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UV Fluorescence and Photoluminescence Measurements by the MDIS-f8 Spectrometer

UV fluorescence spectroscopy analyzes fluorescence spectrum from a sample, and is used in scientific researches and technique applications, such as in the chemical, biochemical, medical, physical, mineralogical, gemological research fields. The  multifunction dual integrating sphere (MDIS) spectrometer has 8 functions, and can measure UV fluorescence of a sample with a UV laser diode, a UV light emitting diode (LED) or any other UV radiation sources. It can also measure photoluminescence with a visible laser diode or a visible LED. Figure 1 shows the optical arrangement of the spectrometer for fluorescence and photoluminescence measurements.

 

Figure 1. Optical arrangement of the dual integrating sphere spectrometer for fluorescence measurement. 1. measurement integrating sphere, 2. sample integrating sphere, 3. sample platform, 4. aperture, 5. glass filter, 6. collimator, 7. light trap, 8. diffuse block, 9. visible light source, 10. UV or visible excitation source, 11. sample, 12 spectrometer, and 13. computer. 

The excitation source emits UV or visible light to excite the sample from the top of the sample integrating sphere. The sample emits fluorescence or photoluminescence light into the measurement integrating sphere. The fluorescence or photoluminescence light is sent to the spectrometer by the collimator through an optical cable. The spectrometer separates the light into spectrum signals, and the computer receive the spectral signals, and then calculates the fluorescence or photoluminescence spectrum. 

The MDIS-f8 spectrometer can enhance the measured UV fluorescence by the magnitudes of X10, X100, and X1000. UV fluorescence spectrum is often enhanced due to that UV fluorescence of most samples are very weak, although a weak fluorescence appear intense in dark.

Sample holder or curettes is not needed for UV fluorescence and photoluminescence measurements by the spectrometer, because a sample is placed on the sample platform, and the LED illuminates the sample from top of the sample integrating sphere. If the sample is liquid or soft tissue, it can be put in a glass dish, such as a Petri dish, a culture dish, or even a glass slide,  on the sample platform for the measurement. This type of sample arrangement is very easy and convenience for scientific research and medical examination, especially for biological.  biochemical, pharmaceutical and medical researches involving liquid and soft tissue samples.  

It is the most advantage that the dual integrating sphere spectrometer can directly measure UV fluorescence and photoluminescence of diamonds under room temperature, no liquid nitrogen is needed to obtain the phonon spectrum of color centers in diamonds for identification.  

 

Fluorescence Measurement of Liquid and Soft Tissue

Figure 2. shows a UV fluorescence spectrum of a blue fluorescence ink. When measuring the UV fluorescence, the ink is in a 35 mm culture dish on the sample platform. The excitation wavelength is at 290 nm, and the magnitude is X10. The UV fluorescence spectrum has a short wavelength band approximately from 430 to 550 nm, and the spectral maximum is at about 450, therefore, the UV fluorescence appears blue.

Figure 2. UV fluorescence spectrum of a blue fluorescence ink, 290 nm and magnitude X1.

The optical arrangement and measurement method of the spectrometer is particular suitable for the fluorescence measurement of liquid and soft tissue. The spectrometer also has the capability of amplifying the intensity of weak fluorescence up to 1000 times. This spectrometer can be easily used in the biological, biochemical, pharmaceutical and medical research fields involving liquid and soft tissue samples.

 

Fluorescence Measurement of Diamonds

The spectrometer can measure the UV fluorescence with the zero line, peaks, and side band of phonons of color centers in diamonds at room temperature. Figure 3 shows a UV fluorescence spectrum of a milky white diamond. The UV fluorescence spectrum is measured under a 255 nm LED with the magnitude of X1000. The 415 nm peak is the zero phonon line of the N3 center. The first, second peaks and side band of phonon of N3 center are also clearly shown in the UV fluorescence spectrum. The diamond can be identified as type Ia natural diamond.  

Figure 3. UV fluorescence spectrum of a milky white diamond, 255 nm and magnitude X1000.

Figure 4. Shows the UV fluorescence spectrum of a pink diamond under a 290 nm LED with the magnitude X100. The 575 nm spectral peak is the zero phonon line of the N-V+ center, and the long wavelength fluorescence band is the side band of the N-V+ center. The pink diamond is a treated synthetic diamond. The N-V+ center is caused by irradiation and heat treatment.

Figure 4. UV fluorescence spectrum of a pink diamond, 290 nm and magnitude X100.

The most advantage of using the spectrometer to measure the fluorescence of diamonds is that the zero phonon lines of color centers can be obtained under room temperature, not like other spectroscopy methods must be under liquid nitrogen temperature.

 

Photoluminescence Measurement

Photoluminescence is the luminescence or fluorescence induced by visible light. By using a laser diode or a LED in visible light range as the exciting light, photoluminescence can be directly measured by the spectrometer. Figure 5 shows a photoluminescence spectrum of the milky white diamond under a 405 nm laser diode at amplification X10. This photoluminescence spectrum shows the first and second peaks and the side band of the phonon of the N3 center. Based on this photoluminescence, this milky white diamond can be identified as a type Ia natural diamond.

Figure 5. Photoluminescence spectrum of the milky white diamond, 405 nm laser diode, X10.

Figure 6 shows a photoluminescence spectrum of the synthetic pink diamond under a 405 laser diode at amplification X10. The photoluminescence spectrum shows the zero line, first peak, second peak and side band of the phonon of the N-V+ center. The photoluminescence spectrum is almost identical to the UV fluorescence spectrum in Figure 4. Therefore, based on this photoluminescence spectrum, the pink diamond can be identified as a treated synthetic diamond.

Figure 6. Photoluminescence spectrum of the synthetic pink diamond, 405 nm laser diode, X10.  

Figure 7 shows a photoluminescence spectrum of a ruby measured under a 400 nm LED at the magnitude X1.There are three spectral bands in the photoluminescence spectrum: a short wavelength band center at about 400 nm, another short wavelength band centered at about 450 nm, and a long wavelength band from 560 to 730 nm with the spectral peak at 693 nm. The short wavelength band centered at about 400 nm is the excitation light from the LED. The short wavelength band centered at about 450 nm and the long wavelength band is the photoluminescence induced by the 400 nm light from the LED. 

Figure 7. Photoluminescence spectrum of a ruby, 400 nm and magnitude X1.

Figure 8. shows another photoluminescence spectrum of the ruby. This photoluminescence is induced by the visible light at about 525 nm. The very strong band centered at 525 nm is the exciting light from the LED, and the long wavelength band with the 693 nm peak is the photoluminescence band induced by the 525 nm visible light. The long wavelength band with the spectral peak at 693 nm is the same photoluminescence band in figure 5. The short wavelength band with the spectral peak at 693 nm is caused by the Cr3+ in ruby.

Figure 8. Photoluminescence spectrum of the ruby, 525 nm and magnitude X1.

 

Identify "B" Type Jadeite

The "B" type jadeite is impregnated with polymers. The polymers can emit visible light under UV light source, which is UV fluorescence. The polymers actually can also emit visible light under short wavelength visible light, which is photoluminescence. The dual integrating sphere spectrometer can identify "B" type jadeite by measuring UV fluorescence or photoluminescence. If a UV fluorescence spectrum or a photoluminescence spectrum of a piece of jadeite shows a luminescence emission band, the jadeite can be identified as type "B" jadeite. Since short wavelength visible light is much less harmful to the human eye and visible excitation source is much easy to handle. photoluminescence is usually measured for identifying "B" type jadeite.

Figure 9 shows the photoluminescence spectrum of a type "B" white jadeite. The photoluminescence spectrum is measured with a 405 nm laser diode with an amplification X10. The photoluminescence spectrum shows a very strong luminescence emission band at the short wavelength range. The luminescence band indicates that the jadeite is impregnated with a polymer. Therefore, the jadeite is identified as type "B".

   

Figure 9. Photoluminescence spectrum of a type "B" white jadeite, 450 nm and amplification X10.

Figure 10 shows the photoluminescence spectrum of a type "B" green jadeite. The photoluminescence spectrum is measured with a 405 nm laser diode with an amplification X10. The photoluminescence spectrum shows a  strong luminescence emission band at the green wavelength range. The luminescence band indicates that the jadeite is impregnated with a polymer. Therefore, the jadeite is identified as type "B". The green band is caused by that the absorption of the green jadeite to the polymer luminescence band at short wavelength range in Figure 9.

Figure 10. Photoluminescence spectrum of a type "B" green jadeite, 405 nm and amplification X10.

 

 

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Last modified: 01/22/15.