Chemical Solution Route Research Articles

Near-infrared broadly emissive AgInSe2/ZnS quantum dots for biomedical optical imaging

Highly luminescent AgInSe2/ZnS core/shell quantum dots (AISe/ZnS QDs) have been synthesized via a facile low-temperature solution chemistry route. The as-prepared core/shell QDs have a narrow size distribution, and exhibit composition-tunable photoluminescence (PL) emission in the near-infrared (NIR) range from 700 to 820 nm with a maximum PL quantum yield (QY) of 40%. By using the poly(acrylic acid)–octylamine (PAA-based) amphiphilic polymer, these oil-soluble AISe/ZnS core/shell QDs could be effectively solubilized in water, while retaining their initial morphology, crystal structure and PL properties. Importantly, the results from animal and cell experiments confirm that these highly luminescent, broadly emissive AISe/ZnS QDs are new promising fluorescent probes for biomedical optical imaging (namely, in vivo animal and in vitro cell imaging), as an alternative for Cd-, Hg- and Pb-based QDs and organic dyes.

Structural and Multiferroic Properties of Bi3.4La0.6Ti3O12/CoFe2O4 Composite Thin Films

Bi3.4La0.6Ti3O12 and CoFe2O4 were synthesized by chemical solution route, and Bi3.4La0.6Ti3O12/CoFe2O4 multilayers were deposited by spin coating on Pt substrate. X-ray diffraction of multilayer structures reveals composite-like polycrystalline film. Leakage current is less than 10−5 A at electric field < 90 KV/cm and follows the Ohmic behavior. Dielectric response shows relaxation and the loss (tan δ) is below 3% at 106 Hz. Room temperature ferrroelectric polarization (Pr) = 20.2 μC/cm2 and ferromagnetic memory (Mr) = 46.5 emu/cm3 has been obtained. Co-existence of FE and FM response can be attributed to stress and different permeability and permittivity involved in multilayer structures.

Synthesis and enhanced properties of cerium doped ZnO nanorods

Pure and 1mol% Ce doped ZnO nanoparticles were synthesized by the wet chemical solution route. Ce doping shifted XRD peaks to a slightly higher angle. Transmission electron microscopy revealed the rod type morphology of both the nanoparticles with decrease in length and diameter of Ce doped ZnO in the range of 80–120nm and 16–20nm, respectively. A sharp lower cutoff at 190nm and reduction in the bandgap from 3.22eV to 3.08eV were observed in UV–vis study. Ce3+ doping resulted in the broadening of the green emission photoluminescence band. An enhanced ionic behavior in doped ZnO resulted in a significant increase in dielectric constant (ε=368), piezoelectric coefficient (d33=30pC/N) and ferroelectric properties (Pr=40μC/cm2 ). Rectifying I–V characteristics were observed for both the nanoparticles.

Rapid Solution Chemistry Approach for Synthesizing Mo6S8 Chevrel Phase Cathode for Rechargeable Magnesium Battery

Recently, energy storage systems based on bivalent Mg2+ ions spurred considerable interest as a promising high energy density alternative battery system among others [1, 2]. Magnesium (Mg) has several positive attributes which set it apart from Li-ion battery system. It is environmental friendly, cost effective (~$ 2700/ton for Mg compared to $64,000/ton for Li) and is relatively more abundant in the earth’s crust (~13.9% Mg compared to ~0.0007% of Li) compared to hitherto used popular systems. Additionally, magnesium is more stable in air compared to lithium, and is theoretically capable of rendering higher volumetric capacity (3832 mAh/cc for Mg vs. 2062 mAh/cc for Li).In the year 2000, Aurbach and coworkers successfully demonstrated a prototype Mg cell using the Mo6S8 Chevrel Phase a new class of cathodes, Mg anode, and the 0.25 molar Mg(AlCl2EtBu)2/tetrahydrofuran electrolyte where Mg2+ can be (de)intercalated reversibly ~ 1-1.2V offering an energy density ~ 60 Whkg-1 up to 2000 cycles with little fade in capacity [3]. Relatively fast and easy intercalation of Mg2+ ions at room temperature makes Mo6S8 a model cathode for magnesium battery. However, Mo6S8 is a metastable phase at room temperature, and is therefore indirectly stabilized when generated via leaching of the metal from the thermodynamically stable ternary Chevrel phase compounds, MxMo6T8 (M = metal, T = S, Se, Te) [4]. Typical synthesis approach of CuxMo6S8 (CuxCP) requires high temperature reactions of elemental blends in an evacuated quartz ampoules (EQA) at ~1150○C for 7 days [3] or by a molten salt (MS) route using Mo-MoS2-CuS reactants in a KCl salt, and heat treating the reaction mixtures at ~850○C for 60h in an Ar atmosphere [5]. Both approaches are extremely tedious and require chemical leaching either in 6 molar HCl/H2O or 0.2 molar I2/acetonitrile solutions for several days at room temperature for complete removal of copper [5].Herein, we report a rapid solution chemistry route (total manufacturing time required for the synthesis of CP is only ~12h) for the synthesis of Mo6S8 following modification of a previous report [6] which only reported the synthesis of the Cu analog of the Mo6S8 phase. The structural analysis (XRD and SEM) shows the formation of phase-pure micrometer (~1-1.5 mm) size cuboidal shaped Cu2Mo6S8 and Mo6S8 crystals [See Fig. 1(a-d)]. Electrochemical performance of the resultant Mo6S8 cathode exhibits a discharge capacity ~ 76 mAhg-1 with excellent capacity retention up to ~100 cycles, when cycled at a current rate of 20mA/g (~C/6). The excellent cyclability, rate capability and high Coulombic efficiency (~99.3% at ~1.C rate) of the Mo6S8 cathode, renders the solution chemistry route a convenient approach for synthesizing the electrochemically active model Chevrel phase Mo6S8. Results of these studies will be presented and discussed.

3D Branched ZnO Nanowire Arrays Decorated with Plasmonic Au Nanoparticles for High-Performance Photoelectrochemical Water Splitting

Plasmonic photoelectrochemical (PEC) water splitting is very promising in the conversion of abundant solar energy into chemical energy. However, the solar-to-hydrogen efficiencies reported so far are still too low for practical use, which can be improved by optimizing the design and synthesis of individual blocks (i. e., the compositions, sizes, shapes of the metal and the coupling semiconductors) and the assembly of these blocks into targeted three-dimensional (3D) structures. Here, we constructed a composite plasmonic metal/semiconductor photoanode by decorating gold nanoparticles (Au NPs) on 3D branched ZnO nanowire arrays (B-ZnO NWs) through a series of simple solution chemical routes. The 3D ordered Au/B-ZnO NWs photoanodes exhibited excellent PEC activities in both ultraviolet and visible region. The improved photoactivities in visible region were demonstrated to be caused by the surface-plasmon-resonance effect of Au NPs. The photoconversion efficiency of Au/B-ZnO NWs photoanode reached 0.52% under simulated sunlight illumination. This is a high value of solar-to-hydrogen efficiencies reported till nowadays for plasmonic PEC water splitting, which was mainly benefit from the extensive metal/semiconductor interfaces for efficient extraction of hot electron from Au NPs and excellent charge-carries collection efficiency of the 3D ordered Au/B-ZnO NWs photoelectrode.

Synthesis and characterization of Lanthanum doped Bismuth Ferrite

B1-xLaxFeO3 (x = 0.0, 0.025) crystallites were prepared by chemical solution route. XRD analysis confirmed the phase formation of the materials. Thermal characterization was done by DSC-TGA to confirm crystallization and thermal behavior for phase development. Morphological studies by FESEM showed the agglomerated nature of the ferrite and EDX analysis confirmed the degree of doping. FTIR studies were done to determine the molecular signature of both undoped and doped sample.

Chemical solution route to synthesize claw-like ZnO nanorod array and its optical properties

By using a low-cost and facile hydrothermal method, a peculiar claw-like ZnO nanorod array is successfully synthesized. The hydrothermal growth is done in an aqueous solution with equimolar zinc acetate (ZAc, Zn(CH3COO)2·2H2O) and hexamethylenetetramine (HMTA, C6H12N4). The obtained ZnO nanorod array is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that the nanorods are high-quality monocrystals. The photoluminescence (PL) spectrum is performed to investigate the optical properties of this product.

Controlled Synthesis and Catalytic Activity of Copper Sulfide Nanostructured Assemblies with Different Morphologies

A simple, template-free and mild solution chemistry route was employed to synthesize diverse copper sulfide (CuS) nanostructured assemblies at 70 °C by varying the solvent (water or ethylene glycol, or their ratios (3:1, 1:1 and 1:3)). The CuS structures in the shape of spheres and nanotubes were found to be assemblies of either nanoplates or nanoparticles. The nanotube formation was elaborately studied by varying the synthesis parameters such as temperature, reaction duration, precursor's ratio, and counterions. Counterions such as NO3(-) and SO4(2-) were found to be suitable for nanotube formation whereas in the presence of Cl(-) and OAc(-) ions, CuS flake-like and nanoparticle assemblies are obtained, respectively. The optical bandgaps for the CuS with different morphologies were measured to be in the range of 1.88-2.16 eV. The bandgap of CuS in the visible region of electromagnetic radiation prompted it to be used as photocatalyst in the past under natural light. However, we demonstrate here the similar catalytic performance of as-synthesized CuS nanostructures for the degradation of methylene blue in the dark, suggesting that light does not play a role in its catalytic behavior.

A Convenient Approach to Mo6S8 Chevrel Phase Cathode for Rechargeable Magnesium Battery

A two-step solution chemistry route was used to synthesize ternary Chevrel phase (Cu2Mo6S8) with 5 h annealing at 1000°C under reducing atmosphere. The approach marks a synthesis route different from hitherto described conventional solid-state methods. X-ray diffraction and scanning electron micrograph shows the formation of ∼1–1.5 μm size cuboidal shape Cu2Mo6S8 crystals with unit cell dimensions a ∼ 0.96245 nm and c ∼ 1.01987 nm of molar volume ∼818.14 × 10−3 nm3. De-cuprated Mo6S8 exhibits a discharge capacity ∼76 mAhg−1 with good capacity retention up to ∼50 cycles when cycled at the current rate of 20 mA/g (∼C/6). The excellent rate capability and high Coulombic efficiency (∼99.3% at ∼1.5C rate) of the Mo6S8 cathode renders the solution chemistry route an alternative approach for the synthesis of cuprated Chevrel phase: a known cathode system for magnesium battery.

Chemical solution route to self-assembled epitaxial oxide nanostructures

Self-assembly of oxides as a bottom-up approach to functional nanostructures goes beyond the conventional nanostructure formation based on lithographic techniques. Particularly, chemical solution deposition (CSD) is an ex situ growth approach very promising for high throughput nanofabrication at low cost. Whereas strain engineering as a strategy to define nanostructures with tight control of size, shape and orientation has been widely used in metals and semiconductors, it has been rarely explored in the emergent field of functional complex oxides. Here we will show that thermodynamic modeling can be very useful to understand the principles controlling the growth of oxide nanostructures by CSD, and some attractive kinetic features will also be presented. The methodology of strain engineering is applied in a high degree of detail to form different sorts of nanostructures (nanodots, nanowires) of the oxide CeO2 with fluorite structure which then is used as a model system to identify the principles controlling self-assembly and self-organization in CSD grown oxides. We also present, more briefly, the application of these ideas to other oxides such as manganites or BaZrO3. We will show that the nucleation and growth steps are essentially understood and manipulated while the kinetic phenomena underlying the evolution of the self-organized networks are still less widely explored, even if very appealing effects have been already observed. Overall, our investigation based on a CSD approach has opened a new strategy towards a general use of self-assembly and self-organization which can now be widely spread to many functional oxide materials.

Studies of the fine-grain sub-layer in the printed CZTSSe photovoltaic devices

Cu2ZnSn(S, Se)4 (CZTSSe) is a promising low-cost and earth-abundant photovoltaic (PV) absorber material. Using binary and ternary chalcogenide nanoparticles as precursors, we have developed a chemical solution route to produce CZTSSe PV devices with the device efficiency as high as 8.8%. The cross-sectional view of the CZTSSe film shows an interesting bilayer microstructure which consists of an upper micrometer-sized polycrystalline (large-grain) layer and a lower layer with a dense, smooth bottom amorphous (fine-grain) morphology. In this paper, we present the composition and properties of the layers and our understanding on the fine-grain layer's impact on the device performance. Based on the observed optoelectronic properties, a numerical model for the CZTSSe-based PV device is developed, and the simulation results show that the fine-grain layer does not affect the device's performance. An experimental design of CZTSSe PV devices with different thicknesses of the fine-grain layers has also confirmed our findings.

Multifunctional polymer–metal nanocomposites via direct chemical reduction by conjugated polymers

Noble metal nanoparticles (MNPs) have attracted continuous attention due to their promising applications in chemistry, physics, bioscience, medicine and materials science. As an alternative to conventional solution chemistry routes, MNPs can be directly synthesized through a conjugated polymer (CP) mediated technique utilizing the redox chemistry of CPs to chemically reduce the metal ions and modulate the size, morphology, and structure of the MNPs. The as-prepared multifunctional CP-MNP nanocomposites have shown application potentials as highly sensitive surface enhanced Raman spectroscopy (SERS) substrates, effective heterogeneous catalysts for organic synthesis and electrochemistry, and key components for electronic and sensing devices. In this tutorial review, we begin with a brief introduction to the chemical nature and redox properties of CPs that enable the spontaneous reduction of noble metal ions to form MNPs. We then focus on recent progress in control over the size, morphology and structure of MNPs during the conjugated polymer mediated syntheses of CP-MNP nanocomposites. Finally, we highlight the multifunctional CP-MNP nanocomposites toward their applications in sensing, catalysis, and electronic devices.

Solution-Chemical Route to Generalized Synthesis of Metal Germanate Nanowires with Room-Temperature, Light-Driven Hydrogenation Activity of CO2 into Renewable Hydrocarbon Fuels

A facile solution-chemical route was developed for the generalized preparation of a family of highly uniform metal germanate nanowires on a large scale. This route is based on the use of hydrazine monohydrate/H2O as a mixed solvent under solvothermal conditions. Hydrazine has multiple effects on the generation of the nanowires: as an alkali solvent, a coordination agent, and crystal anisotropic growth director. Different-percentage cobalt-doped Cd2Ge2O6 nanowires were also successfully obtained through the addition of Co(OAc)2·4H2O to the initial reaction mixture for future investigation of the magnetic properties of these nanowires. The considerably negative conduction band level of the Cd2Ge2O6 nanowire offers a high driving force for photogenerated electron transfer to CO2 under UV-vis illumination, which facilitates CO2 photocatalytic reduction to a renewable hydrocarbon fuel in the presence of water vapor at room temperature.

Sunlight photocatalytic activity enhancement and mechanism of novel europium-doped ZnO hierarchical micro/nanospheres for degradation of phenol

Europium-doped ZnO hierarchical micro/nanospheres (Eu/ZnO) were synthesized for the first time via a facile and surfactant-free chemical solution route. The as-synthesized products were characterized by X-ray diffraction, field-emission scanning electron microscopy, energy dispersion X-ray analysis, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV–visible diffuse reflectance spectroscopy, nitrogen adsorption–desorption and photoluminescence spectroscopy. The results showed that the as-synthesized products were well-crystalline and accumulated by large amount of interleaving nanosheets. It was also observed that the Eu doping increased the light absorption ability of Eu/ZnO and a red shift for Eu/ZnO appeared when compared to pure ZnO. Under natural sunlight irradiation, the Eu/ZnO exhibited much higher photocatalytic activity than those of pure ZnO, Eu-doped ZnO nanorods (Eu/ZNRs) and commercial TiO2 for the degradation of phenol. The photocatalytic enhancement of Eu/ZnO products was attributed to their high charge separation efficiency and hydroxyl radical generation ability as evidenced by the photoluminescence spectra. By using several radical scavengers, hydroxyl radical was determined to play a pivotal role for the phenol degradation. Furthermore, the Eu/ZnO could be easily separated and reused, showing great potential for practical applications in environmental cleanup and solar energy conversion.

Graphene and N-Doped Graphene Coated with SnO2 Nanoparticles as Supercapacitor Electrodes

In this work, both graphene and nitrogen-doped graphene coated with SnO2 nanoparticles were synthesized through a chemical-solution route, graphene-based thin films were prepared by a blade coating method, and solid-state supercapacitors were fabricated employing graphene-based films and polyvinyl alcohol (PVA)-H3PO4 gel as electrodes and electrolyte, respectively. Scanning electron microscopy was used to characterize the morphology of the obtained graphene based films. Energy dispersive X-ray and X-ray diffraction analyses were carried out to investigate the composition and crystal structure of the as-obtained graphene based materials. The electrochemical performance of the as-fabricated supercapacitors was measured using cyclic voltammetry. Thermo gravimetric analysis was conducted to study the thermal stability of the added polymer (acrylic resin) during heat treatment.

Facile synthesis of highly luminescent Mg(II), Cu(I)-codoped CdS/ZnSe core/shell nanoparticles

Magnesium and copper doped CdS/ZnSe (core/shell) nanoparticles were synthesized through direct chemical solution routes in organic solvent. X-ray powder diffraction (XRD) pattern confirmed the mixing of cubic and wurtzite structures. The Mg or Cu-doped CdS shows the obvious blue shift of photolumimescent spectra due to the replacement of Cd ions with Mg or Cu ions. However, the concomitant presence of Mg and Cu, emission peaks relatively shifts to the red range in comparison with that of Cu-doped CdS. The photoluminescent intensity of CdS:Mg,Cu/ZnSe are much higher than that of the undoped CdS and CdS/ZnSe. The PL intensities were also strongly affected by the presence of octadecylamine and increased more than 4 times. The dopant ions, Mg and Cu, play an important role in energy transfer in the lattice. The results shows that CdS:Mg,Cu/ZnSe NPs give not only the luminescences in various region but also the excellent properties of CdS/ZnSe.

Shape and Size Tunable Synthesis of Coordination Polymer Mn2W(CN)8·xH2O Microcrystals through a Simple Solution Chemical Route

AbstractBy using a simple solution chemistry approach with polyvinyprrolidone (PVP) as a capping agent, Mn2W(CN)8·xH2O microcrystals with unique morphologies including rice‐like, rod, octahedron, square platelet, and hollow‐core square platelet have been successfully synthesized. The influence of experimental parameters such as reaction temperature, feed ratio of Mn2+ to PVP, reaction time, and reactant concentration on the morphology and size of Mn2W(CN)8·xH2O microcrystals were systematically investigated. The reaction temperature proved to be a key factor for morphological evolution of the products. It was found that 20, 55, and 85 °C were key points of morphological transformation. A possible growth mechanism of the Mn2W(CN)8·xH2O microcrystals is proposed.

Facile synthesis of porous ZnO nanowires consisting of ordered nanocrystallites and their enhanced gas-sensing property

Porous ZnO nanowires were obtained by a facile chemical solution route combined with subsequent calcination. Calcination of the precursors produced porous ZnO nanowires, which consist of numerous ordered nanocrystallites with high porosity resulting from the thermal decomposition of the as-prepared precursors, i.e., wire-like zinc hydroxide carbonate. Moreover, the nanostructures were characterized through X-ray diffraction, field emission scanning electron microscopy, thermogravimetric-differential thermal analysis, and Brunauer–Emmett–Teller N2 adsorption–desorption analyses, among others. The BET surface area of the porous ZnO nanowires can be calculated to be 39.1m2g−1. Furthermore, the gas sensing properties of the as-prepared porous ZnO nanowires were investigated using volatile organic compounds. Compared with the ZnO monocrystalline nanowires, the porous ZnO nanowires exhibited higher response with certain organic vapors, such as toluene, 2-propanol, and acetone. The responses to 100ppm toluene, 2-propanol and acetone were 29.1, 53.7, and 57.2, respectively, at a working temperature of 300°C. These results showed that the porous ZnO nanowires consisting of nanocrystallites are highly promising candidates for gas sensing applications.

Self-assembly fabrication of ZnO hierarchical micro/nanospheres for enhanced photocatalytic degradation of endocrine-disrupting chemicals

ZnO hierarchical micro/nanospheres were successfully synthesized via a facile and surfactant-free chemical solution route. The field emission scanning electron microscopy and transmission electron microscopy observations showed that the ZnO micro/nanospheres were assembled by large amounts of interleaving nanosheets with the thickness of about 17nm. The X-ray diffraction, energy dispersion X-ray and Raman results revealed that the as-synthesized products were well-crystalline and possessing wurtzite hexagonal phase pure ZnO. Under UV irradiation, the ZnO micro/nanospheres showed an enhanced photocatalytic performance compared with the ZnO nanorods and commercial TiO2 in the degradation of phenol. The photocatalytic enhancement of ZnO micro/nanospheres was attributed to their unique hierarchical porous surface structure and large surface area which can enhance the electron–hole separation and increased the yield of hydroxyl radical quantities as evidenced by the photoluminescence spectra. By using a certain of radical scavengers, hydroxyl radical was determined to play a pivotal role for the phenol degradation. Moreover, the as-synthesized ZnO micro/nanospheres could be easily recycled without any significant loss of the photocatalytic activity. Other endocrine-disrupting chemicals such as resorcinol, bisphenol A and methylparaben were also successfully photodegraded under identical conditions. These characteristics showed the practical applications of the ZnO micro/nanospheres in environmental remediation.

Photocatalytic performance of novel samarium-doped spherical-like ZnO hierarchical nanostructures under visible light irradiation for 2,4-dichlorophenol degradation

A novel samarium-doped spherical-like ZnO hierarchical nanostructure (Sm/ZnO) was synthesized via a facile and surfactant-free chemical solution route. The as-synthesized products were characterized by X-ray diffraction, Brunauer–Emmett–Teller surface area analysis, field emission scanning electron microscopy together with an energy dispersion X-ray spectrum analysis, transmission electron microscopy, UV–visible diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The results revealed that Sm ion was successfully doped into ZnO. It was also observed that the Sm doping increased the visible light absorption ability of Sm/ZnO and a red shift for Sm/ZnO appeared when compared to pure ZnO. The photocatalytic studies revealed that the Sm/ZnO exhibited excellent photocatalytic degradation of 2,4-dichlorophenol (2,4-DCP) compared with the pure ZnO and commercial TiO2 under visible light irradiation. The photocatalytic enhancement of Sm/ZnO products was attributed to their high charge separation efficiency and OH generation ability as evidenced by the photoluminescence spectra. The photocatalytic investigation also showed that various parameters exerted their individual influence on the degradation rate of 2,4-DCP. By using a certain of radical scavengers, OH was determined to play a pivotal role for the 2,4-DCP degradation. Moreover, the Sm/ZnO could be easily separated and reused, indicating great potential for practical applications in environmental cleanup.