小分子有机酸改性尿素的多谱学分子结构表征

尿素是我国主要的氮肥品种,但其活性高,在土壤中水解后极易通过挥发和淋洗损失,利用率低,造成养分资源浪费并污染环境。使用有机酸对尿素进行改性可以延缓尿素分解,提高尿素利用率,但有机酸与尿素的结合方式及其增效机理尚不明确。研究中选取柠檬酸和水杨酸两种小分子有机酸作为添加剂,分别加入到熔融尿素中,获得柠檬酸尿素与水杨酸尿素。利用傅里叶变换红外光谱（FTIR）和X射线光电子能谱（XPS）分析材料的化学结构,利用液相色谱-质谱联用（LC-MS）研究材料的物质组成及相对分子质量,尝试通过以上多谱学的分析方法,明晰两种有机酸与尿素的结合方式。结果表明,柠檬酸和水杨酸与尿素结合后,FTIR在3 348 cm-1处产生了加强的伯胺振动峰,推测小分子有机酸与尿素在伯胺处发生了反应。XPS C(1s)和N(1s)图谱分别出现新的碳结构（-CX）和新的氮结构（-NX）,降低了柠檬酸/水杨酸中原有羧基碳结构和尿素中酰胺基氮结构的相对含量,O(1s)图谱出现C-OH化学键断裂,表明,柠檬酸/水杨酸的羧基与尿素的酰胺基相互作用生成了新的物质。LC-MS分析发现柠檬酸尿素/水杨酸尿素中的新物质可能是柠檬酸/水杨酸的羧基与尿素的酰胺基发生脱水反应,生成含有O═CNHC(O)NH₂结构的物质。因此,利用光谱分析等手段明晰了有机酸与尿素的结合方式与结合产物特征,为有机高分子与尿素反应机理的研究提供了理论依据,为后续高效肥料增效剂的筛选提供了方向。     

Synthesis of nitrogen-doped ZnO nanocrystallites with one-dimensional structure and their catalytic activity for ammonium perchlorate decomposition

Journal of Nanoparticle Research - In this study, nitrogen-doped ZnO (N-doped ZnO) nanocrystallites with a one-dimensional structure were synthesized successfully via an advanced wet chemical...     

Hydrothermal synthesis of highly nitrogen-doped carbon powder

Nitrogen-doped carbon powder (NCP) with high and controllable dopant concentration was facilely synthesized via hydrothermal treatment of sucrose under ammonia followed by calcination. The dopant concentration of the as-synthesized carbon powder can be easily adjusted in the range of 4.37-17.82 wt.% by careful choice of the reaction conditions. The precursor with high nitrogen content was prepared by aminization reaction between sucrose and ammonia in hydrothermal condition, amine groups are successfully introduced into the precursor molecule, which groups convert finally to pyridinic-like and graphitic-like structure in the followed heat-treatment process. Various techniques, including the elemental analysis, TG-DTA, XPS, XRD, SEM and FTIR, were employed to characterize and assess the compositional and structural properties of the precursor and final nitrogen-doped materials. The present work propose a novel method for synthesis of highly nitrogen-doped carbon materials.     

Synthesis and optical properties of flower-like ZnO nanorods by thermal evaporation method

Flower-like ZnO nanorods have been synthesized by heating a mixture of ZnO/graphite powders using the thermal evaporation and vapor transport on Si (1 0 0) substrates without any catalyst. The structures, morphologies and optical properties of the products were characterized in detail by using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and Raman spectroscopy. The synthesized products consisted of large quantities of flower-like ZnO nanostructures in the form of uniform nanorods. The flower-like ZnO nanorods had high purity and well crystallized wurtzite structure, whose high crystalline quality was proved by Raman spectroscopy. The as-synthesized flower-like ZnO nanorods showed a strong ultraviolet emission at 386 nm and a weak and broad yellow-green emission in visible spectrum in its room temperature photoluminescence (PL) spectrum. In addition, the growth mechanism of the flower-like ZnO nanorods was discussed based on the reaction conditions.     

氮掺杂碳量子点的合成及作为荧光探针对Hg~(2+)的检测

与传统量子点相比,碳量子点作为一种新型的荧光碳纳米材料,由于其良好的生物相容性、易于表面功能化、低毒性等优点受到了广泛关注。采用柠檬酸为碳源,氨水为氮源,热解法制备出水溶性好的氮掺杂碳量子点(NCDs)。透射电镜(TEM)观察NCDs的粒径在3nm左右;X射线光电子能谱(XPS)和傅里叶红外光谱(FIIR)证明NCDs的表面被羧基、氨基、羟基、羰基等官能团功能化,说明NCDs有很好的水溶性。研究还发现Hg~(2+)对NCDs的荧光有良好的猝灭作用,可作为荧光探针检测水中Hg~(2+)含量。在PBS缓冲液中(0.1mol·L~(-1) pH 7.0),NCDs的荧光猝灭率(F/F0)与汞离子浓度在0.001~0.1μmol·L~(-1)之间存在良好的线性关系,检出限为2.1nmol·L~(-1)。该方法灵敏度高、选择性好、方法简便,可应用于Hg~(2+)快速、灵敏的检测。     

Synthesis and properties of boron doped ZnO nanorods on silicon substrate by low-temperature hydrothermal reaction

Boron doped ZnO nanorods were fabricated by hydrothermal technique on silicon substrate covered with a ZnO seed layer. It is found that the concentration of boric acid in the reaction solution plays a key role in varying the morphology and properties of the products. The growth rate along the [0 0 0 1] orientation (average size in diameter) of the doped ZnO nanorods decreased (increased) with the increase of boric acid concentration. Based on the results of XRD, EDX and XPS, it is demonstrated that the boron dopants tend to occupy the octahedral interstice sites. The photoluminescence of the ZnO nanorods related to boron doping are investigated.     

40% Efficiency enhancement in solar cells using ZnO nanorods as shell prepared via novel hydrothermal synthesis

Herein, rod-like ZnO nanostructures were synthesized via a novel hydrothermal route using Zn(OAc)₂, ethylenediamine and hydrazine as a new set of starting reagents. The as-synthesized products were characterized by techniques including XRD, EDS, SEM, XPS, Pl and FTIR. The prepared ZnO nanostructures were utilized as shell on TiO₂ film in DSSCs. Effect of precursor type, morphology and thickness of ZnO shell (number of electrophoresis cycle) on solar cells efficiency were well studied. Our results showed that ethylenediamine has crucial effect on morphology of synthesized ZnO nanostructures and using ZnO nanostructures leads to an increase in DSSCs efficiency compared to bare TiO₂ from 4.66 to 7.13% (~40% improvement). Moreover, highest amount of solar cell efficiency (7.13%) was obtained by using ZnO nanorods with two cycle of electrophoresis for deposition.     

水热法制备均一形貌的ZnO微米棒

以Zn（Ac）2· 2H2O、KI和N2H4· H2O反应物,在未使用任何表面活性剂的简单水热反应体系中制得了ZnO微米棒.采用X射线粉末衍射仪（XRD）、扫描电子显微镜（SEM）对产物的晶体结构、形貌进行了表征和分析.测试结果表明,所得产物为六方纤锌矿结构ZnO微米棒,平均直径为1μm,长度4μm.     

Structural and optical properties of Co-doped ZnO nanocrystallites prepared by a one-step solution route

Zinc oxide (ZnO) nanocrystallites with different Co-doping levels were successfully synthesized by a simple one-step solution route at low temperature (95 °C) in this study. The structure and morphology of the samples thus obtained were characterized by XRD, EDS, XPS and FESEM. Results show that cobalt ions, in the oxidation state of Co²⁺, replace Zn²⁺ ions in the ZnO lattice without changing its wurtzite structure. The dopant content varies from 0.59% to 5.39%, based on Co-doping levels. The pure ZnO particles exhibit well-defined 3D flower-like morphology with an average size of 550 nm, while the particles obtained after Co-doping are mostly cauliflower-like nanoclusters with an average size of 120 nm. Both the flower-like pure ZnO and the cauliflower-like Co:ZnO nanoclusters are composed of densely arrayed nanorods. The optical properties of the ZnO nanocrystallites following Co-doping were also investigated by UV–Visible absorption and Photoluminescence spectra. Our results indicate that Co-doping can change the energy-band structure and effectively adjust the luminescence properties of ZnO nanocrystallites.     

Donor-acceptor pair luminescence in nitrogen-doped ZnO films grown on lattice-matched ScAlMgO4 (0001) substrates

We have grown nitrogen-doped ZnO (ZnO:N) films by laser molecular-beam epitaxy. The use of lattice-matched ScAlMgO₄ substrates prevented the degradation of crystallinity induced by the nitrogen incorporation to the films. Despite this improvement, we have not obtained ZnO:N films which showed p-type conductivity. We studied the optical properties of these ZnO:N films. Donor-acceptor pair (DAP) luminescence was observed. The results indicate the formation of an acceptor state. The energy position of the DAP luminescence is lower than that reported by Look et al. [Appl. Phys. Lett. 81 (2002) 1830]. The DAP luminescence band shifts to lower energy with increasing nitrogen concentration. A photoluminescence recombination possibly due to the free-electron-to-acceptor (FA) transition was observed at temperatures higher than 40 K. The acceptor ionization energy was estimated from the energy position of the FA luminescence to be 266 meV.     

Nitrogen binding behavior in ZnO films with time-resolved cathodoluminescence

ZnO film with (1 0 0) orientation was produced on silicon substrate and doped with nitrogen using plasma immersion ion implantation. The effects due to N doping were investigated using cathodoluminescence (CL). In the heavily nitrogen-doped ZnO film, the intensity of ultraviolet (UV) band decreases and that of the visible band increases as a function of the electron bombardment cycle i.e. time. Based on the X-ray photoelectron spectroscopy (XPS) analysis, the unstable ZnN bond is responsible for the CL behavior and the experimental results agree well with the first-principle calculation. Our work is helpful to our understanding of the role of p-type dopants in ZnO.     

硫掺杂ZnO纳米线的电化学制备及发光特性

"采用电场辅助电化学沉积法,利用阳极氧化铝模板模板制备了高度择优取向的硫掺杂ZnO单晶纳米线．X射线衍射仪、隧道电子显微镜、选取电子衍射对所得样品的结构、形貌分析表明,所得纳米线是沿(101)择优取向的六方纤锌矿结构单晶纳米线,长约几十微米、平均直径约70 nm. X射线光电子能谱对化学组成的分析进一步证实掺杂硫原子的存在．用荧光光谱仪(PL)对S掺杂前后的ZnO纳米线进行光学特性测量发现,S掺杂较大地改变了ZnO纳米线的发光性质．在PL谱中,除了有典型的ZnO纳米线在378、392 nm处的强紫外发光峰     

CVD synthesis of nitrogen-doped graphene using urea

This work provides an effective low-cost synthesis and in-depth mechanistic study of high quality large-area nitrogen-doped graphene(NG) films. These films were synthesized using urea as nitrogen source and methane as carbon source, and were characterized by scanning electron microscopy(SEM), Raman spectroscopy and X-ray photoelectron spectroscopy(XPS). The N doping level was determined to be 3.72 at.%, and N atoms were suggested to mainly incorporated in a pyrrolic N configuration. All distinct Raman peaks display a shift due to the nitrogen-doping and compressive strain. The increase in urea concentration broadens the D and 2D peak's Full Width at Half Maximum(FWHM), due to the decrease of mean free path of phonons. The N-doped graphene exhibited an n-type doping behavior with a considerably high carrier mobility of about 74.1 cm2/(V s), confirmed by electrical transport measurements.     

Preparation of ferromagnetic γ - Fe2O3 nanocrystallites by oxidative co-decomposition of PEG 6000 and ferrocene

Highly crystalline and ferromagnetic γ-Fe₂O₃ nanocrystallites were prepared by controlled oxidative co-decomposition of PEG 6000 and ferrocene at a temperature of 450 ^°C under air atmosphere. The morphology, crystalline structure and preliminary magnetic properties of the as-synthesized nanocrystallites have been characterized by using transmission electron microscope (TEM), X-ray powder diffraction (XRD) and vibrating sample magnetometer (VSM). The highly crystalline γ-Fe₂O₃ nanocrystallites are in quasi-cubic shape with an average size of 30 nm and exhibit room-temperature ferromagnetism. The capping effect of PEG 6000 has also been investigated by thermogravimetry analysis (TGA) and Fourier transform infrared (FTIR) regarding controlling the size of the nanocrystallites and preventing the volatilization of ferrocene and thus raising the yield of the products. This simple method has a high yield of over 80% as well as low cost.     

ZnO microbowls grown on ITO glass substrate through thermal evaporation

Novel ZnO microbowls are successfully synthesized by thermal evaporating of a mixture of ZnS powder and Zn powder. The morphologies of the as-synthesized products can be adjusted by changing the temperature and the type of substrate. The morphologies, microstructures, and photoluminescence properties are investigated by X-ray diffraction, Raman spectroscopy, scanning electron microscope, and photoluminescence spectroscopy respectively. The growth mechanism of the as-synthesized ZnO microbowls is proposed based on the experimental results. ZnO microbowls presented here can be used as building blocks to fabricate optical and optoelectronic micro/nano devices.     

ZnO microbowls grown on an ITO glass substrate through thermal evaporation

Novel ZnO microbowls are successfully synthesized by the thermal evaporating of a mixture of ZnS powder and Zn powder. The morphologies of the as-synthesized products can be adjusted by changing the temperature and the type of substrate. The morphologies, microstructures, and photoluminescence properties are investigated by X-ray diffraction, Raman spectroscopy, scanning electron microscope, and photoluminescence spectroscopy respectively. The growth mechanism of the as-synthesized ZnO microbowls is proposed based on the experimental results. ZnO microbowls presented here can be used as building blocks to fabricate optical and optoelectronic micro/nano devices.     

富锌条件下生长氮掺杂氧化锌薄膜的光学和电学性质

报道了采用等离子体辅助分子束外延方法(P-MBE),利用NO作为N源和O源,在c-面蓝宝石(c-Al₂O₃)衬底上外延生长了N掺杂ZnO薄膜。X射线衍射谱(XRD)和吸收谱中都出现了不同于未掺杂样品的特性,X射线光电子谱(XPS)中也发现了N的受主信号。但是在霍尔效应(Hall-effect)测量中,发现该样品并没有出现预期的p型导电特性,而是出现载流子浓度很高(2.15×10²⁰cm^-3)的n型导电特性。结合XPS结果和理论分析,认为在富Zn条件下生长会导致过量的填隙Zn原子,补偿了全部的受主后,又促使其出现了从半导体-金属的Mott转变。     

Characterization and aging effect study of nitrogen-doped ZnO nanofilm

The influence of sputtering and annealing conditions and aging effect on properties of sputtered ZnO:N thin films were investigated. Achieved results confirmed a planar growth of nitrogen-doped ZnO film with a high uniform and smooth surface morphology. Incorporation of nitrogen in the ZnO films made new Raman shifts. X-ray diffraction spectra showed only the ZnO (0 0 2) diffraction peak, which was slightly shifted toward lower angels, compared to pure ZnO, which is the result of incorporating nitrogen in the ZnO films. The amount of this shift was proportional to N concentration. In addition, annealed samples showed better crystallinity with lower shift due to dramatically reduction of N atoms during the annealing. The Hall effect measurements exhibited p-type behaviour on annealed ZnO:N thin films while the un-annealed samples showed n-type conductivity. Aging effect studies demonstrated that the N content of thin films decreased dramatically as time passed. The reduction of N concentration in annealed samples was lower than un-annealed ones after 6 months.     

ZnO nanorod arrays with tunable size and field emission properties on an ITO substrate achieved by an electrodeposition method

In the present work,vertically aligned ZnO nanorod arrays with tunable size are successfully synthesized on nonseeded ITO glass substrates by a simple electrodeposition method.The effect of growth conditions on the phase,morphology,and orientation of the products are studied in detail by X-ray diffraction(XRD),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).It is observed that the as-prepared nanostructures exhibit a preferred orientation along c axis,and the size and density of the ZnO nanorod can be controlled by changing the concentration of ZnCl2.Field emission properties of the as-synthesized samples with different diameters are also studied,and the results show that the nanorod arrays with a smaller diameter and appropriate rod density exhibit better emission properties.The ZnO nanorod arrays show a potential application in field emitters.     

Influence of nitrogen and magnesium doping on the properties of ZnO films

Undoped ZnO and doped ZnO films were deposited on the MgO(111) substrates using oxygen plasma-assisted molecular beam expitaxy. The orientations of the grown ZnO thin film were investigated by in situ reflection high-energy electron diffraction and ex situ x-ray diffraction(XRD). The film roughness was measured by atomic force microscopy, which was correlated with the grain sizes determined by XRD. Synchrotron-based x-ray absorption spectroscopy was performed to study the doping effect on the electronic properties of the ZnO films, compared with density functional theory calculations.It is found that, nitrogen doping would hinder the growth of thin film, and generate the NOdefect, while magnesium doping promotes the quality of nitrogen-doped ZnO films, inhibiting(N_2)Oproduction and increasing nitrogen content.