Optimized strategies of green and grey infrastructures for integrated control objectives of runoff, waterlogging and WWDP in old storm drainages.

Frequent waterlogging occurs in old high-density urban areas where the sewage is inappropriately connected to storm drainages, resulting in serious wet weather discharge pollution (WWDP). To address urban waterlogging and runoff, the optimization of green infrastructures (GIs) and grey infrastructures (GRs) has been proposed to improve rainwater management efficiency. However, most strategies neglect WWDP and fail to achieve integrated control of runoff, waterlogging, and discharge pollution. In the present study, a new optimization method was introduced to identify optimal solutions for renovating outdated storm drainage systems, considering the management of discharge pollution in wet weather. A case study in Shanghai, China was conducted to demonstrate the application of the method. The cost-benefit index (CBI) of optimized GIs (0.06) was lower than that of optimized GRs (2.78) under 22.2 mm rainfall (no runoff and WWDP), but the costs of the former were only half those of the latter. In a 5-year return period storm (no waterlogging), optimized GIs had a significantly higher CBI (2.85 times) compared to optimized GRs, costing only 44 % of the latter. When WWDP reached the control objective (COD≤70 mg/L), the optimized GIs needed to be further optimized with GRs. The CBI of optimized GI-GRs was higher than GRs by 2.50, and the cost was 58% of the latter. In areas with frequent low-intensity rainfall, optimized GIs and GRs should be selected based on local cost or benefit requirements for drainage reconstruction. In high-intensity storm-prone areas, the optimized GI-GR combination should be selected for drainage reconstruction. The proposed method can compensate for the shortcomings of existing optimization methods in controlling WWDP for the reconstruction of old storm drainages.

Reply to the 'Comment on "Regulating the valence level arrangement of high-Al-content AlGaN quantum wells using additional potentials with Mg doping"' by W. Lambrecht, Phys. Chem. Chem. Phys., 2023, 25, DOI: 10.1039/D2CP01080A.

We are happy to receive the attention of Prof. Lambrecht regarding our paper and we appreciate his comments. However, it is hard to agree with his judgement about the "incorrect application", "incorrect interpretation", and the work being "misleading". Therefore, we would like to provide a defense and further discussion in this reply.

Assessment of carbon emission reduction contribution of Chinese power grid enterprises based on MCS-GA-ELM method.

To achieve China's "double carbon" goal, it is necessary to make quantitative evaluation of the power grid enterprises' contribution to carbon emission reduction. This paper analyzes the contribution of power grid enterprises to carbon emission reduction from three points: power generation side, power grid side, and user side. Then, PLS-VIP method is used to screen the key influencing factors of carbon emission reduction contribution of power grid enterprises from three aspects: consumption of clean energy emission reduction, reduction of line loss emission reduction, and substitution of electric energy. Based on GA-ELM combined machine learning algorithm, we establish an intelligent evaluation model of power grid enterprises' carbon emission reduction contribution. Furthermore, according to the distribution law of key influencing factors, this paper uses Monte Carlo simulation method to calculate the contribution of power grid enterprises to carbon emission reduction by scenario, so as to evaluate the contribution of power grid enterprises to carbon emission reduction. Finally, combined with the relevant data of power grid enterprises from 2003 to 2019, this paper makes an empirical study on the completion of carbon emission reduction contribution and the promotion path.

Towards n-type conductivity in hexagonal boron nitride.

Asymmetric transport characteristic in n- and p-type conductivity has long been a fundamental difficulty in wide bandgap semiconductors. Hexagonal boron nitride (h-BN) can achieve p-type conduction, however, the n-type conductivity still remains unavailable. Here, we demonstrate a concept of orbital split induced level engineering through sacrificial impurity coupling and the realization of efficient n-type transport in 2D h-BN monolayer. We find that the O 2pz orbital has both symmetry and energy matching to the Ge 4pz orbital, which promises a strong coupling. The introduction of side-by-side O to Ge donor can effectively push up the donor level by the formation of another sacrificial deep level. We discover that a Ge-O2 trimer brings the extremely shallow donor level and very low ionization energy. By low-pressure chemical vapor deposition method, we obtain the in-situ Ge-O doping in h-BN monolayer and successfully achieve both through-plane (~100 nA) and in-plane (~20 nA) n-type conduction. We fabricate a vertically-stacked n-hBN/p-GaN heterojunction and show distinct rectification characteristics. The sacrificial impurity coupling method provides a highly viable route to overcome the n-type limitation of h-BN and paves the way for the future 2D optoelectronic devices.

Upconversion under Photon Trapping in ZnO/BN Nanoarray: An Ultrahigh Responsivity Solar-Blind Photodetecting Paper.

Solar-blind photodetectors (PDs) are widely applicable in special, military, medical, environmental, and commercial fields. However, high performance and flexible PD for deep ultraviolet (UV) range is still a challenge. Here, it is demonstrated that an upconversion of photon absorption beyond the energy bandgap is achieved in the ZnO nanoarray/h-BN heterostructure, which enables the ultrahigh responsivity of a solar-blind photodetecting paper. The direct growth of ultralong ZnO nanoarray on polycrystalline copper paper induced by h-BN 2D interlayer is obtained. Meanwhile, strong photon trapping takes place within the ZnO nanoarray forest through the cyclic state transition of surface oxygen ions, resulting in an extremely high absorption efficiency (> 99.5%). A flexible photodetecting paper is fabricated for switchable detections between near UV and deep UV signals by critical external bias. The device shows robust reliability, ultrahigh responsivity up to 700 A W-1 @ 265-276 nm, and high photoconductive gain of ≈2 × 103 . A negative differential resistance effect is revealed for driving the rapid transfer of up-converted electrons between adjacent energy valleys (Γ to A) above the critical bias (3.9 V). The discovered rationale and device structure are expected to bring high-efficiency deep UV detecting and future wearable applications.

Unidirectional Elimination of Hydrogen by a Giant Local Field Saves First- and Last-Mile Performances of Semiconductor Devices.

Hydrogen, the smallest element, easily forms bonds to host/dopant atoms in semiconductors, which strongly passivates the original electronic characteristics and deteriorates the final reliability. Here, we demonstrate a concept of unidirectional elimination of hydrogen from semiconductor wafers as well as electronic chips through a giant local electric field induced by compact chloridions. We reveal an interactive behavior of chloridions, which can rapidly approach and take hydrogen atoms away from the device surface. A universal and simple technique based on a solution-mediated three-electrode system achieves efficient hydrogen elimination from various semiconductor wafers (p-GaN, p-AlGaN, SiC, and AlInP) and also complete light emitting diodes (LEDs). The p-type conductivity and light output efficiency of H-eliminated UVC LEDs have been significantly enhanced, and the lifetime is almost doubled. Moreover, we confirm that under a one-second irradiation of UVC LEDs, bacteria and COVID-19 coronavirus can be completely killed (>99.93%). This technology will accelerate the further development of the semiconductor-based electronic industry.

Regulating the valence level arrangement of high-Al-content AlGaN quantum wells using additional potentials with Mg doping.

Quantum states and arrangement of valence levels determine most of the electronic and optical properties of semiconductors. Since the crystal field split-off hole (CH) band is the top valence band in high-Al-content AlGaN, TM-polarized optical anisotropy has become the limiting factor for efficient deep-ultraviolet (DUV) light emission. Additional potentials, including on-site Coulomb interaction and orbital state coupling induced by magnesium (Mg) doping, are proposed in this work to regulate the valence level arrangement of AlN/Al0.75Ga0.25N quantum wells (QWs). Diverse responses of valence quantum states |pi〉 (i = x, y, or z) of AlGaN to additional potentials due to different configurations and interactions of orbitals revealed by first-principles simulations are understood in terms of the linear combination of atomic orbital states. A positive charge and large Mg dopant in QWs introduce an additional Coulomb potential and modulate the orbital coupling distance. For the CH band (pz orbital), the Mg-induced Coulomb potential compensates the orbital coupling energy. Meanwhile, the heavy/light hole (HH/LH) bands (px and py orbitals) are elevated by the Mg-induced Coulomb potential. Consequently, HH/LH energy levels are relatively shifted upward and replace the CH level to be the top of the valence band. The inversion of optical anisotropy and enhancement of TE-polarized emission are further confirmed experimentally via spectroscopic ellipsometry.

Role of Strain-Induced Microscale Compositional Pulling on Optical Properties of High Al Content AlGaN Quantum Wells for Deep-Ultraviolet LED.

A systematic study was carried out for strain-induced microscale compositional pulling effect on the structural and optical properties of high Al content AlGaN multiple quantum wells (MQWs). Investigations reveal that a large tensile strain is introduced during the epitaxial growth of AlGaN MQWs, due to the grain boundary formation, coalescence and growth. The presence of this tensile strain results in the microscale inhomogeneous compositional pulling and Ga segregation, which is further confirmed by the lower formation enthalpy of Ga atom than Al atom on AlGaN slab using first principle simulations. The strain-induced microscale compositional pulling leads to an asymmetrical feature of emission spectra and local variation in emission energy of AlGaN MQWs. Because of a stronger three-dimensional carrier localization, the area of Ga segregation shows a higher emission efficiency compared with the intrinsic area of MQWs, which is benefit for fabricating efficient AlGaN-based deep-ultraviolet light-emitting diode.

Enhancing deep-UV emission at 234 nm by introducing a truncated pyramid AlN/GaN nanostructure with fine-tuned multiple facets.

The external quantum efficiency of a high-Al content (>0.6) AlGaN deep-ultraviolet (DUV) light-emitting diode is typically below 1% in the sub-250 nm wavelength range. One of the main reasons for this low efficiency is the fundamental properties of high-Al content AlGaN comprising the transverse-magnetic (TM)-dominant emission and low light extraction due to the total internal reflection (TIR). This work demonstrates a truncated pyramid nanostructure with fine-tuned multiple facets in an (AlN)8/(GaN)2 digital alloy to achieve highly efficient DUV emission at 234 nm. By applying nanoimprint lithography, dry and wet etching, a hexagonal truncated pyramid nanohole structure is fabricated featuring multiple crystal facets of (0001), (10-13), and (20-21) planes. These fine-tuned multiple facets act as reflecting mirrors that can effectively modulate the light propagation and extraction patterns to overcome the TIR via multiple reflections and enhanced scattering. Consequently, significant light extraction enhancements of 5.6 times and 1.1 times for TM and transverse-electric emissions are achieved in the truncated pyramid nanohole structure, respectively. The total luminous intensity of this unique nanostructure is greatly increased by 191% compared to that of a conventional planar structure. The truncated pyramid AlN/GaN nanostructure with fine-tuned multiple facets used in this work provides a promising approach for realizing highly efficient sub-250 nm DUV light-emitting devices.

Designs of InGaN Micro-LED Structure for Improving Quantum Efficiency at Low Current Density.

Here we report a comprehensive numerical study for the operating behavior and physical mechanism of nitride micro-light-emitting-diode (micro-LED) at low current density. Analysis for the polarization effect shows that micro-LED suffers a severer quantum-confined Stark effect at low current density, which poses challenges for improving efficiency and realizing stable full-color emission. Carrier transport and matching are analyzed to determine the best operating conditions and optimize the structure design of micro-LED at low current density. It is shown that less quantum well number in the active region enhances carrier matching and radiative recombination rate, leading to higher quantum efficiency and output power. Effectiveness of the electron blocking layer (EBL) for micro-LED is discussed. By removing the EBL, the electron confinement and hole injection are found to be improved simultaneously, hence the emission of micro-LED is enhanced significantly at low current density. The recombination processes regarding Auger and Shockley-Read-Hall are investigated, and the sensitivity to defect is highlighted for micro-LED at low current density.Synopsis: The polarization-induced QCSE, the carrier transport and matching, and recombination processes of InGaN micro-LEDs operating at low current density are numerically investigated. Based on the understanding of these device behaviors and mechanisms, specifically designed epitaxial structures including two QWs, highly doped or without EBL and p-GaN with high hole concentration for the efficient micro-LED emissive display are proposed. The sensitivity to defect density is also highlighted for micro-LED.

Insight into the surface activity of defect structure in α-MnO2 nanorod: first-principles research.

The contribution of defect structure to the catalytic property of α-MnO2 nanorod still keeps mysterious right now. Using microfacet models representing defect structure and bulk models with high Miller index, several parameters, such as cohesive energy, surface energy, density of state, electrostatic potential, et al., have been used to investigate the internal mechanism of their chemical activities by first-principles calculation. The results show that the trend in surface energies of microfacet models follows as Esurface[(112 × 211)] > Esurface[(110 × 211)] > Esurface[(100 × 211)] > Esurface[(111 × 211)] > Esurface[(112 × 112)] > Esurface[(111 × 112)], wherein all of them are larger than that of bulk models. So the chemical activity of defect structure is much more powerful than that of bulk surface. Deep researches on electronic structure show that the excellent chemical activity of microfacet structure has larger value in dipole moments and electrostatic potential than that of bulk surface layer. And the microfacet models possess much more peaks of valent electrons in deformantion electronic density and molecular orbital. Density of state indicates that the excellent chemical activity of defect structure comes from their proper hybridization in p and d orbitals.

Cu Nanowires Passivated with Hexagonal Boron Nitride: An Ultrastable, Selectively Transparent Conductor.

The copper nanowire (Cu NW) network is considered a promising alternative to indium tin oxide as transparent conductors for advanced optoelectronic devices. However, the fast degradation of copper in ambient conditions largely overshadows its practical applications. Here we demonstrate a facile method for epitaxial growth of hexagonal boron nitride (h-BN) of a few atomic layers on interlaced Cu NWs by low-pressure chemical vapor deposition, which exhibit excellent thermal and chemical stability under high temperature (900 °C in vacuum), high humidity (95% RH), and strong base/oxidizer solution (NaOH/H2O2). Meanwhile, their optical and electrical performances remain similar to those of the original Cu NWs (e.g., high optical transmittance (∼93%) and high conductivity (60.9 Ω/□)). A smart privacy glass is successfully fabricated based on a Cu@h-BN NW network and liquid crytal, which could rapidly control the visibility from transparent to opaque (0.26 s) and, at the same time, strongly block the mid-infrared light for energy saving by screening radiative heat. This precise engineering of epitaxial Cu@h-BN core-shell nanostructure offers broad applications in high-performance electronic and optoelectronic devices.

Enhanced Emission of Deep Ultraviolet Light-Emitting Diodes through Using Work Function Tunable Cu Nanowires as the Top Transparent Electrode.

Deep ultraviolet light-emitting diodes (DUV LEDs) (<280 nm) have been important light sources for broad applications in, e.g., sterilization, purification, and high-density storage. However, the lack of excellent transparent electrodes in the DUV region remains a challenging issue. Here, we demonstrate an architectural engineering scheme to flexibly tune the work function of Cu@shell nanowires (NWs) as top transparent electrodes in DUV LEDs. By fast encapsulation of shell metals on Cu NWs and a shift of electron binding energy, the electronic work function could be widely tailored down to 4.37 eV and up to 5.73 eV. It is revealed that the high work function of Cu@Ni and Cu@Pt NWs could overcome the interfacial barrier to p-AlGaN and achieve direct ohmic contact with high transparency (91%) in 200-400 nm. Completely transparent DUV LED chips are fabricated and successfully lighted with sharp top emission (wall-plug efficiency reaches 3%) under a turn-on voltage of 6.4 V. This architectural strategy is of importance in providing highly transparent ohmic electrodes for optoelectronic devices in broad wavelength regions.

Strain manipulation of the polarized optical response in two-dimensional GaSe layers.

We report tunable optical performances of gallium selenide (GaSe) layers in phonon vibrations, band edge emission, circular polarization, and anisotropic response via strain manipulation. By applying a uniaxial tensile strain, frequency shift and peak broadening are observed in Raman spectra. A shrink in bandgap is demonstrated in photoluminescence (PL) spectra and confirmed by first-principles calculations. A continuously growing circular polarization from 3.8% to 37.9% is detected at room temperature when the tensile strain is increased from 0% to 0.35%, which is almost a ten-fold enhancement compared with that under the non-resonant excitation. Through the theoretical calculations, the decrease in exciton lifetime is revealed to be responsible for the overwhelming enhanced circular polarization. By deforing the lattices of GaSe layers, the Raman intensity was found to be suppressed in the strain direction. The intrinsic fourfold-symmetry of the E2g1 mode in angle-dependent Raman spectra is tuned to a two-fold symmetry. An anisotropic PL response is further regulated by changing the structural symmetry of GaSe lattices. A maximal polarization of 66.0% is achieved when the detection polarizations are perpendicular to the strain direction. All the findings in this study suggest a route for tuning the optical properties, particularly the polarized response in two-dimensional (2D) materials, and provide a strategy for developing flexible and anisotropic 2D optical devices.

Optical Performance of Top-Down Fabricated AlGaN Nanorod Arrays with Multi-Quantum Wells Embedded.

Deep ultraviolet AlGaN-based nanorod (NR) arrays were fabricated by nanoimprint lithography and top-down dry etching techniques from a fully structural LED wafer. Highly ordered periodic structural properties and morphology were confirmed by scanning electron microscopy and transmission electron microscopy. Compared with planar samples, cathodoluminescence measurement revealed that NR samples showed 1.92-fold light extraction efficiency (LEE) enhancement and a 12.2-fold internal quantum efficiency (IQE) enhancement for the emission from multi-quantum wells at approximately 277 nm. The LEE enhancement can be attributed to the well-fabricated nanostructured interface between the air and the epilayers. Moreover, the reduced quantum-confined stark effect accounted for the great enhancement in IQE.

Research on the removal mechanism of antimony on α-MnO2 nanorod in aqueous solution: DFT + U method.

Although previous papers have reported the desorption process of antimony (Sb) ions adsorbed on α-MnO2 nanomaterials, some trace Sb(OH)4- molecular observed in experiments have not been understood clearly. Using two models as popular bulk surface and new microfacet, several parameters, such as adsorption energy, bond length, total density of state (TDOS) and activation energy, were calculated to research and analyze the catalytic reaction of Sb oxides on α-MnO2. The results show that the bulk surface model has the "mirror effect" in revealing the catalytic property of α-MnO2 nanorods. Using MnO2[(100 × 110)] microfacet model, a new molecular Sb(OH)4- molecular appears in the reaction process of Sb(OH)3 + H2O → Sb(OH)4- + H+. Further comparing the geometric morphology and TDOS of Sb(OH)4- with Sb(OH)6- molecular, it is found that their bonding length, dihedral and energy orbital of bonding peaks are too close to set the Sb(OH)4- as the precursor product of Sb(OH)6- molecular. Then the desorption process of Sb ions on α-MnO2 nanorods is virtually transformed into Sb(OH)3 → Sb(OH)4-  → Sb(OH)6- way in aqueous solution. Thus, our findings open an avenue for detailed and comprehensive theoretical studies of catalytic reaction by nanomaterials.

p-Type conductivity of hexagonal boron nitride as a dielectrically tunable monolayer: modulation doping with magnesium.

Hexagonal boron nitride (h-BN) is the widest band gap 2D material (>6 eV), which has attracted extensive attention. For exploring potential applications in optoelectronic devices, electrical conductivity modulation (n or p type) is of extreme importance. Here, we report the achievement of a large-scale and high quality h-BN monolayer with p-type conductivity by modulation doping of Mg using a low pressure chemical vapor deposition method. A large-scale monolayer h-BN (>10 inches) was grown by using a wound Cu foil roll on a multi-prong quartz fork. Magnesium nitride is used as a dopant precursor in a separate line due to its appropriate melting point and decomposition temperature. Density functional theory calculations revealed that the acceptor level introduced by Mg is almost pinned into the valence band and the activated holes are highly delocalized into the surrounding h-BN lattices. The h-BN:Mg monolayer showed a p-type conductivity with a considerable surface current of over 12 µA and a hole density of 1.7 × 1014 cm-2. The dielectrically tunable h-BN monolayer makes the fabrication of advanced 2D optoelectronic devices in short wavelength possible.

In-plane Anisotropy of Quantum Transport in Artificial Two-dimensional Au Lattices.

We report an experimental observation and direct control of quantum transport in artificial two-dimensional Au lattices. Combining the advanced techniques of low-temperature deposition and newly developed double-probe scanning tunneling spectroscopy, we display a two-dimensional carrier transport and demonstrate a strong in-plane transport modulation in the two-dimensional Au lattices. In well-ordered Au lattices, we observe the carrier transport behavior manifesting as a band-like feature with an energy gap. Furthermore, controlled structural modification performed by constructing coupled "stadiums" enables a transition of system dynamics in the lattices, which in turn establishes tunable resonant transport throughout a wide energy range. Our findings open the possibility of the construction and transport engineering of artificial lattices by the geometrical arrangement of scatterers and quantum chaotic dynamics.

Brief introduction of current technologies in isolation of broadly neutralizing HIV-1 antibodies.

HIV/AIDS has become a worldwide pandemic. Before an effective HIV-1 vaccine eliciting broadly neutralizing monoclonal antibodies (bnmAbs) is fully developed, passive immunization for prevention and treatment of HIV-1 infection may alleviate the burden caused by the pandemic. Among HIV-1 infected individuals, about 20% of them generated cross-reactive neutralizing antibodies two to four years after infection, the details of which could provide knowledge for effective vaccine design. Recent progress in techniques for isolation of human broadly neutralizing antibodies has facilitated the study of passive immunization. The isolation and characterization of large panels of potent human broadly neutralizing antibodies has revealed new insights into the principles of antibody-mediated neutralization of HIV. In this paper, we review the current effective techniques in broadly neutralizing antibody isolation.

Construction of a recombinant full-length membrane associated IgG library.

HIV/AIDS has become a global pandemic. Development of an effective HIV-1 vaccine eliciting broadly neutralizing monoclonal antibodies (bnmAbs) remains a big challenge. Before an effective vaccine comes out, passive treatment for prevention and protection of HIV-1 infection may alleviate the burden caused by the pandemic. Numerous bnmAbs have been isolated against different epitopes in HIV-1 envelope glycoprotein via phage/yeast display, EBV-immortalization, single cell sorting and micro neutralization. Recombinant antibody library with extended diversity and enlarged size of units are applicable by phage/yeast display and mammalian cell display for monoclonal antibody isolation. Here, we constructed an immune recombinant membrane associated full length IgGs library based on mammalian cell display system. This library can be used for monoclonal antibody screening/isolation by target cell sorting. A full length antibody mz2F11 was screened with potent neutralizing activities against a panel of viruses tested. Our study provides a novel way of antibody library construction and monoclonal antibody screening. Antibodies screened via this method can help broaden the knowledge in passive treatment and prevention against HIV-1 infection.