Simple Solution Route Research Articles

Facile synthesis of self-supported Mn3O4@C nanotube arrays constituting an ultrastable and high-rate anode for flexible Li-ion batteries

An anode of self-supported Mn3O4@C nanotube arrays has been fabricated by a simple solution route which shows superior electrochemical performance.

Efficiency enhancement in inverted planar perovskite solar cells by synergetic effect of sulfated graphene oxide (sGO) and PEDOT:PSS as hole transporting layer

We report a simple solution route for preparing a sGO-PEDOT composite HTL by combining solution-processable sGO with commercialized PEDOT:PSS solution. The PSCs based on these sGO-PEDOT composite HTLs were systematically investigated.

FeNi alloy supported on nitrogen-doped graphene catalysts by polyol process for oxygen reduction reaction (ORR) in proton exchange membrane fuel cell (PEMFC) cathode

A non-precious metal FeNi electrocatalyst (FeNi/NG) was prepared by a simple solution route called the polyol process for use as the oxygen reduction reaction (ORR) catalyst in polymer exchange membrane fuel cells. The nitrogen-doped graphene (NG) was synthesized from graphite oxide (GO) in a one-pot reactor via thermal annealing of GO-mixed melamine. The obtained NG presents high content of pyridinic-N and quaternary-N types with acceptable activity of ORR in acidic media by XPS and cyclic voltammetry techniques, respectively. The non-precious FeNi alloy nanoparticles (spherical-like nanoparticles mixed with hexagonal plate-like features) were successfully synthesized and well dispersed on the prepared NG by the polyol process confirmed by SEM-BSE and TEM analysis. The XRD and SAED results found FeNi and the carbon phase in the prepared catalysts. Finally, the CV technique shows that the peak potential of FeNi/NG is in the range of 0.12–0.34 V, which is close to that of the commercial Pt/C catalyst (0.35 V). To summarize, the obtained catalyst (FeNi/NG) revealed reliable electrocatalytic properties for ORR in a proton exchange membrane fuel cell cathode.

Operando Mössbauer Spectroscopy Investigation of the Electrochemical Reaction with Lithium in Bronze-Type FeF3·0.33H2O

The electrochemical reaction of bronze-type FeF3·0.33H2O, synthesized via a simple room-temperature solution route, with lithium was investigated by operando Mossbauer spectroscopy and X-ray diffraction. The two techniques revealed a complex electrochemical mechanism where the pristine crystalline compound is gradually transformed into an amorphous material containing nanodomains of a FeF2-like rutile structure mixed to iron nanoparticles. Upon charge, two steps are dominating the electrochemical behavior: partial reformation of the initial bronze structure and oxidation to Fe(III). This reaction mechanism, however, is not constant, and noticeable variation can be observed during galvanostatic cycling (up to 55 cycles) until eventually an amorphous material containing rutile nanodomains composes the final active electrode. The material performance, under the form of a fluoride/graphene oxide composite, is also assessed with respect to the long-term effect of the depth of first discharge.

Microwave Absorbing Properties of NiFe2O4 Nanosheets Synthesized Via a Simple Surfactant-Assisted Solution Route

NiFe2O4 nanosheets have been synthesized via a simple surfactant-assisted solution route, which are confirmed by X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. The NiFe2O4 sample exhibits the sheet-like structure, with width varying from 200 to 800 nm and thickness ranging from 20 to 60 nm. The electromagnetic properties of NiFe2O4 nanosheets-paraffin composites have been deeply investigated. The multiple dielectric relaxation loss in NiFe2O4 nanosheets is attributed to the size distribution and morphology of the NiFe2O4 nanosheets. The magnetic loss in the present system is caused mainly by the natural resonance. An absorber with a thickness of 4.3 mm exhibits an optimal reflection loss (RL) value of -47.1 dB at 7.67 GHz. RL values exceeding -20 dB in the 2.68-17.96 GHz range are obtained by choosing an appropriate absorption-layer thickness between 1.9 and 10 mm. Not only the RL peak frequency but also the number of the peaks can be well explained by the quarter-wavelength cancellation model.

Mesoporous WN/WO3-Composite Nanosheets for the Chemiresistive Detection of NO2 at Room Temperature

Composite materials, which can optimally use the advantages of different materials, have been studied extensively. Herein, hybrid tungsten nitride and oxide (WN/WO3) composites were prepared through a simple aqueous solution route followed by nitriding in NH3, for application as novel sensing materials. We found that the introduction of WN can improve the electrical properties of the composites, thus improving the gas sensing properties of the composites when compared with bare WO3. The highest sensing response was up to 21.3 for 100 ppb NO2 with a fast response time of ~50 s at room temperature, and the low detection limit was 1.28 ppb, which is far below the level that is immediately dangerous to life or health (IDLH) values (NO2: 20 ppm) defined by the U.S. National Institute for Occupational Safety and Health (NIOSH). In addition, the composites successfully lower the optimum temperature of WO3 from 300 °C to room temperature, and the composites-based sensor presents good long-term stability for NO2 of 100 ppb. Furthermore, a possible sensing mechanism is proposed.

Gas Sensors: Diverse Adsorption/Desorption Abilities Originating from the Nanostructural Morphology of VOC Gas Sensing Devices Based on Molybdenum Trioxide Nanorod Arrays (Adv. Mater. Interfaces 14/2016)

3D-network of ultra-fine single-crystal α-MoO3 nanorod array based gas sensors show a prompt response and discrimination to volatile organic compounds (VOCs). S. Cong, T. Sugahara, and co-workers illustrate that performance of the sensors strongly depends on the specific morphologies of the nanorod arrays, such as length, number and coverage of nanorods in the 3D network in the article 1600252. The nanorod arrays are spontaneously grown with functionally tunable morphology by a simple single-step solution route. The conductance modulation of the nanorod arrays is attributed to hydrogen ions decomposed from VOCs intercalated into the van de Waals's gaps of layered α-MoO3 and the subsequent reduction of cornered oxygen to H2O.

Cuboctahedral Sb2O3Mesocrystals Organized from Octahedral Building Blocks: More than Self-Similarity

Assembly of nanoparticle building blocks over multiple length scales into hierarchically ordered structures plays an essential role in the nonclassical crystallization pathway. Although random particle aggregates are constantly observed in crystallization experiments, mesocrystals with well-shaped morphology and ordered hierarchical structure have been seldomly reported. Here, we describe the successful production of remarkable cuboctahedral Sb2O3 mesocrystals with hierarchical three-dimensional superstructures through a simple solution route. This is the first example of well-defined polyhedral mesocrystals with a cuboctahedral external morphology differing from the octahedral morphology of the building subunits. Electrostatic interactions between cetyltrimethylammonium cations (CTA+) and tartrate anions and hydrophobic interactions between the cetyltrimethylammonium bromide tails were supposed to be the driving force for the aggregation-based growth process. This novel mesocrystal formation breaks through the classical crystallization pattern and opens up a new pathway to construct mesoscale-transformed mesocrystals with hierarchical superstructures.

Enhanced photoelectrochemical performance of novel p-type MoBiCuSe4 thin films deposited by a simple surfactant-mediated solution route

Nanostructured MoBiCuSe4 thin films with different morphologies deposited using different surfactants, such as PEG, SDS and TOPO, through a surfactant-mediated modified chemical route for PEC application.

Ambient synthesis of a multifunctional 1D/2D hierarchical Ag–Ag2S nanowire/nanosheet heterostructure with diverse applications

A new type of unique 1D/2D hierarchical Ag–Ag2S hybrids is fabricated by an extremely simple solution route under ambient conditions. The diffusion and Ostwald ripening processes dominate the evolution of heterostructure.

Amorphous Inorganic Electron-Selective Layers for Efficient Perovskite Solar Cells: Feasible Strategy Towards Room-Temperature Fabrication.

Inorganic electron-selective layers (ESLs) are fabricated at extremely low temperatures of 70°C or even 25°C by a simple solution route. This is of great significance because the attained PCEs confirm the feasibility of room-temperature coating of inorganic amorphous ESLs through a solution method for the first time.

The preparation of a Eu3+-doped ZnO bi-functional layer and its application in organic photovoltaics

Recently, spectra conversion has been used to minimize energy loss in photovoltaic devices. In this work, we explore the development of a novel Eu3+-doped ZnO bi-functional layer for use in organic solar cells. The bi-functional layer acts as both a spectra conversion and an electron transporting layer. Compared to conventional spectra conversion layers, it has a simpler device structure, is easier to fabricate, and has a wider spectrum-sensitized region. A series of Eu3+-doped ZnO nanocrystals were synthesized using the simple solution route. X-ray powder diffraction patterns (XRD), transmission electron microscopy (TEM), and UV-visible absorbance spectra were used to characterize the obtained ZnO nanocrystals. The results reveal that the size and bandgap of ZnO nanocrystals can be controlled through regulation of the doping concentration of Eu3+ ions. The energy transfer of ZnO → Eu3+ is observed by photoluminescence (PL) spectra. At a bandgap excitation of around 300–400 nm, a typical emission band from the Eu3+ is obtained. By employing the Eu3+- doped ZnO nanocrystals as a buffer layer in a P3HT:PC61BM bulk heterojunction device, the obtained performance is similar to the undoped ZnO device, indicating that the electrical properties of ZnO are not affected by Eu3+ doping. Due to the down-conversion energy transfer between ZnO and Eu3+, the external quantum efficiency of the ZnO:Eu3+ device at 300–400 nm is higher than that of the pure ZnO device, which subsequently leads to an increase in short circuit current density (JSC). This work proves that it is possible to improve the solar spectrum response in the ultraviolet region of organic solar cells effectively by incorporating the bi-functional layer.

Wet chemistry synthesis of ZnO crystals with hexamethylenetetramine(HMTA): Understanding the role of HMTA in the formation of ZnO crystals

ZnO crystals have been prepared via a simple aqueous solution route using zinc acetate-hexamethylenetetramine (HMTA) solution. To understand the role of HMTA in the formation processes of ZnO crystals, concentration measurements of Zn(II) remaining in the solution as well as SEM and XRD analyzes of the solid product have been made at regular intervals. The results demonstrated that the HMTA concentration has determinative effects on the growth rate of obtained ZnO products by controlling the composition of zinc complex species and mediating the transformation rate of building blocks. XRD results revealed the single phase nature with the wurtzite structure of the as prepared ZnO rods. X-ray photoelectron spectroscopy confirmed high purity of the ZnO rods. By varying the concentration of HMTA in the solution, the average size of rods was varied from 5μm to 10μm. Photoluminescence spectra indicated that the photoluminescent intensity of the emission peak at 380nm increase to different degree with increasing HMTA concentration. These results revealed that the concentration of HMTA plays a vital role to control the properties of ZnO crystals.

Preparation of α-Fe2O3/ZnO composites and their photocatalytic activity under simulated sunlight irradiation

Using only zinc nitrate, ferric nitrate and sodium hydroxide as reactants, rod-like and flower-like α-Fe2O3/ZnO composites were prepared via a simple and rapid solution route by controlling the composition of precursor solution. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and UV-vis diffuse reflectance spectra (UV-vis DRS). Photocatalytic activity of the as-prepared α-Fe2O3/ZnO composites was evaluated by degradation of methyl orange (MO) under simulated solar light. The results indicated that both α-Fe2O3/ZnO composites possess higher photocatalytic activity than commercial P25 TiO2. In addition, possible reasons why α-Fe2O3/ZnO composites have excellent photocatalytic performance were discussed.

Nano Copper Powders Synthesized by a Polymer Solution Method at Low Temperature.

Copper (Cu) nano particles were successfully fabricated at a significantly low temperature through a simple polymer solution route. In the process, the organic-inorganic precursor sols were turned to porous gels exhibiting volume expansion during the drying process. The PVA polymer, as an organic carrier, contributed to make an atom-scale homogeneous copper precursor gel, which resulted in fully crystallized, nano-sized copper powders through a low calcination temperature of 300 °C under Ar-4%H2 atmosphere. Variations in the processing technique, such as the content of PVA and calcination temperature, affected the microstructure and crystallization behavior of the synthesized powders. The copper powder synthesized with the PVA content of 4:1 ratio showed a crystallite size of about 10 nm or less with a high surface area. In this paper, the PVA solution technique for the fabrication of a nano-sized copper powder is introduced. The effects of the PVA content and calcination conditions on the powder morphology and crystallization are also studied. The characterization of the synthesized powders is conducted by using XRD, DTA/TG, SEM and TEM.

One dimensionally spinel NiCo2O4 nanowire arrays: facile synthesis, water oxidation, and magnetic properties

Development of efficient, affordable, non-precious metal oxides catalysts is critical for the oxygen evolution reaction (OER). Herein, we present a spinel NiCo2O4 nanowire arrays (NWAs), synthesized by a simple solution route, as an inexpensive, efficient anode electrocatalyst for water electrolysis. The as-prepared NiCo2O4 NWAs contains Ni2+/Ni3+ which replace Co in octahedral sites of the spinel Co3O4, exhibiting higher catalytic activity than that of Co3O4 and NiO. The enhanced catalytic activity of NiCo2O4 NWAs is correlated with a large surface area, one-dimensional (1D) architecture, high conductivity and synergistic behavior of Ni/Co bifunctional catalyst. Besides, oxygen vacancies, which favor efficient electrons transport, supply more active sites, and assist in the adsorption of OH−, can be conducive to make high utilization of catalytic materials in the OER. Moreover, the magnetic properties of NiCo2O4 NWAs are also investigated in detail. The results indicate that NiCo2O4 NWAs could be a promising economical and environmentally benign bifunctional electrocatalyst for water splitting and other applications.

Facile synthesis of ZnAl-layered double hydroxide microspheres with core–shell structure and their enhanced adsorption capability

We have developed a simple solution route for the synthesis of hierarchical ZnAl-layered double hydroxide (ZnAl-LDH) microspheres with core–shell structure, which have great practical application as the efficient adsorbent for wastewater purification. The evolution of the morphology with time suggests that the hierarchical ZnAl-LDH microspheres formed by a stepwise growth mechanism. The results demonstrate that the as-prepared ZnAl-LDH microspheres exhibit more excellent adsorption capacity (523mg/g) towards methyl orange in aqueous solutions as compared with the LDH microspheres previously reported, result of which is attributed to their enhanced surface area and suitable mesopore distribution. This work provides a promising approach for the synthesis of hierarchical porous materials with excellent adsorption capacity, which can be potentially used in wastewater treatment.

α-Fe2O3 modified ZnO flower-like microstructures with enhanced photocatalytic performance for pentachlorophenol degradation

Novel α-Fe2O3 modified ZnO flower-like microstructures were successfully prepared via a simple and rapid solution route with different α-Fe2O3 contents. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV–vis diffuse reflectance spectra (UV–vis DRS) and N2 adsorption/desorption. Photocatalytic activity of the as-prepared α-Fe2O3/ZnO composites was evaluated by degradation of pentachlorophenol (PCP) under simulated solar light. The results indicated that α-Fe2O3/ZnO composites showed higher photocatalytic activity than pure ZnO. The optimum photocatalytic activity of α-Fe2O3/ZnO composite with molar ratio of 1:7 was nearly 2 times as high as that of pure ZnO. The remarkably increased performance of α-Fe2O3/ZnO was mainly attributed to the synergistic effect between α-Fe2O3 and ZnO. In addition, the α-Fe2O3/ZnO composites also showed excellent circulation stability.

Preparation of surface-modified ZnO quantum dots through an ultrasound assisted sol–gel process

A synthetic process of zinc oxide quantum dots (QDs) is presented. It is based on a sol–gel process, carried out in an ultrasonic bath. It allows the formation of the stable colloids, containing surface-modified ZnO QDs with the aid of 3-aminopropyltriethoxysilane (APTES) as a capping agent. For this purpose, alcoholic solutions of zinc acetate dihydrate and potassium hydroxide were used as the reactants. Effect of KOH concentration, ultrasonic irradiation, and also the presence of capping agent on the characteristics of the final product were investigated. The synthesized samples were characterized by various analytical techniques such as XRD, TEM, FT-IR, UV–vis and PL spectroscopy. XRD analysis revealed the direct formation of hexagonal wurtzite nanocrystals with average size of ∼3nm confirmed by TEM and UV–vis spectroscopy. The PL spectroscopy indicated the influence of the capping agent on reducing the defects formation during the growth of the QDs. The present synthesis method was found to be a cost-effective and simple solution route for producing pure semiconductor ZnO QDs, exhibiting the quantum confinement effects, suitable for optical and optoelectronic applications.

Simulated monazite crystalline wasteform La0.4Nd0.1Y0.1Gd0.1Sm0.1Ce0.1Ca0.1(P0.9Mo0.1O4): Synthesis, phase stability and chemical durability study

In this work, incorporation of hexavalent molybdenum and selected trivalent lanthanides using divalent calcium as charge compensator into the monazite structure were studied. Rare earth substituted phosphomolybdates of the formula REE0.9Ca0.1P0.9Mo0.1O4 (REE=Ce, Nd, Sm, Gd) and the wasteform La0.4Nd0.1Y0.1Gd0.1Sm0.1Ce0.1Ca0.1P0.9Mo0.1O4 were synthesized by simple solution route. The prepared compounds were characterized by powder X-ray diffraction, Fourier transformed infrared spectra, thermogravimetric analysis, energy dispersive X-ray analysis and scanning electron microscopic techniques. Chemical durability of the wasteform was studied by dynamic MCC-5 test for a period of one month. Normalized elemental mass loss and leach rate of molybdenum was found to be in the order of 103g/m2 and 103–101g/m2/d respectively. Polymer-monazite composite wasteform was prepared to control the leaching of molybdenum. The composite approach reduced molybdenum leach rate order from 101 to 10−4g/m2/d.