Photonics / Fotonik
Permanent URI for this collectionhttps://hdl.handle.net/11147/2590
Browse
11 results
Search Results
Article Citation - WoS: 7Citation - Scopus: 7Breaking the Boundaries of the Goldschmidt Tolerance Factor With Ethylammonium Lead Iodide Perovskite Nanocrystals(American Chemical Society, 2024) Güvenç, Çetin Meriç; Toso, Stefano; Ivanov, Yurii P.; Saleh, Gabriele; Balcı, Sinan; Divitini, Giorgio; Manna, LiberatoWe report the synthesis of ethylammonium lead iodide (EAPbI3) colloidal nanocrystals as another member of the lead halide perovskites family. The insertion of an unusually large A-cation (274 pm in diameter) in the perovskite structure, hitherto considered unlikely due to the unfavorable Goldschmidt tolerance factor, results in a significantly larger lattice parameter compared to the Cs-, methylammonium- and formamidinium-based lead halide perovskite homologues. As a consequence, EAPbI3 nanocrystals are highly unstable, evolving to a nonperovskite delta-EAPbI3 polymorph within 1 day. Also, EAPbI3 nanocrystals are very sensitive to electron irradiation and quickly degrade to PbI2 upon exposure to the electron beam, following a mechanism similar to that of other hybrid lead iodide perovskites (although degradation can be reduced by partially replacing the EA+ ions with Cs+ ions). Interestingly, in some cases during this degradation the formation of an epitaxial interface between (EA x Cs1-x )PbI3 and PbI2 is observed. The photoluminescence emission of the EAPbI3 perovskite nanocrystals, albeit being characterized by a low quantum yield (similar to 1%), can be tuned in the 664-690 nm range by regulating their size during the synthesis. The emission efficiency can be improved upon partial alloying at the A site with Cs+ or formamidinium cations. Furthermore, the morphology of the EAPbI3 nanocrystals can be chosen to be either nanocube or nanoplatelet, depending on the synthesis conditions.Article Citation - WoS: 6Citation - Scopus: 6Polar Solvent-Free Room Temperature Synthesis of Cspbx3 (x = Br, Cl) Perovskite Nanocubes(Royal Society of Chemistry, 2023) Güvenç, Çetin Meriç; Kocabaş, Aşkın; Balcı, SinanConventionally, colloidal lead halide perovskite nanocubes have been synthesized by the hot-injection or ligand-assisted reprecipitation (LARP) methods. We herein demonstrate a polar solvent-free room temperature method for the synthesis of CsPbX3 (X = Br, Cl) nanocubes. In addition to the commonly used ligand pair of oleylamine and oleic acid, guanidinium (GA) has been used to passivate the surface of the nanocrystals. Our study demonstrates that GA inhibits the formation of low dimensional structures such as nanowires and nanoplatelets and further supports the formation of perovskite nanocubes. In fact, GA diminishes the restricted monomer-addition effect of long-chain oleylammonium (OLAM) ions to the nanocrystal. We show that above a critical GA/OLAM molar ratio, the synthesis yields homogeneous CsPbX3 (X = Br, Cl) nanocubes. Importantly, we observe the nucleation and growth kinetics of the GA-assisted CsPbBr3 nanocube formation by using in situ absorption and photoluminescence (PL) measurements. Small nanocrystals with an excitonic absorption peak at around 435 nm and photoluminescence (PL) maxima at 447 nm were nucleated and continuously shifted to longer wavelengths during the growth period. Crucially, our method allows the synthesis of CsPbCl3 nanocubes at room temperature without using polar organic solvents. The synthesized CsPbBr3, CsPb(Cl0.5Br0.5)3, and CsPbCl3 nanocubes have PL peaks at 508 nm, 443 nm, and 405 nm, photoluminescence quantum yields (PLQY) of 85%, 58% and 5%, and lifetimes of 18.98 ns, 18.97 ns, and 14.74 ns, respectively.Article Citation - WoS: 13Citation - Scopus: 14Synthesis of Albumin Nanoparticles in a Water-Miscible Ionic Liquid System, and Their Applications for Chlorambucil Delivery To Cancer Cells(Elsevier, 2022) Akdoğan, Yaşar; Sözer, Sümeyra Çiğdem; Akyol, Cansu; Başol, Merve; Karakoyun, Çiğdem; Çakan Akdoğan, GülçinSerum albumin has been a preferred protein to generate biodegradable and non-toxic nanoparticles (NPs) for drug delivery applications. Different methods applied for the preparation of serum albumin NPs mostly used organic solvents. Here, we prepared serum albumin NPs in an ionic liquid (IL) system. ILs are considered to be green and designer solvents with unique properties that can replace organic solvents in the synthesis of albumin NPs. Bovine serum albumin (BSA) proteins dissolved in water were transformed into BSA NPs in a water/ Triton™X (TX-100), 1-butanol/1-butyl-3-methylimidazolium trifluoromethanesulfonate (BmimCF3SO3) microemulsion-like system by using a high-speed homogenizer and crosslinker glutaraldehyde. The obtained BSA NPs have been used in drug loading and release studies with a hydrophobic anticancer drug chlorambucil (Chl). Drug loading increased as increasing the ratio of Chl incubated with BSA NPs. Monitoring the drug release by UV–Vis spectroscopy revealed a burst release at first 4 h, but two-thirds of drugs stayed with NPs upon diffusion method. On the other hand, cellular uptake of Chl loaded BSA NPs caused a significant MCF7 breast cancer cell death, whereas free Chl and unloaded BSA NPs did not have a significant effect on the cell viability. Furthermore, in vivo toxicity assessment of BSA NPs obtained in the IL system was conducted in the zebrafish animal model. It showed that zebrafish body is able to eliminate BSA NPs without any toxic side effects and encapsulation of Chl into NPs reduced the toxicity of free Chl. In summary, we showed that BSA NPs with size smaller than 200 nm could be prepared in BmimCF3SO3 mediated system. They can be used for Chl loading (up to 6.9 wt%) with a sustainable release and they induce significant cell death in Chl sensitive cancer cells up to 45% in 24 h. These results indicate that BSA NPs could be prepared alternatively in IL systems and used in drug delivery studies.Article Citation - WoS: 7Citation - Scopus: 6L2[gaxfa1–xpbi3]pbi4 (0 ≤ X ≤ 1) Ruddlesden–popper Perovskite Nanocrystals for Solar Cells and Light-Emitting Diodes(American Chemical Society, 2022) Güvenç, Çetin Meriç; Tunç, İlknur; Balcı, SinanThe main challenges to overcome for colloidal 2D Ruddlesden–Popper (RP) organo-lead iodide perovskite nanocrystals (NCs) are phase instability and low photoluminescence quantum yield (PLQY). Herein, we demonstrate colloidal synthesis of guanidinium (GA)-L2[GAPbI3]PbI4, formamidinium (FA)-L2[FAPbI3]PbI4, and GA and FA alloyed L2[GA0.5FA0.5PbI3]PbI4 NCs without using polar or high boiling point nonpolar solvents. Importantly, we show that optical properties and phase stability of L2[APbI3]PbI4 NCs can be affectively tuned by alloying with guanidinium and formamidinium cations. Additionally, the band gap of NCs can be rapidly engineered by bromide ion exchange in L2[GAxFA1–xPbI3]PbI4 (0 ≤ x ≤ 1) NCs. Our approach produces a stable dispersion of L2[FAPbI3]PbI4 NCs with 12.6% PLQY that is at least three times higher than the previously reported PLQY in the nanocrystals. Furthermore, L2[GAPbI3]PbI4 and L2[GA0.5FA0.5PbI3]PbI4 NC films exhibit improved ambient stability over 10 days, which is significantly higher than L2[FAPbI3]PbI4 NC films, which transform to an undesired 1D phase within 6 days. The colloidally synthesized guanidinium- and formamidinium-based 2D RP organo-lead iodide perovskite NCs with improved stability and high PLQY demonstrated in this study may find applications in solar cells and light-emitting diodes. Therefore, large A-site cation-alloyed 2D RP perovskite NCs may provide a new way to rationalize high-performance and stable perovskite solar cells and light-emitting diodes.Article Citation - WoS: 7Citation - Scopus: 6Anisotropic Etching of Cvd Grown Graphene for Ammonia Sensing(Institute of Electrical and Electronics Engineers Inc., 2022) Yağmurcukardeş, Nesli; Bayram, Abdullah; Aydın, Hasan; Yağmurcukardeş, Mehmet; Açıkbaş, Yaser; Peeters, François M.; Çelebi, CemBare chemical vapor deposition (CVD) grown graphene (GRP) was anisotropically etched with various etching parameters. The morphological and structural characterizations were carried out by optical microscopy and the vibrational properties substrates were obtained by Raman spectroscopy. The ammonia adsorption and desorption behavior of graphene-based sensors were recorded via quartz crystal microbalance (QCM) measurements at room temperature. The etched samples for ambient NH3 exhibited nearly 35% improvement and showed high resistance to humidity molecules when compared to bare graphene. Besides exhibiting promising sensitivity to NH3 molecules, the etched graphene-based sensors were less affected by humidity. The experimental results were collaborated by Density Functional Theory (DFT) calculations and it was shown that while water molecules fragmented into H and O, NH3 interacts weakly with EGPR2 sample which reveals the enhanced sensing ability of EGPR2. Apparently, it would be more suitable to use EGRP2 in sensing applications due to its sensitivity to NH3 molecules, its stability, and its resistance to H2O molecules in humid ambient.Article Citation - WoS: 13Citation - Scopus: 14Strong Plasmon-Exciton Coupling in Colloidal Halide Perovskite Nanocrystals Near a Metal Film(Royal Society of Chemistry, 2020) Güvenç, Çetin Meriç; Polat, Nahit; Balcı, SinanAll inorganic colloidal halide perovskite nanoplatelets and nanowires are highly anisotropic shaped semiconductor nanocrystals with highly tunable optical properties in the visible spectrum. These nanocrystals have large exciton binding energies and high oscillator strengths due to their strongly quantum confined natures. The optical properties of the halide perovskites are tunable by variation of halide composition and morphology of the nanocrystals. We herein demonstrate that colloidal perovskite nanocrystals (NCs) placed in close proximity to chemically functionalized metal films show mixed plasmon-exciton formation, plexciton formation, in the strong coupling regime. The optical properties of all-inorganic lead halide perovskite NCs were controlled by colloidally synthesizing NCs with different morphologies such as nanowires and nanoplatelets or by controlling the composition of the halides in the NCs. The experimentally observed Rabi splitting energies are around 90 meV, 70 meV, and 55 meV for CsPbI3 nanoplatelets, CsPbI3 nanowires, and CsPb(Br/I)(3) nanoplatelets, respectively. In addition, the numerical simulations are in good agreement with the experimentally obtained data. The results show that colloidal all-inorganic halide perovskite NCs are promising and strong candidates for studying light-matter interaction at nanoscale dimension.Article Citation - WoS: 4Citation - Scopus: 4Color-Tunable All-Inorganic Cspbbr3 Perovskites Nanoplatelet Films for Photovoltaic Devices(American Chemical Society, 2019) Özcan, Mehmet; Özen, Sercan; Topçu, Gökhan; Demir, Mustafa Muammer; Şahin, HasanHerein, we demonstrate a novel coating approach to fabricate CsPbBr3 perovskite nanoplatelet film with heat-free process via electrospraying from precursor solution. A detailed study is carried out to determine the effect of various parameters such as ligand concentration, electric field, flow rate, etc. on the optical properties. By controlling the volume ratios of the oleylamine (OAm) and oleic acid (OA), the coalescing and thickness of the resulting nanoplatelets can be readily tuned that results in control over emission in the range of 100 nm without any antisolvent crystallization or heating processes. The varying electrical field and flow rate was found as inefficient on the emission characteristics of the films. In addition, the crystal films were obtained under ambient conditions on the ITO coated glass surfaces as in the desired pattern. As a result, we demonstrated a facile and reproducible way of synthesizing and coating of CsPbBr3 perovskite nanoplatelets which is suitable for large-scale production. In this method, the ability of tuning the degree of quantum confinement for perovskite nanoplatelets is promising approach for the one-step fabrication of crystal films that may enable the use in optoelectronics.Article Citation - WoS: 18Citation - Scopus: 46Phosphor-Based White Led by Various Glassy Particles:control Over Luminous Efficiency(The Optical Society, 2019) Yüce, Hürriyet; Güner, Tuğrul; Balcı, Sinan; Demir, Mustafa MuammerGenerating white light through a mainstream remote phosphor design suffers from phosphor conversion efficiency loss due to a backscattering of light. Such a loss also reduces luminous efficiency of the resulting white light. To overcome this issue, various glassy scatterers with different morphologies such as glass bubbles, glass beads, and nanosized silica particles were employed as scatterers, together with a fixed amount of yellow phosphor (YAG:Ce3+) and a poly(dimethylsiloxane) (PDMS) matrix. In addition, the simulation of the system validates the rigorous multiple scattering of the incoming light most probably due to refractive index mismatch between the glass bubbles and surrounding PDMS matrix along with the internal reflections. (C) 2019 Optical Society of AmericaArticle Citation - WoS: 15Citation - Scopus: 16Monitoring the Crystal Orientation of Black-Arsenic Via Vibrational Spectra(Royal Society of Chemistry, 2019) Kandemir, Ali; İyikanat, Fadıl; Şahin, HasanIn this study, the structural, mechanical, and vibrational properties of a recently discovered anisotropic ultra-thin material, black-arsenic (b-As), are investigated by using density functional theory. Direction dependent elastic constants such as in-plane stiffness, Young's modulus and Poisson's ratio of single-layer b-As are calculated and compared with those of the structural cousin black-phosphorus (b-P). The calculated Poisson's ratio of b-As for the zigzag direction is nearly 1, which is quite higher than that of b-P, 0.65. Besides, it is found that all the three elastic constants are highly anisotropic and their values in the zigzag direction are almost three times higher than that of the armchair direction. The mechanical strength of the material is also calculated and high-toughness is seen in both armchair and zigzag directions. It is revealed that the material is quite stiff against straining along the zigzag direction; in contrast, it is quite flexible along the armchair direction. Vibrational stability analysis shows that the material is stable up to 9% biaxially applied strain, and 12% and 45% uniaxially applied strain in the zigzag and armchair directions, respectively. Furthermore, the prominent Raman active peaks of the b-As structure show strong anisotropy in the strain dependent vibrational spectra and they can also be used for easy-determination of the crystal orientation of b-As from Raman measurements.Article Citation - WoS: 10Citation - Scopus: 12The Effect of Dopa Hydroxyl Groups on Wet Adhesion To Polystyrene Surface: an Experimental and Theoretical Study(Elsevier, 2020) Yıldız, Remziye; Özen, Sercan; Şahin, Hasan; Akdoğan, YaşarMussels wet adhesive performance has been arousing curiosity for a long time. It is found that 3,4-dihydroxyphenylalanine (DOPA) is responsible for adhesive properties of mussels. Despite a large body of research characterizing the interactions DOPA with hydrophilic surfaces, relatively few works have addressed the mechanism of interactions with hydrophobic surfaces. The benzene ring of DOPA is the main attributor to the adhesion on hydrophobic polystyrene (PS) surface. However, here we showed that two hydroxyl groups of catechol have also effects on wet adhesion. We studied wet adhesive properties of DOPA, tyrosine and phenylalanine functionalized PEG polymers, PEG-(N-Boc-L-DOPA)(4), PEG-(N-Boc-L-Tyrosine)(4), PEG-(N-Boc-L-Phenylalanine)(4), on spin labeled PS nanobeads (SL-PS) by electron paramagnetic resonance (EPR) spectroscopy. Surface coverage ratio of SL-PS upon additions of PEG-(N-Boc-L-DOPA)(4), PEG-(N-Boc-L-Tyrosine)(4) and PEG-(N-Boc-L-Phenylalanine)(4) showed that SL-PS was covered with 70%, 50% and 0%, respectively. This showed that spontaneous wet adhesion on PS increases with the number of amino acids hydroxyl groups. This is also supported with the density functional theory (DFT) energy calculations and ab-initio molecular dynamics (AIMD) simulations. In water, interactions between water molecules and hydroxyl groups on the catechol induce catechol adhesion via 7C-7C stacking between the catechol and double styrene rings which were already tilted out with water.