Long-Lived Afterglow from Elemental Sulfur Powder: Synergistic Effects of Impurity and Structure.

Elemental sulfur is not traditionally considered as an afterglow material, even though it can be endowed with fluorescence properties through processing it into nanodots. Herein, we discovered that elemental sulfur powder could emit room temperature phosphorescence (RTP) with a lifetime of 3.7 ms. A long-lived (>12 s) afterglow emission at 77 K could also be observed by the naked eye. Detailed investigations suggested that such a special phenomenon was attributed to impurity-related traps coupled with conduction and valence bands. After the sulfur is processed into nanodots, the rigid environment formed by the cross-linking of the surface ligands could stabilize the excited charges from quenching. This results in the promotion of RTP intensity and lifetime to achieve an emission lifetime of 200 ms. These results confirm the unique RTP of elemental sulfur powder, and also suggest the potential of sulfur-based materials as versatile components for the development of RTP materials.

Highly Selective Detection of Paraoxon in Food Based on the Platform of Cu Nanocluster/MnO2 Nanosheets.

Selective and sensitive identification of paraoxon residue in agricultural products is greatly significant for food safety but remains a challenging task. Herein, a detection platform was developed by integrating Cu nanoclusters (Cu NCs) with MnO2 nanosheets, where the fluorescence of Cu NCs was effectively quenched. Upon introducing butyrylcholinesterase and butyrylcholine into the system, their hydrolysate, thiocholine, leads to the decomposition of the platform through a reaction between the MnO2 nanosheets and thiol groups on thiocholine. The electron-rich groups on thiocholine can further promote the fluorescence intensity of Cu NCs through host-guest interactions. Adding paraoxon results in the failure of fluorescence recovery and further promotion, which could be utilized for the quantitative detection of paraoxon, and a limit of detection as low as 0.22 ng/mL can be achieved. The detection platform shows strong tolerance to common interference species, which endows its applications for the detection of paraoxon in vegetables and fruit. These presented results not only open a new door for the functionalization of metal nanoclusters but also offer an inspiring strategy for analytic techniques in nanomedicine and environmental science.

Point-of-care testing of butyrylcholinesterase activity through modulating the photothermal effect of cuprous oxide nanoparticles.

Butyrylcholinesterase (BChE) is an important indicator for clinical diagnosis of liver dysfunction, organophosphate toxicity, and poststroke dementia. Point-of-care testing (POCT) of BChE activity is still a challenge, which is a critical requirement for the modern clinical diagnose. A portable photothermal BChE assay is proposed through modulating the photothermal effects of Cu2O nanoparticles. BChE can catalyze the decomposition of butyrylcholine, producing thiocholine, which further reduce and coordinate with CuO on surface of Cu2O nanoparticle. This leads to higher efficiency of formation of Cu9S8 nanoparticles, through the reaction between Cu2O nanoparticle and NaHS, together with the promotion of photothermal conversion efficiency from 3.1 to 59.0%, under the excitation of 1064 nm laser radiation. An excellent linear relationship between the temperature change and the logarithm of BChE concentration is obtained in the range 1.0 to 7.5 U/mL, with a limit of detection of 0.076 U/mL. In addition, the portable photothermal assay shows strong detection robustness, which endows the accurate detection of BChE in human serum, together with the screening and quantification of organophosphorus pesticides. Such a simple, sensitive, and robust assay shows great potential for the applications to clinical BChE detection and brings a new horizon for the development of temperature based POCT.

High-efficient and environmentally friendly enrichment of semiconducting single-walled carbon nanotubes by combining short-time electrochemical pre-oxidation and combustion.

High purity semiconducting single-walled carbon nanotubes (s-SWCNTs) have bright prospects in the field of microelectronics, but their enrichment processes are usually very complicated and cost time and energy, which represent a major impediment for their future applications. Here, we report on a new efficient covalent modification enrichment approach that tackles this problem. Our method is to first selectively functionalize the surface of arc-discharge metallic single-walled carbon nanotubes (m-SWCNTs) rapidly by electrochemical pre-oxidation at 7.0 V in 0.1 M KCl aqueous solution, and subsequently followed up by removing the m-SWCNTs with a short-time combustion process at 600 °C for 30 s to enrich high purity s-SWCNTs. Although the surface of the s-SWCNTs was functionalized and heat-treated, the intrinsic tubular structure and electronic characteristics were well maintained. Besides, our approach, without any complex equipment or toxic reagents, is energy and time saving and can be easily scaled up. Milligrams of high-quality s-SWCNTs with high purity of more than 95 wt% can be easily obtained in only several minutes. The retention rate of s-SWCNTs after combustion is as high as 61 wt%.

Enrichment of semiconducting single-walled carbon nanotubes by simple equipment and solar radiation.

High-purity semiconducting (s-) single-walled carbon nanotubes (SWCNTs) have great potential to replace silicon-based materials for microelectronic devices. However, the enrichment methods of s-SWCNTs usually required complex devices and non-renewable energy. In this study, instead of a traditional heating method, renewable solar was employed to dramatically increase the heating rate and improve the reaction to be simple and more controllable, thereby water was successfully used to selectively etch metallic (m-) SWCNTs. In this work, purified SWCNTs films were wetted by water and then exposed to focused solar radiation, causing the surface temperature of the SWCNT films to reach about 800 °C within 2 s. In this case, the m-SWCNTs could be selectively etched by water rapidly. Finally, s-SWCNTs with a purity of about 95 wt% were obtained in several minutes without any complex devices or non-renewable energy.