Polyoxometalate-based ionic liquids: efficient reversible phase transformation-type catalysts for thiolation of alcohols to construct C-S bonds.

As important building blocks in natural products and organic synthesis, thioethers have a wide range of potential applications. Herein, polyoxometalate-based ionic liquids (POM-ILs-SO3H) derived from N-alkyl imidazole were synthesized and used for the first time for the thiolation of alcohols to construct C-S bonds in a series of benzyl thioethers. This type of POM-ILs-SO3H catalyst exhibited high catalytic activity, providing up to 98% yield of thioether within 1 h at 70 °C. The alkyl chain length of the imidazole had a certain effect on the solubility of the POM-ILs-SO3H catalysts in the reaction solvent, and then affected their catalytic activity. The catalytic system had a wide substrate scope and was suitable for the reaction of tertiary and secondary benzyl alcohols with thiophenols or cycloalkyl thiols. In particular, [PIMPS]3PW12O40 (PIM = 1-propylimidazole, PS = propane sulfonate) as a reversible phase transformation-type catalyst, combining the advantages of homogeneous and heterogeneous catalysts, exhibited high activity and good recyclability with only a slight decrease in the yield after five runs. Additionally, a carbocation mechanism was proposed for the thiolation reaction of alcohols.

Silica Cross-Linked Micelle-Based Theranostic System for the Imaging and Treatment of Acute and Chronic Kidney Injury.

Acute kidney injury (AKI) is a common and serious disease with high mortality and morbidity, and the persistent inflammatory environment brought about by AKI promotes its deterioration into chronic kidney disease (CKD). An efficient and timely targeted drug delivery to the renal tubules is crucial for AKI treatment. Here, we prepared silica cross-linked micelles (SCLMs) with different sizes and studied their targeting ability to the injured kidney. It is found that the SCLMs with a size of 13 nm could rapidly accumulate and remain in the damaged kidney. Immunofluorescence results confirmed that SCLMs are selectively located in the damaged tubular cells but cannot be found in healthy renal tissue. Therefore, fluorescent dye-labeled SCLMs were used for the imaging of the injured kidney, which could reflect the status of the kidney injury. Furthermore, atorvastatin, an antioxidative and anti-inflammatory drug, was loaded in SCLMs as the therapeutic agents for the treatment of ischemia/reperfusion-induced AKI and CKD. Renal function indexes, such as tubular necrosis, collagen deposition, and inflammation, were effectively improved after the treatment.

Myocardium-Targeted Micelle Nanomedicine That Salvages the Heart from Ischemia/Reperfusion Injury.

Cardioprotective medication is the common treatment to relieve myocardial ischemia/reperfusion (I/R) injury. However, limited by the low bioavailability of therapeutic drugs, the therapeutic outcome is barely satisfactory. Because the I/R injury can enhance the permeability of the vasculature and allow the extravasation of nanoparticles into the surrounding tissue, herein we formulate the cardiotonic drug olprinone (Olp) in cross-linked micelles as the nanomedicine to achieve myocardium-targeted delivery after systematic administration. As a result, the local concentration of Olp in the injured myocardium is raised by orders of magnitude with prolonged drug duration time. The treatment successfully preserves the pumping efficiency of the heart, alleviates ventricular remodeling, and thus stops the positive feedback loop for the deteriorated cardiac function. Consequently, the myocardium-targeted nanomedicine significantly salvages the heart from I/R injury before irreversible pathological changes take place.

Electrical and thermal transport properties of high crystalline PdTe2 nanoribbons under a strong magnetic field.

The low-temperature superconductivity and topological properties of two-dimensional PdTe2 have shown great potential in the fields of optics and electronics, and its electrical and thermal transport properties under a strong magnetic field are very important for basic research and practical applications. In this study, the electrical resistivity and thermal conductivity of high crystalline PdTe2 nanoribbons were comprehensively measured by applying the direct current heating method, eliminating the thermal and electrical contact resistances at different magnetic field intensities and temperatures. It is found that the PdTe2 nanoribbons exhibited a low electrical resistivity of ∼27 µΩ cm and a high thermal conductivity of ∼130 W m-1 K-1 at room temperature. Moreover, the magnetoresistance of PdTe2 nanoribbons increased with the decrease in temperature and reached 114% at 20 K and 14 T. The thermal conductivity change rate caused by the 14 T magnetic field increased at low temperatures, reaching -11.3% at 20 K.

A simple paper-based ratiometric luminescent sensor for tetracyclines using copper nanocluster-europium hybrid nanoprobes.

Tetracyclines (TCs), as one of the broad-spectrum antibiotics, are widely used to treat bacterial infections. The residues of TCs in animal-origin foods and drinking water have raised safety concerns and affected the public health. Thus, there is a high demand to develop a simple and rapid method for the detection of TCs. In this work, we developed a ratiometric luminescence probe for the sensitive and visualized detection of TCs. Specifically, tannic acid-stabilized copper nanoclusters (TA-CuNCs) with blue emission at 433 nm were synthesized. The luminescence of TA-CuNCs attenuated partially by the europium ions (Eu3+) due to the aggregation-induced quenching. When TCs were added to the TA-CuNCs-Eu3+ system, the luminescence of TA-CuNCs at 433 nm can be further quenched by the inner-filter effect, and the characteristic luminescence of Eu3+ at 617 nm emerged due to the formation of Eu3+-TCs complex. The ratio of the luminescence at 617 nm-433 nm increased linearly to the concentration of TCs. Additionally, we demonstrated the detection of oxytetracycline in real samples such as tap and lake water, milk, pharmaceutical industry wastewater, honey and soil extract with high recovery rate (97.25%-103.44%). Furthermore, a portable paper device is fabricated by the luminescent probe to conduct the on-site analysis of TCs.

Electroplating Deposition of Bismuth Absorbers for X-ray Superconducting Transition Edge Sensors.

An absorber with a high absorbing efficiency is crucial for X-ray transition edge sensors (TESs) to realize high quantum efficiency and the best energy resolution. Semimetal Bismuth (Bi) has shown greater superiority than gold (Au) as the absorber due to the low specific heat capacity, which is two orders of magnitude smaller. The electroplating process of Bi films is investigated. The Bi grains show a polycrystalline rhombohedral structure, and the X-ray diffraction (XRD) patterns show a typical crystal orientation of (012). The average grain size becomes larger as the electroplating current density and the thickness increase, and the orientation of Bi grains changes as the temperature increases. The residual resistance ratio (RRR) (R300 K/R4.2 K) is 1.37 for the Bi film (862 nm) deposited with 9 mA/cm2 at 40 °C for 2 min. The absorptivity of the 5 µm thick Bi films is 40.3% and 30.7% for 10 keV and 15.6 keV X-ray radiation respectively, which shows that Bi films are a good candidate as the absorber of X-ray TESs.

Influence of the Interface Composition to the Superconductivity of Ti/PdAu Films.

In this work, the interface composition of the superconducting Ti/PdAu bilayer is tuned by an annealing process in N2 from 100 to 500 °C to control the superconducting transition temperature (Tc). This Ti-PdAu composition layer is characterized with a high-resolution transmission electron microscopy (HRTEM) and energy-dispersive spectrometer (EDS) to show the infiltration process. The surface topography, electrical, and cryogenic properties are also shown. The inter-infiltration of Ti and PdAu induced by the thermal treatments generates an intermixed layer at the interface of the bilayer film. Due to the enforced proximity effect by the annealing process, the Tc of Ti (55 nm)/PdAu (60 nm) bilayer thin films is tuned from an initial value of 243 to 111 mK which is a temperature that is suitable for the application as the function unit of a superconducting transition edge sensor.

Essential role of enhanced surface electron-phonon interactions on the electrical transport of suspended polycrystalline gold nanofilms.

The electrical resistivity of suspended polycrystalline gold nanofilms with different lengths has been measured over the temperature range of 2 K to 340 K, which dramatically increases compared with bulk gold and slightly increases with length. Classical size effect theories considering surface and grain boundary scatterings cannot explain the increased film resistivity, especially the temperature dependence of resistivity, over the whole temperature range. Considering the fact that the reduction of the coordination number of atoms at the surface and the interface leads to a decrease of the phonon spectrum frequency and consequently affects the surface phonon spectrum, the electron-phonon interaction as a relatively independent surface effect is taken into account. The theoretical predictions and the experimental measured film resistivity match very well over the whole temperature range and the extracted surface Debye temperature decreases significantly compared to the bulk value, which illustrates the essential role of enhanced surface electron-phonon interactions on the electrical transport of the present gold nanofilms.

Selective fabrication of quasi-parallel single-walled carbon nanotubes on silicon substrates.

We have fabricated single-walled carbon nanotube (SWNT) arrays, about 85% of which are semiconducting. Fe nanoparticles, which were used as a catalyst, were produced simply and cheaply from Wistar rat blood. The SWNT arrays generally grow parallel to the gas flow. Hundreds of devices with varying SWNT density in the channel were measured and we found that the on-off ratio for such devices with the quasi-parallel, semiconducting-rich SWNTs in the channel can be easily increased via an electrical breakdown method. Thus, large-scale fabrication of FET devices is possible simply by controlling the width of the channel. Finally, we determined that the mobility of the devices reached 3900 cm(2) V(-1) s(-1).

Fabrication of ultralong and electrically uniform single-walled carbon nanotubes on clean substrates.

We report the controlled growth of ultralong single-wall carbon nanotube (SWNT) arrays using an improved chemical vapor deposition strategy. Using ethanol or methane as the feed gas, monodispersed Fe-Mo as the catalyst, and a superaligned carbon nanotube (CNT) film as the catalyst supporting frame, ultralong CNTs over 18.5 cm long were grown on Si substrates. The growth rate of the CNTs was more than 40 mum/s. No catalyst-related residual material was found on the substrates due to the use of a CNT film as the catalyst supporting frame, facilitating any subsequent fabrication of SWNT-based devices. Electrical transport measurements indicated that the electrical characteristics along a single ultralong SWNT were uniform. We also found that maintaining a spatially homogeneous temperature during the growth process was a critical factor for obtaining constant electrical characteristics along the length of the ultralong SWNTs.

Measuring the thermal conductivity of individual carbon nanotubes by the Raman shift method.

The thermal contact resistance is a difficult problem that has puzzled many researchers in measuring the intrinsic thermal conductivity of an individual carbon nanotube (CNT). To avoid this problem, a non-contact Raman spectra shift method is introduced, by which we have successfully measured the thermal conductivity (kappa) of an individual single-walled carbon nanotube and a multi-walled carbon nanotube. The measured kappa values are 2400 W m(-1) K(-1) and 1400 W m(-1) K(-1), respectively. The CNT was suspended over a trench and heated by electricity. The temperature difference between the middle and the two ends of the CNT indicated its intrinsic heat transfer capability. The temperature difference was determined by the temperature-induced shifts of its G band Raman spectra. This new method can eliminate the impact of the thermal contact resistance which was a Gordian knot in many previous measurements.