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We report a paper-based photodetector made from mixed cation organic perovskite halide MA1–xFAxPbI3 (MA = methylammonium (CH3NH3); FA = formamidium CH(NH2)2). The detector shows a substantial photo...

Functionalized graphene oxide papers are assembled materials with a wide range of potential applications; however, scientific studies about how the physical properties of functionalized graphene oxide papers are affected by the presence of new functional groups have not been addressed. Here, electrical resistance, optical band gap, and mechanical properties of flexible and free-standing functionalized graphene oxide papers with nitroxide moieties (NGOP’s) have been studied, and two of them (mechanicals and electricals) were correlated with the interlayer d spacing for the first time; herein, a new insight about the key role that an optimum amount of functionalization agent plays over the physical properties of NGOP’s is presented. In all cases, (functionalized or pristine) graphene oxide papers were prepared using anhydrous DMF instead water in order to study and highlight the pure effect of the functionalized groups over their physical properties. The functionalized nanomaterials exhibited significantly ...

We study long-term electrochemical sodium and lithium cycling, and tensile testing behavior of thermally reduced graphene oxide (rGO) paper electrodes. We find strong dependence of annealing temperature and gas environment on the electrical conductivity, electrochemical capacity, and rate capability of the electrodes. The effect, however, was opposing for the two cell types. Lithium charge capacity increased with increasing annealing temperatures reaching a stable value of ∼325 mAh·ganode–1 (∼100 mAh·cm–3anode at ∼48 μA·cm–2 with respect to total volume of the electrode) for specimen annealed at 900 °C, while a sharp decline in Na charge capacity was noted for rGO annealed above 500 °C. Maximum sodium charge capacity of ∼140 mAh·g–1anode at 100 mA·g–1anode (∼98 mAh·cmanode–3 at ∼70 μA·cm–2) was realized for specimen reduced at 500 °C. These values are the highest reported for GO paper electrodes. More important, annealing of GO in NH3 environment resulted in a complete shutdown of its Na-ion cyclability s...

Scanning positive column of atmospheric-pressure glow discharge (AGD) plasma is proposed as an eco-friendly and cost-effective strategy toward the instantaneous (∼2 s) reduction of graphene oxide (GO) paper, further leading to a reduced graphene oxide (rGO) paper with unimpeded liquid permeation for high performance supercapacitors. Unlike previous finding that AGD plasma has no effect on GO, a well-designed AGD plasma containing scanning positive column region is demonstrated to be capable of converting GO paper to rGO paper. With the synergy of energetic electrons (electron density 1.03 × 1016 cm–3) and surface touch heating (translational temperature ∼800 K), restoration of graphene’s excellent electrical properties is realized, evidenced by a substantially (5 orders of magnitude) improved electrical conductivity. Moreover, the ultrafast reduction of oxygen functionalities results in the creation of exposed open channels and the expansion of graphene layers, leading to a rGO paper supercapacitor electr...

Due to the expeditious expansion of wearable electronics, all-solid-state flexible supercapacitors are being contemplated as promising energy-storage devices. Through the successful preparation of ...

Herein, the manufacturing of a free-standing N-doped mesoporous carbon (CPPY) paper by straightforward carbonization of polypyrrole-coated nanocellulose paper is described. The deposition of Na and...

Electrochemical measurement of pH on paper artifacts is a very important tool to assess the state of paper conservation. Different methods using different types of electrodes have been standardized to provide reproducible pH values of paper. One of these methodologies is not very invasive since it is made on the paper surface by means of a surface electrode in contact with the paper through a small layer of water previously added at the measurement point. This method is very convenient but suffers from the fact that the pH value given by the instrument is continuously changing during the measurement with a very fast rate in the first seconds and tending to reach a plateau value after very long time. Usually, the measure is taken at a time after which the rate of pH change is below a given value, i.e., when the value can be considered constant. This condition is usually signaled by an automatic instrumental alert provided to the operator. This pH value, however, is not the asymptotic one, which can be reac...

Flexible, paper-based graphene and graphene oxides are now emerging as a new class of materials with a variety of applications in electrochemical devices, novel composites, antibacterial agents, separation membranes, and so on. But the tight layer and the poor permeability limit their applications in the fields requiring permeable layers and tunable layer spacing. We demonstrate that the temperature-dependent decomposition reaction of ammonium nitrate can be utilized to modulate the layer spacing of graphene oxide paper and modify its permeability. Unlike the commonly used intercalation method, our strategy enables the layer spacing of the paper to be expanded over large range (123%–20 000%) and avoids the occupation of layer room by guest molecules. Dependent on the expansion amplitude, the papers exhibit a variety of interesting applications, including the highly efficient exclusion of small organic molecules, the separation of ultrathin nanoparticles, and the loading of polar and nonpolar guest molecul...

Graphene's excellent electrical conductivity benefits from its highly conjugated structure. Therefore, the manipulation of graphene's electronic and mechanical properties should be realized by controlled destruction of its in-sheet conjugation. Here, we report the manipulation of the conductivity of graphene papers, at the molecular level, via either covalent bonding or π–π stacking interactions using either monofunctional or bifunctional molecules. The graphene papers can be tailored with controllable conductivity from around 100 to below 0.001 S/cm. The controlled destruction of the in-sheet graphene conjugation system using monoaryl diazonium salts (MDS) resulted in a tunable decrease in the graphene paper conductivity. However, when the graphene was modified with bifunctional aryl diazonium salts (BDS), a more subtle decrease in conductivity of the graphene papers was observed. It is suggested that the modification of the graphene with the bifunctional BDS linker showed more subtle changes in conducti...

Recently, organic diodes have attracted great research interest because of their unique applications in flexible electronics. Electronic paper is one of the most attractive organic electronic devices. Hereby, we report a transparent, flexible, ionic diode paper made of two oppositely charged microfibrillated cellulose (MFC) sublayers. The current rectification ratio is around 15 at ±5 V and exhibits good repeatability at room temperature. Instead of forming a depletion region to rectify current, this paper diode uses asymmetric charge distribution to selectively control the ion diffusion direction. The asymmetric charge distribution inside the diode paper can selectively transport cations and anions under positive and negative bias, to allow an electric current to pass in one direction while being blocked in the opposite direction. Although the mechanism is quite different from semiconductor-based p–n junction, the phenomenon turns out to be very similar. It was found that the moisture content, thickness ...

We have developed a new type of flexible electrodes based on Cu nanocube-decorated free-standing graphene paper (GP) using a facile electrodeposition method. The Cu nanocubes–graphene paper (Cu–GP) hybrid electrode processes remarkable electrocatalytic activity with an onset potential of −0.10 V toward hydrazine oxidation in alkaline solutions and can serve as the catalyst layer for direct hydrazine fuel cells. One interesting finding is that a copper hydroxide/oxide layer in situ formed on Cu nanocube surfaces plays an important role in enhancing the electrocatalytic activity and durability of the electrocatalyst. A totally irreversible and diffusion-controlled oxidation of hydrazine occurs on the electrocatalyst, eventually leading to environmentally friendly products such as nitrogen and water.

A low-cost foldable asymmetric supercapacitor (ASC) with remarkable capacitive performances is fabricated by using conventional filter papers as substrate via a simple and cost-effective method. A ...

Lithium–sulfur batteries (LSBs) are of great interest as a promising energy storage device because of their high theoretical capacity and energy density. However, they exhibit poor discharge capacity and capacity retention during long-term cycling because of their inherent drawbacks including the poor conductivity of sulfur and lithium sulfide, the shuttle effect of lithium polysulfides (LiPSs), and the large volume expansion of sulfur to lithium sulfide. An effective approach that can solve these problems is to use an interlayer inserted between the separator and the cathode. Nevertheless, the underlying adsorption mechanism of LiPSs on the interlayer has not yet been widely investigated. Herein, the effect of lithium bond chemistry on the adsorption of LiPSs on the functionalized carbon fiber paper (CFP) interlayer containing hydroxyl, carboxyl, or amide functional groups is investigated by a density functional theory approach. It is found that the functionalized CFP exhibits a strong lithium bond inter...

Non-annealed graphene paper, prepared via reduction of prefabricated graphene oxide paper with hydrazine hydrate, was employed as the sole component of a binder-free lithium-ion battery anode, circumventing the polymer binders and other additives required for the fabrication of conventional electrodes. The binder-free anode fabricated from this non-annealed paper possessed excellent cyclability, while exhibiting a voltage versus capacity profile similar to that of a polymer-bound graphene powder anode. Kinetic barriers may exist for Li ion diffusion through the layered paper structure as decreasing the current rate from 50 to 10 mA·g−1 increased the reversible capacity by over 150%.

In this work, it is shown how solid-state NMR combined with dynamic nuclear polarization (DNP) can be employed as a powerful tool to selectively enhance the spectral intensity of functional groups on the surface of cellulose fibers in paper materials. As a model system, a poly(benzyl methacrylate) (PBEMA)-functionalized paper material is chosen that contains hydrophobic and hydrophilic domains. Detailed analysis of the DNP NMR data and of T1ρ data suggests that inhomogeneous 1H–1H spin diffusion is responsible for the observed differences in signal enhancement. These findings are fundamental for structural understanding of complex paper substrates for fluid transport or sensor materials.

Photodegradation of lignin is one of the major postprocessing problems in paper production, as this renders yellowing of the paper and reduced paper quality. In this study, we have explored the photochemical properties of substituted stilbene derivatives believed to be key chromophores in the photodegradation of lignin derived from cinnamyl alcohol. In particular, the present work focuses on the computation of UV/vis electronic absorption spectra for different methoxylated stilbenes and their proposed photodegradation products. All calculations were performed using the time-dependent formalism of density functional theory (TD-DFT) and the B3LYP hybrid functional. It is concluded that the methodology employed is capable of reproducing not only the overall spectra, but also subtle features owing to the effects of different substitution patterns. For the strongly absorbing first excited singlet state (HOMO --LUMO excitation) of the methoxylated stilbenes, the calculated transition energies are, albeit somewhat fortuitously, in excellent agreement with experimental data. The light-induced yellowing indirectly caused by the presence of stilbenes can be rationalized in terms of the absorption spectra of the resulting photodegraded o-quinones, for which distinct transitions in the 420-500 nm region of the visible spectrum lacking prior to degradation are observed.

The hopping charge transfer between polarons and bipolarons and metal-like band structure in polaron lattice of polyaniline makes it of high scientific worth. With above views polyaniline has been deposited on paper by a low cost chemical method to make the paper electrically conductive and functional. The prepared conductive papers were characterized using X-ray diffraction measurement, FTIR, UV–vis–NIR spectrophotometric measurement, and electrical conductivity measurement. Impressive electrical properties with good optical transparency were obtained with a highest light transmittance of 94.0% at 550 nm and electrical sheet resistance of 8.92 × 105 Ω/□. In addition, repeated cycles of deformation of the electrically conductive polyaniline incorporated flexible paper do not produce any noticeable change in its electrical conductivity and optical absorbance. The electrically conductive papers are of significant interest in preparing flexible and foldable circuits. The polyaniline-deposited conductive pape...

Surface-enhanced Raman spectroscopy (SERS) is a powerful tool for the specific, rapid, and nondestructive detection of small molecules. For detection applications, it is desirable to develop means for synthesizing SERS substrates that provide large and consistent Raman enhancement, are inexpensive and simple to synthesize, and are active for a wide variety of molecules. Here we demonstrate that nanoparticle colloids (ranging in size from 5 to 100 nm) that are purposely aggregated using electrolytes can be stabilized in the solid state using common filter paper. The SERS substrate enhancement factor (EF) is characterized using trans-1,2-bis(4-pyridyl)ethylene, and it is observed that an intermediate aggregation state provides the largest substrate EF of ∼3 × 104. Generalized Mie theory is used to investigate the relationship between nanoparticle aggregation extent, cluster geometry, and plasmonic enhancement. Overall, the electrodynamics simulations are in good agreement with experimental EF values and pro...

A survey of solvent usage for papers published in Organic Process Research & Development has been carried out for the years 1997–2012. Three solvent categories were studied: (i) solvents of concern, (ii) dipolar aprotic solvents, and (iii) neoteric solvents. In the analysis of dipolar aprotic solvent use it was found that nearly 50% of DMF/DMAc/NMP/DMSO usage is attributed to nucleophilic substitution reactions (mostly SNAr and SN2 reactions). Ideas on how to minimise the use of these four solvents in nucleophilic substitution reactions are presented, and it is hoped that these ideas will be adopted by chemists looking at SN type reactions at all stages of development. The only neoteric solvent showing any significant use is 2-methyltetrahydrofuran; usage of this solvent grew rapidly during the survey period.

Lightweight, biodegradable, and inexpensive materials are desirable to enable low-cost photovoltaics. Paper fulfills these requirements and is compatible with standard roll-to-roll printing processes. Here we report 4% efficient organic solar cells fabricated on paper substrates with a zinc-coating acting as the back contact and evaporated MoO3/Ag/MoO3 semitransparent top electrodes. We demonstrate that the rough surface of paper does not preclude its use in high-efficiency organic photovoltaics.

A paper-like self-standing film electrode composed of hierarchical mesoporous anatase TiO2 was designed and prepared through a facile route of filter paper templating in combination with an additional deep hydrolysis treatment process. The specific surface area of hierarchical mesoporous TiO2 increased to 155.6 m2 g–1 compared to the sample without the additional deep hydrolysis, which is only 16.0 m2 g–1. The results are consistent with a simple model of sphere stacking which suggests that the rich mesopores were from the void space created by the TiO2 stacking. By applying such film as binder-free electrode in lithium-ion batteries (LIBs), good rate performance was demonstrated, and the capacity was still 100 mA h g–1 even at the high rate of 20 C. The contributions of Li+ insertion/extraction reaction and capacitive effect on the capacities were investigated by cyclic voltammetry and calculation. With the sweep rate increased from 0.1 to 10 mV s–1, the contributions of capacitive effects increased from...

A humidity sensor on cellulose paper is demonstrated using single-walled carbon nanotubes functionalized with carboxylic acid. The conductance shift of the nanotube network entangled on the microfibril cellulose is utilized for the humidity sensing. Compared to the control sensor made on a glass substrate, the cellulose-mediated charge transport on the paper substrate enhances the sensitivity. The sensor response exhibits linear behavior up to a relative humidity of 75% with good repeatability and low hysteresis. A simple circuit model is used to explain the sensor results. This approach is a step toward future paper electronics for low-cost disposable applications.

We report sensitivity to infrared radiation from a simple paper-made device, which increases its conductivity when exposed to hot objects. We propose that the conductivity of this device is due to ionic currents involving electrolyte salts dissolved in thin film of liquid dispersed over the paper surface, thus the current increases because of heating caused by absorption of infrared light from hot sources. The fast response to stimulus exposure of this sensor suggests that the heating effect is related to a radiative interaction rather than to another kind of heat transfer such as convection or conduction.

We build sensors, capable of detecting and measuring ultraviolet (UV) light, by depositing zinc oxide (ZnO) powder from a solvent suspension over common white paper. Although these sensors are easy to fabricate and require inexpensive materials, they feature characteristics similar to those of UV sensors made with complex and expensive procedures. The good performance in terms of conductivity change of our simple devices can be attributed to the conductivity and porosity properties of paper, which effectively binds the ZnO crystals. We perform analyses using quantum chemistry methods to describe possible mechanisms that explain the conductivity changes observed on the ZnO surface due to doping interactions with interstitial hydrogen and doping depletion caused by oxygen adsorption.

The emerging field of free-standing and flexible paperlike materials based on graphene sheets has become the focus of considerable research in recent years because of the scientific and technological significance of these materials. In particular, multifunctional flexible graphene-based films or papers are in high demand for various applications. Herein, we report the fabrication of magnetic, electrically conducting, and flexible paper composed of graphene and nanoscale Fe3O4 particles made using a simple yet versatile solution-processed approach. The conductive, magnetic, and mechanical properties of these free-standing hybrid papers with different loadings of nanoscale Fe3O4 particles were investigated. In addition to the excellent electrical conductivity and mechanical strength, the obtained flexible graphene/Fe3O4 hybrid papers also show superparamagnetism, which can be tuned easily through modulation of the loading of Fe3O4 nanoparticles. Combining all of these outstanding properties, we have fabrica...

Flexible silicon/single-walled carbon nanotube (Si/SWCNT) composite paper was prepared using the pulsed laser deposition (PLD) method to deposit Si onto SWCNT paper. In the composite, Si mainly shows nanoworm-like morphology. Increasing deposition time results in an increased amount of Si microspheres. Electrochemical measurements show that the capacity of the composite paper is improved by the presence of Si. The Si/SWCNT composite with only 2.2% Si shows a capacity of 163 mA h g−1 at a current density of 25 mA g−1 up to 50 cycles, which is more than 60% improvement of the capacity of pristine CNT paper. The Si contribution in the 2.2%-Si/SWCNT sample is calculated to be higher than 3000 mA h g−1.

We demonstrate that vertically aligned carbon nanotubes can be synthesized directly on conductive carbon papers and used as excellent electrochemical capacitors. The carbon nanotubes were synthesized with use of an Al/Fe catalyst via water-assisted chemical vapor deposition. They grew as fast as ∼100 μm/min and approximately 70% of them had double walls with an average diameter of ∼6 nm. Interestingly, the carbon nanotube forest showed microscale patterns defined by the structure of underlying carbon papers. The nanotubes were attached well to the carbon papers and maintained their adhesion under mild ultrasonication in solution. Owing to the direct integration, naturally patterned structure, and good alignment, the carbon nanotubes showed excellent performance as supercapacitors. In aqueous 1 M H2SO4 solution, specific capacitance, energy, and power measured at the current density of 20 A/g were ca. 200 F/g, 20 Wh/kg, and 40 kW/kg, respectively. A specific energy of >100 Wh/kg was achieved when organic e...

Cellulose has been discovered as a smart material, which is termed as electro-active paper (EAPap). EAPap actuator revealed large displacement upon low actuation voltage and low electrical power consumption. However, the performance of the actuator was reduced as the actuation time increased. To investigate the performance degradation of the actuator, field emission scanning electron microscope (FESEM) images were taken on the surfaces of gold electrode of the actuator, and energy dispersive spectroscopy (EDS) was performed on them. Nanoparticles and nanoholes were observed on the surfaces of gold electrode after actuation, which might be strongly associated with the degradation of the actuator performance. The compositions of nanoparticles were gold and sodium. The degradation rate of the actuator performance and the number of nanoparticles at a low actuation frequency (2 Hz) were larger than those of a higher frequency (5 Hz). As the actuation voltage increased, the actuator performance degraded rapidly.

The electrochemical cycling performance of high purity single wall carbon nanotube (SWCNT) paper electrodes has been measured vs lithium metal for a series of electrolyte solvent compositions. The addition of propylene carbonate (PC) into the conventional ethylene carbonate (EC):dimethyl carbonate (DMC) cosolvent mixture enabled a reversible lithium ion capacity of 520 mAh/g for high purity SWCNTs. The free-standing SWCNT electrode (absent of polymer binder or metal substrate support) with this electrolyte combination demonstrates enhanced cycleability, retaining >95% of the initial capacity after 10 cycles. The first cycle hysteresis, common in these materials, is shown to vary dramatically with solvent selection and illustrates the importance of the solid−electrolyte−interface (SEI) formation on SWCNT capacity. The effect of galvanostatic charge rate (i.e., C-rate) on lithium ion capacity shows a 2× improvement [in capacity per current] over reported values for conventional graphite anode materials. The...

The causes of Au-electrode damage to an electroactive paper (EAPap) actuator coated with Au and polypyrrole (PPy) were investigated with various electric field frequencies and strengths. The resonance frequency of 3.5 Hz was obtained for 3 and 4 V. Electric field frequencies below (2 Hz) the resonance frequency yielded a faster bending displacement reduction than those of the higher resonance frequency. High electric field strength (4 V) shows a faster reduction of bending displacement than lower field strength (3 V). The degree of Au-electrode damage after a certain period of actuation is shown in field emission scanning electron microscope (FESEM) images. The electric field strength and frequency and bending displacement reduction were found to be closely related to the degree of Au-electrode damage.

Multiwalled carbon nanotubes (MWCNTs) were grown on the fibers of a commercial porous carbon paper used as carbon-collecting electrodes in fuel cells. The tubes were then covered with Pt nanoparticles in order to test these gas diffusion electrodes (GDEs) for oxygen reduction in H2SO4 solution and in H2/O2 fuel cells. The Pt nanoparticles were characterized by cyclic voltammetry, transmission electron microscopy, and X-ray photoelectron spectroscopy. The majority of the Pt particles are 3 nm in size with a mean size of 4.1 nm. They have an electrochemically active surface area of 60 m2/g Pt for Pt loadings of 0.1-0.45 mg Pt/cm2. Although the electroactive Pt surface area is larger for commercial electrodes of similar loadings, Pt/MWCNT electrodes largely outperform the commercial electrode for the oxygen reduction reaction in GDE experiments using H2SO4 at pH 1. On the other hand, when the same electrodes are used as the cathode in a H2/O2 fuel cell, they perform only slightly better than the commercial electrodes in the potential range going from approximately 0.9 to approximately 0.7 V and have a lower performance at lower voltages.

A DSC chart can be turned into a phase diagram generally only with the aid of other experimental information, such as solubility measurements or slurrying experiments. There are several ways of presenting phase behaviour diagrammatically. It is shown how to produce a phase diagram and how to avoid some of the potential errors of the experimental measurements.

Departamento de Qui´mica, Instituto Militar de Engenharia,Pracua General Tibu´rcio, 80, 22290-070, Rio de Janeiro-RJ,Brazil, Departamento de Qui´mica Geral e Inorgaˆnica,Instituto de Qui´mica, UniVersidade do Estado do Rio deJaneiro, Rua Sa˜o Francisco XaVier, 524, 20550-013 Rio deJaneiro-RJ, Brazil, and Departamento de Qui´mica,UniVersidade Federal de LaVras, Campus UniVersita´rio,CP 3037, 37200-000 LaVras-MG, BrazilReceiVed: June 2, 2006Recently, we proposed the frontier effective-for-reactionmolecular orbital (FERMO) concept terminology to identify themolecular orbital (MO) that drives a type of reaction.