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    Metal Ion-Engineered Carbon Quantum Dots From Hazelnut Shell via Solid-State Synthesis for Efficient OLED Devices
    (Wiley, 2026) Cengiz, Fatmanur Uyumaz; Turksoy, Figen; Tekin, Emine; Utkan, Guldem; Cengiz, Erhan Sukru; Yumusak, Gorkem; Kahraman, Memet Vezir
    In this study, we report a scalable and green solid-state synthesis of nitrogen-doped carbon quantum dots (CQDs) from hazelnut shell biomass, using citric acid and urea as carbon and nitrogen sources. Controlled BaCl2 and ZnCl2 doping was applied to tailor nucleation, crystallinity, and surface chemistry. Structural analyses (FTIR, XRD, STEM, XPS, and DLS) revealed that BaCl2-assisted CQDs exhibited higher graphitization, narrower size distribution (7-13 nm), and fewer defects, while ZnCl2-assisted CQDs showed more amorphous and heteroatom-rich surfaces. Optical measurements indicated strong pi-pi* absorption (approximate to 280 nm), bright blue emission (lambda(em) 405-412 nm), and quantum yields of 63.4% (BaCl2) and 50.1% (ZnCl2), with > 95% stability after 30 days. When used as OLED emissive layers, BaCl2-CQDs achieved a luminous efficiency of 0.75 cd A(-1), nearly four times that of ZnCl2-CQDs (0.20 cd A(-1)), despite lower maximum luminance (48.9 vs. 308.1 cd m(-2)). These results highlight metal ion-assisted nucleation as an effective strategy to engineer CQD properties and enhance device performance, paving the way for sustainable, scalable OLED technologies.
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    Sustainable Lignocellulose-Derived Carbon Quantum Dots with Controlled Ba/Zn Doping as High-Performance Emissive Layers for OLEDs
    (Wiley-V C H Verlag Gmbh, 2026) Cengiz, Fatmanur Uyumaz; Utkan, Guldem; Tekin, Emine; Turksoy, Figen; Cengiz, Erhan Sukru; Kahraman, Memet Vezir
    Organic light-emitting diodes (OLEDs) offer lightweight, flexible, and high-performance displays but face challenges such as high production cost and limited operational stability. Here, we present a sustainable one-step solid-state synthesis of nitrogen-doped carbon quantum dots (CQDs) from lignocellulosic biomass using citric acid and urea. Controlled BaCl2 and ZnCl2 doping tunes CQD crystallinity, surface chemistry, and optical properties. Structural analyses (XRD, STEM, XPS) show BaCl2 promotes graphitized, crystalline CQDs, whereas ZnCl2 yields amorphous, oxygen-rich structures. Ba-doped CQDs exhibit strong blue emission, high quantum yield (60.2%), and superior OLED device performance (256 cd m- 2), highlighting the role of metal-ion-assisted nucleation in enhancing charge transport and exciton recombination. This study provides a green, scalable route to high-efficiency CQD-based OLEDs.