Facile Route to Control over the Morphological Evolution of β-Ga_2O_3 from Nanowires to Nanoflags and to Nanosheets

We report the fabrication of β-Ga_2O_3 nanostructures on Au-coated(0001) sapphire substrate by chemical vapor deposition. The morphologies and structural properties of β-Ga_2O_3 nanostructures were characterized by scanning electron microscopy, X-ray diffraction and transmission electron microscopy. Different morphologies including nanowire, nanoflag and nanosheet were controllably synthesized by adjusting the important growth parameters of ambient source contents. It is suggested that the relative ratio of oxygen and gallium contents plays a significant role in determining the morphologies of β-Ga_2O_3 nanostructure.     

Preparation of Single Crystalline V6O13 Nanobelts

Ultralong beltlike nanostructures was successfully synthesized for V6O13 crystal by a hydrothermal route. The products are characterized by means of X-ray powder diffraction, transmission electron microscopy and high-resolution transmission electron microscopy. The experimental results give the evidence that the V6O13 nanobelts are pure, structurally uniform and single crystalline, with typical widths of 50 to 300 nm and lengths of up to a few millimeters.     

Synthesis of dandelion-like three-dimensional nickel nanostructures via solvothermal route

The objectives of the present research are synthesizing three-dimensional （3D） nickel nanostructures and investigating their magnetic properties. Thus a template-free method was used to prepare 3D dandelion-like nickel nanostructures via reducing of nickel chloride with hydrazine hydrate in ethylene glycol solution at 100 ℃. The resulting Ni nanostructures were characterized by means of powder X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and selected-area electron diffraction （SAED）. And the magnetic properties of the 3D Ni nanostructures were measured as well. Results indicated that solvothermal process could be successfully used to prepare 3D dandelion-like nanostructures of Ni at a relatively mild temperature of 100℃. And the conclusions were made as follows： as-prepared Ni samples had obvious shape anisotropy and were composed of fine nanocrystallites, while they had significantly enhanced ferromagnetic properties than bulk Ni and Ni nanoparticles.     

Preparation and characterization of gadolinium hydroxide single-crystalline nanorods by a hydrothermal process

The Gd(OH)3 nanorods with diameters of ca.40-60 nm and lengths of more than 400-550 nm have been prepared by a novelhydrothermal technique.The structural features and chemical composition of the nanorods were investigated by X-ray diffraction(XRD),transmission electron microscopy(TEM),and field emission scanning electron microscope(FESEM),selected areaelectron diffraction(SAED),and high resolution transmission electron microscopy(HRTEM).The possible mechanism for theformation of Gd(OH)3 nanorods was proposed.     

Synthesis and Characterization of La（OH）3 Nanorods by Hydrothermal Microemulsion Method

La（OH）3 nanorods with diameters of 20-40 nm and lengths of 200-300 nm were synthesized by a hydrothermal microemulsion method. The structure and morphology of the final products were characterized by X-ray powder diffraction （XRD）, transmission electron microscopy （TEM）, and field emission scanning electron microscope （FESEM）.     

Morphology,Size-controlled Synthesis of CoO Nanostructure and Its Magnetic Property

CoO nanostructures with tunable morphology and size have been prepared via a simple one-pot solvothermal synthesis. The as-prepared nanoparticles were fully characterized using X-ray diffraction（XRD）, transmission electron microscopy（TEM）, field-emission scanning electron microscope（FESEM）, etc. The morphology and size of the product can be easily controlled by adjusting the raw materials added. Reaction time and the solvent ratio also play important roles in the synthesis of octahedral nanostructures. The magnetic property of the as-prepared samples was also investigated.     

Synthesis and Characterization of SnO2 One-dimensional Nanostructures

Single-crystalline SnO2 nanowires have been successfully prepared in large scale on Au-coated silicon substrate by heating the mixture of self-made high-purity SnO2 powders and graphite powders at 900℃. Besides the line type nanowires some more features were observed. The products were characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and Raman spectrum techniques. The results indicate that the tin dioxide nanowires have a rutile structure with diameters ranging from 30 to 120 nm and lengths up to several tens of micrometers. The possible mechanism of the growth and reaction for the nanowires was also discussed.     

A Novel Synthesis of Alkaline Earth Silicate Phosphor Sr3MgSi2O8： Eu^2＋, Dy^3＋

A novel method for synthesizing long afterglow silicate phosphor Sr3MgSi2O8：Eu^2＋,Dy^3＋using TEOS and inorganic powders as reactants was reported. Acetic acid as a catalyzer controlled the hydrolysis of TEOS by adjusting pH value of the system. The morphologies of precursor were characterized by transmission electron microscope （TEM）. The structure and optical properties of the phosphor powders were systematically investigated by means of X-ray diffraction and spectrofluorometry. TEM images have reflected the core-shell structure and quasi-spherical morphology of the precursor particles. It was found that the single-phase Sr3MgSi2O8 crystalline structures were obtained at 1050 and 1250 ℃ for the samples prepared with the nano-coating method and the solid state reaction, respectively. The emission intensities of the phosphors prepared by the present method were higher than those by the conventional process. Also, the afterglow characteristic was better than that prepared by solid-state reaction in the comparable condition.     

Supramolecular vesicles of cationic gemini surfactants modulated by p-sulfonatocalix[4]arene

Supramolecular binary vesicles were constructed by host-guest complex formation between p-sulfonatocalix[4]arene and three cationic gemini surfactants, which were identified by UV-vis, dynamic laser scattering, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, and surface tension experiments. The critical aggregation concentration of gemini surfactants decreased pronouncedly by a factor of ca. 1000 owing to the complexation of p-sulfonato-calix[4]arene.     

铝热反应法制备双股类螺旋Zn2SnO4单晶纳米带

This paper reports the preparation in large quantity of bifilar helix-like nanobelts of single crystal ine Zn2SnO4, a face-centered cubic spinel and transparent semiconductor that possesses wide applications in photovoltaic devices and sensors for humidity and combustible gases, by using a unique approach that combines chemical vapor deposition, aluminothermal reaction, vapor-liquid-solid growth, mergence of polar planes, and kinetic control by steady-state turbulent flow. The bifilar helix-like nanobelt was formed by the twisting and merging of two independent Zn2SnO4 nanobelts, as analyzed by scanning electron microscopy, transmission electron microscopy, electron diffraction, X-ray diffraction, Raman spectroscopy, and photoluminescence. It had a periodicity along the axial direction and hence, is actual y a super-lattice material. The photoluminescence measurements showed a strong light emission at 326.1 nm from the as-prepared sample with a line width of about 1.5 nm. The combined approach used in this study, in particular its aluminothermal reaction and steady-state turbulent gas flow perturbation steps, may be helpful in preparing other similar materials.     

同轴静电纺丝技术制备Y_2O_3:Eu~(3+)@SiO_2豆角状纳米电缆与表征

采用同轴静电纺丝技术,以氧化钇、氧化铕、正硅酸乙酯(C8H20O4Si)、无水乙醇、PVP和DMF为原料,成功制备出大量的Y2O3:Eu3+@SiO2豆角状纳米电缆.用TG-DTA,XRD,SEM,TEM和荧光光谱等分析技术对样品进行了系统地表征.结果表明,得到的产物为Y2O3:Eu3+@SiO2豆角状纳米电缆,以无定型SiO2为壳层,晶态Y2O3:Eu3+球为芯,电缆直径约为200nm,内部球平均直径约150nm,壳层厚度约为25nm,电缆长度300μm.纳米电缆内部为球状结构,沿着纤维长度方向有序排列,形貌均一.Y2O3:Eu3+@SiO2豆角状纳米电缆在246nm紫外光激发下,发射出Eu3+离子特征的波长为614nm的明亮红光.对其形成机理进行了初步讨论.     

水热法制备多层核壳结构Gd_2O_3:Eu~(3+)空心微球

以稀土硝酸盐-葡萄糖的混合溶液作为前驱体,采用一步水热法和随后的热处理得到了多层核壳结构Gd_2O_3:Eu~(3+)空心微球,并用X-射线衍射(XRD)、场发射扫描电镜(FESEM)、透射电镜(TEM)、X-射线能量色散光谱(EDS)和荧光光谱等测试手段对所得样品进行了表征.结果表明:所得空心球样品为纯的立方相的Gd_2O_3.具有规则的多层核壳空心结构,空心球的直径在2～3μm左右,壁厚约为100 nml,并且Gd_2O_3:Eu~(3+)空心球是由尺寸约为30 nm的球形纳米颗粒白组装而成.样品中含有Gd、Eu、O元素.该空心球样品具有强的Eu~(3+)的特征红光发射以及长的荧光寿命,可以用来作为时间分辨荧光标记物.     

Y_2O_2S:Eu~(3+)空心微球的制备与性能

以单分散的碳球为硬模板,采用均匀共沉淀法合成了Y_2O_2S:Eu~(3+)心微球.通过XRD、SEM、TEM、荧光光谱对其进行表征.X射线衍射测试表明所制备的Y_2O_2S:Eu~(3+)空心微球为单相,六方晶.扫描电子显微镜(SEM)和透射电子显微镜(TEM)测试表明所制备的Y_2O_2S:Eu~(3+)空心微球粒径小,分布均匀.激发和发射光谱测试表明Eu~(3+)离子能有效地掺入硫氧化钇基质中,并具有良好的发光性能.     

六边形及圆形SmF3微米盘的水热合成与表征

以Sm(NO3)3·6H2O和不同的氟化物(NaBF4,NH4F)在120℃的低温水热条件下反应得到了六边形及圆形的SmF3微米盘.通过X射线衍射(XRD)、场发射扫描电子显微镜(FE-SEM)和透射电子显微镜(TEM)对产物的晶相和形貌进行了表征.XRD结果显示所得的产物是结晶良好的六方晶系.SEM和TEM测试表明得到大量均匀的厚度约为200 nm的盘状结构.研究发现氟化物种类以及反应时间对形成不同形貌的盘有重要影响.讨论了可能的形成机理.进一步研究了SmF3:Tb3+和SmF3:Eu3+掺杂后的产物的荧光性质.     

铽-铕共掺杂的硅酸铝钠荧光体的光致发光性能及能量传递

采用温和的固相反应法合成了具有四方相结构的铽一铕共掺杂的硅酸铝钠(NaAlSiO_4:Tb~(3+),Eu~(3+))发光材料.利用粉末X射线衍射(XRD)、荧光光谱(PL)、时间分辨光谱(TRPL)以及荧光寿命等手段对合成的样品进行表征.研究结果表明:通过改变NaAlSiO_4:Tb~(3+),Eu~(3+)中Eu~(3+)离子的掺杂浓度,可实现其绿光及红光发射的调控;由于Tb~(3+),Eu~(3+)离子间的有效能量传递,Tb~(3+)离子的共掺杂可显著增强该基质中Eu~(3+)离子的发光性能;该能量传递现象可由TRPL光谱等手段进行证实,根据荧光寿命的数值计算可知,从Tb3~(3+)向Eu~(3+)离子的能量传递效率高达95%.     

在卵磷脂体系中合成EuF_3纳米线

利用大豆卵磷脂在水中自发形成的囊泡作模板,先制备出含有Eu~(3+)的卵磷脂乳液,Eu~(3+)与卵磷脂亲水头部的磷氧键相结合形成Eu--O--P键,经用NH_4F沉淀后制得前驱体,该前驱体在600℃灼烧,得到EuF_3纳米线,其直径约为10-20 nm.通过对各阶段产物的荧光光谱、傅里叶变换红外(FTIR)光谱、热重-差热分析(TG-DTA)、透射电镜(TEM)等的对比分析,确认形成了Eu--O--P键,所得到的纳米线是多晶相EuF_3.     

纳米晶LaAlO3掺Eu3+的复合沉淀法制备及发光性质

以NH₃·H₂O-NH₄HCO₃混合溶液为复合沉淀剂,制备了LaAlO₃:Eu³⁺纳米晶体.通过X射线衍射、扫描电镜和透射电镜对产物进行了表征,用荧光光度计测试了样品的三维荧光光谱、激发光谱和发射光谱.结果表明:前驱沉淀物经800℃焙烧处理2h,制备出球型形貌,颗粒分散性好、尺寸约为40nm的立方相LaAlO₃纳米晶.由三维荧光光谱确定了LaAlO₃:Eu³⁺的最佳监测波长和激发波长,在395nm波长光的激发下观察到纳米LaAlO₃中Eu³⁺的591nm(⁵D₀-⁷F₁)和613nm(⁵D₀-⁷F₂)特征发射谱,磁偶极跃迁⁵D₀-⁷F₁的发射峰强度要比电偶极跃迁⁵D₀-⁷F₂更强,而且这种趋势随着焙烧温度的升高明显增强,说明由该法制备的纳米LaAlO₃中Eu³⁺离子占据的位置具有高的对称性.     

YF3:Ln3+ (Ln = Ce, Tb, Pr) submicrospindles: hydrothermal synthesis and luminescence properties

YF(3):Ln(3+) (Ln = Ce, Tb, Pr) microspindles were successfully fabricated by a facile hydrothermal method. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), lifetimes, photoluminescence (PL) and low-voltage cathodoluminescence (CL) were used to characterize the resulting samples. The lengths and diameters of YF(3):0.02Ce(3+) microspindles are around 760 nm and 230 nm, respectively. Adding dilute acid and trisodium citrate (Cit(3-)) are essential for obtaining YF(3) microspindles. A potential formation mechanism for YF(3) microspindles has been presented. PL spectroscopy investigations show that YF(3):Ce(3+) and YF(3):Tb(3+) microcrystals exhibit the characteristic emission of Ce(3+) 5d → 4f and Tb(3+ 5)D(4)→(7)F(J) (J = 6-3) transitions, respectively. In addition, the energy transfer from Ce(3+) to Tb(3+) was investigated in detail for YF(3):Ce(3+), Tb(3+) microspindles. Under the excitation of electron beams, YF(3):Pr(3+) show quantum cutting emission and YF(3):Ce(3+), Tb(3+) phosphors exhibit more intense green emission than the commercial phosphor ZnO:Zn.     

Electrospinning synthesis and luminescence properties of one-dimensional La(9.33)(SiO4)6O2: Ln3+ (Ln = Ce, Eu, Tb) microfibers

One-dimensional La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) microfibers were fabricated by a simple and cost-effective electrospinning method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and low voltage cathodoluminescence (CL) as well as kinetic decay were used to characterize the resulting samples. SEM and TEM results indicated that the diameter of the microfibers annealed at 1000 °C for 3 h was 200-245 nm. The microfibers were further composed of fine and closely linked nanoparticles. La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) phosphors showed the characteristic emission of Ce(3+) (5d → 4f), Eu(3+) ((5)D(0)→(7)F(J)) and Tb(3+) ((5)D(3,4)→(7)F(J)) under ultraviolet excitation and low-voltage electron beams (3-5 kV) excitation. An energy transfer from Ce(3+) to Tb(3+) was observed in the La(9.33)(SiO(4))(6)O(2): Ce(3+), Tb(3+) phosphor under ultraviolet excitation and low-voltage electron beam excitation. Luminescence mechanisms were proposed to explain the observed phenomena. Blue, red and green emission can be realized in La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) microfibers by changing the doping ions. So the La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) phosphors have potential applications in full-color field emission displays.     

铒镱共掺磷酸镧纳晶的合成和近红外荧光性质

以磷酸三丁酯作为配体,使用高温溶液法合成了掺铒磷酸镧纳米晶体,高分辨电镜和XRD结果表明产物尺寸均一,直径4nm左右,具有高度的结晶性,在甲苯等有机溶剂中分散性良好.近红外发光光谱表明,产物在1535 nm处有发光峰,半高全宽为50 nm,高于目前掺铒光纤放大器(EDFA)的增益带宽.通过IR、元素分析研究发现,使用真空干燥等方法不能有效去除纳晶表面的羟基.为了进一步消除表面缺陷和猝灭基团对纳晶发光性质的影响,我们尝试在其外围生长一层LaPO₄壳做成核壳粒子以消除表面缺陷和隔离猝灭基团,结果表明,新的纳晶的发光强度得到了显著提高.