ZnO/ZnS Heterostructured Nanorod Arrays and Their Efficient Photocatalytic Hydrogen Evolution

Semiconducting heterostructures have been widely applied in photocatalytic hydrogen evolution due to their variable band gaps and high energy conversion efficiency. As typical semiconducting heterostructures, ZnO/ZnS heterostructured nanorod arrays (HNRAs) have been obtained through a simple anion‐exchange process in this work. Structural characterization indicates that the heterostructured nanorods (HNRs) are all composed of hexagonal wurtzite ZnO core and cubic zinc‐blende ZnS shell. As expected, the as‐obtained one‐dimensional heterostructures not only lower the energy barrier but also enhance the separation ability of photogenerated carriers in photocatalytic hydrogen evolution. Through comparisons, it is found that 1D ZnO/ZnS HNRAs exhibit much better performance in photocatalytic hydrogen evolution than 1D ZnO nanorod arrays (NRAs) and 1D ZnS NRAs. The maximum H₂ production is 19.2 mmol h^?1 for 0.05 g catalyst under solar‐simulated light irradiation at 25 °C and the corresponding quantum efficiency is 13.9 %, which goes beyond the economical threshold of photocatalytic hydrogen evolution technology.     

一维ZnO纳米棒阵列的水热合成

以锌片为衬底,用硝酸锌和氨水为原材料,在90 ℃时由水热法合成了有序生长的ZnO纳米棒阵列。 纳米棒长度为500～800 nm,直径约为100 nm,SEM图片显示该纳米棒顶部截面是六边形。 XRD谱表明,ZnO纳米棒为六方纤锌矿结构。 考察了制备温度、时间和物料比对合成的材料形貌和结构的影响。     

ZnS微米花的水热合成及光催化性质研究

本文采用简便的水热法一步合成ZnS微米花,通过X射线衍射仪、扫描电子显微镜等表征手段研究了合成产物的形貌及微观结构,并考察了合成产物的光催化性质。合成产物的光催化测试结果表明,在紫外光辐照下,产物对亚甲基蓝、甲基橙和曙红都有很好的降解效果。为了测试产物循环利用的光催化能力,对其进行了5次降解实验,结果显示产物依然保持良好的光催化活性。     

水热法制备Sb2S3纳米棒有序阵列

以Sb(S₂CNEt₂)₃为单源前驱体，通过改变时间、温度、表面活性剂等反应条件，用水热法成功合成了各种尺寸的Sb₂S₃纳米棒及其有序阵列。X-射线衍射(XRD)、能量分散光谱(EDS)以及选区电子衍射(SAED)研究表明纳米棒由正交晶系Sb₂S₃单晶构成。扫描电子显微镜(SEM)和透射电子显微镜(TEM)研究显示Sb₂S     

ZnO微晶的水热合成及形貌控制研究

以Zn(NH3)4(Ac)2为前驱体,不加任何模板剂和表面活性剂,低温下通过改变反应条件(如前驱体浓度、反应时间及反应温度),实现了对ZnO微晶形貌和尺度的有效控制.所得花状、蜂窝状、柱状ZnO用X射线衍射仪和扫描电镜进行了鉴定和表征,并初步探讨了不同形貌ZnO微晶的生长机理.     

One‐Pot Template‐Free Synthesis of Monodisperse Zinc Sulfide Hollow Spheres and Their Photocatalytic Properties

Little hollow! Monodisperse ZnS hollow nanospheres (see figure) of about 200 nm in size have been fabricated on a large scale by a hydrothermal method and they show good photocatalytic activity in the decolorization of an aqueous solution of rhodamine B under UV irradiation.

     

Hydrothermal Synthesis and Optical Properties of ZnO Nanostructured Films Directly Grown from/on Zinc Substrates

Uniform ZnO nanorods arrays are grown directly from and on Zn foils in pure water under hydrothermal conditions at a relatively low temperature. The nanorods are 80–200 nm in diameter and ∼ 1 μm in length, which grow on the Zn foil along the [001] direction. By changing the pure water to a urea solution, a Zn compound ([Zn₅(OH)₆(CO₃)₂], a precursor of ZnO nanoflowers film, is created by self-assembly. The ZnO nanoflowers film can be easily obtained by heating the [Zn₅(OH)₆(CO₃)₂] compound in N₂ at 350∘C for 5–6 hours. Possible growth processes of the ZnO nanorods arrays and the [Zn₅(OH)₆(CO₃)₂] nanoflowers are discussed. Photoluminescence properties of the as-prepared ZnO nanostructures have been measured. The ZnO nanorods array synthesized using our method has minimal defects so that only band-gap emission is observed. However, the ZnO nanoflowers film, obtained by heating the [Zn₅(OH)₆(CO₃)₂] nanoflower precursor in N₂, is polycrystalline and displays strong defect-related emission.     

ZnS微米球的水热合成及光催化性能研究

以L-半胱氨酸为硫源,明胶作为组装剂,采用水热方法制备了粒径均一的ZnS微米球。利用XRD,TEM,FESEM,FTIR探讨了明胶、反应时间和反应温度对产物形貌和尺寸的影响,其结果表明ZnS微米球是由ZnS纳米颗粒组装而成的3D多级结构。光催化性能研究表明,明胶的加入提高了最终产物的光催化性能。利用产物的荧光发光性能解释了其光催化性能产生差异的原因。     

Cd2+掺杂ZnWO4纳米棒的合成和光致发光性能研究

采用简单的水热法合成了Cd2+掺杂ZnWO4纳米棒.通过SEM、TEM、EDX和XRD等手段对产物进行了表征.实验结果表明,产物为直径约20 nm.长300～500 nm的Cd2+掺杂ZnWO4纳米棒.研究了Cd2+掺杂量对ZnWO4纳米棒的光致发光性能的影响,随着Cd2+掺杂量的增加,ZnWO4纳米棒的光致发光强度随之增强.     

水热法制备MoO3-GQDs的三甲胺气敏性能

采用水热法制备了一系列具有不同碳量子点(GQDs)含量的MoO3?GQDs纳米复合材料,利用X射线衍射、扫描电子显微镜、透射电子显微镜、FTIR等对MoO3?GQDs复合材料进行了表征,研究了其气敏性能。结果表明,复合材料中GQDs的含量对MoO3?GQDs复合材料的气敏响应和选择性有显著影响。MoO3?GQDs纳米复合材料(S?6,GQDs悬浮液的含量为6 mL)传感器在230℃时对三甲胺(TMA)表现出高的气敏响应和好的气敏选择性;该传感器对1000μL·L^-1 TMA的响应为74.08;对1000μL·L^-1 TMA的响应时间和恢复时间分别为73和34 s;S?6复合材料气敏传感器在230℃时可以检测到1μL·L^-1的TMA。     

Hydrothermal Synthesis and Properties of Controlled α‐Fe2O3 Nanostructures in HEPES Solution

A facile, template‐free, and environmentally friendly hydrothermal strategy was explored for the controllable synthesis of α‐Fe₂O₃ nanostructures in HEPES solution (HEPES=2‐[4‐(2‐hydroxyethyl)‐1‐piperazinyl]ethanesulfonic acid). The effects of experimental parameters including HEPES/FeCl₃ molar ratio, pH value, reaction temperature, and reaction time on the formation of α‐Fe₂O₃ nanostructures have been investigated systematically. Based on the observations of the products, the function of HEPES in the reaction is discussed. The different α‐Fe₂O₃ nanostructures possess different optical, magnetic properties, and photocatalytic activities, depending on the shape and size of the sample. In addition, a novel and facile approach was developed for the synthesis of Au/α‐Fe₂O₃ and Ag/α‐Fe₂O₃ nanocomposites in HEPES buffer solution; this verified the dual function of HEPES both as reductant and stabilizer. This work provides a new strategy for the controllable synthesis of transition metal oxide nanostructures and metal‐supported nanocomposites, and gives a strong evidence of the relationship between the property and morphology/size of nanomaterials.     

Hydrothermal Synthesis and Phase‐, Morphology‐Evolution Mechanism of Lead Titanate Nanostructures Assisted with Tetramethylammonium Hydroxide

Lead titanate nanostructures with different phases and morphologies, layered hexagonal PbTiO₂(CO₃)_0.3‐ (NO₃)_0.35(OH) nanosheets, pyrochlore Pb₂Ti₂O₆ nanodendites, pre‐perovskite PbTiO₃ nanofibres and perovskite PbTiO₃ nanoplates, have been synthesized via a conventional hydrothermal route assisted with different concentrations of tetramethylammonium hydroxide (TMAH). X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high‐resolution TEM (HRTEM) were employed to characterize the phase, morphology and growth behavior of the synthesized samples. The results reveal that at low TMAH concentration the obtained samples are mainly of PbTiO₂(CO₃)_0.3(NO₃)_0.35(OH) nanosheets. With the TMAH concentration increasing, the obtained samples change to pyrochlore Pb₂Ti₂O₆ nanodendites, pre‐perovskite PbTiO₃ nanofibres and perovskite PbTiO₃ nanoplates in turn. With the basis of the experimental results, the phase‐ and morphology‐evolution mechanism of the lead titanate nanostructures is discussed by combining the analysis of the lattice structure feature and the properties of TMAH.     

One‐Step Hydrothermal Synthesis of Carboxyl‐Functionalized Upconversion Phosphors for Bioapplications

In this paper, we report a facile one‐step hydrothermal method to synthesize phase‐, size‐, and shape‐controlled carboxyl‐functionalized rare‐earth fluorescence upconversion phosphors by using a small‐molecule binary acid, such as malonic acid, oxalic acid, succinic acid, or tartaric acid as capping agent. The crystals, from nano‐ to microstructures with diverse shapes that include nanospheres, microrods, hexagonal prisms, microtubes, microdisks, polygonal columns, and hexagonal tablets, can be obtained with different reaction times, reaction temperatures, molar ratios of capping agent to sodium hydroxide, and by varying the binary acids. Fourier transform infrared, thermogravimetric analysis, and upconversion luminescence spectra measurements indicate that the synthesized NaYF₄:Yb/Er products with hydrophilic carboxyl‐functionalized surface offer efficient upconversion luminescent performance. Furthermore, the antibody/secondary antibody conjugation can be realized by the carboxyl‐functionalized surfaces of the upconversion phosphors, thus indicating the potential bioapplications of these kinds of materials.     

Tuning the Dimensions of ZnO Nanorod Arrays for Application in Hybrid Photovoltaics

ZnO nanorod arrays are a very eligible option as electron acceptor material in hybrid solar cells, owing to their favorable electrical properties and abundance of available, easy, and low‐cost synthesis methods. To become truly effective in this field, a major prerequisite is the ability to tune the nanorod dimensions towards optimal compatibility with electron‐donating absorber materials. In this work, a water‐based seeding and growth procedure is used to synthesize ZnO nanorods. The nanorod diameter is tuned either by modifying the zinc concentration of the seeding solution or by changing the concentration of the hydrothermal growth solution. The consequences of this morphological tailoring in the performance of hybrid solar cells are investigated, which leads to a new record efficiency of 0.82 % for hydrothermally grown ZnO nanorods of size 300 nm in combination with poly(3‐hexylthiophene‐2,5‐diyl) (P3HT). This improvement is attributed to a combined effect of nanorod diameter and orientation, and possibly to a better alignment of the P3HT backbone resulting in improved charge transport.     

Fabrication of NiC/MoC/NiMoO4 Heterostructured Nanorod Arrays as Stable Bifunctional Electrocatalysts for Efficient Overall Water Splitting

Developing noble‐metal‐free, earth‐abundant, highly active, and stable electrocatalysts with high efficiency for both hydrogen and oxygen evolution reactions is of great importance for the development of overall water‐splitting devices, but still remains a challenging issue. Herein, a 3D heterostructured NiC/MoC/NiMoO₄ electrocatalyst was prepared through a facile synthetic procedure. The electrocatalyst shows a superior catalytic activity and stability toward the hydrogen and oxygen evolution reactions. The optimized NiC/MoC/NiMoO₄ catalyst presents low overpotentials of 68 and 280 mV to reach a current density of 10 mA cm^?2 in 1.0 m KOH for the hydrogen and oxygen evolution reactions, respectively. Assembled as an electrolyzer for overall water splitting, such a heterostructure shows quite a low cell voltage of 1.52 V at 10 mA cm^?2 and remarkable stability for more than 20 h. This work provides a facile but efficient approach for the design and preparation of highly efficient bifunctional and self‐supported heterostructured electrocatalysts that can serve as promising candidates in electrochemical energy storage and conversion.     

One‐Step Hydrothermal Synthesis of a Porous Cu2O Film and Its Photoelectrochemical Properties

A cuprous oxide (Cu₂O) film with a novel porous structure is successfully synthesized on Cu foil by using a simple hydrothermal method. A redox reaction occurs between Cu and Cu²⁺ in aqueous solution to form the Cu₂O film. The porous structures are formed as a result of the Ostwald ripening mechanism. In addition, photoluminescence measurements indicate that the porous Cu₂O film may reduce the recombination of photogenerated electrons and holes. The UV/Vis absorption property of the porous Cu₂O film is better than that of the granular Cu₂O film, and its high photocurrent is expected to make the porous Cu₂O film more suitable for solar energy applications.     

Dipole Field Guided Orientated Attachment of Nanocrystals to Twin‐Brush ZnO Mesocrystals

Mesocrystals of ZnO were synthesized hydrothermally by using gum arabic as a structure‐directing agent. Their hierarchical structure has a unique twin‐brush form consisting of vertically aligned nanorods in a single‐crystal‐like porous form. The formation mechanism of the twin‐brush ZnO was investigated by quenching a series of samples at different times and examining them by TEM, SEM, and XRD. The alignment of ZnO crystal units can be modulated by adding simple salts such as KCl to change the units from nanorods to nanoplates. This can be explained by screening the dipolar force of the polar crystal. Local cathodoluminescence of twin‐brush ZnO was used to follow the local structure changes.