Direct comparison of the capabilities of photoacoustic and diffuse reflectance spectroscopies in the ultraviolet, visible, and near-infrared regions

Abstract

A dlrect comparlson of the capabllitles of photoacoustlc (PA) and dkfuse reflectance (DR) spectroscoples In the ultraviolet, visible, and nearinfrared spectral regions was made by collecting both types of spectra under nearly Identical conditions. This comparison focused on the followlng aspects: (1) slgnal-to-nolse ratio and sensltlvlty; (2) spectral deflnltlon and those factors, such as saturation and partlcle 8/28, whlch affect spectral deflnltlon; and (3) sample preparation conslderatlons for both qualltatlve and quantltatlve analysls. I n terms of signal-to-noise ratlo and spectral deflnltlon the two techniques are vMuaHy lndlstlngulshable for weakly absorbing, finely dlvlded powders. DRS Is slightly more SenSnlve but has a lower saturatlon llmA than does PAS and Is more severely affected by changes In particle slze. For particles larger than 100 pm, DR spectra are distorted and spectral deflnltlon Is degraded. I n terms of sample Preparation, especially when only qualitative results are desired, PAS Is clearly superlor. For quantitative resuits both techniques requlre careful control of particle 8/28, packing density, and total absorption.

Spectroscopic Study of Maghemite Nanoparticles Surface-Grafted with DMSA

“…Notice that the photoacoustic effect has been successfully used in quality control [42][43][44] while correlation between the data taken from photoacoustic spectroscopy and well-established analytical techniques has been extensively reported in the literature. [45][46][47] It is worth mentioning the linear relationship observed in the data displayed in Figure 4, despite the differences among the two spectroscopic techniques (RS and PAS). This finding strength the nondestructive analytical approach proposed in this study for probing thiol-and disulfide-containing moieties attached to the surface of nanosized materials.…”

“…Particularly interesting is the use of the PAS in quantitatively probe both the S−S and S−H moieties as a simple and inexpensive experimental technique. Notice that the photoacoustic effect has been successfully used in quality control − while correlation between the data taken from photoacoustic spectroscopy and well-established analytical techniques has been extensively reported in the literature. − …”

An Infrared Study of a Polyacrylate Flocculant Adsorbed on Hematite

“…Samples (0.024 ± 0.06 g) were intimately mixed with previously dried KBr (1.176 ± 0.05 g) by gentle grinding so as to minimize particle break up. To maximize reflectance and minimize spectral distortion, the sample−KBr mixtures were passed through a 150 μm stainless steel sieve and the <150 μm fraction used. This material (0.30 ± 0.05 g) was loosely packed into the sample cup and leveled with a spatula, and spectra were obtained against a similarly sized KBr background.…”

Analysis of Nitrogen Defects in Diamond with VUV Photoluminescence

“…This result demonstrates that DRIFTS is infeasible for a diamond sample of powder smaller than 10 μm. DRIFTS is also not practical for diamonds of particles larger than 100 μm, 34 not to mention the gem diamond. Although IR spectra provide detailed information about defects and impurities contained in diamond, this spectral method has revealed a limited scope of performance for diamonds in various forms.…”