Improving Formate and Methanol Fuels: Catalytic Activity of Single Pd Coated Carbon Nanotubes

The oxidations of formate and methanol on nitrogen-doped carbon nanotubes decorated with palladium nanoparticles were studied at both the single-nanotube and ensemble levels. Significant voltammetric differences were seen. Pd oxide formation as a competitive reaction with formate or methanol oxidation is significantly inhibited at high overpotentials under the high mass transport conditions associated with single-particle materials in comparison with that seen with ensembles, where slower diffusion prevails. Higher electro-oxidation efficiency for the organic fuels is achieved

Data_Sheet_1_Improvement of thermostability and catalytic efficiency of xylanase from Myceliophthora thermophilar by N-terminal and C-terminal truncation.docx

IntroductionExtracting xylanase from thermophilic filamentous fungi is a feasible way to obtain xylanase with good thermal stability.MethodsThe transcriptomic data of Myceliophthora thermophilic destructive ATCC42464 were differentially expressed and enriched. By comparing the sequences of Mtxylan2 and more than 10 xylanases, the N-terminal and C-terminal of Mtxylan2 were truncated, and three mutants 28N, 28C and 28NC were constructed.Results and discussionGH11 xylan Mtxylan2 was identified by transcriptomic analysis, the specific enzyme activity of Mtxylan2 was 104.67 U/mg, and the optimal temperature was 65°C. Molecular modification of Mtxylan2 showed that the catalytic activity of the mutants was enhanced. Among them, the catalytic activity of 28C was increased by 9.3 times, the optimal temperature was increased by 5°C, and the residual enzyme activity remained above 80% after 30 min at 50–65°C, indicating that redundant C-terminal truncation can improve the thermal stability and catalytic performance of GH11 xylanase.</p

Preparation of High-Temperature Resistant Polyimide Fibers by Introducing the <i>p</i>‑Phenylenediamine into Kapton-Type Polyimide

To improve the heat resistance of polyimide (PI) fibers for application in harsh environments and establish a correlation among the chemical structure, fabrication performance, and material properties, a simple and rigid diamine, p-phenylenediamine (p-PDA) was incorporated into the Kapton-type PI synthesized from pyromellitic dianhydride and 4,4-diaminodiphenylmethane (ODA). The comprehensive properties of these co-PI fibers were systematically investigated to assess the impact of p-PDA addition. Two-dimensional wide-angle X-ray diffraction (WAXD) was used to investigate the evolution of the aggregation structure of the co-PI fibers during the processing. The thermogravimetric analyzer (TGA) test shows that the incorporation of p-PDA improves the heat resistance of polyimide fibers, with the 10 wt % weight loss temperature (T10%) ranging from 582 to 605 °C and the maximum decomposition temperature (Tmax) of 611–635 °C for the co-PI fibers with different p-PDA contents. Additionally, the potential degradation mechanism of the PI fibers was examined by utilizing pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and other thermal analyses. By introducing p-PDA, the content of O element (ether bond in ODA) in the system decreases, leading to a reduction in oxygen free radicals from ODA during the decomposition process of polyimides. The decrease in active species can cause a decrease in the decomposition rate and improve the heat resistance of the polyimide fibers. The study of the thermal decomposition mechanism of polyimides provides a valuable foundation for the preparation of high-performance polymer fibers with enhanced thermal resistance and excellent overall performance

New Insights into Fundamental Electron Transfer from Single Nanoparticle Voltammetry

The reductive redox behavior of oxygen in aqueous acid solution leading first to adsorbed superoxide species at single palladium coated multiwalled carbon nanotubes (of length ca. 5 μm and width 130 nm) is reported. The small dimensions of the electroactive surface create conditions of high mass-transport permitting the resolution of electrode kinetic effects. In combination with new theoretical models, it is shown that the physical location of the formed product within the double layer of the electrode profoundly influences the observed electron transfer kinetics. This <i>generically</i> important result gives new physical insights into the modeling of the many electrochemical processes involving adsorbed intermediates

DataSheet1_An ultrathin fiber-based fluorescent imaging probe based on hyperspectral imaging.DOCX

Most fluorescent imaging systems use pre-defined filter sets with limited flexibility in the choice of excitation and emission bands and suffer from crosstalk between different fluorophores for multiplexed imaging. When implemented in the context of optical fibers for biological imaging in a remote setting with space constraints, the size of the fiber probe is crucial. To overcome these challenges, we combined the merits of hyperspectral imaging and an ultrathin optical imaging fiber where fluorescent images at 311 spectral bands in the visible range were captured using a liquid crystal tunable filter with a fiber probe of 500 μm in diameter. Fluorescent experiments were performed on quantum dots mixtures and genetically modified E. coli bacteria mixtures to demonstrate the system’s capabilities for multiplexed imaging. Images were first processed using a Fourier transform filtering technique to remove the fiber core pattern artifact. Subsequently, the classification of different types of bacteria samples was calculated using two methods, namely, spectral unmixing with maximum abundance and spectral matching with minimum spectral angle distance. Finally, the spatial distributions of individual bacteria types were overlaid with the mixture image, and the two classification results matched well. A simple-to-use graphic user interface (GUI) platform for the hyperspectral imaging fiber probe system was developed which performs image processing and displays the classification results. The methods and results presented will appeal to the optical fiber-based imaging and hyperspectral imaging communities in general and have great potential for biological imaging applications.</p

Quantifying Single-Carbon Nanotube–Electrode Contact via the Nanoimpact Method

A new methodology is developed to enable the measurement of the resistance across individual carbon nanotube-electrode contacts. Carbon nanotubes (CNTs) are suspended in the solution phase and occasionally contact the electrified interface, some of which bridge a micron-sized gap between two microbands of an interdigitated gold electrode. A potential difference is applied between the contacts and the magnitude of the current increase after the arrival of the CNT gives a measure of the resistance associated with the single CNT–gold contact. These experiments reveal the presence of a high contact resistance (∼50 MΩ), which significantly dominates the charge-transfer process. Further measurements on ensembles of CNTs made using a dilute layer of CNTs affixed to the interdigitated electrode surface and measured in the absence of solvent showed responses consistent with the same high value of contact resistance

Simultaneously Enhanced Thermostability and Catalytic Activity of Xylanase from Streptomyces rameus L2001 by Rigidifying Flexible Regions in Loop Regions of the N‑Terminus

The GH11 xylanase XynA from Streptomyces rameus L2001 has favorable hydrolytic properties. However, its poor thermal stability hinders its widespread application in industry. In this study, mutants Mut1 and Mut2 were constructed by rationally combining the mutations 11YHDGYF16, 23AP24/23SP24, and 32GP33. The residual enzyme activity of these combinational mutants was more than 85% when incubated at 80 and 90 °C for 12 h, and thus are the most thermotolerant xylanases known to date. The reduced flexibility of the N-terminus, increased overall rigidity, as well as the surface net charge of Mut1 and Mut2 may be partially responsible for the improved thermal stability. In addition, the specific activity and catalytic efficiency of Mut1 and Mut2 were improved compared with those of wild-type XynA. The broader catalytic cleft and enhanced flexibility of the “thumb” of Mut1 and Mut2 may be partially responsible for the improved specific activity and catalytic efficiency

Double Input Capacitively Coupled Contactless Conductivity Detector with Phase Shift

A double input capacitively coupled contactless conductivity detector (DIC⁴D) device which gets higher sensitivity has been described in this paper. The detector consists of two input electrodes and one output electrode. When two alternating current (AC) voltages with the same amplitude and different phases are imposed on each input electrode, the equivalent resistance of the output electrode is reduced because of the interference of the two signals with different phase angles. For a capacitively coupled contactless conductivity detector (C⁴D), the ratio of the response of KCl solution to that of distilled water is 1.6. However, for DIC⁴D, the ratio is 1.55 at a phase difference of 0° and increases to 1.8 at the phase difference of 170°, respectively. For C⁴D, the response of KCl solution is a linear function of the logarithm of concentrations from 10^–5 M to 10^–2 M, and the slope is 5.58. However, the slope of the response increases to 7.13 in DIC⁴D, and the limit of detection (LOD) of DIC⁴D is estimated to be 5 × 10^–8 M. The slope of the three-way DIC⁴D is increased to 69.78. A flow injection device is employed for the evaluation of the applicability of DIC⁴D with the same range, and good reproducibility is confirmed through flow injection of the same solution 10 times. The relative standard deviation (RSD) is 0.7%, which demonstrates a promising application to capillary electrophoresis (CE)

Video1_An ultrathin fiber-based fluorescent imaging probe based on hyperspectral imaging.MP4

Most fluorescent imaging systems use pre-defined filter sets with limited flexibility in the choice of excitation and emission bands and suffer from crosstalk between different fluorophores for multiplexed imaging. When implemented in the context of optical fibers for biological imaging in a remote setting with space constraints, the size of the fiber probe is crucial. To overcome these challenges, we combined the merits of hyperspectral imaging and an ultrathin optical imaging fiber where fluorescent images at 311 spectral bands in the visible range were captured using a liquid crystal tunable filter with a fiber probe of 500 μm in diameter. Fluorescent experiments were performed on quantum dots mixtures and genetically modified E. coli bacteria mixtures to demonstrate the system’s capabilities for multiplexed imaging. Images were first processed using a Fourier transform filtering technique to remove the fiber core pattern artifact. Subsequently, the classification of different types of bacteria samples was calculated using two methods, namely, spectral unmixing with maximum abundance and spectral matching with minimum spectral angle distance. Finally, the spatial distributions of individual bacteria types were overlaid with the mixture image, and the two classification results matched well. A simple-to-use graphic user interface (GUI) platform for the hyperspectral imaging fiber probe system was developed which performs image processing and displays the classification results. The methods and results presented will appeal to the optical fiber-based imaging and hyperspectral imaging communities in general and have great potential for biological imaging applications.</p

Improving Single-Carbon-Nanotube–Electrode Contacts Using Molecular Electronics

We report the use of an electroactive species, acetaminophen, to modify the electrical connection between a carbon nanotube (CNT) and an electrode. By applying a potential across two electrodes, some of the CNTs in solution occasionally contact the electrified interface and bridge between two electrodes. By observing a single CNT contact between two microbands of an interdigitated Au electrode in the presence and absence of acetaminophen, the role of the molecular species at the electronic junction is revealed. As compared with the pure CNT, the current magnitude of the acetaminophen-modified CNTs significantly increases with the applied potentials, indicating that the molecule species improves the junction properties probably via redox shuttling