Emission Properties of Individual AIE‐Luminogens in Solution at Room Temperature

Posted on 24 August 2023 by nYuehua Zhao, nHongbo Chen, nShaojie Geng, nShunjie Liu, nDapeng Wangn

Comprehensive Summary

Here, we combined the photon antibunching analysis, fluorescence correlation spectroscopy, and time-domain fluorescence lifetime imaging microscopy (TD-FLIM) to study the emission properties of a representative AIE-luminogen—4,4’-(benzo[c][1,2,5] thiadiazole-4,7-diyl)bis(N,N-diphenylaniline) (TPA-BT) at the single emitter level in a tetrahydrofuran (THF)/water solution where water is a non-solvent for TPA-BT. Our findings suggest that, at a constant water fraction in the solution, the size of TPA-BT aggregates increases with the TPA-BT concentration; TPA-BT aggregates are not a quantum emitter at room temperature in the solution. Moreover, utilizing TD-FLIM and a gel trapping technique allowed us to study the fluorescence lifetime of individual TPA-BT aggregates. Adding a polar solvent like water does not result in an overall decrease in fluorescence lifetime. Rather, it causes the fluorescence lifetime distribution to become wider, and only some molecules experience a decrease in their fluorescence lifetime. These results could represent a step forward in further understanding the photophysics of AIE-luminogens.

Electronic Structure of the Low‐Lying States of the Triatomic MoS2 Molecule: The Building Block of 2D MoS2

Posted on 24 August 2023 by nMarkella A. Mermigki, nIoannis Karapetsas, nDemeter Tzelin

The triatomic MoS₂ molecule is the building component of solid MoS₂. In this work, the electronic structure and chemical bonding of 16 low-lying states of triatomic MoS₂ are studied. The low-lying septet states of triatomic MoS₂ are found to be involved in the material as a building block, explaining the variety of its morphologies.

Abstract

Molybdenum disulfide (MoS₂) is the building component of 1D-monolayer, 2D-layered nanosheets and nanotubes having many applications in industry, and it is detected in various molecular systems observed in nature. Here, the electronic structure and the chemical bonding of sixteen low-lying states of the triatomic MoS₂ molecule are investigated, while the connection of the chemical bonding of the isolated MoS₂ molecule to the relevant 2D-MoS₂, is emphasized. The MoS₂ molecule is studied via DFT and multireference methodologies, i. e., MRCISD(+Q)/aug-cc-pVQZ(−PP)_Mo. The ground state, ³B₁, is bent (Mo−S=2.133 Å and ϕ(SMoS)=115.9°) with a dissociation energy to atomic products of 194.7 kcal/mol at MRCISD+Q. In the ground and in the first excited state a double bond is formed between Mo and each S atom, i. e., . These two states differ in which d electrons of Mo are unpaired. The Mo−S bond distances of the calculated states range from 2.108 to 2.505 Å, the SMoS angles range from 104.1 to 180.0°, and the Mo−S bonds are single or double. Potential energy curves and surfaces have been plotted for the ³B₁, ⁵A₁ and ⁵B₁ states. Finally, the low-lying septet states of the triatomic molecule are involved in the material as a building block, explaining the variety of its morphologies.

Optimum Yield of Empty Fruit Bunches Cellulose Nanofibers by Deep Eutectic Solvent and Ultrasonication

Posted on 24 August 2023 by

Cellulose nanofibers (CNFs) were successfully extracted from empty fruit bunches (EFBs) using deep eutectic solvent (DES) treatment assisted by ultrasonication. DES, a green solvent created by combining choline chloride and oxalic acid dehydrate, was capable to digest EFB cellulose into CNFs, a process which may serve as foundation for high-yield, industrial-scale synthesis of nanocellulose.

Abstract

Cellulose nanofibers (CNFs) are extensively utilized as affordable, renewable materials. The conventional technique for making CNFs is time-consuming, requires hazardous toxic chemicals, and consumes enormous amounts of energy. CNFs from empty fruit bunches (EFB) were produced via deep eutectic solvent (DES) and ultrasonication. The DES treatment conditions were optimized using the central composite design (CCD) approach of response surface methodology (RSM). Analysis of variance (ANOVA) revealed that the reaction time, DES molar ratio, and temperature were all significant variables. The experimental results closely correspond to the theoretical model of CNFs yield. X-ray diffraction (XRD) studies demonstrated that the crystallinity index of the CNFs increased significantly after sonication. It could be stated that DES treatment and ultrasonication were effective ways to successfully generate CNFs from EFB. This study may serve as foundation for high-yield, industrial-scale synthesis of nanocellulose using DES treatment.