Layer-by-layer (LbL) self-assembled stacked Testudo-like MoS superstructures carrying cancer drugs are formed from nanosheets controllably assembled with sequence-based DNA oligonucleotides. These superstructures can disassemble autonomously in response to cancer cells' heightened ATP metabolism. First, we functionalize MoS nanosheets (MoS-NS) nanostructures with DNA oligonucleotides having thiol-terminated groups (DNA/MoS-NS) via strong binding to sulfur atom defect vacancies on MoS surfaces. The driving force to assemble into a higher-order DNA/MoS-NS superstructure is guided by a linker aptamer that induced interlayer assembly. In the presence of target ATP molecules, these multilayer superstructures disassembled as a consequence of stronger binding of ATP molecules with the linking aptamers. This design plays a dual role of protection and delivery by LbL stacked MoS-NS similar in concept to a Greek Testudo. These superstructures present a protective armor-like shell of MoS-NS, which still remains responsive to small and infiltrating ATP molecules diffusing through the protective MoS-NS, contributing to an enhanced stimuli-responsive drug release system for targeted chemotherapy.

Two‐dimensional (2D) transition metal dichalcogenides (TMDs) nanostructures have been widely applied in environmental and biological analysis, biomedicine, electronic devices, and hydrogen evolution catalysis. Meanwhile, this excitement in 2D TMDs has spilled over to their counterparts of different dimensionalities like one‐dimensional (1D) and zero‐dimensional (0D) TMDs nanostructures. Eventual physical and chemical properties of TMDs nanostructures still remain to be highly dependent on their dimensionalities and size scale, and recently creatively exploring these physical and chemical properties is extremely impactful for the sensing field of TMD nanomaterials. Herein, we review a wide range of sensing applications based on not only graphene‐like 2D TMDs nanostructures but also the rapidly emerging subclasses of 1D, and 0D TMDs nanostructures. Their unique and interesting structures, excellent properties, and valid preparation methods are also included and the analytical objectives, ranging from heavy metal ions to small molecules, from DNA to proteins, from liquids to even vapors, can be met with extremely high selectivity and sensitivity. We have also analyzed our current understanding of 0D and 1D TMDs nanostructures and learning from graphene with the goal of contributing fresh ideas to the overall development of more advanced future TMDs based sensors.

Electrochemically induced Fenton (electro-Fenton) reaction was used for efficient and controllable preparation of hydroxyl radicals, leading to the generation of luminescent quantum dots through etching of as-exfoliated MoS2 nanosheets. Morphologic changes of MoS2 nanosheets during the electro-Fenton reaction were monitored using transmission electron microscopy, showing that etching of MoS2 nanosheets induced by hydroxyl radicals resulted in rapid homogeneous fracturing of the sheets into small dots via a transition of nanoporous morphology. The as-generated dots with vertical dimensional thickness of ca. 0.7 nm and plane size of ca. 5 nm were demonstrated to be MoS2 quantum dots (MoS2-QDs), and their photoluminescence properties were explored based on quantum confinement, edge effect, and intrinsic characteristics. Moreover, the degree of etching and the concomitant porosity of MoS2 nanosheets could be conveniently tuned via the electro-Fenton reaction time, resulting in a new morphology of nanoporous MoS2 nanosheets, with potential new applications in various significant areas.

Size‐dependent optical absorption of semiconductive (2H) layered molybdenum disulfide (MoS2), exhibiting great discrimination abilities to single‐ and double‐stranded DNA (ssDNA) and (dsDNA), is studied. In the presence of high concentration of salt, layered MoS2 trends to aggregate rapidly, leading to the increases of sizes in both vertical and lateral dimensions of the nanosheets, which results from the interplay between van der Waals attraction and electrical double‐layer repulsion. Meanwhile, the aggregation behavior of layered MoS2 is remarkably inhibited by the synergistic effects of DNA oligonucleotides. ssDNA can adsorb on the surface of layered MoS2, resulting in a great dispersion, even in the presence of high concentration of salt, while the dispersion behavior is weakened when ssDNA is replaced by dsDNA. Whereas compared to graphene with zero bandgap energy, layered MoS2, with semiconductive properties, exhibits great characteristic optical absorption in visible wavelength region devoted to exploring the aggregation behavior of layered MoS2. Therefore, DNA oligonucleotides induced size control of layered MoS2, contributing to the regular change of its characteristic absorption in visible region, is considered a label‐free bioassay for the detection of single‐nucleotide polymorphism. Due to its easy operation and high specificity, it is expected that the proposed assay holds great promise for further applications.

Following research on two-dimensional (2D) transition metal dichalcogenides (TMDs), zero-dimensional (0D) TMDs nanostructures have also garnered some attention due to their unique properties; exploitable for new applications. The 0D TMDs nanostructures stand distinct from their larger 2D TMDs cousins in terms of their general structure and properties. 0D TMDs possess higher bandgaps, ultra-small sizes, high surface-to-volume ratios with more active edge sites per unit mass. So far, reported 0D TMDs can be mainly classified as quantum dots, nanodots, nanoparticles, and small nanoflakes. All exhibited diverse applications in various fields due to their unique and excellent properties. Of significance, through exploiting inherent characteristics of 0D TMDs materials, enhanced catalytic, biomedical, and photoluminescence applications can be realized through this exciting sub-class of TMDs. Herein, we comprehensively review the properties and synthesis methods of 0D TMDs nanostructures and focus on their potential applications in sensor, biomedicine, and energy fields. This article aims to educate potential adopters of these excitingly new nanomaterials as well as to inspire and promote the development of more impactful applications. Especially in this rapidly evolving field, this review may be a good resource of critical insights and in-depth comparisons between the 0D and 2D TMDs.

Transition-metal dichalcogenides (TMDs), as a novel category of nanomaterials and a potential alternate to graphene, are attracting great interest of researchers, because of their strong conductivity, superior catalytic performance, and good optical properties. As the most representative type of all TMDs, molybdenum disulfide (MoS 2 )-based nanomaterials are expanded into two-dimensional (2D) nanosheets, quantum dots (QDs), flower-like nanoparticles, nanospheres and nanotubes. These types are regarded as promising nanoplatforms for various applications in biomedicine, such as drug delivery, phototherapy, biosensing, bioimaging, theranostics, and antimicrobials, because of the unique planar structures, superb electronic and optical properties (such as thickness-dependent bandgap, strong near-infrared absorbance, and large surface area), and easily functionalized surface sites. Until now, there have been a few reviews about MoS 2 -based nanomaterials, with regard to functionalization for improvement of properties, such as high drug loading efficiency, dispersibility, physiological stability, biocompatibility, targeting ability, pharmacodynamics, controllable drug release, enhanced treatment and therapeautic efficacy, and even biodegradability and toxicity reduction. Here, we systematically summarized the progress of functionalized MoS 2 -based nanomaterials with improved physicochemical and biological properties for the biomedical applications. First, we emphatically introduced these biomedical applications in drug delivery, anticancer photothermal therapy (PTT), photodynamic therapy (PDT), and combined phototherapy. Besides, other biomedical applications were also introduced in detail including bioimaging, biosensing, theranostics, toxicity, tissue engineering, and antimicrobials. Lastly, the current challenges, opportunities and prospects of MoS 2 -based nanomaterials were also discussed in depth. We expect that this review will contribute to a quick and in-depth understanding of the latest progress in bioapplication of MoS 2 -based nanomaterials, inspiring the creation of various techniques to design and fabricate MoS 2based nanomaterials with multiple capability and high biological safety, and expand them into more application in the field of biomedicine.

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