Green Solvothermal Method Research Articles

Highly efficient adsorption and visible-LEDs-driven photodegradation of tetracycline over novel and green-synthesized p-BiOI/n-Bi2WO6 heterojunctions

Preparing bismuth compounds-based heterojunctions with superior redox capability has emerged as a promising strategy for environmental remediation. Herein, p-BiOI/n-Bi2WO6 heterojunctions were successfully obtained via a novel, facile, and green solvothermal method. The heterojunctions were synthesized using different mass ratios (1:2, 1:1, and 2:1) of BiOI (BI) and Bi2WO6 (BW), with 1:1 as the best ratio, which was decorated with silver nanoparticles (Ag-NPs) and nitrogen-doped graphene (NG) applying green methodologies. The as-prepared BI/BW heterojunctions were characterized by several techniques, and their adsorption capacity and photodegradation activity toward tetracycline (TC) under 19 W visible LEDs illumination were investigated. The capacity of pure BI, BW and BI/BW heterojunctions for adsorbing TC ranged from 14 to 68 mg/g; among the heterojunctions, Ag/1BI/1BW showed the highest TC adsorption capacity, 35 mg/g. Moreover, the photocatalytic tests revealed that the Ag/1BI/1BW exhibited the highest catalytic performance, achieving a TC percentage degradation of 81 % within 120 min. The low nominal power consumption of the LED-based photoreactor (0.0475 kWh) was significantly lower than that reported in the literature for using Xe or Hg lamps. In addition, catalyst dosage, initial TC concentration, and solution pH were investigated, demonstrating that they play important role in TC photodegradation. Scavenger assays determined that the degradation of TC using Ag/1BI/1BW proceeds mainly via superoxide radicals and holes, which agrees with the carrier transfer mechanism postulated for this heterojunction. TOC analysis revealed that the efficiency of Ag/1BI/1BW was 63 %, and reuse tests confirmed its high performance even after three cycles. This research provides new insights into the design of high-performance heterojunctions for water treatment.

Improved properties of CoFe2O4@rGO/PVDF composites prepared through a solution-mixing approach

In this work, a hybrid material based on CoFe2O4 nanoparticles immobilized on reduced graphene oxide (CoFe2O4@rGO) was successfully synthesized through a one-step green solvothermal method. Subsequently, the resultant CoFe2O4@rGO was further modified by aminopropyltriethoxysilane to form the A-CoFe2O4@rGO hybrid, serving as the filler of poly(vinylidene fluoride) (PVDF). The facile preparation of A-CoFe2O4@rGO was confirmed through various microstructural characterization techniques. PVDF-based composites with varying contents of A-CoFe2O4@rGO (1 wt%, 3 wt%, 5 wt%, 7 wt%, and 10 wt%) were prepared using a solution-mixing approach. SEM results revealed uniform distribution of the A-CoFe2O4@rGO filler within the PVDF matrix. The XPS results indicated an obvious interfacial interaction between the A-CoFe2O4@rGO filler and PVDF matrix. Consequently, the crystallization degree and β crystalline content of PVDF matrix in the A-CoFe2O4@rGO(7 wt%)/PVDF composite were enhanced to 52.3 % and 32.1 %, respectively, compared to 42.2 % and 26.0 %, respectively, in pure PVDF. The A-CoFe2O4@rGO(10 wt%)/PVDF composite enhanced electrical conductivity and dielectric constant at 100 Hz, with values of 1.33 × 10−7 S/m and 22.1, respectively, compared to 1.86 × 10−9 S/m and 8.6, respectively, in pure PVDF. In addition, despite the non-magnetic nature of pure PVDF, the A-CoFe2O4@rGO(10 wt%)/PVDF composite possessed a magnetization value of 1.64 emu/g at 60,000 Oe. The comprehensive enhancement in crystallization behavior, electrical, dielectric, and magnetic properties demonstrates the potential of the A-CoFe2O4@rGO/PVDF composite for various applications.

Modulator-Free Green Synthesis of the Calcium-Terephthalate Metal-Organic Framework Derived from Waste Eggshells

Conventionally, the four-component calcium-terephthalate (Ca-BDC) metal–organic framework (MOF), Ca(BDC)(DMF)(H2O), has been synthesized from commercial calcium nitrate (Ca(NO3)2) and calcium carbonate (CaCO3), which in turn are manufactured from naturally-occurring minerals by energy-intensive processes. This study presents a primary investigation on the modulator-free solvothermal synthesis of Ca(BDC)(DMF)(H2O) derived from waste eggshells as green precursors. Ca(BDC)(DMF)(H2O) crystallizes as two possible phases, namely the triclinic (Ca-BDC-tric) and orthorhombic (Ca-BDC-orth) phase. This study presents an in-depth investigation on the influence of reaction temperature and solvent volumes on eggshell-derived Ca(BDC)(DMF)(H2O) product phase. Investigations were conducted at long reaction times to ensure complete reaction of green eggshell precursors. Low water (H2O) and high N,N-dimethylformamide (DMF) volumes were found to inhibit solvothermal synthesis. 7.6 mL H2O was determined to be the minimum H2O volume threshold for successful Ca-BDC-tric synthesis, above which further increasing the H2O volume produced porous Ca-BDC-tric at higher yield, which proved favorable due to reduction of toxic DMF. Ca-BDC-orth and Ca-BDC-tric were obtained at 150 °C and 110 °C respectively, whereas dual-formation of both phases prevailed at 130 °C, thereby informing the rough temperature range at which Ca-BDC-tric morphs into Ca-BDC-orth. Ultimately, this study introduces a green solvothermal method for valorizing eggshell waste into value-added Ca(BDC)(DMF)(H2O) for sustainable eggshell waste management and alleviation of environmental health concerns associated with eggshell disposal.

Synergistic advanced oxidation process for the fast degradation of ciprofloxacin antibiotics using a GO/CuMOF-magnetic ternary nanocomposite

A novel strategy was described to fabricate GO/CuBDC-Fe3O4 ternary nanocomposite using a green solvothermal method. The physicochemical properties of the ternary nanocomposite were probed by ATR-FTIR, WA-XRD, Raman, FE-SEM, TEM/HRTEM, STEM/mapping, and EDS spectroscopy. In this nanocomposite, graphene oxide (GO) nanosheets were used as an ideal platform for CuBDC metal-organic framework (MOF) and Fe3O4 growth, aiming to create a peroxymonosulfate (PMS) activator to degrade ciprofloxacin (CIP) antibiotics expeditiously. The proposed ternary nanocomposite showed highest degradation rate of CIP (98.5%) within 24 min with rate constant of 0.191 min−1. The findings demonstrated that Cu/Fe species and C˭O groups within ternary nanocomposite catalyzed PMS synergistically to the formation of the hydroxyl and sulfate radicals for CIP degradation. Furthermore, the ternary nanocomposite showed good recyclability enabling facile separation of the catalyst from reaction mixtures using an external magnet. On the other hand, radical quenching tests and electron paramagnetic resonance (EPR) reveal that the •OH and SO4•− a vital role in the degradation process. The current protocol can be a useful criterion in designing and fabrication of various ternary nanocomposites and provides new insight into environmental remediation.

Solvothermally grown BiOCl catalyst for photodegradation of cationic dye and fluoroquinolone-based antibiotics

A BiOCl catalyst was prepared via a green solvothermal method without using any surfactant or capping agent. The prepared BiOCl showed a uniform spherical morphology of about 60 nm with an energy band gap of 3.58 eV. Photoluminescence (PL) spectrum of BiOCl (λexcitation = 310 nm) showed the first excitonic peak (near band edge emission peak) at 348 nm indicating the highly crystalline nature of the synthesized catalyst. The BiOCl photocatalyst showed the tetragonal crystal structure with the enhanced photocatalytic performance of 99% toward degradation of Rhodamine B (RhB) dye and three antibiotics, namely, ofloxacin (OFL), norfloxacin (NOR), and ciprofloxacin (CIP) under UV light irradiation. The photocatalytic degradation reaction of each pollutant follows the first-order kinetics with a high rate constant of about 0.0336 min−1. Both electron and hole are the main reactive species involved in degradation of the pollutants. The prepared BiOCl retains its photocatalytic performance even after five cycles of use. The BiOCl catalyst has a high potential for photodegradation of cationic dye and fluoroquinolone antibiotics present in wastewater.

Nanoscale nickel metal organic framework decorated over graphene oxide and carbon nanotubes for water remediation

In this report, highly crystalline and well-dispersed nano-sized nickel metal organic framework (MOFs) was decorated over graphene oxide (GO) and carbon nanotubes (CNTs) platforms to form hybrid nanocomposites. These as-synthesized hybrid nanocomposites were synthesized through a one-pot green solvothermal method. The prepared nanocomposites were characterized by SEM, TEM, EDS, XRD, FT-IR, Raman and TGA techniques. XRD analysis revealed the crystalline structure of the hybrid nanocomposites. Morphological and elemental studies also verified successful decoration of nickel-benzene dicarboxylate (Ni-BDC) MOFs over GO and CNT platforms. Chemical analysis collected through IR, and thermal analysis collected through TGA technique, illustrated the presence of all the components in the hybrid nanomaterials. Methylene blue (MB) was used as a model organic pollutant to analyze the adsorption capacity of the prepared nanocomposites. According to the findings, a strong interaction exists between the MB molecule and the developed adsorbents at which due to the synergistic effect, the hybrid nanocomposites show several times higher adsorption capacity compared to that of parent materials. This improvement can be due to several reasons: high surface area of the MOFs in the composites resulting from the smaller size of MOFs, presence of the pores formed between the MOFs and the platforms and different morphological characteristic of Ni-BDC MOFs in hybrid nanocomposites, compared to bare Ni-BDC MOFs. Furthermore, the isotherm and kinetic studies revealed that the adsorption of MB onto the newly prepared adsorbents could best be explained by the Langmuir and Pseudo-second order kinetic models. A regeneration study demonstrated the highly stable nature of the hybrid nanocomposites.

Sustainable synthesis and remarkable adsorption capacity of MOF/graphene oxide and MOF/CNT based hybrid nanocomposites for the removal of Bisphenol A from water

A series of novel absorbents based on Cu-BDC MOFs decorated over graphene oxide (GrO) and carbon nanotubes (CNTs) hybrid nanocomposites, namely Cu-BDC@GrO and Cu-BDC@CNT, are synthesized via a facile and one-pot green solvothermal method for water remediation. The nanocomposites were characterized by XRD, TEM, SEM, EDS, Raman, FTIR, TGA, XPS, Zetasizer and ICP-OES instruments. XRD results confirmed the high crystalline structure of the synthesized hybrid nanocomposites. Morphological analysis by SEM and TEM verified the successful decoration of nano-sized Cu-BDC MOFs over GrO and CNT platforms; whereas, EDS and XPS analysis confirmed the presence of all components in the hybrid nanocomposites. Bisphenol A was used in this study as a model organic pollutant that is sometimes present in the industrial wastewater to test the adsorption capacity of the prepared hybrid nanomaterials toward their removal from water. The hybrid nanomaterials showed remarkable adsorption capacity of 182.2 and 164.1 mg/g toward the removal of BPA, which was several times higher than that of 60.2 mg/g for Cu-BDC MOF itself. The Langmuir, Freundlich, Temkin and D-R isotherm models were applied to analyze the experimental data and the results revealed that the Freundlich model describes the experimental data best. A kinetic study was carried out and it showed that the prepared nanomaterials could remove maximum amount of BPA from water in 30 min. The pseudo-first order, pseudo-second order and intra-particle diffusion models were applied to evaluate the kinetic data and the results suggested that the kinetics data could be well fitted to the pseudo-second order kinetic model. Additionally, the BAP adsorption process onto the hybrid nanocomposites was spontaneous and exothermic. The π-π interactions between the BPA and hybrid nanomaterials played a vital role during the BPA adsorption process. The higher adsorption capacity and water stability makes them a good candidate for water remediation applications.

Green Synthesis of Boron Carbonitride with High Capacitance.

Boron carbonitrides (BCN) have attracted great interest in superhard or energy storage materials. In this work, thin BCN sheets were synthesized at 250 °C by a facile and green solvothermal method. The structure and morphology were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Based on the results of electrochemical experiments, the thin BCN sheet exhibited excellent capacitance performance (343.1 F/g at a current density of 0.5 A/g) and cycling stability (90%), which showed high potential applications in supercapacitors.

Enhanced magnetic and electrochemical properties of one-step synthesized PANI-Fe3O4 composite nanomaterial by a novel green solvothermal method

In this work, starting with Fe3+ and aniline (An), we demonstrate an environmental one-step solvothermal formation of a series of polyaniline-ferriferrous oxide (PANI-Fe3O4) nanostructured composites. During the solvothermal process, the following reaction processes occur at the same time: (1) Fe3+ ions were partially reduced to Fe2+ ions by An molecules (Fe3++e−→AnFe2+) and then (Fe3+ + Fe2+) ions converted to Fe3O4(Fe3++Fe2+→solvothermalconditionsFe3O4) and (2) the monomer An was catalytically polymerized by Fe3+/2+ ions to produce PANI (An→Fe3+/2+/sovothermalconditionsPANI). Thus the composite material PANI-Fe3O4 could be one-step obtained. It was surprising that the magnetic and electrochemical properties of the composite nanomaterials were remarkably enhanced. The remarkably enhanced magnetic and electrochemical properties were discussed and the induced magnetic field of PANI under applied magnetic field and doping Fe3+/2+ into PANI was herein considered to be important factors. The preparation method is simple, fast, low cost, and environmental, which provides an effective way to realize large-scale synthesis of the composite nanomaterial.

One-step synthesis of magnetic nanocomposite Fe3O4/C based on the waste chicken feathers by a green solvothermal method

The magnetic Fe3O4/C nanocomposite was one-step synthesized via a facile green solvothermal method from Fe(NO3)3·9H2O and waste chicken feathers (CF), without adding any reductive and alkaline reagents. The results demonstrate that Fe3+ ions are adsorbed and enriched on the surface of CF and partially reduced to Fe2+ by CF, which facilitate the in-situ conversion of Fe3+ and Fe2+ to Fe3O4. Simultaneously, Fe3+ ions can enhance/catalyze the carbonization of CF, and thereafter inducing the successful preparation of Fe3O4/C nanocomposites. In addition, the as-prepared Fe3O4/C nanocomposites exhibit increasing magnetic properties with increasing the amount of CF from 0.000 to 2.600g. The enhanced magnetic property was also discussed.

Green synthesis of magnetic MOF@GO and MOF@CNT hybrid nanocomposites with high adsorption capacity towards organic pollutants

Hybrid nanocomposites based on Cu-BTC MOF, graphene oxide (GO), carbon nanotubes (CNTs), and Fe3O4 magnetic nanoparticles (MNPs) were developed via a simple green solvothermal method, at which GO and CNT were used as platforms to load nanostructured Cu-BTC MOF and Fe3O4 MNPs. The as-synthesized hybrid nanocomposites were characterized by XRD, SEM, TEM, XPS, IR, Raman, TGA, and BET techniques. XRD measurements show highly crystalline structures for the prepared hybrid nanocomposites. Morphological analyses carried out by SEM and TEM also confirm successful growth of Fe3O4 MNPs and nanoparticulate Cu-BTC MOF over the carbon-based platforms. Chemical, elemental, and TGA analyses verify chemical bonding and successful compositing of the parent materials. Nitrogen isotherms show a cumulative pore volume of 0.360cm3g−1 for the hybrid nanocomposite of Fe3O4/Cu-BTC@GO compared to 0.030cm3g−1 of the sole Cu-BTC MOF, which suggests potential uses towards small molecule adsorption. We have found that use of GO and CNT substrates (i) diminish the aggregation and increases dispersive forces within the MOFs, (ii) lead to MOFs with different morphology and size, and (iii) result in formation of small pores between the MOF and the platforms. Adsorption capacity of the prepared nanomaterials was examined over methylene blue (MB) as a model organic pollutant. The developed hybrid nanomaterials show enhanced pollutant adsorption capacity compared to that of the parent materials. The improved adsorption capacity is attributed to the synergetic effect of covalent bonding between the parent materials as well as to the unique features of the nanoscale MOF. Overall, these novel materials may be considered as excellent candidates towards a variety of environmental applications such as water remediation.

Facile synthesis of 5 nm NaYF4:Yb/Er nanoparticles for targeted upconversion imaging of cancer cells

5nm intense green emission NaYF4:Yb/Er upconversion nanoparticles (UCNPs) with pure β phase was synthesized with a simple “green” strategy for the first time. Traditional organic solvothermal method is often applied to prepare the high-quality and uniform UCNPs, but the preparation of lanthanide-oleate complexes is laborious as heating and multistep post-treatment for purification are often required. The water-alcohols solvothermal method is environmentally friendly, but the fabricated UCNPs have big size, poor biocompatibility and high cytotoxicity, which limited their application for cell imaging. Herein, NaYF4:Yb/Er UCNPs were prepared with rare-earth nitrates RE(NO3)3 (RE=Y0.80 Yb0.18 Er0.02) as precursors and diethylene glycol (DEG)/ethylene glycol (EG)/water as the solvent. A facile green solvothermal method with the temperature being controlled at 300°C was developed. The as-prepared NaYF4:Yb/Er UCNPs were characterized and were found to have enhanced UC emission and controllable particle size. The as-prepared UCNPs were further functionalized via folic acid coating for the targeted imaging and improved bio- compatibility. It was made the UCNPs potential for upconversion bioimaging of living cells by the strong upconversion luminescence, the excellent biocompatibility, and the super-small size. The good colloidal stability and low cell cytotoxicity of the as-prepared UCNPs and the developed synthesis protocol might advance both the fields of UCNPs and biomolecule-based nanotechnology for future studies.

Co-doped Sb2Te3paramagnetic nanoplates

Paramagnetic Co-doped Sb2Te3nanoplates are fabricated using a facile and green solvothermal method.

Solvothermal fabrication and enhanced visible light photocatalytic activity of Cu2O-reduced graphene oxide composite microspheres for photodegradation of Rhodamine B

The addition of graphene oxide (GO) in the semiconductors has been regarded as one of the effective methods to enhance their photocatalytic activity. In this study, Cu2O-reduced graphene oxide (Cu2O-rGO) composites with low loading (0–0.5wt.%) of graphene oxide (GO) were produced by a one-step green solvothermal method in ethanol system by using Cu(NO3)2·3H2O and glutamic acid as copper precursor and reducing agent, respectively. During the solvothermal treatment, GO was reduced to rGO. The as-prepared Cu2O-reduced graphene oxide composite microspheres exhibited enhanced photocatalytic activity toward the degradation of RhB aqueous solution under visible light irradiation. At the optimal loading of graphene oxide (0.05wt.%), Cu2O-rGO composites showed the highest photocatalytic activity, exceeding that of pure Cu2O and commercial Degussa P25 by a factor of 2.9 and 7.9, respectively. The enhanced photocatalytic activity may be ascribed to the strong coupling interaction between Cu2O particles and rGO nanosheets, which reduces the recombination of charge carriers.

Enhanced dye-sensitized solar cells performance using anatase TiO2 mesocrystals with the Wulff construction of nearly 100% exposed {101} facets as effective light scattering layer

Anatase TiO2 mesocrystals with a Wulff construction of nearly 100% exposed {101} facets were successfully synthesized by a facile, green solvothermal method. Their morphology, and crystal structure are characterized by powder X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). Accordingly, a possible growth mechanism of anatase TiO2 mesocrystals is elucidated in this work. The as-prepared single anatase TiO2 mesocrystal's mean center diameter is about 500 nm, and the length is about 1 μm. They exhibit high light adsorbance, high reflectance and low transmittance in the visible region due to the unique nearly 100% exposed {101} facets. When utilized as the scattering layer in dye-sensitized solar cells (DSSCs), such mesocrystals effectively enhanced light harvesting and led to an increase of the photocurrent of the DSSCs. As a result, by using an anatase TiO2 mesocrystal film as a scattering overlayer of a compact commercial P25 TiO2 nanoparticle film, the double layered DSSCs show a power conversion efficiency of 7.23%, indicating a great improvement compared to the DSSCs based on a P25 film (5.39%) and anatase TiO2 mesocrystal films, respectively. The synergetic effect of P25 and the mesocrystals as well as the latters unique feature of a Wulff construction of nearly 100% exposed (101) facets are probably responsible for the enhanced photoelectrical performance. In particular, we explore the possibility of the low surface area and exposed {101} facets as an efficient light scattering layer of DSSCs. Our work suggests that anatase TiO2 mesocrystals with the Wulff construction is a promising candidate as a superior scattering material for high-performance DSSCs.

Trifold Tellurium One-Dimensional Nanostructures and Their Formation Mechanism

Uniform trifold tellurium nanostructures have been synthesized through a facile and green solvothermal method. Their structural characteristics were investigated by using various electron microscopy techniques. The results showed that tellurium nanostructures are well-crystallized and grow along the [0001] direction. They have the hexagonal crystal structure and trifold morphology with a lateral dimension of less than 100 nm. Through detailed structural analysis of intermediate products and structural modeling, the formation mechanism of trifold tellurium nanostructures has been well illustrated; that is, the trifold Te nanostructures shared two {112̅0} sidewalls of nanowire components with each other to reduce the entire system energy.

Preparation of Nanostructured Cu2SnS3Photocatalysts by Solvothermal Method

Nanostructured Cu-Sn-S powder was prepared by a relatively low-cost, simple, and green solvothermal method. Flower-like Cu2SnS3nanostructures were successfully synthesized in 50 vol% ethanol water solution at 200 °C for 7.5 h. The structure and photophysical properties of the as-obtained samples were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and UV-Vis diffusion reflectance spectroscopy. Results showed that the cubic and tetragonal Cu2SnS3was obtained by varying the ethanol contents. The band-gap energy of tetragonal Cu2SnS3nanocrystals is near the optimum for photovoltaic solar conversion in a single band-gap device.

Facile synthesis of TiO 2(B) crystallites/nanopores structure: A highly efficient photocatalyst

TiO 2(B) was prepared by a facile green solvothermal method and further characterized by the powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), raman spectroscopy and nitrogen sorption analysis, and it has been found that the as-synthesized sample possesses a unique crystallites/nanopores structure and has a very large surface area (484 m 2 g −1). Surprisingly, it exhibits the very high photocatalytic activity and good stability for the decomposition of methyl orange (MO) compared to that of P25.