Progress of Lead‐Free Halide Double Perovskites

The field of halide metal perovskite photovoltaics has caught widespread interest in the last decade. This is seen in the rapid rise of power conversion efficiency, which is currently over 23%. It has also stimulated a widespread application of halide metal perovskites in other fields, such as light‐emitting diodes, field‐effect transistors, detectors, and lasers. Despite the fascinating characteristics of the halide metal perovskites, the presence of toxic lead (Pb) in their chemical composition is regarded as one of the major limiting factors preventing their commercialization. Addressing the toxicity issues in these compounds by a careful and strategic replacement of Pb²⁺ with other nontoxic candidate elements represents a promising direction to fabricate lead‐free optoelectronic devices. Such attempts yield a halide double perovskite structure which allows flexibility for various compositional adjustments. Here, the authors present the current progress and setbacks in crystal structures, materials preparation, optoelectronic properties, stability, and photovoltaic applications of lead‐free halide double perovskite compounds. Prospective research directions to improve the optoelectronic properties of existing materials are given that may help in the discovery of new lead‐free halide double perovskites.     

Fragment-based identification and optimization of a class of potent pyrrolo[2,1-f][1,2,4]triazine MAP4K4 inhibitors

MAP4K4 has been shown to regulate key cellular processes that are tied to disease pathogenesis. In an effort to generate small molecule MAP4K4 inhibitors, a fragment-based screen was carried out and a pyrrolotriazine fragment with excellent ligand efficiency was identified. Further modification of this fragment guided by X-ray crystal structures and molecular modeling led to the discovery of a series of promising compounds with good structural diversity and physicochemical properties. These compounds exhibited single digit nanomolar potency and compounds 35 and 44 achieved good in vivo exposure.     

Historical changes in anthropogenic lead fallout in southern Ontario,Canada

A quantitative historical record of anthropogenic lead deposition has been determined for the Haliburton region of southern Ontario from a) the relative change in lead concentration in undisturbed sediment cores, and b) the total anthropogenic lead deposition measured in the region. The first parameter was measured on two sediment cores from a meromictic lake. Total lead deposition was assumed to be the average of that measured for eight other lakes in the study area. The validity of this historical record was tested on sediment cores from nearby dimictic lakes. Predicted lead concentration profiles closely resembled observed profiles.     

Use of Energy Crop (Ricinus communis L.) for Phytoextraction of Heavy Metals Assisted with Citric Acid

Ricinus communis L. is a bioenergetic crop with high-biomass production and tolerance to cadmium (Cd) and lead (Pb), thus, the plant is a candidate crop for phytoremediation. Pot experiments were performed to study the effects of citric acid in enhancing phytoextraction of Cd/Pb by Ricinus communis L. Citric acid increased Cd and Pb contents in plant shoots in all treatments by about 78% and 18–45%, respectively, at the dosage of 10 mM kg^?1 soil without affecting aboveground biomass production. Addition of citric acid reduced CEC, weakened soil adsorption of heavy metals and activated Cd and Pb in soil solutions. The acid-exchangeable fraction (BCR-1) of Pb remained lower than 7% and significantly increased with citric acid amendment. Respective increases in soil evaluation index induces by 14% and 19% under the Cd1Pb50 and Cd1Pb250 treatments upon addition of citric acid resulted in soil quality improvement. Ricinus communis L. has great potential in citric acid-assisted phytoextraction for Cd and Pb remediation.     

Hyperaccumulator Oilcake Manure as an Alternative for Chelate-Induced Phytoremediation of Heavy Metals Contaminated Alluvial Soils

The ability of hyperaccumulator oilcake manure as compared to chelates was investigated by growing Calendula officinalis L for phytoremediation of cadmium and lead contaminated alluvial soil. The combinatorial treatment T₆ [2.5 g kg^?1oilcake manure + 5 mmol kg^?1 EDDS] caused maximum cadmium accumulation in root, shoot and flower up to 5.46, 4.74 and 1.37 mg kg^?1and lead accumulation up to 16.11, 13.44 and 3.17 mg kg^?1, respectively at Naini dump site, Allahabad (S₃). The treatment showed maximum remediation efficiency for Cd (RR = 0.676%) and Pb (RR = 0.202%) at Mumfordganj contaminated site (S₂). However, the above parameters were also observed at par with the treatment T₅ [2.5 g kg^?1oilcake manure +2 g kg^?1 humic acid]. Applied EDDS altered chlorophyll–a, chlorophyll–b, and carotene contents of plants while application of oilcake manure enhanced their contents in plant by 3.73–8.65%, 5.81–17.65%, and 7.04–17.19%, respectively. The authors conclude that Calendula officinalis L has potential to be safely grown in moderately Cd and Pb-contaminated soils and application of hyperaccumulator oilcake manure boosts the photosynthetic pigments of the plant, leading to enhanced clean-up of the cadmium and lead-contaminated soils. Hence, the hyperaccumulator oilcake manure should be preferred over chelates for sustainable phytoremediation through soil-plant rhizospheric process.     

Influence of vitamin D receptor haplotypes on blood lead concentrations in environmentally exposed children of Uygur and Han populations

Objective: To explore the association between polymorphism of vitamin D receptor (VDR) and lead poisoning in Uygur and Han children in China.

Methods: The BsmI, ApaI and TaqI restriction sites of VDR genotyping were determined by polymerase chain reaction–restriction fragment length polymorphism in 443 Uygur and 469 Han children from Xinjiang province. The correlation between the polymorphism of VDR haplotypes and blood lead levels was explored.

Results: The genotype frequencies of VDR had significant differences in Han and Uygur children (p <0.01). According to VDR–BsmI, ApaI and TaqI haplotype analysis in Han children, haplotypes Atb and AtB were considerably decreased in the lead poisoning group (p <0.05) while haplotype aTb and ATb were significantly increased in the lead poisoning group (p <0.01). However, such results were not found in Uygur children (p?<?0.05).

Conclusion: A significant difference was seen in the frequency distribution of the VDR genotype among the different races. Haplotypes Atb and AtB might be protective factors while haplotypes ATb and aTb might be risk factors in Han children.     

Impacts of Vehicle Emissions and Ambient Atmospheric Deposition in Nigeria on the Pb,Cd, and Ni Content of Fermented Cassava Flour Processed by Sun-Drying

A study of air pollution in Nigeria due to Pb, Cd, and Ni contamination of fermented cassava meant for flour production was carried out by AAS. Fermented cassava samples were purchased from farmers in the study area and one-third of each was oven-dried (OD) while the rest were sun-dried either along roadside (RS-SD) or under ambient atmosphere conditions (AA-SD). Mean concentrations (μg/g) for OD samples in year 2008 were: Pb (0.17 ± 0.04); Cd (0.04 ± 0.01); and Ni (0.27 ± 0.05) while RS-SD samples gave Pb (0.24 ± 0.08), Cd (0.04 ± 0.01), and Ni (0.48 ± 0.17). Mean values (μg/g) in 2009 for OD, AA-SD, and RS-SD, respectively, were Pb (0.03 ± 0.01, 0.05 ± 0.02, 0.15 ± 0.08), Cd (0.18 ± 0.01, 0.04 ± 0.02, 0.05 ± 0.02), and Ni (0.09 ± 0.06, 0.21 ± 0.10, 0.57 ± 0.12). Mean concentrations in sun-dried samples were greater (p < .01), while RS-SD samples were 185% in Pb, 53% in Cd, and 176% in Ni greater (p < .01) than AA-SD samples. With an estimated country-wide annual Pb emissions from petrol and diesel ranging from 616,241 to 968,086 kg, and dust, considered the major source of Cd and Ni, and other extraneous factors including metals adsorbed on pavement surfaces, sun-drying of wet foodstuff on the bare surface of roadside pavements could lead to high levels of Pb, Cd, and Ni in such food compared to drying under factory conditions or oven-drying.     

谷子幼苗对土壤铅、铬的生长响应及吸收积累的差异性

采用盆栽土培试验,研究了谷子幼苗对土壤中不同含量铅（Pb）、铬（Cr）的生长响应和吸收积累的差异性。结果表明,在所试浓度（50～800 mg·kg^-1）范围内,Pb、Cr在谷子幼苗地上部和地下部的积累量存在较大差异,幼苗重金属的吸收富集和转运系数均为Pb大于Cr、Pb、Cr胁迫对幼苗生物量的影响表现为低浓度的促进和高浓度的抑制作用,但Cr对生物量的影响比Pb更强。相同处理条件下,幼苗茎叶中可溶性蛋白质、DNA含量和增色效应对Pb、Cr的响应也有明显差别,Cr对幼苗的生理毒性和DNA损伤效应的作用强度大于Pb。     

Green synthesis of lead sulfide nanoparticles by the lead resistant marine yeast, Rhodosporidium diobovatum

Biosynthesis of nanoparticles using microorganisms has attracted a lot of attention in recent years as this route has the potential to lead to synthesis of monodisperse nanoparticles. Here, we report the intracellular synthesis of stable lead sulfide nanoparticles by a marine yeast, Rhodosporidium diobovatum. The PbS nanoparticles were characterized by UV-visible absorption spectroscopy, X-ray diffraction (XRD) and energy dispersive atomic spectroscopy (EDAX). UV-visible absorption scan revealed a peak at 320 nm, a characteristic of the nanosize range. XRD confirmed the presence of PbS nanoparticles of cubic structure. Crystallite size as determined from transmission electron microscopy was found to be in the range of 2-5 nm. Elemental analysis by EDAX revealed the presence of particles composed of lead and sulfur in a 1:2 ratio indicating that PbS nanoparticles were capped by a sulfur-rich peptide. A quantitative study of lead uptake through atomic absorption spectrometry revealed that 55% of lead in the medium was accumulated in the exponential phase, whereas a further 35% was accumulated in the stationary phase; thus, the overall recovery of PbS nanoparticles was 90%. The lead-exposed yeast displayed a marked increase (280% over the control) in nonprotein thiols in the stationary phase.