Welcome to the Guisbiers research group!

Nano-alloys Symposium

Group News

Press article released concerning our last paper about BiSb!

Chateaubriand fellowship awarded

Atikur Rahman will be sponsored by the Chateaubriand fellowship during its stay in France at the University of Paris-Saclay. Congratulations Atik!

Signature Experience Award: Ceremony of Induction

This year, the nano-physics group obtained 7 of its members among the laureates! The awardees are Tina Hesabizadeh, Patrick Taylor, Evan Hicks, Sakr Elsaidi, Reem Adai, Atikur Rahman and Luke Geoffrion! Congratulations to all of them!

Quantum confinement: Size on the grill!

Our last paper...

Advances in thermodynamic modelling of nanoparticles

A review paper on nano-thermodynamics...

IMRC Congress XXVIII

Dr. Guisbiers presented the latest results of his group and also chaired the Symposium A2 dedicated to Nano-alloys.

Book review for De Gruyter

Dr. Guisbiers reviewed the book "Medical Physics" from Hartmut Zabel published by De Gruyter. 

Invited Seminar at the Universidad de las Americas Puebla (Mexico)

Dr. Guisbiers presented the latest research results from his group!

Prof. Dr. Thomas Webster visited our group!

Dr. Webster visited our Nanophysics group. He discussed with all group's members, he shared his experience and vision in the field of nanomedicine. So enriching experience!

Exceptional Peer Reviewer

Recognition from the Royal Society of Chemistry!

Invited Seminar at the University of Memphis

Dr. Guisbiers presented the research and latest results performed and obtained by his group!

Invited Seminar at Texas Tech University

Dr. Guisbiers presented the research and latest results performed and obtained by his group!

NASA EPSCoR Arkansas Space Grant Consortium

Our collaborative research project "Investigation of E&B Field of Nanowires Beaded by Au Nanoparticles in Si" with Southern Arkansas University has been funded!

ACS Regional Meeting 2018

Congratulations to Matt, Luke, Tina, Patrick and Entidhar who successfully presented their poster at the ACS meeting in Little Rock!

IMRC Congress XXVII

Matt Kusper presented his preliminary results during the Nano-alloys symposium!

IMRC Congress XXVI

1st Nano-alloys symposium organized by Dr. Guisbiers, Dr. Rodrigez-Lopez, Dr. Paz-Borbon and Dr. Mao.

Nanoscale cover!

Nanotechweb: Nanoparticle shape controls SiGe's properties

It is well known that substances behave differently whether they are in nanoparticle or bulk form. Scientists in the US have shown that for SiGe the magnitude of the size effect is determined by the nanoparticle shape, with highly faceted particles experiencing exaggerated changes to their thermal stability and optical properties. In contrast, neither size nor shape were found to have a significant effect on the temperature range over which Si and Ge are immiscible. The results will inform future experimental efforts to create nanoparticles with properties tuned for applications in computing and thermoelectric engineering.

Nanotechweb: Predicting phase transitions in nanocube catalysts

The temperature at which ordered structures form in gold-copper nanocubes, which are widely employed in catalyst applications, is still unknown. A team of physicists in the US and Mexico has now performed new nano-thermodynamics simulations to calculate this temperature, and has backed up its results with transmission electron microscopy observations. The findings could help researchers save time when synthesizing such ordered nanostructures in the future.

Miguel Yacaman's 70th Birthday Celebration at the IMRC-MRS Congress in Cancun

Myself with Dr. Miguel Jose-Yacaman on the 17th August 2016 

MRS Bulletin, February 2016, Nano Focus

A phase diagram is one of the first steps in trying to understand the characteristics of the material, says Grégory Guisbiers, a materials scientist at The University of Texas at San Antonio. And while bulk phase diagrams have been developed for electrum, nothing similar has been achieved on the nanoscale due to technical limitations that do not allow for precise calorimetry. Instead, Guisbiers and his team turned to modeling using nanothermodynamics, the thermodynamics of small systems. Building off previous attempts published by others, they hoped to better understand how size, shape, and segregation effects might alter the nanophase diagram of electrum nanoparticles.

Nanotechweb: Segregation rules predict metal diffusion in nanoalloys

“Our first segregation rule says that if the bulk melting temperature of element A is larger than that of element B, then element A will diffuse to the surface,” explains team member and lead author of the study, Gregory Guisbiers. “If the bulk melting temperature of both elements is more or less the same, then the element will segregate according to how much surface energy it has – and this is our second rule.” In fact, the second rule says that if the solid surface energy of element A is smaller than that of element B, then element A will separate out to the surface, he adds. “To be completely precise, we have to determine the miscibility of the alloy using the so-called Hume-Rothery rules before applying our two segregation rules,” says Guisbiers. “When the alloy is completely or partially miscible, the first rule applies. And when it is completely miscible, then only the second rule applies.”

Nanotechweb: Gold-copper nanostars can kill tumor cells

Gold-copper nanostars can be heated up using light and then used to kill tumour cells. This is the new result from researchers at the University of Texas at San Antonio and the Universidad Nacional Autonoma de Mexico, who found that the nanostructures, which are either rounded or pointed, are stable up to temperatures of at least 150°C. “Such high temperatures make them ideal for use as photothermal agents. Indeed, they work between 37°C and 60°C,” Guisbiers tells nanotechweb.org.

Nanotechweb: Why does "Tumbaga" look like pure gold?

“The nice aspect of our new work is that we were able to experimentally confirm some of our theoretical predictions with several transmission electronic microscope (TEM) observations,” explains Gregory Guisbiers. “In fact the University of Texas at San Antonio has one of the most powerful TEMs in the world (a JEOL-ARM-200F containing an aberration corrector called Helenita), and we were able to see how gold is segregated at the surface of the nanoparticles – just as our calculations predicted.”

Nanowerk: A nano-thermodynamic look at gold-copper alloys

"This alloy exhibits novel physical and chemical properties at the nanoscale," Dr. Grégory Guisbiers from the Department of Physics & Astronomy at the University of Texas at San Antonio (UTSA), tells Nanowerk. "Although the Au-Cu alloy has been extensively studied in the literature both at the bulk and nano-scales, the prediction of phase diagrams at the nanoscale is still missing."

Nanotechweb: Nano-alloy can be two faced

“Our results are exciting because they explain why the Cu-Ni nanoparticles adopt either a mixed or Janus structure,” Gregory Guisbiers tells nanotechweb.org. “They could be useful for engineers because they could allow them to tune their synthesis parameters to create the structure they really want depending on the application required.”

 

 

 

 

 

 

 

 

 

Nanotechweb: Laser pulse cleans up selenium nanoparticle

Researchers at the University of Texas at San Antonio and Northeastern University, both in the US, say they have succeed in synthesizing pure selenium quantum dots and nanoparticles by simply blasting a sample of selenium powder in a glass of water with a laser beam. The nanostructures might be used in two very different applications: as antibacterial agents and as photon harvesters in solar cells.

Mexican newspaper "Antena San Luis": UASLP welcomed a prominent Belgian physicist

Visit at UASLP (Mexico) in August 2013

Meeting with the Cuban Ambassador in Belgium

Visit of the Cuban Ambassador at the University of Mons in June 2012

Materials 360: Researchers Accurately Determine the Surface Energy of Solid Selenium

Researchers in Belgium and France have determined a new value for the surface energy of solid selenium and have found it to be considerably higher than previously thought. Selenium is a key element in nanotechnology and the new result will be important for a variety of applications in which the element is used. These include solar cells, photovoltaic panels, computer memories and antibacterial coatings, as well as light-emitting diodes that rely on cadmium selenide quantum dots. In most of these applications, the material’s surface plays a key role.

Nanowerk: Accurately determining the surface energy of solid selenium

A new study, reported in the December 5, 2012, online edition of Applied Physics Letters ("An accurate determination of the surface energy of solid selenium") now shows that the experimental determination of the solid surface energy of selenium is in excellent agreement with the theoretical predictions coming from nano-thermodynamics."A lower limit value of the solid surface energy of selenium (∼0.175 J/m2) has been determined in 1971 by extrapolating the surface energy of the melt of selenium at 20°C; but an attempt to determine the solid surface energy of selenium from contact angle measurements failed," Dr. Grégory Guisbiers, a senior researcher at the University of Mons in Belgium, tells Nanowerk.Guisbiers and his collaborators therefore set out to experimentally determine the solid surface energy of selenium using different probe liquids in order to support the theoretical findings.

Nanotechweb: Nanothermodynamics improves surface energy measurements

“Generally, conventional probe liquids have a liquid surface energy lower than 0.1 J/m2. But by using non-conventional probe liquids like mercury and gallium, we can cover the theoretically predicted solid surface energy value of selenium (of around 0.285 J/m2), which we first calculated using a nanothermodynamic model,” explains team leader Grégory Guisbiers. “We then chose two liquids that have a lower surface energy than selenium (ethylene glycol and de-ionized water) and two liquids that that have a higher surface energy (mercury and gallium).”

Nanotechweb: Looking at defects on the nanoscale

Vacancies, or lattice point defects, form much more easily in nanomaterials compared to their bulk counterparts. That's the conclusion of a new study by a physicist in Belgium who has developed a theoretical model describing vacancy formation as particle size reduces. The result could help us better understand how defects develop in nanostructures and how vacancies affect nanomaterial properties.

Nanowerk: Size effect and vacancies in nanomaterials

"To understand the processes occurring in nanomaterials during heat treatment and mechanical deformation, the size effects on the vacancy formation energy and entropy have to be considered," Guisbiers explains to Nanowerk. "The new model explains why nanomaterials appear to be perfect – it is due to the limited number of atoms in a particle (nanoparticles generally have less than one million atoms and according to the theory there are less than 1 vacancy per one million atoms)."

Nanotechweb: Universal equation describes how materials behave at nanoscale

The surface-to-volume ratio of a structure increases dramatically as it is made smaller and therefore surface effects can be very important for tiny devices. "My equation links size effects not only to this surface-to-volume ratio but also to the intrinsic nature of the particles involved in the considered material property – that is, whether they are fermions or bosons," says Grégory Guisbiers.

Nanowerk: A universal law for characteristic temperatures at the nanoscale

"It is known that these physical quantities of free-standing nanostructures decrease as the size decreases down to the nanoscale," Guisbiers tells Nanowerk. "The description of different effects observed in nature by only one general equation is the 'Holy Grail' for all physicists. We have achieved this goal for characteristic temperatures through a top-down approach."

Physics World, December 2009, Frontiers

Nano-equation unveiled! Dr. Guisbiers showed that there exist only two types of size effect based on the fermionic or bosonic nature of the material property considered. 

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Physics and Astronomy Department

© 2020 by G. Guisbiers

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