Due to their layered structure, two-dimensional Ruddlesden-Popper perovskites (RPPs), composed of multiple organic/inorganic quantum wells, can in principle be exfoliated down to few and single layers. These molecularly thin layers are expected to present unique properties with respect to the bulk counterpart, due to increased lattice deformations caused by interface strain. Here, we have synthesized centimetre-sized, pure-phase single-crystal RPP perovskites (CH(CH)NH)(CHNH)PbI (n = 1-4) from which single quantum well layers have been exfoliated. We observed a reversible shift in excitonic energies induced by laser annealing on exfoliated layers encapsulated by hexagonal boron nitride. Moreover, a highly efficient photodetector was fabricated using a molecularly thin n = 4 RPP crystal, showing a photogain of 10 and an internal quantum efficiency of ~34%. Our results suggest that, thanks to their dynamic structure, atomically thin perovskites enable an additional degree of control for the bandgap engineering of these materials.

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Controllable synthesis of single atom catalysts (SACs) with high loading remains challenging due to the aggregation tendency of metal atoms as the surface coverage increases. Here we report the synthesis of graphene supported cobalt SACs (Co1/G) with a tuneable high loading by atomic layer deposition. Ozone treatment of the graphene support not only eliminates the undesirable ligands of the pre-deposited metal precursors, but also regenerates active sites for the precise tuning of the density of Co atoms. The Co1/G SACs also demonstrate exceptional activity and high selectivity for the hydrogenation of nitroarenes to produce azoxy aromatic compounds, attributable to the formation of a coordinatively unsaturated and positively charged catalytically active center (Co–O–C) arising from the proximal-atom induced partial depletion of the 3d Co orbitals. Our findings pave the way for the precise engineering of the metal loading in a variety of SACs for superior catalytic activities.

diminishing groundwater resources, mitigated river flows, dwindling lakes, and heavily polluted water. The challenge of providing sufficient and safe freshwater is limited by population growth, climatic changes, industrialization, and contamination of available freshwater sources. [1][2][3][4][5][6] In its latest annual risk report, the world economic forum ranks water crisis as a major global risk in terms of its potential impact. Many problems associated with the scarcity of water not only are restricted to around four billion people lacking access to safe and pure drinking water at least one month of the year, [3,7] high mortality rates, instigation of civil or international conflicts [8,9] but also pose a severe threat to industries, affecting operations and supply chain. [2] The most common reason attributed to this is that only about 3% of the earth's water resources is fresh and the rest is saline and unpalatable. Of the fresh water sources, 2.5% is locked up in the form of glaciers in the Arctic and Antarctic regions and are unavailable for use. Thus humanity, for its sustenance, must rely only on the 0.5% of the total water resources which is stored as underground aquifers, flowing rivers, natural lakes, and manmade storage facilities.Several alternative approaches of water harvesting have been developed lately. These include water harvesting from ambient humid atmospheres using hydrophobic surfaces for easy water condensation, [10] purification of water accompanying the production of shale gas, [11] water harvesting from fog [12,13] using special structures, dewing, [14,15] disinfection and decontamination of polluted water sources, [7,16,17] and desalination of seawater. Inspired by the unique water harvesting abilities of cacti [18] and some of the beetles of the Namib desert, [19] synthesis of biomimetic structures using copper [20,21] and branched ZnO nanowires [18] have been employed for water collection. Fog collectors, employing the principle of forcing fog droplets through a mesh for water collection have been employed recently in many African and European countries to harvest fresh water from moving clouds. [13] However these alternative sources contribute only to a very small fraction of the actual demand for fresh water, which widely varies demographically and totals to a staggering value of ten billion tons per day. [22] Water scarcity is a ubiquitous problem with its magnitude expected to rise in the near future, and efforts to seek alternative water sources are on the rise. Harvesting water from air has intrigued enormous research interest among many groups with Scientific American listing this technology as the second most impactful technology that can bring about a massive change in people's lives. Though desalination offers a huge prospect in mitigating water crisis, its practicality is limited by exorbitant energy requirement. Alternatively, the air above sea water is moisture rich, with the quantity of vapor increasing at the rate of 0.41 kg m −2 . Herein, a method to sustainably h...

Atmospheric humidity, an abundant source of water, is widely considered as a redundant resource demanding expense of energy to maintain it under comfortable levels for human habitation.

The balance between cell proliferation and apoptosis is critical for normal development and for the maintenance of homeostasis in adult organisms. Disruption of this balance has been implicated in a large number of disease processes, ranging from autoimmunity and neurodegenerative disorders to cancer. The ubiquitin-proteasome pathway, responsible for mediating the majority of intracellular proteolysis, plays a crucial role in the regulation of many normal cellular processes, including the cell cycle, differentiation and apoptosis. Apoptosis in cancer cells is closely connected with the activity of ubiquitin-proteasome pathway. The peptide-aldehyde proteasome inhibitor MG132 (carbobenzoxyl-L-leucyl-L-leucyl-L-leucine) induces the apoptosis of cells by a different intermediary pathway. Although the pathway of induction of apoptosis is different, it plays a crucial role in anti-tumor treatment. There are many cancer-related molecules in which the protein levels present in cells are regulated by a proteasomal pathway; for example, tumor inhibitors (P53, E2A, c-Myc, c-Jun, c-Fos), transcription factors (transcription factor nuclear factor-kappa B, IkBa, HIFI, YYI, ICER), cell cycle proteins (cyclin A and B, P27, P21, IAP1/3), MG132 induces cell apoptosis through formation of reactive oxygen species or the upregulation and downregulation of these factors, which is ultimately dependent upon the activation of the caspase family of cysteine proteases. In this article we review the mechanism of the induction of apoptosis in order to provide information required for research.

The ability to precisely engineer the doping of sub-nanometer bimetallic clusters offers exciting opportunities for tailoring their catalytic performance with atomic accuracy. However, the fabrication of singly dispersed bimetallic cluster catalysts with atomic-level control of dopants has been a long-standing challenge. Herein, we report a strategy for the controllable synthesis of a precisely doped single cluster catalyst consisting of partially ligandenveloped Au 4 Pt 2 clusters supported on defective graphene. This creates a bimetal single cluster catalyst (Au 4 Pt 2 /G) with exceptional activity for electrochemical nitrogen (N 2) reduction. Our mechanistic study reveals that each N 2 molecule is activated in the confined region between cluster and graphene. The heteroatom dopant plays an indispensable role in the activation of N 2 via an enhanced back donation of electrons to the N 2 LUMO. Moreover, besides the heteroatom Pt, the catalytic performance of single cluster catalyst can be further tuned by using Pd in place of Pt as the dopant.

The ability to tune both local and global environments of a singlemetal active center on a support is crucial for the development of highly robust and efficient single-atom electrocatalysts (SAECs) that can surmount both thermodynamic and kinetic constraints in electrocatalysis. Here, we designed a core−shellstructured SAEC (Co 1 -SAC) with superior oxygen reduction reaction (ORR) performance. Co 1 -SAC consists of a locally engineered single Co-N 3 C 1 site on a Ndoped microporous amorphous carbon support enveloped by a globally engineered highly conductive mesoporous graphitic carbon shell. Theoretical calculations reveal that Co-N 3 C 1 exhibits near-Fermi electronic states distinct from those of Co-N 2 C 2 and Co-N 4 , which facilitate both the electronic hybridization with O 2 and the subsequent protonation of adsorbed O 2 * toward the formation of OOH*. Engineering Co-N 3 C 1 -SAC into a micro/mesoporous core−shell structure dramatically enhances the mass transport and electron transfer, which further boosts the ORR and Zn-air battery performance (slightly outperforming Pt/C). Our findings open an avenue toward engineering of the local and global environment of SACs for a wide range of efficient electrochemical conversions.