均匀沉淀法制备ZAO纳米棒

采用均匀沉淀法,以尿素、Zn（NO3）2.6H2O和Al（NO3）3.9H2O为原料,在水-乙二醇溶液中制备了Al掺杂ZnO（ZAO）纳米棒.X射线衍射（XRD）分析表明：纳米棒为六方纤锌矿结构,掺杂的Al3＋取代了Zn2＋的位置,形成A1/ZnO固溶体,保持了ZnO的结构.前驱体的红外光谱（FT-IR）分析表明：乙二醇的加入改变了纳米材料的表面状态.扫描电镜（SEM）和高分辨透射电镜（TEM）结果显示：随着反应体系中乙二醇体积比和Al掺杂量的增加,ZAO纳米棒的长径比先增大后减小,在V（水）/V（乙二醇）=4、Al掺杂量为5%（摩尔分数）时,制得长径比最大为25、直径为10nm的纳米棒.     

氧化铁纳米棒的制备、表征及磁性研究

以三氯化铁为铁源,聚乙烯吡咯烷酮为表面活性剂,合成了氧化铁纳米棒,并用X-射线衍射仪﹑扫描电子显微镜﹑透射电子显微镜和磁学测量系统对其进行了表征。结果表明:水热法所制备的氧化铁纳米棒平均直径约为70 nm,长度约300 nm,其剩余磁感应强度为0.07 emu/g,矫顽力为2300 Oe,具有一定的铁磁性。     

ZnO纳米棒水热法生长与表征

采用两步法在FTO导电玻璃衬底上制备ZnO纳米棒,首先利用浸渍-提拉法在FTO导电玻璃衬底上制备ZnO晶种层,然后把有ZnO晶种层的FTO衬底放入盛有生长溶液的反应釜中利用水热法制备ZnO纳米棒.研究了生长溶液的浓度、生长温度和生长时间对所制备的对ZnO纳米棒阵列的微结构和光致发光性能的影响,利用X射线衍射(XRD)、扫描电子显微镜(SEM)和光致发光谱(PL)研究了ZnO样品的结构、形貌和光学性质.实验结果表明:所制备的ZnO纳米棒呈现六方纤锌矿结构,沿(002)晶面择优取向生长,纳米棒的平均直径约为100 nm,长度约为2.5 μm.所制备的ZnO纳米棒在390 nm附近具有很强的紫外发光峰和在550 nm附近有较弱的宽绿光发光峰.     

Bi^3＋掺杂对纳米ZnO形貌及其光催化性能的影响

以硝酸锌为原料,尿素为沉淀剂,采用均匀沉淀法分别制备了未掺杂的纯纳米ZnO粉体和Bi3+离子掺杂纳米ZnO粉体.XRD、TEM分析及光催化试验结果表明:本研究制备的纯相纳米ZnO粉体和Bi3+掺杂纳米ZnO粉体均为六方晶系纤锌矿结构,掺杂并未改变ZnO的晶系结构:但对其晶粒形貌产生了影响,除了球状形貌外,还产生了大量长短不一的棒状结构.与纯相纳米ZnO相比,Bi3+的掺杂降低了其光催化活性,在80min光照下MB的降解率已经由68-26%降低到10.02%,但随着Bi3+掺杂量的增加,其光催化活性有所改善,当掺杂量达到3%时,光催化降解率重又升高到46.98%.     

表面活性剂CTAB辅助溶胶–凝胶法制备硼酸铝纳米棒

以仲丁醇铝(aluminum tri-sec-butoxide,ATSB)和硼酸为原料,采用阳离子表面活性剂(cetyltrimethyl ammonium bromide,CTAB)辅助溶胶–凝胶法于120℃形成白色干凝胶,再进行焙烧得到硼酸铝纳米棒。采用X射线衍射仪、扫描电子显微镜、透射电子显微镜、X射线能量色散谱仪和Fourier变换红外光谱仪对产物结构和形貌进行表征。结果表明:750℃焙烧产物为具有单晶结构的Al4B2O9纳米棒,,其形貌及直径、长度受ATSB和硼酸摩尔比影响;当ATSB与H3BO3摩尔比为1:2时,Al4B2O9纳米棒直径约为15nm,长度为200～300nm。1200℃焙烧的产物为Al18B4O33纳米棒,其直径为200～500nm,长度约为3μm。对硼酸铝纳米棒的形成机理进行了初步探讨。     

簇状氧化锌纳米棒的合成及其光催化性能研究

采用醋酸锌和氨水为原料、水作为溶剂,以水热法在80℃条件下反应20 h制备出了簇状氧化锌纳米棒,用XRD、SEM分别分析了制备产物的物相和形貌。以ZnO纳米棒为光催化剂对有机染料甲基橙进行了光催化降解实验,研究了甲基橙溶液初始浓度和催化剂添加量对光催化的影响。结果表明,合成的氧化锌纳米棒均为六方晶系铅锌矿结构;产物为从中心发散的簇状纳米棒结构,纳米棒直径分布均匀且分散性好,每个簇由几十个纳米棒组成,每个纳米棒平均直径约为150 nm,长度约为5μm。制备的ZnO有良好的光催化性能。     

CdSe:Mn量子点的制备及其光致发光特性研究

采用低温水热法,以柠檬酸为配位稳定剂制备了Mn2 掺杂的CdSe量子点.用紫外吸收光谱、荧光发射光谱、X射线衍射(XRD)、透射电镜(TEM)等进行了表征.研究了Mn2 掺杂浓度对量子点的结构及其光致发光性能的影响.光致发光光谱表明,当粒子尺寸为3 nm时,在580 nm处出现了属于Mn2 的4T1-6A1跃迁的特征发射峰.当激发波长为480nm时,在630nm处出现了CdSe的表面缺陷发射峰.随着Mn2 的掺杂浓度增大,CdSe:Mn表面陷阱态发射峰位置没有显著红移.TEM分析结果显示,CdSe:Mn量子点为单分散的,尺寸约为5 nm的圆形纳米粒子.当Mn2 离子掺杂浓度不大于5%时,Mn2 取代表面晶格中的Cd2 离子位置形成辐射性表面缺陷,产生表面陷阱态发射.吸收光谱显示,随着量子点变小,吸收带边发生蓝移,显示明显的量子尺寸效应.     

溶剂热法合成氧化锌纳米棒

采用PEG辅助溶剂热合成了ZnO纳米棒,通过SEM、EDS和XRD等手段对产物进行了表征。结果显示,合成的ZnO纳米棒直径在20 nm左右,长大约150,且长度和直径分布均匀。研究了PEG的添加量对形成ZnO纳米棒的影响,并且探讨了PEG促进纳米棒生长的机理。     

反溶剂沉淀法合成Fe~(3+)掺杂ZnO纳米结构及其可见光催化性能

以氯化胆碱-草酸低共熔溶剂(ChCl-OA DES)为溶剂,ZnO和Fe_2O_3为原料,通过简单的反溶剂沉淀法制备出不同掺杂浓度的Fe~(3+)掺杂ZnO (Fe-ZnO)纳米结构。采用SEM、XRD、拉曼光谱、XPS等手段对所制Fe-ZnO结构与形貌进行了表征。结果表明,Fe-ZnO是由直径为20～30 nm纳米晶组装而成的微米棒。不同掺杂浓度的Fe-ZnO纳米晶均为六方铅锌矿结构,Fe~(3+)很好地进入ZnO晶格。同时考察了所制Fe-ZnO的光吸收特性和光催化活性,发现Fe~(3+)掺杂使其吸收峰红移至可见光范围,有效增强了可见光区域的催化活性。当Fe掺杂量为1.0%(atom)时,样品的光催化活性最好,比ZnO增大了约102倍。这说明Fe~(3+)掺杂可改善ZnO对可见光光子的捕获能力。     

水热法制备纳米棒状氧化锌及其性能表征

以硝酸锌和氢氧化钠为原料、十二烷基三甲基氯化铵为分散剂,采用温和水热法在100℃条件下,制备了纳米棒状氧化锌.通过XRD物相分析可知,合成ZnO纳米粒子的物相均是六方晶系纤锌矿结构;TEM形貌观察,粒子基本为棒状,纳米棒状ZnO的平均直径约为30～40 nm、长度约60～70 nm.水溶液中次甲基蓝染料在棒状纳米ZnO光催化下、pH为8.0时,能迅速分解,在降解90 min时,次甲基蓝的降解率达到100%.     

One-step synthesis of high purity ZnO micro/nanostructures from pure Zn and pre-alloyed brass powders by vapor phase transport

In this research, vapor phase transport (VPT) was introduced as a facile, inexpensive method to produce ZnO micro/nanostructures from various Zn sources such as pure Zn and alpha brass pre-alloyed powders (Cu–20Zn and Cu–28Zn) at different processing temperatures of 930 °C–1050 °C. Simultaneous thermal analysis (STA) was carried out to investigate Zn evaporation and ZnO micro/nanostructure formation. STA results showed an exothermic peck at 711 °C and 728 °C for Cu–20Zn and Cu–28Zn, respectively, due to oxidation of the evaporated Zn element and formation of ZnO micro/nanostructures. X-ray diffraction results showed that high purity ZnO micro/nanostructures were successfully synthesized via VPT process and the crystallite size was increased from ~60 nm to ~100 nm with increasing processing temperature. Field emission scanning electron microscopy observations showed morphology (e.g. rods, column, tetrapods, and combs) and size of the synthesized micro/nanostructures were dependent on the Zn sources and processing temperature, in which average diameter of the synthesized ZnO structures was increased with increasing the processing temperature. The smallest (98 nm) and largest (603 nm) average diameters of synthesized ZnO micro/nanostructures were attained from the pure Zn and Cu–28Zn brass powders at 930 °C and 1050 °C, respectively.     

Growth mechanism of needle-shaped ZnO nanostructures over NiO-coated Si substrates

ZnO nanostructures were synthesized over NiO-coated Si substrate by a thermal evaporation of Zn powders in a vertical chemical vapor deposition reactor. The ZnO nanostructures had a needle-like morphology and the diameter of the structures decreased linearly from the bottom to the top. The bottom diameters of the ZnO nano-needles normally ranged from 20–100 nm and the lengths were in the range of 2–3 Μm. The clear lattice fringes in HRTEM image indicated the growth of good quality hexagonal single-crystal ZnO. Field emission characteristics of the ZnO nano-needles showed that the turn-on field was about 8.87 V/Μm with a field enhancement factor of about 1099. The growth mechanism of the ZnO nano-needles was proposed on the basis of experimental data.     

室温固相合成掺杂ZnO纳米粉体制备ZnO压敏电阻

以金属离子盐和草酸为原料,采用室温固相化学反应合成掺杂ZnO前驱物,根据DSC-TG分析结果,将其在450℃热分解2 h,得到掺杂ZnO粉体,并用此粉体制备了片式ZnO压敏电阻。借助XRD、TEM、BET等检测手段对粉体产物的物相、形貌、粒度等进行了表征。研究了烧结温度对ZnO压敏电阻电性能的影响。结果表明,所制备的粉体为平均粒径24 nm左右、颗粒呈球状、分散性好的纤锌矿结构掺杂ZnO。在1 080℃烧结时,ZnO压敏电阻的综合电性能达到最佳,电位梯度为791.64 V/mm,非线性系数为24.36,漏电流为43μA。     

Effect of the O2/N2 ratio on the morphology of ZnO nanostructures grown by a thermal evaporation technique

ZnO nanostructures were synthesized by thermal evaporation of Zn powder in an oxygen and nitrogen gas environment at 1000 °C. No substrates or catalysts were used for the formation of the ZnO nanostructures. The ZnO nanostructures were synthesized inside crucibles with Zn source powder. ZnO nanoneedles began to be found at O₂/N₂ ratios of less than 60/40. As the O₂/N₂ ratio increased to 80/20, the ZnO nanostructures mainly grew in the longitudinal direction. Upon increasing the O₂/N₂ ratio to 100/0, the ZnO nanostructures grew mainly in the transverse direction. CL spectra showed that ZnO with a high crystalline quality was obtained at a O₂/N₂ ratio of 80/20.     

不同硅源对水热合成Zn2SiO4:Mn荧光材料形貌及性能的影响

分别以晶态和非晶态SiO2为硅源,在高压釜中采用水热法合成Zn2SiO4:Mn荧光粉,并对其晶体结构、形貌、光吸收及光致发光性能进行表征. 结果表明,在220℃下反应6 d,以晶态SiO2合成的Zn2SiO4:Mn纳米颗粒呈六棱柱状,具有单晶结构,颗粒长约5~8 mm,平均直径约1 mm;以非晶SiO2合成的Zn2SiO4:Mn纳米颗粒呈多晶结构,平均长约500 nm,平均直径约100 nm. 2种硅源所制样品在250 nm以下的紫外光区具有强吸收,且非晶SiO2所制样品在250~350 nm具有良好的紫外光吸收能力. 以不同硅源低温制备的Zn2SiO4:Mn样品在波长215和250 nm的紫外光激发下均能产生520 nm的绿色荧光,且在相同反应时间下非晶硅源制备的样品发光较强.     

Growth and formation mechanism of sea urchin-like ZnO nanostructures on Si

Sea urchin-like nanostructures of ZnO consisting of ZnO nanowires with blunt faceted ends were grown on Si (100) substrates by oxidation of metallic Zn at 600 °C. ZnO nanowires having a diameter of 30–60 nm and length of 2–4 Μm were in similar shape with uniform diameter along its entire length with well faceted blunt ends. X-ray diffraction and transmission electron microscope analysis showed that the as-grown nanostructures were highly crystalline with wurtzite hexagonal structure having lattice constants of a=b=3.25 å and c=5.21 å. Room temperature photoluminescence (PL) measurements showed a weak near band-edge emission at 380 nm, but a strong green emission at 500–530 nm. A model for vapor-solid (VS) growth mechanism of ZnO nanowires was presented, in which nucleation of ZnO is crucial for the growth of the nanostructures.     

Nitroaniline chemi-sensor based on bitter gourd shaped ytterbium oxide (Yb2O3) doped zinc oxide (ZnO) nanostructures

Bitter gourd shaped ytterbium oxide (Yb₂O₃) doped ZnO nanostructures were synthesized through hydrothermal method and analyzed using various techniques including field energy emission scanning electron microscopy (FESEM) accompanied with energy dispersive spectroscopy (EDS), X-ray diffractometry (XRD), UV-visible spectroscopy and Raman spectroscopy. Yb₂O₃ doped ZnO product showed long oblong shaped structures with distinct crunchy and warty exterior texture similar to the bitter gourd fruit. The average length of the bitter-gourd fruit shaped structures was ∼3.5 μm. The calculated average crystallite size and band gap energy of Yb₂O₃ doped ZnO nanostructures were 18.75 nm and 3.34 eV, respectively. The silver electrode (AgE) modified electrochemical sensor fabricated using bitter gourd shaped Yb₂O₃ doped ZnO nanostructures exhibited excellent sensitivity of 117.6 μA.mM⁻¹cm⁻², measured LOD of 0.39 mM, linear dynamic range (LDR) of 0.39 mM–6.25 mM and regression correlation coefficient (R²) = 0.94892.     

Formation of quasi-single crystalline porous ZnO nanostructures with a single large cavity

We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 °C) and a stage in which the temperature is maintained at 120 °C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space.     

Interfacial polymerization of morphologically modified polyaniline: from hollow microspheres to nanowires

BACKGROUND: Polyaniline (PANI) has attracted much attention in many fields due to its chemical and physical properties, and different nanostructures of PANI changing from one‐dimensional to three‐dimensional have been obtained. By changing the concentration of cetyltrimethylammonium bromide (CTAB), the morphology of hydrochloric acid‐doped polyaniline could be changed from one‐dimensional nanoneedles or nanowires with a network structure (50–100 nm in diameter) to three‐dimensional hollow microspheres (ca 400 nm in outer diameter) via combining interfacial polymerization and self‐assembly process. RESULTS These different nanostructures of PANI were proved using scanning electron and transmission electron microscopies. A plausible mechanism of the formation of the changeable nanostructures of PANI may be different from that of interfacial polymerization without surfactant or a traditional homogenous reaction system using CTAB as surfactant. CONCLUSION The results obtained from Fourier transform infrared spectrometry, X‐ray diffraction and the four‐probe method showed that the molecular structure of PANI does not change with increasing CTAB concentration, but crystallinity and conductivity of PANI increase with surfactant concentration. Copyright © 2007 Society of Chemical Industry     

Enhancing the magnetic and antibacterial properties of ZnO nanopowders through Mn+Co doping

Undoped and doubly (Mn+Co) doped ZnO nanopowders were synthesized with different doping levels of Co (1, 2, 3, 4 and 5 at%) and constant Mn doping level (10 at%) using a simple soft chemical route. XRD profiles confirmed that the synthesized material is nanocrystalline ZnO with hexagonal wurtzite structure. No peaks other than the characteristic ZnO peaks were observed in the XRD pattern confirming the absence of any secondary phase. Antibacterial activities of synthesized ZnO nanopowders were tested against Staphylococcus aureus bacteria using agar well diffusion method. It was found that the antibacterial efficiency of the doubly doped ZnO nanopowders was remarkably high when the Co doping level was 5 at%. The obtained PL, SEM and TEM results are corroborated well with the antibacterial activity. Magnetic measurements showed that undoped ZnO sample exhibits diamagnetic behavior and as the Co doping level increases, the nanopowder behaves as a ferromagnetic material.