Escherichia coli inactivation by water-soluble, ozonated C60 derivative: kinetics and mechanisms

An NIR-II-Emissive Photosensitizer for Hypoxia-Tolerant Photodynamic Theranostics

As a common feature in a majority of malignant tumors, hypoxia has become the Achilles' heel of photodynamic therapy (PDT). The development of type-I photosensitizers that show hypoxia-tolerant PDT efficiency provides a straightforward way to address this issue. However, type-I PDT materials have rarely been discovered. Herein, a π-conjugated molecule with A-D-A configuration, COi6-4Cl, is reported. The H₂ O-dispersible nanoparticle of COi6-4Cl can be activated by an 880 nm laser, and displays hypoxia-tolerant type I/II combined PDT capability, and more notably, a high NIR-II fluorescence with a quantum yield over 5%. Moreover, COi6-4Cl shows a negligible photothermal conversion effect. The non-radiative decay of COi6-4Cl is suppressed in the dispersed and aggregated state due to the restricted molecular vibrations and distinct intermolecular steric hindrance induced by its four bulky side chains. These features make COi6-4Cl a distinguished single-NIR-wavelength-activated phototheranostic material, which performs well in NIR-II fluorescence-guided PDT treatment and shows an enhanced in vivo anti-tumor efficiency over the clinically approved Chlorin e6, by the equal stresses on hypoxia-tolerant anti-tumor therapy and deep-penetration imaging. Therefore, the great potential of COi6-4Cl in precise PDT cancer therapy against hypoxia challenges is demonstrated.

Efficient bacteria inactivation by ligand-induced continuous generation of hydroxyl radicals in Fenton-like reaction

Fenton/Fenton-like reaction is often used as an efficient method to generate hydroxyl radicals (HO) for bacteria inactivation in aqueous solution. However, inactivation efficiency of bacteria in aqueous solution using Fenton/Fenton-like reactions needs to further improve as a result of transient generation of HO. In this paper, we found that the formation of Tris-Co(II) complexes could decrease the redox potential of Co(III)/Co(II), facilitating the transformation of Tris-Co(III) complexes into Tris-Co(II) complexes. Therefore, HO could be generated continuously in the presence of H₂O₂. Especially, Tris-Co(II) complexes are apt to combine with Escherichia Coli cells by electrostatic interactions, inducing a higher utilization ratio of the generated HO. Therefore, the proposed Tris-Co(II) complex-H₂O₂ system could be employed as a high-efficiency sterilizing reagent for inactivation of E. Coli. This work provides a promising strategy for bacterial inactivation via an economic and eco-friendly manner.

A mechanism study on the photocatalytic inactivation ofSalmonella typhimuriumbacteria by CuxO loaded rhodium–antimony co-doped TiO2nanorods

A detailed photocatalytic inactivation mechanism forS. typhimurium, using a Cu_xO/Rh–Sb–TiO₂NR was studied under visible light.

Sunlight-mediated inactivation of health-relevant microorganisms in water: a review of mechanisms and modeling approaches

Health-relevant microorganisms present in natural surface waters and engineered treatment systems that are exposed to sunlight can be inactivated by a complex set of interacting mechanisms. The net impact of sunlight depends on the solar spectral irradiance, the susceptibility of the specific microorganism to each mechanism, and the water quality; inactivation rates can vary by orders of magnitude depending on the organism and environmental conditions. Natural organic matter (NOM) has a large influence, as it can attenuate radiation and thus decrease inactivation by endogenous mechanisms. Simultaneously NOM sensitizes the formation of reactive intermediates that can damage microorganisms via exogenous mechanisms. To accurately predict inactivation and design engineered systems that enhance solar inactivation, it is necessary to model these processes, although some details are not yet sufficiently well understood. In this critical review, we summarize the photo-physics, -chemistry, and -biology that underpin sunlight-mediated inactivation, as well as the targets of damage and cellular responses to sunlight exposure. Viruses that are not susceptible to exogenous inactivation are only inactivated if UVB wavelengths (280-320 nm) are present, such as in very clear, open waters or in containers that are transparent to UVB. Bacteria are susceptible to slightly longer wavelengths. Some viruses and bacteria (especially Gram-positive) are susceptible to exogenous inactivation, which can be initiated by visible as well as UV wavelengths. We review approaches to model sunlight-mediated inactivation and illustrate how the environmental conditions can dramatically shift the inactivation rate of organisms. The implications of this mechanistic understanding of solar inactivation are discussed for a range of applications, including recreational water quality, natural treatment systems, solar disinfection of drinking water (SODIS), and enhanced inactivation via the use of sensitizers and photocatalysts. Finally, priorities for future research are identified that will further our understanding of the key role that sunlight disinfection plays in natural systems and the potential to enhance this process in engineered systems.

Synthesis of ZnO-nanorod-based materials for antibacterial, antifungal activities, DNA cleavage and efficient ultrasound-assisted dyes adsorption

Undoped and Au-doped ZnO-nanorods were synthesized in the presence of ultrasound and loaded on activated carbon following characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmittance electron microscopy (TEM), UV-vis spectrophotometry and Fourier transform infrared spectroscopy (FTIR). The Au-doped ZnO-nanorod-loaded activated carbon (Au-ZnO-NRs-AC) was used for the simultaneous removal of methylene blue (MB) and auramine O (AO) from aqueous solutions. Central composite design (CCD) under response surface methodology (RSM) was applied to model and optimize the dyes removal versus adsorbent mass, pH, and initial dyes concentration and sonication time as well as to investigate the possible interaction between these variables. The optimum values of the initial MB and AO dyes concentration, adsorbent mass, pH and sonication time were found to be 12 and 10mgL^-1, 0.0124g, 6.4, and 4min respectively. The rapid adsorption process at neutral pH using very small amount of the adsorbent makes it promising for the wastewater treatment applications. More than 99.5% of both dyes was removed with maximum adsorption capacities in binary-component system (107.5 and 95.7mgg^-1 for MB and AO, respectively). The kinetics and isotherm studies showed that the second-order and Langmuir models apply for the kinetics and isotherm of the adsorption of MB and AO on the adsorbent used here. Moreover, the wastewater treatment by using an antibacterial/antifungal adsorbent makes the process much more valuable. Therefore, additional studies were performed which showed efficient antibacterial/antifungal activities and DNA cleavage of undoped and Au-doped ZnO nanorods as constituent of the adsorbent applied here.

Boosting Photocatalytic Performance of Inactive Rutile TiO2 Nanorods under Solar Light Irradiation: Synergistic Effect of Acid Treatment and Metal Oxide Co-catalysts

In the present work, we accomplish the boosting of photocatalytic performance by the synergistic effect of acid treatment and transition metal oxide co-catalysts on molten salt rutile TiO₂ nanorods. FT-IR and XPS (oxygen deconvolution) results confirmed that the amount of hydroxyl groups increased on the surface of rutile TiO₂ nanorods (TO-NRs) after acid treatment. HR-TEM analysis revealed fine dispersion of metal oxide on the surface of acid treated TiO₂ nanorods (ATO-NRs). The photocatalytic activities of as-prepared (TO-NRs), acid treated (ATO-NRs), metal oxide loaded (MTO-NRs), and both acid treated and metal oxide loaded (MATO-NRs) nanorods were compared based on the rate kinetics and dye degradation efficiencies. Cobalt oxide (1 wt %) loaded and 1.0 M acid treated TiO₂ nanorods (Co/ATO-NR) exhibited the higher photocatalytic degradation efficiency for Orange-II dye degradation and inactivation of S. typhimurium pathogen compared to other photocatalysts under solar irradiation. Photoelectrochemical analysis demonstrated that the charge transfer process in Co/ATO-NR is significantly higher than that in the untreated samples. The improved photocatalytic activity of inactive TO-NRs might be due to enhanced charge transfer of finely dispersed metal oxides on the OH-rich surface of acid treated TiO₂ nanorods.

Degradation and Microbial Uptake of C60 Fullerols in Contrasting Agricultural Soils

The environmental fate of functionalized carbon nanomaterials (CNM) remains poorly understood. Using ¹³C-labeled nanomaterial we present the results of a study investigating the mineralization and microbial uptake of surface-functionalized C₆₀ (fullerols) in agricultural soils with contrasting properties. Soil microcosms rapidly mineralized fullerol C, as determined by ¹³C-content in the respired CO₂, with higher fullerol mineralization in an organic, clay-rich soil versus a silty, low C soil (∼56.3% vs ∼30.9% fullerol C mineralized over 65 days). By tracking the enriched ¹³C from fullerol into microbial phospholipid fatty acids (PLFA) we also report, for the first time, the incorporation of nanomaterial-derived C into soil microbial biomass, primarily by fungi and Gram-negative bacteria. While more fullerol C was incorporated into PLFA in the organic C-rich soil (0.77% vs 0.19% of PLFA C), this soil incorporated fullerol C into biomass less efficiently than the silty, low C soil (0.13% and 0.84% of assimilated fullerol C, respectively). These results demonstrate that, in contrast to pristine C₆₀, surface functionalized C₆₀ are unlikely to accumulate in surface soils and are readily mineralized by a range of soil microorganisms.

The disinfection performance and mechanisms of Ag/lysozyme nanoparticles supported with montmorillonite clay

The fabrication of montmorillonite (Mt) decorated with lysozyme-modified silver nanoparticles (Ag/lyz-Mt) was reported. The lysozyme (lyz) was served as both reducing and capping reagent. Coupling the bactericidal activity of the lyz with AgNPs, along with the high porous structure and large specific surface area of the Mt, prevented aggregation of AgNPs and promoted nanomaterial-bacteria interactions, resulting in a greatly enhanced bactericidal capability against both Gram positive and Gram negative bacteria. This paper systematically elucidated the bactericidal mechanisms of Ag/lyz-Mt. Direct contact between the Ag/lyz-Mt surface and the bacterial cell was essential to the disinfection. Physical disruption of bacterial membrane was considered to be one of the bactericidal mechanisms of Ag/lyz-Mt. Results revealed that Ag(+) was involved in the bactericidal activity of Ag/lyz-Mt via tests conducted using Ag(+) scavengers. A positive ROS (reactive oxygen species) scavenging test indirectly confirmed the involvement of ROS (O2(-), H2O2, and OH) in the bactericidal mechanism. Furthermore, the concentrations of individual ROS were quantified. Results showed that Ag/lyz-Mt nanomaterial could be a promising bactericide for water disinfection.

Visible Light Sensitized Production of Hydroxyl Radicals Using Fullerol as an Electron-Transfer Mediator

Fullerenes and their derivatives are known to photosensitize the production of singlet oxygen (¹O₂), but their role in generating hydroxyl radical (^•OH) under visible light has not been reported. Here, we demonstrate that fullerol can mediate the electron transfer from Rhodamine B dye to O₂ under visible light irradiation, achieving simultaneous dye decolorization and ^•OH-induced degradation of 4-chlorophenol. The hydroxyl radical is proposed to be produced via a consecutive reduction of molecular oxygen by fullerol anion radical, which is formed through the electron transfer from the dye to the triplet state of fullerol. Mechanistic investigations using various probe reagents such as superoxide dismutase (superoxide quencher), t-butanol (^•OH quencher), and coumarin (^•OH probe) provided indirect evidence for the generation of ^•OH under visible light. Furthermore, spin trapping technique directly detected the oxidizing species such as ^•OH, HO₂^•, and ¹O₂ in the visible light irradiated solution of RhB/fullerol mixture. It was proposed that the photochemical oxidation mechanism depends on pH: ^•OH production is favored at acidic pH through fullerol-mediated sequential electron transfer while ¹O₂ is generated as a main oxidant at neutral and alkaline condition through the energy-transfer process. Therefore, the photochemical oxidation can be switchable between ^•OH-driven and ¹O₂-driven mechanism by a simple pH adjustment.

Bioavailability of Fullerene under Environmentally Relevant Conditions: Effects of Humic Acid and Fetal Bovine Serum on Accumulation in Lipid Bilayers and Cellular Uptake

Carbon fullerene (C60) has emerged at the forefront of nanoscale research and application due to its unique properties. As the production of this nanoparticle rapidly increases, it can be released into natural aquatic environments and can accumulate in biological systems. This research examined the effects of humic acid and fetal bovine serum (FBS), which are ubiquitous in aquatic environments and representative of blood plasma in living organisms, respectively, on bioavailability of fullerene. Bioavailability was investigated using in vitro methods for lipid membrane accumulation and cellular uptake studies. Humic acid and FBS significantly changed the characteristics of fullerene including its particle size and surface charge. The effects of humic acid on lipid accumulation of fullerene depended on the lipid head charge. FBS also significantly decreased the lipid accumulation when positively charged and zwitterionic head groups were present on the lipids, possibly due to the higher steric repulsion of the protein coated nanoparticles. In addition, both humic acid and FBS protein effectively lowered the amounts of fullerene taken up by Caco-2 cells, which are derived from a human colorectal adenocarcinoma and have similar functions to the small intestinal epithelium. Results of this study suggest that surface modification of fullerene by environmentally relevant matrices can significantly affect the biological transport, as well as the possible toxicity of this nanomaterial.

Microbial inactivation kinetics and mechanisms of carbon-doped TiO2 (C-TiO2) under visible light

In this study, titanium dioxide nanoparticles doped with carbon (C-TiO2) were synthesized by means of sol-gel methods, and the synthesis was verified by means of X-ray photoelectron spectroscopy. The nanoparticles' photocatalytic disinfection activity of Listeria monocytogenes was tested under UV and visible light. The observed inactivation levels for 150min of visible light exposure with and without UV cutoff filters were 2.10 and 2.45 log, respectively. We also found that traditional reactive oxygen species had insignificant actions on C-TiO2 photocatalysts and that L. monocytogenes inactivation in the C-TiO2 system under visible light was induced in large part by the midgap states (hmid(+)) that was produced photochemically from the visible light response. C-TiO2 was found to accelerate bacterial inactivation (of L. monocytogenes) in the presence of visible light. Our data suggests that the C-TiO2 may be useful in the development of alternative disinfectants for environmental applications.

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. Here, we take a closer look at the molecular phenomena of functionalized fullerene interactions in water utilizing simulation and experimental tools. Molecular dynamic simulations were performed to investigate time-evolved molecular interactions in systems containing fullerenes with water, oxygen, and/or neighboring fullerene molecules, complimented by physical and chemical characterizations of the fullerenes pre- and postaggregation. Aggregates with widely different photoactivities exhibit similar fullerene-water interactions as well as surface and aggregation characteristics. Photoactive fullerene aggregates had weaker fullerene-fullerene and fullerene-O2 interactions, suggesting the importance of molecular interactions in the sensitization route.

Adsorption of MS2 on oxide nanoparticles affects chlorine disinfection and solar inactivation

Adsorption on colloidal particles is one of the environmental processes affecting fate, transport, viability or reproducibility of viruses. This work studied colloidal interactions (adsorption kinetics and isotherms) between different oxide nanoparticles (NPs) (i.e., TiO2, NiO, ZnO, SiO2, and Al2O3) and bacteriophage, MS2. The results shows that that all oxide NPs exhibited strong adsorption capacity for MS2, except SiO2 NPs, which is supported by the extended Derjaguin and Landau, Verwey and Overbeek (EDLVO) theory. Moreover, the implication of such colloidal interactions on water disinfection is manifested by the observations that the presence of TiO2 and ZnO NPs could enhance MS2 inactivation under solar irradiation, whereas NiO and SiO2 decreased MS2 inactivation. By contrast, all of these oxide NPs were found to mitigate chlorine disinfection against MS2 to different extent, and the shielding effect was probably caused by reduced free chlorine and free MS2 in the solution due to sorption onto NPs. Clearly, there is a pressing need to further understand colloidal interactions between engineered NPs and viruses in water to better improve the current water treatment processes and to develop novel nanomaterials for water disinfection.

Reduction of hydroxylated fullerene (fullerol) in water by zinc: reaction and hemiketal product characterization

Water-soluble, hydroxylated fullerene (fullerol) materials have recently gained increasing attention as they have been identified as the primary product(s) during the exposure of fullerenes (as water stable, nanoscale aggregated C60) to UV light in water. The physical properties and chemical reactivity of resulting fullerols, however, have not been thoroughly studied. In this paper, we identified and characterized the reductive transformation of fullerol (C60(OH)x(ONa)y) by solid zinc metal (Zn(0)) through a series of batch reaction experiments and product characterization, including (13)C NMR, FTIR, XPS, UV-vis, DLS, and TEM. Results indicated the facile formation of water stable, pH sensitive hemiketal functionality as part of a relatively reduced fullerol product. Further, aqueous physical behavior of the product fullerol, as measured by octanol partitioning and surface deposition rates, was observed to significantly differ from the parent material and is consistent with a relative increase in molecular (product) hydrophobicity.

Photogeneration of reactive oxygen species on uncoated silver, gold, nickel, and silicon nanoparticles and their antibacterial effects

Oxidative stress induced by reactive oxygen species (ROS) is one of the major toxicity mechanisms of engineered nanoparticles (NPs). To advance our knowledge of the photogeneration of ROS on NPs, this Letter reports the ROS generation kinetics of uncoated silver (AgNPs), gold (AuNPs), nickel (NiNPs), and silicon (SiNPs) NPs in aqueous suspension under UV irradiation (365 nm) and analyzes the potential ROS photogeneration mechanisms as well as the associated antibacterial effects. The results showed that AgNPs generated superoxide and hydroxyl radicals, whereas AuNPs, NiNPs, and SiNPs generated only singlet oxygen. The electronic structure and redox potentials of SiNPs were shown to mediate ROS generation. By contrast, ROS generation on AuNPs, AgNPs, and NiNPs was primarily due to surface plasmon resonance. The antibacterial activities of these NPs toward E. coli cells under UV irradiation were AgNPs (strongest) > SiNPs > NiNPs > AuNPs. ROS generation and metal ion release significantly enhanced the NPs' antibacterial activity.

Photochemical and photophysical properties of sequentially functionalized fullerenes in the aqueous phase

The vast range of C₆₀ derivatives makes it difficult to assess the potential environmental impact of this class of materials, while past environmental studies mostly focused only on pristine C₆₀. Central to derivatized C₆₀'s potential to negatively impact (micro)biological receptors upon unintended release is its unique property of mediating the transfer of light energy to ambient oxygen, producing ¹O₂. To initiate the process of establishing a thorough understanding of the photoinduced adverse biological effects of functionalized fullerenes and their aqueous dispersions, the photochemical properties relevant to ¹O₂ production were evaluated using three selected series of mono-, bis-, and tris-adducted fullerene materials. Differential ¹O₂ production of derivatives in toluene were explained by spectral variations under visible and UVA light conditions. Of the nine functionalities studied only aggregates of two positively charged derivatives showed significant photoactivity under experimental conditions. Laser flash photolysis revealed a triplet excited state in the photoactive aggregates with a sufficiently long lifetime to be quenched by ³O₂. Dynamic light scattering, transmission electron microscopy, and electron diffraction patterns revealed aggregates with sizes typical of aqueous C₆₀ colloids that varied in crystallinity based on functionality. Results raised questions about our current understanding of the photoactivity of fullerene aggregates.

Oxidative dissolution of polymer-coated CdSe/ZnS quantum dots under UV irradiation: mechanisms and kinetics

To advance the knowledge of environmental fate of nanomaterials, we systematically investigated the dissolution of polymer-coated CdSe/ZnS quantum dots (QDs) under UV (254 nm) irradiation. The environmental effects (i.e., irradiation intensity, dissolved oxygen, temperature, and humic acid), as well as the coating effects on dissolution kinetics of QDs were investigated. Our results showed that higher irradiation intensity and temperature increased ion release rates (Cd(2+), SeO(4)(2-), and Zn(2+)), whereas the different polymer coatings varied the dissolution rates. The absence of dissolved oxygen inhibited the dissolution of QDs, and we further demonstrated that the dissolution was a photo-oxidative process involved superoxide radical formation. Humic acid had a twofold effect on dissolution due to its photosensitization and photoabsorption for UV irradiation. Finally, an empirical kinetic law was proposed to interpret the above environmental effects. This study lays groundwork to better understand the environmental fate of QDs.

Escherichia coli Inactivation by UVC-Irradiated C60: kinetics and mechanisms

Motivated by recent studies that documented changes in fullerene toxicity after chemical transformation, C(60) aggregates (nC(60)) were subject to UVC irradiation at monochromatic 254 nm and subsequently evaluated for antibacterial and bactericidal properties against Escherichia coli. The nC(60) treated with UVC irradiation, referred to herein as UVC-irradiated C(60), did not directly inhibit bacterial growth at concentrations up to 20 mg/L. In the presence of UVA and visible light, however, UVC-irradiated C(60) rapidly inactivated E. coli, suggesting that photochemical production of reactive oxygen species (ROS) was involved. The use of ROS scavengers and probes determined that hydroxyl radicals were the primary ROS responsible for the E. coli inactivation. Results from protein release, lipid peroxidation, cell permeability, and intracellular enzyme assays suggest that the inactivation mechanism involves UVC-irradiated C(60) diffusing through E. coli cell membrane and producing hydroxyl radicals within the cell. Further study on water-soluble C(60) derivatives and possible transformative processes is, therefore, recommended based on the environmental implications of results presented herein that nC(60) exposed to UVC irradiation is more toxic than parent nC(60).

Inactivation and surface interactions of MS-2 bacteriophage in a TiO2 photoelectrocatalytic reactor

Inactivation of MS-2 bacteriophage in a TiO(2) photoelectrocatalytic system was evaluated, wherein TiO(2) particles were coated onto an indium tin oxide (ITO) electrode and an electrical potential was applied under black light blue (BLB) irradiation. MS-2 phage inactivation was greatly enhanced by anodic potential, whereas cathodic potential completely inhibited inactivation. Experiments performed with radical scavengers showed that inactivation was primarily caused by hydroxyl radicals, both in the bulk phase and on the TiO(2) surface. Application of positive potential to the electrode was found to result in two distinct beneficial effects: (i) electrostatic attraction between the negatively charged viral capsid and catalyst surface, causing improved usage of surface-bound hydroxyl radical, in comparison to conventional TiO(2) photocatalytic disinfection; and (ii) higher reactive oxygen species production. Results also suggest that inactivation of various microorganisms including Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Bacillus subtilis spores and Cryptosporidium parvum oocyst was enhanced via positive potential induction to TiO(2).

C60 aminofullerene immobilized on silica as a visible-light-activated photocatalyst

A new strategy is described to immobilize photoactive C(60) aminofullerene on silica gel (3-(2-succinic anhydride)propyl functionalized silica), thus enabling facile separation of the photocatalyst for recycling and repeated use. An organic linker moiety containing an amide group was used to anchor C(60) aminofullerene to the functionalized silica support. The linker moiety prevents aqueous C(60) aggregation/agglomeration (shown by TEM images), resulting in a remarkable enhancement of photochemical (1)O(2) production under visible light irradiation. With no loss in efficacy of (1)O(2) production plus insignificant chemical modification of the aminoC(60)/silica photocatalyst after multiple cycling, the system offers a promising new visible-light-activated photocatalyst. Under visible-light irradiation, the aminoC(60)/silica photocatalyst is capable of effective and kinetically enhanced oxidation of Ranitidine and Cimetidine (pharmaceutical pollutants) and inactivation of MS-2 bacteriophage compared to aqueous solutions of the C(60) aminofullerene alone. Thus, this photocatalyst could enable water treatment in less developed areas by alleviating dependence on major infrastructure, including the need for electricity.

The role of atmospheric transformations in determining environmental impacts of carbonaceous nanoparticles

In studies that have explored the potential environmental impacts of manufactured nanomaterials, the atmosphere has largely been viewed as an inert setting that acts merely as a route for inhalation exposure. Manufactured nanomaterials will enter the atmosphere during production, use, and disposal, and rather than simply being transported, airborne nanoparticles are in fact subject to physical and chemical transformations that could modify their fate, transport, bioavailability, and toxicity once they deposit to aqueous and terrestrial ecosystems. The objective of this paper is to review the factors affecting carbonaceous nanomaterials' behavior in the environment and to show that atmospheric transformations, often overlooked, have the potential to alter nanoparticles' physical and chemical properties and thus influence their environmental fate and impact. Atmospheric processing of naturally occurring and incidental nanoparticles takes place through coagulation, condensation, and oxidation; these phenomena are expected to affect manufactured nanoparticles as well. It is likely that carbonaceous nanomaterials in the atmosphere will be oxidized, effectively functionalizing them. By influencing size, shape, and surface chemistry, atmospheric transformations have the potential to affect a variety of nanoparticle-environment interactions, including solubility, interaction with natural surfactants, deposition to porous media, and ecotoxicity. Potential directions for future research are suggested to address the current lack of information surrounding atmospheric transformations of engineered nanomaterials.

Nanoparticle aggregation: challenges to understanding transport and reactivity in the environment

Unique forms of manufactured nanomaterials, nanoparticles, and their suspensions are rapidly being created by manipulating properties such as shape, size, structure, and chemical composition and through incorporation of surface coatings. Although these properties make nanomaterial development interesting for new applications, they also challenge the ability of colloid science to understand nanoparticle aggregation in the environment and the subsequent effects on nanomaterial transport and reactivity. This review briefly covers aggregation theory focusing on Derjaguin-Landau-Verwey-Overbeak (DLVO)-based models most commonly used to describe the thermodynamic interactions between two particles in a suspension. A discussion of the challenges to DLVO posed by the properties of nanomaterials follows, along with examples from the literature. Examples from the literature highlighting the importance ofaggregation effects on transport and reactivity and risk of nanoparticles in the environment are discussed.

Visible light sensitized inactivation of MS-2 bacteriophage by a cationic amine-functionalized C60 derivative

Recently, we reported the successful synthesis of various hexakis C60 derivatives (i.e., C60 with six functional groups containing NH3+-, CO2H-, or OH-terminals) with enhanced stability in water for aqueous phase application (Lee et al., Environ. Sci. Technol. 2009, 43, pp 6604-6610). Among these newly synthesized C60 derivatives, the cationic hexakis C60 derivative with amine functionality, C60(CR2)6 (R=CO2(CH2)2NH3+CF3CO2-), was found to exhibit remarkable efficiency to inactivate Escherichia coli and MS-2 bacteriophage under UVA irradiation. Herein, we report that this amine-functionalized C60 derivative is also photoactive in response to visible light from both commercial fluorescence lamps and sunlight. Efficient production of 1O2, facile reaction of 1O2 with proteins in MS-2 phage capsid and electrostatic attraction between positively charged C60 derivative and negatively charged MS-2 phage collectively contributed to high efficiency of MS-2 phage inactivation in this photocatalytic disinfection system. The rate of 1O2 production was evaluated using a probe compound, furfuryl alcohol, and 1O2 CT (the product of 1O2 concentration and exposure time) required to achieve a target level of virus inactivation was quantitatively analyzed. The unique visible-light sensitized virucidal property makes this C60 derivative highly desirable for the development of sustainable disinfection strategies that do not require continuous chemical addition nor an external energy source other than ambient light.