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Preparation of highly thermally conductive and electrically insulating PI/BNNSs nanocomposites by hot-pressing self-assembled PI/BNNSs microspheres
摘要： Traditional polymer-based thermally conductive composites with randomly distributed fillers always yield an undesired heat removal due to the lack of efficient heat transfer pathways. Thus, realization of rational and ordered distribution of thermally conductive nanofillers in polymer matrix is believed to be significant for obtaining a desirable thermal conductivity. Herein, a series of thermally conductive polyimide/boron nitride nanosheets (PI/BNNSs) composites with a highly ordered BNNSs network have been successfully prepared. For achieving an uniform dispersion and high orientation of BN nanosheets in PI matrix, self-assembled PI/BNNSs complex microspheres were firstly prepared via the van der Waals interaction, and then these complex microspheres were further hot-pressed at the Tg of PI matrix, which rendered the alignment of BNNSs during the deformation of complex microspheres and built an efficient heat transfer pathway. As a consequence, the resultant composites possess a much higher in-plane thermal conductivity up to 4.25 W/mK with 12.4 vol% oriented BNNSs than those of pure PI and random distribution composite (0.85 W/mK for pure PI and 1.3 W/mK for the PI/random BNNSs-12.4). Meanwhile, these nanocomposites present excellent electrically insulating properties, improved dimensional stabilities and good thermal stabilities. This facile method provides a new way to design and fabricate highly thermally conductive PI-based composites for applying in heat dissipation of modern portable and collapsible electronic devices.
关键词： Boron nitride nanosheets,Polyimide,Complex microspheres,Hot-pressing,Filler orientation
更新于2025-09-23 15:19:57
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Synthesis and radiation grafting modification of hydroxyl controlled AM/HEMA polymer microspheres
摘要： The, smooth-faced, highly cross-linked, hydroxyl controlled, micrometer-sized polymer micro-spheres of acrylamide (AM) and 2-hydroxyethyl methacrylate (HEMA) were prepared by reverse suspension polymerization. The polymerization parameters showed considerable influence on the morphologies and dispersion of the polymer particles, such as the stirring rate, polymerization temperature, monomer loading, initiator concentration, and crosslinking agent concentration, which makes it flexible to control the hydroxyl number of AM/HEMA microspheres by controlling polymerization conditions. Subsequently, the polymer particles was radiated with 60Co c-rays(dose rate: 4.0 kGy/h) in pure oxygen environment for 24 h, as a result, free radicals are generated on the surface of the polymer microspheres. Afterward, AM was allowed to be graft-polymerized on microspheres AM/HEMA in the manner of “grafting onto,” resulting in the grafted microspheres PAM–AM/HEMA. This work provides optimized parameters to fabricate micron-sized AM/HEMA microspheres, and further expands the functionalization of AM/HEMA microspheres and its application fields.
关键词： polymer microspheres,graft-modification,hydroxyl controlled,Synthesis
更新于2025-09-23 15:19:57
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Synthesis of 3D CQDs/urchin-like and yolk-shell TiO2 hierarchical structure with enhanced photocatalytic properties
摘要： A novel CQDs/TiO2 hierarchical structure with enhanced photocatalytic properties was achieved by uniformly decorating urchin-like and yolk-shell TiO2 microspheres (UYTMs) with carbon quantum dots (CQDs) through an environmentally friendly hydrothermal process. The CQDs were ?rstly synthesized by the electrochemical method, and the TEM, Raman and PL characterizations strongly indicated that the as-prepared CQDs exhibited good dispersion, high crystallinity and unique up-conversion properties. The UYTMs synthesized by a NaOH-assisted hydrothermal process showed stable 3D hierarchical structure and large surface area, which was bene?cial for light absorption and contacting with contamination. The good combination of CQDs and UYTMs was further successfully achieved during the hydrothermal process, and demonstrated by a series of tests. The photocatalytic experiments suggested that the CQDs/UYTMs exhibited better photocatalytic activities than the pure UYTMs and P25 under both visible and UV light irradiation. The CQDs/UYTMs combining with 6 wt% of CQDs showed the best photocatalytic e?ciency, while excessive CQDs tended to inhibit the photocatalytic activity. According to the results and discussions, a possible mechanism in improving the photocatalytic e?ciency of the CQDs/UYTMs is signi?cantly proposed. The up-conversion property of CQDs can broaden the absorption spectrum of CQDs/UYTMs to the visible light. Moreover, the CQDs, as the electron reservoirs, are e?cient to separate the electrons and holes, leading to an improved photocatalytic activity of CQDs/UYTMs.
关键词： Carbon quantum dots,Urchin-like microspheres,Photocatalytic activity,TiO2,Yolk shell
更新于2025-09-23 15:19:57
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Primary Determination of Particle Number Concentration with Light Obscuration and Dynamic Imaging Particle Counters
摘要： Accurate number concentrations of particles in liquid media are needed to assess the quality of water, pharmaceuticals, and other liquids, yet there are limited reference materials or calibration services available with clear traceability to the International System of Units. We describe two methods, based on very simple modifications of commercial particle counter instruments, that can provide traceable number concentration measurements. One method used a light obscuration counter. Fitting a model to the data enabled correction for timing and coincidence errors, and gravimetric calibration of the syringe pump gave a traceable determination of measured volume. Other potential biases were diagnosed by analysis of the particle size distribution. The other method used a dynamic imaging particle counter (a flow imaging microscope). The instrument was intentionally configured so that each particle passing through the flow cell was imaged multiple times. Following the particle image acquisition runs, runs with a rinse solution released and counted microspheres adsorbed to tubing or flow-cell walls. Software assembled the redundant particle images into tracks, and the total number of tracks was assigned as the number of particles counted. Both light obscuration and dynamic imaging methods, when applied to polystyrene microspheres of approximately 4 μm diameter, achieved expanded uncertainties (k = 2) of approximately 2 % of number concentration and agreed to within a difference of 1.1 %.
关键词： number density,light obscuration,flow imaging,microspheres,concentration standard,particle concentration,flow microscopy,dynamic imaging,number concentration
更新于2025-09-23 15:19:57
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Modeling the AC Electrokinetic Behavior of Semiconducting Spheres
摘要： We study theoretically the dielectrophoresis and electrorotation of a semiconducting microsphere immersed in an aqueous electrolyte. To this end, the particle polarizability is calculated from first principles for arbitrary thickness of the Debye layers in liquid and semiconductor. We show that the polarizability dispersion arises from the combination of two relaxation interfacial phenomena: charging of the electrical double layer and the Maxwell–Wagner relaxation. We also calculate the particle polarizability in the limit of thin electrical double layers, which greatly simplifies the analytical calculations. Finally, we show the model predictions for two relevant materials (ZnO and doped silicon) and discuss the limits of validity of the thin double layer approximation.
关键词： microspheres,dielectrophoresis,electrorotation,semiconductors,electrokinetics
更新于2025-09-19 17:15:36
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Synthesis of Multi-mode Quantum Dots Encoded Molecularly Imprinted Polymers Microspheres and Application in Quantitative Detection for Dopamine
摘要： As the promising analytical strategy, multi-mode quantum dots (QDs) encoded molecularly imprinted fluorescent sensors have attracted considerable attention. Here, a novel encoding strategy for water-dispersed QDs molecularly imprinted polymers microspheres (MIPMs) with a high-performance fluorescence intensity and multi-color signal was established. The water-compatible MIPMs were firstly synthesized via integrating the reversible addition-fragmentation chain transfer and precipitation polymerization (RAFT-PP), which could improve the water compatibility by grafting the hydrophilic groups of poly(2-hydroxyrthyl methacrylate) (PHEMA). Then the water-compatible MIPMs were used as embedding matrix to separately incorporate five different QDs, and a series of multi-color QDs encoded MIPs (five single-color and 10 dual-color fluorescent systems) were obtained. The fluorescent characterization of encoded MIPMs was studied in detail. Further, dual-mode fluorescent sensors, including monochromatic and ratiometric, were successfully fabricated for the quantitative detection of dopamine; good linear response in the range of 5-300 μg L-1 and 1-100 μg L-1 and the limit of detection (LOD) with 2 μg L-1 and 0.5 μg L-1 were obtained for monochromatic and ratiometric sensor, respectively. It is the first time to introduce the optical encoding strategy into the fabrication of fluorescent MIPs, which not only greatly simplifies the preparation process of fluorescent imprinted sensor, but also provides more alternatives for the detection method of analyte and the potential of high-throughput multiple analytes at one time.
关键词： Molecularly imprinted polymer,Quantum dot,Fluorescent sensor,Dopamine,Encoded microspheres
更新于2025-09-19 17:13:59
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Plasmon-coupled Charge Transfer in FSZA Core-shell Microspheres with High SERS Activity and Pesticide Detection
摘要： A commercial SeRS substrate does not only require strong enhancement, but also can be reused and recycled in actual application. Herein, fe3o4/Sio2/Zno/Ag (fSZA) have been synthesised, which consisted of fe3o4 core with strong magnetic field response and an intermediate SiO2 layer as an electronic barrier to keep the stability of magnetite particles and outer ZnO and Ag as the effective layers for detecting pollutants. The SERS enhancement factor (EF) of the FSZA was ~8.2 × 105. the enhancement mechanism of the fSZA core-shell microspheres were anatomized. the electromagnetic enhancement of surface deposited Ag, charge transfer, and molecular and exciton resonances act together to cause such high enhancement factors. for practical application, the fSZA core-shell microspheres were also used to detect thiram, moreover, which was collected and separated by an external magnetic field, and maintained the SERS activity without significant decline during multiple tests. So the good enhancement performance and magnetic recyclability make the fSZA core-shell microspheres a promising candidates for practical SeRS detection applications.
关键词： pesticide Detection,plasmon-coupled charge transfer,High SeRS Activity,fSZA core-shell Microspheres
更新于2025-09-19 17:13:59
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Transparent Schottky Photodiode Based on AgNi NWs/SrTiO <sub/>3</sub> Contact with an Ultrafast Photoresponse to Short‐Wavelength Blue Light and UV‐Shielding Effect
摘要： BACKGROUND: Mesoporous double-layer carbon microspheres (DCSs) were synthesized using hollow tin(IV) oxide (SnO2) microspheres as hard template and sucrose as carbon precursor via the hydrothermal method. Sulfonic acid groups (-SO3H) were introduced onto the surfaces of DCS by sulfuric acid heating and sulfanilic acid diazonium coupling, respectively, to form two solid acids (DCS-SS and DCS-DS, respectively). RESULTS: The transmission electron microscopy images showed that the carbon microspheres possessed a hollow double-layer structure with diameters of about 200 to 300 nm and shell thickness of about 30 to 50 nm. Furthermore, the sulfonate treatments caused no changes in the morphology of carbon microspheres. The nitrogen (N2)-Brunauer–Emmett–Teller (BET) results indicate that DCS, DCS-SS, and DCS-DS featured mesopores with an average pore size of 4.5 to 4.8 nm and BET surface areas of 75 m2/g, 57 m2/g, and 53 m2/g, respectively. The X-ray photoelectron spectroscopy and Fourier-transform infrared results confirmed that the DCS-SS and DCS-DS contained a -SO3H group and their surface acid densities are 4.5 and 4.1 mmol/g, respectively. CONCLUSION: DCS-SS and DCS-DS were used to catalyze the transesterification of waste frying oil, and the highest yields of fatty acid methyl esters, that is, 85% and 80%, respectively, could be obtained.
关键词： double-layer carbon microspheres,waste frying oil,sulfonation,characterization,transesterification
更新于2025-09-19 17:13:59
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Protein-based microsphere biolasers fabricated by dehydration
摘要： Biolasers made of biological materials have attracted considerable research attention due to their biocompatibility and biodegradability, and have the potential for biosensing and biointegration. However, the current fabrication methods of biolasers suffer from several limitations, such as complicated processing, time-consuming and environmentally unfriendly nature. In this study, a novel approach with green processes for fabricating solid-state microsphere biolasers has been demonstrated. By dehydration via a modified Microglassificationt technology, dye-doped bovine serum albumin (BSA) droplets could be quickly (less than 10 minutes) and easily changed into solid microspheres with diameters ranging from 10 mm to 150 mm. The size of the microspheres could be effectively controlled by changing either the concentration of the BSA solution or the diameter of the initial droplets. The fabricated microspheres could act as efficient microlasers under an optical pulse excitation. A lasing threshold of 7.8 mJ mm?2 and a quality (Q) factor of about 1700 to 3100 were obtained. The size dependence of lasing characteristics was investigated, and the results showed a good agreement with whispering gallery mode (WGM) theory. Our findings contribute an effective technique for the fabrication of high-Q factor microlasers that may be potential for applications in biological and chemical sensors.
关键词： microspheres,dehydration,whispering gallery mode,bovine serum albumin,biolasers
更新于2025-09-16 10:30:52
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Quantum Dots Luminescence Collection Enhancement and Nanoscopy by Dielectric Microspheres
摘要： In recent years, dielectric microspheres have been used in conjunction with optical microscopes to beat the diffraction limit and to obtain superresolution imaging. The use of microspheres on quantum dots (QDs) is investigated, for the first time, to enhance the light coupling efficiency. The enhancement of the QD luminescence collection in terms of extraction and directionality is demonstrated, as well as the enhancement of spatial resolution. In particular, it is found that a dielectric microsphere, placed on top of an epitaxial QD, increases the collected radiant energy by about a factor of 42, when a low numerical aperture objective is used. Moreover, if two or more QDs are present below the microsphere, the modification of the far field emission pattern allows selective collection of the luminescence from a single QD by simply changing the collection angle. Dielectric microspheres present a simple and efficient tool to improve the QD spectroscopy, and potentially QD-based devices.
关键词： microspheres,photoluminescence,photonic nanojet,near field
更新于2025-09-16 10:30:52