Applied Science and Convergence Technology 2020; 29(5): 113-116
Published online September 30, 2020
Copyright © The Korean Vacuum Society.
Anh Thi Lea , b , Manh Ha Hoangc , Minh Hoa Nguyend , * , T. Anh Thu Doe , and Minh Tan Manb , f , *
aInstitute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam
bFaculty of Natural Sciences, Duy Tan University, Da Nang 550000, Vietnam
cHanoi Architectural University, Hanoi, Vietnam
dFaculty of Fundamental Sciences, Hue University of Medicine and Pharmacy, Hue 530000, Vietnam
eInstitute of Materials Science, Vietnam Academy of Science and Technology, Hanoi 100000, Vietnam
fInstitute of Theoretical and Applied Research, Duy Tan University, Hanoi 100000, Vietnam
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We present an analytical method to model the influence of gold nanoparticle (Au NP) concentration on the energy transfer between Cy3 orange beads (OBs) and Au NPs. The OBs and Au NPs act as donor (D) and acceptor (A), respectively. In the D–A system, the energy transfer efficiency strongly depends on the spectral overlap and separation R between donor and acceptor. Theoretical calculations for a range of R values between 10 and 100 Å produce three parameters that each characterize one of three different resonant energy transfer mechanisms: fluorescence resonant energy transfer, surface resonant energy transfer and Coulomb energy transfer. The values of these parameters provide estimates of the degree of quenching or enhancement of the fluorescence of D–A complexes as a function of concentration. A comparison between experimental and theoretical data confirms the validity of the model.
Keywords: Gold nanoparticle, Resonance energy transfer, Donor–,acceptor, Fluorescence
Non-radiative energy transfer occurs between donor (D) and acceptor (A) chromophores, and this is known as fluorescence resonance energy transfer (FRET). This process requires the donor emission band and acceptor absorption bands to overlap. The mechanism of FRET can be explained by considering the nature of the dipole-dipole D–A pair interaction . FRET effects are widely utilized in the fields of chemistry and physics, and in biological areas such as stem cell research, as well as protein analysis, biometric applications,
To clarify the phenomenon of interactions between molecules, J. Perrin  proposed a hypothesis on the nature of the dipole–dipole interactions based on the concept of molecules
In this work, an analytical model to determine the influence of gold nanoparticle (Au NP) concentration on the energy transfer from Cy3 orange beads (OBs) to Au NPs was investigated. The efficiency of fluorescence resonance energy transfer increases gradually with the concentration of Au NPs
The Golden Rule approximation relates the energy transfer rate
The experimental testing of this Coulomb’s law model for electronic excitation transfer (EET) from a segment of polyfluorene to tetraphenyl porphyrin was reported . For the electric-dipole transition, the normalized FRET rate
The first term of Eq. (5) describes the conventional Förster
Because the absorption spectrum of Au NPs is broad, the entire spectrum contributes to the resonance energy transfer. In experiments on Au NPs involving surface plasmon effects, it is necessary to consider a model of RET that includes the effects of Au NP concentration to investigate fluorescence enhancement and quenching.
For simplicity, we consider the average value of the D–A distance. Equation (5) is rewritten as follows:
From Eq. (6) we propose that the RET includes contributions from three mechanisms, FRET, SET, CET, with terms
Then, we can obtain
rom Eq. (8), assuming linear optical conditions, that
To rationalize experimental fluorescence enhancement results, we propose a model based on Eq. (10) with the conditions
From Eqs. (6), (7), and (9), we can determine the dependence of the fluorescence intensity
To estimate the contribution rate of each of the energy transfer mechanisms, we calculated the dependences on the average distance ⟨
In summary, a model for the energy transfer between OBs and varying concentrations of Au NPs was demonstrated in this work. It was found that the fluorescence intensity, computed as the efficiency of the resonance energy transfer, increases gradually with the Au NP concentration
This work was supported by the Foundation for Science and Technology of Hue University (Grant No. DHH2018-04-83).