An Efficient Bio-inspired Oxygen Reduction Reaction Catalyst:MnO_(x)Nanosheets Incorporated Iron Phthalocyanine Functionalized Graphene

Oxygen reduction reaction(ORR)catalysts play a critical role in energy storage and conversion devices and have been attracted enormous interests,and however,it remains challenging to develop highly active cheap catalysts in a simple and green route.Inspired by the heme-copper oxidases(HOCs),in which the ORR active center is originated from the incorporation of Fe-N_(4)with copper atom,we here developed a fine manganese oxide nanosheets(MnO_(x)NSs)integrated with iron phthalocyanine(FePc)anchored on highly conductive graphene(MnO_(x)/FePc-G)through a green route only involve ethanol as the reagent.The bio-inspired catalyst MnO_(x)/Fe Pc-G demonstrated high ORR activity with a half-wave potential(E_(1/2))of 0.887 V,about 57 mV more positive than that of Pt/C.And the current density(j)at 0.9 V is about 1.9 m A cm^(-2),which is three times of Pt/C and FePc-G.More importantly,the bio-inspired systems show superior stability in comparison to commercial Pt/C,showing a potential of 0.863 V to deliver a j of 3 mA cm^(-2)after 18000 s polarization,about 80 mV higher than that of 0.783 V for Pt/C.The high activity is contributed by the integration of the Fe Pc and MnO_(x)NSs that plays the role to assist the cleavage of the O_(2)bond.Our approach provides a new evidence to develop highly efficient ORR catalysts through imitate the naturally involved systems through a simple route.

Fluorescence life-time imaging microscopy(FLIM)monitors tumor cell death triggered by photothermal therapy with MoS_(2) nanosheets

Recently,photothermal therapy(PTT)has been proved to have great potential in tumor therapy.In the last several years,MoS_(2),as one novel member of nanomaterials,has been applied into PTT due to its excellent photothermal conversion efficacy.In this work,we applied fuorescence lifetime imaging microscopy(FLIM)techniques into monitoring the PPT-triggered cell death under MoS_(2) nanosheet treatment.Two types of MoS_(2) nanosheets(single layer nanosheets and few layer nanosheets)were obtained,both of which exhibited presentable photothermal conversion fficacy,leading to high cell death rates of 4T1 cells(mouse breast cancer cells)under PTT.Next,live cell images of 4T1 cells were obtained via directly labeling the mitochondria with Rodamine123,which were then continuously observed with FLIM technique.FLIM data showed that the fuorescence lifetimes of mitochondria targeting dye in cells treated with each type of MoS_(2) nanosheets significantly increased during PTT treatment.By contrast,the fuorescence lifetime of the same dye in control cells(without nanomaterials)remained constant after laser irradiation.These findings suggest that FLIM can be of great value in monitoring cell death process during PTT of cancer cells,which could provide dynamic data of the cellular microenvironment at single cell level in multiple biomedical applications.

Construction of Fluorescence Sensing Platform on the Basis of Carbon Nitride Nanosheet for the Detection of Interferon-γ

Purpose: Interferon-γ (INF-γ) is a cytokine that participates in the immune reaction of the body. Its level of secretion can reflect the immune response condition after the body is infected by pathogens, which is a significant indication of clinically-related diseases. Therefore, it is of great significance in application to develop a fluorescence biosensor to inspect INF-γ with rapidness, high sensitivity and high practicability. Method: The fluorescence sensor is made on the basis of the two-dimensional nano-material namely Carbon Nitride Nanosheet (CNNS) and the Aptamer probe to identify INF-γ (Apt®INF-γ). CNNS can quickly quench the Cy5 fluorescent dye modified on the Apt®INF-γ probe due to the Photoinduced Electron Transfer (PET), but when the INF-γ exists, Apt®INF-γ specifically identifies and combines it. The complex of Apt®INF-γ and INF-γ is away from CNNS, which can effectively block the fluorescent signal of Apt?INF-γ being quenched by CNNS. Result: The sensitive detection of IFN-γ protein can be achieved through the application of CNNS/Apt®INF-γ fluorescence sensing platform. In this method, the intensity of the fluorescent signal is positively correlated with the concentration of IFN-γ, of which the liner response range is 0.5 - 100 ng/mL and the limit of detection is 0.303 ng/mL. In addition, this fluorescence sensing platform has the advantages of high specificity, simple operation and low costs. It can inspect the content of IFN-γ in clinical serum samples without interference. The actual recovery rate of serum samples is 97.11% - 106.96%. Conclusion: Therefore, the CNNS/Apt®INF-γ sensing platform is expected to be implemented in the actual clinical detection, also conducive to developing a universal fluorescence biosensor to inspect other target materials.

Bio-inspired synthesis of transition-metal oxide hybrid ultrathin nanosheets for enhancing the cycling stability in lithium-ion batteries

Constructing two-dimensional(2D)structures for transition-metal oxides(TMOs)can optimize their electronic structures and enable high specific surface areas,thereby offering routes to enhancing the performance of TMOs in energy storage and conversion.However,most 2D TMOs,e.g.,Fe_(2)O^(3),remain so far synthetically challenging due to their intrinsic non-layered structures.Herein,inspired by the mechanism of biomineralization,we report the synthesis of CuO/Fe_(2)O^(3)hybrid ultrathin nanosheets by using polyvinylpyrrolidone-decorated CuO nanosheets as growth modifiers to modulate the hydrolysis process of Fe^(2+).The formulated“absorption-and-crystallization”two-step formation processes of such 2D hybrid structures accorded well with the biomineralization scheme in nature.Combining the in-situ transmission electron microscopy(TEM)study,theoretical calculation,and control experiments,we validated that the large density of 2D/2D interfaces enabled by this bio-inspired synthesis process can overcome the self-stacking phenomenon during lithium-ion battery cycling,leading to their high operation stability.This work emphasizes the bio-inspired synthesis of 2D TMOs as a promising pathway toward material design and performance optimization.

Self-assembled Nanosheets of Perylene Monoamide Derivative as Sensitive Fluorescent Biosensor for Exonuclease Ⅲ Activity

Enzymes containing 3′→5′exonuclease activities play an important role in various key cellular and physiological processes.The development of fluorescence biosensor is an efficient method to detecting enzyme activity.Herein,a fluorescence resonance energy transfer(FRET)“on”and“off”strategy for detecting exonuclease III(Exo III)activity has been developed.We report here that the double-stranded DNA(dsDNA)enables to bind tightly to self-assembled nanosheets of cationic perylene monoimide derivative(PMI-O7)through electrostatic interaction,and the 6-carboxyfluorescein(FAM)-modified dsDNA could be efficiently quenched via FRET between FAM and PMI-O7.Upon the addition of Exo III,the dsDNA will be digested and the FAM fluorophore will be released,resulting in the fluorescence recovery of FAM.This method provides a simple and sensitive biosensor platform with a low detection limit of 0.077 U/mL for Exo III.Importantly,this method exhibits similar and calibration curves for the detection of Exo III in both buffer and fetal bovine serum samples,indicating that this platform has potential to detect Exo III activity in complex samples.

Anthrax Biomarker:a Fluorescent Probe for Dipicolinic Acid Using Eu(Ⅲ)-doped Nanosheets

A novel two-dimensional nanosheet fluorescent probe embedded with rare earth Eu(Ⅲ)was developed to detect dipicolinic acid(DPA),a biomarker of Bacillus anthracis bacterial spores.DPA,a major component of Bacillus anthracis spores which were highly toxic to humans,was not found in other common bacteria.The ability to detect ultra-low concentrations of DPA would therefore be of great significance.Eu(Ⅲ)-doped ytterbium hydroxide nanosheets were obtained by mechanical exfoliation from layered rare-earth hydroxide(LRH)materials.The crystallinities,layered structure and morphology of the as-synthesized nanosheets were studied by power X-ray diffraction,transmission electron microscopy and atomic force microscopy.Eu(Ⅲ)emission increased linearly with DPA addition in the range of 0.1~30μmol/L.Based on the antenna effect,the detection limit of DPA was 0.078μmol/L and much lower than the infective dose of Bacillus anthracis in humans of 60μmol/L.The nanosheet fluorescent probe exhibited good specificity toward DPA,and the interferences with selected aromatic ligands and amino acids were observed to be negligibly small in comparison with that of DPA.Our findings provide a basis for the application of Eu(Ⅲ)-doped nanosheets for accurate,sensitive,and selective monitoring of DPA as a biomarker of anthrax.

Synthesis of SiC/graphene nanosheet composites by helicon wave plasma

We report an approach to the rapid, one-step, preparation of a variety of wide-bandgap silicon carbide/graphene nanosheet(Si C/GNSs) composites by using a high-density helicon wave plasma(HWP) source. The microstructure and morphology of the Si C/GNSs are characterized by using scanning electron microscopy(SEM), Raman spectroscopy, x-ray diffraction(XRD), x-ray photoelectron spectroscopy(XPS), and fluorescence(PL). The nucleation mechanism and the growth model are discussed. The existence of Si C and graphene structure are confirmed by XRD and Raman spectra.The electron excitation temperature is calculated by the intensity ratio method of optical emission spectroscopy. The main peak in the PL test is observed at 420 nm, with a corresponding bandgap of 2.95 e V that indicates the potential for broad application in blue light emission and ultraviolet light emission, field electron emission, and display devices.

Rapid screening detection of fluoroquinolone residues in milk based on turn-on fluorescence of terbium coordination polymer nanosheets

We report a facile, effective and rapid screening method for the determination of total fluoroquinolones(FQs) in milk using lanthanide coordination polymer nanomaterials as the sensing platform. The nonluminescent coordination polymer nanosheets(CPNSs) used in this work are composed of adenosine monophosphate(AMP) and terbium(Tb^(3+)) ions(AMP/Tb CPNSs). The as-prepared CPNSs were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy and fluorescence techniques. Tb^(3+) acts as the center ion of the coordination polymer, with AMP assembled through phosphate and amine groups. However, the reaction between FQs and AMP/Tb CPNSs noticeably turns on the fluorescence due to the strong coordination interaction between FQs and Tb^(3+). Under optimized conditions, the fluorescence intensity of AMP/Tb at 545 nm shows a linear relationship with FQ concentrations between 0.04 μmol/L and 5.0 μmol/L. The relative standard deviation(RSD) of the intraday precision is below 1%, and detection limits are as low as 0.01 μmol/L. The proposed method was successfully applied to the determination of FQs in milk samples.

Switch-on fluorescence sensor for ascorbic acid detection based on MoS2 quantum dots-MnO2 nanosheets system and its application in fruit samples

In this work,molybdenum disulfide quantum dots（MoS2 QDs） were firstly prepared by hydrothermal method using sodium molybdate and glutathione as precursors,and applied in ascorbic acid detection.When joining MnO2 nanosheets into MoS2 QDs solution,they produced an obvious fluorescence quenching,which should be due to inner filter effect（IFE）.Meanwhile,the fluorescent probe was formed,Interestingly,we found that this quenching phenomenon disappeared with the addition of ascorbic acid,In other words,the fluorescence gradually restored.This recovery phenomenon is mainly due to the reduction effect of ascorbic acid for MnO2 nanosheets.Under the optimum conditions,the limit of detection（LOD） of 39 nmol/L for ascorbic acid was achieved with a linear range of 0.33-5.00 μmol/L.The repeatability was better than 5.0% for ascorbic acid in both standard and fruit samples（n = 3）.Moreover,the as-fabricated fluorescent sensing system was successfully employed to detect the ascorbic acid levels in hawthorn and jujube with satisfactory results.

Enhanced oxidase-like activity of g-C_(3)N_(4) nanosheets supported Pd nanosheets for ratiometric fluorescence detection of acetylcholinesterase activity and its inhibitor

The undesirable enzymatic activity of nanozymes under near neutral p H condition and the traditional single signal output always restrict the analytical application of nanozyme-based biosensors.Herein,graphitic carbon nitride nanosheets supported palladium nanosheets composite (Pd/g-C_(3)N_(4)) with both oxidase-like activity and fluorescent property is synthesized.Notably,Pd/g-C_(3)N_(4)exhibits enhanced oxidase-like activity compared to Pd NSs under p H 7.4.By combining Pd/g-C_(3)N_(4)with o-phenylenediamine(OPD),a ratiometric fluorescence assay for acetylcholinesterase (ACh E) activity detection is developed.Pd/g-C_(3)N_(4)can catalyze oxidation of nonfluorescent OPD to fluorescent oxidized OPD (ox OPD,Em=565nm),which can quench fluorescence of g-C_(3)N_(4)supporter (Em=441 nm) through fluorescence resonance energy transfer (FRET).However,in presence of ACh E,acetylthiocholine can be hydrolyzed into thiocholine,which will block the oxidase-like activity of Pd/g-C_(3)N_(4)and then hamper the FRET process.This ratiometric fluorescence assay is also viable to screen ACh E inhibitor.This work will guide design of ratiometric fluorescence assay based on nanozymes with improved enzymatic activity.

MnO_(2)纳米片与带正电荷的AIE分子荧光检测GSH以及IMP门的构建

谷胱甘肽(glutathione,GSH)是由谷氨酸、半胱氨酸和甘氨酸结合而成的含有巯基的三肽,广泛存在于各种生物当中,对生物体内有着重要的作用。因此,能方便、快速、准确的检测GSH在体内的水平十分有必要。MnO_(2)纳米片是一种带负电的、具有氧化性的过渡金属氧化物。将带有负电荷的MnO_(2)纳米片与带有正电荷的两个季铵盐基团的二苯乙烯基蒽衍生物DSAI结合,制备成DSAI/MnO_(2)复合探针。将DSAI/MnO_(2)复合探针加入GSH后,MnO_(2)纳米片被解,DSAI的荧光得到恢复。基于以上现象可定量GSH,并且构建出以MnO_(2)纳米片和GSH为输入的分子逻辑门。

基于MoS_2纳米片的荧光生物传感器对饮用水中Hg^(2+)的检测

本文利用MoS)2纳米片优异的荧光淬灭能力以及其与DNA分子之间的相互作用,构建了一种检测Hg^(2+)的新型荧光生物传感器,并考察了其用于饮用水中微量Hg^(2+)测定的可行性.实验优化了MoS_2纳米片浓度、p H值、盐浓度及反应时间等参数对荧光生物传感器性能的影响.在此基础上建立了测定饮用水中微量Hg^(2+)的荧光新方法.在最佳条件下,Hg^(2+)浓度在10—900 nmol·L-1范围内与荧光强度的相对值具有良好的线性关系,检测限为6.3 nmol·L^(-1).该方法简单、灵敏、特异性强.该方法已成功用于饮用水中微量Hg^(2+)的测定,回收率为95.7%—103.3%.该研究工作将MoS_2纳米片的应用拓展到了环境监测领域,这对无机类石墨烯材料的深入研究具有重要意义.

基于MnO2纳米片类氧化酶特性的有机磷农药荧光分析方法建立

利用MnO2纳米片类氧化酶特性并结合有机磷农药的酶抑制原理,构建一种快速、简便、高灵敏有机磷农药荧光分析方法。通过测定反应体系荧光强度前后的变化,可以检测样品中有机磷农药的含量。通过优化酶浓度、底物浓度和反应时间,发现乙酰胆碱酯酶浓度为9.375 U/L,底物浓度为10 mmol/L,反应时间为11 min时,该荧光分析方法检测性能最佳,对氧磷的动态检测范围为1.56~200 ng/mL,检出限达到0.5 ng/mL(RSN=3),运用该方法测定标准添加的自来水、卷心菜、燕麦样品的回收率在83.4%~105.9%之间,表明该方法具有很高的灵敏度与准确性,为快速高灵敏测定有机磷农药提供一种新的可能。

纳米石墨片的场发射性能研究与应用

采用(CVD)法制备了一种准二维纳米石墨片,用场发射扫描电镜(FESEM)和Raman光谱对其形貌和结构进行分析,发现其为纳米片状结构构成的团族,宛若花瓣,既有尖端结构又有刃状结构.采用二极结构对其场发射性能进行测试:开启电场为2.5V/μm,对应的电流密度为0.01mA/cm2;高真空下纳米石墨片场发射电流更加稳定;表面吸附气体以及突出尖端对纳米石墨片的场发射性能有明显影响.

石墨相氮化碳纳米片的制备及其性能研究

通过混酸剥离法制备石墨相氮化碳纳米片(CNNS),该方法制备过程简单.透射电子显微镜、X射线衍射光谱、X射线光电子能谱、傅里叶变换红外光谱、紫外可见吸收光谱与荧光光谱对CNNS的形貌等进行表征,结果显示,混酸剥离法可以成功实现CNNS的制备,研究结果同时显示所制备的CNNS的荧光量子产率达到19.3%,且其荧光激发不依赖于发射,同时,通过电化学循环伏安法测试其性能,发现其导电性能优异.

荧光g-C_(3)N_(4)纳米片的制备及对半胱氨酸的检测

半胱氨酸是人体内一种重要的含巯基氨基酸,对其快速定量检测可以为某些疾病的诊断提供依据.该研究利用简单的超声剥离及静电自组装方法制备了C_(3)N_(4)/Ag荧光传感器.该荧光传感器对含巯基的半胱氨酸具有超灵敏的响应,对其检测极限可以低至2.5×10-5 mol/L.该研究为新型超灵敏荧光传感器的构建提供了一条新的途径,具有非常重要的理论价值和实践意义.

聚苯胺纳米片的制备及其光电化学性能研究

利用PMMA-OH作为合成模板成功制备了聚苯胺纳米片,并对其热性能、荧光性能和电化学性能进行了研究。实验结果表明,聚苯胺纳米片具有良好的热稳定性,在紫外区有较好的荧光性能,作为电极时其具有法拉第准电容。因此所制备的聚苯胺可应用于聚合物太阳能电池和超级电容器中。

氧化石墨烯的多色发光及其在荧光成像中的应用

氧化石墨烯作为石墨烯的一种带隙打开的衍生物,极大地丰富了其光学性质,并拓展了它在传感和成像方面的应用,特别是氧化石墨烯限域的π共轭结构对构建发光碳材料提供了十分便利的条件。目前,有大量的研究工作报道了氧化石墨烯及其衍生物能够产生多种颜色的荧光信号,然而,系统地总结这些研究去揭示氧化石墨烯发光机理的相关工作还比较少。本文总结了关于发光氧化石墨烯纳米材料的合成及其在光学成像方面应用的大量研究工作,为进一步开发新型的发光氧化石墨烯材料提供一些建设性意见。

基于聚多巴胺纳米粒子的荧光增强型探针检测乙酰胆碱酶

以多巴胺盐酸盐为原料,在碱性条件下通过氧化反应制备聚多巴胺荧光纳米粒子(F-PDA),再与二氧化锰(MnO2)纳米片进行复合,构建了用于检测乙酰胆碱酶(AChE)的F-PDA@MnO2复合物荧光探针。MnO2纳米片和F-PDA复合,体系的荧光被猝灭。在底物乙酰硫代胆碱(ATCh)存在下,加入AChE后,体系荧光恢复,恢复程度与AChE浓度在5.0~100 mU/mL范围内呈良好的线性关系,检出限为0.14 mU/mL(S/N=3)。该方法用于缓冲溶液中AChE的检测,加标回收率为89.5%~120%,相对标准偏差为1.6%~2.5%,且具有较高的选择性。可为基于F-PDA传感体系构建提供新的方法学模型。

MnO_(2)修饰的NaYF_(4):18%Yb^(3+),0.5%Tm^(3+)/NaYF_(4)核壳纳米晶的制备及防伪应用研究

为了解决当前社会频繁出现的假冒伪劣问题,提出了基于MnO_(2)修饰的高亮度的NaYF_(4):18%Yb^(3+),0.5%Tm^(3+)/NaYF_(4)核壳纳米晶材料的荧光防伪应用研究。首先通过高温热分解法合成了晶相为β-相,形貌特征为六边形,结晶度高,分布均匀的NaYF_(4):18%Yb^(3+),0.5%Tm^(3+)核纳米晶和NaYF_(4):18%Yb^(3+),0.5%Tm^(3+)/NaYF_(4)核壳纳米晶。之后通过水热法合成了花状纳米片形态的MnO_(2)纳米片和物理混合的方法合成了NaYF_(4):18%Yb^(3+),0.5%Tm^(3+)/NaYF_(4)MnO_(2)复合粒子。我们将NaYF_(4):18%Yb^(3+),0.5%Tm^(3+)/NaYF_(4)@MnO_(2)复合粒子水溶液作为防伪材料书写了字母“L”,在自然光下可以观察到黑色的字母,字母“L”在980 nm连续泵浦光照射下无明显变化。字母“L”在涂抹AA水溶液后可在980 nm连续泵浦光照射下显示明亮的蓝紫色荧光。因此可以推断出我们所合成的MnO_(2)修饰的NaYF_(4):18%Yb^(3+),0.5%Tm^(3+)/NaYF_(4)核壳纳米晶材料可以用于荧光防伪。实验表明提出的荧光防伪方法可以进一步提升防伪的安全性。