Spider Webs as Passive Monitors of Microplastic and Its Copollutants in Indoor Environments.

Indoor environments are particularly vulnerable to microplastics (MPs) and associated copollutants due to limited air circulation and particulate matter accumulation. Continuous monitoring is essential to evaluate exposure levels and health risks. We propose using indoor spider webs as passive monitors for MPs and their copollutants.

Generation of 1 MHz 15 fs pulses in the near-infrared with high energy and their application to time-resolved spectroscopy.

Ultrashort pulses with a duration of ∼10 fs are crucial to fully resolve nuclear motions in molecules and materials. Here, we employ nonlinear pulse compression using photonic crystal fiber in the near-infrared region to generate ultrashort pulses at a high repetition rate with significant pulse energy. Femtosecond pulses centered around 1200 nm from a cavity-dumped optical parametric oscillator are compressed to a duration of 15 fs.

Slow solvation dynamics beyond dielectric relaxation by three-pulse photon echo peak shift.

The dynamics of a liquid and its coupling to a solute are crucial for a better understanding of chemical processes in the liquid phase. In isotropic and homogeneous solutions, the time-correlation function of a solute is expected to vanish over time due to the translational and diffusive motions of the solvent. The three-pulse photon echo peak shift (3PEPS) is a third-order nonlinear spectroscopy technique that records the time-correlation function of a solute molecule in a solution, including an offset (inhomogeneity).

Stratum-Confined Solid-State Reaction (SC-SSR) toward Colloidal Silicon-Based Hollow Nanostructures for Bioapplications.

Silicon nanostructures (SiNSs) can provide multifaceted bioapplications; but preserving their subhundred nm size during high-temperature silica-to-silicon conversion is the major bottleneck. The SC-SSR utilizes an interior metal-silicide stratum space at a predetermined radial distance inside silica nanosphere to guide the magnesiothermic reduction reaction (MTR)-mediated synthesis of hollow and porous SiNSs. In depth mechanistic study explores solid-to-hollow transformation encompassing predefined radial boundary through the participation of metal-silicide species directing the in-situ formed Si-phase accumulation within the narrow stratum.

Excited State Intramolecular Proton Transfer Dynamics of Derivatives of the Green Fluorescent Protein Chromophore.

Excited state intramolecular proton transfer (ESIPT) dynamics of the -hydroxy analogs of the green fluorescent protein (GFP) chromophore have been investigated by time-resolved spectroscopies and theoretical calculations. These molecules comprise an excellent system to investigate the effect of electronic properties on the energetics and dynamics of ESIPT and to realize applications in photonics. Time-resolved fluorescence with high enough resolution was employed to record the dynamics and the nuclear wave packets in the excited product state exclusively in conjunction with quantum chemical methods.

Steering the multiexciton generation in slip-stacked perylene dye array via exciton coupling.

Dye arrays from dimers up to larger oligomers constitute the functional units of natural light harvesting systems as well as organic photonic and photovoltaic materials. Whilst in the past decades many photophysical studies were devoted to molecular dimers for deriving structure-property relationship to unravel the design principles for ideal optoelectronic materials, they fail to accomplish the subsequent processes of charge carrier generation or the detachment of two triplet species in singlet fission (SF). Here, we present a slip-stacked perylene bisimide trimer, which constitutes a bridge between hitherto studied dimer and solid-state materials, to investigate SF mechanisms.

A Plausible Mechanism of Uracil Photohydration Involves an Unusual Intermediate.

It is well-known that photolysis of pyrimidine nucleobases, such as uracil, in an aqueous environment results in the formation of hydrate as one of the main products. Although several hypotheses regarding photohydration have been proposed in the past, e.g.

Coherent Vibrational Spectrum via Time-Resolved Fluorescence for Molecular Dynamics and Identification of Emitting Species-Application to Excited-State Intramolecular Proton Transfer.

Time-resolved fluorescence (TF) with high-enough resolution enables recording of a coherent vibrational spectrum (CVS). Because a CVS attained via TF (CVSF) is descended from the frequency modulation of the fluorescence spectrum, it gives the vibrational spectrum of the emitting state. Therefore, CVSF can be a powerful tool for the identification of an emitting state along with the investigation of molecular dynamics in excited states.

Temperature-Dependent Fluorescence of mPlum Fluorescent Protein from 295 to 20 K.

The development of bright fluorescent proteins (FPs) emitting beyond 600 nm continues to be of interest both from a fundamental perspective in understanding protein-chromophore interactions and from a practical perspective as these FPs would be valuable for cellular imaging. We previously reported ultrafast spectral observations of the excited-state dynamics in mPlum resulting from interconversion between direct hydrogen bonding and water-mediated hydrogen bonding between the chromophore acylimine carbonyl and the Glu16 side chain. Here, we report temperature-dependent steady-state and time-resolved fluorescence measurements of mPlum and its E16H variant, which does not contain a side-chain permitting hydrogen bonding with the acylimine carbonyl.

Bismuth organic frameworks exhibiting enhanced phosphorescence.

Bismuth-based organic frameworks (BiOFs) can display interesting phosphorescent properties, but the relationship between structure and optical activity remains underexplored. The structure-dependent phosphorescence properties in the BiOFs are investigated using different multidentate ligands. In-depth analysis of the luminescence properties confirms that the densely packed framework shows long-lasting phosphorescence at room temperature, owing to an efficient electron-hole separation.

Coherent internal conversion from high lying electronic states to S in boron-dipyrromethene derivatives.

Internal conversion is the first step after photoexcitation to high lying electronic states, and plays a central role in many photoinduced processes. In this report, we demonstrate a truly ultrafast internal conversion (IC) in large molecules by time-resolved fluorescence (TF). Following photoexcitation to the S ( ≥ 2) state, TF of the S state was recorded for two boron-dipyrromethene (BODIPY) derivatives in solution.

Role of coherent nuclear motion in the ultrafast intersystem crossing of ruthenium complexes.

Ultrafast intersystem crossing (ISC) in transition metal complexes leads to a long-lived active state with a high yield, which leads to efficient light energy conversion. The detailed mechanism of ISC may lead to a rational molecular design of superior transition metal complexes. Coherent nuclear wave packets observed in femtosecond time-resolved spectroscopies provide important information on the excited-state dynamics.

Non-Born-Oppenheimer Molecular Dynamics Observed by Coherent Nuclear Wave Packets.

The reaction dynamics of a photochemical reaction is typically described by reaction coordinates based on the Born-Oppenheimer (BO) approximation. A strong interaction between electrons and nuclei, conventionally occurring at conical intersections, however, breaks the BO approximation and has major consequences for the efficiency of a photochemical reaction. Despite its importance, related studies into the non-BO dynamics are scarce.

A solvent-solute cooperative mechanism for symmetry-breaking charge transfer.

Symmetry-breaking charge transfer (SBCT) is an important process at the early stages of the photoinduced processes in multichromophore systems such as the photosynthetic apparatus. We investigated the photoinduced SBCT dynamics of 9,9'-bianthracene (BA), a representative molecule showing SBCT, by time-resolved fluorescence (TF) with the highest time-resolution and excited-state quantum mechanics/effective fragment potential molecular dynamics (MD) simulation. TF experiments show that the SBCT kinetics matches quantitatively with the solvation function excluding the initial ultrafast component that is assigned to the inertial motion of the solvent.

Visualizing biofilm by targeting eDNA with long wavelength probe CDr15.

Detection of the biofilm of bacteria would be a counter strategy to detect hidden bacteria in their camouflage. Through unbiased screening of bacteria biofilm, we discovered a long wavelength probe CDr15 with extracellular DNA as the molecular target. CDr15 revealed a real-time geometric distribution of eDNA in a 3D bacterial colony.

Electronic and Structural Dynamics of Dicyanoaurate Trimer in Excited State.

A trimer of dicyanoaurate has been studied as a model system of the covalent chemical bond formation. Here, we report the dynamics of dicyanoaurate trimer in water upon photoexcitation by femtosecond time-resolved luminescence (TL) and luminescence spectra at cyrogenic temperature. Temperature was varied as a means to control the medium flexibility as well as the population of isomers.

Molecular Dynamics of Excited State Intramolecular Charge Transfer in Solution by Coherent Nuclear Wave Packets.

Revealing a proper reaction coordinate in a chemical reaction is the key step towards elucidation of the molecular reaction dynamics. In this report, we investigated the dynamics of intramolecular charge transfer (ICT) of 8-aminopyrene-1,3,6-trisulfonic acid (APTS) occurring in the excited state by time-resolved fluorescence (TF) and TF spectra. Accurate reaction rates and rate-dependent nuclear wave packets in the product state allow detailed investigation of the molecular reaction dynamics.

Ultrafast time-resolved fluorescence at cryogenic temperature.

Time resolved fluorescence at low temperature can be a powerful tool for the study of dynamics and spectroscopy. We have developed a time resolved fluorescence apparatus that provides a time resolution of 45 fs at cryogenic temperature, which is comparable to the best time resolution at ambient temperature. A continuous flow cryostat with a customized vacuum shroud and fluorescence upconversion gating by sum frequency generation were employed.

Excited-State Dynamics of Thioflavin T: Planar Stable Intermediate Revealed by Nuclear Wave Packet Spectroscopies.

Time-domain spectroscopies with time resolution shorter than the vibrational periods of interest were employed to reveal the reaction kinetics and molecular dynamics of the intramolecular charge transfer (ICT) reaction of thioflavin T in liquids. Time-resolved fluorescence spectra provided detailed reaction kinetics, and vibrational wave packets observed in the time-resolved fluorescence and transient absorption provided structural information on the reaction intermediate. Upon photoexcitation, the Franck-Condon state undergoes vibrational relaxation and minor conformational change to form a stable planar intermediate followed by the twisting of the central C-C single bond to form the twisted ICT state.

Femtosecond-Resolved Excited State Relaxation Dynamics of Copper (II) Tetraphenylporphyrin (CuTPP) After Soret Band Excitation.

Excited state relaxation dynamics of Copper (II) tetraphenylporphyrin (CuTPP) after Soret band excitation have been investigated in various solvents by femtosecond broadband transient absorption spectroscopy. Significant role of charge transfer state has been confirmed from fast relaxation of triplet CuTPP in pyridine, giving τ ~ 26.5 ps.

Coherent intermolecular proton transfer in the acid-base reaction of excited state pyranine.

Detailed molecular dynamics simulations of an acid-base reaction have been the subject of extensive investigations. Here we report the excited state proton transfer dynamics of pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid, HPTS) in acetate buffer by time-resolved fluorescence (TF) and quantum mechanical/effective fragment potential molecular dynamics (QM/EFP-MD) simulations. High time resolution in TF and TF spectra measurements allows the acquisition of accurate reaction kinetics.

Reverse Anti-solvent Crystallization Process for the Facile Synthesis of Zinc Tetra(4-pyridyl)porphyrin Single Crystalline Cubes.

Synthesis of morphologically well-defined crystals of metalloporphyrin by direct crystallization based on conventional anti-solvent crystallization method without using any additives has been rarely reported. Herein, we demonstrate an unconventional and additive-free synthetic method named reverse anti-solvent crystallization method to achieve well-defined zinc-porphyrin cube crystals by reversing the order of the addition of solvents. The extended first solvation shell effect mechanism is therefore suggested to support the synthetic process by providing a novel kinetic route for reaching the local supersaturation environment depending on the order of addition of solvents, which turned out to be critical to achieve clean cube morphology of the crystal.

Excitation Intensity Dependent Carrier Dynamics of Chalcogen Heteroatoms in Medium-Bandgap Polymer Solar Cells.

The excitation intensity dependent carrier dynamics of blends with PC[70]BM of three new medium-band gap conjugated polymers with central chalcogen heteroatoms, PBDTfDTBX (X = O, T(Sulphur), Se) were studied. The PBDTfDTBX polymers (Poly[4,8-bis(5-(2-butyloctyl)thiophene-2-yl)benzo[1,2-b;4,5-b']dithiophene-alt-4,7-bis(4-(2-ethylhexyl)-2-thienyl)-dithieno[3',2':3,4;2″,3″:5,6]benzo[1,2-c][1,2,5] furazan or thiadiazole or selenadiazole]) have symmetrical structures but exhibit different solar cell performances. In this study, we determined how the photogenerated charge carrrier dynamics of the PBDTfDTBX:PC[70]BM blends varies with the heteroatom by performing transient absorption measurements at various excitation intensities.