Qualification of an Ultrasonic Instrument for Real-Time Monitoring of Size and Concentration of Nanoparticles during Liquid Phase Bottom-Up Synthesis (original) (raw)
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KONA Powder and Particle Journal, 2017
Size characterization of nanoparticles has gained wide concerns in the past decades, but it remains a challenge for measurement in suspensions up to now. The extremely small scales of particle size result in great difficulty for traditional static light scattering method and optical imaging. In addition to the electron microscopy techniques, the dynamic light scattering (DLS) method is another widely used technique for laboratory analysis of samples. Moreover, the ultrasonic attenuation spectroscopy (UAS) technique is also being developed rapidly to provide an alternative method for nanoparticle sizing. This paper focuses on the latest development in the above two technologies for nanoparticle size characterization. As for the former, advances about the image-based DLS technology in recent years are reviewed, including three different kinds of data processing methods and corresponding measuring experiments using standard polystyrene particles. Methodology principles, models and experimental setup were also reviewed for the latter UAS technology. Samples of the same nanoscale silver particles were tested by the above two methods, as well as by transmission electron microscopy. A sample of Antimony Tin Oxide (ATO) nanoparticles has also been adopted for measurements and comparisons. Relatively consistent results can be found by comparing the particle sizes or distributions with various methods. The dramatically reduced measurement time in image-based DLS indicates the potential for real-time and in-situ nanoparticle sizing. UAS also provides a suitable way for nanoparticle size characterization at high concentrations.
Journal of Colloid and Interface Science, 2010
Monitoring the presence of nanoparticles in dispersions having broad particle size distributions can be a problem for many measurement techniques because large particles or even aggregates of the smaller particles can mask the presence of the sought after nanoparticles. The ability of many existing techniques to detect the nanoparticles when present in broad polydisperse systems is largely unknown, yet it is critical for proper selection of the measuring technique for characterizing a particular nanodispersion. Acoustic spectroscopy is already a known and proven tool for studying nanoparticles in systems with a narrow size distribution. The purpose of this paper is to evaluate the sensitivity of acoustic spectroscopy for determining the nanoparticle content of very polydisperse systems. We used eight different ZnO powders from different manufacturers to prepare 5 wt.% dispersions, each dispersed in water. The stability of each dispersion was optimized by pH adjustment and addition of sodium hexametaphosphate as determined by maximizing the measured f-potential. According to the acoustic measurement, the median size of these different ZnO dispersions varied from 200 nm to 700 nm. Independent TEM photographs in general confirmed the size variation between the samples. Independent DLS measurements failed to provide particle size data correlating with TEM. The acoustic measurements further showed that each dispersion contained a different relative content in the nanoparticle fraction. The precision with which the nanoparticle fraction could be determined was better than 2% of the total solid loading for all samples. In order to verify consistency of this measurement we performed a mixing study by adding dispersion with the largest nanoparticle content to the dispersion with the smallest nanoparticle content, in small increments. This test confirms that the acoustic sensitivity threshold is about 2% of nanoparticles in the broad polydisperse dispersions of dense metal oxide particles.
Experimental study of continuous ultrasonic reactors for mixing and precipitation of nanoparticles
Chemical Engineering Science, 2012
Nanoparticles can be synthesized by precipitation. State-of-the-art is the precipitation of nanoparticles in stirred tanks or high-pressure T-mixers. The study presents two new reactor concepts for continuous precipitation of nanoparticles. Both of them utilize ultrasonic sound as a mixing accelerator. The first reactor has a conical chamber (10 mL), which is used to study the micromixing quality, the cavitation intensity and the precipitation of barium sulfate nanoparticles. The second reactor has a so-called cavitational chamber (2.5 mL), which is an optimized conical reactor. Both reactors are compared with each other with respect to the properties of the products. Additionally, the influence of the ultrasonic output from the transducer to the liquid and the feed rate are demonstrated.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999
The particle size distribution of particles in liquid-based suspensions and emulsions is an important parameter in a wide variety of industrial applications. Many particle-sizing methods require the transmission of light through a sample of the system, and therefore these particulate systems must be severely diluted. Many systems are unstable on dilution and therefore have to be measured at high volume concentration. Sound waves interact with both the suspending medium and the dispersed phase and are able to propagate through concentrated systems. The development of new ultrasonic transducer technology together with advances in digital signal processing has opened the way for a powerful new analysis termed acoustic attenuation spectroscopy. The technique consists of propagating ultrasonic waves of a range of frequencies through the particulate system and accurately measuring the attenuation at each frequency. This attenuation spectrum can be converted to a particle size distribution and a measure of the concentration of the dispersed phase. It offers the particle technologist the means to monitor and control particle formation and reduction processes.
Instrumentation, Metrology, and Standards for Nanomanufacturing, Optics, and Semiconductors V, 2011
Nanoparticles and products incorporating nanoparticles are a growing branch of nanotechnology industry. They have found a broad market, including the cosmetic, health care and energy sectors. Accurate and representative determination of particle size distributions in such products is critical at all stages of the product lifecycle, extending from quality control at point of manufacture to environmental fate at the point of disposal. Determination of particle size distributions is non-trivial, and is complicated by the fact that different techniques measure different quantities, leading to differences in the measured size distributions.
Proceedings of SPIE - The International Society for Optical Engineering
Nanoparticles and products incorporating nanoparticles are a growing branch of nanotechnology industry. They have found a broad market, including the cosmetic, health care and energy sectors. Accurate and representative determination of particle size distributions in such products is critical at all stages of the product lifecycle, extending from quality control at point of manufacture to environmental fate at the point of disposal. Determination of particle size distributions is non-trivial, and is complicated by the fact that different techniques measure different quantities, leading to differences in the measured size distributions.
Evaluation of short cycles of ultrasound application in nanoemulsions to obtain nanocapsules
Ultrasonics Sonochemistry, 2015
Ultrasound is widely used in several chemical reactions and other process, including production of nanocapsules by in situ polymerization. In this work, the main objective was to evaluate the impacts and viability of successive ultrasound application in nanoemulsions to obtain nanocapsules. Initiator potassium persulfate (KPS) concentration, number of ultrasound cycles and reaction time influences on polymerization efficiency and droplet size were evaluated. This work revealed the successful in situ production of nanocapsules using successive shorts cycles of ultrasound. Number of cycles was the only parameter that not exerted significant influence in polymerization yield. Particle size decay was observed in all nanoemulsions after the first ultrasound application, the same was not observed in further cycles. Gravimetric assessment showed remarkable increase of monomer conversion, indicating that once started polymerization continued at least until 28 days after ultrasound application. Concluding, ultrasound short cycles can be used with no harm to formulation, if carefully performed and, furthermore is a potential cost-effective route for polymerization reactions.
Inline high frequency ultrasonic particle sizer
Review of Scientific Instruments, 2013
This paper reports the development of a new method of particle sizing in a liquid. This method uses high frequency focused ultrasounds to detect particles crossing the focal zone of an ultrasonic sensor and to determine their size distribution by processing the reflected echoes. The major advantage of this technique compared to optical sizing methods is its ability to measure the size of particles suspended in an opaque liquid without any dedicated sample preparation. Validations of ultrasonic measurements were achieved on suspensions of polymethyl methacrylate beads in a size range extending from a few micrometer to several hundred micrometer with a temporal resolution of 1 s. The inline detection of aggregate formation was also demonstrated.
Journal of Pharmaceutical Sciences, 2011
There are currently no adequate process analyzers for nanoparticulate viscosity enhancers. This article aims to evaluate ultrasonic resonator technology as a monitoring tool for homogenization of nanoparticulate gels. Aqueous dispersions of colloidal microcrystalline cellulose (MCC) and a mixture of clay particles with xanthan gum were compared with colloidal silicon dioxide in oil. The processing was conducted using a laboratory-scale homogenizing vessel. The study investigated first the homogenization kinetics of the different systems to focus then on process factors in the case of colloidal MCC. Moreover, rheological properties were analyzed offline to assess the structure of the resulting gels. Results showed the suitability of ultrasound velocimetry to monitor the homogenization process. The obtained data were fitted using a novel heuristic model. It was possible to identify characteristic homogenization times for each formulation. The subsequent study of the process factors demonstrated that ultrasonic process analysis was equally sensitive as offline rheological measurements in detecting subtle manufacturing changes. It can be concluded that the ultrasonic method was able to successfully assess homogenization of nanoparticulate viscosity enhancers. This novel technique can become a vital tool for development and production of pharmaceutical suspensions in the future.
Sensitivity of particle sizing by ultrasonic attenuation spectroscopy to material properties
Powder Technology, 2003
Ultrasonic attenuation spectroscopy is a recently developed technique for rapid characterisation of particulate suspensions at high concentrations. Implementation of the full Epstein -Carhart -Allegra -Hawley model, which is used to transform ultrasound attenuation measurements into particle size and concentration information, requires knowledge of seven physical properties of the particulate phase and of a further seven properties of the continuous phase. Reliable data are not always available for all these properties. In this study, an assessment is made of the influence of inaccuracy in the physical properties on the recovered values of particle size and concentration.