Self-assembly of a mesoporous ZnS/mediating interface/CdS heterostructure with enhanced visible-light hydrogen-production activity and excellent stability

We designed and successfully fabricated a ZnS/CdS 3D mesoporous heterostructure with a mediating Zn_1–xCd_xS interface that serves as a charge carrier transport channel for the first time. The H₂-production rate and the stability of the heterostructure involving two sulfides were dramatically and simultaneously improved by the careful modification of the interface state via a simple post-annealing method. The sample prepared with the optimal parameters exhibited an excellent H₂-production rate of 106.5 mmol h^–1 g^–1 under visible light, which was 152 and 966 times higher than CdS prepared using ethylenediamine and deionized water as the solvent, respectively. This excellent H₂-production rate corresponded to the highest value among the CdS-based photocatalysts. Moreover, this heterostructure showed excellent photocatalytic stability over 60 h.     

Glycine-Functionalized CsPbBr3 Nanocrystals for Efficient Visible-Light Photocatalysis of CO2 Reduction

Capping ligands are indispensable for the preparation of metal-halide-perovskite (MHP) nanocrystals (NCs) with good stability; however, the long alkyl-chain capping ligands in conventional MHP NCs will be unfavorable for CO₂ adsorption and hinder the efficient carrier separation on the surface of MHP NCs, leading to inferior catalytic activity in artificial photosynthesis. Herein, CsPbBr₃ nanocrystals with short-chain glycine as ligand are constructed through a facile ligand-exchange strategy. Owing to the reduced hindrance of glycine and the presence of the amine group in glycine, the photogenerated carrier separation and CO₂ uptake capacity are noticeably improved without compromising the stability of the MHP NCs. The CsPbBr₃ nanocrystals with glycine ligands exhibit a significantly increased yield of 27.7 μmol g⁻¹ h⁻¹ for photocatalytic CO₂-to-CO conversion without any organic sacrificial reagents, which is over five times higher than that of control CsPbBr₃ NCs with conventional long alkyl-chain capping ligands.     

Design of well-defined shell–core covalent organic frameworks/metal sulfide as an efficient Z-scheme heterojunction for photocatalytic water splitting

Development of a covalent–organic framework (COF)-based Z-scheme heterostructure is a promising strategy for solar energy driven water splitting, but the construction of a COF-based Z-scheme heterostructure with well-defined architecture, large contact area and intimate contact interfaces is scarce. Herein, we fabricated a direct Z-scheme heterostructure COF–metal sulfide hybrid (T-COF@CdS) with shell–core architecture by self-polymerization of 1,3,5-benzenetricarboxaldehyde and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine in situ on CdS. The formed C–S chemical bonding between T-COF and CdS could provide a very tight and stable interface. Owing to the properly staggered band alignment, strong interfacial interaction and large interfacial contact area between T-COF and CdS, a Z-scheme route for charge separation and transfer is realized, resulting in electron accumulation in CdS for H₂O reduction. The obtained Z-scheme heterostructure T-COF@CdS-3 exhibits a high apparent quantum efficiency of 37.8% under 365 nm monochromatic light irradiation, and long-term stability arising from shell–core structures in which the T-COF shell protects the catalytic centers of CdS against deactivation, as well as acts as oxidation sites to avoid the photocorrosion of CdS. This work provides a strategy for the construction of a shell–core direct Z-scheme heterostructure photocatalyst for water splitting with high performance.

A stable Z-scheme with well-defined architecture by in situ growth of COFs on CdS for photocatalytic water splitting is constructed. The T-COF shell can protect the catalytic center of CdS from deactivation and photocorrosion.     

Suppressing thermal quenching of lead halide perovskite nanocrystals by constructing a wide-bandgap surface layer for achieving thermally stable white light-emitting diodes

Lead halide perovskite nanocrystals as promising ultrapure emitters are outstanding candidates for next-generation light-emitting diodes (LEDs) and display applications, but the thermal quenching behavior of light emission has severely hampered their real-world applications. Here, we report an anion passivation strategy to suppress the emission thermal quenching behavior of CsPbBr₃ perovskite nanocrystals. By treating with specific anions (such as SO₄²⁻, OH⁻, and F⁻ ions), the corresponding wide-bandgap passivation layers, PbSO₄, Pb(OH)₂, and PbF₂, were obtained. They not only repair the surface defects of CsPbBr₃ nanocrystals but also stabilize the phase structure of the inner CsPbBr₃ core by constructing a core–shell like structure. The photoluminescence thermal resistance experiments show that the treated sample could preserve 79% of its original emission intensity up to 373 K, far superior to that (17%) of pristine CsPbBr₃. Based on the thermally stable CsPbBr₃ nanocrystals, we achieved temperature-stable white LED devices with a stable electroluminescence spectrum, color gamut and color coordinates in thermal stress tests (up to 373 K).

Highly thermotolerant CsPbBr₃ perovskite nanocrystals with anti-thermal quenching performance were obtained by constructing wide-bandgap passivation layers coated strongly on the perovskite surface.     

Lattice-matched in-situ construction of 2D/2D T-SrTiO3/CsPbBr3 heterostructure for efficient photocatalysis of CO2 reduction

The elaborate regulation of heterostructure interface to accelerate the interfacial charge separation is one of practicable approaches to improve the photocatalytic CO₂ reduction performance of halide perovskite (HP) materials. Herein, we report an in-situ growth strategy for the construction of 2D CsPbBr₃ based heterostructure with perovskite oxide (SrTiO₃) nanosheet as substrate (CsPbBr₃/SrTiO₃). Lattice matching and matchable energy band structures between CsPbBr₃ and SrTiO₃ endow CsPbBr₃/SrTiO₃ heterostructure with an efficient interfacial charge separation. Moreover, the interfacial charge transfer rate can be further accelerated by etching SrTiO₃ with NH₄F to form flat surface capped with Ti?O bonds. The resultant 2D/2D T-SrTiO₃/CsPbBr₃ heterostructure exhibits an impressive photocatalytic activity for CO₂ conversion with a CO yield of 120.2 ± 4.9 μmol g^?1 h^?1 at the light intensity of 100 mW/cm² and water as electron source, which is about 10 and 7 times higher than those of the pristine SrTiO₃ and CsPbBr₃ nanosheets, surpassing the reported halide perovskite-based photocatalysts under the same conditions.     

Water-triggered conversion of Cs4PbBr6@TiO2 into Cs4PbBr6/CsPbBr3@TiO2 three-phase heterojunction for enhanced visible-light-driven photocatalytic degradation of organic pollutants

Poor stability and light absorption are the main factors hindering the application of Cs₄PbBr₆ nanocrystals (NCs) in photocatalysis, and acquiring heterostructure of semiconductor/perovskite still is a challenging task. Here, we successfully synthesized Cs₄PbBr₆ NCs and then coated with titania (TiO₂) to construct Cs₄PbBr₆/CsPbBr₃@TiO₂ ternary heterojunction by one-pot water-triggered conversion. The newly formed interface phase of CsPbBr₃ between Cs₄PbBr₆ NCs and TiO₂ enhanced visible-light absorption capacity of composites, promoting the effective separation and transfer of photoelectron–hole pairs. CsPbBr₃ interfacial phase levels in Cs₄PbBr₆/CsPbBr₃@TiO₂ can be regulated by controlling water content, and its content can affect the photocatalytic performance of the obtained composites. Ternary Cs₄PbBr₆/CsPbBr₃@TiO₂ composite exhibits highest photocatalytic activity for degradation of Rhodamine B and tetracycline in water system under visible-light irradiation, which is higher than that of CsPbBr₃@TiO₂ and commercial P25, respectively. Meanwhile, the obtained composite shows good stability in the water system. This work demonstrates a critical interface modulation action of CsPbBr₃ for the application of Cs₄PbBr₆ NCs in the fields of photocatalysis.     

2D-C3N4 encapsulated perovskite nanocrystals for efficient photo-assisted thermocatalytic CO2 reduction

Very recently, halide perovskites, especially all-inorganic CsPbBr₃, have received ever-increasing attention in photocatalysis owing to their superior optoelectronic properties and thermal stability. However, there is a lack of study on their application in thermocatalysis and photo-thermocatalysis. Herein, we rationally designed a core–shell heterojunction formed by encapsulating CsPbBr₃ nanoparticles with the 2D C₃N₄ (m-CN) layer via a solid-state reaction (denoted as m-CN@CsPbBr₃). A series of experiments suggest that abundant adsorption and active sites of CO₂ molecules as well as polar surfaces were obtained by utilizing m-CN-coated CsPbBr₃, resulting in significant improvement in CO₂ capture and charge separation. It is found that the m-CN@CsPbBr₃ effectively drives the thermocatalytic reduction of CO₂ in H₂O vapor. By coupling light into the system, the activity for CO₂-to-CO reduction is further improved with a yield up to 42.8 μmol g⁻¹ h⁻¹ at 150 °C, which is 8.4 and 2.3 times those of pure photocatalysis (5.1 μmol g⁻¹ h⁻¹) and thermocatalysis (18.7 μmol g⁻¹ h⁻¹), respectively. This work expands the application of general halide perovskites and provides guidance for using perovskite-based catalysts for photo-assisted thermocatalytic CO₂ reduction.

A water-stable CsPbBr₃ catalyst is designed using core–shell encapsulation of the perovskite nanoparticle by 2D-C₃N₄ for photo-assisted thermocatalytic CO₂ reduction by H₂O. The m-CN@CsPbBr₃ heterojunction shows surprisingly high CO₂-to-CO yield.

The reduction of CO₂ into valuable hydrocarbon fuels via chemical catalytic processes to mitigate the greenhouse-effect has received wide attention.^1,2 Basically, the CO₂ molecule has a straight double-bonded non-polar structure, resulting in a huge activation energy barrier for the CO₂ reduction reaction (CRR).^3,4 Using a catalyst to adsorb and then activate the CO₂ molecules with free electrons is thus imperative.^5,6 Currently, there are three main types of catalytic CO₂ reduction reactions, i.e. thermocatalysis,⁷ electrocatalysis^8a,b and photocatalysis,^4b,c,5c where the catalysts used are referred to as thermocatalysts, electrocatalysts and photocatalysts, respectively. Traditionally, thermocatalysis is regarded as the conventional CRR process where the CO₂ molecules are well-activated and reduced by thermocatalysts using heat and the reductant agent H₂. Hence, thermocatalysis usually shows a relatively higher CRR efficiency compared to the other two cases.^7a,b,9a However, as it is very complex to safely transport and use H₂ for this process, it is more advantageous to use safe and free H₂O as the reductant if high thermocatalytic CRR efficiency can be achieved. Photocatalysis is regarded as an effective approach for CO₂ reduction owing to the merits of utilizing solar energy directly and low energy consumption. However, the efficiency of the photocatalytic CRR is still limited by the sluggish kinetics of CO₂ activation and H₂O dissolving.^4c,9b Very recently, Xu and co-workers reported a novel lead-free perovskite, Cs₃Sb₂I₉, for CO₂ reduction to CO and CH₄via photothermal synergistic catalysis without using any sacrificial agents or cocatalysts.^9c Unfortunately, the perovskite is not stable enough in the working solution. In addition, its activity is still limited. There is still some room to develop a simple method for synthesizing effective and stable photothermal catalysts.All-inorganic perovskites, for example cesium lead tribromide (CsPbBr₃), have emerged as a promising type of photocatalyst for the CRR, owing to their long photogenerated carrier diffusion length, tunable size, wide light-absorption range, etc.^5c,10 CsPbBr₃ perovskites have been widely explored in composites with other materials, such as g-C₃N₄,¹¹ graphene oxide^5a,12 and TiO₂ (ref. 13) to construct heterojunctions for photocatalytic CO₂ reduction. For example, Xu and his co-workers mixed CsPbBr₃ with NH_x-rich g-C₃N₄ nanosheets to construct a heterojunction with a fast carrier-transfer bridge for improved charge separation and hence enhanced photocatalytic activity for CO₂ reduction.^14a Similarly, Lu''s group reported the coating of CsPbBr₃ with graphdiyne as a physical protection layer to tackle the stability issue in photocatalytic CO₂ reduction in H₂O vapor, given that the perovskite shows a low tolerance towards water.^14b It should be mentioned that most of the reported halide perovskite nanocrystals (NCs) were prepared by the solution method using organic solvents, which is troublesome for large-scale production.^15a,b Besides, considering that thermocatalysis usually outperforms photocatalysis in CO₂ reduction, it would be intriguing to explore the catalytic activity of CsPbBr₃ under coupled thermal and irradiation effects. To the best of our knowledge, there are few reports of water-stable CsPbBr₃-based thermal CRR with H₂O as a reducing agent.Herein, using a molten-salt method, we elaborately encapsulate CsPbBr₃ with a 2D m-CN layer to construct a water-stable heterojunction for photo-assisted thermal catalytic CO₂ reduction. We found that under pure thermocatalysis conditions, m-CN@CsPbBr₃ showed the ability to drive the CRR reduction to CO using the CO₂ and H₂O as reactants. Moreover, with the introduction of simulated solar illumination, the corresponding reduction yield rises to 42.8 μmol g⁻¹ h⁻¹, which is 2.3 and 8.4 times those of pure thermocatalysts and photocatalysts, respectively. This is the first report on the fabrication of CsPbBr₃ perovskite NCs by means of a solid-phase reaction. This work expands the application of CsPbBr₃ perovskite and can help us better understand CO₂ reduction by H₂O.A molten-salt method, where ion salts act as a high-temperature liquid solvent to accelerate the dissolution of raw materials, the transport of reactants, and the directional assembly of basic units, was used to prepare perovskite catalysts with a specific morphology.^15c It is worth noting that melem can be obtained by thermal condensation of urea below 450 °C, while g-C₃N₄ can be acquired in the temperature range between 480 °C and 550 °C (Fig. S1a^†).^16a Therefore, the composition of the coating layer may be assigned to an intermediate product (named m-CN) possessing many edge NH_x groups between melem and g-C₃N₄, which is attributed to the higher local temperature (>450 °C) caused by the molten salt. To confirm this, a comparison study is performed at 420 °C and 470 °C for the synthesis of m-CN@CsPbBr₃ catalysts. As revealed in Fig. S1b,^† the best preparation temperature is 450 °C for m-CN@CsPbBr₃ catalysts, while the phase transition of CsPbBr₃ occurs at 470 °C. During the heat treatment, CsPbBr₃ was changed into the solution state, i.e. molten salt (Fig. S2^†). Meanwhile the polymerized monomers of carbon nitride adsorbed onto the surface of CsPbBr₃, and then the micron-sized CsPbBr₃ was “cut” into nanoparticles by encapsulation with m-CN coatings, as shown in Fig. 1a. To elucidate the formation process of m-CN@CsPbBr₃, different coatings with CsPbBr₃-to-urea mass ratios of 1 : 3, 1 : 5 and 1 : 10 were synthesized and are denoted as m-CN@CsPbBr₃-3, m-CN@CsPbBr₃-5 and m-CN@CsPbBr₃-10, respectively. The corresponding XRD and FTIR results also suggest the encapsulation of CsPbBr₃ with m-CN in these samples, as shown in Fig. S3a and b.^† It should be noted that the m-CN@CsPbBr₃-3 sample gives the typical peaks of g-C₃N₄ at 2-theta of 13 and 27°, while the broad XRD peaks of m-CN@CsPbBr₃-10 could be ascribed to melem, suggesting that a certain content of molten salt is required to improve the temperature profile for the thermal polymerization of the CN coating layers.^16b Fourier transform infrared (FTIR) spectroscopy of m-CN@CsPbBr₃-3 and m-CN@CsPbBr₃-10 showed similar peaks, where the peaks in the wide range from 1200 to 1700 cm⁻¹ are attributed to the skeleton signal of g-C₃N₄.^16c The absorption bands from 3000 to 3500 cm⁻¹ come from NH_x and –OH groups.^14a,16b In comparison to m-CN@CsPbBr₃-10, the normalized intensity of the band from 3000 to 3500 cm⁻¹ for m-CN@CsPbBr₃-3 is evidently decreased, which can be ascribed to the stronger interactions of edge NH_x groups and bromide anions of CsPbBr₃.¹⁶ It is also observed that the m-CN@CsPbBr₃-3 peaks shifted to lower values compared with m-CN@CsPbBr₃-10, as shown in the magnified FTIR spectra of Fig. S3,^† suggesting stronger interactions occurred with the introduction of more bromide anions.^14a,16d When the relative mass ratio of urea to CsPbBr₃ is changed, either the amount of loaded CsPbBr₃ particles is lower and sporadic (Fig. S4a,^† m-CN@CsPbBr₃-10) or the CsPbBr₃ particles are larger and exposed (Fig. S4b,^† m-CN@CsPbBr₃-3), whereas the m-CN@CsPbBr₃-5 sample displays completely uniform and coated CsPbBr₃ particles, suggesting that the appropriate ratio of urea to CsPbBr₃ is critical for optimal m-CN@CsPbBr₃ formation. Therefore, the m-CN@CsPbBr₃-5 catalyst with an optimized coating ratio was chosen for further study because it may be endowed with a more heterogeneous interface and excellent stability. For the synthesis of pure CsPbBr₃ for further composition, vacuum was employed to obtain less-defective CsPbBr₃. We also attempted to treat the mixture of CsPbBr₃ and urea in air. However, very little polymerization of urea to carbon nitride occurred, and thus, the N₂ condition was chosen for m-CN@CsPbBr₃ preparation. Therefore, we successfully encapsulated the perovskite CsPbBr₃ with a 2D m-CN layer by utilizing CsPbBr₃ as a molten salt under N₂ conditions. It is greatly emphasized that this is the first report on the fabrication of CsPbBr₃ perovskite NCs by means of a solid-phase reaction. Differing from the traditional synthesis approaches such as ball milling and solution processing strategies, this unique method can avoid some difficulties, including a complicated procedure and the formation of organic branches and undesired phases, showing the attractive application of this method for fabricating catalysts beyond perovskites.Open in a separate windowFig. 1(a) Illustration of the synthesis of m-CN@CsPbBr₃; (b) XRD patterns of m-CN@CsPbBr₃, the reference m-CN and CsPbBr₃; (c and d) TEM image and the corresponding HRTEM result of m-CN@CsPbBr₃, where the yellow arrows mark the thin m-CN layers.As a representative material, m-CN@CsPbBr₃-5 is selected to investigate the influence of encapsulating perovskite nanocrystals with 2D m-CN for boosting photo-assisted thermocatalytic CO₂ reduction. The XRD patterns in Fig. 1b show that the intensity of the peaks ascribed to CsPbBr₃ was obviously decreased after the m-CN encapsulation, suggesting that the crystallinity of CsPbBr₃ is reduced. Magnification of the diffraction region from 21.2 to 22° suggests that the m-CN@CsPbBr₃ sample exhibits a larger full-width at half maximum (FWHM) than bare CsPbBr₃ (Fig. S5^†), further indicating that the particle size was decreased by the calcination treatment. It should also be noted that the as-prepared CsPbBr₃ formed in a vacuum also showed a crystal-lattice orientation, given that the texture coefficient of the [200] peak is much higher than the standard value of 1, while it is less than 1 for CsPbBr₃ prepared in N₂ and air (Fig. S6a and b^†). It is noted that the texture coefficient of the [200] peak is in agreement with CsPbBr₃ prepared in N₂ after m-CN coating, which further proved the melt-crystallization process of CsPbBr₃. The FTIR spectra of m-CN@CsPbBr₃ and melem showed similar peaks (Fig. S7^†), and the normalized intensity of the band from 3000 to 3500 cm⁻¹ of m-CN@CsPbBr₃ is obviously decreased compared to the reference m-CN. Furthermore, compared with the pure m-CN layer, the peaks for m-CN@CsPbBr₃ located at 1250 cm⁻¹, corresponding to the typical stretching mode of aromatic C–N and C N heterocycles in m-CN, are systematically shifted to lower values in the magnified FTIR spectra in Fig. S7,^† suggesting that the edge NH_x groups interact with the bromide anion of CsPbBr₃via ionic bonding.^16,17aFig. 1c displays the transmission electron microscopy (TEM) image of the m-CN@CsPbBr₃ sample. Clearly, it shows that the CsPbBr₃ nanoparticles were uniformly encapsulated by the m-CN layer. The corresponding high-resolution transmission electron microscopy (HRTEM) images further show clear lattice fringes with a measured interplanar spacing of 0.3 nm, as shown in Fig. 1d, which can be assigned to the (002) plane of cubic CsPbBr₃. Additionally, it shows that nano-sized (ca. 8 nm) CsPbBr₃ particles were encapsulated by the m-CN layer in the m-CN@CsPbBr₃ catalyst (Fig. S8^†). In contrast, the reference CsPbBr₃, which was prepared without urea, is micron-sized (Fig. S9^†), further confirming that the particle size of CsPbBr₃ was changed by the in situ encapsulation with the m-CN layer. Fig. S10^† displays the scanning transmission electron microscopy (STEM) image with the corresponding elemental mapping results, which further confirm that the CsPbBr₃ nanoparticles are wrapped by the m-CN layer. The TEM images and the corresponding elemental mapping of the reference synthesized melem are shown in Fig. S11 and S12,^† respectively, and they resemble those of m-CN@CsPbBr₃, further confirming that the coating layer can be attributed to m-CN.X-ray photoelectron spectroscopy (XPS) was carried out to study the chemical environment of the elements in the m-CN@CsPbBr₃ heterojunction. Fig. S13a^† shows the C 1s XPS results of m-CN@CsPbBr₃ and reference m-CN samples. Two main peaks located at ca. 284.8 and 288.2 eV can be detected, and the first is assigned to the C–C in graphitic carbon, while the second comes from the N–C N coordination of triazine rings.^16,17b It should be noted that there is a slight shift of the N–C N signal of m-CN@CsPbBr₃ to higher binding energy as compared with the bare m-CN, indicating there is an interaction between CsPbBr₃ and m-CN. For the corresponding N 1s XPS curves, three main peaks centered at 398.7, 399.7 and 400.9 eV can be detected (Fig. S13b^†), and they can be assigned to C–N C, N–(C)₃ and C–N–H of the carbon nitride skeleton, respectively.¹⁷ However, the weak peak at ca. 404.4 eV is usually regarded as coming from positive charge localization in heterocycles.^17c It almost disappears in m-CN@CsPbBr₃ relative to bare m-CN, further suggesting that there is some chemical interaction between m-CN and CsPbBr₃ for neutralizing the positive charge.^14a Fig. S14a^† gives the Cs 3d XPS results of m-CN@CsPbBr₃ and bare CsPbBr₃. Two main peaks at 724.5 and 738.4 eV can be detected and come from the Cs 3d_5/2 and 3d_3/2 signals.^14,15 However, a slight shift to higher binding energy can be detected for m-CN@CsPbBr₃, further confirming the above mutual interaction between m-CN and CsPbBr₃. In the Pb 4f XPS result in Fig. S14b,^† there are two peaks at ca. 138.4 and 143.3 eV. Similarly, there is a shift to higher binding energy for m-CN@CsPbBr₃ compared with CsPbBr₃. Fig. S14c^† shows the Br 3d XPS results. Clearly, there are two fitted peaks located at ca. 68.3 and 69.3 eV. The sample of m-CN@CsPbBr₃ exhibits a ca. 0.2 eV shift to higher binding energy compared with bare CsPbBr₃. Both the shifts of Pb 4f and Br 3d in the XPS results suggest that chemical bonds of N–Br have been formed during the preparation process.^11b,14aThe UV-vis absorption spectra of the pristine m-CN and micro-sized CsPbBr₃ in Fig. 2a exhibit the typical absorption edges of CsPbBr₃ and m-CN at ca. 553 and 430 nm, corresponding to bandgaps of 2.24 and 2.88 eV, respectively. For the sample of m-CN@CsPbBr₃, two obvious edges were observed, which correspond to the light absorption edges of CsPbBr₃ and m-CN, indicating the successful combination of the two materials. Fig. S15^† displays the photoluminescence (PL) curves from 375 nm excitation. Strong emission at ca. 450 nm was marked for m-CN, and the peak at 524 nm is attributed to CsPbBr₃. There are two peaks in the PL curve of m-CN@CsPbBr₃, confirming the composition of the catalyst. Moreover, compared with the bare m-CN and CsPbBr₃, the PL intensity of m-CN@CsPbBr₃ is lower, which indicates suppressed carrier recombination in m-CN@CsPbBr₃. The time-resolved PL spectrum was further obtained to explore the carrier dynamics of m-CN@CsPbBr₃. Fig. S16a and b^† exhibit the transient PL spectra at 440 and 523 nm, where the signals can be considered as coming from m-CN and CsPbBr₃ (Fig. S15^†), respectively, and the corresponding fitted results are shown in Tables S1 and S2.^† Obviously, compared with pure m-CN at 440 nm (Fig. S16a^†), m-CN@CsPbBr₃ shows much faster decay after the introduction of CsPbBr₃. Interestingly, with respect to pure CsPbBr₃ at 523 nm (Fig. S16b^†), the opposite trend could be observed. The results testify that the photogenerated electrons of m-CN and holes of CsPbBr₃ will migrate towards each other under the effect of a built-in electric field, and the photogenerated electrons may be transported from CsPbBr₃ to the m-CN layer. The steady-state photovoltages (SPV) of the different samples were further compared to evidence the promoted charge separation in the m-CN@CsPbBr₃ heterojunction, as shown in Fig. 2b. Clearly, the samples of m-CN and CsPbBr₃ exhibited negligible SPV signals. Meanwhile, the m-CN@CsPbBr₃-5 sample demonstrated the highest positive photovoltage response compared with the other catalysts with coating layers (m-CN@CsPbBr₃-10 and m-CN@CsPbBr₃-3), suggesting that its surface is populated by a concentration of holes due to the high charge-separation efficiency (Fig. S17a^†).^18a Transient photovoltage (TPV) analysis was further carried out to study the migration dynamics of the photogenerated carriers.¹⁸ Two obvious positive response peaks (peaks 1 and 2) can be detected from the sample of m-CN@CsPbBr₃ under 400 nm illumination (Fig. S17b^†). Peak 1 can be assigned to a fast process related to the migration of photogenerated carriers in the built-in electric fields inside particles,^18b and thus the stronger intensity of peak 1 of m-CN@CsPbBr₃ suggests that more photogenerated carriers are transported to the interface between m-CN and CsPbBr₃. Peak 2 is thought to arise from carrier transport between particles.¹⁸ A further step to study the carrier transfer dynamics was to perform picosecond transient absorption spectroscopy (TA). Both the samples of bare CsPbBr₃ (Fig. S18a^†) and m-CN@CsPbBr₃ (Fig. S18b^†) exhibit obvious negative ground-state bleaching. Fig. 2c shows the corresponding TA kinetic plots monitored at 520 nm with a distinct difference in the delays. As listed in Table S3,^† the fitted average lifetime of m-CN@CsPbBr₃ (197.7 ps) is much longer than that of bare CsPbBr₃ (77.2 ps), consistent with the above transient PL and TPV results. It is concluded that the internal electric field between m-CN and CsPbBr₃ would promote the carrier transfer and separation in the m-CN@CsPbBr₃ heterojunction.¹⁹ According to the direction of carrier transfer and the strong built-in electric field, it can be inferred that an S-scheme heterojunction is formed between m-CN and CsPbBr₃.Open in a separate windowFig. 2(a) UV-Vis absorption spectra of m-CN@CsPbBr₃, the reference m-CN and CsPbBr₃; (b) surface photovoltage plots of the m-CN, CsPbBr₃ and m-CN@CsPbBr₃ samples; (c) transient absorption spectroscopy curves and lifetime fittings at 520 nm; (d) band structure of the m-CN@CsPbBr₃ heterojunction and the corresponding paths of CO₂ photo-reduction.In order to acquire stronger confirmation of the direction of carrier transfer, ultraviolet photoelectron spectroscopy (UPS) was performed to check the valence band (VB) potential and conduction band (CB) potential of the m-CN and CsPbBr₃ samples. The results and corresponding valence/conduction band potentials (vs. vacuum level) are given in Fig. S19^† and Table S4.^† The relative valence/conduction band positions of m-CN and CsPbBr₃ are shown in Fig. 2d, and they can be attributed to an S-scheme heterojunction, agreeing well with the aforementioned analysis. There is an offset of the bands of the m-CN and CsPbBr₃, and thus close contact between these two materials would cause band bending at the interface. Then, a built-in electric field will be formed making the m-CN and CsPbBr₃ centers of positive and negative charges, respectively. Moreover, the unique conduction/valence band structure of this heterojunction results in polar surfaces of m-CN (holes) and CsPbBr₃ (electrons). This built-in electric field would also facilitate the separation of photogenerated charges and thus suppress charge recombination.Considering that the m-CN@CsPbBr₃ catalyst possesses excellent photogenerated carrier separation ability, its photo-assisted thermocatalytic CO₂ reduction activity was then investigated. We evaluated the catalytic CO₂ reduction of the samples in a flow reactor with CO₂ and H₂O vapor as the reactants, such that the H₂O would continuously pass through the catalyst bed. During the flow reaction process, light and heat were applied to the reactor. Thermogravimetric analysis (TGA) was performed to check the temperature tolerance of the m-CN@CsPbBr₃ catalyst in nitrogen, as shown in Fig. S20.^† It indicates that the thermocatalytic CRR can take place at less than 200 °C because of the absence of any decomposition below this temperature. The instability of CsPbBr₃ to humidity has always been a huge obstacle for applications. The m-CN@CsPbBr₃ catalyst with the protection of the m-CN layer was then treated in pure water to check its chemical stability. As shown in Fig. S21a and b,^† after soaking in water for ∼0.5 and 17 h, there is almost no change in color; however, the bare CsPbBr₃ turns white after being in water for less than 1 h. The corresponding XRD results show no change from before to after the water immersion for ∼0.5 and 17 h. Meanwhile, bare CsPbBr₃ exhibited an obvious phase transition. Additionally, the water-treated samples were checked by TEM. As shown in Fig. S22,^† there is almost no change in morphology after the treatment of ∼0.5 and 17 h, in accordance with the above XRD results. Fig. S23^† shows the XPS results of the water-treated samples, and there are almost no changes for all the studied elements. These results suggest that m-CN@CsPbBr₃ exhibited superior water stability due to the m-CN encapsulation. Fig. 3a compares the CO₂ reduction activities of pristine m-CN, micro-sized CsPbBr₃ and m-CN@CsPbBr₃ under three different conditions, with our m-CN@CsPbBr₃ catalyst benefiting from superior durability. Under the pure simulated sunlight condition (Fig. 3a), the sample of m-CN@CsPbBr₃ displays the highest CO₂-to-CO yield of 8.15 μmol g⁻¹ h⁻¹, followed by CsPbBr₃ (4.5 μmol g⁻¹ h⁻¹) and m-CN (2.2 μmol g⁻¹ h⁻¹). For pure thermocatalysis at the temperature of 150 °C, the CO generation of m-CN@CsPbBr₃ is 22.4 μmol g⁻¹ h⁻¹, and those of the bare CsPbBr₃ and m-CN are 8.8 and 0 μmol g⁻¹ h⁻¹, respectively. More impressively, when the light and heat were coupled to drive photo-assisted thermocatalysis, the CO₂-to-CO yield of m-CN@CsPbBr₃ was increased to 42.8 μmol g⁻¹ h⁻¹, which is much higher than those of bare m-CN (5.1 μmol g⁻¹ h⁻¹) and CsPbBr₃ (18.7 μmol g⁻¹ h⁻¹). It is suggested that the light excitation would generate electrons and holes and these electrons and holes would migrate to the surfaces of CsPbBr₃ and m-CN, facilitating the thermocatalytic CRR process. Under all three conditions, i.e., photocatalysis, thermocatalysis and photo-thermocatalysis, the sample of bare CsPbBr₃ gives the lowest activity, further suggesting the significance of the heterojunction for promoting the CRR performance. The photo-thermocatalytic performance of the sample of m-CN@CsPbBr₃ is also comparable to those of the other systems, but exceeds those of most reported CsPbBr₃-based photocatalysts (Table S5^†). Moreover, we checked the impact of coating content on the catalytic activity of m-CN@CsPbBr₃ at 150 °C and 3 suns. As depicted in Fig. S24,^† in comparison with m-CN@CsPbBr₃-3 and m-CN@CsPbBr₃-10, m-CN@CsPbBr₃-5 delivers the highest CO₂-to-CO yield, possibly due to the existence of the enriched heterogeneous interface and strong built-in electric field. Meanwhile, the catalytic stability of m-CN@CsPbBr₃-5 was also tested during the 6 h period of operation (Fig. S25^†), and the result reveals that its reduction ability at the end is comparable to its original performance. Further, the XPS spectra before and after testing m-CN@CsPbBr₃-5 manifest that all elements are almost unchanged (Fig. S26^†), once again verifying its excellent catalytic stability, which is promising for practical application.Open in a separate windowFig. 3(a) The CO₂ reduction to CO performance under the three conditions of photocatalysis, thermocatalysis and photo-thermocatalysis. For the latter two, the temperature is set to 150 °C; (b) mass spectrometry (MS) result of ¹³CO produced over m-CN@CsPbBr₃ from the ¹³CO₂ isotope experiment under thermocatalysis (m/z, mass/charge ratio); (c) CO₂-TPD results of the reference m-CN and the m-CN@CsPbBr₃ catalyst.In addition, a small amount of H₂ was also measured as the reductive by-product from m-CN@CsPbBr₃ samples at different temperatures (Fig. S27^†). These results indicate that the coupling of photo and thermal effects profoundly promotes CO₂ reduction. Fig. 3b shows the result of an isotopic ¹³CO₂ labeling experiment under the thermocatalytic conditions. A clear peak at m/z = 29 (¹³CO) is observed, confirming that the generated CO originates from the thermocatalytic reduction of ¹³CO₂ rather than from contaminants. The corresponding screen shots of the raw mass spectra data are displayed in Fig. S28.^†To understand the promoted performance of m-CN@CsPbBr₃, the adsorption abilities of CO₂ and CO on m-CN and m-CN@CsPbBr₃ were studied. Fig. 3c exhibits the CO₂ temperature-programmed desorption (TPD) curves of m-CN and m-CN@CsPbBr₃, which yield the adsorbed amounts of CO₂ according to the integrated areas of the curves. It is found that m-CN@CsPbBr₃ has a higher adsorbed amount and thus more sites for CO₂ adsorption and activation compared to m-CM, which could be attributed to the polar surfaces of m-CN and CsPbBr₃. Moreover, the desorption peak of the m-CN@CsPbBr₃ catalyst is situated at higher temperature, suggesting that the corresponding adsorption sites can facilitate the CO₂ reduction due to a stronger interaction with the CO₂ molecules. In the CO₂-TPD curve of CsPbBr₃ in Fig. S29,^† a higher desorption temperature of ∼320 °C is observed compared with that of m-CN, which can be responsible for the enhancement of desorption for the m-CN@CsPbBr₃ catalyst. CO-TPD was also performed, and the results are shown in Fig. S30.^† Clearly, both the m-CN and m-CN@CsPbBr₃ samples showed weak CO adsorption, which is thought to benefit CO evolution. Measurements were further performed at two other temperatures (100 and 200 °C) to determine the effect of heating on the CRR efficiency. As shown in Fig. S31^† (100 °C) and Fig. S32^† (200 °C), the yields of CO₂-to-CO were lower than at 150 °C, which may be ascribed to the difference of CO₂ and CO adsorption at different temperatures. The result suggests that there is an optimal reaction temperature for suitable balance of adsorption/desorption of CO₂ and CO to obtain the highest performance of CO₂ reduction. In situ FTIR spectroscopy was further carried out to investigate the possible reaction pathways of the CRR under photo-assisted thermocatalysis conditions. It is evident that increased IR peaks emerge with increasing irradiation time from 0 to 30 minutes (Fig. 4a and b), in which the peaks at 1457 cm⁻¹ and 1646 cm⁻¹ could be assigned to b-HCO₃⁻, while the peaks at 1248 and 1695 cm⁻¹ came from the vibration of the carboxylate (CO₂⁻), and the peak at 1337 cm⁻¹ can be attributed to the bidentate carbonate (b-CO₃²⁻). Also, the peaks located at 1379 and 1507 cm⁻¹ matched well with monodentate carbonate groups (m-CO₃²⁻).²⁰ Meanwhile, for the photo-assisted thermocatalysis in Fig. 4b, almost the same peaks were observed except with relatively stronger peak intensities, corresponding to the improved CRR efficiency under the coupled photo-thermal effect. Note that the peak at 1695 increased in intensity and the peaks at 1457 cm⁻¹ and 1646 cm⁻¹ disappeared compared with the spectrum under bare thermocatalytic conditions, indicating that b-HCO₃⁻ ions on the surface are transformed to surface CO₂⁻ species instead with the assistance of light.Open in a separate windowFig. 4 In situ FTIR spectra of m-CN@CsPbBr₃ under (a) bare thermocatalytic and (b) photo-thermal conditions at ten-minute increments from 0 to 30 min (from top to bottom). (c) Schematic diagram of the possible reaction pathways of the CRR for the sample of m-CN@CsPbBr₃ under photo-thermal conditions.In addition, the m-CO₃²⁻ signals at 1507 cm⁻¹ were more obvious compared to those under bare thermocatalytic conditions, suggesting that the adsorption of the reaction intermediates was adjusted by light irradiation. This can be attributed to the strong light absorption of CsPbBr₃ according to the FTIR curves of the bare CsPbBr₃ sample under the above two conditions (Fig. S33a and b^†). This finding indicates the importance of encapsulating CsPbBr₃ for altering the formation of intermediates and improving CRR activity under photo-assisted thermocatalysis conditions. Moreover, the FTIR curves of the reference m-CN sample are similar to those of m-CN@CsPbBr₃ under bare thermocatalytic conditions (Fig. S34^†). Thus, the possible CRR pathways can be summarized as follows (Fig. 4c): (a) the H₂O molecules are first dissociated into H_ads and OH_ads groups when meeting hot carriers, i.e., holes generated from thermal or photo excitation; (b) the adsorbed CO₂ encounters OH_ads to generate HCO₃⁻ and m-CO₃²⁻ (step i); (c) then the conversion from surface m-CO₃²⁻ (step i) to CO₂⁻ species in the presence of H₂O is proposed, and the surface HCO₃⁻ (step i) species can be converted conveniently into CO₂⁻ under photo-assisted thermocatalysis conditions (step ii); for (c), the CO₂⁻ finally releases CO gas when it encounters H_ads and free electrons (step iii).Herein, a water-stable m-CN@CsPbBr₃ heterojunction was synthesized via a solid-state reaction, where bulk CsPbBr₃ micro-sized particles were melted and converted to nanoparticles with encapsulation by an m-CN coating during the calcination. The intimate contact between m-CN and CsPbBr₃ would induce band bending at the interface and form a built-in electric field, which would separate holes and electrons to m-CN and CsPbBr₃, respectively. As such a heterojunction with two charge poles, m-CN@CsPbBr₃ exhibited an excellent thermocatalytic CO₂-to-CO yield of 42.8 μmol g⁻¹ h⁻¹ under the assistance of irradiation, higher than that of pure photocatalysis (5.1 μmol g⁻¹ h⁻¹) or thermocatalysis (18.7 μmol g⁻¹ h⁻¹). This is the first report of photo-assisted thermocatalysis using CsPbBr₃-based materials. Our work thus expands the application of halide perovskites in CO₂ reduction.     

Carbon–chalcogen bond formation initiated by [Al(NONDipp)(E)]− anions containing Al–E{16} (E{16} = S,Se) multiple bonds

Multiply-bonded main group metal compounds are of interest as a new class of reactive species able to activate and functionalize a wide range of substrates. The aluminium sulfido compound K[Al(NON^Dipp)(S)] (NON^Dipp = [O(SiMe₂NDipp)₂]²⁻, Dipp = 2,6-ⁱPr₂C₆H₃), completing the series of [Al(NON^Dipp)(E)]⁻ anions containing Al–E{16} multiple bonds (E{16} = O, S, Se, Te), was accessed via desulfurisation of K[Al(NON^Dipp)(S₄)] using triphenylphosphane. The crystal structure showed a tetrameric aggregate joined by multiple K⋯S and K⋯π(arene) interactions that were disrupted by the addition of 2.2.2-cryptand to form the separated ion pair, [K(2.2.2-crypt)][Al(NON^Dipp)(S)]. Analysis of the anion using density functional theory (DFT) confirmed multiple-bond character in the Al–S group. The reaction of the sulfido and selenido anions K[Al(NON^Dipp)(E)] (E = S, Se) with CO₂ afforded K[Al(NON^Dipp)(κ²E,O-EC{O}O)] containing the thio- and seleno-carbonate groups respectively, consistent with a [2 + 2]-cycloaddition reaction and C–E bond formation. An analogous cycloaddition reaction took place with benzophenone affording compounds containing the diphenylsulfido- and diphenylselenido-methanolate ligands, [κ²E,O-EC{O}Ph₂]²⁻. In contrast, when K[Al(NON^Dipp)(E)] (E = S, Se) was reacted with benzaldehyde, two equivalents of substrate were incorporated into the product accompanied by formation of a second C–E bond and complete cleavage of the Al–E{16} bonds. The products contained the hitherto unknown κ²O,O-thio- and κ²O,O-seleno-bis(phenylmethanolate) ligands, which were exclusively isolated as the cis-stereoisomers. The mechanisms of these cycloaddition reactions were investigated using DFT methods.

Reaction of Al–E (E = S, Se) multiple bonds with C O functionalities generates new C–E bonds.     

Composition‐Dependent Hot Carrier Relaxation Dynamics in Cesium Lead Halide (CsPbX3, X=Br and I) Perovskite Nanocrystals

Cesium‐based perovskite nanocrystals (NCs) have outstanding photophysical properties improving the performances of lighting devices. Fundamental studies on excitonic properties and hot‐carrier dynamics in perovskite NCs further suggest that these materials show higher efficiencies compared to the bulk form of perovskites. However, the relaxation rates and pathways of hot‐carriers are still being elucidated. By using ultrafast transient spectroscopy and calculating electronic band structures, we investigated the dependence of halide in Cs‐based perovskite (CsPbX₃ with X=Br, I, or their mixtures) NCs on the hot‐carrier relaxation processes. All samples exhibit ultrafast (<0.6 ps) hot‐carrier relaxation dynamics with following order: CsPbBr₃ (310 fs)>CsPbBr_1.5I_1.5 (380 fs)>CsPbI₃ NC (580 fs). These result accounts for a reduced light emission efficiency of CsPbI₃ NC compared to CsPbBr₃ NC.     

Novel hydrostable Z-scheme Ag/CsPbBr3/Bi2WO6 photocatalyst for effective degradation of Rhodamine B in aqueous solution

In this study, a hydrostable Z-scheme Ag/CsPbBr₃/Bi₂WO₆ photocatalyst was designed and fabricated for the degradation of Rhodamine B (RhB). The structural instability of CsPbX₃ perovskites in water is one of the main obstacles that restrict their practical application in photocatalytic wastewater treatment. The photocatalyst was prepared in three steps: passivation of CsPbBr₃ nanocrystals (NCs) with 3-mercaptopropionic acid (MPA), construction of a heterojunction between MPA-passivated CsPbBr₃ NCs and Bi₂WO₆ ultrathin nanosheets, and doping Ag nanoparticles as charge mediators in the heterojunction. The as-obtained 5%Ag/20%CsPbBr₃/Bi₂WO₆ exhibits good stability and excellent photocatalytic activity. The degradation rate is 93.9% in 120 min, which is 4.41 times than that of Bi₂WO₆.     

High sensitivity ratiometric fluorescence temperature sensing using the microencapsulation of CsPbBr3 and K2SiF6:Mn4+ phosphor

A dual emission sensing film has been prepared for colorimetric temperature sensing using CsPbBr₃ perovskite nanocrystals (CsPbBr₃ NCs) and manganese doped potassium fluorosilicate (K₂SiF₆:Mn⁴⁺, KSF) encapsulated in polystyrene by a microencapsulation strategy. The CsPbBr₃-KSF-PS film shows good temperature sensing response from 30 °C to 70 °C, with a relative temperature sensitivity (S_r) up to 10.31% °C^?1 at 45 °C. Meanwhile, the film maintains more than 95% intensity after 6 heating-cooling cycles and keeps its fluorescence characteristics after 3 months. The film can be used to monitor temperature change by naked eye under a UV lamp. In particular, the temperature discoloration point of the sensing film can be controlled by the ratio change of CsPbBr₃:KSF to expand its applications. The study of the CsPbBr₃-KSF-PS sensing mechanism in this work is helpful to provide effective strategies for the design of reliable, high sensitivity and stable temperature sensing system using CsPbBr₃ NCs.     

Self-trapped exciton emission and piezochromism in conventional 3D lead bromide perovskite nanocrystals under high pressure

Developing single-component materials with bright-white emission is required for energy-saving applications. Self-trapped exciton (STE) emission is regarded as a robust way to generate intrinsic white light in halide perovskites. However, STE emission usually occurs in low-dimensional perovskites whereby a lower level of structural connectivity reduces the conductivity. Enabling conventional three-dimensional (3D) perovskites to produce STEs to elicit competitive white emission is challenging. Here, we first achieved STEs-related emission of white light with outstanding chromaticity coordinates of (0.330, 0.325) in typical 3D perovskites, Mn-doped CsPbBr₃ nanocrystals (NCs), through pressure processing. Remarkable piezochromism from red to blue was also realized in compressed Mn-doped CsPbBr₃ NCs. Doping engineering by size-mismatched Mn dopants could give rise to the formation of localized carriers. Hence, high pressure could further induce octahedra distortion to accommodate the STEs, which has never occurred in pure 3D perovskites. Our study not only offers deep insights into the photophysical nature of perovskites, it also provides a promising strategy towards high-quality, stable white-light emission.

We first achieved self-trapped exciton emission with outstanding white-light chromaticity coordinates of (0.330, 0.325) in conventional 3D halide perovskite nanocrystals through pressure engineering.     

Revealing the composition-dependent structural evolution fundamentals of bimetallic nanoparticles through an inter-particle alloying reaction

Alloy nanoparticles represent one of the most important metal materials, finding increasing applications in diverse fields of catalysis, biomedicine, and nano-optics. However, the structural evolution of bimetallic nanoparticles in their full composition spectrum has been rarely explored at the molecular and atomic levels, imparting inherent difficulties to establish a reliable structure–property relationship in practical applications. Here, through an inter-particle reaction between [Au₄₄(SR)₂₆]²⁻ and [Ag₄₄(SR)₃₀]⁴⁻ nanoparticles or nanoclusters (NCs), which possess the same number of metal atoms, but different atomic packing structures, we reveal the composition-dependent structural evolution of alloy NCs in the alloying process at the molecular and atomic levels. In particular, an inter-cluster reaction can produce three sets of Au_xAg_44−x NCs in a wide composition range, and the structure of Au_xAg_44−x NCs evolves from Ag-rich [Au_xAg_44−x(SR)₃₀]⁴⁻ (x = 1–12), to evenly mixed [Au_xAg_44−x(SR)₂₇]³⁻ (x = 19–24), and finally to Au-rich [Au_xAg_44−x(SR)₂₆]²⁻ (x = 40–43) NCs, with the increase of the Au/Ag atomic ratio in the NC composition. In addition, leveraging on real-time electrospray ionization mass spectrometry (ESI-MS), we reveal the different inter-cluster reaction mechanisms for the alloying process in the sub-3-nm regime, including partial decomposition–reconstruction and metal exchange reactions. The molecular-level inter-cluster reaction demonstrated in this study provides a fine chemistry to customize the composition and structure of bimetallic NCs in their full alloy composition spectrum, which will greatly increase the acceptance of bimetallic NCs in both basic and applied research.

An inter-particle reaction between atomically precise [Au₄₄(SR)₂₆]²⁻ (SR = thiolate) and [Ag₄₄(SR)₃₀]⁴⁻ nanoparticles reveals the composition-dependent structural evolution of alloy Au_xAg_44−x nanoparticles at the atomic level.     

A (μ-hydrido)diborane(4) anion and its coordination chemistry with coinage metals

A tetra(o-tolyl) (μ-hydrido)diborane(4) anion 1, an analogue of [B₂H₅]⁻ species, was facilely prepared through the reaction of tetra(o-tolyl)diborane(4) with sodium hydride. Unlike common sp²–sp³ diborane species, 1 exhibited a σ-B–B bond nucleophilicity towards NHC-coordinated transition-metal (Cu, Ag, and Au) halides, resulting in the formation of η²-B–B bonded complexes 2 as confirmed by single-crystal X-ray analyses. Compared with 1, the structural data of 2 imply significant elongations of B–B bonds, following the order Au > Cu > Ag. DFT studies show that the diboron ligand interacts with the coinage metal through a three-center-two-electron B–M–B bonding mode. The fact that the B–B bond of the gold complex is much prolonged than the related Cu and Ag compounds might be ascribed to the superior electrophilicity of the gold atom.

A tetra(o-tolyl)(μ-hydrido)diborane(4) anion is facilely prepared via the reaction of tetra(o-tolyl)diborane(4) with NaH. It exhibits a σ-B–B bond nucleophilicity towards NHC-metal halides to give the corresponding η²-B–B bonded metal complexes.     

Cooperativity as quantification and optimization paradigm for nuclear receptor modulators

Nuclear Receptors (NRs) are highly relevant drug targets, for which small molecule modulation goes beyond a simple ligand/receptor interaction. NR–ligands modulate Protein–Protein Interactions (PPIs) with coregulator proteins. Here we bring forward a cooperativity mechanism for small molecule modulation of NR PPIs, using the Peroxisome Proliferator Activated Receptor γ (PPARγ), which describes NR–ligands as allosteric molecular glues. The cooperativity framework uses a thermodynamic model based on three-body binding events, to dissect and quantify reciprocal effects of NR–coregulator binding (K^I_D) and NR–ligand binding (K^II_D), jointly recapitulated in the cooperativity factor (α) for each specific ternary ligand·NR·coregulator complex formation. These fundamental thermodynamic parameters allow for a conceptually new way of thinking about structure–activity-relationships for NR–ligands and can steer NR modulator discovery and optimization via a completely novel approach.

A cooperativity framework describes the formation of nuclear receptor ternary complexes and deconvolutes ligand and cofactor binding into intrinsic affinities and a cooperativity factor, providing a conceptually new understanding of NR modulation.     

Exploring benzylic gem-C(sp3)–boron–silicon and boron–tin centers as a synthetic platform

A stepwise build-up of multi-substituted C_sp³ carbon centers is an attractive, conceptually simple, but often synthetically challenging type of disconnection. To this end, this report describes how gem-α,α-dimetalloid-substituted benzylic reagents bearing boron/silicon or boron/tin substituent sets are an excellent stepping stone towards diverse substitution patterns. These gem-dimetalloids were readily accessed, either by known carbenoid insertion into C–B bonds or by the newly developed scalable deprotonation/metallation approach. Highly chemoselective transformations of either the C–Si (or C–Sn) or the C–B bonds in the newly formed gem-C_sp³ centers have been achieved through a set of approaches, with a particular focus on exploiting the synthetically versatile polarity reversal in organometalloids by λ³-aryliodanes. Of particular note is the metal-free arylation of the C–Si (or C–Sn) bonds in such gem-dimetalloids via the iodane-guided C–H coupling approach. DFT calculations show that this transfer of the (α-Bpin)benzyl group proceeds via unusual [5,5]-sigmatropic rearrangement and is driven by the high-energy iodine(iii) center. As a complementary tool, the gem-dimetalloid C–B bond is shown to undergo a potent and chemoselective Suzuki–Miyaura arylation with diverse Ar–Cl, thanks to the development of the reactive gem-α,α-silyl/BF₃K building blocks.

This work explores divergent reactivity of the benzylic gem-boron–silicon and boron–tin double nucleophiles, including the arylation of the C–B bond with Ar–Cl, along with a complementary oxidative λ³-iodane-guided arylation of the C–Si/Sn moiety.     

In situ Raman spectroscopy reveals the structure evolution and lattice oxygen reaction pathway induced by the crystalline–amorphous heterojunction for water oxidation

One of the most successful approaches for balancing the high stability and activity of water oxidation in alkaline solutions is to use amorphous and crystalline heterostructures. However, due to the lack of direct evidence at the molecular level, the nano/micro processes of amorphous and crystalline heterostructure electrocatalysts, including self-reconstruction and reaction pathways, remain unknown. Herein, the Leidenfrost effect assisted electrospray approach combined with phase separation was used for the first time to create amorphous NiO_x/crystalline α-Fe₂O₃ (a-NiO_x/α-Fe₂O₃) nanowire arrays. The results of in situ Raman spectroscopy demonstrate that with the increase of the potential at the a-NiO_x/α-Fe₂O₃ interface, a significant accumulation of OH can be observed. Combining with XAS spectra and DFT calculations, we believe that more OH adsorption on the Ni centers can facilitate Ni²⁺ deprotonation to achieve the high-valence oxidation of Ni⁴⁺ according to HSAB theory (Fe³⁺ serves as a strong Lewis acid). This result promotes the electrocatalysts to follow the lattice oxygen activation mechanism. This work, for the first time, offers direct spectroscopic evidence for deepening the fundamental understanding of the Lewis acid effect of Fe³⁺, and reveals the synergistic effect on water oxidation via the unique amorphous and crystalline heterostructures.

The amorphous NiO_x/crystalline α-Fe₂O₃ heterojunctions were constructed and exhibited outstanding OER activities. Through the collaboration of multiple characterization techniques, the Lewis acid effect of Fe³⁺ was revealed at molecular level.     

Water‐Assisted Size and Shape Control of CsPbBr3 Perovskite Nanocrystals

Lead‐halide perovskites are well known to decompose rapidly when exposed to polar solvents, such as water. Contrary to this common‐place observation, we have found that through introducing a suitable minor amount of water into the reaction mixture, we can synthesize stable CsPbBr₃ nanocrystals. The size and the crystallinity, and as a result the band gap tunability of the strongly emitting CsPbBr₃ nanocrystals correlate with the water content. Suitable amounts of water change the crystallization environment, inducing the formation of differently shaped perovskites, namely spherical NCs, rectangular nanoplatelets, or nanowires. Bright CsPbBr₃ nanocrystals with the photoluminescence quantum yield reaching 90 % were employed for fabrication of inverted hybrid inorganic/organic light‐emitting devices, with the peak luminance of 4428 cd m^?2 and external quantum yield of 1.7 %.     

Optimizing the quasi-equilibrium state of hot carriers in all-inorganic lead halide perovskite nanocrystals through Mn doping: fundamental dynamics and device perspectives

Hot carrier (HC) cooling accounts for the significant energy loss in lead halide perovskite (LHP) solar cells. Here, we study HC relaxation dynamics in Mn-doped LHP CsPbI₃ nanocrystals (NCs), combining transient absorption spectroscopy and density functional theory (DFT) calculations. We demonstrate that Mn²⁺ doping (1) enlarges the longitudinal optical (LO)–acoustic phonon bandgap, (2) enhances the electron–LO phonon coupling strength, and (3) adds HC relaxation pathways via Mn orbitals within the bands. The spectroscopic study shows that the HC cooling process is decelerated after doping under band-edge excitation due to the dominant phonon bandgap enlargement. When the excitation photon energy is larger than the optical bandgap and the Mn²⁺ transition gap, the doping accelerates the cooling rate owing to the dominant effect of enhanced carrier–phonon coupling and relaxation pathways. We demonstrate that such a phenomenon is optimal for the application of hot carrier solar cells. The enhanced electron–LO phonon coupling and accelerated cooling of high-temperature hot carriers efficiently establish a high-temperature thermal quasi-equilibrium where the excessive energy of the hot carriers is transferred to heat the cold carriers. On the other hand, the enlarged phononic band-gap prevents further cooling of such a quasi-equilibrium, which facilitates the energy conversion process. Our results manifest a straightforward methodology to optimize the HC dynamics for hot carrier solar cells by element doping.

Mn doping modulates the hot carrier dynamics in all-inorganic lead halide perovskite nanocrystals according to the excitation energy.     

Ultrafast Charge Delocalization Dynamics of Ambient Stable CsPbBr3 Nanocrystals Encapsulated in Polystyrene Fiber

CsPbBr₃ nanocrystals (NCs) encapsulated in a transparent polystyrene (PS) fiber matrix (CsPbBr₃@PS) have been synthesized to protect the NCs. The ultrafast charge delocalization dynamics of the embedded NCs have been demonstrated, and the results are compared with the pristine CsPbBr₃ in toluene. The electrospinning method was employed for the preparation of CsPbBr₃@PS fibers by using a polystyrene solution doped with pre-synthesized CsPbBr₃ and characterized by XRD, HRTEM, and X-ray photoelectron spectroscopy (XPS). Energy level diagrams of CsPbBr₃ and PS suggest that CsPbBr₃@PS fibers make a type I core–shell structure. The carrier cooling for CsPbBr₃@PS fibers is found to be much slower than pure CsPbBr₃ NCs. This observation suggests that photoexcited electrons from CsPbBr₃ NCs get delocalized from the conduction band of the perovskite to lowest unoccupied molecular orbital (LUMO) of the PS fiber matrix. The CsPbBr₃@PS fibers possess remarkable stability under ambient conditions as well as in water over months. The clear understanding of charge carrier relaxation dynamics of CsPbBr₃ confined in PS fibers could help to design robust optoelectronic devices.