrical-electrochemical technique monitors bacterial metabolism rapidly and reliably by measuring microbial extracellular electron transfer (EET) and using electrochemical impedance spectroscopy (EIS) across a microbe-electrode interface. Three representative pathogens, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus, form their biofilms controllably within an hour. Within another hour their susceptibilities to three frontline antibiotics with different action modes (gentamicin, ciprofloxacin, and ceftazidime) are examined. Our antibiotic susceptibility testing (AST) technique provides a quantifiable minimum inhibitory concentration (MIC) of those antibiotics against the in vitro biofilm models and characterizes their action mechanisms. The results will have an important positive effect because they provide immediately actionable healthcare information at a reduced cost, revolutionizing public healthcare. [ABSTRACT FROM AUTHOR]

Nanowires synthesized from metal oxides exhibit better conductivity than nanoparticles due to their greater aspect ratio which means that they can transmit electrons over longer distances; in addition, they are also more widely available than pili because their synthesis is not affected by the bacteria themselves. However, there is still little research on the application of metal oxides nanowires to enhance power generation of microbial fuel cells (MFC). In this study, a simple hydrothermal synthesis method was adopted to synthesize α-FeOOH nanowires on carbon paper (α-FeOOH-NWs), which serve as an anode to explore the mechanism of power generation enhancement of MFC. Characterization results reveal α-FeOOH-NWs on carbon paper are approximately 30–50 nm in diameter, with goethite structure. Electrochemical test results indicate that α-FeOOH nanowires could enhance the electrochemical activity of carbon paper and reduce the electron transfer resistance (R ct). Furthermore, α-FeOOH-NWs made the power density of MFC 3.2 times of the control device. SEM result demonstrates that nanowires are beneficial to the formation of biofilms and increase biomass on the electrode surface. Our results demonstrate that nanowires not only improve the electrochemical activity and conductivity of carbon paper but also facilitate the formation of biofilms and increase the biomass of the anode surface. These two mechanisms work together to boost extracellular electron transfer and power generation efficiency of MFC with α-FeOOH-NWs. Our study provides further evidence for the electrical conductivity of metal nanowires, promoting their potential applications in electricity generation such as MFC or other energy development fields. • α-FeOOH nanowires enhanced electron transfer rate and reduced Rct. • α-FeOOH nanowires are beneficial to the formation of biofilms. • α-FeOOH nanowires made the power density of MFC 3.2 times than the control. [ABSTRACT FROM AUTHOR]

Molybdenum oxides are widely used as electrocatalysts due to their polymetallic oxidation state, abundant reactive sites and low production cost. However, the low electrical conductivity and easy agglomeration has limited their practical application. Here, MoO 3 nanowires encapsulated with ZIF-67 polyhedra were grown in situ on expanded graphite paper (EGP) by a simple hydrothermal synthesis method, and then the precursors were pyrolyzed to obtain self-supported Co-MoO x @N-doped carbon/EGP composites. Thanks to the three-dimensional porous structure and the synergistic effect of Co and multi-valance MoO x , the as-prepared Co-MoO x @N-doped carbon/EGP exhibits the excellent performances of OER (η 10 = 256 mV) and HER (η 10 = 138 mV), and a small Tafel slope and good durability. Furthermore, the assembled water splitting device achieved a current density of 10 mA cm−2 at a low voltage of 1.62 V and the excellent stability after 24 h continuous water splitting. [Display omitted] • Self-standing Co-MoO x @NC/EGP exhibits the excellent OER performance with the overpotential of 256 mV at 10 mA cm−2. • Three-dimensional structure and heterogeneous interface can expose more active sites and promote the transfer of electrons. • The assembled water splitting device only require a voltage of 1.62 V to achieve a current density of 10 mA cm−2. [ABSTRACT FROM AUTHOR]

In this work, we present the development of an immunosensor for the direct, selective, and sensitive determination of symmetric dimethylarginine (SDMA) in urine, in view of the emerging role of this molecule as a biomarker for renal disease. SDMA is almost completely excreted by the kidneys, hence in renal dysfunction, the excretion is decreased, resulting in accumulation in plasma. Reference values for plasma or serum have already been established in small animal practice. Values < 15 μg/dL are considered normal, 15–19 μg/dL are values of concern, and at values > 20 μg/dL kidney disease is likely. The proposed electrochemical paper-based sensing platform uses anti-SDMA antibodies for targeted detection of SDMA. Quantification is related to a decrease in the signal of a redox indicator due to the formation of an immunocomplex that interferes with electron transfer. Square wave voltammetry measurements showed a linear correlation of the peak decline for 50 nM - 1 μM SDMA with a detection limit of 15 nM. The influence of common physiological interferences caused no significant peak reduction, indicating excellent selectivity. The proposed immunosensor was successfully applied for the quantification of SDMA in human urine of healthy individuals. Surveillance of SDMA concentration in urine could prove to be very valuable in the diagnosis or monitoring of renal disease. [ABSTRACT FROM AUTHOR]

We report here the rational development of MnO 2 nanorods coated tea bag filter paper (TBFP) as a self-standing, bendable, and disposable electrochemical probe for the sensitive and selective H 2 O 2 detection and addresses their challenges in H 2 O 2 sensing via the replacement of 'O' with 'S' in the form of MnS microcubes and its core@shell architecture with MoS 2. The as-configured MnS@MoS 2 /TBFP overwhelms the constrains of conventional electrochemical probes including time and cost consumed electrode surface renewability and catalyst loading progression, and the practice of an insulating binder. The hierarchical open porous architectures of MoS 2 -shell favour the diffusion of H 2 O 2 into the core-MnS microcubes, facilitating an analyte utilization efficacy at both the core and shell architectures. The impacts of core@shell morphological features, replacement of 'O' with 'S', surface defects, and lattice distribution of MnS@MoS 2 toward non-enzymatic H 2 O 2 sensing performances are elucidated using variant electrochemical techniques. With the synergism of uniformly implanted and exposed metallic active sites, efficient electron transfer rate, and high analyte utilization efficiency, MnS@MoS 2 /TBFP exposes the low detection limit (120 nM), excellent sensitivity (650 μA mM−1 cm−2), and wide linear range (500 nM-5 mM) on H 2 O 2 detection. Furthermore, the scrutinized non-enzymatic H 2 O 2 detection concerts of MnS/MoS 2 /TBFP are selective, decisive, repeatable, and stable, constructing the excellent recovery rates in human urine sample analyses. Thus, the collective benefits of free-standing, flexible, binder-less, re-functional, and cost-efficient MnS@MoS 2 /TBFP probe actualize the evolution of affordable and high performance H 2 O 2 sensors. Image 1 ∙ MnS@MoS 2 architectures are prepared by using a simple hydrothermal technique ∙MnS@MoS 2 modified TBFP is used as an electrochemical probe for H 2 O 2 sensing ∙Growth and formation mechanisms of MnS@MoS 2 architectures are illustrated ∙Mn(IV)/Mo(IV) centres engaged H 2 O 2 electroreduction mechanism is schematized ∙MnS@MoS 2 /TBFP establishes effectual non-enzymatic H 2 O 2 sensing performances ∙MnS@MoS 2 /TBFP's real sample H 2 O 2 sensing relevancy is actualized in human urine [ABSTRACT FROM AUTHOR]

An effective pathway to cope with the sluggish oxygen evolution reaction (OER) is to accelerate the electron transfer kinetics. Transition metal with high valence states doping can accelerate the reaction kinetics to afford high inherent activity. Herein, a novel trimetallic NiFeCr nanoalloy as an OER electrocatalyst is synthesized by replacing partial Fe in the Ni3Fe alloy with Cr. In the OER process, Cr leached from the surface layer of the NiFeCr alloy to form a core–shell NiFeCr@NiFeOOH structure. The electrons from the OER intermediates were significantly accelerated by the high-valence Cr6+ as an electron acceptor at the core–shell interface. As a result, NiFeCr@NiFeOOH exhibited excellent OER performances with a low overpotential of 209 mV at 25 mA cm−2 in 1.0 M KOH on conductive carbon paper, outperforming the Ni3Fe alloy without Cr doping. Our work provides a new strategy to design and synthesize the NiFe-based alloy with high OER activity. [ABSTRACT FROM AUTHOR]

Rapid detection of indoor airborne viruses is critical to prevent the spread of respiratory diseases. Herein, we present sensitive, highly rapid electrochemical measurement of airborne coronaviruses through condensation-based direct impaction onto antibody-immobilized, carbon nanotube-coated porous paper working electrodes (PWEs). Carboxylated carbon nanotubes are drop-cast on paper fibers to make three-dimensional (3D) porous PWEs. These PWEs have higher active surface area-to-volume ratios and electron transfer characteristics than conventional screen-printed electrodes. The limit of detection and detection time of the PWEs for liquid-borne coronaviruses OC43 are 65.7 plaque-forming units (PFU)/mL and 2 min, respectively. The PWEs showed sensitive and rapid detection of whole coronaviruses, which can be ascribed to the 3D porous electrode structure of the PWEs. Moreover, water molecules condense on airborne virus particles during air sampling, and these water-encapsulated virus particles (<4 µm) are impacted on the PWE for direct measurement without virus lysis and elution. The whole detection takes ∼10 min, including air sampling, at virus concentrations of 1.8 and 11.5 PFU/L of air, which can be due to the highly enriching and minimally damaging virus capture on a soft and porous PWE, demonstrating the potential for the rapid and low-cost airborne virus monitoring system. [Display omitted] • Paper working electrodes (PWEs) are used to detect whole coronaviruses in liquids and in air. • Carbon nanotubes are deposited on a fibrous paper to make porous PWEs. • The detection time of PWEs for liquid-borne coronaviruses is 2 min. • Airborne coronaviruses are water-encapsulated and impacted on PWEs for direct measurement without virus lysis and elution. • Detection of airborne coronaviruses takes ∼10 min including air sampling at 1–10 PFU/L of air. [ABSTRACT FROM AUTHOR]

Hemoglobin A1c (HbA1c) is a standard biomarker to measure long-term average glucose concentration for diagnosis and monitoring of diabetes. Various methods have been reported for measuring HbA1c, however, portable and precise determination is still challenging. Herein, a new highly sensitive electrochemical nanobiosensor is developed for the specific determination of HbA1c. A nanocomposite of reduced graphene oxide (rGO) and gold with hierarchical architecture structure was electrochemically deposited on a cheap and flexible graphite sheet (GS) electrode. The nanocomposite increased the surface area, improved the electron transfer on the electrode surface and augmented the signal. It also provided a suitable substrate for linkage of thiolated DNA aptamer as a bioreceptor on the electrode surface by strong covalent bonding. The quantitative label free detection was carried out by differential pulse voltammetry (DPV) in a phosphate-buffered saline (PBS) solution containing redox probe Fe(CN) 6 3−/4-. The detection is based on insulating the surface in presence of HbA1c and decreasing the current, which is directly related to the HbA1c concentration. The nanobiosensor demonstrated high sensitivity of 269.2 μA. cm−2, wide linear range of 1 nM–13.83 μM with a low detection limit of 1 nM. The biosensor was successfully used for measuring HbA1c in blood real sample. Furthermore, it is promising to use it as a part of a point of care device for low-invasive screening and management of diabetes. Image 1 • An electrochemical nano-genosensor is proposed to hemoglobin A1c determination. • Graphite sheet (GS) is used as a cheap electrode and good candidate to commercialize. • A nanostructure of RGO-gold is electrodeposited on the GS by a facile method. • The biosensor exhibited a very high sensitivity for measuring HbA1c. • The developed biosensor is successfully used for HbA1c measurement in blood sample. [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]

[Display omitted] • New biocathode including BOD, 4-APA, and BP electrode (BP/4-APA/BOD is suggested. • The biocathode is prepared by electrografting method. • Membraneless paper type EBFCs using this biocathode are fabricated. • This paper type EBFC is well operated even in a condition of living body fluid. • OCV/MPD of this paper type EBFC are 0.612 ± 0.002 V/92.025 ± 0.892 μW cm−2. A new biocathode consisting of bilirubin oxidase (BOD), 4-aminophthalic acid (4-APA) and buckypaper (BP) electrode is suggested for enzymatic biofuel cells (EBFCs). Here, to enhance the electron transfer rate of BOD, electrografting method is imported. When this method and 4-APA are utilized, BP surface has negative charges by the polarity arrangement of 4-APA, forming BP/4-APA structure. With the modification of surface charge, T1 active site within BODs having positive charges are strongly bonded with the negative charges of BP/4-APA in neutral pH condition, while the orientation of T1 site is well aligned by electrostatic interaction. This treatment increases both reactivities of cathodic reaction and EBFC performance. To prove that, the performance of membraneless paper-type EBFCs using the new flexible BP/4-APA/BOD biocathode is investigated. According to the evaluations, their maximum power density and open circuit voltage are 92.025 ± 0.892 μW cm−2 and 0.612 ± 0.002 V with injection of 10 mM glucose which is a condition of living body fluid. Such performances are far better than those of other membraneless EBFCs and are large enough to be utilized as a power source of implantable devices for the human body. [ABSTRACT FROM AUTHOR]

Electrocatalytic nitrate reduction reaction (NitRR) is an energy-saving and environmentally benign approach to synthesizing ammonia under ambient conditions. However, the development of noble metal-free catalysts with high activity and selectivity is still a significant challenge. In this study, uniformly dispersed amorphous CoBx nanoparticles supported on carbon paper were synthesized VIA a simple wet chemical reduction method. As an efficient nitrate reduction electrocatalyst, CoBx exhibited a maximum faradaic efficiency of 94.00 ± 1.67% and a yield rate of up to 0.787 ± 0.028 mmol h−1 cm−2 for ammonia production. The enhanced NitRR performance could be attributed to a partial electron transfer from B to Co, which is necessary for optimizing the adsorption energies of the reaction intermediates and facilitating electron transport. Thus, selective and cost-effective electroreduction of nitrates to ammonia can be achieved using CoBx nanoparticles. [ABSTRACT FROM AUTHOR]

PPy/Ag/cellulose paper bar, prepared by making use of capillary forces of cellulose paper for liquids, presents sensitive response to multiple inducement of pH, gas (mist and human breath), and mechanical behavior (finger press). These feedback stems from the variation of bipolaron density and the modulation of electrons transfer efficiency in PPy/Ag/cellulose paper bar. [Display omitted] • Efficient and rapid way to couple cellulose paper with conductive polymer and Ag. • PPy/Ag/cellulose paper bar with flexibility, portability, low cost, lightweight. • Paper with sensitive reply to multiple stimulus of pH, mist, breath, and finger press. Cellulose paper is a flexible, biocompatible and portable substrate that possess high potential in smart sensing and electronic application field. The performance of cellulose paper can be regulated to meet special requirements by assembling it with functional material. In this work, we show an efficient way to couple cellulose paper with Polypyrrole (PPy) and Ag within 5 s, driven by capillary forces of cellulose paper for liquids. The prepared PPy/Ag/cellulose paper bar exhibited sensitive feedback to multiple inducement of pH, gas (mist and human breath), and mechanical behavior (finger press). These response is attributed to the variation of bipolaron density and the modulation of electrons transfer efficiency in PPy/Ag/cellulose paper bar. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiCuP electrocatalysts were electrodeposited onto porous carbon paper. • Low-crystallinity of NiCuP facilitates the electron transfer kinetics. • Bimetallic NiCu and electron-rich P of NiCuP enhanced the HER performance. • Electrochemical active sites of NiCuP were increased by employing Cu foam support. • PEMWE with NiCuP/CF/CP cathode exhibited a current density of 0.35 A/cm2 at 2.0 V cell. Transition metal phosphide is a representative electrocatalyst for hydrogen production via water electrolysis, owing to its superior activity and stability. In this study, we prepare NiCuP electrocatalysts on porous carbon paper (CP) using facile electrodeposition, which is a simple technique to modulate the material properties by controlling the deposition parameters. In the half-cell test, their catalytic activities for hydrogen evolution reaction in an acidic medium are significantly affected by the composition and crystallinity. After the optimization, the low-crystalline NiCuP electrocatalyst with a high Cu/Ni ratio is transferred onto a 3D-structured copper foam (CF) support, which provides a larger electrochemical surface area. Then, the NiCuP/CF/CP electrode is used as the cathode of the proton exchange membrane water electrolyzer, and a reasonable single-cell performance is achieved for hydrogen production. [ABSTRACT FROM AUTHOR]

Background: Asymptomatic malaria infections can serve as potential reservoirs for malaria transmission. The density of parasites contained in these infections range from microscopic to submicroscopic densities, making the accurate detection of asymptomatic parasite carriage highly dependent on the sensitivity of the tools used for the diagnosis. This study sought to evaluate the sensitivities of a variety of molecular and serological diagnostic tools at determining the prevalence of asymptomatic Plasmodium falciparum parasite infections in two communities with varying malaria parasite prevalence. Methods: Whole blood was collected from 194 afebrile participants aged between 6 and 70 years old living in a high (Obom) and a low (Asutsuare) malaria transmission setting of Ghana. Thick and thin blood smears, HRP2 based malaria rapid diagnostic test (RDT) and filter paper dried blood spots (DBS) were prepared from each blood sample. Genomic DNA was extracted from the remaining blood and used in Plasmodium specific photo-induced electron transfer polymerase chain reaction (PET-PCR) and Nested PCR, whilst the HRP2 antigen content of the DBS was estimated using a bead immunoassay. A comparison of malaria parasite prevalence as determined by each method was performed. Results: Parasite prevalence in the high transmission site of Obom was estimated at 71.4%, 61.9%, 60%, 37.8% and 19.1% by Nested PCR, the HRP2 bead assay, PET-PCR, HRP2-RDT and microscopy respectively. Parasite prevalence in the low transmission site of Asutsuare was estimated at 50.1%, 11.2%, 5.6%, 0% and 2.2% by Nested PCR, the HRP2 bead assay, PET-PCR, RDT and microscopy, respectively. The diagnostic performance of Nested PCR, PET-PCR and the HRP2 bead assay was similar in Obom but in Asutsuare, Nested PCR had a significantly higher sensitivity than PET-PCR and the HRP2 bead assay, which had similar sensitivity. Conclusions: Nested PCR exhibited the highest sensitivity by identifying the highest prevalence of asymptomatic P. falciparum in both the high and low parasite prevalence settings. However, parasite prevalence estimated by the HRP2 bead assay and PET-PCR had the highest level of inter-rater agreement relative to all the other tools tested and have the advantage of requiring fewer processing steps relative to Nested PCR and producing quantitative results. [ABSTRACT FROM AUTHOR]

Fluorescent test papers are promising for the wide applications in the assays of diagnosis, environments and foods, but unlike classical dye-absorption-based pH test paper, they are usually limited in the qualitative yes/no type of detection by fluorescent brightness, and the colorimetry-based quantification remains a challenging task. Here, we report a single dual-emissive nanofluorophore probe to achieve the consecutive color variations from blue to red for the quantification of blood glucose on its as-prepared test papers. Red quantum dots were embedded into silica nanoparticles as a stable internal standard emission, and blue carbon dots (CDs) were further covalently linked onto the surface of silica, in which the ratiometric fluorescence intensity of blue to red is controlled at 5:1. While the oxidation of glucose induced the formation of Fe 3+ ions, the blue emission of CDs was thus quenched by the electron transfer from CDs to Fe 3+ , displaying a serial of consecutive color variations from blue to red with the dosage of glucose. The high-quality test papers printed by the probe ink exhibited a dosage-sensitive allochromatic capability with the clear differentiations of ~5, 7, 9, 11 mM glucose in human serum (normal: 3–8 mM). The blood glucose determined by the test paper was almost in accordance with that measured by a standard glucometer. The method reported here opens a window to the wide applications of fluorescent test paper in biological assays. [ABSTRACT FROM AUTHOR]