Browsing by Author "Pekdemir, S."
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Item Open Access Antifouling superhydrophobic surfaces with bactericidal and SERS activity(Elsevier BV, 2022-03-01) Şahin, F.; Çelik, N.; Ceylan, A.; Pekdemir, S.; Ruzi, M.; Önses, Mustafa SerdarFouling and contamination of surfaces are prevailing challenges humanities facing today in fields such as healthcare, hospitality, and food manufacturing. These challenges strongly motivate the development of multifunctional surfaces with antifouling and antimicrobial properties that are coupled with sensing capabilities. To address this challenge, we prepared a multifunctional superhydrophobic surface using eco-friendly materials: polydimethylsiloxane (PDMS) and carnauba wax. After deposition of a thin film of Ag, the surface gained surface-enhanced Raman scattering (SERS) activity and bactericidal property. The multifunctional superhydrophobic surface showed extreme liquid repellency towards water and common liquid food. The strong SERS activity enabled the detection of adulterant rhodamine B in a sausage down to a nanomolar level. Notably, the surface showed excellent bactericidal activity towards two common bacteria, E. coli, and S. aureus, significantly reducing their adhesion and killing. Additionally, the surface showed anti-fouling behavior against common liquid food, and even towards sticky foods such as yogurt, honey, and pomegranate sauce, reducing residual food by >97 %. Furthermore, the superhydrophobic surface showed excellent chemical stability in dynamic and static flow conditions and leaching of Ag in neutral and basic solutions was minimal.Item 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. SerdarSpatially 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.Item Open Access Eco-friendly fabrication of plasmonically active substrates based on end-grafted poly(ethylene glycol) layers(American Chemical Society, 2019) Karabel Öcal, S.; Pekdemir, S.; Serhatlıoğlu, Murat; İpekçi, H. H.; Şahmetlioğlu, E.; Narin, İ.; Duman, F.; Elbüken, Çağlar; Demirel, G.; Önses, Mustafa SerdarWe report completely sustainable processes and materials for inexpensive and scalable fabrication of plasmonically active solid substrates, which are critical for emerging applications in sensing, catalysis, and metasurfaces. Our approach involves grafting of poly(ethylene glycol) (PEG) onto silicon oxide terminated solid substrates using all-water based processing leading to an ultrathin (12 nm) and smooth (roughness of ∼1 nm) functional layer. The resulting surfaces facilitate robust and effective immobilization of gold nanoparticles (NPs) with a density that is superior to the organic solvent based processing. This new process achieves size dependent assembly of the citrate-stabilized gold NPs resulting in high plasmonic activity in surface-enhanced Raman scattering (SERS). The use of leaf extracts derived from Quercus pubescens as a reducing and stabilizing agent allowed for green synthesis of gold NPs with an average diameter of 25.6 ± 11.1 nm. The assembly of the green synthesized gold NPs on all-water processed PEG grafted layers enabled a fully sustainable route for fabrication of plasmonically active solid substrates. The resulting substrates exhibited high SERS response over the entire (∼1 cm2) substrate surface with an analytical enhancement factor of 9.48 × 104 for the probe molecule rhodamine 6G under 532 nm laser excitation. A microfluidic device was also constructed on the fabricated platform for SERS mediated simultaneous detection of two nonsteroidal anti-inflammatory drugs, dexketoprofen and ibuprofen, which are widely used in human medicine and present as contaminants in wastewater. The biocompatibility of PEG together with all-water based processing overcome the need for waste management and ventilation of the working place enabling cost and energy efficient, environmentally benign fabrication of plasmonic devices.Item Open Access SERS-active linear barcodes by microfluidic-assisted patterning(Elsevier, 2020-09-28) Pekdemir, S.; Ipekci, H. H.; Serhatlıoğlu, Murat; Elbuken, C.; Onses, M. S.Simple, low-cost, robust, and scalable fabrication of microscopic linear barcodes with high levels of complexity and multiple authentication layers is critical for emerging applications in information security and anti-counterfeiting. This manuscript presents a novel approach for fabrication of microscopic linear barcodes that can be visualized under Raman microscopy. Microfluidic channels are used as molds to generate linear patterns of end-grafted polymers on a substrate. These patterns serve as templates for area-selective binding of colloidal gold nanoparticles resulting in plasmonic arrays. The deposition of multiple taggant molecules on the plasmonic arrays via a second microfluidic mold results in a linear barcode with unique Raman fingerprints that are enhanced by the underlying plasmonic nanoparticles. The width of the bars is as small as 10 μm, with a total barcode length on the order of 100 μm. The simultaneous use of geometric and chemical security layers provides a high level of complexity challenging the counterfeiting of the barcodes. The additive, scalable, and inexpensive nature of the presented approach can be easily adapted to different colloidal nanomaterials and applications.Item Open Access Transferrable SERS barcodes(Wiley-VCH Verlag GmbH & Co. KGaA, 2022-06-13) Sahin, F.; Pekdemir, S.; Sakir, M.; Gozutok, Z.; Önses, Mustafa SerdarThe demand for encoded surfaces has increased significantly over the past decade driven by the rapid digitalization of the world. Surface-enhanced Raman scattering (SERS) offers unique capabilities in generation of encoded surfaces. The challenge is the limited versatility of SERS-based encoding systems in terms of the applicable surfaces. This study addresses this challenge by using a temporary tattoo approach together with simplified fabrication of SERS-active patterns by ink-jet printing of a particle-free reactive silver ink. Plasmonic silver nanostructures form on the tattoo paper upon ink-jet printing and a brief thermal annealing. The SERS activity is sufficient to detect taggant molecules of rhodamine 6G, methylene blue, and rhodamine B with a nanomolar level sensitivity. Raman-active taggants can be incorporated into the ink, for drop-on-demand patterning of multiple molecules in 1D and 2D barcode geometries. The SERS barcodes can be effectively transferred to a range of different substrates retaining high plasmonic activity and geometric integrity. The presented approach decouples the SERS-active pattern preparation from the final substrate and greatly improves the versatility of the barcodes.