Preparation, Characterization, and Magnetic Resonance Imaging of Mn@SiO2 Nanowires.

The deposition time was controlled to prepare Mn nanowires of different lengths and diameters on templates of anodic aluminum oxide (AAO) with different pore sizes. The surface of as-prepared Mn nanowires was modified with SiO2 using the sol-gel method to improve their dispersion in aqueous solution. The effects of the diameter and length of the as-prepared Mn nanowires coated with SiO2 on the relaxivity were investigated. It was found that the Mn@SiO2 nanowires have smaller diameters and a higher longitudinal relaxivity (r1) with an increased length. Mn3@SiO2 nanowires had the highest r1 value of 5.8 mM-1 s-1 among the Mn@SiO2 nanowires (Mn3 nanowires have a diameter of about 30 nm and a length of about 0.5 µm length). Additionally, the biocompatibility and in vivo imaging ability of the Mn3@SiO2 nanowires were evaluated. The Mn3@SiO2 nanowires had good cytotoxicity and biocompatibility, and the kidney of SD rats showed a positive enhancement effect during small animal imaging at 1.5 T. This study showed that the Mn3@SiO2 nanowires could potentially become contrast agents (CAs) of longitudinal relaxation time (T1).

Preparation, characterization, and magnetic resonance imaging of Fe nanowires.

A facile template method was employed to synthesize Fe nanowires of different sizes, dimensions. Comprehensive analyses were conducted to explore their morphology, structure, composition, and magnetic properties. The surface of as-prepared Fe nanowires was modified with SiO2 by sol-gel method to improve the dispersion of as-prepared Fe nanowires in aqueous solution. Furthermore, the relaxation properties, biocompatibility and in vivo imaging abilities of the Fe@SiO2 nanowires were evaluated. The study revealed that the SiO2-coated Fe nanowires functioned effectively as transverse relaxation time (T2) contrast agents (CAs). Notably, as the length of the Fe@SiO2 nanowires increased, their diameter decreased, leading to a higher the transverse relaxivity (r2) value. Our study identified that among the Fe nanowires synthesized, the Fe3@SiO2 nanowires, characterized by a diameter of around 30 nm and a length of approximately 500 nm, exhibited the highest r2 value of 59.3 mM-1 s-1. These nanowires demonstrated good biocompatibility and non-toxicity. Notably, upon conducting small animal imaging a 1.5 T with Sprague-Dawley rats, we observed a discernible negative enhancement effect in the liver. These findings indicate the promising potential of Fe@SiO2 nanowires as T2 CAs, with the possibility of tuning their size for optimized results.

Single-Crystal MoS2 Monolayer Wafer Grown on Au (111) Film Substrates.

Monolayer transition metal dichalcogenides (TMDCs) with high crystalline quality are important channel materials for next-generation electronics. Researches on TMDCs have been accelerated by the development of chemical vapor deposition (CVD). However, antiparallel domains and twin grain boundaries (GBs) usually form in CVD synthesis due to the special threefold symmetry of TMDCs lattices. The existence of GBs severely reduces the electrical and photoelectrical properties of TMDCs, thus restricting their practical applications. Herein, the epitaxial growth of single crystal MoS2 (SC-MoS2 ) monolayer is reported on Au (111) film across a two-inch c-plane sapphire wafer by CVD. The MoS2 domains obtained on Au (111) film exhibit unidirectional alignment with zigzag edges parallel to the <110> direction of Au (111). Experimental results indicated that the unidirectional growth of MoS2 domains on Au (111) is a temperature-guided epitaxial growth mode. The high growth temperature provides enough energy for the rotation of the MoS2 seeds to find the most favorable orientation on Au (111) to achieve a unidirectional ratio of over 99%. Moreover, the unidirectional MoS2 domains seamlessly stitched into single crystal monolayer without GBs formation. The progress achieved in this work will promote the practical applications of TMDCs in microelectronics.

Fe/Mn Multilayer Nanowires as High-Performance T1-T2 Dual Modal MRI Contrast Agents.

A lot of nanomaterials are using T1-T2 dual mode magnetic resonance (MR) contrast agents (CAs), but multilayer nanowire (NW) with iron (Fe) and manganese (Mn) as T1-T2 dual modal CAs has not been reported yet. Herein, we synthesized a Fe/Mn multilayer NW with an adjustable Fe layer, as T1-T2 dual-mode CAs. The relaxation performance of Fe/Mn multilayer NW was studied at 1.5 T. Results show that, when the length of the Fe layer is about 10 nm and the Mn is about 5 nm, the r1 value (21.8 mM-1s-1) and r2 value (74.8 mM-1s-1) of the Fe/Mn multilayer NW are higher than that of Mn NW (3.7 mM-1s-1) and Fe NW (59.3 mM-1s-1), respectively. We predict that our Fe/Mn multilayer NW could be used as T1-T2 dual mode MRI CAs in the near future.

Modelling the effects of media coverage and quarantine on the COVID-19 infections in the UK.

A new COVID-19 epidemic model with media coverage and quarantine is constructed. The model allows for the susceptibles to the unconscious and conscious susceptible compartment. First, mathematical analyses establish that the global dynamics of the spread of the COVID-19 infectious disease are completely determined by the basic reproduction number R0. If R0 ≤ 1, then the disease free equilibrium is globally asymptotically stable. If R0 > 1, the endemic equilibrium is globally asymptotically stable. Second, the unknown parameters of model are estimated by the MCMC algorithm on the basis of the total confirmed new cases from February 1, 2020 to March 23, 2020 in the UK. We also estimate that the basic reproduction number is R0 = 4.2816(95%CI: (3.8882, 4.6750)). Without the most restrictive measures, we forecast that the COVID-19 epidemic will peak on June 2 (95%CI: (May 23, June 13)) (Figure 3a) and the number of infected individuals is more than 70% of UK population. In order to determine the key parameters of the model, sensitivity analysis are also explored. Finally, our results show reducing contact is effective against the spread of the disease. We suggest that the stringent containment strategies should be adopted in the UK.

Electrochemical Strategy for Flexible and Highly Conductive Carbon Films: The Role of 3-Dimensional Graphene/Graphite Aggregates.

Conductive carbon films with good flexibility are ever-increasingly desired for electronics. Previous efforts relying on graphene films to achieve this required special treatment to create wrinkles in the lamellar stacking sheet structure. Here, films with a wrinkled structure were facilely fabricated from electrochemically derived 3-dimiensional (3D) graphene/graphite aggregates, exhibiting excellent flexibility and high conductivity. The resulting films are very flexible that can bear 1000 times fold without breakage. A high conductivity up to 100 000 S m-1 can be achieved after a relatively low temperature annealing (1000 °C) owing to its low content of defect and large size of graphene/graphite aggregates. Based on these properties, an electrothermal heater assembled from these composite films supplies a high saturated temperature (423 °C) at low working voltages (4 V). These superior properties, together with the advantage of environmental friendliness and facile and large-scale fabrication, endow the composite films with great potential applications in flexible electronics.

Effects of carbon-based impurities on graphene growth.

In this paper, we studied the growth of graphene on an untreated Cu substrate and further studied the effect of carbon-based impurities on the nucleation of graphene in different growth environments. It is found that the impurities on the surface of the Cu substrate easily lead to damage of the graphene, and the impurities do not always promote nucleation as previously reported, but inhibit nucleation in a high etching environment. Finally, based on experimental results, a model of nucleation and growth of graphene around impurities is presented.

Growth promotion of vertical graphene on SiO2/Si by Ar plasma process in plasma-enhanced chemical vapor deposition.

This study investigates the growth promotion of vertically oriented graphene in plasma-enhanced chemical vapor deposition through Ar plasma treatment. Combined with various substrate treatments, including hydrofluoric acid etching and oxidation after Ar plasma treatment, Ar plasma pretreatment promotes vertical growth through the microcavity on the rough substrate surface and the active growth sites. The microcavity affects the strain distribution and defects of as-deposited planar films, which benefit the transition of 2D deposition to 3D vertical growth. A growth model on the effect of Ar plasma pretreatment is proposed.