Broad-spectrum Light Research Articles

Laser-induced photothermal generation of flexible and salt-resistant monolithic bilayer membranes for efficient solar desalination

Harvesting solar energy and generating steam through solar thermal energy are viable approaches with diverse applications such as power generation, desalination, and water purification. Particularly, for efficient and stable solar desalination, hierarchically porous materials are desired to enable the required multiple functionalities. However, high thermal/chemical energy required and time consumed remain roadblocks. In this study, a facile, fast, and scalable laser-induced photothermal method to achieve flexible monolithic bilayer sheets (MBS) of hierarchically porous graphitic carbon (HPGC) and polymeric foam for use in salt-resistant and flexible solar steam generators is reported. The MBS-based self-floating solar steam generator shows outstanding solar desalination performance with a solar thermal efficiency of 83.2% (1-sun) and a high salt-rejection ratio (99.9%). Efficient solar thermal energy transformation is achieved by the versatile multi-functionalities of the MBS, including broad-spectrum solar light absorption, heat localization, and capillary action. Anisotropic wetting properties of hydrophobic HPGC and hydrophilic polyimide (PI) foam effectively prevent salt accumulation on the HPGC surface. The salt-resistant MBS enable long-term stability for solar desalination with actual seawater. Our laser-based photothermal method has potential in the development of high-performance solar thermal systems with substantial cost reduction by scalable production of multiscale hierarchically structured materials from micro-structured polymers.

Does changing to brighter road lighting improve road safety? Multilevel longitudinal analysis of road traffic collision frequency during the relighting of a UK city

BackgroundA step change in the night environment is taking place, with the large-scale installation of bright, broad-spectrum road lighting such as white light-emitting diodes (LEDs). One justification for this is...

Broad spectrum light-trapping ternary polymer solar cells based on self-assembled nano-ridged active layer

Ternary blend polymer solar cells (TPSCs) comprising one donor and two fullerene acceptors is efficient method for improving the power conversion efficiency (PCE). In this paper, the PTB7-Th-based TPSCs which is incorporating PC70BM and PC60BM as mixed acceptors are fabricated and investigated. Impressively, the remarkable self-assembled nano-ridged (SANR) structures are discovered in the active layer with the weight ratio of 50% PC60BM in fullerenes. Thanks to the enlarged interface area, enhanced light absorption and balanced carrier transport, the PTB7-Th:PC70BM:PC60BM TPSCs with the SANR active layer gives an optimal PCE of 9.68%. In addition, it is worth emphasizing that by combining the textured-ZnO with the SANR active layer, a double ridge superimposed system (DRSS) with broad spectrum light trapping characteristic is constructed, which can further enhance the light absorption of the devices. Finally, benefiting from the further increase in short circuit current density (Jsc), the PTB7-Th:PC70BM:PC60BM TPSCs with the DRSS gives an optimal PCE of 10.68%. This work provides a feasible ternary strategy to increase the devices performances and is proved be a simple and efficient strategy for fabricating PTB7-Th:PC70BM:PC60BM TPSCs with SANR active layer.

The Role of Sunscreen in Melasma and Postinflammatory Hyperpigmentation.

Photosensitive conditions such as melasma and postinflammatory hyperpigmentation (PIH) are exacerbated by exposure to ultraviolet (UV) rays and visible light making sunscreen use an essential component of treatment. This is especially true in skin of color patients who are less likely to use photoprotection, even if diagnosed with these photoexacerbated conditions. We aimed to evaluate the body of literature to provide evidence for the use of sunscreen in the treatment of melasma and PIH. We reviewed English articles from PubMed, Journals@Ovid Full Text, and Embase using the search terms “sunscreen” and either “melasma” “PIH,” or “post-inflammatory hyperpigmentation.” Nine relevant publications provide evidence that a broad spectrum of protection, including UVA, UVB, and visible light within sunscreens can play an adjuvant role in therapy for melasma and PIH by stabilizing and improving these pigmentary disorders in skin of color patients. This review illustrates the advantages and limitations of sunscreen use, as well as practice gaps in photoprotection in the skin of color patients with melasma and PIH.

Bumblebees land remarkably well in red-blue greenhouse LED light conditions.

ABSTRACTRed–blue emitting LEDs have recently been introduced in greenhouses to optimise plant growth. However, this spectrum may negatively affect the performance of bumblebees used for pollination, because the visual system of bumblebees is more sensitive to green light than to red–blue light. We used high-speed stereoscopic videography to three-dimensionally track and compare landing manoeuvres of Bombus terrestris bumblebees in red–blue light and in regular, broad-spectrum white light. In both conditions, the landing approaches were interspersed by one or several hover phases, followed by leg extension and touchdown. The time between leg extension and touchdown was 25% (0.05 s) longer in red–blue light than in white light, caused by a more tortuous flight path in red–blue light. However, the total landing duration, specified as the time between the first hover phase and touchdown, did not differ between the light conditions. This suggests that the negative effects of red–blue light on the landing manoeuvre are confined to the final phase of the landing.This article has an associated First Person interview with the first author of the paper.

The impact of ZnO configuration as an external layer on the sensitivity of a bi-layer coated polymer optical fiber probe.

Salinity magnitude changes are a critical factor for determining the chemistry of natural water bodies and biological processes. Label-free refractive index sensors are promising devices for detecting these changes. A polymer optical fiber (POF) sensor modified with cladding treatment and a bi-layer zinc oxide/silver (ZnO/Ag) nanostructure coating to determine sodium chloride concentration changes through refractive index variations in water is experimentally demonstrated. The use of three ZnO nanostructure shapes, nanoparticles and horizontally and vertically oriented nanorods, as an external layer and a broad spectrum light source from the visible (Vis) to the near infrared (NIR) region are investigated to achieve optimum sensitivity. The rms roughness, optical band-gap and zeta potential (ZP) value for the vertically oriented sample are 148 nm, 3.19 eV and 5.96 mV, respectively. In the NIR region the wavelength–intensity sensitivity values of probes coated with ZnO nanoparticles and horizontally and vertically oriented nanorods are 104 nm RIU−1–12 dB RIU−1, 63 nm RIU−1–10 dB RIU−1 and 146 nm RIU−1–22 dB RIU−1, respectively, and in the Vis area the values are 65 nm RIU−1–14 dB RIU−1, 58 nm RIU−1–11 dB RIU−1 and 89 nm RIU−1–23 dB RIU−1, respectively. The maximum amplitude sensitivity is obtained for the probe coated with vertically aligned ZnO nanorods in the NIR area due to the deeper penetration of evanescent waves, a higher surface-volume ratio, better crystallinity, more adhesive interactions with salt molecules, larger surface roughness and higher-order dispersion compared to the other coated ZnO nanostructures.

Exposure to Broad-Spectrum Visible Light Causes Major Transcriptomic Changes in Listeria monocytogenes EGDe.

Listeria monocytogenes, the causative agent of the serious foodborne disease listeriosis, can rapidly adapt to a wide range of environmental stresses, including visible light. This study shows that exposure of the L. monocytogenes EGDe strain to low-intensity, broad-spectrum visible light inhibited bacterial growth and caused altered multicellular behavior during growth on semisolid agar compared to when the bacteria were grown in complete darkness. These light-dependent changes were observed regardless of the presence of the blue light receptor (Lmo0799) and the stressosome regulator sigma B (SigB), which have been suggested to be important for the ability of L. monocytogenes to respond to blue light. A genome-wide transcriptional analysis revealed that exposure of L. monocytogenes EGDe to broad-spectrum visible light caused altered expression of 2,409 genes belonging to 18 metabolic pathways compared to bacteria grown in darkness. The light-dependent differentially expressed genes are involved in functions such as glycan metabolism, cell wall synthesis, chemotaxis, flagellar synthesis, and resistance to oxidative stress. Exposure to light conferred reduced bacterial motility in semisolid agar, which correlates well with the light-dependent reduction in transcript levels of flagellar and chemotaxis genes. Similar light-induced reduction in growth and motility was also observed in two different L. monocytogenes food isolates, suggesting that these responses are typical for L. monocytogenes Together, the results show that even relatively small doses of broad-spectrum visible light cause genome-wide transcriptional changes, reduced growth, and motility in L. monocytogenesIMPORTANCE Despite major efforts to control L. monocytogenes, this pathogen remains a major problem for the food industry, where it poses a continuous risk of food contamination. The ability of L. monocytogenes to sense and adapt to different stressors in the environment enables it to persist in many different niches, including food production facilities and in food products. The present study shows that exposure of L. monocytogenes to low-intensity broad-spectrum visible light reduces its growth and motility and alters its multicellular behavior. Light exposure also caused genome-wide changes in transcript levels, affecting multiple metabolic pathways, which are likely to influence the bacterial physiology and lifestyle. In practical terms, the data presented in this study suggest that broad-spectrum visible light is an important environmental variable to consider as a strategy to improve food safety by reducing L. monocytogenes contamination in food production environments.

Nanosystems, Edge Computing, and the Next Generation Computing Systems.

It is widely recognized that nanoscience and nanotechnology and their subfields, such as nanophotonics, nanoelectronics, and nanomechanics, have had a tremendous impact on recent advances in sensing, imaging, and communication, with notable developments, including novel transistors and processor architectures. For example, in addition to being supremely fast, optical and photonic components and devices are capable of operating across multiple orders of magnitude length, power, and spectral scales, encompassing the range from macroscopic device sizes and kW energies to atomic domains and single-photon energies. The extreme versatility of the associated electromagnetic phenomena and applications, both classical and quantum, are therefore highly appealing to the rapidly evolving computing and communication realms, where innovations in both hardware and software are necessary to meet the growing speed and memory requirements. Development of all-optical components, photonic chips, interconnects, and processors will bring the speed of light, photon coherence properties, field confinement and enhancement, information-carrying capacity, and the broad spectrum of light into the high-performance computing, the internet of things, and industries related to cloud, fog, and recently edge computing. Conversely, owing to their extraordinary properties, 0D, 1D, and 2D materials are being explored as a physical basis for the next generation of logic components and processors. Carbon nanotubes, for example, have been recently used to create a new processor beyond proof of principle. These developments, in conjunction with neuromorphic and quantum computing, are envisioned to maintain the growth of computing power beyond the projected plateau for silicon technology. We survey the qualitative figures of merit of technologies of current interest for the next generation computing with an emphasis on edge computing.

Enhanced broad spectrum (vis-NIR) responsive photocatalytic performance of Ag2O/rectorite nanoarchitectures

Although semiconductor/clay photocatalysts have attracted great attention because of their special structures, it is still challenging to achieve higher efficiency under broad spectrum light, even near-infrared (NIR) light irradiation. Herein, we reported the synthesis of wide-spectrum light responsive Ag2O/rectorite (Ag2O/R) nanocomposites via a simple chemical precipitation method. The experimental results showed that Ag2O nanoparticles were properly loaded on rectorite and the nanocomposites exhibited superior photocatalytic activity in the presence of visible light and near-infrared light irradiation. Compared to pure Ag2O and rectorite, 70% Ag2O/rectorite nanocomposite exhibited the highest photocatalytic performance for the degradation of RhB and MO in aqueous solution under visible light and NIR irradiation. Moreover, the Ag2O/rectorite nanocomposites exhibited the highest stability after five recycled photocatalytic degradation experiments under visible and NIR light. Based on the radical trapping experiment, it was found that O2− is active radical species in photocatalytic degradation of pollutants in the presence of visible light and NIR irradiation. Finally, a possible photocatalytic degradation mechanism of pollutants by Ag2O/R nanocomposite was proposed. The current work would offer strong potential in the implementation of clay-based photocatalysts with wide-spectrum light response and be valuable for environmental remediation.

Various Light Quality including QD-LED Affect Growth and Leaf Color of Red Romaine Baby Leaf Lettuce

Light quality has a substantial effect on crops in plant factories. Quantum dot (QD) refers to ultrafine semiconductor particles and is expressed in a variety of wavelength ranges and fine and precise colors and is attracting attention as a next-generation material. This study was conducted to investigate the effects of various light qualities, including a QD-LED light source on the growth and color development of red romaine lettuce in the LED chamber system for plant factories. The light source was red fluorescent (FL), blue (B), red (R), blue + red mixed light (BR), and blue + wide range red + red mixed light QD-LED. The growth index, chlorophyll content, and leaf color were examined. The results showed that the plant length was long without a significant difference in QD-LED and the red (R) wavelength and showed the fastest growth under QD-LED. The photosynthetic rate and chlorophyll content were the highest in QD-LED light with a broad spectrum of red light. The leaf colors a*, b*, the hue angle, and total anthocyanin content showed the highest in QD-LED light, while b* and the hue angle values ​​were the lowest. As the light wavelength range was changed, there was a significant difference in the growth response and leaf color, and it is considered that QD-LED light should be considered positively when applied to plant factories.
 
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 In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 3, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue.
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A metallic hot-carrier photovoltaic device

Hot carrier solar cells overcome the fundamental limitations of conventional devices where charge carriers are photogenerated over a broad energy spectrum but rapidly lose energy to the lattice and are extracted at the lowest energy of the system. In a hot carrier photovoltaic cell, carriers are extracted at higher energies than the absorption threshold, and extraction proceeds sufficiently quickly to avoid dissipative energy loss. We demonstrate a new hot carrier photovoltaic device where a broad spectrum of light is absorbed in metallic layers tens of nanometers thick. Using a semiconductor quantum well resonant tunnel structure we demonstrate energy selective hot carrier extraction from the metal film and show a unique hot carrier signature in the device IV characteristics. Using a multiple beam experiment, we further prove that these carriers arise from a hot electron population rather than via internal photoemission; a necessary requirement for high efficiency photovoltaic operation.

Effect of Capping-Agents on Performance of Copper Nickel Tin Sulfide (CNTS) Nanocrystals Based Solar Cells

In recent years, colloidal semiconductor nanocrystals based solar cells have achieved photo-conversion efficiency closed to 12% which has triggered renewed interest to undertake fundamental investigation on these materials. Among many prospective candidates, quaternary chalcogenides viz. Copper Zinc Tin Sulfide/Selenides (CZTS) and its analogs have been tested extensively due to its high absorption coefficient near 1.1-1.5eV, low elemental cost, non-toxic nature and ability to form alloy structures, without apparent phase segregation. All these characteristics make them very attractive candidate to investigate them for solar cell applications. Their composition dependent band-edge parameters give further opportunity to form tandem heterojunction devices which would absorb broad spectrum of light and give the possibility to push the performance towards betterment. In many such investigation the capping agents used in the preparation of nanocrystals have assumed to be mute candidate in performance of the solar cells. However, our preliminary investigation on copper nickel tin sulfide (CNTS) nanocrystals based solar cell revealed that the nature of capping agents is also an important parameter and impact the solar cell performance. Herein, we report the preparation of CNTS nanocrystals and demonstrated the effect of capping agents on the performance of solar cells. To prepare CNTS nanocrystals, hot-injection method have been used. Two variants have been prepared by varying capping agents; long-chain oleylamine capped CNTS (OLA-CNTS) and short chain Mercaptopropionic acid (MPA) capped CNTS (MPA-CNTS). These were well characterized by UV-Vis-NIR, XRD, Raman, AFM, TEM, FESEM, and EDAX. All these characterizations confirm the formation single phase CNTS. Cyclic voltammetry investigation have been performed on CNTS nanocrystals to estimate the conduction and valence band edge parameters as a function of composition. For the first time, CNTS liquid junction solar cell with an architecture; FTO/TiO2/CdS-CNTS/ZnS/S-/Sn--/CuS/Se/FTO have been prepared. Solar cell prepared out of OLA-CNTS gave very poor power conversion efficiency. While, similar solar cell constructed out of MPA-CNTS displayed better performance having the efficiency and the fill factor in the order of 1.25 % and 0.380, respectively. Furthermore, an electrochemical impedance spectroscopy (EES) measurements revealed that MPA-CNTS has relatively low charge transfer resistance than OLA-CNTS. This property has been attributed to the poor performance of OLA-CNTS. Further investigations to optimize this material and device architecture would expected to increase the efficiency. Figure 1

Nongenetic optical neuromodulation with silicon-based materials.

Optically controlled nongenetic neuromodulation represents a promising approach for the fundamental study of neural circuits and the clinical treatment of neurological disorders. Among the existing material candidates that can transduce light energy into biologically relevant cues, silicon (Si) is particularly advantageous due to its highly tunable electrical and optical properties, ease of fabrication into multiple forms, ability to absorb a broad spectrum of light, and biocompatibility. This protocol describes a rational design principle for Si-based structures, general procedures for material synthesis and device fabrication, a universal method for evaluating material photoresponses, detailed illustrations of all instrumentation used, and demonstrations of optically controlled nongenetic modulation of cellular calcium dynamics, neuronal excitability, neurotransmitter release from mouse brain slices, and brain activity in the mouse brain in vivo using the aforementioned Si materials. The entire procedure takes ~4-8 d in the hands of an experienced graduate student, depending on the specific biological targets. We anticipate that our approach can also be adapted in the future to study other systems, such as cardiovascular tissues and microbial communities.

Skin Erythema and Blood Flow Responses to Acute Ultraviolet Radiation Exposure

Acute exposure to ultraviolet (UV)‐B light elicits an inflammatory response in the skin, resulting in erythema (reddening) and increased skin blood flow over the following 24 hours. However, the time course of, and relation between, these responses is unclear. Likewise, it is unknown whether these responses differ following exposure to broad spectrum (UV‐AB) vs. UV‐B light, as well as how application of sunscreen on the skin impacts these two responses.PurposeTo examine (1) the time course of erythema and skin blood flow responses over 8 h following acute UV‐B and UV‐AB exposure, and (2) the impact of sunscreen application on those responses. We hypothesized that (1) the erythema and blood flow responses would track each other, (2) both responses would be higher following UV‐AB compared to UV‐B exposure, and (3) sunscreen would attenuate responses to both UV‐AB and UV‐B.MethodsThe ventral aspect of both forearms of 10 healthy young adults (25±4 yrs; 6M/4F) were exposed to either UV‐AB (10 mJ/cm2; 6 mJ/cm2 UVA + 4 mJ/cm2 UV‐B) or UV‐B (4 mJ/cm2). Two 2‐cm2 sites on each arm were randomly chosen for acute UV exposure with or without pre‐treatment with topical SPF‐50 sunscreen. Erythema index (EI; reflectance spectrometry) and red cell flux (laser‐Doppler flowmetry) were measured at each site before, immediately after, and 2, 4, 6, and 8 h post‐exposure. Cutaneous vascular conductance was calculated (CVC=flux/MAP) at each time point and both EI and CVC were expressed as change from baseline.ResultsEI increased linearly after exposure to UV‐B (p<0.01 at 4, 6, and 8 h post‐exposure) and UV‐AB (p=0.02 at 6 h, p<0.01 at 8 h). Unlike the immediate increase in EI, no increase was seen for CVC until 4 h post‐UV‐B (p<0.01) and UV‐AB (p=0.06). Sunscreen effectively blocked the EI response to both UV‐B and UV‐AB exposures (p>0.05) and prevented, the CVC responses to UV‐B (p<0.01 at 6 and 8 hours) and UV‐AB (p=0.03 at 8 h).ConclusionExposure to UV‐B or UV‐AB induced an immediate and linear increase in EI, but a delayed (by 4 h) increase in CVC. Sunscreen prevented the EI response and blunted the rise in CVC. These data suggest that the inflammatory response to acute UV exposure is characterized by an immediate erythema response and a delayed blood flow response in the cutaneous microvasculature and that sunscreen may protect against both responses.Support or Funding InformationACSM Foundation Doctoral Student Research GrantThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Investigation of Chirped Well Structures for Broad-Spectrum AlGaInP-Based Light Emitting Diodes.

We investigated broad-spectrum light emitting diodes appropriate for special lighting applications in terms of their optical behaviors and device performances according to the chirped multi-quantum well structures. As the well thickness was increased from 6 to 15 nm, the electroluminescent spectrum was broadened by 43%, the forward bias voltage was lowered by 7% and the light output power was showed similar values in comparison to light emitting diodes having conventional multiquantum well structures. In the case of the chirped multi-quantum well structures having sequentially decreasing the well thickness from 15 nm to 6 nm, the optical output power was decreased by 38% due to the spreading problems of holes into the n-side active region.

Highly visible active Ag2CrO4/Ag/BiFeO3@RGO nano-junction for photoreduction of CO2 and photocatalytic removal of ciprofloxacin and bromate ions: The triggering effect of Ag and RGO

Designing highly optical active photocatalytic heterojunctions with multi-pronged capabilities for environmental applications is still a challenge. In this work the photocatalytic potential of Ag2CrO4/Ag/BiFeO3@RGO was systematically tested via photo-reduction of BrO3−, degradation of Ciprofloxacin (CIF) and photo-reduction of CO2 under broad light spectrum. Among various samples ABR-8 exhibits 99.6% BrO3− photoreduction and 96.3% CIF photo-oxidation in 90 min (nearly 96% in 60 min). ABR-11 (with 11 wt% RGO) selectively generates 180 μmol g−1 of CH4 in 8 h under visible light (260 μmol g−1 under alkali activation) which is approximately 60 times than bare BiFeO3. The excellent performance of ABR series is attributed to successful formation of Z-scheme which assists in efficient charge transfer, reduced recombination and wide spectrum response. In addition the electron donation-mediation of plasmonic Ag0 and adsorption-electron mediation of reduced graphene oxide has a triggering effect on reductive and oxidative capabilities. The band structure analysis, scavenging experiments and electron spin resonance studies make it possible to predict a suitable mechanism for bromate reduction, CIF degradation and CH4 generation. Electron assisted BrO3− reduction, •OH and •O2− radicals powered CIF degradation by Z-scheme mechanism and multi-electron single step proton-coupled mechanism for highly selective CH4 production were predicted. The best performing photocatalyst retain over 95% of performance over five consecutive runs. Suitable optimisations lead to higher performance from BiFeO3 which bears many shortcomings via interfacial junction with Ag2CrO4 with triggering effect from metallic Ag and RGO. Intelligently designed junctions can thus show strong photo-oxidative and reductive capabilities with further scope of fine tuning. Hence this developed heterojunction can be sustainably utilized for multi-pollutant removal and energy/fuel production under broad spectrum of light.

Dim light at night impairs recovery from global cerebral ischemia

Nighttime lighting is one of the great conveniences of modernization; however, there is mounting evidence that inopportune light exposure can disrupt physiological and behavioral functions. Hospital patients may be particularly vulnerable to the consequences of light at night due to their compromised physiological state. Cardiac arrest/cardiopulmonary resuscitation (CA) was used to test the hypothesis in mice that exposure to dim light at night impairs central nervous system (CNS) recovery from a major pathological insult. Mice exposed to dim light at night (5 lx) had higher mortality in the week following cardiac arrest compared to mice housed in dark nights (0 lx). Neuronal damage was significantly greater in surviving mice exposed to dim light at night after CA versus those housed in dark nights. Dim light at night may have elevated neuronal damage by amplifying pro-inflammatory pathways in the CNS; Iba1 immunoreactivity (an indication of microglia activation) and pro-inflammatory cytokine expression were elevated in mice exposed to dim light at night post-CA. Furthermore, selective inhibition of IL-1β or TNFα ameliorated damage in mice exposed to dim light at night. The effects of light at night on CA outcomes were also prevented by using a wavelength of nighttime light that has minimal impact on the endogenous circadian clock, suggesting that replacing broad-spectrum nighttime light with specific circadian-inert wavelengths could be protective. Together, these data indicate that exposure to dim light at night after global cerebral ischemia increases neuroinflammation, in turn exacerbating neurological damage and potential for mortality.

Numerical investigation of coupled optical-electrical-thermal processes for plasmonic solar cells at various angles of incident irradiance

Abstract Plasmonic solar cells include metal nanoparticles deposited on the top surface of substrate, whose output performance is constrained by self-heating, light induced heating, and environmental conditions. In this study, a numerical model for coupled optical-thermal-electrical processes was developed for GaAs based plasmonic solar cells with nanoparticles (Ag, Au). Temperature fluctuation due to hotspots and thermalization was observed. Light absorption, thermalization power, and electric performance of the solar cells at various angles of incident irradiation were analyzed. Results show that the hot spot makes a significant uneven temperature distribution in the layers of plasmonic solar cells. Varied angles of incident irradiance can cause more fluctuation in thermalization power and electrical performance for plasmonic solar cells than for non-plasmonic ones. Ag nanoparticles can enhance the broad-spectrum light absorption (0.3–0.87 μm), and Au nanoparticles can enhance the light absorption near the cutoff wavelength of GaAs (0.7–0.87 μm). It was concluded that plasmonic solar cells with Ag nanoparticles have higher efficiency of optical-electrical conversion at wide angles (of incidence), whereas plasmonic solar cells with Au nanoparticles provide higher efficiency of optical-electrical conversion at a specific angle. Thus, by properly designing the nanoparticle properties, the thermalization loss can be reduced, and the electrical performance can be improved.

Modeling PpIX effective light fluence at depths into the skin for PDT dose comparison.

Daylight-activated PDT has seen increased support in recent years as a treatment method for actinic keratosis and other non-melanoma skin cancers. The inherent variability observed in broad-spectrum light used in this methodology makes it difficult to plan and monitor light dose, or compare to lamp light doses. The present study expands on the commonly used PpIX-weighted effective surface irradiance metric by introducing a Monte Carlo method for estimating effective fluence rates into depths of the skin. The fluence rates are compared between multiple broadband and narrowband sources that have been reported in previous studies, and an effective total fluence for various treatment times is reported. A dynamic estimate of PpIX concentration produced during pro-drug incubation and treatment is used with the fluence estimates to calculate a photodynamic dose. Even when there is up to a 5x reduction between the effective surface irradiance of the broadband light sources, the effective fluence below 250 μm depth is predicted to be relatively equivalent. An effective threshold fluence value (0. 70Jeff/cm2) is introduced based on a meta-analysis of previously published ALA-PpIX induced cell death. This was combined with a threshold PpIX concentration (50 nM) to define a threshold photodynamic dose of 0.035 u M Jeff/cm2. The threshold was used to generate lookup tables to prescribe minimal treatment times to achieve depth-dependent cytotoxic effect based on incubation times and irradiance values for each light source.

Novel LDPE-riboflavin composite film with dual function of broad-spectrum light barrier and antimicrobial activity

Novel composite films of low-density polyethylene (LDPE) containing photosensitizing riboflavin (RB) were developed to enhance the broad-spectrum light barrier for the application of light-sensitive food packaging with an additional antimicrobial property. With the conjugated aromatic ring system of RB, the bright yellowish LDPE-RB composite film has excellent performance for absorbing light in the ultraviolet and short-visible regions, corresponding to the wavelength range of approximately 200–500 nm. The study of using such composite film for extra virgin olive oil (EVOO) effectively preserved the essential pigments, chlorophyll and β-carotene, by preventing the light-induced photodegradation. In addition, the standalone 5% RB composite film exhibits antibacterial activity, with reductions of >99% and 94% in Gram-negative and Gram-positive bacteria, respectively. The results of our studies on the enhanced light-barrier and antimicrobial properties offer unique insights for designing an innovative functional packaging film using natural food ingredients to prolong the quality of food, especially light-sensitive foods.