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Enzymes play significant roles in both life and industry, and increasing enzymatic activity has been a long-term goal of the biochemical science. Recently, it has been reported that nanomaterials can enhance both the specificity and yield of polymerase chain reaction (PCR) though the mechanism of this enhancement remained unclear. By using gold nanoparticles (AuNPs) as model nanomaterials and the cellulase as a typical enzyme, we studied whether and how nanomaterials affect enzymatic activities investigating various aspects of the reaction process. The results showed that the catalytic efficiency of cellulase depends on the concentration of AuNPs. By detailed studying the relation between catalysis and experimental conditions, we found that the enzymatic activity can be increased up to 13.13% upon adding AuNPs in concentration of 0.5 nM into the reaction solution. The optimal pH, temperature, and incubation time for cellulose with 0.5 nM AuNPs were found to be same as those for the cellulose alone. These findings might be useful for enhancing enzymatic activities in the industrial processes.

The interfacial properties of ultrahigh methoxylated pectin (UHMP) prepared via esterification of citrus pectin (CP) were investigated. The intrinsic viscosity ([η]) of pectin was significantly decreased from 1211.5 mL/g to 294.9 mL/g as the degree of methylation (DM) increased from 63.18 ± 0.08% to 91.52 ± 0.11%. Surface tension (γ) analysis indicated that UHMP had a critical micelle concentration (CMC) of 0.8 g/L, which was slightly smaller than that of sugar beet pectin (SBP) (1.0 g/L). The morphology of the UHMP aggregation presented a network structure and irregular clusters at 10 μg/mL and 1 μg/mL based on atomic force microscopy (AFM). Transmission electron microscopy (TEM) observations further confirmed the self-aggregation behaviours and rod-like micelles of UHMP. The surface excess (Γ) was 1.69 ± 0.17 μmol/m2 for UHMP, which was lower than the values of SBP (1.88 ± 0.21 μmol/m2) and CP (2.91 ± 0.57 μmol/m2). Correspondingly, UHMP possessed the highest molecular area (A) of 0.99 ± 0.10 nm2. Thus, UHMP was proposed to be more flexible and extendable at the interface. The interfacial shear rheology study suggested that UHMP was able to form an elastic-dominant interfacial film to stabilize the oil/water interface.

Two twisted π-conjugated cruciform luminophores MDCS-TPA and FMDCS-TPA containing two conjugated donor and acceptor groups intersecting at the central benzene core have been rationally designed and successfully prepared. The two compounds display unique intramolecular charge-transfer (ICT) process from electron-rich triphenylamine and electron-poor cyanostyryl units, which are evidenced by theoretical calculations and spectral analysis. MDCS-TPA and FMDCS-TPA exhibit AIE effects with high fluorescence quantum yields of 0.321 and 0.312 in the solid state. Interestingly, MDCS-TPA and FMDCS-TPA possess the distinct mechanofluorochromic (MFC) behavior. The as-prepared powders of the two luminophores could emit strong green (491 nm) and yellow-green fluorescence (529 nm), and the fluorescence color changed into yellow (542 nm) and orange (576 nm) after grinding, respectively, giving the red shifts of 51 nm and 47 nm. Such mechanochromism is reversible by repeating both the grinding-fuming and grinding-annealing processes. The MFC behavior of MDCS-TPA and FMDCS-TPA originates from the transition between the crystalline and amorphous states and the red-shifts induced by grinding is the result of the planarization of the molecular conformation and subsequent planar intramolecular charge transfer (PICT) under the external force stimuli.

Engineering the surface morphology is an effective way to obtain specific functionalities in applications of smart surfaces. Developing two-dimensional (2D) smart materials, which can undergo morphology changes under appropriate external stimuli, is a promising route to pursue for smart-surface design. In the work presented here, using density-functional-theory calculations, we systematically study the thermodynamic stability, crystal structure, and piezoelectric properties of black phosphorene (black $\mathrm{P}$) doped with metallic atoms on one side with different concentrations. Particularly, $\mathrm{Li}$-doped black $\mathrm{P}$ (${\mathrm{P}}_{4}{\mathrm{Li}}_{2}$) has a ${d}_{31}$ value of 6.28 pm/V, which is at least 4 times larger than that of any other 2D piezoelectric material. Via finite-element-method simulations, we show a ${\mathrm{P}}_{4}{\mathrm{Li}}_{2}$-based prototype design for obtaining a surface-morphology change under a vertical electric field. The surface swelling pattern can be detected by human fingers with an appropriate design of the geometry. This demonstrates the promise of 2D piezoelectric materials for use in smart-surface applications.

Graphene has an extremely high in-plane strength yet considerable out-of-plane softness. High crystalline order of graphene assemblies is desired to utilize their in-plane properties, however, challenged by the easy formation of chaotic wrinkles for the intrinsic softness. Here, we find an intercalation modulated plasticization phenomenon, present a continuous plasticization stretching method to regulate spontaneous wrinkles of graphene sheets into crystalline orders, and fabricate continuous graphene papers with a high Hermans’ order of 0.93. The crystalline graphene paper exhibits superior mechanical (tensile strength of 1.1 GPa, stiffness of 62.8 GPa) and conductive properties (electrical conductivity of 1.1 × 105 S m−1, thermal conductivity of 109.11 W m−1 K−1). We extend the ultrastrong graphene papers to the realistic laminated composites and achieve high strength combining with attractive conductive and electromagnetic shielding performance. The intercalation modulated plasticity is revealed as a vital state of graphene assemblies, contributing to their industrial processing as metals and plastics., Strong but flexible graphene tends to wrinkle, which compromises some properties. Here the authors report a solid plasticization method to prepare continuous graphene papers with high crystalline order, achieving high strength, stiffness, electrical and thermal conductivities.

In this work, we have studied the uniaxial tension behaviors of the silicone–carbon nanotube (CNT) laminated structure (SCLS) with the load capacity of the CNT film comparable to that of silicone rubber, based on which a theoretical model is proposed to explore the underlying mechanism. The uniaxial tension behaviors of SCLS can be clearly divided into three stages corresponding to the uniform deformation of silicone rubber and CNT film, continuous fracture of CNT film, and uniaxial tension of silicone rubber, respectively. A zigzag plateau stress is observed in stage II. Indeed, the CNT film can act as a pinning ligament to constrain the deformation of silicone rubber, while its continuous fracture can gradually release the deformability of silicone rubber which is beneficial to increase the toughness of SCLS. By considering the in-plane tension stress of the CNT film and interface shear stress transfer, a continuous fracture and pinning model is proposed which can describe the uniaxial tension behaviors of SCLS very well. The results presented herein may shed useful insights for the design and optimization of the film-substrate based stretchable electronics.

BaO-K 2 O-Nb 2 O 5 -SiO 2 (BKNS) glass ceramics were prepared by microwave crystallization of transparent glass matrices and the effects of microwave treatment temperature on their dielectric performances, phase structure, microstructure and breakdown strength (BDS) were investigated systematically. X-ray diffraction results suggested that microwave treatment had no significant influence on the type of precipitated phases. The microstructure of the glass ceramics was remarkably optimized via microwave treatment. The dielectric constant and breakdown strength of microwave-treated samples were significantly improved as compared with conventional-heated samples at the same temperature. The maximum theoretical energy storage density of microwave-treatment samples at 750 °C reached 12.7 J/cm 3 , which was larger than that of the conventional-heated samples (8.6 J/cm 3 ).

Helically coiled metastructures made from carbon nanotubes (CNTs) are a promising material for nanoelectromechanical systems due to the helical morphology and fantastic properties of CNTs. Mechanical properties of coiled CNT-metastructures are subtly tailored by changing the geometrical parameters; however, the role of CNT-chirality on their mechanical performances remains unknown. Here, using atomistic simulations, stretching characteristics of helical coiled CNTs (HCCNTs) having six different CNT-chirality are contrasted. High initial stiffness of HCCNTs comes from stretching of intercoil van der Waals (vdW) forces while low initial stiffness is explained by sliding action between coils. HCCNTs show distinct characteristic sawtooth patterns in the stretching stress-strain curves, originating from vdW-induced phase transformations, buckling instability and nanohinge-like plasticity. The sawtooth behavior resulting from phase transformations is described by a theoretical model. HCCNTs are highly resilient, and exhibit excellent stretchability because of two distinct deformation mechanisms depending on the CNT-chirality. For HCCNTs composed of armchair and zigzag CNT-segments, extraordinary extensibility is mainly contributed by well-distributed nanohinge-like plastic deformation, whereas for those consisting of other chiral ones this is accomplished by superelasticity and nanohinge-like fracture mechanisms. The findings shed new light in mechanical design of coiled-CNTs for practical applications in nanodevices in coupling to their other properties.

Barium sodium niobate (BNN) glass ceramics were successfully fabricated with controllable crystallization by technology for heating processing and the effects of crystallization temperatures on phase evolution, microstructure, dielectric properties and breakdown strength were investigated systematically. In addition, the empirical power-law dependence of breakdown strength on thickness ( E b ∝ d - n ) was confirmed in BNN glass-ceramic system with an exponent n of 0.21. Based on the results, the BNN glass ceramic crystallized at 800 °C presents a remarkable breakdown strength (BDS) of 2322 kV/cm with the tested thickness of 30 μm, and the highest energy density of 16.6 J/cm3 was achieved.

In this work, 25.6BaO-6.4K2O-32Nb2O5-36SiO2-xTiO2 (0 ≤ x ≤10 mol%) (BKNST) glass ceramics were synthesized by conventional melts and controllable crystallization method. The effects of different TiO2 addition on the phase composition, dielectric and energy storage properties of BKNS glass ceramics were systematically evaluated. With the TiO2 concentration increasing, a growing content of Ba2TiO4 phase was observed in the glass ceramics. The microstructures appeared to be homogenous and uniform with very low porosity through the addition of TiO2, for which the maximal breakdown strength of 2112 kV/cm and the corresponding energy storage density of 9.48 J/cm3 were obtained with x = 7.5. The extremely low dielectric loss of less than 1‰ (25 °C, 100 kHz) and the obviously improved microstructure contributed to the increased breakdown strength. In addition, the discharge power density of the glass-ceramic capacitor (x = 7.5) was investigated using the RLC charge-discharge circuit and a relatively high value of 16 MW/cm3 at 300 kV/cm was obtained.

The (BaO, R2O)-Nb2O5-SiO2 glasses (where R = Li, Na and K) were prepared by melt-casting method, and the structures were investigated by Raman spectrum, which confirmed that NbO6 units existed in the glass network. The influence of different network modifiers was investigated on the thermal stability, dielectric properties and breakdown strength. All glasses showed improved dielectric constant value of 17–23 with good temperature stability and considerable breakdown strength of 3–4.5 MV/cm with the thickness of 30–50 μm. Particularly, the glass composition of BaO-Na2O-K2O-Nb2O5-SiO2 with highest breakdown strength showed a high energy storage density of ∼19 J/cm3 and a short discharge period of ∼9 ns, indicating a promising candidate in pulsed power application.

In this work, the dynamic behaviors of phase transforming cellular structures (PTCS) consisted of sinusoidal beam with bi-stable configurations are studied. A nonlinear spring-bead model is developed, where the mechanical properties of the sinusoidal beam are described by a nonlinear spring and the mass is concentrated at the bead. Therefore, the PTCS are modeled as a chain of nonlinear spring-bead. Based on the nonlinear spring-bead model, the quasi-static and dynamic behaviors of PTCS are theoretically and numerically studied, which shows abundant dynamic behaviors depending on the loading rate and damping coefficient . For a 2-layered PTCS, there are four deformation patterns, that is the snap through deformation of the sinusoidal beams for relatively small loading rate and damping coefficient, the uniform deformation for relatively large damping coefficient, and the pulse deformation of the springs near bi-stable configurations for relatively large loading rate and small damping coefficient. While, for the multilayer PTCS, their dynamic behaviors are much more complicated due to the combined deformation of the multiple sinusoidal beams. However, the similar snap through and pulse deformation of the sinusoidal beams are also observed, respectively. To our knowledge, this work is the first time to systematically study the dynamic behaviors of PTCS.

Compared with traditional dielectric materials, ferroelectric glass-ceramic capacitors have higher energy storage densities and faster discharge speeds. In this study, 21.6BaO–2.4PbO–6Na2O–30Nb2O5–10Al2O3–30SiO2 glass-ceramics and their single-layer capacitors were successfully prepared. A maximum energy storage density of 20.7 J cm−3 was obtained in these glass-ceramics. For glass-ceramics capacitors crystallized at 900 °C, under an electric field of 400 kV cm−1, the maximum instantaneous power density reached was 78.2 MW cm−3 and the discharge time was

In this work, (100-x)(0.12 SrO-0.3 Na2O-0.1 Nb2O5)-xSiO2 (x = 30, 35, 40, 45, 50 mol%) glass-ceramics were prepared by using the meth-quenching-controlled crystallization method. Phase evolution, Crystallization mechanism, dielectric properties, dielectric breakdown strength (DBS), and energy-storage performances were comprehensively studied by varying SiO2 content. DSC studies revealed simultaneous occurrence of surface and internal crystallization mechanism in the glass-ceramics. XRD results showed three tungsten bronze structure SrNb2O6, Sr6Nb10O30, NaSr2Nb5O15 phases and perovskite structure NaNbO3 phase, which was quantified by the Reietveld refinement. It was found that dielectric constant and theoretical energy-storage density increased firstly and then decreased with the increase of the SiO2 contents. For x = 35 mol%, the theoretical energy-storage density reaches the maximal value of 15.3 J/cm3 due to the highest dielectric constant of 124 and DBS of 1669 kV/cm. And the highest DBS is related to the uniform and dense microstructure for x = 35 mol%. For practical applications in pulsed RLC circuit, the discharged efficiency increases from 74.2% to 91.5% with the increase of the SiO2 contents.

Potassium barium niobate-based glass ceramics doped with different proportion of Gd 2 O 3 were fabricated by conventional melts and controllable crystallization. The influence of Gd 2 O 3 content was further investigated on the phase compositional change, energy storage performance and charge-discharge properties of the optimized glass ceramics (crystallization temperature 900 °C). The microstructure has been remarkably transformed through the addition of Gd 2 O 3 . On the basis of the results, the doping of 1.0% Gd 2 O 3 achieved a remarkable improvement on the energy storage density that reached 12.14 J/cm 3 with a dielectric breakdown strength (BDS) of 1818 kV/cm and dielectric constant of 83. The discharge efficiency of 80% and discharge time of 25 ns were obtained in the glass ceramics with 1.0% Gd 2 O 3 , which illustrated the excellent charge-discharge properties of Gd 2 O 3 -doped glass ceramics.

Phase evolution, dielectric properties, breakdown strength, and energy-storage performance were studied by varying K 2 O content in K 2 O-BaO-Nb 2 O 5 -SiO 2 glass-ceramics. It was found that dielectric loss with the increase of K 2 O content increases owing to the un-crystallized K 2 O into the glass network, while dielectric breakdown strength firstly increases and then decreases due to the competition between two physical mechanisms, i.e., interfacial polarization and bridging-oxygen bond broken by the non-bridging oxygen ions. With the increase of K 2 O content, energy-storage density firstly increased up to 12.06±0.69 J/cm 3 with a high breakdown strength of 1973 kV/cm, and then decreased. Also, the discharged efficiency is obtained as a high value of 92% from P-E hysteresis loops.

We investigate the generation of single photons and photon pairs in a cavity quantum electrodynamics system of a four-level quantum dot coupled to bimodal cavity. By tuning frequencies and intensity ratio of the driving lasers, sub-Poissonian and super-Poissonian photon statistics are obtained in each nondegenerate cavity mode respectively. Single photon emission is characterized as zero-delay second-order correlation function g^2(0)~0.15. Photon pair emission under the two-photon resonance excitation is quantified by Mandel parameter as Q~0.04. The mean cavity photon number in both scenarios can maintain large around 0.1. As a result, single photon emission and two-photon emission can be integrated in our proposed system only by tuning the external parameters of the driving lasers., Comment: 6 pages, 5 figures

Layered materials and structures (LMS), such as van der Waals two-dimensional (2D) layered materials and nacre-like layered structures, often exhibit highly anisotropic mechanical properties, i.e., strong in in-plane directions but weak in out-of-plane direction. Despite the strong anisotropy in their mechanical properties, Timoshenko beam model (TBM) is usually used to describe the bending deformation of LMS. We note, however, that there are two fundamental issues in using TBM to describe LMS: First, the stiffness of LMS approaches zero when the interlayer shear modulus G approaches zero; and second, the first derivative of deflection becomes discontinuous at the point of concentrated force. Clearly, both are not true for LMS. In this work, by introducing the bending energy of monolayer into the potential energy of TBM, we develop a modified Timoshenko beam model (MTBM), which is able to not only address these two issues, but also correctly predict the bending stiffness of LMS without any fitting parameters. Our analysis shows that the bending behaviors of LMS are determined by a dimensionless parameter λ L, where L is the length of the beam and λ = k G A ∕ D 0 + k G A ∕ ( n D b e n d ) , where, kGA and D 0 are, respectively, the shear and bending rigidity of the beam cross-section, D bend is the bending rigidity of monolayer, and n is the number of layer. When λ L → 0 , the MTBM degenerates to the multi-beam model with bending stiffness of nD bend ; while it degenerates to the TBM when λ L → ∞ . Furthermore, if kGA is much larger than D 0 , both MTBM and TBM degenerate to the classical Euler–Bernoulli beam model. We further perform molecular dynamics simulations, finite element simulations and experiments to validate the MTBM. Based on the MTBM, a couple of interesting applications of LMS are also demonstrated. Hence, the MTBM presented here captures the necessary intrinsic deformation modes of LMS and provides an accurate tool for the prediction and optimization of the mechanical properties of LMS.

Two donor–acceptor cruciform luminophores MB-CTPEEB and DFB-CTPEEB with twisted molecular conformations have been prepared. It was found that both cruciforms showed unique intramolecular charge transfer (ICT) emission due to the existence of tetraphenylethene with electron-donating ability and dicyanovinylbenzene with electron-withdrawing ability. Moreover, MB-CTPEEB and DFB-CTPEEB bear obvious aggregation-induced enhanced emission (AIEE) properties and good solid state fluorescence emission with high solid state luminescence efficiency of 0.633 and 0.783, respectively. In particular, both luminophores exhibited substituent-dependent reversible mechanofluorochromic (MFC) behavior. Under external force stimuli, the emission color of DFB-CTPEEB powders changes from initial bright yellowish green (517 nm) to final orange (583 nm), thus large spectral shift of 66 nm, which originates from the planarization of the molecular conformation and subsequent planar intramolecular charge transfer (PICT) caused by destruction of the crystals in the as-prepared samples under external force, is obtained. By sharp contrast, MB-CTPEEB exhibits no MFC behavior. The reason is that MB-CTPEEB possessed less twisted molecular conformation and weaker ICT degree than that of DFB-CTPEEB, which endows the MB-CTPEEB molecules with strong intermolecular forces and close packing, the small deformability and relative weak PICT ability under external force.

Two D-A type cruciform luminophores MODCS-TPE and FMDCS-TPE were successfully prepared via a two-step route involving Suzuki cross-coupling and Knoevenagel condensation reactions, and their intramolecular charge-transfer (ICT) and solid-state fluorescence were studied in detail. The results show that MODCS-TPE and FMDCS-TPE exhibit AIE behavior with high solid state fluorescence efficiency of 0.321 and 0.312. Interestingly, MODCS-TPE and FMDCS-TPE exhibit both typical AIE behavior with the AIE factors of 138 and 51and high contrast MFC effects. Once grinding had been performed, the emission of the two cruciform luminophores was red shifted by 34 nm and 44 nm from the blue regions (λmax = 471 nm and 478 nm) to the green and yellowish green regions (λmax = 505 nm and 522 nm), respectively. Moreover, the mechanochromic switching behavior was reversible and repeated many times without any fatigue in the grinding-heating (for MODCS-TPE) or grinding-fuming (for MODCS-TPE and FMDCS-TPE) fluorochromic process. The mechanism of MFC behavior that the transformation between crystalline and amorphous states upon external stimuli is revealed by PXRD and DSC analysis, and the large red-shifts induced by grinding originate from extended conjugation and subsequent planar intramolecular charge transfer (PICT) after grinding.

In this work, the surface wrinkle modulation mechanism of the three-dimensional (3D) film/substrate system caused by biaxial eigenstrains in the films is studied. A theoretical model based on the energy minimization of the 3D wrinkled film/substrate system is proposed which shows that the change of the surface wrinkle amplitude is determined by four dimensionless parameters, i.e., the eigenstrain in the film, plane strain modulus ratio between the film and substrate, film thickness to wrinkle wavelength ratio, and initial wrinkle amplitude to wavelength ratio. The surface wrinkle amplitude decreases (even almost flat) upon contraction eigenstrain in the film, while increases for that of expansion eigenstrain. Parallel finite element method (FEM) simulations are carried out which have good agreements with the theoretical predictions, and experimental verifications are also presented to verify the findings. Besides, different patterns of 3D surface wrinkles are studied and the similar surface wrinkle modulation is also observed. The findings presented herein may shed useful insights for the design of complex stretchable electronics, cosmetic products, soft devices and the fabrication of 3D complex structures.

In this work, the surface wrinkle modulation of the film/substrate system caused by eigenstrain in the film is studied. A theoretical model is proposed which shows the change of the wrinkle amplitude is completely determined by four dimensionless parameters, i.e., the eigenstrain in the film, the plane strain modulus ratio between the film and the substrate, the film thickness to wrinkle wavelength ratio, and the initial wrinkle amplitude to wavelength ratio. The surface wrinkle amplitude becomes smaller (even almost flat) for the contraction eigenstrain in the film, while for the expansion eigenstrain it becomes larger. If the expansion eigenstrain exceeds a critical value, secondary wrinkling on top of the existing one is observed for some cases. In general, the deformation diagram of the wrinkled film/substrate system can be divided into three regions, i.e., the change of surface wrinkle amplitude, the irregular wrinkling, and the secondary wrinkling, governed by the four parameters above. Parallel finite element method (FEM) simulations are carried out which have good agreement with the theoretical predictions. The findings may be useful to guide the design and performance of stretchable electronics, cosmetic products, biomedical engineering, soft materials, and devices.