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Effect of Molecular Weight of Polyethylene Glycol on the Sheet-thickness and Photocatalytic Performance of MoS2 Nanoparticles
摘要： Molybdenum disulfide (MoS2) nanomaterials have attracted considerable attention recently owing to its unique photoelectrochemistry property and promising applications in the conversion of solar energy to chemical energy and environmental purification. Flower-like MoS2 photocatalyst was synthesised via hydrothermal method in this work. To achieve the MoS2 nanoparticles with various sheet-thickness, polyethylene glycols (PEG) with deferent molecular mass were employed as additives in the preparation process. The effects of the molecular weight of PEG on the micro structure and crystal structure of MoS2 nanoparticles were characterized by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscope (HRTEM) and X-ray diffraction (XRD). The photocatalytic properties of as-synthesized products were evaluated by the degradation of methylene blue (MB) under ultraviolet irradiation. The results suggest that the molecular weight of PEG could affect the sheet thickness of the MoS2 particles. In addition, the degradation rate of MB show that the photocatalytic performance of MoS2 nanoparticles is closely related to their sheet thickness, the photocatalytic activity reduced with the decrease of sheet thickness of MoS2 nanoparticles which is mainly attributed to the reduction of the active sites.
关键词： Photocatalytic performance,MoS2 nanoparticles,Hydrothermal method,PEG,molecular weight,Sheet-thickness
更新于2025-09-23 15:21:01
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Fluorescent emission from a natural carbon matrix incorporating sodium
摘要： The process of functionalization of metals in natural carbon matrices has become an important area of research due to its improved properties and applications. Carbon materials possessing photoluminescence (PL) properties find a wide range of applications in photonics. Among the various carbon materials available in nature, cellulose has critical importance since it is the most abundant and wide-spread biopolymer on Earth, and also, the important component in plants’ skeleton. In the present work, the functionalized carbonaceous material is prepared by the hydrothermal treatment of natural cellulosic source Aloe Vera and the metallic element sodium is properly incorporated into it by adding sodium borohydride to observe the fluorescence emission changes. The incorporation of metal ions in the carbon matrix leads to structural modifications and properties as evidenced by field emission scanning electron microscopy, Energy dispersive spectroscopy, X-ray dot mapping, X-ray Photoelectron spectroscopy, and X-ray diffraction analysis. The optical emission characteristics are studied using Photoluminescence spectroscopy, CIE plot, power spectrum, color purity, and quantum yield. The excitation wavelength dependent photoluminescence emission mechanism shown by the carbon–metal incorporated products obtained from the cellulosic raw materials makes them suitable for biomedical and biosensing applications because of the non-toxic and eco-friendly nature.
关键词： Photoluminescence,Hydrothermal treatment,Sodium incorporation,Carbon matrix,Aloe Vera
更新于2025-09-23 15:21:01
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Q-switched fiber laser based on CdS quantum dots as a saturable absorber
摘要： In this work, a Q-switched fiber laser is demonstrated using quantum dots (QDs) cadmium sulfide (CdS) as a saturable absorber (SA) in an erbium-doped fiber laser (EDFL) system. The QD CdS is synthesized via the microwave hydrothermal assisted method and embedded into polyvinyl alcohol (PVA). The QD CdS/PVA matrix film is sandwiched in between two fiber ferrules by a fiber adapter. The generation of Q-switched fiber laser having a repetition rate, a pulse width, and a peak-to-peak pulse duration of 75.19 kHz, 1.27 μs, and 13.32 μs, respectively. The maximum output power of 3.82 mW and maximum pulse energy of 50.8 nJ are obtained at the maximum pump power of 145.9 mW. The proposed design may add to the alternative material of Q-switched fiber laser generation, which gives a high stability output performance by using quantum dots material as a saturable absorber.
关键词： CdS Quantum Dots,erbium-doped fiber laser,microwave hydrothermal assisted method,saturable absorber,Q-switched fiber laser
更新于2025-09-23 15:19:57
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Femtosecond-laser-irradiation-induced structural organization and crystallinity of Bi2WO6
摘要： controlling the structural organization and crystallinity of functional oxides is key to enhancing their performance in technological applications. in this work, we report a strong enhancement of the structural organization and crystallinity of Bi2Wo6 samples synthetized by a microwave-assisted hydrothermal method after exposing them to femtosecond laser irradiation. X-ray diffraction, UV-vis and Raman spectroscopies, photoluminescence emissions, energy dispersive spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy were employed to characterize the as-synthetized samples. To complement and rationalize the experimental results, first-principles calculations were employed to study the effects of femtosecond laser irradiation. Structural and electronic effects induced by femtosecond laser irradiation enhance the long-range crystallinity while decreasing the free carrier density, as it takes place in the amorphous and liquid states. these effects can be considered a clear cut case of surface-enhanced Raman scattering.
关键词： structural organization,Bi2WO6,femtosecond laser irradiation,crystallinity,microwave-assisted hydrothermal method
更新于2025-09-23 15:19:57
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A Facile Microwave-Assisted Hydrothermal Synthesis of Graphene Quantum Dots for Organic Solar Cell Efficiency Improvement
摘要： Carbon-based nanomaterials have successively remained at the forefront of different research fields and applications for years. Understanding of low-dimension carbon material family (CNT, fullerenes, graphene, and graphene quantum dots) has arrived at a certain extension. In this report, graphene quantum dots were synthesized from graphene oxide with a microwave-assisted hydrothermal method. Compared with conventional time-consuming hydrothermal routes, this novel method requires a much shorter time, around ten minutes. Successful formation of quantum dots derived from graphene sheets was verified with microscopic and spectroscopic characterization. Nanoparticles present a diameter of about 2-8 nm, blue emission under ultraviolet excitation, and good dispersion in polar solvents and can be collected in powder form. The synthesized graphene quantum dots were utilized as a hole transport layer in organic solar cells to enhance the cell quantum efficiency. Such quantum dots possess energy levels (Ec and Ev) relevant to HOMO and LUMO levels of conductive polymers. Mixing P3HT:PCBM polymer and graphene quantum dots of sufficient extent notably helps reduce potential difference at interfaces of the two materials. Overall efficiency consequently advances to 1.43%, an increase of more than 44% compared with pristine cells (0.99%).
关键词： microwave-assisted hydrothermal synthesis,organic solar cells,graphene quantum dots,efficiency improvement
更新于2025-09-23 15:19:57
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Morphology Effect of 1D ZnO Nanostructures Designed by Hydrothermal and Thermal Annealing for Fast Ultraviolet Photodetector Applications
摘要： Zinc oxide (ZnO) nanorods were grown on a ZnO seed layer using the hydrothermal method and subsequently annealed at temperatures of 400–800 °C. The ZnO nanorods annealed at 400 °C exhibited morphology similar to that of the unannealed ZnO nanorods. However, the tips of the ZnO nanorods gradually became rounded and their density and diameter increased with an increase in the annealing temperature. The intensity of the near-band-edge emission increased gradually with an increase in the annealing temperature from 400 to 600 °C but decreased sharply in the case of the nanorods annealed at 800 °C. With respect to the deep-level emissions, broad yellow, orange, and green emissions were observed. Further, the low-temperature photoluminescence spectrum measured at 12 K of the ZnO nanorods annealed at 600 °C contained a donor-bound exciton emission, as well as emissions related to the donor-acceptor pair transition and the first-order and second-order longitudinal optical phonon replicas of the donor-acceptor pair transition. Finally, with respect to the photoresponse, the dark current and photocurrent of the nanorods decreased and their photosensitivity increased with the increase in the annealing temperature.
关键词： Ultraviolet photodetector,Zinc oxide,Photosensitivity,Photoluminescence,Hydrothermal method
更新于2025-09-23 15:19:57
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Controlled synthesis and panchromatic printing of highly luminescent NaYF4:Ln3+ upconversion hollow microtubes for information encryption on various packaging substrates
摘要： Lanthanide-ion doped β-NaYF4 crystals with bright and tunable upconversion luminescence are urgently demanded in anti-counterfeiting printing. Herein, novel highly luminescent hexagonal NaYF4:Ln3+ upconversion hollow microtubes (UCHMs) were controlled synthesized by a one-pot hydrothermal method employing poly(ethylene imine) (PEI) as ligand. The surface of the synthesized UCHMs was decorated by water-soluble polymer of PEI, rendering the hydrophilic nature of UCHMs. Besides, the synthesized UCHMs exhibited bright upconversion luminescence under the irradiation of a 980 nm laser due to the unique structure and morphology. Time-dependent morphology evolution showed that the formation of UCHMs experience a morphology change from nanoparticles to hexahedron to microprisms, and ultimately to microtubes via a dissolution-reconstruction formation mechanism. Furthermore, the resulting UCHMs were used as pigments for preparation of luminescent inks and their application in anti-counterfeiting printing was explored. To realize panchromatic printing, we prepared three-primary-color (RGB) UCHMs by rational tailoring the doping pairs and molar ratio of the lanthanide ions in UCHMs. Based on the superposition principle of the red-green-blue as three primary colors, a wide array of luminescent inks with panchromatic luminescent colors were prepared. The successful creation of securely light-responsive smart encryption patterns on various packaging substrates such as art paper, aluminum sheet, polyethylene terephthalate (PET) film and cardboard by screen printing was demonstrated. Our strategy provides a new route for controlled synthesis of hydrophilic UCHMs and the as-prepared UCHMs have great potential in application of packaging anti-counterfeiting.
关键词： Rare earth ion-doped NaYF4,Anti-counterfeiting,Hollow microtube,Screen printing,Hydrothermal
更新于2025-09-23 15:19:57
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Controlled synthesis of ultrathin MoS <sub/>2</sub> nanoflowers for highly enhanced NO <sub/>2</sub> sensing at room temperature
摘要： Fabrication of a high-performance room-temperature (RT) gas sensor is important for the future integration of sensors into smart, portable and Internet-of-Things (IoT)-based devices. Herein, we developed a NO2 gas sensor based on ultrathin MoS2 nanoflowers with high sensitivity at RT. The MoS2 flower-like nanostructures were synthesised via a simple hydrothermal method with different growth times of 24, 36, 48, and 60 h. The synthesised MoS2 nanoflowers were subsequently characterised by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, energy-dispersive X-ray spectroscopy and transmission electron microscopy. The petal-like nanosheets in pure MoS2 agglomerated to form a flower-like structure with Raman vibrational modes at 378 and 403 cm?1 and crystallisation in the hexagonal phase. The specific surface areas of the MoS2 grown at different times were measured by using the Brunauer–Emmett–Teller method. The largest specific surface area of 56.57 m2 g?1 was obtained for the MoS2 nanoflowers grown for 48 h. This sample also possessed the smallest activation energy of 0.08 eV. The gas-sensing characteristics of sensors based on the synthesised MoS2 nanostructures were investigated using oxidising and reducing gases, such as NO2, SO2, H2, CH4, CO and NH3, at different concentrations and at working temperatures ranging from RT to 150 °C. The sensor based on the MoS2 nanoflowers grown for 48 h showed a high gas response of 67.4% and high selectivity to 10 ppm NO2 at RT. This finding can be ascribed to the synergistic effects of largest specific surface area, smallest crystallite size and lowest activation energy of the MoS2-48 h sample among the samples. The sensors also exhibited a relative humidity-independent sensing characteristic at RT and a low detection limit of 84 ppb, thereby allowing their practical application to portable IoT-based devices.
关键词： gas sensing,room temperature,hydrothermal synthesis,MoS2 nanoflowers,NO2 gas sensor
更新于2025-09-23 15:19:57
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Controlled synthesis and upconversion luminescence properties of Yb3+/Er3+ co-doped Bi2O3 nanospheres for optical and X-ray computed tomography imaging
摘要： Bi2O3 nanospheres co-doped with Yb3t/Er3t upconverting ions pair have been successfully synthesized via a facile hydrothermal method followed by a heat treatment. The resulting Bi2O3:Yb3t,Er3t nanospheres show a monodisperse spherical morphology with narrow size distribution (~180 nm) and display intense upconversion luminescence under 980 nm laser excitation. It is found that the crystal structure, morphology and upconversion luminescence properties of nanospheres have a direct relationship with the doping concentration of Yb3t and the subsequent calcination temperature. These Bi2O3:Yb3t,Er3t nanospheres can be prepared in large quantities and can be easily modified with a layer of biocompatible polyethyleneimine (PEI) molecules. The yielded nanospheres could not only maintain uniform size and morphological characteristics, but also show good water dispersibility and biocompatibility. Remarkably, these Bi2O3:Yb3t,Er3t upconversion nanophosphors could also act as an effective contrast agent for X-ray computed tomography (CT) imaging, which show higher contrast efficacy than commercial iodine-based contrast agent. The proposed facile synthetic route and inexpensive matrix materials pave the way for broad use of these Bi2O3:Yb3t,Er3t nanospheres as ideal dual-mode bio-imaging probes in biomedical field.
关键词： Hydrothermal synthesis,CT imaging,Bi2O3,Upconversion luminescence,Nanophosphors
更新于2025-09-23 15:19:57
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Establishing high photocatalytic H2 evolution from multiwalled titanate nanotubes
摘要： Black TiO2 in various forms has been investigated for numerous photochemical applications. In photocatalytic water splitting, “grey” titania can reach considerable H2 generation rates without using a noble metal co-catalyst. Up to now, a variety of anatase powders or other morphologies has been investigated in grey and black forms. Here we describe that hydrothermal titanate/anatase nanotubes can show a strong noble metal free photocatalytic activity. For optimized “blackening” conditions, a drastically higher photocatalytic H2 production can be obtained than for other nanoscale morphologies. This effect can further be improved with a very mild Pt doping that again shows a clearly stronger photocatalytic H2 production than comparably loaded nanopowders.
关键词： hydrothermal titania nanotubes,hydrogenation,absorption,photocatalysis,hydrogen evolution
更新于2025-09-23 15:19:57