Columns | Column: Lasers and Optics Interface

Dirty beach environment from plastic garbage. | Image Credit: © NPD Stock - stock.adobe.com.

Spectroscopy plays a critical role in both macroscopic and microscopic plastics detection, which is the first step in remediation, and also in the commercial replacement of plastics with biodegradable materials. This piece provides tangible examples of efforts being made today, including details on spectral hardware implementation, but more importantly provides proposals to the reader on how they can make a meaningful difference in their own world.

Tunable narrowband light sources are essential for measuring fluorescence, reaction energetics, and other challenging measurements in chemical, biological, and physical systems. In particular, the optical parametric oscillator (OPO) is an indispensable tool.

An important class of nanoparticles made of “upconversion” materials has found a central role in sensing. These nanoparticles are used to convert longer-wavelength photons into shorter-wavelength fluorescence to detect temperature, pH, gas molecules, ions, and trace biomolecules.

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In the near past, discharge lamps, dye lasers, and optical parametric oscillators were the only useful sources for spectroscopy. New broadband sources, such as supercontinuum lasers, laser-driven plasma sources, and high-brightness light-emitting diodes (LEDs), are now available. We look at what these options offer for spectroscopy.

Mid-infrared (MIR, 3-20 µm) sensor platforms are increasingly adopted in chem/bio analytics, and applied in areas ranging from process monitoring to medical diagnostics. Due to the inherent access to molecule-specific fingerprints via well-pronounced fundamental vibrational, rotational, and roto-vibrational transitions, quantitative information at ppm to ppb concentration levels and beyond is achievable in solids, liquids, and gases. In particular, the combination of quantum cascade lasers (QCLs) with correspondingly tailored waveguide technologies serving as optical transducers – thin-film waveguides for liquid/solid phase analysis, and substrate-integrated hollow waveguides for gaseous samples – facilitates miniaturizable and integrated optical chem/bio sensors and diagnostics applicable in, e.g., exhaled breath analysis, food safety, and environmental monitoring.

Infrared reflectance and absorption spectroscopy have been practiced for decades. New capabilities in detectors and light sources are quickly changing the landscape in the near- and mid-infrared, where fundamental vibrations and overtone bands allow sensitive measurements in applications related to food safety, precision agriculture, energy, and smart manufacturing, to name a few.  This article outlines some of the most recent innovations and how they might be applied in real-world systems.

Vassilia Zorba of Lawrence Berkeley National Laboratory in Berkeley, California, discusses what her studies have revealed about the mechanisms of plasma emission at small scales and what she has found when applying femtosecond LIBS to the study of advanced battery materials.

Vincent Motto-Ros of Lyon 1 University, in Lyon, France, is combining the ability of atomic spectroscopy techniques to detect and quantify metals with the mapping approaches most often used with molecular techniques. He has combined laser-induced breakdown spectroscopy (LIBS) with electron microscopy to map the metals and metallic nanoparticles in biological tissue, as a way of studying the update and clearance of these materials by biological systems. In this interview, he discusses his work applying LIBS to biological analysis, including the methods, advantages, and future directions.

Pages 22–35 Rapid detection of coal and fly ash is significant to improve the efficiency of thermal power plants and reduce environmental pollution. Given its fast response, high sensitivity, real-time, and noncontact features, laser-induced breakdown spectroscopy (LIBS) has a great potential for on-line measurement in these applications. The direct measurement of particles and gases using LIBS was studied, and the method was shown to be effective for this application. 

The monitoring of the processes in steel and metal industry calls for techniques that are capable of measuring the composition of metallic alloys at a distance and on moving conveyor belts. In many cases, such as in the recycling of automotive scrap, the geometry of the objects to be analyzed can vary, and surface coatings can be present. In this paper, we discuss the application of LIBS to two industrial projects to illustrate how the above-mentioned problems can be faced and successfully resolved.

Nanostructured materials are expected to lead to the emergence of new products with enhanced functionalities. Their manufacture often requires the use of particles referred to as nano-objects, their aggregates, and their agglomerates. Laser-induced breakdown spectroscopy (LIBS) was deemed as a potential candidate for the detection of these materials in various contexts. This article discusses examples of the application of LIBS for workplace surveillance and process control of nano-objects.