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Effect of pH on the Properties of BiVO<sub>4</sub> by Hydrothermal Synthesis Method
摘要： Bismuth vanadate (BiVO4 ) powders were synthesized using Bi(NO3)3.5H2O and NH4VO3 as raw materials, NaOH and HNO3 for pH adjustment. The samples were characterized by X-ray diffraction ( XRD ), scanning electron microscopy (SEM ) and UV-vis diffuse reflectance spectra techniques. The results show that the pH of precursor solution has great effect on the composition and morphology of products. Synthetic product was BiVO4 with two kinds of crystal shape ( monoclinic and tetragonal ) with pH of 3; synthetic product was pure monoclinic phase BiVO4 when the pH is between 5-9. Whereas, V2O5 and Bi2O3 appeared when the pH was 11; synthetic product was a mixture of V2O5 and Bi2O3 with pH of 13, and BiVO4 didn’t exist. The photocatalytic activity was evaluated by the degradation of methylene blue solution. It is shown that the synthetic sample has the best photocatalytic ability with pH of 5. The degradation of methylene blue reaches 84.7% when irradiated for 240 min by high pressure mercury lamp, and the sample synthesized at 13 for pH has strong adsorption capacity and poor photocatalytic ability.
关键词： Bismuth vanadate,Photocatalytic activity,pH value,Hydrothermal synthesis
更新于2025-09-23 15:22:29
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Metal-Organic Frameworks Derived from Zero-Valent Metal Substrates: Mechanisms of Formation and Modulation of Properties
摘要： The replicative construction of metal–organic frameworks (MOFs) templated with solvent-insoluble solid substrates is of marked importance, as it allows for the assembly of 2D and 3D macro- and mesoscopic architectures with properties that are challenging to attain by the conventional solution-based synthesis approach. This work reports an in situ and direct construction of MOFs from zero-valent metal substrates via a green hydrothermal oxidation–MOF construction chemistry without the use of any additional metal source, chemical reagents, or acidification of solvent, and elucidates the zero-valent metal derived formation mechanisms of MOFs and their structure modulation to 1D nanofibers (NFs), 2D film, and 3D core–shell microstructures. Through modulation of the competing surface oxidation-dissolution and MOF crystallization kinetics, Al@MIL-53 core–shell microstructures and MIL-53 (Al) NFs are obtained that exhibit unique morphologies and marked properties superior to the conventional MIL-53 (Al) powders. The generality of zero-valent metal-templated synthesis of MOFs is demonstrated with formation of MIL-53 (Al), HKUST-1, and ZIF-7 polycrystalline films on Al, Cu, and Zn metal meshes, elucidating the significance of the approach utilizing solid metal substrate that can be easily processed into various shapes, architectures, and compositions.
关键词： MOF nanofibers,formation mechanism,core–shell structure,templated synthesis,metal–organic framework
更新于2025-09-23 15:22:29
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Effect of grain size and temperature on DC electrical conductivity of tin oxide nanoparticles synthesized by gel combustion method
摘要： Tin oxide (SnO2) nanomaterials of different grain size have been prepared using gel combustion method by varying the fuel (C6H8O7) to oxidizer (HNO3) molar ratio as a process parameter. The prepared samples were characterized by using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Energy Dispersive Analysis X-ray Spectroscope (EDAX). The XRD patterns showed the formation of single phase Tetragonal rutile structure. The average particle size is found to be in the range of 19–34 nm. SEM images show high porosity in the material. The DC electrical conductivity of SnO2 thick film increases with the temperature significantly from 308K to 670K. The DC electrical conductivity of SnO2 thick film decreases with decrease in grain size due to the effect of surface to volume ratio while activation energy increases with decrease of grain size.
关键词： Thick film,Tin oxide,Activation energy,DC conductivity,Combustion synthesis
更新于2025-09-23 15:22:29
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High-Throughput Combinatorial Synthesis of Stimuli-Responsive Materials
摘要： Stimuli-responsive materials find wide applications in different biological and medical settings. Traditionally, stimuli-responsive materials are synthesized and evaluated individually one-by-one. The drawback of this approach is the scarceness of possible combinations that can be practically tested for the purpose of saving time, consumables, and manpower. High-throughput methods are therefore important to accelerate the discovery of stimuli-responsive materials and to screen for biological interactions of interest in parallel. The objective of this article is to provide an overview of the successful employment of combinatorial high-throughput synthesis and screening of stimuli-responsive materials. In particular, these include thermoresponsive and hydroresponsive materials. Advantages of a combinatorial approach as well as of utilizing high-throughput methodologies in the development of stimuli-responsive materials are reviewed. Possible evolution trends of stimuli-responsive materials, advanced by high-throughput methodologies, are discussed.
关键词： combinatorial libraries,material microarrays,smart materials,stimuli-responsive,high-throughput synthesis
更新于2025-09-23 15:22:29
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Comparative study on blue-turquoise silicate apatite phosphors prepared via different synthesis routes
摘要： Different types of gel precursors were obtained via microwave-assisted precipitation, gel-combustion, sol–gel, and Pechini methods in order to prepare Ca2Y7.76Ce0.12Tb0.12(SiO4)6O2 phosphors with apatite structure. The processes involved during the thermal treatment of precursors were revealed by TGA– FT-IR coupling. ICP-OES reveals that the incorporation degree of dopants (Ce3+, Tb3+) in silicate lattice are close to theoretical values while Ca2+ and Y3+ values shows differences depending on the synthesis route. The phosphors composition, morphology, structure, and optical characteristics are revealed by SEM, XRD, FTIR, and luminescent investigations. Pure hexagonal apatite with crystallite size of 76.5 nm was identi?ed in sample prepared by gel-combustion, while cubic-Y2O3 and monoclinic-Y2SiO5, as secondary phases, were found in precipitated samples. The purity phase was enhanced by increasing the TEOS amount during precipitation. As a result of the Ce3+ incorporation into different symmetry sites, the excitation spectra are dominated either by 321 or 360 nm band. Turquoise emission of apatites is shifted toward blue region by increasing the excitation wavelength from 231 to 360 nm.
关键词： Silicate apatite,Luminescence,Wet chemical synthesis,Phosphors
更新于2025-09-23 15:22:29
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Two-Dimensional Conducting Polymers: Synthesis and Charge Transport
摘要： Current technological advances and prolific endeavors have entrenched two-dimensional conducting polymers as the rapidly emerging interface across a diversity of functional materials for flexible electronics, sensors, ion-exchange membranes, biotechnology, catalysis, energy storage, and conversion. Rational design and fabrication of polymeric nanostructures enriched with well-ordered geometry are appealing and endorse significant impact on their inbuilt electrical, optical, and mechanical properties. In particular, recent interest in controlled hierarchical assembly of monomers/oligomers proved the free-standing sheet-like structures with exotic features of high conductivity and flexibility. Yet, the ongoing research to make nanometer-thick polymers suffers from limitations to access large-area, mechanical stability, and high-range internal ordering. In this perspective, we focus on the radical approaches that highlight confinement-entitled features of two-dimensional polymeric materials correlating to their interface or template-assisted synthesis, structure–property relationship, charge transport properties, and future scopes for relevant practical enactments.
关键词： 2D assembly,self-organization,conjugated polymers,charge transport,interfacial synthesis
更新于2025-09-23 15:22:29
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Simultaneous fluorometric determination of the DNAs of Salmonella enterica, Listeria monocytogenes and Vibrio parahemolyticus by using an ultrathin metal-organic framework (type Cu-TCPP)
摘要： Ultrathin (<10 nm) nanosheets of a metal-organic framework (MOF-NSs) were prepared in high-yield and scalable production by a surfactant-assisted one-step method. The MOF-NSs possess distinguished affinity for ssDNA but not for dsDNA. This causes the fluorescence of the labeled DNA to be quenched. On binding to the target DNA (shown here for Salmonella enterica, Listeria monocytogenes and Vibrio parahemolyticus), the labeled duplex is released and the fluorescence of the label is restored. The labels Texas Red, Cy3 and FAM were used and give red, red or green fluorescence depending on the kind of pathogen. The detection limits are 28 pM, 35 pM and 15 pM for the gene segments of Salmonella enterica, Listeria monocytogenes and Vibrio parahemolyticus, respectively.
关键词： FRET,Surfactant-assisted synthesis,Two dimensional nanomaterials,Pathogens,Fluorescence sensor,Multiplex detection
更新于2025-09-23 15:22:29
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Sm3+, Tb3+ co-doped NaLa(MoO4)2 temperature sensing materials based on the fluorescence intensity ratio
摘要： In optical temperature sensors, the method of measuring temperature based on Fluorescence Intensity Ratio (FIR) has been paid tremendous attention due to its fortissimo anti-excitation power noise and the ability of anti-signal transmission channel to transmit light unsteady [1e10]. The above method has the advantages of non-contact, resistance to high temperature, wide temperature range, quick response and being able to measure small objects. The optical temperature sensing technology based on the FIR is used to detect the temperature through detecting the ratio of emitted fluorescence intensity between a pair of specific thermal coupling energy levels related to the temperature [11e15]. The fluorescence emission efficiency of Sm3+ doped oxide in 4G5/2 energy level was quite high. Sm3+ emits bright orange-red color. Tb3+ doped oxide is the strongest fluorescence branch in emission from 5D4- 7F5 [16,17]. If the thermal-quenching trend of luminescence of Sm3+ and Tb3+ is different, the FIR will change with temperature. So FIR can be used to indicate the temperature. Therefore, intensive study of Sm3+ and Tb3+ co-doped materials has great prospects, because it can reveal broad luminescence color variability from green to red. Molybdate has chemical stability and thermal stability, rare earth ions have strong 4f-4f transition absorption and transition emission in this host. Therefore it is a wally host [18,19]. Based on the above-mentioned reasons, in this paper Sm3+, Tb3+ co-doped NaLa(MoO4)2 samples of different morphology have been prepared and studies the temperature sensing characteristics.
关键词： Phosphor,Optical temperature sensing,Chemical synthesis,Luminescence
更新于2025-09-23 15:22:29
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Bichromophoric pyrazoline derivative with solvent-selective photoluminescence quenching
摘要： The quenching of fluorescence in the presence of chloromethanes, which is an unprecedented effect for pyrazolines, has been evidenced for the first time in the case of 1,3-diphenyl-5-{4-[(4-vinylbenzyl)oxy]phenyl}-4,5-dihydropyrazole. The detailed synthesis of this aryl trisubstituted pyrazoline that combines two chromophoric units in a non-conjugated manner is presented. The compound has been extensively characterized from a structural point of view, and its crystal structure has been determined by single crystal X-ray crystallography. The fluorescence study has evidenced the particular behavior of this pyrazoline derivative in solutions of chloromethanes, and the insight gained from the experimental data has been useful in elaborating a plausible fluorescence quenching mechanism. The investigated compound was modeled by Density Functional Theory (DFT) to point out the particularities of the electron transitions in gas phase as well as in the implicit solvents. Also, the HOMO-LUMO energy gap, mapped electrostatic potential, electronic density, dipole moment and polarizability have been reported for the pyrazoline derivative.
关键词： Fluorescence,Synthesis,Quenching,Molecular modelling,Bichromophore,Pyrazoline
更新于2025-09-23 15:22:29
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Medium viscosity effect on fluorescent properties of Sn(IV)-tetra(4-sulfonatophenyl)porphyrin complexes in buffer solutions
摘要： Supramolecular triads consisting of hydrophilic Sn(IV)-tetra(4-sulfophenyl)-porphyrin and two axial guests such as propylphenol, tyrosine, and 2-(2-hydroxyphenyl)-benzoxazole were synthesized. The structures of synthesized complexes were identified by experimental spectroscopic and quantum-chemical simulation methods, and their fluorescent properties were studied in various viscosity media (mixed phosphate buffer-glycerin solvents of different composition). The effect of axial ligand structure on the fluorescent properties of these triads (due to the hydrogen bonding or π-π stacking between the components of ?host-guest? systems) is discussed. The potential use of synthesized complexes as environmental probes of local viscosity is proposed.
关键词： synthesis,ROESY,fluorescent properties,hydrogen bonding,DOSY,2D NMR,DFT,viscosity,Sn(IV)-porphyrins
更新于2025-09-23 15:22:29