Solvothermal System Research Articles

Fabrication of hollow-sphere films of wurtzite CuInS2 on copper substrate

As important semiconductors, I–III–VI2 compounds have attracted wide attention, among which the wurtzite structured CuInS2 has been the research focus due to its metastable phase. In this paper, the wurtzite CuInS2 hollow-sphere films have been successfully prepared on copper substrate in a self-designed solvothermal detached system. The films of Cu(OH)2 one-dimensional nanostructure arrays and thioacetamide were used as the precursors and triethylene glycol was used as the solvent. Experiments showed that the amount of indium trichloride played a determinative role in the final morphology of the products. Meanwhile, the one-dimensional nanostructure arrays and the detached solvothermal system have great influences on the crystal shape as well. Based on the experimental results, a possible formation mechanism for the CuInS2 hollow spheres was also proposed. The UV–Vis absorption spectrum showed a broad absorption over the entire visible light and extending into the near-infrared region and presented the band gap of 1.53 eV for the as-prepared wurtzite CuInS2, which indicates the potential applications in solar cells.

Synthesis of magnetic ZnFe2O4/graphene composite and its application in photocatalytic degradation of dyes

Magnetic ZnFe2O4/graphene composite (ZnFe2O4/G) has been successfully synthesized by a facile one-pot solvothermal method. Graphene oxide (GO) was reduced to graphene and the ZnFe2O4 particles were simultaneously grown on the graphene sheets under the conditions generated in the solvothermal system. Importantly, the ZnFe2O4/G composite showed powerful visible-light-photocatalytic activity for the degradation of Rhodamine B (RhB), methyl orange (MO) and methylene blue (MB) in the presence of H2O2. The ZnFe2O4/G composite serves a dual function as the catalyst for photoelectrochemical degradation of dyes and the generator of a strong oxidant hydroxyl radical (OH) via photoelectrochemical decomposition of H2O2 under visible light irradiation. ZnFe2O4/G composite has excellent magnetic properties, which makes it magnetically recyclable in a suspension system. Therefore, the ZnFe2O4/G magnetic composite may find potential applications in dye water treatment and the degradation of organic dyes.

Morphology transformations in tetrabutyl titanate–acetic acid system and sub-micron/micron hierarchical TiO2 for dye-sensitized solar cells

The concentration of tetrabutyl titanate (TBT) and H2O influence on the reaction kinetics of TBT and acetic acid (AcOH) solvothermal system are systematically studied. It is found that TBT and H2O have greatly accelerated the hydrolysis–condensation process of the TBT–AcOH system. By adjusting those concentrations with reaction time, we prepare five kinds of sub-micron/micron precursors, which are hierarchical structures consisting of different primary building blocks. The morphology of these precursors varies from noninterlaced structures composed of flower-like microsphere and ellipsoid sphere to interlaced structures composed of flower-like microsphere interlaced nanofibers, ellipsoid spheres interlaced flower-like microsphere and nanoparticles interlaced flower-like microsphere. These interlaced structures are synthesized for the first time and are not ordinary mixtures of the noninterlaced structures. After heat treatment, these precursors are transformed to anatase TiO2. Shape-dependent photovoltaic performances of dye-sensitized solar cells (DSSCs) are also discussed. DSSCs based on these hierarchical sub-micron/micron TiO2 show 7.3%–7.9% energy conversion efficiencies, and the devices based on interlaced structures have higher efficiencies (7.4%–7.9%) than those of the devices based on noninterlaced structures (7.3%–7.6%).

Flowerlike assemblies of Bi2S3 nanorods by solvothermal route and their electrochemical hydrogen storage performance

In this paper, the surfactants were introduced into the solvothermal system to guide the growth and assembly of bismuth sulfide nanorods. The flowerlike architectures assembled from the nanorods were successfully constructed using the sodium dodecylbenzenesulfonate, while the monodispersed nanorods were harvested with polyethylene glycol 400. Based on the molecular structure of surfactant and the structural characteristic of micelle, the formation mechanisms of final nanostructures were discussed. The spherical micelle of dodecylbenzenesulfonate with outside hydrophilic sulfonic acid groups will act as a template for the radial growth of nanorods. The electrodes based on the Bi2S3 nanostructures were constructed to study their electrochemical hydrogen storage behaviors and the morphology-dependence of the capacity. The electrochemical hydrogen storage capacity keenly responds to the morphology and microstructure of Bi2S3 nanocrystals. In this report, we found that the rough surfaces of nanorods formed through OA process increased the new hydrogen storage sites excepting the acknowledged interstitial pores and interlayers of Bi2S3 crystals.

Implication de la somnolence au volant dans les accidents de la route : étude sur une population cas-témoins

In this paper, the surfactants were introduced into the solvothermal system to guide the growth and assembly of bismuth sulfide nanorods. The flowerlike architectures assembled from the nanorods were successfully constructed using the sodium dodecylbenzenesulfonate, while the monodispersed nanorods were harvested with polyethylene glycol 400. Based on the molecular structure of surfactant and the structural characteristic of micelle, the formation mechanisms of final nanostructures were discussed. The spherical micelle of dodecylbenzenesulfonate with outside hydrophilic sulfonic acid groups will act as a template for the radial growth of nanorods. The electrodes based on the Bi2S3 nanostructures were constructed to study their electrochemical hydrogen storage behaviors and the morphology-dependence of the capacity. The electrochemical hydrogen storage capacity keenly responds to the morphology and microstructure of Bi2S3 nanocrystals. In this report, we found that the rough surfaces of nanorods formed through OA process increased the new hydrogen storage sites excepting the acknowledged interstitial pores and interlayers of Bi2S3 crystals.

The shape-controlled synthesis and novel lithium storage mechanism of as-prepared CuC2O4·xH2O nanostructures

In a hydrothermal and solvothermal system at 120 °C, cylinder-like and rod-like nanostructures of hydrate copper oxalate (CuC2O4·xH2O) can be thoroughly synthesized in the absence of any shape-controlling additives, respectively. The self-assembly of primary nanocrystals has been investigated considering the polarity of reaction medium, and in the chemical formula of CuC2O4·xH2O the average x value of crystal water is estimated to discuss the superior lithium storage capability of hydrate products. The results show that cylinder-like aggregate of CuC2O4·xH2O (x ∼ 0.14) possesses an initial discharge capacity of 920.3 mAh g−1 with a residual capacity of 970.0 mAh g−1 at 200 mA g−1 over 100 discharge–charge cycles, while rod-like aggregate with a x value of ∼0.53 per chemical formula exhibits a higher initial capacity of 1211.3 mAh g−1 and a lower retention of 849.3 mAh g−1 under the same conditions. Furthermore, time-dependent measurements present a novel crystal-to-amorphous transformation of active substances, suggesting a positive effect of unavoidable crystal water on the superior lithium storage capability of nanostructured CuC2O4·xH2O.

High-rate synthesis of Cu–BTC metal–organic frameworks

The reaction conditions for the synthesis of Cu-BTC (BTC = benzene-1,3,5-tricarboxylic acid) were elucidated using a continuous-flow microreactor-assisted solvothermal system to achieve crystal size and phase control. A high-rate synthesis of Cu-BTC metal-organic frameworks with a BET surface area of more than 1600 m(2) g(-1) (Langmuir surface area of more than 2000 m(2) g(-1)) and with a 97% production yield could be achieved with a total reaction time of 5 minutes.

Novel BN porous-hollow nanorods: synthesis, tunable dimensions, property and formation mechanism

In this paper, we used a high pressure benzene-thermal method to successfully prepare novel BN porous-hollow nanorods. Herein, thiophene is introduced as a catalyst to eliminate the benzene carbonization at high temperature. The alveolate porous wall of the nanorods is stacked up by small nanoflakes aligned vertically in the axial direction. In the high pressure solvothermal system, the diameter and wall thickness of the nanorods can be simply adjusted by the content of thiophene, temperature and pressure. A possible “gas–liquid–solid” mechanism is proposed to explain the formation of 1D BN nanorods. Another novel formation mechanism of the hollow nanorods is elaborated by observing the evolution process of the porous-hollow nanostructures. The method may provide a new idea to be used in preparing other porous-hollow nanostructures. In addition, the hierarchical porous-hollow nanorods exhibit an excellent hydrogen uptake property of 2.6 wt% at 298 K and 90 bar. In particular, the adsorption capacity per unit specific surface area was calculated to be 2.2 × 10−2 wt% m−2 g. This is a rather high value of hydrogen adsorption capacity for BN nanomaterials.

High-throughput studies of highly porous Al-based MOFs

The use of high-throughput (HT) methods for the discovery of compounds as well as for the synthesis optimization in the field of porous aluminum MOFs is summarized. Taking the requirements of an industrial process into account, new synthesis procedures have been developed that demonstrate the versatility of the HT method. This is exemplified by the results that were obtained for the solvothermal system Al2(SO4)3·18H2O/polycarboxylic acid/H2O/DMF. Under rather mild reaction conditions, compared to the previously reported procedures, the Al-MOFs MIL-53-COOH, MIL-96, and MIL-120 were obtained employing 1,2,4-benzenetricarboxylic acid, 1,3,5-benzenetricarboxylic acid, and 1,2,4,5-benzenetetracarboxylic acid, respectively. Applying the HT methodology combined with microwave(MW)-assisted heating, the synthesis procedure were rapidly established, optimized and scaled up. The obtained solids were characterized by X-ray powder diffraction (XRPD), elemental analysis, vibrational spectroscopy and nitrogen sorption measurements. The properties of these MOFs are discussed in comparison with literature values.

Oriented attachment growth of BiOCl nanosheets with exposed {1 1 0} facets and photocatalytic activity of the hierarchical nanostructures

The formation mechanism of nanosheet assembled BiOCl nanostructures in non-aqueous solvothermal system was investigated through time series experiments. The products obtained at different reaction times were characterized by XRD, SEM and (HR)TEM techniques. The photocatalytic property of the samples was measured by decomposing the organic dye of methyl orange. The ability to generate hydroxyl radicals for the samples was also measured by photoluminescence method using coumarin as fluorescence probe molecules. It was revealed that oriented attachment was responsible for the slow transformation of BiOCl from polycrystalline nanoparticles to single crystalline nanosheets. The role of the solvent ethylene glycol and the interaction with the other species during the oriented attachment growth of the BiOCl nanosheets was discussed. The photocatalytic activity tests demonstrated that the BiOCl nanostructures could efficiently decompose methyl orange under either UV light irradiation or visible light irradiation. The high photodegradation efficiency was associated with the atomic arrangement of exposed {110} facets.

Synthesis, characterization and template removal of an iron-containing aluminophosphate molecular sieve with LAU topology

Iron(II)-substituted LAU-zeotype aluminophosphate molecular sieve (denoted as FeAPO-LAU) was synthesized successfully by using imidazole as template in the solvothermal system. The detemplation process was studied to elucidate the stability and microporous characteristics of FeAPO-LAU. In situ temperature-dependent X-ray diffraction analyses indicated that the framework of FeAPO-LAU possessed higher thermal stability and maintained the framework integrity until 923K. The organic templates could be removed by stage-temperature-programmed calcination using lower heating rate in O2 atmosphere, which gave rise to the sample with surface areas of ca. 105m2/g. NH3-temperature programmed desorption (NH3-TPD) analysis showed that detemplated FeAPO-LAU had a weak acidity. Magnetic measurement revealed that both as-synthesized and detemplated FeAPO-LAU showed antiferromagnetic behaviour.

Synthesis and characterization of ZnS tetrapods and ZnO/ZnS heterostructures

ZnS nanomaterials at different dimensions, from nanoparticles, nanobelts to nanotetrapods have been synthesized in the same solvothermal system, which is kinetically controlled by ethylenediamine. Microscopy analysis reveals that the four arms of tetrapod are grown from Zn-terminated surfaces of an octahedral core by alternately stacking zinc blende and wurtzite structures along [111]/[0001] direction, while the ZnS nanobelts are self-assembled along [0001] direction by ultra-small wurtzite nanocrystals. These nanobelts can be transformed into their single-crystal counterparts and ZnO/ZnS heterostructures by thermal treatment. Uv–visible analysis demonstrates that the heterostructure presents a strain-induced staggered Type-II band structure. These investigation results suggest an efficient approach for phase-controlled synthesis of nanostructures in group II–VI semiconductors.

Solvothermal Synthesis of NiCo Alloy Icosahedral Nanocrystals

New dimensional NiCo alloy icosahedral nanocrystals with controllable size have been first reported and synthesized through an Ostwald ripening process in a template-absent solvothermal reaction system. The proposed synthesis is corroborated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The as-obtained NiCo icosahedral nanocrystals exhibit the size- and component-dependent magnetic behaviors. The coercivity (H(c)) depends on both the magnetocrystalline and structure anisotropy, and the saturation magnetizations (M(s)) decided by the content of Co. H(c) decreases from 189.02 to 147.95 Oe with the increase of the icosahedral NCs size from 200 to 850 nm. Especially, the H(c) of the icosahedral NCs at 157.38 Oe is higher than that of nanospheres at 104.02 Oe. In addition, M(s) and H(c) increased with the increasing Co content. It can be an ideal building block for applications in magnetic media, sensors, and other devices.

Synthesis of Size-Controlled Fe<SUB>3</SUB>O<SUB>4</SUB>@SiO<SUB>2</SUB> Magnetic Nanoparticles for Nucleic Acid Analysis

We present a systematic study on the preparation, characteration and potential application of Fe3O4 and Fe3O4@SiO2 nanoparticles. Fe3O4 nanoparticles of controllable diameters were successfully synthesized by solvothermal system with tuning pH. The magnetic properties of nanoparticles were measured by vibration sample magnetometer. Fe3O4@ SiO2 nanoparticles were obtained via classic Stöber process. Streptavidin coated Fe3O4@SiO2 nanoparticles were prepared by covalent interaction. The quantity of streptavidin bound to nanoparticles was determined by UV-Vis spectrometer. To evaluate the binding efficiency and capacity of nucleic acid on nanoparticles, the capture of biotinylated oligonucleotide on streptavidin coated Fe3O4@SiO2 nanoparticles at different concentration was estimated by fluorescence detection. Both Fe3O4 and Fe3O4@SiO2 nanoparticles exhibited well crystallization and magnetic properties. The maximal amount of streptavidin immobilized onto the Fe3O4@SiO2 nanoparticles was 29.3 microg/mg. The saturation ratio of biotinylated oligonucleotides captured on streptavidin coated Fe3O4@SiO2 nanoparticles was 5 microM/mg within 20 minutes, indicating that FeO4@SiO2 nanoparticles immobilized by streptavidin were excellent carriers in nucleic acid analysis due to their convenient magnetic-separation property. Therefore, the synthesized Fe3O4 and Fe3O4@SiO2 nanoparticles with controllable size and high magnetic saturation have shown great application potentials in nucleic acid research.

A facile one-step method to produce Ni/graphene nanocomposites and their application to the thermal decomposition of ammonium perchlorate

A facile one-step method was used to prepare Ni/graphene nanocomposites under solvothermal conditions. During this one-step process graphene oxide was reduced to graphene and Ni nanoparticles were simultaneously anchored on graphene sheets as spacers to keep the neighbouring sheets separated under the conditions generated in the solvothermal system. The size and content of the Ni nanoparticles distributed on the graphene sheets can be easily controlled by altering the starting concentration of NiCl2·6H2O. The catalytic performance of the as-synthesized Ni/graphene nanocomposites on the thermal decomposition of ammonium perchlorate (AP) was investigated by thermal gravimetric and differential thermal analysis (DTA). The results show that Ni/graphene nanocomposites exhibit high catalytic activity. The peak temperature of the high-temperature decomposition of AP decreased by 97.3 °C and at the same time the peak of the low-temperature decomposition disappeared. When 1% Ni/graphene nanocomposites are used, the catalytic performance is the best. As a result, the Ni/graphene nanocomposites could be a promising candidate material for an AP-based propellant.

Layered hybrid organic–inorganic nanobelts: synthesis and removal of trace heavy metal ions

Cobalt phosphate-based organic-inorganic hybrid nanobelts were successfully synthesized in the presence of trioctylamine (TOA) via a solvothermal system. The inorganic cobalt phosphate layers and organic n-octylamine layers in this structure arranged alternately, both of which were parallel to the axial direction of the nanobelts, and the layered distance is 4.0 nm. The formation of this nanostructure proceeds via two reactions. Trioctylamine molecules undergo C-N bond cleavage to form octylamine via the redox reaction between the Co(III) and trioctylamine. Octylamine was protonated to incorporate into the inorganic framework, resulting in the formation of organic-inorganic hybrid nanobelts. In addition, the as-synthesized nanobelts show excellent removal ability for the trace heavy metal ion Pb(2+) in wastewater.

CAU-3: A new family of porous MOFs with a novel Al-based brick: [Al2(OCH3)4(O2C-X-CO2)] (X = aryl)

A new family of Al-based MOFs denoted as CAU-3 (CAU = Christian-Albrechts-Universität) was discovered in the solvothermal system Al(3+)/aryldicarboxylic acid/NaOH/methanol by applying high-throughput-methods. The three compounds reported in this article [Al(2)(OCH(3))(4)BDC], [Al(2)(OCH(3))(4)BDC-NH(2)] and[Al(2)(OCH(3))(4)NDC] (BDC = 1,4-benzenedicarboxylate; NDC = 2,6-naphtalenedicarboxylate) are all based on the same unprecedented inorganic building unit [Al(12)(OCH(3))(24)](12+), which is a dodecameric cyclic aluminium-methanolate-cluster. The material CAU-3-NDC was found to exhibit the highest surface area as well as the highest micropore volume of all Al-based MOFs reported until now.

Light-Driven Transformation of ZnS-Cyclohexylamine Nanocomposite into Zinc Hydroxysulfate: A Photochemical Route to Inorganic Nanosheets

ZnS-CHA (CHA = cyclohexylamine) nanocomposite, a unique inorganic-organic hybrid semiconductor, has been prepared from a mild solvothermal reaction system. This material contains 2 nm-sized ZnS nanoparticles, and is photoactive toward UV light (≤300 nm). Under UV-irradiation, the ZnS-CHA nanocomposite is transformed to crystalline zinc hydroxysulfate nanosheets. The driving force of the light-driven transformation reaction is the photogeneration of charges (electrons and holes) in the ZnS nanoparticles, and these photogenerated charges interact with the CHA molecules and the inorganic S(2-) species, leading to decomposition of the organic component and self-oxidation of the inorganic ZnS nanoparticles to form zinc hydroxysulfate. Through simple thermal treatment, the as-formed zinc hydroxysulfate nanosheets are converted to ultrathin ZnO nanosheets with a porous feature, which exhibit high sensitivity and fast response and recovery for ethanol detection when used as an electrical sensing material.

Facile synthesis via a solvothermal route and characterization of Mg–Al layered double hydroxide (LDH) 3D micro–nano structures

Different Mg–Al layered double hydroxide (LDH) 3D micro–nano structures had been synthesized via a facile solvothermal method. By carefully controlling the fundamental experimental parameters, the morphologies of hexagonal nanoplates, rose-like micro–nano structures, chrysanthemum-like micro–nano structures, and spherical micro–nano structures have been efficiently obtained, respectively. And these micro–nano structures are formed from self-assembly of nanoplates in a spontaneous process in solvothermal system. It is also found that the concentration of the reactant and the dosage of CTAB have significant effects on the morphology of the products. The FT-IR spectra and thermal stability of the micro–nano structures were explored.

Development of Micro-Flow Hydrothermal Monitoring Systems and Their Applications to the Origin of Life Study on Earth

Continuous extensive studies on thermophilic organisms have suggested that life emerged on hydrothermal systems on primitive Earth. Thus, it is well known that hydrothermal reactions are, therefore, very important to study fields deeply related to the origin-of-life study. Furthermore, the importance of hydrothermal and solvothermal systems is now realized in both fundamental and practical areas. Here, our recent investigations are described for the development of real-time and in situ monitoring systems for hydrothermal reactions. The systems were primarily developed for the origin-of-life study, but it was also applicable to fundamental and practical areas. The present techniques are based on the concept that a sample solution is injected to a narrow tubing flow reactor at high temperatures, where the sample is rapidly heated up in a very short time by exposure at to a high-temperature narrow tubing flow reactor with a very short time scale. This enables millisecond to second time-scale monitoring in real time and/or in situ at temperatures of up to 400°C. By using these techniques, a series of studies on the hydrothermal origin-of-life have been successfully carried out.