High Fluorescence Quantum Yield Based on the Through-Space Conjugation of Hyperbranched Polysiloxane

Abstract

Unorthodox luminogenic polymers without aromatic luminogens have attracted great interest in recent years; however, the low fluorescence efficiency is still a big drawback. In this paper, we synthesized a fluorescent hyperbranched polysiloxane with both carbonyl and vinyl groups (P1). Surprisingly, it exhibited nontraditional intrinsic luminescence with the highest quantum yield up to 43.9% among the reported silica-containing hyperbranched fluorescent polymers to date. Reference oligomers P2 and P3, theoretical calculations, and transmission electron microscopy were employed to explore the fluorescence mechanism. The high fluorescence quantum yield is ascribed to the synergism of vinyl and carbonyl groups as well as the Si−O grouppromoted through-space conjugation. Thus, the supramolecular hyperbranched polysiloxane was assembled by conjugation to increase the oscillator strength and decrease the band gap. Moreover, the solvent effect and pH dependency properties of P1 and its application as an Fe 3+ probe were also studied.

Supramolecular Hyperbranched Poly(amino ester)s with Homogeneous Electron Delocalization for Multi‐Stimuli‐Responsive Fluorescence

“…In Figure , HPAE exhibits distinct UV absorbency at about 214 nm in aqueous solutions, which might be caused by n→π* electronic transitions among esters or oxy groups from HPAE backbone. [ 21 ] Moreover, the absorption intensity is enhanced and a bit red‐shifted as its concentration rises. The reason for these phenomena is that the aggregation degree of HPAE becomes higher with the increase of concentration (Figure S5, Supporting Information), and then forms larger electron delocalization.…”

Reevaluating Protein Photoluminescence: Remarkable Visible Luminescence upon Concentration and Insight into the Emission Mechanism

“…[2][3][4][5][6] Their visible emission, however,s hould principally stem from the aggregation of nonaromatic subgroups and the peptide backbone,o n account of their highly similar emission behaviors to those of nonconventional luminogens. [19,[30][31][32][33][34][35] In extremely dilute solutions,o nt he one hand, Tr p residues are inefficient in terms of emission owing to the low concentration and long l ex ,a nd on the other hand, it is difficult to excite and induce emission in the BSA backbone owing to its insufficient conjugation and active molecular motions,thus resulting in the nonemissive feature of dilute solutions.W hent he concentration increases,B SA chains become entangled and aggregated, which allows the clustering of NH 2 ,C =O, OH, and other subunits with p and nelectrons,thus yielding 3D through-space electronic communication. Specifically,electronic orbital overlap among lone pairs and p electrons, dipole-dipole interactions,and n-p*interactions,bring about extended electronic delocalization along with simultaneously rigidified conformations.I np articular,s trong inter-a nd intramolecular hydrogen bonds not only stabilize the molecular conformations,b ut also facilitate contact between the subgroups,w hich is beneficial for light emission.…”

Aggregate Science: From Structures to Properties

“…[200] However, once clusters form in the aggregate state, the energy gap (∆E 2 and ∆E 3 ) become narrow because of the newly generated throughspace conjugation. [201][202][203][204][205][206][207][208] More specifically, the intermolecular interactions between molecules broaden the molecular energy levels such as highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) into electronic bands, i.e., conduction band (CB) and valance band (VB), which is similar to the quantum confinement effect in quantum dots. [209,210] The small energy gap (∆E 2 ) of loose clusters produce a visible clusteroluminescence located in the short-wavelength range.…”