The initial steps of photosynthesis comprise the absorption of sunlight by pigment-protein antenna complexes followed by rapid and highly efficient funneling of excitation energy to a reaction ...center. In these transport processes, signatures of unexpectedly long-lived coherences have emerged in two-dimensional ensemble spectra of various light-harvesting complexes. Here, we demonstrate ultrafast quantum coherent energy transfer within individual antenna complexes of a purple bacterium under physiological conditions. We find that quantum coherences between electronically coupled energy eigenstates persist at least 400 femtoseconds and that distinct energy-transfer pathways that change with time can be identified in each complex. Our data suggest that long-lived quantum coherence renders energy transfer in photosynthetic systems robust in the presence of disorder, which is a prerequisite for efficient light harvesting.
Two-photon polymerization (TPP) is capable of fabricating 3D structures with dimensions from sub-µm to a few hundred µm. As a direct laser writing (DLW) process, fabrication time of 3D TPP structures ...scale with the third order, limiting its use in large volume fabrication. Here, we report on a scalable fabrication method that cuts fabrication time to a fraction. A parallelized 9 multi-beamlets DLW process, created by a fixed diffraction optical element (DOE) and subsequent stitching are used to fabricate large periodic high aspect ratio 3D microstructured arrays with sub-micron features spanning several hundred of µm
. The wall structure in the array is designed with a minimum of traced lines and is created by a low numerical aperture (NA) microscope objective, leading to self-supporting lines omitting the need for line-hatching. The fabricated periodic arrays are applied in a cell - 3D microstructure interaction study using living HeLa cells. First indications of increased cell proliferation in the presence of 3D microstructures compared to planar surfaces are obtained. Furthermore, the cells adopt an elongated morphology when attached to the 3D microstructured surfaces. Both results constitute promising findings rendering the 3D microstructures a suited tool for cell interaction experiments, e.g. for cell migration, separation or even tissue engineering studies.
Accelerating optical beams exhibit exotic features, such as nondiffractive propagation, self-acceleration, and self-healing, which have led their use in a wide range of photonics applications. ...However, spatial light modulator-based generators of such beams suffer from narrow operational bandwidth, high cost, low diffraction efficiency, and limited integration capability. Although recent metasurface-based approaches have yielded generators with significantly improved bandwidths and integration capacities, the resultant devices usually have ultrashort working distances and limited control over characteristic beam parameters, which decreases their utility in optical imaging and manipulation applications. Herein, we describe a synthetic-phase metasurface-based approach that overcomes these problems and increases the degrees of freedom to enable effective control of beam parameters by integrating a cubic phase profile and the phase of a Fresnel holographic lens into a single metasurface. We demonstrate this approach by using the synthetic metasurface to generate a series of Airy beams with controllable focal length (i.e., working distance), narrowed beam width, and extended propagation distance. Crucially, these beam parameters are fully adjustable, which makes these focal-length-modifiable Airy beams particularly appealing for use in high-resolution, large field-of-view imaging, and deep-penetration optical manipulation. Furthermore, we show that imposing the phase of a Dammann grating into a synthetic metasurface generates a 1 × 4 array of Airy beams that exhibit the aforementioned optical properties. These findings suggest that synthetic-phase metasurfaces may significantly broaden the application of accelerating optical beams in various fields, such as light-sheet microscopy, super-resolution stochastic optical-reconstruction microscopy, laser fabrication, and parallel processing and in the development of optical tweezers for use with live samples.
Nanothermometry methods with intracellular sensitivities have the potential to make important contributions to fundamental cell biology and medical fields, as temperature is a relevant physical ...parameter for molecular reactions to occur inside the cells and changes of local temperature are well identified therapeutic strategies. Here we show how the GFP can be used to assess temperature-based on a novel fluorescence peak fraction method. Further, we use standard GFP transfection reagents to assess temperature intracellularly in HeLa cells expressing GFP in the mitochondria. High thermal resolution and sensitivity of around 0.26% °C
and 2.5% °C
, were achieved for wt-GFP in solution and emGFP-Mito within the cell, respectively. We demonstrate that the GFP-based nanothermometer is suited to directly follow the temperature changes induced by a chemical uncoupler reagent that acts on the mitochondria. The spatial resolution allows distinguishing local heating variations within the different cellular compartments. Our discovery may lead to establishing intracellular nanothermometry as a standard method applicable to the wide range of live cells able to express GFP.
Ultrafast dynamics of single molecules Brinks, Daan; Hildner, Richard; van Dijk, Erik M. H. P ...
Chemical Society reviews,
04/2014, Letnik:
43, Številka:
8
Journal Article
Recenzirano
Odprti dostop
The detection of individual molecules has found widespread application in molecular biology, photochemistry, polymer chemistry, quantum optics and super-resolution microscopy. Tracking of an ...individual molecule in time has allowed identifying discrete molecular photodynamic steps, action of molecular motors, protein folding, diffusion,
etc.
down to the picosecond level. However, methods to study the ultrafast electronic and vibrational molecular dynamics at the level of individual molecules have emerged only recently. In this review we present several examples of femtosecond single molecule spectroscopy. Starting with basic pump-probe spectroscopy in a confocal detection scheme, we move towards deterministic coherent control approaches using pulse shapers and ultra-broad band laser systems. We present the detection of both electronic and vibrational femtosecond dynamics of individual fluorophores at room temperature, showing electronic (de)coherence, vibrational wavepacket interference and quantum control. Finally, two colour phase shaping applied to photosynthetic light-harvesting complexes is presented, which allows investigation of the persistent coherence in photosynthetic complexes under physiological conditions at the level of individual complexes.
Room-temperature studies of single molecules at femtosecond timescales provide detailed observation and control of ultrafast electronic and vibrational dynamics of organic dyes and photosynthetic complexes, probing quantum dynamics at ambient conditions and elucidating its role in chemistry and biology.
The control of quantum dot (QD) photoluminescence (PL) is a challenge for many applications. It is well known that plasmonic resonances can enhance this PL. In this work, we couple QDs with silver ...nanoparticles and immerse the system in a photochromic organic material. As these molecules are optical switches going from a transparent to a colored isomer by absorbing UV light, we observe on one hand a Förster Resonant Energy Transfer (FRET) between the QD emission and the absorbing isomer and on the other hand a plasmonic PL enhancement. The photochromic transition leads to the optical control of the FRET, allowing us to control the QD de-excitation preferences (radiative or non-radiative) and so the emitted light.
Influencing proteins: A protein multichromophore system (photosystem I) is exposed to gold nanoparticles (NPs) and silver island films. In the presence of these nanostructures an altered fluorescence ...response of the chromophores is observed (see scheme), indicating a change in the protein function. A model to understand these plasmonic effects is generally applicable to other multichromophore systems.
This work reports on high extraction efficiency in subwavelength GaAs/AlGaAs semiconductor nanopillars. We achieve up to 37-fold enhancement of the photoluminescence (PL) intensity from ...sub-micrometer (sub-µm) pillars without requiring back reflectors, high- Q dielectric cavities, nor large 2D arrays or plasmonic effects. This is a result of a large extraction efficiency for nanopillars <500 nm width, estimated in the range of 33-57%, which is much larger than the typical low efficiency (∼2%) of micrometer pillars limited by total internal reflection. Time-resolved PL measurements allow us to estimate the nonradiative surface recombination of fabricated pillars. We conclusively show that vertical-emitting nanopillar-based LEDs, in the best case scenario of both reduced surface recombination and efficient light out-coupling, have the potential to achieve notable large external quantum efficiency (∼45%), whereas the efficiency of large µm-pillar planar LEDs, without further methods, saturates at ∼2%. These results offer a versatile method of light management in nanostructures with prospects to improve the performance of optoelectronic devices including nanoscale LEDs, nanolasers, single photon sources, photodetectors, and solar cells.
Organ-on-chips and scaffolds for tissue engineering are vital assay tools for pre-clinical testing and prediction of human response to drugs and toxins, while providing an ethical sound replacement ...for animal testing. A success criterion for these models is the ability to have structural parameters for optimized performance. Here we show that two-photon polymerization fabrication can create 3D test platforms, where scaffold parameters can be directly analyzed by their effects on cell growth and movement. We design and fabricate a 3D grid structure, consisting of wall structures with niches of various dimensions for probing cell attachment and movement, while providing easy access for fluorescence imaging. The 3D structures are fabricated from bio-compatible polymer SZ2080 and subsequently seeded with A549 lung epithelia cells. The seeded structures are imaged with confocal microscopy, where spectral imaging with linear unmixing is used to separate auto-fluorescence scaffold contribution from the cell fluorescence. The volume of cellular material present in different sections of the structures is analyzed, to study the influence of structural parameters on cell distribution. Furthermore, time-lapse studies are performed to map the relation between scaffold parameters and cell movement. In the future, this kind of differentiated 3D growth platform, could be applied for optimized culture growth, cell differentiation, and advanced cell therapies.
This work employs spectral and spectral-temporal Photoluminescence (PL) spectroscopy techniques to study the radiative mechanisms in colloidal CdSe/ZnS Quantum Dot (QD) thin films without and with 1% ...PMMA polymer matrix embedding (QD
). The observed bimodal transient-spectral PL distributions reveal bandgap transitions and radiative recombinations after interdot electron transfer. The PMMA polymer embedding protects the QDs during the plasma-sputtering of inorganic layers electroluminescent (EL) devices, with minimal impact on the charge transfer properties. Further, a novel TiO
-based, all-electron bandgap, AC-driven QLED architecture is fabricated, yielding a surprisingly low turn-on voltage, with PL-identical and narrow-band EL emission. The symmetric TiO
bilayer architecture is a promising test platform for alternative optical active materials.
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