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Hexagonal rings are critical to the properties of many nanomaterials by determining their mechanical strength, thermal stability, and electrical conductivity, therefore this kind of structure has been intensively concerned in computational studies. However, existing molecular dynamics (MD) simulation tools lack specialized functions for identifying and characterizing them. To address this gap, we developed HexagonRingCalculator, a tool for identifying hexagonal rings and calculating their geometric properties, including bond lengths, ring area, and circularity, directly from MD simulation data. The code facilitates the analysis of ring deformation under varying conditions, such as temperature changes. We demonstrate its functionality and accuracy through classic and ab initio MD simulations of graphene and cellulose, highlighting its potential to advance computational studies in nanomaterials.

Using CRISPR-Cas9 technology and a microhomology-mediated end-joining repair system, we substituted genes of the gliotoxin pathway in Aspergillus fumigatus with genes responsible for chetomin biosynthesis from Chaetomium cochliodes , leading to the production of three new epipolythiodioxopiperazines (ETPs). This work represents the first successful endeavor to produce ETPs in a non-native host. Additionally, the simultaneous disruption of five genes in a single transformation marks the most extensive gene knockout event in filamentous fungi to date.

Metal-organic framework (MOF) membranes with high ion selectivity are highly desirable for direct lithium-ion (Li + ) separation from industrial brines. However, very few MOF membranes can efficiently separate Li + from brines of high Mg 2+ /Li + concentration ratios and keep stable in ultrahigh Mg 2+ -concentrated brines. This work reports a type of MOF-channel membranes (MOFCMs) by growing UiO-66-(SH) 2 into the nanochannels of polymer substrates to improve the efficiency of MOF membranes for challenging Li + extraction. The resulting membranes demonstrate excellent monovalent metal ion selectivity over divalent metal ions, with Li + /Mg 2+ selectivity up to 10 3 since Mg 2+ should overcome a higher energy barrier than Li + when transported through the MOF pores, as confirmed by molecular dynamics simulations. Under dual-ion diffusion, as the Mg 2+ /Li + mole ratio of the feed solution increases from 0.2 to 30, the membrane Li + /Mg 2+ selectivity decreases from 1516 to 19, corresponding to the purity of lithium products between 99.9 and 95.0%. Further research on multi-ion diffusion that involves Mg 2+ and three monovalent metal ions (K + , Na + , and Li + , referred to as M + ) in the feed solutions shows a significant improvement in Li + /Mg 2+ separation efficiency. The Li + /Mg 2+ selectivity can go up to 1114 when the Mg 2+ /M + molar concentration ratio is 1:1, and it remains at 19 when the ratio is 30:1. The membrane selectivity is also stable for 30 days in a highly concentrated solution with a high Mg 2+ /Li + concentration ratio. These results indicate the feasibility of the MOFCMs for direct lithium extraction from brines with Mg 2+ concentrations up to 3.5 M. This study provides an alternative strategy for designing efficient MOF membranes in extracting valuable minerals in the future.

Chirality is a widespread phenomenon in nature and in living organisms and plays an important role in living systems. The sensitive discrimination of chiral molecular enantiomers remains a challenge in the fields of chemistry and biology. Establishing a simple, fast, and efficient strategy to discriminate the spatial configuration of chiral molecular enantiomers is of great significance. Chiral perovskite nanocrystals (PNCs) have attracted much attention because of their excellent optical activity. However, it is a challenge to prepare perovskites with both chiral and fluorescence properties for chiral sensing. In this work, we synthesized two chiral fluorescent perovskite nanocrystal assembly (PNA) enantiomers by using l- or d-phenylalanine (Phe) as chiral ligands. PNA exhibited good fluorescence recognition for l- and d-proline (Pro). Homochiral interaction led to fluorescence enhancement, while heterochiral interaction led to fluorescence quenching, and there is a good linear relationship between the fluorescence changing rate and l- or d-Pro concentration. Mechanism studies show that homochiral interaction-induced fluorescence enhancement is attributed to the disassembly of chiral PNA, while no disassembly of chiral PNA was found in heterochiral interaction-induced fluorescence quenching, which is attributed to the substitution of Phe on the surface of chiral PNA by heterochiral Pro. This work suggests that chiral perovskite can be used for chiral fluorescence sensing; it will inspire the development of chiral nanomaterials and chiral optical sensors.

Pterostilbene, a derivative of resveratrol, is of increasing interest due to its increased bioavailability and potential health benefits. Sustainable production of pterostilbene is important, especially given the challenges of traditional plant extraction and chemical synthesis methods. While engineered microbial cell factories provide a potential alternative for pterostilbene production, most approaches necessitate feeding intermediate compounds. To address these limitations, we adopted a modular coculture engineering strategy, dividing the pterostilbene biosynthetic pathway between two engineered E. coli strains. Using a combination of gene knockout, atmospheric and room-temperature plasma mutagenesis, and error-prone PCR-based whole genome shuffling to engineer strains for the coculture system, we achieved a pterostilbene production titer of 134.84 ± 9.28 mg/L from glucose using a 1:3 inoculation ratio and 0.1% dimethyl sulfoxide supplementation. This represents the highest reported de novo production titer. Our results underscore the potential of coculture systems and metabolic balance in microbial biosynthesis.

Ion adsorption within nanopores is involved in numerous applications. However, a comprehensive understanding of the fundamental relationship between in-pore ion concentration and pore size, particularly in the sub-2 nm range, is scarce. This study investigates the ion-species-dependent concentration in multilayered graphene membranes (MGMs) with tunable nanoslit sizes (0.5-1.6 nm) using nuclear magnetic resonance and computational simulations. For Na + -based electrolytes in MGMs, the concentration of anions in graphene nanoslits increases in correlation with their chaotropic properties. As the nanoslit size decreases, the concentration of chaotropic ion (BF 4 - ) increases, whereas the concentration of kosmotropic ions (Cit 3- , PO 4 3- ) and other ions (Ac - , F - ) decreases or changes slightly. Notably, anions remain more concentrated than counter Na + ions, leading to electroneutrality breakdown and unipolar anion packing in MGMs. A continuum modeling approach, integrating molecular dynamic simulation with the Poisson-Boltzmann model, elucidates these observations by considering water-mediated ion-graphene non-electrostatic interactions and charge screening from graphene walls.

Combined with the inherent spin-orbital coupling effect, the elemental ferroelectricity of monolayer Bi (bismuthene) is the critical property that renders this system a 2D ferroelectric topological insulator. Here, using first-principles calculations, we systematically investigate the ferroelectric polarization in bismuthene nanoribbons and discover the width size limiting effect arising from the edge effects. The decreasing width led to the spontaneous transformation of the zigzag (ZZ) and armchair (AC) paired Bi nanoribbons into newly discovered high-symmetric nonpolarized nanoribbons. For ZZ-paired nanoribbons, the driving force of the phase transition is attributed to the depolarization field, similar to the conventional perovskite ferroelectric thin films. Instead, edge stress as a novel mechanism played a major role in the phase transition of AC-paired nanoribbons. Inspired by such a revealed mechanism, the phase transition and related ultrahigh piezoelectricity can be achieved by strain engineering in Bi nanoribbons, which could enable new applications for 2D ferroelectric devices.

Methane (CH 4 ) is the primary component of natural gas and must be purified to a certain level before it can be used as pipeline gas or liquified natural gas (LNG). In particular, nitrogen (N 2 ), a common contaminant in natural gas needs to be rejected to increase the heating value of the gas and meet the LNG product specifications. The development of energy-efficient N 2 removal technologies is hampered by N 2 's inertness and its resemblance to CH 4 in terms of kinetic size and polarizability. N 2 -selective materials are so rare. Here, for the first time, we screened 1425 alkali metal cation exchange zeolites to identify the candidates with the best potential for the separation of N 2 from CH 4 . We discovered a few extraordinary zeolite frameworks capable of achieving equilibrium selectivity toward N 2 . Particularly, Li + -RRO-3 zeolite with a specific two-dimensional structure demonstrated a selective N 2 adsorption capacity of 2.94 mmol/g at 283 K and 1 bar, outperforming the capacity of all known zeolites. Through an ab initio density functional theory study, we found that the five-membered ring of the RRO framework is the most stable cationic site for Li + , and this Li + can interact with multiple N 2 molecules but only one CH 4 , revealing the mechanism for the high capacity and selectivity of N 2 . This work suggests promising adsorbents to enable N 2 rejection from CH 4 in the gas industry without going for energy-intensive cryogenic distillations.

The intervertebral disc (IVD) exhibits complex structure and biomechanical function, which supports the weight of the body and permits motion. Surgical treatments for IVD degeneration (e.g., lumbar fusion, disc replacement) often disrupt the mechanical environment of the spine which lead to adjacent segment disease. Alternatively, disc tissue engineering strategies, where cell-seeded hydrogels or fibrous biomaterials are cultured in vitro to promote matrix deposition, do not recapitulate the complex IVD mechanical properties. In this study, we use 3D printing of flexible polylactic acid (FPLA) to fabricate a viscoelastic scaffold with tunable biomimetic mechanics for whole spine motion segment applications. We optimized the mechanical properties of the scaffolds for equilibrium and dynamic moduli in compression and tension by varying fiber spacing or porosity, generating scaffolds with de novo mechanical properties within the physiological range of spine motion segments. The biodegradation analysis of the 3D printed scaffolds showed that FPLA exhibits lower degradation rate and thus has longer mechanical stability than standard PLA. FPLA scaffolds were biocompatible, supporting viability of nucleus pulposus (NP) cells in 2D and in FPLA+hydrogel composites. Composite scaffolds cultured with NP cells maintained baseline physiological mechanical properties and promoted matrix deposition up to 8 weeks in culture. Mesenchymal stromal cells (MSCs) cultured on FPLA adhered to the scaffold and exhibited fibrocartilaginous differentiation. These results demonstrate for the first time that 3D printed FPLA scaffolds have de novo viscoelastic mechanical properties that match the native IVD motion segment in both tension and compression and have the potential to be used as a mechanically stable and biocompatible biomaterial for engineered disc replacement.

Nitrogen (N 2 ) rejection from methane (CH 4 ) is the most challenging step in natural gas processing because of the close similarity of their physical-chemical properties. For decades, efforts to find a functioning material that can selectively discriminate N 2 had little outcome. Here, we report a molecular trapdoor zeolite K-ZSM-25 that has the largest unit cell among all zeolites, with the ability to capture N 2 in favor of CH 4 with a selectivity as high as 34. This zeolite was found to show a temperature-regulated gas adsorption wherein gas molecules' accessibility to the internal pores of the crystal is determined by the effect of the gas-cation interaction on the thermal oscillation of the "door-keeping" cation. N 2 and CH 4 molecules were differentiated by different admission-trigger temperatures. A mild working temperature range of 240-300 K was determined wherein N 2 gas molecules were able to access the internal pores of K-ZSM-25 while CH 4 was rejected. As confirmed by experimental, molecular dynamic, and ab initio density functional theory studies, the outstanding N 2 /CH 4 selectivity is achieved within a specific temperature range where the thermal oscillation of door-blocking K + provides enough space only for the relatively smaller molecule (N 2 ) to diffuse into and through the zeolite supercages. Such temperature-regulated adsorption of the K-ZSM-25 trapdoor zeolite opens up a new approach for rejecting N 2 from CH 4 in the gas industry without deploying energy-intensive cryogenic distillation around 100 K.

A novel cell-free biosynthesis system based on a mixture of chassis cell extracts and purified Spy-cyclized enzymes (CFBS-mixture) was developed. As a demonstration, the CFBS-mixture was applied to chlorogenic acid (CGA) biosynthesis. The mix-and-match and Plackett-Burman experiments demonstrated that Lonicera japonica hydroxycinnamate-CoA quinate transferase and p -hydroxyphenylacetate 3-hydroxylase were the key enzymes for the production of CGA. After optimization of the concentrations of the biosynthetic enzymes in the CFBS-mixture reaction using the Plackett-Burman experimental design and the path of the steepest ascent, 711.26 ± 15.63 mg/L CGA was produced after 16 h, which is 71.1-fold the yield obtained using the conventional crude extract-based CFBS and 9.1-fold the reported yield obtained using the living cells. Based on the CFBS-mixture results, the production of CGA was further enhanced in engineered Escherichia coli . The CFBS-mixture strategy is highly effective and will be useful for high-level CFBS of natural products.

Here, we first developed a combined strain improvement strategy of biosensor-guided atmospheric and room-temperature plasma mutagenesis and genome shuffling. Application of this strategy resulted in a 2.7-fold increase in the production of shikimic acid (SA) and a 2.0-fold increase in growth relative to those of the starting strain. Whole-cell resequencing of the shuffled strain and confirmation using CRISPRa/CRISPRi revealed that some membrane protein-related mutant genes are identified as being closely related to the higher SA titer. The engineered shuffling strain produced 18.58 ± 0.56 g/L SA from glucose with a yield of 68% (mol/mol) by fed-batch whole-cell biocatalysis, achieving 79% of the theoretical maximum. Sucrose-utilizing Escherichia coli was engineered for SA production by introducing Mannheimia succiniciproducens β-fructofuranosidase gene. The resulting sucrose-utilizing E. coli strain produced 24.64 ± 0.32 g/L SA from sucrose with a yield of 1.42 mol/mol by fed-batch whole-cell biocatalysis, achieving 83% of the theoretical maximum.

α-Pinene is an important monoterpene that is widely used as a pharmaceutical product, biofuel, and so forth. We first established a cell-free system with modular cocatalysis for the production of pinene from glucose. After optimization of the compositions of the cell-free reaction mixture using the Plackett-Burman experimental design and the path of steepest ascent, the production of pinene increased by 57%. It was found that ammonium acetate, NAD + , and NADPH are the three most important parameters for the production of pinene. Mix-and-match experiments showed that the simultaneous addition of the lysate of Escherichia coli overexpressing native 4-hydroxy-3-methylbut-2-enyl diphosphate reductase, SufBCD Fe-S cluster assembly protein, isopentenyl-diphosphate isomerase, and Pinus taeda pinene synthase improved the production of pinene. Increasing the enzyme concentration of the extract further enhanced the production of pinene to 1256.31 ± 46.12 mg/L with a productivity of 104.7 mg/L h, almost 1.2-fold faster than any system reported thus far. This study demonstrates that a cell-free system is a powerful and robust platform for biomanufacture.

Astaxanthin is a carotenoid of high commercial value because of its excellent antioxidative, anti-inflammatory, and anticancer properties. Here, we developed a novel strategy for improving the production of astaxanthin via morphology and oxidative stress engineering. First, we identified the morphology-/membrane- and oxidative stress-related genes, which should be knocked down, using the CRISPRi system. Deleting the morphology-/membrane-related genes ( lpp and bamB ) and the oxidative stress-related genes ( uspE and yggE ) generated longer and larger cells with higher reactive oxygen species (ROS) levels, thus enhancing the production of astaxanthin and decreasing cell growth. To not only improve cell growth but also obtain longer and larger cells with higher ROS levels, a complementary expression system using a temperature-sensitive plasmid was established. Complementarily expressing the morphology-/membrane-related genes ( lpp and bamB ) and the oxidative stress-related genes ( uspE and yggE ) further improved the production of astaxanthin to 11.92 mg/g dry cell weight in shake flask cultures.

Porous membranes play an important role in the separation technologies such as gas purification, solute nanofiltration, and desalination. An ideal membrane should be thin to maximize permeation speed, have optimum pore sizes to maximize selectivity, and be stable in various harsh conditions. Here, we show that the nanometer-thick membrane prepared by means of filtration of functionalized boron nitride (FBN) water suspensions can block solutes with hydrated radii larger than 4.3 Å in water. The FBN membranes with abundant nanochannels reduce the path length of ions. As molecular sieves, the FBN membrane can permeate small ions at an ultrahigh rate-a 25-fold enhancement compared with that of its theoretical diffusion rate and much higher than the graphene oxide membrane. Importantly, the FBN membrane exhibits excellent permeability even when it is immersed in acidic, alkaline, and basic salts solutions because of its intrinsic chemical stability. The molecular dynamics simulations further confirmed that the nanocapillaries formed within the FBN membrane in the hydrated state were responsible for high permeation performance. The simple vacuum filtration fabricated FBN membrane with angstrom-sized channels and ultrafast permeation of ions promises great potential applications in the areas of barrier separation and water purification.

Nanoribbons (NRs) of two-dimensional (2D) materials have attracted intensive research interests because of exotic physical properties at edges as well as tunable properties via width control. In this paper, using density functional theory (DFT) calculations, we discover sensitive dependence of magnetic properties of 1T'-MoS 2 NRs, that is, periodic variation of magnetic moments between 0.1 and 1.2 μ B , on NR width (even or odd number of MoS 2 units). Our results reveal that a special edge reconstruction, which is not recognized before, stabilizes the ferromagnetic (FM) ground state. Our results also suggest that the FM state could be stable under ambient condition. This study indicates a promising means to integrate multiple magnetic units for small-scale functional devices, such as information storage and spintronics, on a single piece of MoS 2 NR by designing segments with different width.

Transition metal dichalcogenides, such as MoS 2 and VSe 2 have emerged as promising catalysts for the hydrogen evolution reaction (HER). Substantial work has been devoted to optimizing the catalytic performance by constructing materials with specific phases and morphologies. However, the optimization of adsorption/desorption process in HER is rare. Herein, we concentrate on tuning the dynamics of the adsorption process in HER by applying a back gate voltage to the pristine VSe 2 nanosheet. The back gate voltage induces the redistribution of the ions at the electrolyte-VSe 2 nanosheet interface, which realizes the enhanced electron transport process and facilitates the rate-limiting step (discharge process) under HER conditions. A considerable low onset overpotential of 70 mV is achieved in VSe 2 nanosheets without any chemical treatment. Such unexpected improvement is attributed to the field tuned adsorption-dynamics of VSe 2 nanosheet, which is demonstrated by the greatly optimized charge transfer resistance (from 1.03 to 0.15 MΩ) and time constant of the adsorption process (from 2.5 × 10 -3 to 5.0 × 10 -4 s). Our results demonstrate enhanced catalysis performance in the VSe 2 nanosheet by tuning the adsorption dynamics with a back gate, which provides new directions for improving the catalytic activity of non-noble materials.

Phosphorene, the single-layer form of black phosphorus, as a new member of atomically thin material family, has unique puckered atomistic structure and remarkable physical and chemical properties. In this paper, we report a discovery of an unexpected electromechanical energy conversion phenomenon-shape memory effect-in Li doped phosphorene P4Li2, using ab initio density functional theory simulations. Two stable phases are found for the two-dimensional (2D) P4Li2 crystal. Applying an external electric field can turn on or off the unique adatom switches in P4Li2 crystals, leading to a reversible structural phase transition and thereby the shape memory effect with an tunable strain output as high as 2.06%. Our results demonstrate that multiple temporary shapes are attainable in one piece of P4Li2 material, offering programmability that is particularly useful for device designs. Additionally, the P4Li2 displays superelasticity that can generate a pseudoelastic tensile strain up to 6.2%. The atomic thickness, superior flexibility, excellent electromechanical strain output, the special shape memory phenomenon, and the programmability feature endow P4Li2 with great application potential in high-efficient energy conversion at nanoscale and flexible nanoelectromechanical systems.

In this study, we have demonstrated a simple, scalable, and environmentally friendly route for controllable fabrication of continuous, well-intergrown ZIF-8 on a flexible polymer substrate via contra-diffusion method in conjunction with chemical vapor modification of the polymer surface. The combined chemical vapor modification and contra-diffusion method resulted in controlled formation of a thin, defect-free, and robust ZIF-8 layer on one side of the support in aqueous solution at room temperature. The ZIF-8 membrane exhibited propylene permeance of 1.50 × 10(-8) mol m(-2) s(-1) Pa(-1) and excellent selective permeation properties; after post heat-treatment, the membrane showed ideal selectivities of C3H6/C3H8 and H2/C3H8 as high as 27.8 and 2259, respectively. The new synthesis approach holds promise for further development of the fabrication of high-quality polymer-supported ZIF membranes for practical separation applications.

Germanate nanowires/nanorods with different lengths were synthesized and used as additives for the fabrication of polymer composite membranes for high-flux water filtration. We for the first time demonstrated that at a small nanowire/nanorod loading (e.g., <0.5 wt % on the basis of poly(ether sulfone)), the length of germinate nanowires was a key parameter in determining their migration and diffusion in the polymer solution, and thus affecting polymer precipitation in the membrane formation process. In particular, short Ca2Ge7O16 nanowires with an average length of 138.7 nm and an average diameter of 12.7 nm, and Zn2GeO4 nanorods with an average length of 400 nm and an average diameter of 18.7 nm quickly diffused out of the membrane, leading to a higher pore density on the active layer in comparison with the pristine membranes. The addition of short Ca2Ge7O16 nanowires resulted in greater pore sizes than the addition of Zn2GeO4 nanorods because the out-diffusion of the former was faster than that of the latter. In contrast, the addition of long Ca2Ge7O16 nanowires with lengths of several tens to hundreds of micrometers and an average of 27.3 nm was not effective in promoting the pore formation because of partial embedment of nanowires. Poly(ether sulfone) composite membranes prepared by adding a small amount of Zn2GeO4 nanorods exhibited dramatically enhanced water permeation without losing rejection property. For example, the poly(ether sulfone) (PES) composite membrane prepared with 0.3 wt % Zn2GeO4 nanorods exhibited the highest flux, 1294.5 LMH, which was 3.5 times of the pristine (PES) membrane (384.2 LMH). Our work provides a new strategy for developing high-performance ultrafiltration membranes for practical industrial filtration applications.

Separation of molecules based on molecular size in zeolites with appropriate pore aperture dimensions has given rise to the definition of "molecular sieves" and has been the basis for a variety of separation applications. We show here that for a class of chabazite zeolites, what appears to be "molecular sieving" based on dimension is actually separation based on a difference in ability of a guest molecule to induce temporary and reversible cation deviation from the center of pore apertures, allowing for exclusive admission of certain molecules. This new mechanism of discrimination permits "size-inverse" separation: we illustrate the case of admission of a larger molecule (CO) in preference to a smaller molecule (N(2)). Through a combination of experimental and computational approaches, we have uncovered the underlying mechanism and show that it is similar to a "molecular trapdoor". Our materials show the highest selectivity of CO(2) over CH(4) reported to date with important application to natural gas purification.

The synthesis of a directly linked zinc chlorin dimer was first achieved by a facile and efficient oxidative coupling of zinc chlorin monomers with phenyliodine bis(trifluoroacetate) (PIFA). The reaction shows high regioselectivity at the 20-position near the hydrogenated pyrrole ring producing selective dichlorin in 74% yield.

The fundamental mechanism proposed to explain surface-enhanced Raman scattering (SERS) relies on electromagnetic field enhancement at optical frequencies. In this work, we demonstrate the use of microfabricated, silver nanotextured electrode pairs to study, in situ, the influence of low frequency (5 mHz to 1 kHz) oscillating electric fields on the SERS spectra of thiophenol. This applied electric field is shown to affect SERS peak intensities and influence specific vibrational modes of the analyte. The applied electric field perturbs the polar analyte, thereby altering the scattering cross section. Peaks related to the sulfurous bond which binds the molecule to the silver nanotexture exhibit strong and distinguishable responses to the applied field, due to varying bending and stretching mechanics. Density functional theory simulations are used to qualitatively verify the experimental observations. Our experimental and simulation results demonstrate that the SERS spectral changes relate to electric field induced molecular reorientation, with dependence on applied field strength and frequency. This demonstration creates new opportunities for external dynamic tuning and multivariate control of SERS measurements.

Having demonstrated unparalleled actuation stresses and strains, covalently bonded carbon-based nanomaterials are emerging as the actuators of the future. To exploit their full potential, further investigations into the optimum configurations of these new materials are essential. Using first-principle density functional calculations, we examine so-called clamped and unzipped graphene oxide (GO) as potential electromechanical actuator materials. Very high strains are predicted for hole injection into GO, with reversible and irreversible values of up to 6.3% and 28.2%, respectively. The huge 28% irreversible strain is shown to be the result of a change in the atomic structure of GO from a metastable clamped to more stable unzipped configuration. Significantly, this strain generation mechanism makes it possible to hold a constant strain of 23.8% upon removal of the input power, making this material ideal for long-term, low-power switching applications. A unique contraction of unzipped GO upon electron injection is also observed. It is shown that the origin of this unique behavior is the modulation of the structural rippling effect, which is a characteristic feature of GO. With reversible strains and stresses in excess of 5% and 100 GPa, respectively, GO is poised to be an extremely useful material for micro/nanoelectromechanical system actuators., (© 2011 American Chemical Society)

The electrochemical actuation of covalent carbon materials, such as graphene, immersed in liquid electrolytes has shown immense promise for a myriad of applications. To realize this potential, an intimate understanding of the physics behind the actuation is essential. With the use of ab initio density functional calculations, it is shown that the strain induced in monolayer graphene by the formation of an electrostatic double-layer (DL) is the dominant actuation mechanism. The DL-induced strain (~1%) is found to exceed the quantum-mechanical strain (~0.2%) due to charge injection only, for charges and electric potentials of greater than -0.08 e/C-atom and 1 V, respectively. Various methods of calculating the graphene atomic charges based on first principle charge densities are compared and contrasted. The electrochemical charge-strain and potential-strain relationships for monolayer graphene are shown to be parabolic in nature. This study proves that the origin of the high electrochemical strains in covalent carbon materials is the electrostatic DL potential, and demonstrates the true viability of using monolayer graphene for nanoelectromechanical systems (NEMS) actuators.

A group of ferrocene-containing poly(phenylacetylene)s (PPAs) with different alkyl spacers were synthesized by using organorhodium complexes [Rh(diene)Cl](2) and Rh (+)(nbd)[C(6)H(5)B (-)(C(6)H(5))(3)] as catalysts. With the aid of pi-pi interactions between the walls of carbon nanotubes (CNTs) and the PPA skeleton together with the ferrocene pendants, the polymer (P 1, P2(5) and P2(10)) chains effectively wrapped round the shells of both single-walled carbon nanotubes (SWNTs) and multiwalled carbon nanotubes (MWNTs). The "additive effect" of the PPA skeleton and the ferrocene pendants in dispersing the SWNTs and MWNTs resulted in the generation of highly soluble hybrids. The solubilities of P 1-functionalized SWNTs and MWNTs in tetrahydrofuran (THF) are up to 633 mg/L and 967 mg/L, respectively. They are much higher than the solubilities of M 1-modified SWNTs and MWNTs, which are only 167 mg/L and 133 mg/L in THF. The results indicate the existence of a powerful polymer effect on dispersing CNTs. The high solubilities of the hybrids in organic solvents allowed us to fabricate high-quality and large-area films. Meanwhile, the desirable loading of ferrocene-containing PPAs onto the CNTs offered polymer/CNTs hybrids with multiple redox centers and ferrocene-featured electrochemical properties. The P 1/MWNT hybrid exhibits evident optical-limiting properties. At high incident laser fluence, the optical-limiting power of P 1/MWNT is higher than that of C(60), a well-known optical limiter. Thermal analyses indicate that the decomposition temperatures ( T(d), the temperature at which a sample loses its 5% weight) for P1 and P1/MWNT are 342 and 346 degrees C, respectively, much higher than that for PPA (225 degrees C). Thus the attachment of a ferrocene pendant to a PPA backbone, followed by hybridization with CNTs, improved the thermal stability. Upon pyrolysis, both the polymer and the polymer/CNTs hybrid gave rise to superparamagnetic ceramics; the saturation magnetizations ( M(s)) of the ceramics derived from P1 and P1/MWNT are 29.9 and 26.9 emu/g, respectively. The latter datum is in the list of the best results reported for the magnetic nanocomposites obtained by the attachment of magnetic nanoparticles onto CNTs.