Cu?Cu2O?TiO2 Nanojunction Systems with an Unusual Electron–Hole Transportation Pathway and Enhanced Photocatalytic Properties

Multicomponent Cu? Cu₂O? TiO₂ nanojunction systems were successfully synthesized by a mild chemical process, and their structure and composition were thoroughly analyzed by X‐ray diffraction, transmission electron microscopy, field‐emission scanning electron microscopy, and X‐ray photoelectron spectroscopy. The as‐prepared Cu? Cu₂O? TiO₂ (3 and 9 h) nanojunctions demonstrated higher photocatalytic activities under UV/Vis light irradiation in the process of the degradation of organic compounds than those of the Cu? Cu₂O, Cu? TiO₂, and Cu₂O? TiO₂ starting materials. Moreover, time‐resolved photoluminescence spectra demonstrated that the quenching times of electrons and holes in Cu? Cu₂O? TiO₂ (3 h) is higher than that of Cu? Cu₂O? TiO₂ (9 h); this leads to a better photocatalytic performance of Cu? Cu₂O? TiO₂ (3 h). The improvement in photodegradation activity and electron–hole separation of Cu? Cu₂O? TiO₂ (3 h) can be ascribed to the rational coupling of components and dimensional control. Meanwhile, an unusual electron–hole transmission pathway for photocatalytic reactions over Cu? Cu₂O? TiO₂ nanojunctions was also identified.     

Transmission electron microscopy characterization of colloidal copper nanoparticles and their chemical reactivity

A colloidal synthesis method was developed to produce face centered cubic (fcc) Cu nanoparticles in the presence of surfactants in an organic solvent under an Ar environment. Various synthetic conditions were explored to control the size of the as-prepared nanoparticles by changing the precursor, varying the amount of surfactants, and tuning the reaction temperature. Transmission electron microscopy (TEM), selected-area electron diffraction, and high-resolution TEM were used as the main characterization tools. Upon exposure to air, these nanoparticles are oxidized at different levels depending on their sizes: (1) an inhomogeneous layer of fcc Cu₂O forms at the surface of Cu nanoparticles (about 30 nm); (2) Cu nanoparticles (about 5 nm) are immediately oxidized into fcc Cu₂O nanoparticles (about 6 nm). The occurrence of these different levels of oxidization demonstrates the reactive nature of Cu nanoparticles and the effect of size on their reactivity. Furthermore, utilization of their chemical reactivity and conversion of spherical Cu nanoparticles into CuS nanoplates through the nanoscale Kirkendall effect were demonstrated. The oxidization and sulfidation of Cu nanoparticles were compared. Different diffusion and growth behaviors were involved in these two chemical transformations, resulting in the formation of isotropic Cu₂O nanoparticles during oxidization and anisotropic CuS nanoplates during sulfidation.      

金/氧化亚铜异质球的制备及其可见光催化性能

使用L-半胱氨酸作为连接剂, 利用硼氢化钠原位还原预先吸附在介孔氧化亚铜表面的氯金酸根离子,得到了Au/Cu₂O异质结构. 应用X射线粉末衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱和N₂物理吸附等手段对催化剂进行表征, 并以λ>400 nm的可见光作为光源, 评价了该催化剂光催化降解亚甲基蓝(MB)的活性. 实验结果表明, 直径为4 nm的金颗粒完好地负载在介孔氧化亚铜的表面, 并且介孔氧化亚铜的细微结构与孔径均未发生变化. 研究表明, 以乙醇作为反应溶剂有效抑制了AuCl₄^-与Cu₂O之间的氧化还原反应, 从而有利于氧化亚铜介孔结构的保持及金颗粒的原位还原. 光催化降解亚甲基蓝的结果表明, Au/Cu₂O异质结构的光催化活性比纯氧化亚铜光催化活性有明显提高. 推测其光催化性能提高的主要原因如下: 一方面, 金颗粒良好的导电性有利于氧化亚铜表面电子的快速转移, 实现电子-空穴分离; 另一方面, 金颗粒可能存在的表面等离子共振现象加速了光生电子的产生.     

Improved electrochemical performances of core-shell Cu2O/Cu composite prepared by a simple one-step method

Core-shell Cu₂O/Cu composites were successfully prepared by over-reduction of aqueous CuSO₄ with hydrazine hydrate as reductant. Field emission scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) clearly illuminate that the core is Cu₂O with 400 nm in diameter, and the shell is Cu with about 50 nm in thickness. The core-shell Cu₂O/Cu exhibited weaker polarization and higher coulombic efficiency than pure octahedral Cu₂O, especially in the initial stage of cycles. After 50 cycles, the reversible capacity of Cu₂O/Cu (360 mAh g^?1) was much higher than that of pure Cu₂O (160 mAh g^?1). The improvement of electrochemical properties is attributed to the core-shell structure of Cu₂O/Cu and the catalytic effect of Cu on the decomposition of Li₂O during the charging process.     

Oxidation of Ethanol in Cu-Faujasites Studied by IR Spectroscopy

In this study, IR studies of the coadsorption of ethanol and CO on Cu⁺ cations evidenced the transfer of electrons from ethanol to Cu⁺, which caused the lowering of the frequency of the band attributed to CO bonded to the same Cu⁺ cation due to the more effective π back donation of d electrons of Cu to antibonding π* orbitals of CO. The reaction of ethanol with acid sites in zeolite HFAU above 370 K produced water and ethane, polymerizing to polyethylene. Ethanol adsorbed on zeolite Cu(2)HFAU containing acid sites and Cu⁺_exch also produced ethene, but in this case, the ethene was bonded to Cu⁺ and did not polymerize. C=C stretching, which is IR non-active in the free ethene molecule, became IR active, and a weak IR band at 1538 cm⁻¹ was present. The reaction of ethanol above 370 K in Cu(5)NaFAU zeolite (containing small amounts of Cu⁺_exch and bigger amounts of Cu⁺_ox, Cu²⁺_exch and CuO) produced acetaldehyde, which was further oxidized to the acetate species (CH₃COO⁻). As oxygen was not supplied, the donors of oxygen were the Cu species present in our zeolite. The CO and NO adsorption experiments performed in Cu-zeolite before and after ethanol reaction evidenced that both Cu⁺_ox and Cu²⁺ (Cu²⁺_exch and CuO) were consumed by the ethanol oxidation reaction. The studies of the considered reaction of bulk CuO and Cu₂O as well as zeolites, in which the contribution of Cu⁺_ox species was reduced by various treatments, suggest that ethanol was oxidized to acetaldehyde by Cu²⁺_ox (the role of Cu⁺_ox could not be elucidated), but Cu⁺_ox was the oxygen donor in the acetate formation.     

Hydrothermal synthesis of nickel hydroxide nanostructures in mixed solvents of water and alcohol

Nickel hydroxide nanosheets and flowers have been hydrothermally synthesized using Ni(CH₃COO)₂·4H₂O in mixed solvents of ethylene glycol (EG) or ethanol and deionized water at 200 °C for different time. The phase and morphology of the obtained products can be controlled by adjusting the experimental parameters, including the hydrothermal time and the volume ratio of water to EG or ethanol. The possible reaction mechanism and growth of the nanosheets and nanoflowers are discussed based on the experimental results. Porous nickel oxide nanosheets are obtained by heating nickel hydroxide nanosheets in air at 400 °C. The products were characterized by using various methods including X-ray diffraction (XRD), fourier transform infrared (FTIR), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), field emission scanning electron microscopy (FESEM). The electrochemical property of β-Ni(OH)₂ nanosheets was investigated through the cyclic voltammogram (CV) measurement.     

Crystal Structure and Properties of Strontium Phosphate Apatite with Oxocuprate Ions in Hexagonal Channels

Strontium phosphate apatites containing different amounts of copper were prepared by a solid state reaction at 1100 °C or by arc melting above 1600 °C in air. The samples were characterized by X‐ray diffraction, ICP analysis, scanning electron microscopy, IR spectroscopy, MAS—¹H—NMR, diffuse reflectance spectroscopy, and SQUID magnetometry. X‐ray crystal structure determination was carried out for a single crystal obtained from the melt. The compound is formulated as Sr₅(PO₄)₃(CuO₂)_1/3 and has an apatite structure (space group P6₃/m, a = 9.7815(4)Å, c = 7.3018(4)Å, Z = 2) with linear CuO₂^3— ions occupying hexagonal channels. For solid state synthesized samples, Rietveld refinement of powder XRD patterns was performed. The samples obtained at 1100 °C acquire the composition Sr₅(PO₄)₃Cu_xOH_y, with x changing from 0.01 to 0.62 and y < 1—x. The copper content can be increased to x = 0.85 by annealing in argon at 950 °C. The compounds represent a hydroxyapatite in which part of the protons is substituted by Cu⁺ and Cu²⁺ ions. The ions form linear O—Cu—O units which are progressively condensed creating the Cu—O—Cu bridges on increasing copper content. IR and NMR data testify existence of OH groups, non‐disturbed and disturbed by neighboring Cu atoms. In the electron spectra, the samples exhibit absorption bands at 7800‐7900, 14200‐14500 and 17500‐17550 cm^—1, which were assigned to Cu²⁺ d‐electron transitions. By annealing the sample with x = 0.1 in oxygen at 800 °C copper is fully oxidized while retaining in channels in unusual for Cu²⁺ linear coordination.     

Microwave-assisted template-free synthesis of butterfly-like CuO through Cu2Cl(OH)3 precursor and the electrochemical sensing property

An energy-efficient and environmentally friendly microwave-assisted method was adopted for synthesis of butterfly-like CuO assembled by nanosheets through a Cu₂Cl(OH)₃ precursor, using no template. Formation mechanism of the butterfly-like CuO was explored and discussed systematically for the first time on the basis of both experimental results and crystal structure transformations in atomic level. The electrochemical sensing properties of the butterfly-like CuO modified electrode to ascorbic acid (AA) were studied for the first time. The results reveal that Cu(OH)₂ nanowires were formed once the Cu²⁺ ions, located in between two CuO₄ parallelogram chains of a Cu₂Cl(OH)₃ precursor, dissolve into the solution as Cu(OH)₄²⁻ complex ions after ion exchange reactions and simultaneous assemble along a axis. Upon microwave irradiation, the adjacent CuO₄ parallelogram chains of the Cu(OH)₂ nanowires dehydrate and assemble along c axis, forming CuO nanosheets with (002) as the main exposed facet, which were further assembled to butterfly-like CuO under the action of microwave field, suggesting that microwave field functions like a ‘directing agent’. The butterfly-like CuO modified electrode shows good electrochemical sensing properties to AA with a low detecting limit, short response time and wide linear response range.     

偏压控制Cu2O和Cu在TiO2表面的生长及其光电化学性质

基于TiO₂/Ti 电极在含Cu²⁺溶液中的循环伏安图,调节电沉积的沉积电压,我们在TiO₂平整表面制备出Cu₂O和/或Cu颗粒. 通过扫描电镜（SEM）、X射线衍射（XRD）和X射线光电子能谱（XPS）表征,发现Cu₂O和Cu有不同的生长机制：Cu₂O颗粒在TiO₂表面分散结晶,而Cu颗粒是在已生长的颗粒上成核,从而形成堆积颗粒结构. 这是由于在Cu₂O/TiO₂界面和Cu/TiO₂界面形成不同的能带结构,使得电子的转移方式不同. 与纯TiO₂光阳极比较,可以观察到Cu₂O/TiO₂和Cu/TiO₂异质结构的光电流均有显著增强. 特别地,存在一个电压区间使得Cu₂O和Cu同时生长在TiO₂表面,此时对应的光电流比较稳定并且能达到最大. 紫外-可见（UV-Vis）漫反射光谱、电化学阻抗谱（EIS）和光电流-电压特性曲线均显示,Cu₂O和Cu明显有助于光的可见光吸收,同时Cu/TiO₂在光电转换过程中显示更宽波段的可见光利用率. 此外,开路电压的增加、有效的电荷分离和电极/电解质界面上载流子的快速迁移也增强了材料的光电化学性质.     

油溶性Cu纳米颗粒的两相法制备

在四氢呋喃-饱和氯化钠水溶液的两相体系中利用两相法化学合成了双正十六烷氧基二硫代磷酸(DDP)表面修饰的Cu纳米颗粒. 系统探讨了不同因素对制备Cu纳米颗粒的影响, 并采用透射电子显微镜(TEM)比较分析不同还原剂的用量、Cu^2＋浓度、修饰剂双正十六烷氧基二硫代磷酸铵盐(ADDP)和Cu^2＋的物质的量之比对Cu纳米颗粒粒径及分布的影响; 通过红外光谱仪(IR)、X射线粉末衍射仪(XRD)、X射线光电子能谱仪(XPS)等测试技术对优化条件下所合成的铜纳米颗粒进行了结构表征. 结果表明, 合成粒径细小、分布均匀的铜纳米颗粒的工艺条件为pH值在12左右, 反应温度高于30 ℃, 铜离子浓度小于0.05 mol•L^－1, NaBH₄与Cu^2＋的物质的量之比在8∶1到12∶1之间, ADDP和Cu^2＋的物质的量之比为2∶1和2.5∶1; 所制备的铜纳米颗粒是由无定形的金属Cu无机纳米核及通过化学键键合在其表面的DDP分子所组成, 并且修饰剂在反应前后结构没发生变化.     

Sonochemical Synthesis of Layered Copper Hydroxy Nitrate Nanosheets

Sonochemical reduction of copper nitrate, using 20 kHz ultrasound in aqueous solutions in the presence of urea, led to the formation of layered copper hydroxy nitrate nanosheets, as evidenced by scanning and transmission electron microscopy images. Fourier‐transform infrared, X‐ray diffraction, and X‐ray photoelectron spectroscopy analyses were used to characterize layered Cu₂(OH)₃NO₃ nanosheets. The ultrasound‐assisted progressive hydrolysis of urea and in situ formation of Cu(0) through the sonochemical reduction process induced homogeneous nucleation and crystallization of layered Cu₂(OH)₃NO₃ nanosheets.     

In Situ Fabrication of Inorganic/Organic Hybrid Based on Cu/Co‐ZIF and Cu2O

We successfully fabricate a well‐defined inorganic/organic hybrid Cu₂O@Cu/Co‐ZIF (ZIF=zeolitic imidazolate frameworks) by use of growth of dual‐metal Cu/Co‐ZIF on the obtained Cu₂O hollow spheres. The key point of the strategy is coupling the in situ self‐sacrificing template. Cu₂O and the coordination of metal ions (Cu⁺ and Co²⁺) with 2‐methylimidazole. This new hybrid was characterized by powder X‐ray diffraction, (scanning) transmission electron microscopy, energy‐dispersive spectroscopy mapping, in situ FT‐IR spectroscopy, UV/Vis diffuse reflection spectroscopy, N₂ sorption measurements, and electron spin resonance. It was evidenced that Cu/Co‐ZIF nanocrystals have been assembled to continuous shells surrounding the Cu₂O cores as well as in the voids between layers and inner pores. Cu₂O@Cu/Co‐ZIF exhibits visible light responsiveness and holds potential as narrow band gap semiconductor and visible photocatalyst.     

Structural properties of palladium nanoparticles embedded in inverse microemulsions

Pd nanoparticles were synthesized by reduction of palladium acetate by ethanol in systems containing tetrahydrofuran (THF) as dispersion medium and tetradodecylammonium bromide (TDABr) surfactant as stabilizer. The polar phase (ethanol) acts at the same time as reducing agent. THF/TDABr/H₂O inverse microemulsions containing micelles of various sizes were also prepared, and the structure of complex liquids was studied by density measurements. Sols containing nanosize Pd⁰ particles were synthesized within the water droplets of this micellar system. The stabilized Pd⁰/surfactant system was characterized by density measurements, absorption spectroscopy, and transmission electron microscopy. The stabilizing surfactant layer adsorbed on the liquid/liquid interface and on the surface of the nanoparticles (i.e., the liquid/solid interface) significantly reduced the excess volume for the palladium nanodispersion in organic solvent. Received: 17 July 2000 Accepted: 5 October 2000     

Surface characterization of CuSn thin films deposited by RF co‐sputtering method

CuSn thin films were deposited by the radio‐frequency (RF) magnetron co‐sputtering method on Si(100) with Cu and Sn metal targets with various RF powers. The thickness of the films was fixed at 200 ± 10 nm. The synthesized CuSn thin films mainly consisted of Cu₂₀Sn₆ and Cu₃₉Sn₁₁ phases, which was revealed by an X‐ray diffraction (XRD) study. The high‐resolution Cu 2p XPS and Cu LMM Auger electron spectra indicate that metallic Cu oxidized to Cu⁺ and Cu²⁺ as the RF power on Cu target increased. The atomic ratios of Sn⁰ and Sn⁴⁺ decreased, while that of Sn²⁺ increased with increasing RF power on the Cu target. The polar surface free energy (SFE) component has a different tendency in comparison with the total SFE and the dispersive SFE component. The dispersive SFE component was the dominating contributing factor to the total SFE compared with the polar SFE. Copyright © 2016 John Wiley & Sons, Ltd.     

六边形非化学计量比CuxS纳米片：合成、表征及电化学性质

分别采用乙二醇(EG)和聚乙烯吡咯烷酮(PVP)为溶剂和模板剂,用简单的回流方法合成六角型非化学计量比CuxS纳米片.并用X射线衍射(XRD)、透射电子显微镜(TEM)、紫外可见近红外光谱仪(UV-Vis)、循环伏安法(CV)对产物进行表征.TEM研究表明样品形貌为纳米六角片.XRD结果表明,随着Cu/S物质的量比的逐渐增加,样品物相从靛铜矿(covellite)CuS逐渐转变为蓝辉铜矿(digenite)Cu1.8S.此外,随着样品组分的变化,其光学和电化学性质均发生显著变化.     

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.     

Cu/活性炭催化剂：水合肼还原制备及催化甲醇氧化羰基化

以活性炭为载体,水合肼为还原剂制备了负载型Cu/活性炭催化剂,考察了水合肼/硝酸铜物质的量的比对催化甲醇气相氧化羰基化性能的影响,并采用XRD、XPS、H2-TPR和SEM等手段对催化剂进行了表征。结果表明,不加入还原剂水合肼时,催化剂中仅有CuO;随着水合肼/硝酸铜物质的量的比的增加,二价铜逐步被还原为Cu2O和/或单质Cu0,未被还原的Cu(OH)2在催化剂干燥过程中分解形成分散态CuO存在于催化剂表面。当水合肼/硝酸铜物质的量的比为0.75时,催化剂的催化性能最好,碳酸二甲酯的时空收率为120.62 mg.(g.h)-1,选择性为74.51%,甲醇转化率达到3.88%。在93 h反应时间内,催化剂都保持了较高的反应活性和选择性。此时铜物种以Cu2O和分散态CuO为主,Cu2O是主要的活性物种。     

Green synthesis of biologically active transition metal nanoparticles containing novel Schiff base via catalyst free hydrothermal reaction: Structural,biological and morphology study

Novel cobalt, nickel and copper complexes were synthesized by regular reflux method and nano sized Co(II), Ni(II) and Cu(II) metal complexes were synthesized by a facile hydrothermal method using green solvent at various temperatures without the addition of any capping agent. The structural characterization was done by magnetic susceptibility, molar conductance, elemental analysis, thermal analysis, FT‐IR, ¹H NMR, ¹³C NMR, ESI mass, UV–Visible analysis. The morphology and size of the nano metal complexes were determined using FE‐Scanning electron microscopy, powder X‐ray diffraction data and atomic force microscopic techniques. All the spectral and analytical results reveal 1:2 metal to ligand ratios having [ML₂(H₂O)₂] stoichiometry, here M=Co(II), Ni(II) and Cu(II), L=deprotonated ligand. The non‐electrolytic nature of the compound was confirmed by molar conductance experiment. The synthesized Schiff base and its metal complexes (7, 8 and 9) were tested for their biological activity. All the tested compounds exhibit decent anticancer and DNA cleavage activity and copper complex shows better activity results than other tested compounds.     

Selective synthesis of copper microsheets and ultralong microwires via a surfactant assisted hydrothermal process

The surfactant assisted hydrothermal process for selective preparation of copper nanosheets and ultralong microwires by reducing Cu²⁺ with 2-(bis-phosphonomethylamino)propionic acid (dpc) under the action of cetyltrimethylammonium bromide (CTAB) or polyvinyl pyrrolidine (PVP) is presented. X-ray powder diffraction (XRD) and energy dispersive X-ray analysis (EDX) indicate that the products are pure Cu of cubic phase. The effects of starting material concentration and reaction time on morphology of nanosheets have been studied by scanning electron microscopy (SEM). The presence of CTAB and PVP as capping agents is identified by EDX, transmission electron microscopy (TEM) and FT-IR. The possible growth process for ultralong microwires was studied by stopping the growth at a series of intermediate morphology stages based on SEM observations. Optical properties of Cu nanosheets and ultralong microwires were studied by UV-Vis spectrophotometry.     

Derivatives (Cu/CuO,Cu/Cu2O,and CuS) of Cu superstructures reduced by biomass reductants

Metallic Cu is considered as the promising functional material owing to its high conductivity and harmlessness. Here, metallic Cu which presents a unique interconnected and continuous structure (Cu superstructure) is prepared using Magnolia grandiflora leaves as the biomass reductant, a green process which avoided the release of harmful gases and massive energy consumption. What's more, Cu/CuO, Cu/Cu₂O, and CuS nanosheets with different sizes were fabricated using Cu superstructure as the substrate via facile methods, and the morphology is regulated by controlling the relevant factors. The electrochemical sensors based on the three derivations were fabricated to study the sensing performance of glucose. The unique structure of nanosheets encapsulating Cu superstructure guarantees the excellent conductivity of Cu/CuO and Cu/Cu₂O composites. Moreover, the electrochemical stability is improved owing to the nanosheet protective layer. Although no metallic Cu was maintained in CuS, the integrated multilayer nanosheets endow CuS with short channels for fast interlayer electronic transmission and with structural stability.