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A facile and feasible method for decoration of iron oxide (Fe3O4) submicron-sized particles on carbon paper at room temperature in a short time of 10 min is demonstrated in this work. The Fe3O4-particles decorated carbon papers were used as the negative electrode for an Fe-air rechargeable battery in both an alkaline aqueous solution system and an all-solid-state system. As for the all-solid-state Fe-air rechargeable battery, KOH-ZrO2 electrolyte powder developed by our group was used in the battery fabrication. In the alkaline aqueous solution based Fe-air rechargeable battery, a high initial discharge capacity of 460 mAh g−1(Fe) was achieved. Meanwhile, in the novel all-solid-state Fe-air rechargeable battery system, an initial discharge capacity of 70 mAh g−1(Fe) was obtained demonstrating the feasibility of this system that could be further developed towards a practical Fe-air rechargeable battery for portable and lightweight device application.

Here we report the construction of CoFe2O4 coating on carbon fiber and the coated paper was used as the interlayer between the separator and cathode of Li-S batteries. The amorphous CoFe2O4 coating was deposited by the industry-oriented spray pyrolysis technique and carbon fiber was completely enwrapped by the coating. Compared to the non-coated carbon fiber, the coated carbon fiber as the interlayer exhibits a superior reversible capacity of 1086 mA h g−1 at moderate current of 0.1C and a low decay rate in the capacity of 0.043% per cycle after 1000 cycles at 1C. Excellent long-term cycling life and rate capacity were also achieved through the coated interlayer. The specially designed interlayer showed remarkable capability to trap effectively the intermediate LPS (lithium polysulfide). The significantly inhibited “shuttle effect” of LPS would give insight into designing and making the interlayer by using new coating materials for enhanced performances of the Li-S batteries.

As a typical membrane matrix with attractive flexibility, paper has exhibited great feasibility to serve as surface-enhanced Raman scattering (SERS) substrate in the environmental monitoring and surveillance. In this research, we have designed and fabricated a distinctive hydrophilic-hydrophobic SERS substrate utilizing several ordinary papers loaded with Ag nanowires (Ag NWs). Remarkable SERS activities with an enhancement factor (EF) up to 2.63 × 106 was successfully achieved in the assembly Ag NWs with the optimal amount of nanotips and overlaps. The hydrophilic-hydrophobic strategy could contribute to anchoring microdroplets and thus enrich analytes to improve the homogeneity of substrate with a low relative standard deviation of 10.6%. Furthermore, the sophisticated SERS substrate was also applied in the in-situ detection of trace furazolidone on fish under the interference of malachite green and the reliable recovery rates were demonstrated as well.

In the current efficient energy focused society, metal–air batteries (MAB), which have high theoretical energy densities in comparison with other batteries have attracted tremendous attention for electronics and electric vehicle applications. Efficient utilization of the active material in the negative electrode with oxygen from air as the positive electrode could enable the development of a lightweight and portable metal-air battery with large energy density. Zinc (Zn), which is an abundant and inexpensive material that exhibits small voltage fluctuation during discharge as well as large discharge capacity in a liquid electrolyte-based battery system, is a good candidate as the active material in a MAB. Therefore, in this work, a Zn-air battery is fabricated and characterized using electroplated metallic Zn on carbon paper in order to increase the working contact area between Zn and the carbon paper which serves as the current collector. A near theoretical discharge capacity of 814 mAh g−1 (Zn) was achieved in an aqueous KOH liquid electrolyte system. Meanwhile, an all-solid-state Zn-air battery using a sol-gel-derived KOH-ZrO2 solid electrolyte was also fabricated which demonstrated an initial discharge capacity of 30 mAh g−1 (Zn).

Ag triangular nanoplates have been widely used as the SERS substrate due to their anisotropic morphology and sharp corners. In this work, SERS activity of Ag triangular nanoplates on glass and paper substrates was investigated with different concentration and size. A tiny triangular nuclei based synthesis method was employed to produce Ag triangular nanoplates with different size. And the extinction coefficients of Ag triangular nanoplates with different size were quantified by inductively coupled plasma mass spectrometry (ICP-MS) and transmission electron microscopy (TEM). With definite concentration, Ag triangular nanoplates with small size showed stronger SERS intensity on glass substrate at high concentrations, while large Ag triangular nanoplates exhibited better SERS effect on paper substrate at low concentrations. The possible reasons for distinct SERS activity of Ag triangular nanoplates on glass and paper were discussed with scanning electron microscope (SEM) characterization. These results exhibited important implications for fabricating Raman substrates using Ag triangular nanoplates and could be applied to the SERS sensing with flexile substrate.

Flexible nanohybrid paper electrode (termed as C-I) consisting of multi-walled carbon nanotubes (MWCNTs) and indium sulfide (In2S3) nanoplates is formed via a simple vacuum-assisted assembly and used as an anode for sodium-ion batteries (SIBs). In2S3 nanoplates which are well distributed on and bound to the MWCNTs provide a high Na storage capacity of the nanohybrid electrode as high as 410 mAh g−1 at a specific current of 50 mA g−1 over 100 charge/discharge cycles and ∼97% of rate-retention capability over the specific currents of 50 mA g−1 to 1 A g−1 for at least 50 charge/discharge cycles. Particularly, when In2S3 in the form of nanoplates was added to MWCNTs, the electrochemical performances are considerable as compared to those of bulk In2S3 or MWCNTs film electrodes. This highlights the importance of nanohybrid approach in overcoming the intrinsic complication of In2S3, i.e., the agglomeration of In2S3 into bulk form during assembly, followed by annealing. For C-I nanohybrid electrode, capacitive contribution (∼95%) rather than insertion contribution (∼5%) is predominant during charge/discharge process. The nanohybrid paper electrode is robust and thus retains capacity even under repeated mechanical deformation (flat-bent-flat cycles), demonstrating the potential of the electrode being used for flexible and wearable energy storage.

Here, a novel, simple, cost-effective, environment-friendly, non-invasive and mediator free, reduced graphene oxide (RGO) modified paper-based biosensing platform was reported. A conductive platform was generated over the ivory paper sheet via in-situ reduction of graphene oxide. The conductivity of the RGO paper was found as 0.86 S cm−1. This substrate was used for deposition of cysteine capped gold nanoparticles (Cys-AuNPs) using electrophoretic deposition technique at 60 V for biosensing application. Scanning electron microscopic images show the deposition of Cys-AuNPs in the spherical bunch on the RGO paper. The Cys-AuNPs deposition on RGO paper was confirmed by energy-dispersive x-ray spectroscopy and X-ray photoelectron spectroscopy and used for immobilization of monoclonal antibodies. This paper-based immunosensor based on chronoamperometry technique has the ability of direct electron transfer without using any mediator. This platform can replace commercially available electrodes [Indium Tin Oxide (ITO) and fluorine-doped tin oxide (FTO)] coated glass substrate, glassy carbon and gold] for electronic and electrochemical applications including point-of-care (POC) devices.

paper-like films of reduced graphene oxide with controllable shapes and thickness were prepared via funnel filtration and thermal reduction of graphene oxide (GO), which could work as flexible surface-enhanced Raman scattering (SERS) substrates to detect Rhodamine 6G (R6G) molecules. The SERS signal intensity of R6G on annealed films was found to be related with the annealling temperature. The most intense signal was observed for the film obtained at 800 °C. While for the sample annealed at 1000 °C, no SERS signal could be detected. The underlying mechanism for the difference was discussed. The reported preparation process of flexible rGO paper is simple and cost-effective, which shows great potential in rapid biochemical analysis of agricultural products with irregular surfaces.

Nanoparticles are used in several applications due to the unique properties they possess compared to bulk materials. Production techniques have continuously evolved over the years. Recently, there has been emphasis on environmentally friendly manufacturing processes. Substrate properties often limit the possible production techniques and, for example; until recently, it has been difficult to incorporate nanoparticles into paper. Chemical reduction of a precursor in the presence of paper changes the bulk properties of paper, which may limit intended end-use. In this study, we present a novel technique for incorporating silver nanoparticles into paper surface using a flame pyrolysis procedure known as Liquid Flame Spray. Papers precoated with mineral pigments and plastic are used as substrates. Silver nanoparticles were analyzed using SEM and XPS measurements. Results show a homogeneous monolayer of silver nanoparticles on the surface of paper, which demonstrated antibacterial properties against E. coli . Paper precoated with plastic showed more nanoparticles on the surface compared to pigment coated paper samples except for polyethylene-precoated paper. The results demonstrate a dry synthesis approach for depositing silver nanoparticles directly onto paper surface in a process which produces no effluents. The production technique used herein is up scalable for industrial production of antibacterial paper.

Owing to the high specific surface area and easy accessability to targeting biomolecules, emerging non-noble-metal networks are developed as an ultra-active catalyst for molecular detection. In this work, a facile flexible enzyme-free glucose sensor with superior sensing performance has been successfully constructed by integrating laser-scribed carbon paper (LSCP) with copper network (CN). Remarkably, operation parameters are modeled and optimized by Central Composite Design (CCD) to obtain an optimal conductivity of 4.783 × 107 S·m−1 for CN. Due to the great electronic/ionic pathway between LSCP of ample active sites and CN of excellent conductivity, the disposable biosensor exhibits fast electron transfer kinetics. For glucose detection, LSCP/CN exhibits an excellent sensitivity of 3626.6 μA mM−1 cm−2, a wide linear range from 1 μM to 7.96 mM, an ultra-low detection limit of 30 nM (S/N = 3) as well as favorable reusability. Satisfactory anti-interference capacity to electro-active oxides and selectivity against carbohydrates studied for concentrations up to normal physiologic levels and higher concentrations are systematically investigated. The applications of glucose determination in human serum and perspiration samples are also successful, with recoveries of 100.8% (± 2.28%) and 92.1% (±3.61%), respectively. Experimentally, the current response of the LSCP/CN biosensor is resilient to mechanical deformation with less than 8% decay even after 1000 cycles of 1 mm repeated bending and 180° cyclical folding tests. As such, LSCP/CN can be applicable for flexible, attachable and potentially wearable biosensors to attain real-time physiological monitoring.

A facile and cost-effective method was developed to create superhydrophobic surfaces onto a superhydrophilic commercial paper for the application of droplet splitting of microliter droplets into nano and sub-nano-liter droplets. The high wettability contrast of nearly 180° between the superhydrophobic region created via candle soot coated onto the patterned poly (dimethylsiloxane) and the paper causes the self-partitioning of a 1 µl droplet while sliding through the surface with a speed ranging from 0.001 to 7.3 mm/s. Additionally, the splitting of the droplet demonstrated for µl droplets of surface tension ranging from 72 mN/m to 38.5 mN/m. The plasmonic droplet assay for surface-enhanced Raman spectroscopy was fabricated via in-situ reduction of Ag nanoparticles onto the superhydrophilic region. The Raman scattering studies of methyl orange using the prepared substrates exhibit a limit of detection of 670 pM. Further, by using methyl orange as a probe molecule, selective detection of Hg2+ ions up to a concentration of 100 pM in nanoliter droplet volume is demonstrated. It is envisaged that these cost-effective plasmonic nanoliter droplet assays created via patterned superhydrophilic-superhydrophobic can find applications in high throughput screening, microfluidic bioassays, medical diagnosis.

Hydrophobic paper decorated Ag nanoparticles (NPs) with a uniform distribution was fabricated in an oil-paper-aqueous triphasic system via a facile in situ interfacial reduction approach. Interestingly, the Ag NPs formed at the paper/aqueous interface could migrate to the oil/paper interface. Moreover, these Ag NPs would not continue to migrate away the paper surface into the oil phase but was completely confined in the solid paper matrix. This phase confinement of migrated Ag NPs in the paper matrix creates abundant 3D hot spots for plasmonic enhancement. The obtained Ag-loaded paper exhibits an excellent SERS activity, reliable reproducibility and autofluorescence suppression effect, which enabling it as a promising platform for qualitative and quantitative SERS study. Due to its condensation effect, the hydrophobic paper surface can be used as a concentrator to enrich water-soluble analytes over the SERS active domains for highly sensitive detection (10−9 mol/L−1). Furthermore, the Ag-loaded paper combined with the feature of chromatography and plamon-enhanced optical signals possesses ability to perform synchronous separation and surface-enhanced Raman scattering (SERS) detection of complex samples.

Lithium-sulfur (Li-S) batteries have remarkably high theoretical specific capacity as promising candidates for next-generation energy storage. However, the “polysulfides shuttle” effect hampers its commercial application. Here, we use a kind of rice paper as a raw material to get inorganic oxides doping carbon felt by the facile carbonization method, and then modified by a simple coating process using poly (fluorenyl ether ketone) and Super P slurry. The special structure of the carbon felt derived from rice paper and its modified layer endow the final electronic conductive interlayer with inherent polysulfides absorbents and ion Coulombic repulsion functions, respectively, which show synergistic effect for trapping polysulfides. As an interlayer of Li-S batteries, the obtained carbon felt/poly (fluorenyl ether ketone)& Super P (CFSS) interlayer shows excellent electrochemical performance in improving specific capacity and decreasing polarization. The batteries with CFSS interlayer exhibit a high capacity of 837 mA h g−1 at 2.0 C and a high initial capacity of 1073.4 mA h g−1 and good capacity retention of 824.5 mA h g−1 after 500 cycles at 0.5 C. CFSS interlayer also shows excellent anti-self-discharge performance. Therefore, the simple and economical CFSS interlayer can be considered as a promising component for high performance Li-S batteries.

Mechanically robust graphene papers with both high gravimetric and volumetric capacitances are desired for high-performance energy storages. However, it’s still a challenge to tailor the structure of graphene papers in order to meet this requirement. In this work, a kind of chemical-reduction-tailored mechanically-robust reduced graphene oxide/carbon nanotube hybrid paper has been reported for high-performance electrochemical capacitive energy storages. Gallic acid (GA), as an excellent reducing agent, was used to reduce graphene oxide. Through vacuum filtration of gallic acid reduced graphene oxide (GA-rGO) and carboxylic multiwalled carbon nanotubes (MWCNTs) aqueous suspensions, mechanically robust GA-rGO/MWCNTs hybrid papers were obtained. The resultant hybrid papers showed high gravimetric capacitance of 337.6 F g−1 (0.5 A g−1) and volumetric capacitance of 151.2 F cm−3 (0.25 A cm−3). In addition, the assembled symmetric device based on the hybrid papers exhibited high gravimetric capacitance of 291.6 F g−1 (0.5 A g−1) and volumetric capacitance of 136.6 F cm−3 (0.25 A cm−3). Meanwhile, it exhibited excellent rate capability and cycling stability. Above all, this chemical reduction tailoring technique and the resultant high-performance GA-rGO/MWCNTs hybrid papers give an insight for designing high-performance electrodes and hold a great potential in the field of energy storages.

Nowadays, safe, toughness, flexible and wearable energy storage devices have become a research hotspot. However, the safety and stability of flexible devices are still challenging because traditional wearable energy storage devices are difficult to overcome the problems of leakage, toxic and fragile electrolyte and so on. In this study, we successfully designed and constructed a continuous porous conductive polymer PEDOT:PSS film coated graphene (rGO) and CoFe2O4 nanospheres composite paper electrode material. rGO paper has the advantages of good electrical conductivity and large surface area, but the graphene sheet without oxygen group has very weak adhesion between sheets, and the surface is completely hydrophobic. The water-soluble conductive polymer PEDOT:PSS film successfully increased the toughness and wettability of the graphene composite paper, and the kinetic fitting verified that the polymer improved the rate performance and electrochemical activity of the graphene composite paper. The area specific capacitance, energy density and power density of the symmetric supercapacitor made of rGO/CoFe2O4/PEDOT:PSS paper are 229.6 mF cm−2, 25.9 Wh kg−1 and 135.3 W kg−1. More importantly, the device can be charged in both positive and negative directions, and when change charging direction, the electrochemical performance of the device is also excellent. This solves the safety problem caused by the wrong connection between positive and negative poles of the supercapacitor, and also makes a contribution to the safety development of flexible supercapacitors.

Paper sheets are economic and sustainable materials alleviating the world’s reliance on petroleum plastics, yet the facile preparation of water-proof paper combing high strength with tunable surface properties is difficult. This work exploited a self-crosslinkable polyelectrolyte (poly[1-cyanomethyl-3-vinylimidazolium], PCMVIm) to circumvent this problem. The PCMVIm solution was filled into paper sheets, dried, and treated by mild ammonia (NH3) vapor at 25 °C. Paper sheets incorporated with 0.6 wt% PCMVIm were rendered water-proof (80 °C, 1 week) and acid-resistant (6 M HCl), exhibiting a wet strength that is 6 times higher than pristine paper without PCMVIm. In addition, the hydrophilicity and oleophilicity of NH3-treated paper were easily tuned by modulating the counter anions of PCMVIm. The modified paper sheets show high permeability, selectivity and stability in separating water/oil emulsions containing toluene, petroleum ether, hexane and chloroform, respectively. The facile method of NH3 vapor treatment confers wet-resistance, high strength, and tunable surface properties to paper valorization, leading to sustainable paper sheets for efficient oil/water separation.

For the important applications of gas identification related to specific diseases in healthcare, flexible gas sensors have attracted more attention. Among them, two-dimensional transition metal dichalcogenides (2D TMDs) have been known as good promising flexible gas-sensitive materials. While how to tightly attach 2D materials on flexible substrates is still challenging. Here, we propose an enhanced room-temperature flexible paper-substrate sensors based on 2D tungsten disulfide (WS2) with S defects, which are facilely synthesized by chemical exfoliation and vacuum filtration method. Structure characterization shows that most of the as-prepared 2D WS2 are within 3 layers. Spectroscopic characterization proves the existence of S defects on the surface of 2D WS2 produced by chemical exfoliation. The room-temperature (25 °C) NH3 gas sensitivity results show that the response intensity of 2D WS2 with rich S defects is nearly three times higher than the highly crystalline 2D WS2. The results of the flexible gas sensitivity indicate the fast response and high stability of our devices in breathing detection and bending experiments. Furthermore, the devices can effectively distinguish bending stress changes and gas-sensitive response signals at the same time, realizing multifunctional sensing detection. Our work will be a reference for fabricating flexible sensors based on 2D materials.

Tin-based compounds are potential anode materials for high performance lithium-ion batteries (LIBs). Due to the low melting point of metallic Sn, it is hard to maintain the crystal morphology of Sn during the as-follow process of carbon coating for high performance anode. In this work, the core@shell composite of SnOx@carbon (SnOx@C) is successfully fabricated on the substrate of carbon paper (CP) through electrodeposition and carbonization based on the precursor of Sn nanoparticles. A passivation shell is essentially grown onto Sn particles to obtain a stable structure of SnOx@C, otherwise the Sn particles will be pulverized and fell off the substrate of CP during the subsequent process of carbonization. The as-produced CP/SnOx@C film has excellent flexibility and mechanical stability to be directly served as electrode for LIBs. Carbon shell prevents the detachment and agglomeration of the active particles during lithiation/delithiation processes and maintains the stability of the conductive network. After 100th cycles, CP/SnOx@C electrode delivers 0.8 mAh cm−2, much higher than the capacity 0.37 mAh cm−2 of CP/Sn electrode operated at the current density of 0.1 mA cm−2. These features enable the flexible film of CP/SnOx@C to be attractive applications in energy storage devices.

We presented a three-step method for the preparation of superhydrophobic cellulose filter paper. It involved ZnCl2 pre-treatment to activate the cellulose fibers, a SiO2 sol-gel process to increase surface roughness and grafting of hexadecyl trimethoxysilane groups to chemically enhance the water repellency. The water contact angle of the modified paper reached 154.8°. XRD analysis confirmed silica as the product from the sol-gel process. EDS and SEM analysis showed that pre-treatment results in greater silica adhesion and retention on the paper surface. The modified paper proved to be self-cleaning and resistant to staining. Further tests under various conditions showed that ZnCl2 pre-treatment improved the durability of the superhydrophobic paper. It was concluded that pre-treatment of the filter paper prior to superhydrophobic coating results in a disruption in the cellulose crystalline structure that favours greater silica adhesion and retention.

In this work, a facile method was developed to prepare reactive superhydrophobic paper by the attachment of 10-undecylenoyl chloride onto homogenized α-cellulose followed by one-step spray-coating of the resulting cellulose derivative (α-cellulose 10-undecylenoyl ester, CUE) onto filter paper. By spray-coating a CUE suspension with a concentration of 1.04 wt% for at least 6 mL, the paper surface became superhydrophobic, which had a water contact angle of 152 ± 2° with the advancing and receding angles of 165 ± 2° and 144 ± 2° and the slide angle of 6°. Additionally, the resulting surface showed a good durable stability, acid-base stability and thermal stability. More interestingly, an obvious photoclick thiol-ene reaction could be conducted on such superhydrophobic paper, which would further enlarge the application fields of superhydrophobic surfaces.

In this paper, an effective strategy using potassium dichromate lotion to activate surfaces of commercial carbon papers leading to enhanced electrochemical capacitances was reported. It is revealed that surfaces of activated carbon papers became rougher and their specific surface areas enlarged after treatment. Further, surface hydrophilicity of the treated carbon papers enhanced due to the generation of hydrophilic groups such as hydroxyl (–OH), carbonyl (〉C O) and carboxyl (–COOH) and they act as strong polar sites to absorb water molecules. With the synergistic effect of enlarged specific surface area and enhanced surface hydrophilicity, the activated carbon papers provide high areal capacitances. In general, this strategy offers a feasible pathway to make commercial carbon paper a promising candidate for practical supercapacitors and is expected to extend to other carbon based electrode materials.

Novel sensors based on fluorescent carbon dots were developed for a rapid, selective, and sensitive detection of pyrimethanil, a fungicide widely used in many agricultural crops. The carbon dots were synthesized from maleic anhydride and triethylenetetramine via a facile one-pot pyrolysis. A quenched fluorescence intensity of carbon dots in the presence of pyrimethanil occurred via inner filter effect and strong π-π interaction. The carbon dots were sensitive to pyrimethanil across a linear range from 0.5 to 75 µM with a low detection limit of 14 nM. The sensing results could be generated in 30 s. The fluorescent carbon dots showed excellent stability and selectivity to pyrimethanil in the presence of interferences, including fungicides and metal ions. They were also successfully employed for pyrimethanil detection in apples, cucumbers, and drinking water, yielding 98.6–107.1% recovery. The practical, portable, and reusable paper-based sensor was also developed. The cytotoxicity of carbon dots was tested to demonstrate that they are sufficiently safe to use. The novel pyrimethanil sensor based on fluorescent carbon dots developed in this work can be used as a high-performance sensor and a rapid tool for quality control in food, agricultural, and environmental monitoring.

Superhydrophobic paper with remarkable durability is of considerable interest for its practical applications. In this study, a scalable, inexpensive, and universal surface sizing technique was implemented to prepare superhydrophobic paper with enhanced durability. A thin layer of starch-based composite, acting as a bio-binder, was first coated onto the paper surface by a sophisticated manufacturing technique called surface sizing, immediately followed by a spray coating of hexamethyl disilazane treated silica nanoparticles (HMDS-SiNPs) dispersed in ethanol on the surface of the wet starch-coated sheet, and the dual layers dried at the same time. Consequently, durable superhydrophobic paper with bi-layer structure was obtained after air drying. The as-prepared superhydrophobic paper not only exhibited a self-cleaning behavior, but also presented an enhanced durability against scratching, bending/deformation, as well as moisture. The universal surface sizing of starch-based composites may pave the way for the up-scaled and cost-effective production of durable superhydrophobic paper.

Paper-based surface-enhanced Raman scattering (SERS) substrates receive a great deal of attention due to low cost and high flexibility. Herein, we developed an efficient SERS substrate by gravure printing of sulfonated reduced graphene-oxide (S-RGO) thin film and inkjet printing of silver nanoparticles (AgNPs) on weighing paper successively. Malachite green (MG) and rhodamine 6G (R6G) were chosen as probe molecules to evaluate the enhanced performance of the fabricated SERS-active substrates. It was found that the S-RGO/AgNPs composite structure possessed higher enhancement ability than the pure AgNPs. The Raman enhancement factor of S-RGO/AgNPs was calculated to be as large as 109. The minimum detection limit for MG and R6G was down to 10−7 M with good linear responses (R2 = 0.9996, 0.9983) range from 10−4 M to 10−7 M. In addition, the S-RGO/AgNPs exhibited good uniformity with a relative standard deviation (RSD) of 7.90% measured by 572 points, excellent reproducibility with RSD smaller than 3.36%, and long-term stability with RSD less than 7.19%.

Designing highly efficient electrocatalysts for oxygen evolution reaction is important to meet the requirement of various renewable energy storage and conversion devices. Generally, the performance of OER catalysts can be significantly improved by synergistic action of the underlying conductive substrate. In this work, a commercial graphite paper was used as a facile substrate with catalytic activity. Graphite paper produced 10 mA cm −2 at an overpotential of 447 mV with a Tafel slope of 62 mV dec −1 . By depositing NiFe hydroxide or Mn oxide film onto the graphite paper, the electrode presented a superior activity for water oxidation, which was believed to be synergistically contributed by their available electrochemically active sites associated with the deposited film and the active substrate. High activities were also accompanied by remarkable durability at large current density levels. Our results illustrated a guideline to the design of inexpensive and highly active composite electrode for water oxidation.

Superhydrophobic coatings on paper were achieved by means of incorporating micro-nano hierarchical topography, where the water droplet was repelled and rested in a spherical shape. A silica sol, which was prepared using tetraethylorthosilicate (TEOS) as precursor and trimethylethoxysilane (TMES) as co-precursor, was poured on the paper to form a superhydrophobic surface. The coating was fluorine-free, environmentally friend, and could be easily fabricated on different kinds of papers. Besides, the transmittance of prepared coating reached up to 92% in visible light range, and the words on treated paper showed a good visualization. Moreover, the treated paper showed superior mechanical durability against 100 times of deformation, remarkable stability towards both the acidic and basic solutions. The treated paper could withstand 70 cycles of water condensation test (from 60 °C, 90% relative humidity to 10 °C) without losing superhydrophobicity, suggesting a long-term protection for paper.

Graphene-based all-solid-state supercapacitors (ASSSCs) have received increasing attention. It’s a great challenge to fabricate high-performance flexible solid-state supercapacitors with high areal and volumetric energy storage capability, superior electron and ion conductivity, robust mechanical flexibility, as well as long term stability. Herein, we report a facile method to fabricate flexible ASSSCs based on densely-packed reduced graphene oxide (rGO)/polypyrrole nanoparticle (PPy NP) hybrid papers with a sandwich framework, which consists of well-separated and continuously-aligned rGO sheets. The incorporation of PPy NPs not only provides pseudocapacitance but also facilitates the infiltration of gel electrolyte. The assembled ASSSCs possess maximum areal and volumetric specific capacitances of 477 mF/cm 2 and 94.9 F/cm 3 at 0.5 mA/cm 2 . They also exhibit little capacitance deviation under different bending states, excellent cycling stability, small leakage current and low self-discharge characteristics. Additionally, the maximum areal and volumetric energy densities of 132.5 μWh/cm 2 and 26.4 mWh/cm 3 are achieved, which indicate that this hybrid paper is a promising candidate for high-performance flexible energy storage devices.

The study reports on the preparation of polyacrylonitrile fiber paper (PANFP) functionalized with polydopamine (PD) and silver nanoparticles (Ag NPs), named as Ag NPs/PD/PANFP. The composite material was obtained via a simple two-step chemical process. First, a thin polydopamine layer was coated onto the PANFP surface through immersion into an alkaline dopamine (pH 8.5) aqueous solution at room temperature. The reductive properties of polydopamine were further exploited for the deposition of Ag NPs. The morphology and chemical composition of the composite material were characterized using scanning electron microscopy (SEM), X-ray diffraction pattern (XRD) and X-ray photoelectron spectroscopy (XPS). The catalytic activity of the nanocomposite was evaluated for the reduction of 4-nitrophenol using sodium borohydride (NaBH 4 ) at room temperature. The Ag NPs/PD/PANFP displayed good catalytic performance with a full reduction of 4-nitrophenol into the corresponding 4-aminophenol within 30 min. Moreover, the composite material exhibited a good stability up to 4 cycles without a significant loss of its catalytic activity.

A controlled monolayer-by-monolayer deposition process has been developed to fabricate Pt coating on carbon fiber paper with complex network structures using a dual buffer (Au/Ni) strategy. The X-ray diffraction, electrochemical quartz crystal microbalance, current density analyses, and X-ray photoelectron spectroscopy results conclude that the monolayer deposition process accomplishes full coverage on the substrate and that the thickness of the deposition layer can be controlled on a single atom scale. This development may pave a way to fabricate superior Pt catalysts with the minimal Pt usage. In fact, the present Pt group metal loading is 25 times lower than the U.S. DOE 2017 target value. (C) 2017 Elsevier B.V. All rights reserved.

For lipid–hydrocolloid emulsion based film, the increase of lipid amount would improve its water vapor barrier property, but also reduce the mechanical strength of the film in the meantime thus leading to a compromised lipid content in the film. However, when the emulsion is coated on paper surface, more lipid could be used for emulsion preparation to enhance the moisture resistance without considering the weakened strength of the film induced by lipid, because the mechanical properties of emulsion coated paper is mainly governed by the strength of base paper instead of the coating layer. In this study, beeswax–chitosan emulsion was first prepared and then coated on paper surface to improve paper's water vapor barrier and water resistance properties. The range and variance analysis of orthogonal test design showed that the order of priorities of the factors accordingly was beeswax solid content, drying temperature and chitosan concentration. The effect of drying temperature on water vapor transmission rate (WVTR) and water contact angle of coated paper was further investigated using 1.2 wt% chitosan and 96% beeswax solid content in the coating layer. The results indicated that water vapor barrier property was in accordance with the density of the coating layer. Atomic force microscope (AFM) was also used to characterize the surface morphology and explain the hydrophobicity of beeswax–chitosan coated paper. It was found that surface beeswax particles melted to wrinkle at high drying temperatures, while roughness values maintained at micro-scale over the temperature range investigated.

The portable, low-cost and sensitive biosensors are essential for in vitro diagnostics. Here, with a highly porous poly( l -lactic) acid nanofiber membrane (p-PLLA), an efficient and sensitive bioassay is created for biomarker detection, giving out colorimetric and fluorescence dual signals. A sensitivity-enhancing strategy is achieved based on the high porosity, loading capacity of p-PLLA and gold nanoparticles-based signal amplification. Through a sandwich immunoreaction strategy, the gold nanoparticle-labeled detector antibodies accumulate on the p-PLLA membrane and show a naked-eye-readable red spot starting from a cut-off value of the target biomarker. After adding goat anti-mouse IgG/FITC antibody (IgG-FITC), which is bound to the detector antibody, the concentration of the target biomarker can be accurately calculated by the differences in fluorescence intensity of IgG-FITC solution before and after the immunoreaction. When the liver cancer marker (α-fetoprotein) is used as a model analyte, this bioassay performs with excellent convenience and a high level of sensitivity. The preset visual color mutation point is 10 ng mL−1 (cut-off value) and the limit of detection is 0.17 pg mL−1. It shows good prospects of screening cancer biomarkers and point-of-care diagnostics applications.

Lithium-sulfur (Li-S) battery is next generation battery technology but it’s commercialization is obstructed primarily due to the shuttling effect of lithium polysulfides (LiPSs). Herein, we report an effective approach using pencil coated pyrolyzed cellulose filter paper as an interlayer to suppress the LiPSs dissolution into the electrolyte and thus allowing effective utilization of active sulfur cathode. Here, the binder clay particles (mainly SiO2) of pencil graphite facilitate the adsorption of LiPSs, whereas graphite increases the electrical conductivity and acts as a physical barrier to LiPSs. To investigate further, we utilize three different grades of pencil (4B, HB, 5H) which vary in terms of clay (SiO2) composition. It is observed that the HB pencil coated interlayer has the right balance of silica and graphite, which results in an impressive initial capacity of 1352 and 995 mAh g−1 at the current density of 0.1 and 0.5 A g−1, respectively. The cell exhibit high cycling stability of 900 mAh g−1 at 1 A g−1 (3.0 C) for 350 cycles with a slow capacity decay of 0.07% per cycle. The phenomenon of LiPSs adsorption is further understood using post-cycling analysis, H-cell adsorption testing, and shuttle factor calculation for the development of commercial Li-S batteries.

How to function properly under extreme working conditions is a key challenge for flexible electronic devices because their performance is often susceptible to environmental conditions. Herein, we demonstrated the fabrication, evaluation, and application of a flexible and highly conductive meta-aramid fiber paper (MAFP) by combining oxygen plasma treatment and electroless silver plating. The plasma treatment etched the MAFP surface and introduced large amounts of oxygen-containing groups which led to the formation of continuous silver coating and high interface binding between MAFP and Ag nanoparticles. The results showed that the silver-coated MAFP had an electrical resistance as low as 0.152 Ω/sq and exhibited excellent temperature, mechanical and chemical stability. Finally, these properties of silver-coated MAFP were exploited for its use as electromagnetic interference (EMI) shielding. Experimental results revealed that the EMI shielding effectiveness (SE) of the silver-coated MAFP reached as high as 95.47 dB and a specific EMI SE of 530.38 dB·mm−1. These results have clearly demonstrated that MAFP can become highly electrically conductive after simple plasma treatment and silver coating while keeping its excellent thermal and chemical stability and therefore holds great promise for the development of new kinds of all-weather flexible electronic devices.

Graphene-based all-solid-state supercapacitors (ASSSCs) are one of the most ideal candidates for high-performance flexible power sources. The achievement of high volumetric energy density is highly desired for practical application of this type of ASSSCs. Here, we present a facile method to boost volumetric performances of graphene-based flexible ASSSCs through incorporation of ultrafine polyaniline-poly(4-styrenesulfonate) (PANI-PSS) nanoparticles in reduced graphene oxide (rGO) papers. A compact structure is obtained via intimate contact and π–π interaction between PANI-PSS nanoparticles and rGO sheets. The hybrid paper electrode with the film thickness of 13.5 μm, shows an extremely high volumetric specific capacitance of 272 F/cm3 (0.37 A/cm3 in a three-electrode cell). The assembled ASSSCs show a large volumetric specific capacitance of 217 F/cm3 (0.37 A/cm3 in a two-electrode cell), high volumetric energy and power density, excellent capacitance stability, small leakage current as well as low self-discharge characteristics, revealing the usefulness of this robust hybrid paper for high-performance flexible energy storage devices.

In this study, we report the simple fabrication of an active substrate assisted by gold nanostructures (AuNS) for application in surface-enhanced Raman scattering (SERS) using copier paper, which is a biodegradable and cost-effective material. As cellulose is the main component of paper, it can behave as a reducing agent and as a capping molecule for the synthesis of AuNS on the paper substrate. AuNS can be directly generated on the surface of the copier paper by addition of halides. The AuNS thus synthesized were characterized by ultraviolet–visible spectroscopy, SEM, XRD, and XPS. In addition, the SERS effect of the AuNS–paper substrates synthesized by using various halides was investigated by using rhodamine 6G and melamine as probe molecules.

In this work, a novel polymeric fluorescent brightener based on coumarin (PFBC) was synthesized, using three-step synthetic route, from 7-amino-4-methylcoumarin, coumarin monomer (FBC), Acrylamide (AM) and methacrylatoethyl trimethyl ammonium chloride (DMC). The structure of PFBC was characterized by FT-IR, 1HNMR and GPC. PFBC was applied to paper fiber as light stabilizer, fluorescent brightener and surface sizing agent and its performances were evaluated by measuring the UV–vis, fluorescence, thermal stability, the cationic degree, surface strength and smoothness of paper, the brightness degree of paper and the PC value of paper. Results showed that PFBC had better solubility in water than that of FBC, by measuring the optical properties. Through the surface sizing experiment and UV aging experiment, PFBC not only enhanced the surface strength and smoothness of paper as a surface sizing agent, but also had better effect on anti-UV aging than that of FBC as light stabilizer and fluorescent brightener.

The integration of flexible electronic sensors in clinical diagnostics is visioned to significantly reduce the cost of many diagnostic tests and ultimately make healthcare more accessible. This study concentrates on the characterisation of inkjet-printed bio-functionalised polythiophene films on paper-based ultrathin gold film (UTGF) electrodes and their possible application as biorecognition layers. Physicochemical surface properties (topography, chemistry, and wetting) and electrochemical characteristics of water-soluble regioirregular tetraethylene-glycol polythiophene (TEGPT) and biotin-functionalised TEGPT (b-TEGPT) films were examined and compared. In addition, their specificity towards streptavidin protein was tested. The results show that stable supramolecular biorecognition layers of insulating b-TEGPT and streptavidin were successfully fabricated on a paper-based UTGF by inkjet-printing. Good adhesion of thiophene to UTGF can be attributed to covalent linkage between sulphur and gold, whereas the stability of the streptavidin layer is due to the high affinity between biotin and streptavidin. The device introduced can be utilised in the development of biosensors for clinically relevant analytes e.g. for detecting complementary DNA oligomers or antibody–antigen complexes.

The physics related to superhydrophobic surfaces has been investigated with attention of its potential applications in a variety of industrial and scientific fields. In the present study, a coralloid superhydrophobic coating with numerous nanometer-scale embossments has been fabricated on the filter paper surface by a simple, facile and inexpensive route. The observations show that the wettability of paper sample has been transformed from superhydrophilicity to superhydrophobicity with the WCA of 156°, and had no significant change under ambient condition or in the water, oil and corrosive liquids, displaying an outstanding superhydrophobic stability. Importantly, the coated paper sample possesses not only superhydrophobicity but also superoleophobicity, and presents an excellent property in water–oil separation, which offers an opportunity to extend the range of practical applications for filter paper.

Herein, we proposed a facile strategy for preparing well-distributed Sb-doped SnO2 nanoparticles on carbon paper (CP) via electrodeposition and in-situ oxidation as bifunctional electrodes for vanadium redox flow batteries. SnO2 and Sb-doped SnO2 modified carbon paper (CP-SnO2 and CP-SnO2/Sb) was respectively obtained by electrodepositing metals (Sn and Sn/Sb) nanoparticles, followed by a conversion to metal oxides with in-situ oxidation. CP-SnO2 exhibited better electrochemical performance toward V3+/V2+ and VO2+/VO2+ redox reactions than CP. This is because SnO2 increases active sites and hydrophilicity, which accelerates electrochemical kinetic and mass transfer for vanadium redox reactions. CP-SnO2/Sb had better electrochemical activity than CP-SnO2, because smaller Sb-doped SnO2 nanoparticles more effectively disperse through carbon fibers, producing more active sites. Furthermore, Sb doping improved conductivity of SnO2. Briefly, CP-SnO2/Sb exhibited excellent hydrophilicity, abundant active sites, and good conductivity, resulting in superior electrochemical activity. We next employed CP-SnO2/Sb as bifunctional electrodes in cell. The cell using CP-SnO2/Sb had better cycling stability and more capacity retention during a 50-cycle charge–discharge test at 50 mA cm−2. CP-SnO2/Sb reduced the electrochemical polarization of cell at higher current density. Overall, the cell using CP-SnO2/Sb showed a 9% increase in energy efficiency compared to pristine cell (64.5%) at 150 mA cm−2.