THE INFLUENCE OF SEA WATER TO UV ABSORBER QUENCHING OF FLUORESCENCE

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1 June 8 1, 216, Ljubljana, SLOVEIA TE IFLUECE OF SEA WATER TO UV ABSORBER QUECIG OF FLUORESCECE Tihana Dekanić 1, Anita Tarbuk 1, Tanja Pušić 1, Ana Marija Grancarić 1, Zvonka Čelić 1 1 University of Zagreb, Faculty of Textile Technology, Department of Textile Chemistry and Ecology, Prilaz baruna Filipovića 28a, R-1 Zagreb, Croatia ABSTRACT Textile and clothing provide some sun screening properties which highly depends on large number of factors, e.g. type of fibre, fabric surface and construction, wetness, type and concentration of dyestuff, fluorescent whitening agent (FWA), UV-B protective agents, as well as nanoparticles, if applied. Recently, the new stilbene type UV absorber was developed, for the application in textile finishing and care. Molecules of UV absorbers are able to absorb the damaging UV-R range of 29 nm to 36 nm, and convert it into harmless heat energy. As stilbene-type, this UV absorber show the phenomenon of fluorescence reemitting the energy at the blue region (typically nm) of the spectrum, resulting in better whiteness and UV protection. Therefore, the whiteness and UV protective properties of cotton knitted and woven fabrics achieved by its application were researched in this paper, and the quenching phenomenon of UV absorber fluorescence was discussed. Keywords: UV protection, cotton, UV absorber, fluorescence, whiteness, sea water 1. ITRODUCTIO The skin cancer is primary caused by the long exposure to solar ultraviolet radiation (UV-R) crossed with the amount of skin pigmentation in the population. It is believed that in childhood and adolescence 8 % of UV-R gets absorbed, whilst in the remaining 2 % gets absorbed later in the lifetime. For that reason it is to suggest proper and early photo protection to reduce the risk of subsequent occurrence of skin cancer [1]. This is very important during summer months, when UV index is the highest. Textiles and clothing, as a kind of direct barrier, offer a certain degree of UV protection, but in the most cases it does not provide full sun screening properties. The literature sources claimed that only 33 % of the spring and summer collections give an adequate UV protection [2]. A good fabric UV protection depends on large number of factors such are type of fibre, fabric surface and construction, type and concentration of dyestuff, fluorescent whitening agent (FWA), UV absorbers, as well as nanoparticles, if applied [1-8]. Based on electronically-excited state by energy of UV-A (usually nm) the molecules of FWAs show the phenomenon of fluorescence giving to textiles high whiteness by reemitting the energy at the blue region (typically nm) of the spectrum, what leads to better UV protection [1,4-6]. UV absorbers, as a special type of FWAs, are even more UV effective than typical FWAs. Molecules of UV absorbers are able to absorb the damaging UV-B range of 29 nm to 36 nm, and convert it into harmless heat energy. Recently, the new stilbene type UV absorber was developed for the application in textile finishing and care [5,6]. Therefore, the whiteness and UV protective properties of cotton knitted and woven fabrics achieved by its application were researched in this paper, and the quenching phenomenon of UV absorber fluorescence was discussed. 1

2 June 8 1, 216, Ljubljana, SLOVEIA 2. MATERIAL AD METODS Two cotton fabrics, knitted for T-shirts (B) of mass per unit area of g/m 2 and plain woven of 13 g/m 2 for summer cloths (C), were used for this research. The cotton fabrics were treated by exhaustion procedure at 6 C for 3 minutes in Linitest, Original anau with UV absorber Tinosorb FD, Ciba-Geigy AG (Figure 1) in wide concentration range: c 1 =.1 % owf (over weight of fibre); c 2 =.1 % owf; c 3 =.5 % owf; c 4 = 1 % owf; c 5 = 1 % owf; c 6 = 5 % owf. R' SO 3 R' R'' SO 3 R', R'' - differently substituted amines R'' Figure 1. Tinosorb FD (Ciba-Geigy AG) - stilbene disulphonic acid triazine derivative The discrepancy in whiteness and UV protection was research in distilled (DW) and Adriatic Sea water (SW). Remission spectrophotometer SF 6 PLUS CT (Datacolor) was used for measuring spectral characteristics of cotton fabrics. CIE whiteness degree (W CIE) acc. to ISO 15-J2:1997, Yellowing Index (YI) acc. to DI 6167:198, and the discrepancy in colour ( E) in wet state were calculated automatically. The relative intensity of fluorescence (Φ rel) was measured on adapted spectrophotometer Specol SV (Carl Zeiss). The quenching of fluorescence was calculated according to Stern- Volmer equation [9]. The fabric UV protection was determined according to AS/ZS 4399:1996 on Varian Cary 5 Spectrophotometer. 3. RESULTS AD DISCUSSIO In this paper, the whiteness and UV protective properties of cotton knitted and woven fabrics achieved by application of stilbene type UV absorber were researched. The results of fabric spectral characteristics, whiteness, yellowing, and discrepancy in wet state, are collected in Tables 1-2. The quenching phenomenon of UV absorber fluorescence influenced by concentration and wetness was discussed. The quenching of fluorescence is shown in Figures 2 and 3. The achieved UV protection and its discrepancy in wet state are presented in Figure 4. From the results shown in Tables 1 and 2 can be seen that fluorescent UV absorber, applied even in small concentration, leads to higher whiteness and higher UPF. This UV absorber is fluorescent compound with similar chemical composition (stilbene disulphonic acid derivative) as fluorescent whitening agents (FWAs). Therefore, the UV absorber s blue fluorescence in optimal range of concentration neutralizes the fabric yellowness, giving the high luminosity and most beautiful white. That is the concentration of fluorescent compound at which the maximum of Φ rel or W CIE are observed [9]. From the results of the whiteness and fluorescence can be seen that the concentration of.5 % owf (over weigth of fabric, in relation to mass of material) is the optimum concentration for knitted fabric (B), whilst the.5-1 % owf is the optimal one for woven cotton fabric. Applied in the higher concentration than optimal one, in the case of this UV absorber >1 % owf, from results of remission and wavelength maximums can be seen that the change in emission spectrum occurred. It is a consequence of well-known bathochromic shift of the remission spectrum. 2

3 Φ max /Φ 16 th AUTEX World Textile Conference 216 June 8 1, 216, Ljubljana, SLOVEIA Table 1. CIE whiteness (WCIE), yellowing index (YI), relative intensity of fluorescence ( rel), maximum of remission (Rmax) and wavelength ( max), and the discrepancy of whiteness in wet state of knitted cotton fabrics treated with UV absorber R max Fabric W CIE YI rel [%] [nm] de* Discrepancy B B-DW Darker greener less yellow B-SW Darker greener less yellow B B-.1-DW Darker less blue B-.1-SW Darker redder less blue B B-.1-DW Darker redder bluer B-.1-SW Darker bluer B B-.5-DW Darker less red less blue B-.5-SW Darker less red B B-1-DW Darker less red less blue B-1-SW Darker bluer B B-1-DW Darker greener bluer B-1-SW Darker greener less blue B B-5-DW Darker greener yellow B-5-SW Darker greener yellow max 6 5 B B-DW B-SW y MV =,2858x +,6979 y =,147x + 1,168 y DV =,252x + 1, c-c max Figure 2. Quenching of UV absorber fluorescence in distilled (DW) and sea water (SW) of knitted cotton fabric 3

4 Φ max /Φ 16 th AUTEX World Textile Conference 216 June 8 1, 216, Ljubljana, SLOVEIA Table 2. CIE whiteness (WCIE), yellowing index (YI), relative intensity of fluorescence ( rel), maximum of remission (Rmax) and wavelength ( max), and the discrepancy of whiteness in wet state of woven cotton fabrics treated with UV absorber R max Fabric W CIE YI rel [%] [nm] de* Discrepancy C , C-DW , Darker yellow C-SW , Darker yellow C , C-.1-DW , Darker redder bluer C-.1-SW , Darker redder bluer C , C-.1-DW , Darker redder bluer C-.1- SW , Darker redder bluer C , C-.5-DW , Darker bluer C-.5- SW , Darker less red C , C-1-DW , Darker less red C-1- SW , Darker less red less blue C , C-1-DW , Darker greener less blue C-1- SW , Darker greener less blue C , C-5-DW , Darker greener yellow C-5-SW , Darker greener yellow max C C-DW C-SW y MV =,2858x +,6979 y DV =,252x + 1, y =,658x + 1, c-c max Figure 3. Quenching of UV absorber fluorescence in distilled (DW) and sea water (SW) of woven cotton fabric 4

5 UPF UPF 16 th AUTEX World Textile Conference 216 June 8 1, 216, Ljubljana, SLOVEIA It comes to a reduction of remission intensity with UV absorber s concentrations causing the extinction of fluorescence by quenching phenomenon, with a consequence of yellowness. Chemically bleached cotton fabrics are non-rateable for UV protection. Therefore, for summer clothing additional fabric protection is necessary. Treatment with fluorescent compound, stilbene type UV absorber in wide concentration range, leads to multifunctionality - high whiteness, neutralizing of yellowness, giving to the fabric the high luminosity and protection against UV radiation. Cotton fabrics treated with the highest UV absorbers concentration have the highest UPF in dry state. Similar to the results of the cotton fabrics whiteness and fluorescence, at the optimal concentration of FWA excellent UV protection has been achieved B B-,1 B-,1 B-,5 B-1 B-1 B-5 Dry 5,24 12,53 28,19 41,25 53,24 7,68 194,29 DW 16,92 22,19 48,44 111,66 171,42 243,7 192,6 SW 16,62 28,39 5,65 82,74 123,12 297,16 198, a C C-,1 C-,1 C-,5 C-1 C-1 C-5 Dry 7,28 11,2 37,25 9,43 122,7 424,7 1, DW 3,79 4,56 1,34 58,49 255,49 1, 1, SW 4,34 5,5 14,49 64,24 282,84 999,7 1, b. Figure 4. UV protection in distilled (DW) and sea water (SW) a. knitted, b. woven cotton fabric 5

6 June 8 1, 216, Ljubljana, SLOVEIA UV absorber offers excellent UV protection if applied in optimal concentration of.5 % owf or higher. That is because UV absorbers absorb damaging UV-R range of 29 nm to 36 nm, and convert it into harmless heat energy. owever, the fabrics with the highest intensity of fluorescence do not show the highest UPF values. In dry state, UV protection increase with fluorescent compound concentration, regardless of quenching phenomenon. From the results of discrepancy of whiteness in wet state can be observed that all fabrics get darker and in general bluer and redder. In dry fabric, some of the photons of light are absorbed, but some are reflected and land on the eye's retina what gives the sensation of seeing a certain level of brightness. In wet fabric the water fills in the interyarn spacing, the reflection of light from the fabric is lower and at different angle (refraction). The amount of refraction is affected by both the salinity and temperature of the water, and therefore there is a difference between fabrics treated with sea and distilled water. It is to point out that the salts in sea water act as quenchers of fluorescence as well. Therefore, for UV absorber applied in concentrations higher than optimal one, the whiteness degree decreases for both, knitted and woven cotton fabrics. When applied 1 % owf to knit cotton fabric (B) whiteness degree decreases from 84.9 to 77.9, and for woven one (C) from 99.9 to Applied in maximum concentration it decreases even more, from 51.5 to 13.9 for knit, and from 71.8 to 15.3 for woven one. Considering the results of UV protection discrepancy it can be said that in wet state both cotton fabrics treated with fluorescent UV absorber give off better UV protection than in dry state regardless of the concentration applied. This phenomenon is more enhanced for sea water because some of the UV-R is reflected from the water surface; it is not absorbed, but additionally scattered by molecules suspended in the water, whilst the other part penetrates the water s surface, absorb and converse to other forms of energy, such as heat that warms or evaporates water, or is used by plants to fuel photosynthesis. Considering the applied concentrations, in general it can be said that higher concentration of fluorescent compound applied, better UV protection was achieved in wet state. The only exception is the highest concentration of UV absorber on knit fabric (B-5). From Figure 4a it can be seen that the UV protection in wet state is lower if applied 5 than 1 % owf of UV absorber. As it was observed for the CIE whiteness which significantly decreased, it can be assumed that this drop of UPF in wet state can be result of quenching of fluorescence as well. owever, achieved UV protection is excellent regardless of the drop and can even obey that request regarding UV index during the summer time in Mediterranean countries, as well as Australia and USA, which acquire UPF>UV index* COCLUSIO Chemically bleached cotton fabrics are non-rateable for UV protection. Treatment with fluorescent compound, stilbene type UV absorber in wide concentration range, leads to multi-functionality - high whiteness, neutralizing of yellowness, giving to the fabric the high luminosity and protection against UV radiation. In wet state, regardless of applied water sea or distilled, fabrics get darker, lowering its whiteness. UV light is not absorbed, but reflected from the water contained in the pores of the fabric. On the other hand, because of reflection from water, better UV protection is achieved in wet state. This phenomenon is more evident for sea water, because of additional light scattering since it contains about 4 % of inorganic salts. 5. REFERECES [1] Tarbuk A, Grancarić AM, Šitum M. Skin Cancer and UV Protection, AUTEX research journal Vol. 16, Issue 1, pp. 1-1 (in press), DOI: /aut [2] offmann K, Laperre J, Avermaete A, Altmeyer P, Gambichler T. Defined UV Protection by Apparel Textiles, Archives of Dermatology. 21, Vol. 137, pp

7 June 8 1, 216, Ljubljana, SLOVEIA [3] Farouk A, Textor T, Schollmeyer E, Tarbuk A, Grancarić AM. Sol-gel derived inorganic-organic hybrid polymers filled with ZnO nanoparticles as ultraviolet protection finish for textiles. AUTEX research journal. 21, Vol. 1, Issue 3, pp [4] Riva A, Algaba I, Prieto R. Optical Brightening Agents Based on Stilbene and Distyryl Biphenyl for the Improvement of Ultraviolet Protection of Cotton Fabrics. Tekstil. 27, Vol. 56, Issue 1, pp [5] Dekanić T, Pušić T, Soljačić I. Impact of artificial light on optical and protective effects of cotton after washing with detergent containing fluorescent compounds, Tenside Surfactants Detergents. 214, Vol. 51, Issue 5, pp [6] Dekanić T, Tarbuk A, Pušić T, Grancarić AM, Soljačić I. Light Conversion for UV Protection by Textile Finishing and Care. Sharp S (Editor). Sunscreens: Properties, Role in Skin Cancer Prevention and ealth Effects. ew York: ova Science Publishers, 215, pp [7] ilfiker R, Kaufmann W, Reinert G, Schmidt E. Improving sun protection factors of fabrics by applying UV- absorbers, Textile Research Journal. 1996, Vol. 66, Issue 2, pp [8] Cox Crews P, Zhou Y. The effect of wetness on the UVR transmission of woven fabrics, AATCC Review. 24, Vol. 4, Issue 8, pp [9] Grancarić AM, Soljačić I. Influence exerted by the concentration of optical brighteners on the fluorescence and degree of whiteness of cotton fabrics, Melliand Textilberichte Int. 1981, Vol. 62, Issue 11, pp ACKOWLEDGMET The work has been supported by Croatian Science Foundation under the project 9967 Advanced textile materials by targeted surface modification. Corresponding author: Tihana DEKAIĆ University of Zagreb, Faculty of Textile Technology, Department of Textile Chemistry and Ecology Prilaz baruna Filipovića 28a, R-1 Zagreb, Croatia Phone: Fax: tihana.dekanic@ttf.hr Co-author(s): Anita TARBUK, Tanja PUŠIĆ, Ana Marija GRACARIĆ, Zvonka ČELIĆ University of Zagreb, Faculty of Textile Technology, Department of Textile Chemistry and Ecology Prilaz baruna Filipovića 28a, R-1 Zagreb, Croatia Phone/ / anita.tarbuk@ttf.hr / tpusic@ttf.hr / amgranca@ttf.hr / zvonka31@gmail.com 7