Current water treatment approaches effectively inactivate pathogens; however, they are not designed to remove trace pharmaceuticals and other emerging contaminants. Singlet oxygen (1O2) offers a promising approach to water treatment due to its high oxidation potential while also being safe for humans and aquatic life due to its short lifetime (<4 μs in water) and rapid decay to molecular oxygen. However, this short lifetime makes implementation challenging. Moreover, obstacles to delivering light to the photosensitizer (PS) in turbid water must be overcome. Here, we present a novel reactor for generating 1O2 for water treatment. A water-insoluble PS is coated on the surfaces of roughened PMMA lightguides that are closely packed into a photoreactor and illuminated by a high-power LED. This approach is insensitive to water turbidity as the incident light is coupled to the PS coating. The effects of fluence, surface roughness, and PS loading on 1O2 trapping rates were quantified using uric acid. Destruction of five pharmaceutical compounds was measured by HPLC, and the rate constants demonstrate the influence of substrate structure on reactivity. Disinfection efficacy was demonstrated using 105 CFU/mL Escherichia coli suspensions. Approaches to scaling this system for continuous water treatment are presented.

Antimicrobial photodynamic therapy (aPDT) has been investigated as a promising therapy for treating wound infections. However, its clinical application is limited by tissue hypoxia, poor photosensitizer (PS) penetration, and off-target toxicity. In this work, we use a light-activated, contactless aPDT system that delivers airborne singlet oxygen (1O2) via a compliant, transparent superhydrophobic (SH) bandage. The verteporfin-coated SH membrane generates 1O2 while minimizing direct contact between PS and wound tissue. In a murine third-degree burn model infected with methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa, a single SH-aPDT treatment significantly reduces bacterial burden and accelerates wound closure. It enhances collagen deposition, stimulates angiogenesis, increases α-SMA+ myofibroblast activity, and decreases COX-2 expression, indicating attenuated inflammatory signaling. Administration of two treatments 24 h apart further augments bacterial clearance and improves healing outcomes. SH-aPDT also promotes a pro-regenerative immune response, as evidenced by increased M2 macrophages. These findings demonstrate that airborne 1O2 delivery through SH bandages is a promising approach for the management of infected, hypoxic, or antibiotic-resistant wounds, with great potential for clinical translation in wound care.

Accumulated dust on solar cover glass reduces transmittance, leading to decreased energy efficiency of photovoltaic (PV) modules. Hydrophobic coatings on solar cover glass have been shown to provide anti-soiling properties when exposed to a condensing environment (e.g. dew). The addition of hydrophilic features along the top edge of the hydrophobic coated glass enhances condensation rates and can be used to achieve selfcleaning of the surfaces. However, to date, relatively long times have been required to clean the surfaces. In this study, we developed a new design for hydrophilic features that reduce the time required to clean the surface in laboratory tests as measured by laser scanning microscopy, optical photographs and UV-vis spectroscopy. The dagger-shaped features improve self-cleaning performance by a combination of three factors: a silica nanoparticle (NP) hydrophilic coating which enhances condensation rate due to a low water contact angle (WCA) and nano-scale porosity; the stepwise transition from the low WCA silica NP region to the high WCA silanized hydrophobic region via a bare glass transition zone; and the pointed shape of the hydrophobic dagger features which further minimizes the barrier for transport of droplets from the condensing region to the high-mobility, hydrophobic, region of the surface. The hydrophilic silica nanoparticle-coated dagger features not only improve the self-cleaning efficiency of the hydrophobic surfaces but also increase the overall amount of water harvested. Such coating designs provide an effective approach to reducing maintenance costs as well as increasing the overall energy output of PV panels.

Photosensitizers (PSs) dissolved in solvents generate reactive oxygen species, such as singlet oxygen (1O2), in high yields, especially when the PS is fully solvated and unaggregated. For many applications, such as water treatment, homogenous phase reactions are not practical because the PS will contaminate the solution and be difficult to recover and reuse. Immobilizing PSs on solid polymer supports is an emerging strategy for 1O2 applications, as it prevents the PS from entering the solution and thus enables PS reuse. However, 1O2 yields from polymer-supported PS surfaces are much lower than in solvated systems. In this paper, we employ novel approaches to modify surface topography and surface chemistry of the polymer support to significantly increase 1O2 yields. To fabricate the surfaces we deposit a fluorinated, water-insoluble porphyrin, 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (TFPP) onto polyethylene terephthalate (PET) and polydimethylsiloxane (PDMS) surfaces. We demonstrate that superhydrophobic surfaces exhibit a 2.9-fold higher yield of 1O2 compared to planar, wetted surfaces, even when the planar surfaces exhibit significant roughness from the addition of silica particles. Modifying the polymer surface chemistry to accelerate PS solution spreading decreases PS crystallite size thereby increasing PS surface area and further increasing 1O2 yields. Surface chemistry also affects PS aggregation; the PS forms J-aggregates on PET, but crystallizes in an unaggregated (non-overlapping) form on PDMS. Contrary to conventional assumptions, the PS aggregate state and higher loadings of the PS are not correlated with higher 1O2 yields, whereas reducing the size of PS crystallites significantly increases yields.

Significance Periodontitis is an inflammatory and multifactorial disease, and has been described as one of the most common oral diseases worldwide. Approach Wistar rats (n=148) were subjected to the periodontitis model by the use of a cotton ligature during 7 days. The superhydrophobic (SH) device was dopped with verteporfin (V) or Ce-6 (Ce) for single or consecutive (days 0, 1 and 2) applications using 60 and 125 J/cm2. Mechanical debridement associated or not with chlorhexidine were used as positive and negative controls. CFU counting, clinical parameters, histological and inflammatory conditions were evaluated. Results Three consecutive applications of SH-aPDT decreased P. gingivalis load compared to single and the control groups (p<0.05). Clinical parameters were also improved (p<0.05). Histological and stereometric analyses showed that consecutive applications were more effective than single promoting healing and reducing inflammation. Conclusions SH-aPDT could be an important tool to inhibit biofilm formation while promoting healing and anti-inflammatory responses.

The rise of antimicrobial resistance poses a critical public health threat worldwide. While antimicrobial photodynamic therapy (aPDT) has demonstrated efficacy against multidrug-resistant (MDR) bacteria, its effectiveness can be limited by several factors, including the delivery of the photosensitizer (PS) to the site of interest and the development of bacterial resistance to PS uptake. There is a need for alternative methods, one of which is superhydrophobic antimicrobial photodynamic therapy (SH-aPDT), which we report here. SH-aPDT is a technique that isolates the PS on a superhydrophobic (SH) membrane, generating airborne singlet oxygen (1O2) that can diffuse up to 1 mm away from the membrane. In this study, we developed a SH polydimethylsiloxane dressing coated with PS verteporfin. These dressings contain air channels called a plastron for supplying oxygen for aPDT and are designed so that there is no direct contact of the PS with the tissue. Our investigation focuses on the efficacy of SH-aPDT on biofilms formed by drug-sensitive and MDR strains of Gram-positive (Staphylococcus aureus and S. aureus methicillin-resistant) and Gram-negative bacteria (Pseudomonas aeruginosa and P. aeruginosa carbapenem-resistant). SH-aPDT reduces bacterial biofilms by approximately 3 log with a concomitant decrease in their metabolism as measured by MTT. Additionally, the treatment disrupted extracellular polymeric substances, leading to a decrease in biomass and biofilm thickness. This innovative SH-aPDT approach holds great potential for combating antimicrobial resistance, offering an effective strategy to address the challenges posed by drug-resistant wound infections.

Photochemical generation of singlet oxygen (O-1(2)) often relies on homogenous systems; however, a dissolved photosensitizer (PS) may be unsuitable for some applications because it is difficult to recover, expensive to replenish, and hazardous to the environment. Isolation of the PS onto a solid support can overcome these limitations, but implementation faces other challenges, including agglomeration of the solid PS, physical quenching of O-1(2) by the support, photooxidation of the PS, and hypoxic environments. Here, we explore a superhydrophobic polydimethylsiloxane (SH-PDMS) support coated with the photosensitizer 5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H-porphyrin (TFPP). This approach seeks to address the challenges of a heterogeneous system by using a support that exhibits low O-1(2) physical quenching rates, a fluorinated PS that is chemically resistant to photooxidation, and a superhydrophobic surface that entraps a layer of air, thus preventing hypoxia. Absorbance and fluorescence spectroscopy reveal the monomeric arrangement of TFPP on SH-PDMS surfaces, a surprising but favorable characteristic for a solid-phase PS on O-1(2) yields. We also investigated the effect of incident wavelength on O-1(2) yields for TFPP in aqueous solution and immobilized on SH-PDMS and found overall yields to be dependent on the absorption coefficient, while the yield per absorbed photon exhibited wavelength independence, in accordance with Kasha-Vavilov's rule.

Accumulated dust on solar cover glass reduces the transmittance, leading to decreased energy efficiency of photovoltaic (PV) modules. In this study, we fabricated surfaces designed to harvest dew to self-clean dust from hydrophobic-coated glass surfaces without using external forces such as washing or brushing. Because dew occurs for only short periods of time, we evaluated silica nanoparticle coatings to increase condensate nucleation rate and modified the shape of the hydrophilic features to increase the rate of liquid water roll-off. We evaluated hydrophilic dagger-shaped features coated with three types of nanoparticle silica solutions and compared the performance to uncoated features as well as surfaces uniformly treated to be hydrophobic. UV-vis spectroscopy and optical images obtained within an artificial dew laboratory test chamber were used to quantify performance of the coatings. The coated dagger-shaped features accelerate condensation and so significantly reduce the time required for liquid water to roll off the hydrophilic condensation sites compared to bare glass features of the same shape and half the time required for hydrophobic surfaces without hydrophilic features. Self-cleaning is also significantly improved by a linear array of hydrophilic dagger-shaped features placed along the top edge of the 120 mm long glass samples. The coating and shape of the features decrease roll-off times to a greater extent compared to our previous work with circular or rectangular hydrophilic channels. The hydrophilic silica nanoparticle-coated dagger features not only improve the self-cleaning efficiency of the hydrophobic surfaces, but also increase the overall amount of water harvested. Such coating designs provide an effective approach to reduce maintenance costs as well as increase the overall energy output of PV panels.

The performance of photovoltaic modules is heavily influenced by soiling of their solar cover glass. Anti-soiling coatings are a reliable way to reduce soiling and therefore cleaning costs. Although the efficiencies of these coatings have been demonstrated in field tests and in laboratory experiments, relevant parameters and mechanisms remain not well understood. This study investigated the influence of the surface structure of hydrophilic sol-gel coatings on their anti-soiling performance for dust accumulation and removal, respectively. Surface structure was introduced by adding colloidal silica of different sizes to the sols used in the dip-coating process. A standardized Arizona A2 test dust and dust collected from solar installations were used for dust chamber experiments with controlled humidity and subsequent wind tunnel experiments. A size threshold was identified and particles larger than it showed a strongly reduced accumulation on all coatings compared to an uncoated substrate. The removal of dust particles was significantly influenced by the surface structure. Smoother nanostructured surfaces showed better cleanability than coatings with a rougher nanostructured surface. Furthermore, on increasingly structured coatings a shift was observed which dust type is easier removed from the coating surface by wind. The size and shape of the dust particles was identified as the relevant parameter for this.

Superhydrophobic antimicrobial photodynamic therapy (SH-aPDT) is advantageous wherein airborne singlet oxygen (1O2) is delivered from a device tip to kill a biofilm with no photosensitizer exposure and no bacterial selectivity (Gram + or Gram -). For effective treatment of periodontitis, the frequency of treatment as well as the optical light fluence required is not known. Thus, we sought to determine whether single or repeated SH-aPDT treatments would work best in vivo using two fluence values: 60 and 125 J/cm2. We assessed the efficacy of three protocols: single treatment; interval treatments (days 0, 2, and 7); and consecutive treatments (days 0, 1, and 2). After 30 days of evaluation, we found that, SH-aPDT in 3 consecutive treatments significantly decreased Porphyromonas gingivalis levels compared to single and interval SH-aPDT treatments, as well as SRP-chlorhexidine (CHX) controls (p < 0.05). Notably, clinical parameters also improved (p < 0.05), and histological and stereometric analyses revealed that consecutive SH-aPDT treatments were the most effective for promoting healing and reducing inflammation. Our study shows what works best for SH-aPDT, while also demonstrating SH-aPDT advantages to treatment of periodontitis including no bacterial selectivity (Gram + or Gram -) and preventing the development of bacterial resistance.

Limited options exist for treatment of periodontitis; scaling and root planing (SRP) are not sufficient to eradicate P. gingivalis and the resulting inflammatory disease. Chlorhexidine (CHX), used as an adjuvant to SRP, may reduce bacterial loads but leads to pain and staining, while evidence for its efficacy is lacking. Antibiotics are effective but can lead to drug-resistance. The rising concern of antibiotic resistance limits the future use of this treatment approach. This study evaluates the efficacy of a novel superhydrophobic (SH) antimicrobial photodynamic therapy (aPDT) device as an adjuvant to SRP for the treatment of periodontitis induced in a Wistar rat in vivo model relative to CHX. The SH-aPDT device comprises an SH silicone rubber strip coated with verteporfin photosensitizer (PS), sterilized, and secured onto a tapered plastic optical fiber tip connected to a red diode laser. The superhydrophobic polydimethylsiloxane (PDMS) strips were fabricated by using a novel soluble template method that creates a medical-grade elastomer with hierarchical surface roughness without the use of nanoparticles. Superhydrophobicity minimizes direct contact of the PS-coated surface with bacterial biofilms. Upon insertion of the device tip into the pocket and energizing the laser, the device generates singlet oxygen that effectively targets and eliminates bacteria within the periodontal pocket. SH-aPDT treatment using 125 J/cm2 of red light on three consecutive days reduced P. gingivalis significantly more than SRP-CHX controls (p < 0.05). Clinical parameters significantly improved (p < 0.05), and histology and stereometry results demonstrated SH-aPDT to be the most effective treatment for improving healing and reducing inflammation, with an increase in fibroblast cells and extracellular matrix and a reduction in vascularization, inflammatory cells, and COX-2 expression. The SH-aPDT approach resulted in complete disease clearance assessed 30 days after treatment initiation with significant reduction of the periodontal pocket and re-formation of the junctional epithelium at the enamel-cementum junction. PS isolation on a SH strip minimizes the potential for bacteria to develop resistance, where the treatment may be aided by the oxygen supply retained within the SH surface.

Soiling of solar cover glass is a major cause for efficiency loss of solar photovoltaic modules. Anti-soiling coatings can be used to reduce the rate of soiling and lower cleaning costs. The efficiency of these coatings has been demonstrated in laboratory and field tests, but the mechanisms and relevant parameters are still not well understood.In this article, we present a study on the influence of surface structure of hydrophilic sol-gel coatings on their anti-soiling performance in terms of both, dust accumulation and subsequent indoor tests for dust removal by wind. The surface structure of the films originates from the addition of colloidal silica particles of different sizes to the sols used for film preparation. In the dust deposition experiments, standardized test dust and dust collected from solar installations were used. Repeated tests were conducted under controlled humidity.In the case of dust deposition, the accumulation of dust particles larger than -10 mu m is strongly reduced, in relation to bare glass, by the anti-soiling effect of all coatings regardless of their surface structure.For the dust removal via wind, coatings that bear a smoother surface structure are cleaned more easily than coatings with a rougher surface structure. Additionally, larger and rounder dust particles are removed more easily from coatings with a rougher surface structure (structure height over -40 nm), while smaller and more irregularly shaped dust particles are removed more easily from coatings with a smoother surface structure.

Antimicrobial photodynamic therapy (aPDT) is a promising approach to control biofilms involved in periodontal diseases. However, certain challenges, such as staining of teeth, preferential interaction of photosensitizer (PS) with Gram-positive versus Gram-negative bacteria, and insufficient oxygen in hypoxic periodontal pockets have presented barriers to its use in the clinic. To overcome these challenges, a novel superhydrophobic (SH) film that generates airborne singlet oxygen has been developed. The SH-aPDT approach isolates the PS onto a topologically rough solid SH film on which channels allow air to diffuse to the PS surface, thus ensuring sufficient oxygen supply. Upon illumination, gas phase singlet oxygen (O-1(2)) is produced and diffuses from the SH surface to the underlying biofilm. The killing efficacy was assessed as a function of transmitted fluence (17.9-89.5 J/cm(2)) and chorin e6 loading (96-1110 nmol/cm(2)) by counting of colony forming units, biofilm metabolism by XTT and confocal microscopy. The decrease in viability of both Gram-positive and Gram-negative bacteria in a multi-species biofilm was found to be linearly dependent on the fluence as well as the loading of the PS up to 71.6 J/cm(2) when 1110 nmols/cm(2) of chlorin e6 was used. A > 4.6 log bacterial reduction was observed under these conditions (p < 0.05). This novel SH-aPDT approach shows promise as an effective method to disinfect multi-species bacterial biofilms associated with periodontal disease and will be evaluated in animal models in future studies.

Dew promotes chemical interactions between soilants and glass that lead to increased soiling rates and cleaning costs. Anti-soiling coatings have been developed to address these issues, and prior experiments have quantified the soiling impact of several categories of particle chemistries. In this paper, the impact that the hygroscopicity of a soilant has on soiling and cleaning values was measured on hydrophobic coated glass and compared to bare glass samples. Results will be presented from UV -visible direct transmittance and optical image processing measurements to characterize soiling and self-cleaning of surfaces as a function of particle hygroscopicity in a condensing environment, mimicking natural dew conditions.

This review describes nanoparticle and dye diffusion in bacterial biofilms in the context of antimicrobial photodynamic inactivation (aPDI). aPDI requires the diffusion of a photosensitizer (Sens) into the biofilm and subsequent photoactivation of oxygen for the generation of reactive oxygen species (ROS) that inactivate microbes. Molecular diffusion in biofilms has been long investigated, whereas this review is intended to draw a logical link between diffusion in biofilms and ROS, a combination that leads to the current state of aPDI and superhydrophobic aPDI (SH‐aPDI). This review should be of interest to photochemists, photobiologists and researchers in material and antimicrobial sciences as is ties together conventional aPDI with the emerging subject of SH‐aPDI.

Natural soiling and the subsequent requisite cleaning of photovoltaic (PV) modules result in abrasion damage to the cover glass. The durability of the front glass has important economic consequences, including determining the use of anti-reflective and/or anti-soiling coatings as well as the method and frequency of operational maintenance (cleaning). Artificial linear brush abrasion using Nylon 6/12 bristles was therefore examined to explore the durability of representative PV first-surfaces, i.e., the surface of a module incident to direct solar radiation. Specimens examined include silane surface functionalized-, roughened (etched)-, porous silica-coated-, fluoropolymer-coated-, and ceramic (TiO2 or ZrO2/SiO2/ZrO2/SiO2)-coated-glass, which are compared to monolithic-poly(methyl methacrylate) and -glass coupons. Characterization methods used in this study include: optical microscopy, ultraviolet–visible–near-infrared (UV-VIS-NIR) spectroscopy, sessile drop goniometry, white-light interferometry, atomic force microscopy (AFM), and depth-profiling X-ray photoelectron spectroscopy (XPS). The corresponding characteristics examined include: surface morphology, transmittance (i.e., optical performance), surface energy (water contact angle), surface roughness, scratch width and depth, and chemical composition, respectively. The study here was performed to determine coating failure modes; identify characterization methods that can detect nascent failures; compare the durability of popular contemporary coating materials; identify their corresponding damage characteristics; and compare slurry and dry-dust abrasion. This study will also aid in developing an abrasion standard for the PV industry.

A superhydrophobic (SH) sandwich system has been developed to enable "contact-free" airborne singlet oxygen (1O2) delivery to a water droplet. The contact-free feature means that the sensitizer is physically separated from the droplet, which presents opportunities for photodynamic therapy (PDT). Trapping of airborne 1O2 in a H2O droplet residing on a lower SH surface was monitored with 9,10-anthracene dipropionate dianion by varying distances to an upper 1O2-generating surface. Short distances of 20 μm efficiently delivered airborne 1O2 to the droplet in single-digit picomolar steady-state concentrations. Delivery decreases linearly with distance, but 50% of the 1O2 steady-state concentration is trapped at a distance of 300 μm from the generating surface. The 1270 nm luminescence intensity was measured within the SH sandwich system, confirming the presence of airborne 1O2. Physical quenching of 1O2 to ground-state 3O2 by the water droplet itself and both physical and chemical quenching of 1O2 by the water droplet containing the trap 9,10-anthracene dipropionate dianion are observed. Unlike a majority of work in the field of PDT with dissolved sensitizers, where 1O2 diffuses short (hundreds of nanometers) distances, we show the delivery of airborne 1O2 via a superhydrophobic surface is effective through air in tenths of millimeters distances to oxidize an organic compound in water. Our results provide not only potential relevance to PDT but also surface bacterial inactivation processes.

Soiling of solar cover glass can cause a significant loss of electrical output from PV panels. Dew condensed on the surface exacerbates soiling rates and promotes reactions between dust and glass leading to stronger adhesive forces that make cleaning more expensive. To reduce soiling rates and lower cleaning costs, anti-soiling coatings are being developed. Although the interactions between dust particles and uncoated low-iron glass surfaces are known, the mechanisms by which anti-soiling coatings reduce soiling rates are less well understood. In this paper we report on the effect of wetting properties on both the soiling rate as well as the cleaning efficiency of polymer coated solar cover glass substrates in the presence of condensed water in a controlled environment. Coatings were fabricated with water contact angles (CM) ranging from 149 degrees to 51 degrees and compared to bare glass. Arizona Test Dust was applied onto substrates on which water condensate (i.e. artificial dew) had formed. The surfaces were baked to enable cementation to occur. Such dew-dust-dry cycles were repeated to simulate naturally occurring, cumulative soiling processes. Changes in dust accumulation rates were assessed as a function of coating properties. Hydrophobic coated glass exhibited 42% lower soiling rates compared to hydrophilic glass. A dust "herding" mechanism was identified to account for these reduced soiling rates, by which dust is concentrated into discrete piles during the lateral shrinkage of droplets on low-energy surfaces. These hydrophobic surfaces were also easier to clean with >99% of the original direct transmittance restored using only water.

Dew accelerates the soiling rates and increases the dust adhesion. To use dew for self-cleaning, a fluorinated ethylene propylene coating was applied to suppress the reactions between dust and glass as well as to facilitate the dew to condense as mobile droplets. An array of rectangular hydrophilic channels in the coating increases the condensation rates and droplet slide-off diameters. The durability of the coating was evaluated by artificial UV weathering. Four different types of soilants were used in the artificial soiling tests to assess the effect of soilant type and surface properties on the soiling rates and self-cleaning efficacy under the simulated dew conditions. Soil deposition and self-cleaning mechanisms are being reported.