Aggregation-induced emission (AIE) materials present unique solid-state fluorescence. However, there remains a challenge in the switching of fluorescence quenching/emitting of AIE materials, limiting the application in information encryption. Herein, we report a composite of tetraphenylethylene@graphene oxide (TPE@GO) with switchable microstructure and fluorescence. We choose GO as a fluorescence quencher to control the fluorescence of TPE by controlling the aggregation structure. First, TPE coating with an average thickness of about 31 nm was deposited at the GO layer surface, which is the critical thickness at which the fluorescence can be largely quenched because of the fluorescence resonance energy transfer. After spraying a mixed solvent (good and poor solvents of TPE) on TPE@GO, a blue fluorescence of TPE was emitted during the drying process. During the treatment of mixed solvents, the planar TPE coating was dissolved in THF first and then the TPE molecules aggregated into nanoparticles (an average diameter of 65 nm) in H 2 O during the volatilization of THF. We found that the fluorescence switching of the composite is closely related to the microstructural change of TPE between planar and granular structures, which can make the upper TPE molecules in and out of the effective quenching region of GO. This composite, along with the treatment method, was used as an invisible ink in repeated information encryption and decryption. Our work not only provides a simple strategy to switch the fluorescence of solid-state fluorescent materials but also demonstrates the potential for obtaining diverse material structures through compound solvent treatment.
A homochiral quadruple-stranded helicate, ΔΔ-(Eu2L4), assembled from bis-β-diketone with the preorganized helical chirality shows strong circularly polarized luminescence.
Chitin deacetylases (CDAs) convert chitin into chitosan, the N-deacetylated form of chitin, which influences the mechanical and permeability properties of structures such as the cuticle and peritrophic matrices. In this article, a new CDA encoding gene, Hacda2, was cloned by reverse transcription-polymerase chain reaction method in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), with an open reading frame of 1,611 bp. The deduced protein composed of 536 amino acid residues with a signal peptide, a chitin-binding domain, a low-density lipoprotein receptor class A domain, and a polysaccharide deacetylase-like catalytic domain. The highest expression level of Hacda2 was detected in fat body among tissues tested in the fifth-instar larvae using real-time quantitative polymerase chain reaction method. Feeding of Bacillus thuringiensis (Bt) (Bacillales: Bacillaceae) diet changed the expression level of Hacda1, Hacda2, Hacda5a, and Hacda5b significantly and differentially in the third-instar larvae. Hacda5a and Hacda5b expression were initially down-regulated and then up-regulated, whereas, the expression level of Hacda1 and Hacda2 was suppressed constantly postfeeding on Bt diet. These results suggested that HaCDAs may be involved in the response of H. armigera larvae to Bt and may be helpful to elucidate the roles of HaCDAs in the action of Bt cry toxin. The potential of HaCDAs to be used as synergists of Bt insecticidal protein needs to be further tested.
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