Numerous trap states and low conductivity of compact TiO 2 layers are major obstacles for achieving high power conversion efficiency and high-stability perovskite solar cells. Here we report an effective Na 2 S-doped TiO 2 layer, which can improve the conductivity of TiO 2 layers, the contact of the TiO 2 /perovskite interface, and the crystallinity of perovskite layers. Comprehensive investigations demonstrate that Na cations increase the conductivity of TiO 2 layers while S anions change the wettability of TiO 2 layers, thus improving the crystallinity of perovskite layers and passivate defects at the TiO 2 /PVK interface. The synergetic effects of dopants lead to a champion efficiency as high as 21.25% in unencapsulated perovskite solar cells (PSCs), with much-improved stability. Our work provides new insights on anion dopants in TiO 2 layers, which is usually neglected in previous reports, and also proposes a simple approach to produce low-cost and highperformance electron transport layers for high-performance PSCs.

Mineral–soil organic matter (SOM including DNA, proteins, and polysaccharides) associations formed through various interactions, play a key role in regulating long-term SOM preservation. The mechanisms underlying DNA–mineral and DNA–protein/polysaccharide interactions at nanometer and molecular scales in environmentally relevant solutions remain uncertain. Here, we present a model mineral–SOM system consisting of mineral (mica)–nucleic acid (environmental DNA, eDNA)/protein (bovine serum albumin)/polysaccharide (alginate), and combine atomic force microscopy (AFM)-based dynamic force spectroscopy and PeakForce quantitative nanomechanical mapping using DNA-decorated tips. Single-molecule binding and adhesion force of eDNA to mineral and to mineral adsorbed by protein/polysaccharide reveal the noncovalent bonds and that systematically changing ion compositions, ionic strength, and pH result in significant differences in organic–organic and organic–mineral binding energies. Consistent with the bond-strength measurements, protein, rather than polysaccharide, promotes mineral-bound DNA molecules by ex situ AFM deposition observations in relatively high concentrations of divalent cation-containing acidic solutions. These molecular-scale determinations and nanoscale observations should substantially improve our understanding of how environmental factors influence the organic–mineral interfacial interactions through the synergy of collective noncovalent and/or covalent bonds in mineral–organic associations.

Cadmium (Cd) and Arsenate (As) are the main toxic elements in soil environments and are easily taken up by plants. Unraveling the kinetics of the adsorption and subsequent precipitation/immobilization on mineral surfaces is of considerable importance for predicting the fate of these dissolved species in soils. Here we used in situ atomic force microscopy (AFM) to image the dissolution on the (010) face of brushite (dicalcium phosphate dihydrate, CaHPO·2HO) in CdCl- or NaHAsO-bearing solutions over a broad pH and concentration range. During the initial dissolution processes, we observed that Cd or As adsorbed on step edges to modify the morphology of etch pits from the normal triangular shape to a four-sided trapezium. Following extended reaction times, the respective precipitates were formed on brushite through a coupled dissolution-precipitation mechanism. In the presence of both CdCl and NaHAsO in reaction solutions at pH 8.0, high-resolution transmission electron microscopy (HRTEM) showed a coexistence of both amorphous and crystalline phases, i.e., a mixed precipitate of amorphous and crystalline CdCa (AsO)(PO) OH phases was detected. These direct dynamic observations of the transformation of adsorbed species to surface precipitates may improve the mechanistic understanding of the calcium phosphate mineral interface-induced simultaneous immobilization of both Cd and As and subsequent sequestration in diverse soils.

The organic matrix in forming enamel consists largely of the self-assembled nanospheres of amelogenin monomers that play a critical role in controlling crystal growth of the highly organized apatites. However, little is known about the mechanisms of the monomeric form of the C-terminal tail of the molecule in regulating biomineralization dynamics. We investigated brushite-amelogenin's C-terminus interactions by in situ atomic force microscopy (AFM). At very low concentrations (1-10 nM) within a monomeric form of amelogenin, we directly observe a strong interaction of monomeric amelogenin's C-terminus binding to the brushite (010) face, which modulates the critical length and terrace width of moving steps through modification of the brushite-water interfacial energies. This in turn inhibits crystallization by delaying the formation of active steps on the growing crystal face. These findings provide the underlying thermodynamics for understanding

In nature, simple organisms evolved mechanisms to form intricate biosilica nanostructures, far exceeding current synthetic manufacturing. Based on the properties of extracted biomacromolecules, polycation-polyanion pairs were suggested as moderators of biosilica formation. However, the chemical principles of this polymer-induced silicification remain unclear. Here, we used a biomimetic polycation-polyanion system to study polymer-induced silicification. We demonstrate that it is the polymer phase separation process, rather than silica-polymer interactions, which controls silica precipitation. Since ionic strength controls this electrostatic phase separation, it can be used to tune the morphology and structure of the precipitates. In situ cryo electron microscopy highlights the pivotal role of the hydrated polymer condensates in this process. These results pave the road for developing nanoscale morphologies of bioinspired silica based on the chemistry of liquid-liquid phase separation.