Nano

Viruses like COVID-19 are very small. They are nanometer in diameter. To detect and prevent them, nanotechnology is a crucial tool. This review paper reviews the recent progress of nanomedicine in fighting COVID-19. At the beginning, how nanoparticle works in our body is described here. Recent observations of these medicines’ performance are illustrated with some practical case studies. Different types of vaccines based on nanoparticles and their potentiality of fighting COVID-19 are also described. What can be the potential challenges for this technology along with prospects are also discussed. At the end, some nanomedicines have been suggested that can be effective to fight the virus. This paper can be used as a state-of-the-art at this critical moment to the globe for promising nanotechnology-based therapy related to the survival of people from coronavirus.

Flexible resistive switching memory devices based on graphene oxide (GO) polymer nanocomposite were prepared on flexible substrate to research the influence of bending on resistive switching behavior. The devices showed evident response in resistive switching memory characteristics to flexible bending. The 2000 cycles flexible bending leads to the switch of resistive switching memory characteristic from write-once-read-many time memory (WORM) to static random access memory (SRAM). Both WORM and SRAM memory properties are all repeatable, and the threshold switching voltage also showed good consistency. The resistive switching mechanism is attributed to the formation of carbon-rich conductive filaments for nonvolatile WORM characteristics. The bending-induced micro-crack may be responsible for the partial broken of the electrical channels, and may lead to the volatile SRAM characteristics.

Polypropylene (PP) has some disadvantages when used in food packaging: PP does not have antibacterial properties, and it exhibits low barrier properties. In this study, nanocomposites of PP filled with different amounts of silver-decorated multiwalled carbon nanotubes (MWCNTs-Ag) were fabricated. A new nanomaterial with silver had the advantage of providing antibacterial capabilities, and the contribution of MWCNTs was to reinforce mechanical properties. PP was melt-blended with MWCNTs-Ag, but the ensuing problem was the poor interfacial interaction of fillers with the polymer matrix, especially at high filler content. Nonetheless, a small quantity of fillers resulted in the following improvement in nanocomposite properties, relative to neat PP: better antibacterial ability, lower water vapor permeation flux, lower oxygen barrier performance, higher thermostability, faster crystallization rate and higher tensile strength. Therefore, nanocomposites formed from modifying PP with a low content of MWCNTs-Ag show promise in the field of packaging and medical material applications.

A novel approach to fabricate sandwich-like graphene-supported mesoporous SnO₂ nanosheets (G-SnO₂) as anode materials for lithium-ion batteries (LIBs) was developed. The obtained sandwich-like G-SnO₂ inherit the typical two-dimensional structure of graphene and possess a high specific surface area (64m²g${}^{-1}$), nanosized SnO₂ particles (about 3nm in diameter), mesoporous structure (a pore size of mainly $\sim$3.8nm), large aspect ratio and enhanced electrical conductivity. As a consequence, the G-SnO₂ anode significantly improved the LIBs capacity and cycle performance (536mAhg${}^{-1}$ at 500mAg${}^{-1}$ even after 500 cycles).

Organic pollutants in water pose a serious risk to public health, hence, it is essential to develop new and innovative approaches to the remediation of contaminated water. This work demonstrates a highly effective bubble-propelled micromotor based on the surface coating of symmetrical carbon microspheres (CMSs) with catalytic manganese dioxide (MnO₂) nanoflakes and platinum nanoparticles (Pt NPs) (Pt-MnO₂@CMS). This concept represents a simple and flexible strategy for the decomposition of organic pollutants in water and could be used to construct a wide range of diverse micromotors with applications in drug delivery, sensing, energy generation and environmental remediation. The unique hierarchical structure of the MnO₂ nanoflakes and the uniform dispersion of Pt NPs in this material were confirmed. The resulting micromotors were found to move rapidly as a result of propulsion by oxygen bubbles generated in a H₂O₂ solution via the catalytic actions of the MnO₂ nanoflakes and Pt NPs. In contrast to the intrinsic asymmetry of tubular and Janus structures, the self-driven motion of these symmetrical micromotors can be attributed to morphological variations and the uneven distribution of the cocatalysts. Combining a porous structure, rapid movement and Fenton-like reactions, these Pt-MnO₂@CMS micromotors rapidly degraded methylene blue (MB), providing greater than 99% decolorization in just 30min without the need for external agitation. Analyses of the adsorption mechanism based on pseudo-first-order and pseudo-second-order kinetics models showed that adsorption proceeded via chemical processes. These new micromotors are expected to have important environmental and biomedical applications.

Enhancing the catalytic activity of manganese oxide in oxygen reduction reaction (ORR) is a key issue for its large-scale application in metal-air fuel cells. Ag-doped $\alpha$-MnO₂ nanowires without Ag or Ag₂O have been successfully synthesized via a facile hydrothermal method, and the changes in both the structure and electrochemical catalytic performances after Ag doping are investigated. Compared with the pristine $\alpha$-MnO₂, the as-prepared Ag-doped MnO₂ exhibits a significantly enhanced catalytic activity in both ORR and Mg-air fuel cell application. With Ag/Mn ratio of 1:25, Ag-doped MnO₂ exhibits a typical 4e-reaction pathway and presents a 163 mV higher half-wave potential than that of the pristine $\alpha$-MnO₂. Furthermore, it demonstrates a power density of 75.1mWcm${}^{-2}$ at current density of 134.5mAcm${}^{-2}$ in the Mg-air fuel cells. The enhanced ORR performances are considered to be contributed from the activation of surface lattice oxygen, the improvement in conductivity and the increase in oxygen vacancies of $\alpha$-MnO₂. These findings provide new understanding for developing high-performance manganese oxide catalysts.

Irregular rod-like bismuth sulphochloride (BiSCl) was synthesized by a high efficiency process in which BiCl₃ and Bi₂S₃ were fully ground and mixed in N₂ atmosphere followed by a sintering at 227^∘C for 9 h to achieve crimson BiSCl powder. The products were characterized by X-ray powder diffraction (XRD) and scanning electronic microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX). The BiSCl is an n-type semiconductor with a bandgap of 1.9 eV. In the temperature range of 300–500 K, thermal conductivity, electrical conductivity, Seebeck coefficient and thermoelectric figure of merit ZT of the BiSCl were tested and calculated. It is resulted that the BiSCl has a thermal conductivity of 0.45 Wm⁻¹K⁻¹ at 500 K and a Seebeck coefficient of −579 μVK⁻¹ at 400 K. This work will help inform future in-depth studies on possible applications of BiSCl in the fields of thermoelectricity, optoelectronics and photocatalyticity.

ZnMn₂O₄ nanoparticles (NPs) wrapped by reduced graphene oxide (rGO) were fabricated via a two-step solvothermal method and used as an anode material for lithium-ion batteries (LIBs). Compared to pure ZnMn₂O₄, the ZnMn₂O₄ NPs/rGO composites deliver higher capacities of 1230 mAh g⁻¹ and 578 mAh g⁻¹ after 200 cycles at a current density of 100 mA g⁻¹ and 500 mA g⁻¹, respectively. The enhanced electrochemical performance of ZnMn₂O₄ NPs/rGO composites is mainly attributed to a distinctive structure (ZnMn₂O₄ NPs surrounded by flexible rGO), which can promote the diffusion of Li⁺, accelerate the transport of electrons and buffer volume expansion during the Li⁺ insertion/extraction process. Furthermore, the rGO sheets can effectively prevent the agglomeration of ZnMn₂O₄ NPs, thus, improving structural stability of the composites. The excellent electrochemical performance indicates that such ZnMn₂O₄ NPs/rGO composite structure has a great potential for high-performance LIBs.

The study of the electrical coupling properties of living cells and materials plays an important role in tissue engineering and clinical applications. The electrical coupling between living cells and substrates directly affects the growth, secretion and death of cells, as well as the measurement accuracy of electrophysiological parameters. In this work, the point contact model of the electrical coupling of cells and substrates is studied. It was found that the sealing impedance and effective contact area were the most important parameters affecting the electrical coupling. Moreover, the structure of nano-scale groove was fabricated by direct laser interference patterning (DLIP), and cylindrical arrays were fabricated on resist films after exposed to electron beam lithography (EBL). The two nanostructures were used as the substrates in vitro culture. The electrical coupling properties between living cells and structural substrates were discussed subsequently. In addition, the impedance spectrum of living cells at various frequencies, the relationship between the living cell number and impedance, and the impedance of living cells at different growth periods were measured. Furthermore, the multidimensional impedance information of living cells was obtained, and the impedance deviations between the two structure arrays were analyzed to evaluate the electrical coupling properties between the living cells and substrates. The proposed multidimensional impedance analysis method provides a way for studying the electrical coupling properties of nano-structured substrates and living cells.

Adsorption of gemfibrozil (GF) from aqueous solution by highly/lowly graphitized carbon black (GCB-H/GCB-L) was investigated by batch and fixed-bed experiments. Results showed that the adsorption of GF onto GCB greatly depended on solution pH and graphitization of carbon. The pseudo-second-order kinetic model was found to be more appropriate in describing the adsorption processes of two GCBs. The adsorption equilibriums were well fitted with the Langmuir isotherm model, and GCB-H exhibited a higher adsorption capacity of 47.68 mg g⁻¹ at 298 K, compared with GCB-L of 4.33 mg g⁻¹. GCB-H achieved 69.76% GF removals in simulated water after 6 h, indicating its potential practicability. The GCBs were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR), and the results indicated that the $\pi$-$\pi$ interaction was strongly involved in the adsorption. Thermodynamic studies further suggested that the adsorption of GF on GCB-H was exothermic, which could happen spontaneously at any temperature mainly through $\pi$-$\pi$ interaction for physical adsorption on the surface of the plane.

Titanium dioxide nanoparticles (TiO₂ NPs) are widely used in photodynamic therapy (PDT) of cancer treatment as excellent regenerative photocatalysts. However, there are some challenges because of their poor dispersity. Transferrin (Tf) was tried to modify the surface of TiO₂ NPs to reduce the aggregation, which further affected uptake and excretion on SMMC-7721 human liver cancer cells. Initially, TiO₂ NPs modified with Tf (TiO₂-Tf NPs) entered into the cells faster than the pure TiO₂ NPs which remain attaching on the cell membrane after short-term co-incubation. Tf modification increased the rate and amount of cellular endocytosis. Both TiO₂ NPs and TiO₂-Tf NPs were observed in lysosomes after long-term co-incubation through clathrin-mediated endocytosis pathway. Expulsion of NPs was then observed and it was found that the exocytosis of TiO₂-Tf NPs was fast in the first 24 h, and then slowed down gradually from 24 h to 144 h. Totally, existence of Tf decreased the exocytosis of TiO₂ NPs. Furthermore, the differences of cytotoxicity and genotoxicity between TiO₂ NPs and TiO₂-Tf NPs show that surface-adsorbed Tf components provide some protection from the cytotoxic effect by reducing the production of intracellular ROS. TiO₂-Tf NPs obviously affected cell cycle, indicating a significant G2/M phase cell cycle arrest. Our results offer a promising application of easily aggregated TiO₂ NPs in the nanomedicine field.

Surface-enhanced Raman scattering (SERS) substrates with low cost, high sensitivity and good reproducibility are still challenging in practical application. Herein, we propose a facile method to prepare monolayer ZnS@Ag nanospheres (NSs) by sputtering Ag nanoparticles (NPs) on the surfaces of the monolayer ZnS NSs produced by self-assembly. The monolayer ZnS@Ag NSs have rough surface and nanoscale gaps, which can produce large SERS effect. The dye molecules, Rhodamine 6G (R6G) and Rhodamine B (RhB), were used as probe to evaluate the SERS performance on the monolayer ZnS@Ag NSs. It was found that the monolayer ZnS@Ag NSs showed the high SERS sensitivity in the detection of R6G and RhB, the limit of detection (LOD) down to 9.12×10⁻¹³ M and 8.55×10⁻¹¹ M, respectively. The corresponding enhancement factors (EF) are 3.01×10⁸ and 8.2×10⁶, respectively. Furthermore, the ordered structure makes the monolayer ZnS@Ag NSs substrate with high signal reproducibility and stability, and the relative standard deviation (RSD) values are less than 15%. Therefore, the monolayer ZnS@Ag NSs is a candidate for detecting organic dyes in the environment.

A multifunctional nanodrug, PAMAM@CuS-HA-RB/DOX, was prepared for the real time tracking and chemo-photothermal therapy of tumor cells. The CuS nanoclusters with diameter less than 10nm could be easily ingested by tumor cells and showed good colloid stability and high photothermal conversion efficiency. The hyaluronic acid (HA) coating and rhodamine B (RB) labeling endowed the nanocomposite with low cytotoxity and real time fluorescence imaging ability. In the acidic tumor microenvironment, the doxorubicin linked via the pH-responsive hydrazone bonds was released and worked synergistically with CuS to kill the tumor cells, which showed a high chemo-photothermal therapy capacity. All these properties indicated the PAMAM@CuS-HA-RB/DOX have promising application for the therapy of cancers and tracking of nanodrugs.