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<jats:p>The nitrogen and sulfur co-doped carbon dots (N, S-CDs) with increased luminescence were synthesized by a hydrothermal process in one green pot by using glucose, and a new sulfur-doping source of sodium sulfite was developed. The synergistic effect of the N and S groups was well discussed through the structure analysis of Fourier transform infrared spectra and x-ray photoelectron spectra. The surface states of N, S-CDs embody more complicated functional groups, and S element exists as –SSO<jats:sub>3</jats:sub>, –C–SO<jats:sub>3</jats:sub>, and <jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{SO}}}_{4}^{2-}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">SO</mml:mi> </mml:mrow> <mml:mn>4</mml:mn> <mml:mrow> <mml:mn>2</mml:mn> <mml:mo>−</mml:mo> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_12_128102_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> groups due to the introduction of sodium sulfite. The sulfur-containing groups passivate the surface of the CDs, and the relatively high sulfur groups may reduce the non-radiation centers. The fluorescence is affected by the hydroxyl group of the solvent. The quenching of Fe<jats:sup>3+</jats:sup> ion to fluorescence and the sensitivity of fluorescence to pH were also investigated.</jats:p>

<jats:p>We report the simultaneous enlarged growth of seven single crystal diamond (SCD) plates free from polycrystalline diamond (PCD) rim by using a microwave plasma chemical vapor deposition (MPCVD) system. Optical microscope and atomic force microscope (AFM) show the typical step-bunching SCD morphology at the center, edge, and corner of the samples. The most aggressively expanding sample shows a top surface area three times of that of the substrate. The effective surface expanding is attributed to the utilization of the diamond substrates with (001) side surfaces, the spacial isolation of them to allow the sample surface expanding, and the adoption of the reported pocket holder. Nearly constant temperature of the diamond surfaces is maintained during growth by only decreasing the sample height, and thus all the other growth parameters can be kept unchanged to achieve high quality SCDs. The SCDs have little stress as shown by the Raman spectra. The full width at half maximum (FWHM) data of both the Raman characteristic peak and (004) x-ray rocking curve of the samples are at the same level as those of the standard CVD SCD from Element Six Ltd. The nonuniformity of the sample thickness or growth rate is observed, and photoluminescence spectra show that the nitrogen impurity increases with increasing growth rate. It is found that the reduction of the methane ratio in the sources gas flow from 5% to 3% leads to decrease of the vertical growth rate and increase of the lateral growth rate. This is beneficial to expand the top surface and improve the thickness uniformity of the samples. At last, the convenience of the growth method transferring to massive production has also been demonstrated by the successful simultaneous enlarged growth of 14 SCD samples.</jats:p>

<jats:p>Columbite Zn<jats:sub>0.8</jats:sub>Co<jats:sub>0.2</jats:sub>Nb<jats:sub>2</jats:sub>O<jats:sub>6</jats:sub> crystals were grown by optical floating zone methods. The x-ray diffraction (XRD) was used to check the structure information of the grown Zn<jats:sub>0.8</jats:sub>Co<jats:sub>0.2</jats:sub>Nb<jats:sub>2</jats:sub>O<jats:sub>6</jats:sub> crystal. The room temperature and temperature-dependent Raman spectra were tested to investigate the optical phonon behaviors of columbite Zn<jats:sub>0.8</jats:sub>Co<jats:sub>0.2</jats:sub>Nb<jats:sub>2</jats:sub>O<jats:sub>6</jats:sub>, which exhibited a temperature stable property. The magnetics properties of Zn<jats:sub>0.8</jats:sub>Co<jats:sub>0.2</jats:sub>Nb<jats:sub>2</jats:sub>O<jats:sub>6</jats:sub>, measured by a physical property measurement system (PPMS), were also presented in this work.</jats:p>

<jats:p>In order to obtain higher conversion efficiency and to reduce production cost for hydrogenated amorphous silicon/crystalline silicon (a-Si:H/c-Si) based heterojunction solar cells, an a-Si:H/c-Si heterojunction with localized p–n structure (HACL) is designed. A numerical simulation is performed with the ATLAS program. The effect of the a-Si:H layer on the performance of the HIT (heterojunction with intrinsic thin film) solar cell is investigated. The performance improvement mechanism for the HACL cell is explored. The potential performance of the HACL solar cell is compared with those of the HIT and HACD (heterojunction of amorphous silicon and crystalline silicon with diffused junction) solar cells. The simulated results indicate that the a-Si:H layer can bring about much absorption loss. The conversion efficiency and the short-circuit current density of the HACL cell can reach 28.18% and 43.06 mA/cm<jats:sup>2</jats:sup>, respectively, and are higher than those of the HIT and HACD solar cells. The great improvement are attributed to (1) decrease of optical absorption loss of a-Si:H and (2) decrease of photocarrier recombination for the HACL cell. The double-side local junction is very suitable for the bifacial solar cells. For an HACL cell with n-type or p-type c-Si base, all n-type or p-type c-Si passivating layers are feasible for convenience of the double-side diffusion process. Moreover, the HACL structure can reduce the consumption of rare materials since the transparent conductive oxide (TCO) can be free in this structure. It is concluded that the HACL solar cell is a promising structure for high efficiency and low cost.</jats:p>

<jats:p>This paper reviews the recent progress in the synthesis of near-infrared (NIR) lead chalcogenide (Pb<jats:italic>X</jats:italic>; Pb<jats:italic>X</jats:italic> = PbS, PbSe, PbTe) quantum dots (QDs) and their applications in NIR QDs based light emitting diodes (NIR-QLEDs). It summarizes the strategies of how to synthesize high efficiency Pb<jats:italic>X</jats:italic> QDs and how to realize high performance Pb<jats:italic>X</jats:italic> based NIR-QLEDs.</jats:p>

<jats:p>It is critical to design an effective two-dimensional membrane for hydrogen purification from the mixed gas, due to its wide range of scientific and industrial applications. In this work, we investigate the hydrogen separation performance of P<jats:sub>2</jats:sub>C<jats:sub>3</jats:sub> membranes by density functional theory and molecular dynamics simulations. The results show that the energy barrier of the H<jats:sub>2</jats:sub> molecule through the P<jats:sub>2</jats:sub>C<jats:sub>3</jats:sub> film is only 0.18 eV, while the energy barriers of the CO, N<jats:sub>2</jats:sub>, CO<jats:sub>2</jats:sub>, and CH<jats:sub>4</jats:sub> molecules are 0.77 eV, 0.87 eV, 0.52 eV, and 1.75 eV, respectively. In addition, the P<jats:sub>2</jats:sub>C<jats:sub>3</jats:sub> film has high H<jats:sub>2</jats:sub> selectivity toward other gas molecules and high H<jats:sub>2</jats:sub> permeability at room temperature. Under 6% tensile strain, 82% hydrogen molecules pass through the film with a H<jats:sub>2</jats:sub> permeance of 2.22 × 10<jats:sup>7</jats:sup> gas permeance unit (GPU), while other molecules cannot across the membrane at all. Therefore, the P<jats:sub>2</jats:sub>C<jats:sub>3</jats:sub> membrane is an excellent material for hydrogen purification.</jats:p>

<jats:p>Organo-halide perovskites in planar heterojunction architecture have shown considerable promise as efficient light harvesters in solar cells. We carry out a numerical modeling of a planar lead based perovskite solar cell (PSC) with Cu<jats:sub>2</jats:sub>ZnSnS<jats:sub>4</jats:sub> (CZTS) as the hole transporting material (HTM) using the one-dimensional solar cell capacitance simulator (SCAPS-1D). The effects of numerous parameters such as defect density, thickness, and doping density of the absorber layer on the device performance are investigated. The doping densities and electron affinities of the electron transporting material (ETM) and the HTM are also varied to optimize the PSC performance. It has been observed that a thinner absorber layer of ∼220 nm with a defect density of 10<jats:sup>14</jats:sup> cm<jats:sup>−3</jats:sup> compared to the reference structure improves the device performance. When doping density of the absorber layer increases beyond 2 × 10<jats:sup>16</jats:sup> cm<jats:sup>−3</jats:sup>, the power conversion efficiency (PCE) reduces due to enhanced recombination rate. The defect density at the absorber/ETM interface reduces the PCE as well. Considering a series resistance of 5 Ω · cm<jats:sup>2</jats:sup> and all the optimum parameters of absorber, ETM and HTM layers simultaneously, the overall PCE of the device increases significantly. In comparison with the reference structure, the PCE of the optimized device has been increased from 12.76% to 22.7%, and hence the optimized CZTS based PSC is highly efficient.</jats:p>

<jats:p>Human settlements are embedded in traffic networks with hierarchical structures. In order to understand the spreading mechanism of infectious diseases and deploy control measures, the susceptible-infected-removed spreading process is studied with agents moving globally on the hierarchical geographic network, taking into account agents’ preference for node layers and memory of initial nodes. We investigate the spreading behavior in the case of global infection under different scenarios, including different directions of human flow, different locations of infection source, and different moving behaviors of agents between layers. Based on the above-mentioned analysis, we propose screening strategies based on layer rank and moving distance, and compare their effects on delaying epidemic spreading. We find that in the case of global infection, infection spreads faster in high layers than in low layers, and early infection in high layers and moving to high layers both accelerate epidemic spreading. Travels of high-layer and low-layer residents have different effects on accelerating epidemic spreading, and moving between high and low layers increases the peak value of new infected cases more than moving in the same layer or between adjacent layers. Infection in intermediate nodes enhances the effects of moving of low-layer residents more than the moving of high-layer residents on accelerating epidemic spreading. For screening measures, improving the success rate is more effective on delaying epidemic spreading than expanding the screening range. With the same number of moves screened, screening moves into or out of high-layer nodes combined with screening moves between subnetworks has better results than only screening moves into or out of high-layer nodes, and screening long-distance moves has the worst results when the screening range is small, but it achieves the best results in reducing the peak value of new infected cases when the screening range is large enough. This study probes into the spreading process and control measures under different scenarios on the hierarchical geographical network, and is of great significance for epidemic control in the real world.</jats:p>

<jats:p>Coherence is a fundamental ingredient for quantum physics and a key resource for quantum information theory. Baumgratz, Cramer and Plenio established a rigorous framework (BCP framework) for quantifying coherence [Baumgratz T, Cramer M and Plenio M B <jats:italic>Phys. Rev. Lett.</jats:italic> <jats:bold>113</jats:bold> 140401 (2014)]. In the present paper, under the BCP framework we provide two classes of coherence measures based on the sandwiched Rényi relative entropy. We also prove that we cannot get a new coherence measure <jats:italic>f</jats:italic>(<jats:italic>C</jats:italic>(·)) by a function <jats:italic>f</jats:italic> acting on a given coherence measure <jats:italic>C</jats:italic>.</jats:p>

<jats:p>The non-Hermitian skin effect breaks the conventional bulk–boundary correspondence and leads to non-Bloch topological invariants. Inspired by the fact that the topological protected zero modes are immune to perturbations, we construct a partner of a non-Hermitian system by getting rid of the non-Hermitian skin effect. Through adjusting the imbalance hopping, we find that the existence of zero-energy boundary states still dictate the bulk topological invariants based on the band-theory framework. Two non-Hermitian Su–Schrieffer–Heeger (SSH) models are used to illuminate the ideas. Specially, we obtain the winding numbers in analytical form without the introduction of the generalized Brillouin zone. The work gives an alternative method to calculate the topological invariants of non-Hermitian systems.</jats:p>