Electronic structure and effective mass of pristine and Cl-doped CsPbBr_(3)

Organic–inorganic lead halide perovskites(LHPs) have attracted great interest owing to their outstanding optoelectronic properties.Typically,the underlying electronic structure would determinate the physical properties of materials.But as for now,limited studies have been done to reveal the underlying electronic structure of this material system,comparing to the huge amount of investigations on the material synthesis.The effective mass of the valance band is one of the most important physical parameters which plays a dominant role in charge transport and photovoltaic phenomena.In pristine CsPbBr_(3),the Fr?hlich polarons associated with the Pb–Br stretching modes are proposed to be responsible for the effective mass renormalization.In this regard,it would be very interesting to explore the electronic structure in doped LHPs.Here,we report high-resolution angle-resolved photoemission spectroscopy(ARPES) studies on both pristine and Cl-doped CsPbBr_(3).The experimental band dispersions are extracted from ARPES spectra along both ■ and ■ high symmetry directions.DFT calculations are performed and directly compared with the ARPES data.Our results have revealed the band structure of Cl-doped CsPbBr_(3) for the first time,which have also unveiled the effective mass renormalization in the Cl-doped CsPbBr_(3) compound.Doping dependent measurements indicate that the chlorine doping could moderately tune the renormalization strength.These results will help understand the physical properties of LHPs as a function of doping.

Spatial variations in the trophic status of Favia palauensis corals in the South China Sea:Insights into their different adaptabilities under contrasting environmental conditions

Scleractinian corals exhibit a dual trophic pattern of autotrophic photosynthesis and heterotrophic predation.However,whether corals can adjust their trophic status under contrasting environmental conditions remains unclear.In our study,70 scleractinian corals(Favia palauensis)were collected from Sanya and the Xisha and Nansha Islands in the South China Sea.We measured the zooxanthellae density(ZD)andδ^(13)C of zooxanthellae(δ^(13)C_(z))and host tissue(δ^(13)C_(h))and analyzed the difference betweenδ^(13)C_(h) andδ^(13)C_(z)(i.e.,△^(h-z)^(13)C).The relatively high ZD andδ^(13)C_(z) values in the samples from Sanya indicate that these corals might have higher photosynthetic rates and autotrophic abilities than those from Xisha and Nansha.In contrast,the relatively lowδ^(13)C_(h) and△^(h-z)^(13)C values in the samples from Xisha and Nansha suggest that these corals might have a higher heterotrophic ability than those from Sanya.In addition,we tested the coral tissue biomass and skeletalδ^(13)C(δ^(13)C_(s))in the samples from Sanya and examined their correlations with△^(h-z)^(13)C.The results showed a negative correlation,indicating that the more the organic material produced by the coral,the stronger its heterotrophic ability.Our results show that corals can adjust their trophic status under different environmental and physiological conditions,which is essential for increasing their adaptability to different environmental conditions.

Impacts of tropical cyclones and anthropogenic activities on marine vanadium: A unique perspective from high resolution Porites coral record

As a typical contaminant in fossil fuels,vanadium has undergone dramatically increase due to the impacts from human activities.The excessive anthropogenic vanadium emissions have altered natural geochemical processes.However,research on vanadium geochemistry in the ocean,which is the major sink for vanadium mobilized on land,has lagged much behind relative to those of other contaminants.Here we reconstruct historical patterns of vanadium in surface seawater utilizing a high-resolution temporal record(1984–2015 CE)of geochemical proxies(vanadium/calcium(V/Ca),δ^(18)O,δ^(13)C,etc.)in a Porites coral colony from an offshore non-estuarine island in the northern South China Sea(SCS).We find a close association between the surface winds and the temporal patterns of coral V/Ca ratios,revealing great potential for documenting prehistoric changes in tropical cyclones.Moreover,the coral V/Ca record remarkably captured the temporal patterns of anthropogenic activities,offering a valuable and novel tool for testing the efficacy of specific legislation on pollution prevention.Combined with the other reported coral vanadium data,we recovered the historical changes in vanadium emissions in the northern SCS and identified that changing industrial practices should be responsible for the differences in anthropogenic vanadium emissions at each stage.Our results demonstrated that the coral V/Ca ratio at a high temporal resolution has great potential as a new and direct geochemical proxy for tropical cyclones after removing artificial disturbances in the ocean.