Nanofluidic Scattering Microscopy and Spectroscopy for Single Particle Catalysis
Doctoral thesis, 2024
Nanoparticles are a fundamental asset in modern society, and a cornerstone in global industries where they contribute significantly to the path towards sustainable energy and products. Their ability to facilitate and steer chemical reactions is studied in the field of heterogeneous catalysis, where these tiny particles are characterized regarding their activity and selectivity. However, the characterization is often conducted on large ensembles of particles, thereby disregarding their structural heterogeneity, which possibly leads to erroneous structure-function correlations. Since it is one goal of catalysis research to find “superparticles” with exceptional performance, the need for dedicated single particle studies where the influence of, e.g., shape, size and surface structure is investigated in detail, is obvious.
Methods like fluorescence microscopy, X-ray diffraction/scattering, electron microscopy and plasmonic sensing are commonly used for single particle investigations in catalysis. These methods detect electrons or photons that carry information either on the reactant molecules, the product molecules, changes to the catalyst particle itself or the particle surrounding. However, none of these methods provides direct single particle activity information without either using plasmonic enhancement effects that may also impact the studied reaction itself and limit the range of catalyst materials that can be studied, or using fluorescence that limits reaction conditions to ultralow concentrations and to a narrow range of reactions.
The overarching goal of the work presented in this thesis has been to develop an optical microscopy technique that can quantitatively measure catalytic activity, and in the longer term even selectivity, of a single nanoparticle, without the limitations of existing single particle techniques. At the core of this method - Nanofluidic Scattering Microscopy - are nanofluidic channels that can accurately control the transport of molecules to and from a single, catalytically active, particle localized inside a channel. As a second key trait, the unique light scattering properties of nanochannels render them highly sensitive to refractive index changes of the fluid inside them. Hence, when a catalytic reaction alters the molecular composition of the fluid in a nanochannel, its light scattering characteristics change and reveal in this way the catalytic performance of the nanoparticle, which here is demonstrated for H2O2 decomposition over on single Pt particles. Furthermore, resolving the scattered light spectrally, as I do in Nanofluidic Scattering Spectroscopy, spectral fingerprints of a catalytic reaction can be resolved, as demonstrated for the catalytic reduction of fluorescein on a single Au nanoparticle.
In the wake of these developments, I also have developed a new fluidic platform, chip holder and microscopy setup to harness the full potential of micro- and nanofluidics in combination with optical microscopy and spectroscopy applied to single particle catalysis investigations.
Methods like fluorescence microscopy, X-ray diffraction/scattering, electron microscopy and plasmonic sensing are commonly used for single particle investigations in catalysis. These methods detect electrons or photons that carry information either on the reactant molecules, the product molecules, changes to the catalyst particle itself or the particle surrounding. However, none of these methods provides direct single particle activity information without either using plasmonic enhancement effects that may also impact the studied reaction itself and limit the range of catalyst materials that can be studied, or using fluorescence that limits reaction conditions to ultralow concentrations and to a narrow range of reactions.
The overarching goal of the work presented in this thesis has been to develop an optical microscopy technique that can quantitatively measure catalytic activity, and in the longer term even selectivity, of a single nanoparticle, without the limitations of existing single particle techniques. At the core of this method - Nanofluidic Scattering Microscopy - are nanofluidic channels that can accurately control the transport of molecules to and from a single, catalytically active, particle localized inside a channel. As a second key trait, the unique light scattering properties of nanochannels render them highly sensitive to refractive index changes of the fluid inside them. Hence, when a catalytic reaction alters the molecular composition of the fluid in a nanochannel, its light scattering characteristics change and reveal in this way the catalytic performance of the nanoparticle, which here is demonstrated for H2O2 decomposition over on single Pt particles. Furthermore, resolving the scattered light spectrally, as I do in Nanofluidic Scattering Spectroscopy, spectral fingerprints of a catalytic reaction can be resolved, as demonstrated for the catalytic reduction of fluorescein on a single Au nanoparticle.
In the wake of these developments, I also have developed a new fluidic platform, chip holder and microscopy setup to harness the full potential of micro- and nanofluidics in combination with optical microscopy and spectroscopy applied to single particle catalysis investigations.
spectroscopy
heterogeneous catalysis
setup development
nanofluidics
microfluidics
single particle catalysis
dark-field scattering microscopy
PJ-salen, Fysik Origo, Kemigården 1, Göteborg
Opponent: Prof. Aleksandra Radenovic, Laboratory of Nanoscale Biology, EPFL Lausanne, Schweiz
Author
Björn Altenburger
Chalmers, Physics, Chemical Physics
Label-Free Imaging of Catalytic H2O2 Decomposition on Single Colloidal Pt Nanoparticles Using Nanofluidic Scattering Microscopy
ACS Nano,;Vol. 17(2023)p. 21030-21043
Journal article
Altenburger, B., Fritzsche, J., Langhammer, C. Vis Spectroscopy of Liquid Solutes from Femto- to Attoliter Volumes inside a Single Nanofluidic Channel
Altenburger, B., Fritzsche, J., Langhammer, C. Femtoliter Batch Reactors for Nanofluidic Scattering Spectroscopy Analysis of Catalytic Reactions on Single Nanoparticles
Altenburger, B., Fritzsche, J., Langhammer, C. A temperature-controlled chip holder with integrated electrodes for nanofluidic scattering spectroscopy on highly integrated nanofluidic systems
If a thing is too tiny to see, you may want to look for what it does instead.
In this modern and industrialized world, the scale of processes defines their impact on society. This is especially true for the chemical industry, which provides among many other things fertilizer, fuels and polymers to consumers all around the world, making it one of largest markets. However, it may not be this scale that is most important for mankind since these industries are largely based on chemical reactions that employ catalysts. These are substances that accelerate or enable chemical reactions without being used up themselves. Industrial catalysts are comprised of billions of nanoparticles, each 1000 times smaller than a cell in our bodies, each performing a chemical reaction to the best of their abilities. From that, it is evident that even the tiniest improvements on the scale of these nanoparticles can have large consequences for whole industries.
It is therefore the declared goal of the scientific field of catalysis to understand these tiny yet incredibly numerous promoters of chemical reactions and has therefore sparked the development of many experimental techniques for this task. However, many of these approaches investigate millions, maybe hundreds, of catalytic nanoparticles at a time, thereby masking the contribution of the very active particles in the broad average. In response, this work presents a new approach that can be used to investigate the catalytic activity of an individual nanoparticle, and that without even looking at it. This may sound odd, but the 10 nm or below sized catalytic nanoparticles are challenging to look at without using extensive (and expensive) equipment. In my approach, I make use of the container that holds the single nanoparticle, which is a nanoscale channel in a glass surface. Like a scratch in a windshield, it scatters light effectively, whereby the intensity and spectral composition of this light reveals what is inside this channel. As the particle performs a catalytic reaction, the content of the channel will change and so will the light that is scattered from it. With that, the catalytic activity of individual nanoparticles can be assessed, so that a relation between structure and function can be defined and the best particle be found.
In this modern and industrialized world, the scale of processes defines their impact on society. This is especially true for the chemical industry, which provides among many other things fertilizer, fuels and polymers to consumers all around the world, making it one of largest markets. However, it may not be this scale that is most important for mankind since these industries are largely based on chemical reactions that employ catalysts. These are substances that accelerate or enable chemical reactions without being used up themselves. Industrial catalysts are comprised of billions of nanoparticles, each 1000 times smaller than a cell in our bodies, each performing a chemical reaction to the best of their abilities. From that, it is evident that even the tiniest improvements on the scale of these nanoparticles can have large consequences for whole industries.
It is therefore the declared goal of the scientific field of catalysis to understand these tiny yet incredibly numerous promoters of chemical reactions and has therefore sparked the development of many experimental techniques for this task. However, many of these approaches investigate millions, maybe hundreds, of catalytic nanoparticles at a time, thereby masking the contribution of the very active particles in the broad average. In response, this work presents a new approach that can be used to investigate the catalytic activity of an individual nanoparticle, and that without even looking at it. This may sound odd, but the 10 nm or below sized catalytic nanoparticles are challenging to look at without using extensive (and expensive) equipment. In my approach, I make use of the container that holds the single nanoparticle, which is a nanoscale channel in a glass surface. Like a scratch in a windshield, it scatters light effectively, whereby the intensity and spectral composition of this light reveals what is inside this channel. As the particle performs a catalytic reaction, the content of the channel will change and so will the light that is scattered from it. With that, the catalytic activity of individual nanoparticles can be assessed, so that a relation between structure and function can be defined and the best particle be found.
NACAREI: Nanofluidic Catalytic Reaction Imaging
European Commission (EC) (101043480), 2023-01-01 -- 2027-12-31.
The Sub-10 nm Challenge in Single Particle Catalysis
Swedish Research Council (VR) (2018-00329), 2019-01-01 -- 2024-12-31.
Areas of Advance
Nanoscience and Nanotechnology
Subject Categories
Physical Chemistry
Chemical Process Engineering
Infrastructure
Chalmers Materials Analysis Laboratory
Nanofabrication Laboratory
ISBN
978-91-8103-083-9
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5541
Publisher
Chalmers
PJ-salen, Fysik Origo, Kemigården 1, Göteborg
Opponent: Prof. Aleksandra Radenovic, Laboratory of Nanoscale Biology, EPFL Lausanne, Schweiz