Clustering-Triggered Emission of Carboxymethylated Nanocellulose

Abstract

Non-conjugated polymers with luminescence emission property have recently drawn great attention due to their promising applications in different areas. Most traditional organic synthetic non-conjugated polymers required complicated synthesis. Herein, we report a non-conjugated biomass material, carboxymethylated nanocellulose (C-CNC), which is found to be practically non-luminescent in dilute solutions, while being highly emissive when aggregated as nanosuspensions. We propose that the luminescence of C-CNC originates from the through-space conjugation of oxygen atoms and carboxyl groups of C-CNC. Thus, a clearer mechanism of clusteroluminescence was provided with the subsequent experiments. The effects of concentration of C-CNC, solvent, temperature and pH have also been investigated. In addition, ethylenediamine (EDA) has been employed to “lock” C-CNC material via the bonding of amide groups with carboxylic groups. As prepared C-CNC/EDA confirmed that the clusteroluminescence was attributed to the amide moieties and through-space conjugation between oxygen and carbonyl moieties. Density functional theory (DFT) calculations have also been employed to confirm the luminescence mechanism. It is believed that such clustering-triggered emission mechanism is instructive for further development of unconventional luminogens.

Employing photoluminescence to rapidly follow aggregation and dispersion of cellulose nanofibrils

“…2,25,26 The autofluorescence of poly-and oligo-saccharides, from various sources, has previously been widely reported. 6,[27][28][29][30][31][32][33][34][35] This autofluorescence is generally attributed to contamination of the sample with aromatic compounds, i.e. lignin, or proteins, dependent on the source.…”

“…6,31 In relation to cellulosic nanomaterials with typical surface chemical modifications, Li et al investigated the autofluorescent properties of carboxymethylated nanocellulose. 33 They demonstrated that the particles exhibited two fluorescent bands with an approximate wavelength difference of 40 nm, the second of which increased with concentration. This second peak was attributed to electron transitions between oxygen n orbitals and the carboxyl π* orbitals.…”

“…This second peak was attributed to electron transitions between oxygen n orbitals and the carboxyl π* orbitals. 33 More recently, we tracked changes in the fluorescence of sulfated and hydrophobically-modified CNCs with an increase in concentration. We confirmed that the intensity ratio between the two observed bands, centred at 468 and 504 nm, and attributed to intra-and inter-particle molecular forces respectively, was concentration dependent, enabling a prediction of the critical aggregation concentration (CAC).…”

Generating Circularly Polarized Light from Clustering‐Triggered Emission Using Solid Phase Molecular Self-Assembly

“…Because CTE does not require conjugated groups, it has many advantages over emission from traditional aromatic conjugated molecules, such as facile synthesis, good water solubility, and low biological toxicity 9,[11][12][13][14] . For this reason, CTE has become the potent alternative for the conventional one in many fields, such as color tunable light-emitting [15][16][17][18][19][20] , room-temperature phosphorescence [11][12][13][14][21][22][23][24][25][26] , as well as bioimaging and chemical sensing 13,[22][23][24][27][28][29][30] . It would be very promising if CTE is able to replace traditional emission in an even vast number of fields.…”

Biomass-Based Polymer Nanoparticles With Aggregation-Induced Fluorescence Emission for Cell Imaging and Detection of Fe3+ Ions

“…The preparation of polymeric nanoparticles with AIE property by simple extraction of renewable natural raw material would be very attractive, which was paid little concern. Biomass resources have been extensively studied because of their excellent properties such as wide sources, non-toxic, renewable and so on (An et al, 2019 ; Du et al, 2019 ; Li et al, 2019c ), in addition, they are also used as raw materials for the preparation of fluorescent materials due to their own sustainability (He et al, 2018 ; Li et al, 2019b ). Larch bark is typically regarded as waste, but larch bark extracts (LBE) contain large amounts of catechol-containing compounds (Jiang et al, 2014 , 2016 ; Luo et al, 2019 ).…”