Related Experiment Video
Updated: Feb 14, 2026
05:16
UV-Vis Spectroscopic Characterization of Nanomaterials in Aqueous Media
Published on: October 25, 2021
11.0K
A UV-Vis photoacoustic spectrophotometer
Joseph R Wiegand1, L Dalila Mathews, Geoffrey D Smith
1Department of Chemistry, University of Georgia , Athens, Georgia 30602, United States.
Analytical Chemistry
|June 7, 2014
Summary
A new photoacoustic spectrophotometer (PAS) accurately measures gas and aerosol light absorption across UV-visible wavelengths. This novel instrument reveals significant UV absorption increases in ambient aerosols, aiding particle characterization.
Area of Science:
- Atmospheric Science
- Spectroscopy
- Analytical Chemistry
Background:
- Accurate measurement of light absorption by atmospheric gases and aerosols is crucial for understanding climate and air quality.
- Existing methods for UV-visible absorption measurements can be limited by artifacts, particularly for aerosols.
- Characterizing the spectral absorption properties of aerosols is essential for determining their climate impact and sources.
Purpose of the Study:
- To describe a novel photoacoustic spectrophotometer (PAS) designed for measuring gas-phase and aerosol absorption.
- To validate the performance of the PAS instrument using known substances like acetone and nigrosin aerosol.
- To demonstrate the PAS instrument's capability in measuring ambient aerosol absorption spectra in the UV-visible region.
Main Methods:
- A broadband Hg arc lamp source filtered into eight specific bands (300-700 nm) and modulated by an optical chopper.
- Utilized a photoacoustic cell for detecting light absorption by gas-phase and aerosol samples.
- Validated the instrument by measuring absorption cross-sections of acetone and nigrosin aerosol, comparing results with established data and Mie theory.
Main Results:
- The PAS instrument achieved detection limits better than 3.0 Mm⁻¹ for most bands within 20 seconds.
- Measurements of acetone and nigrosin aerosol showed agreement within 10% of previously reported values.
- Ambient aerosol measurements revealed a substantial increase in UV absorption, with a 300% rise from 405 nm to 301 nm.
Conclusions:
- The developed PAS instrument provides reliable UV-visible absorption spectra for gases and aerosols without filter-based artifacts.
- The instrument's ability to measure spectra across the UV-visible range is valuable for classifying and quantifying light-absorbing ambient particles.
- The observed dramatic increase in UV absorption by ambient aerosols highlights the importance of UV spectral measurements for atmospheric research.
Related Concept Videos
01:30UV–Vis Spectrum
2.2K
When light passes through a substance, a portion of the light is absorbed while the remaining light is reflected or transmitted. If the molecule absorbs light between the wavelengths of 180–400 nm range, the UV spectrum is obtained, and if it absorbs light in the 400–780 nm wavelength range, the visible spectrum is obtained.
The UV–Vis spectrum of a molecule is the plot of its absorbance versus wavelength. The plot is drawn by taking molar...
The UV–Vis spectrum of a molecule is the plot of its absorbance versus wavelength. The plot is drawn by taking molar...
2.2K
01:14UV–Vis Spectrometers
3.8K
The absorbance of UV and visible (UV–visible) radiations is measured using a UV–visible spectrophotometer. Deuterium lamps, which emit UV radiation, and tungsten lamps, which produce radiation in the visible region, are used as light sources in UV–visible spectrophotometers. A monochromator or prism is used for diffraction grating, i.e., to split the incoming radiation into different wavelengths. A system of slits is used to focus the desired wavelength on the sample cell.
3.8K
01:29IR and UV–Vis Spectroscopy of Aldehydes and Ketones
7.5K
Infrared spectroscopy, also known as vibrational spectroscopy, is mainly used to determine the types of bonds and functional groups in molecules. In aldehydes and ketones, the carbonyl (C=O) bond shows an absorption around 1710 cm-1. The C=O bond vibration of an aldehyde occurs at lower frequencies than that of a ketone. In addition to the C=O absorption in an aldehyde, the aldehydic C–H bond also gives two peaks in the 2700–2800 cm-1 range. This absorption, coupled with the...
7.5K
01:28IR and UV–Vis Spectroscopy of Carboxylic Acids
5.9K
In IR spectroscopy of carboxylic acids, the C=O bond shows a characteristic band between 1710 and 1760 cm⁻¹, and the O–H bond exhibits a broad band between 2500 and 3300 cm⁻¹.
However, the stretching absorptions for the C=O bond vary depending on the structure of carboxylic acids. The C=O bond of the free carboxylic acids shows a higher stretching frequency, 1760 cm−1, while H-bonded carboxylic acids (dimers) exhibit stretching absorptions at a lower frequency,...
However, the stretching absorptions for the C=O bond vary depending on the structure of carboxylic acids. The C=O bond of the free carboxylic acids shows a higher stretching frequency, 1760 cm−1, while H-bonded carboxylic acids (dimers) exhibit stretching absorptions at a lower frequency,...
5.9K
01:32UV–Vis Spectroscopy of Conjugated Systems
8.5K
Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
One of the factors influencing λmax is the extent of conjugation in...
One of the factors influencing λmax is the extent of conjugation in...
8.5K
01:02Ultraviolet and Visible (UV–Vis) Spectroscopy: Overview
6.9K
Ultraviolet–visible (UV–visible or UV–Vis) spectroscopy is an analytical technique that investigates the interaction between matter and UV–Vis light within the electromagnetic spectrum. This method is widely used for its versatility, simplicity, and relatively quick data acquisition, making it valuable for both qualitative and quantitative analysis. When UV–Vis radiation passes through a material, molecules absorb light depending on the energy required for...
6.9K