Kinetics and Mechanisms of Solar UVB Disinfection of Vesicle-Cloaked Murine Norovirus Clusters and Free Noroviruses.

Human norovirus, a major global cause of gastroenteritis, forms vesicle-cloaked virus clusters (known as viral vesicles), showing increased infectivity and persistence in aquatic environments. We investigated UVB disinfection, a key mechanism of solar disinfection commonly employed in developing countries, targeting murine norovirus vesicles and free murine noroviruses as surrogates for human noroviruses. At low viral concentrations of 10 gene copies per liter, viral infectivity loss as quantified by the integrated cell culture-reverse transcription-quantitative polymerase chain reaction (ICC-RT-qPCR) indicated that vesicles were 1.

Wavelength Sensitive Plastic Photodissolution: Elucidating Quantum Yield Trends for Solar Activation Spectra.

Plastic photodissolution into dissolved organic carbon (DOC) is a key proposed loss pathway for plastic in aquatic environments. However, the specific solar excitation wavelengths that drive photodissolution remain unknown, limiting our ability to model and predict photodissolution rates in natural aquatic environments. To better understand the impact of solar excitation wavelength on plastic photodissolution rates, we measured the wavelength sensitivity of photodissolution for a variety of transparent and semitransparent commercial and postconsumer plastic films with wide-spanning polymer chemistries.

Singlet Oxygen Quantum Yields of Pyrogenic Dissolved Organic Matter from Lab-Prepared and Wildfire Chars.

Wildfires or prescribed fires release pyrogenic dissolved organic matter (pyDOM) into the environment, which can photochemically produce singlet oxygen (O) in sun-lit surface waters. O quantum yields (Φ) are well-studied for non-pyrogenic DOM, but little is understood about the O generation from pyDOM, especially the Φ values from real wildfire samples and their wavelength dependence. In this study, time-resolved O phosphorescence was used to determine the wavelength-dependent Φ values for pyDOM generated from wildfire char and a series of lab-prepared chars produced by combusting oak and pine wood.

The Overlooked Photochemistry of Iodine in Aqueous Suspensions of Fullerene Derivatives.

Fullerene's low water solubility was a serious challenge to researchers aiming to harness their excellent photochemical properties for aqueous applications. Cationic functionalization of the fullerene cage provided the most effective approach to increase water solubility, but common synthesis practices inadvertently complicated the photochemistry of these systems by introducing iodide as a counterion. This problem was overlooked until recent work noted a potentiation effect which occurred when photosensitizers were used to inactivate microorganisms with added potassium iodide.

Singlet Oxygen Quantum Yields in Environmental Waters.

Singlet oxygen (O) is a reactive oxygen species produced in sunlit waters via energy transfer from the triplet states of natural sensitizers. There has been an increasing interest in measuring apparent O quantum yields (Φ) of aquatic and atmospheric organic matter samples, driven in part by the fact that this parameter can be used for environmental fate modeling of organic contaminants and to advance our understanding of dissolved organic matter photophysics. However, the lack of reproducibility across research groups and publications remains a challenge that significantly limits the usability of literature data.

Hand-ground fullerene-nanodiamond composite for photosensitized water treatment and photodynamic cancer therapy.

The unique capability of fullerene (C) to absorb light and generate reactive oxygen species (ROS) has been extensively studied for photosensitized water treatment and cancer therapy. Various material synthesis strategies have been proposed in parallel to overcome its intrinsic hydrophobicity and to enhance availability in water and physiological media. We present here a strikingly simple approach to make C available to these applications by hand-grinding dry C powder with nanodiamond (ND) using a mortar and pestle.

Dissolved Organic Matter Singlet Oxygen Quantum Yields: Evaluation Using Time-Resolved Singlet Oxygen Phosphorescence.

Singlet oxygen (O) generation quantum yields from chromophoric dissolved organic matter (CDOM) have been reported for many samples over the past 4 decades. Yet even for standardized isolates such as those from the International Humic Substance Society (IHSS), wide-ranging values exist in the literature. In this manuscript, time-resolved O phosphorescence was used to determine the O quantum yields (Φ) of a variety of dissolved organic matter (DOM) isolates and natural waters.

Sorbic Acid as a Triplet Probe: Reactivity of Oxidizing Triplets in Dissolved Organic Matter by Direct Observation of Aromatic Amine Oxidation.

Sorbic acid (2,4-hexadienoic acid; HDA) isomerization is frequently used to probe triplet-state dissolved organic matter (CDOM*) reactivity, but there remain open questions about the reaction kinetics of CDOM* with HDA due to the difficulties of directly measuring CDOM* quenching rate constants. Using our recently developed approach based on observing the radical cation of ,,','-tetramethyl--phenylenediamine (TMPD) formed through oxidation of TMPD by CDOM*, we studied CDOM* quenching kinetics with HDA monitored via transient absorption spectroscopy. A competition kinetics-based approach utilizing formation yields of TMPD was developed, validated with model sensitizers, and used to determine bimolecular rate constants between CDOM* oxidants and HDA for diverse DOM isolates and natural waters samples, yielding values in the range of (2.

Sorbic Acid as a Triplet Probe: Triplet Energy and Reactivity with Triplet-State Dissolved Organic Matter via O Phosphorescence.

Sorbic acid (2,4-hexadienoic acid; HDA) is commonly used as a probe and quencher for triplet-excited chromophoric dissolved organic matter (CDOM*), an important transient species in natural waters, yet much remains unknown about its reactivity with CDOM* and its triplet energy. To better understand the quenching behavior of HDA, we measured HDA quenching rate constants for various humic substance isolates and whole waters with singlet oxygen (O) phosphorescence and determined the triplet energy of HDA. Low-temperature phosphorescence measurements determined the triplet energy of HDA to be 217 kJ mol, whereas a complementary method based on triplet quenching kinetics found a triplet energy of 184 ± 7 kJ mol.

Differences in photochemistry between seawater and freshwater for two natural organic matter samples.

We report changes in the excitation and resolved fluorescence spectra, inferred triplet formation and singlet oxygen formation abilities of two different Natural Organic Matter samples (NOM) in seawater vs. freshwater or NaCl solution. In artificial seawater solution (but not in NaCl solution), the natural water-derived NOM samples Suwannee River Natural Organic Matter (SRNOM) and Nordic Reservoir Natural Organic Matter (NRNOM) display large enhancements in fluorescence intensity.

Singlet Oxygen Phosphorescence as a Probe for Triplet-State Dissolved Organic Matter Reactivity.

Triplet-state chromophoric dissolved organic matter (CDOM*) plays an important role in aquatic photochemistry, yet much remains unknown about the reactivity of these intermediates. To better understand the kinetic behavior and reactivity of CDOM*, we have developed an indirect observation method based on monitoring time-resolved singlet oxygen (O) phosphorescence kinetics. The underpinning principle of our approach relies on the fact that O quenches almost all triplets with near diffusion limited rate constants, resulting in the formation of O, which is kinetically linked to the precursors.

Dual-Functionality Fullerene and Silver Nanoparticle Antimicrobial Composites via Block Copolymer Templates.

We present the facile prepartion of C and Ag nanoparticle (NP) loaded block copolymer (BCP) thin films, with C and Ag NPs working in tandem to provide virucidal and bactericidal activities, respectively. Polystyrene-block-poly-4-vinylpyridine (PS-P4VP) was used as a template, allowing C integration into PS domains and in situ formation of Ag NPs in P4VP domains, while providing control of the nanoscale spatial distribution of functionality as a function of BCP molecular weight (MW). C loaded PS-P4VP films were found to generate significant amounts of O under visible light illumination with no apparent dependence on BCP MW.

Porous Silicon's Photoactivity in Water: Insights into Environmental Fate.

Interest in porous silicon (pSi) (and, more broadly, silicon nanoparticles (NPs)) has increased along with their concomitant use in various commercial and consumer products, yet little is known about their behavior in the natural environment. In this study, we have investigated the photosensitization, optical, and surface properties of pSi as a function of time in aqueous systems. Samples were prepared via an anodic electrochemical etching procedure, resulting in pSi particles with diameters of ca.

Differential photoactivity of aqueous [C60] and [C70] fullerene aggregates.

Many past studies have focused on the aqueous photochemical properties of colloidal suspensions of C60 and various [C60] fullerene derivatives, yet few have investigated the photochemistry of other larger cage fullerene species (e.g., C70, C74, C84, etc.

Improving the Visible Light Photoactivity of Supported Fullerene Photocatalysts through the Use of [C₇₀] Fullerene.

We herein present the first instance of employing [C₇₀] fullerene for photocatalytic ¹O₂ production in water, through covalent immobilization onto a mesoporous silica support via nucelophilic amine addition directly to fullerene's cage. This attachment approach prevents the aggregation of individual fullerene molecules in water, thus allowing fullerene to retain its photoactivity, yet is much less complex than other techniques commonly pursued to create such supported-fullerene materials, which typically rely on water-soluble fullerene derivatives and elaborate immobilization methods. The solid-supported C₇₀ material exhibits significantly improved aqueous visible-light photoactivity compared to previous C₆₀- and C₆₀-derivative-based supported fullerene materials.

Functionalized fullerenes in water: a closer look.

The excellent photophysical properties of C60 fullerenes have spurred much research on their application to aqueous systems for biological and environmental applications. Spontaneous aggregation of C60 in water and the consequent diminution of photoactivity present a significant challenge to aqueous applications. The mechanisms driving the reduction of photoactivity in fullerene aggregates and the effects of functionalization on these processes, however, are not well understood.

Electron transfer mediation by aqueous C₆₀ aggregates in H₂O₂/UV advanced oxidation of indigo carmine.

C60 fullerene has long been known to exhibit favorable electron accepting and shuttling properties, but little is known about the possibility of electron transfer mediation by fullerene aggregates (nC60) in water. In this study, we investigated the electron shuttling capabilities of nC60 using UV/H2O2 as a model oxidation process in the presence of an electron donor, indigo carmine (IC). nC60 addition to the IC/H2O2 system was found to drastically increase IC degradation and shift the reactive oxygen species (ROS) balance, favoring the formation of superoxide and perhydroxyl radical species compared to hydroxyl radicals.

Simple synthetic method toward solid supported c60 visible light-activated photocatalysts.

Solid supported fullerene materials are prepared in aims of creating a fullerene-based photocatalyst that is capable of producing (1)O2 in the aqueous phase. Past studies of using fullerene as a photocatalyst in water have exclusively focused on using water soluble fullerene derivatives and employed sophisticated chemistry to create immobilized fullerene materials. The method presented herein is much less synthetically complex and utilizes pristine fullerene, providing a drastically simpler route to supported fullerene materials and furthering their potential for use in environmental applications.

[C70] fullerene-sensitized triplet-triplet annihilation upconversion.

We herein report the first instance of using pristine C70 as a heavy-atom free organic sensitizer for efficient triplet-triplet annihilation upconversion (UC) for both green-to-blue and red-to-green UC using 9,10-bis(phenylethynyl)anthracene and perylene as acceptors, respectively. C70 achieved quantum yields of 8% and 0.8% for green-to-blue and red-to-green UC, 25 to 35 times higher than C60, and showed improved stability under continuous laser irradiation compared to the benchmark platinum(II)-octaethylporphyrin.