- 标题
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Dispute in photocatalytic and photoluminescence behavior in ZnO/graphene oxide core-shell nanoparticles
摘要： ZnO/graphene oxide core-shell nanoparticles (ZGNPs) were prepared by via in-situ chemical synthesis and electrolysis. This report addresses the disagreement in the photocatalytic and photoluminescence behavior in this system. XRD, Raman, HRTEM, PL and UV-Vis were able to confirm ZnO nanoparticles and core-shell structures formation at various temperatures. A little shift was observed in Raman for ZGNPs after conjugating. PL showed a few peaks that were not related to the graphene, which depends on the synthesis route and defects. After conjugating between ZnO and Graphene, two mechanisms are suggested. The first is band structure modification in the boundary of core and shell. The second one is diffusion of functional group in GO as a dopant on ZnO surface.
关键词： Nanoparticles,Photoluminescence,Photocatalysts,Core-Shell,Nanocomposites,ZnO-Graphene
更新于2025-09-23 15:23:52
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Core-shell type Tourmaline@ZnO composites equipped with carbon dots for high efficiency photocatalyst
摘要： Here we report that a novel type of Tourmaline@ZnO core-shell composite equipped with carbon dots (CDs) as multi-band light active sensitizer has been successfully designed and efficiently utilized as the superior photocatalyst towards the degradation of methyl orange (MO) under Xenon lamp at room temperature. The bare ZnO, CDs/ZnO, Tourmaline@ZnO and CDs/Tourmaline@ZnO were systemically synthesized following the facile homogeneous precipitation process and characterized in detail by XRD, FTIR, FESEM, HRTEM, UV-Vis, PL, PC and EIS investigations in succession. Bare ZnO displays as 3-dimensional hierarchical nano-flowers with large specific surface area reaching up to 62.049 m2/g by BET measurement, while the other composite products confirm the core-shell structures with CDs inlaying on ZnO layer surfaces. The photocatalytic activities of the polynary hybridations obtain effective enhancements compared to pure ZnO, the ternary system (CDs/Tourmaline@ZnO) deserves more attention for achieving the maximum (91.25%). It should been the synergistic effect on the highly efficient catalysis performances exerting by the presence of CDs modifier and the Tourmaline core, which make ZnO matrix receive more photo-generated electrons and broaden the visible light response originated from CDs, and synchronously hinder the recombination of electrons-hole pairs by the spontaneous polarization and surface electric field of Tourmaline.
关键词： Tourmaline,photocatalysis,ZnO,core-shell,CDs
更新于2025-09-23 15:23:52
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An infrared IgG immunoassay based on the use of a nanocomposite consisting of silica coated Fe3O4 superparticles
摘要： A reliable, rapid and ultrasensitive immunoassay is described for determination of immunoglobulin G (IgG). It is making use of biofunctional magnetite (Fe3O4) superparticles coated with SiO2 and serving as an infrared (IR) probe. The unique IR fingerprint signals originating from the transverse and longitudinal phonon modes, respectively, of the asymmetric stretching of the Si–O–Si bridges display a satisfactory resistance to optical interference from the environment. The adoption of Fe3O4 superparticles instead of Fe3O4 nanoparticles as the magnetic core warrants a controllable structure and a strong magnetic response. This facilitates the efficient purification of the probes and the alleviation of the interfacial resistance between the liquid-solid interfaces by using a magnet. The gold-coated substrate was used to immobilize goat-anti-human IgG. The analyte (human IgG) was incubated with the IR probes, and then captured by the substrate immobilized antibody with the assistance of an external magnetic field. The integral area of the IR absorption band between 1250 cm?1 – 900 cm?1 was chosen for quantitative assay. The limit of detection is 95 fM, which is two orders of magnitude better than that without the magnetic field. The assay time was shortened from 2 h to 1 min. High selectivity, specificity, and long-term stability of the immunoassay were achieved. The performance of the assay when analyzing blood samples confirmed the practicability of the method.
关键词： Molecular vibration,IR spectroscopy,Core-shell,Sandwich immunoassay,Self-assembly,Protein,Blood,Superparamagnetism,Magnetic beads
更新于2025-09-23 15:23:52
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Silica-coating of nano-$$\hbox {Y}_{3} \hbox {Al}_{5} \hbox {O}_{12}{:}\hbox {Ce}^{3+}$$Y3Al5O12:Ce3+ synthesized by self-combustion
摘要： Y2.91Ce0.09Al5O12 is obtained by self-combustion, grinding and sol–gel coating. X-ray diffraction, transmission electron microscopy, photoluminescence and absorption measurements were used to identify the structural and optical properties of each step of the process. The process is composed of a combination of chemical and physico-chemical processes including combustion and thermal steps, followed by grinding, powder dispersion by acidic passivation, stabilization of particle dispersions with citrate ligands and embedding of yttrium aluminium garnet (YAG) particles into SiO2 shells using a seeded growth process before drying. The initial state of the obtained powder is composed of 35 nm crystallites, sintered and agglomerated. The grinding step breaks the sintered bridge, while the passivation and citrate adsorption steps separate the particles by electrostatic repulsion before the silica coating. The optical characterizations are performed and compared separately for the powdered samples that represent the initial and ?nal states of our process, and the dispersion sample represents the intermediate state of our process. The optical measurement revealed an important amount of optical defects at the surface of the particles, compared with micrometric commercial particles. The grinding, nitric acid and citrate steps remove some of these defects. The ?nal state of the sample still possesses lower quantum ef?ciency than that of a micrometric sample, but the SiO2 coating allows for a perfect separation of the particle, suitable for implementation in small devices.
关键词： Self-combustion,YAG,core–shell,SiO2 coating
更新于2025-09-23 15:23:52
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Core-shell structure of ZnO/Co3O4 composites derived from bimetallic-organic frameworks with superior sensing performance for ethanol gas
摘要： In recent years, metal-organic frameworks (MOFs), especially zeolite-imidazole frameworks (ZIFs), have been attracting widespread attention as templates for the synthesis of sensing materials. Limited researches, however, have been carried out to utilize bimetallic ZIFs in gas sensing, as the existing studies mostly involve mono-metallic ZIFs. Here in, the core-shell structure of ZnO and Co3O4 composite (CS-ZnO/Co3O4) was synthesized via chemical etched to Co/Zn based zeolitic imidazolate framework (Co/Zn-ZIF) with subsequent annealing. The morphology, composition and surface characteristics of the as-obtained samples were confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET). Moreover, the gas sensing measurements were implemented under various atmospheres. The response of CS-ZnO/Co3O4 sensor to 100 ppm ethanol at 200 °C achieves 38.87, which is 2.8 times that of single-shell ZnO/Co3O4 (SS-ZnO/Co3O4). The improved response is mainly attributed to the core-shell structure, which offers larger surface area, more active sites for gas diffusion and the formation of p-n heterojunction between ZnO and Co3O4.
关键词： Bimetallic-organic framework,Core-shell structure,ZnO/Co3O4,Ethanol gas sensor
更新于2025-09-23 15:23:52
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Revealing the role of kapok fibre as bio-template for In-situ construction of C-doped g-C3N4@C, N co-doped TiO2 core-shell heterojunction photocatalyst and its photocatalytic hydrogen production performance
摘要： For the first time, C-doped g-C3N4@C, N co-doped TiO2 core-shell heterojunction photocatalyst was successfully prepared by an in-situ one-pot hydrothermal bio-template approach, assisted by calcination treatment at 500?°C. Kapok fibre was used as a bio-templates and in-situ C doping in g-C3N4 and TiO2 during the formation of core-shell heterojunction photocatalyst. Moreover, the used of urea as g-C3N4-precursor also contribute to band-gap narrowing by an in-situ carbon and nitrogen doping in TiO2. Various characterisation techniques were employed to understand the effect TiO2 precursor concentration on the evolution of core-shell nanostructure heterojunction photocatalyst that can affect and boost the catalytic activity. The detailed understanding of the concurrent growth of C-doped g-C3N4 (CCN) and C, N co-doped TiO2 mechanism, as well as the formation of core-shell nanostructures heterojunction formation, are also proposed in this study. Our finding indicated that the bio-template core-shell nanostructure heterojunction photocatalysts showed a dramatic increase in photoinduced electron-hole separation efficiency as demonstrated by the photoelectrochemical and photoluminescence analyses. The enhancement in photogenerated charge carrier separation and narrower band gap resulted in superior photocatalytic activities with the highest rate of hydrogen production was recorded by CCN/T-1.5 sample (625.5 μmol h-1 g-1) in methanol aqueous solution. The well-developed interconnected heterojunction formation with appropriate CCN and TiO2 contents in core-shell nanoarchitectures system is a prime factor for the future design of a highly efficient visible-light-driven photocatalyst.
关键词： Bio-template,Heterojunction photocatalyst,Core-shell,Co-doping,Photocatalytic hydrogen production,Visible light
更新于2025-09-23 15:23:52
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Enhanced upconversion luminescence intensity of core-shell NaYF4 nanocrystals guided by morphological control
摘要： How to further increase the upconversion luminescence (UCL) efficiency of core-shell upconversion nanoparticles (UCNPs) is highly desirable for their photoelectric and biological applications. Herein, a novel but facile strategy is proposed to substantially enhance the UCL intensity of NaYF4 based core-shell UCNPs by morphological control. The morphologies of core-shell UCNPs can be optimized from rod-like to spherical like by changing the ratio of oleic acid (OA) to 1-octadecene (ODE) during the shell growth process with other reaction conditions constant. The mechanism of shape control is further investigated based on the competitive absorption between OA molecules and lanthanide ions (Y3+, Yb3+, Er3+ or Tm3+) onto the different crystal axes (a, b and c) to guide their shell growth speed. The absolute quantum yields were up to 2.7 % and 1.8 % for spherical and rod like core-shell UCNPs under excitation of 980 nm laser (power density of 1.6 W/cm2), respectively. Moreover, the UCL intensity and effective lifetime (τeff) of Er3+ emission at 541 nm of spherical like core-shell UCNPs increased by 11.7 and 1.82 folds than rod like core-shell UCNPs. Therefore, our designed novel strategy can greatly improve the UCL efficiency of core-shell UCNPs and promote their development in diverse applications.
关键词： upconversion nanoparticles,upconversion luminescence,core-shell structure,morphological control
更新于2025-09-23 15:23:52
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Novel design of photocatalyst coaxial ferromagnetic core and semiconducting shell microwire architecture
摘要： We report a novel design of coaxial core-shell magnetic-semiconductor microwire, as a catalyst under sunlight irradiation. The nano/micro hierarchical architecture-like device is comprised of a coaxial core-shell microwire where the core is the ferromagnetic Fe metal and the shell is formed by a semiconducting hematite layer. The fabrication process of our substrate-free device is simply based on controlled thermal oxidation process revealing a simple and low-cost method. The hematite outer microlayer has a mesoporous structure decorated with nanowires. The ferromagnetic and metallic core assume fundamental importance as to mechanical stability, collect the generated photoelectrons, and to be removed back from the dye solution by a magnetic field gradient or simply a magnet. This nano/micro device has exhibited photocatalytic activity to degrade the methylene blue dye under simulated sunlight irradiation. Additionally, the coaxial magnetic/semiconducting can also be designed as a photoanode to drive water oxidation reaction. The coaxial magnetic/semiconducting photoanode response has shown good chemical stability and long activity under simulated sunlight radiation. In fact, this designed architecture gives novel perspective in the development of substrate free photocatalyst.
关键词： Photoelectrochemical performance,Hematite photoanodes,Photodegradation,Micro/nano architecture,Core-shell microstructures,Thermal oxidation
更新于2025-09-23 15:23:52
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Fabrication and photocatalytic activity of core@shell Ag3PO4@Cu2O heterojunction
摘要： Novel Ag3PO4@Cu2O core@shell heterojunction photocatalysts were fabricated through liquid phase reduction and chemical deposition method. Flower-like structures Cu2O were loaded on the surface of Ag3PO4 nanorods. The prepared Ag3PO4@Cu2O exhibited highly efficient photocatalytic activity for photodegradation of MB under visible-light irradiation. The possible mechanism for the excellent performance of this structure was also established.
关键词： Nanocomposites,Semiconductors,Core@shell,Photocatalytic,Flower-like Cu2O,Ag3PO4 nanorod
更新于2025-09-23 15:23:52
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Composite BNT-BT0.08/CoFe2O4 with core-shell nanostructure for piezoelectric and ferromagnetic applications
摘要： In this work, we report on the synthesis and characterization of BNT-BT0.08/CoFe2O4 biphasic composite with core-shell structure. This artificial core (BNT-BT0.08)/shell (CoFe2O4) heterostructure was prepared by sol-gel method and the resulting composite was characterized in term of microstructure, dielectric, piezoelectric and magnetic properties. BNT-BT0.08/CoFe2O4 sintered ceramic shows high permittivity (ε′ ≥ 30) and high dielectric losses (tan δ ≥ 10) in the low frequency range (ν ≤ 104 Hz), remnant polarization (Pr) of ～7.7 μC/cm2 and, remanent magnetization (Mr) of 24 emu/g at 5 K and of 14 emu/g, at room temperature. The present study reveals that the ferroelectric, piezoelectric and magnetic properties of this new architectured composite depend on the amount of each component and, can be tailored by adjusting their synthesis conditions. BNT-BT0.08/CoFe2O4 core-shell material investigated in this work provides a novel way to exploit new applications for the multifunctional composite, such as piezoelectric sensor, magnetoelectronic sensors and data storage devices.
关键词： Sol-gel processes,Composite core-shell,((Bi0.5Na0.5)0.92Ba0.08TiO3),Cobalt ferrite (CoFe2O4),Lead-free piezoelectric
更新于2025-09-23 15:23:52