ACCEPTED MANUSCRIPT This is an early electronic version of an as-received manuscript that hasbeen accepted for publication in the Journal of the Serbian Chemical Society but has not yet been subjected to the editing process and publishing procedure applied by the JSCS Editorial Office. Please cite this article as M. Simović Pavlović, M. Pagnacco, D. Mara, A. Radulović, B. Bokić, D. Vasiljević and B. Kolarić, J. Serb. Chem. Soc. (2023) https://doi.org/10.2298/JSC230327042P This “raw” version of the manuscript is being provided to the authors and readers for their technical service. It must be stressed that the manuscript still has to be subjected to copyediting, typesetting, English grammar and syntax correc- tions, professional editing and authors’ review of the galley proof before it is published in its final form. 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Soc.00(0)1-5 (2023) Note JSCS–12332 Published DD MM, 2023 1 Thermal investigation of material derived from the species Apatura iris MARINA SIMOVIĆ PAVLOVIĆ1*, MAJA PAGNACCO2, DIMITRIJE MARA3, ALEKSANDRA RADULOVIĆ3, BOJANA BOKIĆ4, DARKO VASILJEVIĆ4 AND BRANKO KOLARIĆ4,5 1Faculty of Mechanical Engineering, University of Belgrade, Kraljice Marije 16, Belgrade, Serbia; 2Institute of Chemistry, Technology and Metallurgy, University of Belgrade, Njegoševa 12, Belgrade, Serbia; 3Institute of General and Physical Chemistry, Studentski trg 12/V, Belgrade, Serbia; 4Photonics Center, Institute of Physics, University of Belgrade, Pregrevica 118, Belgrade, Serbia, 5Micro- and Nanophotonic Materials Group, University of Mons, Place du Parc 20, 7000 Mons, Belgium (Received 27 March; Revised 20 April; Accepted 21 July 2023) Abstract: The material's size and shape influence its physical, chemical, and mechanical properties. This study describes an investigation of natural photonic structure of the butterfly’s wing, mainly composed of chitin. The effect of corrugations at the nanoscale on material's optical response is unambiguously revealed in presented thermal measurements. Furthermore, the presented study shows the possibility of exploiting holography to monitor dynamics in situ. Keywords: Apatura iris butterfly; biopolymer chitin; sensing dynamics in situ. INTRODUCTION Apatura iris butterfly’s wing used for this study is shown in Figure 13. Butterfly wings are made of the biopolymer chitin4, with general formula (C8H13O5N)n. The chitin composition of different parts of the butterfly's body is described elsewhere.5 The paper revealed that chitins from different parts are chemically very similar, but with significant differences in their surface morphologies. *Corresponding author. E-mail: simovicmarina99@gmail.com https://doi.org/10.2298/JSC230327042P A cc ep te d m an us cr ip t https://doi.org/10.2298/JSC230327042P SIMOVIĆ PAVLOVIĆ et al.. Fig 1. Apatura iris butterfly: (A) An optical image of the whole butterfly; (B) SEM image of a ground scale of the wing. In this study surface morphology is characterized by JEOL JSM 6610 LV (Japan), Scanning Electron Microscope (SEM) in conjunction with the Energy Dispersive Spectroscopy (EDS) detector model X-Max Large Area Analytical Silicon Drift connected with INCA Energy 350 Microanalysis (detection of elements Z ≥ 5, detection limit: ~ 0.1 mas. %, resolution 126 eV). Micro-elemental (EDS) analysis of Apatura iris butterfly’s wing in two selected points, scale cell and the wing membrane, given in Figure 2, showed presence of carbon (C), oxygen (O) and nitrogen (N) originated from chitin. As it can be seen, the content of C, N, and O slightly differs in scale cell and the wing membrane, indicating different chitin compositions in different surface structures. The presence of gold (Au) originates from sample preparation for SEM/EDS analysis. Thermal camera "FLIR A65" (640 x 512 pixel, thermal resolution 50 mK, focal length 13 mm, field of view angle 45° x 37°) is used to measure the temperature of the sample after the irradiation with laser. Later, holographic method will be used to characterize the interaction of the photonic structure with light 6,7. A scheme of the holographic setup that is going to be used in the experiment is described elsewhere8. The setup will allow simultaneous recording of deformation and temperature. A cc ep te d m an us cr ip t THERMAL INVESTIGATION OF APATURA IRIS 3 Fig 2. (A) SEM image of the scale cells and the wing membrane of Apatura iris butterfly’s wing, (B) EDS analysis of the wing at the scale cell (Spectrum 1), (C) EDS analysis of the wing at the wing membrane (Spectrum 2). RESULTS AND DISCUSSION Six samples are individually irradiated by external lasers operating at four different wavelengths (450 nm, 532 nm, 660 nm, and 980nm) keeping the power and illuminated spot diameter constant at 1 mW and 1 mm, respectively. Thermal measurement is made over the period that includes the time before the start of heating (interaction with laser), during the heating itself, and after the irradiation stopped, more precisely the cooling of the sample. The difference in temperature due to heating by laser at different wavelengths has been observed. The highest temperature is caused by the interaction with 450 nm light, while the lowest is recorded for the wavelength of 532 nm. However, the complete reversible cooling (reaching the initial state) has not been observed for the wavelengths of 450 nm and 980 nm. A complete return to the initial state is observed for the wavelengths of 532 nm and 660 nm. Analyzing data in depth is vital to link thermal measurement with the reflectance spectrum9 (Figure 3A) and the heating/cooling process as a function of time. Figure 3B is showing the change in temperature over time, as a function of wavelengths. Finally, the thermal measurements match the reflectance pattern and the heating/cooling dynamics as a function of time. It is evident that the temperature maximum in Figure 3B at 450 nm corresponds to the reflectance maximum. The maximum value recorded at 450 nm is followed by 660 nm, while reflectance is at minimum around 532 nm. A cc ep te d m an us cr ip t SIMOVIĆ PAVLOVIĆ et al.. Fig 3. (A) Apatura iris reflectance spectrum; (B) Cooling dynamics as a function of time after the irradiation with four different wavelengths. The lasers have been switched on at 2nd second and switched off at 9th second in order to record heating/cooling dynamics. (Reflectance spectrum is taken from the reference 9) The only observed discrepancy refers to the wavelength which does not belong to the visible part of the spectrum and for which completely different rules apply. The photon at 980 nm carries the energy that cannot cause any electronic transitions but can affect the vibrational one within the system as well as thermal management by vibrational relaxation. The observed asymmetric heating/cooling response scales perfectly with the measured reflectance response. CONCLUSION This paper presents an investigation of Apatura iris's natural photonic structures under the light irradiation at different wavelengths. The correlation between the reflectance at different wavelengths and thermal response is revealed. Acknowledgements: B.K., D.V., and B.B. acknowledge funding provided by the Institute of Physics Belgrade, through the institutional funding by the Ministry of Education, Science, and Technological Development of the Republic of Serbia. Additionally, B.K. acknowledges support from F.R.S.-FNRS. M.P. acknowledges support from the Ministry of Education, Science and Technological Development of the Republic of Serbia (Grant No. 451-03-47/2023- 01/200026). D.M. and A.R. acknowledges support from Ministry of Science, Technological Development, and Innovation of the Republic of Serbia Contract number: 451-03-47/2023- 01/200051. All authors acknowledge the support of the Office of Naval Research Global through the Research Grant N62902-22-1-2024. A cc ep te d m an us cr ip t THERMAL INVESTIGATION OF APATURA IRIS 5 И З В О Д ТЕРМАЛНО ИСПИТИВАЊЕ МАТЕРИЈАЛА ИЗ ЛЕПТИРА APATURA IRIS МАРИНА СИМОВИЋ ПАВЛОВИЋ1, МАЈА ПАЊАКО2, ДИМИТРИЈЕ МАРА3, АЛЕКСАНДРА РАДУЛОВИЋ3, БОЈАНА БОКИЋ4, ДАРКО ВАСИЉЕВИЋ4 И БРАНКО КОЛАРИЋ4,5 1Машински факултет – Универзитет у Београду, Краљице Марије 16, Београд, Србија; 2Институт за хемију, технологију и металургију, Универзитет у Београду, Његошева 12, Београд, Србија; 3Институт за општу и физичку хемију, Студентски трг 12/V, Београд, Србија; 4Центар за фотонику, Институт за физику, Универзитет у Београду, Прегревица 118, Београд, Србија, 5Група за микро и нанофотонске материјале, Универзитет у Монсу, Парк трг 20, 7000 Монс, Белгија Облик и величина материјала утичу на његове физичке, хемијске и механичке особине. Ова студија описује проучавање природних фотонских структура, крила лептира која се претежно састоје од полимера хитина. 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