•The accessibility of parks for the study area has improved overall.•Intra-urban inequalities of park access and changes of park access have been identified.•Significant differences among ...socioeconomic groups in terms of park access and changes in that access have not been detected.•The analysis of changes in park access is a key indicator to measure the effectiveness of urban policies.
As important city and community assets, parks provide ideal open spaces for public recreation, outdoor activities, and residents’ socialization. Using the Gaussian-based 2SFCA method, this study evaluates park accessibility by two thresholds across the 41 sub-districts in Hangzhou and highlights the issue of the changing accessibility of parks over the past decade. The results of this study show that more parks were provided from 2000 to 2010, the accessibility of parks for the study area has improved overall, and significant differences among socioeconomic groups in terms of park access and changes in that access have not been detected. However, intra-urban spatial inequalities have been identified. By situating park access within different cultural and geographical contexts in China, this study enriches the current equity theory framework by introducing equity as a process and equity as a synchronic phenomenon, and introduces an effective approach to the evaluation of the validity of current policies or planning to other cities both in China and the United States.
For the first time, multinuclear noble‐metal clusters have been successfully stabilized by Ti‐oxo clusters. Two unprecedented Ag6@Ti16‐oxo nanoclusters with precise atomic structures were prepared ...and characterized. The octahedral Ag6 core has strong Ag−Ag bonds (ca. 2.7 Å), and is further stabilized by direct Ag−O−Ti coordination interactions. Moreover, as a result of different acidic/redox conditions in synthesis, the Ag6 core can adopt diverse geometric configurations inside the Ti16‐O shell. Correspondingly, structural differences greatly influence their optical limiting effects. The transmittance reduction activity of the clusters towards 532 nm laser shows a nearly linear concentration dependence, and can be optimized up to about 43 %. This work not only opens a new direction for multimetallic semiconductive nanoclusters with interesting optical properties, but also provides molecular models for important noble‐metal/TiO2 heterogeneous materials.
Silver core: Two Ag6@Ti16‐oxo nanoclusters with atomic core–shell structures show optical limiting effects towards 532 nm laser. The differences between the two clusters lie in the orientation of the Ag6 cluster inside the semiconductive Ti−O shell. This orientation influences the optical properties of the nanoclusters.
Defects, such as halide interstitials, act as charge recombination centers, induce degradation of halide perovskites, and create major obstacles to applications of these materials. Alkali metal ...dopants greatly improve perovskite performance. Using ab initio nonadiabatic molecular dynamics, it is demonstrated that alkalis bring favorable effects. The formation energy of halide interstitials increases by up to a factor of four in the presence of alkali dopants, and therefore, defect concentration decreases. When defects are present, alkali metals strongly bind to them. Halide interstitials introduce mid‐gap states that rapidly trap charge carriers. Alkalis eliminate the trap states, helping to maintain high current density. Further to charge trapping, the interstitials accelerate charge recombination. By passivating the interstitials, alkalis make carrier lifetimes up to seven times longer than in defect‐free perovskites and up to thirty times longer than in defective perovskites.
Alkalis passivate iodine interstitial defects in lead perovskites, eliminate the mid‐gap states, and suppress the nonradiative recombination. Theoretical guidelines are developed for defect inactivation in perovskite solar cells and other devices.
Developing Type‐I photosensitizers is considered as an efficient approach to overcome the deficiency of traditional photodynamic therapy (PDT) for hypoxic tumors. However, it remains a challenge to ...design photosensitizers for generating reactive oxygen species by the Type‐I process. Herein, we report a series of α,β‐linked BODIPY dimers and a trimer that exclusively generate superoxide radical (O2−.) by the Type‐I process upon light irradiation. The triplet formation originates from an effective excited‐state relaxation from the initially populated singlet (S1) to triplet (T1) states via an intermediate triplet (T2) state. The low reduction potential and ultralong lifetime of the T1 state facilitate the efficient generation of O2−. by inter‐molecular charge transfer to molecular oxygen. The energy gap of T1‐S0 is smaller than that between 3O2 and 1O2 thereby precluding the generation of singlet oxygen by the Type‐II process. The trimer exhibits superior PDT performance under the hypoxic environment.
Heavy‐atom‐free boron dipyrromethene (BODIPY)‐based photosensitizers generate ROS exclusively by the Type‐I process upon near‐infrared light illumination for tumor ablation.
An organic crystal of 4,4′‐bis(N‐carbazolyl)‐1,1′‐biphenyl (pCBP) exhibits time‐dependent afterglow color from blue to orange over 1 s. Both experimental and computational data confirm that the color ...evolution results from well‐separated, long‐persistent thermally activated delayed fluorescence (TADF) and room‐temperature phosphorescence (RTP) with different but comparable decay rates. TADF is enabled by a small S1–T1 energy gap of 0.7 kcal mol−1. The good separation of TADF and RTP is due to a 11.8 kcal mol−1 difference in the S0 energies of the S1 and T1 structures, indicating that apart from the excited‐state properties, tuning the ground state is also important for luminescence properties. This afterglow color evolution of pCBP allows its applications in anticounterfeiting and data encryption with high security levels.
Organic sunset: A time‐dependent afterglow color in a single‐component organic molecular crystal was observed. It originates from well‐separated, long‐persistent thermally activated delayed fluorescence and room‐temperature phosphorescence with different but comparable decay rates.
Conversion of naturally abundant nitrogen to ammonia is a key (bio)chemical process to sustain life and represents a major challenge in chemistry and biology. Electrochemical reduction is emerging as ...a sustainable strategy for artificial nitrogen fixation at ambient conditions by tackling the hydrogen- and energy-intensive operations of the Haber-Bosch process. However, it is severely challenged by nitrogen activation and requires efficient catalysts for the nitrogen reduction reaction. Here we report that a boron carbide nanosheet acts as a metal-free catalyst for high-performance electrochemical nitrogen-to-ammonia fixation at ambient conditions. The catalyst can achieve a high ammonia yield of 26.57 μg h
mg
and a fairly high Faradaic efficiency of 15.95% at -0.75 V versus reversible hydrogen electrode, placing it among the most active aqueous-based nitrogen reduction reaction electrocatalysts. Notably, it also shows high electrochemical stability and excellent selectivity. The catalytic mechanism is assessed using density functional theory calculations.
Increasingly stringent environmental regulations and consumer awareness around environmental protection and sustainability are driving forces in the hotel industry. We explore the Proactive ...Environmental Strategies being implemented in the hotel industry using Resource-Based View (RBV) and Resource Dependence Theory (RDT) to help companies with Eco-Innovation, Green Core Competences, and Green Competitive Advantages. We investigated the correlations between Proactive Environmental Strategies, Eco-Innovations, Green Competitive Advantages, and Green Core Competences in the hotel industry. With 366 responses, the correlation of Proactive Environmental Strategies with Eco-Innovation and how these are related to Green Competitive Advantage and Green Core Competence were explored. The results revealed that Proactive Environmental Strategies positively influence Eco-Innovation, which in turn directly affects Green Core Competence. Moreover, Green Core Competence affects Green Competitive Advantage. However, the effects of Eco-Innovation on Green Competitive Advantage were not significant. Therefore, companies must either re-consider existing or develop new technologies to become more innovative to meet the emerging environmental demands and green competitiveness strategies. This study also contributes to our understanding of how Eco-Innovation affects guest satisfaction and repeat patronage in the hotel image. The practical and theoretical implications of the findings provide guidance to managers in the hotel industry.
Electronic skin sensing devices are an emerging technology and have substantial demand in vast practical fields including wearable sensing, robotics, and user‐interactive interfaces. In order to ...imitate or even outperform the capabilities of natural skin, the keen exploration of materials, device structures, and new functions is desired. However, the very high resistance and the inadequate current switching and sensitivity of reported electronic skins hinder to further develop and explore the promising uses of the emerging sensing devices. Here, a novel resistive cloth‐based skin‐like sensor device is reported that possesses unprecedented features including ultrahigh current‐switching behavior of ≈107 and giant high sensitivity of 1.04 × 104–6.57 × 106 kPa−1 in a low‐pressure region of <3 kPa. Notably, both superior features can be achieved by a very low working voltage of 0.1 V. Taking these remarkable traits, the device not only exhibits excellent sensing abilities to various mechanical forces, meeting various applications required for skin‐like sensors, but also demonstrates a unique competence to facile integration with other functional devices for various purposes with ultrasensitive capabilities. Therefore, the new methodologies presented here enable to greatly enlarge and advance the development of versatile electronic skin applications.
A newly designed cloth‐based resistive electronic skin features ultrahigh current switching of ≈107 and extremely high sensitivity of 1.04 × 104–6.57 × 106 kPa–1 at pressures <3 kPa. And, notably, both features are achieved by a very low working voltage of 0.1 V. Taking these traits, our devices not only function as ultrasensitive sensors but can also be integrated with various functional components for multipurpose uses.
We report a 3.6 nm Ti52–oxo cluster with precise atomic structure, which presents a largest size record in the family of titanium–oxo clusters (TOCs). The crystal growth of such large Ti52 is based ...on a stepwise interlayer assembly approach from Ti6 substructures. The possible growth mechanism of Ti52 could be deduced from crystal structures of two substructures, Ti6 and Ti17, which were also synthesized under similar conditions as Ti52. Moreover, these TOCs show cluster-size-dependent photocatalytic hydrogen evolution activities with Ti52 giving a H2 production rate up to 398 μmol/h/g, which is also the highest record in the family of TOCs. This work not only represents a milestone in constructing large TOCs with comparable sizes as TiO2 nanoparticles but also brings significant advances in improving photocatalytic behaviors of TOCs.
The perovskite CH3NH3PbI3 excited‐state lifetimes exhibit conflicting experimental results under humid environments. Using ab initio nonadiabatic (NA) molecular dynamics, we demonstrate that the ...interplay between lead vacancy and water can rationalize the puzzle. The lead vacancy reduces NA coupling by localizing holes, slowing electron–hole recombination. By creating a deep electron trap state, the coexistence of a neutral lead vacancy and water molecules enhances NA coupling, accelerating charge recombination by a factor of over 3. By eliminating the mid‐gap state by accepting two photoexcited electrons, the negatively charged lead vacancy interacting with water molecules increases the carrier lifetime over 2 times longer than in the pristine system. The simulations rationalize the positive and negative effects of water on the solar cell performance exposure to humidity.
The interplay between lead vacancy and water rationalizes the positive and negative effects of water on the charge carrier lifetimes in the organic–inorganic perovskite MAPbI3. The obtained results provide a theoretical understanding of how the complex charge dynamics in perovskites are affected by defects and water.
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