Semiconducting quantum dots:Modification and applications in biomedical science

Semiconductor quantum dots(SQDs)have received much attention due to their high quantum yield(QY),tunable emission spectrum,and excellent photostability.These unique optical properties endow SQDs with excellent biomedical application prospects,including biomedical imaging,drug delivery,clinical diagnosis,photodynamic therapy,DNA hybridization,and RNA profiling.This review introduces the classification of QDs and provides a brief description of the characteristics of QDs under each classification.Taking the type II B-VI A QDs as an example,inorganic and organic modification methods,and the corresponding advantages and disadvantages are summarized and discussed.Controlled modification approaches make them exhibit different functions in the bioimaging and drug delivery fields.The typical or classic instances are also listed to present the highlights of the applications of SQDs in the biomedical field.Based on these,this review raises a variety of possible challenges and perspectives of SQDs in biomedical applications in the future.

Quantum tunneling in two-dimensional van der Waals heterostructures and devices

Quantum tunneling with band-structure engineering has been feasibly developed for many applications in electrical,optoelectrical,and magnetic devices.It relies on layer-by-layer design and fabrication,which is an interdisciplinary research field covering material science and technology.Ever since the discovery of two-dimensional(2 D)layered materials,tunneling devices based on 2D van der Waals(vd W)heterostructures have been extensively studied as potential next-generation devices.2 D materials are thin at the atomic scale and extremely flat without surface dangling bonds.Because of these unique characteristics,2 D vd W heterostructures offer superior tunneling performance that reaches the benchmark of traditional Si technology and possess additional ability to scale down device size.Here,we comprehensively review quantum tunneling in 2 D vd W heterostructures,in addition to their unique mechanisms and applications.Moreover,we analyze the possibilities and challenges currently faced by 2 D tunneling devices and provide a perspective on their exploitation for advanced future applications.The investigation of technology-and performancecontrol of 2 D tunneling devices is at their beginning stages;however,these devices should emerge as competitive candidates for realizing low-power supply,fast-speed capability,and high-frequency operating devices.