B&W Tek, Inc.

Articles

This case study demonstrates how the Tactic-ID GP handheld Raman analyzer was used to detect contamination in a commercial hand sanitizer. 


Detecting Methanol Contamination in Hand Sanitizers

	Quality control in the food industry is a key issue that requires rapid, efficient, and selective methods that could discriminate the products, detect fraudulent or accidental adulterations, and identify the content of some biomarkers within a particular process of storage conditions. Along these lines, Raman spectroscopy in conjunction with the optical properties of metallic nanostructures is a powerful technique that can be implemented in food analysis.

Applications of Portable Raman Spectroscopy E-Book

Fast and Selective Detection of Trigonelline, a Coffee Quality Marker, Using a Portable Raman Spectrometer

While crystalline silicon (c-Si) is still the material of choice for modern solar cell manufacturing, the drive toward lower cost, more efficient solar cells is prompting a renewed interest in thin-film amorphous silicon (a-Si). In light of this, it is more important than ever to have the ability to quickly identify Si crystallinity, both qualitatively and quantitatively. In this application note, we evaluate how a portable Raman spectrometer can be used in conjunction with a portable video microscope to measure crystallinity. 

  from B&W Tek, was chosen due to fact that it is the highest resolution (~3 cm

 ) portable Raman spectrometer on the market. This, in conjunction with its TE cooled CCD and convenient fiber optic probe, made it the ideal solution for both "at line" and laboratory measurement. The minimal fluorescence background of Si allowed for the use of 532 nm excitation to take advantage of the higher photon energy and shallower penetration depth as compared to longer excitation wavelengths. 

  was coupled to the BAC151A video microscope from B&W Tek to facilitate accurate sample positioning for the measurement. Figure 1a shows the experiment setup of the i-Raman

  and the video microscope sampling system. The sample set for this experiment contained samples with differing crystallinity, ranging from < 10% to pure crystalline Si. These Si samples were deposited on glass substrates. 

Figure 1: (a) Experimental setup of the i-Raman coupled to the BAC151A video microscope, and (b) Raman spectrum of Si at varying degrees of crystallinity.			

Two Raman peaks are related to silicon crytallinity: the peak at 480 cm

  is associated to the amorphous phase and the peak at 520 cm

Figure 1b overlays the Raman spectra of all five samples in the set. The red and blue spectra represent samples with a crystallinity < 10%, the brown spectrum is of a sample with a crystallinity between 40% and 60%, the green spectrum is of a sample with > 90% crystallinity and the dark blue spectrum is of pure c-Si. The shifting of the Si band from 480 cm

  can be clearly observed in the data. As silicon crytallinity increases, the amorphous peak 480 cm

  reduces while the microcrystalline silicon peak 520 cm

Figure 1b shows how Raman spectroscopy can easily be used as a qualitative measurement to determine the difference between a-Si and c-Si, but the high resolution of the iRaman

  also makes it possible for the development of calibration curves using chemometric algorithms in a software package such as B&W Tek's new BWIQ

  software package. From these curves, a method can be developed for the quantitative analysis of Si crystallinity. 

  spectrometer, when coupled with a BAC151A video microscope sampling system, is an ideal setup for Si crystallinity analysis. The compact form factor and light weight (~6.6 lb) of the i-Raman when coupled with low noise TE cooled detector and high resolution F/2 spectrograph make it the ideal solution for both laboratory and field analysis. 

While crystalline silicon (c-Si) is still the material of choice for modern solar cell manufacturing, the drive toward lower cost, more efficient solar cells is prompting a renewed interest in thin-film amorphous silicon (a-Si). In light of this, it is more important than ever to have the ability to quickly identify Si crystallinity, both qualitatively and quantitatively. In this application note, we evaluate how a portable Raman spectrometer can be used in conjunction with a portable video microscope to measure crystallinity.

Raman Analysis of Si Crystallinity

nnoRam™, has been developed to provide research-grade performance in either a lab or a mobile environment. The Raman analysis of carbon nanotubes using 

nnoRam in comparison with a Raman spectrometer using a conventional front illuminated CCD demonstrates distinctive improvements for 

nnoRam in both sensitivity and signal-to-noise ratio (SNR).

nnoRam™, is a research-grade Raman spectrometer with high sensitivity and application versatility. The innoRam's back-thinned 2D vertically binned CCD detector with TE-cooling to –20 °C ensures research-grade performance. The application discussed in this paper is a comparison of Raman analysis of carbon nanotubes between innoRam and a Raman spectrometer with front-illuminated linear CCD detector with TE-cooling to 14 °C. 

Compared with a conventional front-illuminated CCD with quantum efficiency around 50%, the back-thinned or back-illuminated CCD quantum efficiency can reach up to 90%. The lower QE of a front-illuminated CCD is due to the incident photons being largely reflected and absorbed by gate structures (Poly-Si, BPSG, gate oxide) while traveling through the front side of the CCD. A back-thinned CCD minimizes these losses by etching the Si substrate (to limit the absorption) and illuminating the CCD from behind. This greatly increases its quantum efficiency by reducing the photon loss. Due to the low photon efficiency of the Raman phenomenon (10

), detectors used in Raman spectrometry must have readout noise and dark noise that is very low to identify the Raman signal from the sample. TE-cooling of the CCD device effectively reduces the dark noise: the dark noise halves for each 7 °C decrease in device temperature. The deep TE-cooled detector allows long integration time (up to 16 minutes for 

nnoRam), which greatly increases the detection limit. 2D binning, which is to combine two or more vertical rows of the CCD array, is another technique to improve signal-to-noise ratio. The characteristics of the detector make 

nnoRam ideal for low-light level applications. 

The Raman spectrum of carbon nanotubes was collected using B&W Tek's 

nnoRam Raman spectrometer system (Figure 1a) with 785 nm laser excitation. The Raman spectrum of carbon nanotubes measured from 

nnoRam is shown in Figure 1 (b). The Raman spectrum of the same carbon nanotubes using a Raman spectrometer with a front-illuminated linear CCD TE-cooled to 14 °C is shown in Figure 1 (c). In order to have a direct comparison, the same laser power (25 mW) and integration time (10 sec) were used for both Raman measurements. The comparison of Figure 1 (b) and (c) shows distinctive improvement of SNR and increase of intensity in the spectrum from the 

nnoRam Raman spectrometer system, featuring a back-thinned 2D vertically binned CCD detector with TE-cooling to –20 °C, provides research-grade performance with high sensitivity and SNR, which is clearly demonstrated by the comparison of Raman analysis of carbon nanotubes between 

nnoRam and a Raman system using a conventional front-illuminated linear CCD with TE-cooling to 14 °C.  

A new Raman spectrometer system, innoRamâ„¢, has been developed to provide research-grade performance in either a lab or a mobile environment. The Raman analysis of carbon nanotubes using innoRam in comparison with a Raman spectrometer using a conventional front illuminated CCD demonstrates distinctive improvements for innoRam in both sensitivity and signal-to-noise ratio (SNR).

B&W Tek, Inc.

Articles

Detecting Methanol Contamination in Hand Sanitizers

Fast and Selective Detection of Trigonelline, a Coffee Quality Marker, Using a Portable Raman Spectrometer

Raman Analysis of Si Crystallinity

A Comparison of Raman Analysis of Carbon Nanotubes