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27 July 2021 | Story Leonie Bolleurs | Photo UFS Photo Archive
Prof Hendrik Swart played a key role in the Department of Physics acquiring the PHI Quantes XPS system, the first in Africa and one of only 20 in the world.

The state-of-the-art equipment in the Department of Physics at the University of the Free State (UFS) differentiates this department from its competitors. Availability of the equipment makes it possible for researchers as well as students to deliver work that receives national and international recognition. 

Recently, the department acquired a PHI Quantes XPS system, the first in Africa and one of only 20 in the world. 

Creating better phosphor 

“The Quantes XPS system uses X-rays to determine the chemical composition of molecules on the surface of a sample. The system is unique in the sense that it also has an extra X-ray source that can determine the chemical state below the surface, which was not possible in the past.  This will help us to dictate the position of defects in our phosphor materials that will consequently enable us to create better phosphor for solid state lighting as well as solar cell applications,” explains Prof Hendrik Swart, Senior Professor in the Department of Physics, who also holds the SARChI Chair in Solid State Luminescent and Advanced Materials.

After he had the opportunity to observe the system in the factory in Chigasaki, Kanagawa, Japan, where he attended a conference, Prof Swart was very impressed by its performance. He discussed it with Prof Koos Terblans, Head of the department, and other colleagues, and started making plans to buy the system. 

When the department first bought the X-ray photoelectron spectroscopy (XPS) system in 2007/2008, it became the national facility on XPS measurements. Not only is this an upgrade of the XPS system bought 14 years ago, but the new system will enable the department to do more measurements. “The number of samples that we have to handle has just become too much for one system. The new system’s increased capacity for making measurements addresses this challenge and it also gives UFS scientists and postgraduate students more time to spend on fundamental measurements to develop research of a higher level,” says Prof Swart.

(The Quantes XPS system. Photo:Supplied)

Explaining about the measurements, Prof Swart says: “This advanced X-ray photoelectron spectroscopy (XPS) instrument has the capability to analyse the very small area that the user is interested in and a large area of the uniform sample surface. The two different types of X-ray sources – the hard X-ray source and the more conventional soft X-ray source – can be switched automatically, allowing users to analyse the same area and/or points of a sample. The PHI Quantes XPS system ensures the availability of superior features such as automatic analysis, automatic sample transfer, turnkey charge neutralisation, and advanced data processing.”

“This XPS instrument is designed to pioneer new methods and applications transcending conventional ideas of what is possible.”

Optimising efficiency of materials

Prof Swart says the Department of Physics, especially the Research Chair in Advanced and Luminescent Materials, is developing new high-technology materials on a daily basis. “It is very important to know the chemical composition and defect distribution of the materials in order to add value to the fabrication of these materials,” he adds.

“The distribution of these defects is vital for the efficiency of the phosphor materials. If we know where these defects are located, we can determine the mechanisms of the light output coming from these phosphors,” describes Prof Swart.

Research conducted as part of the Research Chair in Solid State Luminescent and Advanced Materials will benefit significantly from this new system.

(Prof Koos Terblans, Head of the Department of Physics next to the Quantes XPS system. Photo:Supplied) 

“We are currently concentrating on phosphors as sensors (temperature), light-emitting diodes (LEDs), and solar cells, where we optimise the efficiency and durability of these materials. Any new knowledge, which I believe the PHI Quantes XPS system will provide us, will help us to reach our goal much quicker,” he says. 

Apart from the positive impact on research, the PHI Quantes XPS system will also be a benefit to society in the long term. Improved LEDs can be used to save electricity, and better solar cells can help to generate electricity, to mention but two examples. 

News Archive

Childhood obesity should be curbed early
2017-03-15

Description: Child obesity Tags: Child obesity

Serious intervention by parents is required to deal
with childhood obesity. Prof Louise van den Berg and
a group of final-year PhD students worked on a study
about the prevalence of obesity in six-year-olds in
South Africa.
Photo: Supplied

If your child is overweight when they start school at the age of six, unless you do something about it at that point, the indications are they are going to be overweight teenagers and obese adults. This is according to University of the Free State’s Prof Louise van den Berg.

Evidence has shown that overweight children and teenagers have a greater risk of developing lifestyle diseases such as type 2 diabetes, hypertension and cardiovascular disease later in life, and dying prematurely.

Obesity is a global pandemic rapidly spreading among adults and children, in developed and developing countries alike.

Dr Van den Berg worked with Keagan Di Ascenzo, Maryke Ferreira, Monja-Marie Kok, Anneke Lauwrens, all PhD students with the Department of Nutrition and Dietetics, to conduct the study. Their research found that children who are overweight by the time they turn six should be screened for weight problems.

Why six-year-olds?
Children who are overweight between the ages of two and five are five times more likely to be overweight when they are 12. There are two periods in a normal life cycle when the body makes new fat cells. The first is in the uterus and the second is around the age of six. The second phase lasts from the age of six to puberty.

The study assessed the prevalence of obesity in six-year-olds as part of a campaign in South Africa to raise awareness of the problem among parents and educators.

A total of 99 children were chosen from seven schools in Mangaung, the capital city of Free State. The schools were chosen from quintile four and five schools, which when measured by their own resources and economic circumstances, are well resourced and serve largely middle-class and wealthy communities.

The children’s weight, height and waist circumference were measured and used to calculate a body mass index score and waist-to-height ratio. Both these figures are good predictors for future lifestyle disease risks such as type 2 diabetes, hypertension and cardiovascular disease. A person with a good waist-to-height ratio can wrap a piece of string equal to their height around their waist at least twice.

When the children had a higher body mass index, they also had an increased waist to height ratio. The study found one in four children from the schools surveyed were overweight when they started primary school.

Nipping the fat in the bud
Although there are many factors that play a role in preventing childhood obesity, parents’ perceptions of their children’s weight play an important role. A recent study found that more than 50% of parents underestimate the weight of their obese children. These parents remain unaware of the risks their children face and are not motivated to take any action.

At least half of the parents whose children are overweight struggle to recognise their children’s weight problems fearing that they will be labelled or stigmatised. By the time they turn six overweight children should be referred to dieticians and nutritionists who are qualified to guide their parents in getting them to eat well and be more physically active at pre-primary and primary school.

The high prevalence of weight problems among six-year-olds found in this study is an urgent call to healthcare professionals to step up and empower parents, educators and children with the necessary skills for healthy dietary practices and adequate physical activity.

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