Search

Two-dimensional (2D) materials have attracted extensive attention for use in fiber lasers for pulse generation due to their unique nonlinear optical properties. While 2D materials with tunable band...

Photocatalytic water splitting, an environmentally friendly approach for producing hydrogen, is a feasible and efficient solution for the environmental and energy crisis. A major challenge for photocatalytic water splitting is searching for catalysts with suitable band gap and band alignment with promising electronic and optical properties. Herein, we predict a novel two-dimensional material, monolayer RhTeCl, which is potentially exfoliable from its bulk counterparts with a small cleavage energy (~0.39 J/m2). Dynamical, thermal, and mechanical stabilities, as well as suitable direct band gap (2.49 eV) and band edge positions qualify monolayer RhTeCl as a promising candidate for photocatalytic water splitting. High electron mobility and exciton binding energy further suppress the electron-hole recombination, and good light harvesting ability is presented with pronounced optical absorbance in the visible light and ultraviolet regions. In addition, the Gibbs free energy diagram shows that water splitting on...

Traffic-induced air pollutant emissions are currently rising rapidly. However, measurement of the roadside environment and calculation of the emission factors for traffic-induced PM2.5 are restricted to certain locations and periods due to the limitations of conventional air monitoring techniques. This paper introduces a portable sensor package with a laser light-scattering PM2.5 sensor and an electrochemical CO sensor to measure roadside PM2.5 and CO concentrations. The low-cost sensor package underwent local calibration using reference instruments at the Chinese Research Academy of Environmental Sciences (CRAES). The results showed a high level of correlation (r in the range of 0.94-0.95 and 0.81-0.83 for PM2.5 and CO, respectively) between measurements using the sensor packages and those measured by the reference equipment. The study found that the low-cost sensor packages were able to deliver reliable measurements of PM2.5 and CO concentrations. Four low-cost sensor packages were deployed along a short section of an expressway to measure roadside PM2.5 and CO concentrations. The directly measured concentrations were firstly calibrated with the temperature and humidity. The corrected PM2.5 concentrations from each side of the road were different, while the corrected CO concentrations were similar on both sides of the road. Therefore, only the PM2.5 measurements were applied in this study's box model. The assumption of perfect mixing in order for the box model to be applied was shown by the results to be valid to some extent. The PM2.5 emission factors for opposite sides of the road should be calculated separately based on the direction of traffic flow. The PM2.5 emission factors calculated in this study were variable, being impacted by traffic conditions and meteorological conditions. The paper presents a method for obtaining PM2.5 emission factors based on a box model. This method is a promising way of monitoring air pollution in the roadside environment.

Low-cost air quality sensors are increasingly being used in many applications; however, many of their performance characteristics have not been adequately investigated. This study was conducted over a period of 13 months using low-cost air quality monitors, each comprising two low-cost sensors, which were subjected to a wide range of pollution sources and concentrations, relative humidity and temperature at four locations in Australia and China. The aim of the study was to establish the performance characteristics of the two low-cost sensors (a Plantower PMS1003 for PM2.5 and an Alphasense CO–B4 for carbon monoxide, CO) and the KOALA monitor as a whole under various conditions. Parameters evaluated included the inter-variability between individual monitors, the accuracy of monitors in comparison with the reference instruments, the effect of temperature and RH on the performance of the monitors, the responses of the PM2.5 sensors to different types of aerosols, and the long-term stability of the PM2.5 and CO sensors. The monitors showed high inter-correlations (r > 0.91) for both PM2.5 and CO measurements. The monitor performance varied with location, with moderate to good correlations with reference instruments for PM2.5 (0.44

We investigate the electronic and magnetic properties of substitutional metal atom impurities in two-dimensional (2D) blue phosphorene nanoribbons using first-principles calculations. In impure zigzag blue phosphorene nanoribbons (zBPNRs), a metal atom substitutes for a P atom at position "A/B". The V-"B"structure shows half-metallic properties, while the Mn-"A/B", V-"A", Fe-"B", and Cr-"A/B" structures show magnetic semiconductor properties. In addition, the Fe-"A" system shows magnetic metallic properties. On the other hand, for metal-doped armchair blue phosphorene nanoribbons (aBPNRs), the Mn-"A/B", V-"A", Fe-"A/B", and Cr-"A/B" structures show magnetic semiconductor properties, while the V-"B" structure shows nonmagnetic properties. We find that the magnetic properties of such substitutional impurities can be understood by regarding the exchange splitting of the metal 3d orbitals. And from analyzing the electron orbitals, we conclude that the main contribution of the DOS for every system comes from the d and p orbitals. These results suggest excellent candidates for new magnetic semiconductors and half-metals for spintronic devices based on blue phosphorenes.

Surface modification is an essential step in engineering high performance nickel-rich layered (NLO) cathode materials that can withstand the increasingly harsh environment encountered in lithium-ion batteries. However, most traditional technologies suffer disadvantages such as low diffusion kinetics, processing difficulties and/or compatibility issues. Here, based on the dual-Kirkendall effect, we report an efficient, self-guided way for fabricating a multifunctional NiTiO3 (NTO) nanocoating to stabilize the cathode/electrolyte interface for NLO. The NTO nanocoating can epitaxially and chemically bond to the surface framework of NLO particles and eliminate surface lithium residues by evolving into a Li–Ni–Ti–O mixed phase coating that is mainly composed of Li2−xTiO3. Taking full advantage of such a novel multifunctional NTO nanocoating, the structural degradation in NLO cathodes can be effectively suppressed, leading to excellent rate capability and cyclability. This method provides insights into novel surface chemistry that prevents high performance layered electrode materials from structural degradation.

Using first-principle calculations, the magnetic properties of the monovacancies and the Sb-related defects including VZn, VO, SbZn, SbO, SbZn-VZn and SbZn-2VZn are studied. It is found that the isolated VZn with the charge state of 0 and −1 can contribute to ferromagnetism in ZnO material. The substitution of Sb on O sites (SbO0) also results in magnetic property. Moreover, the SbZn-2VZn complex is another defect having non-zero magnetic moment and energetically favors for the ferromagnetic state. The resultant density of states (DOS) and spin density distribution clearly show that the ferromagnetic interaction is majorly due to the O-p Zn-d and Sb-p states. To check this calculation, Sb-doped ZnO samples were grown by pulsed laser deposition with different Sb composition under P(O2) = 1.3 Pa. SQUID study showed that all of these samples are ferromagnetic at room temperature. The variation of the saturation magnetization against the Sb composition is discussed.

Converting heat energy directly into useable electricity by harvesting low-cost energy resources, such as solar energy and the waste heat, has attracted great interest recent years. Thermoelectricity offers a promising technology to convert heat from solar energy and to recover waste heat from industrial sectors and automobile exhausts. Classically, a number of inorganic compounds have been considered as the best thermoelectric materials. Organic materials in particular intrinsically conducting polymers had been considered as competitors of classical thermoelectric since their figure of merit has been improved several orders of magnitude in last year. In addition, the applications of thermoelectric polymers at low temperatures have shown various advantages such as easy and low cost of fabrication, light weight, and flexibility. Therefore, organic thermoelectric materials will be the best candidates to compete with inorganic materials in the future. In this review, we focused on exploring different types of organic thermoelectric materials and the factors affecting their thermoelectric properties, and discussed various strategies to improve the performance of thermoelectric materials. In addition, a review on theoretical studies of thermoelectric transport in polymers is also given.

This paper presents a solution to detect pedestrian and vehicle using a 16-line LIDAR. Unlike prior researches, the downward-looking LIDAR is mounted on a bridge over road lanes instead of mounting on a moving vehicle. The sensor detects motorized and non-motorized traffic and classifies the traffic into different modes. The detected object is tracked with the Kalman filter method. Compared with the high-end sensor of high resolution, the 16-line LIDAR is affordable and cost-effective, and the experiment demonstrates its acceptable detection rate and trajectory estimation precision. Beside detection range, the application of downward-looking LIDAR has a satisfied result.

We study the magnetic behavior of a tetrameric magnetic system with four antiferromagnetic couplings(J1-J2-J3-J4), where J4 is the inter-cell coupling and J1,J2,J3 are the intra-cell couplings, by using Green’s function theory. The Magnetic-field curves shows that there are three plateaus (M = 0, 1 and saturated magnetization) and two gapless phases distinguished by four critical lines, and the plateaus widen or narrow with the inter-cell coupling(J4), which are further explained using the energy spectrum. In addition, it is found that the magnetic contribution from each site of the unit cell is different due to the competition of the nearest neighboring pair interactions, which is demonstrated by the concurrence of the biparticle quantum state.

We report the electronic transport properties of the MnAs(001)/InP(001) magnetic tunnel junctions by first principles calculations. The half-metallic MnAs was predicted as a result of 100% spin polarization and then minority spin current is absolutely inhibited when the bias voltage is applied to terminals of both MnAs and InP. Majority spin current is inhibited when the bias voltage is less than 0.8 V and “relaxed” when the bias voltage increases. Spin-up and spin-down currents flowing in opposite directions are proved to be induced by temperature difference between left and right electrodes called Seebeck Effect rather than external electrical bias. Thermal current was demonstrated perfect spin filtering effects to indicating possible use for fabrication of highly-efficient spin filter devices in this study.

Magnetic properties of spin-1/2 antiferromagnetic three-leg Heisenberg ladders, where antiferromagnetic interactions in legs are J 1 , J 2 and J 1 respectively and in the rungs are J ⊥ , have been investigated by bond-mean field method. As J ⊥ changes, magnetization curves show different behavior. For J ⊥ =0.5, there are cusps in magnetization curves, while for J ⊥ =3.0, the 1/3 magnetization plateau appears, which can be explained by energy spectra. Furthermore, for J ⊥ =3.0 the 1/3 magnetization plateaus will become wider or narrow down with J 2 changing. In addition, the mean-field bond parameters and the concurrences, which confirm the phase transitions, are also studied.

The contacted properties of metal substrates with single layer (monolayer) blue phosphorus are calculated by first principles. We analyze the charge transfer, atomic orbital overlap, electronic properties and potential barrier at the interface of metal contacted blue phosphorene (BuleP) to understand how to effectively inject electrons from the metal into the contacted blue phosphorus. We inquire into interfacial effect of blue phosphorene directly in contact with five representative metallic substrates – Au (111), Ag(111), Al(111), Co(111) and Sc(0001), which are having minimal lattice mismatch with the BlueP. We find that the contact properties of these five metals are ohmic contact and schottky contact. Of the five different contact metals, Co-BlueP heterojunction has the best electrical conductivity. The lower SBH in the Al contact can also lead to a good substrate for a Schottky contact for the heterojunction. These results can provide guidance for the future design of BlueP-based electronic devices and for the exploration of new low-dimensional semiconductor transport processes.

The research on the mixed rare earth-iron based permanent magnet compounds by doping rare earth elements in Nd-Fe-B or Pr-Fe-B permanent magnet has been a hot topic in recent years. In this paper, La doped Pr-Fe-B ((LaxPr1-x)3Fe14B, x=0, 0.3, 0.6, (La, Pr)-Fe-B) ribbons were prepared by vacuum arc melting technique and subsequently melt-spinning method at the optimal quenching speed. The microstructure, phase distribution and magnetic properties of the nanocomposite magnets were investigated. It is found that the samples present 2:14:1 main phase, La2O3 phase and minor α-Fe phase. No excess amorphous phase is observed, indicating that 20 m/s is an optimization of preparation condition to fabricate the (La, Pr)-Fe-B ribbons in this work. The EBSD results reveal that La-rich phases distribute mostly over the grain boundary. The substitution of La for Pr in Pr-Fe-B has some influence on the coercivity, but little on the saturation magnetization. This is thought to be related with the agglomeration of rare earth-rich intermetallic phase. We hope that this work can provide new ideas in the exploration of mixed rare earth-iron based permanent magnet compounds, which possess a cost advantage and a promising potential for practical applications.

By performing first-principle quantum transport calculations, we studied the electronic and transport properties of zigzag α-graphyne nanoribbons in different magnetic configurations. We designed the device based on zigzag α-graphyne nanoribbon and studied the spin-dependent transport properties, whose current-voltage curves show obvious spin-polarization and conductance plateaus. The interesting transport behaviours can be explained by the transport spectra under different magnetic configurations, which basically depends on the symmetry matching of the electrodes’ bandstructures. Simultaneously, spin Seebeck effect is also found in the device. Thus, according to the transport behaviours, zigzag α-graphyne nanoribbons can be used as a dual spin filter diode, a molecule signal converter and a spin caloritronics device, which indicates that α-graphyne is a promising candidate for the future application in spintronics.

By performing first-principle quantum transport calculation, the spin-dependent transport properties of zigzag-edged bilayer graphene nanoribbon based devices are investigated. There are four kinds of structures with different stacking sequences and treatment of dangling bonds considered in our work. It is shown that the devices are perfect spin-filters with extremely large spin polarization as well as substantial negative differential resistance effects, which are affected by the stacking sequences and edge structures. All these phenomena can be explained by the spin-resolved local density of states and the tranmission spectra.