Water pollution presents a notable peril to both our environment and human well-being [1]. Detecting minute levels of pollutants in soil, groundwater, or seawater is imperative for preserving our water reservoirs. Conventional detection analytical techniques like chromatography and spectroscopy tend to be costly, time-intensive, and reliant on specialized apparatus. A promising solution is harnessing the synergy of additive manufacturing (AM) and surface-enhanced Raman scattering (SERS).
Additive Manufacturing (AM), also known as 3D printing, is a flexible fabrication technique enabling the precise creation of intricate geometries layer-by-layer, forming lattices with controlled architectures [2,3]. These lattices resemble porous solids with repeating patterns akin to three-dimensional meshes. By incorporating nanoparticles (NPs) such as metal NPs, carbon nanotubes (CNTs), and graphene nanoplatelets (GNPs) into these lattices, unique attributes like enhanced strength, conductivity, and self-sensing capabilities are achieved.
Plasmonic NPs, such as gold and silver (AuNPs, AgNPs), exhibit optical properties that can significantly enhance the Raman signal of molecules adsorbed on their surface. This phenomenon, known as SERS, is a powerful vibrational spectroscopic technique for detecting and identifying trace amounts of molecules.[4] This enhancement can lead to orders of magnitude increase in Raman signal intensity, making SERS highly sensitive for detecting trace amounts of analytes. The SERS technique also offers advantages such as rapid detection, high sensitivity, and the possibility of on-site analysis if sensitive sensors and portable Raman instruments are available.
The utilization of AM presents numerous advantages compared to traditional approaches in water quality monitoring. These advancements include creating lattices with distinctive architectures to maximize surface area and improve interaction between sensor material and target pollutants. Additionally, the cost-effectiveness, scalability, outstanding long-term stability, and portability of these sensors make them more economical and suitable for extended monitoring and on-the-spot water quality assessments.
The application of this technology in water quality monitoring has far-reaching implications. The development of AM-enabled SERS sensors for water pollutants detection represents a significant advancement in environmental monitoring technologies. The high sensitivity and specificity of the nanocomposite lattice decorated with plasmonic NPs make it a powerful tool for detecting a wide range of water pollutants, from heavy metals and pesticides to organic contaminants.
Our investigation into SERS sensors explored AM-enabled nanocomposite lattices comprising multi-walled CNTs and polypropylene coated with AgNPs. We demonstrated the detection of organic dyes, pesticides, and herbicides in complex water samples at concentrations as low as 100 nM, which is comparable to or even better than the detection limits of conventional methods.[5] The stability of the sensor over time was also investigated, and it retained its sensitivity for at least three months. These characteristics hold promise for real-world applications, suggesting that the sensors could be utilized for long-term water quality monitoring.
The study also highlights the potential of AM-enabled SERS sensors for real-time water quality monitoring, providing a rapid and accurate method for identifying and quantifying various on-site pollutants, including rivers, reservoirs, and wastewater treatment plants. This technology has the potential to revolutionize water quality monitoring, enabling not only the early detection and prevention of water contamination but also the monitoring of water pollution caused by agricultural runoff or industrial effluents.
Despite the promising results of using AM-enabled SERS sensors in water pollutant detection, some challenges remain. The SERS performance of the sensors can be further enhanced by optimizing the plasmonic NPs loading and distribution on the lattice surface. This could involve employing novel morphologies of the NPs or surface modifications to maximize the Raman signal enhancement. Incorporating additional functionalities, such as catalytic or electrochemical activity, could extend the capabilities of AM-enabled SERS sensors beyond water pollutant detection. For instance, the sensors could be designed to remove pollutants or generate real-time remediation solutions. Additionally, collaboration between academia, industry stakeholders, and regulatory bodies is essential to ensure this technology’s responsible development and deployment. By addressing these challenges and pursuing these future directions, AM-enabled SERS sensors have the potential to revolutionize water quality monitoring, providing real-time, portable, and selective detection of a wide range of pollutants, contributing to a cleaner and healthier environment.
1. M. Syafrudin, R. A. Kristanti, A. Yuniarto, T. Hadibarata, J. Rhee, W. A. Al-Onazi, T. S. Algarni, A. H. Almarri, A. M. Al-Mohaimeed, Int. J. Environ. Res. Public Health 2021, 60, 125.
2. P. Verma, J. Ubaid, K. M. Varadarajan, B. L. Wardle, S. Kumar, ACS applied materials & interfaces, 2022, 14, 8361.
3. S. Kumar, J. Ubaid, R. Abishera, A. Schiffer, V. S. Deshpande, ACS applied materials & interfaces 2019, 11, 42549.
4. S. Fateixa, H. I. S. Nogueira, T. Trindade, Phys. Chem. Chem. Phys. 2015, 17, 21046.
5. S. Fateixa, M. Landauer, J. Schneider, S. Kumar, R. Böhm, Macromol. Mater. Eng. 2023, 2300060.
Dr. Sara Fateixa is a Researcher at the University of Aveiro and CICECO- Aveiro Institute of Materials. She graduated in Industrial Chemistry and Management (2006), completed her Master's degree in Analytical Chemistry (2007) and obtained her PhD degree in Nanoscience and Nanotechnology (2013). She has been interested in new strategies of synthesis, characterisation, and surface modification of inorganic nanoparticles, such as plasmonic nanoparticles (gold and silver) and 2D layered materials (graphene and transition metal dichalcogenides), with potential interest for bio-applications, sensors, and water quality monitoring by using Raman spectroscopic methods (SERS, TERS and Raman imaging).
Professor S. Kumar leads the Multifunctional Materials and Additive Manufacturing Laboratory at the University of Glasgow’s James Watt School of Engineering. He obtained his Ph.D. in Solid Mechanics and Materials Engineering from the University of Oxford. His research focuses on materials innovation & design and additive manufacturing. Kumar serves on editorial boards for key journals and has authored over 120 journal publications. He was recently honoured with the VAIBHAV fellowship by the Department of Science and Technology, India. Additionally, he contributes to the ASME Structures and Materials TC and collaborates internationally with institutions like Cambridge, MIT, and University of Sydney.
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