| 11. |
- Pekkari, Anna, 1989, et al.
(författare)
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Continuous Microfluidic Synthesis of Pd Nanocubes and PdPt Core–Shell Nanoparticles and Their Catalysis of NO2 Reduction
- 2019
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Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 11:39, s. 36196-36204
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Tidskriftsartikel (refereegranskat)abstract
- Faceted colloidal nanoparticles are currently of immense interest due to their unique electronic, optical, and catalytic properties. However, continuous flow synthesis that enables rapid formation of faceted nanoparticles of single or multi-elemental composition is not trivial. We present a continuous flow synthesis route for the synthesis of uniformly sized Pd nanocubes and PdPt core-shell nanoparticles in a single-phase microfluidic reactor, which enables rapid formation of shaped nanoparticles with a reaction time of 3 min. The PdPt core-shell nanoparticles feature a dendritic, high surface area with the Pt shell covering the Pd core, as verified using high-resolution scanning transmission electron microscopy and energy dispersive X-ray spectroscopy. The Pd nanocubes and PdPt core-shell particles are catalytically tested during NO2 reduction in the presence of H2 in a flow pocket reactor. The Pd nanocubes exhibited low-temperature activity (i.e., <136 °C) and poor selectivity performance toward production of N2O or N2, whereas PdPt core-shell nanoparticles showed higher activity and were found to achieve better selectivity during NO2 reduction retaining its basic structure at relatively elevated temperatures, making the PdPt core-shell particles a unique, desirable synergic catalyst material for potential use in NOx abatement processes.
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| 12. |
- Quant, Maria, 1985, et al.
(författare)
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Low Molecular Weight Norbornadiene Derivatives for Molecular Solar-Thermal Energy Storage
- 2016
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Ingår i: Chemistry - A European Journal. - : Wiley. - 1521-3765 .- 0947-6539. ; 22:37, s. 13265-13274
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Tidskriftsartikel (refereegranskat)abstract
- Molecular solar-thermal energy storage systems are based on molecular switches that reversibly convert solar energy into chemical energy. Herein, we report the synthesis, characterization, and computational evaluation of a series of low molecular weight (193-260 g mol(-1)) norbornadiene-quadricyclane systems. The molecules feature cyano acceptor and ethynyl-substituted aromatic donor groups, leading to a good match with solar irradiation, quantitative photo-thermal conversion between the norbornadiene and quadricyclane, as well as high energy storage densities (396-629 kJ kg(-1)). The spectroscopic properties and energy storage capability have been further evaluated through density functional theory calculations, which indicate that the ethynyl moiety plays a critical role in obtaining the high oscillator strengths seen for these molecules.
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| 13. |
- Quant, Maria, 1985, et al.
(författare)
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Solvent effects on the absorption profile, kinetic stability, and photoisomerization process of the norbornadiene-quadricyclanes system
- 2019
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 123:12, s. 7081-7087
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Tidskriftsartikel (refereegranskat)abstract
- Molecular photoswitches based on the norbornadiene-quadricyclane (NBD-QC) couple can be used to store solar energy and to release the stored energy as heat on demand. In this context, the energy storage time as well as the quantum yield of the energy storing reaction are important parameters. Here, we explore for the first time solvent effects on these processes for a series of four NBD-QC compounds in four different solvents with different polarity (acetonitrile, tetrahydrofuran, toluene, and hexane). We show that the energy storage time of the QC forms can vary by up to a factor of 2 when going from the most to the least polar solvent. Moreover, we show that for the norbornadiene derivatives with an asymmetric 1,2 substitution pattern, the quantum yield of conversion is highly solvent dependent, whereas this is not the case for the symmetrically substituted compounds. The spectroscopic observations are further rationalized using classical molecular dynamics (MD) simulations and time-dependent density functional theory (TDDFT) calculations. These demonstrate the importance of vibrational and rotational excitations for obtaining broad-band absorption, which is a prerequisite for capturing a wide range of the solar spectrum.
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| 14. |
- Aissaoui, Nesrine, 1983, et al.
(författare)
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FRET enhancement close to gold nanoparticles positioned in DNA origami constructs
- 2017
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Ingår i: Nanoscale. - Cambridge, United Kingdom : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 9:2, s. 673-683
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Tidskriftsartikel (refereegranskat)abstract
- Here we investigate the energy transfer rates of a Förster resonance energy transfer (FRET) pair positioned in close proximity to a 5 nm gold nanoparticle (AuNP) on a DNA origami construct. We study the distance dependence of the FRET rate by varying the location of the donor molecule, D, relative to the AuNP while maintaining a fixed location of the acceptor molecule, A. The presence of the AuNP induces an alteration in the spontaneous emission of the donor (including radiative and non-radiative rates) which is strongly dependent on the distance between the donor and AuNP surface. Simultaneously, the energy transfer rates are enhanced at shorter D-A (and D-AuNP) distances. Overall, in addition to the direct influence of the acceptor and AuNP on the donor decay there is also a significant increase in decay rate not explained by the sum of the two interactions. This leads to enhanced energy transfer between donor and acceptor in the presence of a 5 nm AuNP. We also demonstrate that the transfer rate in the three "particle" geometry (D + A + AuNP) depends approximately linearly on the transfer rate in the donor-AuNP system, suggesting the possibility to control FRET process with electric field induced by 5 nm AuNPs close to the donor fluorophore. It is concluded that DNA origami is a very versatile platform for studying interactions between molecules and plasmonic nanoparticles in general and FRET enhancement in particular.
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| 15. |
- 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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| 16. |
- Börjesson, Karl, 1982, et al.
(författare)
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Photon upconversion with directed emission
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Photon upconversion has the potential to increase the efficiency of single bandgap solar cells beyond the Shockley Queisser limit. Efficient light management is an important point in this context. Here we demonstrate that the direction of upconverted emission can be controlled in a reversible way, by embedding anthracene derivatives together with palladium porphyrin in a liquid crystalline matrix. The system is employed in a triplet-triplet annihilation photon upconversion scheme demonstrating controlled switching of directional anti Stokes emission. Using this approach an emission ratio of 0.37 between the axial and longitudinal emission directions and a directivity of 1.52 is achieved, reasonably close to the theoretical maximal value of 2 obtained from a perfectly oriented sample. The system can be switched for multiple cycles without any visible degradation and the speed of switching is only limited by the intrinsic rate of alignment of the liquid crystalline matrix.
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| 17. |
- 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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| 18. |
- Dreos, Ambra, 1987, et al.
(författare)
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Exploring the potential of a hybrid device combining solar water heating and molecular solar thermal energy storage
- 2017
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 10:3, s. 728-734
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Tidskriftsartikel (refereegranskat)abstract
- A hybrid solar energy system consisting of a molecular solar thermal energy storage system (MOST) combined with a solar water heating system (SWH) is presented. The MOST chemical energy storage system is based on norbornadiene- quadricyclane derivatives allowing for conversion of solar energy into stored chemical energy at up to 103 kJ mol(-1) (396 kJ kg(-1)). It is demonstrated that 1.1% of incoming solar energy can be stored in the chemical system without significantly compromising the efficiency of the solar water heating system, leading to efficiencies of combined solar water heating and solar energy storage of up to 80%. Moreover, prospects for future improvement and possible applications are discussed.
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| 19. |
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| 20. |
- Dreos, Ambra, 1987, et al.
(författare)
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Three-Input Molecular Keypad Lock Based on a Norbornadiene-Quadricyclane Photoswitch
- 2018
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 9:21, s. 6174-6178
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Tidskriftsartikel (refereegranskat)abstract
- Copyright © 2018 American Chemical Society. The photo- and acidochromic properties of a new generation norbornadiene derivative have been harnessed for the realization of a three-input keypad lock, where a specific sequence of inputs induces a unique output. Reversible quadricyclane/norbornadiene photoisomerization is reported, and this rare feature allows the first example of a norbornadiene-based molecular logic system. The function of this system is clearly rationalized in terms of the interconversion scheme and the absorption spectra of the involved species.
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