| 1. |
- Bharmoria, Pankaj, et al.
(författare)
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Far-red triplet sensitized Z-to-E photoswitching of azobenzene in bioplastics
- 2022
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Ingår i: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 13, s. 11904-11911
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Tidskriftsartikel (refereegranskat)abstract
- We report the first example of direct far-red triplet sensitized molecular photoswitching in a condensed phase wherein a liquid azobenzene derivative (Azo1) co-assembled within a liquid surfactant-protein film undergoes triplet sensitized Z-to-E photoswitching upon far-red/red light excitation in air. The role of triplet sensitization in photoswitching has been confirmed by quenching of sensitizer phosphorescence by Z-Azo1 and temperature-dependent photoswitching experiments. Herein, we demonstrate new biosustainable fabrication designs to address key challenges in solid-state photoswitching, effectively mitigating chromophore aggregation and requirement of high energy excitations by dispersing the photoswitch in the trapped liquid inside the solid framework and by shifting the action spectrum from blue-green light (450-560 nm) to the far-red/red light (740/640 nm) region.
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| 2. |
- Bharmoria, Pankaj, 1985, et al.
(författare)
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Recyclable optical bioplastics platform for solid state red light harvesting via triplet-triplet annihilation photon upconversion
- 2022
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7496 .- 2050-7488. ; 10:40, s. 21279-21290
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Tidskriftsartikel (refereegranskat)abstract
- Sustainable photonics applications of solid-state triplet-triplet annihilation photon upconversion (TTA-UC) are limited by a small UC spectral window, low UC efficiency in air, and non-recyclability of polymeric materials used. In a step to overcome these issues, we have developed new recyclable TTA-UC bioplastics by encapsulating TTA-UC chromophores liquid inside the semicrystalline gelatin films showing broad-spectrum upconversion (red/far-red to blue) with high UC efficiency in air. For this, we synthesized a new anionic annihilator, sodium-TIPS-anthracene-2-sulfonate (TIPS-AnS), that combined with red/far-red sensitizers (PdTPBP/Os(m-peptpy)(2)(TFSI)(2)), a liquid surfactant Triton X-100 reduced (TXr) and protein gelatin (G) formed red/far-red to blue TTA-UC bioplastic films just by air drying of their aqueous solutions. The G-TXr-TIPS-AnS-PdTPBP film showed record red to blue (633 to 478 nm) TTA-UC quantum yield of 8.5% in air. The high UC quantum yield has been obtained due to the fluidity of dispersed TXr containing chromophores and oxygen blockage by gelatin fibers that allowed efficient diffusion of triplet excited chromophores. Further, the G-TXr-TIPS-AnS-Os(m-peptpy)(2)(TFSI)(2) bioplastic film displayed far-red to blue (700-730 nm to 478 nm) TTA-UC, demonstrating broad-spectrum photon harvesting. Finally, we demonstrated the recycling of G-TXr-TIPS-AnS-PdTPBP bioplastics by developing a downstream approach that gives new directions for designing future recyclable photonics bioplastic materials.
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| 3. |
- Ghasemi, Shima, 1993, et al.
(författare)
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Exploring the impact of select anchor groups for norbornadiene/quadricyclane single-molecule switches
- 2023
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Ingår i: Journal of Materials Chemistry C. - 2050-7534 .- 2050-7526. ; 11:44, s. 15379-15776
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Tidskriftsartikel (refereegranskat)abstract
- To achieve the ultimate limit of device miniaturization, it is necessary to have a comprehensive understanding of the structure–property relationship in functional molecular systems used in single-molecule electronics. This study reports the synthesis and characterization of a novel series of norbornadiene derivatives capped with thioether and thioester anchor groups. Utilizing the mechanically controllable break junction technique, the impact of these capping groups on conductance across single-molecule junctions is investigated. Among the selection of anchor groups, norbornadiene capped with thioacetate and tert-butyl groups exhibits higher conductance (G ≈ 4 × 10−4 G0) compared to methyl thioether (G ≈ 2 × 10−4 G0). Electronic transmission through the considered set of single-molecule junctions has been simulated. The computational results for electron transport across these junctions align closely with the experimental findings, with the thioacetate- and tert-butyl-substituted systems outperforming the methyl thioether-capped derivative. In terms of junction stability, the methyl thioether-capped system is the most resilient, maintaining consistent conductance even after approximately 10 000 cycles. Meanwhile, the likelihood of observing molecular plateaus in both the thioacetate- and tert-butyl-substituted systems declines over time. These findings substantially advance both the design and understanding of functional molecular systems in the realm of single-molecule electronics, particularly in the context of molecular photoswitches.
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| 4. |
- Ghasemi, Shima, 1993
(författare)
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Molecular photoswitches toward single-molecule electronics applications
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The drive towards miniaturization of electronic devices has sparked a growing interest in finding alternatives to conventional silicon-based technology. Over the years, molecular electronics has emerged as a promising avenue for the fabrication of electronic components with advanced functions. Incorporating organic molecules into electronic devices provides a new pathway to fabricate a wide range of devices with tailor-made properties. However, controlling the molecule-electrode interface in the junctions has been challenging. In this thesis, a series of photoswitches featuring the Norbornadiene-Quadricyclane (NBD-QC) systems have been studied for molecular electronics applications. NBDs terminated with various anchoring groups are synthesized, characterized and their properties for formation of reliable and reproducible junctions are investigated. The NBDs with thiol-substituted anchoring groups showed an improvement in the conductance values through the gold electrode | NBD | gold electrode junctions. The conductance of the molecular systems was investigated by using mechanically controllable break junction (MCBJ) and combined Raman / scanning tunnelling microscope break junction (STM-BJ) technique. Furthermore, a family of NBDs with amine-substituted anchoring groups was investigated for their switching properties in mCNT | NBD | mCNT (metallic carbon nanotubes) nanojunctions. The NBDs substituted with pyrene anchoring groups were found to be potential candidates for the formation of stable junctions with 2D materials such as graphene electrodes. Beyond NBD, this thesis also investigates the potential of azobenzene derivatives as efficient solid-state photoswitches with red-shifted action spectra via triplet-sensitization for low energy excitations to avoid heating effects in optoelectronics. Overall, this thesis reveals the molecular and optical properties of photoswitches and provides insight into how to apply these molecular systems in molecular electronics.
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| 5. |
- Ghasemi, Shima, 1993, et al.
(författare)
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Pyrene Functionalized Norbornadiene-Quadricyclane Fluorescent Photoswitches: Characterization of their Spectral Properties and Application in Imaging of Amyloid Beta Plaques
- 2024
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Ingår i: Chemistry - A European Journal. - 1521-3765 .- 0947-6539. ; 30:34
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Tidskriftsartikel (refereegranskat)abstract
- This study presents the synthesis and characterization of two fluorescent norbornadiene (NBD) photoswitches, each incorporating two conjugated pyrene units. Expanding on the limited repertoire of reported photoswitchable fluorescent NBDs, we explore their properties with a focus on applications in bioimaging of amyloid beta (Aβ) plaques. While the fluorescence emission of the NBD decreases upon photoisomerization, aligning with what has been previously reported, for the first time we observed luminescence after irradiation of the quadricyclane (QC) isomer. We deduce how the observed emission is induced by photoisomerization to the excited state of the parent isomer (NBD) which is then the emitting species. Thorough characterizations including NMR, UV-Vis, fluorescence, X-ray structural analysis and density functional theory (DFT) calculations provide a comprehensive understanding of these systems. Notably, one NBD-QC system exhibits exceptional durability. Additionally, these molecules serve as effective fluorescent stains targeting Aβ plaques in situ, with observed NBD/QC switching within the plaques. Molecular docking simulations explore NBD interactions with amyloid, unveiling novel binding modes. These insights mark a crucial advancement in the comprehension and design of future photochromic NBDs for bioimaging applications and beyond, emphasizing their potential in studying and addressing protein aggregates.
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| 6. |
- Ghasemi, Shima, 1993, et al.
(författare)
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Single molecule electronic devices with carbon-based materials: Status and opportunity
- 2021
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 13:2, s. 659-671
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Forskningsöversikt (refereegranskat)abstract
- The field of single molecule electronics has progressed remarkably in the past decades by allowing for more versatile molecular functions and improving device fabrication techniques. In particular, electrodes made from carbon-based materials such as graphene and carbon nanotubes (CNTs) may enable parallel fabrication of multiple single molecule devices. In this perspective, we review the recent progress in the field of single molecule electronics, with a focus on devices that utilizes carbon-based electrodes. The paper is structured in three main sections: (i) controlling the molecule/graphene electrode interface using covalent and non-covalent approaches, (ii) using CNTs as electrodes for fabricating single molecule devices, and (iii) a discussion of possible future directions employing new or emerging 2D materials. This journal is
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| 7. |
- Olesund, Axel, 1990, et al.
(författare)
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Approaching the Spin-Statistical Limit in Visible-to-Ultraviolet Photon Upconversion
- 2022
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 144:8, s. 3706-3716
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Tidskriftsartikel (refereegranskat)abstract
- Triplet-triplet annihilation photon upconversion (TTA-UC) is a process in which triplet excitons combine to form emissive singlets and holds great promise in biological applications and for improving the spectral match in solar energy conversion. While high TTA-UC quantum yields have been reported for, for example, red-to-green TTA-UC systems, there are only a few examples of visible-to-ultraviolet (UV) transformations in which the quantum yield reaches 10%. In this study, we investigate the performance of six annihilators when paired with the sensitizer 2,3,5,6-tetra(9H-carbazol-9-yl)benzonitrile (4CzBN), a purely organic compound that exhibits thermally activated delayed fluorescence. We report a record-setting internal TTA-UC quantum yield (φUC,g) of 16.8% (out of a 50% maximum) for 1,4-bis((triisopropylsilyl)ethynyl)naphthalene, demonstrating the first example of a visible-to-UV TTA-UC system approaching the classical spin-statistical limit of 20%. Three other annihilators, of which 2,5-diphenylfuran has never been used for TTA-UC previously, also showed impressive performances with φUC,g above 12%. In addition, a new method to determine the rate constant of TTA is proposed, in which only time-resolved emission measurements are needed, circumventing the need for more challenging transient absorption measurements. The results reported herein represent an important step toward highly efficient visible-to-UV TTA-UC systems that hold great potential for driving high-energy photochemical reactions.
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| 8. |
- Olesund, Axel, 1990, et al.
(författare)
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Bulky Substituents Promote Triplet-Triplet Annihilation Over Triplet Excimer Formation in Naphthalene Derivatives
- 2023
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Ingår i: Journal of the American Chemical Society. - 1520-5126 .- 0002-7863. ; 145:40, s. 22168-22175
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Tidskriftsartikel (refereegranskat)abstract
- Visible-to-ultraviolet (UV) triplet-triplet annihilation photochemical upconversion (TTA-UC) has gained a lot of attention recently due to its potential for driving demanding high-energy photoreactions using low-intensity visible light. The efficiency of this process has rapidly improved in the past few years, in part thanks to the recently discovered annihilator compound 1,4-bis((triisopropylsilyl)ethynyl)naphthalene (N-2TIPS). Despite its beneficial TTA-UC characteristics, the success of N-2TIPS in this context is not yet fully understood. In this work, we seek to elucidate what role the specific type and number of substituents in naphthalene annihilator compounds play to achieve the characteristics sought after for TTA-UC. We show that the type of substituent attached to the naphthalene core is crucial for its performance as an annihilator. More specifically, we argue that the choice of substituent dictates to what degree the sensitized triplets form excimer complexes with ground state annihilators of the same type, which is a process competing with that of TTA. The addition of more bulky substituents positively impacts the upconverting ability by impeding excimer formation on the triplet surface, an effect that is enhanced with the number of substituents. The presence of triplet excimers is confirmed from transient absorption measurements, and the excimer formation rate is quantified, showing several orders of magnitude differences between different derivatives. These insights will aid in the further development of annihilator compounds for solar energy applications for which the behavior at low incident powers is of particular significance.
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| 9. |
- Quant, Maria, 1985, et al.
(författare)
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Synthesis, characterization and computational evaluation of bicyclooctadienes towards molecular solar thermal energy storage
- 2022
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Ingår i: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6539 .- 2041-6520. ; 13:3, s. 834-841
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Tidskriftsartikel (refereegranskat)abstract
- Molecular solar-thermal energy storage (MOST) systems are based on photoswitches that reversibly convert solar energy into chemical energy. In this context, bicyclooctadienes (BODs) undergo a photoinduced transformation to the corresponding higher energy tetracyclooctanes (TCOs), but the photoswitch system has not until now been evaluated for MOST application, due to the short half-life of the TCO form and limited available synthetic methods. The BOD system degrades at higher temperature via a retro-Diels-Alder reaction, which complicates the synthesis of the compounds. We here report a cross-coupling reaction strategy that enables an efficient synthesis of a series of 4 new BOD compounds. We show that the BODs were able to switch to the corresponding tetracyclooctanes (TCOs) in a reversible way and can be cycled 645 times with only 0.01% degradation. Half-lives of the TCOs were measured, and we illustrate how the half-life could be engineered from seconds to minutes by molecular structure design. A density functional theory (DFT) based modelling framework was developed to access absorption spectra, thermal half-lives, and storage energies which were calculated to be 143-153 kJ mol(-1) (0.47-0.51 MJ kg(-1)), up to 76% higher than for the corresponding norbornadiene. The combined computational and experimental findings provide a reliable way of designing future BOD/TCO systems with tailored properties.
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| 10. |
- Wang, Zhihang, 1989, et al.
(författare)
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Hybrid solar energy device for simultaneous electric power generation and molecular solar thermal energy storage
- 2024
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Ingår i: Joule. - 2542-4351. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- The performance of photovoltaic (PV) solar cells can be adversely affected by the heat generated from solar irradiation. To address this issue, a hybrid device featuring a solar energy storage and cooling layer integrated with a silicon-based PV cell has been developed. This layer employs a molecular solar thermal (MOST) energy storage system to convert and store high-energy photons—typically underutilized by solar cells due to thermalization losses—into chemical energy. Simultaneously, it effectively cools the PV cell through both optical effects and thermal conductivity. Herein, it was demonstrated that up to 2.3% of solar energy could be stored as chemical energy. Additionally, the integration of the MOST system with the PV cell resulted in a notable decrease in the cell's surface temperature by approximately 8°C under standard solar irradiation conditions. The hybrid system demonstrated a solar utilization efficiency of 14.9%, underscoring its potential to achieve even greater efficiencies in forthcoming advanced hybrid PV solar energy systems.
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