UV Exposition Research Articles

Cobalt oxide-chitosan based nanocomposites: Synthesis, characterization and their potential pharmaceutical applications

This research aimed to prepare, characterize, and investigate the biological efficacy of chitosan‑cobalt (II) oxide hybrid nanocomposites against a variety of micrograms. Analytical methods, FTIR, SEM, XRD, and EDX, were utilized to thoroughly characterize the produced CS-CoO nanocomposite. In FTIR spectra, the presence of the chitosan peaks in addition to that of CoO at 681 and 558 cm−1 confirmed that CoO molecules interact with the chitosan backbone. Moreover, in the XRD measurements, significantly less chitosan crystallinity was observed. Due to the incorporation of a larger amount of cobalt oxide within the polymer matrix. Applying the Debye-Sherrer calculation, the crystallite size was obviously reduced from 48.24 nm (5 wt %) to 19.27 nm (20 wt %) for the obtained nanocomposites. Furthermore, SEM measurements showed a transformation in the chitosan surface with the physical adsorption of CoO molecules on the surface active sites of chitosan that were visible in SEM graphs. Additionally, EDX determined the amount of Co element within the chitosan, with the sample of 20 wt % weight being found to be 19.26 wt %. The variable dose well-diffusion method was utilized to assess the efficacy of the CS-Co nanocomposite against a wide range of bacteria and fungi. CS − CoO nanocomposite is more effective than chitosan alone as an antibacterial agent against both Gram-positive and Gram-negative bacteria. Moreover, the MTT approach was employed to measure the cytotoxicity based on the cell viability of different cancer cell lines under different UV expositions. The proportion of the destroyed cells elevated due to the easy diffusion of CS − CoO nanocomposite into cancer cells as UV-free anticancer activity. UV exposition has stimulated the anticancer activity, which was attributed to an increase in ROS generation caused by the increased dose of the chitosan and its CS − CoO nanocomposites. Furthermore, the antioxidant capacities of the prepared nano-composites thin films were validated using the DPPH free radical scavenging method and showed good antioxidant activities with the DPPH radical compared with standard vitamin C. It has been noticed that by increasing the content of CoO nanoparticles from 5 to 20 wt %, the biological activity of the prepared nanocomposites was enhanced.

A Cocktail-Based Formula for the Design of Nanosized Cosmeceuticals as Skincare and Anti-Age Products.

Nasco and Bovale grape pomace extracts, alone or in association, were loaded in nanoemulsions tailored for cosmetic application, using Kolliphor®RH40 (kolliphor) as the synthetic surfactant, Olivem®1000 (olivem) as the natural one, and lecithin as the cosurfactant. Pink transparent or milky dispersions, as a function of the used extract and surfactant, were obtained to be used as cosmeceutical serum or milk. The sizes of the nanoemulsion droplets were small (≈77 nm with kolliphor and ≈141 nm with olivem), homogenously dispersed (~0.24 with kolliphor and ~0.16 with olivem), highly negatively charged (≈-43 mV irrespective of the used surfactant) and their stability either on storage or under stressing conditions was affected by the used extract and surfactant. Formulations protected the extracts from the degradation caused by UV exposition, were biocompatible against keratinocytes, protected them against oxidative damages induced using hydrogen peroxide and inhibited the release of nitrite induced in macrophages using the lipopolysaccharide inflammatory stimulus. The overall results underlined the key role played by the composition of the formula to achieve a suitable cosmeceutical for skin care but even for the prevention of premature aging and chronic damages caused by the stressing conditions.

Antioxidant and anti-photoaging properties of red marine macroalgae: Screening of bioactive molecules for cosmeceutical applications

Oxidative stress generated by UV exposition plays an important role on photoaging. Understanding the cell physiological responses due to the action of oxidative molecules process helps to develop approaches to reduce its impact on skin cells. In this context, algae can be source of biomolecules with antioxidant, inhibition of metalloproteinases and photoprotective capacities, such as mycosporine-like amino acids and phenolic compounds. This study focuses on the characterization of aqueous and hydroethanolic extracts of six red marine macroalgae: Phycocalidia acanthophora, Porphyra linearis, Condracanthus teedei, Gracilaria cornea, Osmundea pinnatifida and Plocamium cartilagineum (from two different sites). Besides their biochemical characterization, we also evaluated antioxidant capacity, potential to collagenase inhibition, and photoprotective capacity by different biological effective protection factors (BEPFs). Results evidenced a better correlation among the compounds of interest and bioactivity when using water as solvent rather than hydroethanolic solution. P. acanthophora and P. linearis aqueous extracts were highlighted in all analyses. Considering this fact, these two extracts were incorporate onto a cosmeceutical formulation. BEPFs evidenced that the incorporation of the extracts increased the photoprotection factors when compared to the control without physical filters. According to the findings herein described, the potential of red macroalgae as source of bioactive compounds with antiaging potential is reinforced.

Revealing the diversity of bacteria and fungi in the active layer of permafrost at Spitsbergen island (Arctic) – Combining classical microbiology and metabarcoding for ecological and bioprospecting exploration

Arctic soils are constantly subjected to extreme environmental conditions such as low humidity, strong winds, high salinity, freeze-thaw cycles, UV exposition, and low nutrient availability, therefore, they have developed unique microbial ecosystems. These environments provide excellent opportunities to study microbial ecology and evolution within pristine (i.e. with limited anthropogenic influence) regions since the High Arctic is still considered one of the wildest and least explored environments on the planet. This environment is also of interest for the screening and recovery of unique microbial strains suitable for various biotechnological applications. In this study, a combination of culture-depended and culture-independent approaches was used to determine the cultivation bias in studies of the diversity of cold-active microorganisms. Cultivation bias is a reduction in recovered diversity, introduced when applying a classical culturing technique. Six different soil types, collected in the vicinity of the Polish Polar Station Hornsund (Spitsbergen, Norway), were tested. It was revealed that the used media allowed recovery of only 6.37 % of bacterial and 20 % of fungal genera when compared with a culture-independent approach. Moreover, it was shown that a combination of R2A and Marine Broth media recovered as much as 93.6 % of all cultivable bacterial genera detected in this study. Based on these results, a novel protocol for genome-guided bioprospecting, combining a culture-dependent approach, metabarcoding, next-generation sequencing, and genomic data reuse was developed. With this methodology, 14 psychrotolerant, multi-metal-resistant strains, including the highly promising Rhodococcus spp., were obtained. These strains, besides increased metal tolerance, have a petroleum hydrocarbon utilization capacity, and thus may be good candidates for future bioremediation technologies, also suited to permanently cold regions.

Ascorbic acid-loaded gliadin nanoparticles as a novel nutraceutical formulation

Ascorbic acid (AA) is one of the foremost antioxidants. Unfortunately, its sensitivity to different external stimuli such as light, heat and oxygen are concrete limitations for its use. Various approaches have been investigated in order to circumvent this problem and enhance the stability of the active compound, besides promoting its use for different applications. In this investigation, AA was encapsulated in a vegetal protein-based matrix made up of gliadin, the prolamin obtained from wheat kernels, with the aim of proposing a novel nutraceutical formulation. The nanosystems were characterized by an average diameter of < 200 nm and a negative surface charge of ∼ −40 mV. The samples were not destabilized after incubation at different temperatures (up to 70 °C) or after the pasteurization procedure. Suitable stability was also observed in NaCl 100 mM, as well as after cryodesiccation when 10 % w/v of mannose was used. The gliadin nanoparticles showed the ability to retain high amounts of AA, promoting its prolonged release in PBS and under simulated gastrointestinal conditions. The nanosystems enhanced the antioxidant features of the compound as compared to its free form and preserved its chemical stability following UV exposition. The results demonstrate the potential application of the investigated nanoparticles as a novel nutraceutical formulation or as food fortificants.

Development of a New Formulation Based on In Situ Photopolymerized Polymer for the Treatment of Spinal Cord Injury.

Spinal Cord Injury (SCI) promotes a cascade of inflammatory events that are responsible for neuronal death and glial scar formation at the site of the injury, hindering tissue neuroregeneration. Among the main approaches for the treatment of SCI, the use of biomaterials, especially gelatin methacryloyl (GelMA), has been proposed because it is biocompatible, has excellent mechanical properties, favoring cell adhesion and proliferation. In addition, it can act as a carrier of anti-inflammatory drugs, preventing the formation of glial scars. The present work presents the development and in situ application of a light-curing formulation based on GelMA containing a natural extract rich in anti-inflammatory, antioxidant and neuroprotective substances (hydroalcoholic extract of red propolis—HERP) in an experimental model of SCI in rats. The formulations were prepared and characterized by time of UV exposition, FTIR, swelling and degradation. The hydrogels containing 1 mg/mL of HERP were obtained by the exposure to UV radiation of 2 μL of the formulation for 60 s. The locomotor evaluation of the animals was performed by the scale (BBB) and demonstrated that after 3 and 7 days of the injury, the GelMA-HERP group (BBB = 5 and 7) presented greater recovery compared to the GelMA group (BBB = 4 and 5). Regarding the inflammatory process, using histomorphological techniques, there was an inflammation reduction in the groups treated with GelMA and GelMA-HERP, with decreases of cavitation in the injury site. Therefore, it is possible to conclude that the use of GelMA and GelMA-HERP hydrogel formulations is a promising strategy for the treatment of SCI when applied in situ, as soon as possible after the injury, improving the clinical and inflammatory conditions of the treated animals.

Monitoring UV-accelerated alteration processes of paintings by means of hyperspectral micro-FTIR imaging and chemometrics

We explored the potential of infrared hyperspectral microimages to investigate the alteration of organic binders in pictorial layers after artificial UV light ageing. A set of paint mockups was prepared considering three different binders, namely, rabbit glue (a collagen-based proteinaceous binder), linseed oil (representative of drying oils) and egg tempera (a mixture of egg yolk and linseed oil). Four pigments (vermilion, orpiment, azurite and lead white) were considered in order to investigate the influence of pigment-binder interaction, following color changes by means of fiber optic reflectance spectroscopy (FORS). FTIR micro-images provided a representative picture of the complex and heterogeneous structure of paintings since each pixel contained the whole spectrum of the sample area from it was recorded. Principal component analysis (PCA) was used to analyze the FTIR images data in order to extract useful information about spectral changes taking place during UV induced ageing.Significant trends were observed, mainly depending on the binders and their degradation as a consequence of UV exposition in this pilot study on model samples. Several processes, such as the oxidation of proteins with the formation of carbonyl moieties and changes in amide band positions have been detected in the case of rabbit skin glue. The evaporation of linseed oil, probably due to the breakdown of the triacylglycerols, has been noticed for the binder alone but not when it was mixed with the pigments. In these cases, other spectral features depending on the pigment have been observed in the loading plots upon oxidation, namely the broadening of the carbonyl band, the appearance of carboxylic and dicarboxylic acids and the formation of metal carboxylates. For egg tempera, the main changes detected were related to the oxidation of lipidic components present in egg yolk fraction. Furthermore, in this case, the trend observed in the score graphs suggested that the presence of lead white accelerates its oxidation. It is interesting to note the major stability of the colored pigments when using this binder.

Antitumor activities of carboplatin–doxorubicin–ZnO complexes in different human cancer cell lines (breast, cervix uteri, colon, liver and oral) under UV exposition

This study aimed to examine the pharmacological profiles of multiple chemo drug candidates in systematic circulation to enhance their specific interactions with five human cancer cell lines. ZnO nanoparticles were successfully bound with chemo drugs via physical adsorption. The drug loading capacity was confirmed by FTIR, whereas the loading efficiency was determined via UV–vis spectrometry. The mean hydrodynamic size increased to 69–82 nm after chemo-drug immobilization via non-covalent interaction with ZnO. Among the nine formulated chemo drugs, the carboplatin (CP)–doxorubicin (DOX)–ZnO complex under UV light irradiation exhibited high sensitivity towards human breast adenocarcinoma cells without affecting human keratinocyte immortal cells with an IC50 of 0.137 µg/mL, whereas the loading capacity and efficiency of CP–DOX–ZnO were 77.81% and 99.05%, respectively. Fluorescence images confirmed that CP–DOX–ZnO using DOX served as a fluorescence enhancer specifically bound onto the cell membranes, which became almost saturated after 24 h incubation. Carboplatin–DOX–ZnO was possibly endocytosed by cancer cells and was selectively internalized into the target cells; thus, free chemo drug was released in the cytoplasm, which induced acute apoptosis. This resulted in complete inhabitation of growth signal of target cancer cells.

Selection of material model of chosen photocurable resin for application in finite element analyses

The paper deals with numerical simulations of materials printed with SLA technology. SLA (stereolitography) is an additive manufacturing technique, which main idea is printing with the use of a photocurable resin, e.g. epoxy or acrylic. The crosslinking is carried out under UV exposition. The chosen resin was experimentally tested and then numerical analyses were carried out using material models available in LS Dyna library (MAT_24, MAT_168, MAT_081). The results were compared. The best convergence was achieved for MAT_168.

Activation Treatments and SiO2/Pd Modification of Sol–Gel TiO2 Photocatalysts for Enhanced Photoactivity under UV Radiation

The objective of this work is to improve the efficiency of TiO2 photocatalysts by activation treatments and by modification with palladium nanoparticles and doping with SiO2. The influence of the additive loading was explored, and two activation treatments were performed: UV exposition and H2 reduction. TiO2/SiO2/Pd photocatalysts were synthesized by an original cogelation method: a modified silicon alkoxide, i.e., [3-(2-aminoethyl)aminopropyl]trimethoxysilane (EDAS), was used to complex the palladium ions, thanks to the ethylenediamine group, while the alkoxide groups reacted with TiO2 precursors. Pure TiO2 was also synthesized by the sol–gel process for comparison. X-ray diffraction evidenced that the crystallographic structure of TiO2 was anatase and that Pd was present, either in its oxidized form after calcination, or in its reduced form after reduction. The specific surface area of the samples varied from 5 to 145 m2 g-1. Transmission electron microscopy allowed us to observe the homogeneous dispersion and nanometric size of Pd particles in the reduced samples. The width of the band gap for pure TiO2 sample, measured by UV/Visible diffuse reflectance spectroscopy at approximately 3.2 eV, corresponded to that of anatase. The band gap for the TiO2/SiO2/Pd composite samples could not be calculated, due to their high absorption in visible range. The photocatalytic activity of the various catalysts was evaluated by the degradation of a methylene blue solution under UV radiation. The results showed that the photocatalytic activity of the catalysts was inversely proportional to the content of silica present in the matrix. A small amount of silica improved the photocatalytic activity, as compared to the pure TiO2 sample. By contrast, a high amount of silica delayed the crystallization of TiO2 in its anatase form. The activation treatment under UV had little influence on photocatalytic efficiency. The introduction of Pd species increased the photocatalytic activity of the samples because it allowed for a decrease in the rate of electron–hole recombinations in TiO2. The reduction treatment improved the activity of photocatalysts, whatever the palladium content, thanks to the reduction of Ti4+ into Ti3+, and the formation of defects in the crystallographic structure of anatase.

In situ photocrosslinkable formulation of nanocomposites based on multi-walled carbon nanotubes and formononetin for potential application in spinal cord injury treatment

Carbon nanotubes (CN) have been studied to treat spinal cord injuries because of its electrical properties and nanometric dimensions. This work aims to develop a photopolymerizable hydrogel containing CN functionalized with an anti-inflammatory molecule to be used in situ on spinal cord injuries. The CN functionalization step was done using the drug (formononetin). The nanocomposites were characterized by morphological analysis, FTIR, Raman Spectroscopy, thermal analysis and cytotoxicity assays (MTT and HET-CAM). The nanocomposites were incorporated into gelatin methacryloyl hydrogel and exposed to UV light for photopolymerization. The volume of the formulation and the UV exposition time were also analyzed. The CN characterization showed that formononetin acted as a functionalization agent. The functionalized CN showed safe characteristics and can be incorporated in photocrosslinkable formulation. The UV exposition time for the formulation photopolymerization was compatible with the cell viability and also occurred in the injury site.

Qualitative Assessment of the UV Exposition Process Near the Diffraction Limits

In the presented work the technological parameters that influence the shape of the resist structures are reported. The experimental results are compared with the simulations results, based on the solution of Maxwell’s equations using the RF module of COMSOL Multiphysics software. The electric field intensity distribution in the resist layer was analyzed for the mask slits that are larger and comparable to the applied wavelength. The differences in wave energy absorption in the resist layer are presented and discussed. For both cases, the impact of the chromium film thickness of the mask on the pattern profile of the resist is studied and the comparison is performed between the simulation and experimental results.

Colorimetric and photometric characterisation of clear and coloured pavements for urban spaces

A widespread use of clear and coloured pavements was internationally encouraged in recent years for different urban spaces. Unlike traditional “black” pavements, the design of the appropriate colour and visibility represent key factors for these wearing courses in environmental and monumental valuable contexts, where the aesthetic and the appearance of the finished layer represent essential characteristics. Operational methodologies and experimental measurements for the colorimetric and photometric characterisation of coloured pavements were presented. Due to cost consideration, thin pigmented slurry seals produced with two different clear synthetic emulsions and three inorganic pigments (red, green and blue) were taken into account. Physical parameters were monitored both at the construction phase and after an accelerated laboratory weathering, to evaluate the UV photo-oxidative effects. The obtained results highlighted three main findings: importance of a correct mix design, progressive colour change over UV exposition time and possible conversion of photometric parameters measured with different instruments.

UV sensor based on polyurethane foam

Ultraviolet light (UV) present in solar radiation has an important effect on the health of human skin. For that reason, we developed a disposable and easy-to-manufacture UV light sensor based on surface color change of a polyurethane (PU) film and examined its performance against radiation received from a lamp or from the sun. The chemical modification after UV exposition and the consequent color variation from light yellow to brown in PU sensor were studied by using RGB image analysis and a reflectance prototype containing an Arduino board. It was found that the photochemical modification of PU films increases absorption of visible radiation in the blue spectrum range. Furthermore, PU surface was more sensitive to UV (<390) than that found in visible light when exposed to sunlight, which was associated with the presence of a chromophore in the material modified. In addition, it was found that the extract obtained from irradiated PU showed its maximum absorption at 309 nm. Hence, the use of this economical light radiation sensor seems to be a very promising tool to determine exposure to UV light from the solar spectrum.

Head & Neck Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine tumor of the skin. Even if it is quite rare, the incidence has increased about two fold during the last twenty years. Mortality is higher than in malignant melanoma. Risk factors are chronic UV exposition and immunosuppression. MCC are most common in patients over 70 years and half of them manifest in the head and neck region. They early metastasize to regional lymph nodes. Surgical therapy should include wide resection of the primary tumor and diagnostic lymph node excision. In the head and neck region this means usually ipsilateral selective neck dissection. Adjuvant radiotherapy of the primary tumor bed and associated lymph nodes of the head and neck region decreases recurrence and should be performed in every patient regardless of the T- and N-stage. In the head and neck region adjuvant radiotherapy can only be spared in selected patients with low-risk profile (wide excisional margins > 2 cm, primary tumor size > 1 cm, absent lymphovascular infiltration, no immunosuppression and pathologic negative cervical lymph nodes). Isolated radiotherapy or systemic therapies are usually applied in patients with metastasized MCC. Disease recurrence is most common in the first two years after initial diagnosis. Patients should be examined at short intervals during this time.

Interactions between Zn2+ or ZnO with TiO2 to produce an efficient photocatalytic, superhydrophilic and aesthetic glass

Abstract Zinc was coupled with titanium dioxide using different methods. SiO2 and Zn-SiO2 doped TiO2 films, on the one hand, and Zn doped TiO2 on the other hand, have been produced using controlled sol-gel processes by alcoholic, cogelation and aqueous ways. From these syntheses, films were deposited on soda lime glass. These samples were compared to ZnO samples but also to bilayer samples constituting one layer of TiO2 and one layer of ZnO. The physico-chemical properties of the films were characterized by grazing-incidence X-ray diffraction, profilometry and UV–vis absorption analyses. The photocatalytic activity has been evaluated from the degradation of methylene blue under UV-A light, from the degradation of p-nitrophenol under visible light and from the degradation of H2O2 under halogen light (UV-A + visible light). Superhydrophilicity was evaluated from contact angle measurement after UV exposition and also from hysteresis effects. Finally, a haze measurement was performed to evaluate the impact of the coating on the aesthetic property of the coated glass. Aqueous films have better photocatalytic activity and superhydrophilicity than samples from alcoholic synthesis. The crystallization of the sample appears to be one key factor: alcoholic films required calcination to ensure the crystallization of TiO2, but the alkali migration from the glass support prevents this crystallization, while aqueous synthesis promotes crystallized particles at low temperatures without alkali interference. It appears that the relative activity from one sample to another depends on the nature of the illumination and on the nature of the molecule to be degraded. Nevertheless, the sample with ZnO layer deposited on first TiO2 layer (ZnO 500 Alc/TiO2 100 AQ) composite is found to be the best sample, maintaining a high hydrophilicity similar to TiO2 and a good activity.

154 The role of hyaluronan in the treatment of epidermal atrophy

Senile skin atrophy is a common side effect of intrinsic aging and UV exposition and it affects both dermal and epidermal layers of the skin. While dermal atrophy is mostly associated with the loss of connective tissue, epidermal atrophy manifests as overall thinning of epidermis, reduction of keratinocyte size and flattening of the dermoepidermal junction. Compared to senile atrophy, steroid skin atrophy frequently arises during glucocorticoid therapy and causes serious skin damages, particularly when applied to fragile skin. The anti-atrophic potential of sodium hyaluronate (SH) has been studied previously and it was demonstrated on a group of patients affected by steroid atrophy (Kaya et al., 2006). In this study, we investigated the ability of high (1500 kDa, HMW-SH), low (320 kDa, LMW-SH) and very low (15 kDa, VLMW-SH) molecular weight SH to reverse the main signs of epidermal atrophy (viability, total protein level, MMP expression) in the model of steroid-treated HaCaT keratinocytes. We also performed two double-blind, placebo-controlled, six-week in vivo studies to evaluate the effect of VLMW-SH and LMW-SH topical application on thickness of epidermis using the method of in vivo reflectance confocal microscopy. In both studies, 28 healthy female volunteers with living epidermal thickness below 50 μm participated, applying a cream with 0,2 % VLMW-SH (1st study) or 0,2 % LMW-SH (2nd study) on the face. Our results show that VLMW-SH significantly reverses all the studied signs of steroid-induced atrophy in HaCaT keratinocytes and increases the average epidermal thickness of aged skin in vivo. HMW-SH demonstrated less pronounced effect and LMW-SH showed no significant anti-atrophic abilities neither in vitro nor in vivo. In conclusion, we confirmed the importance of SH in senile and steroid-induced skin atrophy. However, therapeutic potentials of HMW, LMW and VLMW-SH show significant differences and should be investigated in detail. These results support the beneficial effects of SH and the possibility of its application in the therapy of atrophic epidermal skin.

Prognostic factors in head and neck melanoma according to facial aesthetic units.

Head and neck melanoma is a clinical challenge. Indeed, cutaneous head and neck melanoma shows a worse prognosis in comparison to melanomas of other body sites. Although the emphasis on facial cosmetic preservation plays a pivotal role in comparison to other body areas, specific Facial Aesthetic Units (FAU) could also play a key role in the prognostic evaluation of the malignancy. The aim of the current study was to evaluate the general outcome and clinicopathological features of head and neck melanoma and to detect prognostic differences according to each FAU. The Kaplan-Meier product was used to calculate survival curves, while Cox proportional-hazard regression was performed to evaluate the predictive value of each FAU. A total of 221 head and neck melanoma patients was included in our analysis. In the nasal FAU, we found a high rate of local recurrence, which affected significantly disease-free survival. The worse prognosis was observed in melanoma of the scalp, which showed a greater tendency to skip metastases in internal organs. Moreover, we found that scalp showed a low incidence of non-melanoma skin cancers, if compared to other FAU, highlighting that the scalp local milieu might play a more prominent role in melanoma biology than chronic UV exposition. Although FAUs have an aesthetic function, they could also play a role in the evaluation and follow-up of melanoma.

Metastability of a-SiOx:H thin films for c-Si surface passivation

The adoption of a-SiOx:H films obtained by PECVD in heterojunction solar cells is a key to further increase their efficiency, because of its transparency in the UV with respect to the commonly used a-Si:H. At the same time this layer must guarantee high surface passivation of the c-Si to be suitable in high efficiency solar cell manufacturing. On the other hand the application of amorphous materials like a-Si:H and SiNx on the cell frontside expose them to the mostly energetic part of the sun spectrum, leading to a metastability of their passivation properties. Moreover as for amorphous silicon, thermal annealing procedures are considered as valuable steps to enhance and stabilize thin film properties, when performed at opportune temperature. In this work we explored the reliability of a-SiOx:H thin film layers surface passivation on c-Si substrates under UV exposition, in combination with thermal annealing steps. Both p- and n-type doped c-Si substrates were considered. To understand the effect of UV light soaking we monitored the minority carriers lifetime and SiH and SiO bonding, by FTIR spectra, after different exposure times to light coming from a deuterium lamp, filtered to UV-A region, and focused on the sample to obtain a power density of 50μW/cm2. We found a certain lifetime decrease after UV light soaking in both p- and n-type c-Si passivated wafers according to a a-SiOx:H/c-Si/a-SiOx:H structure. The role of a thermal annealing, which usually enhances the as-deposited SiOx passivation properties, was furthermore considered. In particular we monitored the UV light soaking effect on c-Si wafers after a-SiOx:H coating by PECVD and after a thermal annealing treatment at 300°C for 30min, having selected these conditions on the basis of the study of the effect due to different temperatures and durations. We correlated the lifetime evolution and the metastability effect of thermal annealing to the a-SiOx:H/c-Si interface considering the evolution of hydrogen in the film revealed by FTIR spectra, and we developed a model for the effect of both treatments on the SiH bonding and the metastability shown in the lifetime of a-SiOx:H/c-Si/a-SiOx:H structure. We found that, after UV exposure, thermal annealing steps can be used as a tool for the c-Si passivation recovery and enhancement.

ChemInform Abstract: Chemical Modification in the Design of Immobilized Enzyme Biocatalysts: Drawbacks and Opportunities

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