Dual-mode fluorimetric and colorimetric sensors based on iron and nitrogen co-doped carbon dots for the detection of dopamine.

Determination of dopamine (DA) is crucial for its intimate relationship with clinical trials and biological environment. Herein, Fe, N co-doped carbon dots (AFC-CDs) were fabricated by optimizing precursors and reaction conditions for fluorimetric/colorimetric dual-mode sensing of DA. With synergistic influence of Förster resonance energy transfer and static quenching effect, DA significantly quenched the blue luminescence of AFC-CDs at 442 nm, the production of recognizable tan-brown complex caused evident colorimetric response, achieved the dual-mode fluorimetric/colorimetric sensing for DA. The excellent selectivity and satisfied sensitivity can be confirmed with the limit of detection at 0.29 µM and 2.31 µM via fluorimetric/colorimetric mode respectively. The reliability and practicability were proved by recovery of 94.81-101.61% in real samples. Notably, the proposed electron transfer way between AFC-CDs and DA was hypothesized logically, indicated dual-mode probe provided a promising platform for the sensing of trace DA, and could be expanded in environment and food safety.

Chloroplast DNA Structural Variation, Phylogeny, and Age of Divergence among Diploid Cotton Species.

The cotton genus (Gossypium spp.) contains 8 monophyletic diploid genome groups (A, B, C, D, E, F, G, K) and a single allotetraploid clade (AD). To gain insight into the phylogeny of Gossypium and molecular evolution of the chloroplast genome in this group, we performed a comparative analysis of 19 Gossypium chloroplast genomes, six reported here for the first time. Nucleotide distance in non-coding regions was about three times that of coding regions. As expected, distances were smaller within than among genome groups. Phylogenetic topologies based on nucleotide and indel data support for the resolution of the 8 genome groups into 6 clades. Phylogenetic analysis of indel distribution among the 19 genomes demonstrates contrasting evolutionary dynamics in different clades, with a parallel genome downsizing in two genome groups and a biased accumulation of insertions in the clade containing the cultivated cottons leading to large (for Gossypium) chloroplast genomes. Divergence time estimates derived from the cpDNA sequence suggest that the major diploid clades had diverged approximately 10 to 11 million years ago. The complete nucleotide sequences of 6 cpDNA genomes are provided, offering a resource for cytonuclear studies in Gossypium.