Gold nanoclusters (Au NCs) stand for a new type of fluorescent nanomaterials with outstanding optical properties due to their discrete electronic energy and direct electron transition. However, relative low quantum yield (QY) of Au NCs in aqueous or solid state has limited their photofunctional applications. To improve the fluorescent performances of Au NCs and find an effective approach for the fabrication of Au NCs-based films, in this work, Au NCs are localized onto 2D layered double hydroxides (LDHs) nanosheets via a layer-by-layer assembly process; the as-fabricated (Au NCs/LDH)_n ultrathin films (UTFs) show an ordered and dense immobilization of Au NCs. The localization and confinement effects imposed by LDH nanosheets induce significantly increased emissive Au(I) units as confirmed by X-ray photoelectron spectroscopy and periodic density functional theoretical simulation, which further results in promoted QY (from 2.69% to 14.11%) and prolonged fluorescence lifetime (from 1.84 µs to 14.67 µs). Moreover, the ordered (Au NCs/LDH)_n UTFs exhibit well-defined temperature-dependent photoluminescence (PL) and electrochemiluminescence (ECL) responses. Therefore, this work supplies a facile strategy to achieve the immobilization of Au NCs and obtain Au NCs-based thin films with high luminescent properties, which have potential applications in PL and ECL temperature sensors.

Development of electrode materials with well-defined architectures is a fruitful and profitable approach for achieving highly-efficient energy storage systems. A molecular-scale hybrid system is presented based on the self-assembly of CoNi-layered double hydroxide (CoNi-LDH) monolayers and the conducting polymer (poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate), denoted as PEDOT:PSS) into an alternating-layer superlattice. Owing to the homogeneous interface and intimate interaction, the resulting CoNi-LDH/PEDOT:PSS hybrid materials possess a simultaneous enhancement in ion and charge-carrier transport and exhibit improved capacitive properties with a high specific capacitance (960 F g^–1 at 2 A g^–1) and excellent rate capability (83.7% retention at 30 A g^–1). In addition, an in-plane supercapacitor device with an interdigital design is fabricated based on a CoNi-LDH/PEDOT:PSS thin film, delivering a significantly enhanced energy and power output (an energy density of 46.1 Wh kg^–1 at 11.9 kW kg^–1). Its application in miniaturized devices is further demonstrated by successfully driving a photodetector. These characteristics demonstrate that the molecular-scale assembly of LDH monolayers and the conducting polymer is promising for energy storage and conversion applications in miniaturized electronics.

TiO₂@CoAl-layered double hydroxide (LDH) core–shell nanospheres are fabricated via hydrothermal synthesis of TiO₂ hollow nanospheres followed by in situ growth of CoAl-LDH shell, which exhibit an extraordinarily high photocatalytic activity toward oxygen evolution from water oxidation. The O₂ generation rates of 2.34 and 2.24 mmol h⁻¹ g⁻¹ are achieved under full sunlight (>200 nm) and visible light (>420 nm), respectively, which are among the highest photocatalytic activities for oxygen production to date. The reason is attributed to the desirable incorporation of visible- light-active LDH shell with UV light-responsive TiO₂ core for promoted solar energy utilization. Most importantly, the combined experimental results and computational simulations reveal that the strong donor–acceptor coupling and suitable band matching between TiO₂ core and LDH shell facilitate the separation of photoinduced electron-hole pairs, accounting for the highly efficient photocatalytic performance. Therefore, this work provides a facile and cost-effective strategy for the design and fabrication of hierarchical semiconductor materials, which can be applied as photocatalyst toward water splitting and solar energy conversion.

The selective hydrogenation of benzene to cyclohexene is of high value for the chemical industry owing to its inexpensive feedstock, atom economy, and operational simplicity. A tunable catalytic behavior towards the selective hydrogenation of benzene was obtained over Cu-decorated Ru catalysts supported on a layered double hydroxide (denoted as Ru_xCu_y/MgAl-LDH), reaching a maximum cyclohexene yield of 44.0 % over Ru_1.0Cu_0.5/MgAl-LDH at 150 °C and 5.0 MPa without employment of any additives. CO-TPD (TPD=temperature-programmed desorption) and in situ CO-FTIR techniques demonstrated that Cu atoms preferentially deposit on the surface of low-coordinated Ru atoms in Ru_xCu_y/MgAl-LDH catalysts, resulting in a low adsorption energy of cyclohexene on the modified sites as revealed by DFT calculations. This work not only gives an understanding of the correlation between the surface exposure of Ru active sites and the resulting selectivity, but also provides a green and additive-free catalytic process for the selective hydrogenation of benzene.

Well-aligned hierarchical nanoarrays containing ZnO core and layered double hydroxide (LDH) nanoplatelets shell have been synthesized via a facile electrosynthesis method. The resulting ZnO@CoNi–LDH core−shell nanoarray exhibits promising behavior in photoelectrochemical water splitting, giving rise to a largely enhanced photocurrent density as well as stability; much superior to those of ZnO-based photoelectrodes. This is attributed to the successful integration of photogenerated electron–hole separation originating from the ZnO core and the excellent electrocatalytic activity of LDH shell. This work provides a facile and cost-effective strategy for the fabrication of multifunctional nanoarrays with a hierarchical structure, which can be potentially used in energy storage and conversion devices.

A hierarchical nanostructure composed of NiMn-layered double hydroxide (NiMn-LDH) microcrystals grafted on carbon nanotube (CNT) backbone is constructed by an in situ growth route, which exhibits superior supercapacitive performance. The resulting composite material (NiMn-LDH/CNT) displays a three-dimensional architecture with tunable Ni/Mn ratio, well-defined core-shell configuration, and enlarged surface area. An electrochemical investigation shows that the Ni₃Mn₁-LDH/CNT electrode is rather active, which delivers a maximum specific capacitance of 2960 F g^–1 (at 1.5 A g^–1), excellent rate capability (79.5% retention at 30 A g^–1), and cyclic stability. Moreover, an all-solid-state asymmetric supercapacitor (SC) with good flexibility is fabricated by using the NiMn-LDH/CNT film and reduced graphene oxide (RGO)/CNT film as the positive and negative electrode, respectively, exhibiting a wide cell voltage of 1.7 V and largely enhanced energy density up to 88.3 Wh kg^–1 (based on the total weight of the device). By virtue of the high-capacity of pseudocapacitive hydroxides and desirable conductivity of carbon-based materials, the monolithic design demonstrated in this work provides a promising approach for the development of flexible energy storage systems.

A supermolecular photosensitizer with excellent anticancer behavior when used for photodynamic therapy (PDT) is fabricated by the incorporation of zinc phthalocyanines (ZnPc) into the gallery of a layered double hydroxide (LDH). The composite material possesses uniform particle size (hydrodynamic diameter ∼120 nm), and the host–guest and guest–guest interactions result in a high dispersion of ZnPc in a monomeric state in the interlayer region of the LDH matrix, with high singlet oxygen production efficiency. In vitro tests performed with HepG2 cells reveal a satisfactory PDT effectiveness of the ZnPc(1.5%)/LDH composite photosensitizer: a cellular damage as high as 85.7% is achieved with a rather low dosage of ZnPc (10 μg/mL). An extraordinarily high specific efficacy is demonstrated (31.59 μg⁻¹ (J/cm²)⁻¹), which is over 185.5% enhancement compared with the previously reported photosensitizers under similar test conditions. Furthermore, an in vivo study of the ZnPc(1.5%)/LDH demonstrates excellent PDT performance with an ultra-low dose (0.3 mg/kg) and a low optical fluence rate (54 J/cm²). In addition, the ZnPc/LDH photosensitizer displays high stability, good biocompatibility, and low cytotoxicity, which would guarantee its practical application. Therefore, this work provides a facile approach for design and fabrication of inorganic–organic supermolecular materials with greatly enhanced anticancer behavior.

Transparent and flexible multilayer films are fabricated based on the alternating assembly of cellulose acetate (CA) and layered double hydroxide (LDH) nanoplatelets followed by thermal annealing treatment. The films exhibit tremendously enhanced oxygen barrier properties. The oxygen transmission rate (OTR) of the resulting (CA/LDH)_n multilayer films can be tuned by changing the aspect ratio of high-crystalline LDH nanoplatelets from 20 to 560. The (CA/LDH)₂₀ film displays excellent oxygen-barrier behavior with an OTR equal to or below the detection limit of commercial instrumentation (<0.005 cm³ m⁻² day⁻¹), much superior to the previously reported inorganic flake-filled barrier film. Molecular dynamics simulations reveal that a hydrogen bonding network occurs at the interface of highly oriented LDH nanoplatelets and CA molecules, accounting for the suppression of oxygen transportation and the resulting largely improved barrier behavior. In addition, the durability of (CA/LDH)_n films against humidity, temperature, and light irradiation is successfully demonstrated, which would guarantee their practical application. Therefore, this work provides a facile and cost-effective strategy for the fabrication of an LDH-based oxygen barrier material, which could potentially be used in flexible displays and drug and food packaging.

The chemoselective hydrogenation of alkyne is of great importance in the chemical industry, in which intermetallic compounds (IMCs) have attracted extensive interest as efficient catalysts. Herein, we demonstrate the preparation of several supported Ni–Ga IMCs (Ni₃Ga, Ni₅Ga₃, and NiGa) via a facile in situ reduction of layered double hydroxide (LDH) precursors, which demonstrate significantly improved catalytic activity and selectivity for the selective hydrogenation of phenylacetylene to styrene. The composition and particle size of Ni–Ga IMCs can be tuned by adjusting the Ni/Ga ratio or reduction temperature during the topotactic transformation process of LDHs, and the best catalytic behavior can be obtained over the Ni₃Ga IMC with a styrene yield of 87.7 % (particle size=7.2 nm at 40 °C and 0.3 MPa), which is better than that of most of the reported Ni catalysts. The X-ray absorption fine-structure characterization and DFT calculations reveal the electron transfer from Ga to Ni and active-site isolation by Ga in Ni–Ga IMCs, which account for the excellent hydrogenation selectivity. The significantly improved catalytic performance makes Ni–Ga IMC catalysts promising candidates for the selective hydrogenation of alkyne.

Hierarchical MgFe-layered double hydroxide (LDH) microspheres with tunable interior structure are synthesized by a facile and cost-effective surfactant-templated method. Scanning and transmission electron microscopy images reveal that the obtained microspheres display a three-dimensional architecture with hollow, yolk−shell and solid interior structure, respectively, with continuous changes in specific surface area and pore-size distribution. Moreover, the hollow MgFe-LDH microspheres exhibit excellent electrocatalytic oxidation of ethanol in alkaline fuel cell, including high activity, long-term durability and cycling stability, owing to the significantly improved faradaic redox reaction and mass transport. Therefore, this work provides a promising approach for the design and synthesis of structure tunable materials with largely enhanced ethanol electrooxidation behavior, which can be potentially used in noble metal-free alkaline fuel cells.

The combination of magnetic particles and layered double hydroxide (LDHs) materials leads to the formation of hierarchical composites that can take full advantages of each component; this is an effective approach for achieving multifunctional materials with intriguing properties. This Concept article summarizes several important strategies for the fabrication of magnetic-core/LDH-shell hierarchical nanocomposites, including direct coprecipitation, layer-by-layer assembly, and in situ growth methods. The obtained nanocomposites exhibit excellent performance as multifunctional materials for promising applications in targeted drug delivery, efficient separation, and catalysis. The fabrication and application of magnetic-core/LDH-shell nanocomposite materials represent a new direction in the development of LDH-based multifunctional materials, which will contribute to the progress of chemistry and material science.

Quantum dots (QDs) luminescent films have broad applications in optoelectronics, solid-state light-emitting diodes (LEDs), and optical devices. This work reports the fabrication of multicolor-light-emitting ultrathin films (UTFs) with 2D architecture based on CdTe QDs and MgAl layered double hydroxide (LDH) nanosheets via the layer-by-layer deposition technique. The hybrid UTFs possess periodic layered structure, which is verified by X-ray diffraction. Tunable light emission in the red-green region is obtained by changing the particle size of QDs (CdTe-535 QDs and CdTe-635 QDs with green and red emision respectively), assembly cycle number, and sequence. Moreover, energy transfer between CdTe-535 QDs and CdTe-635 QDs occurs based on the fluorescence resonance energy transfer (FRET), which greatly enhances the fluorescence efficiency of CdTe-635 QDs. In addition, a theoretical study based on the Förster theory and molecular dynamics (MD) simulations demonstrates that CdTe QDs/LDH UTFs exhibit superior capability of energy transfer owing to the ordered dispersion of QDs in the 2D LDH matrix, which agrees well with the experimental results. Therefore, this provides a facile approach for the design and fabrication of inorganic-inorganic luminescent UTFs with largely enhanced luminescence efficiency as well as stability, which can be potentially applied in multicolor optical and optoelectronic devices.

A family of photocatalysts for water splitting into hydrogen was prepared by distributing TiO₆ units in an MTi-layered double hydroxide matrix (M=Ni, Zn, Mg) that displays largely enhanced photocatalytic activity with an H₂-production rate of 31.4 μmol h⁻¹ as well as excellent recyclable performance. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) mapping and XPS measurement reveal that a high dispersion of TiO₆ octahedra in the layered doubled hydroxide (LDH) matrix was obtained by the formation of an M²⁺-O-Ti network, rather different from the aggregation state of TiO₆ in the inorganic layered material K₂Ti₄O₉. Both transient absorption and photoluminescence spectra demonstrate that the electron–hole recombination process was significantly depressed in the Ti-containing LDH materials relative to bulk Ti oxide, which is attributed to the abundant surface defects that serve as trapping sites for photogenerated electrons verified by positron annihilation and extended X-ray absorption fine structure (EXAFS) techniques. In addition, a theoretical study on the basis of DFT calculations demonstrates that the electronic structure of the TiO₆ units was modified by the adjacent MO₆ octahedron by means of covalent interactions, with a much decreased bandgap of 2.1 eV, which accounts for its superior water-splitting behavior. Therefore, the dispersion strategy for TiO₆ units within a 2D inorganic matrix can be extended to fabricate other oxide or hydroxide catalysts with greatly enhanced performance in photocatalysis and energy conversion.

Multicolor luminescent films have great potential for use in optoelectronics, solid-state light-emitting materials, and optical devices. This work describes a systematic investigation of the ordered assembly of two- (blue/green, blue/orange, red/blue, red/green) and three-color (blue/red/green) light-emitting ultrathin films (UTFs) by using different photofunctional anions [bis(N-methylacridinium)@polyvinylsulfonate ion pairs and anionic derivatives of poly(p-phenylene), poly(phenylenevinylene), and poly(thiophene)] and Mg-Al-layered double hydroxide nanosheets as building blocks. The rational combination of luminescent components affords precise control of the emission wavelengths and intensity, and multicolored luminescent UTFs can be precisely tailored covering most of the visible spectral region. The assembly process of the UTFs and their luminescence properties, as monitored by UV–vis absorption and fluorescence spectroscopy, resulted in a gradual change in luminescence color in the selected light-emitting spectral region upon increasing the number of deposition cycles. X-ray diffraction demonstrates that the UTFs are periodic layered structures involving heterogeneous superlattices associated with individual photoactive anion–LDH units. These UTFs also exhibit well-defined multicolor polarized fluorescence with high polarization anisotropy, and the emissive color changes with polarization direction. Therefore, this work provides a way of fabricating heterogeneous UTFs with tunable-color luminescence as well as polarized multicolor emission, which have potential applications in the areas of light displays and optoelectronic devices.

The composite of carboxymethyl-modified β-cyclodextrin-intercalated ZnAl-layered double hydroxide (CMCD-LDH) was investigated for selective adsorption of phenol (Ph) and nitrobenzene (NB). The Freundlich model can be used to describe satisfactorily the adsorption isotherms of Ph and NB. The adsorption capacity of CMCD-LDH for Ph and NB increases with the increase of temperature, indicating the endothermic nature of this sorption process. CMCD-LDH exhibits preferential adsorption for Ph over NB at pH 6.5 due to the selective recognition of the interlayer CMCD cavity. Pseudo-first-order and pseudo-second-order kinetic models were applied to simulate the kinetics of the adsorption process. The calculated q_e values based on the pseudo-second-order model are much closer to the experimental data q_e,exp. As a result, the pseudo-second-order kinetic model is more reasonable to describe the adsorption process of Ph and NB onto the CMCD-LDH composite. CMCD-LDH can be potentially applied in selective adsorption and separation of wastewater pollutants.

The preparation of a highly oriented photoluminescent film of fluorescein (FLU) and 1-heptanesulfonic acid sodium (HES) co-intercalated in a layered double hydroxide (LDH) matrix by electrophoretic deposition (EPD) is reported, and its application as an optical pH sensor is demonstrated. The FLU-HES/LDH films with thickness ranging from nanometer to micrometer on indium tin oxide substrates exhibite good c-orientation of LDH platelets (the ab-plane of the LDH platelets parallel to the substrate), as confirmed by X-ray diffraction and scanning electron microscopy. Polarized luminescence of the film is observed with anisotropy value r = 0.29, resulting from the highly oriented FLU in the LDH gallery. Furthermore, the optical pH sensor with film thickness of 300 nm exhibits a broad linear dynamic range for solution pH (5.02–8.54), good repeatability (relative standard deviation (RSD) less than 1.5% in 20 consecutive cycles) and reversibility (RSD less than 1.5% in 20 cycles), high photostability and storage stability (ca. 95.2% of its initial fluorescence intensity remains after one month) as well as fast response time (2 s). Therefore, this work creates new opportunities for the preparation and application of LDH-based chromophores in the field of optical sensors.

A film of carboxymethyl-β-cyclodextrin-intercalated Zn–Al layered double hydroxide (CMCD–LDH) was investigated for selective adsorption of the nucleosides adenosine (A) and guanosine (G). The effects of pH value and adsorption time on the adsorption behavior were studied. The CMCD–LDH film shows a higher selectivity for G than A under identical conditions of G and A, which results from the ability of selective recognition of the interlayer CMCD. The kinetic studies show that adsorption of A and G by the CMCD–LDH film can be described satisfactorily by the slab diffusion model. Both the values of diffusion coefficient (D) and adsorption capability (q_e) of G by the CMCD–LDH film are larger than those of A, demonstrating the selective adsorption of the CMCD–LDH film for nucleosides. Due to its easy preparation and manipulation, this film is expected to be successfully applied in the field of selective adsorption and separation.