Two-dimensional (2D) halide perovskites have recently been recognized as a promising avenue in perovskite solar cells (PSCs) in terms of encouraging stability and defect passivation effect. However, the efficiency (less than 15%) of ultra-stable 2D Ruddlesden-Popper PSCs still lag far behind their traditional three-dimensional (3D) perovskite counterparts. Here, we report a rationally designed 2D-3D perovskite stacking-layered architecture by in-situ growing 2D PEA 2 PbI 4 capping layers on top of 3D perovskite film, which drastically improved the stability of PSCs without compromising their high performance. Such 2D perovskite capping layer induces larger Fermi-level splitting in the 2D-3D perovskite film under light illumination, resulting in an enhanced open-circuit voltage (V oc ) and thus a higher efficiency of 18.51% in the 2D-3D PSCs. The time-resolved photoluminescence (TRPL) decay measurements indicate the facilitated hole-extraction in the This article is protected by copyright. All rights reserved. 22D-3D stacking-layered perovskite films, which is ascribed to the optimized energy band alignment and reduced non-radiative recombination at the sub gap states. Benefiting from the high moisture resistivity as well as suppressed ion migration of the 2D perovskite, the 2D-3D PSCs show significantly improved long-term stability, retaining nearly 90% of the initial PCE after 1000 h exposure in the ambient conditions with a high relative humidity level of 60±10%.

The increasing demand of clinical biomedicine and fast development of nanobiotechnology has substantially promoted the generation of a variety of organic/inorganic nanosystems for biomedical applications. Biocompatible two-dimensional (2D) graphene analogues (e.g., nanosheets of transition metal dichalcogenides, transition metal oxides, g-C3N4, Bi2Se3, BN, etc.), which are referred to as 2D-GAs, have emerged as a new unique family of nanomaterials that show unprecedented advantages and superior performances in biomedicine due to their unique compositional, structural and physicochemical features. In this review, we summarize the state-of-the-art progress of this dynamically developed material family with a particular focus on biomedical applications. After the introduction, the second section of the article summarizes a range of synthetic methods for new types of 2D-GAs as well as their surface functionalization. The subsequent section provides a snapshot on the use of these biocompatible 2D-GAs for a broad spectrum of biomedical applications, including therapeutic (photothermal/photodynamic therapy, chemotherapy and synergistic therapy), diagnostic (fluorescent/magnetic resonance/computed tomography/photoacoustic imaging) and theranostic (concurrent diagnostic imaging and therapy) applications, especially on oncology. In addition, we briefly present the biosensing applications of these 2D-GAs for the detection of biomacromolecules and their in vitro/in vivo biosafety evaluations. The last section summarizes some critical unresolved issues, possible challenges/obstacles and also proposes future perspectives related to the rational design and construction of 2D-GAs for biomedical engineering, which are believed to promote their clinical translations for benefiting the personalized medicine and human health.

This paper reports on the swelling and exfoliation behavior of a layered protonic manganese oxide, H(0.13)MnO(2).0.7H(2)O, in a solution of tetrabutylammonium (TBA) hydroxide and the formation and characterizations of unilamellar two-dimensional crystallites of MnO(2). At low doses of TBA ions, layered manganese oxide was observed to undergo normal intercalation, yielding a TBA intercalated phase with a gallery height of 1.25 nm. With a large excess of TBA ions, osmotic swelling occurred, giving rise to a very large intersheet separation of 3.5-7 nm. In an intermediate TBA concentration range, the sample exhibited a broad X-ray diffraction profile with superimposed diffraction features due to intercalation and osmotic swelling. The component responsible for the broad profile was isolated by centrifuging the mixture twice at different speeds, and the recovered colloid was identified as a pile of MnO(2) nanosheets, corresponding to the individual host layer of the precursor layered manganese oxide. Observations by transmission electron microscopy and atomic force microscopy revealed high two-dimensional anisotropy with a lateral dimension of submicrometers and a thickness of approximately 0.8 nm. The nanosheet exhibited broad optical absorption with a peak at 374 nm (epsilon = 1.13 x 10(4) mol(-1) dm(3) cm(-1)). The restacking process of the colloidal MnO(2) nanosheets was followed by aging the colloid at a relative humidity of 95%. The broad diffraction pattern due to the exfoliated sheets weakened with time and eventually resolved into two sharp distinct profiles attributable to a TBA intercalation compound with an intersheet spacing of 1.72 nm and an osmotically swollen hydrate with >10 nm at a very early stage. As drying progressed, the former phase became more abundant without a change in interlayer distance, while the degree of swelling of the latter phase gradually decreased to 2.7 nm that remained unchanged on further aging. Subsequent drying at a lower humidity collapsed the 2.7 nm phase. The resulting single 1.72 nm phase was dehydrated by heating at 150 degrees C to produce a phase with a contracted interlayer spacing of 1.3 nm.

The mixed caesium and formamidinium lead triiodide perovskite system (Cs1-xFAxPbI3) in the form of quantum dots (QDs) offers a new pathway towards stable perovskite-based photovoltaics and optoelectronics. However, it remains challenging to synthesize such multinary QDs with desirable properties for high-performance QD solar cells (QDSCs). Here we report an effective ligand-assisted cation exchange strategy that enables controllable synthesis of Cs1-xFAxPbI3 QDs across the whole composition range (x: 0-1), which is inaccessible in large-grain polycrystalline thin films. The surface ligands play a key role in driving the cross-exchange of cations for the rapid formation of Cs1-xFAxPbI3 QDs with suppressed defect density. The hero Cs0.5FA0.5PbI3 QDSC achieves a certified record power conversion efficiency (PCE) of 16.6% with negligible hysteresis. We further demonstrate that QD devices exhibit substantially enhanced photostability compared to their thin film counterparts because of the suppressed phase segregation, retaining 94% of the original PCE under continuous 1-sun illumination for 600 hours.

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Emerging evidence indicates that osteoclasts direct osteoblastic bone formation. MicroRNAs (miRNAs) have a crucial role in regulating osteoclast and osteoblast function. However, whether miRNAs mediate osteoclast-directed osteoblastic bone formation is mostly unknown. Here, we show that increased osteoclastic miR-214-3p associates with both elevated serum exosomal miR-214-3p and reduced bone formation in elderly women with fractures and in ovariectomized (OVX) mice. Osteoclast-specific miR-214-3p knock-in mice have elevated serum exosomal miR-214-3p and reduced bone formation that is rescued by osteoclast-targeted antagomir-214-3p treatment. We further demonstrate that osteoclast-derived exosomal miR-214-3p is transferred to osteoblasts to inhibit osteoblast activity in vitro and reduce bone formation in vivo. Moreover, osteoclast-targeted miR-214-3p inhibition promotes bone formation in ageing OVX mice. Collectively, our results suggest that osteoclast-derived exosomal miR-214-3p transfers to osteoblasts to inhibit bone formation. Inhibition of miR-214-3p in osteoclasts may be a strategy for treating skeletal disorders involving a reduction in bone formation.

The CH3 NH3 PbI3- x Clx organic-inorganic hybrid perovskite material demonstrates remarkable resistive switching behavior, which can be applicable in resistive random access memory devices. The simply designed Au/CH3 NH3 PbI3- x Clx /FTO structure is fabricated by a low-temperature, solution-processable method, which exhibits remarkable bipolar resistive switching and nonvolatile properties.