Recent Advances and Perspectives of Lewis Acidic Etching Route:An Emerging Preparation Strategy for MXenes

Since the discovery in 2011,MXenes have become the rising star in the field of two-dimensional materials.Benefiting from the metallic-level conductivity,large and adjustable gallery spacing,low ion diffusion barrier,rich surface chemistry,superior mechanical strength,MXenes exhibit great application prospects in energy storage and conversion,sensors,optoelectronics,electromagnetic interference shielding and biomedicine.Nevertheless,two issues seriously deteriorate the further development of MXenes.One is the high experimental risk of common preparation methods such as HF etching,and the other is the difficulty in obtaining MXenes with controllable surface groups.Recently,Lewis acidic etching,as a brand-new preparation strategy for MXenes,has attracted intensive attention due to its high safety and the ability to endow MXenes with uniform terminations.However,a comprehensive review of Lewis acidic etching method has not been reported yet.Herein,we first introduce the Lewis acidic etching from the following four aspects:etching mechanism,terminations regulation,in-situ formed metals and delamination of multi-layered MXenes.Further,the applications of MXenes and MXene-based hybrids obtained by Lewis acidic etching route in energy storage and conversion,sensors and microwave absorption are carefully summarized.Finally,some challenges and opportunities of Lewis acidic etching strategy are also presented.

Freestanding and Flexible Interfacial Layer Enables Bottom-Up Zn Deposition Toward Dendrite-Free Aqueous Zn-Ion Batteries

Aqueous rechargeable zinc ion batteries are regarded as a competitive alternative to lithium-ion batteries because of their distinct advantages of high security,high energy density,low cost,and environmental friendliness.However,deep-seated problems including Zn dendrite and adverse side reactions severely impede the practical application.In this work,we proposed a freestanding Zn-electrolyte interfacial layer composed of multicapsular carbon fibers(MCFs)to regulate the plating/stripping behavior of Zn anodes.The versatile MCFs protective layer can uniformize the electric field and Zn^(2+)flux,meanwhile,reduce the deposition overpotentials,leading to high-quality and rapid Zn deposition kinetics.Furthermore,the bottom-up and uniform deposition of Zn on the Zn-MCFs interface endows long-term and high-capacity plating.Accordingly,the Zn@MCFs symmetric batteries can keep working up to 1500 h with 5 mAh cm^(−2).The feasibility of the MCFs interfacial layer is also convinced in Zn@MCFs||MnO_(2) batteries.Remarkably,the Zn@MCFs||α-MnO_(2)batteries deliver a high specific capacity of 236.1 mAh g^(−1)at 1 A g^(−1)with excellent stability,and maintain an exhilarating energy density of 154.3 Wh kg^(−1) at 33%depth of discharge in pouch batteries.

Effects ofβ-alanine on intestinal development and immune performance of weaned piglets

Beta-alanine is an important amino acid involved in several metabolic reactions in the body.The study aimed to investigate the effect ofβ-alanine supplementation on intestinal development and the immune performance of weaned piglets.Thirty-two 21-day-old healthy weaned piglets(half female and half male;Duroc×Landrace×Yorkshire)with an initial body weight of 8.11±0.21 kg were randomly divided into 4 groups with 8 replicates of 1 pig each.The control group was fed a basal diet and the three experimental treatment groups were fed diets supplemented with 300,600 and 1,200 mg/kgβ-alanine,respectively.The trial lasted 28 days and the diets fed were divided into 2 phases:the late lactation period(day 1 to 14)and the nursery period(day 15 to 28),during which the weaned piglets had free access to food and water.The regulatory effects ofβ-alanine were further investigated in vitro using organoids obtained from the jejunum of piglets.In vivo,the addition ofβ-alanine to the diet had no significant effect on the growth performance of weaned piglets(P>0.05),but significantly reduced serum levels of immunoglobulin G(IgG)(P<0.01),immunoglobulin M(IgM)(P=0.005),and complement 3(C3)(P=0.017).The serum interleukin-6(IL-6)levels(P<0.01)were significantly reduced in the 1,200 mg/kg treatment group.The addition ofβ-alanine increased ileal villus height,with the most significant effect at a concentration of 300 mg/kg(P=0.041).The addition of 600 mg/kgβ-alanine significantly up-regulated the expression of superoxide dismutase(SOD)activity(P=0.020)and the zonula occludens-1(ZO-1)gene(P=0.049)in the jejunum.Diets supplemented with 300 mg/kgβ-alanine significantly increased the number of Ki67 positive cells in the jejunal crypts(P<0.01).In vitro,β-alanine increased the organoid budding rates(P=0.001)and the budding height of the crypt significantly(P=0.004).In conclusion,β-alanine can improve intestinal morphology and barrier function,reduce inflammatory responses and alleviate the adverse effects of weaning stress on piglet intestinal health.

Nonparametric probabilistic seismic demand model and fragility analysis of subway stations using deep learning techniques

A novel and computationally efficient method for developing a nonparametric probabilistic seismic demand model(PSDM)is pro-posed to conduct the fragility analysis of subway stations accurately and efficiently.The probability density evolution method(PDEM)is used to calculate the evolutionary probability density function of demand measure(DM)without resort to any assumptions of the dis-tribution pattern of DM.To reduce the computational cost of a large amount of nonlinear time history analyses(NLTHAs)in the PDEM,the one-dimensional convolutional neural network(1D-CNN)is used as a surrogate model to predict the time history of struc-tural seismic responses in a data-driven fashion.The proposed nonparametric PSDM is adopted to conduct the fragility analysis of a two-story and three-span subway station,and the results are compared with those from two existing parametric PSDMs,i.e.,two-parameter lognormal distribution model and probabilistic neural network(PNN)-based PSDM.The results show that the PDEM-based PSDM has the best performance in describing the probability distribution of seismic responses of underground structures.Differ-ent from the fragility curves,the time-dependent fragility surface of the subway station shows how the exceedance probability of damage state changes over time.It can be used to estimate the escape time and thus the number of casualties in an earthquake,which are impor-tant indexes when conducting the resilience-based seismic evaluation.

Effects of dietary energy on growth performance, carcass characteristics, serum biochemical index, and meat quality of female Hu lambs

This study evaluated the effects of dietary energy levels on growth performance,carcass traits,meat quality,and serum biochemical of female Hu lambs.Seventy female Hu lambs(aged 4 months)were randomly allotted to 5 dietary treatments.Lambs were fed diets with 5 levels of metabolizable energy(ME):9.17(E1),9.59(E2),10.00(E3),10.41(E4),and 10.82 MJ/kg(E5).The lambs were adapted to the experimental diets for 10 d and the experiment period lasted for 60 d.Dry matter intake and feed conversion ratio linearly(P<0.001)increased and decreased(P<0.001),respectively,with increasing dietary ME levels.Average daily gain(ADG)linearly(P<0.001)increased with increasing dietary ME levels,with the highest final body weight(P=0.041)observed in E4 group.Moreover,dietary energy level was associated with linear increases in serum total protein(TP)(P<0.001),albumin(ALB)(P=0.017),glucose(GLU)(P=0.004),and low-density lipoprotein cholesterol(LDLC)(P=0.006)concentrations,and it was associated with a quadratic decrease in serum triglyceride(TG)concentration(P=0.002).Serum ammonia concentration,which was firstly decreased and then increased,was quadratically affected by dietary ME levels(P=0.013).Compared with E1 group,lambs in E4 group had higher(P<0.05)live weights,carcass weights,mesenteric fat ratio,non-carcass fat ratio,and larger loin muscle area,but lower(P<0.05)meat colour a*and b*values,and lesser(P<0.05)C17:0,C20:0,C18:1 n-9 t,C18:3 n-3,and n-3 polyunsaturated fatty acids(PUFA),but greater(P<0.05)C18:3 n-6 and n-6:n-3 ratios in longissimus dorsi(LD)muscle tissue,and lesser(P<0.05)C17:0,C18:3 n-3,C22:6 n-3,and n-3 PUFA in the biceps femoris(BF)muscle tissue.The results demonstrated that increasing dietary energy level improved the growth performance and affected carcass traits,serum biochemical indexes,and fatty acid profiles in different muscles of female Hu lambs.For 4-month-old female Hu lambs,the recommended fattening energy level is 10.41 MJ/kg.

Hierarchical utilization of raw Ti_(3)C_(2)T_(x) MXene for fast preparation of various Ti_(3)C_(2)T_(x) MXene derivatives

Due to easy re-stacking,low yield of few-layered MXenes(f-MXenes),the applications of MXenes are mainly restricted in multi-layered MXenes(m-MXenes)state.Although f-MXenes can be prepared from m-MXenes,after exfoliation process,a mass of sediments which are still essentially compact MXenes are usually directly discarded,leading to low utilization of raw m-MXenes.Herein,a classified preparation strategy is adopted to exploit the raw m-MXenes and traditional MXenes sediments,taking multi-layered Ti_(3)C_(2)T_(x)MXene as an example.Via rational delamination and subsequent treatment to Ti_(3)C_(2)T_(x)sediments,we succeed in achieving classified and large-scale preparation of various Ti_(3)C_(2)T_(x)MXene derivatives,including few-layered Ti_(3)C_(2)T_(x)(f-Ti_(3)C_(2)T_(x))powders,f-Ti_(3)C_(2)T_(x)films,and Ti_(3)C_(2)T_(x)MXene-derived nanowires with heterostructure of potassium titanate and Ti_(3)C_(2)T_(x).We demonstrate the necessity of“step-by-step delamination”towards traditional Ti_(3)C_(2)T_(x)sediments to improve the yield of f-Ti_(3)C_(2)T_(x)from 15%to 72%;the feasibility of“solution-phase flocculation(SPF)”to fundamentally solve the re-stacking phenomenon,and oxidation degradation issues of f-Ti_(3)C_(2)T_(x)during storage;as well as the convenience of SPF to deal with time-consuming issues of fabricating Ti_(3)C_(2)T_(x)films.What’s more,alkali-heat treatment of final Ti_(3)C_(2)T_(x)sediments turns waste into treasure of Ti_(3)C_(2)T_(x)-derived nanowires,leading to 100%utilization of raw Ti_(3)C_(2)T_(x).The content of one-dimensional(1D)nanowires in the hybrids can be adjusted by controlling alkalization time.The 3D architecture heterostructure composed of 1D nanowires and 2D nanosheets exhibits gorgeous application potential.This work can expand preparation and application of various MXenes derivatives,promoting process of various MXenes.

Fabrication of Fe nanocomplex pillared few-layered Ti_(3)C_(2)T_(x)MXene with enhanced rate performance for lithium-ion batteries

Pillaring technologies have been considered as an effective way to improve lithium storage performance of Ti_(3)C_(2)T_(x)MXene.Nevertheless,the pillared hybrids suffer from sluggish Li^(+)diffusion kinetics and electronic transportation due to the compact multi-layered MXene structure,thus exhibiting inferior rate performance.Herein,the few-layered Ti_(3)O_(2)MXene(f-Ti_(3)C_(2)MXene)which is free from restacking can be prepared quickly based on the NH4^(+)ions method.Besides,Fe nanocomplex pillared few-layered Ti_(3)C_(2)T_(x)(FPTC)heterostructures are fabricated via the intercalation of Fe ions into the interlayer of f-Ti_(3)C_(2)MXene.The f-Ti_(3)C_(2)MXene which is immune to restacking can provide a highly conductive substrate for the rapid transport of Li+ions and electrons and possess adequate electrolyte accessible area.Moreover,f-Ti_(3)C_(2)MXene can efficiently relieve the aggregation,prevent the pulverization and buffer the large volume change of Fe nanocomplex during lithiation/delithiation process,leading to enhanced charge transfer kinetics and excellent structural stability of FPTC composites.Consequently,the FPTC hybrids exhibit a high capacity of 535 mAh·g^(-1)after 150 cycles at 0.5 A·g^(-1)and an enhanced rate performance with 310 mAh·g^(-1)after 850 cycles at 5 A·g^(-1).This strategy is facile,universal and can be extended tofabricate various few-layered MXene-derived hybrids with superior rate capability.

Effects of varying dietary folic acid during weaning stress of piglets

The present study was conducted to evaluate the effect of dietary folic acid on the growth performance,intestinal morphology,and intestinal epithelial cells renewal in post-weaning piglets.Twenty-eight piglets(weaned at day 21,initial body weight of 6.73±0.62 kg)were randomly allotted to 4 treat-ments with 7 pens per diet and 1 piglet per pen.The piglets were fed the same antibiotic-free and zinc oxide-free basal diets supplemented with folic acid at 0,3,9,and 18 mg/kg for 14 days.The results showed that dietary supplementation with folic acid increased villus height(VH)(P=0.003;linear,P=0.001),VH-to-crypt depth(VH:CD)ratio(P=0.002;linear,P=0.001),villus surface area(VSA)(P=0.026;linear,P=0.010).The analyzed parameters ADG,serum urea nitrogen(BUN)content,VH,VSA,and serum folate(SF)concentration responded linearly to the dietary folic acid concentration when the dietary folic acid concentration was below 4.42,5.26,4.79,3.47,and 3.53 mg/kg respectively(R2=0.995,0.995,0.999,0.999,0.872,P=0.09,0.07,0.09,0.09,0.36,respectively),as assessed by a two-linear broken-line regression.Above these breakpoints,the response of ADG,VH,VSA,and SF plateaued in response to changes in dietary folic acid concentration.Moreover,dietary supplementation with folic acid significantly increased the lactase(P=0.001;linear,P=0.001)and sucrase activities(P=0.021;linear,P=0.010)in the jejunal mucosa of weaned piglets.The mRNA expression of solute carrier family 6 member 19(SLC6a19),solute carrier family 1 member 1(SLC7a1),tumor necrosis factor-α(TNF-α),the number of Ki67 positive cells,and cell shedding rate had a significant linear contrast(P=0.023,0.021,0.038,0.049,and 0.008,respectively)in dietary folic acid groups.In conclusion,our results indicate that folic acid supplementation can improve the growth performance and intestinal morphology of weaned piglets by maintaining the balance of epithelial cell renewal.