Amorphous Copper-Based Nanoparticles with Clusterization-Triggered Phosphorescence for Ultrasensing 2,4,6-Trinitrotoluene.

Amorphous metal-based nanostructures have attracted great attention recently due to their facilitative electron transfer and abundant reactive sites, whereas it remains enigmatic as to whether amorphous copper-based nanoparticles (CuNPs) can be achieved. Here, for synthesizing amorphous CuNPs, glutathione is adopted as a ligand to inhibit the nucleation and crystallization process via its electrostatic repulsion. By subtly tailoring the solvent polarity, not only can amorphous glutathione-functionalized CuNPs (GSH-CuNPs) with phosphorescent performance be achieved after transferring the non-conjugation of GSH ligand to through-space conjugation, namely clusterization-triggered emission, but also the phosphorescence-off of GSH-CuNPs toward 2,4,6-trinitrotoluene (TNT) can be realized by the photoinduced electron-transfer process through the hydrogen bond channel, which is established between carboxyl and amino groups of GSH-CuNPs with the nitryl group of TNT. Benefitting from the intrinsic superiorities of the amorphous CuNPs, desired phosphorescence and detection performances of GSH-CuNPs toward airborne TNT microparticulates are undoubtedly realized, including high quantum yield (13.22%), excellent specificity in 33 potential interferents, instantaneous response, and ultralow detection limit (1.56 pg). The present GSH-CuNPs are expected to stretch amorphous metal-based nanostructures and deepen the insights into amorphous materials for optical detection.

Polyethyleneimine-capped copper nanoclusters for detection and discrimination of 2,4,6-trinitrotoluene and 2,4,6-trinitrophenol.

The detection and discrimination of 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrophenol (TNP) from analogues are of great importance to global security and are full of challenges in the field of trace sensing. Here, benefitting from the strong electrophilicity of TNT, a sensing strategy is established by synthesizing polyethyleneimine capped copper nanoclusters (PEI-Cu NCs) with abundant -NH2 groups. By carefully controlling the size and structure of PEI-Cu NCs, Förster resonance energy transfer (FRET) from PEI-Cu NCs to the Meisenheimer complex occurs resulting from their spectral overlap when detecting TNT, while, due to the energy level match of TNP with PEI-Cu NCs, as well as the strong affinity between its -OH and -NH2 in PEI-Cu NCs, photo-induced electron transfer (PET) is feasibly expected. As a result, TNT and TNP could be detected from 26 types of analogues and cations with a limit of detection (LOD) of 26.57 and 12.82 nM, respectively. Besides, owing to the brown color of the Meisenheimer complex, the discrimination of TNT and TNP could be additionally realized by colorimetric detection. We expect that the proposed methodology would not only shine light on the detection and discrimination of TNT and TNP that mitigate against public security concerns, but also pave a way for the deep understanding of FRET and PET related fluorescence quenching mechanisms from the aspect of controllable sensing material design and synthesis.

Phylogenetic position of Chinese endemic Drosophila curviceps species subgroup in the Drosophila immigrans group.

In order to investigate the phylogenetic position of Chinese endemic Drosophila curviceps species subgroup within the D. immigrans group on DNA molecular level, the ITS1 region of ribosomal DNA and part of Adh gene for 12 species represented all the five subgroups in D. immigrans group were sequenced. Molecular phylogenetic trees were constructed by using parsimony and neighbor-joining methods based on ITS1, Adh and combined sequences. In the molecular trees, species of the D. curviceps subgroup cluster together, strongly supporting establishment of a separating subgroup suggested in an initial morphologic study. This subgroup is the sister taxa of the D. quadrilineata subgroup. They are the younger subgroups, splitting about 3.4 Mya. The D. hypocausta subgroup is located at the base of the molecular tree, diverged first in this group about 9.2 Mya. Taking the geographic distribution into account, we can conclude that D. curviceps subgroup originated from tropic zones, agreeing with the previous morphologic and biogeographic suggestions. The position of D. neohypocausta was also discussed in this report and it seems that it is closer to the D. immigrans subgroup than to the D. hypocausta subgroup.

[Molecular phylogeny of Drosophila auraria species complex].

Drosophila auraria species complex consists of five sibling species D. auraria, D. biauraria, D. triauraria, D. quadraria and D. subauraria. The complete sequences of nuclear ITS1 (internal transcribed specer 1) and mitochondrial CO II (Cytochrome Oxdase II), and partial sequences of nuclear Adh (alcohol dehydrogenase) of these five sibling species and their closely-related species, D. rufa, were determined. Using D. rufa, D. melanogaster and D. yukuba as outgroups, both most-parsimony (MP) and neighbor-joining (NJ) trees were constructed based on the sequences of each genetic marker. In each tree, D. subauraria always branched off first within Drosophila auraria species complex. Combined sequences of ITS1, Adh and CO II are 2327 bp (excluding gaps), of which 255 sites are parsimony informative. Phylogenetic analyses based on the combined data sets can resolve the phylogenetic relationships of the five sibling species relatively well. According to the MP and NJ trees based on the combined sequences, D. subauraria was the first to emerge within Drosophila auraria species complex, thereafter D. biauraria branched off, D. auraria, D. triauraria and D. quadraria had a relatively recent speciation history. In this paper we propose a hypothesis about divergence events in Drosophila auraria species complex: The ancestor of this species complex diverged with D. rufa in warm-temperate regions about 2.33 myr ago, then they invaded into cold-temperate regions. In cold-temperate regions, D. subauraria was firstly derived from the ancestor of Drosophila auraria species complex about 0.88 myr ago, thereafter D. biauraria emerged about 0.31 myr ago. During the process the ancestor reinvading into warm-temperate and subtropical regions, speciations of D. auraria, D. triauraria and D. quadraria were gradually completed. This hypothesis does not agree on the previous opinion that D. quadraria was the ancestral species of Drosophila auraria species complex.