Investigation on the effect of fine solid wastes on the runoff purification performance of porous asphalt mixture.

Fine solid wastes such as coal fly ash (CFA), diatomite, and red mud have been widely applied as alternative fillers for porous asphalt pavement (PAP), and have varying impacts on the mechanical performance of materials. However, whether they will affect the runoff purification performance of PAP has not been studied yet. Based on the laboratory simulation rainfall test, this study investigated the purification performance of porous asphalt mixture (PA) with three fine solid wastes fillers. Combined with the analysis of multi-scale pore characteristics of PA, the purification mechanism was further discussed. The results show that pollutants are mainly removed within 3 cm on the surface of PA in 20-30min rainfall. Diatomite and red mud fillers can effectively increase the removal rates of some heavy metals and nutrients by 20-40%. On the one hand, diatomite and red mud can leach some ions, which are conducive to physical adsorption and chemical degradation (including chemical precipitation and ion change) of pollutants. On the other hand, they also contain abundant porous structures and large specific surface areas, which significantly improve the micro-surface physical properties of PA and enhance the interaction between PA and pollutants.

Thermal conductivity of isotopically modified graphene.

In addition to its exotic electronic properties graphene exhibits unusually high intrinsic thermal conductivity. The physics of phonons--the main heat carriers in graphene--has been shown to be substantially different in two-dimensional (2D) crystals, such as graphene, from in three-dimensional (3D) graphite. Here, we report our experimental study of the isotope effects on the thermal properties of graphene. Isotopically modified graphene containing various percentages of 13C were synthesized by chemical vapour deposition (CVD). The regions of different isotopic compositions were parts of the same graphene sheet to ensure uniformity in material parameters. The thermal conductivity, K, of isotopically pure 12C (0.01% 13C) graphene determined by the optothermal Raman technique, was higher than 4,000 W mK(-1) at the measured temperature T(m)~320 K, and more than a factor of two higher than the value of K in graphene sheets composed of a 50:50 mixture of 12C and 13C. The experimental data agree well with our molecular dynamics (MD) simulations, corrected for the long-wavelength phonon contributions by means of the Klemens model. The experimental results are expected to stimulate further studies aimed at a better understanding of thermal phenomena in 2D crystals.

Developing descriptors to predict mechanical properties of nanotubes.

Descriptors and quantitative structure property relationships (QSPR) were investigated for mechanical property prediction of carbon nanotubes (CNTs). 78 molecular dynamics (MD) simulations were carried out, and 20 descriptors were calculated to build quantitative structure property relationships (QSPRs) for Young's modulus and Poisson's ratio in two separate analyses: vacancy only and vacancy plus methyl functionalization. In the first analysis, C(N2)/C(T) (number of non-sp2 hybridized carbons per the total carbons) and chiral angle were identified as critical descriptors for both Young's modulus and Poisson's ratio. Further analysis and literature findings indicate the effect of chiral angle is negligible at larger CNT radii for both properties. Raman spectroscopy can be used to measure C(N2)/C(T), providing a direct link between experimental and computational results. Poisson's ratio approaches two different limiting values as CNT radii increases: 0.23-0.25 for chiral and armchair CNTs and 0.10 for zigzag CNTs (surface defects <3%). In the second analysis, the critical descriptors were C(N2)/C(T), chiral angle, and M(N)/C(T) (number of methyl groups per total carbons). These results imply new types of defects can be represented as a new descriptor in QSPR models. Finally, results are qualified and quantified against experimental data.

Photoswitchable upconversion nanoparticles with excitation-dependent emission for programmed stepwise NIR phototherapy.

Programmable control over therapeutic processes in phototherapy, like photodynamic therapy (PDT), is promising but challenging. This study uses an energy segmentation-based strategy to synthesize core-multi-shell upconversion nanoparticles (UCNPs), which can release three different colors (red, green, and blue) upon exposure to different near-infrared light (1550 nm, 808 nm, and 980 nm). By combining these UCNPs with photosensitizers and nitric oxide (NO) donors, a smart "off-on" PDT nanoplatform is developed. UCNPs enable independent activation of imaging, release of NO, and generation of reactive oxygen species using specific light wavelengths. The results show that sequential NO release before PDT can greatly alleviate tumor hypoxia by reducing oxygen consumption. This stepwise approach shows potential for precise NIR light-activated and imaging-guided phototherapy.

Graphene-Ni (001) interface study.

The interfacial properties for a carbon nanotube on a Ni (001) surface are modeled by a piece of vertical graphene standing on a Ni (001) surface. The interaction between the graphene and the nickel (001) surface is investigated using density functional theory (DFT) calculations. Zigzag type graphene can stand on the hollow sites of the Ni (001) surface along the [linear span]110[linear span] direction. For such a configuration, Ni (001)-graphene interfacial mechanical properties are studied, and we find that Ni-Ni bonds near the interface will break first under tensile strain. C-C bond lengths near the interface are longer than the C-C bonds of graphene, and the charge density of those bonds decrease due to the formation of interfacial Ni-C bonds. It suggests that C-C bonds near the interface may break during the carbon nanotube growth processes.