WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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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: 19Citation - Scopus: 22Influence of Thixotropy Determined by Different Test Methods on Formwork Pressure of Self-Consolidating Concrete(Elsevier Ltd., 2018) Tuyan, Murat; Ahari, Reza Saleh; Erdem, Tahir Kemal; Andiç Çakır, Özge; Ramyar, KambizIn this experimental study, the influence of thixotropy determined by different test methods on the formwork pressure of self-consolidating concrete (SCC) with varying compositions was investigated. In order to determine the effect of water/binder (w/b) ratio, slump flow diameter and coarse aggregate/total aggregate (CA/TA) ratio on thixotropy and formwork pressure of SCC, fifteen concrete mixtures were prepared. Four different test methods i.e., “structural break-down area” (SBDA), “break-down percentage” (BDP), “drop in apparent viscosity” (DAV) and “yield value at rest” (YVR) were performed to determine the thixotropy of the SCC mixtures. Test results showed that the SBDA, DAV and YVR methods were more appropriate to evaluate the thixotropy of SCC than the BDP method. A strong correlation between thixotropy and formwork pressure was found using SBDA, DAV and YVR methods in SCC mixtures having low w/b ratio. There was a strong relationship between thixotropy determined by SBDA, BDP and DAV methods and formwork pressure in low slump flow SCC mixtures, while thixotropy determined by the YVR method showed good correlation with the formwork pressure in SCC mixtures having high slump flow values. Finally, new models were developed to estimate the formwork pressure of all kinds of mixtures as a function of thixotropy and time. The models were found to be successful for each of the thixotropy measurement method.Article Citation - WoS: 47Citation - Scopus: 49Simultaneous Identification of Spectral Properties and Sizes of Multiple Particles in Solution With Subnanometer Resolution(John Wiley and Sons Inc., 2016) Karabudak, Engin; Brookes, Emre; Lesnyak, Vladimir; Gaponik, Nikolai; Eychmüller, Alexander; Walter, Johannes; Segets, Doris; Peukert, Wolfgang; Wohlleben, Wendel; Demeler, Borries; Cölfen, HelmutWe report an unsurpassed solution characterization technique based on analytical ultracentrifugation, which demonstrates exceptional potential for resolving particle sizes in solution with sub-nm resolution. We achieve this improvement in resolution by simultaneously measuring UV/Vis spectra while hydrodynamically separating individual components in the mixture. By equipping an analytical ultracentrifuge with a novel multi-wavelength detector, we are adding a new spectral discovery dimension to traditional hydrodynamic characterization, and amplify the information obtained by orders of magnitude. We demonstrate the power of this technique by characterizing unpurified CdTe nanoparticle samples, avoiding tedious and often impossible purification and fractionation of nanoparticles into apparently monodisperse fractions. With this approach, we have for the first time identified the pure spectral properties and band-gap positions of discrete species present in the CdTe mixture.