Molecule‐based micro‐/nanomaterials have attracted considerable attention because their properties can vary greatly from the corresponding macro‐sized bulk systems. Recently, the construction of ...multicomponent molecular solids based on crystal engineering principles has emerged as a promising alternative way to develop micro‐/nanomaterials. Unlike single‐component materials, the resulting multicomponent systems offer the advantages of tunable composition, and adjustable molecular arrangement, and intermolecular interactions within their solid states. The study of these materials also supplies insight into how the crystal structure, molecular components, and micro‐/nanoscale effects can influence the performance of molecular materials. In this review, we describe recent advances and current directions in the assembly and applications of crystalline multicomponent micro‐/nanostructures. Firstly, the design strategies for multicomponent systems based on molecular recognition and crystal engineering principles are introduced. Attention is then focused on the methods of fabrication of low‐dimensional multicomponent micro‐/nanostructures. Their new applications are also outlined. Finally, we briefly discuss perspectives for the further development of these molecular crystalline micro‐/nanomaterials.
Small design: The formation of multicomponent materials based on molecular recognition and self‐assembly has emerged as a strategy for the design and fabrication of molecule‐based micro‐/nanomaterials with tunable composition, crystal structures, solid‐state morphologies and properties.
Glassy materials, with desirable mechanical rigidity, shaping ability, high transparency, are attracting great interest in diverse fields. However, optically bulk molecule‐based glasses are still ...rare, mainly due to limited monomeric species and harsh preparation conditions. Herein, we report a facile bottom‐up solution fabrication process to obtain metal‐free supramolecular glasses (SMGs) at the macroscopic scale using L‐Histidine and hexamethylenetetramine as building blocks. The chiral SMGs possess color‐tunable ultralong room temperature phosphorescence (decay lifetime up to 141.2 ms) and circular polarized luminescence (g factor up to 8.7×10−3). The strong hydrogen bonds effectively drive the formation of SMGs, and provide a rigid microenvironment to boost triplet exciton generation. By virtue of excitation‐ and temperature‐dependent ultralong phosphorescence of the SMGs, applications including multicolored displays, visual UV detection, and persistently luminescent thermometer are demonstrated.
Large‐sized chiral metal‐free supramolecular glasses using L‐histidine and hexamethylenetetramine as the building blocks can be obtained through a facile solution fabrication process. Visible color‐tunable ultralong room temperature phosphorescence emissions are successfully realized in these glasses (namely L‐H‐M and L‐H‐M‐AC). AC: acetonitrile; R.T.: room temperature; UV: Ultra Violet.
The excited‐state tuning of luminescent metal–organic compounds has made great progress in the fields of optical imaging, photocatalysis, photodynamic therapy, light‐emitting devices, sensors, and so ...on. Although metal–organic compounds with high luminescence efficiency can be realized via enhanced molecular rigidity and heavy‐atom effect, their corresponding luminescence lifetimes are still limited on the order of a nanosecond to a millisecond, owing to the inherent competition between luminous efficiency and lifetime. Therefore, the advanced applications (i.e., persistent afterglow imaging, information security, anti‐counterfeiting, and smart materials, among others) related with long persistent luminescence (LPL, typically with the excited‐state lifetime larger than millisecond) are seriously hindered. This review gives a timely and systematic summary of metal–organic compounds for realizing room‐temperature phosphorescence (RTP)‐type and thermally activated delayed fluorescence (TADF)‐type LPL during last few years. Particularly, based on the perspectives of time, space, and energy dimensions, fundamental materials design and coordination assembly are systematically described for the first time. Moreover, the internal and external factors of influencing the LPL properties in terms of luminescence efficiency, lifetime, and color are illustrated. Last but not least, perspectives and challenges are also discussed for developing LPL from metal–organic compounds.
This review systematically summarizes the latest progress of metal–organic compounds (infinite and discrete structures) for realizing room‐temperature phosphorescence (RTP)‐type and thermally activated delayed fluorescence (TADF)‐type long persistent luminescence, which provides helpful guidance for developing this promising field with respect to the mechanism of structure–property relationship, optimization of luminescent performance, and extension of practical applications.
The oxygen evolution reaction (OER), as an important process involved in water splitting and rechargeable metal–air batteries, has drawn increasing attention in the context of clean energy generation ...and efficient energy storage. This review concerns the progress and new discoveries in the field of Ni/Fe‐based micro/nanostructures toward electrochemical and photo‐electrochemical (PEC) water oxidation during last few years. First, toward the design and construction of new electrocatalysis, different types of current Ni/Fe‐based compounds for OER are summarized. The mechanism studies of the active phases and positions of Ni/Fe‐based micro/nanostructures are further introduced to understand the properties of catalytic active sites, which could facilitate further improving the performance of Ni/Fe‐based OER electrocatalysts. Second, splitting water using sunlight with low overpotential is another important target in making solar‐to‐hydrogen micro/nanodevices, and thus attention is then focused on the development of several important Ni/Fe‐based PEC catalysts. Third, the recent theoretical calculations on the OER mechanism during water splitting and insights into electronic structures are analyzed; finally, the future trends and perspectives are also discussed briefly.
The oxygen evolution reaction, as an important process involved in water splitting and rechargeable metal–air batteries, has drawn increasing attention in the context of clean energy generation and efficient energy storage. This review concerns the progress and new discoveries in the field of design of Ni/Fe‐based micro/nanostructures toward electrochemical and photo‐electrochemical water oxidation during the last few years.
Molecular room‐temperature phosphorescent (RTP) materials with long‐lived excited states have attracted widespread attention in the fields of optical imaging, displays, and sensors. However, ...accessing ultralong RTP systems remains challenging and examples are still limited to date. Herein, a thermally activated delayed fluorescence (TADF)‐assisted energy transfer route for the enhancement of persistent luminescence with an RTP lifetime as high as 2 s, which is higher than that of most state‐of‐the‐art RTP materials, is proposed. The energy transfer donor and acceptor species are based on the TADF and RTP molecules, which can be self‐assembled into two‐component ionic salts via hydrogen‐bonding interactions. Both theoretical and experimental studies illustrate the occurrence of effective Förster resonance energy transfer (FRET) between donor and acceptor molecules with an energy transfer efficiency as high as 76%. Moreover, the potential for application of the donor–acceptor cocrystallized materials toward information security and personal identification systems is demonstrated, benefitting from their varied afterglow lifetimes and easy recognition in the darkness. Therefore, the work described in this study not only provides a TADF‐assisted FRET strategy toward the construction of ultralong RTP, but also yields hydrogen‐bonding‐assembled two‐component molecular crystals for potential encryption and anti‐counterfeiting applications.
Two‐component co‐crystallized materials formed by melamine and isophthalic acid through hydrogen‐bonding exhibit ultralong room temperature phosphorescence (RTP) with a lifetime of 2 seconds, which has been further designed for encryption and finger identification. Effective energy transfer occurs between melamine (thermally activated delayed fluorescence molecule) and isophtalic acid, like carriers in traps triggered by thermal excitation in inorganic persistent phosphors.
The development of high-efficiency electrocatalysts for oxygen evolution reactions (OERs) plays an important role in the water-splitting process. Herein, we report a facile way to obtain ...two-dimensional (2D) single-unit-cell-thick layered double hydroxide (LDH) nanosheets (NSs, ∼1.3 nm) within only 5 min. These nanosheets presented significantly enhanced OER performance compared to bulk LDH systems fabricated using the conventional co-precipitation method. The current strategy further allowed control over the chemical compositions and electrochemical activities of the LDH NSs. For example, CoFe-LDH NSs presented the lowest overpotential of 0.28 V at 10 mA/cm
2
, and the NiFe-LDHs NSs showed Tafel slopes of 33.4 mV/decade and nearly 100% faradaic efficiency, thus outperforming state-of-the-art IrO
2
water electrolysis catalysts. Moreover, positron annihilation lifetime spectroscopy and high-resolution transmission electron microscopy observations confirmed that rich defects and distorted lattices occurred within the 2D LDH NSs, which could supply abundant electrochemically active OER sites. Periodic calculations based on density functional theory (DFT) further showed that the CoFe- and NiFe-LDHs presented very low energy gaps and obvious spin-polarization behavior, which facilitated high electron mobility during the OER process. Therefore, this work presents a combined experimental and theoretical study on 2D single-unit-cell-thick LDH NSs with high OER activities, which have potential application in water splitting for renewable energy.
Information security of photonic communications has become an important societal issue and can be greatly improved when photonic signals are propagated through active waveguides with tunable ...wavelengths in different time and space domains. Moreover, the development of active waveguides that can work efficiently at extreme temperatures is highly desirable but remains a challenge. Herein, we report new types of low-dimensional Zn(
ii
)-organic halide microcrystals with fluorescence and room-temperature phosphorescence (RTP) dual emission for use as 1D color-tunable active waveguides. Benefiting from strong intermolecular interactions (
i.e.
, hydrogen bonds and π-π interactions), these robust waveguide systems exhibit colorful photonic signals and structural stability at a wide range of extreme simulated temperatures (>300 K), that covers natural conditions on Earth, Mars, and the Moon. Both experimental and theoretical studies demonstrate that the molecular self-assembly can regulate the singlet and triplet excitons to allow thermally assisted spectral separation of fluorescence and RTP, in combination with the single-component standard white-light emission. Therefore, this work demonstrates the first use of metal-organic halide microcrystals as temperature-gating active waveguides with promising implications for high-security information communications and high-resolution micro/nanophotonics.
1D zinc-organic halide microcrystals exhibiting thermally assisted spectral separation of fluorescence and phosphorescence could be used as single-component standard white-light and temperature-gating active waveguides.
Molecular solid‐state materials with long‐lived luminescence (such as thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) systems) are promising for display, ...sensoring, and bio‐imaging applications. However, the design of such materials that exhibit both long luminescent lifetime and high solid‐state emissive efficiency remains an open challenge. Two‐dimensional (2D) organic–metal halide perovskite materials have a high blue‐emitting quantum yield of up to 63.55 % and ultralong TADF lifetime of 103.12 ms at ambient temperature and atmosphere. Our design leverages the combined influences of a 2D space/electronic confinement effect and a modest heavy‐atom tuning strategy. Photophysical studies and calculations reveal that the enhanced quantum yield is due to the rigid laminate structure of perovskites, which can effectively inhibit the non‐radiative decay of excitons.
All aglow: Organic–metal halide perovskite materials present a high blue photoluminesence quantum yield of up to 63.55 %, an ultralong TADF lifetime of 103.12 ms, and optical waveguide properties. These endow the 2D perovskite micro/nanosheets with both space and time dual‐resolved visible luminescence.
Materials with ultralong phosphorescence have wide-ranging application prospects in biological imaging, light-emitting devices, and anti-counterfeiting. Usually, molecular phosphorescence is ...significantly quenched with increasing temperature, rendering it difficult to achieve high-efficiency and ultralong room temperature phosphorescence. Herein, we spearhead this challenging effort to design thermal-quenching resistant phosphorescent materials based on an effective intermediate energy buffer and energy transfer route. Co-crystallized assembly of zero-dimensional metal halide organic-inorganic hybrids enables ultralong room temperature phosphorescence of (Ph
P)
Cd
Br
that maintains luminescent stability across a wide temperature range from 100 to 320 K (ΔT = 220 °C) with the room temperature phosphorescence quantum yield of 62.79% and lifetime of 37.85 ms, which exceeds those of other state-of-the-art systems. Therefore, this work not only describes a design for thermal-quenching-resistant luminescent materials with high efficiency, but also demonstrates an effective way to obtain intelligent systems with long-lasting room temperature phosphorescence for optical storage and logic compilation applications.
Smart molecular crystals with light‐driven mechanical responses have received interest owing to their potential uses in molecular machines, artificial muscles, and biomimetics. However, challenges ...remain in control over both the dynamic photo‐mechanical behaviors and static photonic properties of molecular crystals based on the same molecule. Herein, we show the construction of isostructural co‐crystals allows their light‐induced cracking and jumping behaviors (photosalient effect) to be controlled. Hydrogen‐bonded co‐crystals from 4‐(1‐naphthylvinyl)pyridine (NVP) with co‐formers (tetrafluoro‐4‐hydroxybenzoic acid (THA) and tetrafluorobenzoic acid (TA)) crystallize as isostructural crystals, but have different static and dynamic photo‐mechanical behaviors. These differences are due to alternations in the orientation of NVP and hydrogen‐bonding modes of the co‐formers. After light activation, the 1D NVP‐TA crystal splits and shears off within 1 s. For NVP‐THA, its photostability and high quantum yield give novel photonic properties, including low optical waveguide loss, highly polarized anisotropy, and efficient up‐conversion fluorescence.
Two 1D isostructural hydrogen‐bonded molecular cocrystals have light‐induced dynamic movement and static photonic properties, which can be attributed to the alternations of the geometric orientation of photoactive molecules and hydrogen‐bonding modes within the co‐assembled units.
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