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Upconversion luminescence properties of Y2O3: Yb3+/Er3+/Tm3+ nanocrystal doped PMMA nanocomposites
摘要： Y2O3 nanocrystals triply doped with Yb3+, Er3+, Tm3+ ions were synthesized via alginic acid-assisted gelation using thermal decomposition method and annealed at 800 °C for 24 h. Nanopowders were embedded into PMMA matrix via free-radical polymerization in an ultrasonic bath. X-ray diffraction and transmission electron microscopy measurements have shown that the crystal grain sizes decreased significantly with the narrow size distributions of the nanocrystals in PMMA matrix. A diode laser at 975 nm was used to measure the upconversion luminescence of the annealed nanopowders and those embedded in PMMA between the 400–850 nm wavelength region. The Er3+ concentration and the excitation power density dependencies of the relative intensities for red, green and blue upconversion luminescence in the nanopowder and PMMA nanocomposites are found to be different. The measured CIE-1931 color coordinates of the upconversion luminescence in PMMA nanocomposites show appreciable color stability under different excitation power densities, which is required for potential applications in the field of photonics.
关键词： Color Tunable Emission,Upconversion Luminescence,Polymer nanocomposites,Color Stability,Polymethyl methacrylate (PMMA)
更新于2025-09-23 15:21:21
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Investigation and Prediction on Regulation of Hydrophobicity of Polymethyl Methacrylate (PMMA) Surface by Femtosecond Laser Irradiation
摘要： This study presents the contact angle prediction model of a trapezoidal groove structure based on the laser irradiation on polymethyl methacrylate (PMMA). The trapezoidal groove structure was designed and proposed according to the characteristics of a femtosecond laser. First, the complete wetting model and incomplete wetting model which were compatible with the characteristics of the laser mechanism were constructed based on the Gibbs free energy and the structural parameters of the trapezoidal groove structure. Then, based on the contact angle prediction models constructed, the samples were divided into two groups according to the designed structural parameters, and the experimental investigations were carried out. The result demonstrated that the incomplete wetting prediction model was more in line with the actual situation. The convex width and the top edge length of spacing of the trapezoidal groove structure both affected the contact angle prediction results. From both the experimental contact angles and the contact angles predicted by the incomplete wetting model, it could be known that the contact angle reached 138.09° when the ratio of the convex width to the top edge length of spacing was 0.25, indicating that the smaller the ratio of the convex width to the top edge length of spacing, the better the hydrophobicity of PMMA.
关键词： femtosecond laser,trapezoidal groove structure,polymethyl methacrylate,hydrophobicity
更新于2025-09-23 15:21:01
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Analyzing physical characteristics and shielding efficiency for non-lead medical radiation shielding sheets improved using PMMA
摘要： Recently, the research for replacing heavy lead goods, such as medical radiation shielding sheets with environmentally friendly shielding materials has been widely carried out. The use of tungsten injected into the base material of polyethylene resin may be a good alternative for manufacturing lightweight shielding sheets. However, the increase of the mass ratio of tungsten in the shielding sheets is accompanied by the degradation of their physical properties such as tensile strength and flexibility. In this report, we have tried to fix this problem by adding Polymethyl Methacrylate (PMMA) to the mixing process of materials. If the portion of the added PMMA is 20%, it leads to a 25% increase of the particle packing ratio while there is a simultaneous 28% enhancement of tensile strength compared to before adding it. In the final test for shielding efficiency, it also turned out that the increase of the particle packing ratio for tungsten exhibits the same shielding efficiency as that of 0.2 mmPb. This consequence may imply that mass production of sheets that can prevent scattering rays in the medical radiation frequency range is possible through the calender process using a 0.3 mm tungsten sheet.
关键词： Polymethyl Methacrylate,shielding efficiency,shielding sheet,Radiation,X-rays
更新于2025-09-19 17:15:36
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Self‐Assembled Polyamidoamine Dendrimer on Poly (methyl meth‐ acrylate) for Plasmonic Fiber Optic Sensors
摘要： We report a novel one-step polyamidoamine (PAMAM) dendrimer based polymethyl methacrylate (PMMA) surface functionalization strategy for the development of polymeric optical (POF) based plasmonic sensors utilizing gold nanoparticles (AuNP). Simple contact angle measurements over PMMA sheets reveal the ability of the dendrimers to strongly bind to PMMA surface without additional acid/alkali pretreatment, unlike the conventional hexamethylene diamine (HMDA) based surface modification. Subsequently, U-bent POF probes with high evanescent wave absorbance sensitivity were exploited for relative quantification of the surface amine groups using fluorescein isothiocyanate (FITC) binding and efficient chemisorption of gold nanoparticles (AuNP) in order to identify the optimum conditions viz. dendrimer concentration, incubation time and dendrimer generation. While FITC binding showed a proportional increase in amine functional density with PAMAM concentration and time, interestingly the AuNP (40 nm) binding studies revealed the formation of loose PAMAM multilayers and their desorption. PAMAM (G4) concentration as low as 5 mM and incubation time of 24 h provide faster binding rate with densely packed AuNP and the RI sensitivity of ~ 15 (A546 nm/RIU). This simpler and inexpensive strategy could also be exploited for the development of functional PMMA substrates for various applications including nanotechnology, bio-imaging, drug delivery and analytical separations.
关键词： gold nanoparticles (AuNP),dendrimers,plasmonic sensors,polymethyl methacrylate (PMMA),polymeric optical fibers (POF),evanescent wave absorbance
更新于2025-09-11 14:15:04
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Picosecond Laser Interference Patterning of Periodical Micro-Architectures on Metallic Molds for Hot Embossing
摘要： In this work, it is demonstrated that direct laser interference patterning (DLIP) is a method capable of producing microtextured metallic molds for hot embossing processes. Three different metals (Cr, Ni, and Cu), relevant for the mold production used in nanoimprinting systems, are patterned by DLIP using a picosecond laser source emitting at a 532 nm wavelength. The results show that the quality and surface topography of the produced hole-like micropatterns are determined by the laser processing parameters, such as irradiated energy density and the number of pulses. Laser-induced periodic surface structures (LIPSS) are also observed on the treated surfaces, whose shapes, periodicities, and orientations are strongly dependent on the accumulated fluence. Finally, the three structured metals are used as embossing molds to imprint microlenses on polymethyl methacrylate (PMMA) foils using an electrohydraulic press. Topographical profiles demonstrate that the obtained structures are comparable to the masters showing a satisfactory reproduction of the texture. The polymeric microlens arrays that showed the best surface homogeneity and overall quality were those embossed with the Cr molds.
关键词： direct laser interference patterning,microstructures,hot embossing,polymethyl methacrylate,laser-induced periodic surface structures
更新于2025-09-11 14:15:04
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Improving the stability of silver nanowire/polyimide composite films for transparent film heaters
摘要： Flexible and transparent heaters have gradually attracted considerable attention because of its widely application in defrosting or demisting windows and medical thermotherapy. The stability of the heater under ambient conditions during working is one of the important properties. In this paper, we fabricated a highly stable and transparent film heater (TFH) through a simple drop-coating approach with burying silver nanowires (AgNWs) between colorless polyimide (cPI) and polymethyl methacrylate (PMMA). The developed TFH exhibited higher stability with the resistance increasing by 17% only for the initial value of 9.6 ? after accelerating test at 105 °C and 100% relative humidity for 36 h, which was much lower than that of 83% for TFH without PMMA. Furthermore, the fabricated film heater covered with PMMA showed extreme stability in hydrogen sulfide oven. Meanwhile, there was no significant influence in the transmittance, mechanical flexibility and heating performance after coating a PMMA layer. Finally, we applied the film heater to demisting demonstration.
关键词： transparent film heaters,polyimide,polymethyl methacrylate,silver nanowires,stability
更新于2025-09-10 09:29:36
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The Influence of Molecular Weight on the Orientation and Properties of Polymethyl Methacrylate Sheets
摘要： The influence of molecular weight on the process of orientation stretching and the combination of physicomechanical characteristics of specimens of polymethyl methacrylate (PMMA) is examined. Orientation stretching and increase in the molecular weight of PMMA from 0.52 to 4.6 × 106 g/mol lead to a considerable increase in strength and elastic modulus (σt by a factor of 2.6, E by a factor of 2.5). It is established that the deformation characteristics of oriented PMMA specimens increase by a factor of 10 when the molecular weight is increased from 0.52 to 4.6 × 106 g/mol, which opens up new possibilities in the processing of sheets and films of PMMA.
关键词： physicomechanical properties,molecular weight,elongation factor,polymethyl methacrylate,orientation
更新于2025-09-09 09:28:46