SpecSI 2025 Abstracts

Area 1 - Spectroscopy and Spectral Imaging
Short Papers

Area 1 - Spectroscopy and Spectral Imaging

Nr: 63
Title:

Low-Energy Laser Induced Breakdown Spectroscopy at GHz Pulse Repetition Rate
Authors:

Parviz Elahi, Emre Hasar and Ayesha Noor
Abstract: Laser-Induced Breakdown Spectroscopy (LIBS) is a powerful technique for material identification and component characterization. This work presents a significant advancement in LIBS technology by employing extremely low pulse energies (below 200 nJ) at an ultrahigh pulse repetition rate (GHz-range). This was achieved using our recently developed Yb-doped fiber laser system, which delivers 25 ps pulses at 14 W average power with an intra-burst repetition rate of 2.8 GHz. LIBS experiments were conducted on various materials, including stainless steel, copper, and aluminum. The laser beam (25-ps long pulses at 1030 central wavelength nm) was directed through a Galvo scanner and focused onto the sample using a 56 mm F-theta lens, resulting in a spot size of approximately 17 µm. The plasma generated by the laser pulses was collected and analyzed using a fiber-coupled spectrometer. Systematic experiments were performed with bursts of pulses at a 100 kHz burst repetition rate, varying the number of intra-burst pulses and adjusting the burst and pulse energies. For example, at a burst repetition rate of 100 kHz and a burst width of 83 ns (containing 232 intra-burst pulses), we tested pulse energies of 26 nJ, 35 nJ, 57 nJ, 82 nJ, 103 nJ, 127 nJ, 151 nJ, 172 nJ, and 197 nJ. The threshold pulse energy required to observe sharp spectral peaks was determined, and the influence of blackbody radiation on the background signal was investigated. The LIBS data were analyzed to calculate the electron temperature and density of the plasma. Furthermore, we studied the effects of varying burst and pulse energies on these parameters, providing insights into optimizing LIBS performance under ultrahigh repetition rates and low-energy conditions. To the best of our knowledge, this is the first demonstration of a LIBS experiment conducted with nJ-level pulse energies and a GHz-range laser operating in burst mode. This system holds significant promise as a potential alternative to traditional LIBS systems, which typically rely on much higher pulse energies in the mJ or µJ range and operate at low repetition rates (Hz-level).
Nr: 103
Title:

Laser-Induced Breakdown Spectroscopy: A Key Technique for Industrial Applications
Authors:

Diana Capela, Tomás Lopes, Rafael Cavaco, Joana Teixeira, Paulo Magalhães, Pedro A. S. Jorge, Nuno A. Silva and Diana Guimarães
Abstract: Laser-Induced Breakdown Spectroscopy (LIBS) has proven to be a promising and versatile chemical analysis technique with the potential to revolutionise the industrial sector. Its numerous advantages, including minimal or no sample preparation, rapid real-time analysis, and multi-element detection[1], make it a valuable tool across various fields of application. This study addresses the applicability of LIBS in distinct industrial sectors, focusing on cork, minerals, glass and wood waste. In cork analysis, LIBS was employed to assess the quality of functional coatings deposited on cork stoppers, ensuring product performance[2]. In the particleboard industry, LIBS was utilised to detect hazardous materials in recycled wood wastes, ensuring its safe incorporation into new particleboard production and promoting sustainable practices[3]. In the mineral sector, LIBS demonstrated its capacity to analyse the chemical composition of various rock samples, enabling the determination of their mineralogical composition[4]. This can help to improve mineral classification tasks and resource exploration studies such as for Lithium prospection purposes. This work underscores the potential of LIBS to enhance industrial processes by providing fast, accurate, and reliable analytical capabilities. Its application speeds up material’s chemical analysis and supports sustainability across diverse materials and industrial applications. Acknowledgements: This work is financed by Component 5 - Capitalization and Business Innovation, integrated in the Resilience Dimension of the Recovery and Resilience Plan within the scope of the Recovery and Resilience Mechanism (MRR) of the European Union (EU), framed in the Next Generation EU, for the period 2021 - 2026, within project AgendaTransform, with reference 34. This work is also financed by National Funds through the Portuguese funding agency, FCT - Fundação para a Ciência e a Tecnologia, within project LA/P/0063/2020 (DOI 10.54499/LA/P/0063/2020). References: [1] Cremers, D. A., & Radziemski, L. J. (2013). Handbook of laser-induced breakdown spectroscopy. John Wiley & Sons. [2] Ferreira, M. F., Guimarães, D., Oliveira, R., Lopes, T., Capela, D., Marrafa, J., ... & Jorge, P. A. (2023). Characterization of Functional Coatings on Cork Stoppers with Laser-Induced Breakdown Spectroscopy Imaging. Sensors, 23(22), 9133. [3] Guimarães, D., Capela, D., Lones, T., Magalhães, P., Pessanha, S., Jorge, P. A., & Silva, N. A. (2024, July). Screening Chromium Contamination in Wood Samples using Laser-Induced Breakdown Spectroscopy Imaging. In 2024 IEEE Sensors Applications Symposium (SAS) (pp. 1-5). IEEE. [4] Capela, D., Ferreira, M. F., Lima, A., Dias, F., Lopes, T., Guimarães, D., ... & Silva, N. A. (2023). Robust and interpretable mineral identification using laser-induced breakdown spectroscopy mapping. Spectrochimica Acta Part B: Atomic Spectroscopy, 206, 106733.
Nr: 109
Title:

Understanding Persistent Luminescence in LiYGeO4 Through Temperature-Dependent Photoluminescence
Authors:

Inês Proença, José Daniel Gouveia, Florinda Costa, Luís Rino, Teresa Monteiro and Joana Rodrigues
Abstract: Persistent luminescence (PersL) is a fascinating optical phenomenon that has been extensively explored in recent years. In this regard, LiYGeO4 has garnered considerable interest due to its notable defect abundance, rendering it a promising host candidate for supporting PersL. Specifically, when doped with bismuth (Bi), a well-studied luminescence activator, this material has demonstrated exceptional PersL performance, with reported durations of 9 hours to 300 hours.[1–3] In this study, we synthesised samples of undoped and doped LiYGeO4 with 0.5 mol% of Bi by solid-state reaction. The samples were subjected to structural analysis by X-Ray diffraction, which confirmed the presence of the desired LiYGeO4 phase, although residual amounts of yttrium germanate were also identified. To provide new theoretical insights, we calculated the band structure of this material using hybrid density functional theory, a contribution that had not been documented previously. The estimated bandgap from this theoretical calculation is well aligned with the experimental results of ~6.53 eV, obtained by diffuse reflectance measurements. Additionally, and although this fundamental property of LiYGeO4 has been a subject controversial, these theoretical calculations indicate that this material has a direct gap. The room temperature (RT) photoluminescence (PL) and PL excitation (PLE) analysis showed that all samples exhibited a strong emission band peaked around 350-360 nm, which can be excited using wavelengths of 250 nm and 300 nm. Furthermore, the PLE spectra exhibit a significant absorption band at 245 nm, which is attributed to a metal-to-metal charge transfer transition. Despite the extensive research conducted on LiYGeO4:Bi3+, the mechanisms underlying the PersL phenomenon remain to be elucidate. To address this and aiming to elucidate the origin of the PersL emission, we present a temperature-dependent luminescence study on this material, from 15 K up to RT, using excitation wavelengths of 261 nm and 325 nm. As the temperature rose, distinct behaviours were observed depending on the excitation wavelengths. We propose that, at room temperature, the observed emission arises from the overlap of the 3P1(1) and 3P1(2) sublevels of the 3P1 state, which are completely split when the ion is introduced in the Y sites with Cs symmetry. These results underline the necessity of meticulous investigations into the fundamental properties of luminescent materials to enhance our understanding of the mechanisms associated with the observed phenomena. Subsequently, afterglow measurements were conducted, revealing that PersL emission could be achieved for nearly 7 h when the samples were excited with 250 nm (4.96 eV) photons for 10 min. In contrast, wavelengths longer than ~260 nm were found to be inefficient for PersL. [1] P. Shao, P. Xiong, Y. Xiao, Q. Chen, Y. Sun, N. Yan, D. Chen, Z. Yang, J Mater Chem C Mater 2022, 102, 16670. [2] J. Shi, X. Sun, S. Zheng, X. Fu, Y. Yang, J. Wang, H. Zhang, Adv Opt Mater 2019, 7, 1900526. [3] W. J. Zhang, L. Zheng, S. C. Qi, J. X. Li, D. M. Xue, X. Q. Liu, L. B. Sun, J Mater Chem A Mater 2023, 11, 17484.
Short Papers
Paper Nr: 6
Title:

Microplastic Detection in Lawaye River, San Juan, Batangas City, Philippines Using Front-Face Fluorescence Spectroscopy
Authors:

Jowi Rapha Cruz, Jowi Tsidkenu Cruz, Jejomar Bulan, Aubrey Razon, Michaelina Smith and Galvez Maria Cecilia
Abstract: The Lawaye River in San Juan, Batangas plays a crucial role in sustaining the very complex local ecosystem within the city. As it is utilized for irrigation for agricultural activities, household needs, fishing, and tourism. However, increasing human activities pose significant threats to these vital bodies of water. Pollution, particularly from microplastics, is a major concern due to its detrimental impacts on aquatic life and potential human health risks. Studies have demonstrated the widespread presence of microplastics in various organisms and their ability to accumulate in vital organs, including the brain. This study investigated the presence of microplastics in the Lawaye River. Surface water samples (50 cm depth) were collected and subjected to initial debris removal. Subsequently, samples were treated with a KOH solution to dissolve organic matter and filtered through a 0.3 mm glass filter. Microscopic examination revealed the presence of microplastics in various forms, including fragments, fibers, and films. Further fluorescence spectroscopy analysis, based on known excitation-emission wavelengths of different plastics, suggested the potential presence of microplastics, specifically Polypropylene (PP) and potentially Polystyrene (PS) which is commonly used on single-use plastics.
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