Photonics / Fotonik
Permanent URI for this collectionhttps://hdl.handle.net/11147/2590
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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, Sinan; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of TechnologyConventionally, 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: 12Citation - Scopus: 14Laser Assisted Synthesis of Anisotropic Metal Nanocrystals and Strong Light-Matter Coupling in Decahedral Bimetallic Nanocrystals(Royal Society of Chemistry, 2021) Balcı, Fadime Mert; Balcı, Sinan; Polat, Nahit; Güvenç, Çetin Meriç; Karadeniz, Uğur; Tertemiz, Necip Ayhan; Balcı, Sinan; 04.04. Department of Photonics; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyThe 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; Polat, Nahit; Balcı, Sinan; Balcı, Sinan; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of TechnologyAll 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: 15Citation - Scopus: 16Monitoring the Crystal Orientation of Black-Arsenic Via Vibrational Spectra(Royal Society of Chemistry, 2019) Kandemir, Ali; İyikanat, Fadıl; Şahin, Hasan; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of TechnologyIn 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: 67Citation - Scopus: 66Bilayers of Janus Wsse: Monitoring the Stacking Type: Via the Vibrational Spectrum(Royal Society of Chemistry, 2018) Kandemir, Ali; Şahin, Hasan; Şahin, Hasan; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of TechnologyMotivated by the recent successful synthesis of Janus type single layers of transition metal dichalcogenides, we investigate the stability, vibrational and electronic properties of the Janus single layer structure of WSSe and its bilayers by means of density functional theory. The structural and vibrational analysis show that the Janus single layer of WSSe forms a dynamically stable structure in the 2H phase. Owing to its non-centrosymmetric structure, the Janus WSSe single layer has two in-plane (E) and two out-of-plane (A) Raman active phonon modes. The eigen-frequencies of the prominent Raman active modes are calculated to be 277 (A) and 322 (E) cm-1. Similar to single layer WS2 and WSe2, Janus WSSe is a direct band gap semiconductor that has two electronically different faces. In addition, the possible bilayer stacking orders of the Janus WSSe single layers are investigated. It is found that there are 3 stacking types of bilayer Janus WSSe and each stacking type has distinctive Raman characteristics in its vibrational spectrum. Our results show that thanks to the vibrational characteristics, which stem from the distinctive interlayer interactions at different sides, the stability and stacking types of the bilayer of WSSe Janus structure can be monitored.