New insight into pyrrolic-N site effect towards the first NIR window absorption of pyrrolic-N-rich carbon dots

Controlled C-N configurations,i.e.,pyrrolic-N,pyridinic-N,and graphitic-N,are promising strategies to tailor the carbon dots’(CDs)optical properties into the first near infrared(NIR)window(650-900 nm),a responsive range for biomedical application.However,a deep understanding of the role of the C-N configuration in the CDs’properties is still challenging and thoughtprovoking owing to their complex structure.Here,an underlying pyrrolic-N concentration and position effect on the pyrrolic-N-rich CDs’absorption was comprehensively elucidated based on the integrated experimental and computational studies.The assynthesized pyrrolic-N-rich CDs exhibit a first NIR window absorption centered at 650 nm with high photothermal conversion.Pyrrolic-N concentrations from 1.4%to 11.3%and positions(edge and mid-site)were systematically investigated.A mid-site pyrrolic-N was subsequently generated after the pyrrolic-N concentration more than 10%.Edge-site pyrrolic-N induces a frontier orbital hybridization,reducing bandgap energy,while mid-site pyrrolic-N plays a critical role in inducing a first NIR window absorption owing to their high charge transfer.Also,pyrrolic-N-rich CDs inherit a bowl-like topological feature,elevating the CDs’layer thickness as much as 0.71 nm.This study shed light on the design and optimization of pyrrolic-N on CDs for the first NIR window responsive materials in any biomedical application.

密度泛函理论计算筛选锂硫电池用单原子催化剂

探索具有高催化作用的活性中心结构,对于开发锂硫电池用单原子催化剂(SACs)至关重要.基于密度泛函理论计算,本工作提出了一种新型吡咯氮配位结构,用于负载3d过渡金属原子,以设计出高性能SACs.相比于传统的吡啶氮配位结构,该吡咯氮配位结构可实现对多硫化物更高的吸附及催化转化作用,从而提升锂硫电池活性物质的利用率、循环稳定性及倍率性能.基于对不同配位结构中的金属原子d轨道与多硫化物中硫原子p轨道杂化方式的分析,本工作阐明了吡咯氮配位结构可对多硫化物实现更强吸附作用的原因.此外,采用数据驱动的研究手段,探索出影响多硫化物催化转化效率的本征因素.因此,本工作提出了新型锂硫电池用SACs活性中心结构,并揭示了SACs的性能调控机制,为锂硫电池用SACs的设计提供了新策略.