Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ultra-thin superlattices from gold nanoparticles for nanophotonics

21.05.2019

Physical chemistry: Publication in ACS Applied Materials & Interfaces

The group "Colloids and Nanooptics" of Prof. Dr. Matthias Karg at the Institute of Physical Chemistry has come up with a simple yet precise technique for developing highly ordered particle layers. The group is using tiny, soft and deformable spherical polymer beads with a hydrogel-like structure.


Ultra-thin layer of spherical hydrogel cores with gold particles transferred to a glass substrate.

Credit: HHU / Christoph Kawan


Producing the layer structure, (from left): First a solution containing the spherical hydrogel cores with the gold particles included is carefully applied to a water surface. This rapidly forms an ultra-thin, shimmering layer that can subsequently be lifted off using a glass substrate.

Credit: HHU / Christoph Kawan

Hydrogels are water swollen, three-dimensional networks. For example, we are familiar with these structures as super-absorbers in babies' nappies that have the ability to soak up large quantities of liquids.

Within these hydrogel beads are tiny gold or silver particles, just a few nanometres in size, that Karg's team synthesizes at HHU using metal salts in a reduction process.

"We can adjust the size of the gold particles very precisely, because the hydrogel shells are permeable to dissolved metal salts, allowing for successive overgrowth of the gold cores."

The structure of these core-shell particles can be roughly compared with that of a cherry, where a hard core is surrounded by soft pulp. However, the particles from the laboratory are roughly one hundred thousand times smaller.

The Duesseldorf-based researchers can then use a dilute solution of these hydrogel beads to produce thin monolayers. They apply the beads to a water surface, where a highly ordered and colourfully shimmering layer self-assembles. They transfer this layer from the water surface onto glass substrates. This transfer makes the entire glass substrate shimmer.

Looking at this layer with an electron microscope reveals a regular, hexagonally ordered particle array. "These are the gold particles in their shells," explains doctoral student Kirsten Volk, "and we see that they are arranged in a single, highly ordered layer."

It's the gold particles that determine the colour of the layer: They reflect visible light with certain wavelengths, which interferes and thus creates the impression of a different colour from different angles.

"These thin layers are very interesting for optoelectronics - i.e. the transfer and processing of data using light. It may also be possible to use them to build miniaturised lasers," explains Prof. Karg. These nanolasers are only nanometres in size, thus constituting a key technology in the field of nanophotonics.

In a study now published in the journal ACS Applied Materials & Interfaces, the Duesseldorf-based researchers have overcome a major obstacle on the path to such nanolasers. They succeeded in creating collective resonances in the gold particles by incident light.

This means that the gold particles are not excited individually; instead, all excited particles are in resonance. This collective resonance is the basic prerequisite for building lasers. The special aspect of the research findings published is that not only can the particle layers be created very easily and on a large scale, they are also especially thin.

For optoelectronic applications and nanolasers, the resonant modes will have to be amplified further in the thin layers. Prof. Karg: "Next we will try to amplify the resonance further by means of doping with emitters. In the long term, this could also allow us to realise electrically powered nanolasers."

###

Original publication

Kirsten Volk, Joseph P. S. Fitzgerald, and Matthias Karg, In-Plane Surface Lattice and Higher Order Resonances in Self-Assembled Plasmonic Monolayers: From Substrate-Supported to Free-Standing Thin Films, ACS Appl. Mater. Interfaces 2019 11 (17), 16096-16106

DOI: 10.1021/acsami.9b03197

Arne Claussen | EurekAlert!
Further information:
http://dx.doi.org/10.1021/acsami.9b03197

More articles from Materials Sciences:

nachricht Capturing 3D microstructures in real time
03.04.2020 | DOE/Argonne National Laboratory

nachricht Graphene-based actuator swarm enables programmable deformation
02.04.2020 | Science China Press

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Harnessing the rain for hydrovoltaics

Drops of water falling on or sliding over surfaces may leave behind traces of electrical charge, causing the drops to charge themselves. Scientists at the Max Planck Institute for Polymer Research (MPI-P) in Mainz have now begun a detailed investigation into this phenomenon that accompanies us in every-day life. They developed a method to quantify the charge generation and additionally created a theoretical model to aid understanding. According to the scientists, the observed effect could be a source of generated power and an important building block for understanding frictional electricity.

Water drops sliding over non-conducting surfaces can be found everywhere in our lives: From the dripping of a coffee machine, to a rinse in the shower, to an...

Im Focus: A sensational discovery: Traces of rainforests in West Antarctica

90 million-year-old forest soil provides unexpected evidence for exceptionally warm climate near the South Pole in the Cretaceous

An international team of researchers led by geoscientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) have now...

Im Focus: Blocking the Iron Transport Could Stop Tuberculosis

The bacteria that cause tuberculosis need iron to survive. Researchers at the University of Zurich have now solved the first detailed structure of the transport protein responsible for the iron supply. When the iron transport into the bacteria is inhibited, the pathogen can no longer grow. This opens novel ways to develop targeted tuberculosis drugs.

One of the most devastating pathogens that lives inside human cells is Mycobacterium tuberculosis, the bacillus that causes tuberculosis. According to the...

Im Focus: Physicist from Hannover Develops New Photon Source for Tap-proof Communication

An international team with the participation of Prof. Dr. Michael Kues from the Cluster of Excellence PhoenixD at Leibniz University Hannover has developed a new method for generating quantum-entangled photons in a spectral range of light that was previously inaccessible. The discovery can make the encryption of satellite-based communications much more secure in the future.

A 15-member research team from the UK, Germany and Japan has developed a new method for generating and detecting quantum-entangled photons at a wavelength of...

Im Focus: Junior scientists at the University of Rostock invent a funnel for light

Together with their colleagues from the University of Würzburg, physicists from the group of Professor Alexander Szameit at the University of Rostock have devised a “funnel” for photons. Their discovery was recently published in the renowned journal Science and holds great promise for novel ultra-sensitive detectors as well as innovative applications in telecommunications and information processing.

The quantum-optical properties of light and its interaction with matter has fascinated the Rostock professor Alexander Szameit since College.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

13th AKL – International Laser Technology Congress: May 4–6, 2022 in Aachen – Laser Technology Live already this year!

02.04.2020 | Event News

“4th Hybrid Materials and Structures 2020” takes place over the internet

26.03.2020 | Event News

Most significant international Learning Analytics conference will take place – fully online

23.03.2020 | Event News

 
Latest News

Capturing 3D microstructures in real time

03.04.2020 | Materials Sciences

First SARS-CoV-2 genomes in Austria openly available

03.04.2020 | Life Sciences

Do urban fish exhibit impaired sleep? Light pollution suppresses melatonin production in European perch

03.04.2020 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>