We experimentally studied the formation of CH-(A) radicals in butane seeded plasma generated with chirp-controlled ultrashort laser pulses (∼760 μJ/pulse, 890 nm, 1 kHz, 8 fs). The focused beam with high peak intensity (∼1014-1016 W/cm2) caused Coulomb explosion (CE). The time-dependent emission spectra were observed with the Fourier-transform Visible spectroscopy (FTVis) step-scan method. The average signal intensity decreased with the chirp in the Ar+ > C2 > H-α ∼ CH-(A) order, with a plateau for CH-(A) in the -200 to -100 fs2 range. The short rise time of the CH-(A) emission signal, the monoexponential emission decay and the nearly constant rotational and vibrational temperatures of the CH-(A) radicals (∼3000 and ∼3800 K) all support their potential formation as a primary product (<120 fs) or in other photodissociation, neutralization processes before collisions of the fragments (<2 ns). Our TDDFT calculations predict that CH and many other fragments can be formed beyond CE at ∼7 × 1014 W/cm2 intensity. The average charge of CH (+0.6) and its relative abundance (0.5%) support the formation of detectable CH-(A) within 120 fs. Suitable optical gating techniques and measurement of the temporal evolution of the electron density in plasma could elucidate the relative importance of the different formation pathways of the CH-(A) radicals in the first nanosecond after CE.

Fragmentation dynamics in the Coulomb explosion of hydrocarbons, specifically methane, ethane, propane, and butane, are investigated using time-dependent density functional theory (TDDFT) simulations. The goal of this work is to elucidate the distribution of fragments generated under laser-driven Coulomb explosion conditions. Detailed analysis reveals the types of fragments formed, their respective charge states, and the optimal laser intensities required for achieving various fragmentations. Our results indicate distinct fragmentation patterns for each hydrocarbon, correlating with the molecular structure and ionization potential. Additionally, we identify the laser parameters that maximize fragmentation efficiency, providing valuable insights for experimental setups. This research advances our understanding of Coulomb explosion mechanisms and offers a foundation for further studies in controlled molecular fragmentation.

In this work, temperature dependent transient absorption spectroscopy measurements are presented on gallium-alloyed CdSe/ZnS core-shell nanoparticles between 30 and 130 degrees C. To our knowledge, temperature dependent measurements in these systems have been reported only in a few papers, although all processes related to carrier recombination are affected by temperature. For these experiments, gallium-alloyed CdSe/ZnS QD samples were used with nominal doping percentages of 2.5%, 7.5%, 15%. The experimental results show that the transient absorption decay is faster for the pristine CdSe/ZnS samples than in the gallium-alloyed samples at all temperatures. It is assumed that Ga-alloying promotes the formation of trions in the samples by introducing occupied impurity levels within the bandgap of CdSe. The resulting Coulomb blockade will, in turn, prolong the hot-electron relaxation process. By variation of the temperature, the distribution of charge carriers in the different recombination channels can be altered to accelerate recombination in the Ga-alloyed samples at higher temperatures. These measurements demonstrated their usefulness for observing the redistribution of charge carriers among different relaxation pathways.

2D transition metal dichalcogenides are an attractive family of materials in the field of electronics and optoelectronics. They are excellent candidates for sensitive photodetectors, light harvesting devices (photovoltaics, photocatalysts or photoelectrodes), lasers or non-linear optical devices. All these applications rely on light-matter interactions, which processes will ultimately decide the efficiency of the derived devices. Understanding carrier dynamics and the interaction of various exotic quasi-particles (excitons, trions) in these materials is of paramount importance to design better performing devices. Pump-probe transient absorption/reflection spectroscopy (TAS/TRS) is a powerful technique to study photophysical processes involved in charge carrier generation and recombination on the ultrafast timescale. In MoS2 photoelectrodes after light excitation different types of excitons are generated, and their decay can be monitored with these techniques. Coupling electrochemical techniques with these ultrafast methods, allows to probe the decay of the excited state in these materials under working conditions. In this manner the effect of trap state filling [1] or the effect of charge extraction [2] on the charge carrier dynamics of photoelectrochemical systems can be revealed. In my presentation I will show ultrafast spectroelectrochemical measurements on ITO/MoS2 photoelectrodes and reveal how the decay of excitons are influenced by the applied electrochemical bias. By comparing results from TAS/TRS spectroscopy the separation of carrier dynamics on the surface and bulk of these systems can be performed. These measurements reveal that the dissociation of excitons occurs at the ITO/MoS2 interface, resulting in a long living exciton population on the surface of these samples. Charging/discharging studies carried out in these systems reveal that the trap states involved in the dissociation of excitons in these systems can be permanently filled. The electrochemical filling of these trap states allows the tuning of the excited state lifetime of these systems, which can aid the better design of photoelectrochemical devices based on MoS2. References [1] ACS Energy Lett. 2019, 4, 3, 702–708 [2] J. Am. Chem. Soc. 2018, 140, 1, 86–89

We measured the exciton dynamics in van der Waals heterojunctions of transition metal dichalcogenides (TMDCs) and organic semiconductors (OSs). TMDCs and OSs are semiconducting materials with rich and highly diverse optical and electronic properties. Their heterostructures, exhibiting van der Waals bonding at their interfaces, can be utilized in the field of optoelectronics and photovoltaics. Two types of heterojunctions, MoS2-pentacene and WSe2-pentacene, were prepared by layer transfer of 20 nm pentacene thin films as well as MoS2 and WSe2 monolayer crystals onto Au surfaces. The samples were studied by means of transient absorption spectroscopy in the reflectance mode. We found that A-exciton decay by hole transfer from MoS2 to pentacene occurs with a characteristic time of 21 ± 3 ps. This is slow compared to previously reported hole transfer times of 6.7 ps in MoS2-pentacene junctions formed by vapor deposition of pentacene molecules onto MoS2 on SiO2. The B-exciton decay in WSe2 shows faster hole transfer rates for WSe2-pentacene heterojunctions, with a characteristic time of 7 ± 1 ps. The A-exciton in WSe2 also decays faster due to the presence of a pentacene overlayer; however, fitting the decay traces did not allow for the unambiguous assignment of the associated decay time. Our work provides important insights into excitonic dynamics in the growing field of TMDC-OS heterojunctions.

CH(A2Δ) radical formation was observed in bromoform and methanol vapor in argon plasma with near-infrared femtosecond laser pulses (43 fs, 1030 nm, 100 kHz, 250 μJ/pulse). The beam was focused with an achromatic lens, creating very high intensity in the plasma that caused Coulomb explosion (calculated intensity was ∼1.1 × 1016 W/cm2 in the focal point). The emitted fluorescence light was measured with high spectral (1-10 cm-1) and temporal resolution (5 ns) with an FT-Vis spectrometer. The step-scan technique allowed the reconstruction of the time-resolved fluorescence spectra from CH(A-X) emission. The emission from atomic lines such as H, Br, C, and O was observed and also from C+ cations and CH and C2 radicals. This indicates that in a significant portion of these organic molecules, all chemical bonds were cleaved in the Coulomb explosion. For both organics, the peak maximum of the CH(A) emission occurred at about 10 ns after excitation by the femtosecond pulse. After the maximum, a rapid emission decay was observed in the case of bromoform (monoexponential decay, t = 10 ns). The fluorescence decay was biexponential when methanol was used as the source for CH(A) generation. It can be assumed that CH(A) generation involved a fast and a slower path with some secondary reactions via the stepwise loss of hydrogen atoms from the CH3 group. The time constants were t1 = 7.8-8.3 ns and t2 = 78-82 ns for the fast and slow components, respectively, and very similar values were obtained at 10 and 25 mbar total pressures. However, in the case of bromoform, the C-Br bonds are significantly weaker; therefore, these atoms can be removed even in a single step via multiphoton absorption. The rotational temperature of CH(A) radicals generated from methanol decreased rapidly in the 30-55 ns time period from 2770 ± 80 to 1530 ± 50 K. The vibrational temperature increased from 3530 ± 450 to 9810 ± 760 K in the 30-80 ns time period and then started to decrease (the average temperatures were Trot = 910 ± 20 K and Tvib = 7490 ± 340 K at 100 ns). This initial increase of Tvib is thought to be the result of electron collision with the CH radicals. The high temperatures of the fragment may indicate the roaming reaction associated with the Coulomb explosion of the parent molecule. We demonstrated that CH(A) radicals can be produced from both organic compounds, and the step-scan technique is ideal for the characterization of their time-resolved spectra using the 100 kHz high repetition rate near-infrared femtosecond laser pulses. The FT/UV-vis step-scan technique can detect neutral species directly with high spectral and time resolution, thus it is a complementary technique to the experiments utilizing ion detection schemes, such as velocity map imaging.

Exploring the formation of diatomic radicals in femtosecond plasmas is important to establish the most dominant kinetic pathways following ionization and dissociation of small molecules. In this work, cyano radical formation has been studied from bromoform, acetonitrile, and methanol in nitrogen and argon plasmas created with a focused femtosecond laser beam operating at 100 kHz repetition rate and 1030 nm wavelength with 43 fs pulse length and 250 μJ pulse energy. Time-resolved Fourier transform fluorescence spectroscopy was applied in the ultraviolet-visible (UV-vis) spectral range for the characterization of the rotational and vibrational temperatures of the CN(B) radicals via fitting the experimental data. The high repetition rate of the laser allows efficient coupling with the step-scan Fourier transform spectroscopy method. Coulomb explosion at the very high intensity (∼1016 W/cm2) resulted in the formation of nascent atoms, ions, and electrons. The condensation reactions of carbon and reactive nitrogen species resulted in the formation of CN(B2Σ+) radicals and C2(d3Πg) dicarbon molecules/radicals. The CN(B) radicals were formed at the highest concentration in the case of bromoform because the weak carbon-bromine bonds resulted in reactive carbon atoms and CH radicals, which are reactive precursors for the CN(B) radical formation. In the case of acetonitrile, immediate production of CN(B) is observed with nanosecond resolution, which suggests that the CN is formed either via photodetachment or via roaming reaction associated with the Coulomb explosion of the parent molecule. The nascent rotational temperature was very high (∼6000-8500 K) and rapidly decreased in all instances within 40 ns with bromoform and acetonitrile. The highest vibrational temperature (∼7800 K) was observed in an acetonitrile/Ar mixture that decreased in about 30 ns and then increased in the observed time window. The vibrational temperature increased in all samples between 30 and 200 ns. The time dependence of fluorescence is described with a monoexponential decay in the case of acetonitrile/Ar and with biexponential decays in all other instances in the 0-250 mbar total pressure range. The shorter time constant is close to the radiative lifetime of CN(B) emission (∼60-80 ns), which can be attributed to the CN(B) radicals produced in the first few collisions at lower pressures. The longer CN(B) emission is from CN(B) created by slower chemical reactions involving carbon atoms, C2 radicals, and reactive nitrogen-containing species.

Tenofovir-associated renal toxicity is influenced by several factors, including plasma exposure and genetic variants in transporter-encoding genes. Tenofovir plasma exposure has been associated with a polymorphism in SLC28A2 gene (encoding the concentrative nucleoside transporter 2, CNT2): particularly, SLC28A2 124 CT/TT genotype patients show higher plasma tenofovir concentrations, compared to CC group. In literature, substrate studies are lacking; for this reason, our aim was to understand if tenofovir and tenofovir-alafenamide are CNT2 substrates. We performed an in vitro study using CNT2 expressing MDCKII cells. We observed that tenofovir and tenofovir-alafenamide are not substrates of CNT2. Tenofovir-alafenamide influx pathway remains to be clarified.

The aim of this review was to define appropriate 11B delivery agents for boron proton-capture enhanced proton therapy (BPCEPT) taking into account the accumulated knowledge on boron compounds used for boron neutron capture therapy (BNCT). BPCEPT is a promising treatment approach which uses a high linear energy transfer (LET) dose component in conjunction with conventional proton therapy to increase the relative biological effectiveness of highly-selective charged particle therapy. Boron proton fusion reactions occur with highest cross section at certain proton energy level and thus can be tailored to the target volume with careful treatment planning that defines the 675 MeV proton distribution with high accuracy. Appropriate 11B compounds are required in order to achieve relevant high LET dose contribution from the boron proton-capture reaction. Previous scientific results and experiences with BNCT provide background knowledge and information regarding the optimization of boronated compound development, their characterization, measurement and imaging. However, there are substantial differences between BNCT and BPCEPT, which in turn places special unique chemical, physical and biological demands on 11B-carrier compounds for BPCEPT. In this review, we evaluate well-known and recently developed boron compounds for BPCEPT.

TAK-875 (fasiglifam), a GPR40 agonist in development for the treatment of type 2 diabetes (T2D), was voluntarily terminated in Phase III trials due to adverse liver effects. The potential mechanisms of TAK-875 toxicity were explored by combining in vitro experiments with quantitative systems toxicology (QST) using DILIsym, a mathematical representation of drug-induced liver injury. In vitro assays revealed that bile acid transporters were inhibited by both TAK-875 and its metabolite, TAK-875-Glu. Experimental data indicated that human bile salt export pump (BSEP) inhibition by TAK-875 was mixed whereas sodium taurocholate co-transporting polypeptide (NTCP) inhibition by TAK-875 was competitive. Furthermore, experimental data demonstrated that both TAK-875 and TAK-875-Glu inhibit mitochondrial electron transport chain (ETC) enzymes. These mechanistic data were combined with a physiologically based pharmacokinetic (PBPK) model constructed within DILIsym to estimate liver exposure of TAK-875 and TAK-875-Glu. In a simulated population (SimPops) constructed to reflect T2D patients, 16/245 (6.5%) simulated individuals developed alanine aminotransferase (ALT) elevations, an incidence similar to that observed with 200 mg daily dosing in clinical trials. Determining the mode of bile acid transporter inhibition (K-i) was critical to accurate predictions. In addition, simulations conducted on a sensitive subset of individuals (SimCohorts) revealed that when either BSEP or ETC inhibition was inactive, ALT elevations were not predicted to occur, suggesting that the two mechanisms operate synergistically to produce the observed clinical response. These results demonstrate how utilizing QST methods to interpret in vitro experimental results can lead to an improved understanding of the clinically relevant mechanisms underlying drug-induced toxicity.

BACKGROUND:ABCB1 is a key ABC efflux transporter modulating the pharmacokinetics of a large percentage of drugs. ABCB1 is also a site of transporter mediated drug-drug interactions (tDDI). It is the transporter most frequently tested for tDDIs both in vitro and in the clinic.OBJECTIVE:Understanding the limitations of various in vitro and in vivo models, therefore, is crucial. In this review we cover regulatory aspects of ABCB1 mediated drug transport as well as inhibition and the available models and methods. We also discuss protein structure and mechanistic aspects of transport as ABCB1 displays complex kinetics that involves multiple binding sites, potentiation of transport and probe-dependent IC50 values.RESULTS:Permeability of drugs both passive and mediated by transporters is also a covariate that modulates apparent kinetic values. Levels of expression as well as lipid composition of the expression system used in in vitro studies have also been acknowledged as determinates of transporter activity. ABCB1-mediated clinical tDDIs are often complex as multiple transporters as well as metabolic enzymes may play a role. This complexity often masks the role of ABCB1 in tDDIs.CONCLUSION:It is expected that utilization of in vitro data will further increase with the refinement of simulations. It is also anticipated that transporter humanized preclinical models have a significant impact and utility.

Research Group of Environmental Chemis Szeged, H-6720, Szeged, Tisza Lajos krt. u-szeged.hu; Fax: +36-62-544338; Tel: +36-6 Department of Process Engineering, Faculty 6725, Szeged, Moszkvai krt. 9, Hungary Faculty of Chemistry and Chemical Engineer Arany János 11, Cluj-Napoca, Romania Faculty of Physics, Babes–Bolyai University Napoca, Romania Institute for Interdisciplinary Research on B Laurian 42, Cluj-Napoca, Romania Department of Applied and Environmental Rerrich tér 1, Szeged, Hungary Cite this: RSC Adv., 2015, 5, 66636

For the visible light driven photocatalytic performance of rutile the presence of Ti–O–O– entities is more preferable than Ti3+.

As visible light driven photocatalysis became more and more intensively studied, the first commercial products showed up on the market. Simultaneously controversial results appeared in the literature generating an intensive debate regarding the advantages and draw-backs of nitrogen doping of titania. Hence, the present work focuses on two commercially available and four sal gel made nitrogen modified titania powders regarding their structure and activity. It is demonstrated that the interstitial nitrogen entities "leak out" from the catalysts if the material is irradiated with UV light, while substitutional nitrogen remains stable. However, the latter one was proven to be less important in the photocatalytic point of view. These observations were also valid in the case of sol gel made nitrogen modified titanias. Furthermore, the results obtained after applying different spectroscopic methods (IR, XPS and DRS) shown that the yellow color of the titanias, does not necessary mean that a successful doping is achieved. (C) 2014 Elsevier B.V. All rights reserved.

A simple method of persistent immobilization was developed for the fixing of highly efficient precrystallized (or even doped) titania (TiO 2 ) based photocatalysts. TiO 2 nanoparticles (Aeroxide P25 and VLP7000) were immobilized on the surface of Al 2 O 3 -based ceramic paper. For the immobilization, a titanium alkoxide (Ti(OEt) 4 ) was applied as a fixing agent. This type of immobilization resulted in a photocatalytically active surface, which was used in fixed-bed flow reactors through the application of different forms of artificial or solar irradiation to activate the TiO 2 . To verify the stability, the decomposition of phenol was repeatedly measured on the same TiO 2 -covered ceramic paper; the photocatalytic performance proved to remain constant throughout five 2-h cycles. The potential for application on an industrial scale was demonstrated by a pilot-plant-scale flow reactor. The developed immobilization method is a simple technique that can be used to investigate the long-term efficiency of novel TiO 2 samples, or can be applied in real air/water treatments.

The primary objective of the experiments was to investigate the differences in the photocatalytic performance when commercially available Aeroxide P25 TiO2 photocatalyst was deposited with differently sized Pt nanoparticles with identical platinum content (1 wt%). The noble metal deposition onto the TiO2 surface was achieved by in situ chemical reduction (CRIS) or by mixing chemically reduced Pt nanoparticle containing sols to the aqueous suspensions of the photocatalysts (sol-impregnated samples, CRSIM). Fine and low-scale control of the size of resulting Pt nanoparticles was obtained through variation of the trisodium citrate concentration during the syntheses. The reducing reagent was NaBH4. Photocatalytic activity of the samples and the reaction mechanism were examined during UV irradiation (λmax = 365 nm) in the presence of oxalic acid (50 mM) as a sacrificial hole scavenger component. The H2 evolution rates proved to be strongly dependent on the Pt particle size, as well as the irradiation time. A significant change of H2 formation rate during the oxalic acid transformation was observed which is unusual. It is probably regulated both by the decomposition rate of accumulated oxalic acid and the H+/H2 redox potential on the surface of the catalyst. The later potential is influenced by the concentration of the dissolved H2 gas in the reaction mixture.

One weight percent of differently sized Au nanoparticles were deposited on two commercially available TiO2 photocatalysts: Aeroxide P25 and Kronos Vlp7000. The primary objective was to investigate the influence of the noble metal particle size and the deposition method on the photocatalytic activity. The developed synthesis method involves a simple approach for the preparation of finely-tuned Au particles through variation of the concentration of the stabilizing agent. Au was deposited on the TiO2 surface by photo- or chemical reduction, using trisodium citrate as a size-tailoring agent. The Au-TiO2 composites were synthetized by in situ reduction or by mixing the titania suspension with a previously prepared gold sol. The H2 production activities of the samples were studied in aqueous TiO2 suspensions irradiated with near-UV light in the absence of dissolved O2, with oxalic acid or methanol as the sacrificial agent. The H2 evolution rates proved to be strongly dependent on Au particle size: the highest H2 production rate was achieved when the Au particles measured ~6 nm.

In this study visible light active iodine doped titanium dioxide samples prepared by sol-gel method were investigated. Photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray fluorescence spectroscopy (XFS), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and by Brunauer-Emmett-Teller (BET) surface area technique.Different iodine/titanium ratios (eta(I)/eta(Ti) = 0.0-2.6) were applied during the synthesis and the optimum value was determined by phenol degradation under UV and VIS irradiations. The photocatalytic efficiency towards phenol degradation and the inactivation of Escherichia coli (E. coli) contaminated water under visible light illumination (conventional 24W energy-saving compact fluorescence lamps) of the most active iodine-doped TiO2 (eta(I)/eta(Ti) = 0.5; 79.5 m(2)/g; 98 wt% anatase) was compared with well known reference photocatalysts, that are Aeroxide P25 and Aldrich anatase (>85 nm primary crystallite size). Results showed that our iodine doped TiO2 was far more efficient at inactivating the E. coli and decomposing the phenol than Aeroxide P25. Electron spin resonance (ESR) measurements confirmed the formation of highly reactive OH center dot radicals by the iodine doped titania under VIS irradiation. In contrast, singlet oxygen and superoxide radical ions were not detected. The performed experiments also proved that dissolved iodine was produced in very low concentrations (about 0.01-0.025 mg/L) from the irradiated titanium dioxide. The dissolved iodine could have some contribution to the phenol oxidation and the disinfection effects. This study demonstrated this property of iodine-doped titanias for the first time. (C) 2012 Elsevier B.V. All rights reserved.

Titanium dioxide multiwall carbon nanotube (TiO2/MWCNT) composite photocatalysts were synthesized by the hydrolysis of titanium containing precursor adsorbed on the surface of MWCNT. Annealing was applied to convert amorphous titania oxide-hydroxide to crystalline material. The prepared photocatalysts were characterized with TEM, XRD and Raman spectroscopy. XRD and Raman results showed that only anatase-phase titanium dioxide is present in the samples. Generally this is the preferred phase as it is photocatalytically more active than all other TiO2 phases. TEM investigations revealed that the prepared photocatalysts have well defined structures; the MWCNTs were decorated with TiO2 nanoparticles. The photocatalysts were tested in aqueous-phase photocatalytic reactions using sol-gel prepared TiO2 as references. The choice of model compounds was based on their aromatic and polar characteristics. The concentration of the model compounds (phenol and oxalic acid) was measured by HPLC technique. These investigations showed that photocatalytic activity does depend on the model compound and the percentage of MWCNT content. The sample containing 5% MWCNT was the most efficient for oxalic acid decomposition under UV irradiation while the sample containing 1% MWCNT performed the best in phenol decomposition under our experiment conditions. For both model compounds, there are MWCNTs containing samples which are better than the similar way prepared TiO2 reference samples. (C) 2013 Elsevier B.V. All rights reserved.

This study aimed at comparing the photocatalytic efficiencies of various TiO2 based photocatalysts for phenol degradation and bacteria inactivation under illumination with visible light. Commercial undoped anatase and rutile (both from Aldrich), Aeroxide P25 (Evonik Industries), nitrogen-doped anatase (Sumitomo TP-S201, Sumitomo Chemical Inc.), nitrogen and sulphur co-doped anatase (Kronos VLP7000, Kronos Titan GmbH), and our custom-synthesized nitrogen- and iron-doped TiO2, as well as nitrogen and sulphur co-doped Aeroxide P25 and silver- and gold-deposited Aeroxide P25 were studied. The photocatalytic efficiency of different types of titanium dioxide based photocatalysts was determined by inactivation of Escherichia coli K12 bacteria and by phenol decomposition. Electron spin resonance (ESR) in combination with spin trapping was used to get insight into the reactive oxygen species (ROS)-mediated photocatalytic processes in the presence of TiO2-based photocatalysts. ESR results confirmed that titanias which generated OH radicals were efficient in E. coli disinfection, whereas titanias that were unable to produce OH radicals did not reveal significant bactericidal action. Three of our home-made titanias (iron-, nitrogen-, nitrogen/sulphur) as well as the commercial nitrogen/sulphur codoped Kronos VLP7000 TiO2 showed higher efficiency of phenol degradation than the well-established reference photocatalyst, Aeroxide P25, but showed much lower (if any) activity for bacteria inactivation, including Kronos VLP7000, which revealed extremely high efficiency for phenol decomposition. Interestingly undoped Aldrich rutile (with large particles - 100–700nm) had the highest efficiency for inactivation of E. coli and also had fairly high activity of phenol degradation.