Environmental significance of PAH photoproduct formation: TiO nanoparticle influence, altered bioavailability, and potential photochemical mechanisms.

Interactions between polycyclic aromatic hydrocarbons (PAHs) and titanium dioxide (TiO) nanoparticles (NPs) can produce unforeseen photoproducts in the aqueous phase. Both PAHs and TiO-NPs are well-studied and highly persistent environmental pollutants, but the consequences of PAH-TiO-NP interactions are rarely explored. We investigated PAH photoproduct formation over time for benzo[a]pyrene (BaP), fluoranthene (FLT), and pyrene (PYR) in the presence of ultraviolet A (UVA) using a combination of analytical and computational methods including, identification of PAH photoproducts, assessment of expression profiles for gene indicators of PAH metabolism, and computational evaluation of the reaction mechanisms through which certain photoproducts might be formed.

Infrared photodesorption of CO from astrophysically relevant ices studied with a free-electron laser.

The infrared excitation and photodesorption of carbon monoxide (CO) and water-containing ices have been investigated using the FEL-2 free-electron laser light source at the FELIX laboratory, Radboud University, The Netherlands. CO-water mixed ices grown on a gold-coated copper substrate at 18 K were investigated. No CO photodesorption was observed, within our detection limits, following irradiation with light resonant with the C-O vibration (4.

A Spontaneously Electrical State of Matter.

ConspectusMolecular deposition on solid surfaces forms crystalline or amorphous/glassy thin solid films. Intermolecular interactions govern the packing and dynamics of these films. The connection between molecular structure and intermolecular interactions is based on understanding electrostatic forces, dispersion forces and hydrogen bonding.

Plasma degradation of contaminated PPE: an energy-efficient method to treat contaminated plastic waste.

The use of PPE has drastically increased because of the SARS-CoV-2 (COVID-19) pandemic as disposable surgical face masks made from non-biodegradable polypropylene (PP) polymers have generated a significant amount of waste. In this work, a low-power plasma method has been used to degrade surgical masks. Several analytical techniques (gravimetric analysis, scanning electron microscopy (SEM), attenuated total reflection-infra-red spectroscopy (ATR-IR), x-ray photoelectron spectroscopy (XPS), thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) and wide-angle x-ray scattering (WAXS)) were used to evaluate the effects of plasma irradiation on mask samples.

A theoretical study on spontaneous dipole orientation in ice structures.

Spontaneous dipole orientation is studied for a set of simulated porous ASW ice films on a substrate held at temperatures ranging from 10 K to 140 K. It is found that the water dipoles in the films obtained at the lower temperatures are oriented such that a negative electric field with a magnitude of 10-10 V m is obtained. The magnitude of the field increases approximately linearly with height above the substrate, akin to experimental observations, although the magnitude of our field increases faster.

Time-Related Alteration of Aqueous-Phase Anthracene and Phenanthrene Photoproducts in the Presence of TiO Nanoparticles.

Polycyclic aromatic hydrocarbons (PAHs) and titanium dioxide (TiO) nanoparticles (NPs) are photoactive environmental pollutants that can contaminate aquatic environments. Aqueous-phase interactions between PAHs and TiO-NPs are of interest due to their emerging environmental relevance, particularly with the deliberate application of TiO-NPs to remediate pollution events (e.g.

A new technique for determining the refractive index of ices at cryogenic temperatures.

A reflection-absorption optical (RAO) spectrometer, operating across the ultra-violet/visible (UV/visible) wavelength region, has been developed that allows simultaneous measurements of optical properties and thickness of thin solid films at cryogenic temperatures in ultrahigh vacuum. The RAO spectrometer enables such measurements to be made after ice deposition, as opposed to most current approaches which make measurements during deposition. This allows changes in the optical properties and in the thickness of the film to be determined subsequent to thermal, photon or charged particle processing.

Correction: Surface heterogeneity and inhomogeneous broadening of vibrational line profiles.

Correction for 'Surface heterogeneity and inhomogeneous broadening of vibrational line profiles' by Skandar Taj et al., Phys. Chem.

Surface heterogeneity and inhomogeneous broadening of vibrational line profiles.

The surface heterogeneity of amorphous silica (aSiO) has been probed using coverage dependent temperature programmed desorption (TPD) of a simple probe molecule, carbon monoxide (CO). The resulting distribution of interaction energies is the foundation from which an environmentally broadened vibrational line profile synthesis has been undertaken. These simulations are compared with measured line profiles recorded at 0.

Molecular hydrogen production from amorphous solid water during low energy electron irradiation.

This work investigates the production of molecular hydrogen isotopologues (H, HD, and D) during low energy electron irradiation of layered and isotopically labelled thin films of amorphous solid water (ASW) in ultrahigh vacuum. Experimentally, the production of these molecules with both irradiation time and incident electron energy in the range 400 to 500 eV is reported as a function of the depth of a buried DO layer in an HO film. H is produced consistently in all measurements, reflecting the HO component of the film, though it does exhibit a modest reduction in intensity at the time corresponding to product escape from the buried DO layer.

Peeling the astronomical onion.

Water ice is the most abundant solid in the Universe. Understanding the formation, structure and multiplicity of physicochemical roles for water ice in the cold, dense interstellar environments in which it is predominantly observed is a crucial quest for astrochemistry as these are regions active in star and planet formation. Intuitively, we would expect the mobility of water molecules deposited or synthesised on dust grain surfaces at temperatures below 50 K to be very limited.

Electrons, excitons and hydrogen bonding: electron-promoted desorption from molecular ice surfaces.

Desorption of benzene (CH) from thick methanol (CHOH) and diethyl ether (CHCHOCHCH) ices during irradiation with 250 eV electrons is reported and compared with our previous work on CH desorption from water (HO) ice systems. CH electron-promoted desorption (EPD) is seen to be sensitive to the chemical nature of the substrate reflecting both the importance of the excitations localised around the O-atom versus those involving the C-atom; and the role of hydrogen bonding interactions in transporting non-dissociative electronic excitation to the substrate/CH interfaces during the electron irradiation.

Non-covalent interaction of benzene with methanol and diethyl ether solid surfaces.

We present laboratory experiments on binary, layered ices comprised of benzene (C6H6) on methanol (CH3OH) and on diethyl ether (CH3CH2OCH2CH3). Temperature programmed desorption (TPD) and reflection-absorption infrared spectroscopy (RAIRS) have been used to investigate the growth mechanisms in these systems. Ab initio quantum chemical calculations on simple gas-phase model clusters are used to aid interpretation of the experimental data by highlighting the key interactions established at the interface.

Effect of humic substances aggregation on the determination of fluoride in water using an ion selective electrode.

The control of drinking water quality is critical in preventing fluorosis. In this study humic substances (HS) are considered as representative of natural organic matter (NOM) in water. We show that when HS aggregate the response of fluoride ion selective electrodes (ISE) may be perturbed.

Efficient electron-promoted desorption of benzene from water ice surfaces.

Desorption of benzene (C6H6) from solid water surfaces [compact amorphous solid water (c-ASW) and crystalline ice (CI)] during irradiation of ultrathin solid films with low energy (250-300 eV) electrons has been investigated. The observed desorption behaviour is complex but typically two desorption components, with particularly large cross-sections, were present in the observed signal. A fast component, with a cross-section up to 10(-15) cm(2), is attributed to desorption of isolated C6H6 molecules that are hydrogen-bonded to small clusters of water (H2O) molecules on the solid water surface.

Spontaneous polarization of solid CO on water ices and some astrophysical implications.

Reflection absorption infrared spectroscopy (RAIRS) is used to show that when 20 monolayer (ML) films of solid CO are laid down on solid water substrates at 20 to 24 K, the films polarize spontaneously. CO films were prepared on three types of water ice: porous amorphous solid water (CO-pASW), crystalline water (CO-CSW) and compact amorphous solid water (CO-cASW) with corresponding fields of 3.76 ± 0.

Spontaneous electric fields in solid carbon monoxide.

Reflection-absorption infrared spectroscopy (RAIRS) is shown to provide a means of observing the spontelectric phase of matter, the defining characteristic of which is the occurrence of a spontaneous and powerful static electric field within a film of material. The presence of such a field is demonstrated here through the study of longitudinal-transverse optical splitting in RAIR spectra in films of carbon monoxide, based upon the deposition temperature dependence of this splitting. Analysis of spectral data, in terms of the vibrational Stark effect, allows the measurement of the polarization of spontelectric films, showing for example that solid carbon monoxide at 20 K may maintain a spontelectric field of 3.

Spontaneously electrical solids in a new light.

Reflection-absorption infrared spectroscopy (RAIRS) of nitrous oxide (N2O) thin films is shown to provide an independent means of observing the spontelectric state, the first new structural phase of matter, with unique electrical properties, to have emerged in decades. The presence of a spontaneous and powerful static electric field within the film, the defining characteristic of spontelectric solids, is demonstrated through observations of longitudinal-transverse optical (LO-TO) splitting in RAIR spectra, using an analysis based on the vibrational Stark effect. In particular the dependence of the LO-TO splitting on the film deposition temperature may be wholly attributed to the known temperature dependence of the spontelectric field.

Investigations into the nature of spontelectrics: nitrous oxide diluted in xenon.

The recent discovery of a new class of solids displaying bulk spontaneous electric fields as high as 10(8) V m(-1), so-called 'spontelectrics', poses fundamental and unresolved problems in solid state physics. The purpose of the present work is to delve more deeply into the nature of the interactions which give rise to the spontelectric effect in films of nitrous oxide (N2O), by observing the variation of the spontaneous field as the N2O molecules are physically removed from one another by dilution in Xe. Data, obtained using the ASTRID storage ring, are presented for films diluted by factors ξ = Xe/N2O of 0.