Raman microscopes

Plenary 8. J Grave et al, e-mail address J.Greve tn.utwente.nl (RS). Confocal direct unaging Raman microscope (CDIRM) for probing of the human eye lens. High spatial resolution of the distribution of water and cholesterol in lenses. 

Evans R, Smith I, Munz W D, Williams K J P and Yanwood J 1996 Raman microscopic studies of ceramic coatings based on titanium aluminum nitride ICORS 96 XVth Int. Conf. on Raman Spectroscopy ed S A Asher and P B Stein (New York Wiley) pp 596-7... 

With regard to the confinement and enhancement ability of a metallic nano-tip, we have proposed near-field Raman microscopy using a metallic nano-tip [9]. The metallic nano-tip is able to enhance not only the illuminating light but also the Raman scattered light [9, 15, 16]. Figure 2.5 illustrates our nano-Raman microscope that mainly comprises an inverted microscope for illumination and collection of Raman... 

Figure 2.5 A tip-enhanced near-field Raman microscope which we have developed. The microscope is based on AFM for control of the metallic nano-tip, an inverted optical microscope for illumination/collection of the light field and a polychromator for measurement of the Raman signal.

In this section, we will describe some experiments which we have performed using the above-mentioned nano-Raman microscope. Figure 2.6a shows the Raman spectmm of an adenine nanocrystal of height 7 nm and width 30 nm [19]. Several Raman bands are observed as the probe tip is near enough to the sample (AFM operation is made in contact mode). These bands, except the one appearing at 924 cm, are assigned as the vibrational modes, inherent to the adenine molecule, according to the molecular orbital calculation. For examples, two major bands, one at... 

Duncan, M. D., Reintjes, J. and Manucda, T. J. (1982) Scanning coherent anti-Stokes Raman microscope. Opt. Lett., 7, 350-352. 

The samples were collected from the cathodes 2.5 cm away from the current collector tab, washed in pure dimethyl carbonate (DMC), and soaked in DMC for 30 minutes after removal from Li-ion cells inside an argon-filled glove box. This procedure removed electrolyte salt from the electrode to prevent its reaction with air and moisture. An integrated Raman microscope system Labram made by ISA Groupe Horiba was used to analyze and map the cathode surface structure and composition. The excitation source was an internal He-Ne (632 nm) 10 mW laser. The power of the laser beam was adjusted to 0.1 mW with neutral filters of various optical densities. The size of the laser beam at the sample was 1.2 pm. 

Cathode surface-average Raman spectra were produced with the Raman microscope. Raman spectra were collected from multiple 52x75pm sections of the cathode surfaces at 0.7pm resolution and averaged into one representative spectrum for each cathode. MicroRaman surface-average spectra of the cathode from the virgin cell, and cathodes removed from cells,... 

Figure 1. Average Raman microscope spectra of the fresh composite LiNio.sCoonAlo.05O2 cathode (a), and the cathode from cells that exhibited 10 (b),...

A Raman microscope (Renishaw, 785-nm laser, spectral range 800-100cm ) with a line-mapping detector (21 pixels/line) was used to analyze a solid dosage form. The image size was 105 x 88 pixels, that is, 325 pm x 270 pm, and acquisition time was about 40 min. Spectra were smoothed and normalized. Peak heights were determined for the three main compounds—API, lactose, and cellulose (Figure 11)—in order to create distribution maps. 

Fig. 3.12. Non-invasive Raman spectra of pharmaceutical capsules. The spectra were obtained using a laboratory instrument configured in the transmission Raman geometry and a standard commercial Raman microscope (Renishaw) in conventional backscattering geometry. The Raman spectra of an empty capsule shell (lowest trace) and the capsule content itself (top trace, the capsule content was transferred into an optical cell) are shown for comparison. The dashed lines indicate the principal Raman bands of the capsule and of the API (this figure was published in [65], Copyright Elsevier (2008))...

In summary, the analyst has a number of options in deciding which Raman method to use for their specific analysis. As a general rule of thumb FT-Raman spectroscopy should be used for bulk samples (ca. >1-10 mg sample). A dispersive Raman microscope system is generally the best option for individual particles or small areas of larger samples. 

Dong, J., Atwood, C.S., Anderson, V.E., et al. (2003) Metal binding and oxidation of amyloid-beta within isolated senile plaque cores Raman microscopic evidence. Biochemistry 42, 2768-2773. 

Figure 3.17 illustrates the layout of a typical Raman microscope. The excitation source is monochromatic, since the small signals are recorded as shifts, or Av, from the excitation line. Lasers are universally used since as well as providing monochromatic light, they offer high power and collimation. The exciting laser... 

Figure 3.17 Block diagram of a typical confocal Raman microscope employing CCD detection...

The changes in the composition of the gas phases can be interpreted by considering the parallel changes in the solid phase. The progress of the chemical transformation of the solid phase in course of LP process was monitored by a Raman microscope. 

Fig. 8. Raman spectrum of a single cell of Clostridium beijeinckii, of a size of about 2x4 pm. Peaks are marked with the wavenumber of the Raman shift, and tentative attributions of the bands are given. Insert Video image showing a C. beijerinckii cell in the focused laser beam of the Raman microscope. The diameter of the laser focus, which determines the sampling volume by the excitation of the Raman effect, is about the same size as the cell, (from [89])...

Bruker has introduced an FT-Raman microscope which is an accessory to an FT-IR spectrometer (42). The coupling between the microscope and the Raman module is made by NIR-fiber optics. In the wavelength range of the Raman experiment excited by a Nd YAG laser, the fiber optics transmission is at a maximum, thus allowing the experiment to be successful (43). Spatial resolution down to 5//m can be achieved. The technique appears to be a capable adjunct to FT-IR microscopy. 

The combination of resonance Raman microscope spectrometry and the CLM method allowed us to directly observe the Raman spectra of the liquid-liquid interface and the bulk phases by shifting the focal point of an objective lens. A schematic diagram of the measurement system is shown in Fig. 6. CLM/ Raman microscope spectrometry was applied in order to measure the rate of complex formation between Pd(II) and 5-Br-PADAP (HL) at the heptane-water interface and it was demonstrated that this method was highly useful for the kinetic measurement of the interfacial reaction [37],... 

Fig. 8. Raman microscope for the measurement of SERS spectra of liquid-liquid interface organic phase 250 pi and aqueous phase 250 pi.

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