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Chemical Science Jun 2024Study of alternating DNA GC sequences by different time-resolved spectroscopies has provided fundamental information on the interaction between UV light and DNA, a...
Study of alternating DNA GC sequences by different time-resolved spectroscopies has provided fundamental information on the interaction between UV light and DNA, a process of great biological importance. Multiple decay paths have been identified, but their interplay is still poorly understood. Here, we characterize the photophysics of GC-DNA by integrating different computational approaches, to study molecular models including up to 6 bases described at a full quantum mechanical level. Quantum dynamical simulations, exploiting a nonadiabatic linear vibronic coupling (LVC) model, coupled with molecular dynamics sampling of the initial structures of a (GC) DNA duplex, provide new insights into the photophysics in the sub-picosecond time-regime. They indicate a substantial population transfer, within 50 fs, from the spectroscopic states towards G → C charge transfer states involving two stacked bases (CT), thus explaining the ultrafast disappearance of fluorescence. This picture is consistent with that provided by quantum mechanical geometry optimizations, using time dependent-density functional theory and a polarizable continuum model, which we use to parametrize the LVC model and to map the main excited state deactivation pathways. For the first time, the infrared and excited state absorption signatures of the various states along these pathways are comprehensively mapped. The computational models suggest that the main deactivation pathways, which, according to experiment, lead to ground state recovery on the 10-50 ps time scale, involve CT followed by interstrand proton transfer from the neutral G to C. Our calculations indicate that CT is populated to a larger extent and more rapidly in GC than in CG steps and suggest the likely involvement of monomer-like and interstrand charge transfer decay routes for isolated and less stacked CG steps. These findings underscore the importance of the DNA sequence and thermal fluctuations for the dynamics. They will also aid the interpretation of experimental results on other sequences.
PubMed: 38939156
DOI: 10.1039/d4sc00910j -
ACS Nano Jun 2024Rapid hot-carrier/exciton cooling constitutes a major loss channel for photovoltaic efficiency. How to decelerate the hot-carrier/exciton relaxation remains a crux for...
Rapid hot-carrier/exciton cooling constitutes a major loss channel for photovoltaic efficiency. How to decelerate the hot-carrier/exciton relaxation remains a crux for achieving high-performance photovoltaic devices. Here, we demonstrate slow hot-exciton cooling that can be extended to hundreds of picoseconds in colloidal HgTe quantum dots (QDs). The energy loss rate is 1 order of magnitude smaller than bulk inorganic semiconductors, mediated by phonon bottleneck and interband biexciton Auger recombination (BAR) effects, which are both augmented at reduced QD sizes. The two effects are competitive with the emergence of multiple exciton generation. Intriguingly, BAR dominates even under low excitation fluences with a decrease in interparticle distance. Both experimental evidence and numerical evidence reveal that such efficient BAR derives from the tunneling-mediated interparticle excitonic coupling induced by wave function overlap between neighboring HgTe QDs in films. Thus, our study unveils the potential for realizing efficient hot-carrier/exciton solar cells based on HgTe QDs. Fundamentally, we reveal that the delocalized nature of quantum-confined wave function intensifies BAR. The interparticle excitonic coupling may cast light on the development of next-generation photoelectronic materials, which can retain the size-tunable confinement of colloidal semiconductor QDs while simultaneously maintaining high mobilities and conductivities typical for bulk semiconductor materials.
PubMed: 38935537
DOI: 10.1021/acsnano.4c05061 -
Nature Jun 2024Titanium:sapphire (Ti:sapphire) lasers have been essential for advancing fundamental research and technological applications, including the development of the optical...
Titanium:sapphire (Ti:sapphire) lasers have been essential for advancing fundamental research and technological applications, including the development of the optical frequency comb, two-photon microscopy and experimental quantum optics. Ti:sapphire lasers are unmatched in bandwidth and tuning range, yet their use is restricted because of their large size, cost and need for high optical pump powers. Here we demonstrate a monocrystalline titanium:sapphire-on-insulator (Ti:SaOI) photonics platform that enables dramatic miniaturization, cost reduction and scalability of Ti:sapphire technology. First, through the fabrication of low-loss whispering-gallery-mode resonators, we realize a Ti:sapphire laser operating with an ultralow, sub-milliwatt lasing threshold. Then, through orders-of-magnitude improvement in mode confinement in Ti:SaOI waveguides, we realize an integrated solid-state (that is, non-semiconductor) optical amplifier operating below 1 μm. We demonstrate unprecedented distortion-free amplification of picosecond pulses to peak powers reaching 1.0 kW. Finally, we demonstrate a tunable integrated Ti:sapphire laser, which can be pumped with low-cost, miniature, off-the-shelf green laser diodes. This opens the doors to new modalities of Ti:sapphire lasers, such as massively scalable Ti:sapphire laser-array systems for several applications. As a proof-of-concept demonstration, we use a Ti:SaOI laser array as the sole optical control for a cavity quantum electrodynamics experiment with artificial atoms in silicon carbide. This work is a key step towards the democratization of Ti:sapphire technology through a three-orders-of-magnitude reduction in cost and footprint and introduces solid-state broadband amplification of sub-micron wavelength light.
PubMed: 38926612
DOI: 10.1038/s41586-024-07457-2 -
Scientific Reports Jun 2024Direct laser acceleration (DLA) of electrons in plasmas of near-critical density (NCD) is a very advancing platform for high-energy PW-class lasers of moderate...
Direct laser acceleration (DLA) of electrons in plasmas of near-critical density (NCD) is a very advancing platform for high-energy PW-class lasers of moderate relativistic intensity supporting Inertial Confinement Fusion research. Experiments conducted at the PHELIX sub-PW Nd:glass laser demonstrated application-promising characteristics of DLA-based radiation and particle sources, such as ultra-high number, high directionality and high conversion efficiency. In this context, the bright synchrotron-like (betatron) radiation of DLA electrons, which arises from the interaction of a sub-ps PHELIX laser pulse with an intensity of 10 W/cm with pre-ionized low-density polymer foam, was studied. The experimental results show that the betatron radiation produced by DLA electrons in NCD plasma is well directed with a half-angle of 100-200 mrad, yielding (3.4 ± 0.4)·10 photons/keV/sr at 10 keV photon energy. The experimental photon fluence and the brilliance agree well with the particle-in-cell simulations. These results pave the way for innovative applications of the DLA regime using low-density pre-ionized foams in high energy density research.
PubMed: 38926535
DOI: 10.1038/s41598-024-65490-7 -
International Journal of Dermatology Jun 2024The 1064-nm picosecond laser with holographic optics demonstrated significant efficacy in treating atrophic acne scars.
Comparison of the fractionated Nd: YAG 1064-nm picosecond laser with holographic optics and the fractional CO laser in atrophic acne scar treatment: a prospective, randomized, split-face study.
KEY POINT
The 1064-nm picosecond laser with holographic optics demonstrated significant efficacy in treating atrophic acne scars.
BACKGROUND
Picosecond lasers with fractionated optics have enabled the development of a breakthrough skin rejuvenation method. The authors compared the fractionated, non-ablative neodymium-doped yttrium aluminum garnet 1064-nm picosecond laser with holographic optics and the fractional CO laser in treating atrophic acne scars.
METHODS
One side of each patient's face was randomly allocated and treated with three sessions of the 1064-nm picosecond laser with holographic optics at 2-month intervals. In contrast, the other side was treated with the fractional CO laser. Participants were followed up 3 months after the final session. The primary outcome included the physicians' evaluation using the ECCA grading scale and a four-point scale to assess improvement. The patients' assessment of progress, their overall satisfaction and preferences, and the side effects were also evaluated.
RESULTS
No significant difference was observed between the two lasers in terms of the mean ECCA scores after treatments (P = 0.209). The physicians' improvement assessment was more significant for the fractional CO laser (P = 0.001). The patients' evaluation of improvement and subjective satisfaction were consistent with physicians' four-point scale results. The picosecond laser side had fewer adverse effects (P < 0.001).
CONCLUSION
The fractionated, non-ablative Nd: YAG 1064-nm picosecond laser with holographic optics and the fractional CO laser were effective and safe in treating atrophic acne scars. Significantly better clinical outcomes were observed with the fractional CO laser, whereas fewer adverse effects were noted with the 1064-nm picosecond laser with holographic optics.
PubMed: 38924534
DOI: 10.1111/ijd.17296 -
Dermatologic Surgery : Official... Jun 2024Patients frequently complain about fine lines, wrinkles, dyschromia, and photoaging, for which lasers and energy-based devices can treat each of these. Pairing various...
BACKGROUND
Patients frequently complain about fine lines, wrinkles, dyschromia, and photoaging, for which lasers and energy-based devices can treat each of these. Pairing various devices in a single treatment session can be safe and effective, but different technologies, mechanisms, histologies, parameters, and techniques must be considered.
OBJECTIVE
To examine the utility of a paired treatment regimen using radiofrequency microneedling and 755-nm picosecond laser with fractionated lens array to improve the clinical appearance of facial wrinkles and photoaging.
MATERIALS AND METHODS
A prospective clinical study investigated this paired treatment regimen using 4 monthly sessions.
RESULTS
Twenty-five subjects were enrolled, while 18 subjects completed 3-month follow-up. The mean age was 54 years, and 92% were women. Fitzpatrick Skin Types I to IV were represented. Assessments compared baseline with the 3-month follow-up. Two of 3 blinded reviewers agreed in identifying pretreatment and post-treatment photographs for 94.4% of cases. For physician Global Aesthetic Improvement Scale, 100% of subjects had clinical improvement. Overall, 88.9% of subjects were considered to be satisfied with their treatment. No serious or unanticipated adverse events occurred.
CONCLUSION
Paired treatment using radiofrequency microneedling and 755-nm picosecond laser with fractionated lens array can safely and effectively improve facial wrinkles and photoaging.
PubMed: 38924506
DOI: 10.1097/DSS.0000000000004302 -
Nanomaterials (Basel, Switzerland) Jun 2024Femtosecond high-intensity laser pulses at intensities surpassing 10 W/cm can generate a diverse range of functional surface nanostructures. Achieving precise control...
Femtosecond high-intensity laser pulses at intensities surpassing 10 W/cm can generate a diverse range of functional surface nanostructures. Achieving precise control over the production of these functional structures necessitates a thorough understanding of the surface morphology dynamics with nanometer-scale spatial resolution and picosecond-scale temporal resolution. In this study, we show that single XFEL pulses can elucidate structural changes on surfaces induced by laser-generated plasmas using grazing-incidence small-angle X-ray scattering (GISAXS). Using aluminium-coated multilayer samples we distinguish between sub-picosecond (ps) surface morphology dynamics and subsequent multi-ps subsurface density dynamics with nanometer-depth sensitivity. The observed subsurface density dynamics serve to validate advanced simulation models representing matter under extreme conditions. Our findings promise to open new avenues for laser material-nanoprocessing and high-energy-density science.
PubMed: 38921926
DOI: 10.3390/nano14121050 -
Frontiers in Medicine 2024Riehl's melanosis is a pigmented dermatitis that manifests as brown-gray facial pigmentation with pigment incontinence and infiltration of cells in the upper dermis. The...
Riehl's melanosis is a pigmented dermatitis that manifests as brown-gray facial pigmentation with pigment incontinence and infiltration of cells in the upper dermis. The associated inflammation is induced by a variety of products such as drugs and cosmetics. Henna, commonly referred to as a hypoallergenic cosmetic, has been reported to cause Riehl's melanosis in some cases. Although skin depigmenting agents have been occasionally used, satisfactory results have not been obtained and no established therapeutic strategies exist to treat Riehl's melanosis. Meanwhile, picosecond lasers effectively treat other hyperpigmentation disorders. In this study, we report safe and effective treatment of henna induced-atypical Riehl's melanosis using a 755-nm picosecond Alexandrite laser. Immunohistochemical analyses revealed a potential role of CD8-positive lymphocytes in henna-induced inflammation and hyperpigmentation of the basal layer, and a role of melanophages in the pigmented dermis of Riehl's melanosis.
PubMed: 38919937
DOI: 10.3389/fmed.2024.1401938 -
The Journal of Chemical Physics Jun 2024Simulations of photochemical reaction dynamics have been a challenge to the theoretical chemistry community for some time. In an effort to determine the predictive...
Simulations of photochemical reaction dynamics have been a challenge to the theoretical chemistry community for some time. In an effort to determine the predictive character of current approaches, we predict the results of an upcoming ultrafast diffraction experiment on the photodynamics of cyclobutanone after excitation to the lowest lying Rydberg state (S2). A picosecond of nonadiabatic dynamics is described with ab initio multiple spawning. We use both time dependent density functional theory (TDDFT) and equation-of-motion coupled cluster singles and doubles (EOM-CCSD) theory for the underlying electronic structure theory. We find that the lifetime of the S2 state is more than a picosecond (with both TDDFT and EOM-CCSD). The predicted ultrafast electron diffraction spectrum exhibits numerous structural features, but weak time dependence over the course of the simulations.
PubMed: 38912674
DOI: 10.1063/5.0203800 -
Proceedings of the National Academy of... Jun 2024The photoinduced all-trans to 13-cis isomerization of the retinal Schiff base represents the ultrafast first step in the reaction cycle of bacteriorhodopsin (BR)....
The photoinduced all-trans to 13-cis isomerization of the retinal Schiff base represents the ultrafast first step in the reaction cycle of bacteriorhodopsin (BR). Extensive experimental and theoretical work has addressed excited-state dynamics and isomerization via a conical intersection with the ground state. In conflicting molecular pictures, the excited state potential energy surface has been modeled as a pure S[Formula: see text] state that intersects with the ground state, or in a 3-state picture involving the S[Formula: see text] and S[Formula: see text] states. Here, the photoexcited system passes two crossing regions to return to the ground state. The electric dipole moment of the Schiff base in the S[Formula: see text] and S[Formula: see text] state differs strongly and, thus, its measurement allows for assessing the character of the excited-state potential. We apply the method of ultrafast terahertz (THz) Stark spectroscopy to measure electric dipole changes of wild-type BR and a BR D85T mutant upon electronic excitation. A fully reversible transient broadening and spectral shift of electronic absorption is induced by a picosecond THz field of several megavolts/cm and mapped by a 120-fs optical probe pulse. For both BR variants, we derive a moderate electric dipole change of 5 [Formula: see text] 1 Debye, which is markedly smaller than predicted for a neat S[Formula: see text]-character of the excited state. In contrast, S[Formula: see text]-admixture and temporal averaging of excited-state dynamics over the probe pulse duration gives a dipole change in line with experiment. Our results support a picture of electronic and nuclear dynamics governed by the interaction of S[Formula: see text] and S[Formula: see text] states in a 3-state model.
Topics: Bacteriorhodopsins; Retinaldehyde; Terahertz Spectroscopy; Schiff Bases; Halobacterium salinarum; Isomerism
PubMed: 38900801
DOI: 10.1073/pnas.2319676121