Optimal Synthetic Conditions Research Articles

Synthesis and Defect Characterization of Phase-Pure Zr-MOFs Based on Meso-tetracarboxyphenylporphyrin.

The reaction of zirconium salts with meso-tetra(4-carboxyphenyl)porphyrin (TCPP) in the presence of different modulators results in the formation of a diverse set of metal-organic frameworks (MOFs), each displaying distinct crystalline topologies. However, the synthesis of phase-pure crystalline frameworks remains challenging due to the concurrent formation of different polymorphs. The acidity and concentration of the modulator greatly influence the outcome of the MOF synthesis. By systematically varying these two parameters, selective framework formation can be achieved. In the present study, we aimed to elucidate the effect of modulator on the synthesis of zirconium-based TCPP MOFs. With the help of powder X-ray diffraction and scanning electron microscopy, modulator candidates and the optimal synthetic conditions yielding phase-pure PCN-222, PCN-223, and MOF-525 were identified. 1H nuclear magnetic resonance analysis, thermogravimetric analysis, and N2 gas sorption measurements were performed on select MOFs to gain insight into the relationship between their defectivity and modulator properties.

Novel mesoporous MnO2/SnO2 nanomaterials synthesized by ultrasonic-assisted co-precipitation method and their application in the catalytic decomposition of hydrogen peroxide

Novel mesoporous MnO2/SnO2 catalysts were successfully synthesized via traditional and ultrasonic co-precipitation methods. Moreover, their catalytic efficiencies were evaluated in decomposition of hydrogen peroxide (H2O2). Interestingly, it was found that the mixing of MnO2 with SnO2 catalyst led to a significant improvement in their catalytic efficiencies compared with single oxides catalysts. However, the influence of ultrasonic power and irradiation time on MnO2/SnO2 nanomaterials were compared to get optimum synthetic condition. Subsequently, the catalysts were characterized by X-ray diffraction (XRD), N2 adsorption-desorption analysis and high-resolution transmission electron microscopy (HR-TEM). Results represented that the effect of ultrasonic power and irradiation time on MnO2/SnO2 catalysts exerted a great influence on the BET surface area and average particle diameter. Furthermore, the results showed that the best catalytic efficiency was obtained for the mesoporous MnO2/SnO2 catalyst which is sonicated at power of 60% for 30 min as optimum conditions. Finally, the outcomes appeared that the catalysts synthesized by ultrasonic co-precipitation method were more efficient than those synthesized by traditional co-precipitation in catalyzing H2O2 decomposition.

PROSPECTS OF CELLULOSE NITRATES FROM UNCONVENTIONAL FEEDSTOCKS FOR USE IN COMPOSITE EX-PLOSIVES

Research on the synthesis of in-demand industrial-grade cellulose nitrates from unconventional feedstocks such as Miscanthus, oat hulls, intermediate flax straw is of the most immediate interest due to a lack of national cotton and to encountered problems with wood cellulose. The celluloses derived herein from the said unconventional feedstocks are inhomogeneous in nature, are composed mostly of short fibers, and have non-cellulosic constituents as opposed to elite cotton – these all pose certain difficulties in developing such a nitrocellulose production technology. Besides, it is worth noting that cellulosic fibers of the said feedstocks are peculiar in nature on their own. The findings obtained herein suggest that the research problem can successfully be solved. The pulp samples obtained in this study from the unconventional biomasses by the nitric-acid process have 85−95% α-cellulose and 580−1420 degree of polymerization. These specimens similar in properties to industrial Colloxylin were obtained under optimal synthetic conditions for highly soluble cellulose nitrates by using commercial mixed acid: 11.97–12.29% N, 8–15 mPa∙s, and 98% solubility in alcohol–ester mixture. The morphological features of the resultant cellulose nitrates were characterized by scanning electron microscopy. Infrared spectroscopy revealed the intrinsic frequencies (2560–2550, 1670–1660, 1650–1620, 1280–1270, 830–810, 750–740, 680–670 cm-1) that identify the resultant products as cellulose nitroesters. The practical importance of this research is that the nitrocelluloses obtained from the unconventional non-woody feedstocks can be used as the promising component in the manufacture of explosive formulations.

Cerasomes containing magnetic nanoparticles: synthesis and gel-filtration chromatographic characterization

Cerasomes containing encapsulated magnetic nanoparticles were synthesized and characterized by gel filtration chromatography, elemental analysis, and photon correlation spectroscopy. Laboratory microwave system was used for the preparation of magnetic nanoparticles. The optimal synthetic conditions were revealed, and the inclusion of nanoparticles in the cerasome composition was experimentally confirmed.

Ultrasonic-Assisted Synthesis of a Zn(II) Coordination Polymer in Aqueous Media and Its High-Performance Luminescent Sensing for 2,4,6-Trinitrophenol

A novel Zn(II) coordination polymer based on 5-(3-pyridyl)-1,3,4-oxadiazole-2-thiol (Hpzt), namely [Zn(pzt)2]n or Zn-CP, was synthesized by two different synthetic methods. The bulk polycrystals and single crystals of Zn-CP were obtained by a conventional solvothermal method at 90 °C. Zn-CP exhibits a two-dimensional (2D) coordination network that contains the uncoordinated Lewis basic sites within each layer. Interestingly, a simple and environmentally friendly sonochemical synthesis of the Zn-CP in an aqueous media could be performed at room temperature. The optimal synthetic conditions were studied. The uniform microplates of Zn-CP were obtained within 30 min with the addition of pyridine, acting as a size modulator and a deprotonating reagent. The influence of the amount of the modulator and the sonication time on the crystal size was investigated. Moreover, a Zn-CP suspension in an ethanolic media has been used as a luminescence sensor for the detection of nitroaromatic compounds. It shows highly sel...

Synthesis of hollow carbon spheres from polydopamine for electric double layered capacitors application

This paper reports a surfactant-assisted template method for synthesis of hollow carbon nanospheres by using polydopamine (PDA) as carbon source and ZnO as template. In the help of surfactant micelles, spherical ZnO particles are firstly formed and then coated with PDA films at room temperature without structure damage by the alkaline conditions needed for self-polymerization of dopamine. After carbonization in N2 atmosphere followed by ZnO removal, hollow carbon spheres with adjustable particle size (150–300 nm), high specific surface area (SSA, ~1100 m2 g−1) and optimized mesopore size distribution are obtained. The effects of surfactant content and carbonization temperature on the morphology and the electrochemical properties of the as-prepared carbons have been further investigated. The hollow carbon spheres obtained at optimum synthetic conditions exhibit outstanding electrochemical properties including high capacitance (156 F g−1 at 2 mV s−1) and rate capability (125 F g−1 even at 200 mV s−1) as well as cycling stability with 98% capacitive retention after 16,000 cycles, suggesting that it is a promising electrode material for the application of electric double layered capacitors.

Synthesis of ATN‐Type FeAPO‐39 Molecular Sieves without Solvent using the Additional Structure‐Directing Effect of the Iron Source

ATN‐type FeAPO‐39 molecular sieves with high iron content has been successfully synthesized under non‐solvent conditions, which is the first example of iron‐incorporated aluminophosphate with the ATN‐zeotype structure. The optimum synthetic conditions of this material were refined. It was found that the following synthetic conditions, i.e. a low P2O5/Al2O3 ratio, a high DPA/Al2O3 ratio (DPA: di‐n‐propylamine) and an elevated crystallization temperature, seemed to be more favorable for the non‐solvent synthesis of ATN phase. The composition and structural characteristics of resultant relatively pure FeAPO‐39 molecular sieves were intensively studied by XRD, FT‐IR, TG‐DTA, CHN elemental analysis, ICP‐AES, SEM, TEM, N2 physisorption, UV/Vis diffuse reflectance spectroscopy and Mössbauer spectroscopy analyses. The iron content and zeolite yield of FeAPO‐39 material were found to be as high as 5.56 wt.‐% and 82.6 %, respectively. The results of FT‐IR, TG‐DTA and CHN elemental analysis indicate that DPA molecules may co‐direct the synthesis of ATN zeolites along with additional structure‐directing agent NH4+ ions resulting from iron source. Owing to the specific structure‐directing role provided by iron source, the synthetic strategy presented here may find a potential application in the non‐solvent synthesis of other aluminosilicate and aluminophosphate zeolites with novel frameworks.

Microwave-assisted ionothermal synthesis of Fe-LEV molecular sieve with high iron content in low-dosage of eutectic mixture

Abstract Iron-containing aluminophosphate molecular sieve with LEV topology (Fe-LEV molecular sieve) has been successfully synthesized by a microwave-assisted ionothermal method in low-dosage of eutectic mixture solvent, which is the first example of Fe incorporated aluminophosphates with the LEV-zeotype structure. The optimum synthetic conditions of this material were refined. The structure and morphology of a representative Fe-LEV sample, as well as the structure directing effect of eutectic mixture were thoroughly analyzed by various techniques including XRD, 27Al and 31P MAS NMR, ICP-AES, DR UV-Vis, ESR, XPS, N2 adsorption/desorption, NH3-TPD, SEM, TEM, EDX, CHN elemental analysis, TG-DTA and FT-IR spectra. It was found that the combined effect of the starting precursor and a suitable structure-directing agent yielded an appropriate crystallization system of Fe-LEV molecular sieve, for which choline cations and intact tetraethylammonium bromide molecules were identified to be the structure-directing agents. The calcined Fe-LEV molecular sieve exhibits higher specific surface area and iron content, as well as a medium acidity and special hierarchical structure with both micropores and mesopores, implying that these zeolitic materials have a great potential in some industrially relevant applications.

Rapid SERS detection of acid orange II and brilliant blue in food by using Fe3O4@Au core–shell substrate

With the widespread application of synthetic pigments in the food industry, food safety incidents caused by illegal addition of pigments have become more frequent. In this study, we synthesized core–shell nanomaterials for use in sensitive, fast, convenient, nondestructive detection and having good surface-enhanced Raman scattering (SERS) effect. The optimal synthetic conditions were selected to study semi-quantitative detection. Calculations for acid orange II and brilliant blue were done using density functional theory, and the characteristic peaks and vibration conditions for each pigment were identified. Acid orange II and brilliant blue in the food samples yellow croaker, braised pork, red pepper, green dumpling, and red wine were detected by SERS screening. Results were compared with those obtained by standard high-performance liquid chromatography method in order to verify the SERS method. The core–shell nanoparticles showed good performance in the rapid detection of pigments in food.

Integrating Superwettability within Covalent Organic Frameworks for Functional Coating

Summary Despite the availability of a variety of skeletons for covalent organic frameworks (COFs), control of pore-surface wettability remains undeveloped, which could immensely expand their overall versatility. Herein, we contribute an effective strategy for imparting superwettability on COFs by chemically coating the pore surface with perfluoroalkyl groups to confer them with superhydrophobicity. Taking advantage of controllable modification, the resultant COFs retain the porosity and crystallinity of the pristine COFs. Benefiting from the bulk superhydrophobicity of the COF crystals and the feasibility of COF synthesis, they can be used as a coat or in situ integrated within various substrates; once applied, this renders them superhydrophobic. Given the modular nature, this protocol is compatible with the development of various specific wettabilities in COFs, which thereby constitutes a step for expanding the scope of COF applications and provides many opportunities for the processing of advanced materials and devices.

Antibacterial activity and catalytic activity of biosynthesised silver nanoparticles by flavonoids from petals of Lilium casa blanca

Biosynthesis of silver nanoparticles (AgNPs) by flavonoids extracts from petals of Lilium casa blanca was reported. Reaction conditions such as pH, concentration of flavonoids or silver nitrite, reaction temperature and reaction time were optimised to control the formation of the AgNPs. Synthesised AgNPs were characterised by UV–Vis spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential measurement and Fourier transform infrared (FT-IR) spectroscopy. Stability, antibacterial and catalytic activities of the synthesised AgNPs were also discussed. The optimum synthetic conditions were 10 mL 20 mM AgNO3 added to 1 mL flavonoids extracts, adjusting pH to 10, and reacted at 70°C for 1 h. The formation of AgNPs was confirmed by UV–Vis spectroscopic analysis, which showed maximum absorption peak at 404 nm. TEM analysis revealed spherical particles with size about 12.7 nm. FT-IR spectra revealed flavonoids were present on the surface of the AgNPs. AgNPs showed highest antibacterial activity against Escherichia coli and Salmonella, and the lesser antibacterial activity of AgNPs was found against Bacillus subtilis and Staphylococcus aureus. The biosynthesised AgNPs showed good catalytic activity as well by hydroboration of p-nitrophenol. Catalytic reduction followed pseudo-first-order kinetic.

Synthesis of copper oxides films via anodic oxidation of copper foil followed by thermal reduction

Copper oxides films were successfully synthesized via anodic oxidation of copper foil at various conditions followed by thermal reduction of oxidized samples in inert nitrogen atmosphere. The morphology and phase composition of final and intermediate products were determined by scanning electron microscopy, X-ray diffraction and Raman spectroscopy techniques. Optimal synthetic conditions of Cu2O films on copper foil surface were established.

One‐Pot Hydrothermal Synthesis of Highly Fluorescent Polyethyleneimine‐capped Copper Nanoclusters for Specific Detection of Rifampicin

Herein, a novel bright‐green and highly fluorescent polyethyleneimine capped copper nanoclusters (CuNCs@PEI) has been hydrothermally synthesized, which is employed as a fluorescence probe to determine rifampicin. Under optimum synthetic conditions, the morphology, surface chemistry and optical features of resulting CuNCs@PEI are well characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, UV–Vis absorption spectra, transient and steady‐state fluorescence. In comparison to previous reports, the new species with a larger diameter of approximately 3 nm exhibit higher fluorescence quantum yield (QY) up to nearly 10.7%, and demonstrate tolerability to extreme pH, high ionic strengths as well as long‐term UV irradiation. These excellent optical properties ascribe to unique grain size and surface chemical features of products, which are further discussed in this work. In addition, we employed as‐prepared CuNCs@PEI to detect rifampicin based on fluorescence quenching phenomenon. The fluorescence intensity of probe is linearly proportional to rifampicin over the concentration rage from 0 to 20 μM, where the limit of detection (LOD) is 50 nM. Besides, this probe can be also used to assay rifampicin in serum samples with satisfactory recoveries.

Hydrothermal synthesis and upconversion luminescent properties of Sr2LaF7 doped with Yb3+ and Er3+ nanophosphors

Upconversion phosphors Sr2LaF7 co-doped with Yb3+ and Er3+ are synthesized via hydrothermal method. The phase compositions of Sr2LaF7 phosphors with different amounts of Yb3+ and Er3+ dopants, pH values, and complexing agents are characterized by X-ray diffraction (XRD). The crystal structure and morphology of Sr2LaF7 phosphor doped with 15% Yb3+/ 1% Er3+ is refined by the Rietveld method and transmission electron microscopy (TEM). Under 980 nm laser excitation, Yb3+ and Er3+ co-doped Sr2LaF7 phosphors exhibit red emission around 670 nm generated by the 4F9/2 → 4I15/2 transition and green emissions centering around 550 nm and 523 nm generated by the 4S3/2 → 4I15/2 and 2H11/2 → 4I15/2 transitions of Er3+, respectively. The optimum synthetic conditions for upconversion luminescence for Sr2LaF7 co-doped with Yb3+ and Er3+ are discussed and determined to be 15% Yb3+/ 1% Er3+ with EDTA-2Na as the complexing agent under pH value = 8, and the corresponding Commission International de L′Eclairage (CIE) coordinates are calculated to be x = 0.4293 and y = 0.5589 with reddish yellow color visible to naked eyes under the 980 nm laser excitation. The related upconversion mechanisms of Yb3+ and Er3+ co-doped Sr2LaF7 depending on the pump power are also studied in detail.

Fabrication of a Biomass-Based Hydrous Zirconium Oxide Nanocomposite for Advanced Phosphate Removal

Wheat straws were modified by 3-chloro-2-hydroxypropyl trimethylammonium chloride (CTA) to obtain aminated wheat straw St-N'. The optimum synthetic conditions were determined to be NaOH with 30% mass fraction, CTA of 100 mL, reaction temperature of 80℃, and reaction time of 3 h, which was verified by orthogonal experiments. Nano-sized hydrous zirconium oxides (HZO) were immobilized into St-N' by an in situ precipitation method to obtain the nanocomposite St-N'-Zr. The SEM, TEM, XRD, and BET results indicated that the nano-sized HZO with 50-100 nm sizes were uniformly loaded onto the inner surface of the biomass-based carrier St-N' that was amorphous in nature. A Langmuir adsorption isotherm fitted the adsorption process well, and the maximum adsorption amount was calculated to be 33.90 mg·g-1. The optimal pH range was 1.8-6.0, displaying good removal capacity of phosphate in acidic waters. In the presence of high levels of competing anions, the phosphate adsorption still retained more than 70% of the original amount, showing the higher preference of St-N'-Zr towards phosphate than towards the commercial anion exchanger D-201. After 10 cycles of adsorption-desorption, the removal efficiency remained stable, confirming the good regeneration ability and potential application of St-N'-Zr.

Na3V2(PO4)3/C Composite Prepared by Sol-Gel Method as Cathode for Sodium Ion Batteries

Na3V2(PO4)3 (NVP) composites were prepared by a facile sol-gel method. The optimal synthetic conditions were systematically investigated by orthogonal test method and single factor of calcination temperature, which had maximum effect on the electrochemical properties of the sample. The optimal Na3V2(PO4)3/C (denoted as Opt-NVP/C) has been prepared under the condition of the calcination temperature at 800°C, the molar ratio of NVP to C as 1:1, sol-gel reaction temperature at 80°C and the calcination time of 16 h. The capacity retention decreased by only 2% from the initial value of 106.7 mAh g−1 to 104.5 mAh g−1 after 100 cycles at 0.2C. Enhanced electrochemical performance can be attributed to reduced polarization and stable operating voltage window. The high purity and crystallinity at the proper calcination temperature and porous particles morphologies are related to lower polarization and higher Na+ diffusion coefficient, respectively.

Preparation of a Cationic Environment-friendly Fixing Agent

Initially waste feather protein was used to prepare a reactive cationic crosslinking modified agent, WLS, as a starting material which was used to prepare a quaternary ammonium type cationic environment-friendly fixing agent (named WLSPR) for dyeing cotton fabric with reactive dyes after solid colour processing. In this paper, the degree of staining on white cloth from colored cloth after a soaping process was assessed (by determination of the K/S value) as well as the washing fastness etc. as the evaluation indices. The optimum synthetic conditions of fixing agent WLSPR were determined, and the structure and properties of the additives characterised. The results show that the maximum absorption wavelength of the cationic protein fixing agent WLSPR is 195nm. Synthesis of the environment-friendly fixing agent WLSPR using optimum conditions can reduce white staining during soap washing , effectively improving the cotton fabric in terms of colour fastness to washing and rubbing fastness. Based on infrared spectral characterisation, it was confirmed that the protein-based cationic auxiliary additives were synthesised.

One-pot solid phase pyrolysis synthesis of highly fluorescent nitrogen-doped carbon dots and the interaction with human serum albumin

One kind of fluorescent nitrogen–doped carbon dots (denoted as NCDs) was successfully fabricated by a simple and facile one–pot solid phase pyrolysis process using citric acid and glycine as raw materials. The obtained NCDs under the optimal synthetic conditions have a fluorescence quantum yield up to 35.6% and show a spherical shape with an average diameter of about 3.0nm. Moreover, NCDs can emit strong blue fluorescence and the surfaces when excited at 345nm and their surfaces were decorated with lots of carboxyl, hydroxyl and amine groups. In order to further elucidate the effect of NCDs to protein, steady state/time-resolved fluorescence, UV–vis absorption, circular dichroism (CD), and Raman spectroscopic techniques as well as cyclic voltammetry (CV) were employed to explore the interaction of the as-synthesized NCDs with human serum albumin (HSA) in the simulated physiological environment. The experimental data reveal that NCDs could quench the intrinsic fluorescence of HSA via the formation of a ground-state complex with the association constants of the order of 104L/mol. The values of thermodynamic parameters obtained at three different temperatures suggest that the binding reaction of NCDs with HSA mainly driven by hydrophobic forces and hydrogen bonds was spontaneous. Furthermore, the displacement experiments confirm that the binding of NCDs primarily took place in site I of HSA. The average distance between NCDs and tryptophan (Trp) residue of HSA was estimated to be 2.3nm according to the theory of Förster non-radiation energy transfer. Finally, the analysis of synchronous fluorescence, three-dimensional fluorescence (3D), Raman, and CD spectra manifests that HSA underwent some conformational changes by unfolding the polypeptides of protein and increasing the polarity of the microenvironment surrounding both Trp and tyrosine (Tyr) residues in the presence of NCDs.

Optimal synthetic conditions for oxetane-substituted chitosan (OXE-CHI) and polyethylene glycol (PEG) network self-healing agent

Optimal synthetic conditions for oxetane-substituted chitosan (OXE-CHI) and polyethylene glycol (PEG) network self-healing agent

Nano and Submicron Olivine Synthesized by Hydrothermal Process

Development of cobalt free olivine material as a cathode for lithium ion battery was carried out. Especially, in this study, Mn substituted olivine was synthesized by hydrothermal process. With the reaction conditions, such as hydrothermal reaction temperature and times, the morphology and particle size were variable. Under the optimum synthetic condition, finer olivine particle was obtained by hydrothermal process. In addition, the effect of Mn addition on the microstructure of olivine was investigated.