The reemergence of chemistry for post-graphene two-dimensional nanomaterials

Prospective applications of two-dimensional materials beyond laboratory frontiers: A review

The development of nanotechnology has been advancing for decades and gained acceleration in the 21st century. Two-dimensional (2D) materials are widely available, giving them a wide range of material platforms for technological study and the advancement of atomic-level applications. The design and application of 2D materials are discussed in this review. In order to evaluate the performance of 2D materials, which might lead to greater applications benefiting the electrical and electronics sectors as well as society, the future paradigm of 2D materials needs to be visualized. The development of 2D hybrid materials with better characteristics that will help industry and society at large is anticipated to result from intensive research in 2D materials. This enhanced evaluation might open new opportunities for the synthesis of 2D materials and the creation of devices that are more effective than traditional ones in various sectors of application.

Photodynamic Therapeutic Effect of Nanostructured Metal Sulfide Photosensitizers on Cancer Treatment

Photodynamic therapy (PDT) utilizes photosensitizers (PSs) to produce reactive oxygen species (ROSs) upon irradiation, which causes the shutdown of vessels and deprives the tumor of nutrients and oxygen, and in turn induces adverse effects on the immune system. However, significant efforts are needed to increase the efficiency in PDT in terms of light delivery to specific PSs for the clinical treatment of tumors located deep under the skin. Even though PDT offers a disease site-specific treatment modality, current efforts are directed to improve the solubility (in body fluids and injectable solvents), photostability, amphiphilicity (for tissue penetration), elimination, and systemic toxicity of traditional PSs based on porphyrin derivatives. Nanostructured materials show promising features to achieve most of such combined efforts. They can be artificially engineered to carry multiple theranostic agents onto targeted tumor sites. However, recent studies on photosensitive Cd-based nanostructures, mostly used in PDT, indicate that leeching of Cd²⁺ ions is stimulated when they are exposed to harsh biological conditions for continuous periods of time, thus making them acutely toxic and hindering their applications in in vivo settings. Since nanostructured materials are not completely immune to degradation, great strides have been made to seek new alternatives. In this review, we focus on the latest advances of Cd-free nanostructured metal transition sulfides (MTSs) as alternative PSs and study their high-energy transfer efficiency, rational designs, and potential applications in cancer-targeted PDT. Nanostructured MTSs are discussed in the context of their versatility to serve as phototherapy agents and superior properties, including their strong absorption in the NIR region, excellent photothermal conversion efficiency, controlled reactive oxygen species (ROS) production, versatile surface chemistry, high fluorescence, and structural and thermal stability. We discuss the latest advancements in correlating the self-aggregation of MTSs with their passive tumor cell targeting, highlighting their ability to efficiently produce ROSs, and mitigating their dark toxicity through polymeric functionalization. Treatment of deep-seated tumors by using these PSs upon preferential uptake by tumor tissues (due to the enhanced permeability and retention effect) is also reviewed. We finally summarize the main future perspectives of MTSs as next-generation PSs within the context of cancer theranostics.

One-Step Reduction of Graphene Oxide with Phosphorus/Silicon-Containing Compound and Its Flame Retardancy in Epoxy Resin

A novel graphene-based phosphorus/silicon-containing flame retardant (GO-DOPO-V) was obtained via one-step reduction of graphene oxide (GO) with phosphorus/silicon-containing compound (DOPO-V). The Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectrometer (XPS), Atomic force microscope (AFM) and Thermogravimetric analysis (TGA) measurements were used to confirm the structure and morphology. After incorporation of 2 wt% GO-DOPO-V, the maximum decreases of 28.8% in peak heat release rate and 15.6% in total heat release are achieved compared to that of pure epoxy resin (EP). Furthermore, TGA and Scanning electron microscopy (SEM) measurement showed that GO-DOPO-V significantly enhanced the thermal stability and residual char strength of EP. Thus, attributed to the barrier effect of GO and phosphorus/silicon layer formation by DOPO-V, GO-DOPO-V was a high-efficient flame retardant to improve the combustion behavior of EP nanocomposite.

Functionalization of Graphene Oxide with Polysilicone: Synthesis, Characterization, and Its Flame Retardancy in Epoxy Resin

A novel polysilicone flame retardant (PMDA) has been synthesized and covalently grafted onto the surfaces of graphene oxide (GO) to obtain GO-PMDA. The chemical structure and morphology of GO-PMDA was characterized and confirmed by the Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectrometer (XPS), atomic force microscope (AFM), and thermogravimetric analysis (TGA). The results of dynamic mechanical analysis (DMA) indicated that the grafting of PMDA improved the dispersion and solubility of GO sheets in the epoxy resin (EP) matrix. The TGA and cone calorimeter measurements showed that compared with the GO, GO-PMDA could significantly improve the thermal stability and flame retardancy of EP. In comparison to pure EP, the peak heat release rate (pHRR) and total heat release (THR) of EP/GO-PMDA were reduced by 30.5% and 10.0% respectively. This greatly enhanced the flame retardancy of EP which was mainly attributed to the synergistic effect of GO-PMDA. Polysilicone can create a stable silica layer on the char surface of EP, which reinforces the barrier effect of graphene.

Defect/Edge-Selective Functionalization of Carbon Materials by "Direct" Friedel-Crafts Acylation Reaction

Popularly utilized oxidation media, via nitric acid/sulfuric acid mixtures, are too corrosive and oxidizing to preserve structural integrity of highly ordered graphitic materials (carbon nanotubes (CNTs) and graphene). Here, for the most commonly used oxidation method, the important advantages of defect/edge-selective functionalization of carbon materials (CNTs/graphene/graphite) in a polyphosphoric acid (PPA)/phosphorous pentoxide (P₂ O₅ ) medium are elucidated. The optimized PPA/P₂ O₅ medium is a mild acid that is not only less corrosive than popularly utilized oxidation media, but also has a strong capability to drive Friedel-Crafts acylation by covalently modifying carbon materials. With a broader spectrum of functional groups accessible, the PPA/P₂ O₅ -driven Friedel-Crafts acylation offers more options for tailoring the properties and processing of carbon materials.

Two-Dimensional Nanomaterials for Cancer Nanotheranostics

Emerging nanotechnologies show unprecedented advantages in accelerating cancer theranostics. Among them, two-dimensional nanomaterials (2DNMs) represent a novel type of material with versatile physicochemical properties that have enabled a new horizon for applications in both cancer diagnosis and therapy. Studies have demonstrated that 2DNMs may be used in diverse aspects, including i) cancer detection due to their high propensity towards tumor markers; ii) molecular imaging for guided tumor therapies, and iii) drug and gene loading, photothermal and photodynamic cancer therapies. However, their biomedical applications raise concerns due to the limited understanding of their in vivo metabolism, transformation and possible toxicities. In this comprehensive review, the state-of-the-art development of 2DNMs and their implications for cancer nanotheranostics are presented. The modification strategies to enhance the biocompatibility of 2DNMs are also reviewed.

Development of theoretical approach for describing electronic properties of hetero-interface systems under applied bias voltage

We have developed a theoretical approach for describing the electronic properties of hetero-interface systems under an applied electrode bias. The finite-temperature density functional theory is employed for controlling the chemical potential in their interfacial region, and thereby the electronic charge of the system is obtained. The electric field generated by the electronic charging is described as a saw-tooth-like electrostatic potential. Because of the continuum approximation of dielectrics sandwiched between electrodes, we treat dielectrics with thicknesses in a wide range from a few nanometers to more than several meters. Furthermore, the approach is implemented in our original computational program named grid-based coupled electron and electromagnetic field dynamics (GCEED), facilitating its application to nanostructures. Thus, the approach is capable of comprehensively revealing electronic structure changes in hetero-interface systems with an applied bias that are practically useful for experimental studies. We calculate the electronic structure of a SiO₂-graphene-boron nitride (BN) system in which an electrode bias is applied between the graphene layer and an electrode attached on the SiO₂ film. The electronic energy barrier between graphene and BN is varied with an applied bias, and the energy variation depends on the thickness of the BN film. This is because the density of states of graphene is so low that the graphene layer cannot fully screen the electric field generated by the electrodes. We have demonstrated that the electronic properties of hetero-interface systems are well controlled by the combination of the electronic charging and the generated electric field.

Nano Day: Celebrating the Next Decade of Nanoscience and Nanotechnology

Nanoscience and nanotechnology are poised to contribute to a wide range of fields, from health and medicine to electronics, energy, security, and more. These contributions come both directly in the form of new materials, interfaces, tools, and even properties as well as indirectly by connecting fields together. We celebrate how far we have come, and here, we look at what is to come over the next decade that will leverage the strong and growing base that we have built in nanoscience and nanotechnology.

Electric field effects on the electronic properties of the silicene–amine interface

The mechanism of band gap variation in silicene–amine hetero-interface systems with an applied electric field is revealed by carrying out first-principles calculations.