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The efficient nondestructive assessment of quality and homogeneity for two-dimensional (2D) MoS2 is critically important to advance their practical applications. Here, we presented a rapid and large-area assessment method for visually evaluating the quality and uniformity of chemical vapor deposition (CVD)-grown MoS2 monolayers simply with conventional optical microscopes. This was achieved through one-pot adsorbing abundant sulfur particles selectively onto as-grown poorer-quality MoS2 monolayers in a CVD system without any additional treatment. We further revealed that this favorable adsorption of sulfur particles on MoS2 originated from their intrinsic higher-density sulfur vacancies. Based on unadsorbed MoS2 monolayers, superior performance field effect transistors with a mobility of ∼49 cm2 V-1 s-1 were constructed. Importantly, the assessment approach was noninvasive due to the all-vapor-phase and moderate adsorption-desorption process. Our work offers a new route for the performance and yield optimization of devices by quality assessment of 2D semiconductors prior to device fabrication.

Redox-active Metal–Organic Frameworks (MOFs) are considered as promising platforms for assembling high quantities of solution-accessible molecular catalysts on conductive surfaces, toward their uti...

Photo-active metal–organic frameworks (MOFs) are considered as promising materials for the study of photo-electrochemical cells (PECs). They can be utilized as porous, high surface area scaffolds for the assembly of molecular chromophores atop semiconducting electrodes. Usually, however, the lack of prominent electronic interactions between adjacent MOF-installed chromophores impedes the development of PECs based solely on MOFs (without the use of a semiconducting electrode, e.g. TiO2). Here we demonstrate that unlike standard semiconducting photo-electrodes, the photo-electrochemical behavior of a MOF-based electrode can be switched from photo-anodic to photo-cathodic by using appropriate redox mediators in the electrolyte. Additionally, a proof-of-principle photo-electrocatalytic H2 production using a MOF-based photo-cathode is provided. Thus, these findings have a clear impact on the design of MOF-based PECs for solar fuel generation.

Semiconductor photocatalyst as a new type of green and sustainable energy material has extensively used in wastewater and gas treatment. In this work, we prepared Pt/h-BN/BiOBr composite by an alcohol-soluble hydrolysis-assisted photoreduction method. The photocatalytic activity was evaluated by the degradation of bisphenol A under simulated sunlight, and the degradation efficiency of BiOBr, h-BN/BiOBr, Pt/BiOBr, and Pt/h-BN/BiOBr were 55.13%, 74.91%, 89.00%, and 98.54%, respectively. The results showed single composited with h-BN or Pt could improve the photocatalytic performance of BiOBr, while double composited with h-BN and Pt could play a synergistic effect on further improving the activity. The interaction between h-BN and BiOBr was electrostatic interactions, and that Pt as a plasma metal was coupling with BiOBr due to its localized surface plasmon resonance (LSPR) effect. The composition, morphology, optical property, and separation efficiency of photo-induced carriers and dominant active radicals were investigated. Based on the results, a possible mechanism was proposed. The excellent photocatalytic activity of Pt/h-BN/BiOBr composite photocatalyst could be attributed to the broadened light-response range after Pt loading, and enhanced electron–hole separation efficiency due to the electron capturer role of Pt and the hole transfer function of h-BN.

A tetragonal (Ba,Ca)(Zr,Ti)O3 (BCZT) single crystal was grown by a flux method, and the piezoelectric coefficient (d33) was characterized. The piezoelectric response was proved to be associated with polarization extension, which was successfully used to explain the variation in d33*. From the intrinsic aspect, the compositional effect on Landau free-energy profiles was discussed, showing an “extender” nature of the as-grown crystal and the increasing tendency of structural instability toward the morphotropic phase boundary. From the extrinsic aspect, the evolution of domain structure under various external fields (electric and temperature) was studied, revealing that the fine-domain structure of the as-grown BCZT single crystal was stable to E-field and temperature. The results manifest possibilities of further improving the piezoelectric property of the BCZT single crystal, which requires optimization of the crystal growth technique in future work.

Sensitive and selective detection of microRNAs (miRNAs) in cancer cells derived exosomes have attracted rapidly growing interest owing to their potential in diagnostic and prognostic applications. Here, we design a ratiometric electrochemical biosensor based on bipedal DNA walkers for the attomolar detection of exosomal miR-21. In the presence of miR-21, DNA walkers are activated to walk continuously along DNA tracks, resulting in conformational changes as well as considerable increases of the signal ratio produced by target-respond and target-independent reporters. With the signal cascade amplification of DNA walkers, the biosensor exhibits ultrahigh sensitivity with the limit of detection (LOD) down to 67 aM. Furthermore, owing to the background-correcting function of target-independent reporters termed as reference reporters, the biosensor is robust and stable enough to be applied in the detection of exosomal miR-21 extracted from breast cancer cell lines and serums. In addition, because locked nucleic acid (LNA) modified toehold mediate strand displacement reaction (TMSDR) has extraordinary discriminative ability, the biosensor displays excellent selectivity even against the single-base-mismatched target. It is worth mentioning that our sensor is regenerative and stable for at least 5 cycles without diminution in sensitivity. In brief, the high sensitivity, selectivity and reproducibility, together with cheap, make the proposed biosensor a promising approach for exosomal miRNAs detection, in conjunction with early point-of-care testing (POCT) of cancer.

Organic–inorganic hybrid perovskite single crystals have shown superior photophysical properties when compared with their polycrystalline film counterparts. Perovskite single crystal thin films are highly desirable for high-performance optoelectronic devices, but their growth remains a challenge, particularly for perovskite single crystal thin films with controllable thicknesses. Herein, we report a facile top-down strategy to fabricate hybrid perovskite single-crystalline film from its bulk single crystal. The film thickness can be controlled from several millimetres to 15 micrometres. Most importantly, the strategy is feasible for the fabrication of different types of hybrid perovskite single-crystalline films (such as CH3NH3PbI3, CH3NH3PbBr3, and CH3NH3PbCl3) of arbitrary orientations. We demonstrate that vertical-structured photodetectors based on (100)-oriented CH3NH3PbI3 single-crystalline thin films show obvious thickness-dependent photoelectric responses. Such a top-down approach provides a general route to the fabrication of perovskite single-crystalline thin film and may pave the way for the production of a variety of high-performance optoelectronic devices.

Recently, many studies have shown the potential use of circulating exosomes as novel biomarkers for monitoring and predicting a number of complex diseases, including cancer. However, reliable and cost-effective detection of exosomes in routine clinical settings, still remain a difficult task, mainly due to the lack of adequately easy and fast assay platforms. Therefore, we demonstrate here the development of a visible and simple method for the detection of exosomes by integrating single-walled carbon nanotubes that being excellent water solubility (s-SWCNTs) and aptamer. Aptamers, specific to exosomes transmembrane protein CD63, are absorbed onto the surface of s-SWCNTs and improve the minic peroxidase activity of s-SWCNTs, which can efficiently catalyze H2O2-mediated oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) and lead to a change from colorless to blue in solution. However, after adding exosomes, the aptamers are bound with CD63, leaving from the surface of s-SWCNTs through conformational changes, which results the color of solution from deep to moderate, and this can be observed by the naked eye and monitored by UV-vis spectrometry. Under optimal conditions, the linear range of exosomes is estimated to be 1.84×106 to 2.21×107 particles/μL with a detection of limit (LOD) of 5.2×105 particles/μL. Consequently, a visible and simple approach detecting exosomes is successfully constructed. Moreover, this proposed colorimetric aptasensor can be universally applicable for the detection of other targets by simple change the aptamer.

Pb(In1/2Nb1/2)O3–PbZrO–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PZ–PMN–PT) quaternary system relaxor ferroelectric materials possess a high ferroelectric phase transition temperature (TFE–FE > 120 °C) due to the enhanced A–B repulsion intensity in the ABO3 lattice caused by the incorporation of In3+ and Zr4+ cations. Due to these additions, excellent piezoelectric property (d33[001]* = 1820 pm V−1) at room temperature and good thermal stability were observed in the PIN–PZ–PMN–PT single crystals. Strong frequency dispersion (frequency ∼0.1–100 kHz) and small short-range correlation length (〈ξ〉 ∼ 118 nm) of polar nanoregions (PNRs) illustrate the high degree of relaxor nature of these quaternary-system single crystals in comparison with the PMN–0.2PT relaxor single crystal (〈ξ〉 ∼ 210 nm). The high relaxor nature is speculated to be caused by In3+ and Zr4+ cations and is considered one of the main reasons for the excellent piezoresponse of the PIN–PZ–PMN–PT single crystal. Moreover, PNRs with orthorhombic 〈011〉 polarization might have a modulation effect on the (011) surface, leading to the anisotropic nanodomain structures. A lower free energy for domain switching on the (011) surface was needed than that on the (001) surface, which was confirmed by the piezoresponse hysteresis loops and local domain poling behavior studies.

The anisotropy of moisture erosion was observed in CH3NH3PbI3 single crystals. When exposed to moisture, the (001) facet exhibited greater sensitivity to water molecules and showed a faster erosion rate compared to the (100) facet and (112) facet. Structural and chemical origins responsible for anisotropic moisture erosion were elucidated.

Nanostructured Co3O4 with near-cubic morphology was synthesised using the solvothermal method, and a non-enzymatic electrochemical glucose sensor (Co3O4–CuNPs/Pt) was successfully constructed by dropping and potentiostatic depositing technologies. The obtained Co3O4 and Co3O4–CuNPs were characterised and investigated by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Quantitative analysis of glucose was performed using the amperometric (i–t) method, and a plot of current difference versus concentration of glucose was linear in the range 0.5–336 μM, with a linear correlation coefficient (R2) of 0.9989 and limit of detection (LOD) of 0.43 μM. When the linear range was reduced to 0.5–76.5 μM, R2 and LOD were 0.9997 and 0.17 μM, respectively. The sensitivity of the sensor was evaluated as 3.58 × 104 and 4.03 × 104 μA μM−1 cm−2 for the above two linear ranges, respectively. This novel sensor produced satisfactory reproducibility and stability and was applied to monitor trace amounts of glucose in human serum samples.

The introduction of oxygen vacancies (OVs) on the surface of photocatalysts has already been proven to be an effective way to extend the light response to visible light and trap charge carriers, thereby promoting the photocatalytic performance. In this study, h-BN/OV-BiOCl composites were prepared using hexagonal boron nitride (h-BN) to further improve the visible-light photocatalytic activity of oxygen-vacancy-enriched bismuth oxychloride (OV-BiOCl). The composition and morphology of these materials were investigated, and the photocatalytic performance experiments showed that the introduction of h-BN could significantly improve the visible-light photocatalytic activity of OV-BiOCl, which was 1.7 and 1.4 times that of pure OV-BiOCl for the degradation of rhodamine B (RhB) and bisphenol A (BPA) when the h-BN content was 5 wt%, respectively. The role of h-BN was comprehensively investigated, and the results revealed that the presence of negatively charged h-BN could improve the separation efficiency of photoinduced electrons (e−) and holes (h+) by promoting the migration of positively charged h+ to the surface of the photocatalyst, as expected. Moreover, the oxygen vacancies in OV-BiOCl were increased in the presence of h-BN; this favored the activation of more adsorbed O2 for the oxidation of pollutants. Finally, a probable mechanism was proposed for the improved photocatalytic activity of the h-BN/OV-BiOCl composites. This study provides an insight into the roles of h-BN in oxygen-vacancy-enriched photocatalysts.

Currently, organic artificial enzymes as biocatalysts have been extensively used to construct various colorimetric sensors. However, exploiting a potential organic artificial enzyme with high catalytic efficiency still remains a challenge. To address this issue, herein, we synthesize an acridone derivative 10-benzyl-2-amino-acridone (BAA). The synthesized BAA exhibits an intrinsic visible-light-stimulated oxidase-like activity, which is capable of oxidizing various chromogenic substrates without destructive hydrogen peroxide (H2O2) under visible light stimulation, resulting in colored products. The reaction system can be regulated by switching light on and off, which is milder and more reliable means than others H2O2-dependent. The photocatalytic mechanism of BAA is investigated in detail. However, l -ascorbic acid (AA), an antioxidant generating from the acid phosphatase (ACP)-mediated hydrolysis of 2-phospho- l -ascorbic acid (AAP), is able to inhibit the catalytic activity of BAA. Based on the above properties, a facile, photo-switchable and low-cost colorimetric sensing strategy is developed for ACP detection. The linear range is 0.05–2.5 U/L (r = 0.9994), and the limit of detection (LOD) is 0.0415 U/L. Moreover, the proposed sensing system can be applied for monitoring ACP activity in practical samples, demonstrating promising applications in clinical analysis and biosensor platform.

Achieving high-resolution imaging of bone-cracks and even monitoring them in live organisms are of great significance for understanding their extreme biological effects but remain quite challenging, especially for adopting commercial imaging systems. Herein, we explore the use of the clinical gemstone spectral computed tomography (GSCT) technique as a powerful tool for targeted imaging of bone-cracks in rats via intramuscularly administrating crack-targeted ytterbium-based contrast agents (CAs). Material density images of GSCT reveal that bone-cracks targeted with CAs can be successfully differentiated from healthy bone based on their different X-ray attenuation characteristics, giving GSCT a distinct advantage over conventional CT. More importantly, the superior imaging capability of GSCT allows us to real-time monitor the targeting and accumulation of CAs toward bone-crack in vivo. These results highlight that clinical GSCT, combined with ytterbium-based CAs, provides a promising opportunity for understanding bone-related diseases in the future.

PIN–PMN–PT single crystals near the morphotropic phase boundary with low level of In 3+ doping were grown through slow cooling their high temperature solution. Temperature-dependent dielectric constants and pyroelectric coefficients indicated two phase transitions, i.e. orthorhombic (O)–tetragonal (T)–cubic (C), took place in 19PIN–45PMN–36PT single crystals upon heating from 35 °C to 250 °C. The dielectric constant of O phase was higher than that of T phase, which was related to the polarization rotation. When the temperature approached to the depolarization temperature, tetragonal macrodomains converted to microdomains. The polarization change led to the analogous observed in the plots of temperature-dependent pyroelectric coefficients and dielectric constants. However, the temperature-dependent remanent polarization indicated a lower O–T phase transition temperature. Such a discrepancy in T ot could be ascribed to the decline of ferroelectric phase transition energy caused by the superposition of the AC field at each temperature test point when perform bipolar ferroelectric hysteresis loops measuring. The domain structure variation upon heating an unpoled [0 0 1] c -oriented 19PIN–45PMN–36PT single crystal was observed with a polarized light microscopy, further indicating the occurrence of the two phase transitions.

Developing non-precious metal electrocatalysts (NPMCs) for the oxygen reduction reaction (ORR) is of paramount importance for commercial implementation of several clean energy techniques (e.g. proton exchange membrane fuel cells). However, limited understanding of the ORR catalytic mechanism of NPMCs greatly hinders the progress in the precise fabrication of NPMCs at the molecular or atomic level. Recently, an increasing number of studies have demonstrated the crucial role of a carbon matrix in exposing, stabilizing, and activating the catalytic sites, thus providing a platform to identify the nature of NPMCs. Herein, the unique structural effects of a carbon matrix in NPMCs are first reviewed to inspire the development of more advanced NPMCs for the ORR.

Studies on the contractile dynamics of heart cells have attracted broad attention for the development of both heart disease therapies and cardiomyocyte-actuated micro-robotics. In this study, a linear dynamic model of a single cardiomyocyte cell was proposed at the subcellular scale to characterize the contractile behaviors of heart cells, with system parameters representing the mechanical properties of the subcellular components of living cardiomyocytes. The system parameters of the dynamic model were identified with the cellular beating pattern measured by a scanning ion conductance microscope. The experiments were implemented with cardiomyocytes in one control group and two experimental groups with the drugs cytochalasin-D or nocodazole, to identify the system parameters of the model based on scanning ion conductance microscope measurements, measurement of the cellular Young's modulus with atomic force microscopy indentation, measurement of cellular contraction forces using the micro-pillar technique, and immunofluorescence staining and imaging of the cytoskeleton. The proposed mathematical model was both indirectly and qualitatively verified by the variation in cytoskeleton, beating amplitude, and contractility of cardiomyocytes among the control and the experimental groups, as well as directly and quantitatively validated by the simulation and the significant consistency of 90.5% in the comparison between the ratios of the Young's modulus and the equivalent comprehensive cellular elasticities of cells in the experimental groups to those in the control group. Apart from mechanical properties (mass, elasticity, and viscosity) of subcellular structures, other properties of cardiomyocytes have also been studied, such as the properties of the relative action potential pattern and cellular beating frequency. This work has potential implications for research on cytobiology, drug screening, mechanisms of the heart, and cardiomyocyte-based bio-syncretic robotics.

Recently, $\mathrm{Pb}(\mathrm{I}{\mathrm{n}}_{1/2}\mathrm{N}{\mathrm{b}}_{1/2}){\mathrm{O}}_{3}\text{\ensuremath{-}}\mathrm{PbZr}{\mathrm{O}}_{3}\text{\ensuremath{-}}\mathrm{Pb}(\mathrm{M}{\mathrm{g}}_{1/3}\mathrm{N}{\mathrm{b}}_{2/3}){\mathrm{O}}_{3}\text{\ensuremath{-}}\mathrm{PbTi}{\mathrm{O}}_{3}$ (PIN-PZ-PMN-PT) relaxor single crystals were demonstrated to possess improved temperature-insensitive properties, which would be desirable for high-power device applications. The relaxor character associated with the development of local random fields (RFs) and a high rhombohedral-tetragonal (R-T) ferroelectric transition temperature $({T}_{\mathrm{R}\ensuremath{-}\mathrm{T}}g120{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C})$ would be critical for the excellent properties. A significant effect of the chemical substitution of $\mathrm{I}{\mathrm{n}}^{3+}$ and $\mathrm{Z}{\mathrm{r}}^{4+}$ in PMN-PT to give PIN-PZ-PMN-PT is the development of local strain heterogeneity, which acts to suppress the development of macroscopic shear strains without suppressing the development of local ferroelectric moments and contribute substantially to the RFs in PIN-PZ-PMN-PT. Measurements of elastic and anelastic properties by resonant ultrasound spectroscopy show that PIN-PZ-PMN-PT crystal has a quite different form of elastic anomaly due to Vogel-Fulcher freezing, rather than the a discrete cubic-$T$ transition seen in a single crystal of PMN-28PT. It also has high acoustic loss of the relaxor phase down to ${T}_{\mathrm{R}\ensuremath{-}\mathrm{T}}$. Analysis of piezoresponse force microscopy phase images at different temperatures provides a quantitative insight into the extent to which the RFs influence the microdomain structure and the short-range order correlation length $\ensuremath{\langle}\ensuremath{\xi}\ensuremath{\rangle}$.

Two-dimensional nanocarbons are intriguing functional materials for energy storage. However, the serious aggregation problems hinder their wider applications. To address this issue, we developed a unique two-dimensional hierarchical carbon architecture (2D-HCA) with ultrasmall graphene-like carbon nanosheets uniformly grown on hexagonal carbon nanoplates. The obtained 2D-HCA shows an interconnected porous structure and abundant heteroelement doping. When employed as anode for lithium ion batteries, it exhibits a high discharge capacity of 748 m Ah g–1 even after 400 cycles at 2 A g–1.