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Even after centuries-old experience in carbonizing materials we can still learn new lessons and find new applications for carbonized materials. In the past decades, laser-assisted syntheses of materials have emerged as versatile tools for the fabrication of micro- and nanostructured functional devices. In this regard, laser-carbonization is of particular interest, as it provides a method for patterning eco-friendly and potentially biodegradable electronic materials for future applications in comparison to the state-of-the-art in flexible electronics. However, using molecular precursors for laser-carbonization has been a challenge for many years. We identified a set of three different precursors and conducted an in-depth morphological and compositional study to understand how molecular precursors must be prepared for the high-speed carbonization reactions used in laser-patterning. The resulting laser-patterned carbons (LP-C) or N-doped carbons (LP-NC) are different from their conventionally pyrolyzed reference products mostly in terms of morphology. A generally porous structure and a carbonization gradient induced by the top-to-bottom energy input are the most remarkable features. Additionally, the microstructure, the elemental composition and the resulting electronic properties are different as demonstrated by X-ray photoelectron spectroscopy (XPS) and wide-angle X-ray scattering (WAXS) analysis.

Graphene oxide (GO) membranes have great potential for separation applications due to their low-friction water permeation combined with unique molecular sieving ability. However, the practical use of deposited GO membranes is limited by the inferior mechanical robustness of the membrane composite structure derived from conventional deposition methods. Here, we report a nanostructured GO membrane that possesses great permeability and mechanical robustness. This composite membrane consists of an ultrathin selective GO nanofilm (as low as 32 nm thick) and a postsynthesized macroporous support layer that exhibits excellent stability in water and under practical permeability testing. By utilizing thin-film lift off (T-FLO) to fabricate membranes with precise optimizations in both selective and support layers, unprecedented water permeability (47 L·m-2·hr-1·bar-1) and high retention (>98% of solutes with hydrated radii larger than 4.9 A) were obtained.

For the past 30 years, thin-film membrane composites have been the state-of-the-art technology for reverse osmosis, nanofiltration, ultrafiltration, and gas separation. However, traditional membrane casting techniques, such as phase inversion and interfacial polymerization, limit the types of material that are used for the membrane separation layer. Here, we describe a novel thin-film liftoff (T-FLO) technique that enables the fabrication of thin-film composite membranes with new materials for desalination, organic solvent nanofiltration, and gas separation. The active layer is cast separately from the porous support layer, allowing for the tuning of the thickness and chemistry of the active layer. A fiber-reinforced, epoxy-based resin is then cured on top of the active layer to form a covalently bound support layer. Upon submersion in water, the cured membrane lifts off from the substrate to produce a robust, freestanding, asymmetric membrane composite. We demonstrate the fabrication of three novel T-FLO membranes for chlorine-tolerant reverse osmosis, organic solvent nanofiltration, and gas separation. The isolable nature of support and active-layer formation paves the way for the discovery of the transport and selectivity properties of new polymeric materials. This work introduces the foundation for T-FLO membranes and enables exciting new materials to be implemented as the active layers of thin-film membranes, including high-performance polymers, two-dimensional materials, and metal-organic frameworks.

The facile fabrication of functionally graded all-graphene films using a single-step casting process is reported. The films consist of a self-assembled graphene oxide (GO) precursor that can be reduced to different levels on an active metal substrate. Control of processing conditions such as the underlying substrate metal and the film-drying environment results in an ability to tailor the internal architecture of the films as well as to functionally grade the reduction of GO. A gradient arrangement within each film, where one side is electrically conductive reduced GO (rGO) and the other side is insulating GO, was confirmed by scanning electron microscopy, Raman, X-ray diffraction, Fourier transform infrared, and X-ray photoelectron spectroscopy characterization studies. All-graphene-based freestanding films with selectively reduced GO were used in transient electronic applications such as flexible circuitry and RFID tag antennas, where their decommissioning is easily achieved by capitalizing on GO's ability to readily dissociate and create a stable suspension in water. Furthermore, the functionally graded structure was found to exhibit differential swelling behavior, and its potential applications in graphene-based actuators are outlined.

Carbon-based supercapacitors exhibit great rate capability, power density and cycle life, but suffer from relatively low energy density. Polyaniline provides high specific capacitance, but lacks cycling stability. By combining carbon-based materials with tetraaniline, an oligomer of polyaniline, a hybrid composite is formed that demonstrates improved supercapacitor performance relative to either material alone. In this study, the reduced graphene oxide-oligoaniline composites have been synthesized by a one-step hydrothermal process without the need for adding any oxidizing or reducing agents. FTIR, Raman spectroscopy, XPS, and MALDI-TOF mass spectroscopy indicate the successful reduction of GO to rGO and the formation of aniline oligomers. Unlike most polyaniline nanostructures for which charge storage kinetics are limited by slow diffusion-controlled reactions, the majority of oligoaniline in this composite is exposed to the electrolyte and stores charge through fast surface-controlled reactions. The unique microstructure of the rGO-oligoaniline composites facilitates transport of ions and electrons, leading to greater utilization of the active materials, high specific capacitance of 640 F/g at 0.2 mA/cm2 (corresponding to 707 C/g specific capacity), great rate capability and good cycle stability (91% retention after 2000 cycles).

The conversion of small bio-based molecules into electro-active functional carbon nanomaterials such as carbon nanodots or graphene is attracting increasing interest. In this communication we demonstrate the use of laser-reduced carbon nanodots (lrCND) as electrodes for electrochemical capacitors. A CO2-laser-assisted process is utilized to convert CNDs into highly conductive 3D-carbon monoliths. Exclusion of molecular oxygen from the reaction environment has a positive effect on device parameters and particularly on the frequency response. Using this simple and inexpensive method, an extremely fast RC time constant of 0.29 ms and a capacitance of 0.259 mF cm−2 at 120 Hz were obtained. This can be attributed to an effective conversion of CNDs into graphitic carbon in an oxygen-free environment and the presence of unconverted CNDs in the 3D-carbon network acting as doping agents.

Thin-film composite (TFC) membranes are favored for precise molecular sieving in liquid-phase separations; they possess high permeability due to the minimal thickness of the active layer and the high porosity of the support layer. However, current TFC membrane fabrication techniques are limited by the available materials for the selective layer and do not demonstrate the level of structural control needed to substantially advance organic solvent nanofiltration (OSN) membrane technology. In this work, we employ the newly developed thin-film lift-off (T-FLO) technique to fabricate polybenzimidazole (PBI) TFC membranes with porous support layers uniquely tailored to OSN. The drop-cast dense PBI selective layers endow the membranes with an almost complete rejection of common small dye molecules. The polymeric support layer is optimized by a combinatorial approach using four different monomers that alter the cross-linking density and polymer chain flexibility of the final composite. These two properties substantially affect the porogen holding capacity of the reticular polymer network, leading to the formation of different macropore structures. With a 150 nm thick PBI selective layer and fine-tuning of the support layer, the resulting membrane achieves stable and superior permeance of 14.0, 11.7, 16.4, 11.4, 17.1, and 19.7 L m-2 h-1 bar-1 for water, ethanol, methanol, isopropanol, tetrahydrofuran (THF), and acetonitrile, respectively.

Modified polyolefin separators fabricated via a roll-to-roll system exhibit markedly improved compatibility with lithium ion battery electrolytes. Zwitterionic molecules containing a perfluorophenyl azide functional group were synthesized and covalently bound to the surface of commercial polyolefin separators via UV-activated photochemistry. A roll-to-roll prototype system was constructed allowing for the functionalization of large areas of separator under ambient conditions at low cost. Lithium-ion battery cells containing the modified separators exhibit superior electrochemical performance using a common commercial electrolyte. The modified separators, both monolayer PE and trilayer PP/PE/PP, are wetted instantly upon contact with liquid electrolytes lacking linear carbonates. These electrolytes have been designed for use in batteries with advanced thermal stability properties and/or higher voltage windows, which have previously been hindered by incompatibility with commercial trilayer polyolefin separa...

Supercapacitors are energy storage and conversion devices that display high power. In order to increase energy density, redox-active materials can be incorporated into the carbonaceous electrode(s). Although in recent years many studies have offered different redox-active candidates and composite methods, there is a constant search for an effective, easily producible and stable composite material. Here, we present a graphene/ferrocene composition as a redox active 3-D supercapacitor electrode material. The combination of highly reversible, conductive and strongly attached ferrocene with the high surface area and open porous structure of graphene results in high-power, high-energy density supercapacitors. The graphene scaffold is converted from graphene-oxide (GO) by laser irradiation, a facile, fast and eco-friendly method. The ferrocene is chemically bonded to the graphene by two different approaches that take advantage of the strong and stable pi–pi interactions between the carbon and the aromatic ligands. The excellent bonding between the components results in low internal resistance and high reversibility of the redox reaction. The composite demonstrated a 205% increase in specific capacitance from 87 F g−1 for pure laser reduced graphene oxide to 178 F g−1 for the composite with ferrocene. This is equivalent to an energy density of 6.19 W h kg−1 while maintaining a power density of 26.0 kW kg−1.

Producing highly oriented graphene is a major challenge that constrains graphene from fulfilling its full potential in technological applications. The exciting properties of graphene are impeded in practical bulk materials due to lattice imperfections that hinder charge mobility. A simple method to improve the structural integrity of graphene by utilizing laser irradiation on a composite of carbon nanodots (CNDs) and 3D graphene is presented. The CNDs attach themselves to defect sites in the graphene sheets and, upon laser-assisted reduction, patch defects in the carbon lattice. Spectroscopic experiments reveal graphitic structural recovery of up to 43% and electrical conductivity four times larger than the original graphene. The composites are tested as electrodes in electrochemical capacitors and demonstrate extremely fast RC time constant as low as 0.57 ms. Due to their low defect concentrations, the reduced graphene oxide-carbon nanodot (rGO-CND) composites frequency response is sufficiently fast to operate as AC line filters, potentially replacing today's electrolytic capacitors. Using this methodology, demonstrated is a novel line filter with one of the fastest capacitive responses ever reported, and an aerial capacitance of 68.8 mF cm-2 . This result emphasizes the decisive role of structural integrity for optimizing graphene in electronic applications.

Solid solutions of tungsten diboride (WB2) with increasing substitution of tungsten (W) by tantalum (Ta) and niobium (Nb)—ranging from 0 to 50 at. % on a metals basis—were synthesized through resis...

High degrees of dispersion are a prerequisite for functional composite materials for applications in electronics such as sensors, charge and data storage, and catalysis. The use of small precursor materials can be a decisive factor in achieving a high degree of dispersion. In this study, carbon nanodots are used to fabricate a homogeneous, finely dispersed Fe2 O3 -graphene composite aerogel in a one-step conversion process from a precursor mixture. The laser-assisted conversion of small size carbon nanodots enables a uniform distribution of 6.5 nm Fe2 O3 nanoparticles during the formation of a highly conductive carbon matrix. Structural and electrochemical characterization shows that the features of both material entities are maintained and successfully integrated. The presence of Fe2 O3 nanoparticles has a positive effect on the active surface area of the carbon aerogel and thus on the capacitance of the material. This is demonstrated by testing the performance of the composite in supercapacitors. Faradaic reactions are exploited in an aqueous electrolyte through the high accessible surface of the incorporated small Fe2 O3 nanoparticles boosting the specific capacitance of the 3D turbostratic graphene network significantly.