Soaking Up Some Sun: How the Loeb Research Lab at McGill is Harnessing Sunlight as a New Option for Water Purification

Written by: Yael Bisson

Edited by: Alon Ronen

Junior Division

Access to clean water is not a given for a significant part of the globe, with almost 30% of the world’s population lacking clean drinking water (WHO, 2021). Safe, non-polluted water is an essential part of human health and societal growth, so its consistent supply has been the center of much debate and attention for decades. Traditionally, water purification was done through advanced oxidation processes (AOPs), which consist of using highly reactive chemicals like hydroxyl radicals to quickly break down organic materials present in contaminated water. However, this industrial process is costly, since it requires the continuous supply of oxidizing chemicals. Additionally, some of the chemicals are hazardous to handle, and can cause environmental issues (Wasim & Loeb, 2026). 

As technology continues to advance, researchers look to new and developing methods to purify water in a more efficient and sustainable manner. While UV light has been used for wastewater purification since the 1980s, researchers are attempting to industrialize the use of sunlight, since it is a very readily available and plentiful resource (Whitby, 2004). One such group is the Loeb Lab at McGill University, led by Dr. Stephanie Loeb, Assistant Professor in the Department of Civil Engineering. The lab draws on knowledge from different fields ranging from photochemistry to environmental engineering to better understand the possible uses of sunlight in water treatment. Their main research focus is to develop technical solutions to light-driven environmental processes, such as water purification, as an alternative to many of the polluting and expensive methods. Before joining McGill, Dr. Loeb was a postdoctoral fellow at Stanford where she studied the sunlight inactivation of human norovirus, having previously received her PhD from Yale University and MASc and bachelor’s degrees from the University of Toronto (Fratino, 2020). Additionally, the Loeb Research Group works with the Brace Water Centre, a McGill interfaculty center advancing research on water issues in Quebec and internationally, where Dr. Loeb serves as an assistant director (Brace Water Centre). 

Published in Feb. 2026, “Aluminum nanoparticle enhanced TiO₂ photocatalysis of organic pollutants under solar and UV-B irradiation” was co-authored by Dr. Loeb and environmental engineering PhD student Saadia Wasim. The research paper, published in “npj Clean Water,” studies the use of a photocatalyst containing titanium dioxide (TiO₂) and aluminum (Al) nanoparticles in water purification under solar light, specifically to degrade amaranth. Amaranth is an anionic (negatively charged) synthetic dye commonly used in the textile and food industries; when discharged into industrial wastewater, it becomes a significant hazard for aquatic life and humans, as it possesses carcinogenic and genotoxic properties (Steter, 2014). The light-driven breakdown of amaranth includes several components, starting with figuring out the best possible reagent. In this research, the group modified the TiO₂ semiconductor with plasmonic nanoparticles and ligands. A semiconductor is a material with moderate conductive abilities, between a conductor (like metals) and an insulator (like glass wool or wood). This type of material is used for photocatalysis of water treatment reactions because it absorbs a similar wavelength to the sun’s rays, specifically visible and UV light. When absorbed, the semiconductor can act as a catalyst to speed up the degradation of amaranth and other organic pollutants. TiO₂ was used specifically for this study because it is cheap, chemically stable, and highly reactive. However, TiO₂ mostly absorbs wavelengths that correspond to UV radiation, with only four percent of visible light enabling conductivity by exciting electrons in the valence shell (Hou & Cronin, 2012). To solve this problem, researchers added aluminum plasmonic nanoparticles, very small metallic structures that act as light antennae, to the surface of the titanium oxide to absorb even more photons. This, in turn, enhances the TiO₂’s photosensitivity, which is a structure’s ability to change physically or chemically when exposed to light. When testing the efficiency of different combinations of materials, the Loeb group compared them to P25 TiO₂, a common benchmark used for industrial photocatalysis. The mixing of the Al nanoparticles and TiO₂ semiconductor makes a heterostructure, which is more effective as a photocatalyst than P25 TiO₂ because of the nanoparticles. Moreover, the Al/TiO₂ structure is inexpensive to create, as Al nanoparticles are abundant and chemically stable. In fact, the research group synthesized the nanoparticles over a month before data collection, demonstrating their durability. 

To further enhance the photosensitivity of the structure, the Loeb group tested the effect of different ligands. A ligand is an ion or molecule that binds to the surface of a central structure, usually a metal ion, by forming a dative bond (uneven sharing of electrons where the ligand provides both electrons). These structures enhance photosensitivity of heterostructures because they create bonds with Al and TiO₂, stabilizing the particle. Ligand-modification was tested with three different structures (cysteine, GSH, and DMSA), and cysteine was found to improve the photocatalytic efficiency of Al/ TiO₂ the best. In fact, the researchers found that the Al/ TiO₂ cysteine (Cys) heterostructure increased the break-down of amaranth by 60% compared to the regular P25 TiO₂ under solar illumination. It was also more effective than just aluminum-enhanced TiO₂, which was a significant step towards finding the best structure for the reaction. Additionally, the cysteine-modified heterostructure performed well when tested six consecutive times, which proves that it is also durable and reusable compared to the P25 TiO₂ standard. On the other hand, the researchers found that Al/ TiO₂ Cysteine did not perform as well when breaking down neutral compounds like phenol, compared to anionic compounds like amaranth. 

While further studies are required to evaluate its long-term performance in realistic water treatment applications, the Al/ TiO₂ Cysteine heterostructure represents a substantial step forward in water-treating photocatalysis, because it is stable, durable, and efficient in breaking down anionic organic pollutants like the amaranth dye under solar illumination. The Loeb research group’s work in this field has been a significant advancement towards the understanding and optimization of photocatalysts in water purification.   

Wasim and Loeb write that the cysteine-modified Al/TiO2 has potential for integration into small scale water treatments. A broader challenge faced by many researchers in materials science is translating these successful academic-level results into large-scale industrial settings. Nevertheless, the potential of such work being developed into an impactful technology is promising, as Wasim and Loeb’s findings can be used and improved upon by other labs across the globe. As advancements in light absorption technology for water treatment continue to emerge, researchers move towards a greener way of providing clean water for all.

---

Reference List

Brace Water Centre. (n.d.). About us. McGill University. https://www.mcgill.ca/brace/about-us

Fratino, A. (2021, October 1). Meet our new faculty members. McGill University, Faculty of Engineering. https://www.mcgill.ca/engineering/article/news/meet-our-new-faculty-members

Hou, W., & Cronin, S. B. (2013). A review of surface plasmon resonance-enhanced photocatalysis. Advanced Functional Materials, 23(13), 1612–1619. https://doi.org/10.1002/adfm.201202148

Loeb Research Group. (n.d.). The Loeb Lab. https://www.loeblightlab.com/

Steter, J. R., Barros, W. R. P., Lanza, M. R. V., & Motheo, A. J. (2014). Electrochemical and sonoelectrochemical processes applied to amaranth dye degradation. Chemosphere, 117, 200–207. https://doi.org/10.1016/j.chemosphere.2014.06.085

UK Health Security Agency. (2024, October 1). Phenol: Toxicological overview. GOV.UK. https://www.gov.uk/government/publications/phenol-properties-incident-management-and-toxicology/phenol-toxicological-overview

Wasim, S., & Loeb, S. K. (2026). Aluminum nanoparticle enhanced TiO₂ photocatalysis of organic pollutants under solar and UV-B irradiation. npj Clean Water, 9(1), Article 29. https://doi.org/10.1038/s41545-026-00560-z

Whitby, E. G., & Scheible, O. K. (2004). The history of UV and wastewater. IUVA News, 6(3), 15–26. https://www.researchgate.net/publication/268198002_The_History_of_UV_and_Wastewater

World Health Organization & UNICEF. (2021). Progress on household drinking water, sanitation and hygiene 2000–2020: Five years into the SDGs. https://washdata.org/report/jmp-2021-wash-households