Article Cite This: Langmuir XXXX, XXX, XXX−XXX
pubs.acs.org/Langmuir
Synergistic Enhancement of Electron-Accepting and -Donating Ability of Nonconjugated Polymer Nanodot in Micellar Environment Arpan Bhattacharya and Tushar Kanti Mukherjee* Discipline of Chemistry, Indian Institute of Technology Indore, Simrol, Khandwa Road, Indore 453552, Madhya Pradesh India S Supporting Information *
ABSTRACT: Understanding the fundamental electron-transfer dynamics in photoactive carbon nanoparticles (CNPs) is vitally important for their fruitful application in photovoltaics and photocatalysis. Herein, photoinduced electron transfer (PET) to and from the nonconjugated polymer nanodot (PND), a new class of luminescent CNP, has been investigated in the presence of N,N-dimethylaniline (DMA) and methyl viologen (MV2+) in homogeneous methanol and sodium dodecyl sulfate (SDS) micelles. It has been observed that both DMA and MV2+ interact with the photoexcited PND and quench the PL intensity as well as excited-state lifetime in bulk methanol. While in bulk methanol, purely diffusion-controlled PET from DMA to MV2+ via PND has been observed, the mechanism and dynamics differ significantly in SDS micelles. In contrast to homogeneous methanol medium, a distinct synergic effect has been observed in SDS micelles. The presence of both DMA and MV2+ enhances the electron-accepting and -donating abilities of PND in SDS micelles. Time-resolved photoluminescence (PL) measurements reveal that the PET process in SDS micelles is nondiffusive in nature mainly due to instantaneous electron transfer at the confined micellar surface. These results have been explained on the basis of heterogeneous microenvironments of SDS micelles which compartmentalize the donor and acceptor inside its micellar pseudo phase. The present findings provide valuable insights into the intrinsic relation between redox and PL properties of nonconjugated PND. PL blinking, and nontoxicity.20,30−33 However, the origin of their intense PL is a matter of debate and not yet entirely understood. Earlier, it has been proposed that CDs containing carboxylic and hydroxyl moieties are highly luminescent as surface oxidation introduces surface defects into CDs which are responsible for their PL.34,35 Owing to their unique structure and surface functionalities, CDs show excellent electrondonating and -accepting ability which has been welldocumented in the literature. For example, Wang et al. have studied PET involving polyethylene glycol diamine (PEG1500N) functionalized CDs with various electron donors and acceptors by PL quenching experiments.36 Similarly, Mondal et al. have demonstrated pH-dependent reversible PET to and from dopamine functionalized CDs.37 Kokal et al. have studied the amplification of solar energy conversion capability of a TiO2/ CdS photoanode by highly conducting CDs.38 Recently, efficient visible light water splitting by CDs and its nanocomposites as photocatalyst have also been demonstrated.39,40 These studies clearly highlight the potential of CDs toward the photoelectrochemical and photocatalytic applications as a consequence of their exceptional charge transport ability. Hence, understanding and exploring the underlying electron transfer dynamics and the influence of surrounding environ-
1. INTRODUCTION Over the past few years, carbon-based nanomaterials have attracted enormous attention in technology related applications such as photovoltaic,1,2 photocatalyst,3,4 supercapacitor,5,6 and biomedical imaging7,8 owing to their superior physicochemical and optoelectronic properties compared to heavy-metal-based quantum dots (QDs). Among these materials, small (
