Science China Materials最新文献

Lead-halide perovskite single crystal (SC) heterojunctions have attracted significant attention for X-ray detection owing to their unique combination of high sensitivity, resolution, stability and low detection limit. However, the toxicity of lead in those perovskite heterojunctions limits their practical applications. Herein, we report the construction of the first all-inorganic lead-free Cs₂AgBiBr₆/Cs₃Bi₂Br₉ SC heterojunctions with an area of 20 × 20 mm² via a facile liquid-phase epitaxial method through temperature-lowering crystallization. The epitaxial crystallization of the three-dimensional (3D) Cs₂AgBiBr₆ SC film on a 2D Cs₃Bi₂Br₉ SC substrate requires a large driving force for transitioning from the Volmer–Weber mode to the layer-by-layer growth mode under a rapid cooling rate. The Cs₂AgBiBr₆/Cs₃Bi₂Br₉ SC heterojunction detector achieves a high sensitivity of 1390 µC Gy_air⁻¹ cm⁻² for 100 keV hard X-ray detection at room temperature, which is enhanced to 2075 µC Gy_air⁻¹ cm⁻² at 75°C, demonstrating impressive high-temperature stability. Moreover, the detector achieves a detection limit of 37.48 nGy_air s⁻¹ and excellent stability for 90 days without any encapsulation. This work demonstrates the feasibility of using the epitaxial mechanism of perovskite formation on a high-surface-energy substrate for the controllable construction of a 3D/2D heterojunction that significantly enhances X-ray detection performance.

Smart materials with tunable multiple-color emissions have been widely investigated in the fields of bioimaging, display, and information encryption. Herein, multicolor emissive molecules with hydrazone bridged triphenylamines and pyridinium groups are reported. The protonation of the pyridine subunit by various acids leads to aggregation-induced emission with broad emission colors ranging from blue to red in multiple states and spectra of λ_PL, dichloromethane solution = 463–584 nm, λ_PL,powder = 455–620 nm, and λ_PL,crystal = 485–657 nm, respectively. Upon grinding or heating, hydrazone with CF₃COO⁻ exhibit blue-shift emissions from red to yellow due to weakened molecular packing and conformational rigidity. In contrast, hydrazone with (CF₃SO₂)₂N⁻ exhibited redshift emission from green to yellow due to the decreased electron-donating ability of the triphenylamine unit upon transformation from a rigid pyramidal shape to a planar structure. These are rare, charged organic examples exhibiting predictable mechanochromic and thermochromic strong emissions through facile anion exchanges, potentially providing new insights into the design of smart materials.

Molybdenum-based catalysts have demonstrated significant potential in the electrocatalytic hydrogen evolution reaction (HER). However, the limited exposure of active sites and strong hydrogen adsorption result in suboptimal performance. Herein, a Mo₂N–MoSe₂ heterojunction is prepared on carbon cloth (MNS/CC) to enhance the HER. The strong electronic interaction between Mo₂N and MoSe₂, combined with the lower work function of Mo₂N, creates an intrinsic electric field at the heterojunction interface, which markedly improves charge transfer efficiency. Additionally, the optimized electronic structure of Mo sites further enhances charge transfer and intrinsically catalytic activity in HER. As a result, MNS/CC requires overpotentials of mere 65 and 210 mV to achieve current densities of 20 mA cm⁻² and 1 A cm⁻², respectively, with a Tafel slope of only 96 mV dec⁻¹. Moreover, MNS/CC maintains stable operation at 1 A cm⁻² for 240 h without significant degradation. The results offer insights into the design of non-precious metal-based electro-catalysts for industrial hydrogen production.

Colloids are a vital component of perovskite precursor solutions (PPSs), significantly influencing the quality of perovskite film formation. Despite their importance, a comprehensive understanding of these colloids remains elusive. In this work, we explored the colloidal compositions of two distinct PPS types: the monomer-mixing dissolution (MMD) and the pre-synthesized perovskite single crystal redissolution (SCR). We have uncovered a new dissolution chemical equilibrium mechanism where the transition from mixed monomers to the 3C cubic phase (α-phase) involves a reversible transformation. Our findings indicate that although colloidal size significantly affects the nucleation during perovskite crystallization, the composition of the colloids plays a more crucial role. The MMD method yields poly Pb-I·solvent clusters while the colloids derived from the SCR approach produce hexagonal lead-halide-based perovskite phase clusters. These divergent colloidal compositions lead to markedly different impacts on the perovskite film formation process. Notably, hexagonal-phase colloids act as favorable nucleation sites, promoting the generation of the α-phase perovskite films with larger grains, more homogeneous phases, and fewer defects. This work demonstrates the importance of tailoring colloidal compositions and provides theoretical insights into the beneficial effects of redissolving perovskite in forms such as powder, microcrystals, and single crystals.

The A-D-A′-D-A-type non-fused ring electron acceptors (NFREAs), consisting of electron-donating unit (D) as the bridge to link electron-accepting units (A and A′), have emerged as promising electron acceptors for organic solar cells (OSCs) and organic photodetectors (OPDs). As the units are linked by the carbon-carbon single bonds, these electron acceptors generally possess feasible synthesis and tunable optoelectronic properties. Herein, the recent progress of A-D-A′-D-A-type NFREAs is reviewed, including molecular design, device performance, structure-property relationships, and their applications in OSCs and OPDs. Finally, we discuss the challenges and propose the perspectives for the further development of A-D-A′-D-A-type NFREAs.

Ultrasmall gold nanoparticles (AuNPs, d < 3 nm) have become an outstanding type of theranostic probe because of tunable luminescence, superior pharmacokinetics, low toxicity, and rich surface chemistry. The second near-infrared (NIR-II) luminescence offers unique merits, such as deep tissue penetration, high spatial resolution, and admirable signal-noise ratio, creating many opportunities and challenges for ultrasmall AuNPs in advanced biomedical applications. Herein, this review illustrates the recent advances of ultrasmall AuNPs in understanding the NIR-II mechanisms, clearance pathways, and related biomedical applications. We firstly elucidate the present understanding of the NIR-II mechanisms of ultrasmall AuNPs, along with some effective strategies for enhancing NIR-II luminescence, namely heterometal doping and surface rigidification. Then, we discuss the impact of their structures on liver clearance and kidney clearance. Further, we highlight the major biomedical applications of these ultrasmall AuNPs in bioimaging, antibacterial, nanomedicine, and drug delivery. Finally, we offer some outlooks on the challenges and chances of ultrasmall AuNPs for later research endeavors to promote their clinical translation in the biomedical field.

Post-resection recurrence remains a severe problem in melanoma treatment. New therapeutic strategies, such as chemodynamic therapy (CDT), exhibit high specificity and responsiveness, demonstrating potential to elicit antitumor immune responses by triggering immunogenic cell death (ICD). However, the efficacy of CDT still faces challenges from the immunosuppressive tumor microenvironment (TME) characterized by elevated lactate levels. Herein, we propose a strategy to construct an immunomodulatory hydrogel to synergistically reprogram tumor-associated macrophages and amplify ICD to inhibit melanoma recurrence after surgery. The hyaluronic acid hydrogel containing borosilicate glasses (BGs) and Fe₃O₄ nanoparticles (HBF hydrogel) are obtained, which can neutralize tumor acidity to reprogram macrophages to M1 phenotype. Furthermore, the HBF hydrogel induces reactive oxygen species production in melanoma cells, which could induce ICD through CDT and stimulate strong antitumor immune responses, thereby promoting tumor immunotherapy. The cooperative ICD induced by CDT and immunosuppressive TME remodeling leads to effective suppression of tumor recurrence. This work provides a promising strategy for immunomodulation-enhanced melanoma therapy through the fabrication of hydrogel to prevent postsurgical tumor recurrence.