A high H_2 evolution rate under visible light of a CdS/TiO_2@Ni S catalyst due to a directional electron transfer between the phases

The photocatalytic activity of CdS can be greatly improved by co-modification of NiS and TiO_2 materials; furthermore the order of connection affects much. A directional electron transfer route via CdS → TiO_2→ NiS is found crucial to the enhancement of ternary catalyst, where TiO_2 acts as an electron reservoir and Ni S works as an effective cocatalyst. Cd S/TiO_2@Ni S with Ni S loaded on TiO_2 has an activity of H_2 evolution 2.5 times higher than NiS@Cd S/TiO_2 with Ni S pre-loaded on Cd S. Faster e-/h+separation rates is obtained of Cd S/TiO_2@Ni S under visible light than under extra UV light irradiation, which in turn demonstrates the importance of directional electron transfer route.

Direct Electron－transfer Reaction of Cytochrome C at a Bare Spectrographic Graphite Electrode

he electrochemistry of cytochrome C was investigated at a spectrographicgraphite electrode. In phosphate buffer solution (pH= 7. 0) , cytochrome C showedstable and quasi-reversible response. The formal potential E￣(o') was 0. 015 V (at25℃ , vs. SCE) and the heterogeneous electron transfer rate constant k_s obtainedvaried form 1. 10×10￣(-3) cm · s￣(-1) to 1. 80k×10￣(-3) cm · s￣(-1). The thermodynamic pa-rameters of the electron transfer reaction of cvtochrome C was also estimated. Fur-thermore, the effect of the various electrode surface states on the electrochemistryof cytochrome C was discussed.

Direct Electron Transfer Reactions of Glucose Oxidase and D-Amino Acid Oxidase at a Glassy Carbon Electrode in Organic Media

Cyclic voltammetry is employed to demonstrate feasibility of direct electron transfer of glucose oxidase and D amino acid oxidase at a glassy carbon electrode in organic media. The reversible slight conformational change of glucose oxidase is observed by changing 0.1 mol/L phosphate buffer to acetonitrile containing 10% v/v of water and 0.05 mol/L tetrabutyalammonium perchlorate, and vice versa.

Coupling biomass pretreatment for enzymatic hydrolysis and direct biomass-to-electricity conversion with molybdovanadophosphoric heteropolyacids as anode electron transfer carriers

Owing to their acidity,oxidizing ability and redox reversibility,molybdovanadophosphoric heteropolyacids(H_(n+3)PMo_(12-n)VnO40,abbreviated as PMo_(12-n)Vn) were employed as electron transfer carriers for coupling biomass pretreatment for enzymatic hydrolysis and direct biomass-to-electricity conversion.In this novel coupled process,PMo_(12-n)Vn pretreatment that causes deconstruction of cell wall structure with PMo_(12-n)Vn being simultaneously reduced can be considered as the "charging" process.The reduced PMo_(12-n)Vn are further re-oxidized with release of electrons in a liquid flow fuel cell(LFFC) to generate electricity is the "discharging" process.Several Keggin-type PMo_(12-n)Vn with different degree of vanadium substitution(DSV, namely n) were prepared.Compared to Keggin-type phosphomolybdic acid(PMo_(12)),PMo_(12-n)Vn(n=1-6) showed higher oxidizing ability but poorer redox reversibility.The cellulose enzymatic digestibility of PMo_(12-n)Vn pretreated wheat straw generally decreased with increase in DSV, but xylan enzymatic digestibility generally increased with DSV.PMo_(12) pretreatment of wheat straw at 120℃ obtained the highest enzymatic glucan conversion(EGC) reaching 95%,followed by PMo11V1 pretreatment(85%).Discharging of the reduced heteropolyacids in LFFC showed that vanadium substitution could improve the maximum output power density(Pmax).The highest Pmax was obtained by PMo9 V3(44.7 mW/cm^(2)) when FeCl_(3) was used as a cathode electron carrier,while PMo_(12) achieved the lowest Pmax(27.4 mW/cm^(2)).All the heteropolyacids showed good electrode Faraday efficiency(>95%) and cell discharging efficiency(>93%).The energy efficiency of the coupled process based on the heat values of the products and generated electric energy was in the range of 18%-25% depending on DSV.PMo_(12) and PMo11V1 seem to be the most suitable heteropolyacids to mediate the coupled process.

Combined pretreatment using CaO and liquid fraction of digestate of rice straw: Anaerobic digestion performance and electron transfer

To improve anaerobic digestion(AD)efficiency of rice straw,solid alkaline CaO and the liquid fraction of digestate(LFD)were used as pretreatment agents of rice straw.The results showed that AD performance of rice straw with CaOLFD pretreatment was optimal in different pretreatment methods of the CaO+LFD,CaOLFD,LFD+CaO,CaO,and LFD.The maximum methane yield(314 ml(g VS)^(-1))and the highest VFAs concentration(14851 mg·L^(-1) on day 3)of the CaOLFD pretreatment group were 81%and 118%higher than that of the control group,respectively.Under the action of solid alkaline CaO,the bacteria of Clostridium,Atopostipes,Sphaerochaeta,Tissierella,Thiopseudomonas,Rikenellaceae,and Sedimentibacter could build up co-cultures with the archaeal of Methanosaeta,Methanobacterium,and Methanosarcina performing direct interspecies electron transfer(DIET)and improving AD performance of rice straw.Therefore,the combined pretreatment using CaO and LFD could not only pretreat rice straw but also stimulate co-cultures of microorganism to establish DIET enhancing AD efficiency.

Electrically conductive nanowires controlled one pivotal route in energy harvest and microbial corrosion via direct metal-microbe electron transfer

Extracellular electron transfer(EET)plays a critical role in bioelectrochemical processes,allowing cou-pling between microorganisms and extracellular solid-state electrodes,metals,or other cells in energy metabolism.Previous studies have suggested a role for outer-surface c-type cytochromes in direct metal-to-microbe electron transfer by Geobacter sulfurreducens,a model electroactive bacterium.Here,we ex-amined the possibility of other microbially produced electrical contacts by deleting the gene for PilA,the protein monomer that G.sulfurreducens assembles into electrically conductive protein nanowires(e-pili).Deleting pilA gene inhibited electron extraction from pure iron and 316L stainless steel up to 31%and 81%,respectively more than deleting the gene for the outer-surface cytochrome OmcS.This PilA-deficient phenotype,and the observation that relatively thick biofilms(21.7μm)grew on the metal surfaces at multi-cell distances from the metal surfaces suggest that e-pili contributed significantly to microbial cor-rosion via direct metal-to-microbe electron transfer.These results have implications for the fundamental understanding of electron harvest via e-pili by electroactive microbes,their uses in bioenergy production,as well as in monitoring and mitigation of metal biocorrosion.

改善剩余污泥厌氧消化产甲烷性能的新策略:导电材料介导微生物种间直接电子传递

综述了近年来关于碳基和铁基导电材料促进DIET产甲烷的研究进展,归纳了直接种间电子传递的机制,总结了碳基和铁基导电材料的结构特征、电子传递机理和强化剩余污泥厌氧产甲烷效果。指出了当前研究存在的不足,并对未来的研究方向做出了展望。

A direct electrochemical biosensor for rapid glucose detection based on nitrogen-doped carbon nanocages

Given the increasing number of diabetic patients,rapid and accurate detection of glucose in body fluids is critical.This study developed a direct electrochemical biosensor for glucose based on nitrogen-doped carbon nanocages(NCNCs).NCNCs possess a large specific surface area of 1395 m^(2)·g^(-1),a high N atomic content of 9.37%and good biocompatibility,which is favorable for enzyme loading and electron transfer.The surface average concentration of electroactive glucose oxidase on NCNCs was 2.82×10^(-10)mol·cm^(-2).The NCNC-based direct electrochemical biosensor exhibited a high sensitivity of 13.7μA·(mmol·L^(-1))^(-1)·cm^(-2),rapid response time of 5 s and an impressive electron-transferrate constant(ks)of 1.87 s^(-1).Furthermore,we investigated an NCNC-based direct electron transfer(DET)biosensor for sweat glucose detection,which demonstrated tremendous promise for non-invasive wearable diabetes diagnosis.

Direct Electron Transfer between Glucose Oxidase and Multi-walled Carbon Nanotubes

The direct electrochemical behavior between the glucose oxidase (GOD) and the multi walled carbon nanotubes (MWNTs) has been studied. Two pairs of cyclic voltammetric peaks corresponding to the two different processes, i.e. mass transport and surface reaction of GOD are observed on this MWNTs. The formal potentials with E o′=-0.45 V and E o′=-0.55 V were obtained respectively. The GOD film was observed on the carbon nanotube by the TEM.

Electron transfer to direct oxidation of aqueous organics by perovskites

The residual of oxidant chemicals in advanced oxidation processes(AOPs)resulted in both economic cost and secondary pollution.Herein,we report a direct oxidation of phenolic pollutants induced by Ca-Mn-O perovskites without using an oxidant.Governed by one-electron transfer process(ETP)from the phenolics to the Ca-Mn-O perovskites,this direct oxidation proceeds in fast reaction kinetics with activation energy of 51.4 kJ/mol,which was comparable with those AOPs-based catalytic systems.Additionally,mineralization and polymerization reactions occurred on the Ca-Mn-O surface and ensured the complete removal of phenolics.The high spin state Mn(III)within Ca-Mn-O structure was the dominant active site for this ETP.The elongated axial Mn(III)–O bonds within the[MnO_(6)]octahedron facilitated the acceptance of the electrons from the phenolics and thus promoted the initiation of the direct oxidation process.Mn(III)in the high spin state can also activate dissolved O_(2)to produce singlet oxygen(^(1)O_(2))for a fast removal of phenolics.The mixed Mn(III)/Mn(IV)within Ca-Mn-O accelerated the ETP by enhancing the electrical conductivity.This efficient Ca-Mn-O-induced ETP for removal of organic contaminants casts off the dependence on external chemical and energy inputs and provides a sustainable approach for transforming the toxic organic pollutants into value-added polymers.

Extending the operational lifetimes of all-direct electron transfer enzymatic biofuel cells by magnetically assembling and exchanging the active biocatalyst layers on stationary electrodes

Enzymatic biofuel cells promise green power generation from a variety of natural resources, yet these systems all suffer from time-dependent degradati on effects, in particular progress! ng inactivation of enzymes, which severely limit the operati on al lifetimes of such power sources. To extend operational lifetimes, we introduce a method to magnetically exchange exhausted enzymes for fresh ones. To this end, anodic and cathodic enzymes or enzyme cascades are immobilized on carbon coated magnetic nanoparticles. Under the action of suitable magnetic field gradie nts, these nano particles are assembled on the respective stati onary electrodes, or released from the electrodes for collection and subsequent excha nge. We dem on strate this method on a fructose/oxygen con suming biofuel cell emplo ying fructose dehydroge nase and bilirubin oxidase as well as on anodic and cathodic cascades employing fructose dehydrogenase/invertase and bilirubin oxidase/catalase, respectively. The en zyme-modified nan oparticles support direct electro n transfer bioelectrocatalytic curre nts by wiring the redox active cofactors to the carbonaceous coating and from there to the electrode surfaces. The facile injection, assembly, and removal of enzyme-modified magnetic nan oparticles along with fuel solutio n provides a promisi ng approach to exte nd the operati on al lifetime of enzymatic biofuel cells without the need for exchanging entire systems including chambers and electrodes.

Different outer membrane c‐type cytochromes are involved in direct interspecies electron transfer to Geobacter or Methanosarcina species

Direct interspecies electron transfer(DIET)may be most important in methanogenic environments,but mechanistic studies of DIET to date have primarily focused on cocultures in which fumarate was the terminal electron acceptor.To better understand DIET with methanogens,the transcriptome of Geobacter metallireducens during DIET‐based growth with G.sulfurreducens reducing fumarate was compared with G.metallireducens grown in coculture with diverse Methanosarcina.The transcriptome of G.metallireducens cocultured with G.sulfurreducens was significantly different from those with Methanosarcina.Furthermore,the transcriptome of G.metallireducens grown with Methanosarcina barkeri,which lacks outer‐surface c‐type cytochromes,differed from those of G.metallireducens cocultured with M.acetivorans or M.subterranea,which have an outer‐surface c‐type cytochrome that serves as an electrical connect for DIET.Differences in G.metallireducens expression patterns for genes involved in extracellular electron transfer were particularly notable.Cocultures with c‐type cytochrome deletion mutant strains,ΔGmet_0930,ΔGmet_0557 andΔGmet_2896,never became established with G.sulfurreducens but adapted to grow with all three Methanosarcina.Two porin–cytochrome complexes,PccF and PccG,were important for DIET;however,PccG was more important for growth with Methanosarcina.Unlike cocultures with G.sulfurreducens and M.acetivorans,electrically conductive pili were not needed for growth with M.barkeri.Shewanella oneidensis,another electroactive microbe with abundant outer‐surface c‐type cytochromes,did not grow via DIET.The results demonstrate that the presence of outer‐surface c‐type cytochromes does not necessarily confer the capacity for DIET and emphasize the impact of the electron‐accepting partner on the physiology of the electron‐donating DIET partner.

乙醇发酵预处理耦合生物炭强化城镇有机固废厌氧产甲烷

当前厌氧消化的核心技术原理是种间氢传递(IHT),其对扩散传质依赖高,在处理城镇有机固废(MOSW,主要包括餐厨垃圾和剩余污泥)时易受阻,导致厌氧产甲烷停滞。直接种间电子传递(DIET)对扩散传质依赖低,可取代IHT,成为城镇有机固废厌氧产甲烷的主要工作模式。乙醇型发酵预处理和投加碳基导电材料是促进厌氧消化中DIET的两大手段。以实际城镇有机固废为底物,采用乙醇型发酵预处理耦合生物炭的方法,对强化厌氧产甲烷性能进行探究。结果显示:(1)通过优化酿酒酵母培养时间、接种比及培养基组成,获得了酿酒酵母的最佳培养条件(培养时间为21.17 h,接种比为15%,每30 mL液体培养基组成为3.00 g葡萄糖、0.12 g蛋白胨、0.12 g酵母浸出粉及微量元素);(2)通过优化乙醇型发酵预处理的温度和酿酒酵母的接种比,获得了乙醇型发酵预处理的最佳工艺条件(最佳发酵温度为37℃,酿酒酵母接种比为20 mL/L);(3)设计半连续流厌氧消化实验,探究乙醇型发酵预处理耦合生物炭对城镇有机固废甲烷产量和底物去除的影响。相比于对照组,乙醇型发酵预处理(接种20 mL/L酿酒酵母)耦合生物炭(2 g/L)组的甲烷产量提高了102.50%,底物去除率提高了16.15%;(4)微生物群落分析发现,乙醇型发酵预处理耦合生物炭提高了Methanosaeta的相对丰度。优化了酿酒酵母的培养条件,确定了乙醇型发酵预处理的最佳温度和接种比,降低了经济成本。通过乙醇型发酵预处理耦合生物炭,构建了厌氧消化中DIET,强化了厌氧产甲烷,提高了城镇有机固废的资源化和减量化。

Combining metal-microbe and microbe-microbe dual direct electron transfer on Fe(0)-cathode of bio-electrochemical system to enhance anaerobic digestion of cellulose wastewater

Considering that cathode of microbial electrochemical system(MES)is a good electrons source for methane production via direct/indirect electron transfer to electroactive microorganisms,and that Fe(0)is also a confirmed electron donor for some electroactive microorganisms through metal-microbe direct electron transfer(DET),Fe(0)-cathode was equipped into an MES digester to enhance cathodic methane production.The results of this study indicated that the potential DET participator,Clostridium possibly obtained electrons directly from Fe(0)-cathode via metal-microbe electrons transfer,then transferred electrons directly to the definite DET participators,Methanosarcina/Methanothrix via microbemicrobe electrons transfer for CH_(4)production.In addition,Methanobacterium is another specially enriched methanogen on Fe(0)-cathode,which might obtain electrons directly from Fe(0)-cathode to produce CH_(4) via metal/electrode-microbe DET.The increment of conductivity of cathodic sludge in Fe(0)-cathode MES digester(R1)further confirmed the enrichment of electroactive microorganisms participating in DET process.As a consequence,a higher CH_(4) production(1205–1508 m L/d)and chemical oxygen demand(COD)removal(79.0%-93.8%)were achieved in R1 compared with graphite-cathode MES digester(R2,720–1090 m L/d and 63.6%-85.6%)and the conventional anaerobic digester(R3,384–428 m L/d and 35.2%-41.0%).In addition,energy efficiency calculated indicated that the output energy of CH_(4) production was 8.16 folds of electricity input in Fe(0)-cathode MES digester.

基于辣根过氧化物酶/纳米金/辣根过氧化物酶/多壁纳米碳管修饰的过氧化氢生物传感器的研究

以固定在玻碳电极上的多壁纳米碳管为基底吸附辣根过氧化物酶,再固定纳米金,然后再结合一层辣根过氧化物酶,利用多壁纳米碳管对辣根过氧化物酶的直接电化学催化特性及纳米金对蛋白质的强吸附能力及强的电子传导特性制备了无电子媒介体的过氧化氢生物传感器.采用循环伏安法,在无电子媒介体时,该传感器对H2O2仍能具有良好的催化活性,放大了电信号,提高了该酶传感器的灵敏度及稳定性.实验证明,该传感器在H2O2浓度为1.0×10-6～1.0×10-3mol?L-1范围内有线性响应,线性相关系数r2=0.9964.并探讨了电极的稳定性、寿命及重现性.

聚芳酰胺-多壁碳纳米管混合物固定漆酶电极的电化学行为

以聚芳酰胺-多壁碳纳米管混合物为载体,利用漆酶表面氨基与聚芳酰胺主链端羧基的共价偶联以及碳纳米管与漆酶间的疏水作用,构筑了具有较高稳定性和电催化活性的漆酶修饰电极.并对该固酶修饰电极的固酶量、酶活力、电化学行为及其电催化氧还原的性能进行了表征.对漆酶分子具有亲和力的聚芳酰胺芳环结构及聚芳酰胺端羧基与漆酶表面氨基的共价偶联避免了漆酶的脱落和变性.而碳纳米管与聚芳酰胺的混合使得该三维修饰电极具有良好的电子导电性,并成功地实现了漆酶的氧化还原活性位与电极之间的直接电荷转移,这一点可由在0.73和0.38V附近观察到漆酶的T1和T2(漆酶的T1,T2铜活性位的形式电位分别为0.78和0.39V(vsNHE))铜活性位的两对氧化还原峰确认.漆酶的担载量为56.0mg·g-1,具有电化学活性的漆酶占总担载漆酶量的68%.在pH=4.4磷酸盐缓冲溶液中,该修饰电极上氧气还原的起始电位为0.55V,其对氧气的米氏常数KM为55.8μmo·lL-1,对氧气的检测限为0.57μmo·lL-1.在4℃下保存两个月后能实现直接电荷转移的漆酶量仅下降了14%左右而氧还原超电势提高了约50mV.结果表明该修饰电极有望用作酶基生物燃料电池的阴极和电流型氧气传感器.

肌红蛋白在碳纳米管修饰电极上的直接电化学和电催化性能(英文)

将肌红蛋白(Mb)通过吸附的方法固定在碳纳米管(CNT)表面,用AFM、XPS、UV-Vis和FTIR对其进行了表征,研究了CNT对Mb直接电子转移反应的促进作用.循环伏安结果表明,Mb在CNT表面能进行有效和稳定的直接电子转移反应,其循环伏安曲线上表现出一对良好的、几乎对称的氧化还原峰;在20-160mV·s-1的扫速范围内,式量电位E0′几乎不随扫速而变化,其平均值为(-0.343±0.001)V(vsSCE,pH7.0);Mb在CNT表面直接电子转移的表观速率常数为(3.11±0.98)s-1;式量电位E0′与溶液pH的关系表明,Mb的直接电化学过程是一个有H+参与的电极过程.进一步的实验结果显示,固定在CNT表面的Mb能保持其对H2O2和O2还原的生物电催化活性.

超氧阴离子自由基电化学分析的新进展

超氧阴离子自由基(O2·-)是分子氧在生物体内氧化还原反应中产生的活性中间体,其动态变化可以提供丰富的生理、病理信息。因此,实时、在体检测O2·-自由基的分析方法越来越受到人们的关注。电化学分析方法具有直观、简单、易微型化等优点,在O2·-自由基检测中得到了广泛的应用。本文从溶液/电极界面的设计入手,利用酶的直接电子传递,结合O2·-自由基的分析特性,简要评述了近几年电化学分析在细胞和活体内O2·-自由基检测方面的研究进展。

细胞色素c在Fe2O3修饰电极上的直接电化学和电催化特性

采用全氟磺酸树脂Nafion将金属氧化物Fe2O3颗粒细胞色素c(Cyt c)固定玻碳电极(GCE)表面,制备了Nafion-Cyt c-Fe2O3修饰的玻碳电极,构建了基于直接电子传递的过氧化氢生物传感器。在0.10mol/L pH7.0的磷酸盐缓冲溶液中,修饰电极的循环伏安曲线上显示出一对准可逆的氧化还原峰,式量电位为22mV。Cyt c在修饰电极表面的异相电子转移速率常数为1.21s-1。修饰后的电极对过氧化氢有良好响应,响应时间小于10s,电极的安培响应与过氧化氢浓度在2.0×10-6～3.0×10-3mol/L范围内成线性关系,检出限为1.0×10-6mol/L,米氏常数为1.35mmol/L,显示出较好的亲和力。

陆地生态系统甲烷产生和氧化过程的微生物机理

陆地生态系统存在许多常年性或季节性缺氧环境,如:湿地、水稻土、湖泊沉积物、动物瘤胃、垃圾填埋场和厌氧生物反应器等。每年有大量有机物质进入这些环境,在缺氧条件下发生厌氧分解。甲烷是有机质厌氧分解的最终产物。产生的甲烷气体可通过缺氧-有氧界面释放到大气,产生温室效应,是重要的温室气体。产甲烷过程是缺氧环境中有机质分解的核心环节,而甲烷氧化是缺氧-有氧界面的重要微生物过程。甲烷的产生和氧化过程共同调控大气甲烷浓度,是全球碳循环不可分割的组成部分。对陆地生态系统甲烷产生和氧化过程的微生物机理研究进展进行了概要回顾和综述。主要内容包括:新型产甲烷古菌即第六和第七目产甲烷古菌和嗜冷嗜酸产甲烷古菌的发现;短链脂肪酸中间产物互营氧化过程与直接种间电子传递机制;新型甲烷氧化菌包括厌氧甲烷氧化菌和疣微菌属好氧甲烷氧化菌的发现;甲烷氧化菌生理生态与环境适应的新机制。这些研究进展显著拓展了人们对陆地生态系统甲烷产生和氧化机理的认识和理解。随着新一代土壤微生物研究技术的发展与应用,甲烷产生和氧化微生物研究领域将面临更多机遇和挑战,对未来发展趋势做了展望。