WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394
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Article Citation - WoS: 4Citation - Scopus: 4Transparent Films Made of Highly Scattering Particles(Amer Chemical Soc, 2020-01-13) Erdem, Talha; Yang, Lan; Xu, Peicheng; Altintas, Yemliha; O'Neil, Thomas; Caciagli, Alessio; Eiser, ErikaToday, colloids are widely employed in various products from creams and coatings to electronics. The ability to control their chemical, optical, or electronic features by controlling their size and shape explains why these materials are so widely preferred. Nevertheless, altering some of these properties may also lead to some undesired side effects, one of which is an increase in optical scattering upon concentration. Here, we address this strong scattering issue in films made of binary colloidal suspensions. In particular, we focus on raspberry-type polymeric particles made of a spherical polystyrene core decorated by small hemispherical domains of acrylate with an overall positive charge, which display an unusual stability against aggregation in aqueous solutions. Their solid films display a brilliant red color due to Bragg scattering but appear completely white on account of strong scattering otherwise. To suppress the scattering and induce transparency, we prepared films by hybridizing them with oppositely charged PS particles with a size similar to that of the bumps on the raspberries. We report that the smaller PS particles prevent raspberry particle aggregation in solid films and suppress scattering by decreasing the spatial variation of the refractive index inside the film. We believe that the results presented here provide a simple strategy to suppress strong scattering of larger particles to be used in optical coatings.Article Sustainable Next-Generation Color Converters From P. Harmala Seed Extracts for Solid-State Lighting(Royal Soc Chemistry, 2024) Erdem, Talha; Orenc, Ali; Akcan, Dilber; Duman, Fatih; Soran-Erdem, ZelihaTraditional solid-state lighting heavily relies on color converters, which often have a significant environmental footprint. As an alternative, natural materials such as plant extracts could be employed if their low quantum yields (QYs) in liquid and solid states were higher. With this motivation, here, we investigate the optical properties of aqueous P. harmala extract, develop efficient color-converting solids through a cost-effective and environmentally friendly method, and integrate them with light-emitting diodes (LEDs). To achieve high-efficiency solid hosts for P. harmala-based fluorophores, we optically and structurally compare two crystalline and two cellulose-based platforms. Structural analyses reveal that sucrose crystals, cellulose-based cotton, and paper platforms enable a relatively homogeneous distribution of fluorophores compared to KCl crystals. Optical characterization demonstrates that the extracted solution and the extract-embedded paper possess QYs of 75.6% and 44.7%, respectively, whereas the QYs of the cotton, sucrose, and KCl crystals remain below 10%. We demonstrated that the paper host with the highest efficiency causes a blueshift in the P. harmala fluorescence, whereas the cotton host induces a redshift. We attribute this to the passivation of nonradiative transitions related to the structure of the hosts. Subsequently, as a proof-of-concept demonstration, we integrate the as-prepared efficient solids of P. harmala for the first time with a light-emitting diode (LED) chip to produce a color-converting LED. The resulting blue-emitting LED achieves a luminous efficiency of 21.9 lm W-elect(-1) with CIE color coordinates of (0.139, 0.070). These findings mark a significant step toward the utilization of plant-based fluorescent biomolecules in solid-state lighting, offering promising environmentally friendly organic color conversion solutions for future lighting applications.Article Citation - WoS: 1Citation - Scopus: 1Osmotic-Pressure Nematic Ordering in Suspensions of Laponite and Carboxy Methyl Cellulose(Amer Chemical Soc, 2020-10-12) Xu, Peicheng; Yazici, Ahmet F.; Erdem, Talha; Lekkerkerker, Henk N. W.; Mutlugun, Evren; Eiser, ErikaLaponite is a synthetic clay that is known to form gels in aqueous suspensions at low concentrations (0.01 g/cm(3)) Although it is expected to form lyotropic liquid crystals, such phases usually do not form, as a consequence of laponite's tendency to form gels at concentrations below the threshold for liquid crystal formation. Here we show that macroscopic, birefringent phases of laponite can be prepared through osmotic compression of a laponite solution by an aqueous solution of carboxy methyl cellulose (CMC). We present polarization imaging studies showing how the initially dilute, isotropic laponite phase shrinks while developing typical birefringence colors between crossed polarizers. Using the MichelLevy interference charts, we were able to extract the refractive index and orientation of the laponite nanodisks in the compressed region. Our observations allow us to propose a tentative state diagram, indicating the concentration regions for which we obtain optically anisotropic gels.Article Citation - WoS: 50Citation - Scopus: 63Optical Detection of Microplastics in Water(Springer Heidelberg, 2021-01-19) Iri, Ahmet H.; Shahrah, Malek H. A.; Ali, Ali M.; Qadri, Sayed A.; Erdem, Talha; Ozdur, Ibrahim T.; Icoz, KutayUnfortunately, the plastic pollution increases at an exponential rate and drastically endangers the marine ecosystem. According to World Health Organization (WHO), microplastics in drinking water have become a concern and may be a risk to human health. One of the major efforts to fight against this problem is developing easy-to-use, low-cost, portable microplastic detection systems. To address this issue, here, we present our prototype device based on an optical system that can help detect the microplastics in water. This system that costs less than $370 is essentially a low-cost Raman spectrometer. It includes a collimated laser (5 mW), a sample holder, a notch filter, a diffraction grating, and a CCD sensor all integrated in a 3D printed case. Our experiments show that our system is capable of detecting microplastics in water having a concentration less than 0.015% w/v. We believe that the designed portable device can find a widespread use all over the world to monitor the microplastic content in an easier and cost-effective manner.Article Citation - WoS: 12Citation - Scopus: 13Numerical Analysis and Experimental Verification of Optical Scattering From Microplastics(Royal Soc, 2023-08) Genc, Sinan; Icoz, Kutay; Erdem, TalhaAccurate and fast characterization of the micron-sized plastic particles in aqueous media requires an in-depth understanding of light interaction with these particles. Due to the complexity of Mie scattering theory, the features of the scattered light have rarely been related to the physical properties of these tiny objects. To address this problem, we reveal the relation of the wavelength-dependent optical scattering patterns with the size and refractive index of the particles by numerically studying the angular scattering features. We subsequently present a low-cost setup to measure the optical scattering of the particles. Theoretical investigation shows that the angular distribution of the scattered light by microplastics carries distinct signatures of the particle size and the refractive index. The results can be used to develop a portable, low-cost setup to detect microplastics in water.