Defining the Difference Between a-Si and c-Si in Tertiary Mixtures of Methanol Using Handheld Raman

Raman spectroscopy is a well-advanced and adopted quantitative technique for molecular identification. However, in recent years, the use of Raman has been extended to perform accurate and quality measurements of mixtures and reactions, thanks to the development of high-resolution handheld Raman spectrometers and sophisticated chemometric modeling software.

This article discusses the application of BWIQ, the sophisticated chemometric modeling software from B&W Tek, to detect unknown methanol concentrations in a tertiary mixture of water, acetonitrile, and methanol.

Instrumentation

For this analysis, B&W Tek’s i-Raman was selected as it has the highest resolution (~3cm-1) available in the market. This capability coupled with convenient fiber optic probe and TE cooled CCD makes the Raman spectrometer ideal for coupling to a cuvette holder.

The minimal fluorescence background enabled the use of 532nm excitation to leverage the higher photon energy. The experimental setup of the i-Raman spectrometer in conjunction with a BAC151A video microscope sampling system is illustrated in Figure 1.

Experimental setup of the i-Raman spectrometer coupled to the BAC151A video microscope

Figure 1. Experimental setup of the i-Raman spectrometer coupled to the BAC151A video microscope

Experimental Procedure and Results

The 10mm disposable cuvettes were used to prepare known methanol, water and acetonitrile standards for development of a calibration curve. The i-Raman and BCR100A double-pass cuvette holder were then used to measure the cuvettes. All measurements were performed under the following conditions:

  • 532nm excitation wavelength set to ~30mW power output
  • An integration time of 7.5 seconds

No averaging was employed in this analysis and all spectra correspond to a single acquisition.

Figure 2 illustrates the convenience of Raman spectroscopy to be utilized as a qualitative measurement to detect the variations between between a-Si and c-Si. Moreover, the high resolution of the iRaman facilitates the development of calibration curves utilizing chemometric algorithms in a software package, like B&W Tek’s new BWIQ software. It is possible to develop a method for the quantitative analysis of Si crystallinity from these curves.

Raman spectrum of Si at varying degrees of crystallinity

Figure 2. Raman spectrum of Si at varying degrees of crystallinity

Conclusion

The combination of B&W Tek’s i-Raman spectrometer and BAC151A video microscope sampling system provides an ideal setup to perform Si crystallinity analysis. With a compact form factor and lightweight of roughly 6.6lbs, the i-Raman spectrometer equipped with a high-resolution F/2 spectrograph and a low noise TE cooled detector is an ideal system for both field and lab analysis.

This information has been sourced, reviewed and adapted from materials provided by B&W Tek.

For more information on this source, please visit B&W Tek.

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    B&W Tek. (2019, July 13). Defining the Difference Between a-Si and c-Si in Tertiary Mixtures of Methanol Using Handheld Raman. AZoM. Retrieved on July 17, 2019 from https://www.azom.com/article.aspx?ArticleID=10291.

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