Photoacoustic spectroscopy, monitoring

The Use of Photoacoustic Spectroscopy to Characterize and Monitor Soot in Combustion Processes... 

Photoacoustic Spectroscopy.—Photoacoustic spectroscopy (PAS) and its applications have been recently reviewed. A single-beam i.r. PAS spectrometer has been constructed for the range 800—4000 cm using a broad-band carbon rod spectral source in preference to a laser. A double-beam in-time PAS instrument has been described, in which a single microphone was used to monitor both the... 

Yasmin, Z., Khachatryan, E., Lee, Y.-H., Maswadi, S., Glickman, R., Nash, Ki., 2015. In vitro monitoring of oxidative processes with self-aggregating gold nanoparticles using all-optical photoacoustic spectroscopy. Biosens. Bioelectron. 64, 676—682. 

Sigrist MW (1995) Trace gas monitoring by laser-photoacoustic spectroscopy. Infrared Physics and Technology 36 415-425. 

The methodology involved the monitoring of diffused gas by a photoacoustic analyser. Diffusion coefficients measured for carbon dioxide and oxygen were 2.77 X 10 cmVs and 1.68 x 10 cmVs, respectively. To support the gas diffusion results, thermal properties were studied using photoacoustic spectroscopy and... 

This work involved the use of photothermal techniques for determining the diffusion coefficients of O2 and CO2 of commercial LDPE. The methodology involved the monitoring of diffused gas hy a photoacoustic analysen Diffusion coefficients measured for CO2 and O2 were 2.77 x 10 cm Vs and 16.8 x 10 cm Vs, respectively. To support the gas diffusion results, thermal properties were studied using photoacoustic spectroscopy and crystallinity was determined using X-ray diffraction. Values obtained for the thermal diffusivity and specific heat capacity were 0.00165 cm and 2.33 J/cm /K, respectively, which were in good agreement with the values found in the literature for pure LDPE and thus, assured the reliability of the diffusion coefficient values. 

Hairen FJM, Cotti G, Oomens J, te Lintel Hekkert S. 2000. Photoacoustic spectroscopy in trace gas monitoring . In Encyclopedia of Analytical Chemistry, Meyers RA (ed.). Wiley Chichester 2203-2226. 

The systems studied served as model mixtures for dielectric coatings for printed circuits. The curing behavior was monitored by FTIR spectroscopy, also in combination with photoacoustic spectroscopy. These methods provided information on the... 

Meyer PL, Sigrist MW (1990) Atmospheric pollution monitoring using CO -laser photoacoustic spectroscopy and other techniques. Rev Sci Instrum 61 1779-1807... 

M.W. Sigrist Air monitoring by laser photoacoustic spectroscopy. In Air Monitoring by Spectroscopic Techniques, ed. by M.W. Sigrist (Whey, New York 1994)... 

F.J.M. Harren Photoacoustic spectroscopy in trace gas monitoring. In Encyclopedia of Analytical Chemistry Applications, Theory and Instrumentation, ed. by R.A. Meyers (Wiley, New York 2000) p.2203... 

Laser photoacoustic spectroscopy (LPAS) can be used for selective monitoring of analytes [100]. The... 

Sigrist MW (1994) Air monitoring hy laser photoacoustic spectroscopy. In Sigrist MW (ed) Air Monitoring by Spectroscopic Techniques, Chemical Analysis Series, Vol 127, Chapter 4. New York Wiley. 

Plate 46 Photoacoustic Multi-gas Monitor. See Photoacoustic Spectroscopy, Methods and Instrumentation. Reproduced with permission from INNOVA AirTech Instruments. 

Plate 48 A photoacoustic spectroscopy (PAS) measuring cell, shown with the germanium window half removed. The gas analysis is based on the same principle as conventional infra-red (IR) monitoring except that here the amount of IR light absorbed is measured directly by determining the amount of sound energy emitted upon the absorption. See Photoacoustic Spectroscopy, Methods and Instrumentation. Reproduced with permission from INNOVA AirTech Instruments. 

Another very sensitive method directly monitors the absorbed energy rather than relying on a difference measurement (Ij -Ij). The energy IgaxA absorbed per second in a volume V = Ax can either be converted into fluorescence energy and monitored with a fluorescence detection system excitation spectroscopy) or it can be converted by collisions into thermal energy with a resultant temperature and pressure rise, which is monitored by a sensitive microphone photoacoustic spectroscopy). 

Another non-electrical measurement for < eh was reported by Tam using photoacoustic spectroscopy [293]. Tam assumed that if the major photophysical processes of the photoconductor are photogeneration of e-h pairs and charge recombination to generate heat, one can study the photogeneration process by monitoring the acoustic signal (S) of the photoconductive device as a function of E after optical excitation. The assumption is quite reasonable because the fluorescence quantum yield and the yield of photochemical reaction of the photoconductor are usually very small. Thus... 

The experimental design for the photoacoustic experiment is relatively simple. The apparatus is quite similar to that employed for nanosecond absorption spectroscopy with the major difference being that a piezoelectric transducer is used to monitor the acoustic waves rather than a photomultiplier tube to analyze the incident light. A representative schematic for PAC is shown in Fig. 2. 

ATR FT-IR spectroscopy has also been employed to monitor the solid-phase synthesis of substituted benzopyranoisoxazoles [180]. Finally, Huber et al. [181] have also reported that this technique is particularly suitable for the characterization of supported molecules in combinatorial chemistry, as well as for the identification of side products and for Photoacoustic (PA) FT-IR. 

Figure 3 shows one of our photoacoustic cell for X-ray spectroscopy of solid samples The cylindrical cell has a sample chamber at the center with volume of 0.16 cm which has two windows of beryllium (18 mm x 0.5 mm thickness). A microphone cartridge is commercially available electret type (10 mm ) and the electronics of preamplifier for this microphone is detailed elsewhere Figure 4 shows the typical experimental setup for spectroscopic study X-ray was monochromated by channel cut silicon double crystal (111) and ion chamber was set to monitor the beam intensity. Photoacoustic signal intensity was always divided by the ion chamber current for the normalization against the photon flux. X-ray was modulated by a rotating lead plate (1 mm thick) chopper with two blades. 

---