Determination of the size of quantum dots by fluorescence spectroscopy

Abstract

There has been a lack of quick, simple and reliable methods for determination of nanoparticle size. An investigation of the size of hydrophobic (CdSe) and hydrophilic (CdSe/ZnS) quantum dots was performed by using the maximum position of the corresponding fluorescence spectrum. It has been found that fluorescence spectroscopy is a simple and reliable methodology to estimate the size of both quantum dot types. For a given solution, the homogeneity of the size of quantum dots is correlated to the relationship between the fluorescence maximum position (FMP) and the quantum dot size. This methodology can be extended to the other fluorescent nanoparticles. The employment of evolving factor analysis and multivariate curve resolution-alternating least squares for decomposition of the series of quantum dots fluorescence spectra recorded by a specific measuring procedure reveals the number of quantum dot fractions having different diameters. The size of the quantum dots in a particular group is defined by the FMP of the corresponding component in the decomposed spectrum. These results show that a combination of the fluorescence and appropriate statistical method for decomposition of the emission spectra of nanoparticles may be a quick and trusted method for the screening of the inhomogeneity of their solution.

Synthesis, Optical Characterization, and Size Distribution Determination by Curve Resolution Methods of Water-Soluble CdSe Quantum Dots

“…On average, [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] emission spectra were collected for each CdSe QDs dispersion obtained at different synthesis time of reaction by varying the excitation wavelength by 5 nm. To include all the geometric characteristics of the emission spectrum, for each sample, the initial excitation wavelength was defined in such a way that recording of the emission spectra began between 50 and 60 nm before the emission increased sharply.…”

“…Unfortunately, these methods still have limitations like time-consuming sample preparation, limited instrument availability, laborious data processing, and low resolution. 27 The color of the QD emission depends on nanocrystal size, while the width of the PL peak depends on nanocrystal size distribution. Hence, on the basis of previous studies, correlation fluorescence spectra could afford the maximum diameter of QDs.…”

“…Radotic et al 27 developed the first method to estimate the size of QDs on the basis of their emission properties. These authors employed statistical methods (EFA-evolving factor analysis and MCR-ALS-multivariate curve resolutionalternating least square) to decompose the emission spectra of nanoparticles and identify fractions of QDs with different diameters.…”

Synthesis and characterization of chitosan-based polyelectrolyte complexes, doped by quantum dots

“…The emission peaks of CdTe and CdSe/ZnS are at 531 nm and 525 nm in buffer solution, respectively. The maxima correspond to QD core size of 2.4 nm [9] for CdTe core type QDs and 2.0 nm [10,11] for CdSe/ZnS core-shell type QDs. PL spectra of the encapsulated QDs were found to be shifted (about 4 nm for core-shell, 14 nm for core type QDs) towards lower energies in comparison with those of the QDs in buffer solution (Figure 3).…”

“…No any pronounced effect of the encapsulation on the PL lifetime was observed. The difference in the lifetime values for two types of QDs (40 ns for CdTe and 13 ns for CdSe/ZnS) can be attributed to their different core size [10,11] due to the strong dependence of PL lifetimes of QDs on their size [12]. …”