During the past decade there has been intense activity in the field of laser-induced breakdown spectroscopy (LIBS). This activity includes studies of laser ablation and properties of the laser spark, the development of methods to enhance LIBS detection capabilities, and the application of LIBS to specific analysis needs. The unique capabilities of LIBS make it particularly suited for applications that cannot be addressed by conventional analytical methods. Potential applications of the method are numerous and several applications have been realized, resulting in on-line operating instruments. Other applications will require that the method be developed further to improve analytical performance. Here we present an overview of the LIBS method, discussing its many advantages and some important limitations as an analytical method and how these relate to potential applications.

Laser-Induced Breakdown Spectroscopy—Capabilities and Limitations

Laser-induced breakdown spectroscopy (LIBS) has been regarded as a future superstar for chemical analysis for years due to its unique features such as little or no sample preparation, remote sensing, and fast and multi-element analysis. Chinese LIBS community is one of the most dynamically developing communities in the World. The aim of the work is to inspect what have been done in China for LIBS development and, based on the understanding of the overall status, to identify the challenges and opportunities for the future development. In this paper, the scientific contributions from Chinese LIBS community are reviewed for the following four aspects: fundamentals, instrumentation, data processing and modeling, and applications; and the driving force of LIBS development in China is analyzed, the critical issues for successful LIBS application are discussed, and in our opinion, the potential direction to improve the technology and to realize large scale commercialization in China is proposed.

Laser-induced breakdown spectroscopy in China

Laser induced breakdown spectroscopy inside liquids: Processes and analytical aspects

Effects of the background environment on formation, evolution and emission spectra of laser-induced plasmas

Laser-induced breakdown spectroscopy (LIBS) has been widely studied due to its unique advantages such as remote sensing, real-time multi-elemental detection and none-to-little damage. With the efforts of researchers around the world, LIBS has been developed by leaps and bounds. Moreover, in recent years, more and more Chinese LIBS researchers have put tremendous energy in promoting LIBS applications. It is worth mentioning that the application of LIBS in a specific field has its special application background and technical difficulties, therefore it may develop in different stages. A review summarizing the current development status of LIBS in various fields would be helpful for the development of LIBS technology as well as its applications especially for Chinese LIBS community since most of the researchers in this field work in application. In the present work, we summarized the research status and latest progress of main research groups in coal, metallurgy, and water, etc. Based on the current research status, the challenges and opportunities of LIBS were evaluated, and suggestions were made to further promote LIBS applications.

Development in the application of laser-induced breakdown spectroscopy in recent years: A review

Hydrothermal vent fluids, cold seep fluids, their associated chemosynthetic communities, and the biogeochemical anaerobic oxidation of methane (AOM) play very important roles in the biogeochemical sulfur and carbon cycles in the ocean. Based on our previous success developing and deploying a deep-sea sediment pore water Raman probe, we developed a new deep-sea hybrid Raman insertion probe (RiP) designed to operate at temperatures up to 450 °C that can be inserted directly into high-temperature fluids emerging from hydrothermal vents. By routinely exchanging the various tips and optics of the probe, we can analyze the geochemistry of hydrothermal vent fluids, cold seep fluids, and sediment pore water profiles (0–60 cm) in situ . The instrument ensemble also includes a new deep-sea laser Raman spectrometer in a custom-designed, 6000-m titanium pressure housing, which is powered, controlled and deployed by the remotely operated vehicle (ROV) Faxian down to a maximum water depth of 4500 m. The new RiP was deployed at the Izena Hole hydrothermal area in the middle Okinawa Trough back-arc basin; the Papua–Australia–Canada–Manus (PACManus) hydrothermal vent area in the Manus back-arc basin, Papua New Guinea; and a cold seep field at Formosa Ridge in the northern South China Sea. The Raman peaks of CO 2 , CH 4 , H 2 S, HS - , SO 4 2- and S 8 were obtained in situ from high-temperature hydrothermal vents (290 °C), low-temperature cold seep fluids (2 °C) and the surrounding sediment pore water. Dissolved CH 4 and S 8 were identified for the first time in the fluids under the lush chemosynthetic communities of the cold seep. Several sediment pore water profiles collected near the cold seep were characterized by the loss of SO 4 2- and increased CH 4 , H 2 S and HS - peaks. Additionally, the in situ pH range of the pore water profile was between 6.95 and 7.22. Thus, the RiP system provides a very useful tool for investigating the geochemistry of hydrothermal vent and cold seep fluids.

Development of a new deep-sea hybrid Raman insertion probe and its application to the geochemistry of hydrothermal vent and cold seep fluids

The exploitation and research of deep-sea hydrothermal vent has been an issue of great interest in ocean research in recent years. Laser-induced breakdown spectroscopy (LIBS) has great potential for ocean application due to the capabilities of stand-off, multiphase, and multielement analysis. In this work, a newly developed compact 4000 m rated LIBS system (LIBSea) is introduced with preliminary results of sea trials. The underwater system consists of an Nd:YAG single-pulsed laser operating at 1064 nm, an optical fiber spectrometer, an optics module, and an electronic controller module. The whole system is housed in an L800  mm×ϕ258  mm pressure housing with an optical window on the end cap. It was deployed on the remote operated vehicle Faxian on the research vessel Kexue, and in June 2015 was successfully applied for hydrothermal field measurements at the Manus area. The obtained results are shown that the LIBS system is capable of detecting elements Li, Na, K, Ca, and Mg in the hydrothermal area. Profiles of LIBS signals of elements K and Ca have also been obtained during the sea trial. The results show that the K emission line is gradually broadened with depth from sea surface to sea floor (1800 m or so); the K intensity shows a hump shape with maximum value at about 1050 m. The Ca emission line is rapidly broadened below 400 m and slowly narrowed to the sea floor; the Ca intensity shows no obvious change below 400 m and increases continuously to sea floor. A very interesting finding is that the small fluctuations of intensity profile curve of Ca show a degree of correlation with seawater temperature change. The sea trial results prove the performance of LIBSea. After further optimization, it is hoped to apply the LIBS system to the in situ mineral deposits and hydrothermal vent fluid detection in deep sea.

Development of a compact underwater laser-induced breakdown spectroscopy (LIBS) system and preliminary results in sea trials.

In this study, an ultrasonic nebulizer unit was established to improve the quantitative analysis ability of laser-induced breakdown spectroscopy (LIBS) for liquid samples detection, using solutions of the heavy metal element Pb as an example. An analytical procedure was designed to guarantee the stability and repeatability of the LIBS signal. A series of experiments were carried out strictly according to the procedure. The experimental parameters were optimized based on studies of the pulse energy influence and temporal evolution of the emission features. The plasma temperature and electron density were calculated to confirm the LTE state of the plasma. Normalizing the intensities by background was demonstrated to be an appropriate method in this work. The linear range of this system for Pb analysis was confirmed over a concentration range of 0–4,150ppm by measuring 12 samples with different concentrations. The correlation coefficient of the fitted calibration curve was as high as 99.94% in the linear range, and the LOD of Pb was confirmed as 2.93ppm. Concentration prediction experiments were performed on a further six samples. The excellent quantitative ability of the system was demonstrated by comparison of the real and predicted concentrations of the samples. The lowest relative error was 0.043% and the highest was no more than 7.1%.

Quantitative analysis of lead in aqueous solutions by ultrasonic nebulizer assisted laser induced breakdown spectroscopy

The laser induced breakdown spectroscopy (LIBS) is an element analysis technique with the advantages of real time detection, simultaneous multi-element identification, and in-situ and stand-off capacities. To evaluate its potential of ocean applications, in this paper, the time resolved laser-induced breakdown spectroscopy for calcium concentration detection in water is investigated. With the optimum experimental parameters, the plasma emission lifetime is determined to be about 500 ns with 532 nm laser excitation, and 1000 ns with 1064 nm laser excitation. The lowest detection concentration of 50 ppm is achieved for calcium detection in CaCl2 water solution using the 532 nm LIBS. Even better detection sensitivity is achieved using the 1064 nm LIBS, and the resulted lowest detection concentration of calcium is 25 ppm. The results suggest that it is feasible to develop LIBS as an on-line sensor for metal element monitoring in the sea.

Time resolved laser-induced breakdown spectroscopy for calcium concentration detection in water

Because of the complex factors in bulk water, the effect of LIBS on the analysis of liquid sample is limited in liquid sample. Under this circumstances, a new method of LIBS assisted by ultrasonic nebulizing technology has been introduced. According to this method, the liquid sample is transformed into dense droplets by ultrasonic nebulizing technology, and these dense droplets are subjected to the analysis of LIBS later. Based on this thought, a detection experimental system was established, composing of ultrasonic system, 1 064 nm ND: YAG laser, and ICCD system. A series of experiments and analysis were carried out to detect the magnesium element dissolved in pure water using the detection experimental system mentioned above. The results showed that even with a very low laser pulse energy (30 mJ), the signals of LIBS still have a long lifetime and a high signal to background ratio. The limit of detection for magnesium element could reach as low as 0.242 ppm. At the same time, the electron density of plasma was calculated utilizing the Halpha line to give the evolution features of plasma induced by this new method.

Kai Cheng

Papers

Development of a new deep-sea hybrid Raman insertion probe and its application to the geochemistry of hydrothermal vent and cold seep fluids

Development of a compact underwater laser-induced breakdown spectroscopy (LIBS) system and preliminary results in sea trials.

Quantitative analysis of lead in aqueous solutions by ultrasonic nebulizer assisted laser induced breakdown spectroscopy

Time resolved laser-induced breakdown spectroscopy for calcium concentration detection in water

Ultrasonic nebulizer assisted LIBS for detection of trace metal elements dissolved in water