Langmuir and langmuir blodgett studies of cadmium selenide (CdSe) quantum dots

Vanlı, Zuhal Selvi
Various methods can be used to prepare layered thin films with the sensitivity of molecular level. Langmuir Blodgett method, draws attraction since its discovery both in thin film production and in transferring the films produced onto a solid surface. Langmuir films have the application areas of biosensors, coating studies, electronic molecular and optoelectronic devices and semi-permeable barriers. In this work, firstly the alignment of silver nanoparticles on air water interphase was planned. Therefore, to provide optimum conditions for LB film of silver nanoparticles we tried to obtain stable cetyltrimethylammonium bromide (CTAB) films on deionized water subphase. However, at low concentration of CTAB (0.07 mg/mL) we could not get stable monolayers. To increase the stability of monolayer of CTAB, a new technique namely "gluing technique" was used and its effect on the stability of CTAB monolayers were investigated by using Poly(4-styrenesulfonate) (PSS) as gluing reagent. As a result of both surface pressure versus mean molecular area (π – MMA) isotherms and hysteresis experiments it was concluded that more stable monolayers of CTAB were obtained at low concentration with gluing technique. However, in the continuation part of the study; hoping that the fluorescence emission of the nanoparticles that were arranged on the surface can be seen by using hand-hold UV light, we decided to prepare LB thin films of Cadmium Selenide (CdSe) quantum dots instead of silver nanoparticles. Their synthesis and characterization were done by thermal decomposition method and fluorescence spectrometry respectively. The emission intensity of the QDs, at the excitation wavelength of 400 nm, was observed at 558 nm. The morphological characterization of quantum dots was done with Transmission Electron Microscopy (TEM). The monolayer formation of CdSe quantum dots and their mixture with stearic acid (SA) were achieved on water air sub-phase. During these studies, parameters corresponding compression rate and volume of CdSe quantum dots that spread onto sub-phase were optimized. Addition of SA as a spacer was improved spreading property of QDs and consequently facilitated the stable monolayer formation. Langmuir monolayer of CdSe quantum dots deposited on to the glass substrates and first characterization of these layers were done with Confocal Microscopy. In accordance of the information acquired with confocal microscopy, the selection of thin films of quantum dots that would be characterized by TEM was selected. TEM patterns have clearly shown that the homogeneous and closely arranged CdSe quantum dots films were obtained on the entire surface of the substrate. 


Sol-Gel processing of organically modified ITO thin films and characterization of their optoelectronic and microstructural properties
Kesim, Mehmet Tümerkan; Durucan, Caner; Department of Metallurgical and Materials Engineering (2012)
Indium tin oxide (ITO) thin films were formed on glass substrates by sol-gel method. Coating sols were prepared using indium chloride tetrahydrate (InCl3•4H2O) and tin-chloride pentahydrate (SnCl4•5H2O) stabilized in organic solvents (acetylacetone and ethanol). First attempt was to synthesize ITO thin films using standard/unmodified coating sols. The effect of calcination treatment in air (300 – 600 °C) and number of coating layer(s) (1, 4, 7 or 10) on optoelectronic properties (electrical conductivity and...
Hydrogen absorption in magnesium based crystalline thin films
Akyildiz, Hasan; Ozenbas, Macit; Öztürk, Tayfur (2006-08-01)
A study is carried out for hydrogenation of Mg based thin films produced via thermal evaporation. Films produced were pure Mg, Mg capped with Au-Pd, Mg-Cu co-deposited and Mg-Cu multilayered. The films under the experimental conditions employed were crystalline with columnar grains with some degree of preferred orientation. In multi-component systems, the films in the as-deposited state were made of individual elements, but upon hydrogenation at temperatures greater than 473K, the elements react with each o...
Use of gold nanoparticle containing poly (allylamine hydrochloride)/ poly (acrylic acid) multilayer films as sers substrates
Kölemen, Birsu; Ertaş, Gülay; Erel Göktepe, İrem; Department of Chemistry (2015)
Surface-enhanced Raman spectroscopy (SERS) is a surface sensitive vibrational spectroscopy technique that results in the enhancement of Raman scattering by molecules adsorbed on rough metal surfaces. It is a powerful, sensitive and non-destructive technique which is used in chemical, material and life sciences including biosensing, catalysis, spectroelectrochemistry, criminology, single molecule SERS applications and many others. Nanoparticle (NP) embedded multilayer films using Layer by Layer (LbL) techniq...
Investigation of structural and optical characteristics of thermally evaporated Ga2Se3 thin films
Isik, M.; Hasanlı, Nızamı (2020-09-01)
Ga2Se3 thin films were prepared by thermal evaporation technique and structural, optical characteristics of the deposited thin films were investigated in the present study. X-ray diffraction pattern of the thin film exhibited one intensive and sharp peak associated with (111) plane of cubic crystalline structure of the compound. Energy dispersive spectroscopic analyses pointed out the atomic compositional ratio of the constituent elements as consistent with chemical formula of Ga2Se3. The optical characteri...
Secondary growth of microporous vanadosilicate AM-6 films
Kuzyaka, Duygu; Galioglu, Sezin; Akata Kurç, Burcu (2016-10-01)
Oriented vanadosilicate AM-6 thin films with an average thickness of 1-2 mu m were prepared on the ITO coated glass substrates using secondary growth method with a partial a(b)-out-of-plane preferred crystal orientation for the first time. In secondary growth method, titanosilicate ETS-10 crystals were deposited on the substrate from a colloidal suspension to form seed layers. Then, the hydrothermal growth of the seed crystals was conducted to form AM-6 films. It was observed that the AM-6 films formed poss...
Citation Formats
Z. S. Vanlı, “Langmuir and langmuir blodgett studies of cadmium selenide (CdSe) quantum dots,” M.S. - Master of Science, Middle East Technical University, 2017.