Wrinkled, wavelength-tunable graphene-based surface topographies for directing cell alignment and morphology

A Convenient Ultraviolet Irradiation Technique for Synthesis of Antibacterial Ag-Pal Nanocomposite

In the present work, palygorskite (Pal) was initially subjected to an ion-exchange reaction with silver ions (Pal-Ag(+)). Subsequently, Ag-Pal nanocomposites were assembled by a convenient ultraviolet irradiation technique, using carbon dots (CDs) derived from wool fiber as the reducing agent. The obtained nanocomposites were characterized by powder X-ray diffraction (XRD), ultraviolet-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy. The XRD patterns and UV-vis absorption spectra confirmed the formation of the Ag nanoparticles (NPs). Meanwhile, the TEM images showed that the Ag NPs, which exhibited sizes in the range of 3-7 nm, were located on the surface of the Pal nanofiber structures. Furthermore, the antibacterial activity of the nanocomposites was evaluated against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria by applying the disc diffusion method and minimum inhibitory concentration test. Owing to their good antibacterial properties, the Ag-Pal nanocomposites are considered to be a promising bactericide with great potential applications.

Computational design of graphene sheets for withstanding the impact of ultrafast projectiles

A multi-scale method is employed in this paper to conduct a virtual study of the high-strain behavior of single- and multi-layer graphene sheets and to investigate the design of related graphene-based devices. By bridging the length and time scales by combining the Molecular Dynamics and Finite Element methods together, a comprehensive multiscale model is developed to study the fascinating capabilities of single- and multi-layer graphene sheets in withstanding the impact of ultrafast projectiles. In order to contribute to future developments and innovations in this field, several quantitative and qualitative comparisons are also performed. By employing the validated model, the effects of several parameters on the impact resistance efficiency of the examined sheets are evaluated. The specific penetration energy of multilayer graphene sheets is several times greater than that of metal sheets. It is demonstrated that the number of layers, aspect ratio, sheet size, interlayer distance, delamination, and projectile shape significantly influence the impact resistance of graphene sheets. The specific critical rupture velocity decreases asymptotically with the increase in the number of layers. A large-scale array of fewer graphene layers can withstand bullets of much higher velocities than a multilayer graphene sheet with equivalent weight. Finally, the coefficient of restitution for the oblique collision of gold and steel nanoparticles with multilayer graphene sheets is calculated at different impact velocities.

Multiscale Graphene Topographies Programmed by Sequential Mechanical Deformation

Multigenerational graphene oxide architectures can be programmed by specific sequences of mechanical deformations. Each new deformation results in a progressively larger set of features decorated by smaller preexisting patterns, indicating a structural "memory." It is shown that these multiscale architectures are superhydrophobic and display excellent functionality as electrochemical electrodes.

Construction of specific magnetic resonance imaging/optical dual-modality molecular probe used for imaging angiogenesis of gastric cancer

The purpose of the study was to construct specific magnetic resonance imaging (MRI)/optical dual-modality molecular probe. Tumor-bearing animal models were established. MRI/optical dual-modality molecular probe was construed by coupling polyethylene glycol (PEG)-modified nano-Fe₃O₄ with specific targeted cyclopeptide GX1 and near-infrared fluorescent dyes Cy5.5. MRI/optical imaging effects of the probe were observed and the feasibility of in vivo double-modality imaging was discussed. It was found that, the double-modality probe was of high stability; tumor signal of the experimental group tended to be weak after injection of the probe, but rose to a level which was close to the previous level after 18 h (p > 0.05). We successively completed the construction of an ideal MRI/optical dual-modality molecular probe. MRI/optical dual-modality molecular probe which can selectively gather in gastric cancer is expected to be a novel probe used for diagnosing gastric cancer in the early stage.

Biological and environmental interactions of emerging two-dimensional nanomaterials

Two-dimensional materials have become a major focus in materials chemistry research worldwide with substantial efforts centered on synthesis, property characterization, and technological application. These high-aspect ratio sheet-like solids come in a wide array of chemical compositions, crystal phases, and physical forms, and are anticipated to enable a host of future technologies in areas that include electronics, sensors, coatings, barriers, energy storage and conversion, and biomedicine. A parallel effort has begun to understand the biological and environmental interactions of synthetic nanosheets, both to enable the biomedical developments and to ensure human health and safety for all application fields. This review covers the most recent literature on the biological responses to 2D materials and also draws from older literature on natural lamellar minerals to provide additional insight into the essential chemical behaviors. The article proposes a framework for more systematic investigation of biological behavior in the future, rooted in fundamental materials chemistry and physics. That framework considers three fundamental interaction modes: (i) chemical interactions and phase transformations, (ii) electronic and surface redox interactions, and (iii) physical and mechanical interactions that are unique to near-atomically-thin, high-aspect-ratio solids. Two-dimensional materials are shown to exhibit a wide range of behaviors, which reflect the diversity in their chemical compositions, and many are expected to undergo reactive dissolution processes that will be key to understanding their behaviors and interpreting biological response data. The review concludes with a series of recommendations for high-priority research subtopics at the "bio-nanosheet" interface that we hope will enable safe and successful development of technologies related to two-dimensional nanomaterials.