School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK.
Lab Chip. 2017 May 2;17(9):1616-1624. doi: 10.1039/c6lc01393g.
Fourier transform infrared micro-spectroscopy provides an effective means of performing rapid, non-destructive, and label-free analysis of specimens according to their vibrational modes. However, as water absorbs very strongly in the infrared region, analysis of aqueous solutions in transmission mode can suffer from problems with signal saturation. We here describe the fabrication of a novel microfluidic device that overcomes this problem. Devices with channel depths of just 3 μm were constructed from calcium fluoride using photolithography and hot embossing bonding, where calcium fluoride was selected due to its transparency in the IR region. The utility of this device was then demonstrated by employing it to follow the precipitation pathways of calcium sulfate and calcium carbonate using synchrotron FTIR micro-spectroscopy. Importantly, due to the high brightness provided by synchrotron radiation, and the fact that the reacting ions (HCO, CO and SO) and the different mineral polymorphs all have finger print spectra in the measured IR range, this method can be used to acquire time-resolved, hyperspectral maps of the mineral particles formed within the sample cell, and then study the interaction and evolution of particles. The data provide new insight into the formation pathway of a population of crystals in confined volumes, and demonstrate that this in situ, real-time detection system provides a powerful tool for studying crystallization processes.
傅里叶变换红外微光谱学提供了一种根据振动模式对样品进行快速、非破坏性和无标记分析的有效手段。然而，由于水在红外区域强烈吸收，因此在透射模式下分析水溶液可能会受到信号饱和的问题的影响。我们在这里描述了一种新型微流控器件的制造，该器件克服了这个问题。使用光刻和热压印键合技术从氟化钙中制造出深度仅为 3μm 的通道，选择氟化钙是因为它在红外区域具有透明性。然后，通过使用同步辐射 FTIR 微光谱法来跟踪硫酸钙和碳酸钙的沉淀途径，证明了该器件的实用性。重要的是，由于同步辐射提供的高亮度，以及反应离子（HCO、CO 和 SO）和不同的矿物多晶型都在测量的红外范围内具有指纹谱，因此该方法可用于在样品室中形成的矿物颗粒获得时间分辨、高光谱图谱，然后研究颗粒的相互作用和演化。这些数据为在受限体积中形成晶体的种群的形成途径提供了新的见解，并证明了这种原位、实时检测系统为研究结晶过程提供了有力的工具。
