UV Exposure

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Wearable Nanoplasmonic Patch-Detecting Sun / UV Exposure Jessica G. Barajas-Carmona, Leydi Francisco-Aldana, and Eden Morales-Narváez Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.analchem.7b04066 • Publication Date (Web): 20 Nov 2017 Downloaded from http://pubs.acs.org on November 21, 2017

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Analytical Chemistry

Wearable Nanoplasmonic Patch-Detecting Sun / UV Exposure Jessica G. Barajas-Carmonaa, Leydi Francisco-Aldanaa, Eden Morales-Narváez*a a

Biophotonic Nanosensors Laboratory, Centro de Investigaciones en Óptica, A. C., Loma del Bosque 115, Lomas del Campestre, León, Guanajuato, 37150, México. *E-mail: [email protected] Keywords: Nanophotonics, UV-responsive devices, noble metal nanoparticles, nanocellulose, nanocomposites

Abstract Sun exposure is known to yield beneficial health outcomes, including synthesis of adequate levels of vitamin D, beneficial modulation of blood pressure and is a valuable factor in mental health care. However, the increasing incidence of sun/UV exposure-related illness, such as skin cancer, is seriously concerning public health authorities as well as the scientific community. Consequently, moderate sun/UV exposure is strongly recommended. A wearable nanoplasmonic patch whose original color changes upon sun exposure due to its UV-responsive capabilities that are visually detectable has been engineered. The main scaffold of this patch is made of nanopaper, which is a flexible, lightweight, optically transparent and biocompatible material. Moreover, its UV-responsive agent is based on silver nanoparticles (AgNP), whose nanoplasmonic properties and safe use in bioapplications are widely covered in the literature. As UV light can modulate the size of AgNP significantly, the nanoplasmonic properties of the AgNP-decorated nanopaper are also modulated leading to a change in color, which is readily observable upon sun exposure. This facilitates that the users can be alerted to a moderate sun exposure and may prevent skin damage. Given the transparent nanoplasmonic nature of the resulting device, after 15 min of artificial sunlight exposure, the change in color of the patch was proven 1 ACS Paragon Plus Environment


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more observable in skins with the highest and moderate risk of developing skin cancer (skin types I, II, III, IV) than in skin types V, VI – which are reported to tolerate relatively high levels of sun exposure safely. This low-cost wearable device is amenable to facilitating healthcare in low-resource settings using biomaterials and nanoplasmonics.

1.Introduction The electromagnetic spectrum derived from sunlight reaching the planet’s surface is generally categorized into three wavelength sets, including ultraviolet (UV, 200–400 nm), visible (Vis, 400–760 nm) and infrared radiation (760–106 nm), where 6% of this spectrum is UV, 52% visible and 42% is infrared light. Among these categories, UV radiation is known to offer beneficial health outcomes and it is typically categorized into three subsets UVC (100–290 nm), UVB (290–320 nm) and UVA (320–400 nm). UVC is filtered by the ozone layer in a highly efficient way, whereas the rest of UV components are able to penetrate and interact with skin surface. Nevertheless, the degradation of the ozone layer is prone to raise the intensity of global UV irradiance. Importantly, latitude, season, altitude, time of day and environmental conditions also have a crucial effect on the intensity of UV radiation reaching the surface of the planet.1 Human being relies on sunlight for their vitamin D requirement. Moreover, sunlight exposure has a positive effect on blood pressure modulation and is an effective resource in terms of mental health care, especially to avoid depressive disorders. It is worth mentioning that nowadays vitamin D deficiency is a pandemic problem that should not be underestimated.2 However, non-moderate sunlight exposure is prone to provoke skin damage such as sunburn or photoaging and the same UVB radiation that is responsible for the photoproduction of vitamin D also plays a critical role in skin cancer development.3–5 2 ACS Paragon Plus Environment

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In fact, according to Skin Cancer Foundation Statistics, 20% of the American population are prone to develop skin cancer in their lifetime.6 Hence, moderate sun/UV exposure is strongly recommended and there are growing demands for simple devices for the monitoring of a moderate dose of this type of radiation. Bearing in mind such a critical issue, the scientific and technological community are actively working to tackle this challenge, specifically developing flexible sun/UV detectors reporting on a moderate sun/UV exposure and preventing skin damage. Recently, the literature reported two innovative UV detectors mainly based on paper, dyes and photoactive polymers.7,8 However, the paper-based detector designed by Khiabani and colleagues needed an extra component such as UV neutral density filters to tune the detector’s behavior according to different skin types,7 while the polymer-based detector developed by Lee and Armani required several layers of polymers.8 Overall, these features increase the complexity and the total cost of these novel devices. Moreover, their epidermal behavior has not been particularly shown. We report on a wearable nanoplasmonic patch for the detection of moderate sun/UV exposure, whose synthesis process is green. This simple device is made of bacterial cellulose nanopaper embedding silver nanoparticles (AgNPs). It should be remarked that nowadays AgNPs are utilized in more than 200 consumer goods, including cosmetics and food products.9 We employ the advantageous features offered by a biocompatible nanoscaffold such as nanopaper to build a flexible, lightweight and wearable device.10,11 As the nanoplasmonic properties of noble metal nanoparticles can be modulated by changing their size,12–14 and UV radiation is able to affect the size of AgNP via photolysis,9,15,16 the nanoplasmonic properties of AgNPs embedded in nanopaper are used to report moderate UV/sun exposure via a change in color that is visually observable (see Figure 1). We also tested the performance of the 3 ACS Paragon Plus Environment


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nanoplasmonic patch in the six skin types conventionally reported by the World Health Organization (skin types I–VI).6

2. Material and methods All the reagents were of analytical grade and handled according to the material safety data sheets suggested by the suppliers. NaOH and AgNO3 were purchased from Sigma-Aldrich (Toluca, Mexico State, Mexico). Bacterial cellulose nanopaper was acquired from Nano Novin Polymer Co. (Mazandaran, Iran). All aqueous solutions were freshly prepared in ultrapure water. Tattoo paper was from Silhouette America Inc. (Orem, Utah, USA). Reference patches were manufactured using tattoo paper and a HP OfficeJet Pro 8710 Printer (Hewlett-Packard, Palo Alto, California, USA). A spectrophotometer was used to analyze UV-Vis absorbance (Cytation 5, BioTek, Winooski, Vermont, USA). An Oriel Sol 3A solar simulator (Newport, Irvine, California, USA) was utilized to expose the nanoplasmonic patches to the respective UV light (1000 W m-2). The pictures were taken using a mobile phone camera (Moto G, Motorola, Chicago, Illinois, USA). SEM analysis was carried out through an equipment JSM-7800F (Jeol USA Inc., Peabody, Massachusetts, USA) –the silver nanoparticle-decorated bacterial cellulose nanopaper (AgNP-BC) specimens were analyzed onto adhesive carbon tape. The particle size distributions were determined using ImageJ 1.51j8 (Wayne Rasband, National Institutes of Health, USA). Informed signed consent was obtained from the volunteers who kindly tested the nanoplasmonic patch. A total of 16 AgNP-BCs were synthesized using previously reported methods,10,17,18 where different synthesis times (15, 20, 30 and 120 min) were executed and various volumes of an aqueous solution of AgNO3 were added in the synthesis (5, 6.25, 7.5 and 8.75 mL 4 ACS Paragon Plus Environment

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concentrated at 0.1% v/v), respectively. As the synthesis occurs in suspension, the resulting AgNP-BCs have to be dried following the aforementioned methods.10,17,18 Briefly, the resulting pieces of AgNP-BC are sandwiched and clamped between two pieces of conventional paper and two glass slides. The material is then dried overnight at room temperature. Once the material was dried, it was extracted from the aforementioned glass slides and cut in form of circles using a punch tool of 6 mm diameter. The resulting nanoplasmonic patches can be easily adhered to skin using tattoo paper. In order to perform the studies of sun/UV effect on the nanoplasmonic patches, the nanoplasmonic devices were placed in the solar simulator at a distance around 17 cm from the light source. In order to avoid any possible change in the refractive index due to humidity provided by perspiration, the nanoplasmonic patches tested in epidermal conditions were dried in a hotplate at 40 °C during 15 min before UV-Vis analysis. Safety. Importantly, no skin irritation was observed or reported by the volunteers.

3. Results and Discussion The literature reports that UV exposure has a photolytic effect on AgNP that leads to a modulation in the respective particle size distribution, generally showing a diameter decrease and eventually aggregation. However, this phenomenon has been reported to evolve throughout thousands of min of UV/sun exposure in colloidal suspensions of AgNP. 9,15,16

Consequently, it is not obvious that the particle size distribution of AgNPs can be

readily modulated in tens of min of sun/UV exposure. Therefore, first and foremost, we judiciously studied the behavior of several films of AgNPs-decorated nanopaper (AgNPBC) upon sun/UV exposure using a solar simulator. The nanopaper was produced via bacterial synthesis using Acetobacter xylinum, whose average fiber diameter is ~45 nm and 5 ACS Paragon Plus Environment


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length around ~10 µm. This nanocellulose-based material also has a crystallinity of 82% and a Young’s modulus of 17 GPa, as previously characterized.10 Importantly, we have previously demonstrated that due to the nanostructure of bacterial cellulose, “the spatial distribution of nanoparticles deposited within nanopaper is completely different when compared with the disposition of nanoparticles embedded within other conventional paper substrates such as nitro/cellulose”. Moreover, it is worth mentioning that nanopaper and its optical transparency facilitates that the plasmonic properties of the embedded nanoparticles can be virtually completely exposed.10

The typical thickness of the studied AgNP-decorated nanocellulose films is around 16 µm and the green synthesis of the explored nanocomposite can be tuned in terms of nanoparticles density by simply varying the main parameters of the synthesis such as time and concentration of the precursor, where short times and low concentrations are expected to give rise to low nanoparticle densities. To this end, we used previously reported approaches exploiting nanocellulose as a reducing agent and AgNO3 as a precursor of the embedded AgNPs,10,17 and we explored the behavior of different AgNP-BCs upon solar simulator exposure (c.a. 1000 W m-2). These AgNP-BCs were obtained at different synthesis times (15, 20, 30 and 120 min) and various volumes of the precursor to be added in the synthesis (5, 6.25, 7.5 and 8.75 mL concentrated at 0.1% v/v). Importantly, the UVVis absorbance of small pieces of the resulting AgNP-BCs (around 36 mm2) can be easily analyzed through a microplate reader. The employed methods are provided in the experimental section. In order to demonstrate that the employed scaffold made of bacterial cellulose is not UV-responsive itself, we exposed several pieces of bare nanopaper to the

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solar simulator during 15 min. Figure S1 displays that no changes were observed neither in the UV-Vis spectra, nor in the color of the explored bare nanopaper. The following statement illustrates an overall example of moderate sun exposure to acquire suitable levels of vitamin D, “White people with Type II skins at 40 degrees latitude can obtain their annual requirements of vitamin D by spending about 15 min in the sun with face, arms and legs exposed (half that time if in a bathing suit) 2 to 3 times a week between 11 a.m. and 3 p.m. during the months of May through October” 4. Moreover, in a northern mid-latitude, the median effective solar UV radiation producing vitamin D on summer days is around 7700 W m-2 day-1, whereas on winter days it is around 1000 W m-2 day-1 5. In this context, as proof of concept, we sought to find the most sensitive modulation of the explored UV-Vis absorbance spectra by comparing the area under the curve of the normalized initial UV-Vis spectrum (A0) with the area under the curve of the normalized UV-Vis spectrum obtained upon 15 min of solar simulator exposure (A1). The solar simulator operated at 1000 W m-2. Although a comparative analysis of the full width at half maximum of the resulting spectra could be a useful parameter to follow the sensitivity of the studied phenomenon, this parameter is not feasible to obtain systematically in the resulting spectra as not all of them display a Gaussian distribution. Figure 2A shows the obtained spectra. Thus we defined the A1/A0 ratio as an indicator on how the spectra were modulated, where those values greater than one suggest that the spectra tend to be broadened, whereas those values less than one suggest that the spectra tend to be narrowed. Firstly, we started with AgNP-BCs synthesized with our conventional conditions (120 min and a precursor volume around 5 mL),10,18 these materials display a relatively strong modulation of the UV-Vis absorbance upon solar simulator exposure, until 0.91 units in terms of the A1/A0 ratio; however, due to their relatively high optical density (up to c.a. 1.8 7 ACS Paragon Plus Environment


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units) such nanoplasmonic changes are not easy to detect visually. We then reasoned that probably lower densities of AgNPs embedded in nanopaper, obtained via shorter synthesis times, could be more useful in the studied approach. Although the strongest modulation of the overall UV-Vis absorbance spectra was achieved with those AgNP-BCs synthesized during 15 min, that is, up to 1.27 units in terms of the A1/A0 ratio, such nanoplasmonic changes are not easy to detect visually in this case due to their relatively low optical density, which reaches a maximum value of c.a. 0.35 units. Moreover, those syntheses executed during 20 and 30 min, respectively, were observed to undergo similar modulation of the A1/A0 ratio levels ranging between ~0.98 and ~1.03 units, whereas a change in color upon solar simulator exposure was easier to observe using these AgNP-BCs. Importantly, the maximum optical density of these materials is around 0.54 units for the AgNP-BCs synthesized during 20 min and 0.85 units for the AgNP-BCs synthesized during 30 min. Figure 2B-C shows the resulting ratios and the color of the nanoplasmonic patches before and after solar simulator exposure. Analyzing the results summarized in Figure 2, we had to find a balance between visually observable changes in color and the overall modulation of the studied UV-Vis absorbance. Given the aforementioned results, we decided to continue our experimental approach using AgNP-BCs synthesized during 20 min, whose change in color is relatively easier to observe upon solar simulator exposure and its synthesis requires less resources in terms of time. We then analyzed the behavior of these nanoplasmonic composites across different times of solar simulator exposure. Figure 3A shows how the UV-Vis spectra of the analyzed materials are modulated upon solar simulator exposure at different times (15, 30, 45 and 60 min). Such a modulation can be quantified in terms of the previously defined A1/A0 ratio (Figure 3B). Accordingly, A0, represents the area under the curve of the normalized starting 8 ACS Paragon Plus Environment

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UV-Vis spectrum, while A1 represents the area under the curve of the normalized UV-Vis spectrum obtained upon the respective time of solar simulator exposure. Overall, it can be observed that the nanoplasmonic composites fabricated with a precursor volume of 7.5 and 8.5 mL exhibit the strongest changes in terms of the A1/A0 ratio. Moreover, the nanoplasmonic composite synthesized with 5 mL of the precursor volume tends to narrow its UV-Vis spectrum throughout one hour of solar simulator exposure, whereas the nanoplasmonic composite synthesized with 8.75 mL of the precursor volume tends to broaden its UV-Vis spectrum throughout one hour of solar simulator exposure. In contrast, the behavior of the syntheses executed with a precursor volume of 6.25 and 7.5 mL oscillate their behavior and broaden and narrow their corresponding spectra throughout one hour of solar simulator exposure. Interestingly, ingeneral, a slight blue shift (~2-4 nm) can be noted in the analyzed spectra suggesting that the average size of the AgNPs is likely to undergo a reduction due to a photolytic effect. Figure S2 displays the resulting colors. Motivated by the obtained results, we then configured a wearable device to be tested in epidermal conditions. In accordance with the World Health Organization, skin types are generally classified in six groups (I-VI). People with skin types I and II include citizens with pale or freckled skin, typically Caucasians, which have the highest risk of developing skin cancer. Dark-haired and dark-eyed citizens who do not typically get suntanned (skin types III and IV) have medium risk of developing skin cancer. However, in general, naturally brown and black citizens (skin types V and VI) can bear relatively high levels of sun/UV exposure in a safe way6. Accordingly, aiming at testing the overall epidermal performance of the developed device in different skin types, consenting volunteers with skin types I to VI participated in epidermal studies of the wearable nanoplasmonic patch. To this end, the nanoplasmonic patches were adhered to skin utilizing tattoo paper. Figure 4 9 ACS Paragon Plus Environment


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shows the resulting wearable device and demonstrates its flexible nature. Interestingly, as a proof of principle, the patch was worn by a volunteer during 8 hours (avoiding sun/UV exposure) without causing skin irritation or any other symptom. We then tested the nanoplasmonic patch obtained with the aforementioned synthesis executed during 20 min. Different patches embedding a different density of AgNPs, depending on the volume of the precursor applied in the synthesis process, were adhered on the volunteers’ skin. Surprisingly, after 15 min of solar simulator exposure, we discovered that the sensitivity of the detector can be tailored according to both, the density of nanoparticles embedded in the patch and the skin type in which the nanoplasmonic device will be employed. Figure S3 displays all the pictures collected throughout these epidermal studies, while Figure 5 summarizes those patches that are usually most sensitive according to each skin type and also shows the corresponding UV-Vis spectra. Control experiments without sun/UV exposure were also carried out (see Figure S4). Overall, those patches fabricated with a precursor volume of 7.5 or 8.75 mL are useful in skin types I and II, while those patches synthesized with a precursor volume of 6.25 mL are useful in skin types III and IV. Table 1 shows their respective A1/A0 ratio.

It should be highlighted that the nanoplasmonic device worn on skins types V and VI, which are reported to tolerate relatively high levels of sun exposure safely, did not display a clearly observable change in color in any case. These phenomena can be attributed to the fact that the visually observable color of transparent nanoplasmonic substrates can strongly depend on a given background color.14 Thus, as observed in Figure 5, we found that the background color contributed by the explored skin type also plays a critical role in the final visually observable color. 10 ACS Paragon Plus Environment

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We have previously demonstrated that the color of AgNP-BC can be modified by modulating the size distribution and/or the population density of the AgNPs embedded in nanopaper.10,18 Thus, aiming at confirming such a phenomenon in the resulting device, we performed a scanning electron microscopy (SEM) analysis of the wearable nanoplasmonic patch utilized in epidermal conditions. Due to the relatively low density of AgNPs embedded in the explored nanoplasmonic patch, it was not straightforward to carry out such analysis, when compared with our previous AgNP-BC and their respective SEM analyses.10,18 In fact, we found hard to obtain SEM micrographs of those nanoparticles synthesized at low volumes of the precursor (5.00, 6.25 and 7.50 mL, see Figure S5). Though, as the highest density of nanoparticles available within our analyzed samples is achieved with that synthesis executed with 8.75 mL of precursor volume, we managed to perform a SEM analysis using this class of nanoplasmonic patch. Figure 6 displays the details of this analysis, where we found a blue shift of ~10 units in the peak of the analyzed UV-Vis spectra (Figure 6B). Comparing this blue shift of ~10 nm with the aforementioned blue shift of ~2-4 nm, we believe that this resulting phenomenon of a larger blue shift could be due to an influence of sun/UV exposure combined with perspiration, which consists in water, minerals, lactate and urea and is also able to release Ag ions from AgNP)19–21. Importantly, epidermal control experiments without sun/UV exposure show a negligible visually observable change in color (Figure S4), suggesting that the aforementioned effect of perspiration is not able to modulate the nanoplasmonic properties of the patch itself dramatically. We also found that the particle size in the initial conditions had a mean of 7.6 ± 4.6 nm, whereas the particle size of the nanoplasmonic patch utilized in epidermal conditions upon 15 min of solar simulator exposure reaches a mean of 5.8 ± 2.8 nm (Figure 11 ACS Paragon Plus Environment


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S6 shows the SEM micrographs involved in this study, where a population of 100 AgNPs was analyzed, respectively). This analysis suggests that the AgNPs of the studied nanoplasmonic patch is likely to undergo photolysis upon sun/UV exposure. Previous approaches propose the determination of a threshold to determine a clearly observable visual contrast in the resulting UV-responsive device, for example a visual discoloration of film around ∼74% reflectance in the wavelength of 630 nm.7 Here, we observed that those patches undergoing an A1/A0 ratio greater than 1.10 upon sun exposure display a clearly observable visual contrast (Table 1). However, visual determination of color may be subjective, thus aiming at determining a color change in the proposed device safely; this concern prompted us to manufacture a reference patch whose color is similar to that of the initial color of the nanoplasmonic patch in order to compare the final color of the resulting device. This reference patch can be easily produced using tattoo paper and a home printer (see details in the experimental section). Figure 7 shows how the change in color of the nanoplasmonic patch can be monitored using a reference patch safely.

4.Conclusions A wearable nanoplasmonic patch enabling the detection of moderate sun/UV exposure has been developed and successfully tested in epidermal conditions. The proposed device is a film made of AgNPs embedded in nanopaper which due to its flexible nature simply needs an adhesive layer to be worn (ex. tattoo paper). Experimentally, we found the conditions in which the embedded nanoparticles can undergo a size reduction via a photolysis driven by UV/sun light exposure, leading to a sensitive modulation of the nanoplasmonic properties of the device and thus a change in its color that is visually observable. Although the visual contrast of other previously reported sun/UV exposure detection approaches may be better 12 ACS Paragon Plus Environment

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than that of this approach,7,8 the visual contrast of this approach improves when the nanoplasmonic device operates in epidermal conditions as demonstrated above. Futhermore, the performance of the nanoplasmonic patch can be easily monitored via a reference patch and the sensitivity of the developed device can be adapted according to the skin type of the user without adding extra components. Moreover, the synthesis of the nanoplasmonic patch is simple, green and low-cost (around 0.05 USD each patch). As a conceptually new epidermal device, this detector is able to alert the users to a moderate sun exposure and prevents skin damage caused by UV radiation by undergoing a simple change in color that can be visually spotted by the user. This approach opens up the opportunity to facilitate healthcare in low-resource settings using nanophotonics. Supporting Information Supplementary Figures S1-S6 are supplied as Supporting Information. Acknowledgements The authors acknowledge the overall financial support from CONACYT (Mexico). J.G.B.C. acknowledges financial support from Center for Research in Optics (Academic Department). E.M.-N. acknowledges the support from National System of Researchers, CONACYT (Mexico, Grant 74314). The authors also acknowledge the technical support provided by M. C. Albor-Cortes (SEM technician at CIO). References (1) Polefka, T. G.; Meyer, T. A.; Agin, P. P.; Bianchini, R. J. J. Cosmet. Dermatol. 2012, 11 (2), 134–143. (2) Holick, M. F. Rev. Endocr. Metab. Disord. 2017, 18 (2), 153–165. (3) Holick, M. F. In Sunlight, Vitamin D and Skin Cancer; Reichrath, J., Ed.; Springer New York: New York, NY, 2008; pp 1–15. (4) Hoel, D. G.; Berwick, M.; de Gruijl, F. R.; Holick, M. F. Dermatoendocrinol. 2016, 8 (1), e1248325. (5) Serrano, M.-A.; Cañada, J.; Moreno, J. C.; Gurrea, G. Sci. Total Environ. 2017, 574, 744–750. (6) (7) Khiabani, P. S.; Soeriyadi, A. H.; Reece, P. J.; Gooding, J. J. ACS Sens. 2016, 1 (6), 775–780. (8) Lee, M. E.; Armani, A. M. ACS Sens. 2016, 1 (10), 1251–1255. (9) Cheng, Y.; Yin, L.; Lin, S.; Wiesner, M.; Bernhardt, E.; Liu, J. J. Phys. Chem. C 2011, 115 (11), 4425–4432. 13 ACS Paragon Plus Environment


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(10) Morales-Narváez, E.; Golmohammadi, H.; Naghdi, T.; Yousefi, H.; Kostiv, U.; Horák, D.; Pourreza, N.; Merkoçi, A. ACS Nano 2015, 9 (7), 7296–305. (11) Golmohammadi, H.; Morales-Narváez, E.; Naghdi, T.; Merkoçi, A. Chem. Mater. 2017, 29 (13), 5426–5446. (12) Howes, P. D.; Chandrawati, R.; Stevens, M. M. Science 2014, 346 (6205). (13) Stockman, M. I. Science 2015, 348 (6232), 287. (14) Yu, R.; Mazumder, P.; Borrelli, N. F.; Carrilero, A.; Ghosh, D. S.; Maniyara, R. A.; Baker, D.; García de Abajo, F. J.; Pruneri, V. ACS Photonics 2016, 3 (7), 1194– 1201. (15) Gorham, J. M.; MacCuspie, R. I.; Klein, K. L.; Fairbrother, D. H.; Holbrook, R. D. J. Nanoparticle Res. 2012, 14 (10), 1139. (16) Mittelman, A. M.; Fortner, J. D.; Pennell, K. D. Environ. Sci. Nano 2015, 2 (6), 683– 691. (17) Pourreza, N.; Golmohammadi, H.; Naghdi, T.; Yousefi, H. Biosens. Bioelectron. 2015, 74, 353–359. (18) Heli, B.; Morales-Narváez, E.; Golmohammadi, H.; Ajji, A.; Merkoçi, A. Nanoscale 2016, 8 (15), 7984–7991. (19) Nyein, H. Y. Y.; Gao, W.; Shahpar, Z.; Emaminejad, S.; Challa, S.; Chen, K.; Fahad, H. M.; Tai, L.-C.; Ota, H.; Davis, R. W.; Javey, A. ACS Nano 2016, 10 (7), 7216– 7224. (20) Hedberg, J.; Skoglund, S.; Karlsson, M.-E.; Wold, S.; Odnevall Wallinder, I.; Hedberg, Y. Environ. Sci. Technol. 2014, 48 (13), 7314–7322. (21) Wagener, S.; Dommershausen, N.; Jungnickel, H.; Laux, P.; Mitrano, D.; Nowack, B.; Schneider, G.; Luch, A. Environ. Sci. Technol. 2016, 50 (11), 5927–5934.

Table 1. Modulation of the A1/A0 ratio of the nanoplasmonic patch utilized in epidermal conditions. Skin Type

PV (mL)

A1/A0 ratio

I

7.50

1.32

II

7.50

1.21

III

6.25

1.53

IV

6.25

1.26

V

8.75

1.24

VI

8.75

1.21

PV, precursor volume. 14 ACS Paragon Plus Environment

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Figure 1. Operational mechanism of the wearable nanoplasmonic patch. Before sun exposure (A), the patch embeds silver nanoparticles with an average diameter a. The original size of the particles embedded in the patch undergoes a modulation caused by a photolytic phenomenon upon Sun/UV radiation (B) resulting in a new average particle diameter b. This modulation of the nanoplasmonic properties of the patch is responsible for a change in color that is visually observable.



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Figure 2. Analysis of different syntheses of AgNP-BC produced by varying the synthesis time (15, 20, 30 and 120 min) and the precursor volume (5, 6.25, 7.5 and 8.75 mL). A. UVVis spectra before and after solar simulator (SS) exposure (15 min). Each spectrum represents the mean of 3 spectra recorded under the respective conditions. ST, synthesis time. B. Analysis of the area under the curve of the spectra using the A1/A0 ratio. A0, area under the curve of the normalized initial UV-Vis spectrum. A1, area under the curve of the normalized UV-Vis spectrum obtained upon 15 min of solar simulator exposure. C. Photographs taken as experimental examples of the analyzed AgNP-BCs. A white background color was utilized to take these pictures. PV, precursor volume.


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Figure 3. Performance of the nanoplasmonic composite across different times of solar simulator exposure. The nanocomposite was synthesized using different precursor volumes (PV, 5, 6.25, 7.5 and 8.75 mL) during 20 min. A. UV-Vis spectra upon solar simulator exposure (15, 30, 45 and 60 min). Each spectrum represents the mean of 3 spectra recorded under the respective conditions. B. Behavior of the area under the curve of the spectra using the A1/A0 ratio. A0, area under the curve of the normalized initial UV-Vis spectrum. A1, area under the curve of the normalized UV-Vis spectrum obtained upon the respective time of solar simulator exposure.



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Figure 4. Pictures of the wearable nanoplasmonic patch demonstrating its flexible nature.


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Figure 5. Epidermal studies of the wearable nanoplasmonic patch. The synthesis of the displayed nanoplasmonic patches was executed throughout 20 min. ST, skin type; PV, precursor volume. Further details are provided in the Supporting Information (Figure S3).



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Figure 6. Analysis of the nanoplasmonic patch utilized in epidermal conditions (skin type II). SEM micrographs of the nanoplasmonic patch before (A) and after solar simulator (SS) exposure (B). UV-Vis absorbance of the nanoplasmonic patch before (control) and after SS exposure (C). Analysis of the particle size distribution of the AgNPs embedded in the nanoplasmonic device before (control) and after SS exposure (D), the box plots show the median, mean (+), 25th and 75th percentiles and the extreme values of the respective size distributions. The analysis was performed using AgNP-BC synthesized with 8.75 mL of precursor volume during 20 min.


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Figure 7. Performance of the nanoplasmonic patch accompanied by a control patch (skin type II). A, C, reference patch before and after solar simulator exposure, respectively. B, D nanoplasmonic patch before and after solar simulator exposure, respectively. The experiments were performed using AgNP-BC synthesized with 7.5 mL of precursor volume during 20 min. Exposure time, 15 min.



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TOC Figure


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UV Exposure

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