Specific Defect Structures Research Articles

COF-derived porous nitrogen-doped carbon for removal of emerging organic contaminants and efficient uranium extraction from seawater

The development of adsorbents for efficient and highly selective seawater extraction of uranium was instrumental in fostering sustainable progress in energy and addressing the prevailing energy crisis. However, the complex background composition of the marine environment, including radionuclides, organic pollutants, and a large number of co-existing heavy metal ions, were non-negligible obstacles to the extraction of uranium from seawater. The present investigation successfully employed a self-templated approach to synthesize porous nitrogen-doped carbon (PNC) derived from COF, which exhibited tremendous potential as an adsorbent for pollutant removal in environmental treatment. LZU1@PNC not only retained the structural features of the original COF-LZU1, but also overcame the acid-base instability problem commonly found in COFs. Subsequently, the removal process of two typical water pollutants on the material was investigated using 2,4-DCP and [UO2(CO3)3]4-. The results demonstrated that LZU1@PNC exhibited superior removal performance for the target pollutants compared to COF-LZU1, owing to its larger specific surface area and abundant defect structure. After six desorption-regeneration cycles, LZU1@PNC still maintained a high removal rate of the target contaminants, demonstrating the stability of this material and its excellent recyclability. In addition, based on various characterization techniques, the removal mechanism of 2,4-DCP was presumed to be mainly electrostatic attraction, hydrogen bonding, and π-π stacking interactions. Conversely, the elimination process of [UO2(CO3)3]4- predominantly relied on surface complexation phenomena. The present investigation provided new perspectives and stimulated a broader study of other COF-derived carbon materials and their modifications as adsorbents for uranium extraction from seawater and other applications.

Atomic and Electronic Structure of Defects in hBN: Enhancing Single-Defect Functionalities.

Defect centers in insulators play a critical role in creating important functionalities in materials: prototype qubits, single-photon sources, magnetic field probes, and pressure sensors. These functionalities are highly dependent on their midgap electronic structure and orbital/spin wave function contributions. However, in most cases, these fundamental properties remain unknown or speculative due to the defects being deeply embedded beneath the surface of highly resistive host crystals, thus impeding access through surface probes. Here, we directly inspected the atomic and electronic structures of defects in thin carbon-doped hexagonal boron nitride (hBN:C) by using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). Such investigation adds direct information about the electronic midgap states to the well-established photoluminescence response (including single-photon emission) of intentionally created carbon defects in the most commonly investigated van der Waals insulator. Our joint atomic-scale experimental and theoretical investigations reveal two main categories of defects: (1) single-site defects manifesting as donor-like states with atomically resolved structures observable via STM and (2) multisite defect complexes exhibiting a ladder of empty and occupied midgap states characterized by distinct spatial geometries. Combining direct probing of midgap states through tunneling spectroscopy with the inspection of the optical response of insulators hosting specific defect structures holds promise for creating and enhancing functionalities realized with individual defects in the quantum limit. These findings underscore not only the versatility of hBN:C as a platform for quantum defect engineering but also its potential to drive advancements in atomic-scale optoelectronics.

Highly-efficient peroxymonosulfate activation by porous nano-MgO for tetracycline degradation: Surface hydroxyl groups and oxygen vacancies synergetic mediated nonradical process

Heterogeneous transition metal activation of peroxymonosulfate (PMS)-based advanced oxidation processes is limited by low cycling efficiency, secondary contamination, and high toxicity. In this study, a non-transition metal porous nano-MgO catalyst from natural dolomite was synthesized and PMS activation was performed to degrade tetracycline (TC). The nano-MgO/PMS system could achieve TC degradation of 88.09 % within 20 min under the optimum parameters (nano-MgO dosage of 0.2 g·L−1, PMS concentration of 0.3 mM), exceeding the efficiency of the PMS-alone system (11.66 %) by 7-fold, which was related to large specific surface area (41.19 m2·g−1) and defect structure of porous nano-MgO catalysts. As revealed by the quenching tests and electron paramagnetic resonance (EPR) analysis, different from transition metal activation PMS where radicals are generated, singlet oxygen (1O2) was essential in the nano-MgO/PMS oxidation process. Notably, the density functional theory (DFT) calculations demonstrated that nano-MgO with surface hydroxyl groups and oxygen vacancies exhibited the longer O-O bond length (1.47 Å), stronger adsorption energy of PMS (-4.07 eV), and faster electron transfer (0.91 e) than the only nano-MgO with surface hydroxyl groups, proving the surface hydroxyl groups and oxygen vacancies active sites in nano-MgO could synergistically mediate the PMS activation process. Furthermore, the proposed three TC degradation pathways and the toxicity evaluation of intermediates suggested that nano-MgO/PMS system have good ecological safety. This work offers an innovative approach for the cost-effective preparation of porous magnesium oxide with highly efficiency, offering a new perspective for understanding the PMS activation mechanism induced by non-transition metal.

Characterization of defects in additively manufactured materials from mechanical properties

Minimization of defects in additively manufactured components is essential for material development and the determination of fabrication process windows. Here, a purely mechanical means of quantifying porosity in a material is developed based on the Mori–Tanaka mean field theory. The micromechanics based defect quantification approach developed here links the elastic properties of a material with the specific defect structures that must exist within it to obtain those properties. Laser powder bed fusion is used to fabricate aluminum 6061 with three different processing conditions to produce nominally identical samples with unique defect microstructures. Test samples are imaged with microcomputed X-ray tomography (μCT) and the images are classified with a machine learning method to identify the volume fraction of pores, solidification cracks, and the orientation distribution function of the solidification cracks. Tensile tests are then conducted in the z-axis and within the xy-plane to measure the respective elastic moduli and the Poisson’s ratio. These three commonly measured material properties are the only inputs to the new micromechanics based approach used to infer the same defect descriptors that were extracted from μCT. Excellent agreement is found between defect descriptors obtained with both methods, and quantities derived from the mechanical properties are found to carry substantially lower uncertainty. Full error propagation maps for the micromechanics based technique are calculated. Notably, defect descriptors from the micromechanics based approach are calculated from strain and load measurements, which are measured on much larger length scales than the defect size. This enables simple quantification of defects for materials containing small defects that are challenging to image.

High-Performance Hydrogen-Selective Pd-Ag Membranes Modified with Pd-Pt Nanoparticles for Use in Steam Reforming Membrane Reactors.

A unique method for synthesizing a surface modifier for metallic hydrogen permeable membranes based on non-classic bimetallic pentagonally structured Pd-Pt nanoparticles was developed. It was found that nanoparticles had unique hollow structures. This significantly reduced the cost of their production due to the economical use of metal. According to the results of electrochemical studies, a synthesized bimetallic Pd-Pt/Pd-Ag modifier showed excellent catalytic activity (up to 60.72 mA cm-2), long-term stability, and resistance to COads poisoning in the alkaline oxidation reaction of methanol. The membrane with the pentagonally structured Pd-Pt/Pd-Ag modifier showed the highest hydrogen permeation flux density, up to 27.3 mmol s-1 m-2. The obtained hydrogen flux density was two times higher than that for membranes with a classic Pdblack/Pd-Ag modifier and an order of magnitude higher than that for an unmodified membrane. Since the rate of transcrystalline hydrogen transfer through a membrane increased, while the speed of transfer through defects remained unchanged, a one and a half times rise in selectivity of the developed Pd-Pt/Pd-Ag membranes was recorded, and it amounted to 3514. The achieved results were due to both the synergistic effect of the combination of Pd and Pt metals in the modifier composition and the large number of available catalytically active centers, which were present as a result of non-classic morphology with high-index facets. The specific faceting, defect structure, and unusual properties provide great opportunities for the application of nanoparticles in the areas of membrane reactors, electrocatalysis, and the petrochemical and hydrogen industries.

Boosted persulfate activation by hierarchically porous carbonaceous materials: Pivotal role of pore structure and electron-accepting capacity

Porous carbonaceous materials (CMs) have been praised as superior candidates in activating persulfate for antibiotic wastewater decontamination. Whereas, as one of the frequently reported nonradical pathways, the formation mechanism of the reactive complexes and their correlation with physicochemical properties of CMs have not been comprehensively unveiled. Herein, a series of carbonaceous materials (CMs) with different specific surface area (SSA) and defect structures were fabricated by using KCl, MgCl2, KHCO3 and K2C2O4 as porogenic agents to activate peroxydisulfate (PDS) for sulfadiazine (SDZ) degradation. Results showed that the total pore volume of CMs exhibited a good linearity with degradation rate, attributing to the combined effect of SSA, defect degree and oxygen-containing functional groups according to multiple regression model. The reactive complexes (CM/PDS*) were proved as the foremost active species for SDZ oxidation via a suite of solid evidences. Compared with that after PS addition, the current direction was reversed after SDZ addition in i-t curves shedding light on the sharp enhanced potential of CM/PDS* and much low potential of SDZ. Furthermore, the inner-sphere CM/PDS* originating from the formation of new covalent bonds between CMs and PDS was inferred due to the poor dependence between electron-donating capacity and SDZ degradation result. The CM/PDS* with considerably higher potential can extract electron from SDZ based on the excellent positive relationship between electron-accepting capacity of CMs and SDZ degradation effect. This study advances the mechanistic comprehension of nonradical PDS activation, and provides a multiple regression model to predict degradation effects of carbon materials.

LSPR-enhanced carbon-coated In2O3/W18O49 S-scheme heterojunction for efficient CO2 photoreduction

The special defect structure and localized surface plasmon resonance (LSPR) effect offer W18O49 extraordinary potential and research value in photocatalysis. The LSPR effect optimizes the design of W18O49-sensitized photocatalytic composites and broadens the light-response range of W18O49. However, the high-energy “hot electrons” generated by W18O49 under the LSPR effect exhibit an extremely short lifetime and cannot be fully utilized. Therefore, the high electron conductivity of carbon can be used to increase the rate of hot-electron transfer, thereby extending the lifetime of hot electrons. In this study, a heterojunction photocatalyst was formed by growing a high-absorbance one-dimensional nanowire W18O49 on the surface of carbon-coated porous In2O3 nanorods (C-In2O3) derived from In-MOF. The C-In2O3/W18O49composites exhibited optical responses in both the visible and near-infrared regions. The carbon coatings acted as transport channels to accelerate the transfer of carriers and hot electrons, and the activity of photocatalytic CO2 reduction (PCR) was significantly enhanced. The 40%C-In2O3/W18O49 composites had the highest CO yield in the photocatalytic reactions, which was 2.99 and 2.84 times greater than that of pure C-In2O3 and W18O49, respectively. The internal electronic transfer in the S-scheme heterojunction and LSPR-induced hot electrons injected into C-In2O3 achieved dual-path electron transfer for PCR.

Lower oxygen vacancy concentration in BiPO4 with unexpected higher photocatalytic activity

Defect engineering has been demonstrated to be an appealing strategy to boost the photocatalytic activity of materials. However, can higher defect concentration bring about higher photocatalytic activity? This is an open question. In this work, BiPO4 photocatalysts with controllable oxygen vacancy concentrations were successfully synthesized. The photocatalytic activity of the obtained BiPO4 photocatalysts was determined by the removal of ciprofloxacin and 4-chlorophenol, as well as CO2 photoreduction. The BiPO4 materials with lower oxygen vacancy concentration could display unexpected higher photocatalytic efficiency. Through the investigation of different factors which may affect the photocatalytic performance, such as crystal structure, morphology, specific surface area, defect, and energy band structure, it can be found that the energy band structure difference was responsible for the enhanced photocatalytic activity.

First-principles modeling of the highly dynamical surface structure of a MoS2 catalyst with S-vacancies.

Vacancy sites, e.g., S-vacancies, are essential for the performance of MoS2 catalysts. As earlier studies have revealed that the size and shape of the S-vacancies may affect the catalytic activity, we have studied the behavior and mobility of such vacancies on MoS2 using DFT calculations and kinetic Monte-Carlo (kMC) simulations. The diffusion barriers for the S-vacancies are highly dependent on the immediate environment: isolated single S-vacancies are found to be immobile. In contrast, small nS-vacancies formed from n = 2 to 5 neighboring S-vacancies are often highly dynamic systems that can move within a confined area. Large extended nS-vacancies are generally unstable and transform quickly into alternating patterns of S-atoms and vacancy sites. These results illustrate the importance of recognizing MoS2 (but also other catalysts) as dynamic structures when trying to tune their catalytic performances by introducing specific defect structures.

Facile Synthesis of Cobalt Tungstate with Special Defect Structure with Enhanced Optical, Photoluminescence, and Supercapacitive Performances

Facile Synthesis of Cobalt Tungstate with Special Defect Structure with Enhanced Optical, Photoluminescence, and Supercapacitive Performances

Liquid exfoliation of TiN nanodots as novel sonosensitizers for photothermal-enhanced sonodynamic therapy against cancer

Ultrasound (US)-activated sonodynamic therapy (SDT), as a non-invasive therapy method, has the advantages of large tissue penetration depth promising for treatment of large internal tumors. However, due to the hypoxic characteristic of tumor microenvironment and lack of effective sonosensitizers, the efficacy of SDT is still not satisfactory. In addition, there is still a lot of space for the exploration of SDT-based collaborative cancer treatment. Herein, ultra-small titanium nitride (TiN) nanodots are successfully synthesized for photothermal-enhanced SDT against cancer. Ultra-small TiN nanodots with an average size of 1.5 nm are prepared by the liquid exfoliation method. The obtained TiN nanodots have satisfactory second near-infrared (NIR II) absorption, which can be used for photoacoustic (PA) imaging and photothermal therapy (PTT) of tumors. Interestingly, TiN nanodots can also be used as efficient sonosensitizers to generate reactive oxygen species (ROS) under US irradiation owing to the special defect structure and surface partial oxidation to TiO2 for sonodynamic cancer therapy. The mild photothermal heating of tumors generated by TiN nanodots under NIR II laser irradiation can facilitate intra-tumoral blood flow and improve tumor oxygenation, thereby achieving a significant synergistic treatment effect by combining PTT and SDT. Importantly, most of these TiN nanodots due to their ultra-small size can be promptly metabolized from the mouse body, thus avoiding the concerns about long-term toxicity of nanomaterials. Our work thus for the first time demonstrates the potential use of metal nitride nanomaterials as a new type of multifunctional nano-agents with intriguing properties for cancer theranostic applications.

Photoinduced phase separation in the lead halides is a polaronic effect.

We present a perspective on recent observations of the photoinduced phase separation of halides in multi-component lead-halide perovskites. The spontaneous phase separation of an initial homogeneous solid solution under steady-state illumination conditions is found experimentally to be reversible, stochastic, weakly dependent on morphology, yet strongly dependent on composition and thermodynamic state. Regions enriched in a specific halide species that form upon phase separation are self-limiting in size, pinned to specific compositions, and grow in number in proportion to the steady-state carrier concentration until saturation. These empirical observations of robustness rule out explanations based on specific defect structures and point to the local modulation of an existing miscibility phase transition in the presence of excess charge carriers. A model for rationalizing existing observations based on the coupling between composition, strain, and charge density fluctuations through the formation of polarons is reviewed.

Correlative NanoSIMS and electron microscopy methods for understanding deuterium distributions after fatigue testing of 304/304L stainless steel in deuterated water

There is no single methodology that can map the distribution of hydrogen and relate it to specific crystallographic phases or defect structures. Here, we present a case study demonstrating two methodologies towards achieving this goal: Correlating nanoscale secondary ion mass spectrometry (NanoSIMS) deuterium maps with electron backscattered diffraction (EBSD) data ahead of crack tips in a 304 stainless steel sample fatigue tested in deuterated water, and secondly correlating NanoSIMS deuterium maps with (scanning) transmission electron microscopy ((S)TEM) data from focused ion beam (FIB) lift-out samples. Correlating NanoSIMS/EBSD images, we confirmed an association of deuterium with martensitic lath structures. Furthermore, we discovered localized enrichments of deuterium along the martensitic laths, with a higher associative preponderance to ε−martensite. Applying correlative NanoSIMS/(S)TEM imaging of the fracture surface, we found deuterium accumulation at the metal oxide interface. However, in the pre-crack region, the deuterium was clearly concentrated underneath the oxide layer.

Applications of molybdenum oxide nanomaterials in the synergistic diagnosis and treatment of tumor

The synergistic diagnosis and treatment of tumors have become a developing trend in cancer treatment. Optical diagnosis and therapy with low toxicity, high efficacy, and safety have attracted wide attention. However, because of the poor water solubility and rapid clearance of imperfect materials, the clinical use of phototherapy is still hindered. Molybdenum oxide nanomaterials, as important transition metal oxides, have become a hot topic in nanomedicine in recent years since they can carry with oxygen to form a variety of molybdenum oxides (MoOx, 1 < x ≤ 3) and show a variety of special morphologies, structures, and properties. Because of their special defect structure, molybdenum oxide nanoparticles show strong optical absorption in the visible and near-infrared region. On the other hand, their low biological toxicity, ease of excretion, and capability of photoacoustic imaging make them good photothermal material. In this review, we emphasize recent progress on the principle and research status of phototherapy based on molybdenum oxide nanoparticles in terms of chemical synthesis, mechanism, and future prospects.

In-situ N-doped MnCO3 anode material via one-step solvothermal synthesis: Doping mechanisms and enhanced electrochemical performances

In-situ N-doped MnCO3 microcrystal was prepared by a mild one-step solvothermal process for the first time. The influences of N-doping on microstructures and electrochemical performances of MnCO3 microcrystal have been investigated systematically. A plausible mechanism for the in-situ N-doping in MnCO3 also has been proposed. It is found that nitrogen was successfully doped into the MnCO3 by the substitution of lattice oxygen, generating a specific defect structure with oxygen vacancies and narrowing the band gap of MnCO3 effectively from 5.021 to 3.885 eV. When used as anode material, the as-obtained N-doped MnCO3 exhibits outstanding electrochemical performances: it delivers a large capacity of 685 mAh g−1 after 600 cycles at 1 C; exhibits a superior high-rate performance and long-term stability with a high capacity of 437 mAh g−1 even after 1000 cycles at a very large current rate of 5 C. Compared with the pristine MnCO3, such the outstanding electrochemical performances of N-doped MnCO3 should be attributed to the specific defect structure provided by N-doping, which can not only create more active sites for lithium storage, but also improve the poor electronic conductivity of MnCO3. This work can offer an effective and facile strategy to realize in-situ N-doping by wet chemical synthesis route, as well as enhance the electrochemical performances of transition metal carbonates.

Identifying the local defect structure in (Na0.5K0.5)NbO3: 1 mol. % CuO lead-free ceramics by x-ray absorption spectra

The local defect structure around dopant atoms in 1 mol. % CuO doped (Na0.5K0.5)NbO3 lead-free ceramics was investigated by means of x-ray absorption spectra as compared with the local structure around the host Nb site. The Cu K-edge and O K-edge x-ray absorption near-edge structure spectra demonstrate divalent Cu ions that occupy the octahedrally coordinated Nb sites and also reveal the existence of oxygen vacancy VO¨ in the nearest neighboring around the Cu atom evidently. Moreover, the Cu and Nb K-edge extended x-ray absorption fine structure clearly suggests that the oxygen vacancies should be located at two O22 sites with the two longest Cu-O22 bond lengths, thus producing trimeric bent VO¨-CuNb″′-VO¨ defect complexes with a dipole moment PD parallel to the spontaneous polarization Ps, instead of dimeric CuNb″′-VO¨ and straight VO¨-CuNb″′-VO¨ defect complexes. This kind of special defect structure is also different from that observed in conventional Pb-based perovskite ferroelectrics in which only dimeric CuTi″-VO¨ defect dipoles were observed. Finally, the influence of the defect complexes on the macroscopic properties was specially discussed by taking into account the interaction between Ps and PD.

Identification of defective two dimensional semiconductors by multifractal analysis: The single-layer [formula omitted] case study

Two dimensional semiconductor such as single-layer transition metal dichalcogenides (SL-TMD) have attracted most attentions as an atomically thin layer semiconductor materials. Typically, lattice point defects (sulfur vacancy) created by physical/chemical method during growth stages, have disadvantages on electronic properties. However, photoluminescence (PL) spectroscopy is conventionally used to characterize single-layer films but until now it has not been used to show the presence of defects or estimate their population due to overall similarity of general feature PL spectra. To find a feasible and robust method to determine the presence of point defects on single layer MoS2 without changing the experimental setup, Multifractal Detrended Fluctuation Analysis (MF-DFA) and Multifractal Detrended Moving Average Analysis (MF-DMA) are applied on the PL spectrum of single layer MoS2. We compare the scaling behavior of PL spectrum of pristine and defective single layer MoS2 determined by MF-DFA and MF-DMA. Our results reveal that PL spectrum has multifractal nature and different various population of point defects (sulfur vacancy) on single layer MoS2 change dramatically multifractality characteristics (Hurst, Hölder exponents) of photoluminescence spectrum. It is exhibited creating more lattice point leads to smaller fluctuations in luminescent light that it can help to design special defect structure for light emitted devices. The relative populations of point defects are almost elucidated without utilizing expensive characterization instruments such as scanning tunneling microscopy (STM) and high resolution transmission electron microscopy (HR-TEM).

1 billion tons of nanostructure – segregation engineering enables confined transformation effects at lattice defects in steels

The microstructure of complex steels can be manipulated by utilising the interaction between the local mechanical distortions associated with lattice defects, such as dislocations and grain boundaries, and solute components that segregate to them. Phenomenologically these phenomena can be interpreted in terms of the classical Gibbs adsorption isotherm, which states that the total system energy can be reduced by removing solute atoms from the bulk and segregating them at lattice defects. Here we show how this principle can be utilised through appropriate heat treatments not only to enrich lattice defects by solute atoms, but also to further change these decorated regions into confined ordered structural states or even to trigger localized decomposition and phase transformations. This principle, which is based on the interplay between the structure and mechanics of lattice defects on the one hand and the chemistry of the alloy’s solute components on the other hand, is referred to as segregation engineering. In this concept solute decoration to specific microstructural traps, viz. lattice defects, is not taken as an undesired effect, but instead seen as a tool for manipulating specific lattice defect structures, compositions and properties that lead to beneficial material behavior. Owing to the fairly well established underlying thermodynamic and kinetic principles, such local decoration and transformation effects can be tuned to proceed in a self-organised manner by adjusting (i) the heat treatment temperatures for matching the desired trapping, transformation or reversion regimes, and (ii) the corresponding timescales for sufficient solute diffusion to the targeted defects. Here we show how this segregation engineering principle can be applied to design self-organized nano- and microstructures in complex steels for improving their mechanical properties.

Experimental and numerical investigation of the residual yield strength of aluminium alloy EN AW-2024-T3 affected by artificially produced pitting corrosion

In this study, the behaviour of the residual yield strength of aluminium alloy EN AW-2024-T3 affected by the morphology and numbers of corrosion pits (defects) is presented. Since specific defect structures are not reproducible during experimental corrosion tests, metal sheets with different numbers of pits and pit shapes are produced using laser micro structuring. The defect structures are measured using laser scanning microscopy. To compare the stress states of the micro structured and real corroded metal sheets, FE-analysis is used. Afterwards, uniaxial tensile tests are carried out and critical defect parameters in terms of yield strength reduction of the investigated aluminium alloy are detected.

Vesicle Leakage Reflects the Target Selectivity of Antimicrobial Lipopeptides from Bacillus subtilis

Cyclic lipopeptides act against a variety of plant pathogens and are thus highly efficient crop-protection agents. Some pesticides contain Bacillus subtilis strains that produce lipopeptide families, such as surfactins (SF), iturins (IT), and fengycins (FE). The antimicrobial activity of these peptides is mainly mediated by permeabilizing cellular membranes. We used a fluorescence-lifetime based leakage assay to examine the effect of individual lipid components in model membranes on lipopeptide activity. Leakage induction by FE was strongly inhibited by cholesterol (CHOL) as well as by phosphatidylethanolamine (PE) and -glycerol (PG) lipids. Already moderate amounts of CHOL increased the tolerable FE content in membranes by an order of magnitude to 0.5 FE per PC + CHOL. This indicates reduced FE-lipid demixing and aggregation, which is known to be required for membrane permeabilization and explains the strong inhibition by CHOL. Ergosterol (ERG) had a weak antagonistic effect. This confirms results of microbiological tests and agrees with the fungicidal activity and selectivity of FE. SF is known to be much less selective in its antimicrobial action. In line with this, liposome leakage by SF was little affected by sterols and PE. Interestingly, PG increased SF activity and changed its leakage mechanism toward all-or-none, suggesting more specific, larger, and/or longer-lived defect structures. This may be because of the reduced energetic cost of locally accumulating anionic SF in an anionic lipid matrix. IT was found largely inactive in our assays. B. subtilis QST713 produces the lipopeptides in a ratio of 6 mol SF: 37 mol FE: 57 mol IT. Leakage induced by this native mixture was inhibited by CHOL and PE, but unaffected by ERG and by PG in the absence of PE. Note that fungi contain anionic lipids, but little PE. Hence, our data explain the strong, fungicidal activity and selectivity of B. subtilis QST713 lipopeptides.