Studies involving transition-metal dichalcogenides (TMDs) have been around for many decades and in recent years, many were focused on using TMDs to synthesize inorganic analogues of carbon nanotubes, fullerene, as well as graphene and its derivatives with the ultimate aim of employing these materials into consumer products. In view of this rising trend, we investigated the cytotoxicity of three common exfoliated TMDs (exTMDs), namely MoS2 , WS2 , and WSe2 , and compared their toxicological effects with graphene oxides and halogenated graphenes to find out whether these inorganic analogues of graphenes and derivatives would show improved biocompatibility. Based on the cell viability assessments using methylthiazolyldiphenyl-tetrazolium bromide (MTT) and water-soluble tetrazolium salt (WST-8) assays on human lung carcinoma epithelial cells (A549) following a 24 h exposure to varying concentrations of the three exTMDs, it was concluded that MoS2 and WS2 nanosheets induced very low cytotoxicity to A549 cells, even at high concentrations. On the other hand, WSe2 exhibited dose-dependent toxicological effects on A549 cells, reducing cell viability to 31.8 % at the maximum concentration of 400 μg mL(-1) ; the higher cytotoxicity displayed by WSe2 might be linked to the identity of the chalcogen. In comparison with graphene oxides and halogenated graphenes, MoS2 and WS2 were much less hazardous, whereas WSe2 showed similar degree of cytotoxicity. Future in-depth studies should be built upon this first work on the in vitro cytotoxicity of MoS2 and WS2 to ensure that they do not pose acute toxicity. Lastly, nanomaterial-induced interference control experiments revealed that exTMDs were capable of reacting with MTT assay viability markers in the absence of cells, but not with WST-8 assay. This suggests that the MTT assay is not suitable for measuring the cytotoxicity of exTMDs because inflated results will be obtained, giving false impressions that the materials are less toxic.

Black phosphorus (BP), the latest addition to the family of 2D layered materials, has attracted much interest owing to potential optoelectronics, nanoelectronics, and biomedicine applications. Little is known about its toxicity, such as whether it could be as toxic as white phosphorus. In response to the possibility of BP employment into commercial products and biomedical devices, its cytotoxicity to human lung carcinoma epithelial cells (A549) was investigated. Following a 24 h exposure of the cells with different BP concentrations, cell viability assessments were conducted using water-soluble tetrazolium salt (WST-8) and methylthiazolyldiphenyltetrazolium bromide (MTT) assays. The toxicological effects were found to be dose-dependent, with BP reducing cell viabilities to 48% (WST-8) and 34% (MTT) at 50 μg mL(-1) exposure. This toxicity was observed to be generally intermediate between that of graphene oxides and exfoliated transition-metal dichalcogenides (MoS2, WS2, WSe2). The relatively low toxicity paves the way to utilization of black phosphorus.

There has been enormous interest in autonomous self-propelled micro-/nanomotors, especially those that relied on the decomposition of hydrogen peroxide fuel to generate oxygen bubbles and usually consisted of platinum on their surface which acts as an efficient catalyst. In this study, we developed Pt-free tubular micromotors by using a less expensive silver catalyst for bubble propulsion.

Despite demonstrating potential for environmental remediation and biomedical applications, the practical environmental applications of autonomous self-propelled micro-/nanorobots have been limited by the inability to fabricate these devices in large (kilograms/tons) quantities. In view of the demand for large-scale environmental remediation by micro-/nanomotors, which are easily synthesized and powered by nontoxic fuel, we have developed bubble-propelled Fe(0) Janus nanomotors by a facile thermally induced solid-state procedure and investigated their potential as decontamination agents of pollutants. These Fe(0) Janus nanomotors, stabilized by an ultrathin iron oxide shell, were fuelled by their decomposition in citric acid, leading to the asymmetric bubble propulsion. The degradation of azo-dyes was dramatically increased in the presence of moving self-propelled Fe(0) nanomotors, which acted as reducing agents. Such enhanced pollutant decomposition triggered by biocompatible Fe(0) (nanoscale zero-valent iron motors), which can be handled in the air and fabricated in ton quantities for low cost, will revolutionize the way that environmental remediation is carried out.

Fluorinated graphenes (F-G) might inevitably be released into the environment through disposal and wearing of future commercial products incorporated with F-G. Therefore, we determined their cytotoxicity in this study.

The prospective intensive utilization of two-dimensional (2D) nanomaterials, such as graphene, transition metal dichalcogenides, and black phosphorus, increased the requirements for thorough comprehension of their potential impact on the environment and health.

1 of 26) 1604759 the flow of electrons in such a "fuel cell", leading to self-electrophoretic motion. In the same frame, electrochemical techniques such as electrodeposition, offers a precise and low cost option for the fabrication of these multi-component microand nanostructured objects. Additionally, electrochemistry and electric fields can be used for controlling the motion of these nano/micro or macrorobots. These selfpropelling nano-and microrobots can enhance electrochemical sensing, which in turn can be used to detect motion of the robots. Furthermore, the microrobots themselves can be utilized as active parts of electrochemical and electrical energy generation devices. While a general coverage of the fabrication of nano/micromotors has been accomplished, [2,15,16] an in-depth discussion of the central role of electrochemistry from the electrosynthesis of these nano/microdevices, electrochemical principles behind their operations, to the application stage is found wanting. The flow of electrons vis-à-vis the locomotion of nano/microparticles is an integral component in order for movement in the miniaturized scale to occur. Here, we provide a review of this intimate relationship between electrochemistry and nano/ microrobots.In this article, we highlight the role of electrochemistry in synthesizing materials for self-powered nano/microdevices, the aspect of charge transfer and changes in electrochemical potentials for locomotion, control of self-propelled motion using electrochemistry and electric fields, possible applications in electrochemical sensing and energy generation using nano/ microscale motion. The arrangement of the review is built from a bottom-up approach. Namely, they will be divided into: (i) Fabrication of nano/microrobot by electrochemical methods, (ii) Electrochemically powered nano/microrobots based on self-electrophoresis, (iii) Control of nano/microrobot motion through electrochemistry and electric fields and (iv) Applications of nano/microrobots in electrochemical sensing, mixing and energy generation. Fabrication of Nano/Microrobot by Electrochemical MethodsThe electrochemical methods represent a versatile way for producing nano/microscale robots using simple experimental procedures, low-cost equipment and reagents, while being easy Artificial autonomous self-propelled nano and microrobots are an important part of contemporary technology. They are typically self-powered, taking chemical energy from their environment and converting it to motion. They can move in complex environments and channels, deliver cargo, perform nanosurgery, act as chemotaxis and perform sense-and-act actions. The electrochemistry is closely interwoven within this field. In the case of self-electrophoretically driven nano/microrobots, electrochemical mechanism has been the basis of power, which translates chemical energy to motion. Electrochemistry is also a major tool for the fabrication of these micro and nanodevices. Electrochemistry and electric fields can be used for the directing of nanorobots and for det...

The absence of bandgap in graphene has opened exploration in a new class of 2D nanomaterials: layered semiconductor chalcogenides. Research has found that they have promising properties which are advantageous for applications in a wide range of fields such as solar energy conversion, field effect transistors, optoelectronic devices, energy storage, and is expanding into biomedical applications.However, little is known about their toxicity effects. In view of the possibility of employing these materials into consumer products, we investigated the cytotoxicity of two common layered semiconductor chalcogenides, namely GaSe and GeS, based on cell viability assessments using watersoluble tetrazolium salt (WST-8) and methyl-thiazolyldiphenyl-tetrazolium bromide (MTT) assays after a 24 h exposure to varying concentrations of the nanomaterials on human lung carcinoma epithelial cells (A549). The cytotoxicity results indicated that GaSe is relatively more toxic than another group of 2D layered chalcogenide: transition metal dichalcogenides (MoS 2 , WS 2 , WSe 2 ). On the other hand, GeS appeared to be non-toxic, with the concentration of GeS introduced having a positive correlation with the cell viability. Control experiments in cell-free conditions revealed that both GaSe and GeS interfered with the absorbance data gathered in the two assays, but the interference effect induced by GaSe could be minimized by additional washing steps to remove the nanomaterials prior to the cell viability assessments. In the case of GeS, however, the interference effect between GeS and both assay dyes were still significant despite the washing steps adopted, thereby giving rise to the false cytotoxicity results observed for GeS. Therein, we wish to highlight that control experiments should always be carried out to check for any possible interferences between the test specimen and cell viability markers when conducting cell viability assessments for cytotoxicity studies.