微波溶剂热法制备掺氮石墨烯用于碱性氧还原反应

采用微波处理氧化石墨烯(GO)与乙二醇(EG)、乙二胺(ED)混合液的方法制备氮掺杂石墨烯(NG),使用旋转圆盘电极对NG催化氧还原在碱性溶液中反应进行研究,并考察了不同微波辐射时间、ED与EG之比对反应性能的影响。采用X射线衍射仪(XRD)、透射电子显微镜(TEM)、拉曼光谱(Raman)和傅里叶变换红外光谱(FT-IR)研究了NG催化剂的结构与性质。相比于未掺氮的石墨烯样品,NG表现出更正的起始电位和接近四电子的转移过程。NG中掺杂氮原子的键合方式通过XPS进行表征,结果表明起始电位的高低取决于石墨氮含量。此外,所有表征结果表明总氮含量与氧还原反应性能没有直接关系。     

微波溶剂热法制备掺氮石墨烯用于碱性氧还原反应

采用微波处理氧化石墨烯（GO）与乙二醇（EG）、乙二胺（ED）混合液的方法制备氮掺杂石墨烯（NG）,使用旋转圆盘电极对NG催化氧还原在碱性溶液中反应进行研究,并考察了不同微波辐射时间、ED与EG之比对反应性能的影响。采用X射线衍射仪（XRD）、透射电子显微镜（TEM）、拉曼光谱（Raman）和傅里叶变换红外光谱（FT-IR）研究了NG催化剂的结构与性质。相比于未掺氮的石墨烯样品,NG表现出更正的起始电位和接近四电子的转移过程。NG中掺杂氮原子的键合方式通过XPS进行表征,结果表明起始电位的高低取决于石墨氮含量。此外,所有表征结果表明总氮含量与氧还原反应性能没有直接关系。     

硝酸酯增塑剂力学性能和界面相互作用的分子动力学模拟

运用分子动力学(MD)方法, 模拟研究了硝化甘油(NG)及其与硝化三乙二醇(TEGDN)组成的硝酸酯增塑剂的低温力学性能. 结果表明, NG/TEGDN混合体系较NG单组分体系的刚性减弱, 延展性和各向同性增强. 结合能计算和径向分布函数分析揭示了混合型硝酸酯增塑剂组分之间的相互作用及其本质.     

氮掺杂石墨烯的制备及其表面增强拉曼散射效应

为了提高氮掺杂石墨烯(NG)薄膜的氮掺杂浓度(氮原子质量分数)并控制掺氮类型,通过化学气相沉积法,采取气态源与固态源相结合的方式制备了高质量的单层NG薄膜。通过调控生长时间、三聚氰胺用量(碳/氮源)、制备温度等工艺参数,研究了NG薄膜的形貌、氮掺杂浓度、掺氮类型。结果表明:NG薄膜在生长过程中包括成核、生长、成膜等;适宜的制备温度(990℃)有利于氮原子掺入到碳碳平面内;高温(超过1 000℃)不利于石墨氮的生成,而有助于吡咯氮的生长;氮掺杂浓度随三聚氰胺用量的增加先升后降,最大氮掺杂浓度可达6.98%;在一定范围内,增加三聚氰胺的用量有利于吡啶氮的生成;此外,与石墨烯相比,NG薄膜可以将罗丹明B分子的检出限降低至10~(-5) mol/L。     

柚皮苷印迹β-环糊精聚合物的制备及性能研究

以柚皮苷(NG)为印迹分子, β-环糊精为功能体, 六亚甲基二异氰酸酯为交联剂, 采用乳液聚合法制备了对NG具有特定识别能力的吸附材料: 棒状印迹聚合物. 扫描电镜及比表面分析仪测试结果表明印迹聚合物具有较大的孔隙及比表面积|红外及核磁共振谱研究证实了识别位点来自β-环糊精与NG羟基间的氢键作用. 采用平衡吸附实验方法研究了聚合物的吸附性能和选择性能. 实验结果表明, 棒状印迹聚合物(RMIP)对NG具有较高的亲和性和选择性. Scatchard分析表明, MIP在识别NG过程中存在2类结合位点: K_D1＝0.016 mmol/L, B_max1＝15.31 μmol/g, K_D2＝0.24 mmol/L, B_max2＝98.41 μmol/g. 当NG浓度为 0.02 mg/mL时, MIP及相应NIP对 NG的分配系数 K_{D 分别为4.38和2.86, 印迹因子α为1.53.}     

多贝斯在纳米金修饰玻碳电极上的电化学行为与测定

采用循环伏安法将纳米金电沉积于玻碳电极表面,制备了纳米金修饰玻碳电极(NG/GCE).在0.05 mol/L H2SO4溶液中,用循环伏安法研究了多贝斯在NG/GCE上的电化学行为.结果表明,NG/GCE对多贝斯的氧化还原反应有明显的电催化作用.建立了测定多贝斯的新方法,用方波伏安法测得多贝斯的氧化峰电流与其浓度在4....     

基于有序介孔碳/纳米金/L-半胱氨酸修饰电极测定铜(Ⅱ)

将纳米金(NG)电沉积在有序介孔碳(OMC)修饰玻碳电极表面,并将L-半胱氨酸(L-Cys)自组装至OM C/NG修饰电极表面,制备了OM C/NG/L-Cys修饰电极。采用透射电子显微镜考察了OM C的结构,扫描电子显微镜研究了OMC/NG/L-Cys修饰电极的表面形貌。考察了Cu2+在该修饰电极上的电化学行为,优化了Cu2+的测定条件。在最优条件下,溶出峰峰电流与Cu2+浓度在0.05~6.0μmol/L范围内呈良好线性关系,检出限为0.03μmol/L(S/N=3)。方法用于河水样品分析,其加标回收率在92.7%~101.6%之间。     

N-环已烷氨基乙酸和N-β-萘氨基乙酸的离解常数

在25°及0.10M高氯酸鈉存在下,N-环己烷氨基乙酸(CyG)和N-β-萘氨基乙酸 (βNG)在30％(体积)乙醇中的表观离解常数用pH法測定为:CyG:pK_(COOH)=2.70,pK_(R_2NH_2~+)=9.83;βNG:pK_(COOH)=2.26,pX_(R_2NH_2~+)=4.46。前者(CyG)的酸碱強度均与氨基乙酸(G)的相似,但后者(βNG)的碱性却小于其异构体N-α-萘氨基乙酸(αNG)的碱性約百万倍,而与N-苯氨基乙酸(φG)的碱性相似。这进一步說明αNG上的8位氫原子和1位上羧甲氨基之間的空間效应是导致其碱性增強的主要原因。βNG的酸性較αNG略強,可能是在共軛程度較高的βNG分子中,N的电子密度較低的β-萘氨基对于羧基所产生較大的誘导效应之結果。     

氮掺杂石墨烯量子点/Ru(bpy)_3~(2+)体系电致化学发光法检测邻苯二酚

采用简单的方法合成了氮掺杂石墨烯量子点(NG QDs),并分别用荧光光谱仪和透射电子显微镜进行了表征。研究了NG QDs对Ru(bpy)_3~(2+)电致化学发光(ECL)体系的增敏作用。实验优化了体系pH、Ru(bpy)_3~(2+)用量、NG QDs用量以及扫速等条件。在最优条件下,根据邻苯二酚对NG QDs/Ru(bpy)_3~(2+)耦合ECL体系信号的猝灭作用,建立了测定邻苯二酚的新方法。邻苯二酚浓度(1.0×10~(-8)～1.0×10~(-5) mol/L)的对数值与ECL信号强度差之间呈线性关系,检测限低至5.0×10~(-9) mol/L,而且选择性和重现性好,实际样品检测结果令人满意。     

端羟基聚丁二烯/增塑剂共混物相容性的分子动力学模拟

固体推进剂和炸药的力学性能在很大程度上依赖于配方中高分子粘结剂与增塑剂的相容性. 本文对相容和非相容两种体系进行了分子动力学(MD)模拟, 以考察分子模拟方法的实用性. 为预测固体推进剂中端羟基聚丁二烯(HTPB)与增塑剂癸二酸二辛酯(DOS)、硝化甘油(NG)的相容性, 采用MD模拟方法在COMPASS力场下, 对HTPB、DOS、NG和共混物HTPB/DOS、HTPB/NG的密度、内聚能密度及溶度参数等进行了模拟计算. 通过比较溶度参数差值(△δ)的大小、分子间径向分布函数和模拟前后体系密度变化情况均可以预测HTPB/DOS属于相容体系,而HTPB/NG属于不相容体系, 与实验结果一致. 径向分布函数分析同时揭示了HTPB/增塑剂组分之间的相互作用及本质. 本文的模拟方法可以作为预测聚合物与增塑剂相容性的有利工具, 也可以为固体推进剂和炸药的配方设计提供理论指导.     

Structure and Stability of (NG)nCN3Be3+ Clusters and Comparison with (NG)BeY0/+

The noble gas binding ability of CN₃Be₃⁺ clusters was assessed both by ab intio and density functional studies. The global minimum structure of the CN₃Be₃⁺ cluster binds with four noble‐gas (NG) atoms, in which the Be atoms are acting as active centers. The electron transfer from the noble gas to the Be atom plays a key role in binding. The dissociation energy of the Be? NG bond gradually increases from He to Rn, maintaining the periodic trend. The HOMO–LUMO gap, an indicator for stability, gives additional insight into these NG‐bound clusters. The temperature at which the NG‐binding process is thermodynamically feasible was identified. In addition, we investigated the stability of two new neutral NG compounds, (NG)BeSe and (NG)BeTe, and found them to be suitable candidates to be detected experimentally such as (NG)BeO and (NG)BeS. The dissociation energies of the Be? NG bond in monocationic analogues of (NG)BeY (Y=O, S, Se, Te) were found to be larger than in the corresponding neutral counter‐parts. Finally, the higher the positive charge on the Be atoms, the higher the dissociation energy for the Be? NG bond becomes.     

Formation and Photoinduced Electron Transfer in Porphyrin- and Phthalocyanine-Bearing N-Doped Graphene Hybrids Synthesized by Click Chemistry

Graphene doped with heteroatoms such as nitrogen, boron, and phosphorous by replacing some of the skeletal carbon atoms is emerging as an important class of two-dimensional materials as it offers the much-needed bandgap for optoelectronic applications and provides better access for chemical functionalization at the heteroatom sites. Covalent grafting of photosensitizers onto such doped graphenes makes them extremely useful for light-induced applications. Herein, we report the covalent functionalization of N-doped graphene (NG) with two well-known electron donor photosensitizers, namely, zinc porphyrin (ZnP) and zinc phthalocyanine (ZnPc), using the simple click chemistry approach. Covalent attachment of ZnP and ZnPc at the N-sites of NG in NG−ZnP and NG−ZnPc hybrids was confirmed by using a range of spectroscopic, thermogravimetric and imaging techniques. Ground- and excited-state interactions in NG−ZnP and NG−ZnPc were monitored by using spectral and electrochemical techniques. Efficient quenching of photosensitizer fluorescence in these hybrids was observed, and the relatively easier oxidations of ZnP and ZnPc supported excited-state charge-separation events. Photoinduced charge separation in NG−ZnP and NG−ZnPc hybrids was confirmed by using the ultrafast pump-probe technique. The measured rate constants were of the order of 10¹⁰ s,⁻¹ thus indicating ultrafast electron transfer phenomena.     

Naringenin protects HaCaT human keratinocytes against UVB-induced apoptosis and enhances the removal of cyclobutane pyrimidine dimers from the genome

Many naturally occurring agents are believed to protect against UV-induced skin damage. In this study, we have investigated the effects of naringenin (NG), a naturally occurring citrus flavonone, on the removal of UVB-induced cyclobutane pyrimidine dimers (CPD) from the genome and apoptosis in immortalized p53-mutant human keratinocyte HaCaT cells. The colony-forming assay shows that treatment with NG significantly increases long-term cell survival after UVB irradiation. NG treatment also protects the cells from UVB-induced apoptosis, as indicated by the absence of the 180 base pair DNA ladders and the appearance of sub-G1 peak using agarose gel electrophoresis and flow cytometric analysis, respectively. The UVB-induced poly (ADP-ribose) polymerase-1 (PARP-1) cleavage, caspase activation and Bax/Bcl2 ratio were modulated following NG treatment, indicating an antiapoptotic effect of NG in UVB-damaged cells that occurs at least in part via caspase cascade pathway. Moreover, treatment of UVB-irradiated HaCaT cells with NG enhances the removal of CPD from the genome, as observed by both direct quantitation of CPD in genomic DNA and immuno-localization of the damage within the nuclei. The study provides a molecular basis for the action of NG as a promising natural flavonoid in preventing skin aging and carcinogenesis.     

快速微波法制备掺氮石墨烯用于碱性氧还原电催化剂

采用微波法在氨气气氛下快速加热石墨烯（G）制备了含氮量在4.05 wt%-5.47 wt%的掺氮石墨烯（NG）. 将上述的掺氮石墨烯用作碱性电解质条件下的氧还原电催化剂,起始还原电势为0.17 V（vs SHE）,接近商用碳载铂催化剂的0.21 V（vs SHE）. 采用透射电子显微镜、拉曼光谱和X射线光电子能谱研究了掺氮石墨烯的形貌、结构和掺杂氮原子的键合方式. 结果发现,掺氮石墨烯的氧还原起始电位随着石墨氮原子含量的提高而上升,说明石墨类型的氮含量是影响其氧还原催化活性的关键因素. 实验结果表明,微波法快速制备的掺氮石墨烯在碱性条件下表现出较高的氧还原催化活性,具有作为碱性燃料电池阴极催化剂的潜力.     

Surpassing electrocatalytic limit of earth-abundant Fe~(4+) embedded in N-doped graphene for(photo)electrocatalytic water oxidation

Developing highly active,cost-effective,and environmental friendly oxygen evolution reaction(OER)electrocatalysts facilitates various(photo)electrochemical processes.In this work,Fe3N nanoparticles encapsulated into N-doped graphene nanoshells(Fe₃N@NG)as OER electrocatalysts in alkaline media were reported.Both the experimental and theoretical comparison between Fe₃ N@NG and Fe₃N/NG,specifically including in situ Mossbauer analyses,demonstrated that the NG nanoshells improved interfacial electron transfer process from Fe₃N to NG to form high-valence Fe⁴⁺ions(Fe⁴⁺@NG),thus modifying electronic properties of the outer NG shells and subsequently electron transfer from oxygen intermediate to NG nanoshells for OER catalytic process.Meanwhile,the NG nanoshells also protected Fe-based cores from forming OER inactive and insulated Fe₂O₃,leading to high OER stability.As a result,the as-formed Fe⁴⁺@NG shows one of the highest electrocatalytic efficiency among reported Fe-based OER electrocatalysts,which can as well highly improve the photoelectrochemical water oxidation when used as the cocatalysts for the Fe₂O₃ nanoarray photoanode.     

Nitrogen‐doped graphene‐cerium oxide (NG‐CeO2) photocatalyst for the photodegradation of methylene blue in waste water

This study shows a facile approach for the preparation of CeO₂ nanoparticles decorated with porous nitrogen‐doped graphene (NG) nanosheets for effective photocatalytic degradation of methylene blue (MB). NG nanosheets were first synthesized using a hydrothermal method and then nitrogen‐doped graphene‐cerium oxide (NG‐CeO₂) was prepared through mixing of cerium nitrate with different concentrations of NG under ultrasonication followed by hydrothermal treatment. The synthesized nanocomposites were characterized using X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FE‐SEM). The photocatalytic activity of the synthesized nanocomposites was analyzed against MB dye. Results showed that the nanocomposites of NG‐CeO₂ have an average particle size of 20 nm. The as‐prepared NG‐CeO₂ nanocomposites exhibited outstanding photocatalytic activity for dye degradation under visible light irradiation, which could be attributed to synergistic effects between the NG nanosheets and CeO₂. The quantum of photodegradation increases with the increase of the NG content in the nanocomposites.     

Solvating gas chromatography with chemiluminescence detection of nitroglycerine and other explosives

A separation technique known as solvating gas chromatography (SGC), which utilizes packed capillary columns and neat carbon dioxide as mobile phase, was used for the separation of nitroglycerine (NG) and other nitrogen-containing explosives including 2,6-dinitrotoluene (2,6-DNT), 2,4-dinitrotolulene (2,4-DNT), 2,4,6-trinitrotoluene (2,4,6-TNT), and pentaerythritol tetranitrate (PETN). SGC was coupled for the first time to a selective chemiluminescence thermal energy analyzer (TEA) detector for nitro-functional group specificity and sensitive detection of these compounds. TEA calibration curve for NG showed linearity in the sub-microg ml(-1) range. Soil samples containing NG were used to test the validity of the technique. Detector response of SGC-TEA versus SGC-flame ionization detection for NG was also evaluated.     

Magnetically separable ZnO/ZnFe2O4 and ZnO/CoFe2O4 photocatalysts supported onto nitrogen doped graphene for photocatalytic degradation of toxic dyes

Advanced oxidation processes (AOPs) counting heterogeneous photocatalysis has confirmed as one of the preeminent method for waste water remediation. In the present work, we have successfully fabricated novel visible-light-driven nitrogen-doped graphene (NG) supported magnetic ZnO/ZnFe₂O₄ (ZnO/ZF/NG) and ZnO/CoFe₂O₄ (ZnO/CF/NG) nanocomposites. ZnO synthesized via direct precipitation method. Hydrothermal method was used for the preparation of nitrogen-doped graphene supported magnetic ZnO/ZF (ZnO/ZnFe₂O₄) and ZnO/CF (ZnO/CoFe₂O₄) nanocomposites. The procured materials were scrutinized by assorted characterizations to acquire information on their chemical composition, crystalline structure and photosensitive properties. The absorption and photocatalytic performance of photocatalysts were studied via UV–Visible spectra. Photodegradation performance of the synthesized nanocomposites was estimated toward mineralization of methyl orange (MO) and malachite green (MG) dyes in aqueous solution. The high surface area of ZnO/ZF/NG and ZnO/CF/NG was suitable for adsorptive removal of MO and MG dyes. The photodegradation performance of heterojunction photocatalysts was superior to bare photocatalyst in 140 min under visible-light irradiation. Spectrophotometer, GC–MS (Gas chromatography–mass spectrometry) elucidation was carried out to expose the possible intermediates formed. Both ZnO/ZF/NG and ZnO/CF/NG were rapidly isolated from the aqueous phase by applying an external magnetic field in 20 sec and 2 min, respectively. The photocatalytic performance and stability of ZnO/ZF/NG and ZnO/CF/NG nanocomposites were confirmed by conducting 10 consecutive regeneration cycles. Owing to recyclability of ZnO/ZF/NG and ZnO/CF/NG, these heterogeneous nanocomposites might be used as cost-effective for treatment of discarded water. The observations endorse that the synthesized ternary heterogeneous nanocomposites facilitates wastewater decontamination using photocatalytic technology.     

Sequence‐Independent DNA Nanogel as a Potential Drug Carrier

DNA nanostructures largely rely on pairing DNA bases; thus, sequence designing is required. Here, this study demonstrates a sequence‐independent strategy to fabricate DNA nanogel (NG) inspired by cisplatin, a chemotherapeutic drug that acts as a DNA crosslinker. A simple heating and cooling of the genomic DNA extracts and cisplatin produces DNA NG with a size controlled by the heating time. Furthermore, the drug‐loaded NG is formulated by spontaneously mixing DNA segments, cisplatin, and doxorubicin. The in vitro cell studies demonstrate that the doxorubicin‐loaded NG alters the drug distribution in cells while its cytotoxic potential is well‐maintained. This chemotherapeutic‐inspired method provides a facile one‐pot and cost‐effective strategy to fabricate size‐controllable DNA NG that potentially acts as drug carrier.