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1.
Chem Commun (Camb) ; 56(53): 7217-7232, 2020 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-32495753

RESUMO

Dynamic nuclear polarization with photo-excited triplet electrons (triplet-DNP) has the potential to enhance the sensitivity of nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) at a moderate temperature. While many efforts have been devoted to achieving a large nuclear polarization based on triplet-DNP, the application of triplet-DNP has been limited to nuclear physics experiments. The recent introduction of materials chemistry into the field of triplet-DNP has achieved air-stable and water-soluble polarizing agents as well as the hyperpolarization of nanomaterials with a large surface area such as nanoporous metal-organic frameworks (MOFs) and nanocrystal dispersion in water. This Feature Article overviews the recently-emerged materials chemistry of triplet-DNP that paves new paths towards unprecedented biological and medical applications.

2.
Chem Commun (Camb) ; 56(51): 7017-7020, 2020 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-32441716

RESUMO

Upconverting near-infrared (NIR) light (λ > 700 nm) to violet light (λ < 450 nm) based on triplet-triplet annihilation (TTA) is achieved for the first time by developing a silyl-substituted anthracene violet emitter and its sensitization by an osmium complex showing a singlet-to-triplet (S-T) absorption in the NIR range.

4.
Chem Commun (Camb) ; 56(26): 3717-3720, 2020 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-32159544

RESUMO

Triplet dynamic nuclear polarization (triplet-DNP) allows hyperpolarization at a moderate temperature. While the triplet-DNP of water is strongly desired, water-soluble triplet polarizing agents have not yet been reported. Herein, the first example of triplet-DNP of crystalline ice is demonstrated by molecularly dispersing a novel water-soluble polarizing agent into ice.

5.
J Phys Chem B ; 124(15): 3137-3144, 2020 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-32203661

RESUMO

The use of task-specific chromophoric ionic liquids as energy transfer media in triplet-triplet annihilation photon upconversion (TTA-UC) processes has produced several examples of systems with signifficantly enhanced performances. In this work, we use molecular dynamics simulations to probe the relation between the nanostructure of chromophoric ionic liquids and their ability to achieve high TTA-UC quantum yields. The existing atomistic and systematic force fields commonly used to model different ionic liquids are extended to include substituted anthracene moieties, thus allowing the modeling of several chromophoric ionic liquids. The simulation results show that the polar network of the ionic liquids can orient the anthracene moieties within the nonpolar domains preventing direct contacts between them but allowing orientations at the optimal distance for triplet energy migration.

6.
Angew Chem Int Ed Engl ; 59(26): 10252-10264, 2020 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-32092207

RESUMO

The addition of stimuli-responsiveness to anti-Stokes emission provides a unique platform for biosensing and chemosensing. Particularly, stimuli-responsive photon upconversion based on triplet-triplet annihilation (TTA-UC) is promising due to its occurrence at low excitation intensity with high efficiency. This Minireview summarizes the recent developments of TTA-UC switching by external stimuli such as temperature, oxygen, chemicals, light, electric field, and mechanical force. For the systematic understanding of the underlying general mechanisms, the switching mechanisms are categorized into four types: 1) aggregation-induced UC; 2) assembly-induced air-stable UC; 3) diffusion-controlled UC; and 4) energy-transfer-controlled UC. The development of stimuli-responsive smart TTA-UC systems would enable sensing with unprecedented sensitivity and selectivity, and expand the scope of TTA-UC photochemistry by combination with supramolecular chemistry, materials chemistry, mechanochemistry, and biochemistry.

7.
J Phys Chem A ; 123(46): 10197-10203, 2019 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-31663744

RESUMO

For the consistent development of the field of photon upconversion via triplet-triplet annihilation (TTA-UC), it is pivotal to know the true quantum yield of TTA-UC emission. Although TTA-UC quantum yields have been determined by common relative measurements using quantum yield standards, there is still a discrepancy between the reported values even for the benchmark sensitizer-emitter pair of platinum(II) octaethylporphyrin (PtOEP) and 9,10-diphenylanthracene (DPA). Here, to resolve this situation, we show a method to obtain the absolute quantum yield of TTA-UC photoluminescence. The difficulty in obtaining absolute TTA-UC quantum yield by the integrating sphere measurement is to accurately calibrate the contribution of reabsorbed upconverted emission by triplet sensitizers. The reabsorption correction is successfully carried out by comparing sensitizer phosphorescence with and without the integrating sphere. An absolute TTA-UC quantum yield of the PtOEP-DPA pair is obtained as 36%, which shows a good agreement with the relative TTA-UC quantum yield. An absolute TTA-UC quantum yield of another red-to-blue TTA-UC pair, platinum(II) meso-tetraphenyltetrabenzoporphyrin (PtTPBP) and 2,5,8,11-tetra-tert-butylperylene (TTBP), is obtained as 27%. These absolute TTA-UC quantum yields can be used as certified values to check the measurement setup and sample condition for determining relative TTA-UC quantum yields in each laboratory.

8.
Angew Chem Int Ed Engl ; 58(49): 17827-17833, 2019 12 02.
Artigo em Inglês | MEDLINE | ID: mdl-31544993

RESUMO

Photon upconversion (UC) from near-infrared (NIR) light to visible light has enabled optogenetic manipulations in deep tissues. However, materials for NIR optogenetics have been limited to inorganic UC nanoparticles. Herein, NIR-light-triggered optogenetics using biocompatible, organic TTA-UC hydrogels is reported. To achieve triplet sensitization even in highly viscous hydrogel matrices, a NIR-absorbing complex is covalently linked with energy-pooling acceptor chromophores, which significantly elongates the donor triplet lifetime. The donor and acceptor are solubilized in hydrogels formed from biocompatible Pluronic F127 micelles, and heat treatment endows the excited triplets in the hydrogel with remarkable oxygen tolerance. Combined with photoactivatable Cre recombinase technology, NIR-light stimulation successfully performs genome engineering resulting in the formation of dendritic-spine-like structures of hippocampal neurons.

9.
ACS Appl Mater Interfaces ; 11(30): 26571-26580, 2019 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-31274281

RESUMO

A recyclable, aqueous phase functioning and biocompatible photon upconverting system is developed. Hollow mesoporous silica microcapsules (HMSMs) with ordered radial mesochannels were employed, for the first time, as vehicles for the post-encapsulation of oil phase triplet-triplet annihilation upconversion (TTA-UC), with the capability of homogeneous suspension in water. In-depth characterization of such upconverting oil-laden HMSMs (UC-HMSMs) showed that the mesoporous silica shells reversibly stabilized the encapsulated UC oil in water to allow efficient upconverted emission, even under aerated conditions. In addition, the UC-HMSMs were found to actively bind to the surface of human mesenchymal stem cells without significant cytotoxicity and displayed upconverted bright blue emission under 640 nm excitation, indicating a potential of our new TTA-UC system in biophotonic applications. These findings reveal the great promise of UC-HMSMs to serve as ideal vehicles not only for ultralow-power in vivo imaging but also for stem cell labeling, to facilitate the tracking of tumor cells in animal models.


Assuntos
Materiais Biocompatíveis/química , Cápsulas/química , Animais , Sistemas de Liberação de Medicamentos , Humanos , Imagem Molecular/métodos , Fótons , Dióxido de Silício/química , Água/química
10.
Phys Chem Chem Phys ; 21(30): 16408-16412, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31282507

RESUMO

While dynamic nuclear polarization using photo-excited triplet electrons (triplet-DNP) can improve the sensitivity of nuclear magnetic resonance at room temperature, it has not been carried out in water. Here, we report the first example of triplet-DNP in water by downsizing the conventional bulk crystals to nanocrystals.

11.
J Phys Chem Lett ; 10(9): 2208-2213, 2019 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-30933529

RESUMO

Triplet dynamic nuclear polarization (triplet-DNP), a method to enhance nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) sensitivity using photoexcited triplet electrons, has great potential to hyperpolarize nuclear spins at room temperature. Since the first report of room-temperature triplet-DNP in 1990, pentacene has been the only and best option of triplet polarizing agent. However, the poor air stability of pentacene has severely limited the applicability of triplet-DNP. We report the first example of polarizing agents with significant air stability as well as high polarizing ability comparable to pentacene. The introduction of electron-withdrawing diaza-substitution to pentacene and tetracene reduces the lowest unoccupied molecular orbital level and endows much improved stability under the ambient conditions. Importantly, the diaza-substituted pentacene and tetracene offer similar, or even slightly better, 1H NMR signal enhancement compared with pentacene in the prototypical triplet-DNP test using p-terphenyl crystals. This work removes one of the largest obstacles toward the application of triplet-DNP for the hyperpolarization of biological molecules.

12.
Gels ; 5(1)2019 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-30917611

RESUMO

Recent progress in the development of gels showing triplet-triplet annihilation based photon upconversion (TTA-UC) is reviewed. Among the two families of upconverting gels reported, those display TTA-UC based on molecular diffusion show performances comparable to those in solutions, and the TTA-UC therein are affected by dissolved molecular oxygen. Meanwhile, air-stable TTA-UC is achieved in organogels and hydrogels by suitably accumulating TTA-UC chromophores which are stabilized by hydrogen bonding networks of the gelators. The unique feature of the air-stable upconverting gels is that the self-assembled nanostructures are protected from molecular oxygen dissolved in the microscopically interconnected solution phase. The presence of the bicontinuous structures formed by the upconverting fibrous nanoassemblies and the solution phase is utilized to design photochemical reaction systems induced by TTA-UC. Future challenges include in vivo applications of hydrogels showing near infrared-to-visible TTA-UC.

13.
Chemistry ; 25(24): 6124-6130, 2019 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-30714218

RESUMO

A common challenge in chemistry that deals with photoexcited states is to avoid oxygen quenching. This is crucial for hot research fields such as photon upconversion (UC), in which oxygen-sensitive triplet excited states play pivotal roles. However, methods to avoid oxygen quenching in aqueous media are far more limited despite eagerly anticipated catalytic and biological applications. This work introduces a simple strategy to achieve air-stable triplet-triplet annihilation (TTA)-based UC in water, namely, supramolecular crowding. Amphiphilic cationic acceptor molecules and anions with long alkyl chains co-assemble in water in which hydrophobic donor molecules are molecularly dispersed. Despite the common notion that oxygen molecules diffuse readily across hydrophobic domains in water, more than 80 % of the TTA-UC emission of the obtained hydrophobic co-assemblies is maintained in air-saturated water. This work demonstrates the new promising potential of supramolecular chemistry for photophysical and photochemical functions with oxygen-sensitive species.

14.
Chem Asian J ; 14(10): 1723-1728, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-30600914

RESUMO

Molecular self-assembly is a powerful means to construct nanoscale materials with advanced photophysical properties. Although the protection of the photo-excited states from oxygen quenching is a critical issue, it still has been in an early phase of development. In this work, we demonstrate that a simple and typical molecular design for aqueous supramolecular assembly, modification of the chromophoric unit with hydrophilic oligo(ethylene glycol) chains and hydrophobic alkyl chains, is effective to avoid oxygen quenching of triplet-triplet annihilation-based photon upconversion (TTA-UC). While a TTA-UC emission is completely quenched when the donor and acceptor are molecularly dispersed in chloroform, their aqueous co-assemblies exhibit a clear upconverted emission in air-saturated water even under extremely low chromophore concentrations down to 40 µm. The generalization of this nano-encapsulation approach offers new functions and applications using oxygen-sensitive species for supramolecular chemistry.

15.
J Am Chem Soc ; 140(46): 15606-15610, 2018 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-30403476

RESUMO

While dynamic nuclear polarization based on photoexcited triplet electrons (triplet-DNP) has the potential to hyperpolarize nuclear spins of target substrates in the low magnetic field at room temperature, there has been no triplet-DNP system offering structural rigidity and substrate accessibility. Here, we report the first example of triplet-DNP of nanoporous metal-organic frameworks. Accommodation of a carboxylate-modified pentacene derivative in a partially deuterated ZIF-8 (D-ZIF-8) results in a clear 1H NMR signal enhancement over thermal equilibrium.

16.
J Phys Chem Lett ; 9(22): 6399-6403, 2018 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-30362354

RESUMO

The monodisperse pore structure of MOFs (metal-organic frameworks) is advantageous for investigating how porosity influences diffusion. Here we report translational and rotational diffusion using fluorescence correlation spectroscopy and time-correlated single-photon counting, using the three-dimensional pores of the zeolitic-like metal-organic framework family. We compare the influence of size and electric charge as well as dependence on pore size that we controlled through postsynthetic cation-exchange modifications. Charge-charge interactions with the MOF appeared to produce transient adsorption, manifested as a relatively fast and a slower diffusion process, but diffusants without net electric charge displayed a single diffusion process. Obtained from this family of guest molecules selected to be fluorescent, these findings suggest potentially useful general design rules to predict how pore size, guest size, and host-guest interaction control guest mobility within nanopores. With striking fidelity, diffusion coefficient scales with the ratio of cross-sectional areas of diffusant and host pores when charge is taken into account.

17.
J Am Chem Soc ; 140(34): 10848-10855, 2018 08 29.
Artigo em Inglês | MEDLINE | ID: mdl-30052038

RESUMO

Exploration of triplet-triplet annihilation based photon upconversion (TTA-UC) in aqueous environments faces difficulty such as chromophores insolubility and deactivation of excited triplets by dissolved oxygen molecules. We propose a new strategy of biopolymer-surfactant-chromophore coassembly to overcome these issues. Air-stable TTA-UC with a high upconversion efficiency of 13.5% was achieved in hydrogel coassembled from gelatin, Triton X-100 and upconverting chromophores (triplet sensitizer and emitter). This is comparable to the highest UC efficiency observed to date for air-saturated aqueous UC systems. Moreover, this is the first example of air-stable TTA-UC in the form of hydrogels, widening the applicability of TTA-UC in biological applications. The keys are two-fold. First, gelatin and the surfactant self-assemble in water to give a developed hierarchical structure with hydrophobic domains which accommodate chromophores up to high concentrations. Second, thick hydrogen-bonding networks of gelatin backbone prevent O2 inflow to the hydrophobic interior, as evidenced by long acceptor triplet lifetime of 4.9 ms. Air-stable TTA-UC was also achieved for gelatin with other nonionic surfactants (Tween 80 and Pluronic f127) and Triton X-100 with other gelling biopolymers (sodium alginate and agarose), demonstrating the versatility of current strategy.

18.
J Phys Chem Lett ; 9(16): 4613-4624, 2018 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-30059619

RESUMO

Triplet-triplet annihilation-based photon upconversion (TTA-UC) is a process wherein longer-wavelength light (lower-energy photons) is converted into shorter-wavelength light (higher-energy photons) under low excitation intensity in multichromophore systems. There have been many reports on highly efficient TTA-UC in solution; however, significant challenges remain in the development of solid-state upconverters in order to explore real-world applications. In this Perspective, we discuss the advantages and challenges of different approaches for TTA-UC in solvent-free solid systems. We consider that the energy migration-based TTA-UC has the potential to achieve ideal materials with high UC efficiency at weak solar irradiance. While the UC performance of such systems is still limited at this moment, we introduce recently developed important concepts to improve it, including kinetic/thermodynamic donor dispersion in acceptor assemblies, defectless crystals, and triplet-singlet dual energy migration. Future integration of these concepts into a single material would realize the ideal TTA-UC system.

19.
J Am Chem Soc ; 140(28): 8788-8796, 2018 07 18.
Artigo em Inglês | MEDLINE | ID: mdl-29940103

RESUMO

It is pivotal to achieve efficient triplet-triplet annihilation based photon upconversion (TTA-UC) in the solid-state for enhancing potentials of renewable energy production devices. However, the UC efficiency of solid materials is largely limited by low fluorescence quantum yields that originate from the aggregation of TTA-UC chromophores and also by severe back energy transfer from the acceptor singlet state to the singlet state of the triplet donor in the condensed state. In this work, to overcome these issues, we introduce a highly fluorescent singlet energy collector as the third component of donor-doped acceptor crystalline films, in which dual energy migration, i.e., triplet energy migration for TTA-UC and succeeding singlet energy migration for transferring energy to a collector, takes place. To demonstrate this scheme, a highly fluorescent singlet energy collector was added as the third component of donor-doped acceptor crystalline films. An anthracene-based acceptor containing alkyl chains and a carboxylic moiety is mixed with the triplet donor Pt(II) octaethylporphyrin (PtOEP) and the energy collector 2,5,8,11-tetra- tert-butylperylene (TTBP) in solution, and simple spin-coating of the mixed solution gives acceptor films of nanofibrous crystals homogeneously doped with PtOEP and TTBP. Interestingly, delocalized singlet excitons in acceptor crystals are found to diffuse effectively over the distance of ∼37 nm. Thanks to this high diffusivity, only 0.5 mol % of doped TTBP can harvest most of the singlet excitons, which successfully doubles the solid-state fluorescent quantum yield of acceptor/TTBP blend films to 76%. Furthermore, since the donor PtOEP and the collector TTBP are separately isolated in the nanofibrous acceptor crystals, the singlet back energy transfer from the collector to the donor is effectively avoided. Such efficient singlet energy collection and inhibited back energy transfer processes result in a large increase of UC efficiency up to 9.0%, offering rational design principles toward ultimately efficient solid-state upconverters.

20.
J Org Chem ; 83(15): 7928-7938, 2018 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-29808679

RESUMO

In this work, we demonstrate that useful C-C bond-forming photoredox catalysis can be performed in air using easily prepared gel networks as reaction media to give similar results as are obtained under inert atmosphere conditions. These reactions are completely inhibited in homogeneous solution in air. However, the supramolecular fibrillar gel networks confine the reactants and block oxygen diffusion, allowing air-sensitive catalytic activity under ambient conditions. We investigate the mechanism of this remarkable protection, focusing on the boundary effect in the self-assembled supramolecular gels that enhances the rates of productive reactions over diffusion-controlled quenching of excited states. Our observations suggest the occurrence of triplet-sensitized chemical reactions in the gel networks within the compartmentalized solvent pools held between the nanofibers. The combination of enhanced viscosity and added interfaces in supramolecular gel media seems to be a key factor in facilitating the reactions under aerobic conditions.

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