2D MXenes: the lowest-emissivity black materials

Black materials with low infrared absorption/emission are rare in nature but highly desired in numerous areas, such as solar-thermal energy harvesting, infrared camouflage, and anti-counterfeiting. Due to the lack of spectral selectivity in intrinsic materials, such counter-intuitive properties are generally realized by constructing complicated subwavelength artificial nanostructures with precise nanofabrication techniques. Here, we report that 2D Ti3C2Tx MXenes embrace both a low emissivity (down to 10%) and a high solar absorptance (up to 90%), yielding the best spectral selectivity (8.2) and the highest solar-thermal efficiency among the reported intrinsic solar absorbing materials. We demonstrate their appealing potentials in the aforementioned areas. Moreover, the spectral selectivity relies on both the nanoflake orientations and terminal groups, providing great tunability. First-principles calculations suggest more potential low-emissivity MXenes such as Ti2CTx, Nb2CTx, and V2CTx. This work opens the avenue to further exploration of a family of low-emissivity black materials with over 70 members.

Nanostructure Fabrication in Oil Media for Enhanced Thermophysical Properties

Recently, researchers have focused on molten-salt-based nanofluids, relying on their unique ability to form special fractallike nanostructures due to the interaction between molten salt ionic molecules and the nanoparticles. These nanostructures are thought to be causing the observed heat capacity enhancement. Thus far, this phenomenon was believed to be exclusive to molten salt nanofluids. In this study, the nanostructure observed in molten-salt-based nanofluids is mimicked, and similar fractallike nanostructures were formed in-situ in polyalphaolefin (PAO) oil as the base fluid by dispersing alumina (Al2O3) nanoparticles (1% wt. concentration) in the PAO and adding hydroxyl-ended polymer (PPG) (1% wt. concentration) as surfactants to form “artificial” nanostructures by ionically bonding to the nanoparticle’s surface. The effect of these artificial nanostructures was studied to confirm that they affect the base fluid similar to the nanostructures formed in molten salt nanofluids. Results showed an increase of 4.86% in heat capacity, and a 42% increase in viscosity was measured at high shear rates, as well as a noticeable non-Newtonian rheological behavior at low shear rates. These results show that the nanostructure has formed and that the thermophysical and rheological properties of the oil have been affected as expected.

Structural DNA Nanotechnology: Artificial Nanostructures for Biomedical Research

Structural DNA nanotechnology utilizes synthetic or biologic DNA as designer molecules for the self-assembly of artificial nanostructures. The field is founded upon the specific interactions between DNA molecules, known as Watson–Crick base pairing. After decades of active pursuit, DNA has demonstrated unprecedented versatility in constructing artificial nanostructures with significant complexity and programmability. The nanostructures could be either static, with well-controlled physicochemical properties, or dynamic, with the ability to reconfigure upon external stimuli. Researchers have devoted considerable effort to exploring the usability of DNA nanostructures in biomedical research. We review the basic design methods for fabricating both static and dynamic DNA nanostructures, along with their biomedical applications in fields such as biosensing, bioimaging, and drug delivery.

Storylines in intercalation chemistry

Intercalation chemistry taking into account the interstratification and disorder phenomena is a valuable preparative tool for the design of artificial layered artificial nanostructures.