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Carbonization of biomasses is an effective and important approach to recycle biomass waste. The tissue papers are one of the most common household trash and waste lots of natural resources and energies. Herein, the one-step carbonization and activation treatment was applied on two kinds of tissue papers to transform them into porous carbons. It was found the precursor structure and composition as well as the calcination temperatures play key roles to control the pore structures. As the active materials of supercapacitor electrodes, the resultant porous carbons obtained from different paper precursors and calcination temperatures (700–900 °C) presented different electrochemical performances. The microporous carbons derived from the 700 °C calcination of the tissue paper using the wood pulp as the raw material showed high capacitance up to ~ 200 F/g, providing a simple but effective way to recycle biomasses.

In the present study, low cost novel cellulose filter paper based silver nanoparticles (CF-AgNPs) sensor was developed. AgNPs were synthesized via green approach using aqueous leaf extract of Convolvulus cneorum (C. cneorum). The prepared AgNPs were characterized by UV–visible spectroscopy, powder X-ray diffraction (XRD), field emission scanning electronic microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDX). Fourier-transform infrared spectroscopy (FTIR) study revealed the role of C. cneorum metabolites in the reduction of Ag+ ions into AgNPs and their stabilization. Fast, low cost, single step and selective detection of carcinogenic heavy metals in the environmental sample is significant to take safety action. Prepared AgNPs showed a potential colorimetric detection limit for toxic mercury HgII around 5 ppb and CrVI up to 5 ppm. Addition of HgII, CrVI and ammonia showed marked blue shift in the surface plasmon resonance (SPR) peak of AgNPs. Of importance, this AgNPs probe was not only successfully applied for the detection of HgII, but also it could be used in the sensing of CrVI and aqueous ammonia. Thus, due to the distinctive localized SPR, high sensitivity, simplicity, lower detection limit at ppb level and rapid response time are the most useful for the colorimetric detection of aqueous ammonia and HgII at room temperature.

In recent era of modern and bendable technology, energy dearth arises as a paramount subject around the globe with a dire demand of flexible and lightweight energy storage devices. This study targets fabrication of reduced graphene oxide (rGO) and utility of abundantly available, cost effective, and environment friendly lignocelluloses (LC) fibers extracted from Carica papaya source, as a binder to bind active material (rGO) as robust and compact paper sheet. Fabricated samples were analyzed by X-ray diffraction for crystallographic analysis, Scanning electron microscopy, Transmission electron microscope for morphology, Fourier transform infrared spectroscopy for structural bonding, and Raman spectroscopy for vibrational modes. Robust and bendable rGO/LC paper electrode was tested for energy storage application by employing in different characterizations, i.e., cyclic voltammetry for capacitive behavior, galvanostatic charge–discharge for symmetric EDLC, and electrochemical impedance spectroscopy for resistive charge kinetics, respectively. rGO/LC composite sheet employed as working electrode in 3-electrode CV measurements and revealed specific capacitance of 591 F/g at a scan rate of 5 mV/s by keeping the undistorted shape of voltammograms at higher scan rates which present it as a suitable candidate for modern flexible and energy storage devices. rGO/LC-based symmetric cell revealed the highest specific capacitance of 228 F/g at applied current density of 0.1 A/g, the energy density of 6.3 Wh/kg, and power density of 129 W/kg, respectively. rGO/LC-based symmetric cell confirmed the cycling stability by revealing capacitance retention of 82% after 200 cycles. It can conclude that biomass-based rGO paper sheet can be a potential candidate as environmentally safe with remarkable electrochemical activity in energy storage applications.

Flexible and lightweight shielding materials recently have attracted increasing attention for terahertz wave due to the deteriorated performance of electronic equipment interferenced by electromagnetic yielding. Herein, flexible reduced graphene oxide (rGO) papers were prepared by solution evaporation method to attenuate the electromagnetic wave in terahertz field. They exhibited excellent electrical conductivity and remarkable electromagnetic interference shielding effectiveness. The electrical conductivity of the rGO papers was improved from 54.07 to 78.67 S/cm after annealing at 400 °C. The rGO paper annealed at 400 °C was only ~ 370 µm in thickness and particularly exhibited an outstanding absorption performance of 17.6 dB at 0.7 THz. It has been found that the maximum absorption performance of rGO papers was basically equivalent to that of the metamaterials. Moreover, electromagnetic interference shielding effectiveness of 72.1 dB of the rGO papers was obtained at 0.6 THz, which indicated that ~ 99.99% of the power was shielded. Thus, the flexible rGO papers maybe a promising candidate for optimized electromagnetic shielding materials in the terahertz band.

The rapid development of smart electronics devices has stimulated intensive research on flexible supercapacitors with high mechanical tolerance and energy density. Up to date, most of the asymmetric devices are fabricated using carbon-based materials as negative electrode materials. However, the lower capacitance of carbon-based materials limited its applicability widely. Also, the device unavoidably carries unnecessary mass and volume, leads to poor contact and performance to repeated bending of devices, and occupies more space in the electronics devices. Herein, we prepared flexible, light-weight, and thin graphite paper current collectors to fabricate flexible supercapacitors. Further, the titanium oxynitride (TiOxNy) coatings were deposited by DC magnetron sputtering over a flexible and light-weight graphite substrate as a potential negative electrode. The presence of nitrogen content in transition metal oxynitrides adds wettability to the material; hence more electrolyte ions get adsorps onto the surface of the electrode owing to their hydrophilic nature. The resultant TiOxNy/graphite electrode exhibited a high areal capacitance of 62 mF cm−2 and also showed 100% capacitance retention even after 1500 GCD cycles. The results of a series of tests indicated that the flexible electrode has better capacitive performance, suggesting that as-prepared film is a favorable candidate for light-weight and flexible supercapacitors. published

Oil-paper insulation system is an important insulation structure of converter transformer. At present study, polyamic acid introduced was synthesized firstly, then perform electrospinning and thermal imidization to prepare polyimide (PI) porous fiber membrane, and the nano-SiO2 was introduced into the fiber membrane by in-situ polymerization. FT-IR was used to characterize PI porous fiber membrane chemical structure. Consequently, when the SiO2 addition amount is 4 wt.%, the breakdown voltage of the SiO2/PI composite fiber reaches the maximum, which is 74 kV/mm. The dielectric constant and dielectric loss of the composite fiber film are 1.98–0.0013 (107 Hz). It is worth noticing that nano-SiO2 available in PI significantly improved its electrical performance.

Disposable nonenzymatic glucose sensors are constructed by electrodepositing NiPt nanosheet arrays on carbon papers. The obtained NiPt nanosheet arrays are fully examined by various techniques including SEM, TEM, XRD and XPS. The glucose sensing performance of the optimal NiPt-3 nanosheet electrode is studied using cyclic voltammetry and chronoamperometry techniques in alkaline electrolyte (0.1 M NaOH). Compared with the counterpart of Ni electrode, the NiPt-3 nanosheet electrode shows highly improved nonenzymatic glucose sensing performance. The sensors achieve a wider linear detection range between 1 μM-10.8 mM with high sensitivity of 2225.5 μA·mM−1·cm−2. The detection limit at 0.55 V is estimated to be 0.4 μM (S/N = 3). The improved glucose sensing performance of NiPt-3 nanosheets may be due to the sheet-like structure and the incorporation of Pt into the NiPt alloy nanosheets. In addition, the high selectivity and preferable feasibility for serum sample analysis demonstrate that the NiPt-3 nanosheet may be a promising disposable electrode for nonenzymatic glucose sensing measurements.

In the commented paper, there are some questionable data which should be explained or corrected by the Authors, Thangamani et al. In this comment, I have tried to pinpoint incorrect data or inconsistencies and to verify the correctness of the data presented in the crystallographic part of the paper.

Herein, we introduce a low-cost and straightforward method for preparing pH sensors based on parchment-type paper and pencil traces as a base and electrode, respectively. The hydrophobic feature of the parchment paper supports the relatively long life of the proposed pH sensor. The results indicate that the present sensors have a Nernstian response with a Nernstian slope of 52.1 ± 1.5 mV/pH and a good linearity of 0.995 from pH 4 to 10. The stability of the proposed electrode is approximately 0.75 mV/h. The prepared electrodes show a relatively long operating life compared with the published results of ordinary paper-based pH devices. However, the Nernstian factor decreases over time and stabilizes at approximately 28 mV/pH after two months. This approach provides a low-cost and reproducible pH sensor.

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

The new analysis of the previously published data on the nanocrystalline CaYTiNbO7:Eu indicates an occurrence of the size-induced structural phase transition like in other nanocrystalline phosphors of pyrochlore structure.

Graphene has recently attracted great attention as a heat spreading material due to its unique thermal transfer property. Structural defects introduced into graphene unavoidably during graphene growth or processing are significantly affect its thermal transfer property. In this study, we choose four aromatic molecules (naphthalene, anthracene, tetracene and perylene) as “molecular patches” to heal structural defects in graphene, and free-standing paper-like heat spreading films based on graphene oxide (GO)-aromatic molecule composites have been fabricated via a synchronous reduction and assembly procedure, showing tunable optical transmittance and low sheet resistance. The Raman and X-ray diffraction characterizations of the as-prepared films indicate that the aromatic molecules have been adsorbed successfully by the GO and have partially restored the intrinsic quality of graphene. Preliminary studies on heat spreading materials using GO-aromatic molecule composite films demonstrate that the films can lead to obvious reduction in temperature of the hot source, indicating that these films are promising heat spreading materials for commercial portable electronics.

Oil-paper (cellulose) insulation is the main insulation of converter transformer, and the space charge accumulation inside the oil-impregnated paper is a serious problem. To decrease the space charge accumulation and improve the breakdown field strength, the oil-impregnated paper (OIP) with different Al2O3 nanoparticles content was prepared. The test results show that the space charge accumulation in the non-modified paper and 3.75 wt% Al2O3 paper is serious under DC electric field, and the decay amplitude and decay speed of space charge are larger and faster in the short circuit test. Suppression effect of space charge in the 2.5 wt% Al2O3 paper is the best, and the decay amplitude and decay speed of space charge are the lest and slowest. Moreover, the surface potential of non-modified paper decay faster, and that of 2.5 wt% Al2O3 paper decay slowest. The breakdown field strength and resistivity of Al2O3-modified OIP are larger than those of the non-modified paper. The breakdown field strength of 2.5 wt% Al2O3 paper increases most, about 16%. Suitable Nano-Al2O3-modified increases the traps level and density of deep traps in oil-impregnated paper, resulting in the space charge suppression and breakdown field strength improvement.

PI fiber insulation paper has excellent insulation and heat resistance, which can replace traditional insulation paper to provide a new high-performance material. In this paper, we adopt a two-step method to synthesize PI, that is, firstly synthesize polyamic acid, and then perform electrospinning and thermal imidization to prepare PI porous fiber membrane. The test results show that the breakdown field strength of the PI porous film is 50 kV/mm. Further research shows that the insulation structure has the characteristics of continuous multiple breakdown. When the fiber film is repeatedly broken down to 25 times at the same point, the field strength of each breakdown of the fiber film changes between 40 and 55 kV/mm, and the average breakdown field strength is 53 kV/mm. Nano-Al2O3 was introduced into the fiber membrane by in situ polymerization. The breakdown field strength of the composite fiber film can reach 74.89 kV/mm after doping 2 wt% nano-Al2O3, which is higher than that of the pure film. At the same time, this kind of fiber paper also has repeatable breakdown characteristics, and the breakdown voltage distribution width of multiple breakdown is reduced. This characteristic provides the maintenance free characteristic of DC over-voltage for the insulation structure composed of this fiber paper, and can improve the service life of transformer under DC over-voltage such as lightning stroke.

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

In this paper, Ag/paper-based composites with low dielectric loss were obtained by introduce the concept of metamaterial into the fabrication process. In this kind of metacomposite, single-layer paper was used as basic block to build up a matrix with sandwich structure, in which Ag particles are embedded and silver particles are evenly distributed. The microstructure and phase composition were characterized by scanning electron microscope and X-ray diffractometer. The impedance spectrum of the composites in 20 Hz–1 MHz region was measured by using LCR Meter, which can be well fitted by equivalent circuit method. The results show that, compared to the composite in which Ag particles disorder distributed, the dielectric loss of the layer-by-layer structured metacomposite can be effectively reduced (tan θ ≤ 0.1), without negative effect on the dielectric constant. Moreover, the dielectric properties of metacomposites show obvious anisotropy in the horizontal and vertical directions, which might give a feasible way for flexible smart material in its design.

Unconventional and alternative resources are proved incredibly useful for flexible and bendable energy storage devices to meet the demand of modern disposable and bendable technology. Nickle hydroxide [Ni(OH)2] based composites are considered as high-performance electrodes for supercapacitor and batteries applications due to high specific capacitance at higher scan rates. This study presents the fabrication Ni(OH)2 and incorporation of lignocelluloses(LC) fibers as binders to address the inherent rigid structure. Furthermore, electrically conductive properties are address by synthesis of composites with Polypyrrole and Polyaninline. X-Ray diffraction (XRD) results confirm the successful formation of nickel hydroxide whereas scanning microscopy results (SEM) reveal the nanoparticle morphology. Incorporation of LC fibers within Ni(OH)2 particles presented as compact and flexible composite paper electrodes which can be cut with help of scissor in any shape for bulk use. Fourier Transform Infrared (FTIR) confirmed the composite formation and cyclic voltammetry (CV) measurements were performed for all the fabricated samples to observe the electrochemical kinetics by which the best specific capacitance is shown by Ni(OH)2/PPy/LC i.e. 630 Fg−1. These fabricated composites can be used further as flexible electrodes in energy storage applications because of enhanced electrochemical properties. Presented flexible Ni(OH)2 based paper sheets will be highly feasible for modern bendable and disposable energy storage devices due to light-weight and environmentally safe characteristics.

Poly (para-phenylene terephthamide) PPTA-based specialty paper suffers from limited mechanical and electrical insulation properties due to weak interfacial interactions between chemically inert PPTA microfibers. Herein, in order to activate the fiber surface, PPTA nanofibers were prepared through DMSO/KOH deprotonation process. Whereafter, a composite paper with reinforced concrete structure was constructed by combining PPTA microfibers and PPTA nanofibers through vacuum-assisted filtration process. The results show that the composite paper has a high mechanical strength of ~ 84.8 MPa, high Young’s modulus of ∼ 2.4 GPa, and elongation at break of ∼ 7%. Meanwhile, the Weibull distribution model predicts the dielectric breakdown strength of composite paper as high as 74.4 kV/mm. In addition, the composite paper also exhibited high-temperature resistance and UV resistance, indicating great advantages for operating under high temperature and electrical insulation conditions.

Cu-doped zinc oxide (Cu–ZnO) nanostructure was prepared using Whatman filter paper as a template by combustion method. For the synthesis of porous Cu–ZnO nanostructures the stoichiometric amount of precursors were impregnated in the filter papers and processed, thermally. The formation of wurtzite phase having crystallite size in the range of 20–24 nm was confirmed by X-ray diffraction (XRD) analysis. The morphological study by field emission scanning electron microscopy (FESEM) and field emission transmission electron microscopy (FETEM) shows size of nanoparticles in the range of 25–50 nm. The optical study shows red shift i.e. extended absorbance in the visible region due to Cu doping. The photoluminescence study of Cu–ZnO results quenching in the photoluminescence peak as effect of Cu doping in ZnO lattice. Considering the extended band gap in the visible region of as synthesized Cu–ZnO, the photocatalytic dye degradation activity of methylene blue (MB) was executed in presence of sunlight irradiation. The effect of salt concentration and PH on dye degradation activity also studied. The highest photocatalytic activity was observed for Cu–ZnO with 4% doping as compared with other Cu–ZnO and ZnO nanostructure. The photocatalytic performance of Cu–ZnO shows complete degradation of MB dye within 30 min for 4% Cu–ZnO nanostructure. The photocatalytic activity obtained is much higher as compare to earlier reports. The synthesis of Cu doped ZnO by paper templated method and its photocatalytic activity is hitherto unattempted.

The nanocomposites consisting of graphene oxide (GO) and ferroelectric copolymer poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] have been successfully synthesized by a co-evaporation method. The structural, dielectric and ferroelectric properties of the composite papers are investigated. The Raman spectroscopy analyses on the nanocomposites GO/P(VDF-TrFE) reveal that the defects in GOs are reduced significantly by the loading of ferroelectric P(VDF-TrFE). The IG/ID ratio increases from 1.02 (for pure GO) to 1.17 [for GO/P(VDF-TrFE)-10%], revealing that the defects are reduced by the introduction of the nano-fillers due to a strong interaction between GO and P(VDF-TrFE) in the nanocomposites. The permittivity of the nanocomposites is enhanced by almost 3-times as compared to that of the pristine GOs. The nanocomposites show a notably raised polarization with high applied electric field. Furthermore, due to the high dielectric constants, the electrical energy storage density of the nanocomposites is as high as ~ 39.89 J cm−3 at 2.8 MV cm−1. The large energy density and high dielectric break down strength suggest that GO/P(VDF-TrFE) could be the promising novel materials for electrical energy storage.

Cellulosic conductive paper/film reinforced by graphene is a promising substrate for energy storage applications due to its comparable conductivity, great flexibility and low cost. However, how to balance the content ratio of graphene/cellulose well is still a challenge. Because conductive paper of low graphene content usually has poor electrical property, while high graphene content is also discouraged owing to the decrease in other properties though electrically improved. Based on this, we developed a different method to produce the graphene/cellulose composite conductive paper. Instead of a separate intermediate-fabrication, starting materials here are continuously one-pot processed, in prior to casting the intermediate paper (solid phase). Next, it is reduced by the l-ascorbic acid solution (liquid phase), followed by a filtration to give the hetero-reduced conductive paper (HRCP). Our results indicate that HRCP possesses high conductivity up to 376 ± 4 S/m, along with good thermal and dynamic behaviors, at a relatively low graphene content of 20 wt%. Therefore, HRCP is expected to be utilized in the field of emerging energy storage.

The synthesis of ZnO nanowires (NWs) on aramid fiber (AF) surface via a facile in situ hydrothermal method was studied and the as-obtained AFs@ZnO NWs acting as the thermal conductive fiber fillers in the fabrication of aramid paper-based materials by wet-forming process were also investigated. SEM showed a dense and uniform ZnO NWs layer with vertical alignment was well established on surface of AFs. EDS and XRD characterization further confirmed the formation of ZnO NWs on AFs surface. Compared with the pristine paper, the composite paper exhibited better thermal conductivity increased by 129% from 0.0867 to 0.1985 W/m K and kept good insulating properties inherent to aramid paper. The excellent thermal conductivity of aramid paper was mainly attributed to the effective heat conduction networks formed by the AFs@ZnO NWs within the aramid paper. This study proposed an innovative way to fabricate fibrous thermally conductive filler, which effectively improved the dispersion, retention of fillers and interfacial bonding between fillers and fibers.

Electrode materials as an important component for the supercapacitors (SC) mainly undertake energy storage. Hence, the research hotspots in the SC fields are focused on the active materials of the electrode. In this study, we have provided a facile synthesis method to prepare reduced graphene oxide (RGO) and cobalt carbonate hydroxide (Co(CO3)0.5(OH)0.11·H2O) nanorod composites. The RGO films were obtained by vacuum filtration of GO papers and hydrothermal method. And during this hydrothermal, Co(CO3)0.5(OH)0.11·H2O nanorods also grow on the surface of RGO films. The as-fabricated RGO/Co(CO3)0.5(OH)0.11·H2O composites are characterized by SEM, EDS, XRD measurement. According to the electrochemical research results, the RGO/Co(CO3)0.5(OH)0.11·H2O electrodes own an ultrahigh volumetric capacitance of 1627 F cm−3 at a current density of 0.5 A g−1. Besides, the energy density of the symmetrical supercapacitor (SSc) assembled with the RGO/Co(CO3)0.5(OH)0.11·H2O electrode material is 9.22 mW h cm−3, and the capacity can be maintained 100.0% after 10,000 cycles when the composite material at the current density of 1 A g−1, these promote an efficient electrode material for electrochemical supercapacitor applications.

In this study, CuCo2S4 directly grown on carbon fiber papers (CFP) were prepared by a low-cost hydrothermal method. We also studied the influence of two different sulfur sources on the morphology and performance of CuCo2S4. Compared to TAA as sulfur source, the performance and morphology of CuCo2S4 by Na2S·9H2O are better. The CuCo2S4–Na2S nanotubes possess irregular diameters from 100 to 200 nm. An electrode made of the synthesized CuCo2S4–Na2S nanotubes/CFP composite exhibits a maximum specific capacitance of 456 F g−1 at 1 A g−1 and 83% of capacitance retention after 5000 cycles at 5 A g−1. The synthesized CuCo2S4–Na2S/CFP is used to construct an all-solid-state asymmetric supercapacitor (ASC) as the positive electrode, while and the negative electrode is made of a Fe2O3/reduced graphene oxide (rGO) composite on Ni foam. This asymmetric device has delivered an energy density of 50 W h kg−1 and a power density of 700 W kg−1 at an operating voltage of 1.5 V. It retains a long cycling life—78.2% capacity retention ratio after 5000 cycles. This work demonstrates the feasibility of the CuCo2S4–Na2S nanotubes in the applications of high-performance supercapacitors.

Metal oxide based electrodes are attractive for energy storage applications with limited characteristics of flexibility due to inherent rigid structure. However, incorporation of flexible insulating matrix within metal oxide composites result in poor electrically conductive and energy storage characteristics. This study presents the fabrication of flexible MnO2 based composite electrodes prepared by incorporation of lignocelluloses (LC) fibers, directly collected from a self-growing plant, Monochoria Vaginalis. Furthermore electrodeposition of silver (Ag) nanoparticles was performed on LC/MnO2 in potentiostatic mode to address the electrically conductive characteristics. Morphology, structural, conductive and energy storage properties of fabricated electrodes are analyzed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), impedance analyzer and potentiostat, respectively. SEM images clearly indicate the deposition of Ag nanoparticles on MnO2 nanorods embedded in LC fibers whereas FTIR results confirm the bonding of the functional groups. Cyclic voltammetry measurements showed efficient kinetics of LC/MnO2 after electrodeposition of Ag nanoparticles. The effects on electrical properties associated with blending MnO2 nanorods in lignocelluloses fibers and Ag deposition on MnO2 in LC/MnO2 are explored in wide frequency range between 10 Hz and 5 MHz. However, deposition of Ag nanoparticles on MnO2 nanorods surfaces acts as a conductive path and reduces the associated resistance. Incorporated flexibility in rigid structure of MnO2 and further improvements in conductive and energy storage characteristics will open the possibilities to be used as electrode in modern bendable energy storage devices.

Developing two dimensional (2D) materials based ink is an advanced method for fabricating printable and flexible electronic devices. 2D few-layered molybdenum disulfide (MoS2) reveals a great potential for capacitive energy storage because of its layered structure (for ion intercalation), high surface area (provide active sites) and multi-valence state of Mo (introduce pseudocapacitive reactions). These unique properties could intensively improve the potential of MoS2 for supercapacitors. However, MoS2 is a semiconductor with low conductivity, which limits its performance in electrochemistry. In the meantime, MoS2 based ink for flexible energy storage application has been barely investigated. In this work, we design a MoS2 and carbon nanotube (MoS2/CNT) hybrid ink that uses exfoliated MoS2 nanosheet and CNT to fabricate a paper-based supercapacitor. A strong synergistic effect between MoS2 and CNT in capacitive performance was observed due to the good conductivity of CNT and high capacitance of MoS2. Paper-based solid-state device is also fabricated which reveals good flexibility and high capacitive performance. This hybrid ink represents a new road for flexible paper-based devices.

Ni3S4@MoS2 nanosheets grown on the carbon fiber paper (Ni3S4@MoS2/CFP) were successfully prepared via a facile one-step hydrothermal technique. Serving as a supercapacitor electrode, the obtaining Ni3S4@MoS2/CFP exhibits a remarkable specific capacitance of 1296 F/g, high rate capability of 57.8%, and excellent cycling stability of 96.2% retention after 5000 cycles. The superior electrochemical properties of Ni3S4@MoS2/CFP nanocomposite is attributed to the synergistic effects of the layeredNi3S4, MoS2 and the conductive CFP.

In this work, a facile and scalable method to produce cellulose based flexible electrodes is introduced. Composite paper electrodes from recycled paper pulp and graphene oxide (GO) were fabricated by solvent casting at room temperature. Electrical conductivity and surface chemistry of the nanocomposite samples were tuned by chemical reduction of GO. Contact angle measurements showed a change in water droplet angle from 0° to 89° depending on the GO content and degree of reduction. Electrical measurements depicted high electrical conductivity with an ideal Ohmic behavior for the composite paper electrodes. Sheet resistance of the sample containing 4 wt% of reduced GO (rGO) was 1.649 × 103 Ω/□ which is 5 orders of magnitude higher than paper pulp. The obtained sheet resistance for the sample with 16 wt% rGO was remarkably high for cellulose based conductive electrode compared with previously reported data. Moreover, the sample containing only 0.5 wt% of rGO showed 40% higher modulus than the neat recycled paper in tension. The resultant nanocomposite can be introduced as a highly conductive and low cost flexible electrode.

In this paper, user-defined copper conductive patterns were successfully fabricated via electroless deposition onto paper substrate by using a four-step treatment process. The pristine paper samples are first dipped in 3-aminopropyltrimethoxysilane (APTMS) solution to form a uniform layer for the subsequent absorption of gold nanoparticles. Then the paper samples were wax patterned and immersed in gold nanoparticles solution in preparation for the next step electroless deposition. Herein, wax pattern was achieved via a stylus printer to print desired stencil dot matrix, which acted as hydrophobic channels, onto the paper substrate. FT-IR measurement, ultrasonic washing test and Scotch®-tape test were utilized to investigate the interaction mechanism between APTMS molecules and paper substrate. Contact angle measurement demonstrated that the hydrophobic surface of wax patterned paper. SEM images showed that the thickness of copper conductive patterns was estimated to be 2.44 μm, which was corresponding well with Surface Profiler measurement. X-ray diffraction analysis showed that the copper films deposited on paper substrate has a structure with Cu (1 1 1) preferred orientation and the resistivity of Cu patterns measured by a digital four-point probe was 6.8 µΩ cm, which was 4.2 times of the bulk Cu. Notably, only one cycle of printing wax on paper substrate could successfully regulate the deposition area of Cu films. Those above advantages make this method a promising candidate for applications in constructing functional flexible electronic devices.

Conductive Cu patterns were constructed on flexible paper via selectively electroless plating method, which including multistep procedures, namely, 3-aminopropyltrimethoxysilane (APTMS)-modification, selective Cu0-seeding and Cu-lines deposition. Herein, the Cu0 activation process could be divided into two stages: the Cu2+-absorption in cupric citrate solution and subsequently the Cu2+-reduction using a roller pen filled with sodium borohydride ink. The interaction of APTMS onto paper was confirmed by FT-IR measurement and the results indicated that the –NH2 groups originating from APTMS were grafted on the paper. The elemental analysis of the samples in each step was conducted using XPS measurement. Paper-based conductive patterns were investigated by SEM, XRD and Scotch®-tape test. SEM images illustrated that the Cu lines on the APTMS modified paper substrate was compact and composed of ball-shaped copper nuclei. Moreover, the Cu lines could be selectively plated on the required area of the paper substrate. XRD analysis showed that the obtained Cu patterns had a structure with Cu (1 1 1) preferred orientation, revealing an excellent electromigration resistivity. The resultant Cu patterns exhibited an admired adhesion to modified paper, while the Cu patterns obtained in absence of APTMS modification suffered a failure in the adhesive Scotch®-tape test. The resistivity of copper patterns characterized by the digital four-point probe was 10.3 µΩ cm, which was 6.3 times of the bulk Cu. Meanwhile, paper-based Cu pattern remained excellent conductivity after multifolding. Those results indicated that the method proposed in the present work offered a robust and efficient alternative to manufacture flexible electronics.

Carbon nanotubes (CNTs) grown on the carbon fiber paper (CFP) via chemical vapor deposition system is used as flexible substrate. NiO nanoparticles are electrodeposited onto CNTs/CFP flexible substrate by electrochemical deposition technique, which is used as a flexible electrode for supercapacitors. The NiO@CNTs/CFP electrode displays specific capacitance as high as 1317 F g−1 at a current density of 1.2 A g−1, which can preserve a capacitance retention of 90.6 % with a high current density of 9.6 A g−1. After 3000 cycles, the composite electrode can retain 90 % of initial capacitance, showing good cyclability. Meanwhile, the 3D porous nanostructure of NiO@CNTs/CFP electrode can offer a great opportunity to fabricate a high-performance flexible binder-free supercapacitor electrode, in which all of the materials could take part in the charge-storage process with their surface in direct contact with the electrolyte.

Free-standing microporous paper-like graphene films with electrodeposited polypyrrole (PPy) coatings were prepared. The microporous structures were produced by employing PS microspheres as sacrificial templates. PPy was coated on the films using an electrochemical deposition process to further improve the performance of these graphene electrode materials. The electrochemical performance of PPy coated microporous graphene films is evaluated and compared with solid graphene films. The results reveal that the incorporation of PPy and microporous structures significantly improve the electrochemical performance of graphene based electrodes for supercapacitors. Microporous films have higher capacitance than their solid counterparts although they have slightly lower conductivity, which reveals that microporous structures play an important role in the electrochemical performance of the electrode materials. The PPy coated microporous graphene films have the better electrochemical performance than uncoated counterparts, which indicates that PPy coatings have significant effects on graphene based electrodes. This in-depth research on free-standing microporous paper-like graphene with electrodeposited PPy coatings provides a new route to combine the advantages of both graphene and PPy so as to produce high performance electrodes for supercapacitors.

A simple and effective method of synthesizing nanorods (NRs) and the ability to control the size and aspect ratio of them are crucial for fabricating nanodevices. In this paper, we present a systematic study of the growth of ZnO NRs on common paper substrates using a hydrothermal approach by adjusting the growth conditions. By a slight variation of the solution concentration and the growth time, significant changes in morphology and size (aspect ratio) of the obtained ZnO NRs have been controlled. Moreover, the piezoelectric power generation from ZnO-paper nanogenerators grown with different precursor concentration and growth time are also investigated. It is found that the morphology and aspect ratio of NRs have significant influence on the piezoelectric behavior. This type of flexible piezoelectric nanogenerator will have potential applications in implantable biosensors and wearable self-powered electronic devices.

Monolayer-protected silver nanoparticles sized 5 nm were directly synthesized in relatively high concentration (0.093 M) in water phase using cheap chemicals. The ink (20 % silver) prepared with the silver nanoparticles was written on sulfuric paper by a facile pen-on-paper paradigm. The effect factors on the formation and conductive mechanism of the nanosilver films from the silver ink were studied, including the microstructure, size evolution and interaction of particles and so on. Results show that the silver nanoink allows for a low sintering temperature and with a relatively high conductivity. The grown particle, increased inter-particle contact area and off dodecanoic acid layer were the three dominating factors responded to the conductivity of the nanosilver films.

Thirumalaisamy et al. (J Mater Sci Mater Electron 26:6683, 2015), erroneously characterized a variable chemical composition of their solid solution as Ca1−xYbxF2, whereas its chemical formula should be Ca1−xYbxF2+x. As a result, Thirumalaisamy et al. calculations do not account for the additional fluoride ions that are necessary to compensate the excessive positive charge of ytterbium cations that replace calcium.