| 1. |
- Eklöf, Johnas, 1988, et al.
(författare)
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Guided selective deposition of nanoparticles by tuning of the surface potential
- 2017
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Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 119:1
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Tidskriftsartikel (refereegranskat)abstract
- Guided deposition of nanoparticles onto different substrates is of great importance for a variety of applications such as biosensing, targeted cancer therapy, anti-bacterial coatings and single molecular electronics. It is therefore important to gain an understanding of what parameters are involved in the deposition of nanoparticles. In this work we have deposited 60 nm, negatively charged, citrate stabilized gold nanoparticles onto microstructures consisting of six different materials, (vanadium (V), silicon dioxide (SiO2), gold (Au), aluminum (Al), copper (Cu) and nickel (Ni)). The samples have then been investigated by scanning electron microscopy to extract the particle density. The surface potential was calculated from the measured surface charge density maps measured by atomic force microscopy while the samples were submerged in a KCl water solution. These values were compared with literature values of the isoelectric points (IEP) of different oxides formed on the metals in an ambient environment. According to measurements, Al had the highest surface potential followed by Ni and Cu. The same trend was observed for the nanoparticle densities. No particles were found on V, SiO2 and Au. The literature values of the IEP showed a different trend compared to the surface potential measurements concluding that IEP is not a reliable parameter for the prediction of NP deposition.
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| 2. |
- Eklöf, Johnas, 1988, et al.
(författare)
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Parallel Fabrication of Self‐Assembled Nanogaps for Molecular Electronic Devices
- 2018
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 14:50
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Tidskriftsartikel (refereegranskat)abstract
- Single molecule electronics might be a way to add additional function to nanoscale devices and continue miniaturization beyond current state of the art. Here, a combined top‐down and bottom‐up strategy is employed to assemble single molecules onto prefabricated electrodes. Protodevices, which are self‐assembled nanogaps composed by two gold nanoparticles linked by a single or a few molecules, are guided onto top‐down prefabricated nanosized nickel electrodes with sandwiched palladium layers. It is shown that an optimized geometry of multilayered metallic (top‐down) electrodes facilitates the assembly of (bottom‐up) nanostructures by surface charge interactions. Moreover, such assembly process results in an electrode–nanoparticle interface free from linking molecules that enable electrical measurements to probe electron transport properties of the nanoparticle–molecule–nanoparticle protodevices.
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| 3. |
- Fernandez, Yuri A. Diaz, 1978, et al.
(författare)
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The conquest of middle-earth: combining top-down and bottom-up nanofabrication for constructing nanoparticle based devices
- 2014
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 6:24, s. 14605-14616
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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.
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| 4. |
- Gschneidtner, Tina, 1985, et al.
(författare)
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Toward Plasmonic Biosensors Functionalized by a Photoinduced Surface Reaction
- 2013
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:28, s. 14751-14758
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Tidskriftsartikel (refereegranskat)abstract
- We present a method for efficient coupling of amine nucleophilic molecules of choice to a nanostructured gold surface via photoinduced surface chemistry. The method is based on photoactive self-assembled monolayers and can be used to functionalize localized surface plasmon resonance (LSPR) based biosensors with biorecognition motifs while reducing nonspecific binding via introduction of hydrophilic units. The photoactive linker molecule, 5-bromo-7-nitroindoline, couples nucleophilic molecules such as biotin ethylenediamine to a surface when exposed to UV-light. The specific, noncovalent recognition between biotin and streptavidin is used for demonstration of a simple biorecognition assay based on the LSPR sensing principle. By doing so, one can envision that the binding of any streptavidin fusion protein, being attached to specific spots at the gold surface, is monitored by an LSPR peak shift. Since the surface functionalization is based on a photoinduced reaction, this method can be used to functionalize the surface in a local and site-specific way, and biomedical applications such as drug-screening platforms, microarrays, solid support protein synthesis, and even single molecule experiments can be envisioned.
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| 5. |
- Syrenova, Svetlana, 1987, et al.
(författare)
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Hydride formation thermodynamics and hysteresis in individual Pd nanocrystals with different size and shape
- 2015
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Ingår i: Nature Materials. - 1476-4660 .- 1476-1122. ; 14:12, s. 1236-1244
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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.
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| 6. |
- Zengin, Gülis, 1982, et al.
(författare)
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Evaluating Conditions for Strong Coupling between Nanoparticle Plasmons and Organic Dyes Using Scattering and Absorption Spectroscopy
- 2016
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:37, s. 20588-20596
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Tidskriftsartikel (refereegranskat)abstract
- Interactions between surface plasmons in metal nano particles and electronic excitations in organic chromophores have resulted in many notable findings, including single-molecule Raman scattering, nanoscale lasing, and enhanced fluorescence. Recently, plasmon-exciton interactions have been shown to reach the strong coupling limit, a nonperturbative regime in which a coupled plasmon-exciton system should be treated as a unified hybrid. Strong coupling effects could open up exciting possibilities for manipulating nano particle plasmons via molecular degrees of freedom, or vice versa. Optical properties of such hybrid systems can differ drastically from those of noninteracting components. Specifically, optical spectra of a strongly coupled system are expected to exhibit mode splitting due to Rabi oscillations of excitation energy between the system components. However, the interpretation of optical spectra in terms of strong coupling is not a straightforward matter. Here we clarify the nature of plasmon-exciton coupling for the case of rhodamine-6G (R6G) interacting with localized surface plasmons in silver nanodisks using scattering and absorption spectroscopy. We show that this system is only marginally able to reach the strong coupling limit, even for very high molecular concentrations and despite the appearance of obvious mode splitting in scattering. For lower molecular concentrations, the mode splitting we observe should be interpreted as being due to surface-enhanced absorption rather than strong coupling. These results allow us to evaluate the critical concentration necessary for reaching the strong coupling limit and propose conditions for observing strong coupling between single-particle plasmons and organic dyes, such as R6G.
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| 7. |
- Bradley, Siobhan J., et al.
(författare)
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Heterogeneity in the fluorescence of graphene and graphene oxide quantum dots
- 2017
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Ingår i: Microchimica Acta. - : Springer Science and Business Media LLC. - 0026-3672 .- 1436-5073. ; 184:3, s. 871-878
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Tidskriftsartikel (refereegranskat)abstract
- Heterogeneity is an inherent property of a wealth of real-world nanomaterials and yet rarely in the reporting of new properties is its effect sufficiently addressed. Graphene quantum dots (GQDs) – fluorescent, nanoscale fragments of graphene - are an extreme example of a heterogeneous nanomaterial. Here, top-down approaches – by far the most predominant – produce batches of particles with a distribution of sizes, shapes, extent of oxidation, chemical impurities and more. This makes characterization of these materials using bulk techniques particularly complex and comparisons of properties across different synthetic methods uninformative. In particular, it hinders the understanding of the structural origin of their fluorescence properties. We present a simple synthetic method, which produces graphene quantum dots with very low oxygen content that can be suspended in organic solvents, suggesting a very pristine material. We use this material to illustrate the limitations of interpreting complex data sets generated by heterogeneous materials and we highlight how misleading this “pristine” interpretation is by comparison with graphene oxide quantum dots synthesized using an established protocol. In addition, we report on the solvatochromic properties of these particles, discuss common characterization techniques and their limitations in attributing properties to heterogeneous materials.
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| 8. |
- Dewi, M. R., et al.
(författare)
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Monofunctionalization and Dimerization of Nanoparticles Using Coordination Chemistry
- 2015
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 9:2, s. 1434-1439
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a strategy for controlled nanoparticle dimerization by using a solid support approach. Two types of nanoparticles have been linked by using a 5-([2,2':6',2"-terpyridine]-4'-yloxy)pentan-1-amine (terpy-amine) iron complex. The strategy includes two major steps: first, the monofunctionalization of individual nanoparticles with terpy-amine ligand molecules on a solid support, followed by release of monofunctionalized particles and subsequent dimerization. The versatility of the approach was demonstrated by dimerizing two different types of nanoparticles: spherical gold and cube-shaped iron oxide nanoparticles.
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| 9. |
- Eklöf, Johnas, 1988, et al.
(författare)
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Controlling deposition of nanoparticles by tuning surface charge of SiO2 by surface modifications
- 2016
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:106, s. 104246-104253
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Tidskriftsartikel (refereegranskat)abstract
- The self-assembly of nanoparticles on substrates is relevant for a variety of applications such as plasmonics, sensing devices and nanometer-sized electronics. We investigate the deposition of 60 nm spherical Au nanoparticles onto silicon dioxide (SiO2) substrates by changing the chemical treatment of the substrate and by that altering the surface charge. The deposition is characterized by scanning electron microscopy (SEM). Kelvin probe force microscopy (KPFM) was used to characterize the surface workfunction. The underlying physics involved in the deposition of nanoparticles was described by a model based on Derjaguin–Landau–Verwey–Overbeek (DLVO) theory combined with random sequential adsorption (RSA). The spatial statistical method Ripley's K-function was used to verify the DLVO–RSA model (ERSA). The statistical results also showed that the adhered particles exhibit a short-range order at distances below ~300 nm. This method can be used in future research to predict the deposition densities of charged nanoparticles onto charged surfaces.
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| 10. |
- Fernandez, Yuri A. Diaz, 1978, et al.
(författare)
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Research Update: Progress in synthesis of nanoparticle dimers by self-assembly
- 2014
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Ingår i: APL Materials. - : AIP Publishing. - 2166-532X. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- This article highlights recent advances in the controlled self-assembly of nanoparticles to produce dimeric nanoparticle structures. The relevance of this emergent field is discussed in terms of recent applications in plasmonics and chemical catalysis. The concept of bond-valence applied to nanoparticles will be discussed, emphasizing some general approaches that have been successfully used to build these structures. Further, the asymmetric functionalization of nanoparticles surfaces as a path to drive selective aggregation, the use of biomolecules to self-assemble nanoparticles into dimers in solution, and the confinement of aggregates in small cavities are discussed.
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