"Three Musketeers" Enhances Photodynamic Effects by Reducing Tumor Reactive Oxygen Species Resistance.

Photodynamic therapy (PDT) based on upconversion nanoparticles (UCNPs) has been widely used in the treatment of a variety of tumors. Compared with other therapeutic methods, this treatment has the advantages of high efficiency, strong penetration, and controllable treatment range. PDT kills tumors by generating a large amount of reactive oxygen species (ROS), which causes oxidative stress in the tumor. However, this killing effect is significantly inhibited by the tumor's own resistance to ROS. This is because tumors can either deplete ROS by high concentration of glutathione (GSH) or stimulate autophagy to eliminate ROS-generated damage. Furthermore, the tumor can also consume ROS through the lactic acid metabolic pathway, ultimately hindering therapeutic progress. To address this conundrum, we developed a UCNP-based nanocomposite for enhanced PDT by reducing tumor ROS resistance. First, Ce6-doped SiO2 encapsulated UCNPs to ensure the efficient energy transfer between UCNPs and Ce6. Then, the biodegradable tetrasulfide bond-bridged mesoporous organosilicon (MON) was coated on the outer layer to load chloroquine (CQ) and α-cyano4-hydroxycinnamic acid (CHCA). Finally, hyaluronic acid was utilized to modify the nanomaterials to realize an active-targeting ability. The obtained final product was abbreviated as UCNPs@MON@CQ/CHCA@HA. Under 980 nm laser irradiation, upconverted red light from UCNPs excited Ce6 to produce a large amount of singlet oxygen (1O2), thus achieving efficient PDT. The loaded CQ and CHCA in MON achieved multichannel enhancement of PDT. Specifically, CQ blocked the autophagy process of tumor cells, and CHCA inhibited the uptake of lactic acid by tumor cells. In addition, the coated MON consumed a high level of intracellular GSH. In this way, these three functions complemented each other, just as the "three musketeers" punctured ROS resistance in tumors from multiple angles, and both in vitro and in vivo experiments had demonstrated the elevated PDT efficacy of nanomaterials.

Temperature and pressure-induced excitation-dependent emissions in zero-dimensional hybrid metal halides with mixed halogens.

Zero-dimensional (0D) hybrid metal halides (HMHs) have emerged as a promising platform for exploring excitation-dependent multicolor luminescent materials owing to their diverse crystal structures and chemical compositions. Nevertheless, understanding the mechanism behind excitation-dependent emissions (EDEs) in 0D HMHs and achieving precise modulation remains challenging. In this work, the delicate regulations on the EDE of 0D (DMEDABr)4SnBr3I3 (DMEDA: N, N'-dimethylethylenediamine) with mixed halogens are achieved under low temperature and high pressure, respectively. The inhomogeneous halogen occupation at the atomic scale leads to the formation of Br-rich and I-rich SnX6 (X = Br, I) octahedra, which act as distinct luminescent centers upon photoexcitation. At low temperatures, the narrowed photoluminescence spectra could distinguish the individual emissions from different luminescent centers, resulting in a pronounced EDE of (DMEDABr)4SnBr3I3. In addition, the contraction and distortion of the luminescent SnX6 (X = Br, I) centers at high pressure further result in different degrees of emission shifts, giving rise to the gradual emergence and disappearance of EDE. This work elucidates the underlying mechanism of EDE in 0D HMHs and highlights the crucial role of halogens in determining the optical properties of metal halides.

Manipulating Chiroptical Activities in 0D Chiral Hybrid Manganese Bromides by Solvent Molecular Engineering.

0D hybrid metal halides (0D HMHs) with fully isolated inorganic units provide an ideal platform for studying the correlations between chiroptical activities and crystal structures at atomic levels. Here, through the incorporation of different solvent molecules, a series of 0D chiral manganese bromides (RR/SS-C20H28N2)3MnBr8·2X (X = C2H5OH, CH3OH, or H2O) are synthesized to elucidate their chiroptical properties. They show negligible circular dichroism signals of Mn absorptions due to C2v-symmetric [MnBr4]2- tetrahedra. However, they display distinct circularly polarized luminescence (CPL) signals with continuously increased luminescence asymmetry factors (glum) from 10-4 (X = C2H5OH) to 10-3 (X = H2O). The increased glum value is structurally revealed to originate from the enhancement of [MnBr4]2- tetrahedral bond-angle distortions, due to the presence of different solvent molecules. Furthermore, (RR/SS-C20H28N2)MnBr4·H2O enantiomers with larger bond-angle distortions of [MnBr4]2- tetrahedra are synthesized based on hydrobromic acid-induced structural transformation of (RR/SS-C20H28N2)3MnBr8·2H2O enantiomers. Therefore, such (RR/SS-C20H28N2)MnBr4·H2O enantiomers exhibit enhanced CPL signals with |glum| up to 1.23 × 10-2. This work provides unique insight into enhancing chiroptical activities in 0D HMH systems.

Efficient Ultraviolet Circularly Polarized Luminescence in Zero-Dimensional Hybrid Cerium Bromides.

Ultraviolet circularly polarized luminescence (UV-CPL) with high photon energy shows great potential in polarized light sources and stereoselective photopolymerization. However, developing luminescent materials with high UV-CPL performance remains challenging. Here, we report a pair of rare earth Ce3+-based zero-dimensional (0D) chiral hybrid metal halides (HMHs), R/S-(C14H24N2)2CeBr7, which exhibits characteristic UV emissions derived from the Ce 5d-4f transition. The compounds show simultaneously high photoluminescent quantum yields of (32-39)% and large luminescent dissymmetry factor (|glum|) values of (1.3-1.5)×10-2. Thus, the figures of merits of R/S-(C14H24N2)2CeBr7 are calculated to be (4.5-5.8)×10-3, which are superior to the reported UV-CPL emissive materials. Additionally, nearly 91 % of their PL intensities at 300 K can be well preserved at 380 K (LED operating temperature) without phase transition or decomposition, demonstrating the excellent structural and optical thermal stabilities of R/S-(C14H24N2)2CeBr7. Based on these enantiomers, the fabricated UV-emitting CP-LEDs exhibit high polarization degrees of ±1.0 %. Notably, the UV-CPL generated from the devices can significantly trigger the enantioselective photopolymerization of diacetylene with remarkable stereoselectivity, and consequently yield polymerized products with the anisotropy factors of circular dichroism (gCD) up to ±3.9×10-2, outperforming other UV-CPL materials and demonstrating their great potential as UV-polarized light sources.

Dynamic Reversible Full-Color Piezochromic Fluorogens Featuring Through-Space Charge-Transfer Thermally Activated Delayed Fluorescence and their Application as X-Ray Imaging Scintillators.

Thermally activated delayed fluorescence (TADF) emitters featuring through-space charge transfer (TSCT) can be excellent candidates for piezochromic luminescent (PCL) materials due to their structural dynamics. Spatial donor-acceptor (D-A) stacking arrangements enable the modulation of inter- and intramolecular D-A interactions, as well as spatial charge transfer states, under varying pressure conditions. Herein, we demonstrate an effective approach toward dynamic reversible full-color PCL materials with TSCT-TADF characteristics. Their single crystals exhibit a full-color-gamut PCL process spanning a range of 170 nm. Moreover, the TSCT-TADF-PCL emitters display a unity photoluminescence quantum yield, and show promising application in X-ray scintillator imaging.

Bright Circularly Polarized Mechanoluminescence from 0D Hybrid Manganese Halides.

Hybrid metal halides (HMHs) with efficient circularly polarized luminescence (CPL) have application prospects in many fields, due to their abundant host-guest structures and high photoluminescence quantum yield (PLQY). However, CPLs in HMHs are predominantly excited by light or electricity, limiting their use in multivariate environments. It is necessary to explore a novel excitation method to extend the application of chiral HMHs as smart stimuli-responsive optical materials. In this work, an enantiomeric pair of 0D hybrid manganese bromides, [H2(2R,4R)-(+)/(2S,4S)-(-)-2,4-bis(diphenylphosphino)pentane]MnBr4 [(R/S)-1] is presented, which exhibits efficient CPL emissions with near-unity PLQYs and high dissymmetry factors of ± 2.0 × 10-3. Notably, (R/S)-1 compounds exhibit unprecedented and bright circularly polarized mechanoluminescence (CPML) emissions under mechanical stimulation. Moreover, (R/S)-1 possess high mechanical force sensitivities with mechanoluminescence (ML) emissions detectable under 0.1 N force stimulation. Furthermore, this ML emission exhibits an extraordinary antithermal quenching effect in the temperature range of 300-380 K, which is revealed to originate from a thermal activation energy compensation mechanism from trap levels to Mn(II) 4T1 level. Based on their intriguing optical properties, these compounds as chiral force-responsive materials are demonstrated in multilevel confidential information encryption.

Pressure-Induced Free Exciton Emission in a Quasi-Zero-Dimensional Hybrid Lead Halide.

Structural dimensionality and electronic dimensionality play a crucial role in determining the type of excitonic emission in hybrid metal halides (HMHs). It is important but challenging to achieve free exciton (FE) emission in zero-dimensional (0D) HMHs based on the control over the electronic dimensionality. In this work, a quasi-0D HMH (C7 H15 N2 Br)2 PbBr4 with localized electronic dimensionality is prepared as a prototype model. With increasing pressure onto (C7 H15 N2 Br)2 PbBr4 , the broad and weak self-trapped exciton (STE) emission at ambient conditions is considerably enhanced before 3.6 GPa, which originates from more distorted [PbBr4 ]2- seesaw units upon compression. Notably, a narrow FE emission in (C7 H15 N2 Br)2 PbBr4 appears at 3.6 GPa, and then this FE emission is gradually strengthened up to 8.4 GPa. High pressure structural characterizations reveal that anisotropic contraction of (C7 H15 N2 Br)2 PbBr4 results in a noticeable reduction in the distance between adjacent [PbBr4 ]2- seesaw units, as well as an obvious enhancement of crystal stiffness. Consequently, the electronic connectivity in (C7 H15 N2 Br)2 PbBr4 is sufficiently promoted above 3.6 GPa, which is also supported with theoretical calculations. The elevation of electronic connectivity and enhanced stiffness together lead to pressure-induced FE emission and subsequent emission enhancement in quasi-0D (C7 H15 N2 Br)2 PbBr4 .

Distinct Excitonic Emissions in 2D (C7 H7 N2 )2 PbX4 (X = Cl, Br) under Compression.

Two dimensional (2D) hybrid metal halides (HMHs) usually exhibit free excitonic (FE) emission, and self-trapped excitonic (STE) emission can also be achieved by adopting appropriate halogens and organic cations. Recently, significant efforts have been made to modulate and then clarify the transformation and connection between these two types of excitonic emissions in 2D HMHs. In this study, intriguing pressure-tuned transitions between FE emission and STE emission are observed in 2D (C7 H7 N2 )2 PbCl4 . In contrast, only FE emissions with tunable emission energies are observed in 2D (C7 H7 N2 )2 PbBr4 which possesses a similar structure with (C7 H7 N2 )2 PbCl4 under compression. Such distinct halide-dependent optical responses under pressure are experimentally revealed to arise from the intricate interplay among several factors in these HMHs, including the stiffness of the structure, the Coulomb force between the organic cations and the inorganic octahedra, and the magnitude of inorganic octahedral distortion. These high-pressure optical explorations can unravel the underlying interrelationship between the crystal structure and excitonic emission in 2D HMHs.

Pressure-Regulated Excitonic Transitions in Emergent Metal Halides.

ConspectusEmergent metal halides are generating significant interest as novel optical materials, and their diverse applications have brought them to the spotlight of chemistry and material science. The optical properties of semiconducting metal halides are fundamentally dominated by excitonic transitions, which refer to the complex processes of excitonic formation, self-trapping, as well as subsequent transitions of intersystem crossing (ISC) and internal conversion (IC). In this regard, high pressure has recently opened a new research dimension to regulate excitonic transitions in metal halides via continuous structural modulations, to understand the intriguing excitonic emissions from a new perspective. In this Account, we aim to rationalize the fundamental strategy for modulating and optimizing the optical properties of metal halides based on delicate exciton regulation via high-pressure method. First, the band gaps of metal halides that are directly related to the efficiency of excitonic formation, are accurately modulated through contraction, distortion, and destruction of metal-halogen polyhedra under compression. Then, considerable enhancement of self-trapped exciton emission is demonstrated by inducing proper polyhedral distortions via high-pressure method. Furthermore, the emission energy of metal halides could also be controllably and widely tuned through pressure-modulated excitonic transitions. Upon compression on different metal halides, excitonic IC is promoted with sufficient polyhedral distortions, and different sets of ISC could also be achieved. In the end, we emphasize the significance of high-pressure investigations in uncovering the complex excitonic transitions in emergent metal halides and predicting novel metal halides with desired optical properties at ambient conditions. It is expected that these discussions could inspire researchers in different fields to perform interdisciplinary high-pressure studies on novel functional materials.

Integrating Achiral and Chiral Organic Ligands in Zero-Dimensional Hybrid Metal Halides to Boost Circularly Polarized Luminescence.

Chiral zero-dimensional hybrid metal halides (0D HMHs) could combine excellent optical properties and chirality, making them promising for circularly polarized luminescence (CPL). However, chiral 0D HMHs with efficient CPL have been rarely reported. Here, we propose an efficient strategy to achieve simultaneously high photoluminescence quantum yield (PLQY) and large dissymmetry factor (glum ), by integrating achiral and chiral ligands into 0D HMHs. Specifically, three pairs of chiral 0D hybrid indium-antimony chlorides are synthesized by combing achiral guanidine with three types of chiral methylbenzylammonium-based derivatives as the organic cations. These chiral 0D HMHs exhibit near-unity PLQY and large glum values up to around ±1×10-2 . The achiral guanidine ligand is not only essential to crystallize these hybrid indium-antimony chlorides to achieve near-unity PLQYs, but also greatly enhances the chirality induction from organic ligands to inorganic units in these 0D HMHs. Furthermore, the choice of different chiral ligands can modify the strength of hydrogen bonding interactions in these 0D HMHs, to maximize their glum values. Overall, this study provides a robust way to realize efficient CPL in chiral HMHs, expanding their applications in chiroptical fields.

Defect-Engineered Cu-Based Nanomaterials for Efficient CO2 Reduction over Ultrawide Potential Window.

High conversion efficiency over a wide operating potential window is important for the practical application of CO2 reduction electrocatalysis, yet that remains a huge challenge in differentiating the competing CO2 reduction and H2 evolution. Here we introduce point defects (Sn doping) and planar defects (grain boundary) into the Cu substrate. This multidimensional defect integration strategy guides the fabrication of highly diluted SnCu polycrystal, which exhibits high Faradaic efficiencies (>95%) toward CO2 electroreduction over an ultrawide potential window (ΔE = 1.3 V). The theoretical study indicates that the introduction of Sn doping and grain boundary synergistically provides an optimized electronic effect, which helps suppress H2 evolution and promotes the hydrogenation of *CO2.

Circularly Polarized Luminescence from Zero-Dimensional Hybrid Lead-Tin Bromide with Near-Unity Photoluminescence Quantum Yield.

Zero-dimensional (0D) hybrid metal halides with perfect host-guest structures are promising candidates to construct circularly polarized luminescence (CPL)-active materials. However, it still remains challenging to obtain 0D chiral metal halides with simultaneously strong CPL and high photoluminescence quantum yield. Here, a new enantiomeric pair of 0D hybrid lead-tin bromides, (RR/SS-C6 N2 H16 )2 Pb0.968 Sn0.032 Br6 ⋅ 2H2 O (R/S-PbSnBr ⋅ H2 O), is reported. The R/S-PbSnBr ⋅ H2 O compounds not only show intriguing self-trapped exciton emissions with near-unity quantum yield, but also present intense CPL with a dissymmetry factor glum of ±3.0×10-3 . Such CPL activities originate from the asymmetric [SnBr6 ]4- luminophores in R/S-PbSnBr ⋅ H2 O, due to the induced structural chirality by the organic ligands via N-H⋅⋅⋅Br hydrogen bonds. Furthermore, CPL emissions with tunable colors from R/S-PbSnBr ⋅ H2 O and dehydrated compounds are reversibly observed, which extends their chiroptical applications.

High-Entropy Intermetallic PtRhBiSnSb Nanoplates for Highly Efficient Alcohol Oxidation Electrocatalysis.

The control of multimetallic ensembles at the atomic-level is challenging, especially for high-entropy alloys (HEAs) possessing five or more elements. Herein, the one-pot synthesis of hexagonal-close-packed (hcp) PtRhBiSnSb high-entropy intermetallic (HEI) nanoplates with intrinsically isolated Pt, Rh, Bi, Sn, and Sb atoms is reported, to boost the electrochemical oxidation of liquid fuels. Taking advantage of these combined five metals, the well-defined PtRhBiSnSb HEI nanoplates exhibit a remarkable mass activity of 19.529, 15.558, and 7.535 A mg-1 Pt+Rh toward the electrooxidation of methanol, ethanol, and glycerol in alkaline electrolytes, respectively, representing a state-of-the-art multifunctional electrocatalyst for alcohol oxidation reactions. In particular, the PtRhBiSnSb HEI achieves record-high methanol oxidation reaction (MOR) activity in an alkaline environment. Theoretical calculations demonstrate that the introduction of the fifth metal Rh enhances the electron-transfer efficiency in PtRhBiSnSb HEI nanoplates, which contributes to the improved oxidation capability. Meanwhile, robust electronic structures of the active sites are achieved due to the synergistic protections from Bi, Sn, and Sb sites. This work offers significant research advances in developing well-defined HEA with delicate control over compositions and properties.

Organic Cation-Directed Modulation of Emissions in Zero-Dimensional Hybrid Tin Bromides.

Zero-dimensional hybrid metal halides (0D HMHs) are attractive due to their intriguing self-trapped exciton (STE) emission properties. However, the effect of organic cations on the emission of 0D HMHs is relatively underexplored. Herein, we report two types of 0D hybrid tin bromides, (BMe)2SnBr6 (BMe = C8N2H18) and (MeH)2SnBr6 (MeH = C7N2H16), which share similar structural features with different hydrogen bonding (HB) interactions between [SnBr6]4- anions and organic cations. The (BMe)2SnBr6 with weak HB interactions exhibits only STE emission, while the (MeH)2SnBr6 exhibits both STE and charge transfer exciton emissions owing to the strong HB interactions, resulting in an excitation-dependent emission at cryogenic conditions. Detailed structural analyses and Hirshfeld surface calculations confirm that the enhanced HB interactions are essential to obtain the multiple emissions in (MeH)2SnBr6.

Zero-dimensional hybrid binuclear manganese chloride with thermally stable yellow emission.

Photoluminescence (PL) thermal quenching of hybrid metal halides blocks their applications. Herein, a novel type of 0D hybrid metal halide, [Pb(C12H24O6)Cl]2[Mn2Cl6], with broad yellow emission and near-unity PL quantum yield is reported. Importantly, it preserves outstanding thermal stability up to 450 K.

Dangling Octahedra Enable Edge States in 2D Lead Halide Perovskites.

The structural reconstruction at the crystal layer edges of 2D lead halide perovskites (LHPs) leads to unique edge states (ES), which are manifested by prolonged carrier lifetime and reduced emission energy. These special ES can effectively enhance the optoelectronic performance of devices, but their intrinsic origin and working mechanism remain elusive. Here it is demonstrated that the ES of a family of 2D Ruddlesden-Popper LHPs [BA2 CsPb2 Br7 , BA2 MAPb2 Br7 , and BA2 MA2 Pb3 Br10 (BA = butylammonium; MA = methylammonium)] arise from the rotational symmetry elevation of the PbBr6 octahedra dangling at the crystal layer edges. These dangling octahedra give rise to localized electronic states that enable an effective transport of electrons from the interior to layer edges, and the population of electrons in both the interior states and the ES can be manipulated via controlling the external fields. Moreover, the abundant phonons, activated by the dangling octahedra, can interact with electrons to facilitate radiative recombination, counterintuitive to the suppressive role commonly observed in conventional semiconductors. This work unveils the intrinsic atomistic and electronic origins of ES in 2D LHPs, which can stimulate the exploration of ES-based exotic optoelectronic properties and the corresponding design of high-performance devices for these emergent low-dimensional semiconductors.

Integrated Afterglow and Self-Trapped Exciton Emissions in Hybrid Metal Halides for Anti-Counterfeiting Applications.

0D hybrid metal halides (0D HMHs) are considered to be promising luminescent emitters. 0D HMHs commonly exhibit self-trapped exciton (STE) emissions originating from the inorganic metal halide anion units. Exploring and utilizing the emission features of the organic cation units in 0D HMHs is highly desired to enrich their optical properties as multifunctional luminescent materials. Here, tunable emissions from organic and inorganic units are successfully achieved in triphenylsulfonium (Ph3 S+ )-based 0D HMHs. Notably, integrated afterglow and STE emissions with adjustable intensities are obtained in (Ph3 S)2 Sn1- x Tex Cl6 (x = 0-1) via the delicate combination of [SnCl6 ]2- and [TeCl6 ]2- . Moreover, such a strategy can be readily extended to develop other HMH materials with intriguing optical properties. As a demonstration, 0D (Ph3 S)2 Zn1- x Mnx Cl4 (x = 0-1) are constructed to achieve integrated afterglow and Mn2+ d-d emissions with high efficiency. Consequently, these novel 0D HMHs with colorful afterglow and STE emissions are applied in multiple anti-counterfeiting applications.

Pressure-Induced Amorphization and Crystallization of Heterophase Pd Nanostructures.

Control of structural ordering in noble metals is very important for the exploration of their properties and applications, and thus it is highly desired to have an in-depth understanding of their structural transitions. Herein, through high-pressure treatment, the mutual transformations between crystalline and amorphous phases are achieved in Pd nanosheets (NSs) and nanoparticles (NPs). The amorphous domains in the amorphous/crystalline Pd NSs exhibit pressure-induced crystallization (PIC) phenomenon, which is considered as the preferred structural response of amorphous Pd under high pressure. On the contrary, in the spherical crystalline@amorphous core-shell Pd NPs, pressure-induced amorphization (PIA) is observed in the crystalline core, in which the amorphous-crystalline phase boundary acts as the initiation site for the collapse of crystalline structure. The distinct PIC and PIA phenomena in two different heterophase Pd nanostructures might originate from the different characteristics of Pd NSs and NPs, including morphology, amorphous-crystalline interface, and lattice parameter. This work not only provides insights into the phase transition mechanisms of amorphous/crystalline heterophase noble metal nanostructures, but also offers an alternative route for engineering noble metals with different phases.

Hexagonal PtBi Intermetallic Inlaid with Sub-Monolayer Pb Oxyhydroxide Boosts Methanol Oxidation.

Engineering multicomponent nanocatalysts is effective to improve electrocatalysis in many applications, yet it remains a challenge in constructing well-defined multimetallic active sites at the atomic level. Herein, the surface inlay of sub-monolayer Pb oxyhydroxide onto hexagonal PtBi intermetallic nanoplates with intrinsically isolated Pt atoms to boost the methanol oxidation reaction (MOR) is reported. The well-defined PtBi@6.7%Pb nanocatalyst exhibits 4.0 and 7.4 times higher mass activity than PtBi nanoplates and commercial Pt/C catalyst toward MOR in the alkaline electrolyte at 30 °C. Meanwhile, it also achieves a record-high mass activity of 51.07 A mg-1 Pt at direct methanol fuel cells operation temperature of 60 °C. DFT calculations reveal that the introduction of Pb oxyhydroxide on the surface not only promotes the electron transfer efficiency but also suppresses the CO poisoning effect, and the efficient p-d coupling optimizes the electroactivity of PtBi@6.7%Pb nanoplates toward the MOR process with low reaction barriers. This work offers a nanoengineering strategy to effectively construct and modulate multimetallic nanocatalysts to improve the electroactivity toward the MOR in future research.