Enhanced proton transfer of an electrospun, single chitosan fiber doped by TFA in the presence of hydrogen in 75% relative humidity.

Two-photon lithography allows writing of arbitrary nanoarchitectures in photopolymers. This design flexibility opens almost limitless possibilities for biological studies, but the acrylate-based polymers frequently used do not allow for adhesion and growth of some types of cells. Indeed, we found that lithographically defined structures made from OrmoComp do not support E18 murine cortical neurons. We reacted OrmoComp structures with several diamines, thereby rendering the surfaces directly permissive for neuron attachment and growth by presenting a surface coating similar to the traditional cell biology coating achieved with poly-d-lysine (PDL) and laminin. However, in contrast to PDL-laminin coatings that cover the entire surface, the amine-terminated OrmoComp structures are orthogonally modified in deference to the surrounding glass or plastic substrate, adding yet another design element for advanced biological studies.

From healthcare to environmental sensors, small operational devices are being developed to monitor and report in a host of new environments. These varied environments require widely varying material properties to meet operational challenges. Unfortunately, the tools used for device fabrication are not fully compatible with the breadth of substrates being utilized. The ability to transfer operational devices from a fabrication‐friendly substrate to any arbitrary substrate is essential to meet needs. Single layer hydrogenated graphene (HG) is an excellent candidate to support the transfer of operational devices. Hydrogenation of graphene weakens the film's van der Waals interaction with its substrate, allowing it to delaminate in water. The free‐floating HG layer can then be placed onto a new substrate. In this work, this property is exploited to transfer working field‐effect transistors (FETs) and gas‐sensing polymer films onto representative hard and flexible substrates. The transferred devices are operational in place and are spaced only one atomic layer away from their final substrate surface. The versatility of HG‐assisted device transfer is also demonstrated by transferring devices onto curved, irregular, and fragile surfaces that are otherwise not fabrication‐friendly, including an nuclear magnetic resonance (NMR) spectroscopy tube, plastic water bottle, waxy plant leaf, and a culture of live neurons.

Electronic structures built on hydrogenated graphene can be delaminated from their substrate by simply dipping them in water. This allows the mild transfer of pre-built electronics onto arbitrary substrates, including fragile polymers and living cells. More details can be found in article number 1801974 by Woo-Kyung Lee, Paul E. Sheehan, and co-workers.

The integration of graphene and 2D materials into device technologies requires a detailed understanding of how intrinsic and extrinsic forces impact their properties, as well as the development of engineering strategies to vary their properties for a specific response. In this paper we describe and review our efforts for hybridizing graphene in different ways so as to modify or enhance a range of properties. This hybridization comes in the form of chemical or electronic modification for use in applications ranging from chem/bio sensors to nanoelectronics. We discuss results on exploiting chemistry and defects in graphene for chemical vapor sensing, on hybridizing graphene with fluorine atoms for potential use in nanoelectronics, and on electronically hybridizing graphene in multilayer stacks that give rise to new optical and surface properties.

Functional surfaces find application in a number of areas, such as designing flexible electronic devices and integrating electronic systems with biological ones. However, the preparation of functional surfaces entails processing that is destructive to fragile polymer or biological substrates. A benign transfer method is thus needed to move pre-functionalized surfaces from a stable substrate to a fragile one. Chemical hydrogenation of graphene weakens the adhesion force between the graphene and its substrate. We exploit this phenomenon to construct a method for transferring graphene with pre-formed chemical, physical, and electronic functionalities from a heat-, vacuum-, and chemical-stable substrate such as silicon to several less robust ones, including polymers and living cells. We also discuss reversibility of graphene hydrogenation and the implications for re-adhering graphene securely to new substrates.

Sensing devices based on Graphene Field Effect Transistors (G-FET) have been demonstrated by several groups to show excellent sensitivity for a variety of chemical agents. These devices are based on measuring changes in the electrical conductivity of graphene when exposed to various chemicals. However, because of its unique band structure, graphene also exhibits changes in its optical response upon chemical exposure. The conical intersection of the valence and conduction bands results in a low density of states near the Dirac point. At this point, chemical doping resulting from molecular binding to graphene can result in dramatic changes in graphene's optical absorption. Here we will discuss our recent work in developing a graphene planar lightwave circuit (PLC) sensor which exploits these optical and electronic properties of graphene to demonstrate chemical sensitivity. The devices are based on a strong evanescent coupling of graphene via electrically gated silicon nanowire waveguides. A strong response in the form of a reversible optical attenuation change of 6 dB is shown when these devices interact with toxic industrial chemicals such as iodine and ammonia. The optical transition can also be tuned to the optical c-band (1530-1565 nm) which enables these devices to operate at telecom wavelengths.

We show that dehydrogenation of hydrogenated graphene proceeds much more slowly for bilayer systems than for single layer systems. We observe that an underlayer of either pristine or hydrogenated graphene will protect an overlayer of hydrogenated graphene against a number of chemical oxidants, thermal dehydrogenation, and degradation in an ambient environment over extended periods of time. Chemical protection depends on the ease of oxidant intercalation, with good intercalants such as Br2 demonstrating much higher reactivity than poor intercalants such as 1,2-dichloro-4,5-dicyanonbenzoquinone (DDQ). Additionally, the rate of dehydrogenation of hydrogenated graphene at 300 °C in H2/Ar was reduced by a factor of roughly 10 in the presence of a protective underlayer of graphene or hydrogenated graphene. Finally, the slow dehydrogenation of hydrogenated graphene in air at room temperature, which is normally apparent after a week, could be completely eliminated in samples with protective underlayers over the course of 39 days. Such protection will be critical for ensuring the long-term stability of devices made from functionalized graphene.

In article number 1600751, Alon A. Gorodetsky and co-workers describe color-changing devices that are inspired by the constituent components of optically-active ultrastructures found in cephalopod skin cells. These devices are electrically controlled and exhibit distinct shifts in their reflectance and coloration due to the injection/extraction of protons. The findings hold significance for developing novel camouflage technologies, understanding ion-transporting biological systems, and engineering improved bioelectronic platforms.

Cephalopods possess remarkable camouflage capabilities, which are enabled by their complex innervated skin architectures and advanced nervous systems. As such, cephalopod skin constitutes an exciting model for biomimetic camouflage technologies. This study draws inspiration from the constituent components of optically active ultrastructures found in squid skin cells to help design color-changing bioelectronic devices, which consist of a proton-transporting active layer contacted by a proton-conducting actuating electrode. The devices exhibit distinct shifts in their reflectance and coloration, which are attributed to active layer thickness changes induced by the direct electrical injection/extraction of protons. The reported findings may hold relevance for developing novel color-changing technologies, understanding ion-transporting biological systems, and engineering improved bioelectronic platforms.

The crystallization of amorphous germanium telluride (GeTe) thin films is controlled with nanoscale resolution using the heat from a thermal AFM probe. The dramatic differences between the amorphous and crystalline GeTe phases yield embedded nanoscale features with strong topographic, electronic, and optical contrast. The flexibility of scanning probe lithography enables the width and depth of the features, as well as the extent of their crystallization, to be controlled by varying probe temperature and write speed. Together, these technologies suggest a new approach to nanoelectronic and opto-electronic device fabrication.

Nanometer-scale crystals of the two-dimensional oxide molybdenum trioxide (MoO3) were formed atop the transition metal dichalcogenides MoS2 and MoSe2. The MoO3 nanocrystals are partially commensurate with the dichalcogenide substrates, being aligned only along one of the substrate's crystallographic axes. These nanocrystals can be slid only along the aligned direction and maintain their alignment with the substrate during motion. Using an AFM probe to oscillate the nanocrystals, it was found that the lateral force required to move them increased linearly with nanocrystal area. The slope of this curve, the interfacial shear strength, was significantly lower than for macroscale systems. It also depended strongly on the duration and the velocity of sliding of the crystal, suggesting a thermal activation model for the system. Finally, it was found that lower commensuration between the nanocrystal and the substrate increased the interfacial shear, a trend opposite that predicted theoretically.

Advances in drug potency and tailored therapeutics are promoting pharmaceutical manufacturing to transition from a traditional batch paradigm to more flexible continuous processing. Here we report the development of a multistep continuous-flow CGMP (current good manufacturing practices) process that produced 24 kilograms of prexasertib monolactate monohydrate suitable for use in human clinical trials. Eight continuous unit operations were conducted to produce the target at roughly 3 kilograms per day using small continuous reactors, extractors, evaporators, crystallizers, and filters in laboratory fume hoods. Success was enabled by advances in chemistry, engineering, analytical science, process modeling, and equipment design. Substantial technical and business drivers were identified, which merited the continuous process. The continuous process afforded improved performance and safety relative to batch processes and also improved containment of a highly potent compound.

is often presented schematically as one or more continuous sheet(s) of planar carbon atoms. In reality the sheets are not planar[1,2] and have contaminants, particularly disordered carbonaceous materials, which are introduced during growth, handling, and transfer to specific substrates. the area of pristine graphene, this contamination must be characterized accurately and reproducibly enough to provide a metric for improvements within a given ‘lot’ of graphene or graphene-based heterostructures on a specific substrate. Since Raman microscopy is relatively insensitive to disordered carbon, and very thin layers might be overlooked by high-resolution transmission electron microscopy (HRTEM), aberration-corrected scanning transmission electron microscopes (ac-STEMs) are the most reliable tools to confirm and quantify the presence of this contamination.

Hydrogenated graphene undergoes elimination and substitution reactions in the presence of radical initiators.

Single-layer graphene chemically reduced by the Birch process delaminates from a Si/SiOx substrate when exposed to an ethanol/water mixture, enabling transfer of chemically functionalized graphene to arbitrary substrates such as metals, dielectrics, and polymers. Unlike in previous reports, the graphene retains hydrogen, methyl, and aryl functional groups during the transfer process. This enables one to functionalize the receiving substrate with the properties of the chemically modified graphene (CMG). For instance, magnetic force microscopy shows that the previously reported magnetic properties of partially hydrogenated graphene remain after transfer. We also transfer hydrogenated graphene from its copper growth substrate to a Si/SiOx wafer and thermally dehydrogenate it to demonstrate a polymer- and etchant-free graphene transfer for potential use in transmission electron microscopy. Finally, we show that the Birch reduction facilitates delamination of CMG by weakening van der Waals forces between graphene and its substrate.