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Methods for the development and testing of polymeric hybrid photovoltaic thermal (PVT) collector for indoor experiments
摘要： The purpose of this article is to present the methods for the development and testing of polymeric hybrid Photovoltaic Thermal (PVT) collectors for indoor experiments. Polymeric material has been used in hybrid PVT collectors and even longer used on flat plate collectors. We have developed a method to make a hybrid PVT collector with an absorber made of a polymethyl-methacrylate (PMMA) and combined with a copper sheet. To understand the details of the thermal and electrical performance, we have developed a method to test this PVT collector by conducting a series of experiments by varying the mass flow rate, irradiance, and inlet water temperature. The results showed that PMMA as a thermal absorber with a copper sheet can provide a beneficial cooling effect of around 80% thermal efficiency and a 0.03 %/oC decrease in electrical efficiency. This method makes PVT collector hybrids easily and cheaply using simple equipment.
关键词： Polymeric material,PMMA,The method for testing PVT collector,PVT collector,The method for development PVT collector,Indoor testing
更新于2025-09-16 10:30:52
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Experimental Investigation of Varying Laser Pass on Micro-channel Characteristics of Thick PMMA by Laser Transmission Micro-machining
摘要： Depth of fabrication is an essential characteristic of micro-channels. The laser beam machining process is one of the most suitable processes to fabricate micro-channels. This process has an excellent potential for the fabrication of microfluidic devices which are instrumental for various biomedical applications such as electrophoresis, chromatography, blood protein studies, DNA analysis, etc. In this research work, an attempt has been made to fabricate micro-channels on a thick Polymethyl methacrylate (PMMA) plate at submerged condition by utilizing laser transmission micro-machining process. The laser transmission micromachining operation is conducted here at submerged condition to reduce the adverse thermal effect during machining. Nanosecond pulsed Nd: YAG laser with wavelength in near infrared region has been used here. The depth of micro-channel and heat affected zone (HAZ) width has been taken into account as machining responses. Total 3 sets of experiments which contain 31 experiments in each set have been conducted for three different laser beam pass with the aid of response surface methodology (RSM). The effects of varying laser beam pass on the depth and HAZ width has been studied.
关键词： Nd: YAG laser,laser transmission machining,micro-channeling,PMMA
更新于2025-09-16 10:30:52
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Direct measurement of electrostatic interactions between poly(methyl methacrylate) microspheres with optical laser tweezers
摘要： In this study, we measured the force of electrostatic interactions between poly(methyl methacrylate) (PMMA) particles dispersed in organic solvent mixtures of cyclohexyl bromide (CHB) and n-decane. Optical laser tweezers were employed to directly measure interactive forces between paired PMMA particles in a CHB medium that contained n-decane in various volume ratios. CHB, having a moderate dielectric constant, provided an environment with a high charge storage capacity. The addition of n-decane lowered the effective refractive index of the medium, which increased the optical trapping efficiency. We also fabricated microscope flow cells with a commonly used UV-curable adhesive and quantified the effects of dissolved adhesive compounds through interactive force measurements and nuclear magnetic resonance analysis. In addition, we studied the impact of CHB dissociation into H+ and Br? ions, which could screen electrostatic interactions.
关键词： UV-curable adhesive,NMR analysis,electrostatic interactions,optical laser tweezers,CHB,PMMA particles,n-decane
更新于2025-09-16 10:30:52
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<i>In situ</i> synthesis of monolayer graphene on silicon for near-infrared photodetectors
摘要： Direct integration of monolayer graphene on a silicon (Si) substrate is realized by a simple thermal annealing process, involving a top copper (Cu) layer as the catalyst and an inserted polymethylmethacrylate (PMMA) as the carbon source. After spin-coating the PMMA carbon source on the Si substrate, the Cu catalyst was deposited on PMMA/Si by electron beam evaporation. After that, graphene was directly synthesized on Si by decomposition and dehydrogenation of PMMA and the catalyzation effect of Cu under a simple thermal annealing process. Furthermore, under an optimized growth condition, monolayer graphene directly formed on the Si substrate was demonstrated. Utilizing the as-grown graphene/Si heterojunction, near-infrared photodetectors with high detectivity ((cid:1)1.1 (cid:3) 1010 cm Hz1/2 W(cid:4)1) and high responsivity (50 mA W(cid:4)1) at 1550 nm were directly fabricated without any post-transfer process. The proposed approach for directly growing graphene on silicon is highly scalable and compatible with present nano/micro-fabrication systems, thus promoting the application of graphene in microelectronic fields.
关键词： thermal annealing,PMMA,silicon,photodetectors,copper catalyst,graphene
更新于2025-09-16 10:30:52
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Controlled surface modification of poly(methyl methacrylate) film by fluoroalkyl end-capped vinyltrimethoxysilane oligomeric silica/hexagonal boron nitride nanocomposites
摘要： Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF-(CH2CHSi(OMe)3)n-RF; n = 2, 3; RF = CF(CF3)OC3F7] undergoes sol–gel reactions in the presence of hexagonal boron nitride (h-BN) nanoparticles under alkaline or acidic conditions at room temperature to afford the corresponding fluorinated oligomeric silica/h-BN nanocomposites in good isolated yields (≥ 80%), respectively. The fluorinated oligomeric silica/h-BN nanocomposites thus obtained were found to exhibit a good dispersibility toward the traditional organic media including water. These two kinds of fluorinated nanocomposites were applied to the surface modification of poly(methyl methacrylate) (PMMA). The fluorinated nanocomposites prepared under alkaline conditions can give not only a good oleophobic characteristic imparted by longer fluoroalkyl groups in the composites but also the higher fluorescent emission related to the presence of h-BN on the only surface side of the modified PMMA film. In contrast, the fluorinated nanocomposites prepared under acidic conditions can provide a good oleophobic characteristic and a higher fluorescent emission on both the surface and even on the reverse side of the PMMA film. Such unique controlled surface modification ability will be discussed by 29Si solid-state NMR spectra of these two types of the nanocomposites.
关键词： Surface arrangement ability,Fluorescent ability,Oleophobicity,Hexagonal boron nitride,Surface modification,Fluorinated oligomeric nanocomposite,PMMA
更新于2025-09-16 10:30:52
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Raman spectroscopy of poly (methyl methacrylate) under laser shock and static compression
摘要： Time-resolved Raman spectroscopy for visualizing molecular fingerprint snapshots at nanosecond time scale is a useful tool for detailed understanding of in situ shock behaviour of materials. This technique was applied to study the changes in molecular vibrations of poly (methyl methacrylate) (PMMA) under laser driven shock compression up to ~1.9 GPa in a confinement geometry. A layered target configuration is used to enhance the shock pressure. The vibrational modes are measured as a function of dynamic shock and static compression. The Grüneisen parameters and bond anharmonicities in PMMA are determined using compression behaviour of Raman modes. The deduced shock velocity (~3.5 ± 0.4 km/s) in PMMA based on the time evolution of shocked Raman mode at 1.9 GPa is in agreement with the one calculated (~3.7 km/s) from 1-D radiation hydrodynamic simulations. A comparative study on shock experiment and static high pressure Raman spectroscopic measurements is done. Static pressure measurement up to ~16 GPa show rapid blue shifting of C–H stretching modes.
关键词： Raman spectroscopy,PMMA,confinement geometry,Raman shift,laser shock,diamond anvil cell (DAC),static experiment
更新于2025-09-16 10:30:52
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Improvement of CsPbBr3 photodetector performance by tuning the morphology with PMMA additive
摘要： The optoelectrical properties of semiconductor devices are strongly related to the film morphology. Here, we found that, for CsPbBr3 thin films prepared by spray coating, the addition of polymethyl methacrylate (PMMA) can completely eliminate voids and greatly reduce the surface roughness of the as-deposited films. As a consequence, the optoelectronic properties of the photodetectors fabricated as a simple vertical structure of Au/CsPbBr3(PMMA)/ITO can be improved. With the addition of PMMA, the dark current of the photodetector is reduced at least four times, and the photodetector exhibits a favourable optical response. With the illumination ranging from 400 to 510 nm, the calculated responsivity varies from 3.70 to 5.20 A/W. A good response speed with a rise time of 6.6 ms and a decay time of 11.3 ms can be achieved. Moreover, unlike the inorganic-organic hybrid perovskite detectors, this inorganic perovskite photodetector without encapsulation shows a favourable stability with a decay of 20% after 40 days under ambient air at 20% humidity.
关键词： Photodetector,Spray coating,PMMA,Surface roughness,CsPbBr3
更新于2025-09-12 10:27:22
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Influence of distance between target surface and focal point on CN emission of nanosecond laser-induced PMMA plasma in air
摘要： Laser-induced breakdown spectroscopy (LIBS) is a technique for spectral composition analysis of materials containing atomic and ionic emission lines, as well as a few molecular emission bands. Here we focused our study on molecular emission from CN (B2∑+→X2∑+) based on LIBS method. Polymethyl methacrylate (PMMA) was ablated by employing a Nd:YAG laser system in air under atmospheric pressure. In the ultraviolet range, the molecular emission intensities of CN violet bands were observed with a spectrometer equipped with an intensified CCD detector. The effect of distance between sample surface and focal point (DTSFP) on the intensities of molecular emission was studied in detail. The results showed that the molecular emission intensities of CN violet bands exhibited a strong dependence on the DTSFP. As the surface of the PMMA sample approached the focal point gradually, the emission intensity of CN increased at first and then dropped down. In addition, vibrational temperature of CN molecule was also calculated. The vibrational temperature showed the similar change in the emission intensity, while the position at the maximum vibrational temperature was inconsistent with the position at the CN intensity.
关键词： CN,distance between sample surface and focal point,laser-induced breakdown spectroscopy,PMMA
更新于2025-09-12 10:27:22
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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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Terahertz absorption characteristics of multilayer graphene/polymer
摘要： In this article, we fabricated two different graphene structure samples, composed of single-layer graphene and multilayer graphene/PMMA structures. When w samples are pumped by the 980 nm laser with different powers, we measure the time-domain and frequency domain spectra of the terahertz transmission using the terahertz time domain spectroscopy system. The measured results show that the average terahertz transmission can be actively controlled by changing the pump power or the layer number of graphene, which exhibits potential applications in the terahertz absorption devices.
关键词： graphene/PMMA structure,pump power,Terahertz
更新于2025-09-11 14:15:04