Light-Induced Chiral Iron Copper Selenide Nanoparticles Prevent β-Amyloidopathy In Vivo

The accumulation and deposition of β-amyloid (Aβ) plaques in the brain is considered a potential pathogenic mechanism underlying Alzheimer's disease (AD). Chiral l/d -Fe_xCu_ySe nanoparticles (NPs) were fabricated that interfer with the self-assembly of Aβ42 monomers and trigger the Aβ42 fibrils in dense structures to become looser monomers under 808 nm near-infrared (NIR) illumination. d -Fe_xCu_ySe NPs have a much higher affinity for Aβ42 fibrils than l -Fe_xCu_ySe NPs and chiral Cu_2−xSe NPs. The chiral Fe_xCu_ySe NPs also generate more reactive oxygen species (ROS) than chiral Cu_2−xSe NPs under NIR-light irradiation. In living MN9D cells, d -NPs attenuate the adhesion of Aβ42 to membranes and neuron loss after NIR treatment within 10 min without the photothermal effect. In-vivo experiments showed that d -Fe_xCu_ySe NPs provide an efficient protection against neuronal damage induced by the deposition of Aβ42 and alleviate symptoms in a mouse model of AD, leading to the recovery of cognitive competence.     

Porous Tantalum Nitride Single Crystal at Two-Centimeter Scale with Enhanced Photoelectrochemical Performance

Porous tantalum nitride (Ta₃N₅) single crystals, combining structural coherence and porous microstructure, would substantially improve the photoelectrochemical performance. The structural coherence would reduce the recombination of charge carriers and maintain excellent transport properties while the porous microstructure would not only reduce photon scattering but also facilitate surface reactions. Here, we grow bulk-porous Ta₃N₅ single crystals on a two-centimeter scale with (002), (023), and (041) facets, respectively, and show significantly enhanced photoelectrochemical performance. We show the preferential facet growth of porous crystals in a lattice reconstruction strategy in relation to lattice match and lattice channel. We present the facet engineering to enhance light absorption, exciton lifetime and transport properties. The porous Ta₃N₅ single crystal boosts photoelectrochemical oxidation of alcohols with the (002) facet showing the highest performance of >99 % alcohol conversion and >99 % aldehyde/ketone selectivity.     

TiCl3-Mediated Synthesis of 2,3,3-Trisubstituted Indolenines: Total Synthesis of (+)-1,2-Dehydroaspidospermidine, (+)-Condyfoline,and (−)-Tubifoline

2,3,3-Trisubstituted indolenine constitutes an integral part of many biologically important monoterpene indole alkaloids. We report herein an unprecedented access to this skeleton by a TiCl₃-mediated reductive cyclization of tetrasubstituted alkenes bearing a 2-nitrophenyl substituent. The proof of concept is demonstrated firstly by accomplishing a concise total synthesis of (+)-1,2-dehydroaspidospermidine featuring a late-stage application of this key transformation. A sequence of reduction of nitroarene to nitrosoarene followed by 6π-electron-5-atom electrocyclization and a 1,2-alkyl shift of the resulting nitrone intermediate was proposed to account for the reaction outcome. A subsequent total synthesis of (+)-condyfoline not only illustrates the generality of the reaction, but also provides a mechanistic insight into the nature of the 1,2-alkyl shift. The exclusive formation of (+)-condyfoline indicates that the 1,2-alkyl migration follows a concerted Wagner–Meerwein pathway, rather than a stepwise retro-Mannich/Mannich reaction sequence. Conditions for almost quantitative conversion of (+)-condyfoline to (−)-tubifoline by way of a retro-Mannich/1,3-prototropy/transannular cyclization cascade are also documented.     

Tailoring A Poly(ether sulfone) Bipolar Membrane: Osmotic-Energy Generator with High Power Density

Osmotic energy, obtained through different concentrations of salt solutions, is recognized as a form of a sustainable energy source. In the past years, membranes derived from asymmetric aromatic compounds have attracted attention because of their low cost and high performance in osmotic energy conversion. The membrane formation process, charging state, functional groups, membrane thickness, and the ion-exchange capacity of the membrane could affect the power generation performance. Among asymmetric membranes, a bipolar membrane could largely promote the ion transport. Here, two polymers with the same poly(ether sulfone) main chain but opposite charges were synthesized to prepare bipolar membranes by a nonsolvent-induced phase separation (NIPS) and spin-coating (SC) method. The maximum power density of the bipolar membrane reaches about 6.2 W m⁻² under a 50-fold salinity gradient, and this result can serve as a reference for the design of bipolar membranes for osmotic energy conversion systems.     

ACQ-to-AIE Transformation: Tuning Molecular Packing by Regioisomerization for Two-Photon NIR Bioimaging

The traditional design strategies for highly bright solid-state luminescent materials rely on weakening the intermolecular π–π interactions, which may limit diversity when developing new materials. Herein, we propose a strategy of tuning the molecular packing mode by regioisomerization to regulate the solid-state fluorescence. TBP-e-TPA with a molecular rotor in the end position of a planar core adopts a long-range cofacial packing mode, which in the solid state is almost non-emissive. By shifting molecular rotors to the bay position, the resultant TBP-b-TPA possesses a discrete cross packing mode, giving a quantum yield of 15.6±0.2 %. These results demonstrate the relationship between the solid-state fluorescence efficiency and the molecule's packing mode. Thanks to the good photophysical properties, TBP-b-TPA nanoparticles were used for two-photon deep brain imaging. This molecular design philosophy provides a new way of designing highly bright solid-state fluorophores.     

Degradation of Structurally Defined Graphene Nanoribbons by Myeloperoxidase and the Photo-Fenton Reaction

As an emerging member of the graphene family, structurally defined graphene nanoribbons (GNRs) have shown promising applications in various fields. The evaluation of the degradability of GNRs is particularly important for assessing the persistence level and risk of these materials in living organisms and the environment. However, there is a void in the study of the degradation of GNRs. Here, we report the degradation behavior of GNRs in the presence of human myeloperoxidase (hMPO) or treated with the photo-Fenton (PF) reaction. With the assistance of potassium hydroxide or imidazole, which facilitates the dispersion of GNRs in the aqueous solution, GNRs underwent only partial degradation after 25-hour incubation with hMPO, while, the PF reaction degraded GNRs almost completely after 120 hours. These results indicate that structurally precise GNRs can be efficiently degraded under suitable conditions, providing more opportunities for future applications in different fields.     

A Universal Graphene Quantum Dot Tethering Design Strategy to Synthesize Single-Atom Catalysts

A general graphene quantum dot-tethering design strategy to synthesize single-atom catalysts (SACs) is presented. The strategy is applicable to different metals (Cr, Mn, Fe, Co, Ni, Cu, and Zn) and supports (0D carbon nanosphere, 1D carbon nanotube, 2D graphene nanosheet, and 3D graphite foam) with the metal loading of 3.0–4.5 wt %. The direct transmission electron microscopy imaging and X-ray absorption spectra analyses confirm the atomic dispersed metal in carbon supports. Our study reveals that the abundant oxygenated groups for complexing metal ions and the rich defective sites for incorporating nitrogen are essential to realize the synthesis of SACs. Furthermore, the carbon nanotube supported Ni SACs exhibits high electrocatalytic activity for CO₂ reduction with nearly 100 % CO selectivity. This universal strategy is expected to open up new research avenues to produce SACs for diverse electrocatalytic applications.     

Programmable Live-Cell CRISPR Imaging with Toehold-Switch-Mediated Strand Displacement

The widespread application of CRISPR-Cas9 has transformed genome engineering. Nevertheless, the precision to control the targeting activity of Cas9 requires further improvement. We report a toehold-switch-based approach to engineer the conformation of single guide RNA (sgRNA) for programmable activation of Cas9. This activation circuit is responsive to multiple inputs and can regulate the conformation of the sgRNA through toehold-switch-mediated strand displacement. We demonstrate the orthogonal suppression and activation of Cas9 with orthogonal DNA inputs. Combination of toehold switches leads to a variety of intracellular Cas9 activation programs with simultaneous and orthogonal responses, through which multiple genome loci are displayed in different colors in a controllable manner. This approach provides a new route for programing CRISPR in living cells for genome imaging and engineering.     

Mercury forms and their transformation in pyrite under weathering

Pyrite is considered to be the major carrier of mercury in coal. Here, the chemical characteristics of two natural pyrite samples of different weathering degrees were characterized by time-of-flight secondary ion mass spectrometry (TOF-SIMS). Thermal stability of Hg was also analyzed via temperature programmed desorption experiment (TPD). Characteristic ions such as S⁻, Fe⁺, FeS⁻, and FeS₂⁻ were detected on the surface of fresh pyrite. The release temperature of Hg ranged between 180°C and 300°C, and the characteristic peak of black HgS was recorded. In addition, abundant Fe₂O₃⁻, FeSO⁻, SO₄⁻, and HSO₄⁻ were detected on the surface of weathered pyrite, and the release temperature of Hg therein was mainly distributed at 260°C to 380°C and 520°C to 600°C, corresponding to the characteristic peaks of red HgS and HgSO₄, respectively. The results show that pyrite is acidified during weathering and that Hg forms in pyrite are transformed from the original state (HgS) to HgSO₄.     

Oxygen- and Nitrogen-Embedded Zigzag Hydrocarbon Belts

Despite the aesthetically appealing structures and tantalizing physical and chemical properties, zigzag hydrocarbon belts and their heteroatom-embedded analogues remain challenging synthetic targets. We report herein the synthesis of diverse O/N-doped zigzag hydrocarbon belts based on selective bridging of the fjords of resorcin[4]arene derivatives through intramolecular S_NAr and palladium-catalyzed intermolecular C−N bond formation reactions. Preorganized conformations of mono-macrocyclic, half-belt and quasi-belt compounds were revealed to facilitate cyclization reactions to construct heteroatom-linked octahydrobelt[8]arenes. The acquired products had strained square-prism-shaped belt structures in which all six-membered heterocyclic rings adopted an unusual boat conformation with equatorially configured alkyl groups. The unprecedented heteroatom-bearing belts also exhibited different photophysical and redox properties to those of octahydrobelt[8]arene analogues.