Browsing by Author "Önses, M. Serdar"

Now showing 1 - 6 of 6

Open Access
Chemical funneling of colloidal gold nanoparticles on printed arrays of end-grafted polymers for plasmonic applications
(American Chemical Society, 2020-06) Pekdemir, S.; Torun, İ.; Şakir, M.; Ruzi, M.; Rogers, J. A.; Önses, M. Serdar
Spatially defined assembly of colloidal metallic nanoparticles is necessary for fabrication of plasmonic devices. In this study, we demonstrate high-resolution additive jet printing of end-functional polymers to serve as templates for directed self-assembly of nanoparticles into architectures with substantial plasmonic activity. The intriguing aspect of this work is the ability to form patterns of end-grafted poly(ethylene glycol) through printing on a hydrophobic layer that consists of fluoroalkylsilanes. The simultaneous dewetting of the underlying hydrophobic layer together with grafting of the printed polymer during thermal annealing enables fabrication of spatially defined binding sites for assembly of nanoparticles. The employment of electrohydrodynamic jet printing and aqueous inks together with reduction of the feature size during thermal annealing are critically important in achieving high chemical contrast patterns as small as ∼250 nm. Gold nanospheres of varying diameters selectively bind and assemble into nanostructures with reduced interparticle distances on the hydrophilic patterns of poly(ethylene glycol) surrounded with a hydrophobic background. The resulting plasmonic arrays exhibit intense and pattern-specific signals in surface-enhanced Raman scattering (SERS) spectroscopy. The localized seed-mediated growth of metallic nanostructures over the patterned gold nanospheres presents further routes for expanding the composition of the plasmonic arrays. A representative application in SERS-based surface encoding is demonstrated through large-area patterning of plasmonic structures and multiplex deposition of taggant molecules, all enabled by printing.
Open Access
Multiplexed patterning of cesium lead halide perovskite nanocrystals by additive jet printing for efficient white light generation
(Elsevier, 2020-08-12) Altıntaş, Y.; Torun, İ.; Yazıcı, A. F.; Beşkazak, E.; Erdem, T.; Önses, M. Serdar
Inorganic perovskite nanocrystals (PNCs) offer the ability to precisely but also flexibly control the peak emission wavelength while also possessing narrow-band emission spectra and high quantum yields. Owing to these features, PNCs have been already employed as color converters on LEDs. Nevertheless, the anion exchange reactions that prevent the blending of perovskites of different colors remain as an important bottleneck. As a remedy to this issue, here we employ additive jet printing to form separated stripes of these nanocrystals. Within this framework, we first present the synthesis of CsPbBr3 and CsPbBrxI3−x nanocrystals spanning the whole visible regime and optimize the cleaning procedure to obtain PNCs possessing photoluminescence quantum yields as high as 91% and emission linewidths as narrow as 15 nm, making them suitable for high quality white light generation. Next, we employ electrohydrodynamic jet printing to form closely spaced stripes of PNCs of various colors and integrated these films with a blue LED to create a white LED. Our proof-of-concept LED achieves high photometric performance as it possesses a color rendering index of 91.3, luminous efficacy of optical radiation > 300 lm/Wopt, and correlated color temperature of ca. 7000 K. We believe that additive jet printing technique will pave the way for a ubiquitous use of these PNCs in light-emitting devices in the near future.
Open Access
Natural wax-stabilized perovskite nanocrystals as pen-on-paper inks and doughs
(American Chemical Society, 2022-05-27) Karabel Ocal, S.; Kiremitler, N. B.; Yazici, A. F.; Çelik, N.; Önses, M. Serdar; Mutlugün, Evren
Perovskite nanocrystals (PNCs) are emerging luminescent materials for a wide range of technological applications. The broad adaptation of PNCs will be greatly improved by addressing their intrinsically low stability and developing processes for their assembly into 2D and 3D structures using facile approaches. Inspired by the mechanism of natural protection of leaves, this paper proposes natural carnauba wax (CW) as an encapsulation material for PNCs. The synthesis of PNCs is performed in the presence of CW, which is derived from the leaves of Copernicia prunifera palm. CW acts as a solvent and replaces the commonly used octadecene in the preparation of PNCs. The facile synthesis in CW results in PNCs with greatly improved thermal, water, and air stability. Furthermore, the thermal and mechanical properties make PNC-Wax a highly suitable solid ink for versatile processing of these materials into 2D and 3D architectures. PNC-Wax can be printed via a pen-on-paper approach by heating at modest temperatures. The rapid plasticization of PNC-Wax by mechanical agitation enables hand-shaping of the material in a manner similar to playdoughs, which would possibly enable the versatile use of this material for various applications. © 2022 American Chemical Society. All rights reserved.
Open Access
pH tunable patterning of quantum dots
(Wiley-VCH Verlag GmbH & Co. KGaA, 2023-09-01) Torun, I.; Huang, C.; Kalay, M.; Shim, M.; Önses, M. Serdar
Patterning of quantum dots (QDs) is essential for many, especially high-tech, applications. Here, pH tunable assembly of QDs over functional patterns prepared by electrohydrodynamic jet printing of poly(2-vinylpyridine) is presented. The selective adsorption of QDs from water dispersions is mediated by the electrostatic interaction between the ligand composed of 3-mercaptopropionic acid and patterned poly(2-vinylpyridine). The pH of the dispersion provides tunability at two levels. First, the adsorption density of QDs and fluorescence from the patterns can be modulated for pH > approximate to 4. Second, patterned features show unique type of disintegration resulting in randomly positioned features within areas defined by the printing for pH <= approximate to 4. The first capability is useful for deterministic patterning of QDs, whereas the second one enables hierarchically structured encoding of information by generating stochastic features of QDs within areas defined by the printing. This second capability is exploited for generating addressable security labels based on unclonable features. Through image analysis and feature matching algorithms, it is demonstrated that such patterns are unclonable in nature and provide a suitable platform for anti-counterfeiting applications. Collectively, the presented approach not only enables effective patterning of QDs, but also establishes key guidelines for addressable assembly of colloidal nanomaterials.
Open Access
Rapid fabrication of high-performance transparent electrodes by electrospinning of reactive silver ink containing nanofibers
(Elsevier, 2020) Kiremitler, N. B.; Esidir, A.; Gözütok, Z.; Özdemir, A. T.; Önses, M. Serdar
All-solution processable fabrication of high performance transparent conductive electrodes is vital for next-generation optoelectronics applications. In this study, rapid and versatile fabrication of high-performance transparent electrodes by synergetic integration of electrospun nanofibers and particle-free reactive silver inks is reported. Direct electrospinning of reactive silver ink containing polymer blend solution followed by a swift thermal annealing enables fabrication of transparent conductive electrodes (TCEs) with a sheet resistance of ∼1.9 Ω/sq with 90% transmission. The high-performance TCEs were fabricated within couple of minutes including the electrospinning and thermal annealing duration. The key aspects of our strategy are the use of a polymer blend consisting of poly(ethylene oxide) (PEO) and polyvinylpyrrolidone (PVP) and particle-free nature of reactive silver inks. Practical utility of the fabricated transparent electrodes in Joule heaters that work at temperatures as high as 300 °C is presented. The simple, versatile, inexpensive, and rapid fabrication of transparent conductive electrodes can enable broad range of applications.
Open Access
Solid substrates decorated with Ag nanostructures for the catalytic degradation of methyl orange
(Elsevier, 2018) Şakır, M.; Önses, M. Serdar
There is a strong demand for development of catalytically active solid substrates for heterogeneous catalysis applications. This study reports fully solution-processable and scalable fabrication of solid substrates decorated with Ag nanostructures for the degradation of organic dyes. Ag nanostructures were prepared by direct surface-growth from Pt nanoparticles that were immobilized on Si substrates modified with a layer of end-grafted poly(2-vinylpyridine). The proper choice of the growth conditions and seed-selective growth from Pt nanoparticles were critically important in fabricating Ag nanostructures with high catalytic activity and large surface coverage. The catalytic performance of the presented platform was studied by the reduction of methyl orange by borohydride ions and monitored using UV–visible spectrometry. The substrates exhibited high catalytic activity enabling degradation of 10−5 M methyl orange solution in less than an hour with an apparent reaction rate constant of 33.5 × 10−3 min−1. The substrates can be easily removed from the degradation medium and used multiple times. Our approach presents an effective strategy for waste water management applications avoiding the agglomeration and separation issues of colloidal catalysts and overcoming the need for tedious and costly fabrication of thin films.