[en] We predict a new two-dimensional allotrope of phosphorus, which we call red phosphorene, by restructuring the segments of the previously proposed blue and black phosphorenes. Its atomic and electronic structures as well as the thermodynamic and dynamic stabilities are systematically studied by first-principles calculations. The results indicate that the red phosphorene is dynamically stable and possesses remarkably thermodynamical stability comparable to that of the black one. Because of the sp"3-hybridization and the formation of a localized lone pair, red phosphorene is a semiconductor with an indirect band gap of about 1.96 eV, which can be effectively modulated by in-plane strains due to its wave-like configuration. We find that the red, black and blue phosphorenes show evident distinction in their layer thicknesses, surface work functions, and possible colors, based on which one can distinguish them in future experiments. (paper)

[en] A pyrolysis method was employed to recycle the metals and brominated compounds blended into printed circuit boards. This research investigated the effect of particle size and process temperature on the element composition of IC boards and pyrolytic residues, liquid products, and water-soluble ionic species in the exhaust, with the overall goal being to identify the pyrolysis conditions that will have the least impact on the environment. Integrated circuit (IC) boards were crushed into 5-40 mesh (0.71-4.4 mm), and the crushed particles were pyrolyzed at temperatures ranging from 200 to 500 deg. C. The thermal decomposition kinetics were measured by a thermogravimetric (TG) analyzer. The composition of pyrolytic residues was analyzed by Energy Dispersive X-ray Spectrometer (EDS), Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). In addition, the element compositions of liquid products were analyzed by ICP-AES and ICP-MS. Pyrolytic exhaust was collected by a water-absorption system in an ice-bath cooler, and IC analysis showed that the absorbed solution comprised 11 ionic species. Based on the pyrolytic kinetic parameters of TG analysis and pyrolytic residues at various temperatures for 30 min, the effect of particle size was insignificant in this study, and temperature was the key factor for the IC board pyrolysis. Two stages of decomposition were found for IC board pyrolysis under nitrogen atmosphere. The activation energy was 38-47 kcal/mol for the first-stage reaction and 5.2-9.4 kcal/mol for the second-stage reaction. Metal content was low in the liquid by-product of the IC board pyrolysis process, which is an advantage in that the liquid product could be used as a fuel. Brominate and ammonium were the main water-soluble ionic species of the pyrolytic exhaust. A plan for their safe and effective disposal must be developed if the pyrolytic recycling process is to be applied to IC boards