Achieving Solidification and Redispersion of Semiconducting Polymer

Nov 27, 2017 - Fluorescent comparison of (a) yellow PDs (PFBT) and (b) red PDs (PFBT-DBT) with the corresponding PLDH composites. ...... Jiang , Y.; U...
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Achieving Solidification and Redispersion of Semiconducting Polymer Dots by Layered Double Hydroxide Incorporation Xiao-Jie Liu, Wei Wang, You-Hong Chen, Joey Andrew Valinton, Yang-Hsiang Chan, and Chun-Hu Chen ACS Appl. Nano Mater., Just Accepted Manuscript • DOI: 10.1021/acsanm.7b00029 • Publication Date (Web): 27 Nov 2017 Downloaded from http://pubs.acs.org on November 29, 2017

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ACS Applied Nano Materials

Achieving Solidification and Redispersion of Semiconducting Polymer Dots by Layered Double Hydroxide Incorporation Xiao-Jie Liu, Wei Wang, Yo-Hong Chen, Joey Andrew A. Valinton, Yang-Hsiang Chan* and Chun-Hu Chen* Department of Chemistry, National Sun Yat-sen University, 70 Lien Hai Road, Kaohsiung, Taiwan 80424. * E-mail: [email protected] (YH Chan), [email protected] (CH Chen)

ABSTRACT: Solidification and aqueous redispersion of fluorophores are characteristically challenging due to aggregation quenching and random shifts of emission. Carbon-based polymer dots (PDs) have recently shown superior photoluminescent performance to conventional dyes and inorganic quantum dots (QDs), but suffer from significant fluorescence quenching and irreversible aqueous dispersion after solidification, which limits their applications in practical biomedicine and optical devices. In this work, we have compared three strategies by utilizing layered double hydroxide (LDH) to effectively solidify PDs as robust and redispersible composites with well-preserved high brightness against wide pH (pH = 4 to 12) and strong ionic

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strength conditions, more stable than the pristine PDs. The resulting PD-LDH nanocomposites also show in vitro/in vivo bio-imaging ability with low cytotoxicity and improved photostability. In addition, these composites exhibit high thermal stability at 150 ºC for at least 96 h. The composites produced by onr-step physical mixing approach (~ 10 min) of LDH and PDs (pPLDH) exhibited comparable PL performance as compared to the conventional multi-step composites (m-PLDH) which require tremendous efforts (at least 7 days) to be prepared. Structural studies further revealed that the de-shaping behaviors of PDs and inter-flake sandwich assembly of LDH contributed to the robust fluorescence properties. Owing to the simple synthesis, durable photostability, high aqueous redispersion, and multicolor emissions (ranging from blue to near-infrared) of these PD-LDH nanocomposites, we believe that they are promising candidates for advanced bio-related technologies and optoelectronics.

KEYWORDS:

layered

double

hydroxides,

Polymer

dots,

bioimaging,

solidification,

photoluminescence, sandwich assembly

1. INTRODUCTION Photoluminescent (PL) stable materials are highly desired for emission devices, biological imaging, and specific labeling.1-4 However their solidification and aqueous redispersion without sacrificing PL properties are difficult to achieve due to aggregation quenching and unpredictable shifts of emission colors. Optical device miniaturization with concentrated brightness relies on the success of fluorophore solidification, while aqueous redispersion capability governs probing stability and diversity in biological imaging. Great efforts have been made to address these issues

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for high photostability, long-term storage, and convenient device engineering. For example, solidification of carbon dots (CDs) has been demonstrated by poly(vinyl alcohol) to generate soft grating films with bright emission; but the shift of emission wavelength, relatively low thermal stability (