Search

Metalloporphyrins based on open-shell transition metals, such as Ni(II), exhibit typically fast excited-state relaxation. In this work, we shed light into the nonradiative relaxation mechanism in a nanographene-Ni(II) porphyrin conjugate. Variable temperature transient absorption and global fit analysis are combined to produce a picture of the relaxation pathways. At room temperature, photoexcitation of the lowest π-π* transition is followed by vibrational cooling in 1.6 ps, setting a short 20 ps temporal window wherein a small fraction of relaxed singlets radiatively decay to the ground state before intersystem crossing proceeds. Following intersystem crossing, triplets relax rapidly to the ground state (S 0 ) in a few tens of picoseconds. By performing measurements at low temperature, we provide evidence for a competition between two terminal relaxation pathways from the lowest (metal-centered) triplet to the ground state: a slow ground state relaxation process proceeding in time scales beyond 1.6 ns and a faster pathway dictated by a sloped conical intersection, which is thermally accessible at room temperature from the triplet state. The overall triplet decay at a given temperature is dictated by the interplay of these two contributions. This observation bears significance in understanding the underlying fast relaxation processes in Ni-based molecules and related transition metal complexes, opening avenues for potential applications for energy harvesting and optoelectronics.

Broadband Coherent anti-Stokes Raman (BCARS) microscopy is an imaging technique that can acquire full Raman spectra (400-3200 cm -1 ) of biological samples within a few milliseconds. However, the CARS signal suffers from an undesired non-resonant background (NRB), deriving from four-wave-mixing processes, which distorts the peak line shapes and reduces the chemical contrast. Traditionally, the NRB is removed using numerical algorithms that require expert users and knowledge of the NRB spectral profile. Recently, deep-learning models proved to be powerful tools for unsupervised automation and acceleration of NRB removal. Here, we thoroughly review the existing NRB removal deep-learning models (SpecNet, VECTOR, LSTM, Bi-LSTM) and present two novel architectures. The first one combines convolutional layers with Gated Recurrent Units (CNN + GRU); the second one is a Generative Adversarial Network (GAN) that trains an encoder-decoder network and an adversarial convolutional neural network. We also introduce an improved training dataset, generalized on different BCARS experimental configurations. We compare the performances of all these networks on test and experimental data, using them in the pipeline for spectral unmixing of BCARS images. Our analyses show that CNN + GRU and VECTOR are the networks giving the highest accuracy, GAN is the one that predicts the highest number of true positive peaks in experimental data, whereas GAN and VECTOR are the most suitable ones for real-time processing of BCARS images., (© 2024. The Author(s).)

Graphene-based materials (GBMs) are of considerable interest for biomedical applications, and the pilot study on the toxicological and immunological impact of pristine graphene (GR) and graphene oxide (GO) using swine as a close-to-human provides valuable insights. First, ex vivo experiments are conducted on swine blood cells, then GBMs are injected intraperitoneally (i.p.) into swine. Hematological and biochemical analyses at various intervals indicate that neither GO nor GR cause systemic inflammation, pro-coagulant responses, or renal or hepatic dysfunction. Importantly, no systemic toxicity is observed. Analysis of a panel of 84 immune-related genes shows minimal impact of GO and GR. The animals are sacrificed 21 days post-injection, and transient absorption imaging and Raman mapping show the presence of GO and GR in the mesentery only. Histological evaluation reveals no signs of alterations in other organs. Thus, clusters of both materials are detected in the mesentery, and GO aggregates are surrounded only by macrophages with the formation of granulomas. In contrast, modest local reactions are observed around the GR clusters. Overall, these results reveal that i.p. injection of GBMs resulted in a modest local tissue reaction without systemic toxicity. This study, performed in swine, provides essential guidance for future biomedical applications of graphene., (© 2024 The Author(s). Advanced Healthcare Materials published by Wiley‐VCH GmbH.)

Background: Nowadays, Thoracic Surgery is technologically advanced; therefore, it also focuses its attention on nursing care. The aim of the study is to evaluate the effect of the assessment of a dedicated team of nurses (DTN) in all onco-hematological patients undergoing VATS lobectomy for lung cancer on the outcome of the patient, preventing pressure injuries, reducing perioperative stress, duration of operations, complications, and hospital stay times. Methods: We performed a single-center observational retrospective study, including 31 DTN and 760 onco-hematological patients who underwent thoracic surgery between 30 October 2018 and 30 June 2023 at "Vanvitelli" University of Naples. Results : DTN ensures good nursing care before, during, and after surgery. Operative time was reduced by approximately 20 min, decreasing hospital infections in the DNT period and reducing intraoperative complications such as bleeding and hospital costs ( p < 0.05). Conclusions: Thoracic surgery nurses require more specialized training to adapt to the development of sophisticated.

Understanding the nature of the photoexcitation and ultrafast charge dynamics pathways in organic halide perovskite nanocubes and their aggregation into superlattices is key for potential applications as tunable light emitters, photon-harvesting materials, and light-amplification systems. In this work, we apply two-dimensional coherent electronic spectroscopy (2DES) to track in real time the formation of near-infrared optical excitons and their ultrafast relaxation in CH(NH 2 ) 2 PbI 3 nanocube superlattices. Our results unveil that the coherent ultrafast dynamics is limited by the combination of the inherent short exciton decay time (≃40 fs) and the dephasing due to the coupling with selective optical phonon modes at higher temperatures. On the picosecond time scale, we observe the progressive formation of long-lived localized trap states. The analysis of the temperature dependence of the excitonic intrinsic line width, as extracted by the antidiagonal components of the 2D spectra, unveils a dramatic change of the excitonic coherence time across the cubic to tetragonal structural transition. Our results offer a new way to control and enhance the ultrafast coherent dynamics of photocarrier generation in hybrid halide perovskite synthetic solids., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Optical diffraction tomography (ODT) is a powerful noninvasive 3D imaging technique, but its combination with broadband light sources is difficult. In this study, we introduce ultrabroadband ODT, covering over 150 nm of visible spectral bandwidth with a lateral spatial resolution of 150 nm. Our work addresses a critical experimental gap by enabling the measurement of broadband refractive index changes in 3D samples, crucial information that is difficult to assess with existing methodologies. We present broadband, spectrally resolved ODT images of HeLa cells, obtained via pulse-shaping-based Fourier transform spectroscopy. The spectral observations enabled by ultrabroadband ODT, combined with material-dependent refractive index responses, allow for precise three-dimensional identification of nanoparticles within cellular structures. Our work represents a crucial step toward time and spectrally resolved tomography of complex 3D structures with implications for life and materials science applications., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Obesity is defined as a complex, systemic disease characterized by excessive and dysfunctional adipose tissue, leading to adverse health effects. This condition is marked by low-grade inflammation, oxidative stress, and metabolic abnormalities, including mitochondrial dysfunction. These factors promote energy dysregulation and impact body composition not only by increasing body fat but also by promoting skeletal muscle mass atrophy. The decline in muscle mass is associated with an increased risk of all-cause mortality in individuals with this disease. The European Food Safety Authority approved pyrroloquinoline quinone (PQQ), a natural compound, as a dietary supplement in 2018. This narrative review aims to provide a comprehensive overview of the potential role of PQQ, based on its anti-inflammatory and antioxidant properties, in addressing dysfunctional adipose tissue metabolism and related disorders.

Switching of light polarization on the sub-picosecond timescale is a crucial functionality for applications in a variety of contexts, including telecommunications, biology and chemistry. The ability to control polarization at ultrafast speed would pave the way for the development of unprecedented free-space optical links and of novel techniques for probing dynamical processes in complex systems, as chiral molecules. Such high switching speeds can only be reached with an all-optical paradigm, i.e., engineering active platforms capable of controlling light polarization via ultrashort laser pulses. Here we demonstrate giant modulation of dichroism and birefringence in an all-dielectric metasurface, achieved at low fluences of the optical control beam. This performance, which leverages the many degrees of freedom offered by all-dielectric active metasurfaces, is obtained by combining a high-quality factor nonlocal resonance with the giant third-order optical nonlinearity dictated by photogenerated hot carriers at the semiconductor band edge., (© 2024. The Author(s).)

Using heterodyne transient grating spectroscopy, we observe a significant enhancement of exciton diffusion in a monolayer WSe 2 stacked on graphene. The diffusion dynamics can be optically tuned within a few picoseconds by altering the photoexcited carrier density in graphene. The effective diffusion constant in initial picoseconds in the WSe 2 /graphene heterostructure is (40.3 ± 4.5) cm 2 s -1 , representing a substantial improvement over (2.1 ± 0.8) cm 2 s -1 , typical for an isolated WSe 2 monolayer. This enhancement can be understood in terms of a transient screening of impurities, charge traps, and defect states in WSe 2 by photoexcited charge carriers in graphene. Furthermore, diffusion within WSe 2 is affected by interlayer interactions, such as charge transfer, varying with the incident excitation fluence. These findings underscore the dynamical nature of screening and diffusion processes in heterostructures of 2D semiconductors and graphene and provide insights for future applications of these systems in ultrafast optoelectronic devices.

Van der Waals heterostructures based on transition metal dichalcogenides (TMDs) have emerged as excellent candidates for next-generation optoelectronics and valleytronics, due to their fascinating physical properties. The understanding and active control of the relaxation dynamics of heterostructures play a crucial role in device design and optimization. Here, we investigate the back-gate modulation of exciton dynamics in a WS 2 /WSe 2 heterostructure by combining time-resolved photoluminescence (TRPL) and transient absorption spectroscopy (TAS) at cryogenic temperatures. We find that the non-radiative relaxation lifetimes of photocarriers in heterostructures can be electrically controlled for samples with different twist-angles, whereas such lifetime tuning is not present in standalone monolayers. We attribute such an observation to doping-controlled competition between interlayer and intralayer recombination pathways in high-quality WS 2 /WSe 2 samples. The simultaneous measurement of TRPL and TAS lifetimes within the same sample provides additional insight into the influence of coexisting excitons and background carriers on the photo-response, and points to the potential of tailoring light-matter interactions in TMD heterostructures.

Transition metal dichalcogenides (TMDs) are quantum confined systems with interesting optoelectronic properties, governed by Coulomb interactions in the monolayer (1L) limit, where strongly bound excitons provide a sensitive probe for many-body interactions. Here, we use two-dimensional electronic spectroscopy (2DES) to investigate many-body interactions and their dynamics in 1L-WS 2 at room temperature and with sub-10 fs time resolution. Our data reveal coherent interactions between the strongly detuned A and B exciton states in 1L-WS 2 . Pronounced ultrafast oscillations of the transient optical response of the B exciton are the signature of a coherent 50 meV coupling and coherent population oscillations between the two exciton states. Supported by microscopic semiconductor Bloch equation simulations, these coherent dynamics are rationalized in terms of Dexter-like interactions. Our work sheds light on the role of coherent exciton couplings and many-body interactions in the ultrafast temporal evolution of spin and valley states in TMDs.

Accurate, rapid and non-invasive cancer cell phenotyping is a pressing concern across the life sciences, as standard immuno-chemical imaging and omics require extended sample manipulation. Here we combine Raman micro-spectroscopy and phase tomography to achieve label-free morpho-molecular profiling of human colon cancer cells, following the adenoma, carcinoma, and metastasis disease progression, in living and unperturbed conditions. We describe how to decode and interpret quantitative chemical and co-registered morphological cell traits from Raman fingerprint spectra and refractive index tomograms. Our multimodal imaging strategy rapidly distinguishes cancer phenotypes, limiting observations to a low number of pristine cells in culture. This synergistic dataset allows us to study independent or correlated information in spectral and tomographic maps, and how it benefits cell type inference. This method is a valuable asset in biomedical research, particularly when biological material is in short supply, and it holds the potential for non-invasive monitoring of cancer progression in living organisms., (© 2024. The Author(s).)

Using as showcase the DNA dinucleotide 5'-dTpdG-3', in which the thymine (T) is located at the 5' end with respect to the guanine (G), we study the photoinduced electronic relaxation of coupled chromophores in solution with an unprecedented refinement. On the one hand, transient absorption spectra are recorded from 20 fs to 45 ps over the 330-650 nm range with a temporal resolution of 30 fs; on the other hand, quantum chemistry calculations determine the ground state geometry of the 4 possible conformers with stacked nucleobases, the associated Franck-Condon states, and map the relaxation pathways leading to excited state minima. Important spectral changes occurring before 100 fs are correlated with concomitant G + → T - charge transfer and T → G energy transfer processes. The lifetime of the excited charge transfer state is only 5 ps and the absorption spectrum of a long-lived nπ*T state is detected. Our experimental results match the transient spectral properties computed for the anti - syn conformer of 5'-dTpdG-3', which is characterized by the lowest ground state energy and differs from that encountered in B-form duplexes., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Natural light harvesting is exceptionally efficient thanks to the local energy funnel created within light-harvesting complexes (LHCs). To understand the design principles underlying energy transport in LHCs, ultrafast spectroscopy is often complemented by mutational studies that introduce perturbations into the excitonic structure of the natural complexes. However, such studies may fall short of identifying all excitation energy transfer (EET) pathways and their changes upon mutation. Here, we show that a synergistic combination of first-principles calculations and ultrafast spectroscopy can give unprecedented insight into the EET pathways occurring within LHCs. We measured the transient absorption spectra of the minor CP29 complex of plants and of two mutants, systematically mapping the kinetic components seen in experiments to the simulated exciton dynamics. With our combined strategy, we show that EET in CP29 is surprisingly robust to the changes in the exciton states induced by mutations, explaining the versatility of plant LHCs.

Acoustic vibrations of matter convey fundamental viscoelastic information that can be optically retrieved by hyperfine spectral analysis of the inelastic Brillouin scattered light. Increasing evidence of the central role of the viscoelastic properties in biological processes has stimulated the rise of non-contact Brillouin microscopy, yet this method faces challenges in turbid samples due to overwhelming elastic background light. Here, we introduce a common-path Birefringence-Induced Phase Delay (BIPD) filter to disentangle the polarization states of the Brillouin and Rayleigh signals, enabling the rejection of the background light using a polarizer. We demonstrate a 65 dB extinction ratio in a single optical pass collecting Brillouin spectra in extremely scattering environments and across highly reflective interfaces. We further employ the BIPD filter to image bone tissues from a mouse model of osteopetrosis, highlighting altered biomechanical properties compared to the healthy control. Results herald new opportunities in mechanobiology where turbid biological samples remain poorly characterized., (© 2024. The Author(s).)

Molecular aggregation is a powerful tool for tuning advanced materials' photophysical and electronic properties. Here we present a novel potential for the aqueous-solvated aggregated state of boron dipyrromethene (BODIPY) to facilitate phototransformations otherwise achievable only under harsh chemical conditions. We show that the photoinduced symmetry-breaking charge separation state can itself initiate catalyst-free redox chemistry, leading to selective α-C(sp 3 )-H bond activation/C sp 3 -C sp 3 coupling on the BODIPY backbone. The photoproduction progress was tracked by monitoring the evolution of the strong Stokes-shifted near-infrared emission, resulting from selective self-assembly of the terminal heterodimeric photoproduct into well-ordered J-aggregates, as revealed by X-ray structural analysis. These findings provide a facile and green route to further explore the promising frontier of packing-triggered selective photoconversions via supramolecular engineering.

Leukemia comprises a diverse group of bone marrow tumors marked by cell proliferation. Current diagnosis involves identifying leukemia subtypes through visual assessment of blood and bone marrow smears, a subjective and time-consuming method. Our study introduces the characterization of different leukemia subtypes using a global clustering approach of Raman hyperspectral maps of cells. We analyzed bone marrow samples from 19 patients, each presenting one of nine distinct leukemia subtypes, by conducting high spatial resolution Raman imaging on 319 cells, generating over 1.3 million spectra in total. An automated preprocessing pipeline followed by a single-step global clustering approach performed over the entire data set identified relevant cellular components (cytoplasm, nucleus, carotenoids, myeloperoxidase (MPO), and hemoglobin (HB)) enabling the unsupervised creation of high-quality pseudostained images at the single-cell level. Furthermore, this approach provided a semiquantitative analysis of cellular component distribution, and multivariate analysis of clustering results revealed the potential of Raman imaging in leukemia research, highlighting both advantages and challenges associated with global clustering.

Excitation energy transfer (EET) is a key photoinduced process in biological chromophoric assemblies. Here we investigate the factors which can drive EET into efficient ultrafast sub-ps regimes. We demonstrate how a coherent transport of electronic population could facilitate this in water solvated NADH coenzyme and uncover the role of an intermediate dark charge-transfer state. High temporal resolution ultrafast optical spectroscopy gives a 54±11 fs time constant for the EET process. Nonadiabatic quantum dynamical simulations computed through the time-evolution of multidimensional wavepackets suggest that the population transfer is mediated by photoexcited molecular vibrations due to strong coupling between the electronic states. The polar aqueous solvent environment leads to the active participation of a dark charge transfer state, accelerating the vibronically coherent EET process in favorably stacked conformers and solvent cavities. Our work demonstrates how the interplay of structural and environmental factors leads to diverse pathways for the EET process in flexible heterodimers and provides general insights relevant for coherent EET processes in stacked multichromophoric aggregates like DNA strands., (© 2024. The Author(s).)

Upconverting nanoparticles (UCNPs) doped with Yb 3+ and Tm 3+ are near-infrared (NIR) to ultraviolet (UV) transducers that can be used for NIR-controlled drug delivery. However, due to the low quantum yield of upconversion, high laser powers and long irradiation times are required to trigger this drug release. In this work, we report the one-step synthesis of a nanocomposite consisting of a LiYbF 4 :Tm 3+ @LiYF 4 UCNP coated with mesoporous UV-breakable organosilica shells of various thicknesses. We demonstrate that a thin shell accelerates the breakage of the shell at 1 W/cm 2 NIR light exposure, a laser power up to 9 times lower than that of conventional systems. When the mesopores are loaded with hydrophobic vitamin D 3 precursor 7-dehydrocholesterol (7-DH), shell breakage results in subsequent cargo release. Its minimal toxicity in HeLa cells and successful internalization into the cell cytoplasm demonstrate its biocompatibility and potential application in biological systems. The tunability of this system due to its simple, one-step synthesis process and its ability to operate at low laser powers opens up avenues in UCNP-powered NIR-triggered drug delivery toward a more scalable, flexible, and ultimately translational option.

Many applications of ultrafast and nonlinear optical microscopy require the measurement of small differential signals over large fields-of-view. Widefield configurations drastically reduce the acquisition time; however, they suffer from the low frame rates of two-dimensional detectors, which limit the modulation frequency, making the measurement sensitive to excess laser noise. Here we introduce a self-referenced detection configuration for widefield differential imaging. Employing regions of the field of view with no differential signal as references, we cancel probe fluctuations and increase the signal-to-noise ratio by an order of magnitude reaching noise levels only a few percent above the shot noise limit. We anticipate broad applicability of our method to transient absorption, stimulated Raman scattering and photothermal-infrared microscopies.

In view of developing photoelectrosynthetic cells which are able to store solar energy in chemical bonds, water splitting is usually the reaction of choice when targeting hydrogen production. However, alternative approaches can be considered, aimed at substituting the anodic reaction of water oxidation with more commercially capitalizable oxidations. Among them, the production of bromine from bromide ions was investigated long back in the 1980s by Texas Instruments. Herein we present optimized perylene-diimide (PDI)-sensitized antimony-doped tin oxide (ATO) photoanodes enabling the photoinduced HBr splitting with >4 mA/cm 2 photocurrent densities under 0.1 W/cm 2 AM1.5G illumination and 91 ± 3% faradaic efficiencies for bromine production. These remarkable results, among the best currently reported for the photoelectrochemical Br - oxidation by dye sensitized photoanodes, are strongly related to the occupancy extent of ATO's intragap (IG) states, generated upon Sb-doping, as demonstrated by comparing their performances with PDI-sensitized analogues on both undoped SnO 2 - and TiO 2 -passivated ATO scaffolds by means of (spectro)electrochemistry and electrochemical impedance spectroscopy. The architecture of the ATO-PDI photoanodic assembly was further modified via the introduction of a molecular iridium-based water oxidation catalyst, thus proving the versatility of the proposed hybrid interfaces as photoanodic platforms for photoinduced oxidations in PEC devices.

The appropriate use of predictive equations in estimating body composition through bioelectrical impedance analysis (BIA) depends on the device used and the subject's age, geographical ancestry, healthy status, physical activity level and sex. However, the presence of many isolated predictive equations in the literature makes the correct choice challenging, since the user may not distinguish its appropriateness. Therefore, the present systematic review aimed to classify each predictive equation in accordance with the independent parameters used. Sixty-four studies published between 1988 and 2023 were identified through a systematic search of international electronic databases. We included studies providing predictive equations derived from criterion methods, such as multi-compartment models for fat, fat-free and lean soft mass, dilution techniques for total-body water and extracellular water, total-body potassium for body cell mass, and magnetic resonance imaging or computerized tomography for skeletal muscle mass. The studies were excluded if non-criterion methods were employed or if the developed predictive equations involved mixed populations without specific codes or variables in the regression model. A total of 106 predictive equations were retrieved; 86 predictive equations were based on foot-to-hand and 20 on segmental technology, with no equations used the hand-to-hand and leg-to-leg. Classifying the subject's characteristics, 19 were for underaged, 26 for adults, 19 for athletes, 26 for elderly and 16 for individuals with diseases, encompassing both sexes. Practitioners now have an updated list of predictive equations for assessing body composition using BIA. Researchers are encouraged to generate novel predictive equations for scenarios not covered by the current literature.Registration code in PROSPERO: CRD42023467894., (© 2024. The Author(s).)

Internal conversion (IC) is a common radiationless transition in polyatomic molecules. Theory predicts that molecular vibrations assist IC between excited states, and ultrafast experiments can provide insight into their structure-function relationship. Here we elucidate the dynamics of the vibrational modes driving the IC process within the Q band of a functionalized porphyrin molecule. Through a combination of ultrafast multidimensional spectroscopies and theoretical modeling, we observe a 60 fs Q y -Q x IC and demonstrate that it is driven by the interplay among multiple high-frequency modes. Notably, we identify 1510 cm -1 as the leading tuning mode that brings the porphyrin to an optimal geometry for energy surface crossing. By employing coherent wave packet analysis, we highlight a set of short-lived vibrations (1200-1400 cm -1 ), promoting the IC within ≈60 fs. Furthermore, we identify one coupling mode (1350 cm -1 ) that is responsible for vibronic mixing within the Q states. Our findings indicate that porphyrin-core functionalization modulates IC effectively, offering new opportunities in photocatalysis and optoelectronics.

Regarding skeletal muscle hypertrophy, resistance training and nutrition, the most often discussed and proposed supplements include proteins. Although, the correct amount, quality, and daily distribution of proteins is of paramount importance for skeletal muscle hypertrophy, there are many other nutritional supplements that can help and support the physiological response of skeletal muscle to resistance training in terms of muscle hypertrophy. A healthy muscle environment and a correct whole muscle metabolism response to the stress of training is a prerequisite for the increase in muscle protein synthesis and, therefore, muscle hypertrophy. In this review, we discuss the role of different nutritional supplements such as carbohydrates, vitamins, minerals, creatine, omega-3, polyphenols, and probiotics as a support and complementary factors to the main supplement i.e., protein. The different mechanisms are discussed in the light of recent evidence., Competing Interests: The authors declare no conflict of interest., (Copyright: © Academy of Physical Education in Katowice.)

Eumelanins play a crucial role as photoprotective agents for living organisms, yet the nature of the stationary and transient species involved in the light absorption and deactivation processes remains controversial. Moreover, the critical sub-100 fs time scale, which is key to the characterization of the primary excited species, has remained unexplored. Here, we study the eumelanin analogue polydopamine (PDA) and employ a combination of steady-state and transient optical spectroscopies to reveal the presence of spectrally broad coupled electronic transitions with, at least partial, charge-transfer (CT) character. We monitor the CT state dynamics using tunable sub-20 fs pulses. We find that high photon energy excitation results in accelerated (sub-20 fs) CT formation times while activating pathways, which lead to long-lived (≫1 ns), possibly reactive CT species. On the other hand, visible light excitation results in a slower (≈45 fs) formation of bound CT states, which, however, recombine on the ultrafast sub-2 ps time scale.

We combine site-directed mutagenesis with picosecond time-resolved fluorescence and femtosecond transient absorption (TA) spectroscopies to identify excitation energy transfer (EET) processes between chlorophylls (Chls) and xanthophylls (Xant) in the minor antenna complex CP29 assembled inside nanodiscs, which result in quenching. When compared to WT CP29, a longer lifetime was observed in the A 2 mutant, missing Chl a612, which closely interacts with Xant Lutein in site L1. Conversely, a shorter lifetime was obtained in the A 5 mutant, in which the interaction between Chl a603 and Chl a609 is strengthened, shifting absorption to lower energy and enhancing Chl-Xant EET. Global analysis of TA data indicated that EET from Chl a Q y to a Car dark state S* is active in both the A 2 and A 5 mutants and that their rate constants are modulated by mutations. Our study provides experimental evidence that multiple Chl-Xant interactions are involved in the quenching activity of CP29.

Substantial global restoration commitments are occurring alongside a rapid expansion in land-hungry tropical commodities, including to supply increasing demand for wood products. Future commercial tree plantations may deliver high timber yields, shrinking the footprint of production forestry, but there is an as-yet unquantified risk that plantations may expand into priority restoration areas, with marked environmental costs. Focusing on Brazil-a country of exceptional restoration importance and one of the largest tropical timber producers-we use random forest models and information on the economic, social, and spatial drivers of historic commercial tree plantation expansion to estimate and map the probability of future monoculture tree plantation expansion between 2020 and 2030. We then evaluate potential plantation-restoration conflicts and opportunities at national and biome-scales and under different future production and restoration pathways. Our simulations show that of 2.8 Mha of future plantation expansion (equivalent to plantation expansion 2010-2020), ~78,000 ha (3%) is forecast to occur in the top 1% of restoration priority areas for terrestrial vertebrates, with ~547,500 ha (20%) and ~1,300,000 ha (46%) in the top 10% and 30% of priority areas, respectively. Just ~459,000 ha (16%) of expansion is forecast within low-restoration areas (bottom 30% restoration priorities), and the first 1 Mha of plantation expansion is likely to have disproportionate impacts, with potential restoration-plantation overlap starkest in the Atlantic Forest but prominent in the Pampas and Cerrado as well. Our findings suggest that robust, coherent land-use policies must be deployed to ensure that significant trade-offs between restoration and production objectives are navigated, and that commodity expansion does not undermine the most tractable conservation gains under emerging global restoration agendas. They also highlight the potentially significant role an engaged forestry sector could play in improving biodiversity outcomes in restoration projects in Brazil, and presumably elsewhere., (© 2024 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)

Introduction: Benign tracheobronchial stenosis is a abnormal tracheal lumen narrowing that may incur progressive dyspnea and life-threatening hypoxemia. There is no consensus on which patients should be treated with endoscopic or surgical method. This study investigates the outcomes of bronchoscopic dilatation in the treatment of benign tracheal stenosis using a device equipped with a blade to cut the stenotic lesions with dense fibrosis., Materials and Methods: The procedure was carried out in an operating room under general anesthesia. All patients were intubated with a Rigid Bronchoscope (RB) placed just above the stenosis. Through Rigid Bronchoscopy combined modalities were used as needed: radial incisions of the mucosal stenosis with blade at the levels of 4, 8 and 12 o'clock, with back and forth movements, then the stenotic area was dilated more easily with a rigid bronchoscope. Dilatation was performed by passing the RB of increasing diameter through stenotic areas and then Balloon dilatation of increasing diameter. There were no complications during the procedure., Result: We conducted an observational, retrospective, single-centre study in the Thoracic Surgery Unit of the University of 'Luigi Vanvitelli' of Naples from November 2011 to September 2021. We included all consecutive patients with benign tracheal stenosis inoperable. During the study period, 113 patients were referred to our department with benign tracheal stenosis inoperable. 61 patients were treated with the blade. During the follow-up, a recurrence of the stenosis was observed in 8 patients in the first month and in 4 patients in the third month. Instead in the patients treated with the use of laser (52 patients), during the follow-up a recurrence was observed in 16 patients in the first month and in 6 patients in the third month; no patient relapsed after 6 months and after 1 year. Long term successful bronchoscopic management with blade was attained by 99% in simple and 93% in mixed stenosis and in complex type stenosis., Conclusion: Our study underlines the importance of the use of the blade in bronchoscopic treatment as a valid conservative approach in the management of patients with inoperable benign tracheal stenosis as an alternative to the use of the laser, reducing the abnormal inflammatory reaction in order to limit recurrences., (© 2024. The Author(s).)

Structurally well-defined graphene nanoribbons (GNRs) are nanostructures with unique optoelectronic properties. In the liquid phase, strong aggregation typically hampers the assessment of their intrinsic properties. Recently we reported a novel type of GNRs, decorated with aliphatic side chains, yielding dispersions consisting mostly of isolated GNRs. Here we employ two-dimensional electronic spectroscopy to unravel the optical properties of isolated GNRs and disentangle the transitions underlying their broad and rather featureless absorption band. We observe that vibronic coupling, typically neglected in modeling, plays a dominant role in the optical properties of GNRs. Moreover, a strong environmental effect is revealed by a large inhomogeneous broadening of the electronic transitions. Finally, we also show that the photoexcited bright state decays, on the 150 fs time scale, to a dark state which is in thermal equilibrium with the bright state, that remains responsible for the emission on nanosecond time scales.

The ultrafast carrier dynamics of junctions between two chemically identical, but electronically distinct, transition metal dichalcogenides (TMDs) remains largely unknown. Here, we employ time-resolved photoemission electron microscopy (TR-PEEM) to probe the ultrafast carrier dynamics of a monolayer-to-multilayer (1L-ML) WSe 2 junction. The TR-PEEM signals recorded for the individual components of the junction reveal the sub-ps carrier cooling dynamics of 1L- and 7L-WSe 2 , as well as few-ps exciton-exciton annihilation occurring on 1L-WSe 2 . We observe ultrafast interfacial hole (h) transfer from 1L- to 7L-WSe 2 on an ∼0.2 ps time scale. The resultant excess h density in 7L-WSe 2 decays by carrier recombination across the junction interface on an ∼100 ps time scale. Reminiscent of the behavior at a depletion region, the TR-PEEM image reveals the h density accumulation on the 7L-WSe 2 interface, with a decay length ∼0.60 ± 0.17 μm. These charge transfer and recombination dynamics are in agreement with ab initio quantum dynamics. The computed orbital densities reveal that charge transfer occurs from the basal plane, which extends over both 1L and ML regions, to the upper plane localized on the ML region. This mode of charge transfer is distinctive to chemically homogeneous junctions of layered materials and constitutes an additional carrier deactivation pathway that should be considered in studies of 1L-TMDs found alongside their ML, a common occurrence in exfoliated samples.

With Europe's ageing population and rising demand for palliative care, it is crucial to examine the use of palliative care among older adults during their last years of life and understand the factors influencing their access and end-of-life circumstances. This study employed a cohort of SHARE participants aged 65 years or older who had passed away between Wave 6 (2015) and Wave 7 (2017). Information on death circumstances, palliative care utilization, and associated variables were analysed. The study revealed that nearly 13.0% of individuals across these countries died under palliative care, with Slovenia having the lowest rate (0.3%) and France the highest (30.4%). Palliative care utilization in the last 30 days before death was observed in over 24.0% of participants, with the Czech Republic having the lowest rate (5.0%) and Greece the highest (48.8%). A higher risk of using or dying in palliative care was significantly associated with cognitive impairment (low verbal fluency), physical inactivity, and good to excellent self-perceived health. This work highlights the urgent need for enhanced global access to palliative care and advocates for the cross-country comparison of effective practices within Europe, tailored to the unique healthcare needs of older adults.

Tissue histopathology, based on hematoxylin and eosin (H&E) staining of thin tissue slices, is the gold standard for the evaluation of the immune reaction to the implant of a biomaterial. It is based on lengthy and costly procedures that do not allow longitudinal studies. The use of non-linear excitation microscopy in vivo , largely label-free, has the potential to overcome these limitations. With this purpose, we develop and validate an implantable microstructured device for the non-linear excitation microscopy assessment of the immune reaction to an implanted biomaterial label-free. The microstructured device, shaped as a matrix of regular 3D lattices, is obtained by two-photon laser polymerization. It is subsequently implanted in the chorioallantoic membrane (CAM) of embryonated chicken eggs for 7 days to act as an intrinsic 3D reference frame for cell counting and identification. The histological analysis based on H&E images of the tissue sections sampled around the implanted microstructures is compared to non-linear excitation and confocal images to build a cell atlas that correlates the histological observations to the label-free images. In this way, we can quantify the number of cells recruited in the tissue reconstituted in the microstructures and identify granulocytes on label-free images within and outside the microstructures. Collagen and microvessels are also identified by means of second-harmonic generation and autofluorescence imaging. The analysis indicates that the tissue reaction to implanted microstructures is like the one typical of CAM healing after injury, without a massive foreign body reaction. This opens the path to the use of similar microstructures coupled to a biomaterial, to image in vivo the regenerating interface between a tissue and a biomaterial with label-free non-linear excitation microscopy. This promises to be a transformative approach, alternative to conventional histopathology, for the bioengineering and the validation of biomaterials in i n vivo longitudinal studies., Competing Interests: The authors have no conflicts to disclose., (© 2024 Author(s).)

Broadband coherent anti-Stokes Raman scattering (BCARS) is a powerful spectroscopy method combining high signal intensity with spectral sensitivity, enabling rapid imaging of heterogeneous samples in biomedical research and, more recently, in crystalline materials. However, BCARS encounters spectral distortion due to a setup-dependent non-resonant background (NRB). This study assesses BCARS reproducibility through a round robin experiment using two distinct BCARS setups and crystalline materials with varying structural complexity, including diamond, 6H-SiC, KDP, and KTP. The analysis compares setup-specific NRB correction procedures, detected and NRB-removed spectra, and mode assignment. We determine the influence of BCARS setup parameters like pump wavelength, pulse width, and detection geometry and provide a practical guide for optimizing BCARS setups for solid-state applications.

Background: Bioelectrical impedance analysis (BIA) is a rapid and user-friendly technique for assessing body composition in sports. Currently, no sport-specific predictive equations are available, and the utilization of generalized formulas can introduce systematic bias. The objectives of this study were as follows: (i) to develop and validate new predictive models for estimating fat-free mass (FFM) components in male elite soccer players; (ii) to evaluate the accuracy of existing predictive equations., Methods: A total of 102 male elite soccer players (mean age 24.7 ± 5.7 years), participating in the Italian first league, underwent assessments during the first half of the in-season period and were randomly divided into development and validation groups. Bioelectrical resistance (R) and reactance (Xc), representing the bioimpedance components, were measured using a foot-to-hand BIA device at a single frequency of 50 kHz. Dual-energy X-ray absorptiometry was employed to acquire reference data for FFM, lean soft tissue (LST), and appendicular lean soft tissue (ALST). The validation of the newly developed predictive equations was conducted through regression analysis, Bland-Altman tests, and the area under the curves (AUC) of regression receiver operating characteristic (RROC) curves., Results: Developed models were: FFM = - 7.729 + (body mass × 0.686) + (stature 2 /R × 0.227) + (Xc × 0.086) + (age × 0.058), R 2  = 0.97, Standard error of estimation (SEE) = 1.0 kg; LST = - 8.929 + (body mass × 0.635) + (stature 2 /R × 0.244) + (Xc × 0.093) + (age × 0.048), R 2  = 0.96, SEE = 0.9 kg; ALST = - 24.068 + (body mass × 0.347) + (stature 2 /R × 0.308) + (Xc × 0.152), R 2  = 0.88, SEE = 1.4 kg. Train-test validation, performed on the validation group, revealed that generalized formulas for athletes underestimated all the predicted FFM components (p < 0.01), while the new predictive models showed no mean bias (p > 0.05), with R 2 values ranging from 0.83 to 0.91, and no trend (p > 0.05). The AUC scores of the RROC curves indicated an accuracy of 0.92, 0.92, and 0.74 for FFM, LST, and ALST, respectively., Conclusions: The utilization of generalized predictive equations leads to an underestimation of FFM and ALST in elite soccer players. The newly developed soccer-specific formulas enable valid estimations of body composition while preserving the portability of a field-based method., (© 2023. The Author(s).)

In this work, we show how the structural features of photoactive azobenzene derivatives can influence the photoexcited state behavior and the yield of the trans/cis photoisomerization process. By combining high-resolution transient absorption experiments in the vis-NIR region and quantum chemistry calculations (TDDFT and RASPT2), we address the origin of the transient signals of three poly-substituted push-pull azobenzenes with an increasing strength of the intramolecular interactions stabilizing the planar trans isomer (absence of intramolecular H-bonds, methyl, and traditional H-bond, respectively, for 4-diethyl-4'-nitroazobenzene, Disperse Blue 366, and Disperse Blue 165) and a commercial red dye showing keto-enol tautomerism involving the azo group (Sudan Red G). Our results indicate that the intramolecular H-bonds can act as a "molecular lock" stabilizing the trans isomer and increasing the energy barrier along the photoreactive CNNC torsion coordinate, thus preventing photoisomerization in the Disperse Blue dyes. In contrast, the involvement of the azo group in keto-enol tautomerism can be employed as a strategy to change the nature of the lower excited state and remove the nonproductive symmetric CNN/NNC bending pathway typical of the azo group, thus favoring the productive torsional motion. Taken together, our results can provide guidelines for the structural design of azobenzene-based photoswitches with a tunable excited state behavior.

Considering the multidimensionality of chronic pain, it is crucial to develop comprehensive strategies for its effective management. However, establishing well-defined, evidence-based guidelines for such approaches remains challenging. To overcome this, we present the finding from a 4-month intervention to enhance the management of non-cancer chronic pain in older adults with pre-frailty and frailty. The intervention's core elements comprised a multidisciplinary individualized plan, a case manager, and patient education. This pilot study involved 22 participants (≥65 years). It assessed changes in pain frequency and intensity (pain scale), frailty (Fried frailty phenotype criteria), and medication adherence (Brief Adherence Rating Scale) before and after the 4-month intervention. The results were encouraging: pain frequency and intensity and frailty score tended to decrease, and medication adherence showed significant improvement. This preliminary small-scale pilot study provides a foundation for further research and for exploring the potential scalability of this multidisciplinary patient-centred intervention.

Background: A well-balanced diet is essential in sport. Due to its typical content in high-quality proteins, low glycemic index foods, and unsaturated fats, Mediterranean Diet (MD) may represent a good choice to cover nutritional needs of athletes. The aim of this study was to explore how the dietary habits of elite athletes, such as those competing at the XXX Summer Universiade, comply with the MD model. A comparison between athletes coming from the Mediterranean and non-Mediterranean countries was also assessed. Methods: The Mediterranean Diet Serving Score (MDSS) questionnaire was administered to a sample of 433 university student athletes from all over of the world to evaluate the level of adherence to the MD pattern and possible differences between geographical areas. Results: The total sample showed a medium adherence to the MD, with a mean MDSS of 15.73 ± 3.71 out of a total of 23 points. A satisfactory consumption of fruits and vegetables was reported. Athletes from Northern European countries had a lower MD pattern adherence than the other ones. Conclusions: These findings suggest that the MD model is common among elite athletes, and it may be promoted as a healthy dietary pattern in the sport setting., Competing Interests: Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Semiconducting transition metal dichalcogenides are important optoelectronic materials thanks to their intense light-matter interaction and wide selection of fabrication techniques, with potential applications in light harvesting and sensing. Crucially, these applications depend on the lifetimes and recombination dynamics of photogenerated charge carriers, which have primarily been studied in monolayers obtained from labour-intensive mechanical exfoliation or costly chemical vapour deposition. On the other hand, liquid phase exfoliation presents a high throughput and cost-effective method to produce dispersions of mono- and few-layer nanosheets. This approach allows for easy scalability and enables the subsequent processing and formation of macroscopic films directly from the liquid phase. Here, we use transient absorption spectroscopy and spatiotemporally resolved pump-probe microscopy to study the charge carrier dynamics in tiled nanosheet films of MoS 2 and WS 2 deposited from the liquid phase using an adaptation of the Langmuir-Schaefer technique. We find an efficient photogeneration of charge carriers with lifetimes of several nanoseconds, which we ascribe to stabilisation at nanosheet edges. These findings provide scope for photocatalytic and photodetector applications, where long-lived charge carriers are crucial, and suggest design strategies for photovoltaic devices., Competing Interests: The authors declare no competing conflict of interest., (This journal is © The Royal Society of Chemistry.)

The DNA polarity, i.e ., the order in which nucleobases are connected together via the phosphodiester backbone, is crucial for several biological processes. But, so far, there has not been experimental evidence regarding its effect on the relaxation of DNA electronic excited states. Here we examine this aspect for two dinucleotides containing adenine and guanine: 5'-dApdG-3' and 5'-dGpdA-3' in water. We used two different femtosecond transient absorption setups: one providing high temporal resolution and broad spectral coverage (330-650 nm) between 30 fs and 50 ps, and the other recording decays at selected wavelengths until 1.2 ns. The transient absorption spectra corresponding to the minima in the potential energy surface of the first excited state were computed by quantum chemistry methods. Our results show that the excited charge transfer state in 5'-dGpdA-3' is formed with a ∼75% higher quantum yield and exhibits slower decay (170 ± 10 ps vs 112 ± 12 ps) compared to 5'-dApdG-3'.

Vertical heterostructures of transition metal dichalcogenides (TMDs) host interlayer excitons with electrons and holes residing in different layers. With respect to their intralayer counterparts, interlayer excitons feature longer lifetimes and diffusion lengths, paving the way for room temperature excitonic optoelectronic devices. The interlayer exciton formation process and its underlying physical mechanisms are largely unexplored. Here we use ultrafast transient absorption spectroscopy with a broadband white-light probe to simultaneously resolve interlayer charge transfer and interlayer exciton formation dynamics in a MoSe 2 /WSe 2 heterostructure. We observe an interlayer exciton formation timescale nearly an order of magnitude (~1 ps) longer than the interlayer charge transfer time (~100 fs). Microscopic calculations attribute this relative delay to an interplay of a phonon-assisted interlayer exciton cascade and thermalization, and excitonic wave-function overlap. Our results may explain the efficient photocurrent generation observed in optoelectronic devices based on TMD heterostructures, as the interlayer excitons are able to dissociate during thermalization., (© 2023. The Author(s).)

The coupling of the electron system to lattice vibrations and their time-dependent control and detection provide unique insight into the nonequilibrium physics of semiconductors. Here, we investigate the ultrafast transient response of semiconducting monolayer 2 H -MoTe 2 encapsulated with h BN using broadband optical pump-probe microscopy. The sub-40 fs pump pulse triggers extremely intense and long-lived coherent oscillations in the spectral region of the A' and B' exciton resonances, up to ∼20% of the maximum transient signal, due to the displacive excitation of the out-of-plane A 1g phonon. Ab initio calculations reveal a dramatic rearrangement of the optical absorption of monolayer MoTe 2 induced by an out-of-plane stretching and compression of the crystal lattice, consistent with an A 1g -type oscillation. Our results highlight the extreme sensitivity of the optical properties of monolayer TMDs to small structural modifications and their manipulation with light.

Anticancer therapy screening in vitro identifies additional treatments and improves clinical outcomes. Systematically, although most tested cells respond to cues with apoptosis, an appreciable portion enters a senescent state, a critical condition potentially driving tumor resistance and relapse. Conventional screening protocols would strongly benefit from prompt identification and monitoring of therapy-induced senescent (TIS) cells in their native form. We combined complementary all-optical, label-free, and quantitative microscopy techniques, based on coherent Raman scattering, multiphoton absorption, and interferometry, to explore the early onset and progression of this phenotype, which has been understudied in unperturbed conditions. We identified TIS manifestations as early as 24 hours following treatment, consisting of substantial mitochondrial rearrangement and increase of volume and dry mass, followed by accumulation of lipid vesicles starting at 72 hours. This work holds the potential to affect anticancer treatment research, by offering a label-free, rapid, and accurate method to identify initial TIS in tumor cells.

Strain engineering is an attractive approach for tuning the local optoelectronic properties of transition metal dichalcogenides (TMDs). While strain has been shown to affect the nanosecond carrier recombination dynamics of TMDs, its influence on the sub-picosecond electronic relaxation dynamics is still unexplored. Here, we employ a combination of time-resolved photoemission electron microscopy (TR-PEEM) and nonadiabatic ab initio molecular dynamics (NAMD) to investigate the ultrafast dynamics of wrinkled multilayer (ML) MoS 2 comprising 17 layers. Following 2.41 eV photoexcitation, electronic relaxation at the Γ valley occurs with a time constant of 97 ± 2 fs for wrinkled ML-MoS 2 and 120 ± 2 fs for flat ML-MoS 2 . NAMD shows that wrinkling permits larger amplitude motions of MoS 2 layers, relaxes electron-phonon coupling selection rules, perturbs chemical bonding, and increases the electronic density of states. As a result, the nonadiabatic coupling grows and electronic relaxation becomes faster compared to flat ML-MoS 2 . Our study suggests that the sub-picosecond electronic relaxation dynamics of TMDs is amenable to strain engineering and that applications which require long-lived hot carriers, such as hot-electron-driven light harvesting and photocatalysis, should employ wrinkle-free TMDs.

Mechanical stimuli from the extracellular environment affect cell morphology and functionality. Recently, we reported that mesenchymal stem cells (MSCs) grown in a custom-made 3D microscaffold, the Nichoid, are able to express higher levels of stemness markers. In fact, the Nichoid is an interesting device for autologous MSC expansion in clinical translation and would appear to regulate gene activity by altering intracellular force transmission. To corroborate this hypothesis, we investigated mechanotransduction-related nuclear mechanisms, and we also treated spread cells with a drug that destroys the actin cytoskeleton. We observed a roundish nuclear shape in MSCs cultured in the Nichoid and correlated the nuclear curvature with the import of transcription factors. We observed a more homogeneous euchromatin distribution in cells cultured in the Nichoid with respect to the Flat sample, corresponding to a standard glass coverslip. These results suggest a different gene regulation, which we confirmed by an RNA-seq analysis that revealed the dysregulation of 1843 genes. We also observed a low structured lamina mesh, which, according to the implemented molecular dynamic simulations, indicates reduced damping activity, thus supporting the hypothesis of low intracellular force transmission. Also, our investigations regarding lamin expression and spatial organization support the hypothesis that the gene dysregulation induced by the Nichoid is mainly related to a reduction in force transmission. In conclusion, our findings revealing the Nichoid's effects on MSC behavior is a step forward in the control of stem cells via mechanical manipulation, thus paving the way to new strategies for MSC translation to clinical applications., Competing Interests: Since December 5, 2019, M.T.R., G.C., and R.O. are co-founders of MOAB S.r.l and hold stock in the company. The other authors declare no competing financial interest., (© 2023 Author(s).)

Defects in two-dimensional (2D) transition metal dichalcogenides (TMDs) greatly influence their electronic and optical properties by introducing localized in-gap states. Using different non-invasive techniques, we have investigated the spatial distribution of intrinsic defects in as-grown chemical vapor deposition (CVD) MoS 2 monolayers and correlated the results with the growth temperature of the sample. We have shown that by increasing the CVD growth temperature the concentration of defects decreases and their spatial distribution and type change, influencing the sample's electronic and optical properties., (© 2023 IOP Publishing Ltd.)

Background & Aims: The bioelectrical impedance vector analysis (BIVA) represents a qualitative analysis of body composition. The vector, defined by resistance (R) and reactance (Xc) standardized by stature, can be evaluated compared to the 50%,75%, and 95% tolerance ellipses representative of the reference populations. The tolerance ellipses for healthy adults have been provided in 1995 and were developed by mixing underage, adult, and elderly subjects, possibly misrepresenting the actual adult population. The current multicentric, cross-sectional study aimed to provide new tolerance ellipses specific for the general adult population and as a secondary aim to present centile curves for the bioelectrical phase angle., Methods: R, Xc, and phase angle were measured in 2137 and 2230 males and females using phase-sensitive foot-to-hand analyzers at 50 kHz. A minimum of 35 subjects were included for each sex and age category from 18 to 65 years., Results: The new mean vectors showed a leftward shift on the R-Xc graph with respect to the former reference values (males: F = 75.3; p < 0.001; females: F = 36.6, p < 0.001). The results provided new 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, and 97th percentile curves for phase angle, identifying time point phases of decrement (males: -0.03° per year at 33.0-51.0 years and -0.05° per year after 51 years; females: -0.03° per year from 37.2 to 57.9 years)., Conclusions: Compared to the original references, the new data are characterized by a different distribution within the R-Xc graph with a higher phase angle. Thirty years after the BIVA invention, the current study presents new tolerance ellipses and phase angle reference values for the adult population., Competing Interests: Conflicts of interest The authors declare that they have no competing interests., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Nonlinear spectroscopy with quantum entangled photons is an emerging field of research that holds the promise to achieve superior signal-to-noise ratio and effectively isolate many-body interactions. Photon sources used for this purpose, however, lack the frequency tunability and spectral bandwidth demanded by contemporary molecular materials. Here, we present design strategies for efficient spontaneous parametric downconversion to generate biphoton states with adequate spectral bandwidth and at visible wavelengths. Importantly, we demonstrate, by suitable design of the nonlinear optical interaction, the scope to engineer the degree of spectral correlations between the photons of the pair. We also present an experimental methodology to effectively characterize such spectral correlations. Importantly, we believe that such a characterization tool can be effectively adapted as a spectroscopy platform to optically probe system-bath interactions in materials., (© 2023 Author(s). Published under an exclusive license by AIP Publishing.)

One-dimensional (1D) linear nanostructures comprising sp -hybridized carbon atoms, as derivatives of the prototypical allotrope known as carbyne, are predicted to possess outstanding mechanical, thermal, and electronic properties. Despite recent advances in their synthesis, their chemical and physical properties are still poorly understood. Here, we investigate the photophysics of a prototypical polyyne (i.e., 1D chain with alternating single and triple carbon bonds) as the simplest model of finite carbon wire and as a prototype of sp -carbon-based chains. We perform transient absorption experiments with high temporal resolution (<30 fs) on monodispersed hydrogen-capped hexayne H─(C≡C) 6 ─H synthesized by laser ablation in liquid. With the support of computational studies based on ground state density functional theory (DFT) and excited state time-dependent (TD)-DFT calculations, we provide a comprehensive description of the excited state relaxation processes at early times following photoexcitation. We show that the internal conversion from a bright high-energy singlet excited state to a low-lying singlet dark state is ultrafast and takes place with a 200 fs time constant, followed by thermalization on the picosecond time scale and decay of the low-energy singlet state with hundreds of picoseconds time constant. We also show that the time scale of these processes does not depend on the end groups capping the sp -carbon chain. The understanding of the primary photoinduced events in polyynes is of key importance both for fundamental knowledge and for potential optoelectronic and light-harvesting applications of low-dimensional nanostructured carbon-based materials.