Yüksek Sıcaklıkta Uzun Bir Süre Çekirdekleştirilen Kolloidal CdSe Kuantum Noktalarının Sentezi ve Optik Karakterizasyonu

Year 2019, Volume: 7 Issue: 2, 229 - 236, 25.05.2019

Çağdaş Allahverdi

https://doi.org/10.21541/apjes.389919

Cited By: 1

Abstract

Kolloidal CdSe kuantum noktaları, koordine olmayan oktadesen çözücü içerisinde sıcak-enjeksiyon tekniği kullanılarak yaklaşık
300oC’de 15 s çekirdekleştirildi ve 272oC’de 245 dakikaya kadar büyütüldü. CdSe kuantum noktalarının sentezinde stearik asit
bir kaplama ajanı olarak kullanıldı. Bu çalışmada kullanılan çekirdekleşme zamanı literatürdekilere göre oldukça uzundu ve
optik özelliklere olan etkisi incelendi. Birinci eksiton soğurma ve karşılık gelen rekombinasyon tepeleri, sırasıyla, optik soğurma
ve fotolüminesans spektrumlarında gözlendi. Stokes kayma değeri 70 meV’ye kadar değişti. 20 dakika için büyütülen numunenin
optik soğurma ve fotolüminesans spektrumlarında bir tepe ve omuz yapısı elde edildi. Yüksek sıcaklık altında yeterince uzun bir
sürede çekirdekleştirilen bu kuantum noktalarının çift büyüklük dağılımına sahip olabileceği gösterildi. CdSe kuantum
noktalarının görüntüleri geçirgenlik elektron mikroskopi vasıtasıyla elde edildi. Resimleri, ImageJ görüntü işleme programı ile
işlendi. 12 dakika büyütülen CdSe kuantum noktalarının ortalama büyüklüğü 2.63 nm olarak bulundu. Büyüklük dağılımı tekil
dağılımlı kuantum noktalarınkine nazaran 4.6 kat arttı. Cd ve Se elementlerine ait X-ışınları enerji geçiş tepeleri enerji dağılımlı
X-ışınları spektrumlarında gözlendi. Bu kuantum noktalarını saran stearik asit moleküllerinin simetrik ve asimetrik tireşim
modları Fourier dönüşümlü kızıl ötesi spektroskopi kullanılarak, sırasıyla, 2848 cm-1 ve 2914 cm-1
civarında belirlendi.

Keywords

optik soğurma, fotolüminesans, Fourier dönüşümlü kızılötesi spektroskopi, geçirimli elektron mikroskopi, CdSe kuantum noktaları, geçirimli elektron mikroskopi

Synthesis and Optical Characterization of Colloidal CdSe Quantum Dots Nucleated for A Long Time at High Temperature

Abstract

Colloidal CdSe quantum dots were nucleated at about 300oC for 15 s and growth at 272oC up to 245 min in non-coordinating
solvent octadecene by using hot-injection technique. Stearic acid was used as a capping agent in the synthesis of CdSe quantum
dots. The nucleation time used in this study was considerably longer than those in the literature and its effect on the optical
properties was examined. The first excitonic absorption and corresponding recombination peaks were observed in their optical
absorption and photoluminescence spectra, respectively. The value of Stokes shift changed up to 70 meV. A peak and shoulder
structure was obtained in the optical absorption and photoluminescence spectra of the sample growth for 20 min. It was indicated
that CdSe quantum dots which are nucleated at high temperature for a sufficiently long period may have double size distribution.
The images of CdSe quantum dots were obtained via transmission electron microscopy. Their images were processed with the
image processing program ImageJ. The average size of CdSe quantum dots growth for 12 min was found as 2.63 nm. The size
dispersion increased 4.6 times with respect to that of the monodisperse quantum dots. The X-ray energy transition peaks belong to Cd and Se elements were observed in their energy dispersive X-ray spectra. Symmetric and asymmetric vibrational modes of
stearic acid molecules capping these quantum dots were determined at about 2848 cm-1
and 2914 cm-1
, respectively, by using
Fourier transform infrared spectroscopy.

Keywords

optical absorption, photoluminescence, Fourier transform infrared spectroscopy, transmission electron microscopy, : CdSe quantum dots, transmission electron microscopy

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