Nature’s quantum blueprint

Prof Tjaart Krüger is decoding how plants harvest sunlight and translating those mechanisms into new approaches for cleaner energy

Tracy Lee Stark

Prof Tjaart Krüger describes his work in simple terms. “Colloquially and very broadly,” he says, “I’m shooting plants with lasers.” Prof Krüger in the Department of Physics at the University of Pretoria (UP) then explains the science behind the phrase: developing and assembling ultra-sensitive single-molecule spectroscopy systems to study how natural systems convert sunlight into usable energy, and how those principles may inform future energy technologies.

His curiosity began early, rooted in a fascination with how the natural world can be described through physical laws and mathematical relationships. Over time, this developed into a focus on biophysics, where biological systems are studied through the principles of physics.

“Mixing the complex beauty of biology with the rigour of physics still amazes me every day,” he says.

A green leaf is one of nature’s most efficient energy systems. Through photosynthesis, plants capture sunlight and convert it into chemical energy using water and carbon dioxide. These systems continuously adapt to changing light conditions, balancing efficient energy capture with protection against damage.

Krüger’s work focuses on understanding the molecular processes that make this possible, particularly how energy is transferred and regulated within photosynthetic complexes. This knowledge is also relevant to the development of artificial photosynthesis and organic solar energy systems.

When he joined UP in 2013, he began developing the laboratory infrastructure needed for this research. From 2014 onwards, with support from the National Research Foundation (NRF) National Equipment Programme, he helped establish a single-molecule spectroscopy (SMS) facility at the university.

The system was built using more than 100 optical and electronic components and allows researchers to study the behaviour of individual light-harvesting molecular complexes with very high temporal resolution. Because suitable commercial software was not available, custom control and analysis tools were developed within the laboratory. The facility was formally established in 2017 and continues to support ongoing research and development.

For Krüger, the project demonstrates that advanced experimental science can be developed locally through careful design and collaboration, even within constrained research environments.

His research has contributed to new understanding of how photosynthetic systems function at the molecular level. One area of focus is the role of molecular disorder in energy transfer processes. Rather than being purely detrimental, his work and that of collaborators suggests that structural variation may in some cases play a functional role in biological energy systems.

Another area of research examines how photosynthetic complexes switch between light-harvesting and photoprotective states, a process that remains an active topic of study in the field.

These findings have been published in more than 40 peer-reviewed journal articles and presented at international conferences. Krüger holds an NRF B2 rating.

He has also extended this research direction into agricultural applications through a United Kingdom (UK)-African collaboration focused on low-cost imaging systems for monitoring plant health. Using accessible platforms such as Raspberry Pi and Arduino components, prototype multispectral cameras have been developed at significantly lower cost than commercial systems.

This work is aimed at supporting crop monitoring and contributing to food security research. It is being developed in collaboration with UP’s Forestry and Agricultural Biotechnology Institute (FABI), supported by a 2025 UK research and innovation fellowship focused on frugal innovation for societal challenges in Africa.

Training and capacity development form a central part of his work. Krüger runs annual short courses on photosynthesis and solar energy, having trained more than 75 postgraduate students from multiple disciplines. He contributes to broader African scientific collaboration through the African Strategy for Fundamental and Applied Physics (ASFAP), where he leads a biophysics focus group.

He has supervised a range of postgraduate research students at honours, masters and doctoral level, contributing to the development of early-career researchers in biophysics and related fields.

His more recent work includes participation in quantum science and technology initiatives at UP, where research is exploring the intersection between quantum phenomena and biological light-harvesting systems. In collaboration with international partners, early-stage studies are investigating bio-inspired approaches to organic photovoltaics.

The leaf continues to serve as a model for understanding complex energy systems. Krüger’s work remains focused on uncovering how these natural processes function, one molecule at a time.

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