A reduced graphene oxide (R-GO)-based field-effect transistor (FET) biosensor used for ultrasensitive label-free detection of DNA via peptide nucleic acid (PNA)–DNA hybridization is reported. In this ...work, R-GO was prepared by reduction of GO with hydrazine, and the FET biosensor was fabricated by drop-casting the R-GO suspension onto the sensor surface. PNA instead of DNA as the capture probe was employed, and DNA detection was performed through PNA–DNA hybridization by the R-GO FET biosensor. The detection limit as low as 100 fM was achieved, which is 1 order of magnitude lower than that of the previously reported graphene FET DNA biosensor based on DNA–DNA hybridization. Moreover, the R-GO FET biosensor was able to distinguish the complementary DNA from one-base mismatched DNA and noncomplementary DNA. Interestingly, the fabricated DNA biosensor was found to have a regeneration capability. The developed R-GO FET DNA biosensor shows ultrasensitivity and high specificity, indicating its potential applications in disease diagnostics as a point-of-care tool.
Tuning the nature and profile of acidic and basic sites on the surface of redox-active metal oxide nanostructures is a promising approach to constructing efficient catalysts for the oxidative removal ...of chlorinated volatile organic compounds (CVOCs). Herein, using dichloromethane (DCM) oxidation as a model reaction, we report that phosphate (PO x ) Brønsted acid sites can be incorporated onto a CeO2 nanosheet (NS) surface via an organophosphate-mediated route, which can effectively enhance the CeO2’s catalytic performance by promoting the removal of chlorine poisoning species. From the systematic study of the correlation between PO x composition, surface structure (acid and basic sites), and catalytic properties, we find that the incorporated Brønsted acid sites can also function to decrease the amount of medium-strong basic sites (O2–), reducing the formation of chlorinated organic byproduct monochloromethane (MCM) and leading to the desirable product, HCl. At the optimized P/Ce ratio (0.2), the PO x –CeO2 NSs can perform a stable DCM conversion of 65–70% for over 10 h at 250 °C and over 95% conversion at 300 °C, superior to both pristine and other phosphate-modified CeO2 NSs. Our work clearly identifies the critical role of acid and basic sites over functionalized CeO2 for efficient catalytic CVOCs oxidation, guiding future advanced catalyst design for environmental remediation.
Lithium–sulfur (Li–S) batteries have a distinct advantage over other rechargeable battery systems since their high specific energy and low cost. However, the diffusion of polysulfides from cathode to ...anode leads to poor electrochemical stability of Li–S batteries, which is a main factor that restricts their further development. Herein, for the first time we present a separator with nitrogen-doped porous hollow carbon sphere (NHC) coating, with which Li–S cells enormously improve the utilization of active material and enhance excellent electrochemical performance. An initial discharge capacity of 1656 mAh g−1 (0.2 C) and a low fading rate of 0.11% per cycle within 500 cycles (1 C) are achieved, which ascribe to the chemical and physical adsorption properties of porous and nitrogen-doped NHCs. The NHC-decorated separator is of low cost and can effectively improve energy density of Li–S cells, exhibiting potential for further development of Li–S batteries.
Nitrogen-doped porous hollow carbon spheres are prepared by pyrolysis of a polydopamine (PDA) carbon precursor on the surface of silicon dioxide (SiO2) temple. After washed with HF, the NHCs are coated onto one side of the separator with a slurry-coated method. With the NHC-decorated separator, an initial discharge capacity of 1656 mAh g−1 (0.2 C) and a low fading rate of 0.11% per cycle within 500 cycles (1 C) are achieved. The excellent results are attributed to the high specific surface area and pore volume of the NHCs which ensure electrolyte infiltration and act as a barrier for polysulfides. Furthermore, the high nitrogen content in NHCs can improve electronic conductivity and enhance interaction between nitrogen atoms and polysulfides. Display omitted
•NHCs are prepared by pyrolysis of a PDA carbon precursor.•NHC-decorated separator exhibits excellent electrochemical performance.•NHC-decorated separator would be a promising solution for Li–S batteries.
Solution-derived carbon nanotube (CNT) network films with high semiconducting purity are suitable materials for the wafer-scale fabrication of field-effect transistors (FETs) and integrated circuits ...(ICs). However, it is challenging to realize high-performance complementary metal-oxide semiconductor (CMOS) FETs with high yield and stability on such CNT network films, and this difficulty hinders the development of CNT-film-based ICs. In this work, we developed a doping-free process for the fabrication of CMOS FETs based on solution-processed CNT network films, in which the polarity of the FETs was controlled using Sc or Pd as the source/drain contacts to selectively inject carriers into the channels. The fabricated top-gated CMOS FETs showed high symmetry between the characteristics of n- and p-type devices and exhibited high-performance uniformity and excellent scalability down to a gate length of 1 μm. Many common types of CMOS ICs, including typical logic gates, sequential circuits, and arithmetic units, were constructed based on CNT films, and the fabricated ICs exhibited rail-to-rail outputs because of the high noise margin of CMOS circuits. In particular, 4-bit full adders consisting of 132 CMOS FETs were realized with 100% yield, thereby demonstrating that this CMOS technology shows the potential to advance the development of medium-scale CNT-network-film-based ICs.
Generalized synthetic strategies for nanostructures with well-defined physical dimensions and broad-range chemical compositions are at the frontier of advanced nanomaterials design, ...functionalization, and application. Here, we report a composition-programmable synthesis of multimetallic phosphide CoMP x nanorods (NRs) wherein M can be controlled to be Fe, Ni, Mn, Cu, and their binary combinations. Forming Co2P/MP x core/shell NRs and subsequently converting them into CoMP x solid-solution NRs through thermal post-treatment are essential to overcome the obstacle of morphology/structure inconsistency faced in conventional synthesis of CoMP x with the different M compositions. The resultant CoMP x with uniform one-dimensional (1-D) structure provides us a platform to unambiguously screen the M synergistic effects in improving the electrocatalytic activity, as exemplified by the oxygen evolution reaction. This new approach mediated by core/shell nanostructure formation and conversion can be extended to other multicomponent nanocrystal systems (metal alloy, mixed oxide, and chalcogenide, etc.) for diverse applications.
Mafic dykes are observed in the Korla region along the northern Tarim Block, NW China. Our sensitive high-resolution ion microprobe U-Pb zircon ages, the first determined for these dykes, indicate ...that the mafic dykes were mainly formed at 650-630 Ma, and thus document the youngest known igneous activity associated with rifting in the Tarim Block during the Neoproterozoic. Combined with previous geochronological data, at least three pulses of magmatic activity, from c. 830 to 800 Ma, from c. 790 to 740 Ma and from c. 650 to 630 Ma, are recognized, which reveal that multiple episodes of rifting occurred within the Tarim Block, implying that the breakup of the Rodinia supercontinent in the Tarim Block may have been a long-lasting process.
Glutamine synthetase (GS) isozymes play critical roles in nitrogen (N) metabolism. However, the exact relationship between GS and nitrogen use efficiency (NUE) remain unclear. We have selected and ...compared two wheat cultivars, YM49 and XN509, which were identified as the N-efficient and N-inefficient genotypes, respectively. In this study, agronomical, morphological, physiological and biochemical approaches were performed. The results showed that TaGS1 was high expressed post-anthesis, and TaGS2 was highly expressed pre-anthesis in N-efficient genotype compared to N-inefficient genotype. GS1 and GS2 isozymes were also separated by native-PAGE and found that the spatial and temporal distribution of GS isozymes, their expression of gene and protein subunits in source-sink-flow organs during development periods triggered the pool strength and influenced the N flow. According to the physiological role of GS isozymes, we illustrated four metabolic regulation points, by which acting collaboratively in different organs, accelerating the transport of nutrients to the grain. It suggested that the regulation of GS isozymes may promote flow strength and enhance NUE by a complex C-N metabolic mechanism. The relative activity or amount of GS1 and GS2 isozymes could be a potential marker to predict and select wheat genotypes with enhanced NUE.
Coarse-grained (CG) simulations have allowed access to larger length scales and longer time scales in the study of the dynamic processes of large biomolecules than all-atom (AA) molecular dynamics ...(MD) simulations. Backmapping from CG models to AA structures has long been studied because it enables us to gain detailed structure insights from CG simulations. Many methods first construct an AA structure from the CG model by fragments, random placement, or geometrical rules and subsequently optimize the solution via energy minimization, simulated annealing or position-restrained simulations. However, such methods may only work well on residue-level CG models and cannot consider the deviations of CG models. In this work, we describe, to the best of our knowledge, a new backmapping method based on Bayesian inference and restrained MD simulations. Restraints with log harmonic energy terms are defined according to the target CG model using the Bayesian inference in which the CG deviations can be estimated. From an initial AA structure obtained from either high-resolution experiments or homology modeling, a MD simulation with the aforementioned restraints is performed to obtain a final AA structure that is a backmapping of the target CG model. The method was validated using multiresolution CG models of the soluble extracellular region of the human epidermal growth factor receptor and was further applied to construct AA structures from CG simulations of the nucleosome core particle. The results demonstrate that our method can generate accurate AA structures of different types of biomolecules from multiple CG models with either residue-level resolution or much lower resolution than one-site-per-residue.
Summary Background On March 30, a novel influenza A subtype H7N9 virus (A/H7N9) was detected in patients with severe respiratory disease in eastern China. Virological factors associated with a poor ...clinical outcome for this virus remain unclear. We quantified the viral load and analysed antiviral resistance mutations in specimens from patients with A/H7N9. Methods We studied 14 patients with A/H7N9 disease admitted to the Shanghai Public Health Clinical Centre (SPHCC), China, between April 4, and April 20, 2013, who were given antiviral treatment (oseltamivir or peramivir) for less than 2 days before admission. We investigated the viral load in throat, stool, serum, and urine specimens obtained sequentially from these patients. We also sequenced viral RNA from these specimens to study the mutations associated with resistance to neuraminidase inhibitors and their association with disease outcome. Findings All patients developed pneumonia, seven of them required mechanical ventilation, and three of them further deteriorated to become dependent on extracorporeal membrane oxygenation (ECMO), two of whom died. Antiviral treatment was associated with a reduction of viral load in throat swab specimens in 11 surviving patients. Three patients with persistently high viral load in the throat in spite of antiviral therapy became ECMO dependent. An Arg292Lys mutation in the virus neuraminidase (NA) gene known to confer resistance to both zanamivir and oseltamivir was identified in two of these patients, both also received corticosteroid treatment. In one of them, wild-type sequence Arg292 was noted 2 days after start of antiviral treatment, and the resistant mutant Lys292 dominated 9 days after start of treatment. Interpretation Reduction of viral load following antiviral treatment correlated with improved outcome. Emergence of NA Arg292Lys mutation in two patients who also received corticosteroid treatment led to treatment failure and a poor clinical outcome. The emergence of antiviral resistance in A/H7N9 viruses, especially in patients receiving corticosteroid therapy, is concerning, needs to be closely monitored, and considered in pandemic preparedness planning. Funding National Megaprojects of China for Infectious Diseases, Shanghai Municipal Health and Family Planning Commission, the National Key Basic Research Program of China, Ministry of Science and Technology, and National Natural Science Foundation of China.
Using physical vapor deposition (PVD) technology, GeSe nanowires were successfully fabricated by heating GeSe powder at temperatures of 500 °C, 530 °C, 560 °C, 590 °C, and 620 °C. The microstructure, ...crystal morphology, and chemical composition of the resulting materials were thoroughly analyzed employing methods like Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), plus Raman Spectroscopy. Through a series of photoelectric performance tests, it was discovered that the GeSe nanowires prepared at 560 °C exhibited superior properties. These nanowires not only possessed high crystalline quality but also featured uniform diameters, demonstrating excellent consistency. Under illumination at 780 nm, the GeSe nanowires prepared at this temperature showed higher dark current, photocurrent, and photoresponsivity compared to samples prepared at other temperatures. These results indicate that GeSe nanomaterials hold substantial potential in the field of photodetection. Particularly in the visible light spectrum, GeSe nanomaterials exhibit outstanding light absorption capabilities and photoresponse.
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