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Exploring the Intrinsic Piezofluorochromic Mechanism of TPE-An by STS Technique.

Jin S, Tian Y, Liu F, Deng S, Chen J, Xu N - Nanoscale Res Lett (2015)

Bottom Line: A theoretical calculation was carried out to find the relationship between the bandgap of TPE-An and the external force by combination of the classical tunneling theory and STS results.It is found that when the pressure variation on the surface of TPE-An film was increased to be over 4.38 × 10(4) Pa, the shrink of the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap can arrive at 1.1 eV.It is concluded that the piezofluorochromic behaviors of TPE-An should originate from the shrinking effect of the bandgap under external force.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory of Display Material and Technology, Sun Yat-sen University, Guangzhou, 510275, People's Republic of China.

ABSTRACT
9,10-bis(4-(1,2,2-triphenylvinyl)styryl)anthracene (TPE-An) materials have attracted considerable attention in recent years because they have high luminescence efficiency and excellent piezofluorochromic properties, which have potential applications in organic light-emitting display (OLED) area. Scanning tunneling spectroscopy (STS) technique was used to study the piezofluorochromic mechanism of aggregation-induced emission (AIE) materials for the first time. Photoluminescence (PL) experiments revealed that the emission peak of TPE-An is observed to exhibit a red-shift with the increase of the grinding time. A theoretical calculation was carried out to find the relationship between the bandgap of TPE-An and the external force by combination of the classical tunneling theory and STS results. It is found that when the pressure variation on the surface of TPE-An film was increased to be over 4.38 × 10(4) Pa, the shrink of the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap can arrive at 1.1 eV. It is concluded that the piezofluorochromic behaviors of TPE-An should originate from the shrinking effect of the bandgap under external force. Moreover, this research method may shed light on comprehending and adjusting the piezofluorochromic characters of other AIE materials.

No MeSH data available.


The AFM image (a) and the corresponding potential image (b) of TPE-An film (371.4 × 371.4 nm)
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Fig5: The AFM image (a) and the corresponding potential image (b) of TPE-An film (371.4 × 371.4 nm)

Mentions: To calculate the electrostatic force between W tip and TPE-An’s surface in STS experiments, the surface work function of TPE-An film must be worked out firstly. Here, KPFM technique is used to obtain the work function TPE-An film by measuring the contact potential difference VCPD between AFM tip and sample. VCPD can be described as:3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {V}_{\mathrm{CPD}}=\frac{\phi_{\mathrm{sample}}-{\phi}_{\mathrm{tip}}}{-e} $$\end{document}VCPD=ϕsample−ϕtip−ewhere e is the electron charge, and Фtip and Фsample are respectively the work function of AFM tip and sample. It is necessary to get the work function of the AFM tip in KPFM measurements in advance according to Eq. (3). Firstly, Фtip is measured to be 5.14 eV by using the standard Au film (work function is 5.1 eV) as a reference [41, 42]. Subsequently, KPFM measurements were performed on TPE-An film by using the AFM tip with the known work function. Figure 5a, b provides the AFM image and the potential image of TPE-An film, respectively. The contact potential difference VCPD is confirmed to be 0.16 ± 0.03 eV by analysis of Fig. 5b. Finally, the averaged surface work function of TPE-An (Фsample) can be determined to be 4.98 ± 0.03 eV based on Eq. (3).Fig. 5


Exploring the Intrinsic Piezofluorochromic Mechanism of TPE-An by STS Technique.

Jin S, Tian Y, Liu F, Deng S, Chen J, Xu N - Nanoscale Res Lett (2015)

The AFM image (a) and the corresponding potential image (b) of TPE-An film (371.4 × 371.4 nm)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4558996&req=5

Fig5: The AFM image (a) and the corresponding potential image (b) of TPE-An film (371.4 × 371.4 nm)
Mentions: To calculate the electrostatic force between W tip and TPE-An’s surface in STS experiments, the surface work function of TPE-An film must be worked out firstly. Here, KPFM technique is used to obtain the work function TPE-An film by measuring the contact potential difference VCPD between AFM tip and sample. VCPD can be described as:3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {V}_{\mathrm{CPD}}=\frac{\phi_{\mathrm{sample}}-{\phi}_{\mathrm{tip}}}{-e} $$\end{document}VCPD=ϕsample−ϕtip−ewhere e is the electron charge, and Фtip and Фsample are respectively the work function of AFM tip and sample. It is necessary to get the work function of the AFM tip in KPFM measurements in advance according to Eq. (3). Firstly, Фtip is measured to be 5.14 eV by using the standard Au film (work function is 5.1 eV) as a reference [41, 42]. Subsequently, KPFM measurements were performed on TPE-An film by using the AFM tip with the known work function. Figure 5a, b provides the AFM image and the potential image of TPE-An film, respectively. The contact potential difference VCPD is confirmed to be 0.16 ± 0.03 eV by analysis of Fig. 5b. Finally, the averaged surface work function of TPE-An (Фsample) can be determined to be 4.98 ± 0.03 eV based on Eq. (3).Fig. 5

Bottom Line: A theoretical calculation was carried out to find the relationship between the bandgap of TPE-An and the external force by combination of the classical tunneling theory and STS results.It is found that when the pressure variation on the surface of TPE-An film was increased to be over 4.38 × 10(4) Pa, the shrink of the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap can arrive at 1.1 eV.It is concluded that the piezofluorochromic behaviors of TPE-An should originate from the shrinking effect of the bandgap under external force.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory of Display Material and Technology, Sun Yat-sen University, Guangzhou, 510275, People's Republic of China.

ABSTRACT
9,10-bis(4-(1,2,2-triphenylvinyl)styryl)anthracene (TPE-An) materials have attracted considerable attention in recent years because they have high luminescence efficiency and excellent piezofluorochromic properties, which have potential applications in organic light-emitting display (OLED) area. Scanning tunneling spectroscopy (STS) technique was used to study the piezofluorochromic mechanism of aggregation-induced emission (AIE) materials for the first time. Photoluminescence (PL) experiments revealed that the emission peak of TPE-An is observed to exhibit a red-shift with the increase of the grinding time. A theoretical calculation was carried out to find the relationship between the bandgap of TPE-An and the external force by combination of the classical tunneling theory and STS results. It is found that when the pressure variation on the surface of TPE-An film was increased to be over 4.38 × 10(4) Pa, the shrink of the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap can arrive at 1.1 eV. It is concluded that the piezofluorochromic behaviors of TPE-An should originate from the shrinking effect of the bandgap under external force. Moreover, this research method may shed light on comprehending and adjusting the piezofluorochromic characters of other AIE materials.

No MeSH data available.