Tag Archives: Au (gold)

Using natural proteins to grow gold nanoclusters for hybrid bionanomaterials

While there’s a January 10, 2022 news item on Nanowerk, the research being announced was made available online in the Fall of 2021 and is now available in print,

Gold nanoclusters are groups of a few gold atoms with interesting photoluminescent properties. The features of gold nanoclusters depend not only on their structure, but their size and also by the ligands coordinated to them. These inorganic nanomaterials have been used in sensing, biomedicine and optics and their coordination with biomolecules can endow multiple capabilities in biological media.

A research collaboration between the groups of Dr. Juan Cabanillas, Research Professor at IMDEA Nanociencia and Dr. Aitziber L. Cortajarena, Ikerbasque Professor and Principal Investigator at CIC biomaGUNE have explored the use of natural proteins to grow gold nanoclusters, resulting in hybrid bionanomaterials with tunable photoluminescent properties and with a plethora of potential applications.

A January 10, 2022 IMDEA Nanociencia press release, which originated the news item, provides more technical detail about the research,

The nanoclusters –with less than 2 nm in size- differentiate from larger nanoparticles (plasmonic) since they present discrete energy levels coupled optically. The groups of amino acids within the proteins coordinate the gold atoms and allow the groups to be arranged around the gold nanocluster, facilitating the stabilization and adding an extra level of tailoring. These nanoclusters have interesting energy harvesting features. Since the discrete energy levels are optically coupled, the absorption of a photon leads to promotion of an electron to higher levels, which can trigger a photophysical process or a photochemical reaction.  

The results by Cabanillas and Cortajarena groups, published in Advanced Optical Materials and Nano Letters, explore the origin of the photoluminescence in protein-designed gold nanoclusters and shed light into the strong influence of environmental conditions on the nature of luminescence. Nanocluster capping by two types of amino acids (histidine and cysteine) allow for changing the emission spectral range from blue to red, paving the way to tune the optical properties by an appropriate ligand choice. The nature of emission is also changed with capping, from fluorescence to phosphorescence, respectively. The synergistic protein-nanocluster effects on emission are still not clear, and the groups at IMDEA Nanociencia and CIC biomaGUNE are working to elucidate the mechanisms behind. There are potential applications for the aforementioned nanoclusters, in solid state as active medium in laser cavities. Optical gain properties from these nanoclusters are yet to be demonstrated, which could pave the way to a new generation of potentially interesting laser devices. As the combination of gold plus proteins is potentially biocompatible, many potential applications in biomedicine can also be envisaged.

A related publication of the groups in Nano Letters demonstrates that the insertion of tryptophans, amino acids with high electron density, in the vicinity of the nanocluster boosts its photoluminescence quantum efficiency up to 40% in some cases, values relevant for solid state light emission applications. Researchers also observed an antenna effect: the tryptophans can absorb light in a discrete manner and transfer the energy to the cluster. This effect has interest for energy harvesting and for sensing purposes as well.

The proteins through the biocapping enable the synthesis of the nanoclusters and largely improve their quantum efficiency. “The photoluminescence quantum efficiency is largely improved when using the biocapping” Dr. Cabanillas says. He believes this research work means “a new field opening for the tuning of optical properties of nanoclusters through protein engineering, and much work is ahead for the understanding of the amplification mechanism”. Dr. Cortajarena emphasizes “we have already demonstrated the great potential of engineered photoluminescent protein-nanocluster in biomedical and technological fields, and understanding the fundamental emission mechanisms is pivotal for future applications“. A variety of further applications include biosensors, as the protein admits functionalization with recognition molecules, energy harvesting, imaging and photodynamic therapies. Further work is ahead this opening avenue for photophysics research.

This research is a collaboration led by Dr. Juan Cabanillas and Dr. Aitziber L. Cortajarena research groups at IMDEA Nanociencia and CIC biomaGUNE, with contributions from researchers at the Diamond Light Source Ltd. [synchrotron] and DIPC. It has been cofounded by the projects AMAPOLA, NMAT2D, FULMATEN, Atracción de Talento from Comunidad de Madrid and the Severo Ochoa Centre of Excellence award to IMDEA Nanociencia. CIC biomaGUNE acknowledges support by the projects ERC-ProNANO, ERC-NIMM, ProTOOLs and the Maria de Maeztu Units of Excellence Programme.

Here are links to and citations for the papers,

Tuning the Optical Properties of Au Nanoclusters by Designed Proteins by Elena Lopez-Martinez, Diego Gianolio, Saül Garcia-Orrit, Victor Vega-Mayoral, Juan Cabanillas-Gonzalez, Carlos Sanchez-Cano, Aitziber L. Cortajarena. Advanced Optical Materials Volume 10, Issue 1 January 4, 2022 2101332 DOI: https://doi.org/10.1002/adom.202101332 First published: 31 October 2021

This paper is open access.

Boosting the Photoluminescent Properties of Protein-Stabilized Gold Nanoclusters through Protein Engineering by Antonio Aires, Ahmad Sousaraei, Marco Möller, Juan Cabanillas-Gonzalez, and Aitziber L. Cortajarena. Nano Lett. 2021, 21, 21, 9347–9353 DOI: https://doi.org/10.1021/acs.nanolett.1c03768 Publication Date: November 1, 2021 Copyright © 2021 American Chemical Society

This paper is behind a paywall.

Not being familiar with either of the two research institutions mentioned in the press release, I did a little digging.

Here’s a little information about IMDEA Nanociencia (IMDEA Nanoscience Institute), from its Wikipedia entry, Note: All links have been removed,

IMDEA Nanoscience Institute is a private non-profit foundation within the IMDEA Institutes network, created in 2006-2007 as a result of collaboration agreement between the Community of Madrid and Spanish Ministry of Education and Science. The foundation manages IMDEA-Nanoscience Institute,[1] a scientific centre dedicated to front-line research in nanoscience, nanotechnology and molecular design and aiming at transferable innovations and close contact with industries. IMDEA Nanoscience is a member of the Campus of International excellence, a consortium of research institutes promoted by the Autonomous University of Madrid and Spanish National Research Council (UAM/CSIC).[2]

As for CIC biomaGUNE, here’s more from its institutional profile on the science.eus website,

The Centre for Cooperative Research in Biomaterials-CIC biomaGUNE, located in San Sebastian (Spain), was officially opened in December 2006. CIC biomaGUNE is a non-profit research organization created to promote scientific research and technological innovation at the highest levels in the Basque Country following the BioBasque policy in order to create a new business sector based on biosciences. Established by the Department of Industry, Technology & Innovation of the Government of the Autonomous Community of the Basque Country, CIC biomaGUNE constitutes one of the Centres of the CIC network, the largest Basque Country research network on specific strategic areas, having the mission to contribute to the economical and social development of the country through the generation of knowledge and speeding up the process that leads to technological innovation.

A fatigue-free stretchable conductor for foldable electronics

There’s been a lot of talk about foldable, stretchable, and/or bendable electronics, which is exciting in itself but I find this work on developing a fatigue-free conductor particularly intriguing. After all, who hasn’t purchased something that stretches, folds, etc. only to find that it becomes ‘fatigued’ and is now ‘stretched out’.

A Sept. 23, 2015 news item on Azonano describes the new conductors,

Researchers have discovered a new stretchable, transparent conductor that can be folded or stretched and released, resulting in a large curvature or a significant strain, at least 10,000 times without showing signs of fatigue.

This is a crucial step in creating a new generation of foldable electronics – think a flat-screen television that can be rolled up for easy portability – and implantable medical devices. The work, published Monday [Sept. 21, 2015] in the Proceedings of the National Academy of Sciences, pairs gold nanomesh with a stretchable substrate made with polydimethylsiloxane, or PDMS.

The research is the result of an international collaboration including the University of Houston (US), Harvard University (US), Methodist Research Institute (US), Zhengzhou University (China), Lawrence Berkeley National Laboratory (LBNL; US).

A Sept. 22, 2015 University of Houston news release by Jeannie Kever, which originated the news item, describes this -fatigue-free material in more detail,

The substrate is stretched before the gold nanomesh is placed on it – a process known as “prestretching” – and the material showed no sign of fatigue when cyclically stretched to a strain of more than 50 percent.

The gold nanomesh also proved conducive to cell growth, indicating it is a good material for implantable medical devices.

Fatigue is a common problem for researchers trying to develop a flexible, transparent conductor, making many materials that have good electrical conductivity, flexibility and transparency – all three are needed for foldable electronics – wear out too quickly to be practical, said Zhifeng Ren, a physicist at the University of Houston and principal investigator at the Texas Center for Superconductivity, who was the lead author for the paper.

The new material, produced by grain boundary lithography, solves that problem, he said.

In addition to Ren, other researchers on the project included Chuan Fei Guo and Ching-Wu “Paul” Chu, both from UH; Zhigang Suo, Qihan Liu and Yecheng Wang, all from Harvard University, and Guohui Wang and Zhengzheng Shi, both from the Houston Methodist Research Institute.

In materials science, “fatigue” is used to describe the structural damage to a material caused by repeated movement or pressure, known as “strain cycling.” Bend a material enough times, and it becomes damaged or breaks.    That means the materials aren’t durable enough for consumer electronics or biomedical devices.

“Metallic materials often exhibit high cycle fatigue, and fatigue has been a deadly disease for metals,” the researchers wrote.

“We weaken the constraint of the substrate by making the interface between the Au (gold) nanomesh and PDMS slippery, and expect the Au nanomesh to achieve superstretchability and high fatigue resistance,” they wrote in the paper. “Free of fatigue here means that both the structure and the resistance do not change or have little change after many strain cycles.”

As a result, they reported, “the Au nanomesh does not exhibit strain fatigue when it is stretched to 50 percent for 10,000 cycles.”

Many applications require a less dramatic stretch – and many materials break with far less stretching – so the combination of a sufficiently large range for stretching and the ability to avoid fatigue over thousands of cycles indicates a material that would remain productive over a long period of time, Ren said.

The grain boundary lithography involved a bilayer lift-off metallization process, which included an indium oxide mask layer and a silicon oxide sacrificial layer and offers good control over the dimensions of the mesh structure.

The researchers used mouse embryonic fibroblast cells to determine biocompatibility; that, along with the fact that the stretchability of gold nanomesh on a slippery substrate resembles the bioenvironment of tissue or organ surfaces, suggest the nanomesh “might be implanted in the body as a pacemaker electrode, a connection to nerve endings or the central nervous system, a beating heart, and so on,” they wrote.

Here’s a link to and citation for the paper,

Fatigue-free, superstretchable, transparent, and biocompatible metal electrodes by Chuan Fei Guo, Qihan Liu, Guohui Wang, Yecheng Wang, Zhengzheng Shi, Zhigang Suo, Ching-Wu Chu, and Zhifeng Ren. PNAS (Proceedings of the National Academy of Sciences)  doi: 10.1073/pnas.1516873112 Published online Sept. 21, 2015

This paper appears to be open access.