Browsing by Author "Sapelkin, A."
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Item Open Access A bean-like formation of germanium nanoparticles inside CNTs by the subsequent operation of colloidal synthesis and catalytic chemical vapor deposition methods(Wiley, 2018) Karatutlu, Ali; Boi, F. S.; Wilson, R. M.; Ersoy, O.; Ortac, Bülend; Sapelkin, A.The first attempts of implanting Ge nanoparticles (Ge NPs) inside iron filled CNTs (IF-CNTs) by a subsequent use of the bench top colloidal synthesis and chemical vapor deposition (CVD) approach is shown. Ge NPs are colloidally synthesized (with a 3.8 ± 0.6 nm in size) before the deposition. The hybrid Ge NPs/IF-CNTs structure and morphology are characterized using high-resolution transmission electron microscopy, scanning electron microscopy, selective area electron diffraction, and X-ray diffraction studies. After the deposition, Ge NPs appear to be grown in size and to be sprinkled almost homogeneously into the IF-CNTs similar to a bean-like deposition. CNTs diameter is also identified to be enlarged drastically when using Ge NPs as a catalyst in CVD compared to the CNTs formation without Ge NPs. In addition, micro-length rectangular Ge µPs are also found outside the nanotube core. Rietveld analysis shows the presence of γ-Fe (Fm-3m), ferromagnetic α-Fe (Im-3m), Fe3C, Ge (Fd-3m), and multiwall CNTs. The results indicate that Ge NPs and IF-CNTs demonstrate cocatalytic activity in increasing the respective sizes, which are dramatically larger than those obtained by the conventional approaches.Item Open Access Liquid-phase synthesis of nanoparticles and nanostructured materials(Elsevier, 2018) Karatutlu, A.; Barhoum, A.; Sapelkin, A.Nanoparticles less than 100nm in size have attracted significant interest over the past 20 years due to their unique properties led by quantum size effect. This chapter evaluates the synthesis methods in liquid phase conducted under operation in high/room temperature and at vacuum/atmospheric environment for nanoparticles and nanostructured materials. We draw attention to the fact that various synthesis methods for formation of colloidally stable matrix-free nanoparticles are available. These methods including chemical stain etching, electrodeposition methods, direct-precipitation methods, sol-gel methods, colloidal synthesis methods, hot-injection synthesis methods, hydrothermal and solvothermal methods, microwave-assisted synthesis methods, ultrasonic synthesis methods, and laser ablation in liquid-phase.Item Open Access Structural, optical, electrical and electrocatalytic activity properties of luminescent organic carbon quantum dots(Wiley-Blackwell, 2018) Karatutlu, Ali; Patil, Bhushan; Şeker, İ.; İstengir, S.; Bolat, A.; Yıldırım, O.; Sevgen, Y. N.; Bakış, Y.; Ortaç, Bülend; Yılmaz, Eda; Sapelkin, A.Carbon is an essential element in human life and recently becoming technologically prominent due to the emerging field of “Carbononics”. We demonstrate organic carbon quantum dots (qdots) containing nitrile bonded (C≡N bond) d-glucose-like traces in various sizes obtained from wheat flour to be promising for imaging applications and to possess a relaxor ferroelectric property and an enhanced electrocatalytic activity that could reduce the cost of energy devices and simple to scale up for the commercialization. The secondary electron microscopy (SEM) imaging shows that the particle size of carbon qdots can be controlled via the sonication exposure time. Elemental analysis and vibrational spectroscopy results show that carbon qdots are sensitive to N2 gas in the atmosphere and could weaken its “carbogenic” property by making a stable C≡N bond at ambient atmosphere. Rietveld analysis and HR-TEM studies demonstrate that the structure of the C qdots was found to fit best with an acentric primitive orthorhombic lattice. The laser scanning confocal microscopy (LSCM) images show enhancement of the light emission when reducing the size and characteristic excitation wavelength-dependent light emission of C qdots. The photoluminescence and UV-Vis absorption spectroscopy techniques show surface dominant emission and absorption upon the nitrile bonding.Item Open Access Theories of nanoparticle and nanostructure formation in liquid phase(Elsevier, 2018) Karatutlu, A.; Barhoum, A.; Sapelkin, A.Nanoparticles (NPs) and nanostructured materials exhibit shape- and size-dependent properties that are desired for a wide variety of applications, such as catalysis, sensing, drug delivery, energy production, and storage. In view of this, it is essential to produce well-defined NPs and nanostructures with desired characteristics, to understand their formation and growth mechanisms, and to define the critical size below which they act differently from bulk materials in order to develop synthetic strategies. For example, quantum dots (below 20nm) are mainly single nanocrystals characterized by a single-domain crystalline lattice without grain boundaries. These tiny individual crystals differ drastically from bulk polycrystalline materials. In fact, existing investigations indicated that ordered polycrystalline particles are preferably formed at high supersaturations, where rapid nucleation generates many NPs, which subsequently tend to aggregate randomly at high NP concentrations. Single crystals, such as quantum dots, form at low supersaturations. The reduction of the supersaturation to a level at which primary NPs are still formed in solution yields mesocrystals. This chapter discusses the advanced nucleation and growth theories that are used to explain the growth of the obtained nanoparticles and nanostructures to the desired structures.