Optical manipulation from the microscale to the nanoscale: fundamentals, advances and prospects

Since the invention of optical tweezers,optical manipulation has advanced significantly in scientific areas such as atomic physics,optics and biological science.Especially in the past decade,numerous optical beams and nanoscale devices have been proposed to mechanically act on nanoparticles in increasingly precise,stable and flexible ways.Both the linear and angular momenta of light can be exploited to produce optical tractor beams,tweezers and optical torque from the microscale to the nanoscale.Research on optical forces helps to reveal the nature of light–matter interactions and to resolve the fundamental aspects,which require an appropriate description of momenta and the forces on objects in matter.In this review,starting from basic theories and computational approaches,we highlight the latest optical trapping configurations and their applications in bioscience,as well as recent advances down to the nanoscale.Finally,we discuss the future prospects of nanomanipulation,which has considerable potential applications in a variety of scientific fields and everyday life.

Photon momentum transfer in inhomogeneous dielectric mixtures and induced tractor beams

The determination of optical force as a consequence of momentum transfer is inevitably subject to the use of the proper momentum density and stress tensor.It is imperative and valuable to consider the intrinsic scheme of photon momentum transfer,particularly when a particle is embedded in a complex dielectric environment.Typically,we consider a particle submerged in an inhomogeneous background composed of different dielectric materials,excluding coherent illumination or hydrodynamic effects.A ray-tracing method is adopted to capture the direct process of momentum transfer from the complex background medium,and this approach is validated using the modified Einstein–Laub method,which uses only the interior fields of the particle in the calculation.In this way,debates regarding the calculation of the force with different stress tensors using exterior fields can be avoided.Our suggested interpretation supports only the Minkowski approach for the optical momentum transfer to the embedded scatterer while rejecting Peierls’s and Abraham’s approaches,though the momentum of a stably moving photon in a continuous background medium should be considered to be of the Abraham type.Our interpretation also provides a novel method of realizing a tractor beam for the exertion of negative force that offers an alternative to the use of negative-index materials,optical gain,or highly non-paraxial or multiple-light interference.

Preparation and electrocatalytic properties of triuranium octoxide supported on reduced graphene oxide

Triuranium 减少 octoxide 的 graphene 氧化物(U < 潜水艇 class= “ a-plus-plus ” > 3 O < 潜水艇 class= “ a-plus-plus ” > 8 个 /rGO) 混血儿被一个二拍子的圆舞答案阶段方法准备了。存在去是必要的以便获得纯阶段 U < 潜水艇 class= “ a-plus-plus ” > 3 O < 潜水艇 class= “ a-plus-plus ” > 8 。U < 潜水艇 class= “ a-plus-plus ” > 3 O < 潜水艇 class= “ a-plus-plus ” > 8 个 /rGO 混血儿为氧减小反应展出了优秀 electrocatalytic 活动。电子转移数字被计算在 0.7 V 是 3.9 (对 Ag/AgCl ) 从 Koutecky-Levich 阴谋的斜坡。U < 潜水艇 class= “ a-plus-plus ” > 3 O < 潜水艇 class= “ a-plus-plus ” > 8 个 /rGO 混血儿比商业 Pt/C 催化剂更稳定。而且，当甲醇是在场的时， U < 潜水艇 class= “ a-plus-plus ” > 3 O < 潜水艇 class= “ a-plus-plus ” > 8 个 /rGO 混血儿仍然保留了高活动。另外， U < 潜水艇 class= “ a-plus-plus ” > 3 O < 潜水艇 class= “ a-plus-plus ” > 8 个 /rGO 混血儿能也催化氢的减小过氧化物。

Reduced graphene oxide decorated with Bi2O2.33 nanodots for superior lithium storage

Bismuth oxides are important battery materials owing to their ability to electrochemically react and alloy with Li,which results in a high capacity level,which substantially exceeds that of graphite anodes.However,this high Li-storage capability is often compromised by the poor electrochemical cyclability and rate capability of bismuth oxides.To address these challenges,in this study,we design a hybrid architecture composed of reduced graphene oxide （rGO） nanosheets decorated with ultrafine Bi2O2.33 nanodots （denoted as Bi2O2.33/rGO）,based on the selective and controlled hydrolysis of a Bi precursor on graphene oxide and subsequent crystallization via solvothermal treatment.Because of its high conductivity,large accessible area,and inherent flexibility,the Bi2O2.33/rGO hybrid exhibits stable and robust Li storage （346 mA＆#183;h＆#183;g-1 over 600 cycles at 10 C）,significantly outperforming previously reported Bi-based materials.This superb performance indicates that decorating rGO nanosheets with ultrafine nanodots may introduce new possibilities for the development of stable and robust metal-oxide electrodes.

Routing emission with a multi-channel nonreciprocal waveguide

In this work, we present a multi-channel nonreciprocal waveguide, which is composed of a gyrotropic-bounded dielectric on the bottom and a plasmonic material on the top. The Lorentz reciprocity in the time-invariant system is broken when applying an external static magnetic field on the gyrotropic material. The nonreciprocal emission from the dipole source located in the center of the waveguide is observed in extended waveband channels. The proposed heterostructure serves as a photonic dichroism once the dielectric is replaced by a nonlinear material.The associated second harmonic generated in the nonlinear process can be separated from the fundamental signal under proper magnetic field intensity. Our findings may provide significant guidance for designing nonreciprocal photonic devices with superiorities of a tunable waveband, multiple channels, and small footprint.

短病程溃疡性结肠炎相关性结直肠癌1例

患者男,55岁,因"间断性腹痛、腹泻伴粘液脓血便3年,再发1周",于2021年7月12日收入解放军联勤保障部队第960医院干部病房1科。患者于2018年饮食不当后出现腹泻,7~8次/d左右,为黄色稀便,带有少量暗红色血,伴里急后重感,食欲稍有减退,无恶心、呕吐,发热。自服"黄连素"、"盐酸小襞碱"药物止泻治疗,效果不佳。