Layered double hydroxides:Scale production and application in soil remediation as super-stable mineralizer

Soil contamination by heavy metals has presented severe risks to human health through food chain.As one of the most promising remediation technologies,in-situ immobilization strategy has been widely adopted in practice.However,considering the large quantities of contaminated soil,it is still a huge challenge to design low-cost amendments with strong and long-term immobilization ability.Layered double hydroxides(LDHs)have drawn tremendous attention in fundamental research and practical application because of their unique properties.Moreover,owing to its super-stable mineralization effect to heavy metal ions,LDHs have exhibited great potential in the field of soil remediation.In this work,we mainly focused on the scale production strategy of LDHs with low-cost,and its application in soil remediation.Besides,several key challenges in using LDHs as amendments for immobilization of heavy metal ions are presented.We hope that this mini-review could shed light on the sustainable development of LDHs as amendment for heavy metals in future research directions.

Fe-doped Co3O4@C nanoparticles derived from layered double hydroxide used as efficient electrocatalyst for oxygen evolution reaction

Compared with noble metal catalyst, Co3O4-based electrocatalysts have attracted considerable interesting as low-cost alternatives for oxygen evolution reaction (OER). However, the poor electrocatalytic activity still remains a huge challenge. Herein, we demonstrate a feasible approach through oxidation of CoFe layered double hydroxide (CoFe-LDH) to synthesize Fe-doped Co3O4@C nanopmrticles with size of about 30-50 nm. As OER catalyst, the as-synthesized Fe-doped Co3O4@C nanoparticles exhibited superior OER performance with a small overpotential of 260 mV at the current density of 20 mA cm^-2, a small Tafel slope of 70 mV dec^-1 and long-term durability (there was no obviously OER current density degradation for 100 h) in alkaline solution. The present work opens a new avenue to the exploration of cost-effective and excellent electrocatalysts based on transition metal oxide materials to substitute precious metal materials for water splitting.

The Principle of Introducing Halogen Ions Into β-FeOOH: Controlling Electronic Structure and Electrochemical Performance

Coordination tuning electronic structure of host materials is a quite effective strategy for activating and improving the intrinsic properties.Herein,halogen anion(X-)-incorporated β-FeOOH(β-FeOOH(X),X=F-,Cl-,and Br-) was investigated with a spontaneous adsorption process,which realized a great improvement of supercapacitor performances by adjusting the coordination geometry.Experiments coupled with theoretical calculations demonstrated that the change of Fe-O bond length and structural distortion of β-FeOOH,which is rooted in halogen ions embedment,led to the relatively narrow band gap.Because of the strong electronegativity of X-,the Fe element in β-FeOOH(X)s presented the unexpected high valence state(3+δ),which is facilitating to adsorb S032-species.Consequently,the designed β-FeOOH(X)s exhibited the good electric conductivity and enhanced the contact between electrode and electrolyte.When used as a negative electrode,the β-FeOOH(F) showed the excellent specific capacity of 391.9 F g-1 at 1 A g-1 current density,almost tenfold improvement compared with initial β-FeOOH,with the superior rate capacity and cyclic stability.This combinational design principle of electronic structure and electrochemical performances provides a promising way to develop advanced electrode materials for supercapacitor.

Excitation orthogonalized upconversion nanoprobe for instant visual detection of trinitrotoluene

Excitation-emission orthogonalized luminescent upconversion nanoparticles(OUCNPs),which can respond to changes in external stimuli accordingly,show great promise in many intelligent applications.However,the construction of such materials mostly relies on the selective absorption of Nd3+and Yb3+at different wavelengths and the long-range energy migration between the layers,resulting in complex structures and limited orthogonal luminescence intensity.Herein,we developed a relatively simple structure of OUCNPs(β-NaErF4@NaLuF4@NaYF4:20%Yb,2%Er@NaLuF4),where the fluorescence emission switches from red to green when the excitation wavelength is shifted from 808 to 980 nm.This structure exhibits high-quality,independent,and non-interfering orthogonal luminescence properties without Nd3+sensitization and long-range energy migration.As a proof of concept,we demonstrate the application of the designed OUCNPs in anti-counterfeiting.We also prepared OUCNPs@PEI(PEI=polyethylenimine)self-referencing fluorescent probes to enable quantitative analysis of trinitrotoluene(TNT)in solution with a detection limit of 3.04μM.The probes can be made into test strips for portable on-site visual detection of TNT,and can also be used to image latent fingerprints and detect explosive residues in fingerprints simultaneously.The concept proposed in this work can be extended to the visual detection of a larger range of organic and biological molecules,and is highly promising for practical applications.

双金属复合氢氧化物在重金属污染土壤/水修复方面的研究进展

重金属污染土壤/水形势严峻,修复工作迫在眉睫.开发高效率、低成本、易操作的重金属污染土壤/水修复材料及技术极具重要现实意义.类水滑石(又称双金属复合氢氧化物, LDHs)是一类典型的无机层状结构材料.独特的组成及结构特点使得LDHs在重金属离子去除领域表现出良好的应用前景,特别是在原位修复重金属污染土壤领域已实现应用,表现出超稳矿化性能,修复效果显著,同时为重金属污染水修复工作提供了新的思路.本文总结了近年来LDHs作为修复材料在重金属污染土壤/水修复方面的工作,阐述了LDHs材料的结构与性能间的内在关联和作用机理,并对该材料在去除重金属离子方面存在的问题及应用前景进行了汇总和展望.

An Electrocatalytic Strategy for Dehydrogenative[4+2]Cycloaddition over a Cobalt-Based Catalyst

Exploring the anodic reaction to substitute conventional oxygen evolution reaction(OER)for the synthesis of complex pharmaceutical molecules is highly attractive.Here,we report an electrocatalytic strategy for dehydrogenative[4+2]cycloaddition of N,N-dialkylanilines with maleimides via dual functionalization of both C(sp3)-H and C(sp2)-H bonds,by using an electrochemically activated cobalt carbonate hydroxide hydrate supported on carbon cloth(CCHH-A/CC),affording various tetrahydroquinolines with high yields.This electrochemical transformation proceeds with high activity and stability,as well as good substrate compatibility.Mechanism study shows thatα-aminoalkyl radical exists in the electrooxidation reaction.This strategy shows significant potential for the synthesis of valuable chemicals by using an electrocatalytic strategy.

Construction of self-sensitized LiErF4:0.5%Tm^3+@LiYF4 upconversion nanoprobe for trace water sensing

LiErF4 was commonly used as a dipolar-coupled antiferromagnet,and was rarely considered as a luminescent material.Herein,we achieved the strong red upconversion emission of LiErF4 simply by an inert shell coating,i.e.,LiErF4@LiYF4.Owing to the unique and intrinsic ladder-like energy levels of Er3+ions,this LiErF4 core–shell nanostructures present red emission(~650 nm)under multi-band excitation in the near-infrared(NIR)region(~808,~980,and^1,530 nm).A brighter and monochromic red emission can be further obtained via doping 0.5%Tm3+into the LiErF4 core,i.e.,LiErF4:0.5%Tm3+@LiYF4.The enriched Er3+ions and strong monochromic red emission natures make LiErF4:0.5%Tm3+@LiYF4 nanocrystals very sensitive for trace water probing in organic solvents with detection limit of 30 ppm in acetonitrile,50 ppm in dimethyl sulfoxide(DMSO),and 58 ppm in N,N-dimethylformamide(DMF)under excitation of 808 nm.Due to their superior chemical and physical stability,these nanoprobes exhibit excellent antijamming ability and recyclability,offering them suitable for real-time and long-term water monitoring.