Peixin Du

While all‐inorganic lead halide perovskite quantum dots offer tunable pathways toward programmable optoelectronics, the origin of stimulus‐activated phase transformation and its underlying photophysics remain controversial. Here, by constructing a composition‐tunable dual‐phase Cs ₄ PbBr ₆ ‐CsPbBr ₃ quantum dots platform with direct interfacial contact, we have identified key factors that regulate the emission behavior through careful structural and spectroscopic analyses, including interfacial strain and localized‐states‐induced changes of carrier trapping and recombination pathways. Furthermore, in situ solvent treatment uncovers the hydroxyl‐triggered, polarity‐modulated CsBr extraction mechanism that drives the localized conversion from non‐emissive Cs ₄ PbBr ₆ to green emissive CsPbBr ₃ . Such solvent‐programmable optical activation is further converted into an optical/electrical dual‐mode readout using a planar photoconductor. The dual‐mode response enables discrimination between hydroxyl‐containing and hydroxyl‐free solvents, identification of various protic solvents, and semi‐quantitative analysis of water content in ethanol‐water mixtures. This work provides synthetic and mechanistic strategies for regulating the structure‐property relationships of interphase perovskite quantum dots and establishes a dual‐mode sensing platform that couple photoluminescence activation with photoconductive signatures for solvent identification and discrimination.

Poorly ordered Al/Si phases are widely distributed across the surface of Mars, among which allophane and amorphous silica are the two main constituents. Both allophane and amorphous silica can form in Al‐Si systems through surface chemical weathering or subsurface hydrothermal alteration of volcanic materials. Nevertheless, our comprehension of the products derived from Al‐Si hydrolysis systems remains poorly constrained. Hydrolysis experiments were conducted on Al‐Si systems across an unprecedentedly wide range of Si/(Al + Si) molar ratios ( n , 0 ≤ n ≤ 0.9), followed by characterizing the products using multiple techniques. At n ≤ 0.1, the products consist predominantly of Al ₃₀ (an Al polycation with a Keggin structure) and poorly ordered Al hydroxides. The introduction of Si resulted in formation of a small amount of proto‐allophane. At n = 0.2 and 0.3, poorly ordered materials were still dominant, along with the presence of well‐crystallized bayerite and gibbsite. The proto‐allophane increased in quantity and began to assemble into allophane. At n = 0.5, well‐crystallized minerals were absent and allophane dominated the product. At n = 0.7, the amount of allophane decreased significantly and at n = 0.8 and 0.9, allophane was probably absent, although proto‐allophane still formed. Meanwhile, an increasing amount of amorphous silica was formed. X‐ray diffraction, Fourier transform infrared, and VNIR provide information for differentiating Al‐rich phases and Si‐rich phases but show limited capability in identifying poorly ordered Al/Si‐rich phases. NMR is powerful for identifying poorly ordered Al/Si phases, although widespread iron on the martian surface and the large instrument pose challenges to its application on Mars.

Ferrihydrite, a nanocrystalline iron (oxyhydr)oxide mineral, is widely distributed in soils and sediments on Earth and is probably an important component and/or precursor of widespread nanophase iron minerals on Mars. Terrestrial ferrihydrite often co‐occurs with amorphous silica and/or contains a certain amount of Si in its structure. However, it remains ambiguous how environmental Si concentration affects the formation‐evolution and structure‐spectral features of ferrihydrite in the Fe(III)‐Si systems. To this end, hydrolysis experiments were carried out for Fe‐Si systems at an unprecedentedly wide range of initial Si/(Fe + Si) molar ratios (0–0.80), followed by characterizing the products detailly. X‐ray diffraction, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, Mössbauer spectroscopy, and transmission electron microscopy results showed that at Si/(Fe + Si) molar ratios ≤0.30, the main phase of the products was ferrihydrite, of which the unit cells enlarged, the crystallinity decreased, and the existing state of Fe changed with increased Si contents; at Si/(Fe + Si) molar ratios ≥0.40, ferrihydrite was no longer formed and a novel amorphous Fe‐O‐Si phase was instead obtained, with the excess Si forming amorphous silica. The visible and near‐infrared spectroscopy, the most powerful tool to detect hydrous minerals on the surface of Mars at global or regional scales, showed weakness in identifying ferrihydrite‐like materials obtained in the Fe‐Si systems. Raman spectroscopy can identify ferrihydrite and Si‐containing ferrihydrite but cannot differentiate between them. Mössbauer spectroscopy showed great potential in both identifying and differentiating between ferrihydrite and Si‐containing ferrihydrite, and thus can be used to characterize the poorly ordered iron (oxyhydr)oxides on Mars.

Diatoms play an important role in the biogeochemical cycling of aluminum (Al) in oceans. This occurs via the uptake of biological Al (Al_bio), which is incorporated into the structure of diatom‐derived biogenic silica (DBSi) and the formation of adsorbed Al (Al_ads) on the DBSi surface of post‐mortem diatoms. Al occurrence influences DBSi dissolution and thus diatom‐driven carbon sequestration. However, the mechanism of Al occurrence in DBSi remains unclear. In this study, Al_bio and Al_ads of DBSi from various diatom fossils in marine diatomaceous sediments were identified and quantified by combined focused ion beam thinning, elemental analysis, and the Al K‐edge X‐ray absorption near edge structure. Results showed the coexistence of Al_bio and Al_ads in all diatomaceous sediments and Al‐bearing DBSi thus constitutes a biological Al pool. Al_bio and Al_ads were mainly fourfold‐ and sixfold‐coordinated, respectively and Al_ads was much more abundant than Al_bio. Moreover, even at low concentrations (with an Al/Si atomic ratio of 0.0031), Al_bio can inhibit DBSi dissolution, effectively decreasing the extent of DBSi dissolution by ∼14%. Al_bio also significantly increased the mechanical strength of DBSi. The average Young's modulus (a measure of the stiffness of a material) of cribrum layers in Al‐incorporated DBSi was ∼1.4 times higher than that of Al‐free DBSi. Our results further demonstrate that diatoms play a dominant role in the biogeochemical cycling of Al in oceans, and the Al of DBSi participates in diatom‐driven Si and C coupled cycles in oceans, influencing the effectiveness of diatom‐driven carbon export by regulating the dissolution and mechanical strength of DBSi.

Herein, we present a new strategy to create a highly regenerative and efficient phosphate adsorbent based on activating natural palygorskite structures. Both the regeneration via alkaline activation and synthesis via co-calcination restructured the palygorskite and created adsorptive metal oxides. The phosphate adsorbent exhibits excellent regeneration performance with high removal capacity.