Browsing by Author "Mutlugun, Evren"

Now showing 1 - 20 of 42

Citation - WoS: 1
Citation - Scopus: 1
Tailoring Quantum Dot Shell Thickness and Polyethylenimine Interlayers for Optimization of Inverted Quantum Dot Light-Emitting Diodes
(MDPI, 2024) Yazici, Ahmet F.; Ocal, Sema Karabel; Bicer, Aysenur; Serin, Ramis B.; Kacar, Rifat; Ucar, Esin; Mutlugun, Evren
Quantum dot light-emitting diodes (QLEDs) hold great promise for next-generation display applications owing to their exceptional optical properties and versatile tunability. In this study, we investigate the effects of quantum dot (QD) shell thickness, polyethylenimine (PEI) concentration, and PEI layer position on the performance of inverted QLED devices. Two types of alloyed-core/shell QDs with varying shell thicknesses were synthesized using a one-pot method with mean particle sizes of 8.0 +/- 0.9 nm and 10.3 +/- 1.3 nm for thin- and thick-shelled QDs, respectively. Thick-shelled QDs exhibited a higher photoluminescence quantum yield (PLQY) and a narrower emission linewidth compared to their thin-shelled counterparts. Next, QLEDs employing these QDs were fabricated. The incorporation of PEI layers on either side of the QD emissive layer significantly enhanced device performance. Using PEI on the hole transport side resulted in greater improvement than on the electron injection side. Sandwiching the QD layer between two PEI layers led to the best performance, with a maximum external quantum efficiency (EQE) of 17% and a peak luminance of 91,174 cd/m2 achieved using an optimized PEI concentration of 0.025 wt% on both electron injection and hole injection sides. This study highlights the critical role of QD shell engineering and interfacial modification in achieving high-performance QLEDs for display applications.
Colloidal Photodetectors Based on Engineered Multishelled InP Based Quantum Dots
(IOP Publishing Ltd, 2026) Akrema; Erol, Erdinc; Savas, Muzeyyen; Yazici, Ahmet Faruk; Erdem, Talha; Mutlugun, Evren
In this work, we present a straightforward and cost-effective approach to synthesize multi-shell InP/ZnSe/ZnSeS/ZnS quantum dots (QDs) that show promising potential for use in photodetectors. By carefully layering ZnSe, ZnSeS, and ZnS shells around an InP core, we were able to enhance the stability and optical performance of the QDs, achieving a narrow emission peak of 45 nm and a high photoluminescence quantum yield of 55%. These QDs were then integrated into simple photodetector devices, which possessed impressive sensitivity and detection capabilities. Specifically, our devices achieved a peak responsivity of 0.54 A W-1 and a detectivity of 2.22 x 1011 Jones at 400 nm with a 5 V bias. This study highlights the potential of InP-based QDs as a safer and more sustainable alternative to traditional QDs that contain toxic heavy metals, offering a viable path forward for developing high-performance optoelectronic devices. Our findings suggest that these InP/ZnSe/ZnSeS/ZnS QDs could be a key material for the next generation of high-performance optoelectronic devices, especially in applications that require highly sensitive and stable photodetectors.
Citation - WoS: 12
Citation - Scopus: 11
Long-Time Stable Colloidal Zn-Ag Quantum Dots With Tunable Midgap-Involved Emission
(AIP Publishing, 2021) Sabzevari, Zahra; Sahraei, Reza; Jawhar, Nawzad Nadhim; Yazici, Ahmet Faruk; Mutlugun, Evren; Soheyli, Ehsan
Quaternary Zn-Ag-In-S (ZAIS) quantum dots (QDs) with efficient, tunable, and stable photoluminescence (PL) emission were prepared via a simple, effective, and low-cost reflux method. The structural analysis revealed the dominance of the quantum confinement effect. The calculated PL emission quantum yield was enhanced from 8.2% to 28.7% with experimental parameters indicating their marked influence on the PL emission properties of the final product. Particularly, it was found that by varying the precursors' feeding ratio, tunable emission from green to red was achieved. A set of direct and indirect pieces of evidence such as the broad-band emission spectrum (FWHM>100nm), large Stokes shift more than 120nm, and predominantly a biexponentially long-lived decay profile with an average lifetime of about 366ns were observed, showing the contribution of midgap localized energy levels in the recombination process. These data were obtained independently on the experimental condition used, which confirmed that this is mostly an intrinsic electronic property of quaternary In-based QDs. Finally, to ensure the stability of QDs in terms of colloidal and optical emission, their emission ability was evaluated after 26 months of storage. Colloidal QDs were still luminescent with strong yellowish-orange color with emission efficiency of similar to 20.3% after 26 months. The combination of synthesis simplicity, compositional non-toxicity, PL emission superiority (strong, tunable, stable, and long lifetime emission), and colloidal stabilities confirms that the present ZAIS QDs are promising candidates for a wide range of applications in biomedicine, anticounterfeiting, and optoelectronics.
Citation - WoS: 14
Citation - Scopus: 13
The Effect of Ligand Chain Length on the Optical Properties of Alloyed Core-Shell InPZnS/ZnS Quantum Dots
(Elsevier Science SA, 2017) Altintas, Yemliha; Talpur, Mohammad Younis; Mutlugun, Evren
In this work, we demonstrate the effect of organic ligands on the optical properties of alloyed core-shell InPZnS/ZnS quantum dots (QDs). We have systematically studied the synthesis and characterization of InPZnS/ZnS QDs using short and long chain length ligands i.e., butyric (C4), hexanoic (C6), octanoic (C8), dodecanoic (C12), myristic (C14), palmitic (C16) and stearic acids (C18), respectively. This study achieved more than 85% quantum yield with 43 nm full-width-half maximum value, using dodecanoic acid as the capping ligand. The properties of the QDs with short and long chain length ligands have been analyzed using UV Vis absorption spectrophotometer, steady state and time resolved photoluminescence spectrometer, X-ray diffraction, Zeta sizer, transmission electron microscopy and energy dispersive X-ray spectroscopy. (C) 2017 Published by Elsevier B.V.
Citation - WoS: 59
Citation - Scopus: 63
Electroluminescence Efficiency Enhancement in Quantum Dot Light-Emitting Diodes by Embedding a Silver Nanoisland Layer
(Wiley-VCH Verlag GmbH, 2015) Yang, Xuyong; Hernandez-Martinez, Pedro Ludwig; Dang, Cuong; Mutlugun, Evren; Zhang, Kang; Demir, Hilmi Volkan; Sun, Xiao Wei
A colloidal quantum dot light-emitting diode (QLED) is reported with substantially enhanced electroluminescence by embedding a thin layer of Ag nanoislands into hole transport layer. The maximum external quantum efficiency (EQE) of 7.1% achieved in the present work is the highest efficiency value reported for green-emitting QLEDs with a similar structure, which corresponds to 46% enhancement compared with the reference device. The relevant mechanisms enabling the EQE enhancement are associated with the near-field enhancement via an effective coupling between excitons of the quantum dot emitters and localized surface plasmons around Ag nanoislands, which are found to lead to good agreement between the simulation results and the experimental data, providing us with a useful insight important for plasmonic QLEDs.
Simple, Sustainable Fabrication of Fully Solution-Processed, Transparent, Metal-Semiconductor Photodetectors Using a Surgical Blade as an Alternative to Conventional Tools
(SPIE - The International Society for Optics and Photonics, 2022) Savas, Muzeyyen; Yazici, Ahmet Faruk; Arslan, Aysenur; Mutlugun, Evren; Erdem, Talha
Fabrication of optoelectronic devices relies on the expensive, energy-consuming conventional tools such as chemical vapor deposition, lithography, and metal evaporation. Furthermore, the films used in these devices are usually deposited at elevated temperatures and under vacuum that impose further restrictions to the device fabrication. Developing an alternative technology would contribute to the efforts on achieving a more sustainable optoelectronics technology. Keeping this focus in our focus, here we present a simple technique to fabricate visible photodetectors. These fully solution-processed and transparent metal-semiconductor-metal photodetectors employ silver nanowires (Ag NW) as the transparent electrodes replacing the indium-tin oxide (ITO) commonly used in optoelectronic devices. By repeatedly spin coating Ag NWs on a glass substrate followed by the coating of ZnO nanoparticles, we obtained a highly conductive transparent electrode reaching a sheet resistance of 95 Omega/square as measured by the four-probe method. Optical spectroscopy revealed that the transmittance of the Ag NW-ZnO films was 84% at 450 nm while transmittance of the ITO films was 90% at same wavelength. Following the formation of the conductive film, we scratched it using a heated surgical blade to open a gap. The scanning electron microscope images indicate that a gap of similar to 30 mm is opened forming an insulating line. As the active layer, we drop-casted red-emitting CdSe/ZnS core-shell quantum dots (QDs) on to this gap to form a metal-semiconductor-metal photodetector. These visible QD- based photodetectors exhibited responsivities and detectivities up to 8.5 mA/W and 0.95x10(9) Jones, respectively. These proof-of-concept photodetectors show that the environmentally friendly, low- cost, and energy-saving technique presented here can be an alternative to conventional, more expensive, and energy-hungry techniques while fabricating light-harvesting devices.
Fully Inorganic Colloidal CsPbBr3 Perovskite Nanocrystals with Zn-Doping and Metal Oxide Encapsulation for Luminescent Display Panels
(Amer Chemical Soc, 2025) Khorasani, Azam; Soheyli, Ehsan; Mutlugun, Evren
Perovskite nanocrystals (PeNCs) are emerging as exceptional materials due to their high photoluminescence quantum yield, tunable bandgap, and excellent charge carrier mobility, enabling a wide range of colors and promising applications in optoelectronics and photovoltaics. Despite their advantages, PeNCs face stability challenges caused by environmental factors. In the presented study, a facile and versatile colloidal hot-injection method was used to apply the beneficial aspects of Zn-doping in cesium lead bromide (CsPbBr3) PeNCs. The uniform platelet-shaped Zn-doped CsPbBr3 PeNCs were prepared by doping with a 0.1 molar ratio of zinc-oleate solution in the perovskite precursors during synthesis. Then, zinc-oxide (ZnO) and nickel-oxide (NiO) coating layers were utilized separately to effectively reduce surface defects, encapsulate PeNCs, and improve their stability issues. To fabricate the coated PeNCs with metal oxides, zinc acetate and nickel(II) acetate tetrahydrate solutions were prepared individually and added to the crude perovskite solutions. The quantum yield of Zn-doped CsPbBr3 (CsPb1-xZnxBr3) PeNCs coated with ZnO increased from 50% for bare CsPbBr3 to over 84%, while NiO-coated PeNCs exhibited a higher yield of 90% both of which remarkably enhanced the emission stability. Moreover, NiO coatings represented a proper protection against surface imperfections and improved resistance to external stimuli. The combination of facile/effective preparation method, excellent emission efficiency, and reliable emission stability nominates the prepared colloidal composite for display pixels, detectors, and lasers.
Citation - WoS: 3
Citation - Scopus: 2
Electrochemical and Optical Multi-Detection of Escherichia Coli Through Magneto-Optic Nanoparticles: A Pencil-on Biosensor
(MDPI, 2024) Soysaldi, Furkan; Ekici, Derya Dincyurek; Soylu, Mehmet cagri; Mutlugun, Evren
Escherichia coli (E. coli) detection suffers from slow analysis time and high costs, along with the need for specificity. While state-of-the-art electrochemical biosensors are cost-efficient and easy to implement, their sensitivity and analysis time still require improvement. In this work, we present a paper-based electrochemical biosensor utilizing magnetic core-shell Fe2O3@CdSe/ZnS quantum dots (MQDs) to achieve fast detection, low cost, and high sensitivity. Using electrochemical impedance spectroscopy (EIS) as the detection technique, the biosensor achieved a limit of detection of 2.7 x 10(2) CFU/mL for E. coli bacteria across a concentration range of 10(2)-10(8) CFU/mL, with a relative standard deviation (RSD) of 3.5781%. From an optical perspective, as E. coli concentration increased steadily from 10(4) to 10(7) CFU/mL, quantum dot fluorescence showed over 60% lifetime quenching. This hybrid biosensor thus provides rapid, highly sensitive E. coli detection with a fast analysis time of 30 min. This study, which combines the detection advantages of electrochemical and optical biosensor systems in a graphite-based paper sensor for the first time, has the potential to meet the needs of point-of-care applications. It is thought that future studies that will aim to examine the performance of the production-optimized, portable, graphite-based sensor system on real food samples, environmental samples, and especially medical clinical samples will be promising.
Citation - WoS: 5
Citation - Scopus: 5
Cd-Free Quantum Dot Pellets for Efficient White Light Generation
(Optical Soc Amer, 2017) Altintas, Yemliha; Talpur, Mohammad Younis; Mutlugun, Evren
Semiconductor quantum dots have been on demand for niche optoelectronic applications providing color tenability and possessing high quantum yield and high extinction coefficient. Although the investigation of II-VI have attained a mature level of understanding of the photo physical properties, suppression of the nonradiative decay channels and enhancing the optical properties for III-V material systems still remain a challenge. In this study, we have developed and demonstrated a simple, very fast, and efficient strategy to synthesize the highly luminescent III-V group based In(Zn)P quantum dots (QDs) utilized by the effect of core growth temperature, revealing their emission kinetics and their outstanding application for white light generation. Varying the core growth temperature from 240 degrees C to 90 degrees C, limiting the extent of the precursors involved in the synthesis, and a substantial enhancement of the photoluminescence quantum yield up to 75% is demonstrated. Further modification of the synthesis procedure with optimizing the In:P precursor ratio for the first time up to 88.5 +/- 5.5% quantum yield of alloyed core/shell In(Zn)P/ZnS QDs is achieved, in which the whole synthesis process takes only around one hour. In addition, as a demonstration of Cd-free pellets, versatile pellets of green and orange emitting QDs within KCl macrocrystals are prepared. Hybridizing with blue LED, a white light with correlated color temperature of 4597K along with an unprecedentedly high color rendering index of 90 is presented. (C) 2017 Optical Society of America
Citation - WoS: 11
Citation - Scopus: 14
Nanowire-Shaped MoS2@MoO3 Nanocomposites as a Hole Injection Layer for Quantum Dot Light-Emitting Diodes
(Amer Chemical Soc, 2022) Bastami, Nasim; Soheyli, Ehsan; Arslan, Aysenur; Sahraei, Reza; Yazici, Ahmet Faruk; Mutlugun, Evren
Molybdenum disulfides and molybdenum trioxides are structures that possess the potential to work as efficient charge transport layers in optoelectronic devices. In the present study, as opposed to the existing Mo-based nanostructures in flake, sheet, or spherical forms, an extremely simple and low-cost hydrothermal method is used to prepare nanowires (NWs) of MoS2@MoO3 (MSO) composites. The synthesis method includes several advantages including easy handling and processing of inexpensive precursors to reach stable MSO NWs without the need for an oxygen-free medium, which would facilitate the possibility of mass production of these nanostructures. The structural analysis confirmed the formation of MSO nanocomposites with different Mo valence states, as well as NWs of average length and diameter of 70 nm and 5 nm, respectively. In order to demonstrate their potential for optoelectronic applications, MSO NWs were blended into hole injection layers (HILs) in quantum dot-based light emitting diodes (QLEDs). Electroluminescence measurements show a substantial enhancement in both luminance (from 44,330 to 68,630 cd.m-2) and external quantum efficiency (from 1.6 to 2.3%), based on the increase in the ratio of MSO NWs from 3 to 10%. Interestingly, the addition of 10% volume of MSO NWs resulted in a remarkably smoother HIL with improved current efficiency and stability in green-emitting QLEDs. The simplicity and cost-effective features of the synthesis method along with outstanding favorable morphology demonstrated their ability to enhance the QLED performance and mark them as promising agents for optoelectronics.
Citation - WoS: 5
Citation - Scopus: 3
Photoluminescent and Superhydrophobic Nanocomposites of Perovskite Nanocrystals
(Elsevier, 2024) Ocal, Sema Karabel; Celik, Nusret; Onses, M. Serdar; Mutlugun, Evren
Perovskite nanocrystals (PNCs) have found extensive utility across diverse technological applications in optoelectronics; nevertheless, their susceptibility to environmental instability poses a significant constraint on their practicality. Within this investigation, we present a novel and facile approach for the development of highly stable superhydrophobic PNCs. These engineered superhydrophobic perovskite nanocrystal composites, referred to as HSNPs@PNCs, demonstrate remarkable optoelectronic attributes, provided that their inherent instability can be effectively mitigated. HSNPs@PNCs manifest an impressive water contact angle of 172 degrees and an exceedingly low sliding angle of 1 degrees, thus showcasing their exceptional superhydrophobicity. Of particular note is the extraordinary stability exhibited by HSNPs@PNCs despite aqueous environments, thermal fluctuations, and UV exposure. Remarkably, even after a prolonged 30 -day immersion in water, this nanocomposite maintains an outstanding emission efficiency of 75 %. Furthermore, the method of application through a spray deposition technique circumvents sample size limitations, thereby amplifying their suitability for industrial applications. Moreover, this study extends the practicality of HSNPs@PNCs by enabling their homogeneous coating onto various surfaces such as glass, fabric, and aluminum, yielding luminescent superhydrophobic surfaces. This approach liberates the substrates from constraints, significantly broadening the potential spectrum of applications for these materials within diverse industrial and technological domains.
Citation - WoS: 4
Citation - Scopus: 4
Rec. 2100 Color Gamut Revelation Using Spectrally Ultranarrow Emitters
(SPIE - Society of Photo-Optical Instrumentation Engineers, 2017) Genc, Sinan; Uguz, Mustafa; Yilmaz, Osman; Mutlugun, Evren
We theoretically simulate the performance of ultranarrow emitters for the first time to achieve record high coverage for the International Telecommunication Union Radiocommunication Sector BT. 2100 (Rec. 2100) and National Television System Committee (NTSC) color gamut. Our results, employing more than 130-m parameter sets, include the investigation into peak emission wavelength and full width at half maximum (FWHM) values for three primaries that show ultranarrow emitters, i.e., nanoplatelets are potentially promising materials to fully cover the Rec. 2100 color gamut. Using ultranarrow emitters having FWHM as low as 6 nm can provide the ability to attain 99.7% coverage area of the Rec. 2100 color gamut as well as increasing the NTSC triangle to 133.7% with full coverage. The parameter set that provides possibility to fully reach Rec. 2100 also has been shown to match with D65 white light by making use of the correct combination of those three primaries. Furthermore, we investigate the effect of the fourth color component on the CIE 1931 color space without sacrificing the achieved coverage percentages. The investigation into the fourth color component, cyan, is shown for the first time to enhance the Rec. 2100 gamut area to 127.7% with 99.9% coverage. The fourth color component also provides an NTSC coverage ratio of 171.5%. The investigation into the potential of emitters with ultranarrow emission bandwidth holds great promise for future display applications. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)
Citation - WoS: 12
Citation - Scopus: 13
Highly Luminescent ZnCdTeS Nanocrystals With Wide Spectral Tunability for Efficient Color-Conversion White-Light
(IOP Publishing Ltd, 2021) Soheyli, Ehsan; Zargoush, Sirous; Yazici, Ahmet Faruk; Sahraei, Reza; Mutlugun, Evren
CdTe-based semiconductor nanocrystals (NCs) with size and composition-dependent efficient bandgap properties are historically mature nanomaterials for colloidal optoelectronic applications. In this work, we present the highly luminescent quaternary ZnCdTeS NCs with tunable emission across a wide visible spectrum from green to red spectral range. Prepared via a direct aqueous-based approach, a second capping agent of trisodium citrate (TSC) was used to enhance the photoluminescence (PL) emission efficiency, the chemical stability, and to spectrally widen the coverage of the emission spectra of ZnCdTeS NCs. Adding TCS created a remarkable blue shift from 572 nm in the absence of TSC, to 548 nm. On the other hand, upon optimization of experimental parameters, superior ZnCdTeS NCs with a narrow PL profile typically less than 50 nm, the high quantum efficiency of 76%, and tunable emission from 515-to-645 nm were synthesized in an aqueous solvent. The keynotes were the superior and reproducible luminescent properties for the core only NCs, without shell and using relatively low reaction temperatures. It was shown that in the suggested synthesis method, the high efficiency emitted color of ZnCdTeS NCs can be easily controlled from 515-to-650 nm with excellent stability against harsh conditions. The biexponential decay profiles of samples prepared at different reaction temperatures demonstrated that the average recombination lifetime is below 40 ns and increases with the growth of the ZnCdTeS NCs. Results reveal that the excitonic energy levels have the main role in the recombination process. Finally, to demonstrate the functional advantages of the prepared NCs in optoelectronics, the NCs were used to fabricate color-conversion white light-emitting diodes. The color coordinate of the device is recorded as (0.4951, 0.3647) with CRI of 91, CCT of 1954 K, and LER of 251 lm W-1 by employing only two distinct emitters for color conversion.
Citation - WoS: 16
Citation - Scopus: 17
Solid-State Encapsulation and Color Tuning in Films of Cesium Lead Halide Perovskite Nanocrystals for White Light Generation
(Amer Chemical Soc, 2019) Torun, Ilker; Altintas, Yemliha; Yazici, Ahmet Faruk; Mutlugun, Evren; Onses, M. Serdar
Perovskite nanocrystals (PNCs) are highly demanding nanomaterials for solid-state lighting applications. A challenge for their exploitation in practical applications is the insufficient ambient and water stability associated with their ionic nature. Here we report a novel route for solid-state encapsulation of films of perovskite nanocrystals (PNCs) through vapor-phase deposition of a thin and hydrophobic layer of fluoroalkyltrichlorosilanes (FAS). High quality nanoscale crystals of CsPbBr3 were synthesized with well established colloidal methods and coated on solid substrates. The films of PNCs were then subjected to vapor of FAS for short durations of time (<60 s) in ambient atmosphere, resulting in deposition of a thin (<20 nm) hydrophobic layer. Besides providing a barrier for water and humidity, the vapor-phase deposition of FAS was accompanied by the blue shift of the emission wavelength of the PNCs. The color shift results from the partial exchange of Br with Cl anions, which emerge during the self-hydrolysis of the silane molecules. Throughout this process, we demonstrate the enhanced water stability of the films of PNCs and fine tunability of the wavelength in films from 516 nm to 488 nm. The fabrication of a white-light-emitting diode and tunability of the color coordinates with the duration of the FAS deposition were demonstrated. The rapid, scalable, and inexpensive solid-state encapsulation approach shows great promise for films of halide perovskites.
Citation - WoS: 13
Citation - Scopus: 13
Tuning the Shades of Red Emission in InP/ZnSe Nanocrystals With Narrow Full Width for Fabrication of Light-Emitting Diodes
(Amer Chemical Soc, 2023) Soheyli, Ehsan; Bicer, Aysenur; Ozel, Sultan Suleyman; Tiras, Kevser Sahin; Mutlugun, Evren
While Cd-based luminescent nanocrystals (NCs) are the most mature NCs for fabricating efficient red light-emitting diodes (LEDs), their toxicity related limitation is inevitable, making it necessary to find a promising alternative. From this point of view, multishell-coated, red-emissive InP-based NCs are excellent luminescent nanomaterials for use as an emissive layer in electroluminescent (EL) devices. However, due to the presence of oxidation states, they suffer from a wide emission spectrum, which limits their performance. This study uses tris-(dimethyl-amino)-phosphine (3DMA-P) as a low-cost aminophosphine precursor and a double HF treatment to suggest an upscaled, cost-effective, and one-pot hot-injection synthesis of purely red-emissive InP-based NCs. The InP core structures were coated with thick layers of ZnSe and ZnS shells to prevent charge delocalization and to create a narrow size distribution. The purified NCs showed an intense emission signal as narrow as 43 nm across the entire red wavelength range (626-670 nm) with an emission quantum efficiency of 74% at 632 nm. The purified samples also showed an emission quantum efficiency of 60% for far-red wavelengths of 670 nm with a narrow full width of 50 nm. The samples showed a relatively long average emission lifetime of 50-70 ns with a biexponential decay profile. To demonstrate the practical ability of the prepared NCs in optoelectronics, we fabricated a red-emissive InP-based LEDs. The best-performing device showed an external quantum efficiency (EQE) of 1.16%, a luminance of 1039 cd m(-2), and a current efficiency of 0.88 cd A(-1).
Citation - WoS: 6
Citation - Scopus: 6
Plasmon Enhanced Emission of Perovskite Quantum Dot Films
(Cambridge Univ Press, 2018) Dadi, Seyma; Altintas, Yemliha; Beskazak, Emre; Mutlugun, Evren
We propose and demonstrate the photoluminescence enhancement of CsPbBr3 perovskite quantum dot films in the presence of Au nanoparticles. Embedded into a polymer matrix, Au nanoparticle-quantum dot film assemble prepared by an easy spin coating method enabled the photoluminescence enhancement of perovskite quantum dot films up to 78%. The properties of the synthesized perovskite QDs and gold nanoparticles have been analysed using high resolution transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, UV-Vis absorption spectrophotometer, steady state and time-resolved photoluminescence spectrometer.
Photoluminescent Carbon Dots for Sensitive and Selective Cu2+ Ion Detection
(IOP Publishing Ltd, 2026) Sahin Tiras, Kevser; Karabel Ocal, Sema; Mutlugun, Evren
Green-emitting carbon dots (CDs) were synthesized via a solvent-free, vacuum-assisted method using citric acid and urea. The CDs exhibited strong photoluminescence and served as selective, sensitive probes for Cu2+ detection in water, with a detection limit of 26 nM. Among the tested metal ions, Cu2+ induced the most significant PL quenching. Time-resolved photoluminescence measurements of the CDs in the presence of Cu2+ ions revealed a minimal change in lifetime, despite a significant decrease in PL intensity, along with unchanged UV-vis absorption, indicating a mixed quenching mechanism. The sensor's applicability was confirmed in raisin extract and tea infusion, showing notable PL suppression. With their simplicity, selectivity, and sensitivity, these CDs offer promising potential as nanosensors for detecting Cu2+ in environmental and real-world analytical settings.
Citation - WoS: 21
Citation - Scopus: 21
Efficient Forster Resonance Energy Transfer Donors of In(Zn)P/ZnS Quantum Dots
(Amer Chemical Soc, 2017) Altintas, Yemliha; Talpur, Mohammad Younis; Mutlugun, Evren
We demonstrate a detailed investigation of the effect of the type and concentration of zinc precursor on the optical properties of In(Zn)P/ZnS quantum dots. We achieved up to 87% quantum yield along with 54 nm emission bandwidth for the green emitters with changing the concentration of the Zn precursors. Employing efficient green emitters as the donor species, we demonstrated an efficient Forster resonance energy transfer (FRET) couple of green and red emitting InP-based quantum dots. With a FRET efficiency level of 70.3% achieved (analyzed from the donor lifetime with and without an acceptor), we further demonstrated the enhancement of the acceptor emission nearly twofold due to the energy transfer. Our results provide new insights toward the understanding of the excitonic interactions among donor and acceptor quantum dots of the III-V family for light harvesting applications.
Citation - WoS: 15
Citation - Scopus: 18
FRET Enabled Light Harvesting within Quantum Dot Loaded Nanofibers
(IOP Publishing Ltd, 2018) Altintas, Yemliha; Kiremitler, Nuri Burak; Genc, Sinan; Onses, M. Serdar; Mutlugun, Evren
The spatial control of the nano-emitters in novel light harvesting platforms offers great potential for the manipulation of the excitonic interaction amongst the donor-acceptor pairs of energy transferring agents. In this work, we report colloidal quantum dot loaded electrospun nanofibers as a light harvesting platform to study the excitonic interaction among them. The donor emission lifetime modified from 12.46 ns to 7.45 ns with the change in the ratio of green and red quantum dots in the nanofiber, as a result of confining acceptor quantum dots in close proximity. The spectrally narrow emitter luminescent nanofiber platforms have further been investigated for their potential of white light generation. The hybrid platform of blue LED integrated electrospun nanofibers has been shown to demonstrate a correlated color temperature of 3632.5 K, luminous efficacy of optical radiation value of 307.7 lm/W-opt along with color rendering index value of 60.
Citation - WoS: 3
Citation - Scopus: 3
Superior CdSe/ZnS@Fe2O3 Yolk-Shell Nanoparticles as Optically Active MRI Contrast Agents
(Wiley-VCH Verlag GmbH, 2022) Ekici, Derya D.; Mutlugun, Evren
We have developed a robust synthesis methodology for quantum dots (QDs) nanoparticles with magnetic properties designed for biomodal imaging. These nanocrsytlas consists of a semiconductor quantum dot core with engineered fluorescence, which is located in a paramagnetic iron oxide shell that acts as a magnetic resonance imaging (MRI) contrast agent. Yolk-shell CdSe/ZnS@Fe2O3 nanoparticles (NPs) are synthesized via sonochemical decomposition of iron pentacarbonyl (Fe(CO)(5)) using the oleylamine (OAm) as the ligand. The sonochemical synthesis method of magnetic fluorescent NPs that can be used as MRI contrast agents provided advantages such as improved quantum efficiency and homogeneous size distributions. It has been determined that the luminescence efficiency of quantum dots decreases in coatings that can be made at high temperatures by thermal decomposition. In order to eliminate the disadvantage of elevated temperatures, the sonochemical decomposition method, which allows coating at low temperatures, has been used. With this method, yolk-shell (CdSe/ZnS@Fe2O3) nanoparticles were produced with high photoluminescence quantum efficiency and homogeneous size distributions. The synthesis magnetic fluorescent NPs optimized was determined to have the injection temperature of Fe(CO)(5) at 60 degrees C, Fe(CO)(5)/CdSe@ZnS ratio 0.7, OAm/Fe(CO)(5) volume ratio 1.43 with an oxidation time 5 min. Under these conditions, the quantum efficiency was found to be 78 %, nanoparticle sizes between 11-14 nm and r(1) value was 0.199, r(2) value was 0.518 in MRI analysis. These optically active magnetic fluorescent nanoparticles as positive contrast agents (T1 weighted) are predicted to pave the way for the future of advanced bio-imaging systems.