gold – Lightsources.org

Improved stability of gold nanoparticles for cancer therapy

2025/01/272025/01/30

A study carried out by researchers from POLYMAT-University of the Basque Country, INIFTA-Universidad Nacional de la Plata and the ALBA Synchrotron has made promising advances in the stabilization of gold nanoparticles (AuNPs) for use in cancer therapy. The work, published in the scientific journal Small, describes the synthesis of anisotropic hybrid particles of gold nanoparticles and nanogel, which overcome the challenges that have held back the clinical application of AuNPs, while maintaining their optical properties for the first time.

Gold nanoparticles are considered a powerful tool in photothermal cancer treatment due to their ability to convert light into heat, which is concentrated on tumor cells to destroy them. However, research has shown that unprotected anisotropic gold nanoparticles are prone to to undergo evaporation and condensation processes that result in the loss of their photothermal properties during the duration of the irradiation treatment. A new study, published in the scientific journal Small, presents a novel approach for stabilizing these particles while preserving their critical optical characteristics and, therefore, with the potential to improve the efficacy of cancer therapies.

Anisotropic gold nanoparticles are non-spherical photothermal particles that can be designed for thermal conversion by near-infrared irradiation, which is particularly advantageous in medical applications because of their high penetration depth in biological tissues and low toxicity to normal cells. However, their structural instability precludes prolonged therapeutic use. For this reason, previous studies have attempted to coat gold nanoparticles in gels such as polyethylene glycol (PEG). Yet, while these coatings improved stability, they also altered the unique shape and optical properties of the gold nanoparticles, significantly reducing their photothermal efficacy.

In this new study, researchers from POLYMAT-University of the Basque Country, INIFTA-La Plata National University, and the ALBA Synchrotron, devised a one-pot synthesis method that stabilizes anisotropic gold nanoparticles by coating them in an ultra thin, in situ polymeric nanogel. Using polyacrylamide (pAA) and poly-(N-isopropylacrylamide) (pNIPAM), the team achieved nanogel shells between 2–8 nanometers thick around each individual gold nanoparticle. This ultra thin coating preserved the nanoparticles’ dimensions and shape, ensuring that their unique optical and photothermal properties were unaffected. Notably, rod-shaped and star-shaped nanoparticles retained their structural integrity and optical characteristics, with rod-shaped hybrids showing particularly promising stability and efficiency for photothermal applications. The researchers also found that pNIPAM coatings offered the best protection for the nanoparticles, while pAA coatings exhibited optimal photothermal conversion efficiency.

Conversion of carbon dioxide into raw materials more effective with gold

2024/02/212024/02/23

Carbon dioxide, emitted mainly by combustion of fossil fuels, is harmful to the climate and the main reason for increased global warming. Diverting carbon dioxide into hydrogen carriers or chemicals such as methanol, a valuable raw material and energy carrier, is thus highly desired. Supported metal nanoparticle heterogeneous catalysts such as copper on zinc oxide is used for the catalytic conversion of carbon dioxide to methanol. Researchers have now discovered that it is possible to avoid by-products and at the same time make the process more sustainable by adding a small amount of gold to the catalyst.

Carbon dioxide can be converted into methanol and water by reaction with hydrogen. The reaction is only possible in the presence of a catalytic material such as Au or Cu nanoparticles supported on zinc oxide. The chemical reaction will then take place on the particle surfaces. In a recent study, a research team from Germany, Japan and Sweden have shown that modifying the typical ZnO-supported Cu nanoparticles by a small amount of gold (< 10 weight percent) makes the reaction more selective.

Read more on MAX IV website

Buckyballs on gold are less exotic than graphene

2022/07/212022/08/24

C₆₀ molecules on a gold substrate appear more complex than their graphene counterparts, but have much more ordinary electronic properties. This is now shown by measurements with ARPES at BESSY II and detailed calculations.

Graphene consists of carbon atoms that crosslink in a plane to form a flat honeycomb structure. In addition to surprisingly high mechanical stability, the material has exciting electronic properties: The electrons behave like massless particles, which can be clearly demonstrated in spectrometric experiments. Measurements reveal a linear dependence of energy on momentum, namely the so-called Dirac cones – two lines that cross without a band gap – i.e. an energy difference between electrons in the conduction band and those in the valence bands.

Variants in graphene architecture

Artificial variants of graphene architecture are a hot topic in materials research right now. Instead of carbon atoms, quantum dots of silicon have been placed, ultracold atoms have been trapped in the honeycomb lattice with strong laser fields, or carbon monoxide molecules have been pushed into place on a copper surface piece by piece with a scanning tunneling microscope, where they could impart the characteristic graphene properties to the electrons of the copper.

Artificial graphene with buckyballs?

A recent study suggested that it is infinitely easier to make artificial graphene using C₆₀ molecules called buckyballs. Only a uniform layer of these needs to be vapor-deposited onto gold for the gold electrons to take on the special graphene properties. Measurements of photoemission spectra appeared to show a kind of Dirac cone.

Analysis of band structures at BESSY II

“That would be really quite amazing,” says Dr. Andrei Varykhalov, of HZB, who heads a photoemission and scanning tunneling microscopy group. “Because the C₆₀ molecule is absolutely nonpolar, it was hard for us to imagine how such molecules would exert a strong influence on the electrons in the gold.” So Varykhalov and his team launched a series of measurements to test this hypothesis.

In tricky and detailed analyses, the Berlin team was able to study C₆₀ layers on gold over a much larger energy range and for different measurement parameters. They used angle-resolved ARPES spectroscopy at BESSY II, which enables particularly precise measurements, and also analysed electron spin for some measurements.

Read more on the HZB website

Image: Using density functional theory and measurement data from spin-resolved photoemission, the team investigated the origin of the repeating Au(111) bands and resolved them as deep surface resonances. These resonances lead to an onion-like Fermi surface of Au(111).

Gold protein clusters could be used as environmental and health detectors

2018/04/112018/04/12

Peng Zhang and his collaborators study remarkable, tiny self-assembling clusters of gold and protein that glow a bold red. And they’re useful: protein-gold nanoclusters could be used to detect harmful metals in water or to identify cancer cells in the body.
“These structures are very exciting but are very, very hard to study. We tried many different tools, but none worked,” says Zhang, a Dalhousie University professor.

“These structures are very exciting but are very, very hard to study. We tried many different tools, but none worked,” says Zhang, a Dalhousie University professor.

Image: The protein-gold structure. The protein, which both builds and holds in place the gold cluster, is shown in grey.