Luminescent metal–organic framework films, CPM-5⊃Tb3+ and MIL-100(In)⊃Tb3+, have been constructed by postfunctionalization of two porous indium–organic frameworks with different structures, ...respectively. The MIL-100(In)⊃Tb3+ film shows high oxygen sensitivity (K SV = 7.59) and short response/recovery time (6 s/53 s).
Pt epitaxial layer on a nanoparticle with twinned structure and well-defined shape is highly desirable in order to achieve high performance in both catalytic activity and durability toward oxygen ...reduction reaction (ORR). However, it remains tremendously challenging to produce conformal, heterogeneous, twinned nanostructures due to the high internal strain and surface energy of Pt. In addition, these twinned nanostructures may be subject to degradation in highly corrosive ORR environments due to the high energy of twin boundary. Here we report the synthesis of Au–Pt core–shell star-shaped decahedra bounded mainly by {111} facets, in which Pt shells with controlled thickness epitaxially grew on Au cores with a 5-fold twinned structure. The incorporation of the amine group decreases the surface energy of Pt by strong adsorption and thus facilitates the epitaxial growth of Pt on Au core instead of the dendritic growth. In addition, Br– ion could largely stabilize the {111} facets of Pt, which prevent the formation of spherical nanoparticles. The Au–Pt core–shell decahedra with thicker Pt shell exhibited enhanced ORR properties in terms of activity and durability. Specifically, AuPt1.03 star-shaped decahedra achieved the highest mass activity (0.94 mA/μgPt) and area activity (1.09 mA/cm2 Pt), which is ∼6.7 and 5 times, respectively, as high as those of the commercial Pt/C (ETEK). Significantly, such star-shaped decahedra were highly stable with ∼10% loss in area activity and ∼20% loss in mass activity after 30 000 CV cycles in O2 saturated acid solution.
At the forefront of nanochemistry, there exists a research endeavor centered around intermetallic nanocrystals, which are unique in terms of long‐range atomic ordering, well‐defined stoichiometry, ...and controlled crystal structure. In contrast to alloy nanocrystals with no elemental ordering, it is challenging to synthesize intermetallic nanocrystals with a tight control over their size and shape. Here, recent progress in the synthesis of intermetallic nanocrystals with controllable sizes and well‐defined shapes is highlighted. A simple analysis and some insights key to the selection of experimental conditions for generating intermetallic nanocrystals are presented, followed by examples to highlight the viable use of intermetallic nanocrystals as electrocatalysts or catalysts for various reactions, with a focus on the enhanced performance relative to their alloy counterparts that lack elemental ordering. Within the conclusion, perspectives on future developments in the context of synthetic control, structure–property relationships, and applications are discussed.
Intermetallic nanocrystals are superior catalysts over their alloy counterparts with the same composition but a disordered atomic structure. An account of recent progress in the development of intermetallic nanocrystals with enhanced catalytic properties for various applications is presented.
Highly sensitive photodetection even approaching the single-photon level is critical to many important applications. Graphene-based hybrid phototransistors are particularly promising for ...high-sensitivity photodetection because they have high photoconductive gain due to the high mobility of graphene. Given their remarkable optoelectronic properties and solution-based processing, colloidal quantum dots (QDs) have been preferentially used to fabricate graphene-based hybrid phototransistors. However, the resulting QD/graphene hybrid phototransistors face the challenge of extending the photodetection into the technologically important mid-infrared (MIR) region. Here, we demonstrate the highly sensitive MIR photodetection of QD/graphene hybrid phototransistors by using plasmonic silicon (Si) QDs doped with boron (B). The localized surface plasmon resonance (LSPR) of B-doped Si QDs enhances the MIR absorption of graphene. The electron-transition-based optical absorption of B-doped Si QDs in the ultraviolet (UV) to near-infrared (NIR) region additionally leads to photogating for graphene. The resulting UV-to-MIR ultrabroadband photodetection of our QD/graphene hybrid phototransistors features ultrahigh responsivity (up to ∼109 A/W), gain (up to ∼1012), and specific detectivity (up to ∼1013 Jones).
Tin dioxide (SnO2) has been demonstrated as an effective electron-transporting layer (ETL) for attaining high-performance perovskite solar cells (PSCs). However, the numerous trap states in ...low-temperature solution processed SnO2 will reduce the PSCs performance and result in serious hysteresis. Here, we report a strategy to improve the electronic properties in SnO2 through a facile treatment of the films with adding a small amount of graphene quantum dots (GQDs). We demonstrate that the photogenerated electrons in GQDs can transfer to the conduction band of SnO2. The transferred electrons from the GQDs will effectively fill the electron traps as well as improve the conductivity of SnO2, which is beneficial for improving the electron extraction efficiency and reducing the recombination at the ETLs/perovskite interface. The device fabricated with SnO2:GQDs could reach an average power conversion efficiency (PCE) of 19.2 ± 1.0% and a highest steady-state PCE of 20.23% with very little hysteresis. Our study provides an effective way to enhance the performance of perovskite solar cells through improving the electronic properties of SnO2.
Optoelectronic synaptic devices have been attracting increasing attention due to their critical role in the development of neuromorphic computing based on optoelectronic integration. Here we start ...with silicon nanomembrane (Si NM) to fabricate optoelectronic synaptic devices. Organolead halide perovskite (MAPbI3) is exploited to form a hybrid structure with Si NM. We demonstrate that synaptic transistors based on the hybrid structure are very sensitive to optical stimulation with low energy consumption. Synaptic functionalities such as excitatory post-synaptic current (EPSC), paired-pulse facilitation, and transition from short-term memory to long-term memory (LTM) are all successfully mimicked by using these optically stimulated synaptic transistors. The backgate-enabled tunability of the EPSC of these devices further leads to the LTM-based mimicking of visual learning and memory processes under different mood states. This work contributes to the development of Si-based optoelectronic synaptic devices for neuromorphic computing.
Electrochemically converting CO2 molecules into valuable chemicals and fuels opens up a promising route to utilize CO2 source. To overcome the low efficiency and durability that hinder its practical ...applications, tremendous research efforts have been devoted to nano‐level or atomic‐level catalyst design. The advent of metal–organic frameworks (MOFs) provides novel opportunities for CO2 reduction catalysts, which may integrate the respective advantages of traditional catalysts and single‐atom catalysts. In this review, we summarize the recent advances in two‐dimensional (2D) π‐conjugated MOF catalysts and discuss their practical applications in CO2 reduction reaction (CO2RR). First, we systematically introduce the development of electrocatalysts for CO2RR applications. Meanwhile, various types of 2D porphyrin/phthalocyanine‐based MOFs and corresponding electrocatalytic performances arising from active‐site engineering, surface reconstruction, and thickness control are briefly overviewed. Finally, we highlight their major challenges and opportunities facing CO2RR, and hope that this review can offer new insight into MOF catalyst design.
Two‐dimensional (2D) π‐conjugated metal–organic frameworks (MOFs), including 2D porphyrin‐based and phthalocyanine‐based MOFs, integrate the advantages of traditional catalysts and single‐atom catalysts. The ultrathin thickness, fully exposed active center, structural homogeneity, and light‐coupling capacity endow 2D π‐conjugated MOFs with great potential in CO2 reduction reaction (CO2RR). In this review, their development and practical application in CO2RR and photo‐coupled CO2RR are summarized.
This paper presents the large-scale synthesis of SnO2 nanotube arrays on titanium substrate via ZnO nanowire arrays as sacrificial templates. The SnO2 nanotube arrays on titanium substrate feature ...the large surface area, good electronic conductivity, and adhesion with the current collector, leading to the enhanced performance in lithium-ion batteries.
External fields are introduced to catalytic processes to improve catalytic activities. The light field effect plays an important role in electrocatalytic processes, but is not fully understood. Here ...we report a series of photo-coupled electrocatalysts for CO
reduction by mimicking the structure of chlorophyll. The porphyrin-Au catalyst exhibits a high turnover frequency of 37,069 h
at -1.1 V and CO Faradaic efficiency (FE) of 94.2% at -0.9 V. Under visible light, the electrocatalyst reaches similar turnover frequency and FE with potential reduced by ~ 130 mV. Interestingly, the light-induced positive shifts of 20, 100, and 130 mV for porphyrin-Co, porphyrin-Cu, and porphyrin-Au electrocatalysts are consistent with their energy gaps of 0, 1.5, and 1.7 eV, respectively, suggesting the porphyrin not only serves as a ligand but also as a photoswitch to regulate electron transfer pathway to the metal center.
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