Solvothermal Strategy Research Articles

Ni3S2 Nanosheets in Situ Epitaxially Grown on Nanorods as High Active and Stable Homojunction Electrocatalyst for Hydrogen Evolution Reaction

Development of efficient noble metal-free electrocatalysts for accelerating the sluggish kinetics in the hydrogen evolution reaction (HER) has received a great deal of attention in electrolytic water splitting. Herein, we present a facile one-step solvothermal strategy for controllably constructing the homojunction structures of Ni3S2 nanosheets in situ epitaxially grown on nanorods by using Ni foam as self-support substrate and nickel resource (Ni3S2/NF). In the synthesis, cetyltrimethylammonium bromide and hydrazine hydrate are used to control the formation of nanorods and nanosheets, respectively. The special 3D Ni3S2 nanorods@nanosheets homojunction could provide plentiful catalytically active sites; meanwhile, the intimate contact between Ni3S2 and Ni foam could enhance the long-term stability. The inevitable sulfur vacancies in the Ni3S2 could tune electronic structure of the surface and enhance the catalytic activity. The synergistic effect leads to the as-prepared Ni3S2/NF exhibiting a superior HE...

Porous cobalt sulfide hollow nanospheres with tunable optical property for magnetic resonance imaging-guided photothermal therapy.

Transition-metal chalcogenides with an imaging element and tunable optical property are strongly desired as ideal high-efficiency photothermal theranostic agents to diagnose and eliminate tumors. Herein, we report on a one-pot solvothermal strategy to synthesize various porous cobalt sulfide hollow nanospheres (PCSH NSs) and elucidate the relation between PCSH NSs and their optical absorption as a guide to obtain optimal photothermal therapy (PTT) agents. After PEG modification, PEG-PCSH NSs show superexcellent photothermal conversion efficiency (∼70.1%) which is higher than that of binary transition-metal chalcogenides materials reported to date. A low dose (100 μL, 25 ppm) could completely ablate tumors under an 808 nm laser power of 0.7 W cm-2, reducing in vivo long-term residual agent content and thus lowering the possibility of side effects. Additionally, they also exhibit excellent biocompatibility, good photostability and utility for magnetic resonance imaging. Our results indicate that PCSH NSs can be considered as an outstanding PTT agent and give guidance towards the design of other photothermal theranostic agents.

A nanosensor made of sulfur–nitrogen co-doped carbon dots for “off–on” sensing of hypochlorous acid and Zn(ii) and its bioimaging properties

In this study, we present a facile one-step solvothermal strategy for the fabrication of sulfur–nitrogen co-doped carbon dots (SNCDs) using p-phenylenediamine and cysteamine hydrochloride as the precursors.

Antibacterial gluey silver-calcium phosphate composites for dentine remineralization.

The development of multifunctional dental-restorative biomaterials with antibacterial activity and remineralization effect for damaged tooth repair is urgent since dental caries is still one of the most common tooth diseases in human beings. Herein, we report a facile strategy for the synthesis of gluey silver-calcium phosphate (GSCP) composites using the rapid microwave-assisted solvothermal method. The as-prepared GSCP composite is an organic-inorganic hybrid, and Ag+ ions display a significant influence on the formation of GSCP by interacting with adenosine triphosphate biomolecules. The as-prepared GSCP composite shows good antibacterial properties, in addition, it exhibits a great effect on sheltering dentinal canaliculi and improving the remineralization of dentine in the simulated saliva. The as-prepared GSCP composite is promising for various applications such as oral healthcare, especially, remineralization of dentine, and antibacterial applications.

Phase-controlled synthesis of molybdenum oxide nanoparticles for surface enhanced Raman scattering and photothermal therapy.

Different from their bulk counterparts, plasmonic molybdenum oxide nanomaterials display superior optical and electronic properties, but unfortunately, phase-controlled synthesis of molybdenum oxide nanomaterials with multifunctional performances still remains a challenge. To actualize this, a surfactant-free solvothermal strategy was proposed to fabricate molybdenum oxide nanomaterials with a tunable phase. Encouragingly, the as-prepared molybdenum dioxide nanoparticles (MoO2 NPs) exhibit intense near-infrared (NIR) absorption attributed to the localized surface plasmon resonance (LSPR) effect, which results in their application as a surface enhanced Raman scattering (SERS) substrate to detect trace amounts of molecular species including Rhodamine 6G (R6G), crystal violet (CV), IR-780 iodide (IR780) and methylene blue (MB). The detection limit was as low as 5 × 10-8 M and the maximum enhancement factor (EF) was up to 1.10 × 107, compared to other semiconductor nanostructures, the SERS sensitivity may be the best. Meanwhile, with the significant photothermal conversion efficiency up to 61.3%, the plasmonic MoO2 NPs could also be used as a photothermal therapy (PTT) agent for efficient photothermal ablation of cancer cells in vitro.

Facile synthesis of amine-functional reduced graphene oxides as modified quick, easy, cheap, effective, rugged and safe adsorbent for multi-pesticide residues analysis of tea

Amine-functional reduced graphene oxide (amine-rGO) with different carbon chain length amino groups were successfully synthesized. The graphene oxides (GO) reduction as well as amino grafting were achieved simultaneously in one step via a facile solvothermal synthetic strategy. The obtained materials were characterized by X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectrometry and X-ray photoelectron spectroscopy to confirm the modification of GO with different amino groups. The adsorption performance of catechins and caffeine from tea acetonitrile extracts on different amine functional rGO samples were evaluated. It was found that tributylamine-functional rGO (tri-BuA-rGO) exhibited the highest adsorption ability for catechins and caffeine compared to GO and other amino group functional rGO samples. It was worth to note that the adsorption capacity of catechins on tri-BuA-rGO was 11 times higher than that of GO (203.7mgg−1 vs 18.7mgg−1). Electrostatic interaction, π-π interaction and surface hydrophilic-hydrophobic properties of tri-BuA-rGO played important roles in the adsorption of catechins as well as caffeine. The gravimetric analysis confirmed that the tri-BuA-rGO achieved the highest efficient cleanup preformance compared with traditional dispersive solid phase extraction (dSPE) adsorbents like primary-secondary amine (PSA), graphitized carbon black (GCB) or C18. A multi-pesticides analysis method based on tri-BuA-rGO is validated on 33 representative pesticides in tea using gas chromatography coupled to tandem mass spectrometry or high-performance liquid chromatography coupled with tandem mass spectrometry. The analysis method gave a high coefficient of determination (r2>0.99) for each pesticide and satisfactory recoveries in a range of 72.1–120.5%. Our study demonstrated that amine functional rGO as a new type of QuEChERS adsorbent is expected to be widely applied for analysis of pesticides at trace levels.

Facet and morphology dependent photocatalytic hydrogen evolution with CdS nanoflowers using a novel mixed solvothermal strategy

As the highest energy facet of wurtzite CdS, (0 0 2) facet is well worth investigating toward the contribution in photocatalytic hydrogen (H2) evolution. In this study, flower-like CdS with highly preferred (0 0 2) facet was fabricated through a low temperature mixed-solvothermal strategy. The mixted-solvent of diethylenetriamine (DETA) and ethyl alcohol (EtOH) was used to inhibit the growth of (1 0 0) and (1 0 1) facets. For comparison, porous flower-like, belt-like and net-like CdS samples with different preferred degrees of (0 0 2) facet were controllably synthesized by the addition of H2O in different proportions. The preferred orientation degrees of (0 0 2) facet were qualitative proved by the mathematical fitting of XRD patterns. As expected, the flower-like CdS exhibited the highest photocatalytic activity on H2 evolution under visible light without any co-catalyst. Meanwhile, the photocatalytic H2 production increased with the increasement of exposed (0 0 2) facet, which suggested that (0 0 2) facet of CdS played a critical role in improving the photocatalytic activity. Moreover, the growth mechanisms of CdS with various morphologies were investigated and proposed in detail.

Dendritic Fe-based polyoxometalates @ metal–organic framework (MOFs) combined with ZnO as a novel photoanode in solar cells

In this paper, we propose a novel Fe-based polyoxometalates @ metal–organic framework (POM@MOF(Fe)) material synthesized by a one-step solvothermal strategy to combine the merits of adjustable structure of MOFs and excellent electrochemistry properties of POMs. Fe ions are connected by organic linkers 1,4-H2BDC and 4,4′-bipyridine to build frameworks and combined with Keggin-type H3PW12O40 units inside. A leaf-like structure of POM@MOF(Fe) crystals are obtained which exhibits good optical response in visible range with absorption edge at around 750 nm. Herein, we describe the assembly and characterization of a simplified solar cell based on POM@MOF(Fe) crystals modified the ZnO photoanode. The photovoltaic performance of solar cells with POM@MOF(Fe) modified the ZnO as photoanode without any sensitizer is enhanced compared to the bare ZnO which is clearly ascribed to the POM@MOF(Fe). The results demonstrate that this novel composite of POM@MOF(Fe) is a good electron–hole separation materials thus benefiting the photovoltaic property of ZnO. Hence, solar cells based on this novel photoanode can be expected to exhibit good photovoltaic performance.

Uniform Gd-Based Coordination Polymer Hollow Spheres: Synthesis, Formation Mechanism and Upconversion Properties

In this work, Gd-based coordination polymer (GdCP) hollow spheres have been synthesized by a general, facile and template-free solvothermal strategy. The products were well characterized and analyzed. Results indicate that the uniform hollow nanospheres have diameters of 160–260 nm. Influential factors such as reaction temperature, time, and dosage of reagents on the morphology and size of the GdCP hollow spheres have been systematically investigated. An Ostwald ripening mechanism coupled with a self-assembly process for the hollow structures formation was proposed based on a series of time-dependent experiments. Furthermore, after doping with Yb3+/Er3+ ions, characteristic red upconversion emission from 4F9/2→4I1 5/2 of Er3+ was realized under 980 nm NIR irradiation.

Bimetallic Co-Mn Perovskite Fluorides as Highly-Stable Electrode Materials for Supercapacitors.

Bimetallic Co-Mn perovskite fluorides (KCox Mn1-x F3 , denoted as K-Co-Mn-F) with various Co/Mn ratios (1:0, 12:1, 6:1, 3:1, 1:1, 1:3, 0:1) were prepared through a one-pot solvothermal strategy and further used as electrode materials for supercapacitors. The optimal K-Co-Mn-F candidate (Co/Mn=6:1) showed a size range of 0.1-1 μm and uniform elemental distribution; exhibiting small changes in XRD peaks and XPS binding energy in comparison to the bare K-Co-F and K-Mn-F, due to the structural/electronic effects. Owing to the stronger synergistic effect of Co/Mn redox species, the K-Co-Mn-F (Co/Mn=6:1) electrode exhibited superior specific capacity and rate behavior (113-100 C g-1 at 1-16 Ag-1 ) together with excellent cycling stability (118 % for 5000 cycles at 8 Ag-1 ), and the activated carbon (AC)//K-Co-Mn-F (Co/Mn=6:1) asymmetric capacitor showed superior energy and power densities (8.0-2.4 Wh kg-1 at 0.14-8.7 kW kg-1 ) along with high cycling stability (90 % for 10 000 cycles at 5 Ag-1 ).

Ultrafast synthesis of Mn0.8Co0.2CO3/graphene composite as anode material by microwave solvothermal strategy with enhanced Li storage properties

Carbonate is recently studied as anode material for lithium ion battery due to its relatively high capacity compared to relative oxides. In order to improve the time-efficiency of synthesis, an ultrafast solvothermal process assisted with microwave is carried out to obtain well-constructed Mn0.8Co0.2CO3/graphene composite as anode material for lithium ion batteries. The as-prepared Mn0.8Co0.2CO3/graphene composite with a graphene amount of 17.5wt% exhibits a morphology of cubic particles in graphene without any impurity. Mn0.8Co0.2CO3/graphene delivers high initial charge capacities of 1033mAhg−1. And after 120 cycles, charge/discharge capacities of 737/735mAhg−1 are maintained at 0.2Ag−1. Even at 2Ag−1, the composite can still deliver high charge/discharge capacities of 500/501mAhg−1. It is promising to obtain carbonate/graphene anode materials rapidly through such ultrafast solvothermal process assisted by microwave for application.

Facile fabrication of CNTs@C@MoSe2@Se hybrids with amorphous structure for high performance anode in lithium-ion batteries

Amorphous MoSe2 and Se anchored on amorphous carbon coated multiwalled carbon nanotubes (CNTs@C@MoSe2@Se) have been synthesized by a facile solvothermal strategy. The one dimensional CNTs@C@MoSe2@Se can effectively buffer the volume variation, prohibit the aggregation and facilitate electron and ion transport throughout the electrode. Furthermore, the combination of MoSe2 and Se also provides buffer spaces for the volumetric change during cycling. Thus, the obtained CNTs@C@MoSe2@Se hybrids display the enhanced cycle stability and excellent high rate capacity. The reversible capacity of 1010mAhg−1 can be achieved after 100 cycles at the current density of 0.1Ag−1. Even after 500 cycles, a reversible capacity of 508mAhg−1 is still retained at 5Ag−1.

Layered/Spinel Heterostructured and Hierarchical Micro/Nanostructured Li-Rich Cathode Materials with Enhanced Electrochemical Properties for Li-Ion Batteries.

Although holding a high capacity, Li-rich materials are far from the demand of practical market because of their inherent drawbacks, such as poor initial efficiency and rate capability. Herein, Li-rich materials of Li1.16Mn0.6Ni0.12Co0.12O2 have been prepared via a one-step solvothermal strategy. The detail characterizations demonstrate that the as-prepared materials present morphology of nanoparticle-aggregated hierarchical microspheres and a heterostructure of layered and Li4Mn5O12-type spinel components. Compared to materials of pure-layered structure, layered/spinel heterostructured materials exhibit simultaneously great reversible capacity (302 mAh g-1 at 0.2 C), high initial Coulombic efficiency (94% at 0.2 C) and remarkable rate capability (193 mAh g-1 at 10 C).

Understanding the Photochemical Response of Zeolitic Imidazolate Framework-8 in the Sight of Framework, Uncoordinated 2-Methylimidazole and ZnxOy Clusters

ZIF-8 particles synthesized by solvothermal and self-assembly strategies were used as fluorescence probes to detect a series of analytes based on its “turn on” or “turn off” fluorescence. Besides the electronic transition, the crucial effect of the evolution of structure as well as the ZnxOy clusters and uncoordinated 2-methylimidazole was investigated, and the relevant mechanism of fluorescence response was further explored in this study. It was found that the ZnxOy clusters within the cages of ZIF-8 can increase the fluorescence up to four-fold. Two types of uncoordinated 2-methylimidazole, resulting from the residue or escape of metal center, also make a special contribution to fluorescent response. During the chemical sensing, different substances showed different fluorescence response via one or several of these impacting factors.

Cu2O/TiO2 heterostructures for CO2 reduction through a direct Z-scheme: Protecting Cu2O from photocorrosion

The development of artificial photosynthesis aims to solve the increasing energy demand and associated environmental problems. A model photosynthetic system employing a composite of semiconductors with a Z-scheme can potentially mimic the combined power of photosystems 1 and 2 to transfer electrons. In this work, octahedral cuprous oxide covered with titanium dioxide nanoparticles (Cu2O/TiO2) are synthesized by a solvothermal strategy that provides high morphological and crystallographic control. The formation of a p-n heterojunction and characterization of the Type II band alignment of the composite are performed by diffuse reflectance UV-visible (DRUV) spectroscopy, ultraviolet photoelectron spectroscopy (UPS), and X-ray photoelectron spectroscopy (XPS). Upon UV-visible irradiation (λ≥305nm) of the composite in the presence of water vapor as the hole scavenger, the photoreduction of CO2(g) proceeds selectively to generate CO(g). The production rate of CO by the composite, RCO=2.11μmolgcat−1h−1, is 4-times larger than for pure Cu2O under identical conditions. Contrasting XPS analyses of Cu2O and Cu2O/TiO2, during photocatalysts operation and the detection of photogenerated hydroxyl radicals (HO) in the heterostructure at variance with the results obtained for pure Cu2O are taken as evidences that TiO2 protects Cu2O from undergoing photocorrosion. These results provide direct evidence of an efficient Z-scheme as the main mechanism for harvesting energy during CO2 reduction in the synthesized materials.

Simultaneous removal of U(VI) and humic acid on defective TiO2−x investigated by batch and spectroscopy techniques

In this paper, the defective TiO2−x with abundant oxygen vacancies were fabricated through a simple modified solvothermal strategy and characterized by SEM, TEM, XRD, FT-IR, EDX, Zeta-potential, and XPS techniques in detail. The prepared TiO2−x was applied to remove U(VI) and humic acid (HA) from aqueous solutions to evaluate its sorption performance. The sorption of U(VI) and HA on TiO2−x was examined under various environmental conditions (e.g., contact time, pH, ionic strength, initial HA/U(VI) concentrations, the addition sequences of HA/U(VI) and temperature). According to the Langmuir model simulation, the maximum sorption capacities of U(VI) and HA on TiO2−x at pH = 5.0 were calculated to be 65 and 142mgg−1, respectively, which were higher than most current reported materials. The kinetic results indicated that the sorption of U(VI) and HA onto TiO2−x was better described by the pseudo-second-order kinetic model. The presence of HA enhanced U(VI) sorption on TiO2−x at pH = 5.0, meanwhile, the surface adsorbed U(VI) on TiO2−x also enhanced the sorption capacity of HA, which was mainly attributed to the formation of U(VI)-HA-TiO2−x ternary complexes. Combining FT-IR and XPS analysis, the oxygen vacancies could provide high chemical activity and trap U(VI) in the defective sites of TiO2−x, while the sorption of HA was dominated by surface complexation. The findings might provide an opportunity to estimate and optimize the efficient simultaneous elimination of radionuclides and natural organic substances by using defective TiO2−x.

Various Structured Molybdenum-based Nanomaterials as Advanced Anode Materials for Lithium ion Batteries.

A facile and scalable solvothermal high-temperature treatment strategy was developed to construct few-layered ultrasmall MoS2 with less than three layers. These are embedded in carbon spheres (MoS2-C) and can be used as advanced anode material for lithium ion batteries (LIBs). In the resulting architecture, the intimate contact between MoS2 surface and carbon spheres can effectively avert aggregation and volume expansion of MoS2 during the lithiation-delithiation process. Moreover, it improves the structural integrity of the electrode remarkably, while the conductive carbon spheres provide quick transport of both electrons and ions within the electrode. Benefiting from this unique structure, the resulting hybrid manifests outstanding electrochemical performance, including an excellent rate capability (1085, 885, and 510 mAh g-1 at 0.5, 2, and 5 A g-1), and a superior cycling stability at high rates (maintaining 100% of the initial capacity following 500 cycles at 0.5 A g-1). Using identical methods, molybdenum carbide and phosphide supported on carbon spheres (Mo2C-C, and MoP-C) were prepared for LIBs. As a result, MoS2-C exhibits outstanding lithium storage capacities due to its specific layered structure. This study investigates large-scale production capabilities of few-layered structure ultrasmall MoS2 for energy storage, and thoroughly compares lithium storage performance of molybdenum compounds.

Preparation of hierarchical WO3 dendrites and their applications in NO2 sensing

Hierarchical WO3 dendrites were synthesized via low-cost and environmental-friendly solvothermal strategy. Characterization results indicated that WO3 dendrites were composed of several multi-directional dendritic nanosheets. To further understand the formation of WO3 dendrites, time-dependent experiments were carried out and formation mechanism was investigated. Since such dendritic structures rarely occurred in the field of gas sensing, the synthesized WO3 dendrites were subjected to detailed NO2 sensing tests. Results demonstrated that WO3 dendrites based sensors had low detection limit (200 ppb) and fast response and recovery (7s, 12s to 5 ppm NO2). Moreover, the sensor was also highly sensitive, selective and stable at low optimal operating temperature of 140°C.

One-pot solvothermal synthesis of ternary Ni-Co-P micro/nano-structured materials for high performance aqueous asymmetric supercapacitors

The ternary Ni-Co-P micro/nano-structured materials were synthesized via a facile one-pot solvothermal strategy and further served as positive electrode materials for supercapacitors. X-ray diffraction (XRD) showed that the optimal Ni8-Co1-P materials exhibited the two major phases of M12P5 and M2P (M=Ni, Co). X-ray photoelectron spectroscopy (XPS) revealed the binding energy shifts of P2p, Ni2p and Co2p of Ni8-Co1-P materials compared with the bare Ni-P and Co-P, indicating the formation of ternary materials. Transmission electron microscopy (TEM) and energy dispersive spectrometer (EDS) mapping exhibited the micro/nano-structured morphology with rich surface nanowires (5–10nm in diameter) and the consistent distribution of Ni, Co and P elements of the Ni8-Co1-P materials respectively. Nitrogen sorption measurements illustrated the mesoporous structure of the Ni8-Co1-P materials with the specific surface area of 257m2g−1. Due to the richer Ni, Co surface electroactive sites and the stronger synergistic effect of Ni and Co redox species, the Ni8-Co1-P materials showed superior specific capacitance, rate capability and charge transfer kinetics (1448Fg−1 at 1Ag−1, 1173Fg−1 at 16Ag−1, 333Ω) than the Ni-Co-P with other Ni/Co ratios (1:0, 16:1, 4:1, 2:1, 0:1). The mass ratio optimized activated carbon (AC)//Ni8-Co1-P asymmetric capacitor (m+/m−=1:2) exhibited high energy and power densities (22.8Whkg−1, 4.32kWkg−1) together with excellent cycle life (no decay after 5000 cycles at 4Ag−1). The high performance makes the ternary Ni-Co-P micro/nano-structured materials promising electrode materials for supercapacitors.

Solvothermal synthesis of hydroxyapatite with various morphologies using trimethyl phosphate as organic phosphorus source

Hydroxyapatite (HAP) materials with various morphologies including microrods, nanoparticle-assembled microflowers (NAMs), nanoparticle-assembled dendritic superstructures (NADSs), and microrod-assembled ordered arrays (MAOAs) are prepared by a facile solvothermal synthesis strategy using trimethyl phosphate as an organic phosphorus source. The morphologies of the as-prepared HAP products vary significantly with the change of the solvothermal temperature and amount of NaOH. The present study provides a new platform for the synthesis of HAP materials with various morphologies. Among the as-prepared HAP products, the HAP MAOAs show similar structures to those of apatite in the hard tissues of vertebrates. The as-prepared products show excellent biocompatibility, and thus are potentially useful in biomedical fields.