Heterostructured metal—organic framework (MOF)‐on‐MOF thin films have the potential to cascade the various properties of different MOF layers in a sequence to produce functions that cannot be ...achieved by single MOF layers. An integration method that relies on van der Waals interactions, and which overcomes the lattice‐matching limits of reported methods, has been developed. The method deposits molecular sieving Cu‐TCPP (TCPP=5,10,15,20‐tetrakis(4‐carboxyphenyl)porphyrin) layers onto semiconductive Cu‐HHTP (HHTP=2,3,6,7,10,11‐hexahydrotriphenylene) layers to obtain highly oriented MOF‐on‐MOF thin films. For the first time, the properties in different MOF layers were cascaded in sequence to synergistically produce an enhanced device function. Cu‐TCPP‐on‐Cu‐HHTP demonstrated excellent selectivity and the highest response to benzene of the reported recoverable chemiresistive sensing materials that are active at room temperature. This method allows integration of MOFs with cascading properties into advanced functional materials.
MOF‐on‐MOF thin films were prepared from Cu‐HHTP (HHTP=hexahydrotriphenylene) and Cu‐TCPP (TCPP=tetrakis(4‐carboxyphenyl)porphyrin frameworks). The properties of the MOF layers cascade to produce functionality not achieved by a single layer. The MOF‐on‐MOF films demonstrate excellent selectivity and the highest response to benzene among reported recoverable chemiresistive sensing materials active at room temperature.
The advent of gravitational-wave and multimessenger astronomy has stimulated research on the formation mechanisms of binary black holes (BBHs) observed by the Laser Interferometer Gravitational-Wave ...Observatory (LIGO)/Virgo. In the literature, the progenitors of these BBHs could be stellar-origin black holes (sBHs) or primordial black holes (PBHs). In this paper, we calculate the stochastic gravitational-wave background (SGWB) from BBHs, covering the astrophysical and primordial scenarios separately, together with the one from binary neutron stars (BNSs). Our results indicate that PBHs contribute a stronger SGWB than that from sBHs, and the total SGWB from both BBHs and BNSs has a high possibility of being detected by the future observing runs of LIGO/Virgo and the Laser Interferometer Space Antenna (LISA). On the other hand, the SGWB from BBHs and BNSs also contributes an additional source of confusion noise to LISA's total noise curve, and then weakens LISA's detection abilities. For instance, the detection of massive black hole binary (MBHB) coalescences is one of the key missions of LISA, and the largest detectable redshift of MBHB mergers can be significantly reduced.
Up to now several gravitational-wave events from the coalescences of black hole binaries have been reported by LIGO/VIRGO, and imply that black holes should have an extended mass function. We work ...out the merger rate distribution of primordial black hole (PBH) binaries with a general mass function by taking into account the torques by all PBHs and linear density perturbations. In the future, many more coalescences of black hole binaries are expected to be detected, and the one-dimensional and two-dimensional merger rate distributions will be crucial for reconstructing the mass function of PBHs.
The current observational constraints still leave a substantial mass window ∼10−16,10−14∪10−13,10−12M⊙ for primordial black holes (PBHs) representing all of dark matter (DM) in our Universe. The ...gravitational waves (GWs) induced by the curvature perturbations are inevitably generated during the formation of these PBHs, and fall in the frequency band of LISA. Such scalar induced gravitational waves (SIGWs) are supposed to be definitely detected by LISA even when the second-order local-type non-Gaussianity characterized by the parameter FNL is taken into account. In this letter, we give a comprehensive analysis of the GWs induced by the local-type non-Gaussian curvature perturbations up to the third-order denoted by the non-linear parameter GNL, and we find that a log-dependent slope of SIGWs in the infrared region is generically predicted and the amplitude of SIGWs can be further suppressed by several orders of magnitude. As a result, the null-detection of SIGWs by LISA cannot rule out the possibility of PBHs making up all of DM.
The development of an effective one‐photon excitation pathway to improve the charge‐carrier separation and mobility of semiconductors, which have been proven to be favorable for heterogeneous ...catalysis, is highly desirable but remains a great challenge. Herein, a high‐throughput one‐photon excitation pathway is reported by constructing 0D carbon dots/3D porous carbon nitride nanovesicles (denoted as CDs/PCN NVs) heterostructures for photocatalytic hydrogen evolution. In particular, the optimum CDs/PCN NVs heterostructures exhibit an impressive performance of 14.022 mmol h−1 g−1, which is 56.54 times higher than that of pristine CN. Detailed characterization reveals that the improved performance is primarily attributed to the high‐throughput and one‐photon excitation pathway. The former could be attributed to a great deal of CDs with high charge‐carrier mobility coupled to PCN NVs, which enable more electrons to be photoexcited via the broad absorption response, and the multiple reflection of incident light owing to the porous nanovesicle structure with shortened route of carriers migrating toward the surface; the latter would lead to the photoinduced holes and electrons accumulated at the valence band of PCN NVs and surface of CDs, respectively, achieving an effective spatial separation. The high‐throughput one‐photon excitation pathway demonstrated here may provide insights into the development of nanocomposites for various related applications.
A high‐throughput one‐photon excitation pathway is reported by constructing 0D carbon dots/3D porous carbon nitride nanovesicles (CDs/PCN NVs) heterostructures for visible‐light driven hydrogen evolution. In particular, the covalently bonded CDs on PCN NVs enable a high throughput charge migration in the wide spectrum visible light region and promote effective spatial separation via a one‐photon excitation pathway.
Inductor-capacitor (LC) passive wireless sensors use a transformer with loose coupling between an external readout coil and an inductor that receives power through this inductive coupling. Changes in ...the sensor are wirelessly and remotely detected by the readout coil, which makes them highly useful in applications that require the sensor to be powered remotely and to occupy a small volume, such as harsh and sealed environments, where physical access to the sensor is difficult. Although the sensor to accomplish this function dates from the 1960's, its rapid extension over the past decades has benefited from microelectromechanical systems. This paper provides an overview of the status and challenges in the LC passive wireless sensor toward a wireless sensing platform. The basic sensing principles are first categorized into detecting changes of the sensor in response to the capacitance, resistance, inductance, or coupling distance due to the parameter of interest through monitoring the impedance magnitude and phase spectrum. The present state of the art in sensor applications for pressure, strain, temperature, humidity, biochemical, gas, and so on is then reviewed and compared. For emerging applications from many Internet of Things scenarios, geometrical constraints, such as small and non-invasive coils, reduce the magnetic coupling between the sensor and the readout coil, resulting in a limited interrogation distance. Furthermore, an increasing number of applications also require the simultaneous measurement of multiple parameters. Recent efforts to increase the interrogation distance and to extend the measurement of single parameter to multiple parameters are finally outlined.
Recent theoretical studies suggest that stellar-mass binary black holes (BBHs) would merge more efficiently due to the Kozai-Lidov (K-L) mechanism if these binaries form in the vicinity of ...supermassive black holes (SMBHs). Since SMBHs are likely rotating rapidly, we continue our earlier study on the generalization of the K-L formalism to include the spin of the SMBH and study the evolution of a nearby BBH. We find that the eccentricity and orbital inclination of the BBH are significantly affected, because the spin (i) forces the orbital plane of the center-of-mass of the BBH around the SMBH to precess (the Lense-Thirring effect) and (ii) imposes an additional gravitomagnetic force on the BBH. As a result, the merger time of the BBH could be significantly different. We calculate the waveform from the BBH in one representative example and study its detectability with a milli-Hertz gravitational-wave detector, such as the Laser Interferometer Space Antenna (LISA). We find that the signal is distinguishable from that in the case without spin. Our results imply that the BBHs in the LISA band could potentially be used to probe the spin of the SMBHs in galaxy centers.
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