Graphitic nanomaterials such as graphene layers (G) and single-wall carbon nanotubes (SWCNT) are potential candidates in a large number of biomedical applications. However, little is known about the effects of these nanomaterials on biological systems. Here we show that the shape of these materials is directly related to their induced cellular toxicity. Both G and SWCNT induce cytotoxic effects, and these effects are concentration- and shape-dependent. Interestingly, at low concentrations, G induced stronger metabolic activity than SWCNT, a trend that reversed at higher concentrations. Lactate dehydrogenase levels were found to be significantly higher for SWCNT as compared to the G samples. Moreover, reactive oxygen species were generated in a concentration- and time-dependent manner after exposure to G, indicating an oxidative stress mechanism. Furthermore, time-dependent caspase 3 activation after exposure to G (10 microg/mL) shows evidence of apoptosis. Altogether these studies suggest different biological activities of the graphitic nanomaterials, with the shape playing a primary role.

Dynamic covalent polymer networks (DCPN) have historically attracted attention for their unique roles in chemical recycling and self-healing, which are both relevant for sustainable societal development. Efforts in these directions have intensified in the past decade with notable progress in newly discovered dynamic covalent chemistry, fundamental material concepts, and extension toward emerging applications including energy and electronic devices. Beyond that, the values of DCPN in discovering/designing functional properties not offered by classical thermoplastic and thermoset polymers have recently gained traction. In particular, the dynamic bond exchangeability of DCPN has shown unparalleled design versatility in various areas including shape-shifting materials/devices, artificial muscles, and microfabrication. Going beyond this basic bond exchangeability, various molecular mechanisms to manipulate network topologies (topological transformation) have led to opportunities to program polymers, with notable concepts such as living networks and topological isomerization. In this review, we provide an overview of the above progress with particular focuses on molecular design strategies for the exploitation of functional material properties. Based on this, we point out the remaining issues and offer perspectives on how this class of materials can shape the future in ways that are complementary with classical thermoplastic and thermoset polymers.

Carbon nanotubes (CNTs) were found to penetrate tomato seeds and affect their germination and growth rates. The germination was found to be dramatically higher for seeds that germinated on medium containing CNTs (10-40 mug/mL) compared to control. Analytical methods indicated that the CNTs are able to penetrate the thick seed coat and support water uptake inside seeds, a process which can affect seed germination and growth of tomato seedlings.

Black phosphorus is a two-dimensional material of great interest, in part because of its high carrier mobility and thickness dependent direct bandgap. However, its instability under ambient conditions limits material deposition options for device fabrication. Here we show a black phosphorus ink that can be reliably inkjet printed, enabling scalable development of optoelectronic and photonic devices. Our binder-free ink suppresses coffee ring formation through induced recirculating Marangoni flow, and supports excellent consistency (< 2% variation) and spatial uniformity (< 3.4% variation), without substrate pre-treatment. Due to rapid ink drying (< 10 s at < 60 °C), printing causes minimal oxidation. Following encapsulation, the printed black phosphorus is stable against long-term (> 30 days) oxidation. We demonstrate printed black phosphorus as a passive switch for ultrafast lasers, stable against intense irradiation, and as a visible to near-infrared photodetector with high responsivities. Our work highlights the promise of this material as a functional ink platform for printed devices.