Microwave dielectric heating of non-aqueous droplets in a microfluidic device for nanoparticle synthesis
Microwave dielectric heating of non-aqueous droplets in a microfluidic device for nanoparticle synthesis
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DOI：
10.1039/c3nr00500c
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发表时间：
2013-01-01
期刊：
影响因子：
6.7
通讯作者：
Weitz, David A.
中科院分区：
文献类型：
--
作者：
Koziej, Dorota;Floryan, Caspar;Weitz, David A.
我们描述了一种具有集成微波加热器的微流体装置，该微波加热器专门设计用于使用频率范围在700和900 MHz之间的时变电场介电加热非水性液滴。精确控制频率、功率、温度和施加场的持续时间为常规微波加热无法实现的实验开辟了新的前景。我们使用基于荧光的非接触式温度测量系统来直接确定单个液滴内部的温度。液滴达到的最高温度在15 ms内为50 ℃，这表示比连续相的基础温度增加约25 ℃。此外，我们使用红外摄像机来监控设备的热特性，从而确保加热完全是由于介电加热而不是由于电极或接触缺陷引起的非介电损耗等其他影响。这对于说明介电加热苯甲醇液滴合成金属氧化物的潜力至关重要。我们证明了该技术用于金属氧化物纳米颗粒合成的实用性，实现了氧化钨纳米颗粒的结晶和显着的微观结构，反应时间为64 ms，比传统的加热方法有了很大的改进。
We describe a microfluidic device with an integrated microwave heater specifically designed to dielectrically heat non-aqueous droplets using time-varying electrical fields with the frequency range between 700 and 900 MHz. The precise control of frequency, power, temperature and duration of the applied field opens up new vistas for experiments not attainable by conventional microwave heating. We use a non-contact temperature measurement system based on fluorescence to directly determine the temperature inside a single droplet. The maximum temperature achieved of the droplets is 50 degrees C in 15 ms which represents an increase of about 25 degrees C above the base temperature of the continuous phase. In addition we use an infrared camera to monitor the thermal characteristics of the device allowing us to ensure that heating is exclusively due to the dielectric heating and not due to other effects like non-dielectric losses due to electrode or contact imperfection. This is crucial for illustrating the potential of dielectric heating of benzyl alcohol droplets for the synthesis of metal oxides. We demonstrate the utility of this technology for metal oxide nanoparticle synthesis, achieving crystallization of tungsten oxide nanoparticles and remarkable microstructure, with a reaction time of 64 ms, a substantial improvement over conventional heating methods.