Materials Science and Engineering / Malzeme Bilimi ve Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4719
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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: 49Citation - Scopus: 54Highly Porous Poly(o-Phenylenediamine) Loaded Magnetic Carboxymethyl Cellulose Hybrid Beads for Removal of Two Model Textile Dyes(Springer, 2022) Arıca, Tuğçe Aybüke; Balcı, Fadime Mert; Balcı, Sinan; Arıca, Mehmet YakupEnsuring the removal of complex dyes from wastewater is a topic of great interest as it is vital for the environment. The present study reports a facile preparation method for poly(o-phenylenediamine) [p(o-PDA)] micro-particles loaded to magnetic carboxymethyl cellulose (CMC) hydrogel beads as adsorbents. The prepared products were characterized by FTIR, TGA, VSM, SEM, BET, and zeta sizer. The Fe3O4@p(o-PDA)@CMC beads were used for the removal of Reactive Blue 4 (RB-4) and Congo Red (CR) textile dyes from an aqueous medium. Different factors, such as adsorbent dose, initial pH, ionic strength, contact time, temperatures, and initial RB-4 and CR concentrations were examined. The maximum adsorption capacities of the RB-4 dye and CR at optimum pH 5 reached 398.7 and 524.6 mg/g in 120 min, respectively. The adsorption of RB-4 and CR on the hybrid magnetic beads can be due to the electrostatic, hydrogen bonding, and π-π interactions. Moreover, the magnetic hybrid beads showed easy regeneration ability and good reusability. The adsorbent can be a very good candidate for the efficient removal of micro-pollutant from wastewater.Article Citation - WoS: 17Citation - Scopus: 19Strong Coupling of Carbon Quantum Dots in Liquid Crystals(American Chemical Society, 2022) Sarısözen, Sema; Polat, Nahit; Mert Balcı, Fadime; Güvenç, Çetin Meriç; Kocabaş, Çoşkun; Yağlıoğlu, Halime Gül; Balcı, SinanCarbon quantum dots (CDs) have recently received a tremendous amount of interest owing to their attractive optical properties. However, CDs have broad absorption and emission spectra limiting their application ranges. We herein, for the first time, show synthesis of water-soluble red emissive CDs with a very narrow line width (∼75 meV) spectral absorbance and hence demonstrate strong coupling of CDs and plasmon polaritons in liquid crystalline mesophases. The excited state dynamics of CDs has been studied by ultrafast transient absorption spectroscopy, and CDs display very stable and strong photoluminescence emission with a quantum yield of 35.4% and a lifetime of ∼2 ns. More importantly, we compare J-aggregate dyes with CDs in terms of their absorption line width, photostability, and ability to do strong coupling, and we conclude that highly fluorescent CDs have a bright future in the mixed light-matter states for emerging applications in future quantum technologies.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: 3Citation - Scopus: 1Transition Metal Salt Promoted, Green, and High-Yield Synthesis of Silver Nanowires for Flexible Transparent Conductive Electrodes(Wiley-Blackwell, 2021) Sarısözen, Sema; Tertemiz, Necip Ayhan; Arıca, Tuğçe Aybüke; Polat, Nahit; Kocabaş, Çoşkun; Mert Balcı, Fadime; Balcı, SinanSilver nanowires (AgNWs) have attracted considerable interest from both academia and industry owing to their excellent electrical, optical, and chemical properties. For large-scale synthesis of AgNWs, the polyol method involving ethylene glycol, a toxic alcohol, has been widely used. We herein report on a facile, green, high yield, transition metal salt promoted, open atmosphere method for the synthesis of high quality AgNWs in a glycerol-water mixture. We have shown that transition metal salts have a strong influence on the morphology of AgNWs. Importantly, in the presence of copper(II) chloride, AgNWs with a high aspect ratio of around 400 (length, 36 μm; diameter, 90 nm) were obtained. Additionally, for the first time, we have demonstrated AgNWs based flexible transparent conductive electrodes (TCEs) on poly(sodium 4-styrenesulfonate) (PSS) treated polyethylene terephthalate (PET) substrate with a sheet resistance of 34 Ω/sq and transmittance of 91 % at 550 nm. The PSS layer on the PET substrate generated a highly hydrophilic surface, which boosts interaction of AgNWs with the PET surface. We envision that our results would play a significant role both in the synthesis of AgNWs with high aspect ratio and also in designing new rigid and flexible TCEs having high transmittance and low sheet resistance for applications especially in printable solar cells, organic light emitting diodes, and high performance flexible electronics.Article Citation - WoS: 7Citation - Scopus: 8Seed-Mediated Synthesis of Colloidal 2d Halide Perovskite Nanoplatelets(Wiley, 2021) Güvenç, Çetin Meriç; Balcı, SinanColloidal synthesis of two-dimensional lead halide perovskite nanoplatelets (2D LHP NPLs) with a general formula of L-2[APbX(3)](n-1)PbX4 has been widely performed by using hot-injection or ligand assisted reprecipitation methods. Herein, for the first time, we report on seed-mediated synthesis of two and three monolayers (n=2, 3) lead halide perovskite nanoplatelets without using A-site cation halide salt (AX; A=Cesium, methylammonium, formamidinium and, X=Cl, Br, I) and long chain alkylammonium halide salts (LX; L=oleylammonium, octylammonium, butylammonium and, X=Cl, Br, I). The nanocrystal seeds have been prepared by reacting lead (II) halide salt and coordinating ligands in a nonpolar solvent and then they have been reacted with cesium oleate, formamidinium oleate or methylamine. Our facile synthesis route enabling further understanding of the growth dynamics of LHP NPLs provides highly stable, monodisperse NPLs with very narrow absorption and emission linewidths (min. 68 meV), and high PLQY (max. 37.6%).Article Citation - WoS: 12Citation - Scopus: 14Laser Assisted Synthesis of Anisotropic Metal Nanocrystals and Strong Light-Matter Coupling in Decahedral Bimetallic Nanocrystals(Royal Society of Chemistry, 2021) Mert Balcı, Fadime; Sarısözen, Sema; Polat, Nahit; Güvenç, Çetin Meriç; Karadeniz, Uğur; Tertemiz, Necip Ayhan; Balcı, SinanThe advances in colloid chemistry and nanofabrication allowed us to synthesize noble monometallic and bimetallic nanocrystals with tunable optical properties in the visible and near infrared region of the electromagnetic spectrum. In the strong coupling regime, surface plasmon polaritons (SPPs) of metal nanoparticles interact with excitons of quantum dots or organic dyes and plasmon-exciton hybrid states called plexcitons are formed. Until now, various shaped metal nanoparticles such as nanorods, core-shell nanoparticles, hollow nanoparticles, nanoprisms, nanodisks, nanorings, and nanobipyramids have been synthesized to generate plasmon-exciton mixed states. However, in order to boost plasmon-exciton interaction at nanoscale dimensions and expand the application of plexcitonic nanocrystals in a variety of fields such as solar cells, light emitting diodes, and nanolasers, new plexcitonic nanocrystals with outstanding optical and chemical properties remain a key goal and challenge. Here we report laser-assisted synthesis of decahedral shaped noble metal nanocrystals, tuning optical properties of the decahedral shaped nanocrystals by galvanic replacement reactions, colloidal synthesis of bimetallic decahedral shaped plexcitonic nanocrystals, and strong plasmon-plasmon interaction in bimetallic decahedral shaped noble metal nanocrystals near a metal film. We photochemically synthesize decahedral Ag nanoparticles from spherical silver nanoparticles by using a 488 nm laser. The laser assisted synthesis of silver nanoparticles yields decahedral (bicolored) and prism (monocolored) shaped silver nanocrystals. The decahedral shaped nanoparticles were selectively separated from prism shaped nanoparticles by centrifugation. The optical properties of decahedral nanocrystals were tuned by the galvanic replacement reaction between gold ions and silver atoms. Excitons of J-aggregate dyes and SPPs of decahedral bimetallic nanoparticles strongly couple and hence decahedral shaped plexcitonic nanoparticles are prepared. In addition, localized SPPs of decahedral shaped bimetallic nanocrystals interact strongly with the propagating SPPs of a flat silver film and hence new hybrid plasmonic modes (plasmonic nanocavities) are generated. The experimental results are further fully corroborated by theoretical calculations including decahedral shaped plexcitonic nanoparticles and decahedral nanoparticles coupled to flat metal films.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: 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 America