Effect on electrochemical reduction of nitrogen to ammonia under ambient conditions: Challenges and opportunities for chemical fuels

The nitrogen cycle plays an important role in nature,but N-containing products cannot meet human needs.The electrochemical synthesis of ammonia under ambient conditions has attracted the interest of many researchers because it provides a clean and pollution-free synthesis method;however,it has certain difficulties,including a high activation energy,multiple electron transfer,and hydrogenation.Thermodynamic factors limit the selectivity and activity of ammonia synthesis techniques.This review summarizes progress in the electrochemical synthesis of ammonia from theory and experiment.Theoretically,the reduction of nitrogen molecules is analyzed using orbit theory and the thermodynamic reaction pathways.Experimentally,we first discuss the effect of the experimental setup on the nitrogen reduction reaction,and then the four critical of catalysts,including size,electronic,coordination,and orientation effects.These issues must be considered to produce highly-efficient catalysts for electrochemical nitrogen reduction(eNRR).This review provides an overview of the eNRR to enable future researchers to design rational catalysts.

High-performance self-organized Si nanocomposite anode for lithium-ion batteries

Silicon is being investigated extensively as an anodic material for next-generation lithium ion batteries for portable energy storage and electric vehicles.However,the large changes in volume during cycling lead to the breakdown of the conductive network in Si anodes and the formation of an unstable solid-electrolyte interface,resulting in capacity fading.Here,we demonstrate nanoparticles with a Si@Mn22.6Si5.4C4@C double-shell structure and the formation of self-organized Si-Mn-C nanocomposite anodes during the lithiation/delithiation process.The anode consists of amorphous Si particles less than 10 nm in diameter and separated by an interconnected conductive/buffer network,which exhibits excellent charge transfer kinetics and charge/discharge performances.A stable specific capacity of 1100 mAh·g-1 at 100 mA·g-1 and a coulombic efficiency of 99.2%after 30 cycles are achieved.Additionally,a rate capacity of 343 mAh·g-1 and a coulombic efficiency of 99.4%at 12000 mA·g-1 are also attainable.Owing to its simplicity and applicability,this strategy for improving electrode performance paves a way for the development of high-performance Si-based anodic materials for lithium ion batteries.

Degradation properties of fulvic acid and its microbially driven mechanism from a partial nitritation bioreactor through multi-spectral and bioinformatic analysis

This study employed multispectral techniques to evaluate fulvic acid(FA)compositional characteristic and elucidate its biodegradation mechanisms during partial nitritation(PN)process.Results showed that FA removal efficiency(FRE)decreased from 90.22 to 23.11%when FA concentrations in the reactor were increased from 0 to 162.30 mg/L,and that molecular size,degree of aromatization and humification of the effluent FA macromolecules all increased after treatment.Microbial population analysis indicated that the proliferation of the Comamonas,OLB12 and Thauera exhibit high FA utilization capacity in lower concentrations(<50.59 mg/L),promoting the degradation and removal of macromolecular FA.In addition,the sustained increase in external FA may decrease the abundance of above functional microorganisms,resulting in a rapid drop in FRE.Furthermore,from the genetic perspective,the elevated FA levels restricted carbohydrate(ko00620,ko00010 and ko00020)and nitrogen(HAO,AMO,NIR and NOR)metabolism-related pathways,thereby impeding FA removal and total nitrogen loss associated with N_(2)O emissions.

Single-cell mass spectrometry studies of drug metabolism heterogeneity and primary resistance to gefitinib in non-small cell lung cancer cells

Patients with epidermal growth factor receptor(EGFR)wild-type non-small cell lung cancer(NSCLC)often show primary resistance to gefitinib therapy.It is thus necessary to study the metabolism of gefitinib in NSCLC cells to comprehensively reveal the reasons for the primary resistance of tumors.Herein,we develop a platform for studying drug metabolism heterogeneity based on single-cell mass spectrometry(sDMH-scMS)by integrating living-cell electrolaunching ionization MS(ILCEI-MS)and high-performance liquid chromatography-MS(HPLC-MS)analysis,and the primary resistance of NSCLC cells to gefitinib was studied using this platform.The ILCEI-MS analysis showed that approximately 11.9%of NSCLC single cells contained the gefitinib metabolite M11;HPLC-MS detection diluted the intensity of M11 in subpopulations and concealed the heterogeneity of drug metabolism in tumor single cells.The intensity of gefitinib in EGFR wild-type A549 cells was markedly lower than in mutant PC9 cells,and the intensity of gefitinib metabolites was significantly higher than in PC9 cells,suggesting that the primary resistance of NSCLC cells is related to gefitinib metabolism.Moreover,the combination of gefitinib and the drug-metabolizing enzyme inhibitorα-naphthoflavone was shown to overcome the primary resistance of the NSCLC cells.Overall,the results of this study are expected to be applicable for clinical drug resistance diagnosis and treatment at the single-cell level.

Nano-sized stationary phase packings retained by single-particle frit for microchip liquid chromatography

Modern chromatography is increasingly focused on miniaturization and integration. Compared to conventional liquid chromatography, microfluidic chip liquid chromatography(microchip-LC) has the potential due to its zero-dead volume connection and ease of integration. Nano-sized packings have the potential to significantly enhance separation performance in microchip-LC. However, their application has been hindered by packing difficulties. This study presents a method for packing nano-sized silica particles into a microchannel as the stationary phase. The microchip-LC packed column was prepared by combining the weir and the porous silica single-particle as frit to retain the packing particles. A surface tensionbased single-particle picking technique was established to insert porous single-particle frit into glass microchannels. Additionally, we developed a slurry packing method that utilizes air pressure to inject nano-sized packing into the microchannel. Pressure-driven chromatographic separation was performed using this nano-packed column integrated into a glass microchip. The mixture of four PAHs was successfully separated within just 8 min using a 5 mm separation channel length, achieving high theoretical plates(10~6plates/m). Overall, these findings demonstrate the potential of utilizing nano-sized packings for enhancing chromatographic performance in microchip systems.

基于微流控芯片的体外三维肝脏生理模型的构建及应用

肝脏是身体内最重要器官之一,是生化代谢和合成过程最主要的器官。因此,深入了解肝脏生理生化过程、病理机制等,对于研究、预防、诊断、治疗肝脏相关或代谢相关疾病具有重要意义。肝脏体外培养模型是研究肝脏相关生物学机制的重要实验基础。传统体外细胞培养难以重现肝脏复杂的生理结构和微环境,且缺乏肝脏组织构造的基本三维特征。更重要的是,平面培养过程中细胞的组织形态架构、基因表达、物质代谢过程等与体内相比具有较大差异。微流控技术可以通过精巧设计与布局在微通道结构中培养相应细胞来模拟肝脏的生理结构,结合三维细胞培养技术,可以在微流控芯片上实现更类似于体内肝脏微环境以及与其他组织器官相互作用的体外肝器官模型。本文总结了基于微流控技术构建体外三维肝脏芯片的方法和最新进展,包括基于多孔膜培养、水凝胶培养、细胞团簇培养及生物打印的三维肝脏模型。进一步,我们也探讨了三维培养的肝脏芯片在重塑肝脏生理结构、探究机理和病理机制以及药物筛选和毒性测试方面的应用,并对三维肝脏微流控器官芯片的潜在价值及其面临的挑战进行了展望。

基于聚苯胺/二氧化钛/天然纤维素的污水自清洁太阳能水蒸发装置

水体污染是当前造成淡水短缺的主要原因之一.利用太阳能水蒸发装置从海水或污水中生产淡水是一种简单有效且节能的解决淡水危机的方式,引起了广泛的关注.然而,污染物的共同蒸发或沉积可能会降低水蒸发过程中的效率和淡水质量.本文基于天然木质纤维素(NCF)、聚苯胺(PANI)和二氧化钛(TiO_(2))开发了自清洁太阳能水蒸发器,其具有宽吸收、亲水性强、导热系数低等优点.通过在聚合物溶液中加入木质纤维素,聚苯胺纳米纤维在NCF表面聚合形成介孔网络.P25 TiO_(2)纳米颗粒作为光催化剂分散到上述反应液中,通过简单的过滤形成PANI/TiO_(2)/NCF复合材料.由于太阳水蒸发器装置中PANI的光热效应与TiO_(2)纳米颗粒的光催化降解的协同作用,水蒸发速率可达2.36 kg m^(-2)h^(-1)(1个太阳光照射下),且可有效降解污染物(100 ppm四环素).更重要的是,在工作10 h后,该太阳能水蒸发器装置仍然保持稳定的水蒸发速率,且没有污染物的积聚.光催化和光热效应相结合的双功能太阳能水蒸发装置在有机污染物水中具有自清洁作用,具有很大的应用潜力.

研发双层结构的碳基水凝胶材料提高太阳能水蒸发效率

太阳能水蒸发对于解决净水危机潜力无限.随着研究的深入,研发高效光热转换材料和合理的材料结构设计均可以提高光热蒸发速率.因此,我们设计合成了一种双层碳基水凝胶复合材料.在一个太阳光照条件下,其最大蒸发速率可达2.19 kg m^(−2)h^(−1),光热转换效率可达93.7%.同时,该复合材料展现了优异的海水淡化性能及良好的稳定性,扩展了实际应用范围.除此之外,其可控规模化及便携性可以自如面对多种复杂的应用环境,成本低廉可以使其大规模应用于经济落后地区,为复合结构水凝胶蒸发器的生产提供了可供参考的设计思路和策略.

具有优越电催化析氢性能的超小碳负载FeRu合金

电化学水分解是将可再生能源产生的间歇性电能转化为高纯度氢气的一种极具前景的绿色能源技术.目前,高效制氢催化剂主要由贵金属及其化合物组成,而贵金属的高成本及稀缺性,限制了其在大规模工业化制氢中的应用.因此,探索低成本,高电化学活性、高稳定性的电解水制氢催化剂至关重要.合金化材料以短程或长程有序结构存在,具有增强的电化学性能.因此,本文采用两步法制备超小碳负载FeRu合金纳米电催化剂并将其应用于电催化析氢反应.Fe_(0.05)Ru_(0.05)/XC-72双功能电催化剂粒径为2.1 nm,在碱性淡水和海水电解质中表现出优异的活性和耐久性.10 mA cm^(-2)时,在1 mol L^(-1)KOH、1 mol L^(-1)KOH+0.5 mol L^(-1)NaCl和1 mol L^(-1)KOH+海水中分别表现出13、15和18 mV的过电位.在1 mol L^(-1)KOH介质和-0.07 V(相比于可逆氢电极)条件下,Fe_(0.05)Ru_(0.05)/XC-72的析氢质量活性高达11.32Amg^(-1)_(noble metal).在1 mol L^(-1)KOH中,Fe_(0.05)Ru_(0.05)/XC-72电催化剂具有24 h以上的长期析氢反应(HER)稳定性.理论计算表明,引入Fe形成的FeRu合金可以诱导电子效应,使其对*H的吸附能力增强,进一步提高了HER性能.本工作对制备高电活性、高稳定性的钌基电催化剂具有重要的启发意义.

The critical factors of photocatalytic H2 production from seawater by using TiO_(2)as photocatalyst

The solar H_(2)generation directly from natural seawater is a sustainable way of green energy.However,it is limited by a low H_(2)generation rate even compared to fresh water.In this report,TiO_(2)is chosen as a model photocatalyst to disclose the critical factor to deteriorate the H_(2)generation rate from seawater.The simulated seawater(SSW),which is composed of eight ions(Na^(+),K^(+),Ca^(2+),Mg^(2+),Cl^(−),Br^(−),SO_(4)^(2−),and CO_(3)^(2−)),is investigated the effect of each ion on the H_(2)production.The results indicate that all ions have a negative effect at the same concentration as in the seawater except Br−.The CO_(3)^(2−)has the most serious deterioration,and the H_(2)production rate lowers near 40%even at[CO_(3)^(2−)]of 1.5 mmol·L^(−1).The H_(2)production rate can be recovered to 85%if the CO_(3)^(2−)is excluded from the SSW.To understand the reason,the zeta potential of the TiO_(2)treated with different ions aqueous solution reveals that the zeta potential decreases when it is treated with CO_(3)^(2−)and SO_(4)^(2−)due to they can adsorb on the surface of TiO_(2)nanoparticles.Fourier transform infrared(FTIR)and thermogravimetric analysis-mass spectroscopy(TGA-MS)further confirm that the adsorbed ion is mainly from CO_(3)^(2−).Since the pH of seawater is about 8.9 between pKa1(6.37)and pKa2(10.3)of H_(2)CO3,the CO_(3)^(2−)should exist in the form of HCO3−in the seawater.We proposed a simple method to remove the adsorbed HCO3−from the TiO_(2)surface by adjusting the pH below the pKa1.The results indicate that if a trace amount of HCl(adjusting pH~6.0)is added to the SSW,the H_(2)production rate can be recovered to 85%of that in pure water.

Anomalous enhancement of fluorescence of carbon dots through lanthanum doping and potential application in intracellular imaging of ferric ion

An anomalous enhancement of fluorescence of carbon dots （CDs） was observed via lanthanum （La） doping. La-doped CDs （La-CDs） were prepared through microwave pyrolysis within 4 min. With La^3＋ doping, the emission band shifted from blue to green although LaB＋ is non-fluorescent. The quantum yield and fluorescence lifetime improved by about 20% and 35%, respectively. All experiment results indicate that La^3＋ doping is an effective way to tune fluorescence and improve the performance of CDs. Another unique attribute of La-CDs is high sensitivity to Fe^3＋. The La-CD-based fluorescence probe was established and used for sensitive and selective detection of Fe^3＋ with a limit of detection of 91 nmol/L. The proposed fluorescence probe also was successfully employed to visualize intracellular Fe^3＋ in live HeLa cells through cell imaging. It was also shown that yttrium exhibited the same fluorescence enhancement effect as La. The results may provide a new route for preparing CDs with special properties.

Surface hydrophobic modification enhanced catalytic performance of electrochemical nitrogen reduction reaction

Electrocatalytic nitrogen reduction reaction(NRR)is a sustainable approach for NH_(3)production with low energy consumption.However,competing hydrogen reduction reaction(HER)in aqueous solution results in low NH_(3)production and Faraday efficiency(FE).Here,MoS_(2)nanostructures with a hydrophobic surface are synthesized by alkyl thiols modification.Aerophilic and hydrophobic surface facilitates an efficient three-phase contact of N_(2),H_(2)O,and catalyst.Thus,localized concentrated N_(2)molecules can overcome the mass transfer limitation of N2 and depress the HER due to lowering the proton contacts.Although the active-sites decrease with the increase of the alkyl chain since the thiol may cover the active site,the optimized electrocatalyst achieves NH_(3)yield of 12.86×10^(-11)mol·cm^(-2)·s^(-1)at-0.25 V and 22.23%FE,which are 4.3 and 24 times higher than those of MoS2-CP electrocatalyst,respectively.The increased catalytic performance is attributed to the high N_(2)adsorption and depressed HER.

Recent advances of carbon dots as new antimicrobial agents

Due to the COVID-19 pandemic,many rapid antimicrobial agents have developed intensively.Carbon dots(CDs),a new type of carbon-based nanomaterials,shows great potential against emerging infectious diseases and antimicrobial-resistant infections due to their unique optical properties,excellent biocompatibility,and easy surface modification.With the definition of the CDs structure and properties,synthesis,and characteristic technology improvement,the research on the CDs as antimicrobial agents has made significant progress.However,the lack of high repeatable and exact preparation methods,and the regular antimicrobial activity make it far from practical application.In this review,we summarize the most recent progress and challenges of CDs antimicrobial.First,an overview of the characteristics and properties is given,and the advantage of CDs applied to antimicrobial is further discussed.Then,it focuses on research progress on antimicrobial mechanisms under different conditions,the critical factors affecting their antimicrobial activity,and the practical antimicrobial applications.Finally,the main challenges and future research perspectives of antimicrobial CDs are proposed.

Synthesis and characterization of a novel binuclear iron phthalocyanine/reduced graphene oxide nanocomposite for non-precious electrocatalyst for oxygen reduction

Binuclear iron phthalocyanine/reduced graphene oxide(bi-Fe Pc/RGO) nanocomposite with good electrocatalytic activity for ORR in alkaline medium was prepared in one step. High angle annular dark field image scanning transmission electron microscopy(HAADF-STEM) and energy dispersive X-ray spectroscopy element mapping results show bi-Fe Pc was uniformly distributed on RGO. An obvious cathodic peak located at about-0.23 V(vs. SCE) in CV and an onset potential of-0.004 V(vs. SCE) in LSV indicate the as-prepared bi-Fe Pc/RGO nanocomposite possesses high activity which is closed to Pt/C for ORR. The ORR on bi-Fe Pc/RGO nanocomposite follows four-electron transfer pathway in alkaline medium. Compared with Pt/C, there is only a slight decrease(about 0.02 V vs. SCE) for bi-Fe Pc/RGO nanocomposite when the methanol exists. The excellent activity and methanol tolerance in alkaline solutions proves that bi-Fe Pc/RGO nanocomposite could be considered as a promising cathode catalyst for alkaline fuel cells.

Formation and fluorescent mechanism of red emissive carbon dots from o-phenylenediamine and catechol system

Carbon dots(CDs)as the advancing fluorescent carbon nanomaterial have superior potential and prospective.However,the ambiguous photoluminescence(PL)mechanism and intricate structure-function relationship become the greatest hindrances in the development and applications of CDs.Herein,red emissive CDs were synthesized in high yield from O-phenylenediamine(oPD)and catechol(CAT).The PL mechanism of the CDs is considered as the molecular state fluorophores because 5,14-dihydroquinoxalino[2,3-b]phenazine(DHQP)is separated and exhibits the same PL properties and behavior as the CDs.These include the peak position and shape of the PL emission and PL excitation and the emission dependence on pH and solvent polarity.Both of them display close PL lifetime decays.Based on these,we deduce that DHQP is the fluorophore of the red emissive CDs and the PL mechanism of CDs is similar to DHQP.During the PL emission of CDs,the electron of the molecule state can transfer to CDs.The formation process of DHQP is further confirmed by the reaction intermediates(phthalazine,dimers)and oPD.These findings provide insights into the PL mechanism of this type of CDs and may guide the further development of tunable CDs for tailored properties.

A pico-HPLC-LIF system for the amplification-free determination of multiple miRNAs in cells

MicroRNAs are a class of important biomarkers,and the simultaneous detection of multiple miRNAs can provide valuable information about many diseases and biological processes.Amplification-free determination has been developed for the analysis of multiple miRNAs because of its characteristic low cost and high fidelity.Herein,a method for the amplification-free analysis and simultaneous detection of multiple miRNAs based on a so-called pico-HPLC-LIF system is described.In this process,a bare open capilla ry with an inner diameter of 680 nm is used as a sepa ration column for a sample volume of several hundreds of femtoliters(300 fL),followed by separation and detection.The technique has a zeptomolar limit of detection.The method was applied to detect cellular miRNA from adenocarcinomic human alveolar basal epithelial(A549)cell extracts,and the simultaneous detection of the mir-182,miR-155,and let-7 a was achieved.The results showed that the expression of mir-182 and miR-155 was up-regulated and that of let-7 a was down-regulated in A549 cells.This method for multiple miRNAs detection is expected to have broad applications in miRNA-based disease diagnosis,prognosis,treatment,and monitoring.

Fe_(2)Mo_(3)O_(8)/XC-72 electrocatalyst for enhanced electrocatalytic nitrogen reduction reaction under ambient conditions

To perform the electrochemical nitrogen reduction reaction(NRR)under milder conditions for sustainable ammonia production,electrocatalysts should exhibit high selectivity,activity,and durability.However,the key restrictions are the highly stable N≡N triple bond and the competitive hydrogen evolution reaction(HER),which make it difficult to adsorb and activate N2 on the surface of electrocatalysts,leading to a low ammonia yield and Faraday efficiency.Inspired by the enzymatic nitrogenase process and using the Fe-Mo as the active center,here we report supported Fe_(2)Mo_(3)O_(8)/XC-72 as an effective and durable electrocatalyst for the NRR.Fe_(2)Mo_(3)O_(8)/XC-72 exhibited NRR activity with an NH3 yield of 30.4μg·h^(−1)·mg^(−1)(−0.3 V)and a Faraday efficiency of 8.2%(−0.3 V).Theoretical calculations demonstrated that the electrocatalytic nitrogen fixation mechanism involved the Fe atom in the Fe_(2)Mo_(3)O_(8)/XC-72 electrocatalyst acting as the main active site in the enzymatic pathway(*NH2→*NH3),which activated nitrogen molecules and promoted the NRR performance.

Influence of elution conditions on DNA transport behavior in free solution by hydrodynamic chromatography

We have previously developed bare narrow-bore capillary chromatography. In this work, high-performance DNA separation was realized for a size range of 10–800 base pairs(bp) utilizing bare narrow-bore capillary chromatography with 750 nm- radius capillaries. Separation behavior of double-stranded DNA(ds DNA) fragments was investigated over a range of eluent concentrations and elution pressures. DNA molecules were hydrodynamically separated in a size-dependent manner in free solution without any sieving matrices, with the longer fragments being eluted out from the capillary earlier. It was found that the eluent concentration variously influenced the transport behavior for different-sized DNA fragments depending upon the configuration of DNA molecules and the association of counterions. Ionic strength of the solutions strongly impacted DNA persistence length. Enhanced elution pressure could shorten analysis time with a slight loss in resolution. Excellent efficiency of two million theoretical plates per meter was achieved, which indicates the enormous potential of bare narrow-bore capillary chromatography for the analysis of DNA fragments. These findings would be useful in understanding the transport behavior of DNA fragments in confined dimensions for chromatography in free solution.

Ultra-thin temperature controllable microwell array chip for continuous real-time high-resolution imaging of living single cells

Single-cell imaging,a powerful analytical method to study single-cell behavior,such as gene expression and protein profiling,provides an essential basis for modern medical diagnosis.The coding and localization function of microfluidic chips has been developed and applied in living single-cell imaging in recent years.Simultaneously,chip-based living single-cell imaging is also limited by complicated trapping steps,low cell utilization,and difficult high-resolution imaging.To solve these problems,an ultra-thin temperature-controllable microwell array chip(UTCMA chip)was designed to develop a living single-cell workstation in this study for continuous on-chip culture and real-time high-resolution imaging of living single cells.The chip-based on ultra-thin ITO glass is highly matched with an inverted microscope(or confocal microscope)with a high magnification objective(100×oil lens),and the temperature of the chip can be controlled by combining it with a home-made temperature control device.High-throughput single-cell patterning is realized in one step when the microwell array on the chip uses hydrophilic glass as the substrate and hydrophobic SU-8 photoresist as the wall.The cell utilization rate,single-cell capture rate,and microwell occupancy rate are all close to 100%in the microwell array.This method will be useful in rare single-cell research,extending its application in the biological and medical-related fields,such as early diagnosis of disease,personalized therapy,and research-based on single-cell analysis.

Development of Ultranarrow-Bore Open Tubular High Efficiency Liquid Chromatography

Chromatography theory shows that when the inner diameter of the chromatography column is very narrow(e.g.,1—2μm),the maximum efficiency will be produced in liquid chromatography.In addition,the increasing demand for ultrasmall volume sample analysis has produced the trend of narrowing the diameter of the liquid chromatography column.Experiments have verified that ultranarrow-bore open tubular liquid chromatography(i.d.≤2μm)has the advantages of small sample requirement and high separation efficiency.However,there also exist huge challenges along with such obvious advantages.This review summarizes the efforts made by our research group and other research groups to develop this field.We hope that in the near future,ultranarrow bore open-tube liquid chromatography can be successfully and maturely applied to the application of analytes with ultrasmall size and volume such as single-cell and even subcellular organelles omics research.