| 1. |
- Fernandez, Yuri A. Diaz, 1978, et al.
(författare)
-
The conquest of middle-earth: combining top-down and bottom-up nanofabrication for constructing nanoparticle based devices
- 2014
-
Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 6:24, s. 14605-14616
-
Tidskriftsartikel (refereegranskat)abstract
- The development of top-down nanofabrication techniques has opened many possibilities for the design and realization of complex devices based on single molecule phenomena such as e. g. single molecule electronic devices. These impressive achievements have been complemented by the fundamental understanding of self-assembly phenomena, leading to bottom-up strategies to obtain hybrid nanomaterials that can be used as building blocks for more complex structures. In this feature article we highlight some relevant published work as well as present new experimental results, illustrating the versatility of self-assembly methods combined with top-down fabrication techniques for solving relevant challenges in modern nanotechnology. We present recent developments on the use of hierarchical self-assembly methods to bridge the gap between sub-nanometer and micrometer length scales. By the use of non-covalent self-assembly methods, we show that we are able to control the positioning of nanoparticles on surfaces, and to address the deterministic assembly of nano-devices with potential applications in plasmonic sensing and single-molecule electronics experiments.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Syrenova, Svetlana, 1987, et al.
(författare)
-
Hydride formation thermodynamics and hysteresis in individual Pd nanocrystals with different size and shape
- 2015
-
Ingår i: Nature Materials. - 1476-4660 .- 1476-1122. ; 14:12, s. 1236-1244
-
Tidskriftsartikel (refereegranskat)abstract
- Physicochemical properties of nanoparticles may depend on their size and shape and are traditionally assessed in ensemble-level experiments, which accordingly may be plagued by averaging effects. These effects can be eliminated in single-nanoparticle experiments. Using plasmonic nanospectroscopy, we present a comprehensive study of hydride formation thermodynamics in individual Pd nanocrystals of different size and shape, and find corresponding enthalpies and entropies to be nearly size- and shape-independent. The hysteresis observed is significantly wider than in bulk, with details depending on the specifics of individual nanoparticles. Generally, the absorption branch of the hysteresis loop is size-dependent in the sub-30 nm regime, whereas desorption is size- and shape-independent. The former is consistent with a coherent phase transition during hydride formation, influenced kinetically by the specifics of nucleation, whereas the latter implies that hydride decomposition either occurs incoherently or via different kinetic pathways.
|
|
| 5. |
- Wadell, Carl, 1985, et al.
(författare)
-
Hysteresis-Free Nanoplasmonic Pd-Au Alloy Hydrogen Sensors
- 2015
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 15:5, s. 3563-3570
-
Tidskriftsartikel (refereegranskat)abstract
- The recent market introduction of hydrogen fuel cell cars and the prospect of a hydrogen economy have drastically accelerated the need for safe and accurate detection of hydrogen. In this Letter, we investigate the use of arrays of nanofabricated Pd-Au alloy nanoparticles as plasmonic optical hydrogen sensors. By increasing the amount of Au in the alloy nanoparticles up to 25 atom %, we are able to suppress the hysteresis between hydrogen absorption and desorption, thereby increasing the sensor accuracy to below 5% throughout the investigated 1 mbar to 1 bar hydrogen pressure range. Furthermore, we observe an 8-fold absolute sensitivity enhancement at low hydrogen pressures compared to sensors made of pure Pd, and an improved sensor response time to below one second within the 0-40 mbar pressure range, that is, below the flammability limit, by engineering the nanoparticle size.
|
|
| 6. |
- Antosiewicz, Tomasz, 1981, et al.
(författare)
-
Absorption Enhancement in Lossy Transition Metal Elements of Plasmonic Nanosandwiches
- 2012
-
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 116:38, s. 20522-20529
-
Tidskriftsartikel (refereegranskat)abstract
- Combination of catalytically active transition metals and surface plasmons offers a promising way to drive chemical reactions by converting incident visible light into energetic electron-hole pairs acting as a mediator. In such a reaction enhancement scheme, the conversion efficiency is dependent on light absorption in the metal. Hence, increasing absorption in the plasmonic structure is expected to increase generation of electron-hole pairs and, consequently, the reaction rate. Furthermore, the abundance of energetic electrons might facilitate new reaction pathways. In this work we discuss optical properties of homo- and heterometallic plasmonic nanosandwiches consisting of two parallel disks made of gold and palladium. We show how near-field coupling between the sandwich elements can be used to enhance absorption in one of them. The limits of this enhancement are investigated using finite-difference time-domain simulations. Physical insight is gained through a simple coupled dipole analysis of the nanostructure. For small palladium disks (compared to the gold disk), total absorption enhancement integrated over the near visible solar AM 1.5 spectrum is 8-fold, while for large palladium disks, similar in size to the gold one, it exceeds three.
|
|
| 7. |
- Antosiewicz, Tomasz, 1981, et al.
(författare)
-
Optical activity of catalytic elements of hetero-metallic nanostructures
- 2015
-
Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9781628416237 ; 9502
-
Konferensbidrag (refereegranskat)abstract
- Interaction of light with metals in the form of surface plasmons is used in a wide range of applications in which the scattering decay channel is important. The absorption channel is usually thought of as unwanted and detrimental to the efficiency of the device. This is true in many applications, however, recent studies have shown that maximization of the decay channel of surface plasmons has potentially significant uses. One of these is the creation of electron-hole pairs or hot electrons which can be used for e.g. catalysis. Here, we study the optical properties of hetero-metallic nanostructures that enhance light interaction with the catalytic elements of the nanostructures. A hybridized LSPR that matches the spectral characteristic of the light source is excited. This LSPR through coupling between the plasmonic elements maximizes light absorption in the catalytic part of the nanostructure. Numerically calculated visible light absorption in the catalytic nanoparticles is enhanced 12-fold for large catalytic disks and by more 30 for small nanoparticles on the order of 5 nm. In experiments we measure a sizable increase in the absorption cross section when small palladium nanoparticles are coupled to a large silver resonator. These observations suggest that heterometallic nanostructures can enhance catalytic reaction rates.
|
|
| 8. |
- Antosiewicz, Tomasz, 1981, et al.
(författare)
-
Plasmon-Assisted Indirect Light Absorption Engineering in Small Transition Metal Catalyst Nanoparticles
- 2015
-
Ingår i: Advanced Optical Materials. - : Wiley. - 2195-1071. ; 3:11, s. 1591-1599
-
Tidskriftsartikel (refereegranskat)abstract
- Light absorption in plasmonic nanoantennas constitutes an interesting way of enhancing catalytic reactions occurring at surfaces of metals nanoparticles by forming hot electron-hole pairs. These can either directly transfer to empty orbitals of adsorbed species on the nanoparticle surface or thermalize via electron-phonon coupling and enhance reaction rates via a photothermal reaction channel. While this scheme, in principle, can be efficient for the well-known plasmonic materials Ag and Au due to their large optical cross-sections, other transition metals, which exhibit excellent catalytic properties, have spectrally broad and weak plasmon resonances. Thus, lower plasmon-induced electron-hole pair excitation is expected, especially for sub-10 nm nanoparticles, typical in heterogeneous catalysis. Here, a solution is presented to circumvent these limitations by challenging the established picture that plasmonic nanoparticles also constitute catalytically active entities in a plasmon mediated hot electron catalysis concept. Light absorption in catalyst nanoparticles can be engineered via an adjacent noble metal plasmonic nanoantenna that efficiently collects incident radiation with low losses, and couples it into the catalytic particles where the energy is dissipated due to the intrinsically high optical losses in transition metals at near-visible frequencies. Absorption enhancement of 1-2 orders of magnitude is predicted in 3-4 nm sized Pd catalyst nanoparticles.
|
|
| 9. |
- Frost, Rickard, 1979, et al.
(författare)
-
Core−Shell Nanoplasmonic Sensing for Characterization of Biocorona Formation and Nanoparticle Surface Interactions
- 2016
-
Ingår i: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 1:6, s. 798-806
-
Tidskriftsartikel (refereegranskat)abstract
- Surface properties of nanoparticles imposed by particle size, shape, and surface chemistry are key features that largely determine their environmental fate and effects on biological systems. Consequently, development of analytical tools to characterize surface properties of nanomaterials and their relation to toxicological properties must occur in parallel with applications. As a contribution to this quest, we present a nanoplasmonic sensing strategy that enables systematic in situ characterization of molecule−nanoparticle interactions under well-controlled conditions, in terms of both nanoparticle size and surface chemistry, with particular focus on the importance of surface faceting in crystalline nanoparticles. We assess the performance of our sensing strategy by presenting two case studies. (i) The first is protein corona formation on faceted Au core−SiO2 shell nanoparticles of different sizes, and thus different surface facet-to-edge ratios. Based on 2D and 3D models of the investigated structures, we find that for small particles the curved regions between adjacent facets dominate the response of the corona formation process, whereas the facets dominate the response in the large particle regime. (ii) The second is in situ functionalization of Au core−SiO2 shell nanoparticle surfaces, and analysis of the subsequent protein repellent behavior. Due to the versatility of the presented sensing strategy in studies of nanoparticle surface properties, including in situ surface modifications, and their interactions with (bio)molecules during corona formation, we foresee it to become a valuable tool in the areas of nanomedicine and nanotoxicology.
|
|
| 10. |
|
|
