Anisotropic spin transport and photoresponse characteristics detected by tip movement in magnetic single-molecule junction

Orientation-dependent transport properties induced by anisotropic molecules are enticing in single-molecule junctions.Here,using the first-principles method,we theoretically investigate spin transport properties and photoresponse characteristics in trimesic acid magnetic single-molecule junctions with different molecular adsorption orientations and electrode contact sites.The transport calculations indicate that a single-molecule switch and a significant enhancement of spin transport and photoresponse can be achieved when the molecular adsorption orientation changes from planar geometry to upright geometry.The maximum spin polarization of current and photocurrent in upright molecular junctions exceeds 90%.Moreover,as the Ni tip electrode moves,the tunneling magnetoresistance of upright molecular junctions can be increased to 70%.The analysis of the spin-dependent PDOS elucidates that the spinterfaces between organic molecule and ferromagnetic electrodes are modulated by molecular adsorption orientation,where the molecule in upright molecular junctions yields higher spin polarization.Our theoretical work paves the way for designing spintronic devices and optoelectronic devices with anisotropic functionality base on anisotropic molecules.

Unusual magnetic relaxation in a single-molecule magnet with toroidal magnetic moments

We report the synthesis and characterization of a single-molecule magnet composed of triangular clusters of dysprosium ions.The structural study shows that the symmetry changes from one polar point group(mm2)at room temperature to another polar point group(m)at low temperature.Magnetic studies and theory calculations illustrate that the vortex distribution of magnetic dipoles in the triangular dysprosium clusters forms a toroidal magnetic moment.Interestingly,the analysis of AC magnetic susceptibility reveals the coexistence of three distinct magnetic relaxation processes,corresponding to the Raman,Orbach,and QTM relaxation pathways,respectively.The sum of three modified Debye functions is successfully used to describe the multiple relaxation behavior.

Single-Molecule Confinement Induced Intrinsic Multi-Electron Redox-Activity to Enhance Supercapacitor Performance

Aggregation of polyoxometalates(POM)is largely responsible for the reduced performance of POM-based energy-storage systems.To address this challenge,here,the precise confinement of single Keggin-type POM molecule in a porous carbon(PC)of unimodal super-micropore(micro-PC)is realized.Such precise single-molecule confinement enables sufficient activity center exposure and maximum electron-transfer from micro-PC to POM,which well stabilizes the electron-accepting molecules and thoroughly activates its inherent multi-electron redox-activity.In particular,the redox-activities and electron-accepting properties of the confined POM molecule are revealed to be super-micropore pore size-dependent by experiment and spectroscopy as well as theoretical calculation.Meanwhile,the molecularly dispersed POM molecules confined steadily in the“cage”of micro-PC exhibit unprecedented large-negative-potential stability and multiple-peak redox-activity at an ultra-low loading of~11.4 wt%.As a result,the fabricated solid-state supercapacitor achieves a remarkable areal capacitance,ultrahigh energy and power density of 443 mF cm^(-2),0.12 mWh cm^(-2)and 21.1 mW cm^(-2),respectively.This work establishes a novel strategy for the precise confinement of single POM molecule,providing a versatile approach to inducing the intrinsic activity of POMs for advanced energy-storage systems.

DecodeSTORM:A user-friendly ImageJ plug-in for quantitative data analysis in single-molecule localization microscopy

Quantitative data analysis in single-molecule localization microscopy(SMLM)is crucial for studying cellular functions at the biomolecular level.In the past decade,several quantitative methods were developed for analyzing SMLM data;however,imaging artifacts in SMLM experiments reduce the accuracy of these methods,and these methods were seldom designed as user-friendly tools.Researchers are now trying to overcome these di±culties by developing easyto-use SMLM data analysis software for certain image analysis tasks.But,this kind of software did not pay su±cient attention to the impact of imaging artifacts on the analysis accuracy,and usually contained only one type of analysis task.Therefore,users are still facing di±culties when they want to have the combined use of different types of analysis methods according to the characteristics of their data and their own needs.In this paper,we report an ImageJ plug-in called DecodeSTORM,which not only has a simple GUI for human–computer interaction,but also combines artifact correction with several quantitative analysis methods.DecodeSTORM includes format conversion,channel registration,artifact correction(drift correction and localization¯ltering),quantitative analysis(segmentation and clustering,spatial distribution statistics and colocalization)and visualization.Importantly,these data analysis methods can be combined freely,thus improving the accuracy of quantitative analysis and allowing users to have an optimal combination of methods.We believe DecodeSTORM is a user-friendly and powerful ImageJ plug-in,which provides an easy and accurate data analysis tool for adventurous biologists who are looking for new imaging tools for studying important questions in cell biology.

Combination of density-clustering and supervised classification for event identification in single-molecule force spectroscopy data

Single-molecule force spectroscopy(SMFS)measurements of the dynamics of biomolecules typically require identifying massive events and states from large data sets,such as extracting rupture forces from force-extension curves(FECs)in pulling experiments and identifying states from extension-time trajectories(ETTs)in force-clamp experiments.The former is often accomplished manually and hence is time-consuming and laborious while the latter is always impeded by the presence of baseline drift.In this study,we attempt to accurately and automatically identify the events and states from SMFS experiments with a machine learning approach,which combines clustering and classification for event identification of SMFS(ACCESS).As demonstrated by analysis of a series of data sets,ACCESS can extract the rupture forces from FECs containing multiple unfolding steps and classify the rupture forces into the corresponding conformational transitions.Moreover,ACCESS successfully identifies the unfolded and folded states even though the ETTs display severe nonmonotonic baseline drift.Besides,ACCESS is straightforward in use as it requires only three easy-to-interpret parameters.As such,we anticipate that ACCESS will be a useful,easy-to-implement and high-performance tool for event and state identification across a range of single-molecule experiments.

Magnetic-field-controlled spin valve and spin memory based on single-molecule magnets

A single-molecule magnet is a long-sought-after nanoscale component because it can enable us to miniaturize nonvolatile memory storage devices.The signature of a single-molecule magnet is switching between two bistable magnetic ground states under an external magnetic field.Based on this feature,we theoretically investigate a magnetic-fieldcontrolled reversible resistance change active at low temperatures in a molecular magnetic tunnel junction,which consists of a single-molecule magnet sandwiched between a ferromagnetic electrode and a normal metal electrode.Our numerical results demonstrate that the molecular magnetism orientation can be manipulated by magnetic fields to be parallel/antiparallel to the ferromagnetic electrode magnetization.Moreover,different magnetic configurations can be“read out”based on different resistance states or different spin polarization parameters in the current spectrum,even in the absence of a magnetic field.Such an external magnetic field-controlled resistance state switching effect is similar to that in traditional spin valve devices.The difference between the two systems is that one of the ferromagnetic layers in the original device has been replaced by a magnetic molecule.This proposed scheme provides the possibility of better control of the spin freedom of electrons in molecular electrical devices,with potential applications in future high-density nonvolatile memory devices.

Single-electron transport in H_(2)O@C_(60) single-molecule transistors

Single-molecule transistors(SMTs) based on fullerenes and their derivatives have been recognized as a long-sought platform for studying the single-electron transport properties.H_(2)O@C_(60) is a combination of fullerene and H_(2)O,a typical light molecule.Here we use the 'molecular surgery' technique to synthesize the H_(2)O@C_(60) molecule and then construct the H_(2)O@C_(60) SMTs,together with the C_(60) SMTs.Evidences for single-electron transport have been obtained in our measurements,including explicit Coulomb blockade and Coulomb oscillations.We then calculate the detailed parameters of the H_(2)O@C_(60) and C_(60) SMTs using a capacitance model derived from the Coulomb diamond feature,which gives a capacitance ratio of 1:5.05:8.52 for the H_(2)O@C_(60) SMT and 1:29.5:74.8 for the C_(60) SMT.Moreover,the gate efficiency factor a turns out to be 0.0686 in the H_(2)O@C_(60) SMT,about ten times larger than that in the C_(60) SMT.We propose that the enhanced gate efficiency in H_(2)O@C_(60) SMT may be induced by the closer attachment of molecular orbital electron clouds to the gate substrate due to polarization effects of H_(2)O.

Monomeric type I and type III transforming growth factor-β receptors and their dimerization revealed by single-molecule imaging

Transforming growth factor-β （TGF-β） binds with two transmembrane serine/threonine kinase receptors, type Ⅱ （TβRII） and type Ⅰ receptors （TβRⅠ）, and one accessory receptor, type Ⅲ receptor （TβRⅢ）, to transduce signals across cell membranes. Previous biochemical studies suggested that TβRI and TβRIII are preexisted homo-dimers. Using single-molecule microscopy to image green fluorescent protein-labeled membrane proteins, for the first time we have demonstrated that TβRI and TβRⅢ could exist as monomers at a low expression level. Upon TGF-β1 stimu- lation, TβRI follows the general ligand-induced receptor dimerization model for activation, but this process is TβRⅡ- dependent. The monomeric status of the non-kinase receptor TβRⅢ is unchanged in the presence of TGF-β1. With the increase of receptor expression, both TβRI and TβRIII can be assembled into dimers on cell surfaces.

Single-molecule optoelectronic devices:physical mechanism and beyond

Single-molecule devices not only promise to provide an alternative strategy to break through the miniaturization and functionalization bottlenecks faced by traditional semiconductor devices,but also provide a reliable platform for exploration of the intrinsic properties of matters at the single-molecule level.Because the regulation of the electrical properties of single-molecule devices will be a key factor in enabling further advances in the development of molecular electronics,it is necessary to clarify the interactions between the charge transport occurring in the device and the external fields,particularly the optical field.This review mainly introduces the optoelectronic effects that are involved in single-molecule devices,including photoisomerization switching,photoconductance,plasmon-induced excitation,photovoltaic effect,and electroluminescence.We also summarize the optoelectronic mechanisms of single-molecule devices,with particular emphasis on the photoisomerization,photoexcitation,and photo-assisted tunneling processes.Finally,we focus the discussion on the opportunities and challenges arising in the single-molecule optoelectronics field and propose further possible breakthroughs.

Simultaneous, hybrid single-molecule method by optical tweezers and fluorescence

As studies on life sciences progress toward the single-molecule level,new experiments have put forward more requirements for simultaneously displaying the mechanical properties and conformational changes of biomolecules.Optical tweezers and fluorescence microscopy have been combined to solve this problem.The combination of instruments forms a new generation of hybrid single-molecule technology that breaks through the limitations of traditional biochemical analysis.Powerfulmanipulation and fluorescence visualization have beenwidely used,and these techniques provide new possibilities for studying complex biochemical reactions at the singlemolecule level.This paper explains the features of this combined technique,including the application characteristics of single-trap and dual-traps,the anti-bleaching method,and optical tweezers combined with epifluorescence,confocal fluorescence,total internal reflection fluorescence,and other fluorescence methods.Using typical experiments,we analyze technical solutions and explain the factors and principles that instrument designers should consider.This review aims to give an introduction to this novel fusion technology process and describe important biological results.

Single-molecule biotechnology for protein researches

Cells employ proteins to perform metabolic functions and maintain active physiological state through charge transfer and energy conversion.These processes are carried out in a narrow space precisely and rapidly,which,no doubt,bring great difficulty for their detection and dissection.Fortunately,in recent years,the development and expansion of single-molecule technique in protein research make monitoring the dynamical changes of protein at single-molecule level a reality,which also provides a powerful tool for the further exploration of new phenomena and new mechanisms of life activities.This paper aims to summarize the working principle and essential achievements of single-molecule technique in protein research in recent five years.We focus on not only dissecting the difference of nanopores,atomic force microscope,scanning tunneling microscope,and optical tweezers technique,but also discussing the great significance of these single-molecule techniques in investigating intramolecular and intermolecular interactions,electron transport,and conformational changes.Finally,the opportunities and challenges of the single-molecule technique in protein research are discussed,which provide a new door for single-molecule protein research.

Foreword to the Special Issue on Optical Technologies in Biophysics and Medicine

We are pleased to present the third issue of JIOHS,which focuses on optical technologies of diagnosticsand therapy,These are selected papers presented during Saratov Fall Meeting,1t International Sym-posium on Optics and Biophotonics(September 24-28,2013,Saratov,Russia)in the framework of the Workshops:"Optical Technologies in Biophysics_and Medicine,"Nanobiophotonics,"and"Internet Biophotonics."

Biophysics inspired artificial intelligence for colorectal cancer characterization

Over the last ten years artificial intelligence(AI)methods have begun to pervade even the most common everyday tasks such as email filtering and mobile banking.While the necessary quality and safety standards may have understandably slowed the introduction of AI to healthcare when compared with other industries,we are now beginning to see AI methods becoming more available to the clinician in select settings.In this paper we discuss current AI methods as they pertain to gastrointestinal procedures including both gastroenterology and gastrointestinal surgery.The current state of the art for polyp detection in gastroenterology is explored with a particular focus on deep leaning,its strengths,as well as some of the factors that may limit its application to the field of surgery.The use of biophysics(utilizing physics to study and explain biological phenomena)in combination with more traditional machine learning is also discussed and proposed as an alternative approach that may solve some of the challenges associated with deep learning.Past and present uses of biophysics inspired AI methods,such as the use of fluorescence guided surgery to aid in the characterization of colorectal lesions,are used to illustrate the role biophysicsinspired AI can play in the exciting future of the gastrointestinal proceduralist.

Spin-dependent negative differential conductance in transport through single-molecule magnets

Transport properties are theoretically studied through an anisotropy single-molecule magnet symmetrically connected to two identical ferromagnetic leads. It is found that even though in parallel configuration of leads’ magnetizations, the total current still greatly depends on the spin polarization of leads at certain particular bias region, and thus for large polarization a prominent negative differential conductance （NDC） emerges. This originates from the joint effect of single-direction transitions and spin polarization, which removes the symmetry between spin-up and spin-down transitions. The present mechanism of NDC is remarkably different from the previously reported mechanisms. To clarify the physics of the NDC, we further monitored the shot noise spectroscopy and found that the appearance of the NDC is accompanied by the rapid decrease of Fano factor.

Bias-controlled spin memory and spin injector scheme in the tunneling junction with a single-molecule magnet

A bias-controlled spin-filter and spin memory is theoretically proposed, which consists of the junction with a singlemolecule magnet sandwiched between the nonmagnetic and ferromagnetic(FM) leads. By applying different voltage pulses Vwriteacross the junction, the spin direction of the single-molecule magnet can be controlled to be parallel or anti-parallel to the magnetization of the FM lead, and the spin direction of SMM can be "read out" either by the magneto-resistance or by the spin current with another series of small voltage pulses V_(probe). It is shown that the polarization of the spin current is extremely high(up to 100%) and can be manipulated by the full-electric manner. This device scheme can be compatible with current technologies and has potential applications in high-density memory devices.

The effect of doped ions on single-molecule magnets of the Mn_(12)-Ac family

This paper investigates the single-molecule magnets of pure and Cr/Fe-doped Mn12-Ac. The components of the mixed crystals are identified by AC susceptibility technique. The ground-state spin and anisotropy parameters of doped Mn12-Ac are obtained： （i） MnllCr-Ac （S=19/2, D=0.62K, B=0.0009K, A=63K）, and （ii） Mn11Fe-Ac （S=21/2, D=0.39 K, B=0.001 K, △=55 K）. The single-ion origin of the magnetic anisotropy is discussed.

Transport through artificial single-molecule magnets:Spin-pair state sequential tunneling and Kondo effects

The transport properties of an artificial single-molecule magnet based on a CdTe quantum dot doped with a single Mn＋2 ion（S=5/2） are investigated by the non-equilibrium Green function method.We consider a minimal model where the Mn-hole exchange coupling is strongly anisotropic so that spin-flip is suppressed and the impurity spin S and a hole spin s entering the quantum dot are coupled into spin pair states with（2S＋1） sublevels.In the sequential tunneling regime,the differential conductance exhibits（2S＋1） possible peaks,corresponding to resonance tunneling via（2S＋1） sublevels.At low temperature,Kondo physics dominates transport and（2S＋1） Kondo peaks occur in the local density of states and conductance.These peaks originate from the spin-singlet state formed by the holes in the leads and on the dot via higher-order processes and are related to the parallel and antiparallel spin pair states.

A new manganese-based single-molecule magnet with a record-high antiferromagnetic phase transition temperature

We perform both dc and ac magnetic measurements on the single crystal of Mn30（Et-sao）3（C104）（MeOH）3 single- molecule magnet （SMM） when the sample is preserved in air for different durations. We find that, during the oxidation process, the sample develops into another SMM with a smaller anisotropy energy barrier and a stronger antiferromagnetic intermolecular exchange interaction. The antiferromagnetic transition temperature observed at 6.65 K in the new SMM is record-high for the antiferromagnetic phase transition in all the known SMMs. Compared to the original SMM, the only apparent change for the new SMM is that each molecule has lost three methyl groups as revealed by four-circle x-ray diffraction （XRD）, which is thought to be the origin of the stronger antiferromagnetic intermolecular exchange interaction.

Theoretical design of single-molecule NOR and XNOR logic gates by using transition metal dibenzotetraaza[14]annulenes

The idea of replacing traditional silicon-based electronic components with the ones assembled by organic molecules to further scale down the electric circuits has been attracting extensive research focuses.Among the molecularly assembled components,the design of molecular logic gates with simple structure and high Boolean computing speed remains a great challenge.Here,by using the state-of-the-art nonequilibrium Green’s function theory in conjugation with first-principles method,the spin transport properties of single-molecule junctions comprised of two serially connected transition metal dibenzotetraaza[14]annulenes(TM(DBTAA),TM=Fe,Co)sandwiched between two single-walled carbon nanotube electrodes are theoretically investigated.The numerical results show a close dependence of the spin-resolved current-voltage characteristics on spin configurations between the left and right molecular kernels and the kind of TM atom in TM(DBTAA)molecule.By taking advantage of spin degree of freedom of electrons,NOR or XNOR Boolean logic gates can be realized in Fe(DBTAA)and Co(DBTAA)junctions depending on the definitions of input and output signals.This work proposes a new kind of molecular logic gates and hence is helpful for further miniaturization of the electric circuits.

3-33 Sweet Sorghum Industrialization and Research Progress of Biophysics Group at IMP

IMP has established an industrial chain based on circular economy to develop various biological products and nice feed for cattle since 2010. So far, the planting scale of sweet sorghum has been nearly to 1 million Chinese mu in Gansu Province. According to developmental plan of sweet sorghum industrialization in local government, sweet sorghum will be planted to 5 million mu in Gansu Province in 2020, forming the circular economy industrial chain valued as hundred billion yuan. In 2015, IMP received an award named Innovation Award of Industry University Research Cooperation in China for their promoted progress of Sweet sorghum industrial chain.