Collective Electron Oscillations Research Articles

(Invited) Photochemical Energy Conversion with Integrated Plasmonics

Plasmonic nanostructures can dramatically increase the chemical reaction rates by providing more efficient solar-to-chemical energy conversion. Upon light excitation, metallic nanostructures sustain the collective oscillation of surface electrons, i.e. surface plasmons, producing local field enhancement and after one hundred femtoseconds decaying by generating a non-thermal distribution of hot carriers. Their consequent thermalization results in intense local heating of the nanostructures and their surrounding. All these effects can alter the reaction pathways and boost the reaction kinetics. Such discoveries have boosted the field of plasmonic photocatalysis, which aims at driving industrially-relevant chemical reactions using solar illumination. In this talk, I will present our recent progress in the fabrication of large-area plasmonic metasurfaces exhibiting a rich set of electromagnetic resonances and their integration in photoelectrochemical water splitting cells, direct alcohol fuel cells, and photochemical devices for hydrogen evolution. I will discuss the complex relationship between the optical resonances of the plasmonic metasurfaces with their chemical reactivity by distinguishing the various effects enhancing their photochemical performance. Finally, a new scanning photoelectrochemical method that provide the two-dimensional mapping of the chemical reactivity of plasmonic nanostructures on planar substrates with sub-micron resolution will be introduced.

Enhanced betatron x-ray emission in a laser wakefield accelerator and wiggler due to collective oscillations of electrons

We report x-ray emission caused by betatron motion of electrons in a laser wakefield accelerator driven by high intensity ($\ensuremath{\sim}4\ifmmode\times\else\texttimes\fi{}{10}^{19}\text{ }\text{ }\mathrm{W}/{\mathrm{cm}}^{2}$) laser pulse interaction with a 4-mm long helium gas-jet and study the role of collective oscillation of electrons as well as plasma density. The collective oscillations of electrons, inferred from the observed wavy pattern in the electron beam spectrum (up to 300 MeV) led to enhance peak x-ray flux which was found to be further enhanced at higher plasma densities. A similar correlation between the enhancement in x-ray emission and collective oscillation was also observed in nitrogen gas target. Possible physical pictures for the above observations are also suggested and discussed. For the helium gas jet target, the typically observed x-ray source brightness is $\ensuremath{\ge}1\ifmmode\times\else\texttimes\fi{}{10}^{20}\text{ }\text{ }\mathrm{photons}/\mathrm{s}\text{ }{\mathrm{mm}}^{2}\text{ }{\mathrm{mrad}}^{2}$ in 0.1% BW, with a critical energy of $35\ifmmode\pm\else\textpm\fi{}5\text{ }\text{ }\mathrm{keV}$. We have also demonstrated the application of the betatron x-ray source in high-resolution imaging.

Plasmonic Nanozymes: Leveraging Localized Surface Plasmon Resonance to Boost the Enzyme-Mimicking Activity of Nanomaterials.

Nanozymes, a type of nanomaterials that function similarly to natural enzymes, receive extensive attention in biomedical fields. However, the widespread applications of nanozymes are greatly plagued by their unsatisfactory enzyme-mimicking activity. Localized surface plasmon resonance (LSPR), a nanoscale physical phenomenon described as the collective oscillation of surface free electrons in plasmonic nanoparticles under light irradiation, offers a robust universal paradigm to boost the catalytic performance of nanozymes. Plasmonic nanozymes (PNzymes) with elevated enzyme-mimicking activity by leveraging LSPR, emerge and provide unprecedented opportunities for biocatalysis. In this review, the physical mechanisms behind PNzymes are thoroughly revealed including near-field enhancement, hot carriers, and the photothermal effect. The rational design and applications of PNzymes in biosensing, cancer therapy, and bacterial infections elimination are systematically introduced. Current challenges and further perspectives of PNzymes are also summarized and discussed to stimulate their clinical translation. It is hoped that this review can attract more researchers to further advance the promising field of PNzymes and open up a new avenue for optimizing the enzyme-mimicking activity of nanozymes to create superior nanocatalysts for biomedical applications.

Controlling excitons in the quantum tunneling regime in a hybrid plasmonic/2D semiconductor interface

The electromagnetic field confinement and amplification typical of nano-sized metallic objects supporting localized surface plasmon resonances, i.e., light-induced collective electronic oscillations, can significantly strengthen the interaction of light with atomically thin transition metal dichalcogenides. In view of the realization of plasmon-enhanced devices, it is crucial to investigate the effects induced by light confinement within metallic nanostructures on the excitonic properties of these materials at the nanoscale. Here, we exploit tip-enhanced photoluminescence spectroscopy to locally control the excitons of monolayer molybdenum disulfide (MoS2) coupled with gold nanotriangles in the quantum tunneling regime. The spatial resolution of 10 nm in the tip-enhanced photoluminescence measurements made it possible to image the light-emission related properties of monolayer MoS2 across one single metallic nanostructure and to investigate the effect of the plasmonic enhancement on its photoluminescence peak. Moreover, by taking advantage of the degree of freedom given by the tuning of the tip-sample distance; it was possible to probe the effect of the plasmonic pico-cavity size on the photoluminescence quenching rate of monolayer MoS2.

Polarization-Multiplexed Incoherent Broadband Surface Plasmon Resonance: A New Analytical Strategy for Plasmonic Sensing.

Surface plasmon resonance (SPR) is an interfacial phenomenon, and the plasmonic sensors are based on the optical excitation of the collective oscillations of free electrons at a metal-dielectric interface. Here, we present the new development of an incoherent broadband (IBB)-SPR probe combining the wavelength interrogation technique with polarization-multiplexing (PM). The performance characteristics of the so-called PMIBB-SPR strategy was validated for the detection of nonenzymatic aqueous urea samples as a representative example for plasmonic sensing with an excellent wavelength and phase sensitivities of 0.1363 nm/mM and 10.34597 mM/deg, respectively. We further explored the missing link between plasmonic polariton resonance (PPR) and polarization modulation via the measurements of the Stokes parameters of the reflected light. This deepens our understanding of the fundamentals of polarization-multiplexed SPR phenomenon at the interface. This study thus paves the way to develop a new-generation analytical technique with the aim of tracking various real-time chemical and biological molecular interactions occurring at the interfaces.

Surface-Plasmon-Assisted Growth, Reshaping and Transformation of Nanomaterials.

Excitation of surface plasmon resonance of metal nanostructures is a promising way to break the limit of optical diffraction and to achieve a great enhancement of the local electromagnetic field by the confinement of optical field at the nanoscale. Meanwhile, the relaxation of collective oscillation of electrons will promote the generation of hot carrier and localized thermal effects. The enhanced electromagnetic field, hot carriers and localized thermal effects play an important role in spectral enhancement, biomedicine and catalysis of chemical reactions. In this review, we focus on surface-plasmon-assisted nanomaterial reshaping, growth and transformation. Firstly, the mechanisms of surface-plasmon-modulated chemical reactions are discussed. This is followed by a discussion of recent advances on plasmon-assisted self-reshaping, growth and etching of plasmonic nanostructures. Then, we discuss plasmon-assisted growth/deposition of non-plasmonic nanostructures and transformation of luminescent nanocrystal. Finally, we present our views on the current status and perspectives on the future of the field. We believe that this review will promote the development of surface plasmon in the regulation of nanomaterials.

Piezoelectric Effect Enhanced Photocatalytic Activity of Pt/Bi3.4Gd0.6Ti3O12 Plasmonic Photocatalysis

Novel Pt/Bi3.4Gd0.6Ti3O12 heterojunction was synthesized by a decoration of Pt nanoparticles (PtNPs) on the surface of piezoelectric Bi3.4Gd0.6Ti3O12 (BGTO) through an impregnation process. The photocatalytic, piezo-catalytic, and piezo-photocatalytic activities of the Pt/BGTO heterojunction for methyl orange (MO) degradation were investigated under ultrasonic excitation and whole spectrum light irradiation. The internal piezoelectric field of BGTO and a plasmonic effect have been proven important for the photocatalytic activity of the heterojunctions. Pt/BGTO exhibited an optimum photocatalytic degradation performance of 92% for MO in 70 min under irradiation of whole light spectrum and ultrasonic coexcitation, and this value was about 1.41 times higher than the degradation rate under whole spectrum light irradiation alone. The PtNPs in Pt/BGTO heterojunction can absorb the incident light intensively, and induce the collective oscillation of surface electrons due to the surface plasmon resonance (SPR) effect, thus generating “hot” electron–hole pairs. The internal piezoelectric field produced in BGTO by ultrasonic can promote the separation of SPR-induced “hot” charge carriers and facilitate the production of highly reactive oxidation radicals, thus enhancing Pt/BGTO heterojunction′s photocatalytic activity for oxidizing organic dyes.

Recent advances in ultrafast plasmonics: from strong field physics to ultraprecision spectroscopy

Abstract Surface plasmons, the collective oscillation of electrons, enable the manipulation of optical fields with unprecedented spatial and time resolutions. They are the workhorse of a large set of applications, such as chemical/biological sensors or Raman scattering spectroscopy, to name only a few. In particular, the ultrafast optical response configures one of the most fundamental characteristics of surface plasmons. Thus, the rich physics about photon–electron interactions could be retrieved and studied in detail. The associated plasmon-enhanced electric fields, generated by focusing the surface plasmons far beyond the diffraction limit, allow reaching the strong field regime with relatively low input laser intensities. This is in clear contrast to conventional optical methods, where their intrinsic limitations demand the use of large and costly laser amplifiers, to attain high electric fields, able to manipulate the electron dynamics in the non-linear regime. Moreover, the coherent plasmonic field excited by the optical field inherits an ultrahigh precision that could be properly exploited in, for instance, ultraprecision spectroscopy. In this review, we summarize the research achievements and developments in ultrafast plasmonics over the last decade. We particularly emphasize the strong-field physics aspects and the ultraprecision spectroscopy using optical frequency combs.

Noble Metal Nanoparticle Biosensors: From Fundamental Studies toward Point-of-Care Diagnostics.

Noble metal nanoparticles (NMNPs) have become firmly established as effective agents to detect various biomolecules with extremely high sensitivity. This ability stems from the collective oscillation of free electrons and extremely large electric field enhancement under exposure to light, leading to various light-matter interactions such as localized surface plasmon resonance (LSPR) and surface-enhanced Raman scattering. A remarkable feature of NMNPs is their customizability by mechanisms such as particle etching, growth, and aggregation/dispersion, yielding distinct color changes and excellent opportunities for colorimetric biosensing in user-friendly assays and devices. They are readily functionalized with a large variety of capping agents and biomolecules, with resultant bioconjugates often possessing excellent biocompatibility, which can be used to quantitatively detect analytes from physiological fluids. Furthermore, they can possess excellent catalytic properties that can achieve significant signal amplification through mechanisms such as the catalytic transformation of colorless substrates to colored reporters. The various excellent attributes of NMNP biosensors have put them in the spotlight for developing high-performance in vitro diagnostic (IVD) devices that are particularly well-suited to mitigate the societal threat that infectious diseases pose. This threat continues to dominate the global health care landscape, claiming millions of lives annually. NMNP IVDs possess the potential to sensitively detect infections even at very early stages with affordable and field-deployable devices, which will be key to strengthening infectious disease management. This has been the major focal point of current research, with a view to new avenues for early multiplexed detection of infectious diseases with portable devices such as smartphones, especially in resource-limited settings.In this Account, we provide an overview of our original inspiration and efforts in NMNP-based assay development, together with some more sophisticated IVD assays by ourselves and many others. Our work in the area has led to our recent efforts in developing IVDs for high-profile infectious diseases, including Ebola and HIV. We emphasize that integration with digital platforms represents an opportunity to establish and efficiently manage widespread testing, tracking, epidemiological intelligence, and data sharing backed by community participation. We highlight how digital technologies can address the limitations of conventional diagnostic technologies at the point of care (POC) and how they may be used to abate and contain the spread of infectious diseases. Finally, we focus on more recent integrations of noble metal nanoparticles with Raman spectroscopy for accurate, noninvasive POC diagnostics with improved sensitivity and specificity.

Double profound enhancements of Cu2O nano-octahedrons connected by intertwined Ag nanovines for elevating SERS activity toward ultrasensitive pesticide detection.

Recently, hybrid plasmonic metal/semiconductor-based surface-enhanced Raman scattering (SERS) has attracted ever-increasing attention due to its combined characteristics of electromagnetic (EM) enhancement and chemical (CM) enhancement, holding great potential for trace molecular detection. Herein, we demonstrate an interesting heterostructure by linking Cu2O nano-octahedrons with intertwined Ag nanovines (NVs). The obtained Ag NVs/Cu2O heterostructures exhibit excellent SERS activity, which is about 2.7 and 7.0 times higher than that of monodispersed Ag or Au nanoparticles (NPs) modified Cu2O. The intertwined Ag NVs among adjacent Cu2O octahedrons serve as efficient electron transport channels, which can obviously promote the separation of electrons and holes, reduce the recombination of photogenerated carriers, and then improve the CM enhancement effect. Meanwhile, the accumulated electrons on plasmonic NVs can effectively optimize the collective oscillation of electrons and further improve the EM enhancement. The optimal SERS substrate possesses fascinating multifunctional SERS properties, including ultra-low detection limit (CV, 10-14 M), excellent anti-interference capability and selectivity. Finally, the established nanosensor can be effectively applied for the quantitative detection of pesticide thiram molecules in soil and biological samples, with low detection limits of 0.48 ng g-1 and 10-7 M, respectively. The proposed work demonstrates a high-performance SERS heterostructure with both improved CM enhancement and enhanced EM effect by linking adjacent Cu2O nano-octahedrons with Ag NVs, which is particularly suitable for ultrasensitive residual pesticide detection in real-world environment.

Ag nanoparticles induced modification in microhardness of polyvinyl alcohol

Silver (Ag) nanoparticles play a significant role in nanomaterials science and technology due to many peculiarities. One of the main characteristic of Ag nanoparticles is the occurrence of surface plasmon resonance (SPR) due to the collective oscillation of free electrons in visible region. Due to this distinctive feature Ag nanoparticles have numerous applications such as in catalysis, surface enhanced Raman spectroscopy, photonics, solar cells etc. In the present work, no additional stabilizing agent has been used. The characteristic SPR peak appears at around 405 nm in UV-Visible absorption spectra of PVA-Ag nanocomposite films, thereby confirming the nanocomposite formation. The synthesized nanocomposite films were structurally characterized using fourier transform infrared (FTIR) and Raman spectroscopy. FTIR spectra of PVA-Ag nanocomposite film indicates that PVA matrix is modified by Ag nanoparticles which is in agreement with the results obtained using Raman spectroscopy. TEM as well as FE-SEM micrographs reveal that Ag nanoparticles are mostly spherical in shape. The knoop microhardness number of the nanocomposites was found to increase from 2.4 Kgf/mm2 for PVA to 12.1 kgf/mm2 for PVA-Ag nanocomposite film loaded with 0.062 wt% Ag nanoparticles. Copyright © 2018 VBRI Press.

Reshaping plasmonic resonances using epsilon-near-zero materials for enhanced infrared vibrational spectroscopy

Surface-enhanced infrared absorption (SEIRA) spectroscopy is a powerful technique for a label-free identification of molecular species. The low infrared absorption cross sections of molecules are made up for the huge electromagnetic field enhancement provided by the resonant excitation of collective electron oscillations in metallic nanoantennas. Since these surface plasmons are localized at the nanometer scale, a minute amount of materials is detected leading to a weak SEIRA signal. The design of actual plasmonics detectors is a trade-off between the detection of very small volumes of molecules and the signal to noise ratio level. We demonstrate that an epsilon-near-zero (ENZ) material combined with nano-slits lifts this constraint and provides both extreme enhancement factor up to 107 and highly contrasted SEIRA signal for an extremely low amount of material of interest. These results are explained by the modification of the electromagnetic field of the gap plasmon mode sustained by the slits in the presence of the ENZ material. We propose to implement this concept with a semiconductor whose doping level engineering provides a versatile way to scan the whole molecules' fingerprint frequency range.

High‐Quality Plasmonic Materials TiN and ZnO:Al by Atomic Layer Deposition

Electromagnetic radiation when coupled to collective oscillations of free electrons, dubbed as plasmonics, makes it possible to manipulate light at dimensions well below the diffraction limit and substantially enhances light–matter interaction. Plasmonics has already enabled many novel technologies with a wide variety of application in chemical and biosensing, medical treatments, nonlinear and quantum optics, metamaterials, optical nanotweezers, nanolasers, solar cells, light‐emitting diodes, and telecommunications. Coating the well‐established semiconductor circuitry with metals, such as Au and Ag, imparts the stack with much coveted plasmonic properties, but the metals suffer from high dissipative losses, limited optical tunability, and poor mechanical, chemical, and thermal stabilities, which render them undesirable. Emerging alternative plasmonic materials, such as TiN and ZnO:Al, overcome these limitations and offer wide tunability of their electrical and optical properties. Among a wide range of techniques used for the preparation of TiN and ZnO:Al thin films, atomic layer deposition (ALD) offers advantages such as conformity, scalability, and low growth temperature, which makes this technique the most suitable for the integration of plasmonics with the complementary metal–oxide–semiconductor (CMOS) electronics. Herein, a brief review of recent advances in ALD‐grown TiN and ZnO:Al thin films as pertained to plasmonic applications is given.

Polymer Micelle Directed Magnetic Cargo Assemblies Towards Spin‐wave Manipulation

AbstractSpin‐wave based technologies that use collective oscillation of electrons termed magnons have been proposed for future computing landscapes due to their low energy consumption and high data transfer speeds. Magnonic crystals, materials with magnetic properties periodically varied in space, are central to such technologies. However, they are currently limited by the lithography techniques used for the magnetic patterning. To address this issue, bottom‐up self‐assembly using polymer templates to order magnetic cargo is presented. In this work, block copolymer micelles are used as templates to direct the organization of polyoxometalate (POM) molecules into organized assemblies. The structural organization of these assemblies is evaluated using microscopy and scattering techniques. The organized POM assemblies are demonstrated to modulate spin‐waves excited in permalloy thin films. This work demonstrates the first use of a bottom‐up approach to realize the fabrication of a magnonic assembly at the nanoscale. It further paves the way to achieve magnon‐mediated self‐assembled computing architectures.

Light harvesting enhancement using metal nanoparticles

Metal nanoparticles are very important for their optical properties when they interact with light. Metal nanoparticles have the ability to confine the collective oscillation of electrons, which is called localized surface plasmon resonance (LSPR). In this work, silver nanoparticles have been proposed to enhance light harvesting, which could be useful for different applications. Metal nanoparticles such as gold and silver nanoparticles have the ability to concentrate field in a very small space. In this study, gold and silver nanoparticles optical response was investigated using frequency domain simulation. The resonance wavelength of gold and silver nanoparticles was about 550 nm and 400 nm, respectively. Silver nanoparticles showed better LSPR performance than gold nanoparticles. Therefore, silver nanoparticles were chosen for optical field enhancement. Here silver nanoparticles were placed on a silicon substrate for optical field enhancement. To study the effect of size on the optical response of silver nanoparticles, the optical properties of this structure with different silver nanoparticles diameter values were investigated. Silver nanoparticles with 40 nm diameters showed a better optical response. To study the effect of the distance between silver nanoparticles on the optical response, different gap values were put between silver nanoparticles. The gap value of 4 nm showed a better optical response. The obtained results showed that the localized field is strongly dependent on the metal type, size, and space between nanoparticles. In addition, the optical field concentration can be controlled by tuning the size and space between silver nanoparticles. This will support localized field enhancement. The enhanced localized field will increase the field absorption near the surface, which can be beneficial for energy harvesting applications such as solar cells and detectors

Effect of silver coating on the optical, morphological, PL and crystal structure of Ag– TiO2 thin films

Abstract In this research work, Ag– TiO2 thin films were deposited on microscope glass slides by spray pyrolysis and thermal vacuum evaporation combination techniques. The effect of substrate temperature and silver doping on crystal structure, surface morphology, hydrophilicity, hydrophobicity, and optical properties of the prepared thin layers were investigated by various techniques such as XRD, AFM, SEM, optical and photoluminescence spectroscopy. The results show the root mean square roughness deviation of pure TiO2 films decreased and the water contact angle increased with increasing of substrate temperature as well as silver thickness in the visible range. On the other hand, hydrophilicity nature of Ag–TiO2 layers raised with increase in the time of UV radiation. The optical absorption increased with silver doping due to collective oscillation of free electrons of small noble nanoparticles. The attained results indicate that the optical absorption increases with silver doping, because the radiated photon was trapped by silver nanoparticles in the TiO2 layers and so increases optical absorption. Anatase phase was dominant crystalline phase in all the prepared samples which is the best phase in photo catalyst and self-cleaning applications.

Communication—Tunable Negative Permittivity of Ti3SiC2 MAX Phase Granular Metacomposites

Referring to the original envisage of Ti3SiC2/copper calcium titanate metacomposites, negative permittivity property depends on low-frequency collective plasma oscillation of free electrons in formed conductive Ti3SiC2 networks. It’s confirmed that a transition from hopping conduction to metallic conduction behavior of metacomposites is related to the percolative evolution from isolated Ti3SiC2 fillers to interconnected networks. In typical, the dielectric permittivity value was feasibly tuned by varying Ti3SiC2 content. The positive reactance of epsilon-negative materials indicates that inductive character is one of their inherent natures.

Demonstration of a laser-driven, narrow spectral bandwidth x-ray source for collective x-ray scattering experiments

X-ray Thomson scattering (XRTS) is a powerful diagnostic technique that involves an x-ray source interacting with a dense plasma sample, resulting in a spectrum of elastically and inelastically scattered x-rays. Depending on the plasma conditions, one can measure a range of parameters from the resulting spectrum, including plasma temperature, electron density, and ionization state. To achieve sensitivity to collective electron oscillations, XRTS measurements require limited momentum transfer where the spectral separation of elastic and inelastic scattering is small. Such measurements require an x-ray probe source with a narrow bandwidth in order to reduce the spectral overlap between scattering contributions, allowing for the different features to be more precisely deconvolved. In this investigation, we discuss the theory behind how the bandwidth for a common XRTS probe, Zn He-α emission at 9 keV, can be reduced using a Cu K-edge filter. Proof-of-principle experiments conducted at the OMEGA laser facility confirm that this is an effective method for attenuating the higher energy He-α peak in the Zn emission spectrum. Calibration measurements at the National Ignition Facility show a reduction in spectral bandwidth from 87 eV to 48 eV when using the Cu filter, which will be important to improve the spectral resolution of future XRTS measurements that will probe plasmon oscillations in strongly compressed plasmas of low-Z materials at densities of tens of g/cm3.

Evidence for a spin acoustic surface plasmon from inelastic atom scattering

Closed-shell atoms scattered from a metal surface exchange energy and momentum with surface phonons mostly via the interposed surface valence electrons, i.e., via the creation of virtual electron-hole pairs. The latter can then decay into surface phonons via electron-phonon interaction, as well as into acoustic surface plasmons (ASPs). While the first channel is the basis of the current inelastic atom scattering (IAS) surface-phonon spectroscopy, no attempt to observe ASPs with IAS has been made so far. In this study we provide evidence of ASP in Ni(111) with both Ne atom scattering and He atom scattering. While the former measurements confirm and extend so far unexplained data, the latter illustrate the coupling of ASP with phonons inside the surface-projected phonon continuum, leading to a substantial reduction of the ASP velocity and possibly to avoided crossing with the optical surface phonon branches. The analysis is substantiated by a self-consistent calculation of the surface response function to atom collisions and of the first-principle surface-phonon dynamics of Ni(111). It is shown that in Ni(111) ASP originate from the majority-spin Shockley surface state and are therefore collective oscillation of surface electrons with the same spin, i.e. it represents a new kind of collective quasiparticle: a Spin Acoustic Surface Plasmon (SASP).

Photocatalytic properties of gold nanoarrays driven by surface plasmon

The surface plasmons produced by the collective oscillation of conduction electrons in metal nanostructures can redistribute not only the electromagnetic field spatiotemporally, but also the excited carriers. Various effects caused by surface plasmons, including enhanced electromagnetic fields, local heating, excited electrons and excited holes, can drive chemical reactions. In this work, the regularly-arranged Au nanoarray catalytic substrate is prepared based on an anodic aluminum oxide template. When the excitation light of a specific wavelength irradiates on the substrate, a large number of regularly-arranged local surface plasmon enhancement regions will be generated on its surface. By taking advantage of surface enhanced Raman spectroscopy, the 4,4′-dimercaptoazobenzene is synthesized by the photocatalytic reaction of p-aminothiophenol as a probe driven by local surface plasmon. After that, the sodium borohydride is introduced in situ. Under the same experimental conditions, the product 4,4′-dimercaptoazobenzene is driven by plasma to produce p-aminothiophenol again. This research work will achieve the drawing and erasing of molecular graphics on a micro scale and a nano scale, as well as information encryption, reading and erasing, which has a strong application value.